114 lines
4.2 KiB
Plaintext
114 lines
4.2 KiB
Plaintext
=pod
|
|
|
|
=head1 NAME
|
|
|
|
SSL_get_session, SSL_get0_session, SSL_get1_session - retrieve TLS/SSL session data
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#include <openssl/ssl.h>
|
|
|
|
SSL_SESSION *SSL_get_session(const SSL *ssl);
|
|
SSL_SESSION *SSL_get0_session(const SSL *ssl);
|
|
SSL_SESSION *SSL_get1_session(SSL *ssl);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
SSL_get_session() returns a pointer to the B<SSL_SESSION> actually used in
|
|
B<ssl>. The reference count of the B<SSL_SESSION> is not incremented, so
|
|
that the pointer can become invalid by other operations.
|
|
|
|
SSL_get0_session() is the same as SSL_get_session().
|
|
|
|
SSL_get1_session() is the same as SSL_get_session(), but the reference
|
|
count of the B<SSL_SESSION> is incremented by one.
|
|
|
|
=head1 NOTES
|
|
|
|
The ssl session contains all information required to re-establish the
|
|
connection without a full handshake for SSL versions up to and including
|
|
TLSv1.2. In TLSv1.3 the same is true, but sessions are established after the
|
|
main handshake has occurred. The server will send the session information to the
|
|
client at a time of its choosing, which may be some while after the initial
|
|
connection is established (or never). Calling these functions on the client side
|
|
in TLSv1.3 before the session has been established will still return an
|
|
SSL_SESSION object but that object cannot be used for resuming the session. See
|
|
L<SSL_SESSION_is_resumable(3)> for information on how to determine whether an
|
|
SSL_SESSION object can be used for resumption or not.
|
|
|
|
Additionally, in TLSv1.3, a server can send multiple messages that establish a
|
|
session for a single connection. In that case, on the client side, the above
|
|
functions will only return information on the last session that was received. On
|
|
the server side they will only return information on the last session that was
|
|
sent, or if no session tickets were sent then the session for the current
|
|
connection.
|
|
|
|
The preferred way for applications to obtain a resumable SSL_SESSION object is
|
|
to use a new session callback as described in L<SSL_CTX_sess_set_new_cb(3)>.
|
|
The new session callback is only invoked when a session is actually established,
|
|
so this avoids the problem described above where an application obtains an
|
|
SSL_SESSION object that cannot be used for resumption in TLSv1.3. It also
|
|
enables applications to obtain information about all sessions sent by the
|
|
server.
|
|
|
|
A session will be automatically removed from the session cache and marked as
|
|
non-resumable if the connection is not closed down cleanly, e.g. if a fatal
|
|
error occurs on the connection or L<SSL_shutdown(3)> is not called prior to
|
|
L<SSL_free(3)>.
|
|
|
|
In TLSv1.3 it is recommended that each SSL_SESSION object is only used for
|
|
resumption once.
|
|
|
|
SSL_get0_session() returns a pointer to the actual session. As the
|
|
reference counter is not incremented, the pointer is only valid while
|
|
the connection is in use. If L<SSL_clear(3)> or
|
|
L<SSL_free(3)> is called, the session may be removed completely
|
|
(if considered bad), and the pointer obtained will become invalid. Even
|
|
if the session is valid, it can be removed at any time due to timeout
|
|
during L<SSL_CTX_flush_sessions(3)>.
|
|
|
|
If the data is to be kept, SSL_get1_session() will increment the reference
|
|
count, so that the session will not be implicitly removed by other operations
|
|
but stays in memory. In order to remove the session
|
|
L<SSL_SESSION_free(3)> must be explicitly called once
|
|
to decrement the reference count again.
|
|
|
|
SSL_SESSION objects keep internal link information about the session cache
|
|
list, when being inserted into one SSL_CTX object's session cache.
|
|
One SSL_SESSION object, regardless of its reference count, must therefore
|
|
only be used with one SSL_CTX object (and the SSL objects created
|
|
from this SSL_CTX object).
|
|
|
|
=head1 RETURN VALUES
|
|
|
|
The following return values can occur:
|
|
|
|
=over 4
|
|
|
|
=item NULL
|
|
|
|
There is no session available in B<ssl>.
|
|
|
|
=item Pointer to an SSL_SESSION
|
|
|
|
The return value points to the data of an SSL session.
|
|
|
|
=back
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<ssl(7)>, L<SSL_free(3)>,
|
|
L<SSL_clear(3)>,
|
|
L<SSL_SESSION_free(3)>
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
|
|
|
|
Licensed under the OpenSSL license (the "License"). You may not use
|
|
this file except in compliance with the License. You can obtain a copy
|
|
in the file LICENSE in the source distribution or at
|
|
L<https://www.openssl.org/source/license.html>.
|
|
|
|
=cut
|