1=pod
2
3=head1 NAME
4
5SSL_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
6
7=head1 SYNOPSIS
8
9 #include <openssl/ssl.h>
10
11 void SSL_CTX_sess_set_new_cb(SSL_CTX *ctx,
12			      int (*new_session_cb)(SSL *, SSL_SESSION *));
13 void SSL_CTX_sess_set_remove_cb(SSL_CTX *ctx,
14	   void (*remove_session_cb)(SSL_CTX *ctx, SSL_SESSION *));
15 void SSL_CTX_sess_set_get_cb(SSL_CTX *ctx,
16	   SSL_SESSION (*get_session_cb)(SSL *, unsigned char *, int, int *));
17
18 int (*SSL_CTX_sess_get_new_cb(SSL_CTX *ctx))(struct ssl_st *ssl, SSL_SESSION *sess);
19 void (*SSL_CTX_sess_get_remove_cb(SSL_CTX *ctx))(struct ssl_ctx_st *ctx, SSL_SESSION *sess);
20 SSL_SESSION *(*SSL_CTX_sess_get_get_cb(SSL_CTX *ctx))(struct ssl_st *ssl, unsigned char *data, int len, int *copy);
21
22 int (*new_session_cb)(struct ssl_st *ssl, SSL_SESSION *sess);
23 void (*remove_session_cb)(struct ssl_ctx_st *ctx, SSL_SESSION *sess);
24 SSL_SESSION *(*get_session_cb)(struct ssl_st *ssl, unsigned char *data,
25	       int len, int *copy);
26
27=head1 DESCRIPTION
28
29SSL_CTX_sess_set_new_cb() sets the callback function, which is automatically
30called whenever a new session was negotiated.
31
32SSL_CTX_sess_set_remove_cb() sets the callback function, which is
33automatically called whenever a session is removed by the SSL engine,
34because it is considered faulty or the session has become obsolete because
35of exceeding the timeout value.
36
37SSL_CTX_sess_set_get_cb() sets the callback function which is called,
38whenever a SSL/TLS client proposed to resume a session but the session
39could not be found in the internal session cache (see
40L<SSL_CTX_set_session_cache_mode(3)|SSL_CTX_set_session_cache_mode(3)>).
41(SSL/TLS server only.)
42
43SSL_CTX_sess_get_new_cb(), SSL_CTX_sess_get_remove_cb(), and
44SSL_CTX_sess_get_get_cb() allow to retrieve the function pointers of the
45provided callback functions. If a callback function has not been set,
46the NULL pointer is returned.
47
48=head1 NOTES
49
50In order to allow external session caching, synchronization with the internal
51session cache is realized via callback functions. Inside these callback
52functions, session can be saved to disk or put into a database using the
53L<d2i_SSL_SESSION(3)|d2i_SSL_SESSION(3)> interface.
54
55The new_session_cb() is called, whenever a new session has been negotiated
56and session caching is enabled (see
57L<SSL_CTX_set_session_cache_mode(3)|SSL_CTX_set_session_cache_mode(3)>).
58The new_session_cb() is passed the B<ssl> connection and the ssl session
59B<sess>. If the callback returns B<0>, the session will be immediately
60removed again.
61
62The remove_session_cb() is called, whenever the SSL engine removes a session
63from the internal cache. This happens when the session is removed because
64it is expired or when a connection was not shutdown cleanly. It also happens
65for all sessions in the internal session cache when
66L<SSL_CTX_free(3)|SSL_CTX_free(3)> is called. The remove_session_cb() is passed
67the B<ctx> and the ssl session B<sess>. It does not provide any feedback.
68
69The get_session_cb() is only called on SSL/TLS servers with the session id
70proposed by the client. The get_session_cb() is always called, also when
71session caching was disabled. The get_session_cb() is passed the
72B<ssl> connection, the session id of length B<length> at the memory location
73B<data>. With the parameter B<copy> the callback can require the
74SSL engine to increment the reference count of the SSL_SESSION object,
75Normally the reference count is not incremented and therefore the
76session must not be explicitly freed with
77L<SSL_SESSION_free(3)|SSL_SESSION_free(3)>.
78
79=head1 SEE ALSO
80
81L<ssl(3)|ssl(3)>, L<d2i_SSL_SESSION(3)|d2i_SSL_SESSION(3)>,
82L<SSL_CTX_set_session_cache_mode(3)|SSL_CTX_set_session_cache_mode(3)>,
83L<SSL_CTX_flush_sessions(3)|SSL_CTX_flush_sessions(3)>,
84L<SSL_SESSION_free(3)|SSL_SESSION_free(3)>,
85L<SSL_CTX_free(3)|SSL_CTX_free(3)>
86
87=cut
88