netfilter: nf_conntrack_irc: Fix forged IP logic

[ Upstream commit 0efe125cfb99e6773a7434f3463f7c2fa28f3a43 ]

Ensure the match happens in the right direction, previously the
destination used was the server, not the NAT host, as the comment
shows the code intended.

Additionally nf_nat_irc uses port 0 as a signal and there's no valid way
it can appear in a DCC message, so consider port 0 also forged.

Fixes: 869f37d8e48f ("[NETFILTER]: nf_conntrack/nf_nat: add IRC helper port")
Signed-off-by: David Leadbeater <dgl@dgl.cx>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/netfilter/nf_conntrack_irc.c b/net/netfilter/nf_conntrack_irc.c
index 1972a149f958350c6f6dd5f466d36fed152b76fc..c6a8bdc3a226dddb520ae29daf9bd478d549ebb8 100644 (file)
--- a/net/netfilter/nf_conntrack_irc.c
+++ b/net/netfilter/nf_conntrack_irc.c
@@ -187,8 +187,9 @@ static int help(struct sk_buff *skb, unsigned int protoff,
 
                        /* dcc_ip can be the internal OR external (NAT'ed) IP */
                        tuple = &ct->tuplehash[dir].tuple;
-                       if (tuple->src.u3.ip != dcc_ip &&
-                           tuple->dst.u3.ip != dcc_ip) {
+                       if ((tuple->src.u3.ip != dcc_ip &&
+                            ct->tuplehash[!dir].tuple.dst.u3.ip != dcc_ip) ||
+                           dcc_port == 0) {
                                net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n",
                                                     &tuple->src.u3.ip,
                                                     &dcc_ip, dcc_port);