1=pod 2 3=head1 NAME 4 5SSL_set_num_tickets, 6SSL_get_num_tickets, 7SSL_CTX_set_num_tickets, 8SSL_CTX_get_num_tickets, 9SSL_new_session_ticket 10- control the number of TLSv1.3 session tickets that are issued 11 12=head1 SYNOPSIS 13 14 #include <openssl/ssl.h> 15 16 int SSL_set_num_tickets(SSL *s, size_t num_tickets); 17 size_t SSL_get_num_tickets(const SSL *s); 18 int SSL_CTX_set_num_tickets(SSL_CTX *ctx, size_t num_tickets); 19 size_t SSL_CTX_get_num_tickets(const SSL_CTX *ctx); 20 int SSL_new_session_ticket(SSL *s); 21 22=head1 DESCRIPTION 23 24SSL_CTX_set_num_tickets() and SSL_set_num_tickets() can be called for a server 25application and set the number of TLSv1.3 session tickets that will be sent to 26the client after a full handshake. Set the desired value (which could be 0) in 27the B<num_tickets> argument. Typically these functions should be called before 28the start of the handshake. 29 30The default number of tickets is 2. Following a resumption the number of tickets 31issued will never be more than 1 regardless of the value set via 32SSL_set_num_tickets() or SSL_CTX_set_num_tickets(). If B<num_tickets> is set to 330 then no tickets will be issued for either a normal connection or a resumption. 34 35Tickets are also issued on receipt of a post-handshake certificate from the 36client following a request by the server using 37L<SSL_verify_client_post_handshake(3)>. These new tickets will be associated 38with the updated client identity (i.e. including their certificate and 39verification status). The number of tickets issued will normally be the same as 40was used for the initial handshake. If the initial handshake was a full 41handshake then SSL_set_num_tickets() can be called again prior to calling 42SSL_verify_client_post_handshake() to update the number of tickets that will be 43sent. 44 45To issue tickets after other events (such as application-layer changes), 46SSL_new_session_ticket() is used by a server application to request that a new 47ticket be sent when it is safe to do so. New tickets are only allowed to be 48sent in this manner after the initial handshake has completed, and only for 49TLS 1.3 connections. By default, the ticket generation and transmission are 50delayed until the server is starting a new write operation, so that it is 51bundled with other application data being written and properly aligned to a 52record boundary. If the connection was at a record boundary when 53SSL_new_session_ticket() was called, the ticket can be sent immediately 54(without waiting for the next application write) by calling 55SSL_do_handshake(). SSL_new_session_ticket() can be called more than once to 56request additional tickets be sent; all such requests are queued and written 57together when it is safe to do so and triggered by SSL_write() or 58SSL_do_handshake(). Note that a successful return from 59SSL_new_session_ticket() indicates only that the request to send a ticket was 60processed, not that the ticket itself was sent. To be notified when the 61ticket itself is sent, a new-session callback can be registered with 62L<SSL_CTX_sess_set_new_cb(3)> that will be invoked as the ticket or tickets 63are generated. 64 65SSL_CTX_get_num_tickets() and SSL_get_num_tickets() return the number of 66tickets set by a previous call to SSL_CTX_set_num_tickets() or 67SSL_set_num_tickets(), or 2 if no such call has been made. 68 69=head1 RETURN VALUES 70 71SSL_CTX_set_num_tickets(), SSL_set_num_tickets(), and 72SSL_new_session_ticket() return 1 on success or 0 on failure. 73 74SSL_CTX_get_num_tickets() and SSL_get_num_tickets() return the number of tickets 75that have been previously set. 76 77=head1 SEE ALSO 78 79L<ssl(7)> 80 81=head1 HISTORY 82 83SSL_new_session_ticket() was added in OpenSSL 3.0.0. 84SSL_set_num_tickets(), SSL_get_num_tickets(), SSL_CTX_set_num_tickets(), and 85SSL_CTX_get_num_tickets() were added in OpenSSL 1.1.1. 86 87=head1 COPYRIGHT 88 89Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved. 90 91Licensed under the Apache License 2.0 (the "License"). You may not use 92this file except in compliance with the License. You can obtain a copy 93in the file LICENSE in the source distribution or at 94L<https://www.openssl.org/source/license.html>. 95 96=cut 97