netfilter: Mark SYN/ACK packets as invalid from original direction
authorJozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Fri, 31 Aug 2012 09:55:53 +0000 (09:55 +0000)
committerPablo Neira Ayuso <pablo@netfilter.org>
Sun, 9 Sep 2012 20:13:30 +0000 (22:13 +0200)
commit64f509ce71b08d037998e93dd51180c19b2f464c
tree3ccafa55245faaa0580e86f705548bbfe6cf3108
parent0626af3139572610b56376580d11eb65d45d9dd7
netfilter: Mark SYN/ACK packets as invalid from original direction

Clients should not send such packets. By accepting them, we open
up a hole by wich ephemeral ports can be discovered in an off-path
attack.

See: "Reflection scan: an Off-Path Attack on TCP" by Jan Wrobel,
http://arxiv.org/abs/1201.2074

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
net/netfilter/nf_conntrack_proto_tcp.c