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.\" $OpenBSD: SSL_export_keying_material.3,v 1.1 2017/08/21 10:10:25 schwarze Exp $
.\" OpenSSL a599574b Jun 28 17:18:27 2017 +0100
.\" OpenSSL 23cec1f4 Jun 21 13:55:02 2017 +0100
.\"
.\" This file was written by Matt Caswell <matt@openssl.org>.
.\" Copyright (c) 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,
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: August 21 2017 $
.Dt SSL_EXPORT_KEYING_MATERIAL 3
.Os
.Sh NAME
.Nm SSL_export_keying_material
.Nd obtain keying material for application use
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft int
.Fo SSL_export_keying_material
.Fa "SSL *s"
.Fa "unsigned char *out"
.Fa "size_t olen"
.Fa "const char *label"
.Fa "size_t llen"
.Fa "const unsigned char *context"
.Fa "size_t contextlen"
.Fa "int use_context"
.Fc
.Sh DESCRIPTION
During the creation of a TLS or DTLS connection,
shared keying material is established between the two endpoints.
The function
.Fn SSL_export_keying_material
enables an application to use some of this keying material
for its own purposes in accordance with RFC 5705.
.Pp
An application may need to securely establish the context
within which this keying material will be used.
For example, this may include identifiers for the application session,
application algorithms or parameters, or the lifetime of the context.
The context value is left to the application but must be the same on
both sides of the communication.
.Pp
For a given SSL connection
.Fa s ,
.Fa olen
bytes of data will be written to
.Fa out .
The application specific context should be supplied
in the location pointed to by
.Fa context
and should be
.Fa contextlen
bytes long.
Provision of a context is optional.
If the context should be omitted entirely, then
.Fa use_context
should be set to 0.
Otherwise it should be any other value.
If
.Fa use_context
is 0, then the values of
.Fa context
and
.Fa contextlen
are ignored.
.Pp
In TLSv1.2 and below, a zero length context is treated differently
from no context at all, and will result in different keying material
being returned.
.Pp
An application specific label should be provided in the location pointed
to by
.Fa label
and should be
.Fa llen
bytes long.
Typically this will be a value from the
.Lk https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#exporter-labels "IANA Exporter Label Registry" .
.Pp
Alternatively, labels beginning with "EXPERIMENTAL" are permitted by the
standard to be used without registration.
.Sh RETURN VALUES
.Fn SSL_export_keying_material
returns 1 on success or 0 or -1 on failure.
|
