[PATCH 5/5] netfilter: ip6t_NPT: Ensure to check lower part of prefixes are zero

[pablo@netfilter.org]

From: YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@linux-ipv6.org>

RFC 6296 points that address bits that are not part of the prefix
has to be zeroed.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/ipv6/netfilter/ip6t_NPT.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/ipv6/netfilter/ip6t_NPT.c b/net/ipv6/netfilter/ip6t_NPT.c
index 87b759c..83acc14 100644
--- a/net/ipv6/netfilter/ip6t_NPT.c
+++ b/net/ipv6/netfilter/ip6t_NPT.c
@@ -9,6 +9,7 @@
 #include <linux/module.h>
 #include <linux/skbuff.h>
 #include <linux/ipv6.h>
+#include <net/ipv6.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter_ipv6.h>
 #include <linux/netfilter_ipv6/ip6t_NPT.h>
@@ -18,11 +19,20 @@ static int ip6t_npt_checkentry(const struct xt_tgchk_param *par)
 {
 	struct ip6t_npt_tginfo *npt = par->targinfo;
 	__wsum src_sum = 0, dst_sum = 0;
+	struct in6_addr pfx;
 	unsigned int i;
 
 	if (npt->src_pfx_len > 64 || npt->dst_pfx_len > 64)
 		return -EINVAL;
 
+	/* Ensure that LSB of prefix is zero */
+	ipv6_addr_prefix(&pfx, &npt->src_pfx.in6, npt->src_pfx_len);
+	if (!ipv6_addr_equal(&pfx, &npt->src_pfx.in6))
+		return -EINVAL;
+	ipv6_addr_prefix(&pfx, &npt->dst_pfx.in6, npt->dst_pfx_len);
+	if (!ipv6_addr_equal(&pfx, &npt->dst_pfx.in6))
+		return -EINVAL;
+
 	for (i = 0; i < ARRAY_SIZE(npt->src_pfx.in6.s6_addr16); i++) {
 		src_sum = csum_add(src_sum,
 				(__force __wsum)npt->src_pfx.in6.s6_addr16[i]);
-- 
1.7.10.4

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