IPsec Security Associations

An IPsec security association (SA) specifies security properties that are recognized by communicating hosts. A single SA protects data in one direction. The protection is either to a single host or to a group (multicast) address. Because most communication is either peer-to-peer or client-server, two SAs must be present to secure traffic in both directions.

The following three elements uniquely identify an IPsec SA:

• The security protocol (AH or ESP)

• The destination IP address

• The security parameter index (SPI)

The SPI, an arbitrary 32-bit value, is transmitted with an AH or ESP packet. The ipsecah(7P) and ipsecesp(7P) man pages explain the extent of protection that is provided by AH and ESP. An integrity checksum value is used to authenticate a packet. If the authentication fails, the packet is dropped.

Security associations are stored in a security associations database (SADB). A socket-based administrative interface, PF_KEY enables privileged applications to manage the database. For example, the IKE application and the ipseckeys command use the PF_KEY socket interface.

• For a more complete description of the IPsec SADB, see Security Associations Database for IPsec.

• For more information about how to manage the SADB, see the pf_key(7P) man page.

Key Management in IPsec

Security associations (SAs) require keying material for authentication and for encryption. The managing of this keying material is called key management. The Internet Key Exchange (IKE) protocol handles key management automatically. You can also manage keys manually with the ipseckey command.

SAs on IPv4 and IPv6 packets can use either method of key management. Unless you have an overriding reason to use manual key management, IKE is preferred.

The Service Management Facility (SMF) feature of Oracle Solaris provides the following key management services for IPsec:

• svc:/network/ipsec/ike:default service – Is the SMF service for automatic key management. The ike service runs the in.iked daemon to provide automatic key management. For a description of IKE, see Chapter 17, Internet Key Exchange (Overview). For more information about the in.iked daemon, see the in.iked(1M) man page. For information about the ike service, see the IKE Service.

• svc:/network/ipsec/manual-key:default service – Is the SMF service for manual key management. The manual-key service runs the ipseckey command with various options to manage keys manually. For a description of the ipseckey command, see Utilities for SA Generation in IPsec. For a detailed description of the ipseckey command options, see the ipseckey(1M) man page.