5 SSL_get_session, SSL_get0_session, SSL_get1_session - retrieve TLS/SSL session data
9 #include <openssl/ssl.h>
11 SSL_SESSION *SSL_get_session(const SSL *ssl);
12 SSL_SESSION *SSL_get0_session(const SSL *ssl);
13 SSL_SESSION *SSL_get1_session(SSL *ssl);
17 SSL_get_session() returns a pointer to the B<SSL_SESSION> actually used in
18 B<ssl>. The reference count of the B<SSL_SESSION> is not incremented, so
19 that the pointer can become invalid by other operations.
21 SSL_get0_session() is the same as SSL_get_session().
23 SSL_get1_session() is the same as SSL_get_session(), but the reference
24 count of the B<SSL_SESSION> is incremented by one.
28 The ssl session contains all information required to re-establish the
29 connection without a full handshake for SSL versions up to and including
30 TLSv1.2. In TLSv1.3 the same is true, but sessions are established after the
31 main handshake has occurred. The server will send the session information to the
32 client at a time of its choosing, which may be some while after the initial
33 connection is established (or never). Calling these functions on the client side
34 in TLSv1.3 before the session has been established will still return an
35 SSL_SESSION object but that object cannot be used for resuming the session. See
36 L<SSL_SESSION_is_resumable(3)> for information on how to determine whether an
37 SSL_SESSION object can be used for resumption or not.
39 Additionally, in TLSv1.3, a server can send multiple messages that establish a
40 session for a single connection. In that case the above functions will only
41 return information on the last session that was received.
43 The preferred way for applications to obtain a resumable SSL_SESSION object is
44 to use a new session callback as described in L<SSL_CTX_sess_set_new_cb(3)>.
45 The new session callback is only invoked when a session is actually established,
46 so this avoids the problem described above where an application obtains an
47 SSL_SESSION object that cannot be used for resumption in TLSv1.3. It also
48 enables applications to obtain information about all sessions sent by the
51 A session will be automatically removed from the session cache and marked as
52 non-resumable if the connection is not closed down cleanly, e.g. if a fatal
53 error occurs on the connection or L<SSL_shutdown(3)> is not called prior to
56 In TLSv1.3 it is recommended that each SSL_SESSION object is only used for
59 SSL_get0_session() returns a pointer to the actual session. As the
60 reference counter is not incremented, the pointer is only valid while
61 the connection is in use. If L<SSL_clear(3)> or
62 L<SSL_free(3)> is called, the session may be removed completely
63 (if considered bad), and the pointer obtained will become invalid. Even
64 if the session is valid, it can be removed at any time due to timeout
65 during L<SSL_CTX_flush_sessions(3)>.
67 If the data is to be kept, SSL_get1_session() will increment the reference
68 count, so that the session will not be implicitly removed by other operations
69 but stays in memory. In order to remove the session
70 L<SSL_SESSION_free(3)> must be explicitly called once
71 to decrement the reference count again.
73 SSL_SESSION objects keep internal link information about the session cache
74 list, when being inserted into one SSL_CTX object's session cache.
75 One SSL_SESSION object, regardless of its reference count, must therefore
76 only be used with one SSL_CTX object (and the SSL objects created
77 from this SSL_CTX object).
81 The following return values can occur:
87 There is no session available in B<ssl>.
89 =item Pointer to an SSL_SESSION
91 The return value points to the data of an SSL session.
97 L<ssl(7)>, L<SSL_free(3)>,
99 L<SSL_SESSION_free(3)>
103 Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
105 Licensed under the Apache License 2.0 (the "License"). You may not use
106 this file except in compliance with the License. You can obtain a copy
107 in the file LICENSE in the source distribution or at
108 L<https://www.openssl.org/source/license.html>.