Implement/fix session resumption with TLS 1.3

The session we cache at the end of a handshake is non-resumable
in TLS 1.3, since NewSessionTicket message appears quite some time
after the handshake was complete. OpenSSL has a callback where
we can finally obtain a resumable session and inform an application
about session ticket updated by emitting a signal. Truism: OpenSSL-only.

[ChangeLog][QtNetwork] A new signal introduced to report when a valid session ticket received (TLS 1.3)

Fixes: QTBUG-81591
Change-Id: I4d22fad5cc082e431577e20ddbda2835e864b511
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/network/ssl/qsslsocket.cpp b/src/network/ssl/qsslsocket.cpp
index 19be48a656..8fa9f914a2 100644
--- a/src/network/ssl/qsslsocket.cpp
+++ b/src/network/ssl/qsslsocket.cpp
@@ -322,6 +322,22 @@
     \sa QSslPreSharedKeyAuthenticator
 */
 
+/*!
+    \fn void QSslSocket::newSessionTicketReceived()
+    \since 5.15
+
+    If TLS 1.3 protocol was negotiated during a handshake, QSslSocket
+    emits this signal after receiving NewSessionTicket message. Session
+    and session ticket's lifetime hint are updated in the socket's
+    configuration. The session can be used for session resumption (and
+    a shortened handshake) in future TLS connections.
+
+    \note This functionality enabled only with OpenSSL backend and requires
+    OpenSSL v 1.1.1 or above.
+
+    \sa QSslSocket::sslConfiguration(), QSslConfiguration::sessionTicket(), QSslConfiguration::sessionTicketLifeTimeHint()
+*/
+
 #include "qssl_p.h"
 #include "qsslsocket.h"
 #include "qsslcipher.h"