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
*, 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, unsigned
char *data, int len, int *copy);
int (*new_session_cb)(struct
ssl_st *ssl, SSL_SESSION *sess);
void (*remove_session_cb)(struct
ssl_ctx_st *ctx, SSL_SESSION *sess);
SSL_SESSION *(*get_session_cb)(struct
ssl_st *ssl, 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() allow to retrieve the function pointers
of the provided 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 d2 i_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.
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 onnection, 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).
SEE ALSO
ssl(3),
d2i_SSL_SESSION(3), SSL_CTX_set_session_cache_mode(3), SSL_CTX_flush_sessions(3), SSL_SESSION_free(3), SSL_CTX_free(3)
