netfilter: nf_conntrack_irc: Fix forged IP logic

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>

diff --git a/net/netfilter/nf_conntrack_irc.c b/net/netfilter/nf_conntrack_irc.c
index 1796c456ac98beb96753652934759a81e6980448..992decbcaa5c1edbb72a9e9703df745895c544ca 100644 (file)
--- a/net/netfilter/nf_conntrack_irc.c
+++ b/net/netfilter/nf_conntrack_irc.c
@@ -194,8 +194,9 @@ 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);