|NetLabel CIPSO/IPv4 Protocol Engine
|Paul Moore, firstname.lastname@example.org
|May 17, 2006
|The NetLabel CIPSO/IPv4 protocol engine is based on the IETF Commercial
|IP Security Option (CIPSO) draft from July 16, 1992. A copy of this
|draft can be found in this directory
|(draft-ietf-cipso-ipsecurity-01.txt). While the IETF draft never made
|it to an RFC standard it has become a de-facto standard for labeled
|networking and is used in many trusted operating systems.
|Outbound Packet Processing
|The CIPSO/IPv4 protocol engine applies the CIPSO IP option to packets by
|adding the CIPSO label to the socket. This causes all packets leaving the
|system through the socket to have the CIPSO IP option applied. The socket's
|CIPSO label can be changed at any point in time, however, it is recommended
|that it is set upon the socket's creation. The LSM can set the socket's CIPSO
|label by using the NetLabel security module API; if the NetLabel "domain" is
|configured to use CIPSO for packet labeling then a CIPSO IP option will be
|generated and attached to the socket.
|Inbound Packet Processing
|The CIPSO/IPv4 protocol engine validates every CIPSO IP option it finds at the
|IP layer without any special handling required by the LSM. However, in order
|to decode and translate the CIPSO label on the packet the LSM must use the
|NetLabel security module API to extract the security attributes of the packet.
|This is typically done at the socket layer using the 'socket_sock_rcv_skb()'
|The CIPSO/IPv4 protocol engine contains a mechanism to translate CIPSO security
|attributes such as sensitivity level and category to values which are
|appropriate for the host. These mappings are defined as part of a CIPSO
|Domain Of Interpretation (DOI) definition and are configured through the
|NetLabel user space communication layer. Each DOI definition can have a
|different security attribute mapping table.
|Label Translation Cache
|The NetLabel system provides a framework for caching security attribute
|mappings from the network labels to the corresponding LSM identifiers. The
|CIPSO/IPv4 protocol engine supports this caching mechanism.