: ipt_recent: sanity check hit count

commit be32bceccbf7051ff1433943df7e808c576d1191

Author: Daniel Hokka Zakrisson <[email protected]>
Date:   Thu Mar 20 18:34:39 2008 +0100

[NETFILTER]: ipt_recent: sanity check hit count

If a rule using ipt_recent is created with a hit count greater than ip_pkt_list_tot, the rule will never match as it cannot keep track of enough timestamps. This patch makes ipt_recent refuse to create such rules.

With ip_pkt_list_tot's default value of 20, the following can be used to reproduce the problem.

nc -u -l 0.0.0.0 1234 &
for i in seq 1 100; do echo $i | nc -w 1 -u 127.0.0.1 1234; done

This limits it to 20 packets:
iptables -A OUTPUT -p udp --dport 1234 -m recent --set --name test \
--rsource
iptables -A OUTPUT -p udp --dport 1234 -m recent --update --seconds \
60 --hitcount 20 --name test --rsource -j DROP

While this is unlimited:
iptables -A OUTPUT -p udp --dport 1234 -m recent --set --name test \
--rsource
iptables -A OUTPUT -p udp --dport 1234 -m recent --update --seconds \
60 --hitcount 21 --name test --rsource -j DROP

With the patch the second rule-set will throw an EINVAL.

index 68cbe3c..8e8f042 100644
@@ -252,6 +252,8 @@ recent_mt_check(const char *tablename, const void *ip,
 	if ((info->check_set & (IPT_RECENT_SET | IPT_RECENT_REMOVE)) &&
 	    (info->seconds || info->hit_count))
 		return false;
+	if (info->hit_count > ip_pkt_list_tot)
+		return false;
 	if (info->name[0] == '\0' ||
 	    strnlen(info->name, IPT_RECENT_NAME_LEN) == IPT_RECENT_NAME_LEN)
 		return false;

From: Patrick McHardy <[email protected]>
Date: Thu, 20 Mar 2008 18:55:19 +0100

Also applied, thanks.