| NetLabel CIPSO/IPv4 Protocol Engine |
| ============================================================================== |
| Paul Moore, paul.moore@hp.com |
| |
| May 17, 2006 |
| |
| * Overview |
| |
| 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, consult '00-INDEX' for the filename. 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()' |
| LSM hook. |
| |
| * Label Translation |
| |
| 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. |