Merge pull request FRRouting#5954 from ton31337/feature/rfc7607

 bgpd: Proscribe the use of AS 0 (zero)

bgpd/bgp_aspath.c

@@ -428,6 +428,22 @@ bool aspath_check_as_sets(struct aspath *aspath)
 	return false;
 }
 
+/* Check if aspath has BGP_AS_ZERO */
+bool aspath_check_as_zero(struct aspath *aspath)
+{
+	struct assegment *seg = aspath->segments;
+	unsigned int i;
+
+	while (seg) {
+		for (i = 0; i < seg->length; i++)
+			if (seg->as[i] == BGP_AS_ZERO)
+				return true;
+		seg = seg->next;
+	}
+
+	return false;
+}
+
 /* Estimate size aspath /might/ take if encoded into an
  * ASPATH attribute.
  *

bgpd/bgp_aspath.h

@@ -39,6 +39,7 @@
 #define BGP_PRIVATE_AS4_MAX     4294967294U
 
 /* we leave BGP_AS_MAX as the 16bit AS MAX number.  */
+#define BGP_AS_ZERO		          0
 #define BGP_AS_MAX		     65535U
 #define BGP_AS4_MAX		4294967295U
 /* Transition 16Bit AS as defined by IANA */
@@ -121,6 +122,7 @@ extern bool aspath_left_confed_check(struct aspath *);
 extern unsigned long aspath_count(void);
 extern unsigned int aspath_count_hops(const struct aspath *);
 extern bool aspath_check_as_sets(struct aspath *aspath);
+extern bool aspath_check_as_zero(struct aspath *aspath);
 extern unsigned int aspath_count_confeds(struct aspath *);
 extern unsigned int aspath_size(struct aspath *);
 extern as_t aspath_highest(struct aspath *);

bgpd/bgp_attr.c

@@ -1398,6 +1398,15 @@ static int bgp_attr_aspath(struct bgp_attr_parser_args *args)
 					  0);
 	}
 
+	/* Codification of AS 0 Processing */
+	if (aspath_check_as_zero(attr->aspath)) {
+		flog_err(EC_BGP_ATTR_MAL_AS_PATH,
+			 "Malformed AS path, contains BGP_AS_ZERO(0) from %s",
+			 peer->host);
+		return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_MAL_AS_PATH,
+					  0);
+	}
+
 	/* Set aspath attribute flag. */
 	attr->flag |= ATTR_FLAG_BIT(BGP_ATTR_AS_PATH);
 
@@ -1469,6 +1478,15 @@ static int bgp_attr_as4_path(struct bgp_attr_parser_args *args,
 					  0);
 	}
 
+	/* Codification of AS 0 Processing */
+	if (aspath_check_as_zero(*as4_path)) {
+		flog_err(EC_BGP_ATTR_MAL_AS_PATH,
+			 "Malformed AS4 path, contains BGP_AS_ZERO(0) from %s",
+			 peer->host);
+		return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_MAL_AS_PATH,
+					  0);
+	}
+
 	/* Set aspath attribute flag. */
 	attr->flag |= ATTR_FLAG_BIT(BGP_ATTR_AS4_PATH);
 
@@ -1615,6 +1633,7 @@ static int bgp_attr_aggregator(struct bgp_attr_parser_args *args)
 	struct peer *const peer = args->peer;
 	struct attr *const attr = args->attr;
 	const bgp_size_t length = args->length;
+	as_t aggregator_as;
 
 	int wantedlen = 6;
 
@@ -1632,9 +1651,19 @@ static int bgp_attr_aggregator(struct bgp_attr_parser_args *args)
 	}
 
 	if (CHECK_FLAG(peer->cap, PEER_CAP_AS4_RCV))
-		attr->aggregator_as = stream_getl(peer->curr);
+		aggregator_as = stream_getl(peer->curr);
 	else
-		attr->aggregator_as = stream_getw(peer->curr);
+		aggregator_as = stream_getw(peer->curr);
+
+	/* Codification of AS 0 Processing */
+	if (aggregator_as == BGP_AS_ZERO) {
+		flog_err(EC_BGP_ATTR_LEN,
+			 "AGGREGATOR attribute is BGP_AS_ZERO(0)");
+		return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_MAL_AS_PATH,
+					  args->total);
+	}
+
+	attr->aggregator_as = aggregator_as;
 	attr->aggregator_addr.s_addr = stream_get_ipv4(peer->curr);
 
 	/* Set atomic aggregate flag. */
@@ -1652,6 +1681,7 @@ bgp_attr_as4_aggregator(struct bgp_attr_parser_args *args,
 	struct peer *const peer = args->peer;
 	struct attr *const attr = args->attr;
 	const bgp_size_t length = args->length;
+	as_t aggregator_as;
 
 	if (length != 8) {
 		flog_err(EC_BGP_ATTR_LEN, "New Aggregator length is not 8 [%d]",
@@ -1660,7 +1690,16 @@ bgp_attr_as4_aggregator(struct bgp_attr_parser_args *args,
 					  0);
 	}
 
-	*as4_aggregator_as = stream_getl(peer->curr);
+	/* Codification of AS 0 Processing */
+	aggregator_as = stream_getl(peer->curr);
+	if (aggregator_as == BGP_AS_ZERO) {
+		flog_err(EC_BGP_ATTR_LEN,
+			 "AS4_AGGREGATOR attribute is BGP_AS_ZERO(0)");
+		return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_MAL_AS_PATH,
+					  0);
+	}
+
+	*as4_aggregator_as = aggregator_as;
 	as4_aggregator_addr->s_addr = stream_get_ipv4(peer->curr);
 
 	attr->flag |= ATTR_FLAG_BIT(BGP_ATTR_AS4_AGGREGATOR);

bgpd/bgp_packet.c

@@ -1142,6 +1142,15 @@ static int bgp_open_receive(struct peer *peer, bgp_size_t size)
 		return BGP_Stop;
 	}
 
+	/* Codification of AS 0 Processing */
+	if (remote_as == BGP_AS_ZERO) {
+		flog_err(EC_BGP_PKT_OPEN, "%s bad OPEN, got AS set to 0",
+			 peer->host);
+		bgp_notify_send(peer, BGP_NOTIFY_OPEN_ERR,
+				BGP_NOTIFY_OPEN_BAD_PEER_AS);
+		return BGP_Stop;
+	}
+
 	if (remote_as == BGP_AS_TRANS) {
 		/* Take the AS4 from the capability.  We must have received the
 		 * capability now!  Otherwise we have a asn16 peer who uses

bgpd/bgp_route.c

@@ -1945,6 +1945,10 @@ int subgroup_announce_check(struct bgp_node *rn, struct bgp_path_info *pi,
 		if (aspath_check_as_sets(attr->aspath))
 			return 0;
 
+	/* Codification of AS 0 Processing */
+	if (aspath_check_as_zero(attr->aspath))
+		return 0;
+
 	if (CHECK_FLAG(bgp->flags, BGP_FLAG_GRACEFUL_SHUTDOWN)) {
 		if (peer->sort == BGP_PEER_IBGP
 		    || peer->sort == BGP_PEER_CONFED) {

doc/user/overview.rst

@@ -306,6 +306,8 @@ BGP
   :t:`The Resource Public Key Infrastructure (RPKI) to Router Protocol. R. Bush, R. Austein. January 2013.`
 - :rfc:`6811`
   :t:`BGP Prefix Origin Validation. P. Mohapatra, J. Scudder, D. Ward, R. Bush, R. Austein. January 2013.`
+- :rfc:`7607`
+  :t:`Codification of AS 0 Processing. W. Kumari, R. Bush, H. Schiller, K. Patel. August 2015.`
 - :rfc:`7611`
   :t:`BGP ACCEPT_OWN Community Attribute. J. Uttaro, P. Mohapatra, D. Smith, R. Raszuk, J. Scudder. August 2015.`
 - :rfc:`7999`

tests/bgpd/test_aspath.c

@@ -474,6 +474,20 @@ static struct test_segment {
 		14,
 		{NULL, NULL, 0, 0, 0, 0, 0, 0},
 	},
+	{
+		/* 28 */
+		"BGP_AS_ZERO",
+		"seq(8466,3,52737,0,4096)",
+		{0x2, 0x5,
+		0x21, 0x12,
+		0x00, 0x03,
+		0xce, 0x01,
+		0x00, 0x00,
+		0x10, 0x00},
+		12,
+		{"8466 3 52737 0 4096", "8466 3 52737 0 4096", 5, 0,
+		 NOT_ALL_PRIVATE, 4096, 4, 8466},
+	},
 	{NULL, NULL, {0}, 0, {NULL, 0, 0}}};
 
 #define COMMON_ATTRS                                                           \
@@ -678,6 +692,21 @@ static struct aspath_tests {
 		COMMON_ATTR_SIZE + 3,
 		&test_segments[0],
 	},
+	/* 13 */
+	{
+		"4b AS4_PATH: BGP_AS_ZERO",
+		&test_segments[28],
+		"8466 3 52737 0 4096",
+		AS4_DATA,
+		-1,
+		PEER_CAP_AS4_RCV | PEER_CAP_AS4_ADV,
+		{
+			COMMON_ATTRS,
+			BGP_ATTR_FLAG_TRANS | BGP_ATTR_FLAG_OPTIONAL,
+			BGP_ATTR_AS4_PATH, 22,
+		},
+		COMMON_ATTR_SIZE + 3,
+	},
 	{NULL, NULL, NULL, 0, 0, 0, {0}, 0},
 };
 

tests/bgpd/test_aspath.py

@@ -52,6 +52,7 @@ def _attrtest(self, line):
 TestAspath.parsertest("zero-size overflow")
 TestAspath.parsertest("zero-size overflow + valid segment")
 TestAspath.parsertest("invalid segment type")
+TestAspath.parsertest("BGP_AS_ZERO")
 
 for i in range(10):
     TestAspath.okfail("prepend test %d" % i)
@@ -77,3 +78,4 @@ def _attrtest(self, line):
 TestAspath.attrtest("4b AS_PATH: bad flags")
 TestAspath.attrtest("4b AS4_PATH w/o AS_PATH")
 TestAspath.attrtest("4b AS4_PATH: confed")
+TestAspath.attrtest("4b AS4_PATH: BGP_AS_ZERO")