From ad32e04f3db364694edc678327326ae6b771db9e Mon Sep 17 00:00:00 2001
From: Donatas Abraitis <donatas@opensourcerouting.org>
Date: Tue, 5 Sep 2023 11:30:53 +0000
Subject: [PATCH 1/2] bgpd: Use treat-as-withdraw for tunnel encapsulation
 attribute

Before this path we used session reset method, which is discouraged by rfc7606.

Handle this as rfc requires.

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

CVE: CVE-2023-38802

Upstream-Status: Backport [https://github.com/FRRouting/frr/commit/bcb6b58d9530173df41d3a3cbc4c600ee0b4b186]

Signed-off-by: Narpat Mali <narpat.mali@windriver.com>
---
 bgpd/bgp_attr.c | 61 ++++++++++++++++++++-----------------------------
 1 file changed, 25 insertions(+), 36 deletions(-)

diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c
index 5d06991e2..b10a60351 100644
--- a/bgpd/bgp_attr.c
+++ b/bgpd/bgp_attr.c
@@ -1310,6 +1310,7 @@ bgp_attr_malformed(struct bgp_attr_parser_args *args, uint8_t subcode,
	case BGP_ATTR_LARGE_COMMUNITIES:
	case BGP_ATTR_ORIGINATOR_ID:
	case BGP_ATTR_CLUSTER_LIST:
+	case BGP_ATTR_ENCAP:
		return BGP_ATTR_PARSE_WITHDRAW;
	case BGP_ATTR_MP_REACH_NLRI:
	case BGP_ATTR_MP_UNREACH_NLRI:
@@ -2411,26 +2412,21 @@ bgp_attr_ipv6_ext_communities(struct bgp_attr_parser_args *args)
 }

 /* Parse Tunnel Encap attribute in an UPDATE */
-static int bgp_attr_encap(uint8_t type, struct peer *peer, /* IN */
-			  bgp_size_t length, /* IN: attr's length field */
-			  struct attr *attr, /* IN: caller already allocated */
-			  uint8_t flag,      /* IN: attr's flags field */
-			  uint8_t *startp)
+static int bgp_attr_encap(struct bgp_attr_parser_args *args)
 {
-	bgp_size_t total;
	uint16_t tunneltype = 0;
-
-	total = length + (CHECK_FLAG(flag, BGP_ATTR_FLAG_EXTLEN) ? 4 : 3);
+	struct peer *const peer = args->peer;
+	struct attr *const attr = args->attr;
+	bgp_size_t length = args->length;
+	uint8_t type = args->type;
+	uint8_t flag = args->flags;

	if (!CHECK_FLAG(flag, BGP_ATTR_FLAG_TRANS)
	    || !CHECK_FLAG(flag, BGP_ATTR_FLAG_OPTIONAL)) {
-		zlog_info(
-			"Tunnel Encap attribute flag isn't optional and transitive %d",
-			flag);
-		bgp_notify_send_with_data(peer, BGP_NOTIFY_UPDATE_ERR,
-					  BGP_NOTIFY_UPDATE_ATTR_FLAG_ERR,
-					  startp, total);
-		return -1;
+		zlog_err("Tunnel Encap attribute flag isn't optional and transitive %d",
+			 flag);
+		return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_OPT_ATTR_ERR,
+					  args->total);
	}

	if (BGP_ATTR_ENCAP == type) {
@@ -2438,12 +2434,11 @@ static int bgp_attr_encap(uint8_t type, struct peer *peer, /* IN */
		uint16_t tlv_length;

		if (length < 4) {
-			zlog_info(
+			zlog_err(
				"Tunnel Encap attribute not long enough to contain outer T,L");
-			bgp_notify_send_with_data(
-				peer, BGP_NOTIFY_UPDATE_ERR,
-				BGP_NOTIFY_UPDATE_OPT_ATTR_ERR, startp, total);
-			return -1;
+			return bgp_attr_malformed(args,
+						  BGP_NOTIFY_UPDATE_OPT_ATTR_ERR,
+						  args->total);
		}
		tunneltype = stream_getw(BGP_INPUT(peer));
		tlv_length = stream_getw(BGP_INPUT(peer));
@@ -2473,13 +2468,11 @@ static int bgp_attr_encap(uint8_t type, struct peer *peer, /* IN */
		}

		if (sublength > length) {
-			zlog_info(
-				"Tunnel Encap attribute sub-tlv length %d exceeds remaining length %d",
-				sublength, length);
-			bgp_notify_send_with_data(
-				peer, BGP_NOTIFY_UPDATE_ERR,
-				BGP_NOTIFY_UPDATE_OPT_ATTR_ERR, startp, total);
-			return -1;
+			zlog_err("Tunnel Encap attribute sub-tlv length %d exceeds remaining length %d",
+				 sublength, length);
+			return bgp_attr_malformed(args,
+						  BGP_NOTIFY_UPDATE_OPT_ATTR_ERR,
+						  args->total);
		}

		/* alloc and copy sub-tlv */
@@ -2527,13 +2520,10 @@ static int bgp_attr_encap(uint8_t type, struct peer *peer, /* IN */

	if (length) {
		/* spurious leftover data */
-		zlog_info(
-			"Tunnel Encap attribute length is bad: %d leftover octets",
-			length);
-		bgp_notify_send_with_data(peer, BGP_NOTIFY_UPDATE_ERR,
-					  BGP_NOTIFY_UPDATE_OPT_ATTR_ERR,
-					  startp, total);
-		return -1;
+		zlog_err("Tunnel Encap attribute length is bad: %d leftover octets",
+			 length);
+		return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_OPT_ATTR_ERR,
+					  args->total);
	}

	return 0;
@@ -3332,8 +3322,7 @@ bgp_attr_parse_ret_t bgp_attr_parse(struct peer *peer, struct attr *attr,
		case BGP_ATTR_VNC:
 #endif
		case BGP_ATTR_ENCAP:
-			ret = bgp_attr_encap(type, peer, length, attr, flag,
-					     startp);
+			ret = bgp_attr_encap(&attr_args);
			break;
		case BGP_ATTR_PREFIX_SID:
			ret = bgp_attr_prefix_sid(&attr_args);
--
2.40.0
