Prevent potential NULL pointer dereference in ssl_read_record()

ChangeLog

@@ -12,6 +12,8 @@ Security
      This affects certificates in the user-supplied chain except the top
      certificate. If the user-supplied chain contains only one certificates,
      it is not affected (ie, its notAfter date is properly checked).
+   * Prevent potential NULL pointer dereference in ssl_read_record() (found by
+     TrustInSoft)
 
 Bugfix
    * The length of various ClientKeyExchange messages was not properly checked.

library/ssl_tls.c

@@ -2087,7 +2087,8 @@ int ssl_read_record( ssl_context *ssl )
             return( POLARSSL_ERR_SSL_INVALID_RECORD );
         }
 
-        ssl->handshake->update_checksum( ssl, ssl->in_msg, ssl->in_hslen );
+        if( ssl->state != SSL_HANDSHAKE_OVER )
+            ssl->handshake->update_checksum( ssl, ssl->in_msg, ssl->in_hslen );
 
         return( 0 );
     }