1=================================== 2NetLabel CIPSO/IPv4 Protocol Engine 3=================================== 4 5Paul Moore, paul.moore@hp.com 6 7May 17, 2006 8 9Overview 10======== 11 12The NetLabel CIPSO/IPv4 protocol engine is based on the IETF Commercial 13IP Security Option (CIPSO) draft from July 16, 1992. A copy of this 14draft can be found in this directory 15(draft-ietf-cipso-ipsecurity-01.txt). While the IETF draft never made 16it to an RFC standard it has become a de-facto standard for labeled 17networking and is used in many trusted operating systems. 18 19Outbound Packet Processing 20========================== 21 22The CIPSO/IPv4 protocol engine applies the CIPSO IP option to packets by 23adding the CIPSO label to the socket. This causes all packets leaving the 24system through the socket to have the CIPSO IP option applied. The socket's 25CIPSO label can be changed at any point in time, however, it is recommended 26that it is set upon the socket's creation. The LSM can set the socket's CIPSO 27label by using the NetLabel security module API; if the NetLabel "domain" is 28configured to use CIPSO for packet labeling then a CIPSO IP option will be 29generated and attached to the socket. 30 31Inbound Packet Processing 32========================= 33 34The CIPSO/IPv4 protocol engine validates every CIPSO IP option it finds at the 35IP layer without any special handling required by the LSM. However, in order 36to decode and translate the CIPSO label on the packet the LSM must use the 37NetLabel security module API to extract the security attributes of the packet. 38This is typically done at the socket layer using the 'socket_sock_rcv_skb()' 39LSM hook. 40 41Label Translation 42================= 43 44The CIPSO/IPv4 protocol engine contains a mechanism to translate CIPSO security 45attributes such as sensitivity level and category to values which are 46appropriate for the host. These mappings are defined as part of a CIPSO 47Domain Of Interpretation (DOI) definition and are configured through the 48NetLabel user space communication layer. Each DOI definition can have a 49different security attribute mapping table. 50 51Label Translation Cache 52======================= 53 54The NetLabel system provides a framework for caching security attribute 55mappings from the network labels to the corresponding LSM identifiers. The 56CIPSO/IPv4 protocol engine supports this caching mechanism. 57