Commit 30791ac4 authored Dec 11, 2017 by Christoph Paasch Committed by David S. Miller Dec 12, 2017

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: 9501f972 ("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>

parent 20080971

net/ipv4/tcp_ipv4.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);

net/ipv6/tcp_ipv6.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);
		}

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