• NAME
• SYNOPSIS
• DESCRIPTION
• RETURN VALUES
• SEE ALSO
• HISTORY
• COPYRIGHT

NAME

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

SYNOPSIS

 #include <openssl/ssl.h>
 
 int SSL_set_num_tickets(SSL *s, size_t num_tickets);
 size_t SSL_get_num_tickets(SSL *s);
 int SSL_CTX_set_num_tickets(SSL_CTX *ctx, size_t num_tickets);
 size_t SSL_CTX_get_num_tickets(SSL_CTX *ctx);
 int SSL_new_session_ticket(SSL *s);

DESCRIPTION

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; the default number of tickets sent following a resumption handshake is 1 but this cannot be changed using these functions. The number of tickets following a resumption handshake can be reduced to 0 using custom session ticket callbacks (see 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. 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. 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. 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 RETURN VALUES

SSL_CTX_set_num_tickets(), SSL_set_num_tickets(), and SSL_new_session_ticket() return 1 on success or 0 on failure.

HISTORY

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.

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.