From patchwork Thu Sep 13 10:54:07 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pablo Neira Ayuso X-Patchwork-Id: 183598 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 10B1F2C034E for ; Thu, 13 Sep 2012 20:59:11 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753811Ab2IMKzc (ORCPT ); Thu, 13 Sep 2012 06:55:32 -0400 Received: from mail.us.es ([193.147.175.20]:43694 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757489Ab2IMKz3 (ORCPT ); Thu, 13 Sep 2012 06:55:29 -0400 Received: (qmail 32284 invoked from network); 13 Sep 2012 12:55:28 +0200 Received: from unknown (HELO us.es) (192.168.2.11) by us.es with SMTP; 13 Sep 2012 12:55:28 +0200 Received: (qmail 27314 invoked by uid 507); 13 Sep 2012 10:55:28 -0000 X-Qmail-Scanner-Diagnostics: from 127.0.0.1 by antivirus1 (envelope-from , uid 501) with qmail-scanner-2.10 (clamdscan: 0.97.5/15350. spamassassin: 3.3.2. Clear:RC:1(127.0.0.1):SA:0(-97.8/7.5):. Processed in 5.159362 secs); 13 Sep 2012 10:55:28 -0000 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on antivirus1 X-Spam-Level: X-Spam-Status: No, score=-97.8 required=7.5 tests=BAYES_50,RCVD_IN_PBL, RCVD_IN_SORBS_DUL,RDNS_DYNAMIC,USER_IN_WHITELIST autolearn=disabled version=3.3.2 X-Envelope-From: pablo@netfilter.org Received: from unknown (HELO antivirus1) (127.0.0.1) by us.es with SMTP; 13 Sep 2012 10:55:22 -0000 Received: from 192.168.1.13 (192.168.1.13) by antivirus1 (F-Secure/fsigk_smtp/407/antivirus1); Thu, 13 Sep 2012 12:55:22 +0200 (CEST) X-Virus-Status: clean(F-Secure/fsigk_smtp/407/antivirus1) Received: (qmail 19767 invoked from network); 13 Sep 2012 12:55:22 +0200 Received: from 198.100.221.87.dynamic.jazztel.es (HELO localhost.localdomain) (pneira@us.es@87.221.100.198) by us.es with SMTP; 13 Sep 2012 12:55:22 +0200 From: pablo@netfilter.org To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org Subject: [PATCH 3/4] netfilter: Validate the sequence number of dataless ACK packets as well Date: Thu, 13 Sep 2012 12:54:07 +0200 Message-Id: <1347533648-3451-4-git-send-email-pablo@netfilter.org> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1347533648-3451-1-git-send-email-pablo@netfilter.org> References: <1347533648-3451-1-git-send-email-pablo@netfilter.org> Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org From: Jozsef Kadlecsik 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 Signed-off-by: Pablo Neira Ayuso --- 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 aba98f9..e046b37 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -630,15 +630,9 @@ 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;