From patchwork Tue Jan 31 23:53:18 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shawn Lu X-Patchwork-Id: 138881 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id BC721B6EF3 for ; Wed, 1 Feb 2012 10:54:34 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753549Ab2AaXyG (ORCPT ); Tue, 31 Jan 2012 18:54:06 -0500 Received: from imr4.ericy.com ([198.24.6.9]:49917 "EHLO imr4.ericy.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751874Ab2AaXyF (ORCPT ); Tue, 31 Jan 2012 18:54:05 -0500 Received: from eusaamw0706.eamcs.ericsson.se ([147.117.20.31]) by imr4.ericy.com (8.14.3/8.14.3/Debian-9.1ubuntu1) with ESMTP id q0VNs0Br028959; Tue, 31 Jan 2012 17:54:01 -0600 Received: from prattle.redback.com (147.117.20.214) by eusaamw0706.eamcs.ericsson.se (147.117.20.91) with Microsoft SMTP Server id 8.3.137.0; Tue, 31 Jan 2012 18:53:54 -0500 Received: from localhost (localhost [127.0.0.1]) by prattle.redback.com (Postfix) with ESMTP id AB52D1AB27ED; Tue, 31 Jan 2012 15:53:54 -0800 (PST) Received: from prattle.redback.com ([127.0.0.1]) by localhost (prattle [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 25821-08; Tue, 31 Jan 2012 15:53:54 -0800 (PST) Received: from localhost.localdomain (rbos-pc-12.lab.redback.com [10.12.11.132]) by prattle.redback.com (Postfix) with ESMTP id 205931AB27EC; Tue, 31 Jan 2012 15:53:54 -0800 (PST) From: Shawn Lu To: eric.dumazet@gmail.com CC: davem@davemloft.net, netdev@vger.kernel.org, xiaoclu@gmail.com Subject: [PATCH] tcp: md5: fix md5 RST when both sides have listener Date: Tue, 31 Jan 2012 15:53:18 -0800 Message-ID: <1328053998-2498-1-git-send-email-shawn.lu@ericsson.com> X-Mailer: git-send-email 1.7.0.4 In-Reply-To: References: MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org TCP RST mechanism is broken in TCP md5(RFC2385). When connection is gone, md5 key is lost, sending RST without md5 hash is deem to ignored by peer. This can be a problem since RST help protocal like bgp to fast recove from peer crash. In most case, users of tcp md5, such as bgp and ldp, have listeners on both sides. md5 keys for peers are saved in listening socket. When passive side connection is gone, we can still get md5 key from listening socket. When active side of connection is gone, we can try to find listening socket through source port, and then md5 key. we are not loosing sercuriy here: packet is valified checked with md5 hash. No RST is generated if md5 hash doesn't match or no md5 key can be found. Signed-off-by: Shawn Lu Acked-by: Eric Dumazet Acked-by: Eric Dumazet --- net/ipv4/tcp_ipv4.c | 43 ++++++++++++++++++++++++++++++++++++++++--- net/ipv6/tcp_ipv6.c | 40 ++++++++++++++++++++++++++++++++++++++-- 2 files changed, 78 insertions(+), 5 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index da5d322..adafee8 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -593,6 +593,10 @@ static void tcp_v4_send_reset(struct sock *sk, struct sk_buff *skb) struct ip_reply_arg arg; #ifdef CONFIG_TCP_MD5SIG struct tcp_md5sig_key *key; + const __u8 *hash_location = NULL; + unsigned char newhash[16]; + int genhash; + struct sock *sk1 = NULL; #endif struct net *net; @@ -623,9 +627,36 @@ static void tcp_v4_send_reset(struct sock *sk, struct sk_buff *skb) arg.iov[0].iov_len = sizeof(rep.th); #ifdef CONFIG_TCP_MD5SIG - key = sk ? tcp_md5_do_lookup(sk, - (union tcp_md5_addr *)&ip_hdr(skb)->saddr, - AF_INET) : NULL; + hash_location = tcp_parse_md5sig_option(th); + if (!sk && hash_location) { + /* + * active side is lost. Try to find listening socket through + * source port, and then find md5 key through listening socket. + * we are not loose security here: + * Incoming packet is checked with md5 hash with finding key, + * no RST generated if md5 hash doesn't match. + */ + sk1 = __inet_lookup_listener(dev_net(skb_dst(skb)->dev), + &tcp_hashinfo, ip_hdr(skb)->daddr, + ntohs(th->source), inet_iif(skb)); + /* don't send rst if it can't find key */ + if (!sk1) + return; + + key = tcp_md5_do_lookup(sk1, (union tcp_md5_addr *) + &ip_hdr(skb)->saddr, AF_INET); + if (!key) + goto release_sk1; + + genhash = tcp_v4_md5_hash_skb(newhash, key, NULL, NULL, skb); + if (genhash || memcmp(hash_location, newhash, 16) != 0) + goto release_sk1; + } else { + key = sk ? tcp_md5_do_lookup(sk, (union tcp_md5_addr *) + &ip_hdr(skb)->saddr, + AF_INET) : NULL; + } + if (key) { rep.opt[0] = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | @@ -653,6 +684,12 @@ static void tcp_v4_send_reset(struct sock *sk, struct sk_buff *skb) TCP_INC_STATS_BH(net, TCP_MIB_OUTSEGS); TCP_INC_STATS_BH(net, TCP_MIB_OUTRSTS); + +#ifdef CONFIG_TCP_MD5SIG +release_sk1: + if (sk1) + sock_put(sk1); +#endif } /* The code following below sending ACKs in SYN-RECV and TIME-WAIT states diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index bec41f9..00da65c 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -925,6 +925,13 @@ static void tcp_v6_send_reset(struct sock *sk, struct sk_buff *skb) const struct tcphdr *th = tcp_hdr(skb); u32 seq = 0, ack_seq = 0; struct tcp_md5sig_key *key = NULL; +#ifdef CONFIG_TCP_MD5SIG + const __u8 *hash_location = NULL; + struct ipv6hdr *ipv6h = ipv6_hdr(skb); + unsigned char newhash[16]; + int genhash; + struct sock *sk1 = NULL; +#endif if (th->rst) return; @@ -933,8 +940,31 @@ static void tcp_v6_send_reset(struct sock *sk, struct sk_buff *skb) return; #ifdef CONFIG_TCP_MD5SIG - if (sk) - key = tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->saddr); + hash_location = tcp_parse_md5sig_option(th); + if (!sk && hash_location) { + /* + * active side is lost. Try to find listening socket through + * source port, and then find md5 key through listening socket. + * we are not loose security here: + * Incoming packet is checked with md5 hash with finding key, + * no RST generated if md5 hash doesn't match. + */ + sk1 = inet6_lookup_listener(dev_net(skb_dst(skb)->dev), + &tcp_hashinfo, &ipv6h->daddr, + ntohs(th->source), inet6_iif(skb)); + if (!sk1) + return; + + key = tcp_v6_md5_do_lookup(sk1, &ipv6h->saddr); + if (!key) + goto release_sk1; + + genhash = tcp_v6_md5_hash_skb(newhash, key, NULL, NULL, skb); + if (genhash || memcmp(hash_location, newhash, 16) != 0) + goto release_sk1; + } else { + key = sk ? tcp_v6_md5_do_lookup(sk, &ipv6h->saddr) : NULL; + } #endif if (th->ack) @@ -944,6 +974,12 @@ static void tcp_v6_send_reset(struct sock *sk, struct sk_buff *skb) (th->doff << 2); tcp_v6_send_response(skb, seq, ack_seq, 0, 0, key, 1, 0); + +#ifdef CONFIG_TCP_MD5SIG +release_sk1: + if (sk1) + sock_put(sk1); +#endif } static void tcp_v6_send_ack(struct sk_buff *skb, u32 seq, u32 ack, u32 win, u32 ts,