[11/14] netfilter: synproxy: fix rst sequence number mismatch
diff mbox series

Message ID 20190719164618.29581-2-pablo@netfilter.org
State Accepted
Delegated to: David Miller
Headers show
Series
  • Untitled series #120419
Related show

Commit Message

Pablo Neira Ayuso July 19, 2019, 4:46 p.m. UTC
From: Fernando Fernandez Mancera <ffmancera@riseup.net>

14:51:00.024418 IP 192.168.122.1.41462 > netfilter.90: Flags [S], seq
4023580551,
14:51:00.024454 IP netfilter.90 > 192.168.122.1.41462: Flags [S.], seq
727560212, ack 4023580552,
14:51:00.024524 IP 192.168.122.1.41462 > netfilter.90: Flags [.], ack 1,

Note: here, synproxy will send a SYN to the real server, as the 3whs was
completed sucessfully. Instead of a syn/ack that we can intercept, we instead
received a reset packet from the real backend, that we forward to the original
client. However, we don't use the correct sequence number, so the reset is not
effective in closing the connection coming from the client.

14:51:00.024550 IP netfilter.90 > 192.168.122.1.41462: Flags [R.], seq
3567407084,
14:51:00.231196 IP 192.168.122.1.41462 > netfilter.90: Flags [.], ack 1,
14:51:00.647911 IP 192.168.122.1.41462 > netfilter.90: Flags [.], ack 1,
14:51:01.474395 IP 192.168.122.1.41462 > netfilter.90: Flags [.], ack 1,

Fixes: 48b1de4c110a ("netfilter: add SYNPROXY core/target")
Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_synproxy_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch
diff mbox series

diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c
index 09718e5a9e41..c769462a839e 100644
--- a/net/netfilter/nf_synproxy_core.c
+++ b/net/netfilter/nf_synproxy_core.c
@@ -687,7 +687,7 @@  ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
 	state = &ct->proto.tcp;
 	switch (state->state) {
 	case TCP_CONNTRACK_CLOSE:
-		if (th->rst && !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
+		if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
 			nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
 						      ntohl(th->seq) + 1);
 			break;
@@ -1111,7 +1111,7 @@  ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
 	state = &ct->proto.tcp;
 	switch (state->state) {
 	case TCP_CONNTRACK_CLOSE:
-		if (th->rst && !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
+		if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
 			nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
 						      ntohl(th->seq) + 1);
 			break;