From bdb1ca45454d90410031c4c2054005a995f76180 Mon Sep 17 00:00:00 2001

From: Zdenek Dohnal <zdohnal@redhat.com>

Date: Wed, 6 Apr 2022 15:04:45 +0200

Subject: [PATCH] cups/tls-gnutls.c: Use always GNUTLS_SHUT_WR

The current mode for `gnutls_bye()` in client use cases strictly

follows TLS v1.2 standard, which in this particular part says:

```

Unless some other fatal alert has been transmitted, each party is

required to send a close_notify alert before closing the write

side of the connection.  The other party MUST respond with a

close_notify alert of its own and close down the connection immediately,

discarding any pending writes.  It is not required for the initiator

of the close to wait for the responding close_notify alert before

closing the read side of the connection.

```

and waits for the other side of TLS connection to confirm the close.

Unfortunately it can undesired for reasons:

- we support switching of TLS versions in CUPS, and this mode strictly

  follows TLS v1.2 - so for older version this behavior is not expected

  and can cause delays

- even some TLS v1.2 implementations (like Windows Server 2016) don't

  comply TLS v1.2 behavior even if it says it does - in that case,

  encrypted printing takes 30s till HTTP timeout is reached, because the

  other side didn't send confirmation

- AFAIU openssl's SSL_shutdown() doesn't make this TLS v1.2 difference,

  so we could end up with two TLS implementations in CUPS which will

  behave differently

Since the standard defines that waiting for confirmation is not required

and due the problems above, I would propose using GNUTLS_SHUT_WR mode

regardless of HTTP mode.

---

 cups/tls-gnutls.c | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cups/tls-gnutls.c b/cups/tls-gnutls.c

index c55995b2b..f87b4f4df 100644

--- a/cups/tls-gnutls.c

+++ b/cups/tls-gnutls.c

@@ -1667,7 +1667,7 @@ _httpTLSStop(http_t *http)		/* I - Connection to server */

   int	error;				/* Error code */

-  error = gnutls_bye(http->tls, http->mode == _HTTP_MODE_CLIENT ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);

+  error = gnutls_bye(http->tls, GNUTLS_SHUT_WR);

   if (error != GNUTLS_E_SUCCESS)

     _cupsSetError(IPP_STATUS_ERROR_INTERNAL, gnutls_strerror(errno), 0);

-- 

2.35.1