[ 3.5.y.z extended stable ] Patch "netfilter: Validate the sequence number of dataless ACK" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    netfilter: Validate the sequence number of dataless ACK

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From ca3cc257ff68688f45af083c0ad4ed028234a6ac Mon Sep 17 00:00:00 2001
From: Jozsef Kadlecsik <kadlec at blackhole.kfki.hu>
Date: Fri, 31 Aug 2012 09:55:54 +0000
Subject: [PATCH] netfilter: Validate the sequence number of dataless ACK
 packets as well

commit 4a70bbfaef0361d27272629d1a250a937edcafe4 upstream.

We spare nothing by not validating the sequence number of dataless
ACK packets and enabling it makes harder off-path attacks.

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

Signed-off-by: Jozsef Kadlecsik <kadlec at blackhole.kfki.hu>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 net/netfilter/nf_conntrack_proto_tcp.c |   10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index 6638ad5..942a8f3 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -624,15 +624,9 @@ static bool tcp_in_window(const struct nf_conn *ct,
 		ack = sack = receiver->td_end;
 	}

-	if (seq == end
-	    && (!tcph->rst
-		|| (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
+	if (tcph->rst && seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)
 		/*
-		 * Packets contains no data: we assume it is valid
-		 * and check the ack value only.
-		 * However RST segments are always validated by their
-		 * SEQ number, except when seq == 0 (reset sent answering
-		 * SYN.
+		 * RST sent answering SYN.
 		 */
 		seq = end = sender->td_end;

--
1.7.9.5