Add comments about 1.3 server sending no cert
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index 5fdc527..8f8f8c2 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -472,6 +472,7 @@
mbedtls_free(ssl->session_negotiate->peer_cert);
}
+ /* This is used by ssl_tls13_validate_certificate() */
if (certificate_list_len == 0) {
ssl->session_negotiate->peer_cert = NULL;
ret = 0;
@@ -675,6 +676,11 @@
#endif /* MBEDTLS_SSL_SRV_C */
#if defined(MBEDTLS_SSL_CLI_C)
+ /* Regardless of authmode, the server is not allowed to send an empty
+ * certificate chain. (Last paragraph before 4.4.2.1 in RFC 8446: "The
+ * server's certificate_list MUST always be non-empty.") With authmode
+ * optional/none, we continue the handshake if we can't validate the
+ * server's cert, but we still break it if no certificate was sent. */
if (ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT) {
MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_NO_CERT,
MBEDTLS_ERR_SSL_FATAL_ALERT_MESSAGE);