1SSL_CTX_SESS_SET_GET_CB(3) OpenSSL SSL_CTX_SESS_SET_GET_CB(3)
2
6 SSL_CTX_sess_set_new_cb, SSL_CTX_sess_set_remove_cb,
7 SSL_CTX_sess_set_get_cb, SSL_CTX_sess_get_new_cb,
8 SSL_CTX_sess_get_remove_cb, SSL_CTX_sess_get_get_cb - provide callback
9 functions for server side external session caching
10
12 #include <openssl/ssl.h>
13 void SSL_CTX_sess_set_new_cb(SSL_CTX *ctx,
15 int (*new_session_cb)(SSL *, SSL_SESSION *));
16 void SSL_CTX_sess_set_remove_cb(SSL_CTX *ctx,
17 void (*remove_session_cb)(SSL_CTX *ctx,
18 SSL_SESSION *));
19 void SSL_CTX_sess_set_get_cb(SSL_CTX *ctx,
20 SSL_SESSION (*get_session_cb)(SSL *,
21 const unsigned char *,
22 int, int *));
23 int (*SSL_CTX_sess_get_new_cb(SSL_CTX *ctx))(struct ssl_st *ssl,
25 SSL_SESSION *sess);
26 void (*SSL_CTX_sess_get_remove_cb(SSL_CTX *ctx))(struct ssl_ctx_st *ctx,
27 SSL_SESSION *sess);
28 SSL_SESSION *(*SSL_CTX_sess_get_get_cb(SSL_CTX *ctx))(struct ssl_st *ssl,
29 const unsigned char *data,
30 int len, int *copy);
31
33 SSL_CTX_sess_set_new_cb() sets the callback function, which is
34 automatically called whenever a new session was negotiated.
35 SSL_CTX_sess_set_remove_cb() sets the callback function, which is
37 automatically called whenever a session is removed by the SSL engine,
38 because it is considered faulty or the session has become obsolete
39 because of exceeding the timeout value.
40 SSL_CTX_sess_set_get_cb() sets the callback function which is called,
42 whenever a SSL/TLS client proposed to resume a session but the session
43 could not be found in the internal session cache (see
44 SSL_CTX_set_session_cache_mode(3)). (SSL/TLS server only.)
45 SSL_CTX_sess_get_new_cb(), SSL_CTX_sess_get_remove_cb(), and
47 SSL_CTX_sess_get_get_cb() retrieve the function pointers set by the
48 corresponding set callback functions. If a callback function has not
49 been set, the NULL pointer is returned.
50
52 In order to allow external session caching, synchronization with the
53 internal session cache is realized via callback functions. Inside these
54 callback functions, session can be saved to disk or put into a database
55 using the d2i_SSL_SESSION(3) interface.
56 The new_session_cb() is called, whenever a new session has been
58 negotiated and session caching is enabled (see
59 SSL_CTX_set_session_cache_mode(3)). The new_session_cb() is passed the
60 ssl connection and the ssl session sess. If the callback returns 0, the
61 session will be immediately removed again. Note that in TLSv1.3,
62 sessions are established after the main handshake has completed. The
63 server decides when to send the client the session information and this
64 may occur some time after the end of the handshake (or not at all).
65 This means that applications should expect the new_session_cb()
66 function to be invoked during the handshake (for <= TLSv1.2) or after
67 the handshake (for TLSv1.3). It is also possible in TLSv1.3 for
68 multiple sessions to be established with a single connection. In these
69 case the new_session_cb() function will be invoked multiple times.
70 In TLSv1.3 it is recommended that each SSL_SESSION object is only used
72 for resumption once. One way of enforcing that is for applications to
73 call SSL_CTX_remove_session(3) after a session has been used.
74 The remove_session_cb() is called, whenever the SSL engine removes a
76 session from the internal cache. This happens when the session is
77 removed because it is expired or when a connection was not shutdown
78 cleanly. It also happens for all sessions in the internal session cache
79 when SSL_CTX_free(3) is called. The remove_session_cb() is passed the
80 ctx and the ssl session sess. It does not provide any feedback.
81 The get_session_cb() is only called on SSL/TLS servers with the session
83 id proposed by the client. The get_session_cb() is always called, also
84 when session caching was disabled. The get_session_cb() is passed the
85 ssl connection, the session id of length length at the memory location
86 data. With the parameter copy the callback can require the SSL engine
87 to increment the reference count of the SSL_SESSION object, Normally
88 the reference count is not incremented and therefore the session must
89 not be explicitly freed with SSL_SESSION_free(3).
90
92 SSL_CTX_sess_get_new_cb(), SSL_CTX_sess_get_remove_cb() and
93 SSL_CTX_sess_get_get_cb() return different callback function pointers
94 respectively.
95
97 ssl(7), d2i_SSL_SESSION(3), SSL_CTX_set_session_cache_mode(3),
98 SSL_CTX_flush_sessions(3), SSL_SESSION_free(3), SSL_CTX_free(3)
99
101 Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved.
102 Licensed under the OpenSSL license (the "License"). You may not use
104 this file except in compliance with the License. You can obtain a copy
105 in the file LICENSE in the source distribution or at
106 <https://www.openssl.org/source/license.html>.
1071.1.1c 2019-05-28 SSL_CTX_SESS_SET_GET_CB(3)