[PATCH 1 of 4] SSL: switched to detect log level based on the last error

[Maxim Dounin]

# HG changeset patch
# User Maxim Dounin <mdounin at mdounin.ru>
# Date 1677682263 -10800
#      Wed Mar 01 17:51:03 2023 +0300
# Node ID 4d0a265c1d20f22f196680dfcc9d044f9e711865
# Parent  2acb00b9b5fff8a97523b659af4377fc605abe6e
SSL: switched to detect log level based on the last error.

In some cases there might be multiple errors in the OpenSSL error queue,
notably when a libcrypto call fails, and then the SSL layer generates
an error itself.  For example, the following errors were observed
with OpenSSL 3.0.8 with TLSv1.3 enabled:

SSL_do_handshake() failed (SSL: error:02800066:Diffie-Hellman routines::invalid public key error:0A000132:SSL routines::bad ecpoint)
SSL_do_handshake() failed (SSL: error:08000066:elliptic curve routines::invalid encoding error:0A000132:SSL routines::bad ecpoint)
SSL_do_handshake() failed (SSL: error:0800006B:elliptic curve routines::point is not on curve error:0A000132:SSL routines::bad ecpoint)

In such cases it seems to be better to determine logging level based on
the last error in the error queue (the one added by the SSL layer,
SSL_R_BAD_ECPOINT in all of the above example example errors).  To do so,
the ngx_ssl_connection_error() function was changed to use
ERR_peek_last_error().

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
@@ -3389,7 +3389,7 @@ ngx_ssl_connection_error(ngx_connection_
 
     } else if (sslerr == SSL_ERROR_SSL) {
 
-        n = ERR_GET_REASON(ERR_peek_error());
+        n = ERR_GET_REASON(ERR_peek_last_error());
 
             /* handshake failures */
         if (n == SSL_R_BAD_CHANGE_CIPHER_SPEC                        /*  103 */