MHD_gtls_server_name_recv_params - address CVE-2008-1948

src/daemon/https/tls/ext_server_name.c

@@ -48,75 +48,88 @@ MHD_gtls_server_name_recv_params (MHD_gtls_session_t session,
   ssize_t data_size = _data_size;
   int server_names = 0;
 
-  if (session->security_parameters.entity == GNUTLS_SERVER)
-    {
-      DECR_LENGTH_RET (data_size, 2, 0);
-      len = MHD_gtls_read_uint16 (data);
+  DECR_LENGTH_RET (data_size, 2, 0);
+  len = MHD_gtls_read_uint16 (data);
 
-      if (len != data_size)
-        {
-          /* This is unexpected packet length, but
-           * just ignore it, for now.
-           */
-          MHD_gnutls_assert ();
-          return 0;
-        }
+  if (len != data_size)
+    {
+      /* This is unexpected packet length, but
+       * just ignore it, for now.
+       */
+      MHD_gnutls_assert ();
+      return 0;
+    }
 
-      p = data + 2;
+  p = data + 2;
 
-      /* Count all server_names in the packet. */
-      while (data_size > 0)
-        {
-          DECR_LENGTH_RET (data_size, 1, 0);
-          p++;
+  /* Count all server_names in the packet. */
+  while (data_size > 0)
+    {
+      DECR_LENGTH_RET (data_size, 1, 0);
+      p++;
 
-          DECR_LEN (data_size, 2);
-          len = MHD_gtls_read_uint16 (p);
-          p += 2;
+      DECR_LEN (data_size, 2);
+      len = MHD_gtls_read_uint16 (p);
+      p += 2;
 
+      /* make sure supplied server name is not empty */
+      if (len > 0)
+        {
           DECR_LENGTH_RET (data_size, len, 0);
           server_names++;
-
           p += len;
         }
+      else
+        {
+#if HAVE_MESSAGES
+          MHD__gnutls_handshake_log
+            ("HSK[%x]: Received zero size server name (under attack?)\n",
+             session);
+#endif
+        }
+    }
 
-      session->security_parameters.extensions.server_names_size =
-        server_names;
-      if (server_names == 0)
-        return 0;               /* no names found */
+  /* we cannot accept more server names. */
+  if (server_names > MAX_SERVER_NAME_EXTENSIONS)
+    {
+#if HAVE_MESSAGES
+      MHD__gnutls_handshake_log
+        ("HSK[%x]: Too many server names received (under attack?)\n",
+         session);
+#endif
+      server_names = MAX_SERVER_NAME_EXTENSIONS;
+    }
 
-      /* we cannot accept more server names.
-       */
-      if (server_names > MAX_SERVER_NAME_EXTENSIONS)
-        server_names = MAX_SERVER_NAME_EXTENSIONS;
+  session->security_parameters.extensions.server_names_size = server_names;
+  if (server_names == 0)
+    return 0;                   /* no names found */
 
-      p = data + 2;
-      for (i = 0; i < server_names; i++)
-        {
-          type = *p;
-          p++;
+  p = data + 2;
+  for (i = 0; i < server_names; i++)
+    {
+      type = *p;
+      p++;
 
-          len = MHD_gtls_read_uint16 (p);
-          p += 2;
+      len = MHD_gtls_read_uint16 (p);
+      p += 2;
 
-          switch (type)
+      switch (type)
+        {
+        case 0:                /* NAME_DNS */
+          if (len <= MAX_SERVER_NAME_SIZE)
             {
-            case 0:            /* NAME_DNS */
-              if (len <= MAX_SERVER_NAME_SIZE)
-                {
-                  memcpy (session->security_parameters.
-                          extensions.server_names[i].name, p, len);
-                  session->security_parameters.extensions.server_names[i].
-                    name_length = len;
-                  session->security_parameters.extensions.server_names[i].
-                    type = GNUTLS_NAME_DNS;
-                  break;
-                }
+              memcpy (session->security_parameters.extensions.server_names[i].
+                      name, p, len);
+              session->security_parameters.extensions.
+                server_names[i].name_length = len;
+              session->security_parameters.extensions.server_names[i].type =
+                GNUTLS_NAME_DNS;
+              break;
             }
-
-          /* move to next record */
-          p += len;
         }
+
+      /* move to next record */
+      p += len;
     }
   return 0;
 }