1NetLabel CIPSO/IPv4 Protocol Engine
3Paul Moore,
5May 17, 2006
7 * Overview
9The NetLabel CIPSO/IPv4 protocol engine is based on the IETF Commercial IP
10Security Option (CIPSO) draft from July 16, 1992. A copy of this draft can be
11found in this directory, consult '00-INDEX' for the filename. While the IETF
12draft never made it to an RFC standard it has become a de-facto standard for
13labeled networking and is used in many trusted operating systems.
15 * Outbound Packet Processing
17The CIPSO/IPv4 protocol engine applies the CIPSO IP option to packets by
18adding the CIPSO label to the socket. This causes all packets leaving the
19system through the socket to have the CIPSO IP option applied. The socket's
20CIPSO label can be changed at any point in time, however, it is recommended
21that it is set upon the socket's creation. The LSM can set the socket's CIPSO
22label by using the NetLabel security module API; if the NetLabel "domain" is
23configured to use CIPSO for packet labeling then a CIPSO IP option will be
24generated and attached to the socket.
26 * Inbound Packet Processing
28The CIPSO/IPv4 protocol engine validates every CIPSO IP option it finds at the
29IP layer without any special handling required by the LSM. However, in order
30to decode and translate the CIPSO label on the packet the LSM must use the
31NetLabel security module API to extract the security attributes of the packet.
32This is typically done at the socket layer using the 'socket_sock_rcv_skb()'
33LSM hook.
35 * Label Translation
37The CIPSO/IPv4 protocol engine contains a mechanism to translate CIPSO security
38attributes such as sensitivity level and category to values which are
39appropriate for the host. These mappings are defined as part of a CIPSO
40Domain Of Interpretation (DOI) definition and are configured through the
41NetLabel user space communication layer. Each DOI definition can have a
42different security attribute mapping table.
44 * Label Translation Cache
46The NetLabel system provides a framework for caching security attribute
47mappings from the network labels to the corresponding LSM identifiers. The
48CIPSO/IPv4 protocol engine supports this caching mechanism.

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