tcp md5sig: Use skb's saddr when replying to an incoming segment

The MD5-key that belongs to a connection is identified by the peer's
IP-address. When we are in tcp_v4(6)_reqsk_send_ack(), we are replying
to an incoming segment from tcp_check_req() that failed the seq-number
checks.

Thus, to find the correct key, we need to use the skb's saddr and not
the daddr.

This bug seems to have been there since quite a while, but probably got
unnoticed because the consequences are not catastrophic. We will call
tcp_v4_reqsk_send_ack only to send a challenge-ACK back to the peer,
thus the connection doesn't really fail.

Fixes: b4ee7d36115c ("tcp md5sig: Let the caller pass appropriate key for tcp_v{4,6}_do_calc_md5_hash().")
Signed-off-by: Christoph Paasch <cpaasch@apple.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 77ea45da0fe9c746907a312989658af3ad3b198d..94e28350f4205b1a57809d5471d7e2ade51f5196 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -848,7 +848,7 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
                        tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
                        req->ts_recent,
                        0,
-                       tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&ip_hdr(skb)->daddr,
+                       tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&ip_hdr(skb)->saddr,
                                          AF_INET),
                        inet_rsk(req)->no_srccheck ? IP_REPLY_ARG_NOSRCCHECK : 0,
                        ip_hdr(skb)->tos);

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 1f04ec0e4a7aa2c11b8ee27cbdd4067b5bcf32e5..7178476b3d2f64f01832fe3292c7dec849ec2265 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -994,7 +994,7 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
                        req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
                        tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
                        req->ts_recent, sk->sk_bound_dev_if,
-                       tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr),
+                       tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->saddr),
                        0, 0);
 }