Add extension check for Certificate
@@ -447,6 +447,8 @@ int mbedtls_ssl_tls13_parse_certificate( mbedtls_ssl_context *ssl,
while( p < certificate_list_end )
{
size_t cert_data_len, extensions_len;
+ const unsigned char *extensions_end;
+ uint32_t extensions_present;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, certificate_list_end, 3 );
cert_data_len = MBEDTLS_GET_UINT24_BE( p, 0 );
@@ -504,7 +506,62 @@ int mbedtls_ssl_tls13_parse_certificate( mbedtls_ssl_context *ssl,
extensions_len = MBEDTLS_GET_UINT16_BE( p, 0 );
p += 2;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, certificate_list_end, extensions_len );
- p += extensions_len;
+
+ extensions_end = p + extensions_len;
+ extensions_present = MBEDTLS_SSL_EXT_NONE;
+
+ while( p < extensions_end )
+ {
+ unsigned int extension_type;
+ size_t extension_data_len;
+
+ /*
+ * struct {
+ * ExtensionType extension_type; (2 bytes)
+ * opaque extension_data<0..2^16-1>;
+ * } Extension;
+ */
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, 4 );
+ extension_type = MBEDTLS_GET_UINT16_BE( p, 0 );
+ extension_data_len = MBEDTLS_GET_UINT16_BE( p, 2 );
+ p += 4;
+
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, extension_data_len );
+
+ /* RFC 8446 page 35
+ *
+ * If an implementation receives an extension which it recognizes and
+ * which is not specified for the message in which it appears, it MUST
+ * abort the handshake with an "illegal_parameter" alert.
+ */
+ extensions_present |= mbedtls_tls13_get_extension_mask( extension_type );
+ MBEDTLS_SSL_DEBUG_MSG( 3,
+ ( "encrypted extensions : received %s(%u) extension",
+ mbedtls_tls13_get_extension_name( extension_type ),
+ extension_type ) );
+ if( ( extensions_present & MBEDTLS_SSL_TLS1_3_ALLOWED_EXTS_OF_CT ) == 0 )
+ {
+ MBEDTLS_SSL_DEBUG_MSG(
+ 3, ( "forbidden extension received." ) );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ }
+ switch( extension_type )
+ {
+ default:
+ MBEDTLS_SSL_DEBUG_MSG( 3,
+ ( "Certificate: received %s(%u) extension ( ignored )",
+ mbedtls_tls13_get_extension_name( extension_type ),
+ extension_type ) );
+ break;
+ }
+
+ p += extension_data_len;
+ }
+
+ MBEDTLS_SSL_TLS1_3_PRINT_EXTS( 3, "Certificate", extensions_present );
}
exit:
