From 129adde0aef424778d6c4791b5be10e302db9320 Mon Sep 17 00:00:00 2001
From: Donatas Abraitis <donatas@opensourcerouting.org>
Date: Thu, 13 Jul 2023 22:32:03 +0300
Upstream: yes
References: CVE-2023-38802,bsc#1213284,https://github.com/FRRouting/frr/pull/14290
Subject: [PATCH] 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>
Signed-off-by: Marius Tomaschewski <mt@suse.com>

diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c
index c6177a1b93..188393b752 100644
--- a/bgpd/bgp_attr.c
+++ b/bgpd/bgp_attr.c
@@ -1301,6 +1301,7 @@ 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:
 	case BGP_ATTR_OTC:
 		return BGP_ATTR_PARSE_WITHDRAW;
 	case BGP_ATTR_MP_REACH_NLRI:
@@ -2426,26 +2427,21 @@ 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) {
@@ -2453,12 +2449,11 @@ 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));
@@ -2488,13 +2483,11 @@ 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 */
@@ -2542,13 +2535,10 @@ 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;
@@ -3387,8 +3377,7 @@ enum bgp_attr_parse_ret 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);
-- 
2.35.3