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Sun Java System Web Server 6.1 SP11 Administrator's Guide

Setting Client Security Requirements

After you have completed the process to secure your servers, you can set additional security requirements for your clients.

Requiring Client Authentication

You can enable the listen sockets for your Administration Server and each server instance to require client authentication. When client authentication is enabled, the client’s certificate is required before the server sends a response to a query.

The Sun Java System Web Server supports authenticating client certificates by matching the CA in the client certificate with a CA trusted for signing client certificates. You can view a list of CAs trusted for signing client certificates the Manage Certificates page under Security in the Administration Server. There are four types of CAs:

You can configure the web server to refuse any client that does not have a client certificate from a trusted CA. To accept or reject trusted CAs, you must have set client trust for the CA. For more information, see Managing Certificates.

The Sun Java System Web Server logs an error, rejects the certificate, and returns a message to the client if the certificate has expired. You can view a list of certificates that have expired in the Administration Servers Manage Certificates page.

You can configure your server to collect information from the client certificate and match it with a user entry in an LDAP directory. This ensures that the client has a valid certificate and an entry in the LDAP directory, and also ensure that the client certificate matches the one in the LDAP directory. To learn how to do this, see Mapping Client Certificates to LDAP.

You can combine client certificates with access control. In addition to being from a trusted CA, the user associated with the certificate must match the access control rules (ACLs). For more information, see Using Access Control Files.

You can also process information from client certificates. For more information, see the Sun Java System Web Server 6.1 SP11 NSAPI Programmer’s Guide.

To Require Client Authentication

To require client authentication, perform the following steps:

ProcedureTo require client authentication

  1. Access either the Administration Server or the Server Manager and choose the Preferences tab.

    From the Server Manager you must first select the server instance from the drop-down list.

  2. Click the Edit Listen Sockets link.

    The Edit Listen Sockets page appears.

  3. Click the Listen Socket Id link corresponding to the listen socket you are requiring client authentication for.

    The Edit Listen Socket page appears.

  4. To require client authenticate for the listen socket, select Required from the Client Authentication drop-down list.

  5. Click OK.

  6. From the Server Manager, click Apply, and then Restart for changes to take effect.

    Note –

    Currently, there is a single certificate trust database per web server instance. All the secure virtual servers running under that server instance share the same list of trusted client CAs. If two virtual servers require different trusted CAs, then these virtual servers should be run in different server instances with separate trust databases.

Mapping Client Certificates to LDAP

This section describes the process followed by the Sun Java System Web Server to map a client certificate to an entry in an LDAP directory.

When the server gets a request from a client, it asks for the client’s certificate before proceeding. Some clients send the client certificate to the server along with the request.

Note –

Before mapping client certificates to LDAP, you need to set up the required ACLs. For more information, see Chapter 10, Controlling Access to Your Server.

The server tries to match the CA to the list of trusted CAs in the Administration Server. If there is no match, the Sun Java System Web Server terminates the connection. If a match occurs, the server continues processing the request.

After verifying that the certificate is from a trusted CA, the server maps the certificate to an LDAP entry using the following methods:

The server uses a certificate mapping file called the certmap.conffile to determine how to do conduct LDAP search. The mapping file provides the server with values to get from the client certificate (such as the end-user’s name and email address). The server uses these values to search for a user entry in the LDAP directory. First the server needs to determine where in the LDAP directory it needs to start its search. The certificate mapping file also tells the server where to start.

Once the server knows where to start its search and what it needs to search for (step 1), it performs the search in the LDAP directory (step 2). If it finds no matching entry or more than one matching entry, and the mapping is not set to verify the certificate, the search fails. For a complete list of the expected search result behavior, see the following Table 6-1. Note that you can specify the expected behavior in an ACL. For example, you can specify that Sun Java System Web Server accepts only you if the certificate match fails. For more information regarding how to set ACL preferences, see Using Access Control Files.

Table 6–1 LDAP Search Results

LDAP Search Result  

Certificate Verification ON  

Certificate Verification OFF  

No entry found 

Authentication fails 

Authentication fails 

Exactly one entry found 

Authentication fails 

Authentication succeeds 

More than one entry found 

Authentication fails 

Authorization fails 

After the server finds a matching entry and certificate in the LDAP directory, it can use that information to process the transaction. For example, some servers use certificate-to-LDAP mapping to determine access to another server.

Using the certmap.conf File

Certificate mapping determines how a server scans user entry in the LDAP directory. You can use the certmap.conf to configure how a certificate, designated by name, is mapped to an LDAP entry. You edit this file and add entries to match the structure of your LDAP directory and to list the certificates you want your users to have. Users can be authenticated based on userid, email, or any other value used in the subjectDN. Specifically, the mapping file defines the following information:

The certificate mapping file is located in the following location:

server_root/userdb/certmap.conf

The file contains one or more named mappings, each applying to a different CA. A mapping has the following syntax:

certmap <name> <issuerDN>

<name>:<property> [<value>]

The first line specifies a name for the entry and the attributes that form the distinguished name found in the CA certificate. You can select any name for the entry. However, the issuerDN must exactly match the issuer DN of the CA that issued the client certificate. For example, the following two issuerDN lines have different space separating the attributes, but the server treats these as two separate entries 

certmap sun1 ou=Sun Certificate Authority,o=Sun, c=US
      certmap sun2 ou=Sun Certificate Authority, o=Sun, c=US
Note –

If you are using the Sun Java System Directory Server and experiencing problems in matching the issuerDN, check the Directory Server error logs for useful information.

The second and subsequent lines in the named mapping match properties with values. The certmap.conf file has six default properties (you can use the certificate API to customize your own properties):

Table 6–2 Attributes for x509v3 Certificates

Attribute  

Description  

c

Country 

o

Organization 

cn

Common name 

l

Location 

st

State 

ou

Organizational unit 

uid

UNIX/Linux userid 

email

Email address 

The attribute names for the filters need to be attribute names from the certificate, not from the LDAP directory. For example, some certificates have an e attribute for the user’s email address; whereas LDAP calls refers to this attribute as mail.

For more information on these properties, refer to the examples described in Sample Mappings.

Creating Custom Properties

You can use the client certificate API to create your own properties. For information on programming and using the client certificate API, see the Sun Java System Web Server 6.1 SP11 NSAPI Programmer’s Guide.

Once you have a custom mapping, you reference the mapping as follows:

<name>:library <path_to_shared_library>
 <name>:InitFn <name_of_init_function>

For example:

certmap default1 o=Sun Microsystems, c=US default1:library /usr/sun/userdb/plugin.so default1:InitFn plugin_init_fn default1:DNComps ou o c default1:FilterComps l default1:verifycert on

Sample Mappings

The certmap.conf file should have at least one entry. The following examples illustrate the different ways you can use the certmap.conf file.

Example #1

This example represents a certmap.conf file with only one “default” mapping:

certmap default defaultdefault:DNComps ou, o, cdefault:FilterComps e, uiddefault:verifycert on

Using this example, the server starts its search at the LDAP branch point containing the entry ou=<orgunit>, o=<org>, c=<country> where the text within <> is replaced with the values from the subject’s DN in the client certificate.

The server then uses the values for email address and userid from the certificate to search for a match in the LDAP directory. When it finds an entry, the server verifies the certificate by comparing the one the client sent to the one stored in the directory.

Example #2

The following example file has two mappings: one for default and another for the US Postal Service (USPS):

certmap default defaultdefault:DNCompsdefault:FilterComps e, uid

certmap usps ou=United States Postal Service, o=usps, c=USusps:DNComps ou,o,cusps:FilterComps eusps:verifycert on

When the server gets a certificate from someone other than the USPS , it uses the default mapping, which starts at the top of the LDAP tree and searches for an entry matching the client’s userid and email address. If the certificate is from the USPS, the server starts its search at the LDAP branch containing the organizational unit and searches for matching email addresses. Note that if the certificate is from the USPS, the server verifies the certificate; other certificates are not verified.

Caution – Caution –

The issuer DN (that is, the CA’s information) in the certificate must be identical to the issuer DN listed in the first line of the mapping. In the previous example, a certificate from an issuer DN that is o=United States Postal Service,c=US will not match because there is not a space between the o and the c attributes.

Example #3

The following example uses the CmapLdapAttr property to scan the LDAP database for the certSubjectDN attribute whose value exactly matches the entire subject DN taken from the client certificate.

certmap myco ou=My Company Inc, o=myco, c=USmyco:CmapLdapAttr certSubjectDNmyco:DNComps o, c myco:FilterComps mail, uid myco:verifycert on

If the client certificate subject is:

uid=Walt Whitman, o=LeavesOfGrass Inc, c=US

the server first searches for entries that contain the following information:

certSubjectDN=uid=Walt Whitman, o=LeavesOfGrass Inc, c=US

If one or more matching entries are found, the server proceeds to verify the entries. If no matching entries are found, the server will use DNComps and FilterComps to search for matching entries. In this example, the server would search for uid=Walt Whitman in all entries under o=LeavesOfGrass Inc, c=US.

Note –

This example assumes the LDAP directory contains entries with the certSubjectDN attribute.