SSL_set_num_tickets, SSL_get_num_tickets, SSL_CTX_set_num_tickets,
SSL_CTX_get_num_tickets, SSL_new_session_ticket - control the number of
TLSv1.3 session tickets that are issued
#include <openssl/ssl.h>
int SSL_set_num_tickets(SSL *s, size_t num_tickets);
size_t SSL_get_num_tickets(const SSL *s);
int SSL_CTX_set_num_tickets(SSL_CTX *ctx, size_t num_tickets);
size_t SSL_CTX_get_num_tickets(const SSL_CTX *ctx);
int SSL_new_session_ticket(SSL *s);
SSL_CTX_set_num_tickets() and
SSL_set_num_tickets() can be called
for a server application and set the number of TLSv1.3 session tickets that
will be sent to the client after a full handshake. Set the desired value
(which could be 0) in the
num_tickets argument. Typically these
functions should be called before the start of the handshake.
The default number of tickets is 2. Following a resumption the number of tickets
issued will never be more than 1 regardless of the value set via
SSL_set_num_tickets() or
SSL_CTX_set_num_tickets(). If
num_tickets is set to 0 then no tickets will be issued for either a
normal connection or a resumption.
Tickets are also issued on receipt of a post-handshake certificate from the
client following a request by the server using
SSL_verify_client_post_handshake(3). These new tickets will be
associated with the updated client identity (i.e. including their certificate
and verification status). The number of tickets issued will normally be the
same as was used for the initial handshake. If the initial handshake was a
full handshake then
SSL_set_num_tickets() can be called again prior to
calling
SSL_verify_client_post_handshake() to update the number of
tickets that will be sent.
To issue tickets after other events (such as application-layer changes),
SSL_new_session_ticket() is used by a server application to request
that a new ticket be sent when it is safe to do so. New tickets are only
allowed to be sent in this manner after the initial handshake has completed,
and only for TLS 1.3 connections. By default, the ticket generation and
transmission are delayed until the server is starting a new write operation,
so that it is bundled with other application data being written and properly
aligned to a record boundary. If the connection was at a record boundary when
SSL_new_session_ticket() was called, the ticket can be sent immediately
(without waiting for the next application write) by calling
SSL_do_handshake().
SSL_new_session_ticket() can be called more
than once to request additional tickets be sent; all such requests are queued
and written together when it is safe to do so and triggered by
SSL_write() or
SSL_do_handshake(). Note that a successful return
from
SSL_new_session_ticket() indicates only that the request to send a
ticket was processed, not that the ticket itself was sent. To be notified when
the ticket itself is sent, a new-session callback can be registered with
SSL_CTX_sess_set_new_cb(3) that will be invoked as the ticket or
tickets are generated.
SSL_CTX_get_num_tickets() and
SSL_get_num_tickets() return the
number of tickets set by a previous call to
SSL_CTX_set_num_tickets()
or
SSL_set_num_tickets(), or 2 if no such call has been made.
SSL_CTX_set_num_tickets(),
SSL_set_num_tickets(), and
SSL_new_session_ticket() return 1 on success or 0 on failure.
SSL_CTX_get_num_tickets() and
SSL_get_num_tickets() return the
number of tickets that have been previously set.
ssl(7)
SSL_new_session_ticket() was added in OpenSSL 3.0.0.
SSL_set_num_tickets(),
SSL_get_num_tickets(),
SSL_CTX_set_num_tickets(), and
SSL_CTX_get_num_tickets() were
added in OpenSSL 1.1.1.
Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy in the
file LICENSE in the source distribution or at
<
https://www.openssl.org/source/license.html>.