Don't advance PACKET in ssl_check_for_safari
authorMatt Caswell <matt@openssl.org>
Wed, 7 Oct 2015 14:20:47 +0000 (15:20 +0100)
committerMatt Caswell <matt@openssl.org>
Wed, 7 Oct 2015 15:17:52 +0000 (16:17 +0100)
The function ssl_check_for_safari fingerprints the incoming extensions
to see whether it is one of the broken versions of safari. However it was
failing to reset the PACKET back to the same position it started in, hence
causing some extensions to be skipped incorrectly.

Reviewed-by: Emilia Käsper <emilia@openssl.org>
ssl/t1_lib.c

index 4975c10..f18f502 100644 (file)
@@ -1815,10 +1815,11 @@ static int tls1_alpn_handle_client_hello(SSL *s, PACKET *pkt, int *al)
  * Sadly we cannot differentiate 10.6, 10.7 and 10.8.4 (which work), from
  * 10.8..10.8.3 (which don't work).
  */
-static void ssl_check_for_safari(SSL *s, PACKET *pkt)
+static void ssl_check_for_safari(SSL *s, const PACKET *pkt)
 {
     unsigned int type, size;
     unsigned char *eblock1, *eblock2;
+    PACKET tmppkt;
 
     static const unsigned char kSafariExtensionsBlock[] = {
         0x00, 0x0a,             /* elliptic_curves extension */
@@ -1846,10 +1847,12 @@ static void ssl_check_for_safari(SSL *s, PACKET *pkt)
         0x02, 0x03,             /* SHA-1/ECDSA */
     };
 
-    if (!PACKET_forward(pkt, 2)
-            || !PACKET_get_net_2(pkt, &type)
-            || !PACKET_get_net_2(pkt, &size)
-            || !PACKET_forward(pkt, size))
+    tmppkt = *pkt;
+
+    if (!PACKET_forward(&tmppkt, 2)
+            || !PACKET_get_net_2(&tmppkt, &type)
+            || !PACKET_get_net_2(&tmppkt, &size)
+            || !PACKET_forward(&tmppkt, size))
         return;
 
     if (type != TLSEXT_TYPE_server_name)
@@ -1859,9 +1862,9 @@ static void ssl_check_for_safari(SSL *s, PACKET *pkt)
         const size_t len1 = sizeof(kSafariExtensionsBlock);
         const size_t len2 = sizeof(kSafariTLS12ExtensionsBlock);
 
-        if (!PACKET_get_bytes(pkt, &eblock1, len1)
-                || !PACKET_get_bytes(pkt, &eblock2, len2)
-                || PACKET_remaining(pkt))
+        if (!PACKET_get_bytes(&tmppkt, &eblock1, len1)
+                || !PACKET_get_bytes(&tmppkt, &eblock2, len2)
+                || PACKET_remaining(&tmppkt))
             return;
         if (memcmp(eblock1, kSafariExtensionsBlock, len1) != 0)
             return;
@@ -1870,8 +1873,8 @@ static void ssl_check_for_safari(SSL *s, PACKET *pkt)
     } else {
         const size_t len = sizeof(kSafariExtensionsBlock);
 
-        if (!PACKET_get_bytes(pkt, &eblock1, len)
-                || PACKET_remaining(pkt))
+        if (!PACKET_get_bytes(&tmppkt, &eblock1, len)
+                || PACKET_remaining(&tmppkt))
             return;
         if (memcmp(eblock1, kSafariExtensionsBlock, len) != 0)
             return;