Java Secure Socket Extension (JSSE) Reference Guide

This guide covers the following topics:


Introduction

Data that travels across a network can easily be accessed by someone who is not the intended recipient. When the data includes private information, such as passwords and credit card numbers, steps must be taken to make the data unintelligible to unauthorized parties. It is also important to ensure that the data has not been modified, either intentionally or unintentionally, during transport. The Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols were designed to help protect the privacy and integrity of data while it is being transferred across a network.

The Java Secure Socket Extension (JSSE) enables secure Internet communications. It provides a framework and an implementation for a Java version of the SSL and TLS protocols and includes functionality for data encryption, server authentication, message integrity, and optional client authentication. Using JSSE, developers can provide for the secure passage of data between a client and a server running any application protocol (such as HTTP, Telnet, or FTP) over TCP/IP. For an introduction to SSL, see Secure Sockets Layer (SSL) Protocol Overview.

By abstracting the complex underlying security algorithms and handshaking mechanisms, JSSE minimizes the risk of creating subtle but dangerous security vulnerabilities. Furthermore, it simplifies application development by serving as a building block that developers can integrate directly into their applications.

JSSE provides both an application programming interface (API) framework and an implementation of that API. The JSSE API supplements the core network and cryptographic services defined by the java.security and java.net packages by providing extended networking socket classes, trust managers, key managers, SSL contexts, and a socket factory framework for encapsulating socket creation behavior. Because the SSLSocket class is based on a blocking I/O model, the Java Development Kit (JDK) includes a nonblocking SSLEngine class to enable implementations to choose their own I/O methods.

The JSSE API is capable of supporting SSL versions 2.0 and 3.0 and TLS version 1.0. These security protocols encapsulate a normal bidirectional stream socket, and the JSSE API adds transparent support for authentication, encryption, and integrity protection. The JSSE implementation shipped with the JDK supports SSL 3.0 and TLS 1.0. It does not implement SSL 2.0.

JSSE is a security component of the Java SE platform, and is based on the same design principles found elsewhere in the Java Cryptography Architecture (JCA) framework. This framework for cryptography-related security components allows them to have implementation independence and, whenever possible, algorithm independence. JSSE uses the cryptographic service providers defined by the JCA framework.

Other security components in the Java SE platform include the Java Authentication and Authorization Service (JAAS) and the Java Security Tools. JSSE encompasses many of the same concepts and algorithms as those in JCA but automatically applies them underneath a simple stream socket API.

The JSSE API was designed to allow other SSL/TLS protocol and Public Key Infrastructure (PKI) implementations to be plugged in seamlessly. Developers can also provide alternative logic to determine if remote hosts should be trusted or what authentication key material should be sent to a remote host.

Features and Benefits

JSSE includes the following important features:

Table 1: Cryptographic Functionality Available in JSSE
Cryptographic Algorithm Footnote 1 Cryptographic Process Key Lengths (Bits)
Rivest Shamir Adleman (RSA) Authentication and key exchange 512 and larger
Rivest Cipher 4 (RC4) Bulk encryption 128
128 (40 effective)
Data Encryption Standard (DES) Bulk encryption 64 (56 effective)
64 (40 effective)
Triple DES (3DES) Bulk encryption 192 (112 effective)
Advanced Encryption Standard (AES) Bulk encryption 256 Footnote 2
128
Diffie-Hellman (DH) Key agreement 1024
512
Digital Signature Algorithm (DSA) Authentication 1024

Footnote 1 The SunJSSE implementation uses the JCA for all its cryptographic algorithms.

Footnote 2 Cipher suites that use AES_256 require installation of the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files. See Java SE Download Page.

JSSE Standard API

The JSSE standard API, available in the javax.net and javax.net.ssl packages, provides:

SunJSSE Provider

Oracle's implementation of Java SE includes a JSSE provider named SunJSSE, which comes preinstalled and preregistered with the JCA. This provider supplies the following cryptographic services:

More information about this provider is available in the SunJSSE section of the Oracle Providers Documentation.

Related Documentation

The following list contains links to online documentation and names of books about related subjects:

The Java Runtime Environment (JRE) Installation Directory

The java-home variable placeholder is used throughout this document to refer to the directory where the Java Runtime Environment (JRE) is installed. This directory is determined based on whether you are running JSSE with or without the JDK installed. The JDK includes the JRE, but it is located on a different level in the file hierarchy.

To see the default location of java-home for different installations, refer to Table 2.

Table 2: The JRE Installation Directory
Operating System JDK JRE
Solaris/Linux ~/jdk1.8.0/jre ~/jre1.8.0
Windows C:\jdk1.8.0\jre C:\jre1.8.0

Note: The tilde (~) in the path name represents the current user's home directory on Solaris, Linux, or Mac OS X operating systems.


Terms and Definitions

Several terms relating to cryptography are used within this document. This section defines some of these terms.

authentication

The process of confirming the identity of a party with whom one is communicating.

cipher suite

A combination of cryptographic parameters that define the security algorithms and key sizes used for authentication, key agreement, encryption, and integrity protection.

certificate

A digitally signed statement vouching for the identity and public key of an entity (person, company, and so on). Certificates can either be self-signed or issued by a Certificate Authority (CA) — an entity that is trusted to issue valid certificates for other entities. Well-known CAs include VeriSign, Entrust, and GTE CyberTrust. X509 is a common certificate format that can be managed by the JDK's keytool.

cryptographic hash function

An algorithm that is used to produce a relatively small fixed-size string of bits (called a hash) from an arbitrary block of data. A cryptographic hash function is similar to a checksum and has three primary characteristics: it is a one-way function, meaning that it is not possible to produce the original data from the hash; a small change in the original data produces a large change in the resulting hash; and it does not require a cryptographic key.

Cryptographic Service Provider

Sometimes referred to simply as provider for short, the Java Cryptography Architecture (JCA) defines it as a package (or set of packages) that implements one or more engine classes for specific cryptographic algorithms. An engine class defines a cryptographic service in an abstract fashion without a concrete implementation.

decryption

See encryption/decryption.

digital signature

A digital equivalent of a handwritten signature. It is used to ensure that data transmitted over a network was sent by whoever claims to have sent it and that the data has not been modified in transit. For example, an RSA-based digital signature is calculated by first computing a cryptographic hash of the data and then encrypting the hash with the sender's private key.

encryption/decryption

Encryption is the process of using a complex algorithm to convert an original message (cleartext) to an encoded message (ciphertext) that is unintelligible unless it is decrypted. Decryption is the inverse process of producing cleartext from ciphertext.

The algorithms used to encrypt and decrypt data typically come in two categories: secret key (symmetric) cryptography and public key (asymmetric) cryptography.

handshake protocol

The negotiation phase during which the two socket peers agree to use a new or existing session. The handshake protocol is a series of messages exchanged over the record protocol. At the end of the handshake, new connection-specific encryption and integrity protection keys are generated based on the key agreement secrets in the session.

key agreement

A method by which two parties cooperate to establish a common key. Each side generates some data, which is exchanged. These two pieces of data are then combined to generate a key. Only those holding the proper private initialization data can obtain the final key. Diffie-Hellman (DH) is the most common example of a key agreement algorithm.

key exchange

A method by which keys are exchanged. One side generates a private key and encrypts it using the peer's public key (typically RSA). The data is transmitted to the peer, who decrypts the key using the corresponding private key.

key manager/trust manager

Key managers and trust managers use keystores for their key material. A key manager manages a keystore and supplies public keys to others as needed (for example, for use in authenticating the user to others). A trust manager decides who to trust based on information in the truststore it manages.

keystore/truststore

A keystore is a database of key material. Key material is used for a variety of purposes, including authentication and data integrity. Various types of keystores are available, including PKCS12 and Oracle's JKS.

Generally speaking, keystore information can be grouped into two categories: key entries and trusted certificate entries. A key entry consists of an entity's identity and its private key, and can be used for a variety of cryptographic purposes. In contrast, a trusted certificate entry contains only a public key in addition to the entity's identity. Thus, a trusted certificate entry cannot be used where a private key is required, such as in a javax.net.ssl.KeyManager. In the JDK implementation of JKS, a keystore may contain both key entries and trusted certificate entries.

A truststore is a keystore that is used when making decisions about what to trust. If you receive data from an entity that you already trust, and if you can verify that the entity is the one that it claims to be, then you can assume that the data really came from that entity.

An entry should only be added to a truststore if the user trusts that entity. By either generating a key pair or by importing a certificate, the user gives trust to that entry. Any entry in the truststore is considered a trusted entry.

It may be useful to have two different keystore files: one containing just your key entries, and the other containing your trusted certificate entries, including CA certificates. The former contains private information, whereas the latter does not. Using two files instead of a single keystore file provides a cleaner separation of the logical distinction between your own certificates (and corresponding private keys) and others' certificates. To provide more protection for your private keys, store them in a keystore with restricted access, and provide the trusted certificates in a more publicly accessible keystore if needed.

message authentication code (MAC)

Provides a way to check the integrity of information transmitted over or stored in an unreliable medium, based on a secret key. Typically, MACs are used between two parties that share a secret key in order to validate information transmitted between these parties.

A MAC mechanism that is based on cryptographic hash functions is referred to as HMAC. HMAC can be used with any cryptographic hash function, such as Message Digest 5 (MD5) and Secure Hash Algorithm (SHA), in combination with a secret shared key. HMAC is specified in RFC 2104.

public-key cryptography

A cryptographic system that uses an encryption algorithm in which two keys are produced. One key is made public, whereas the other is kept private. The public key and the private key are cryptographic inverses; what one key encrypts only the other key can decrypt. Public-key cryptography is also called asymmetric cryptography.

Record Protocol

A protocol that packages all data (whether application-level or as part of the handshake process) into discrete records of data much like a TCP stream socket converts an application byte stream into network packets. The individual records are then protected by the current encryption and integrity protection keys.

secret-key cryptography

A cryptographic system that uses an encryption algorithm in which the same key is used both to encrypt and decrypt the data. Secret-key cryptography is also called symmetric cryptography.

session

A named collection of state information including authenticated peer identity, cipher suite, and key agreement secrets that are negotiated through a secure socket handshake and that can be shared among multiple secure socket instances.

trust manager

See key manager/trust manager.

truststore

See keystore/truststore.

Secure Sockets Layer (SSL) Protocol Overview

Secure Sockets Layer (SSL) is the most widely used protocol for implementing cryptography on the web. SSL uses a combination of cryptographic processes to provide secure communication over a network. This section provides an introduction to SSL and the cryptographic processes it uses.

SSL provides a secure enhancement to the standard TCP/IP sockets protocol used for Internet communications. As shown in Table 3, the secure sockets layer is added between the transport layer and the application layer in the standard TCP/IP protocol stack. The application most commonly used with SSL is Hypertext Transfer Protocol (HTTP), the protocol for Internet web pages. Other applications, such as Net News Transfer Protocol (NNTP), Telnet, Lightweight Directory Access Protocol (LDAP), Interactive Message Access Protocol (IMAP), and File Transfer Protocol (FTP), can be used with SSL as well.


Note: There is currently no standard for secure FTP.


Table 3: TCP/IP Protocol Stack with SSL
TCP/IP Layer Protocol
Application Layer HTTP, NNTP, Telnet, FTP, and so on
Secure Sockets Layer SSL
Transport Layer TCP
Internet Layer IP

SSL was developed by Netscape in 1994, and with input from the Internet community, has evolved to become a standard. It is now under the control of the international standards organization, the Internet Engineering Task Force (IETF). The IETF renamed SSL to Transport Layer Security (TLS), and released the first specification, version 1.0, in January 1999. TLS 1.0 is a modest upgrade to the most recent version of SSL, version 3.0. The differences between SSL 3.0 and TLS 1.0 are minor. TLS 1.1 was released in April 2006, and TLS 1.2 in August 2008. However, these updated versions are not as widely supported as TLS 1.0 and SSL 3.0.

Why Use SSL?

Transferring sensitive information over a network can be risky due to the following issues:

SSL addresses each of these issues. It addresses the first issue by optionally allowing each of two communicating parties to ensure the identity of the other party in a process called authentication. Once the parties are authenticated, SSL provides an encrypted connection between the two parties for secure message transmission. Encrypting the communication between the two parties provides privacy and therefore addresses the second issue. The encryption algorithms used with SSL include a secure hash function, which is similar to a checksum. This ensures that data is not modified in transit. The secure hash function addresses the third issue of data integrity.


Note: Both authentication and encryption are optional, and depend on the the negotiated cipher suites between the two entities.


An e-commerce transaction is an obvious example of when to use SSL. In an e-commerce transaction, it would be foolish to assume that you can guarantee the identity of the server with whom you are communicating. It would be easy enough for someone to create a phony web site promising great services if only you enter your credit card number. SSL allows you, the client, to authenticate the identity of the server. It also allows the server to authenticate the identity of the client, although in Internet transactions, this is seldom done.

Once the client and the server are comfortable with each other's identity, SSL provides privacy and data integrity through the encryption algorithms that it uses. This allows sensitive information, such as credit card numbers, to be transmitted securely over the Internet.

Although SSL provides authentication, privacy, and data integrity, it does not provide nonrepudiation services. Nonrepudiation means that an entity that sends a message cannot later deny sending it. When the digital equivalent of a signature is associated with a message, the communication can later be proved. SSL alone does not provide nonrepudiation.

How SSL Works

One of the reasons that SSL is effective is that it uses several different cryptographic processes. SSL uses public-key cryptography to provide authentication, and secret-key cryptography with digital signatures to provide for privacy and data integrity. Before you can understand SSL, it is helpful to understand these cryptographic processes.

Cryptographic Processes

The primary purpose of cryptography is to make it difficult for an unauthorized third party to access and understand private communication between two parties. It is not always possible to restrict all unauthorized access to data, but private data can be made unintelligible to unauthorized parties through the process of encryption. Encryption uses complex algorithms to convert the original message (cleartext) to an encoded message (ciphertext). The algorithms used to encrypt and decrypt data that is transferred over a network typically come in two categories: secret-key cryptography and public-key cryptography. These forms of cryptography are explained in the following subsections.

Both secret-key cryptography and public-key cryptography depend on the use of an agreed-upon cryptographic key or pair of keys. A key is a string of bits that is used by the cryptographic algorithm or algorithms during the process of encrypting and decrypting the data. A cryptographic key is like a key for a lock; only with the right key can you open the lock.

Safely transmitting a key between two communicating parties is not a trivial matter. A public key certificate enables a party to safely transmit its public key, while ensuring the receiver of the authenticity of the public key. Public key certificates are described in a later section.

The descriptions of the cryptographic processes that follow use conventions widely used by the security community: the two communicating parties are labeled with the names Alice and Bob. The unauthorized third party, also known as the attacker, is named Charlie.

Secret-Key Cryptography

With secret-key cryptography, both communicating parties, Alice and Bob, use the same key to encrypt and decrypt the messages. Before any encrypted data can be sent over the network, both Alice and Bob must have the key and must agree on the cryptographic algorithm that they will use for encryption and decryption.

One of the major problems with secret-key cryptography is the logistical issue of how to get the key from one party to the other without allowing access to an attacker. If Alice and Bob are securing their data with secret-key cryptography, and if Charlie gains access to their key, then Charlie can understand any secret messages he intercepts between Alice and Bob. Not only can Charlie decrypt Alice's and Bob's messages, but he can also pretend that he is Alice and send encrypted data to Bob. Bob will not know that the message came from Charlie, not Alice.

Once the problem of secret key distribution is solved, secret-key cryptography can be a valuable tool. The algorithms provide excellent security and encrypt data relatively quickly. The majority of the sensitive data sent in an SSL session is sent using secret-key cryptography.

Secret-key cryptography is also called symmetric cryptography because the same key is used to both encrypt and decrypt the data. Well-known secret-key cryptographic algorithms include the Data Encryption Standard (DES), Triple DES (3DES), Rivest Cipher 2 (RC2), and Rivest Cipher 4 (RC4).

Public-Key Cryptography

Public-key cryptography solves the logistical problem of key distribution by using both a public key and a private key. The public key can be sent openly through the network while the private key is kept private by one of the communicating parties. The public and the private keys are cryptographic inverses of each other; what one key encrypts, the other key will decrypt.

Assume that Bob wants to send a secret message to Alice using public-key cryptography. Alice has both a public key and a private key, so she keeps her private key in a safe place and sends her public key to Bob. Bob encrypts the secret message to Alice using Alice's public key. Alice can later decrypt the message with her private key.

If Alice encrypts a message using her private key and sends the encrypted message to Bob, then Bob can be sure that the data he receives comes from Alice; if Bob can decrypt the data with Alice's public key, the message must have been encrypted by Alice with her private key, and only Alice has Alice's private key. The problem is that anybody else can read the message as well because Alice's public key is public. Although this scenario does not allow for secure data communication, it does provide the basis for digital signatures. A digital signature is one of the components of a public key certificate, and is used in SSL to authenticate a client or a server. Public key certificates and digital signatures are described in later sections.

Public-key cryptography is also called asymmetric cryptography because different keys are used to encrypt and decrypt the data. A well-known public key cryptographic algorithm often used with SSL is the Rivest Shamir Adleman (RSA) algorithm. Another public key algorithm used with SSL that is designed specifically for secret key exchange is the Diffie-Hellman (DH) algorithm. Public-key cryptography requires extensive computations, making it very slow. It is therefore typically used only for encrypting small pieces of data, such as secret keys, rather than for the bulk of encrypted data communications.

Comparison Between Secret-Key and Public-Key Cryptography

Both secret-key cryptography and public-key cryptography have strengths and weaknesses. With secret-key cryptography, data can be encrypted and decrypted quickly, but because both communicating parties must share the same secret key information, the logistics of exchanging the key can be a problem. With public-key cryptography, key exchange is not a problem because the public key does not need to be kept secret, but the algorithms used to encrypt and decrypt data require extensive computations, and are therefore very slow.

Public Key Certificates

A public key certificate provides a safe way for an entity to pass on its public key to be used in asymmetric cryptography. The public key certificate avoids the following situation: if Charlie creates his own public key and private key, he can claim that he is Alice and send his public key to Bob. Bob will be able to communicate with Charlie, but Bob will think that he is sending his data to Alice.

A public key certificate can be thought of as the digital equivalent of a passport. It is issued by a trusted organization and provides identification for the bearer. A trusted organization that issues public key certificates is known as a Certificate Authority (CA). The CA can be likened to a notary public. To obtain a certificate from a CA, one must provide proof of identity. Once the CA is confident that the applicant represents the organization it says it represents, the CA signs the certificate attesting to the validity of the information contained within the certificate.

A public key certificate contains the following fields:

If Bob only accepts Alice's public key as valid when she sends it in a public key certificate, then Bob will not be fooled into sending secret information to Charlie when Charlie masquerades as Alice.

Multiple certificates may be linked in a certificate chain. When a certificate chain is used, the first certificate is always that of the sender. The next is the certificate of the entity that issued the sender's certificate. If more certificates are in the chain, then each is that of the authority that issued the previous certificate. The final certificate in the chain is the certificate for a root CA. A root CA is a public certificate authority that is widely trusted. Information for several root CAs is typically stored in the client's Internet browser. This information includes the CA's public key. Well-known CAs include VeriSign, Entrust, and GTE CyberTrust.

Cryptographic Hash Functions

When sending encrypted data, SSL typically uses a cryptographic hash function to ensure data integrity. The hash function prevents Charlie from tampering with data that Alice sends to Bob.

A cryptographic hash function is similar to a checksum. The main difference is that whereas a checksum is designed to detect accidental alterations in data, a cryptographic hash function is designed to detect deliberate alterations. When data is processed by a cryptographic hash function, a small string of bits, known as a hash, is generated. The slightest change to the message typically makes a large change in the resulting hash. A cryptographic hash function does not require a cryptographic key. Two hash functions often used with SSL are Message Digest 5 (MD5) and Secure Hash Algorithm (SHA). SHA was proposed by the U.S. National Institute of Standards and Technology (NIST).

Message Authentication Code

A message authentication code (MAC) is similar to a cryptographic hash, except that it is based on a secret key. When secret key information is included with the data that is processed by a cryptographic hash function, then the resulting hash is known as an HMAC.

If Alice wants to be sure that Charlie does not tamper with her message to Bob, then she can calculate an HMAC for her message and append the HMAC to her original message. She can then encrypt the message plus the HMAC using a secret key that she shares with Bob. When Bob decrypts the message and calculates the HMAC, he will be able to tell if the message was modified in transit. With SSL, an HMAC is used with the transmission of secure data.

Digital Signatures

Once a cryptographic hash is created for a message, the hash is encrypted with the sender's private key. This encrypted hash is called a digital signature.

The SSL Handshake

Communication using SSL begins with an exchange of information between the client and the server. This exchange of information is called the SSL handshake. The SSL handshake includes the following stages:

  1. Negotiating the cipher suite

    The SSL session begins with a negotiation between the client and the server as to which cipher suite they will use. A cipher suite is a set of cryptographic algorithms and key sizes that a computer can use to encrypt data. The cipher suite includes information about the public key exchange algorithms or key agreement algorithms, and cryptographic hash functions. The client tells the server which cipher suites it has available, and the server chooses the best mutually acceptable cipher suite.

  2. Authenticating the server's identity (optional)

    In SSL, the authentication step is optional, but in the example of an e-commerce transaction over the web, the client will generally want to authenticate the server. Authenticating the server allows the client to be sure that the server represents the entity that the client believes the server represents.

    To prove that a server belongs to the organization that it claims to represent, the server presents its public key certificate to the client. If this certificate is valid, then the client can be sure of the identity of the server.

    The client and server exchange information that allows them to agree on the same secret key. For example, with RSA, the client uses the server's public key, obtained from the public key certificate, to encrypt the secret key information. The client sends the encrypted secret key information to the server. Only the server can decrypt this message because the server's private key is required for this decryption.

  3. Agreeing on encryption mechanisms

    Both the client and the server now have access to the same secret key. With each message, they use the cryptographic hash function, chosen in the first step of the handshake, and shared secret information, to compute an HMAC that they append to the message. They then use the secret key and the secret key algorithm negotiated in the first step of the handshake to encrypt the secure data and the HMAC. The client and server can now communicate securely using their encrypted and hashed data.

The SSL Protocol

The previous section provides a high-level description of the SSL handshake, which is the exchange of information between the client and the server prior to sending the encrypted message. This section provides more detail.

Figure 1 shows the sequence of messages that are exchanged in the SSL handshake. Messages that are sent only in certain situations are noted as optional. Each of the SSL messages is described below the figure.

Sequence of messages exchanged in SSL handshake.

The SSL messages are sent in the following order:

  1. Client hello
    The client sends the server information including the highest version of SSL that it supports and a list of the cipher suites that it supports (TLS 1.0 is indicated as SSL 3.1). The cipher suite information includes cryptographic algorithms and key sizes.
  2. Server hello
    The server chooses the highest version of SSL and the best cipher suite that both the client and server support and sends this information to the client.
  3. Certificate (optional)
    The server sends the client a certificate or a certificate chain. A certificate chain typically begins with the server's public key certificate and ends with the certificate authority's root certificate. This message is optional, but is used whenever server authentication is required.
  4. Certificate request (optional)
    If the server must authenticate the client, then it sends the client a certificate request. In Internet applications, this message is rarely sent.
  5. Server key exchange (optional)
    The server sends the client a server key exchange message if the public key information from the certificate is not sufficient for key exchange. For example, in cipher suites based on Diffie-Hellman (DH), this message contains the server's DH public key.
  6. Server hello done
    The server tells the client that it is finished with its initial negotiation messages.
  7. Certificate (optional)
    If the server requested a certificate from the client, the client sends its certificate chain, just as the server did previously.

    Note: Only a few Internet server applications ask for a certificate from the client.


  8. Client key exchange
    The client generates information used to create a key to use for symmetric encryption. For RSA, the client then encrypts this key information with the server's public key and sends it to the server. For cipher suites based on DH, this message contains the client's DH public key.
  9. Certificate verify (optional)
    This message is sent by the client when the client presents a certificate as previously explained. Its purpose is to allow the server to complete the process of authenticating the client. When this message is used, the client sends information that it digitally signs using a cryptographic hash function. When the server decrypts this information with the client's public key, the server is able to authenticate the client.
  10. Change cipher spec
    The client sends a message telling the server to change to encrypted mode.
  11. Finished
    The client tells the server that it is ready for secure data communication to begin.
  12. Change cipher spec
    The server sends a message telling the client to change to encrypted mode.
  13. Finished
    The server tells the client that it is ready for secure data communication to begin. This is the end of the SSL handshake.
  14. Encrypted data
    The client and the server communicate using the symmetric encryption algorithm and the cryptographic hash function negotiated during the client hello and server hello, and using the secret key that the client sent to the server during the client key exchange. The handshake can be renegotiated at this time. See the next section for details.
  15. Close Messages
    At the end of the connection, each side sends a close_notify message to inform the peer that the connection is closed.

If the parameters generated during an SSL session are saved, then these parameters can sometimes be reused for future SSL sessions. Saving SSL session parameters allows encrypted communication to begin much more quickly.

Handshaking Again (Renegotiation)

Once the initial handshake is finished and application data is flowing, either side is free to initiate a new handshake at any time. An application might like to use a stronger cipher suite for especially critical operations, or a server application might want to require client authentication.

Regardless of the reason, the new handshake takes place over the existing encrypted session, and application data and handshake messages are interleaved until a new session is established.

Your application can initiate a new handshake by using one of the following methods:

Note that a protocol flaw related to renegotiation was found in 2009. The protocol and the Java SE implementation have both been fixed. For more information, see Transport Layer Security (TLS) Renegotiation Issue.

Cipher Suite Choice and Remote Entity Verification

The SSL/TLS protocols define a specific series of steps to ensure a protected connection. However, the choice of cipher suite directly affects the type of security that the connection enjoys. For example, if an anonymous cipher suite is selected, then the application has no way to verify the remote peer's identity. If a suite with no encryption is selected, then the privacy of the data cannot be protected. Additionally, the SSL/TLS protocols do not specify that the credentials received must match those that peer might be expected to send. If the connection were somehow redirected to a rogue peer, but the rogue's credentials were acceptable based on the current trust material, then the connection would be considered valid.

When using raw SSLSocket and SSLEngine classes, you should always check the peer's credentials before sending any data. The SSLSocket and SSLEngine classes do not automatically verify that the host name in a URL matches the host name in the peer's credentials. An application could be exploited with URL spoofing if the host name is not verified.

Protocols such as HTTPS (HTTP Over TLS) do require host name verification. Applications can use HostnameVerifier to override the default HTTPS host name rules. See HttpsURLConnection for more information.

JSSE Classes and Interfaces

To communicate securely, both sides of the connection must be SSL-enabled. In the JSSE API, the endpoint classes of the connection are SSLSocket and SSLEngine. In Figure 2, the major classes used to create SSLSocket and SSLEngine are laid out in a logical ordering. The text following the diagram, explains the contents of the illustration.

Diagram of classes used to create SSLSocket and SSLEngine

An SSLSocket is created either by an SSLSocketFactory or by an SSLServerSocket accepting an inbound connection. In turn, an SSLServerSocket is created by an SSLServerSocketFactory. Both SSLSocketFactory and SSLServerSocketFactory objects are created by an SSLContext. An SSLEngine is created directly by an SSLContext, and relies on the application to handle all I/O.


Note: When using raw SSLSocket or SSLEngine classes, you should always check the peer's credentials before sending any data. The SSLSocket and SSLEngine classes do not automatically verify, for example, that the host name in a URL matches the host name in the peer's credentials. An application could be exploited with URL spoofing if the host name is not verified.


There are two ways to obtain and initialize an SSLContext:

Once an SSL connection is established, an SSLSession is created which contains various information, such as identities established and cipher suite used. The SSLSession is then used to describe an ongoing relationship and state information between two entities. Each SSL connection involves one session at a time, but that session may be used on many connections between those entities, simultaneously or sequentially.

Core Classes and Interfaces

The core JSSE classes are part of the javax.net and javax.net.ssl packages.

SocketFactory and ServerSocketFactory Classes

The abstract javax.net.SocketFactory class is used to create sockets. Subclasses of this class are factories that create particular subclasses of sockets and thus provide a general framework for the addition of public socket-level functionality. For example, see SSLSocketFactory and SSLServerSocketFactory.

The abstract javax.net.ServerSocketFactory class is analogous to the SocketFactory class, but is used specifically for creating server sockets.

Socket factories are a simple way to capture a variety of policies related to the sockets being constructed, producing such sockets in a way that does not require special configuration of the code that asks for the sockets:

SSLSocketFactory and SSLServerSocketFactory Classes

The javax.net.ssl.SSLSocketFactory class acts as a factory for creating secure sockets. This class is an abstract subclass of javax.net.SocketFactory.

Secure socket factories encapsulate the details of creating and initially configuring secure sockets. This includes authentication keys, peer certificate validation, enabled cipher suites, and the like.

The javax.net.ssl.SSLServerSocketFactory class is analogous to the SSLSocketFactory class, but is used specifically for creating server sockets.

Obtaining an SSLSocketFactory

The following ways can be used to obtain an SSLSocketFactory:

The default factory is typically configured to support server authentication only so that sockets created by the default factory do not leak any more information about the client than a normal TCP socket would.

Many classes that create and use sockets do not need to know the details of socket creation behavior. Creating sockets through a socket factory passed in as a parameter is a good way of isolating the details of socket configuration, and increases the reusability of classes that create and use sockets.

You can create new socket factory instances either by implementing your own socket factory subclass or by using another class which acts as a factory for socket factories. One example of such a class is SSLContext, which is provided with the JSSE implementation as a provider-based configuration class.

SSLSocket and SSLServerSocket Classes

The javax.net.ssl.SSLSocket class is a subclass of the standard Java java.net.Socket class. It supports all of the standard socket methods and adds methods specific to secure sockets. Instances of this class encapsulate the SSLContext under which they were created. There are APIs to control the creation of secure socket sessions for a socket instance, but trust and key management are not directly exposed.

The javax.net.ssl.SSLServerSocket class is analogous to the SSLSocket class, but is used specifically for creating server sockets.

To prevent peer spoofing, you should always verify the credentials presented to an SSLSocket.


Note: Due to the complexity of the SSL and TLS protocols, it is difficult to predict whether incoming bytes on a connection are handshake or application data, and how that data might affect the current connection state (even causing the process to block). In the Oracle JSSE implementation, the available() method on the object obtained by SSLSocket.getInputStream() returns a count of the number of application data bytes successfully decrypted from the SSL connection but not yet read by the application.


Obtaining an SSLSocket

Instances of SSLSocket can be obtained in one of the following ways:

SSLEngine Class

SSL/TLS is becoming increasingly popular. It is being used in a wide variety of applications across a wide range of computing platforms and devices. Along with this popularity come demands to use SSL/TLS with different I/O and threading models to satisfy the applications' performance, scalability, footprint, and other requirements. There are demands to use SSL/TLS with blocking and nonblocking I/O channels, asynchronous I/O, arbitrary input and output streams, and byte buffers. There are demands to use it in highly scalable, performance-critical environments, requiring management of thousands of network connections.

Abstraction of the I/O transport mechanism using the SSLEngine class in Java SE allows applications to use the SSL/TLS protocols in a transport-independent way, and thus frees application developers to choose transport and computing models that best meet their needs. Not only does this abstraction allow applications to use nonblocking I/O channels and other I/O models, it also accommodates different threading models. This effectively leaves the I/O and threading decisions up to the application developer. Because of this flexibility, the application developer must manage I/O and threading (complex topics in and of themselves), as well as have some understanding of the SSL/TLS protocols. The abstraction is therefore an advanced API: beginners should use SSLSocket.

Users of other Java programming language APIs such as the Java Generic Security Services (Java GSS) and the Java Simple Authentication Security Layer (Java SASL) will notice similarities in that the application is also responsible for transporting data.

The core class is javax.net.ssl.SSLEngine. It encapsulates an SSL/TLS state machine and operates on inbound and outbound byte buffers supplied by the user of the SSLEngine class. The diagram in Figure 3 illustrates the flow of data from the application, through SSLEngine, to the transport mechanism, and back.

Flow of data through SSLEngine

The application, shown on the left, supplies application (plaintext) data in an application buffer and passes it to SSLEngine. The SSLEngine object processes the data contained in the buffer, or any handshaking data, to produce SSL/TLS encoded data and places it to the network buffer supplied by the application. The application is then responsible for using an appropriate transport (shown on the right) to send the contents of the network buffer to its peer. Upon receiving SSL/TLS encoded data from its peer (via the transport), the application places the data into a network buffer and passes it to SSLEngine. The SSLEngine object processes the network buffer's contents to produce handshaking data or application data.

An instance of the SSLEngine class can be in one of the following states:

Creating an SSLEngine Object

To create an SSLEngine object, you use the SSLContext.createSSLEngine() method. You must configure the engine to act as a client or a server, and set other configuration parameters, such as which cipher suites to use and whether to require client authentication.

Example 1 illustrates how to create an SSLEngine object.


Note: The server name and port number are not used for communicating with the server (all transport is the responsibility of the application). They are hints to the JSSE provider to use for SSL session caching, and for Kerberos-based cipher suite implementations to determine which server credentials should be obtained.


import javax.net.ssl.*;
import java.security.*;

// Create and initialize the SSLContext with key material
char[] passphrase = "passphrase".toCharArray();

// First initialize the key and trust material
KeyStore ksKeys = KeyStore.getInstance("JKS");
ksKeys.load(new FileInputStream("testKeys"), passphrase);
KeyStore ksTrust = KeyStore.getInstance("JKS");
ksTrust.load(new FileInputStream("testTrust"), passphrase);

// KeyManagers decide which key material to use
KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
kmf.init(ksKeys, passphrase);

// TrustManagers decide whether to allow connections
TrustManagerFactory tmf = TrustManagerFactory.getInstance("SunX509");
tmf.init(ksTrust);

sslContext = SSLContext.getInstance("TLS");
sslContext.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);

// Create the engine
SSLEngine engine = sslContext.createSSLengine(hostname, port);

// Use as client
engine.setUseClientMode(true);

Generating and Processing SSL/TLS Data

The two main SSLEngine methods are wrap() and unwrap(). They are responsible for generating and consuming network data respectively. Depending on the state of the SSLEngine object, this data might be handshake or application data.

Each SSLEngine object has several phases during its lifetime. Before application data can be sent or received, the SSL/TLS protocol requires a handshake to establish cryptographic parameters. This handshake requires a series of back-and-forth steps by the SSLEngine object. The "SSL Handshake" section provides more details about the handshake itself.

During the initial handshaking, the wrap() and unwrap() methods generate and consume handshake data, and the application is responsible for transporting the data. The wrap() and unwrap() method sequence is repeated until the handshake is finished. Each SSLEngine operation generates an instance of the SSLEngineResult class, in which the SSLEngineResult.HandshakeStatus field is used to determine what operation must occur next to move the handshake along.

Table 4 shows the sequence of methods called during a typical handshake, with corresponding messages and statuses.

Table 4: Typical Handshake
Client SSL/TLS Message HandshakeStatus
wrap() ClientHello NEED_UNWRAP
unwrap() ServerHello/Cert/ServerHelloDone NEED_WRAP
wrap() ClientKeyExchange NEED_WRAP
wrap() ChangeCipherSpec NEED_WRAP
wrap() Finished NEED_UNWRAP
unwrap() ChangeCipherSpec NEED_UNWRAP
unwrap() Finished FINISHED

When handshaking is complete, further calls to wrap() will attempt to consume application data and package it for transport. The unwrap() method will attempt the opposite.

To send data to the peer, the application first supplies the data that it wants to send via SSLEngine.wrap() to obtain the corresponding SSL/TLS encoded data. The application then sends the encoded data to the peer using its chosen transport mechanism. When the application receives the SSL/TLS encoded data from the peer via the transport mechanism, it supplies this data to the SSLEngine via SSLEngine.unwrap() to obtain the plaintext data sent by the peer.

Example 2 shows an SSL application that uses a nonblocking SocketChannel to communicate with its peer.


Note: The example can be made more robust and scalable by using a Selector with the nonblocking SocketChannel.


In Example 2, the string hello is sent to the peer by encoding it using the SSLEngine created in Example 1. It uses information from the SSLSession to determine how large the byte buffers should be.

// Create a nonblocking socket channel
SocketChannel socketChannel = SocketChannel.open();
socketChannel.configureBlocking(false);
socketChannel.connect(new InetSocketAddress(hostname, port));

// Complete connection
while (!socketChannel.finishedConnect()) {
    // do something until connect completed
}

// Create byte buffers to use for holding application and encoded data
SSLSession session = engine.getSession();
ByteBuffer myAppData = ByteBuffer.allocate(session.getApplicationBufferSize());
ByteBuffer myNetData = ByteBuffer.allocate(session.getPacketBufferSize());
ByteBuffer peerAppData = ByteBuffer.allocate(session.getApplicationBufferSize());
ByteBuffer peerNetData = ByteBuffer.allocate(session.getPacketBufferSize());

// Do initial handshake
doHandshake(socketChannel, engine, myNetData, peerNetData);

myAppData.put("hello".getBytes());
myAppData.flip();

while (myAppData.hasRemaining()) {
    // Generate SSL/TLS encoded data (handshake or application data)
    SSLEngineResult res = engine.wrap(myAppData, myNetData);

    // Process status of call
    if (res.getStatus() == SSLEngineResult.Status.OK) {
        myAppData.compact();

        // Send SSL/TLS encoded data to peer
        while(myNetData.hasRemaining()) {
            int num = socketChannel.write(myNetData);
            if (num == 0) {
                // no bytes written; try again later
            }
        }
    }

    // Handle other status:  BUFFER_OVERFLOW, CLOSED
    ...
}

Example 3 illustrates how to read data from the same nonblocking SocketChannel and extract the plaintext data from it by using the SSLEngine created in Example 1. Each iteration of this code may or may not produce plaintext data, depending on whether handshaking is in progress.

// Read SSL/TLS encoded data from peer
int num = socketChannel.read(peerNetData);
if (num == -1) {
    // The channel has reached end-of-stream
} else if (num == 0) {
    // No bytes read; try again ...
} else {
    // Process incoming data
    peerNetData.flip();
    res = engine.unwrap(peerNetData, peerAppData);

    if (res.getStatus() == SSLEngineResult.Status.OK) {
        peerNetData.compact();

        if (peerAppData.hasRemaining()) {
            // Use peerAppData
        }
    }
    // Handle other status:  BUFFER_OVERFLOW, BUFFER_UNDERFLOW, CLOSED
    ...
}

Understanding SSLEngine Operation Statuses

To indicate the status of the engine and what actions the application should take, the SSLEngine.wrap() and SSLEngine.unwrap() methods return an SSLEngineResult instance, as shown in Example 2. This SSLEngineResult object contains two pieces of status information: the overall status of the engine and the handshaking status.

The possible overall statuses are represented by the SSLEngineResult.Status enum. The following statuses are available:

Example 4 illustrates how to handle the BUFFER_UNDERFLOW and BUFFER_OVERFLOW statuses of the SSLEngine.unwrap() method. It uses SSLSession.getApplicationBufferSize() and SSLSession.getPacketBufferSize() to determine how large to make the byte buffers.

SSLEngineResult res = engine.unwrap(peerNetData, peerAppData);
switch (res.getStatus()) {

case BUFFER_OVERFLOW:
    // Maybe need to enlarge the peer application data buffer.
    if (engine.getSession().getApplicationBufferSize() > peerAppData.capacity()) {
        // enlarge the peer application data buffer
    } else {
        // compact or clear the buffer
    }
    // retry the operation
    break;

case BUFFER_UNDERFLOW:
    // Maybe need to enlarge the peer network packet buffer
    if (engine.getSession().getPacketBufferSize() > peerNetData.capacity()) {
        // enlarge the peer network packet buffer
    } else {
        // compact or clear the buffer
    }
    // obtain more inbound network data and then retry the operation
    break;

    // Handle other status: CLOSED, OK
    ...
}

The possible handshaking statuses are represented by the SSLEngineResult.HandshakeStatus enum. They represent whether handshaking has completed, whether the caller must obtain more handshaking data from the peer or send more handshaking data to the peer, and so on.

Having two statuses per result allows the SSLEngine to indicate that the application must take two actions: one in response to the handshaking and one representing the overall status of the wrap() and unwrap() methods. For example, the engine might, as the result of a single SSLEngine.unwrap() call, return SSLEngineResult.Status.OK to indicate that the input data was processed successfully and SSLEngineResult.HandshakeStatus.NEED_UNWRAP to indicate that the application should obtain more SSL/TLS encoded data from the peer and supply it to SSLEngine.unwrap() again so that handshaking can continue. As you can see, the previous examples were greatly simplified; they would need to be expanded significantly to properly handle all of these statuses.

Example 5 illustrates how to process handshaking data by checking handshaking status and the overall status of the wrap() and unwrap() methods.

void doHandshake(SocketChannel socketChannel, SSLEngine engine,
        ByteBuffer myNetData, ByteBuffer peerNetData) throws Exception {

    // Create byte buffers to use for holding application data
    int appBufferSize = engine.getSession().getApplicationBufferSize();
    ByteBuffer myAppData = ByteBuffer.allocate(appBufferSize);
    ByteBuffer peerAppData = ByteBuffer.allocate(appBufferSize);

    // Begin handshake
    engine.beginHandshake();
    SSLEngineResult.HandshakeStatus hs = engine.getHandshakeStatus();

    // Process handshaking message
    while (hs != SSLEngineResult.HandshakeStatus.FINISHED &&
        hs != SSLEngineResult.HandshakeStatus.NOT_HANDSHAKING) {

        switch (hs) {

        case NEED_UNWRAP:
            // Receive handshaking data from peer
            if (socketChannel.read(peerNetData) < 0) {
                // The channel has reached end-of-stream
            }

            // Process incoming handshaking data
            peerNetData.flip();
            SSLEngineResult res = engine.unwrap(peerNetData, peerAppData);
            peerNetData.compact();
            hs = res.getHandshakeStatus();

            // Check status
            switch (res.getStatus()) {
            case OK :
                // Handle OK status
                break;

            // Handle other status: BUFFER_UNDERFLOW, BUFFER_OVERFLOW, CLOSED
            ...
            }
            break;

        case NEED_WRAP :
            // Empty the local network packet buffer.
            myNetData.clear();

            // Generate handshaking data
            res = engine.wrap(myAppData, myNetData);
            hs = res.getHandshakeStatus();

            // Check status
            switch (res.getStatus()) {
            case OK :
                myNetData.flip();

                // Send the handshaking data to peer
                while (myNetData.hasRemaining()) {
                    socketChannel.write(myNetData);
                }
                break;

            // Handle other status:  BUFFER_OVERFLOW, BUFFER_UNDERFLOW, CLOSED
            ...
            }
            break;

        case NEED_TASK :
            // Handle blocking tasks
            break;

        // Handle other status:  // FINISHED or NOT_HANDSHAKING
        ...
        }
    }

    // Processes after handshaking
    ...
}

Dealing With Blocking Tasks

During handshaking, an SSLEngine might encounter tasks that can block or take a long time. For example, a TrustManager may need to connect to a remote certificate validation service, or a KeyManager might need to prompt a user to determine which certificate to use as part of client authentication. To preserve the nonblocking nature of SSLEngine, when the engine encounters such a task, it will return SSLEngineResult.HandshakeStatus.NEED_TASK. Upon receiving this status, the application should invoke SSLEngine.getDelegatedTask() to get the task, and then, using the threading model appropriate for its requirements, process the task. The application might, for example, obtain threads from a thread pool to process the tasks, while the main thread handles other I/O.

The following code executes each task in a newly created thread:

if (res.getHandshakeStatus() == SSLEngineResult.HandshakeStatus.NEED_TASK) {
    Runnable task;
    while ((task = engine.getDelegatedTask()) != null) {
        new Thread(task).start();
    }
}

The SSLEngine will block future wrap() and unwrap() calls until all of the outstanding tasks are completed.

Shutting Down

For an orderly shutdown of an SSL/TLS connection, the SSL/TLS protocols require transmission of close messages. Therefore, when an application is done with the SSL/TLS connection, it should first obtain the close messages from the SSLEngine, then transmit them to the peer using its transport mechanism, and finally shut down the transport mechanism. Example 6 illustrates this.

// Indicate that application is done with engine
engine.closeOutbound();

while (!engine.isOutboundDone()) {
    // Get close message
    SSLEngineResult res = engine.wrap(empty, myNetData);

    // Check res statuses

    // Send close message to peer
    while(myNetData.hasRemaining()) {
        int num = socketChannel.write(myNetData);
        if (num == 0) {
            // no bytes written; try again later
        }
        myNetData().compact();
    }
}

// Close transport
socketChannel.close();

In addition to an application explicitly closing the SSLEngine, the SSLEngine might be closed by the peer (via receipt of a close message while it is processing handshake data), or by the SSLEngine encountering an error while processing application or handshake data, indicated by throwing an SSLException. In such cases, the application should invoke SSLEngine.wrap() to get the close message and send it to the peer until SSLEngine.isOutboundDone() returns true (as shown in Example 6), or until the SSLEngineResult.getStatus() returns CLOSED.

In addition to orderly shutdowns, there can also be unexpected shutdowns when the transport link is severed before close messages are exchanged. In the previous examples, the application might get -1 or IOException when trying to read from the nonblocking SocketChannel, or get IOException when trying to write to the non-blocking SocketChannel. When you get to the end of your input data, you should call engine.closeInbound(), which will verify with the SSLEngine that the remote peer has closed cleanly from the SSL/TLS perspective. Then the application should still try to shut down cleanly by using the procedure in Example 6. Obviously, unlike SSLSocket, the application using SSLEngine must deal with more state transitions, statuses, and programming. For more information about writing an SSLEngine-based application, see Sample Code Illustrating the Use of an SSLEngine.

SSLSession and ExtendedSSLSession

The javax.net.ssl.SSLSession interface represents a security context negotiated between the two peers of an SSLSocket or SSLEngine connection. After a session has been arranged, it can be shared by future SSLSocket or SSLEngine objects connected between the same two peers.

In some cases, parameters negotiated during the handshake are needed later in the handshake to make decisions about trust. For example, the list of valid signature algorithms might restrict the certificate types that can be used for authentication. The SSLSession can be retrieved during the handshake by calling getHandshakeSession() on an SSLSocket or SSLEngine. Implementations of TrustManager or KeyManager can use the getHandshakeSession() method to get information about session parameters to help them make decisions.

A fully initialized SSLSession contains the cipher suite that will be used for communications over a secure socket as well as a nonauthoritative hint as to the network address of the remote peer, and management information such as the time of creation and last use. A session also contains a shared master secret negotiated between the peers that is used to create cryptographic keys for encrypting and guaranteeing the integrity of the communications over an SSLSocket or SSLEngine connection. The value of this master secret is known only to the underlying secure socket implementation and is not exposed through the SSLSession API.

In Java SE, a TLS 1.2 session is represented by ExtendedSSLSession, an implementation of SSLSession. The ExtendedSSLSession class adds methods that describe the signature algorithms that are supported by the local implementation and the peer. The getRequestedServerNames() method called on an ExtendedSSLSession instance is used to obtain a list of SNIServerName objects in the requested Server Name Indication (SNI) extension. The server should use the requested server names to guide its selection of an appropriate authentication certificate, and/or other aspects of the security policy. The client should use the requested server names to guide its endpoint identification of the peer's identity, and/or other aspects of the security policy.

Calls to the getPacketBufferSize() and getApplicationBufferSize() methods on SSLSession are used to determine the appropriate buffer sizes used by SSLEngine.


Note: The SSL/TLS protocols specify that implementations are to produce packets containing at most 16 kilobytes (KB) of plain text. However, some implementations violate the specification and generate large records up to 32 KB. If the SSLEngine.unwrap() code detects large inbound packets, then the buffer sizes returned by SSLSession will be updated dynamically. Applications should always check the BUFFER_OVERFLOW and BUFFER_UNDERFLOW statuses and enlarge the corresponding buffers if necessary. SunJSSE will always send standard compliant 16 KB records and allow incoming 32 KB records. For a workaround, see the System property jsse.SSLEngine.acceptLargeFragments in Customizing JSSE.


HttpsURLConnection Class

The HTTPS protocol is similar to HTTP, but HTTPS first establishes a secure channel via SSL/TLS sockets and then verifies the identity of the peer before requesting or receiving data. The javax.net.ssl.HttpsURLConnection class extends the java.net.HttpsURLConnection class and adds support for HTTPS-specific features. For more information about how HTTPS URLs are constructed and used, see the API specification sections about the java.net.URL, java.net.URLConnection, java.net.HttpURLConnection, and javax.net.ssl.HttpURLConnection classes.

Upon obtaining an HttpsURLConnection instance, you can configure a number of HTTP and HTTPS parameters before actually initiating the network connection via the URLConnection.connect() method. Of particular interest are:

Setting the Assigned SSLSocketFactory

In some situations, it is desirable to specify the SSLSocketFactory that an HttpsURLConnection instance uses. For example, you might want to tunnel through a proxy type that is not supported by the default implementation. The new SSLSocketFactory could return sockets that have already performed all necessary tunneling, thus allowing HttpsURLConnection to use additional proxies.

The HttpsURLConnection class has a default SSLSocketFactory that is assigned when the class is loaded (this is the factory returned by the SSLSocketFactory.getDefault() method). Future instances of HttpsURLConnection will inherit the current default SSLSocketFactory until a new default SSLSocketFactory is assigned to the class via the static HttpsURLConnection.setDefaultSSLSocketFactory() method. Once an instance of HttpsURLConnection has been created, the inherited SSLSocketFactory on this instance can be overridden with a call to the setSSLSocketFactory() method.


Note: Changing the default static SSLSocketFactory has no effect on existing instances of HttpsURLConnection. A call to the setSSLSocketFactory() method is necessary to change the existing instances.


You can obtain the per-instance or per-class SSLSocketFactory by making a call to the getSSLSocketFactory() or getDefaultSSLSocketFactory() method, respectively.

Setting the Assigned HostnameVerifier

If the host name of the URL does not match the host name in the credentials received as part of the SSL/TLS handshake, then it is possible that URL spoofing has occurred. If the implementation cannot determine a host name match with reasonable certainty, then the SSL implementation performs a callback to the instance's assigned HostnameVerifier for further checking. The host name verifier can take whatever steps are necessary to make the determination, such as performing host name pattern matching or perhaps opening an interactive dialog box. An unsuccessful verification by the host name verifier closes the connection. For more information regarding host name verification, see RFC 2818.

The setHostnameVerifier() and setDefaultHostnameVerifier() methods operate in a similar manner to the setSSLSocketFactory() and setDefaultSSLSocketFactory() methods, in that HostnameVerifier objects are assigned on a per-instance and per-class basis, and the current values can be obtained by a call to the getHostnameVerifier() or getDefaultHostnameVerifier() method.

Support Classes and Interfaces

The classes and interfaces in this section are provided to support the creation and initialization of SSLContext objects, which are used to create SSLSocketFactory, SSLServerSocketFactory, and SSLEngine objects. The support classes and interfaces are part of the javax.net.ssl package.

Three of the classes described in this section (SSLContext, KeyManagerFactory, and TrustManagerFactory) are engine classes. An engine class is an API class for specific algorithms (or protocols, in the case of SSLContext), for which implementations may be provided in one or more Cryptographic Service Provider (provider) packages. For more information about providers and engine classes, see the "Design Principles" and "Concepts" sections of the Java Cryptography Architecture Reference Guide.

The SunJSSE provider that comes standard with JSSE provides SSLContext, KeyManagerFactory, and TrustManagerFactory implementations, as well as implementations for engine classes in the standard java.security API. Table 5 lists implementations supplied by SunJSSE.

Table 5: Implementations Supplied by SunJSEE
Engine Class Implemented Algorithm or Protocol
KeyStore PKCS12
KeyManagerFactory PKIX, SunX509
TrustManagerFactory PKIX (X509 or SunPKIX), SunX509
SSLContext SSLv3, TLSv1, TLSv1.1, TLSv1.2

The SSLContext Class

The javax.net.ssl.SSLContext class is an engine class for an implementation of a secure socket protocol. An instance of this class acts as a factory for SSL socket factories and SSL engines. An SSLContext object holds all of the state information shared across all objects created under that context. For example, session state is associated with the SSLContext when it is negotiated through the handshake protocol by sockets created by socket factories provided by the context. These cached sessions can be reused and shared by other sockets created under the same context.

Each instance is configured through its init method with the keys, certificate chains, and trusted root CA certificates that it needs to perform authentication. This configuration is provided in the form of key and trust managers. These managers provide support for the authentication and key agreement aspects of the cipher suites supported by the context.

Currently, only X.509-based managers are supported.

Creating an SSLContext Object

Like other JCA provider-based engine classes, SSLContext objects are created using the getInstance() factory methods of the SSLContext class. These static methods each return an instance that implements at least the requested secure socket protocol. The returned instance may implement other protocols, too. For example, getInstance("TLSv1") may return an instance that implements TLSv1, TLSv1.1, and TLSv1.2. The getSupportedProtocols() method returns a list of supported protocols when an SSLSocket, SSLServerSocket, or SSLEngine is created from this context. You can control which protocols are actually enabled for an SSL connection by using the setEnabledProtocols(String[] protocols) method.


Note: An SSLContext object is automatically created, initialized, and statically assigned to the SSLSocketFactory class when you call the SSLSocketFactory.getDefault() method. Therefore, you do not have to directly create and initialize an SSLContext object (unless you want to override the default behavior).

To create an SSLContext object by calling the getInstance() factory method, you must specify the protocol name. You may also specify which provider you want to supply the implementation of the requested protocol:

If just a protocol name is specified, then the system will determine whether an implementation of the requested protocol is available in the environment. If there is more than one implementation, then it will determine whether there is a preferred one.

If both a protocol name and a provider are specified, then the system will determine whether an implementation of the requested protocol is in the provider requested. If there is no implementation, an exception will be thrown.

A protocol is a string (such as "SSL") that describes the secure socket protocol desired. Common protocol names for SSLContext objects are defined in Appendix A.

An SSLContext can be obtained as follows:

    SSLContext sc = SSLContext.getInstance("SSL");

A newly created SSLContext should be initialized by calling the init method:

    public void init(KeyManager[] km, TrustManager[] tm, SecureRandom random);

If the KeyManager[] parameter is null, then an empty KeyManager will be defined for this context. If the TrustManager[] parameter is null, then the installed security providers will be searched for the highest-priority implementation of the TrustManagerFactory, from which an appropriate TrustManager will be obtained. Likewise, the SecureRandom parameter may be null, in which case a default implementation will be used.

If the internal default context is used, (for example, an SSLContext is created by SSLSocketFactory.getDefault() or SSLServerSocketFactory.getDefault()), then a default KeyManager and TrustManager are created. The default SecureRandom implementation is also chosen.

The TrustManager Interface

The primary responsibility of the TrustManager is to determine whether the presented authentication credentials should be trusted. If the credentials are not trusted, then the connection will be terminated. To authenticate the remote identity of a secure socket peer, you must initialize an SSLContext object with one or more TrustManager objects. You must pass one TrustManager for each authentication mechanism that is supported. If null is passed into the SSLContext initialization, then a trust manager will be created for you. Typically, a single trust manager supports authentication based on X.509 public key certificates (for example, X509TrustManager). Some secure socket implementations may also support authentication based on shared secret keys, Kerberos, or other mechanisms.

TrustManager objects are created either by a TrustManagerFactory, or by providing a concrete implementation of the interface.

The TrustManagerFactory Class

The javax.net.ssl.TrustManagerFactory is an engine class for a provider-based service that acts as a factory for one or more types of TrustManager objects. Because it is provider-based, additional factories can be implemented and configured to provide additional or alternative trust managers that provide more sophisticated services or that implement installation-specific authentication policies.

Creating a TrustManagerFactory

You create an instance of this class in a similar manner to SSLContext, except for passing an algorithm name string instead of a protocol name to the getInstance() method:
    TrustManagerFactory tmf = TrustManagerFactory.getInstance(String algorithm);
    
    TrustManagerFactory tmf = TrustManagerFactory.getInstance(String algorithm, String provider);
    
    TrustManagerFactory tmf = TrustManagerFactory.getInstance(String algorithm, Provider provider);

A sample call is as follows:

    TrustManagerFactory tmf = TrustManagerFactory.getInstance("PKIX", "SunJSSE");

The preceding call creates an instance of the SunJSSE provider's PKIX trust manager factory. This factory can be used to create trust managers that provide X.509 PKIX-based certification path validity checking.

When initializing an SSLContext, you can use trust managers created from a trust manager factory, or you can write your own trust manager, for example, using the CertPath API. For details, see the Java PKI Programmer's Guide. You do not need to use a trust manager factory if you implement a trust manager using the X509TrustManager interface.

A newly created factory should be initialized by calling one of the init() methods:

    public void init(KeyStore ks);
    public void init(ManagerFactoryParameters spec);

Call whichever init() method is appropriate for the TrustManagerFactory you are using. If you are not sure, then ask the provider vendor.

For many factories, such as the SunX509 TrustManagerFactory from the SunJSSE provider, the KeyStore is the only information required to initialize the TrustManagerFactory and thus the first init method is the appropriate one to call. The TrustManagerFactory will query the KeyStore for information about which remote certificates should be trusted during authorization checks.

Sometimes, initialization parameters other than a KeyStore are needed by a provider. Users of that provider are expected to pass an implementation of the appropriate ManagerFactoryParameters as defined by the provider. The provider can then call the specified methods in the ManagerFactoryParameters implementation to obtain the needed information.

For example, suppose the TrustManagerFactory provider requires initialization parameters B, R, and S from any application that wants to use that provider. Like all providers that require initialization parameters other than a KeyStore, the provider requires the application to provide an instance of a class that implements a particular ManagerFactoryParameters subinterface. In the example, suppose that the provider requires the calling application to implement and create an instance of MyTrustManagerFactoryParams and pass it to the second init() method. The following example illustrates what MyTrustManagerFactoryParams can look like:

    public interface MyTrustManagerFactoryParams extends ManagerFactoryParameters {
        public boolean getBValue();
        public float getRValue();
        public String getSValue():
    }

Some trust managers can make trust decisions without being explicitly initialized with a KeyStore object or any other parameters. For example, they may access trust material from a local directory service via LDAP, use a remote online certificate status checking server, or access default trust material from a standard local location.

PKIX TrustManager Support

The default trust manager algorithm is PKIX. It can be changed by editing the ssl.TrustManagerFactory.algorithm property in the java.security file.

The PKIX trust manager factory uses the CertPath PKIX implementation from an installed security provider. The trust manager factory can be initialized using the normal init(KeyStore ks) method, or by passing CertPath parameters to the the PKIX trust manager using the javax.net.ssl.CertPathTrustManagerParameters class.

The following example illustrates how to get the trust manager to use a particular LDAP certificate store and enable revocation checking:

    import javax.net.ssl.*;
    import java.security.cert.*;
    import java.security.KeyStore;
    ...
    
    // Create PKIX parameters
    KeyStore anchors = KeyStore.getInstance("JKS");
    anchors.load(new FileInputStream(anchorsFile));
    CertPathParameters pkixParams = new PKIXBuilderParameters(anchors, new X509CertSelector());
    
    // Specify LDAP certificate store to use
    LDAPCertStoreParameters lcsp = new LDAPCertStoreParameters("ldap.imc.org", 389);
    pkixParams.addCertStore(CertStore.getInstance("LDAP", lcsp));
    
    // Specify that revocation checking is to be enabled
    pkixParams.setRevocationEnabled(true);
    
    // Wrap PKIX parameters as trust manager parameters
    ManagerFactoryParameters trustParams = new CertPathTrustManagerParameters(pkixParams);
    
    // Create TrustManagerFactory for PKIX-compliant trust managers
    TrustManagerFactory factory = TrustManagerFactory.getInstance("PKIX");
    
    // Pass parameters to factory to be passed to CertPath implementation
    factory.init(trustParams);
    
    // Use factory
    SSLContext ctx = SSLContext.getInstance("TLS");
    ctx.init(null, factory.getTrustManagers(), null);

If the init(KeyStore ks) method is used, then default PKIX parameters are used with the exception that revocation checking is disabled. It can be enabled by setting the com.sun.net.ssl.checkRevocation system property to true. This setting requires that the CertPath implementation can locate revocation information by itself. The PKIX implementation in the provider can do this in many cases but requires that the system property com.sun.security.enableCRLDP be set to true.

For more information about PKIX and the CertPath API, see the Java PKI Programmer's Guide.

The X509TrustManager Interface

The javax.net.ssl.X509TrustManager interface extends the general TrustManager interface. It must be implemented by a trust manager when using X.509-based authentication.

To support X.509 authentication of remote socket peers through JSSE, an instance of this interface must be passed to the init method of an SSLContext object.

Creating an X509TrustManager

You can either implement this interface directly yourself or obtain one from a provider-based TrustManagerFactory (such as that supplied by the SunJSSE provider). You could also implement your own interface that delegates to a factory-generated trust manager. For example, you might do this to filter the resulting trust decisions and query an end-user through a graphical user interface.


Note: If a null KeyStore parameter is passed to the SunJSSE PKIX or SunX509 TrustManagerFactory, then the factory uses the following process to try to find trust material:


  1. If the javax.net.ssl.trustStore property is defined, then the TrustManagerFactory attempts to find a file using the file name specified by that system property, and uses that file for the KeyStore parameter. If the javax.net.ssl.trustStorePassword system property is also defined, then its value is used to check the integrity of the data in the truststore before opening it.

    If the javax.net.ssl.trustStore property is defined but the specified file does not exist, then a default TrustManager using an empty keystore is created.

  2. If the javax.net.ssl.trustStore system property was not specified, then:
    • if the file java-home/lib/security/jssecacerts exists, that file is used;
    • if the file java-home/lib/security/cacerts exists, that file is used;
    • if neither of these files exists, then the SSL cipher suite is anonymous, does not perform any authentication, and thus does not need a truststore.

For information about what java-home refers to, see The Installation Directory.

The factory looks for a file specified via the javax.net.ssl.trustStore security property or for the jssecacerts file before checking for a cacerts file. Therefore, you can provide a JSSE-specific set of trusted root certificates separate from ones that might be present in cacerts for code-signing purposes.

Creating Your Own X509TrustManager

If the supplied X509TrustManager behavior is not suitable for your situation, then you can create your own X509TrustManager by either creating and registering your own TrustManagerFactory or by implementing the X509TrustManager interface directly.

The following example illustrates a MyX509TrustManager class that enhances the default SunJSSE X509TrustManager behavior by providing alternative authentication logic when the default X509TrustManager fails:

class MyX509TrustManager implements X509TrustManager {

     /*
      * The default PKIX X509TrustManager9.  Decisions are delegated
      * to it, and a fall back to the logic in this class is performed
      * if the default X509TrustManager does not trust it.
      */
     X509TrustManager pkixTrustManager;

     MyX509TrustManager() throws Exception {
         // create a "default" JSSE X509TrustManager.

         KeyStore ks = KeyStore.getInstance("JKS");
         ks.load(new FileInputStream("trustedCerts"), "passphrase".toCharArray());

         TrustManagerFactory tmf = TrustManagerFactory.getInstance("PKIX");
         tmf.init(ks);

         TrustManager tms [] = tmf.getTrustManagers();

         /*
          * Iterate over the returned trust managers, looking
          * for an instance of X509TrustManager.  If found,
          * use that as the default trust manager.
          */
         for (int i = 0; i < tms.length; i++) {
             if (tms[i] instanceof X509TrustManager) {
                 pkixTrustManager = (X509TrustManager) tms[i];
                 return;
             }
         }

         /*
          * Find some other way to initialize, or else the
          * constructor fails.
          */
         throw new Exception("Couldn't initialize");
     }

     /*
      * Delegate to the default trust manager.
      */
     public void checkClientTrusted(X509Certificate[] chain, String authType)
                 throws CertificateException {
         try {
             pkixTrustManager.checkClientTrusted(chain, authType);
         } catch (CertificateException excep) {
             // do any special handling here, or rethrow exception.
         }
     }

     /*
      * Delegate to the default trust manager.
      */
     public void checkServerTrusted(X509Certificate[] chain, String authType)
                 throws CertificateException {
         try {
             pkixTrustManager.checkServerTrusted(chain, authType);
         } catch (CertificateException excep) {
             /*
              * Possibly pop up a dialog box asking whether to trust the
              * cert chain.
              */
         }
     }

     /*
      * Merely pass this through.
      */
     public X509Certificate[] getAcceptedIssuers() {
         return pkixTrustManager.getAcceptedIssuers();
     }
}

Once you have created such a trust manager, assign it to an SSLContext via the init() method, as in the following example. Future SocketFactories created from this SSLContext will use your new TrustManager when making trust decisions.

    TrustManager[] myTMs = new TrustManager[] { new MyX509TrustManager() };
    SSLContext ctx = SSLContext.getInstance("TLS");
    ctx.init(null, myTMs, null);

Updating the Keystore Dynamically

You can enhance MyX509TrustManager to handle dynamic keystore updates. When a checkClientTrusted or checkServerTrusted test fails and does not establish a trusted certificate chain, you can add the required trusted certificate to the keystore. You must create a new pkixTrustManager from the TrustManagerFactory initialized with the updated keystore. When you establish a new connection (using the previously initialized SSLContext), the newly added certificate will be used when making trust decisions.

X509ExtendedTrustManager Class

The X509ExtendedTrustManager class is an abstract implementation of the X509TrustManager interface. It adds methods for connection-sensitive trust management. In addition, it enables endpoint verification at the TLS layer.

In TLS 1.2 and later, both client and server can specify which hash and signature algorithms they will accept. To authenticate the remote side, authentication decisions must be based on both X509 certificates and the local accepted hash and signature algorithms. The local accepted hash and signature algorithms can be obtained using the ExtendedSSLSession.getLocalSupportedSignatureAlgorithms() method.

The ExtendedSSLSession object can be retrieved by calling the SSLSocket.getHandshakeSession() method or the SSLEngine.getHandshakeSession() method.

The X509TrustManager interface is not connection-sensitive. It provides no way to access SSLSocket or SSLEngine session properties.

Besides TLS 1.2 support, the X509ExtendedTrustManager class also supports algorithm constraints and SSL layer host name verification. For JSSE providers and trust manager implementations, the X509ExtendedTrustManager class is highly recommended over the legacy X509TrustManager interface.

Creating an X509ExtendedTrustManager

You can either create an X509ExtendedTrustManager subclass yourself (which is outlined in the following section) or obtain one from a provider-based TrustManagerFactory (such as that supplied by the SunJSSE provider). In Java SE 7, the PKIX or SunX509 TrustManagerFactory returns an X509ExtendedTrustManager instance.

Creating Your Own X509ExtendedTrustManager

This section outlines how to create a subclass of X509ExtendedTrustManager in nearly the same way as described for X509TrustManager.

The following example illustrates how to create a class that uses the PKIX TrustManagerFactory to locate a default X509ExtendedTrustManager that will be used to make decisions about trust. If the default trust manager fails for any reason, then the subclass is can add other behavior. In the example, these locations are indicated by comments in the catch clauses.

    import java.io.*;
    import java.net.*;
    
    import java.security.*;
    import java.security.cert.*;
    import javax.net.ssl.*;
    
    public class MyX509ExtendedTrustManager extends X509ExtendedTrustManager {
    
         /*
          * The default PKIX X509ExtendedTrustManager.  Decisions are
          * delegated to it, and a fall back to the logic in this class is
          * performed if the default X509ExtendedTrustManager does not
          * trust it.
          */
         X509ExtendedTrustManager pkixTrustManager;
    
         MyX509ExtendedTrustManager() throws Exception {
             // create a "default" JSSE X509ExtendedTrustManager.
    
             KeyStore ks = KeyStore.getInstance("JKS");
             ks.load(new FileInputStream("trustedCerts"), "passphrase".toCharArray());
    
             TrustManagerFactory tmf = TrustManagerFactory.getInstance("PKIX");
             tmf.init(ks);
    
             TrustManager tms [] = tmf.getTrustManagers();
    
             /*
              * Iterate over the returned trust managers, looking
              * for an instance of X509ExtendedTrustManager. If found,
              * use that as the default trust manager.
              */
             for (int i = 0; i < tms.length; i++) {
                 if (tms[i] instanceof X509ExtendedTrustManager) {
                     pkixTrustManager = (X509ExtendedTrustManager) tms[i];
                     return;
                 }
             }
    
             /*
              * Find some other way to initialize, or else we have to fail the
              * constructor.
              */
             throw new Exception("Couldn't initialize");
         }
    
         /*
          * Delegate to the default trust manager.
          */
         public void checkClientTrusted(X509Certificate[] chain, String authType)
                     throws CertificateException {
             try {
                 pkixTrustManager.checkClientTrusted(chain, authType);
             } catch (CertificateException excep) {
                 // do any special handling here, or rethrow exception.
             }
         }
    
         /*
          * Delegate to the default trust manager.
          */
         public void checkServerTrusted(X509Certificate[] chain, String authType)
                     throws CertificateException {
             try {
                 pkixTrustManager.checkServerTrusted(chain, authType);
             } catch (CertificateException excep) {
                 /*
                  * Possibly pop up a dialog box asking whether to trust the
                  * cert chain.
                  */
             }
         }
    
         /*
          * Connection-sensitive verification.
          */
         public void checkClientTrusted(X509Certificate[] chain, String authType, Socket socket)
                     throws CertificateException {
           try {
               pkixTrustManager.checkClientTrusted(chain, authType, socket);
           } catch (CertificateException excep) {
               // do any special handling here, or rethrow exception.
           }
         }
    
         public void checkClientTrusted(X509Certificate[] chain, String authType, SSLEngine engine)
                     throws CertificateException {
           try {
               pkixTrustManager.checkClientTrusted(chain, authType, engine);
           } catch (CertificateException excep) {
               // do any special handling here, or rethrow exception.
           }
         }
    
         public void checkServerTrusted(X509Certificate[] chain, String authType, Socket socket)
                     throws CertificateException {
           try {
               pkixTrustManager.checkServerTrusted(chain, authType, socket);
           } catch (CertificateException excep) {
               // do any special handling here, or rethrow exception.
           }
         }
    
         public void checkServerTrusted(X509Certificate[] chain, String authType, SSLEngine engine)
                     throws CertificateException {
           try {
               pkixTrustManager.checkServerTrusted(chain, authType, engine);
           } catch (CertificateException excep) {
               // do any special handling here, or rethrow exception.
           }
         }
         
         /*
          * Merely pass this through.
          */
         public X509Certificate[] getAcceptedIssuers() {
             return pkixTrustManager.getAcceptedIssuers();
         }
    }

The KeyManager Interface

The primary responsibility of the KeyManager is to select the authentication credentials that will eventually be sent to the remote host. To authenticate yourself (a local secure socket peer) to a remote peer, you must initialize an SSLContext object with one or more KeyManager objects. You must pass one KeyManager for each different authentication mechanism that will be supported. If null is passed into the SSLContext initialization, then an empty KeyManager will be created. If the internal default context is used (for example, an SSLContext created by SSLSocketFactory.getDefault() or SSLServerSocketFactory.getDefault()), then a default KeyManager is created. Typically, a single key manager supports authentication based on X.509 public key certificates. Some secure socket implementations may also support authentication based on shared secret keys, Kerberos, or other mechanisms.

KeyManager objects are created either by a KeyManagerFactory, or by providing a concrete implementation of the interface.

The KeyManagerFactory Class

The javax.net.ssl.KeyManagerFactory class is an engine class for a provider-based service that acts as a factory for one or more types of KeyManager objects. The SunJSSE provider implements a factory that can return a basic X.509 key manager. Because it is provider-based, additional factories can be implemented and configured to provide additional or alternative key managers.

Creating a KeyManagerFactory

You create an instance of this class in a similar manner to SSLContext, except for passing an algorithm name string instead of a protocol name to the getInstance() method:

    KeyManagerFactory kmf = getInstance(String algorithm);
    
    KeyManagerFactory kmf = getInstance(String algorithm, String provider);
    
    KeyManagerFactory kmf = getInstance(String algorithm, Provider provider);

A sample call as follows:

    KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509", "SunJSSE");

The preceding call creates an instance of the SunJSSE provider's default key manager factory, which provides basic X.509-based authentication keys.

A newly created factory should be initialized by calling one of the init methods:

    public void init(KeyStore ks, char[] password);
    public void init(ManagerFactoryParameters spec);

Call whichever init method is appropriate for the KeyManagerFactory you are using. If you are not sure, then ask the provider vendor.

For many factories, such as the default SunX509 KeyManagerFactory from the SunJSSE provider, the KeyStore and password are the only information required to initialize the KeyManagerFactory and thus the first init method is the appropriate one to call. The KeyManagerFactory will query the KeyStore for information about which private key and matching public key certificates should be used for authenticating to a remote socket peer. The password parameter specifies the password that will be used with the methods for accessing keys from the KeyStore. All keys in the KeyStore must be protected by the same password.

Sometimes initialization parameters other than a KeyStore and password are needed by a provider. Users of that provider are expected to pass an implementation of the appropriate ManagerFactoryParameters as defined by the provider. The provider can then call the specified methods in the ManagerFactoryParameters implementation to obtain the needed information.

Some factories can provide access to authentication material without being initialized with a KeyStore object or any other parameters. For example, they may access key material as part of a login mechanism such as one based on JAAS, the Java Authentication and Authorization Service.

As previously indicated, the SunJSSE provider supports a SunX509 factory that must be initialized with a KeyStore parameter.

The X509KeyManager Interface

The javax.net.ssl.X509KeyManager interface extends the general KeyManager interface. It must be implemented by a key manager for X.509-based authentication. To support X.509 authentication to remote socket peers through JSSE, an instance of this interface must be passed to the init() method of an SSLContext object.

Creating an X509KeyManager

You can either implement this interface directly yourself or obtain one from a provider-based KeyManagerFactory (such as that supplied by the SunJSSE provider). You could also implement your own interface that delegates to a factory-generated key manager. For example, you might do this to filter the resulting keys and query an end-user through a graphical user interface.

Creating Your Own X509KeyManager

If the default X509KeyManager behavior is not suitable for your situation, then you can create your own X509KeyManager in a way similar to that shown in Creating Your Own X509TrustManager.

The X509ExtendedKeyManager Class

The X509ExtendedKeyManager abstract class is an implementation of the X509KeyManager interface that allows for connection-specific key selection. It adds two methods that select a key alias for client or server based on the key type, allowed issuers, and current SSLEngine:

If a key manager is not an instance of the X509ExtendedKeyManager class, then it will not work with the SSLEngine class.

For JSSE providers and key manager implementations, the X509ExtendedKeyManager class is highly recommended over the legacy X509KeyManager interface.

In TLS 1.2 and later, both client and server can specify which hash and signature algorithms they will accept. To pass the authentication required by the remote side, local key selection decisions must be based on both X509 certificates and the remote accepted hash and signature algorithms. The remote accepted hash and signature algorithms can be retrieved using the ExtendedSSLSession.getPeerSupportedSignatureAlgorithms() method.

You can create your own X509ExtendedKeyManager subclass in a way similar to that shown in Creating Your Own X509ExtendedTrustManager.

Support for the Server Name Indication (SNI) extension on the server side enables the key manager to check the server name and select the appropriate key accordingly. For example, suppose there are three key entries with certificates in the keystore:

If the ClientHello message requests to connect to www.example.net in the SNI extension, then the server should be able to select the certificate with subject cn=www.example.net.

Relationship Between a TrustManager and a KeyManager

Historically, there has been confusion regarding the functionality of a TrustManager and a KeyManager.

A TrustManager determines whether the remote authentication credentials (and thus the connection) should be trusted.

A KeyManager determines which authentication credentials to send to the remote host.

Secondary Support Classes and Interfaces

These classes are provided as part of the JSSE API to support the creation, use, and management of secure sockets. They are less likely to be used by secure socket applications than are the core and support classes. The secondary support classes and interfaces are part of the javax.net.ssl and javax.security.cert packages.

The SSLParameters Class

The SSLParameters class encapsulates the following parameters that affect a TLS connection:

You can retrieve the current SSLParameters for an SSLSocket or SSLEngine by using the following methods:

You can assign SSLParameters with the setSSLParameters() method in an SSLSocket, SSLServerSocket and SSLEngine.

You can explicitly set the server name indication with the SSLParameters.setServerNames() method. The server name indication in client mode also affects endpoint identification. In the implementation of X509ExtendedTrustManager, it uses the server name indication retrieved by the ExtendedSSLSession.getRequestedServerNames() method. The following example illustrates this functionality:

SSLSocketFactory factory = ...
SSLSocket sslSocket = factory.createSocket("172.16.10.6", 443);
// SSLEngine sslEngine = sslContext.createSSLEngine("172.16.10.6", 443);

SNIHostName serverName = new SNIHostName("www.example.com");
List<SNIServerName> serverNames = new ArrayList<>(1);
serverNames.add(serverName);
 
SSLParameters params = sslSocket.getSSLParameters();
params.setServerNames(serverNames);
sslSocket.setSSLParameters(params);
// sslEngine.setSSLParameters(params);

In the preceding example, the host name in the server name indication (www.example.com) will be used to make endpoint identification against the peer's identity presented in the end-entity's X.509 certificate.

Cipher Suite Preference

During TLS handshaking, the client requests to negotiate a cipher suite from a list of cryptographic options that it supports, starting with its first preference. Then, the server selects a single cipher suite from the list of cipher suites requested by the client. Normally, the selection honors the client's preference. However, to mitigate the risks of using weak cipher suites, the server may select cipher suites based on its own preference rather than the client's preference, by invoking the method SSLParameters.setUseCipherSuitesOrder(true).

The SSLSessionContext Interface

The javax.net.ssl.SSLSessionContext interface is a grouping of SSLSession objects associated with a single entity. For example, it could be associated with a server or client that participates in many sessions concurrently. The methods in this interface enable the enumeration of all sessions in a context and allow lookup of specific sessions via their session IDs.

An SSLSessionContext may optionally be obtained from an SSLSession by calling the SSLSession getSessionContext() method. The context may be unavailable in some environments, in which case the getSessionContext() method returns null.

The SSLSessionBindingListener Interface

The javax.net.ssl.SSLSessionBindingListener interface is implemented by objects that are notified when they are being bound or unbound from an SSLSession.

The SSLSessionBindingEvent Class

The javax.net.ssl.SSLSessionBindingEvent class defines the event communicated to an SSLSessionBindingListener when it is bound or unbound from an SSLSession.

The HandShakeCompletedListener Interface

The javax.net.ssl.HandShakeCompletedListener interface is an interface implemented by any class that is notified of the completion of an SSL protocol handshake on a given SSLSocket connection.

The HandShakeCompletedEvent Class

The javax.net.ssl.HandShakeCompletedEvent class define the event communicated to a HandShakeCompletedListener upon completion of an SSL protocol handshake on a given SSLSocket connection.

The HostnameVerifier Interface

If the SSL/TLS implementation's standard host name verification logic fails, then the implementation calls the verify() method of the class that implements this interface and is assigned to this HttpsURLConnection instance. If the callback class can determine that the host name is acceptable given the parameters, it reports that the connection should be allowed. An unacceptable response causes the connection to be terminated.

For example:

    public class MyHostnameVerifier implements HostnameVerifier {
    
        public boolean verify(String hostname, SSLSession session) {
            // pop up an interactive dialog box
            // or insert additional matching logic
            if (good_address) {
                return true;
            } else {
                return false;
            }
        }
    }
    
    //...deleted...
    
    HttpsURLConnection urlc = (HttpsURLConnection)
      (new URL("https://www.example.com/")).openConnection();
    urlc.setHostnameVerifier(new MyHostnameVerifier());

See The HttpsURLConnection Class for more information about how to assign the HostnameVerifier to the HttpsURLConnection.

The X509Certificate Class

Many secure socket protocols perform authentication using public key certificates, also called X.509 certificates. This is the default authentication mechanism for the SSL/TLS protocols.

The java.security.cert.X509Certificate abstract class provides a standard way to access the attributes of X.509 certificates.


Note: The javax.security.cert.X509Certificate class is supported only for backward compatibility with previous (1.0.x and 1.1.x) versions of JSSE. New applications should use the java.security.cert.X509Certificate class instead.


The AlgorithmConstraints Interface

The java.security.AlgorithmConstraints interface is used for controlling allowed cryptographic algorithms. AlgorithmConstraints defines three permits() methods. These methods tell whether an algorithm name or a key is permitted for certain cryptographic functions. Cryptographic functions are represented by a set of CryptoPrimitive, which is an enumeration containing fields like STREAM_CIPHER, MESSAGE_DIGEST, and SIGNATURE.

Thus, an AlgorithmConstraints implementation can answer questions like: Can I use this key with this algorithm for the purpose of a cryptographic operation?

An AlgorithmConstraints object can be associated with an SSLParameters object by using the new setAlgorithmConstraints() method. The current AlgorithmConstraints object for an SSLParameters object is retrieved using the getAlgorithmConstraints() method.

The StandardConstants Class

The StandardConstants class is used to represent standard constants definitions in JSSE.

StandardConstants.SNI_HOST_NAME represents a domain name server (DNS) host name in a Server Name Indication (SNI) extension, which can be used when instantiating an SNIServerName or SNIMatcher object.

The SNIServerName Class

An instance of the abstract SNIServerName class represents a server name in the Server Name Indication (SNI) extension. It is instantiated using the type and encoded value of the specified server name.

You can use the getType() and getEncoded() methods to return the server name type and a copy of the encoded server name value, respectively. The equals() method can be used to check if some other object is "equal" to this server name. The hashCode() method returns a hash code value for this server name. To get a string representation of the server name (including the server name type and encoded server name value), use the toString() method.

The SNIMatcher Class

An instance of the abstract SNIMatcher class performs match operations on an SNIServerName object. Servers can use information from the Server Name Indication (SNI) extension to decide if a specific SSLSocket or SSLEngine should accept a connection. For example, when multiple "virtual" or "name-based" servers are hosted on a single underlying network address, the server application can use SNI information to determine whether this server is the exact server that the client wants to access. Instances of this class can be used by a server to verify the acceptable server names of a particular type, such as host names.

The SNIMatcher class is instantiated using the specified server name type on which match operations will be performed. To match a given SNIServerName, use the matches() method. To return the server name type of the given SNIMatcher object, use the getType() method.

The SNIHostName Class

An instance of the SNIHostName class (which extends the SNIServerName class) represents a server name of type "host_name" (see The StandardConstants Class) in the Server Name Indication (SNI) extension. To instantiate an SNIHostName, specify the fully qualified DNS host name of the server (as understood by the client) as a String argument. The argument is illegal in the following cases:

You can also instantiate an SNIHostName by specifying the encoded host name value as a byte array. This method is typically used to parse the encoded name value in a requested SNI extension. Otherwise, use the SNIHostName(String hostname) constructor. The encoded argument is illegal in the following cases:


Note: The encoded byte array passed in as an argument is cloned to protect against subsequent modification.


To return the host name of an SNIHostName object in US-ASCII encoding, use the getAsciiName() method. To compare a server name to another object, use the equals() method (comparison is not case-sensitive). To return a hash code value of an SNIHostName, use the hashCode() method. To return a string representation of an SNIHostName, including the DNS host name, use the toString() method.

You can create an SNIMatcher object for an SNIHostName object by passing a regular expression representing one or more host names to match to the createSNIMatcher() method.

Customizing JSSE

JSSE includes a standard implementation that can be customized by plugging in different implementations or specifying the default keystore, and so on. Table 6 summarizes which aspects can be customized, what the defaults are, and which mechanisms are used to provide customization. The first column of the table provides links to more detailed descriptions of each designated aspect and how to customize it.

Some of the customizations are done by setting system property or security property values. Sections following the table explain how to set such property values.


Note: Many of the properties shown in this table are currently used by the JSSE implementation, but there is no guarantee that they will continue to have the same names and types (system or security) or even that they will exist at all in future releases. All such properties are flagged with an asterisk (*). They are documented here for your convenience for use with the JSSE implementation.


Table 6: Customizable Items in JSSE
Customizable Item Default How to Customize
X509Certificate implementation X509Certificate implementation from Oracle cert.provider.x509v1 security property
HTTPS protocol implementation Implementation from Oracle java.protocol.handler.pkgs system property
Provider implementation SunJSSE The security.provider.n= line in security properties file
Default SSLSocketFactory implementation SSLSocketFactory implementation from Oracle * ssl.SocketFactory.provider security property
Default SSLServerSocketFactory implementation SSLServerSocketFactory implementation from Oracle * ssl.ServerSocketFactory.provider security property
Default keystore None * javax.net.ssl.keyStore system property.
Note that the value NONE may be specified. This setting is appropriate if the keystore is not file-based (for example, it resides in a hardware token).
Default keystore password None * javax.net.ssl.keyStorePassword system property.
It is inadvisable to specify the password in a way that exposes it to discovery by other users, for example, specifying the password on the command line. To keep the password secure, have the application prompt for the password, or specify the password in a properly protected option file.
Default keystore provider None * javax.net.ssl.keyStoreProvider system property
Default keystore type KeyStore.getDefaultType() * javax.net.ssl.keyStoreType system property
Default truststore jssecacerts, if it exists. Otherwise, cacerts. * javax.net.ssl.trustStore system property
Default truststore password None * javax.net.ssl.trustStorePassword system property.
It is inadvisable to specify the password in a way that exposes it to discovery by other users, for example, specifying the password on the command line. To keep the password secure, have the application prompt for the password, or specify the password in a properly protected option file.
Default truststore provider None * javax.net.ssl.trustStoreProvider system property
Default truststore type KeyStore.getDefaultType() * javax.net.ssl.trustStoreType system property
Note that the value NONE may be specified. This setting is appropriate if the truststore is not file-based (for example, it resides in a hardware token).
Default key manager factory algorithm name SunX509 ssl.KeyManagerFactory.algorithm security property
Default trust manager factory algorithm name PKIX ssl.TrustManagerFactory.algorithm security property
Disabled certificate verification cryptographic algorithms MD2, RSA keySize < 1024 jdk.certpath.disabledAlgorithms security property
Disabled cipher suite cryptographic algorithms None jdk.tls.disabledAlgorithms security property
Default proxy host None * https.proxyHost system property
Default proxy port 80 * https.proxyPort system property
Server Name Indication option true * jsse.enableSNIExtension system property.
Server Name Indication (SNI) is a TLS extension, defined in RFC 6066. It enables TLS connections to virtual servers, in which multiple servers for different network names are hosted at a single underlying network address.
Some very old SSL/TLS vendors may not be able handle SSL/TLS extensions. In this case, set this property to false to disable the SNI extension.
Default cipher suites Determined by the socket factory * https.cipherSuites system property. This contains a comma-separated list of cipher suite names specifying which cipher suites to enable for use on this HttpsURLConnection. See the SSLSocket.setEnabledCipherSuites(String[]) method.
Default handshaking protocols Determined by the socket factory * https.protocols system property.
This contains a comma-separated list of protocol suite names specifying which protocol suites to enable on this HttpsURLConnection. See the
SSLSocket.setEnabledProtocols(String[]) method.
Default HTTPS port 443 * Customize via port field in the HTTPS URL.
JCE encryption algorithms used by the SunJSSE provider SunJCE implementations Give alternative JCE algorithm providers a higher preference order than the SunJCE provider
Default sizing buffers for large SSL/TLS packets None * jsse.SSLEngine.acceptLargeFragments system property.
By setting this system property to true, SSLSession will size buffers to handle large data packets by default. This may cause applications to allocate unnecessarily large SSLEngine buffers. Instead, applications should dynamically check for buffer overflow conditions and resize buffers as appropriate.
Allow Unsafe SSL/TLS Renegotiations false * sun.security.ssl.allowUnsafeRenegotiation system property.
Setting this system property to true permits full (unsafe) legacy renegotiation.
Allow Legacy Hello Messages (Renegotiations) true * sun.security.ssl.allowLegacyHelloMessages system property.
Setting this system property to true allows the peer to handshake without requiring the proper RFC 5746 messages.
Default Enabled TLS Protocols None jdk.tls.client.protocols system property.
To enable specific SunJSSE protocols on the client, specify them in a comma-separated list within quotation marks; all other supported protocols are then disabled on the client. For example, if the value of this property is "TLSv1,TLSv1.1", then the default protocol settings on the client for TLSv1 and TLSv1.1 are enabled on the client, while SSLv3, TLSv1.2, and SSLv2Hello are disabled on the client.
Size of ephemeral Diffie-Hellman keys 1024 bits jdk.tls.ephemeralDHKeySize system property.

* This property is currently used by the JSSE implementation, but it is not guaranteed to be examined and used by other implementations. If it is examined by another implementation, then that implementation should handle it in the same manner as the JSSE implementation does. There is no guarantee the property will continue to exist or be of the same type (system or security) in future releases.


Note: Some items are customized by setting java.lang.System properties, whereas others are customized by setting java.security.Security properties. The following sections explain how to set values for both types of properties.


How to Specify a java.lang.System Property

You can customize some aspects of JSSE by setting system properties. There are several ways to set these properties:

How to Specify a java.security.Security Property

You can customize some aspects of JSSE by setting security properties. You can set a security property either statically or dynamically:

Customizing the X509Certificate Implementation

The X509Certificate implementation returned by the X509Certificate.getInstance() method is by default the implementation from the JSSE implementation.

You can optionally cause a different implementation to be returned. To do so, specify the name (and package) of the other implementation's class as the value of a security property named cert.provider.x509v1. For example, if the class is called MyX509CertificateImpl and it appears in the com.cryptox package, then you should add the following line to the security properties file:

    cert.provider.x509v1=com.cryptox.MyX509CertificateImpl

Specifying an Alternative HTTPS Protocol Implementation

You can communicate securely with an SSL-enabled web server by using the HTTPS URL scheme for the java.net.URL class. The JDK provides a default HTTPS URL implementation.

If you want an alternative HTTPS protocol implementation to be used, set the java.protocol.handler.pkgs system property to include the new class name. This action causes the specified classes to be found and loaded before the JDK default classes. See the java.net.URL class documentation for details.


Note: In past JSSE releases, you had to set the java.protocol.handler.pkgs system property during JSSE installation. This step is no longer required unless you want to obtain an instance of com.sun.net.ssl.HttpsURLConnection. For more information, see Code Using the HttpsURLConnection Class in the "Troubleshooting" section.


Customizing the Provider Implementation

JDK 1.4 and later releases come standard with a JSSE Cryptographic Service Provider, or provider for short, named SunJSSE. Providers are essentially packages that implement one or more engine classes for specific cryptographic algorithms. The JSSE engine classes are SSLContext, KeyManagerFactory, and TrustManagerFactory. For more information about providers and engine classes, see the Java Cryptography Architecture Reference Guide.


Note: The transformation strings used when SunJSSE calls Cipher.getInstance() are "RSA/ECB/PKCS1Padding", "RC4", "DES/CBC/NoPadding", and "DESede/CBC/NoPadding". For further information about the Cipher class and transformation strings see the Java Cryptography Architecture Reference Guide.


Before it can be used, a provider must be registered, either statically or dynamically. You do not need to register the SunJSSE provider because it is preregistered. If you want to use other providers, read the following sections to see how to register them.

Registering the Cryptographic Service Provider Statically

You register a provider statically by adding a line of the following form to the security properties file:

    security.provider.n=providerClassName

This declares a provider, and specifies its preference order n. The preference order is the order in which providers are searched for requested algorithms (when no specific provider is requested). "1" is the most preferred, followed by "2", and so on.

The providerClassName is the fully qualified name of the provider class. You obtain this name from the provider vendor.

The standard security provider and the SunJSSE provider shipped with JDK 6 are automatically registered for you; the following lines appear in the java.security security properties file to register the SunJCE security provider with preference order 5 and the SunJSSE provider with preference order 4:

    security.provider.1=sun.security.pkcs11.SunPKCS11 \
    ${java.home}/lib/security/sunpkcs11-solaris.cfg
    security.provider.2=sun.security.provider.Sun
    security.provider.3=sun.security.rsa.SunRsaSign
    security.provider.4=com.sun.net.ssl.internal.ssl.Provider
    security.provider.5=com.sun.crypto.provider.SunJCE
    security.provider.6=sun.security.jgss.SunProvider
    security.provider.7=com.sun.security.sasl.Provider

To use another JSSE provider, add a line registering the other provider, giving it whatever preference order you prefer.

You can have more than one JSSE provider registered at the same time. The registered providers may include different implementations for different algorithms for different engine classes, or they may have support for some or all of the same types of algorithms and engine classes. When a particular engine class implementation for a particular algorithm is searched for, if no specific provider is specified for the search, then the providers are searched in preference order and the implementation from the first provider that supplies an implementation for the specified algorithm is used.

Registering the Cryptographic Service Provider Dynamically

Instead of registering a provider statically, you can add the provider dynamically at runtime by calling the Security.addProvider() method at the beginning of your program. For example, to dynamically add a provider whose provider class name is MyProvider and whose MyProvider class resides in the com.ABC package, you would call:

    Security.addProvider(new com.ABC.MyProvider());

The Security.addProvider() method adds the specified provider to the next available preference position.

This type of registration is not persistent and can only be done by a program with sufficient permissions.

Customizing the Default Keystores and Truststores, Store Types, and Store Passwords

Whenever a default SSLSocketFactory or SSLServerSocketFactory is created (via a call to SSLSocketFactory.getDefault or SSLServerSocketFactory.getDefault), and this default SSLSocketFactory (or SSLServerSocketFactory) comes from the JSSE reference implementation, a default SSLContext is associated with the socket factory. (The default socket factory will come from the JSSE implementation.)

This default SSLContext is initialized with a default KeyManager and a default TrustManager. If a keystore is specified by the javax.net.ssl.keyStore system property and an appropriate javax.net.ssl.keyStorePassword system property, then the KeyManager created by the default SSLContext will be a KeyManager implementation for managing the specified keystore. (The actual implementation will be as specified in Customizing the Default Key and Trust Managers.) If no such system property is specified, then the keystore managed by the KeyManager will be a new empty keystore.

Generally, the peer acting as the server in the handshake will need a keystore for its KeyManager in order to obtain credentials for authentication to the client. However, if one of the anonymous cipher suites is selected, then the server's KeyManager keystore is not necessary. And, unless the server requires client authentication, the peer acting as the client does not need a KeyManager keystore. Thus, in these situations it may be OK if no javax.net.ssl.keyStore system property value is defined.

Similarly, if a truststore is specified by the javax.net.ssl.trustStore system property, then the TrustManager created by the default SSLContext will be a TrustManager implementation for managing the specified truststore. In this case, if such a property exists but the file it specifies does not, then no truststore is used. If no javax.net.ssl.trustStore property exists, then a default truststore is searched for. If a truststore named java-home/lib/security/jssecacerts is found, it is used. If not, then a truststore named java-home/lib/security/cacerts is searched for and used (if it exists). For more information about java-home, see The Installation Directory. Finally, if a truststore is still not found, then the truststore managed by the TrustManager will be a new empty truststore.


Note: The JDK ships with a limited number of trusted root certificates in the java-home/lib/security/cacerts file. As documented in keytool reference pages, it is your responsibility to maintain (that is, add and remove) the certificates contained in this file if you use this file as a truststore.

Depending on the certificate configuration of the servers that you contact, you may need to add additional root certificates. Obtain the needed specific root certificates from the appropriate vendor.


If the javax.net.ssl.keyStoreType and/or javax.net.ssl.keyStorePassword system properties are also specified, then they are treated as the default KeyManager keystore type and password, respectively. If no type is specified, then the default type is that returned by the KeyStore.getDefaultType() method, which is the value of the keystore.type security property, or "jks" if no such security property is specified. If no keystore password is specified, then it is assumed to be a blank string "".

Similarly, if the javax.net.ssl.trustStoreType and/or javax.net.ssl.trustStorePassword system properties are also specified, then they are treated as the default truststore type and password, respectively. If no type is specified, then the default type is that returned by the KeyStore.getDefaultType() method. If no truststore password is specified, then it is assumed to be a blank string "".


Note: This section describes the current JSSE reference implementation behavior. The system properties described in this section are not guaranteed to continue to have the same names and types (system or security) or even to exist at all in future releases. They are also not guaranteed to be examined and used by any other JSSE implementations. If they are examined by an implementation, then that implementation should handle them in the same manner as the JSSE reference implementation does, as described herein.


Customizing the Default Key Managers and Trust Managers

As noted in Customizing the Default Keystores and Truststores, Store Types, and Store Passwords, whenever a default SSLSocketFactory or SSLServerSocketFactory is created, and this default SSLSocketFactory (or SSLServerSocketFactory) comes from the JSSE reference implementation, a default SSLContext is associated with the socket factory.

This default SSLContext is initialized with a KeyManager and a TrustManager. The KeyManager and/or TrustManager supplied to the default SSLContext will be an implementation for managing the specified keystore or truststore, as described in the aforementioned section.

The KeyManager implementation chosen is determined by first examining the ssl.KeyManagerFactory.algorithm security property. If such a property value is specified, then a KeyManagerFactory implementation for the specified algorithm is searched for. The implementation from the first provider that supplies an implementation is used. Its getKeyManagers() method is called to determine the KeyManager to supply to the default SSLContext. Technically, getKeyManagers() returns an array of KeyManager objects, one KeyManager for each type of key material. If no such security property value is specified, then the default value of SunX509 is used to perform the search.


Note: A KeyManagerFactory implementation for the SunX509 algorithm is supplied by the SunJSSE provider. The KeyManager that it specifies is a javax.net.ssl.X509KeyManager implementation.


Similarly, the TrustManager implementation chosen is determined by first examining the ssl.TrustManagerFactory.algorithm security property. If such a property value is specified, then a TrustManagerFactory implementation for the specified algorithm is searched for. The implementation from the first provider that supplies an implementation is used. Its getTrustManagers() method is called to determine the TrustManager to supply to the default SSLContext. Technically, getTrustManagers() returns an array of TrustManager objects, one TrustManager for each type of trust material. If no such security property value is specified, then the default value of PKIX is used to perform the search.


Note: A TrustManagerFactory implementation for the PKIX algorithm is supplied by the SunJSSE provider. The TrustManager that it specifies is a javax.net.ssl.X509TrustManager implementation.


Note: This section describes the current JSSE reference implementation behavior. The system properties described in this section are not guaranteed to continue to have the same names and types (system or security) or even to exist at all in future releases. They are also not guaranteed to be examined and used by any other JSSE implementations. If they are examined by an implementation, then that implementation should handle them in the same manner as the JSSE reference implementation does, as described herein.


Disabled Cryptographic Algorithms

The cryptographic hash algorithm MD2 is no longer considered secure. Java SE 7 included two new security properties and a new API that support disabling specific cryptographic algorithms.

The jdk.tls.disabledAlgorithms property applies to TLS handshaking, whereas the jdk.certpath.disabledAlgorithms property applies to certification path processing.

From JDK 8 onwards, the default value of jdk.certpath.disabledAlgorithms includes RSA keySize < 1024. This means the use of certificates with RSA key size less than 1024 bits in length is restricted. The default value of jdk.certpath.disabledAlgorithms is now as follows:

    jdk.certpath.disabledAlgorithms=MD2, RSA keySize < 1024

This means that any certificate signed with MD2 or with a RSA key of size < 1024, is not acceptable.

Each security property contains a list of cryptographic algorithms that will not be used during certification path processing. The exact syntax of the properties is described in the java-home/lib/security/java.security file, but is briefly summarized here. The algorithm names are separated by commas. Furthermore, you can also specify certain key sizes that cannot be used.

For example, the following line in java.security specifies that the MD2 and DSA algorithms must not be used for certification path processing, and RSA is disabled for key sizes less than 2048 bits.

    jdk.certpath.disabledAlgorithms=MD2, DSA, RSA keySize < 2048

Customizing the Encryption Algorithm Providers

The SunJSSE provider uses the SunJCE implementation for all its cryptographic needs. Although it is recommended that you leave the provider at its regular position, you can use implementations from other JCA or JCE providers by registering them before the SunJCE provider. The standard JCA mechanism can be used to configure providers, either statically via the security properties file java-home/lib/security/java.security, or dynamically via the addProvider() or insertProviderAt() method in the java.security.Security class. For information about java-home, see The Installation Directory.

Customizing Size of Ephemeral Diffie-Hellman Keys

Diffie-Hellman (DH) keys of sizes less than 1024 bits have been deprecated because of their insufficient strength. In JDK 8, you can customize the ephemeral DH key size with the system property jdk.tls.ephemeralDHKeySize. This system property does not impact DH key sizes in ServerKeyExchange messages for exportable cipher suites. It impacts only the DHE_RSA, DHE_DSS, and DH_anon-based cipher suites in the JSSE Oracle provider.

You can specify one of the following values for this property:

The following table summaries the minimum and maximum acceptable DH key sizes for each of the possible values for the system property jdk.tls.ephemeralDHKeySize:

Value of jdk.tls.ephemeralDHKeySize Undefined legacy matched Integer value (fixed)
Exportable DH key size 512 512 512 512
Non-exportable anonymous cipher suites 1024 768 1024 The fixed key size is specified by a valid integer property value, which must be between 1024 and 2048, inclusively.
Authentication certificate 1024 768 The key size is the same as the authentication certificate, but must be between 1024 bits and 2048 bits, inclusively. However, the SunJCE provider only supports 2048-bit DH keys larger than 1024 bits. Consequently, you may use the values 1024 or 2048 only. The fixed key size is specified by a valid integer property value, which must be between 1024 and 2048, inclusively.

Transport Layer Security (TLS) Renegotiation Issue

In the fall of 2009, a flaw was discovered in the SSL/TLS protocols. A fix to the protocol was developed by the IETF TLS Working Group, and current versions of the JDK contain this fix. This section describes the situation in much more detail, along with interoperability issues when communicating with older implementations that do not contain this protocol fix.

The vulnerability allowed for man-in-the-middle (MITM) attacks where chosen plain text could be injected as a prefix to a TLS connection. This vulnerability did not allow an attacker to decrypt or modify the intercepted network communication once the client and server have successfully negotiated a session between themselves.

Additional information is available at CVE-2009-3555 (posted on Mitre's Common Vulnerabilities and Exposures List, 2009) and Understanding the TLS Renegotiation Attack (posted on Eric Rescorla's blog, Educated Guesswork, November 5, 2009).

Phased Approach to Fixing This Issue

The fix for this issue was handled in two phases:


Note: Applications that do not require renegotiations are not affected by the Phase 2 default configuration. However applications that require renegotiations (for example, web servers that initially allow for anonymous client browsing, but later require SSL/TLS authenticated clients):


Description of the Phase 2 Fix

The SunJSSE implementation reenables renegotiations by default for connections to peers compliant with RFC 5746. That is, both the client and server must support RFC 5746 in order to securely renegotiate. SunJSSE provides some interoperability modes for connections with peers that have not been upgraded, but users are strongly encouraged to update both their client and server implementations as soon as possible.

With the Phase 2 fix, SunJSSE has three renegotiation interoperability modes. Each mode fully supports the RFC 5746 secure renegotiation, but has these added semantics when communicating with a peer that has not been upgraded:

The three mode distinctions only affect a connection with a peer that has not been upgraded. Ideally, strict (full RFC 5746) mode should be used for all clients and servers; however, it will take some time for all deployed SSL/TLS implementations to support RFC 5746, because the interoperable mode is the current default.

Table 8 contains interoperability information about the modes for various cases in which the client and/or server are either updated to support RFC 5746 or not.

Table 8: Interoperability Information
Client Server Mode
Updated Updated

Secure renegotiation in all modes.

Legacy Footnote 1 Updated
Updated Legacy Footnote 1
  • Strict
    If the server does not respond with the proper RFC 5746 messages, then the client will immediately terminate the connection (SSLHandshakeException or handshake_failure).
  • Interoperable
    Initial connections from legacy servers are allowed (missing RFC 5746 messages), but renegotiations will not be allowed by the server. Footnote 2 Footnote 3
  • Insecure
    Connections and renegotiations with legacy servers are allowed, but are vulnerable to the original MITM attack.
Legacy Footnote 1 Legacy Footnote 1 Existing SSL/TLS behavior, vulnerable to the MITM attack.

Footnote 1 "Legacy" means the original SSL/TLS specifications (that is, not RFC 5746).

Footnote 2 SunJSSE Phase 1 implementations reject renegotiations unless specifically reenabled. If renegotiations are reenabled, then they will be treated as "Legacy" by the peer that is compliant with RFC 5746, because they do not send the proper RFC 5746 messages.

Footnote 3 In SSL/TLS, renegotiations can be initiated by either side. Like the Phase 1 fix, applications communicating with a peer that has not been upgraded in Interoperable mode and that attempt to initiate renegotiation (via SSLSocket.startHandshake() or SSLEngine.beginHandshake()) will receive an SSLHandshakeException (IOException) and the connection will be shut down (handshake_failure). Applications that receive a renegotiation request from a peer that has not been upgraded will respond according to the type of connection in place:

The following system properties are used to set the mode:

Table 9: Values of the System Properties for Setting the Interoperability Mode
Mode allowLegacyHelloMessages allowUnsafeRenegotiation
Strict false false
Interoperable (default) true false
Insecure true true

Caution: Do not reenable the insecure SSL/TLS renegotiation, as this would reestablish the vulnerability.


For information about how to configure a specific mode by setting a system property, see How to Specify a java.lang.System Property.

Workarounds and Alternatives to SSL/TLS Renegotiation

All peers should be updated to RFC 5746-compliant implementation as soon as possible. Even with this RFC 5746 fix, communications with peers that have not been upgraded will be affected if a renegotiation is necessary. Here are a few suggested options:

Implementation Details

RFC 5746 defines two new data structures, which are mentioned here for advanced users:

Either of these can be used to signal that an implementation is RFC 5746-compliant and can perform secure renegotiations. For more relevant technical discussions, see the IETF email discussion from November 2009 to February 2010.

RFC 5746 enables clients to send either an SCSV or RI in the first ClientHello. For maximum interoperability, SunJSSE uses the SCSV by default, as a few TLS/SSL servers do not handle unknown extensions correctly. The presence of the SCSV in the enabled cipher suites (SSLSocket.setEnabledCipherSuites() or SSLEngine.setEnabledCipherSuites()) determines whether the SCSV is sent in the initial ClientHello, or if an RI should be sent instead.

SSLv2 does not support SSL/TLS extensions. If the SSLv2Hello protocol is enabled, then the SCSV is sent in the initial ClientHello.

Description of the Phase 1 fix

As previously mentioned, the Phase 1 Fix was to disable renegotiations by default until a fix compliant with RFC 5746 could be developed. Renegotiations could be reenabled by setting the sun.security.ssl.allowUnsafeRenegotiation system property. The Phase 2 fix uses the same sun.security.ssl.allowUnsafeRenegotiation system property, but also requires it to use RFC 5746 messages.

All applications should upgrade to the Phase 2 RFC 5746 fix as soon as possible.

Hardware Acceleration and Smartcard Support

The Java Cryptography Architecture (JCA) is a set of packages that provides a framework and implementations for encryption, key generation and key agreement, and message authentication code (MAC) algorithms. The SunJSSE provider uses JCA exclusively for all of its cryptographic operations and can automatically take advantage of JCE features and enhancements, including JCA's support for PKCS#11. This support enables the SunJSSE provider to use hardware cryptographic accelerators for significant performance improvements and to use smartcards as keystores for greater flexibility in key and trust management.

Use of hardware cryptographic accelerators is automatic if JCA has been configured to use the Oracle PKCS#11 provider, which in turn has been configured to use the underlying accelerator hardware. The provider must be configured before any other JCA providers in the provider list. For details on how to configure the Oracle PKCS#11 provider, see the PKCS#11 Guide.

Configuring JSSE to Use Smartcards as Keystores and Truststores

Support for PKCS#11 in JCA also enables access to smartcards as a keystore. For details on how to configure the type and location of the keystores to be used by JSSE, see the Customizing JSSE section. To use a smartcard as a keystore or truststore, set the javax.net.ssl.keyStoreType and javax.net.ssl.trustStoreType system properties, respectively, to pkcs11, and set the javax.net.ssl.keyStore and javax.net.ssl.trustStore system properties, respectively, to NONE. To specify the use of a specific provider, use the javax.net.ssl.keyStoreProvider and javax.net.ssl.trustStoreProvider system properties (for example, set them to SunPKCS11-joe). By using these properties, you can configure an application that previously depended on these properties to access a file-based keystore to use a smartcard keystore with no changes to the application.

Some applications request the use of keystores programmatically. These applications can continue to use the existing APIs to instantiate a Keystore and pass it to its key manager and trust manager. If the Keystore instance refers to a PKCS#11 keystore backed by a Smartcard, then the JSSE application will have access to the keys on the smartcard.

Multiple and Dynamic Keystores

smartcards (and other removable tokens) have additional requirements for an X509KeyManager. Different smartcards can be present in a smartcard reader during the lifetime of a Java application, and they can be protected using different passwords.

The java.security.KeyStore.Builder class abstracts the construction and initialization of a KeyStore object. It supports the use of CallbackHandler for password prompting, and its subclasses can be used to support additional features as desired by an application. For example, it is possible to implement a Builder that allows individual KeyStore entries to be protected with different passwords. The javax.net.ssl.KeyStoreBuilderParameters class then can be used to initialize a KeyManagerFactory using one or more of these Builder objects.

A X509KeyManager implementation in the SunJSSE provider called NewSunX509 supports these parameters. If multiple certificates are available, it attempts to pick a certificate with the appropriate key usage and prefers valid to expired certificates.

The following example illustrates how to tell JSSE to use both a PKCS#11 keystore (which might in turn use a smartcard) and a PKCS#12 file-based keystore.

import javax.net.ssl.*;
import java.security.KeyStore.*;
...

// Specify keystore builder parameters for PKCS#11 keystores
Builder scBuilder = Builder.newInstance("PKCS11", null,
    new CallbackHandlerProtection(myGuiCallbackHandler));

// Specify keystore builder parameters for a specific PKCS#12 keystore
Builder fsBuilder = Builder.newInstance("PKCS12", null,
    new File(pkcsFileName), new PasswordProtection(pkcsKsPassword));

// Wrap them as key manager parameters
ManagerFactoryParameters ksParams = new KeyStoreBuilderParameters(
    Arrays.asList(new Builder[] { scBuilder, fsBuilder }) );

// Create KeyManagerFactory
KeyManagerFactory factory = KeyManagerFactory.getInstance("NewSunX509");

// Pass builder parameters to factory
factory.init(ksParams);

// Use factory
SSLContext ctx = SSLContext.getInstance("TLS");
ctx.init(factory.getKeyManagers(), null, null);

Kerberos Cipher Suites

The SunJSSE provider has support for Kerberos cipher suites, as described in RFC 2712. The following cipher suites are supported but not enabled by default:

To enable the use of these cipher suites, you must do so explicitly. For more information, see the API documentation for the SSLEngine.setEnabledCipherSuites() and SSLSocket.setEnabledCipherSuites() methods. As with all other SSL/TLS cipher suites, if a cipher suite is not supported by the peer, then it will not be selected during cipher negotiation. Furthermore, if the application and/or server cannot acquire the necessary Kerberos credentials, then the Kerberos cipher suites also will not be selected.

The following is an example of a TLS client that will only use the TLS_KRB5_WITH_DES_CBC_SHA cipher suite:

// Create socket
SSLSocketFactory sslsf = (SSLSocketFactory) SSLSocketFactory.getDefault();
SSLSocket sslSocket = (SSLSocket) sslsf.createSocket(tlsServer, serverPort);

// Enable only one cipher suite
String enabledSuites[] = { "TLS_KRB5_WITH_DES_CBC_SHA" };
sslSocket.setEnabledCipherSuites(enabledSuites);

Kerberos Requirements

You must have the Kerberos infrastructure set up in your deployment environment before you can use the Kerberos cipher suites with JSSE. In particular, both the TLS client and server must have accounts set up with the Kerberos Key Distribution Center (KDC). At runtime, if one or more of the Kerberos cipher suites have been enabled, then the TLS client and server will acquire their Kerberos credentials associated with their respective account from the KDC. For example, a TLS server running on the machine mach1.imc.org in the Kerberos realm IMC.ORG must have an account with the name host/mach1.imc.org@IMC.ORG and be configured to use the KDC for IMC.ORG. For information about using Kerberos with Java SE, see the Kerberos Requirements document.

An application can acquire its Kerberos credentials by using the Java Authentication and Authorization Service (JAAS) and a Kerberos login module. The JDK comes with a Kerberos login module. You can use the Kerberos cipher suites with JSSE with or without JAAS programming, similar to how you can use the Java Generic Security Services (Java GSS) with or without JAAS programming.

To use the Kerberos cipher suites with JSSE without JAAS programming, you must use the index names com.sun.net.ssl.server or other for the TLS server JAAS configuration entry, and com.sun.net.ssl.client or other for the TLS client, and set the javax.security.auth.useSubjectCredsOnly system property to false. For example, a TLS server that is not using JAAS programming might have the following JAAS configuration file:

    com.sun.net.ssl.server {
      com.sun.security.auth.module.Krb5LoginModule required
            principal="host/mach1.imc.org@IMC.ORG"
            useKeyTab=true
            keyTab=mach1.keytab
            storeKey=true;
    };

An example of how to use Java GSS and Kerberos without JAAS programming is described in the Java GSS Tutorial. You can adapt it to use JSSE by replacing Java GSS calls with JSSE calls.

To use the Kerberos cipher suites with JAAS programming, you can use any index name because your application is responsible for creating the JAAS LoginContext using the index name, and then wrapping the JSSE calls inside of a Subject.doAs() or Subject.doAsPrivileged() call. An example of how to use JAAS with Java GSS and Kerberos is described in the Java GSS Tutorial. You can adapt it to use JSSE by replacing Java GSS calls with JSSE calls.

If you have trouble using or configuring the JSSE application to use Kerberos, see the Troubleshooting section of the Java GSS Tutorial.

Peer Identity Information

To determine the identity of the peer of an SSL connection, use the getPeerPrincipal() method in the following classes:

Similarly, to get the identity that was sent to the peer (to identify the local entity), use the getLocalPrincipal() method in these classes. For X509-based cipher suites, these methods will return an instance of javax.security.auth.x500.X500Principal; for Kerberos cipher suites, these methods will return an instance of javax.security.auth.kerberos.KerberosPrincipal.

JSSE applications use getPeerCertificates() and similar methods in javax.net.ssl.SSLSession, javax.net.ssl.HttpsURLConnection, and javax.net.HandshakeCompletedEvent classes to obtain information about the peer. When the peer does not have any certificates, SSLPeerUnverifiedException is thrown.

If the application must determine only the identity of the peer or identity sent to the peer, then it should use the getPeerPrincipal() and getLocalPrincipal() methods, respectively. It should use getPeerCertificates() and getLocalCertificates() methods only if it must examine the contents of those certificates. Furthermore, the application must be prepared to handle the case where an authenticated peer might not have any certificate.

Security Manager

When the security manager has been enabled, in addition to the SocketPermission needed to communicate with the peer, a TLS client application that uses the Kerberos cipher suites also needs the following permission:

javax.security.auth.kerberos.ServicePermission(serverPrincipal, "initiate");

In the preceding code, serverPrincipal is the Kerberos principal name of the TLS server that the TLS client will be communicating with (such as host/mach1.imc.org@IMC.ORG). A TLS server application needs the following permission:

javax.security.auth.kerberos.ServicePermission(serverPrincipal, "accept");

In the preceding code, serverPrincipal is the Kerberos principal name of the TLS server (such as host/mach1.imc.org@IMC.ORG). If the server or client must contact the KDC (for example, if its credentials are not cached locally), then it also needs the following permission:

javax.security.auth.kerberos.ServicePermission(tgtPrincipal, "initiate");
In the preceding code, tgtPrincipal is the principal name of the KDC (such as krbtgt/IMC.ORG@IMC.ORG).

Additional Keystore Formats (PKCS12)

The PKCS#12 (Personal Information Exchange Syntax Standard) specifies a portable format for storage and/or transport of a user's private keys, certificates, miscellaneous secrets, and other items. The SunJSSE provider supplies a complete implementation of the PKCS12 java.security.KeyStore format for reading and writing PKCS12 files. This format is also supported by other toolkits and applications for importing and exporting keys and certificates, such as Netscape/Mozilla, Microsoft's Internet Explorer, and OpenSSL. For example, these implementations can export client certificates and keys into a file using the .p12 file name extension.

With the SunJSSE provider, you can access PKCS12 keys through the KeyStore API with a keystore type of PKCS12. In addition, you can list the installed keys and associated certificates by using the keytool command with the -storetype option set to pkcs12. For more information about keytool, see Security Tools.

Server Name Indication (SNI) Extension

The SNI extension is a feature that extends the SSL/TLS protocols to indicate what server name the client is attempting to connect to during handshaking. Servers can use server name indication information to decide if specific SSLSocket or SSLEngine instances should accept a connection. For example, when multiple virtual or name-based servers are hosted on a single underlying network address, the server application can use SNI information to determine whether this server is the exact server that the client wants to access. Instances of this class can be used by a server to verify the acceptable server names of a particular type, such as host names. For more information, see section 3 of TLS Extensions (RFC 6066).

Developers of client applications can explicitly set the server name indication using the SSLParameters.setServerNames(List<SNIServerName> serverNames) method. The following example illustrates this functionality:

 
SSLSocketFactory factory = ...
SSLSocket sslSocket = factory.createSocket("172.16.10.6", 443);
// SSLEngine sslEngine = sslContext.createSSLEngine("172.16.10.6", 443);

SNIHostName serverName = new SNIHostName("www.example.com");
List<SNIServerName> serverNames = new ArrayList<>(1);
serverNames.add(serverName);

SSLParameters params = sslSocket.getSSLParameters();
params.setServerNames(serverNames);
sslSocket.setSSLParameters(params);
// sslEngine.setSSLParameters(params);

Developers of server applications can use the SNIMatcher class to decide how to recognize server name indication. The following two examples illustrate this functionality:

Example 1

 
SSLSocket sslSocket = sslServerSocket.accept();

SNIMatcher matcher = SNIHostName.createSNIMatcher("www\\.example\\.(com|org)");
Collection<SNIMatcher> matchers = new ArrayList<>(1);
matchers.add(matcher);

SSLParameters params = sslSocket.getSSLParameters();
params.setSNIMatchers(matchers);
sslSocket.setSSLParameters(params);

Example 2

 
SSLServerSocket sslServerSocket = ...;

SNIMatcher matcher = SNIHostName.createSNIMatcher("www\\.example\\.(com|org)");
Collection<SNIMatcher> matchers = new ArrayList<>(1);
matchers.add(matcher);

SSLParameters params = sslServerSocket.getSSLParameters();
params.setSNIMatchers(matchers);
sslServerSocket.setSSLParameters(params);

SSLSocket sslSocket = sslServerSocket.accept();

The following list provides examples for the behavior of the SNIMatcher when receiving various server name indication requests in the ClientHello message:

For descriptions of new classes that implement the SNI extension, see:

For examples, see Using the Server Name Indication (SNI) Extension.

Troubleshooting

This section contains information for troubleshooting JSSE. First, it provides some common configuration problems and ways to solve them, and then it describes helpful debugging utilities.

Configuration Problems

This section describes some common configuration problems that might arise when you use JSSE.

CertificateException While Handshaking

Problem: When negotiating an SSL connection, the client or server throws a CertificateException.

Cause 1: This is generally caused by the remote side sending a certificate that is unknown to the local side.

Solution 1: The best way to debug this type of problem is to turn on debugging (see Debugging Utilities) and watch as certificates are loaded and when certificates are received via the network connection. Most likely, the received certificate is unknown to the trust mechanism because the wrong trust file was loaded. Refer to the following sections for more information:

Cause 2: The system clock is not set correctly. In this case, the perceived time may be outside the validity period on one of the certificates, and unless the certificate can be replaced with a valid one from a truststore, the system must assume that the certificate is invalid, and therefore throw the exception.

Solution 2: Correct the system clock time.

java.security.KeyStoreException: TrustedCertEntry Not Supported

Problem: Attempt to store trusted certificates in PKCS12 keystore throws java.security.KeyStoreException: TrustedCertEntry not supported.

Cause: Storing trusted certificates in a PKCS12 keystore is not supported. PKCS12 is mainly used to deliver private keys with the associated certificate chains. It does not have any notion of "trusted" certificates. In terms of interoperability, other PKCS12 vendors have the same restriction. Browsers such as Mozilla and Internet Explorer do not accept a PKCS12 file with only trusted certificates.

Solution: Use the JKS keystore for storing trusted certificates.

Runtime Exception: SSL Service Not Available

Problem: When running a program that uses JSSE, an exception occurs indicating that an SSL service is not available. For example, an exception similar to one of the following is thrown:

    Exception in thread "main" java.net.SocketException:
        no SSL Server Sockets
    
    Exception in thread "main":
        SSL implementation not available

Cause: There was a problem with SSLContext initialization, for example, due to an incorrect password on a keystore or a corrupted keystore (a JDK vendor once shipped a keystore in an unknown format, and that caused this type of error).

Solution: Check initialization parameters. Ensure that any keystores specified are valid and that the passwords specified are correct. One way that you can check this is by trying to use the keytool command-line utility to examine the keystores and the relevant contents.

Runtime Exception: "No available certificate corresponding to the SSL cipher suites which are enabled"

Problem: When trying to run a simple SSL server program, the following exception is thrown:

    Exception in thread "main" javax.net.ssl.SSLException:
        No available certificate corresponding to the SSL cipher suites which are enabled...

Cause: Various cipher suites require certain types of key material. For example, if an RSA cipher suite is enabled, then an RSA keyEntry must be available in the keystore. If no such key is available, then this cipher suite cannot be used. This exception is thrown if there are no available key entries for all of the cipher suites enabled.

Solution: Create key entries for the various cipher suite types, or use an anonymous suite. Anonymous cipher suites are inherently dangerous because they are vulnerable to MITM (man-in-the-middle) attacks. For more information, see RFC 2246.

Refer to the following sections to learn how to pass the correct keystore and certificates:

Runtime Exception: No Cipher Suites in Common

Problem 1: When handshaking, the client and/or server throw this exception.

Cause 1: Both sides of an SSL connection must agree on a common cipher suite. If the intersection of the client's cipher suite set with the server's cipher suite set is empty, then you will see this exception.

Solution 1: Configure the enabled cipher suites to include common cipher suites, and be sure to provide an appropriate keyEntry for asymmetric cipher suites. Also see Runtime Exception: "No available certificate..." in this section.)

Problem 2: When using Netscape Navigator or Microsoft Internet Explorer to access files on a server that only has DSA-based certificates, a runtime exception occurs indicating that there are no cipher suites in common.

Cause 2: By default, keyEntries created with keytool use DSA public keys. If only DSA keyEntries exist in the keystore, then only DSA-based cipher suites can be used. By default, Navigator and Internet Explorer send only RSA-based cipher suites. Because the intersection of client and server cipher suite sets is empty, this exception is thrown.

Solution 2: To interact with Navigator or Internet Explorer, you should create certificates that use RSA-based keys. To do this, specify the -keyalg RSA option when using keytool. For example:

    keytool -genkeypair -alias duke -keystore testkeys -keyalg rsa

Slowness of the First JSSE Access

Problem: JSSE seems to stall on first access.

Cause: JSSE must have a secure source of random numbers. The initialization takes a while.

Solution: Provide an alternative generator of random numbers, or initialize ahead of time when the overhead will not be noticed:

SecureRandom sr = new SecureRandom();
sr.nextInt();
SSLContext.init(..., ..., sr);

The java-home/lib/security/java.security file also provides a way to specify the source of seed data for SecureRandom. See the contents of the file for more information.

Code Using HttpsURLConnection Class Throws ClassCastException in JSSE 1.0.x

Problem: The following code snippet was written using com.sun.net.ssl.HttpsURLConnection in JSSE 1.0.x:

import com.sun.net.ssl.*;
...deleted...
HttpsURLConnection urlc = new URL("https://example.com/").openConnection();

When running under JSSE 1.0.x, this code returns a javax.net.ssl.HttpsURLConnection object and throws a ClassCastException.

Cause: By default, opening an HTTPS URL will create a javax.net.ssl.HttpsURLConnection.

Solution: Previous releases of the JDK (release 6 and earlier) did not ship with an HTTPS URL implementation. The JSSE 1.0.x implementation did provide such an HTTPS URL handler, and the installation guide described how to set the URL handler search path to obtain a JSSE 1.0.x com.sun.net.ssl.HttpsURLConnection implementation.

In the JDK, there is an HTTPS handler in the default URL handler search path. It returns an instance of javax.net.ssl.HttpsURLConnection. By prepending the old JSSE 1.0.x implementation path to the URL search path via the java.protocol.handler.pkgs variable, you can still obtain a com.sun.net.ssl.HttpsURLConnection, and the code will no longer throw cast exceptions.

See the following examples:
    % java -Djava.protocol.handler.pkgs=com.sun.net.ssl.internal.www.protocol YourClass
    System.setProperty("java.protocol.handler.pkgs", "com.sun.net.ssl.internal.www.protocol");

Socket Disconnected After Sending ClientHello Message

Problem: A socket attempts to connect, sends a ClientHello message, and is immediately disconnected.

Cause: Some SSL/TLS servers will disconnect if a ClientHello message is received in a format they do not understand or with a protocol version number that they do not support.

Solution: Try adjusting the enabled protocols on the client side. This involves modifying or invoking some of the following system properties and methods:

Some older server implementations speak only SSLv3 and do not understand TLS. Ideally, these implementations should negotiate to SSLv3, but some simply hang up. For backwards compatibility, some SSL/TLS implementations (such as SunJSSE) can send SSLv3/TLS ClientHello messages encapsulated in an SSLv2 ClientHello packet. The SunJSSE provider supports this feature. (See the section Protocols, which lists the protocols that are enabled by default for the SunJSSE provider.) If you want to use this feature, add the SSLv2Hello protocol to the enabled protocol list, if necessary.

Similarly, some other older server implementations can speak to TLSv1 but do not understand TLSv1.1 or TLSv1.2. In this situation, consider using a SSL/TLS version fallback scheme:

  1. Fall back from TLSv1.2 to TLSv1.1 if the server does not understand TLSv1.2.
  2. Fall back from TLSv1.1 to TLSv1.0 if the previous step does not work.
  3. Fall back from TLSv1.0 to SSLv3.0 if the previous step does not work.

For example, if the enabled protocol list on the client is SSLv3, TLSv1, TLSv1.1, and TLSv1.2, a typical SSL/TLS version fallback scheme may look like:

  1. Try to connect to server. If server rejects the SSL/TLS connection request immediately, go to step 2.
  2. Try the version fallback scheme by removing the highest protocol version (for example, TLSv1.2 for the first failure) in the enabled protocol list.
  3. Try to connect to the server again. If server rejects the connection, go to step 2 unless there is no version to which the server can fall back.
  4. If the connection fails and SSLv2Hello is not on the enabled protocol list, restore the enable protocol list and enable SSLv2Hello. (For example, the enable protocol list should be SSLv2Hello, SSLv3, TLSv1, TLSv1.1, and TLSv1.2.) Start again from step 1.

Note: A fallback to a previous version normally means security strength downgrading to a weaker protocol. It is not suggested to use a fallback scheme unless it is really necessary, and you clearly know that the server does not support a higher protocol version.

SunJSSE Cannot Find a JCA Provider That Supports a Required Algorithm and Causes a NoSuchAlgorithmException

Problem: A handshake is attempted and fails when it cannot find a required algorithm. Examples might include:

Exception in thread ...deleted...
    ...deleted...
    Caused by java.security.NoSuchAlgorithmException: Cannot find any
        provider supporting RSA/ECB/PKCS1Padding
or
Caused by java.security.NoSuchAlgorithmException: Cannot find any
    provider supporting AES/CBC/NoPadding

Cause: SunJSSE uses JCE for all its cryptographic algorithms. By default, the Oracle JDK will use the Standard Extension ClassLoader to load the SunJCE provider located in java-home/lib/ext/sunjce_provider.jar. If the file cannot be found or loaded, or if the SunJCE provider has been deregistered from the Provider mechanism and an alternative implementation from JCE is not available, then this exception will be thrown.

Solution: Ensure that the SunJCE is available by checking that the file is loadable and that the provider is registered with the Provider interface. Try to run the following code in the context of your SSL connection:

import javax.crypto.*;

System.out.println("=====Where did you get AES=====");
Cipher c = Cipher.getInstance("AES/CBC/NoPadding");
System.out.println(c.getProvider());

FailedDownloadException Thrown When Trying to Obtain Application Resources from Web Server over SSL

Problem: If you receive a com.sun.deploy.net.FailedDownloadException when trying to obtain application resources from your web server over SSL, and your web server uses the virtual host with Server Name Indication (SNI) extension (such as Apache HTTP Server), then you may have not configured your web server correctly.

Cause: Because Java SE 7 supports the SNI extension in the JSSE client, the requested host name of the virtual server is included in the first message sent from the client to the server during the SSL handshake. The server may deny the client's request for a connection if the requested host name (the server name indication) does not match the expected server name, which should be specified in the virtual host's configuration. This triggers an SSL handshake unrecognized name alert, which results in a FailedDownloadException being thrown.

Solution: To better diagnose the problem, enable tracing through the Java Console. See Tracing and Logging for more information. If the cause of the problem is javax.net.ssl.SSLProtocolException: handshake alert: unrecognized_name, it is likely that the virtual host configuration for SNI is incorrect. If you are using Apache HTTP Server, see Name-based Virtual Host Support for information about configuring virtual hosts. In particular, ensure that the ServerName directive is configured properly in a <VirtualHost> block.

For more information, see the following:

Debugging Utilities

JSSE provides dynamic debug tracing support. This is similar to the support used for debugging access control failures in the Java SE platform. The generic Java dynamic debug tracing support is accessed with the java.security.debug system property, whereas the JSSE-specific dynamic debug tracing support is accessed with the javax.net.debug system property.


Note: The debug utility is not an officially supported feature of JSSE.


To view the options of the JSSE dynamic debug utility, use the following command-line option on the java command:

-Djavax.net.debug=help

Note: If you specify the value help with either dynamic debug utility when running a program that does not use any classes that the utility was designed to debug, you will not get the debugging options.


The following complete example shows how to get a list of the debug options for an application named MyApp that uses some of the JSSE classes:

java -Djavax.net.debug=help MyApp

MyApp will not run after the debug help information is printed, as the help code causes the application to exit.

Current options are:

all        turn on all debugging
ssl        turn on ssl debugging

The following can be used with ssl:
    record          enable per-record tracing
    handshake       print each handshake message
    keygen          print key generation data
    session         print session activity
    defaultctx      print default SSL initialization
    sslctx          print SSLContext tracing
    sessioncache    print session cache tracing
    keymanager      print key manager tracing
    trustmanager    print trust manager tracing

handshake debugging can be widened with:
    data            hex dump of each handshake message
    verbose         verbose handshake message printing

record debugging can be widened with:
    plaintext       hex dump of record plaintext
    packet          print raw SSL/TLS packets

The javax.net.debug property value must be either all or ssl, optionally followed by debug specifiers. You can use one or more options. You do not have to have a separator between options, although a separator such as a colon (:) or a comma (,) helps readability. It does not matter what separators you use, and the ordering of the option keywords is also not important.

For an introduction to reading this debug information, see the guide, Debugging SSL/TLS Connections.

The following are examples of using the javax.net.debug property:

Code Examples

The following code examples are included in this section:

Converting an Unsecure Socket to a Secure Socket

This section provides examples of source code that illustrate how to use JSSE to convert an unsecure socket connection to a secure socket connection. The code in this section is excerpted from the book Java SE 6 Network Security by Marco Pistoia, et. al.

First, "Socket Example Without SSL" shows sample code that can be used to set up communication between a client and a server using unsecure sockets. This code is then modified in "Socket Example with SSL" to use JSSE to set up secure socket communication.

Socket Example Without SSL

The following examples demonstrates server-side and client-side code for setting up an unsecure socket connection.

In a Java program that acts as a server and communicates with a client using sockets, the socket communication is set up with code similar to the following:

    import java.io.*;
    import java.net.*;
    
    . . .
    
    int port = availablePortNumber;
    
    ServerSocket s;
    
    try {
        s = new ServerSocket(port);
        Socket c = s.accept();
    
        OutputStream out = c.getOutputStream();
        InputStream in = c.getInputStream();
    
        // Send messages to the client through
        // the OutputStream
        // Receive messages from the client
        // through the InputStream
    } catch (IOException e) { }

The client code to set up communication with a server using sockets is similar to the following:

    import java.io.*;
    import java.net.*;
    
    . . .
    
    int port = availablePortNumber;
    String host = "hostname";
    
    try {
        s = new Socket(host, port);
    
        OutputStream out = s.getOutputStream();
        InputStream in = s.getInputStream();
    
        // Send messages to the server through
        // the OutputStream
        // Receive messages from the server
        // through the InputStream
    } catch (IOException e) { }

Socket Example with SSL

The following examples demonstrate server-side and client-side code for setting up a secure socket connection.

In a Java program that acts as a server and communicates with a client using secure sockets, the socket communication is set up with code similar to the following. Differences between this program and the one for communication using unsecure sockets are highlighted in bold.

    import java.io.*;
    import javax.net.ssl.*;
    
    . . .
    
    int port = availablePortNumber;
    
    SSLServerSocket s;
    
    try {
        SSLServerSocketFactory sslSrvFact =
            (SSLServerSocketFactory)SSLServerSocketFactory.getDefault();
        s = (SSLServerSocket)sslSrvFact.createServerSocket(port);
    
        SSLSocket c = (SSLSocket)s.accept();
    
        OutputStream out = c.getOutputStream();
        InputStream in = c.getInputStream();
    
        // Send messages to the client through
        // the OutputStream
        // Receive messages from the client
        // through the InputStream
    }
    
    catch (IOException e) {
    }

The client code to set up communication with a server using secure sockets is similar to the following, where differences with the unsecure version are highlighted in bold:

    import java.io.*;
    import javax.net.ssl.*;
    
    . . .
    
    int port = availablePortNumber;
    String host = "hostname";
    
    try {
        SSLSocketFactory sslFact =
            (SSLSocketFactory)SSLSocketFactory.getDefault();
        SSLSocket s = (SSLSocket)sslFact.createSocket(host, port);
    
        OutputStream out = s.getOutputStream();
        InputStream in = s.getInputStream();
    
        // Send messages to the server through
        // the OutputStream
        // Receive messages from the server
        // through the InputStream
    }
    
    catch (IOException e) {
    }

Running the JSSE Sample Code

The JSSE sample programs illustrate how to use JSSE to:

When you use the sample code, be aware that the sample programs are designed to illustrate how to use JSSE. They are not designed to be robust applications.


Note: Setting up secure communications involves complex algorithms. The sample programs provide no feedback during the setup process. When you run the programs, be patient: you may not see any output for a while. If you run the programs with the javax.net.debug system property set to all, you will see more feedback. For an introduction to reading this debug information, see the guide, Debugging SSL/TLS Connections.


Where to Find the Sample Code

Most of the sample code is located in the samples subdirectory of the same directory as that containing the document you are reading. Follow that link to see a listing of all the sample code files and text files. That page also provides a link to a ZIP file that you can download to obtain all the sample code files, which is helpful if you are viewing this documentation from the web.

The following sections describe the samples. For more information, see README.txt.

Sample Code Illustrating a Secure Socket Connection Between a Client and a Server

The sample programs in the samples/sockets directory illustrate how to set up a secure socket connection between a client and a server.

When running the sample client programs, you can communicate with an existing server, such as a commercial web server, or you can communicate with the sample server program, ClassFileServer. You can run the sample client and the sample server programs on different machines connected to the same network, or you can run them both on one machine but from different terminal windows.

All the sample SSLSocketClient* programs in the samples/sockets/client directory (and URLReader* programs described in Sample Code Illustrating HTTPS Connections) can be run with the ClassFileServer sample server program. An example of how to do this is shown in Running SSLSocketClientWithClientAuth with ClassFileServer. You can make similar changes to run URLReader, SSLSocketClient, or SSLSocketClientWithTunneling with ClassFileServer.

If an authentication error occurs during communication between the client and the server (whether using a web server or ClassFileServer), it is most likely because the necessary keys are not in the truststore (trust key database). For example, the ClassFileServer uses a keystore called testkeys containing the private key for localhost as needed during the SSL handshake. The testkeys keystore is included in the same samples/sockets/server directory as the ClassFileServer source. If the client cannot find a certificate for the corresponding public key of localhost in the truststore it consults, then an authentication error will occur. Be sure to use the samplecacerts truststore (which contains the public key and certificate of the localhost), as described in the next section.

Configuration Requirements

When running the sample programs that create a secure socket connection between a client and a server, you will need to make the appropriate certificates file (truststore) available. For both the client and the server programs, you should use the certificates file samplecacerts from the samples directory. Using this certificates file will allow the client to authenticate the server. The file contains all the common Certificate Authority (CA) certificates shipped with the JDK (in the cacerts file), plus a certificate for localhost needed by the client to authenticate localhost when communicating with the sample server ClassFileServer. The ClassFileServer uses a keystore containing the private key for localhost that corresponds to the public key in samplecacerts.

To make the samplecacerts file available to both the client and the server, you can either copy it to the file java-home/lib/security/jssecacerts, rename it to cacerts, and use it to replace the java-home/lib/security/cacerts file, or add the following option to the command line when running the java command for both the client and the server:

-Djavax.net.ssl.trustStore=path_to_samplecacerts_file

For more information about java-home, see The JRE Installation Directory.

The password for the samplecacerts truststore is changeit. You can substitute your own certificates in the samples by using the keytool utility.

If you use a browser, such as Netscape Navigator or Microsoft's Internet Explorer, to access the sample SSL server provided in the ClassFileServer example, then a dialog box may pop up with the message that it does not recognize the certificate. This is normal because the certificate used with the sample programs is self-signed and is for testing only. You can accept the certificate for the current session. After testing the SSL server, you should exit the browser, which deletes the test certificate from the browser's namespace.

For client authentication, a separate duke certificate is available in the appropriate directories. The public key and certificate is also stored in the samplecacerts file.

Running SSLSocketClient

The SSLSocketClient.java program demonstrates how to create a client that uses an SSLSocket to send an HTTP request and to get a response from an HTTPS server. The output of this program is the HTML source for https://www.verisign.com/index.html.

You must not be behind a firewall to run this program as provided. If you run it from behind a firewall, you will get an UnknownHostException because JSSE cannot find a path through your firewall to www.verisign.com. To create an equivalent client that can run from behind a firewall, set up proxy tunneling as illustrated in the sample program SSLSocketClientWithTunneling.

Running SSLSocketClientWithTunneling

The SSLSocketClientWithTunneling.java program illustrates how to do proxy tunneling to access a secure web server from behind a firewall. To run this program, you must set the following Java system properties to the appropriate values:

java -Dhttps.proxyHost=webproxy
-Dhttps.proxyPort=ProxyPortNumber
SSLSocketClientWithTunneling

Note: Proxy specifications with the -D options are optional. Replace webproxy with the name of your proxy host and ProxyPortNumber with the appropriate port number.

The program will return the HTML source file from https://www.verisign.com/index.html.

Running SSLSocketClientWithClientAuth

The SSLSocketClientWithClientAuth.java program shows how to set up a key manager to do client authentication if required by a server. This program also assumes that the client is not outside a firewall. You can modify the program to connect from inside a firewall by following the example in SSLSocketClientWithTunneling.

To run this program, you must specify three parameters: host, port, and requested file path. To mirror the previous examples, you can run this program without client authentication by setting the host to www.verisign.com, the port to 443, and the requested file path to https://www.verisign.com/. The output when using these parameters is the HTML for the website https://www.verisign.com/.

To run SSLSocketClientWithClientAuth to do client authentication, you must access a server that requests client authentication. You can use the sample program ClassFileServer as this server. This is described in the following sections.

Running ClassFileServer

The program referred to herein as ClassFileServer is made up of two files: ClassFileServer.java and ClassServer.java.

To execute them, run ClassFileServer.class, which requires the following parameters:


Note: The TLS and true parameters are optional. If you omit them, indicating that an ordinary (not TLS) file server should be used, without authentication, then nothing happens. This is because one side (the client) is trying to negotiate with TLS, while the other (the server) is not, so they cannot communicate.


Note: The server expects GET requests in the form GET /path_to_file.


Running SSLSocketClientWithClientAuth with ClassFileServer

You can use the sample programs SSLSocketClientWithClientAuth and ClassFileServer to set up authenticated communication, where the client and server are authenticated to each other. You can run both sample programs on different machines connected to the same network, or you can run them both on one machine but from different terminal windows or command prompt windows. To set up both the client and the server, do the following:

  1. Run the program ClassFileServer from one machine or terminal window, as described in Running ClassFileServer.
  2. Run the program SSLSocketClientWithClientAuth on another machine or terminal window. SSLSocketClientWithClientAuth requires the following parameters:
    • host is the host name of the machine that you are using to run ClassFileServer.
    • port is the same port that you specified for ClassFileServer.
    • requestedfilepath indicates the path to the file that you want to retrieve from the server. You must give this parameter as /filepath. Forward slashes are required in the file path because it is used as part of a GET statement, which requires forward slashes regardless of what type of operating system you are running. The statement is formed as follows:

                                      "GET " + requestedfilepath + " HTTP/1.0"
                                      
      

Note: You can modify the other SSLClient* applications' GET commands to connect to a local machine running ClassFileServer.

Sample Code Illustrating HTTPS Connections

There are two primary APIs for accessing secure communications through JSSE. One way is through a socket-level API that can be used for arbitrary secure communications, as illustrated by the SSLSocketClient, SSLSocketClientWithTunneling, and SSLSocketClientWithClientAuth (with and without ClassFileServer) sample programs.

A second, and often simpler, way is through the standard Java URL API. You can communicate securely with an SSL-enabled web server by using the HTTPS URL protocol or scheme using the java.net.URL class.

Support for HTTPS URL schemes is implemented in many of the common browsers, which allows access to secured communications without requiring the socket-level API provided with JSSE.

An example URL is https://www.verisign.com.

The trust and key management for the HTTPS URL implementation is environment-specific. The JSSE implementation provides an HTTPS URL implementation. To use a different HTTPS protocol implementation, set the java.protocol.handler.pkgs system property to the package name. See the java.net.URL class documentation for details.

The samples that you can download with JSSE include two sample programs that illustrate how to create an HTTPS connection. Both of these sample programs (URLReader.java and URLReaderWithOptions.java) are in the samples/urls directory.

Running URLReader

The URLReader.java program illustrates using the URL class to access a secure site. The output of this program is the HTML source for https://www.verisign.com/. By default, the HTTPS protocol implementation included with JSSE is used. To use a different implementation, set the system property java.protocol.handler.pkgs value to be the name of the package containing the implementation.

If you are running the sample code behind a firewall, then you must set the https.proxyHost and https.proxyPort system properties. For example, to use the proxy host "webproxy" on port 8080, you can use the following options for the java command:

-Dhttps.proxyHost=webproxy
-Dhttps.proxyPort=8080

Alternatively, you can set the system properties within the source code with the java.lang.System method setProperty(). For example, instead of using the command-line options, you can include the following lines in your program:

System.setProperty("java.protocol.handler.pkgs", "com.ABC.myhttpsprotocol");

System.setProperty("https.proxyHost", "webproxy");

System.setProperty("https.proxyPort", "8080");

Running URLReaderWithOptions

The URLReaderWithOptions.java program is essentially the same as the URLReader.java program, except that it allows you to optionally input any or all of the following system properties as arguments to the program when you run it:

To run URLReaderWithOptions, enter the following command:

java URLReaderWithOptions [-h proxyhost -p proxyport] [-k protocolhandlerpkgs] [-c ciphersarray]

Note: Multiple protocol handlers can be included in the protocolhandlerpkgs argument as a list with items separated by vertical bars. Multiple SSL cipher suite names can be included in the ciphersarray argument as a list with items separated by commas. The possible cipher suite names are the same as those returned by the SSLSocket.getSupportedCipherSuites() method. The suite names are taken from the SSL and TLS protocol specifications.

You need a protocolhandlerpkgs argument only if you want to use an HTTPS protocol handler implementation other than the default one provided by Oracle.

If you are running the sample code behind a firewall, then you must include arguments for the proxy host and the proxy port. Additionally, you can include a list of cipher suites to enable.

Here is an example of running URLReaderWithOptions and specifying the proxy host "webproxy" on port 8080:

java URLReaderWithOptions -h webproxy -p 8080

Sample Code Illustrating a Secure RMI Connection

The sample code in the samples/rmi directory illustrates how to create a secure Java Remote Method Invocation (RMI) connection. The sample code is based on an RMI example that is basically a "Hello World" example modified to install and use a custom RMI socket factory.

For more information about Java RMI, see the Java RMI documentation. This web page points to Java RMI tutorials and other information about Java RMI.

Sample Code Illustrating the Use of an SSLEngine

SSLEngine gives application developers flexibility when choosing I/O and compute strategies. Rather than tie the SSL/TLS implementation to a specific I/O abstraction (such as single-threaded SSLSockets), SSLEngine removes the I/O and compute constraints from the SSL/TLS implementation.

As mentioned earlier, SSLEngine is an advanced API, and is not appropriate for casual use. Some introductory sample code is provided here that helps illustrate its use. The first demo removes most of the I/O and threading issues, and focuses on many of the SSLEngine methods. The second demo is a more realistic example showing how SSLEngine might be combined with Java NIO to create a rudimentary HTTP/HTTPS server.

Running SSLEngineSimpleDemo

The SSLEngineSimpleDemo is a very simple application that focuses on the operation of the SSLEngine while simplifying the I/O and threading issues. This application creates two SSLEngine objects that exchange SSL/TLS messages via common ByteBuffer objects. A single loop serially performs all of the engine operations and demonstrates how a secure connection is established (handshaking), how application data is transferred, and how the engine is closed.

The SSLEngineResult provides a great deal of information about the current state of the SSLEngine. This example does not examine all of the states. It simplifies the I/O and threading issues to the point that this is not a good example for a production environment; nonetheless, it is useful to demonstrate the overall function of the SSLEngine.

Running the NIO-Based Server

To fully exploit the flexibility provided by SSLEngine, you must first understand complementary APIs, such as I/O and threading models.

An I/O model that large-scale application developers find of use is the NIO SocketChannel. NIO was introduced in part to solve some of the scaling problem inherent in the java.net.Socket API. SocketChannel has many different modes of operation including:

Sample code for a basic HTTP server is provided that not only demonstrates many of the new NIO APIs, but also shows how SSLEngine can be employed to create a secure HTTPS server. The server is not production quality, but does show many of these new APIs in action.

Inside the samples directory is a README.txt file that introduces the server, explains how to build and configure the server, and provides a brief overview of the code layout. The files of most interest for SSLEngine users are ChannelIO.java and ChannelIOSecure.java.


Note: The server example discussed in this section is included in the JDK. You can find the code bundled in the jdk-home/samples/nio/server directory.


Creating a Keystore to Use with JSSE

This section demonstrates how you can use the keytool utility to create a simple JKS keystore suitable for use with JSSE. First you make a keyEntry (with public and private keys) in the keystore, and then you make a corresponding trustedCertEntry (public keys only) in a truststore. For client authentication, you follow a similar process for the client's certificates.


Note: Storing trust anchors in PKCS12 is not supported. Users should use JKS for storing trust anchors and PKCS12 for private keys.


Note: It is beyond the scope of this example to explain each step in detail. For more information, see the keytool documentation for Solaris, Linux, or Mac OS X or Microsoft Windows.

User input is shown in bold.

  1. Create a new keystore and self-signed certificate with corresponding public and private keys.

        % keytool -genkeypair -alias duke -keyalg RSA -validity 7 -keystore keystore 
        
        Enter keystore password:  password
        What is your first and last name?
        [Unknown]:  Duke
        What is the name of your organizational unit?
        [Unknown]:  Java Software
        What is the name of your organization?
        [Unknown]:  Oracle, Inc.
        What is the name of your City or Locality?
        [Unknown]:  Palo Alto
        What is the name of your State or Province?
        [Unknown]:  CA
        What is the two-letter country code for this unit?
        [Unknown]:  US
        Is CN=Duke, OU=Java Software, O="Oracle, Inc.",
        L=Palo Alto, ST=CA, C=US correct?
        [no]:  yes
        
        Enter key password for <duke>
        (RETURN if same as keystore password):  <CR>
        
    
  2. Examine the keystore. Notice that the entry type is keyEntry, which means that this entry has a private key associated with it).

        % keytool -list -v -keystore keystore
        
        Enter keystore password:  password
        
        Keystore type: jks
        Keystore provider: SUN
        
        Your keystore contains 1 entry
        
        Alias name: duke
        Creation date: Dec 20, 2001
        Entry type: keyEntry
        Certificate chain length: 1
        Certificate[1]:
        Owner: CN=Duke, OU=Java Software, O="Oracle, Inc.",
        L=Palo Alto, ST=CA, C=US
        Issuer: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
        Serial number: 3c22adc1
        Valid from: Thu Dec 20 19:34:25 PST 2001 until: Thu Dec 27 19:34:25 PST 2001
        Certificate fingerprints:
        MD5: F1:5B:9B:A1:F7:16:CF:25:CF:F4:FF:35:3F:4C:9C:F0
        SHA1: B2:00:50:DD:B6:CC:35:66:21:45:0F:96:AA:AF:6A:3D:E4:03:7C:74
        
    
  3. Export and examine the self-signed certificate.

        % keytool -export -alias duke -keystore keystore -rfc -file duke.cer
        Enter keystore password:  password
        Certificate stored in file <duke.cer>
        % cat duke.cer
        -----BEGIN CERTIFICATE-----
        MIICXjCCAccCBDwircEwDQYJKoZIhvcNAQEEBQAwdjELMAkGA1UEBhMCVVMxCzAJBgNVBAgTAkNB
        MRIwEAYDVQQHEwlQYWxvIEFsdG8xHzAdBgNVBAoTFlN1biBNaWNyb3N5c3RlbXMsIEluYy4xFjAU
        BgNVBAsTDUphdmEgU29mdHdhcmUxDTALBgNVBAMTBER1a2UwHhcNMDExMjIxMDMzNDI1WhcNMDEx
        MjI4MDMzNDI1WjB2MQswCQYDVQQGEwJVUzELMAkGA1UECBMCQ0ExEjAQBgNVBAcTCVBhbG8gQWx0
        bzEfMB0GA1UEChMWU3VuIE1pY3Jvc3lzdGVtcywgSW5jLjEWMBQGA1UECxMNSmF2YSBTb2Z0d2Fy
        ZTENMAsGA1UEAxMERHVrZTCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEA1loObJzNXsi5aSr8
        N4XzDksD6GjTHFeqG9DUFXKEOQetfYXvA8F9uWtz8WInrqskLTNzwXgmNeWkoM7mrPpK6Rf5M3G1
        NXtYzvxyi473Gh1h9k7tjJvqSVKO7E1oFkQYeUPYifxmjbSMVirWZgvo2UmA1c76oNK+NhoHJ4qj
        eCUCAwEAATANBgkqhkiG9w0BAQQFAAOBgQCRPoQYw9rWWvfLPQuPXowvFmuebsTc28qI7iFWm6BJ
        TT/qdmzti7B5MHOt9BeVEft3mMeBU0CS2guaBjDpGlf+zsK/UUi1w9C4mnwGDZzqY/NKKWtLxabZ
        5M+4MAKLZ92ePPKGpobM2CPLfM8ap4IgAzCbBKd8+CMp8yFmifze9Q==
        -----END CERTIFICATE-----
        
    

    Alternatively, you could generate a Certificate Signing Request (CSR) with -certreq and send that to a Certificate Authority (CA) for signing, but that is beyond the scope of this example.

  4. Import the certificate into a new truststore.

        % keytool -import -alias dukecert -file duke.cer -keystore truststore
        Enter keystore password:  trustword
        Owner: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
        Issuer: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
        Serial number: 3c22adc1
        Valid from: Thu Dec 20 19:34:25 PST 2001 until: Thu Dec 27 19:34:25 PST 2001
        Certificate fingerprints:
        MD5: F1:5B:9B:A1:F7:16:CF:25:CF:F4:FF:35:3F:4C:9C:F0
        SHA1: B2:00:50:DD:B6:CC:35:66:21:45:0F:96:AA:AF:6A:3D:E4:03:7C:74
        Trust this certificate? [no]:  yes
        Certificate was added to keystore
        
    
  5. Examine the truststore. Note that the entry type is trustedCertEntry, which means that a private key is not available for this entry. It also means that this file is not suitable as a keystore of the KeyManager.

        % keytool -list -v -keystore truststore
        Enter keystore password:  trustword
        
        Keystore type: jks
        Keystore provider: SUN
        
        Your keystore contains 1 entry
        
        Alias name: dukecert
        Creation date: Dec 20, 2001
        Entry type: trustedCertEntry
        
        Owner: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
        Issuer: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
        Serial number: 3c22adc1
        Valid from: Thu Dec 20 19:34:25 PST 2001 until: Thu Dec 27 19:34:25 PST 2001
        Certificate fingerprints:
        MD5: F1:5B:9B:A1:F7:16:CF:25:CF:F4:FF:35:3F:4C:9C:F0
        SHA1: B2:00:50:DD:B6:CC:35:66:21:45:0F:96:AA:AF:6A:3D:E4:03:7C:74
        
    
  6. Now run your applications with the appropriate keystores. Because this example assumes that the default X509KeyManager and X509TrustManager are used, you select the keystores using the system properties described in Customizing JSSE.

        % java -Djavax.net.ssl.keyStore=keystore -Djavax.net.ssl.keyStorePassword=password Server
        
        % java -Djavax.net.ssl.trustStore=truststore -Djavax.net.ssl.trustStorePassword=trustword Client
        
    

Note: This example authenticated the server only. For client authentication, provide a similar keystore for the client's keys and an appropriate truststore for the server.


Using the Server Name Indication (SNI) Extension

This section provides code examples that illustrate how you can use the Server Name Indication (SNI) extension for client-side and server-side applications, and how it can be applied to a virtual infrastructure.

For all examples in this section, to apply the parameters after you set them, call the setSSLParameters(SSLParameters) method on the corresponding SSLSocket, SSLEngine, or SSLServerSocket object.

Typical Client-Side Usage Examples

The following is a list of use cases that require understanding of the SNI extension for developing a client application:

Typical Server-Side Usage Examples

The following is a list of use cases that require understanding of the SNI extension for developing a server application:

Working with Virtual Infrastructures

This section describes how to use the Server Name Indication (SNI) extension from within a virtual infrastructure. It illustrates how to create a parser for ClientHello messages from a socket, provides examples of virtual server dispatchers using SSLSocket and SSLEngine, describes what happens when the SNI extension is not available, and demonstrates how to create a failover SSLContext.

Preparing the ClientHello Parser

Applications must implement an API to parse the ClientHello messages from a socket. The following examples illustrate the SSLCapabilities and SSLExplorer classes that can perform these functions.

SSLCapabilities.java encapsulates the SSL/TLS security capabilities during handshaking (that is, the list of cipher suites to be accepted in an SSL/TLS handshake, the record version, the hello version, and the server name indication). It can be retrieved by exploring the network data of an SSL/TLS connection via the SSLExplorer.explore() method.

SSLExplorer.java explores the initial ClientHello message from a TLS client, but it does not initiate handshaking or consume network data. The SSLExplorer.explore() method parses the ClientHello message, and retrieves the security parameters into SSLCapabilities. The method must be called before handshaking occurs on any TLS connections.

Virtual Server Dispatcher Based on SSLSocket

This section describes the procedure for using a virtual server dispatcher based on SSLSocket.

  1. Register the server name handler.

    At this step, the application may create different SSLContext objects for different server name indications, or link a certain server name indication to a specified virtual machine or distributed system.

    For example, if the server name is www.example.org, then the registered server name handler may be for a local virtual hosting web service. The local virtual hosting web service will use the specified SSLContext. If the server name is www.example.com, then the registered server name handler may be for a virtual machine hosting on 10.0.0.36. The handler may map this connection to the virtual machine.

  2. Create a ServerSocket and accept the new connection.

        ServerSocket serverSocket = new ServerSocket(serverPort);
        Socket socket = serverSocket.accept();
            
    
  3. Read and buffer bytes from the socket input stream, and then explore the buffered bytes.

        InputStream ins = socket.getInputStream();
        
        byte[] buffer = new byte[0xFF];
        int position = 0;
        SSLCapabilities capabilities = null;
        
        // Read the header of TLS record
        while (position < SSLExplorer.RECORD_HEADER_SIZE) {
            int count = SSLExplorer.RECORD_HEADER_SIZE - position;
            int n = ins.read(buffer, position, count);
            if (n < 0) {
                throw new Exception("unexpected end of stream!");
            }
            position += n;
        }
        
        // Get the required size to explore the SSL capabilities
        int recordLength = SSLExplorer.getRequiredSize(buffer, 0, position);
        if (buffer.length < recordLength) {
            buffer = Arrays.copyOf(buffer, recordLength);
        }
        
        while (position < recordLength) {
            int count = recordLength - position;
            int n = ins.read(buffer, position, count);
            if (n < 0) {
                throw new Exception("unexpected end of stream!");
            }
            position += n;
        }
        
        // Explore
        capabilities = SSLExplorer.explore(buffer, 0, recordLength);
        if (capabilities != null) {
            System.out.println("Record version: " + capabilities.getRecordVersion());
            System.out.println("Hello version: " + capabilities.getHelloVersion());
        }
            
    
  4. Get the requested server name from the explored capabilities.

        List<SNIServerName> serverNames = capabilities.getServerNames();
            
    
  5. Look for the registered server name handler for this server name indication.

    If the service of the host name is resident in a virtual machine or another distributed system, then the application must forward the connection to the destination. The application will need to read and write the raw internet data, rather then the SSL application from the socket stream.

        Socket destinationSocket = new Socket(serverName, 443);
        
        // Forward buffered bytes and network data from the current socket to the destinationSocket.
            
    

    If the service of the host name is resident in the same process, and the host name service can use the SSLSocket directly, then the application will need to set the SSLSocket instance to the server:

        // Get service context from registered handler
        // or create the context
        SSLContext serviceContext = ...
        
        SSLSocketFactory serviceSocketFac = serviceContext.getSSLSocketFactory();
        
        // wrap the buffered bytes
        ByteArrayInputStream bais = new ByteArrayInputStream(buffer, 0, position);
        SSLSocket serviceSocket = (SSLSocket)serviceSocketFac.createSocket(socket, bais, true);
        
        // Now the service can use serviceSocket as usual.
        
    

Virtual Server Dispatcher Based on SSLEngine

This section describes the procedure for using a virtual server dispatcher based on SSLEngine.

  1. Register the server name handler.

    At this step, the application may create different SSLContext objects for different server name indications, or link a certain server name indication to a specified virtual machine or distributed system.

    For example, if the server name is www.example.org, then the registered server name handler may be for a local virtual hosting web service. The local virtual hosting web service will use the specified SSLContext. If the server name is www.example.com, then the registered server name handler may be for a virtual machine hosting on 10.0.0.36. The handler may map this connection to the virtual machine.

  2. Create a ServerSocket or ServerSocketChannel and accept the new connection.

        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.bind(...);
        ...
        SocketChannel socketChannel = serverSocketChannel.accept();
            
    
  3. Read and buffer bytes from the socket input stream, and then explore the buffered bytes.

        ByteBuffer buffer = ByteBuffer.allocate(0xFF);
        SSLCapabilities capabilities = null;
        while (true) {
            // ensure the capacity
            if (buffer.remaining() == 0) {
                ByteBuffer oldBuffer = buffer;
                buffer = ByteBuffer.allocate(buffer.capacity() + 0xFF);
                buffer.put(oldBuffer);
            }
    
            int n = sc.read(buffer);
            if (n < 0) {
                throw new Exception("unexpected end of stream!");
            }
    
            int position = buffer.position();
            buffer.flip();
            capabilities = explorer.explore(buffer);
            buffer.rewind();
            buffer.position(position);
            buffer.limit(buffer.capacity());
            if (capabilities != null) {
                System.out.println("Record version: " +
                        capabilities.getRecordVersion());
                System.out.println("Hello version: " +
                        capabilities.getHelloVersion());
                break;
            }
        }
        buffer.flip();  // reset the buffer position and limitation 
            
    
  4. Get the requested server name from the explored capabilities.

        List<SNIServerName> serverNames = capabilities.getServerNames();
            
    
  5. Look for the registered server name handler for this server name indication.

    If the service of the host name is resident in a virtual machine or another distributed system, then the application must forward the connection to the destination. The application will need to read and write the raw internet data, rather then the SSL application from the socket stream.

        Socket destinationSocket = new Socket(serverName, 443);
        
        // Forward buffered bytes and network data from the current socket to the destinationSocket.
            
    

    If the service of the host name is resident in the same process, and the host name service can use the SSLEngine directly, then the application will simply feed the net data to the SSLEngine instance:

        // Get service context from registered handler
        // or create the context
        SSLContext serviceContext = ...
        
        SSLEngine serviceEngine = serviceContext.createSSLEngine();
    
        // Now the service can use the buffered bytes and other byte buffer as usual.
        
    

No SNI Extension Available

If there is no server name indication in a ClientHello message, then there is no way to select the proper service according to SNI. For such cases, the application may need to specify a default service, so that the connection can be delegated to it if there is no server name indication.

Failover SSLContext

The SSLExplorer.explore() method does not check the validity of SSL/TLS contents. If the record format does not comply with SSL/TLS specification, or the explore() method is invoked after handshaking has started, then the method may throw an IOException and be unable to produce network data. In such cases, handle the exception thrown by SSLExplorer.explore() by using a failover SSLContext, which is not used to negotiate an SSL/TLS connection, but to close the connection with the proper alert message. The following example illustrates a failover SSLContext. You can find an example of the DenialSNIMatcher class in Case 2 of the Typical Server-Side Usage Examples.

    byte[] buffer = ...       // buffered network data
    boolean failed = true;    // SSLExplorer.explore() throws an exception
    
    SSLContext context = SSLContext.getInstance("TLS");
        // the failover SSLContext
    
    context.init(null, null, null);
    SSLSocketFactory sslsf = context.getSocketFactory();
    ByteArrayInputStream bais = new ByteArrayInputStream(buffer, 0, position);
    SSLSocket sslSocket = (SSLSocket)sslsf.createSocket(socket, bais, true);
    
    SNIMatcher matcher = new DenialSNIMatcher();
    Collection<SNIMatcher> matchers = new ArrayList<>(1);
    matchers.add(matcher);
    SSLParameters params = sslSocket.getSSLParameters();
    params.setSNIMatchers(matchers);    // no recognizable server name
    sslSocket.setSSLParameters(params);
    
    try {
        InputStream sslIS = sslSocket.getInputStream();
        sslIS.read();
    } catch (Exception e) {
        System.out.println("Server exception " + e);
    } finally {
        sslSocket.close();
    }

Appendix A: Standard Names

The JDK Security API requires and uses a set of standard names for algorithms, certificates and keystore types. The specification names previously found here in Appendix A and in the other security specifications (JCA, CertPath) have been combined in the Standard Names document. Specific provider information can be found in the Oracle Provider Documentation.

Appendix B: Provider Pluggability

JSSE is fully pluggable and does not restrict the use of third-party JSSE providers in any way.


Copyright © 1993, 2014, Oracle and/or its affiliates. All rights reserved.