CVE-2008-1897: Improper Authentication (CWE-287)
value: The IAX2 channel driver (chan_iax2) in Asterisk Open Source 1.0.x, 1.2.x before 1.2.28, and 1.4.x before 1.4.19.1; Business Edition A.x.x, B.x.x before B.2.5.2, and C.x.x before C.1.8.1; AsteriskNOW before 1.0.3; Appliance Developer Kit 0.x.x; and s800i before 1.1.0.3, when configured to allow unauthenticated calls, does not verify that an ACK response contains a call number matching the server's reply to a NEW message, which allows remote attackers to cause a denial of service (traffic amplification) via a spoofed ACK response that does not complete a 3-way handshake.  NOTE: this issue exists because of an incomplete fix for CVE-2008-1923.
CWE description: When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
Published: 2008-04-23T16:05Z
Repository: https://github.com/xrg/asterisk-xrg
Language: C
Files changed: channels/chan_iax2.c
Commit date: 2008-04-22 22:15:36 +0000
Commit message: When we receive a full frame that is supposed to contain our call number,
ensure that it has the correct one.
(closes issue #10078)
(AST-2008-006)

Diff: diff --git a/channels/chan_iax2.c b/channels/chan_iax2.c
index 7c71f33..823c4a3 100644
--- a/channels/chan_iax2.c
+++ b/channels/chan_iax2.c
@@ -1237,17 +1237,17 @@ static struct iax_frame *iaxfrdup2(struct iax_frame *fr)
 
 #define NEW_PREVENT 	0
 #define NEW_ALLOW 	1
 #define NEW_FORCE 	2
 
-static int match(struct sockaddr_in *sin, unsigned short callno, unsigned short dcallno, struct chan_iax2_pvt *cur)
+static int match(struct sockaddr_in *sin, unsigned short callno, unsigned short dcallno, struct chan_iax2_pvt *cur, int full_frame)
 {
 	if ((cur->addr.sin_addr.s_addr == sin->sin_addr.s_addr) &&
 		(cur->addr.sin_port == sin->sin_port)) {
 		/* This is the main host */
-		if ((cur->peercallno == callno) ||
-			((dcallno == cur->callno) && !cur->peercallno)) {
+		if ( (cur->peercallno == 0 || cur->peercallno == callno) &&
+			 (full_frame ? dcallno == cur->callno : 1) ) {
 			/* That's us.  Be sure we keep track of the peer call number */
 			return 1;
 		}
 	}
 	if ((cur->transfer.sin_addr.s_addr == sin->sin_addr.s_addr) &&
@@ -1334,11 +1334,11 @@ static int make_trunk(unsigned short callno, int locked)
 }
 
 /*!
  * \note Calling this function while holding another pvt lock can cause a deadlock.
  */
-static int __find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int return_locked)
+static int __find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int return_locked, int full_frame)
 {
 	int res = 0;
 	int x;
 	struct timeval now;
 	char host[80];
@@ -1347,45 +1347,61 @@ static int __find_callno(unsigned short callno, unsigned short dcallno, struct s
 		/* Look for an existing connection first */
 		for (x=1;(res < 1) && (x<maxnontrunkcall);x++) {
 			ast_mutex_lock(&iaxsl[x]);
 			if (iaxs[x]) {
 				/* Look for an exact match */
-				if (match(sin, callno, dcallno, iaxs[x])) {
+				if (match(sin, callno, dcallno, iaxs[x], full_frame)) {
 					res = x;
 				}
 			}
 			ast_mutex_unlock(&iaxsl[x]);
 		}
 		for (x=TRUNK_CALL_START;(res < 1) && (x<maxtrunkcall);x++) {
 			ast_mutex_lock(&iaxsl[x]);
 			if (iaxs[x]) {
 				/* Look for an exact match */
-				if (match(sin, callno, dcallno, iaxs[x])) {
+				if (match(sin, callno, dcallno, iaxs[x], full_frame)) {
 					res = x;
 				}
 			}
 			ast_mutex_unlock(&iaxsl[x]);
 		}
 	}
 	if ((res < 1) && (new >= NEW_ALLOW)) {
+		int start, found = 0;
+
 		/* It may seem odd that we look through the peer list for a name for
 		 * this *incoming* call.  Well, it is weird.  However, users don't
 		 * have an IP address/port number that we can match against.  So,
 		 * this is just checking for a peer that has that IP/port and
 		 * assuming that we have a user of the same name.  This isn't always
 		 * correct, but it will be changed if needed after authentication. */
 		if (!iax2_getpeername(*sin, host, sizeof(host)))
 			snprintf(host, sizeof(host), "%s:%d", ast_inet_ntoa(sin->sin_addr), ntohs(sin->sin_port));
-		gettimeofday(&now, NULL);
-		for (x=1;x<TRUNK_CALL_START;x++) {
+
+		now = ast_tvnow();
+		start = 1 + (ast_random() % (TRUNK_CALL_START - 1));
+		for (x = start; 1; x++) {
+			if (x == TRUNK_CALL_START) {
+				x = 0;
+				continue;
+			}
+
 			/* Find first unused call number that hasn't been used in a while */
 			ast_mutex_lock(&iaxsl[x]);
-			if (!iaxs[x] && ((now.tv_sec - lastused[x].tv_sec) > MIN_REUSE_TIME)) break;
+			if (!iaxs[x] && ((now.tv_sec - lastused[x].tv_sec) > MIN_REUSE_TIME)) {
+				found = 1;
+				break;
+			}
 			ast_mutex_unlock(&iaxsl[x]);
+			
+			if (x == start - 1) {
+				break;
+			}
 		}
 		/* We've still got lock held if we found a spot */
-		if (x >= TRUNK_CALL_START) {
+		if (x == start - 1 && !found) {
 			ast_log(LOG_WARNING, "No more space\n");
 			return 0;
 		}
 		iaxs[x] = new_iax(sin, host);
 		update_max_nontrunk();
@@ -1418,18 +1434,18 @@ static int __find_callno(unsigned short callno, unsigned short dcallno, struct s
 		res = x;
 	}
 	return res;
 }
 
-static int find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd) {
+static int find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int full_frame) {
 
-	return __find_callno(callno, dcallno, sin, new, sockfd, 0);
+	return __find_callno(callno, dcallno, sin, new, sockfd, 0, full_frame);
 }
 
-static int find_callno_locked(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd) {
+static int find_callno_locked(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int full_frame) {
 
-	return __find_callno(callno, dcallno, sin, new, sockfd, 1);
+	return __find_callno(callno, dcallno, sin, new, sockfd, 1, full_frame);
 }
 
 static void iax2_frame_free(struct iax_frame *fr)
 {
 	AST_SCHED_DEL(sched, fr->retrans);
@@ -6869,11 +6885,11 @@ static int socket_process(struct iax2_thread *thread)
 			ast_log(LOG_WARNING, "Rejecting packet from '%s.%d' that is flagged as a video frame but is too short\n", ast_inet_ntoa(sin.sin_addr), ntohs(sin.sin_port));
 			return 1;
 		}
 
 		/* This is a video frame, get call number */
-		fr->callno = find_callno(ntohs(vh->callno) & ~0x8000, dcallno, &sin, new, fd);
+		fr->callno = find_callno(ntohs(vh->callno) & ~0x8000, dcallno, &sin, new, fd, 0);
 		minivid = 1;
 	} else if ((meta->zeros == 0) && !(ntohs(meta->metacmd) & 0x8000)) {
 		unsigned char metatype;
 
 		if (res < sizeof(*meta)) {
@@ -6927,11 +6943,11 @@ static int socket_process(struct iax2_thread *thread)
 					break;
 				}
 				/* Stop if we don't have enough data */
 				if (len > res)
 					break;
-				fr->callno = find_callno_locked(callno & ~IAX_FLAG_FULL, 0, &sin, NEW_PREVENT, fd);
+				fr->callno = find_callno_locked(callno & ~IAX_FLAG_FULL, 0, &sin, NEW_PREVENT, fd, 0);
 				if (fr->callno) {
 					/* If it's a valid call, deliver the contents.  If not, we
 					   drop it, since we don't have a scallno to use for an INVAL */
 					/* Process as a mini frame */
 					memset(&f, 0, sizeof(f));
@@ -7013,11 +7029,11 @@ static int socket_process(struct iax2_thread *thread)
 		f.frametype = AST_FRAME_NULL;
 		f.subclass = 0;
 	}
 
 	if (!fr->callno)
-		fr->callno = find_callno(ntohs(mh->callno) & ~IAX_FLAG_FULL, dcallno, &sin, new, fd);
+		fr->callno = find_callno(ntohs(mh->callno) & ~IAX_FLAG_FULL, dcallno, &sin, new, fd, ntohs(mh->callno) & IAX_FLAG_FULL);
 
 	if (fr->callno > 0)
 		ast_mutex_lock(&iaxsl[fr->callno]);
 
 	if (!fr->callno || !iaxs[fr->callno]) {
@@ -8508,11 +8524,11 @@ static int iax2_do_register(struct iax2_registry *reg)
 	}
 
 	if (!reg->callno) {
 		if (option_debug)
 			ast_log(LOG_DEBUG, "Allocate call number\n");
-		reg->callno = find_callno_locked(0, 0, &reg->addr, NEW_FORCE, defaultsockfd);
+		reg->callno = find_callno_locked(0, 0, &reg->addr, NEW_FORCE, defaultsockfd, 0);
 		if (reg->callno < 1) {
 			ast_log(LOG_WARNING, "Unable to create call for registration\n");
 			return -1;
 		} else if (option_debug)
 			ast_log(LOG_DEBUG, "Registration created on call %d\n", reg->callno);
@@ -8569,11 +8585,11 @@ static int iax2_provision(struct sockaddr_in *end, int sockfd, char *dest, const
 
 	/* Build the rest of the message */
 	memset(&ied, 0, sizeof(ied));
 	iax_ie_append_raw(&ied, IAX_IE_PROVISIONING, provdata.buf, provdata.pos);
 
-	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd);
+	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd, 0);
 	if (!callno)
 		return -1;
 
 	if (iaxs[callno]) {
 		/* Schedule autodestruct in case they don't ever give us anything back */
@@ -8710,11 +8726,11 @@ static int iax2_poke_peer(struct iax2_peer *peer, int heldcall)
 		iax2_destroy(peer->callno);
 		ast_mutex_unlock(&iaxsl[peer->callno]);
 	}
 	if (heldcall)
 		ast_mutex_unlock(&iaxsl[heldcall]);
-	peer->callno = find_callno(0, 0, &peer->addr, NEW_FORCE, peer->sockfd);
+	peer->callno = find_callno(0, 0, &peer->addr, NEW_FORCE, peer->sockfd, 0);
 	if (heldcall)
 		ast_mutex_lock(&iaxsl[heldcall]);
 	if (peer->callno < 1) {
 		ast_log(LOG_WARNING, "Unable to allocate call for poking peer '%s'\n", peer->name);
 		return -1;
@@ -8790,11 +8806,11 @@ static struct ast_channel *iax2_request(const char *type, int format, void *data
 	}
 
 	if (pds.port)
 		sin.sin_port = htons(atoi(pds.port));
 
-	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd);
+	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd, 0);
 	if (callno < 1) {
 		ast_log(LOG_WARNING, "Unable to create call\n");
 		*cause = AST_CAUSE_CONGESTION;
 		return NULL;
 	}
@@ -10104,11 +10120,11 @@ static int cache_get_callno_locked(const char *data)
 
 	if (option_debug)
 		ast_log(LOG_DEBUG, "peer: %s, username: %s, password: %s, context: %s\n",
 			pds.peer, pds.username, pds.password, pds.context);
 
-	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd);
+	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd, 0);
 	if (callno < 1) {
 		ast_log(LOG_WARNING, "Unable to create call\n");
 		return -1;
 	}
 

Vulnerable code: static int match(struct sockaddr_in *sin, unsigned short callno, unsigned short dcallno, struct chan_iax2_pvt *cur)
		if ((cur->peercallno == callno) ||
			((dcallno == cur->callno) && !cur->peercallno)) {
static int __find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int return_locked)
				if (match(sin, callno, dcallno, iaxs[x])) {
				if (match(sin, callno, dcallno, iaxs[x])) {
		gettimeofday(&now, NULL);
		for (x=1;x<TRUNK_CALL_START;x++) {
			if (!iaxs[x] && ((now.tv_sec - lastused[x].tv_sec) > MIN_REUSE_TIME)) break;
		if (x >= TRUNK_CALL_START) {
static int find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd) {
	return __find_callno(callno, dcallno, sin, new, sockfd, 0);
static int find_callno_locked(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd) {
	return __find_callno(callno, dcallno, sin, new, sockfd, 1);
		fr->callno = find_callno(ntohs(vh->callno) & ~0x8000, dcallno, &sin, new, fd);
				fr->callno = find_callno_locked(callno & ~IAX_FLAG_FULL, 0, &sin, NEW_PREVENT, fd);
		fr->callno = find_callno(ntohs(mh->callno) & ~IAX_FLAG_FULL, dcallno, &sin, new, fd);
		reg->callno = find_callno_locked(0, 0, &reg->addr, NEW_FORCE, defaultsockfd);
	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd);
	peer->callno = find_callno(0, 0, &peer->addr, NEW_FORCE, peer->sockfd);
	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd);
	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd);
Fixed code: static int match(struct sockaddr_in *sin, unsigned short callno, unsigned short dcallno, struct chan_iax2_pvt *cur, int full_frame)
		if ( (cur->peercallno == 0 || cur->peercallno == callno) &&
			 (full_frame ? dcallno == cur->callno : 1) ) {
static int __find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int return_locked, int full_frame)
				if (match(sin, callno, dcallno, iaxs[x], full_frame)) {
				if (match(sin, callno, dcallno, iaxs[x], full_frame)) {
		int start, found = 0;


		now = ast_tvnow();
		start = 1 + (ast_random() % (TRUNK_CALL_START - 1));
		for (x = start; 1; x++) {
			if (x == TRUNK_CALL_START) {
				x = 0;
				continue;
			}

			if (!iaxs[x] && ((now.tv_sec - lastused[x].tv_sec) > MIN_REUSE_TIME)) {
				found = 1;
				break;
			}
			
			if (x == start - 1) {
				break;
			}
		if (x == start - 1 && !found) {
static int find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int full_frame) {
	return __find_callno(callno, dcallno, sin, new, sockfd, 0, full_frame);
static int find_callno_locked(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int full_frame) {
	return __find_callno(callno, dcallno, sin, new, sockfd, 1, full_frame);
		fr->callno = find_callno(ntohs(vh->callno) & ~0x8000, dcallno, &sin, new, fd, 0);
				fr->callno = find_callno_locked(callno & ~IAX_FLAG_FULL, 0, &sin, NEW_PREVENT, fd, 0);
		fr->callno = find_callno(ntohs(mh->callno) & ~IAX_FLAG_FULL, dcallno, &sin, new, fd, ntohs(mh->callno) & IAX_FLAG_FULL);
		reg->callno = find_callno_locked(0, 0, &reg->addr, NEW_FORCE, defaultsockfd, 0);
	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd, 0);
	peer->callno = find_callno(0, 0, &peer->addr, NEW_FORCE, peer->sockfd, 0);
	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd, 0);
	callno = find_callno_locked(0, 0, &sin, NEW_FORCE, cai.sockfd, 0);