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
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.
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).
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)