SSL_CTX_sess_set_get_cb(3) OpenSSL SSL_CTX_sess_set_get_cb(3)
NAME
SSL_CTX_sess_set_new_cb, SSL_CTX_sess_set_remove_cb,
SSL_CTX_sess_set_get_cb, SSL_CTX_sess_get_new_cb,
SSL_CTX_sess_get_remove_cb, SSL_CTX_sess_get_get_cb - provide callback
functions for server side external session caching
SYNOPSIS
#include <openssl/ssl.h>
void SSL_CTX_sess_set_new_cb(SSL_CTX *ctx,
int (*new_session_cb)(SSL *, SSL_SESSION *));
void SSL_CTX_sess_set_remove_cb(SSL_CTX *ctx,
void (*remove_session_cb)(SSL_CTX *ctx,
SSL_SESSION *));
void SSL_CTX_sess_set_get_cb(SSL_CTX *ctx,
SSL_SESSION (*get_session_cb)(SSL *,
const unsigned char *,
int, int *));
int (*SSL_CTX_sess_get_new_cb(SSL_CTX *ctx))(struct ssl_st *ssl,
SSL_SESSION *sess);
void (*SSL_CTX_sess_get_remove_cb(SSL_CTX *ctx))(struct ssl_ctx_st *ctx,
SSL_SESSION *sess);
SSL_SESSION *(*SSL_CTX_sess_get_get_cb(SSL_CTX *ctx))(struct ssl_st *ssl,
const unsigned char *data,
int len, int *copy);
DESCRIPTION
SSL_CTX_sess_set_new_cb() sets the callback function, which is
automatically called whenever a new session was negotiated.
SSL_CTX_sess_set_remove_cb() sets the callback function, which is
automatically called whenever a session is removed by the SSL engine,
because it is considered faulty or the session has become obsolete
because of exceeding the timeout value.
SSL_CTX_sess_set_get_cb() sets the callback function which is called,
whenever a SSL/TLS client proposed to resume a session but the session
could not be found in the internal session cache (see
SSL_CTX_set_session_cache_mode(3)). (SSL/TLS server only.)
SSL_CTX_sess_get_new_cb(), SSL_CTX_sess_get_remove_cb(), and
SSL_CTX_sess_get_get_cb() retrieve the function pointers set by the
corresponding set callback functions. If a callback function has not
been set, the NULL pointer is returned.
NOTES
In order to allow external session caching, synchronization with the
internal session cache is realized via callback functions. Inside these
callback functions, session can be saved to disk or put into a database
using the d2i_SSL_SESSION(3) interface.
The new_session_cb() is called, whenever a new session has been
negotiated and session caching is enabled (see
SSL_CTX_set_session_cache_mode(3)). The new_session_cb() is passed the
ssl connection and the ssl session sess. If the callback returns 0, the
session will be immediately removed again. Note that in TLSv1.3,
sessions are established after the main handshake has completed. The
server decides when to send the client the session information and this
may occur some time after the end of the handshake (or not at all).
This means that applications should expect the new_session_cb()
function to be invoked during the handshake (for <= TLSv1.2) or after
the handshake (for TLSv1.3). It is also possible in TLSv1.3 for
multiple sessions to be established with a single connection. In these
case the new_session_cb() function will be invoked multiple times.
In TLSv1.3 it is recommended that each SSL_SESSION object is only used
for resumption once. One way of enforcing that is for applications to
call SSL_CTX_remove_session(3) after a session has been used.
The remove_session_cb() is called, whenever the SSL engine removes a
session from the internal cache. This happens when the session is
removed because it is expired or when a connection was not shutdown
cleanly. It also happens for all sessions in the internal session cache
when SSL_CTX_free(3) is called. The remove_session_cb() is passed the
ctx and the ssl session sess. It does not provide any feedback.
The get_session_cb() is only called on SSL/TLS servers with the session
id proposed by the client. The get_session_cb() is always called, also
when session caching was disabled. The get_session_cb() is passed the
ssl connection, the session id of length length at the memory location
data. With the parameter copy the callback can require the SSL engine
to increment the reference count of the SSL_SESSION object, Normally
the reference count is not incremented and therefore the session must
not be explicitly freed with SSL_SESSION_free(3).
RETURN VALUES
SSL_CTX_sess_get_new_cb(), SSL_CTX_sess_get_remove_cb() and
SSL_CTX_sess_get_get_cb() return different callback function pointers
respectively.
SEE ALSO
ssl(7), d2i_SSL_SESSION(3), SSL_CTX_set_session_cache_mode(3),
SSL_CTX_flush_sessions(3), SSL_SESSION_free(3), SSL_CTX_free(3)
COPYRIGHT
Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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>.
1.1.1d 2019-09-10 SSL_CTX_sess_set_get_cb(3)
openssl 1.1.1d - Generated Mon Oct 14 16:22:28 CDT 2019