netfilter: ip6t_NPT: Ensure to check lower part of prefixes are zero

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>

1 files changed, 10 insertions, 0 deletions

diff --git a/net/ipv6/netfilter/ip6t_NPT.c b/net/ipv6/netfilter/ip6t_NPT.c
index 87b759c11da5..83acc1405a18 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]);