.\" $OpenBSD: SSL_SESSION_free.3,v 1.6 2018/03/27 17:35:50 schwarze Exp $ .\" full merge up to: OpenSSL b31db505 Mar 24 16:01:50 2017 +0000 .\" .\" This file was written by Lutz Jaenicke .\" and Matt Caswell . .\" Copyright (c) 2000, 2001, 2009, 2017 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: March 27 2018 $ .Dt SSL_SESSION_FREE 3 .Os .Sh NAME .Nm SSL_SESSION_up_ref , .Nm SSL_SESSION_free .Nd SSL_SESSION reference counting .Sh SYNOPSIS .In openssl/ssl.h .Ft int .Fn SSL_SESSION_up_ref "SSL_SESSION *session" .Ft void .Fn SSL_SESSION_free "SSL_SESSION *session" .Sh DESCRIPTION .Fn SSL_SESSION_up_ref increments the reference count of the given .Fa session by 1. .Pp .Fn SSL_SESSION_free decrements the reference count of the given .Fa session by 1. If the reference count reaches 0, it frees the memory used by the .Fa session . If .Fa session is a .Dv NULL pointer, no action occurs. .Pp .Vt SSL_SESSION objects are allocated when a TLS/SSL handshake operation is successfully completed. Depending on the settings, see .Xr SSL_CTX_set_session_cache_mode 3 , the .Vt SSL_SESSION objects are internally referenced by the .Vt SSL_CTX and linked into its session cache. .Vt SSL objects may be using the .Vt SSL_SESSION object; as a session may be reused, several .Vt SSL objects may be using one .Vt SSL_SESSION object at the same time. It is therefore crucial to keep the reference count (usage information) correct and not delete a .Vt SSL_SESSION object that is still used, as this may lead to program failures due to dangling pointers. These failures may also appear delayed, e.g., when an .Vt SSL_SESSION object is completely freed as the reference count incorrectly becomes 0, but it is still referenced in the internal session cache and the cache list is processed during a .Xr SSL_CTX_flush_sessions 3 operation. .Pp .Fn SSL_SESSION_free must only be called for .Vt SSL_SESSION objects, for which the reference count was explicitly incremented (e.g., by calling .Xr SSL_get1_session 3 ; see .Xr SSL_get_session 3 ) or when the .Vt SSL_SESSION object was generated outside a TLS handshake operation, e.g., by using .Xr d2i_SSL_SESSION 3 . It must not be called on other .Vt SSL_SESSION objects, as this would cause incorrect reference counts and therefore program failures. .Sh RETURN VALUES .Fn SSL_SESSION_up_ref returns 1 on success or 0 on error. .Sh SEE ALSO .Xr d2i_SSL_SESSION 3 , .Xr SSL_CTX_flush_sessions 3 , .Xr SSL_CTX_set_session_cache_mode 3 , .Xr SSL_get_session 3 , .Xr SSL_SESSION_new 3 .Sh HISTORY .Fn SSL_SESSION_free first appeared in SSLeay 0.5.2 and has been available since .Ox 2.4 . .Pp .Fn SSL_SESSION_up_ref first appeared in OpenSSL 1.1.0 and has been available since .Ox 6.3 .