| Message ID | 1328085348-6771-1-git-send-email-shawn.lu@ericsson.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
Le mercredi 01 février 2012 à 00:35 -0800, Shawn Lu a écrit : > 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 listener on both sides to accept connection from peer. > md5 keys for peers are saved in listening socket. > > There are two cases in finding md5 key when connection is > lost: > 1.Passive receive RST: The message is send to well known port, > tcp will associate it with listner. md5 key is gotten from > listener. > > 2.Active receive RST (no sock): The message is send to ative > side, there is no socket associated with the message. In this > case, finding listener from source port, then find md5 key from > listener. > > we are not loosing sercuriy here: > packet is 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 <shawn.lu@ericsson.com> > --- > v4: change title and change log. > regerated after "tcp: md5: protects md5sig_info with RCU" Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Thanks ! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Eric Dumazet <eric.dumazet@gmail.com> Date: Wed, 01 Feb 2012 10:54:55 +0100 > Le mercredi 01 février 2012 à 00:35 -0800, Shawn Lu a écrit : >> 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 listener on both sides to accept connection from peer. >> md5 keys for peers are saved in listening socket. >> >> There are two cases in finding md5 key when connection is >> lost: >> 1.Passive receive RST: The message is send to well known port, >> tcp will associate it with listner. md5 key is gotten from >> listener. >> >> 2.Active receive RST (no sock): The message is send to ative >> side, there is no socket associated with the message. In this >> case, finding listener from source port, then find md5 key from >> listener. >> >> we are not loosing sercuriy here: >> packet is 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 <shawn.lu@ericsson.com> >> --- >> v4: change title and change log. >> regerated after "tcp: md5: protects md5sig_info with RCU" > > > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Applied, thanks everyone. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi,Eric With linux support for TCP AO not in picture right now. Are you interested in putting patch to enable md5 key change( RFC4808)? Or do you anybody else is working on linux implementation of TCP AO? I posted this question before and get no response yet. Thanks! Shawn -----Original Message----- From: Eric Dumazet [mailto:eric.dumazet@gmail.com] Sent: Wednesday, February 01, 2012 1:55 AM To: Shawn Lu Cc: davem@davemloft.net; netdev@vger.kernel.org; xiaoclu@gmail.com Subject: Re: [PATCH] tcp: md5: RST: getting md5 key from listener Le mercredi 01 février 2012 à 00:35 -0800, Shawn Lu a écrit : > 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 listener on > both sides to accept connection from peer. > md5 keys for peers are saved in listening socket. > > There are two cases in finding md5 key when connection is > lost: > 1.Passive receive RST: The message is send to well known port, tcp > will associate it with listner. md5 key is gotten from listener. > > 2.Active receive RST (no sock): The message is send to ative side, > there is no socket associated with the message. In this case, finding > listener from source port, then find md5 key from listener. > > we are not loosing sercuriy here: > packet is 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 <shawn.lu@ericsson.com> > --- > v4: change title and change log. > regerated after "tcp: md5: protects md5sig_info with RCU" Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Thanks ! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 567cca9..90e4793 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; + rcu_read_lock(); + 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 +684,14 @@ 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) { + rcu_read_unlock(); + 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 c250181..d16414c 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -923,6 +923,13 @@ 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; @@ -931,8 +938,32 @@ 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; + + rcu_read_lock(); + 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) @@ -942,6 +973,14 @@ 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) { + rcu_read_unlock(); + sock_put(sk1); + } +#endif } static void tcp_v6_send_ack(struct sk_buff *skb, u32 seq, u32 ack, u32 win, u32 ts,
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 listener on both sides to accept connection from peer. md5 keys for peers are saved in listening socket. There are two cases in finding md5 key when connection is lost: 1.Passive receive RST: The message is send to well known port, tcp will associate it with listner. md5 key is gotten from listener. 2.Active receive RST (no sock): The message is send to ative side, there is no socket associated with the message. In this case, finding listener from source port, then find md5 key from listener. we are not loosing sercuriy here: packet is 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 <shawn.lu@ericsson.com> --- v4: change title and change log. regerated after "tcp: md5: protects md5sig_info with RCU" net/ipv4/tcp_ipv4.c | 45 ++++++++++++++++++++++++++++++++++++++++++--- net/ipv6/tcp_ipv6.c | 43 +++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 83 insertions(+), 5 deletions(-)