From f7cdbc0e87fd6a8151165ec51d3c4b01ab77b256 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= <mpg@elzevir.fr>
Date: Fri, 17 Oct 2014 17:02:10 +0200
Subject: [PATCH] Fix potential bad read of length

---
 ChangeLog         |  2 ++
 library/ssl_cli.c | 13 +++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 571cb3ba0..8e49e5c19 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -29,6 +29,8 @@ Bugfix
    * Fix compiler warnings on iOS (found by Sander Niemeijer).
    * x509_crt_parse() did not increase total_failed on PEM error
    * Fix compile error with armcc in mpi_is_prime()
+   * Fix potential bad read in parsing ServerHello (found by Adrien
+     Vialletelle).
 
 Changes
    * Ciphersuites using SHA-256 or SHA-384 now require TLS 1.x (there is no
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 38f9fe720..27abb3efe 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -875,7 +875,7 @@ static int ssl_parse_server_hello( ssl_context *ssl )
 {
     int ret, i, comp;
     size_t n;
-    size_t ext_len = 0;
+    size_t ext_len;
     unsigned char *buf, *ext;
     int renegotiation_info_seen = 0;
     int handshake_failure = 0;
@@ -981,7 +981,7 @@ static int ssl_parse_server_hello( ssl_context *ssl )
      *   42+n . 43+n  extensions length
      *   44+n . 44+n+m extensions
      */
-    if( ssl->in_hslen > 42 + n )
+    if( ssl->in_hslen > 43 + n )
     {
         ext_len = ( ( buf[42 + n] <<  8 )
                   | ( buf[43 + n]       ) );
@@ -993,6 +993,15 @@ static int ssl_parse_server_hello( ssl_context *ssl )
             return( POLARSSL_ERR_SSL_BAD_HS_SERVER_HELLO );
         }
     }
+    else if( ssl->in_hslen == 42 + n )
+    {
+        ext_len = 0;
+    }
+    else
+    {
+        SSL_DEBUG_MSG( 1, ( "bad server hello message" ) );
+        return( POLARSSL_ERR_SSL_BAD_HS_SERVER_HELLO );
+    }
 
     i = ( buf[39 + n] << 8 ) | buf[40 + n];
     comp = buf[41 + n];