[nginx] SSL: logging level of "no suitable signature algorithm".

[Maxim Dounin]

details:   https://hg.nginx.org/nginx/rev/c5d7a72abadc
branches:  stable-1.14
changeset: 7419:c5d7a72abadc
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Tue Sep 25 14:00:04 2018 +0300
description:
SSL: logging level of "no suitable signature algorithm".

The "no suitable signature algorithm" errors are reported by OpenSSL 1.1.1
when using TLSv1.3 if there are no shared signature algorithms.  In
particular, this can happen if the client limits available signature
algorithms to something we don't have a certificate for, or to an empty
list.  For example, the following command:

    openssl s_client -connect 127.0.0.1:8443 -sigalgs rsa_pkcs1_sha1

will always result in the "no suitable signature algorithm" error
as the "rsa_pkcs1_sha1" algorithm refers solely to signatures which
appear in certificates and not defined for use in TLS 1.3 handshake
messages.

The SSL_R_NO_COMMON_SIGNATURE_ALGORITHMS error is what BoringSSL returns
in the same situation.

diffstat:

 src/event/ngx_event_openssl.c |  6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diffs (23 lines):

diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -2062,6 +2062,9 @@ ngx_ssl_connection_error(ngx_connection_
 #ifdef SSL_R_NO_SUITABLE_KEY_SHARE
             || n == SSL_R_NO_SUITABLE_KEY_SHARE                      /*  101 */
 #endif
+#ifdef SSL_R_NO_SUITABLE_SIGNATURE_ALGORITHM
+            || n == SSL_R_NO_SUITABLE_SIGNATURE_ALGORITHM            /*  118 */
+#endif
             || n == SSL_R_BLOCK_CIPHER_PAD_IS_WRONG                  /*  129 */
             || n == SSL_R_DIGEST_CHECK_FAILED                        /*  149 */
             || n == SSL_R_ERROR_IN_RECEIVED_CIPHER_LIST              /*  151 */
@@ -2083,6 +2086,9 @@ ngx_ssl_connection_error(ngx_connection_
             || n == SSL_R_UNEXPECTED_RECORD                          /*  245 */
             || n == SSL_R_UNKNOWN_ALERT_TYPE                         /*  246 */
             || n == SSL_R_UNKNOWN_PROTOCOL                           /*  252 */
+#ifdef SSL_R_NO_COMMON_SIGNATURE_ALGORITHMS
+            || n == SSL_R_NO_COMMON_SIGNATURE_ALGORITHMS             /*  253 */
+#endif
             || n == SSL_R_UNSUPPORTED_PROTOCOL                       /*  258 */
 #ifdef SSL_R_NO_SHARED_GROUP
             || n == SSL_R_NO_SHARED_GROUP                            /*  266 */