[RFC PATCH 5/6] ah6: Be explicit about which routing types are processed.

[Tom Herbert <tom@herbertland.com>]

The current code assumes that all routing headers can be processed
as type 0 when rearranging the routing header for AH verification.
Change this to be explicit. Type 0 and type 2 are supported and are
processed the same way with regards to AH.

Also check if rearranging routing header fails. Update reference
in comment to more current RFC.

Signed-off-by: Tom Herbert <tom@quantonium.net>
---
 net/ipv6/ah6.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index 1e80157..032491c 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -145,7 +145,7 @@ static bool zero_out_mutable_opts(struct ipv6_opt_hdr *opthdr)
 /**
  *	ipv6_rearrange_destopt - rearrange IPv6 destination options header
  *	@iph: IPv6 header
- *	@destopt: destionation options header
+ *	@destopt: destination options header
  */
 static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt)
 {
@@ -204,15 +204,16 @@ static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *des
 #endif
 
 /**
- *	ipv6_rearrange_rthdr - rearrange IPv6 routing header
+ *	ipv6_rearrange_type0_rthdr - rearrange type 0 IPv6 routing header
  *	@iph: IPv6 header
  *	@rthdr: routing header
  *
  *	Rearrange the destination address in @iph and the addresses in @rthdr
  *	so that they appear in the order they will at the final destination.
- *	See Appendix A2 of RFC 2402 for details.
+ *	See Appendix A2 of RFC 4302 for details.
  */
-static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
+static bool ipv6_rearrange_type0_rthdr(struct ipv6hdr *iph,
+				       struct ipv6_rt_hdr *rthdr)
 {
 	int segments, segments_left;
 	struct in6_addr *addrs;
@@ -220,15 +221,13 @@ static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
 
 	segments_left = rthdr->segments_left;
 	if (segments_left == 0)
-		return;
+		return true;
 	rthdr->segments_left = 0;
 
 	/* The value of rthdr->hdrlen has been verified either by the system
 	 * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
 	 * packets.  So we can assume that it is even and that segments is
 	 * greater than or equal to segments_left.
-	 *
-	 * For the same reason we can assume that this option is of type 0.
 	 */
 	segments = rthdr->hdrlen >> 1;
 
@@ -240,6 +239,24 @@ static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
 
 	addrs[0] = iph->daddr;
 	iph->daddr = final_addr;
+
+	return true;
+}
+
+static bool ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
+{
+	switch (rthdr->type) {
+	case IPV6_SRCRT_TYPE_2:
+		/* Simplified format of type 0 so same processing */
+		/* fallthrough */
+	case IPV6_SRCRT_TYPE_0: /* Deprecated */
+		return ipv6_rearrange_type0_rthdr(iph, rthdr);
+	default:
+		/* Bad or unidentified routing header, we don't know how
+		 * to fix this header for security purposes. Return failure.
+		 */
+		return false;
+	}
 }
 
 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len, int dir)
@@ -271,7 +288,11 @@ static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len, int dir)
 			break;
 
 		case NEXTHDR_ROUTING:
-			ipv6_rearrange_rthdr(iph, exthdr.rth);
+			if (!ipv6_rearrange_rthdr(iph, exthdr.rth)) {
+				net_dbg_ratelimited("bad routing header\n");
+				return -EINVAL;
+			}
+
 			break;
 
 		default:
-- 
2.7.4