Merge branch 'mbedtls-1.3' into development

* mbedtls-1.3:
  Add countermeasure against cache-based lucky 13

Conflicts:
	library/ssl_tls.c

ChangeLog

@@ -90,6 +90,8 @@ Security
    * With authmode set to SSL_VERIFY_OPTIONAL, verification of keyUsage and
      extendedKeyUsage on the leaf certificate was lost (results not accessible
      via ssl_get_verify_results()).
+   * Add countermeasure against "Lucky 13 strikes back" cache-based attack,
+     https://dl.acm.org/citation.cfm?id=2714625
 
 Features
    * Add x509_crt_verify_info() to display certificate verification results.

library/ssl_tls.c

@@ -1943,7 +1943,8 @@ static int ssl_decrypt_buf( mbedtls_ssl_context *ssl )
                              ssl->in_msglen );
             mbedtls_md_hmac_finish( &ssl->transform_in->md_ctx_dec,
                              ssl->in_msg + ssl->in_msglen );
-            for( j = 0; j < extra_run; j++ )
+            /* Call md_process at least once due to cache attacks */
+            for( j = 0; j < extra_run + 1; j++ )
                 mbedtls_md_process( &ssl->transform_in->md_ctx_dec, ssl->in_msg );
 
             mbedtls_md_hmac_reset( &ssl->transform_in->md_ctx_dec );