Commit 23cec1f4 authored by Matt Caswell's avatar Matt Caswell
Browse files

Add documentation for the SSL_export_keying_material() function 



Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3735)
parent b5cdec2f

doc/man3/SSL_export_keying_material.pod

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=pod



=head1 NAME



SSL_export_keying_material - obtain keying material for application use



=head1 SYNOPSIS



 #include <openssl/ssl.h>



 int SSL_export_keying_material(SSL *s, unsigned char *out, size_t olen,

                                const char *label, size_t llen,

                                const unsigned char *context,

                                size_t contextlen, int use_context);



=head1 DESCRIPTION



During the creation of a TLS or DTLS connection shared keying material is

established between the two endpoints. The function SSL_export_keying_material()

enables an application to use some of this keying material for its own purposes

in accordance with RFC5705.



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.



For a given SSL connection B<s>, B<olen> bytes of data will be written to

B<out>. The application specific context should be supplied in the location

pointed to by B<context> and should be B<contextlen> bytes long. Provision of

a context is optional. If the context should be omitted entirely then

B<use_context> should be set to 0. Otherwise it should be any other value. If

B<use_context> is 0 then the values of B<context> and B<contextlen> are ignored.

Note that a zero length context is treated differently to no context at all, and

will result in different keying material being returned.



An application specific label should be provided in the location pointed to by

B<label> and should be B<llen> bytes long. Typically this will be a value from

the IANA Exporter Label Registry

(L<https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#exporter-labels>).

Alternatively labels beginning with "EXPERIMENTAL" are permitted by the standard

to be used without registration.



Note that this function is only defined for TLSv1.0 and above, and DTLSv1.0 and

above. Attempting to use it in SSLv3 will result in an error.



=head1 RETURN VALUES



SSL_export_keying_material() returns 0 or -1 on failure or 1 on success.



=head1 COPYRIGHT



Copyright 2017 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

include/openssl/tls1.h

+4 −4
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@@ -212,12 +212,12 @@ __owur int SSL_get_servername_type(const SSL *s); 
 * as specified in RFC 5705. It writes |olen| bytes to |out| given a label and

 * optional context. (Since a zero length context is allowed, the |use_context|

 * flag controls whether a context is included.) It returns 1 on success and

 * zero otherwise.

 * 0 or -1 otherwise.

 */

__owur int SSL_export_keying_material(SSL *s, unsigned char *out, size_t olen,

                                      const char *label, size_t llen,

                               const unsigned char *p, size_t plen,

                               int use_context);

                                      const unsigned char *context,

                                      size_t contextlen, int use_context);



int SSL_get_peer_signature_type_nid(const SSL *s, int *pnid);

ssl/ssl_lib.c

+3 −3
Original line number Diff line number Diff line
@@ -2556,15 +2556,15 @@ void SSL_get0_alpn_selected(const SSL *ssl, const unsigned char **data, 


int SSL_export_keying_material(SSL *s, unsigned char *out, size_t olen,

                               const char *label, size_t llen,

                               const unsigned char *p, size_t plen,

                               const unsigned char *context, size_t contextlen,

                               int use_context)

{

    if (s->version < TLS1_VERSION && s->version != DTLS1_BAD_VER)

        return -1;



    return s->method->ssl3_enc->export_keying_material(s, out, olen, label,

                                                       llen, p, plen,

                                                       use_context);

                                                       llen, context,

                                                       contextlen, use_context);

}



static unsigned long ssl_session_hash(const SSL_SESSION *a)