ipsecah, AH - IPsec Authentication Header
) provides strong integrity, authentication, and
partial sequence integrity (replay protection) to IP
protects the parts of the IP
datagram that can be predicted by the sender
as it will be received by the receiver. For example, the IP TTL
not a predictable field, and is not protected by AH
is inserted between the IP
header and the transport header. The
transport header can be TCP
, or another IP
tunnels are being used.
AH is implemented as a module that is auto-pushed on top of IP. The entry /dev/ipsecah
is used for tuning AH with ndd(8)
Current authentication algorithms supported include HMAC-MD5 and HMAC-
SHA-1. Each authentication algorithm has its own key size and key format
properties. You can obtain a list of authentication algorithms and their
properties by using the ipsecalgs(8)
command. You can also use the
functions described in the getipsecalgbyname(3NSL)
man page to retrieve
the properties of algorithms.
Without replay protection enabled, AH
is vulnerable to replay attacks. AH
does not protect against eavesdropping. Data protected with AH
still be seen by an adversary.
for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|Interface Stability | Committed |
SEE ALSO getipsecalgbyname(3NSL)
Kent, S. and Atkinson, R. RFC 2402, IP Authentication Header
Internet Society, 1998.
September 25, 2009 IPSECAH(4P)