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.\" $OpenBSD: SSL_CTX_set_session_id_context.3,v 1.5 2018/03/21 17:58:58 schwarze Exp $
.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Lutz Jaenicke <jaenicke@openssl.org>.
.\" Copyright (c) 2001, 2004 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 21 2018 $
.Dt SSL_CTX_SET_SESSION_ID_CONTEXT 3
.Os
.Sh NAME
.Nm SSL_CTX_set_session_id_context ,
.Nm SSL_set_session_id_context
.Nd set context within which session can be reused (server side only)
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft int
.Fo SSL_CTX_set_session_id_context
.Fa "SSL_CTX *ctx"
.Fa "const unsigned char *sid_ctx"
.Fa "unsigned int sid_ctx_len"
.Fc
.Ft int
.Fo SSL_set_session_id_context
.Fa "SSL *ssl"
.Fa "const unsigned char *sid_ctx"
.Fa "unsigned int sid_ctx_len"
.Fc
.Sh DESCRIPTION
.Fn SSL_CTX_set_session_id_context
sets the context
.Fa sid_ctx
of length
.Fa sid_ctx_len
within which a session can be reused for the
.Fa ctx
object.
.Pp
.Fn SSL_set_session_id_context
sets the context
.Fa sid_ctx
of length
.Fa sid_ctx_len
within which a session can be reused for the
.Fa ssl
object.
.Sh NOTES
Sessions are generated within a certain context.
When exporting/importing sessions with
.Xr i2d_SSL_SESSION 3
and
.Xr d2i_SSL_SESSION 3 ,
it would be possible to re-import a session generated from another context
(e.g., another application), which might lead to malfunctions.
Therefore each application must set its own session id context
.Fa sid_ctx
which is used to distinguish the contexts and is stored in exported sessions.
The
.Fa sid_ctx
can be any kind of binary data with a given length; it is therefore possible
to use, for instance, the name of the application, the hostname, the service
name...
.Pp
The session id context becomes part of the session.
The session id context is set by the SSL/TLS server.
The
.Fn SSL_CTX_set_session_id_context
and
.Fn SSL_set_session_id_context
functions are therefore only useful on the server side.
.Pp
OpenSSL clients will check the session id context returned by the server when
reusing a session.
.Pp
The maximum length of the
.Fa sid_ctx
is limited to
.Dv SSL_MAX_SSL_SESSION_ID_LENGTH .
.Sh WARNINGS
If the session id context is not set on an SSL/TLS server and client
certificates are used, stored sessions will not be reused but a fatal error
will be flagged and the handshake will fail.
.Pp
If a server returns a different session id context to an OpenSSL client
when reusing a session, an error will be flagged and the handshake will
fail.
OpenSSL servers will always return the correct session id context,
as an OpenSSL server checks the session id context itself before reusing
a session as described above.
.Sh RETURN VALUES
.Fn SSL_CTX_set_session_id_context
and
.Fn SSL_set_session_id_context
return the following values:
.Bl -tag -width Ds
.It 0
The length
.Fa sid_ctx_len
of the session id context
.Fa sid_ctx
exceeded
the maximum allowed length of
.Dv SSL_MAX_SSL_SESSION_ID_LENGTH .
The error is logged to the error stack.
.It 1
The operation succeeded.
.El
.Sh SEE ALSO
.Xr ssl 3 ,
.Xr SSL_SESSION_set1_id_context 3
.Sh HISTORY
.Fn SSL_set_session_id_context
first appeared in OpenSSL 0.9.2b.
.Fn SSL_CTX_set_session_id_context
first appeared in OpenSSL 0.9.3.
Both functions have been available since
.Ox 2.6 .
|
