Add heartbeat extension bounds check.

A missing bounds check in the handling of the TLS heartbeat extension can be used to reveal up to 64k of memory to a connected client or server. Thanks for Neel Mehta of Google Security for discovering this bug and to Adam Langley <agl@chromium.org> and Bodo Moeller <bmoeller@acm.org> for preparing the fix (CVE-2014-0160) (cherry picked from commit 96db902)
openssl · Apr 7, 2014 · 731f431 · johanatan · Apr 9, 2014 · mcvsama
1 parent 4e6c12f
commit 731f431
Show file tree

Hide file tree

Showing 3 changed files with 36 additions and 13 deletions.
diff --git a/CHANGES b/CHANGES
@@ -4,6 +4,15 @@
 
  Changes between 1.0.2 and 1.1.0  [xx XXX xxxx]
 
+  *) A missing bounds check in the handling of the TLS heartbeat extension
+     can be used to reveal up to 64k of memory to a connected client or
+     server.
+
+     Thanks for Neel Mehta of Google Security for discovering this bug and to
+     Adam Langley <agl@chromium.org> and Bodo Moeller <bmoeller@acm.org> for
+     preparing the fix (CVE-2014-0160)
+     [Adam Langley, Bodo Moeller]
+
   *) Fix for the attack described in the paper "Recovering OpenSSL
      ECDSA Nonces Using the FLUSH+RELOAD Cache Side-channel Attack"
      by Yuval Yarom and Naomi Benger. Details can be obtained from:

diff --git a/ssl/d1_both.c b/ssl/d1_both.c
@@ -1330,26 +1330,36 @@ dtls1_process_heartbeat(SSL *s)
 	unsigned int payload;
 	unsigned int padding = 16; /* Use minimum padding */
 
-	/* Read type and payload length first */
-	hbtype = *p++;
-	n2s(p, payload);
-	pl = p;
-
 	if (s->msg_callback)
 		s->msg_callback(0, s->version, TLS1_RT_HEARTBEAT,
 			&s->s3->rrec.data[0], s->s3->rrec.length,
 			s, s->msg_callback_arg);
 
+	/* Read type and payload length first */
+	if (1 + 2 + 16 > s->s3->rrec.length)
+		return 0; /* silently discard */
+	hbtype = *p++;
+	n2s(p, payload);
+	if (1 + 2 + payload + 16 > s->s3->rrec.length)
+		return 0; /* silently discard per RFC 6520 sec. 4 */
+	pl = p;
+
 	if (hbtype == TLS1_HB_REQUEST)
 		{
 		unsigned char *buffer, *bp;
+		unsigned int write_length = 1 /* heartbeat type */ +
+					    2 /* heartbeat length */ +
+					    payload + padding;
 		int r;
 
+		if (write_length > SSL3_RT_MAX_PLAIN_LENGTH)
+			return 0;
+
 		/* Allocate memory for the response, size is 1 byte
 		 * message type, plus 2 bytes payload length, plus
 		 * payload, plus padding
 		 */
-		buffer = OPENSSL_malloc(1 + 2 + payload + padding);
+		buffer = OPENSSL_malloc(write_length);
 		bp = buffer;
 
 		/* Enter response type, length and copy payload */
@@ -1360,11 +1370,11 @@ dtls1_process_heartbeat(SSL *s)
 		/* Random padding */
 		RAND_pseudo_bytes(bp, padding);
 
-		r = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buffer, 3 + payload + padding);
+		r = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buffer, write_length);
 
 		if (r >= 0 && s->msg_callback)
 			s->msg_callback(1, s->version, TLS1_RT_HEARTBEAT,
-				buffer, 3 + payload + padding,
+				buffer, write_length,
 				s, s->msg_callback_arg);
 
 		OPENSSL_free(buffer);

diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
@@ -3969,16 +3969,20 @@ tls1_process_heartbeat(SSL *s)
 	unsigned int payload;
 	unsigned int padding = 16; /* Use minimum padding */
 
-	/* Read type and payload length first */
-	hbtype = *p++;
-	n2s(p, payload);
-	pl = p;
-
 	if (s->msg_callback)
 		s->msg_callback(0, s->version, TLS1_RT_HEARTBEAT,
 			&s->s3->rrec.data[0], s->s3->rrec.length,
 			s, s->msg_callback_arg);
 
+	/* Read type and payload length first */
+	if (1 + 2 + 16 > s->s3->rrec.length)
+		return 0; /* silently discard */
+	hbtype = *p++;
+	n2s(p, payload);
+	if (1 + 2 + payload + 16 > s->s3->rrec.length)
+		return 0; /* silently discard per RFC 6520 sec. 4 */
+	pl = p;
+
 	if (hbtype == TLS1_HB_REQUEST)
 		{
 		unsigned char *buffer, *bp;