Router Advertisement/Solicitation sanity check

Sanity checks according to RFC4861 paragraphs 6.1.1 and 6.1.2

1 files changed, 55 insertions, 1 deletions

diff --git a/src/router.c b/src/router.c
index 0b01a77..a213c84 100644
--- a/src/router.c
+++ b/src/router.c
@@ -130,12 +130,66 @@ static void sigusr1_refresh(_unused int signal)
 			uloop_timeout_set(&iface->timer_rs, 1000);
 }
 
+static int router_icmpv6_valid(struct sockaddr_in6 *source, uint8_t *data, size_t len)
+{
+	struct icmp6_hdr *hdr = (struct icmp6_hdr *)data;
+	struct icmpv6_opt *opt;
+	size_t optlen = len - sizeof(*hdr);
+
+	/* Hoplimit is already checked in odhcpd_receive_packets */
+	if (len < sizeof(*hdr))
+		return 0;
+
+	if (hdr->icmp6_code)
+		return 0;
+
+	switch (hdr->icmp6_type) {
+	case ND_ROUTER_ADVERT:
+		if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
+			return 0;
+
+		opt = (struct icmpv6_opt *)((struct nd_router_advert *)data + 1);
+		break;
+
+	case ND_ROUTER_SOLICIT:
+		opt = (struct icmpv6_opt *)((struct nd_router_solicit *)data + 1);
+		break;
+
+	default:
+		return 0;
+	}
+
+	while (optlen > 0) {
+		size_t l = opt->len << 3;
+
+		if (optlen < sizeof(*opt))
+			return 0;
+
+		if (l > optlen || l == 0)
+			return 0;
+
+		if (opt->type == ND_OPT_SOURCE_LINKADDR && IN6_IS_ADDR_UNSPECIFIED(&source->sin6_addr) &&
+			hdr->icmp6_type == ND_ROUTER_SOLICIT) {
+			return 0;
+		}
+
+		opt = (struct icmpv6_opt *)(((uint8_t *)opt) + l);
+
+		optlen -= l;
+	}
+
+	return 1;
+}
 
 // Event handler for incoming ICMPv6 packets
-static void handle_icmpv6(_unused void *addr, void *data, size_t len,
+static void handle_icmpv6(void *addr, void *data, size_t len,
 		struct interface *iface)
 {
 	struct icmp6_hdr *hdr = data;
+	
+	if (!router_icmpv6_valid(addr, data, len))
+		return;
+
 	if ((iface->ra == RELAYD_SERVER && !iface->master)) { // Server mode
 		if (hdr->icmp6_type == ND_ROUTER_SOLICIT)
 			send_router_advert(&iface->timer_rs);