add signature algorithms extension
@@ -107,11 +107,60 @@ int mbedtls_ssl_tls13_write_sig_alg_ext( mbedtls_ssl_context *ssl,
unsigned char *end,
size_t *olen )
{
- ((void) ssl);
- ((void) buf);
- ((void) end);
+ unsigned char *p = buf;
+ unsigned char *sig_alg_ptr; /* Start of supported_signature_algorithms */
+ size_t sig_alg_len = 0; /* Length of supported_signature_algorithms */
+
*olen = 0;
- MBEDTLS_SSL_DEBUG_MSG( 3, ( "signature_algorithm extension is not available" ) );
+
+ /* Skip the extension on the client if all allowed key exchanges
+ * are PSK-based. */
+#if defined(MBEDTLS_SSL_CLI_C)
+ if( ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT &&
+ !mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) )
+ {
+ return( 0 );
+ }
+#endif /* MBEDTLS_SSL_CLI_C */
+
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "adding signature_algorithms extension" ) );
+
+ /* Check there is space for extension header */
+ MBEDTLS_SSL_CHK_BUF_PTR( p, end, 6 );
+ p += 6;
+
+ /*
+ * Write supported_signature_algorithms
+ */
+ sig_alg_ptr = p;
+ for( const uint16_t *sig_alg = ssl->conf->tls13_sig_algs;
+ *sig_alg != MBEDTLS_TLS13_SIG_NONE; sig_alg++ )
+ {
+ MBEDTLS_SSL_CHK_BUF_PTR( p, end, 2 );
+ MBEDTLS_PUT_UINT16_BE( *sig_alg, p, 0 );
+ p += 2;
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "signature scheme [%x]", *sig_alg ) );
+ }
+
+ /* Length of supported_signature_algorithms*/
+ sig_alg_len = p - sig_alg_ptr;
+ if( sig_alg_len == 0 )
+ {
+ MBEDTLS_SSL_DEBUG_MSG( 1, ( "No signature algorithms defined." ) );
+ return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+ }
+
+ /* Write extension_type */
+ MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_SIG_ALG, buf, 0 );
+ /* Write extension_data_length */
+ MBEDTLS_PUT_UINT16_BE( sig_alg_len + 2, buf, 2 );
+ /* Write length of supported_signature_algorithms */
+ MBEDTLS_PUT_UINT16_BE( sig_alg_len, buf, 4 );
+
+ /* Output the total length of signature algorithms extension. */
+ *olen = p - buf;
+
+ ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_SIG_ALG;
return( 0 );
}
