Default to ignoring potentially evil IPv6 Neighbor Solicitation

messages.

Approved by:    so (cperciva)
Approved by:	re (kensmith)
Security:       FreeBSD-SA-08:10.nd6
Thanks to:      jinmei, bz

4 files changed, 26 insertions, 1 deletions

diff --git a/sys/netinet6/in6.h b/sys/netinet6/in6.h
index db0ab11..ffdb37f4 100644
--- a/sys/netinet6/in6.h
+++ b/sys/netinet6/in6.h
@@ -599,7 +599,9 @@ struct ip6_mtuinfo {
 /* New entries should be added here from current IPV6CTL_MAXID value. */
 /* to define items, should talk with KAME guys first, for *BSD compatibility */
 #define IPV6CTL_STEALTH		45
-#define IPV6CTL_MAXID		46
+
+#define	ICMPV6CTL_ND6_ONLINKNSRFC4861	47
+#define IPV6CTL_MAXID		48
 #endif /* __BSD_VISIBLE */
 
 /*
diff --git a/sys/netinet6/in6_proto.c b/sys/netinet6/in6_proto.c
index c35a1b6..c1caaa5 100644
--- a/sys/netinet6/in6_proto.c
+++ b/sys/netinet6/in6_proto.c
@@ -403,6 +403,7 @@ time_t	ip6_log_time = (time_t)0L;
 #ifdef IPSTEALTH
 int	ip6stealth = 0;
 #endif
+int	nd6_onlink_ns_rfc4861 = 0; /* allow 'on-link' nd6 NS (as in RFC 4861) */
 
 /* icmp6 */
 /*
@@ -576,3 +577,6 @@ SYSCTL_INT(_net_inet6_icmp6, ICMPV6CTL_ND6_MAXNUDHINT,
 	nd6_maxnudhint, CTLFLAG_RW,	&nd6_maxnudhint, 0, "");
 SYSCTL_INT(_net_inet6_icmp6, ICMPV6CTL_ND6_DEBUG,
 	nd6_debug, CTLFLAG_RW,	&nd6_debug,		0, "");
+SYSCTL_INT(_net_inet6_icmp6, ICMPV6CTL_ND6_ONLINKNSRFC4861,
+	nd6_onlink_ns_rfc4861, CTLFLAG_RW, &nd6_onlink_ns_rfc4861, 0,
+	"Accept 'on-link' nd6 NS in compliance with RFC 4861.");
diff --git a/sys/netinet6/nd6.h b/sys/netinet6/nd6.h
index f191d2d..4b4d6ec 100644
--- a/sys/netinet6/nd6.h
+++ b/sys/netinet6/nd6.h
@@ -339,6 +339,7 @@ extern struct llinfo_nd6 llinfo_nd6;
 extern struct nd_drhead nd_defrouter;
 extern struct nd_prhead nd_prefix;
 extern int nd6_debug;
+extern int nd6_onlink_ns_rfc4861;
 
 #define nd6log(x)	do { if (V_nd6_debug) log x; } while (/*CONSTCOND*/ 0)
 
diff --git a/sys/netinet6/nd6_nbr.c b/sys/netinet6/nd6_nbr.c
index 3db6eca..770a40a 100644
--- a/sys/netinet6/nd6_nbr.c
+++ b/sys/netinet6/nd6_nbr.c
@@ -150,6 +150,24 @@ nd6_ns_input(struct mbuf *m, int off, int icmp6len)
 			    "(wrong ip6 dst)\n"));
 			goto bad;
 		}
+	} else if (!nd6_onlink_ns_rfc4861) {
+		struct sockaddr_in6 src_sa6;
+
+		/*
+		 * According to recent IETF discussions, it is not a good idea
+		 * to accept a NS from an address which would not be deemed
+		 * to be a neighbor otherwise.  This point is expected to be
+		 * clarified in future revisions of the specification.
+		 */
+		bzero(&src_sa6, sizeof(src_sa6));
+		src_sa6.sin6_family = AF_INET6;
+		src_sa6.sin6_len = sizeof(src_sa6);
+		src_sa6.sin6_addr = saddr6;
+		if (!nd6_is_addr_neighbor(&src_sa6, ifp)) {
+			nd6log((LOG_INFO, "nd6_ns_input: "
+				"NS packet from non-neighbor\n"));
+			goto bad;
+		}
 	}
 
 	if (IN6_IS_ADDR_MULTICAST(&taddr6)) {