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.\" $OpenBSD: EVP_PKEY_CTX_set_tls1_prf_md.3,v 1.3 2025/04/17 14:58:09 tb Exp $
.\" full merge up to: OpenSSL 1cb7eff4 Sep 10 13:56:40 2019 +0100
.\"
.\" This file was written by Dr Stephen Henson <steve@openssl.org>,
.\" Copyright (c) 2016 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)
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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: April 17 2025 $
.Dt EVP_PKEY_CTX_SET_TLS1_PRF_MD 3
.Os
.Sh NAME
.Nm EVP_PKEY_CTX_set_tls1_prf_md ,
.Nm EVP_PKEY_CTX_set1_tls1_prf_secret ,
.Nm EVP_PKEY_CTX_add1_tls1_prf_seed
.Nd TLS PRF key derivation algorithm
.Sh SYNOPSIS
.In openssl/evp.h
.In openssl/kdf.h
.Ft int
.Fo EVP_PKEY_CTX_set_tls1_prf_md
.Fa "EVP_PKEY_CTX *pctx"
.Fa "const EVP_MD *md"
.Fc
.Ft int
.Fo EVP_PKEY_CTX_set1_tls1_prf_secret
.Fa "EVP_PKEY_CTX *pctx"
.Fa "unsigned char *sec"
.Fa "int seclen"
.Fc
.Ft int
.Fo EVP_PKEY_CTX_add1_tls1_prf_seed
.Fa "EVP_PKEY_CTX *pctx"
.Fa "unsigned char *seed"
.Fa "int seedlen"
.Fc
.Sh DESCRIPTION
The
.Dv EVP_PKEY_TLS1_PRF
algorithm implements the PRF key derivation function for TLS.
It has no associated private key and only implements key derivation using
.Xr EVP_PKEY_derive 3 .
.Pp
.Fn EVP_PKEY_set_tls1_prf_md
sets the message digest associated with the TLS PRF.
.Xr EVP_md5_sha1 3
is treated as a special case which uses the PRF algorithm using both
MD5 and SHA-1 as used in TLS 1.0 and 1.1.
.Pp
.Fn EVP_PKEY_CTX_set_tls1_prf_secret
sets the secret value of the TLS PRF to
.Fa seclen
bytes of the buffer
.Fa sec .
Any existing secret value is replaced and any seed is reset.
.Pp
.Fn EVP_PKEY_CTX_add1_tls1_prf_seed
sets the seed to
.Fa seedlen
bytes of
.Fa seed .
If a seed is already set it is appended to the existing value.
.Sh STRING CTRLS
The TLS PRF also supports string based control operations using
.Xr EVP_PKEY_CTX_ctrl_str 3 .
The
.Fa type
parameter "md" uses the supplied
.Fa value
as the name of the digest algorithm to use.
The
.Fa type
parameters "secret" and "seed" use the supplied
.Fa value
parameter as a secret or seed value.
The names "hexsecret" and "hexseed" are similar except they take a hex
string which is converted to binary.
.Sh NOTES
All these functions are implemented as macros.
.Pp
A context for the TLS PRF can be obtained by calling:
.Bd -literal
EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_TLS1_PRF, NULL);
.Ed
.Pp
The digest, secret value and seed must be set before a key is derived or
an error occurs.
.Pp
The total length of all seeds cannot exceed 1024 bytes in length: this
should be more than enough for any normal use of the TLS PRF.
.Pp
The output length of the PRF is specified by the length parameter in the
.Xr EVP_PKEY_derive 3
function.
Since the output length is variable, setting the buffer to
.Dv NULL
is not meaningful for the TLS PRF.
.Sh RETURN VALUES
All these functions return 1 for success and 0 or a negative value for
failure.
In particular a return value of -2 indicates the operation is not
supported by the public key algorithm.
.Sh EXAMPLES
This example derives 10 bytes using SHA-256 with the secret key "secret"
and seed value "seed":
.Bd -literal
EVP_PKEY_CTX *pctx;
unsigned char out[10];
size_t outlen = sizeof(out);
pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_TLS1_PRF, NULL);
if (EVP_PKEY_derive_init(pctx) <= 0)
/* Error */
if (EVP_PKEY_CTX_set_tls1_prf_md(pctx, EVP_sha256()) <= 0)
/* Error */
if (EVP_PKEY_CTX_set1_tls1_prf_secret(pctx, "secret", 6) <= 0)
/* Error */
if (EVP_PKEY_CTX_add1_tls1_prf_seed(pctx, "seed", 4) <= 0)
/* Error */
if (EVP_PKEY_derive(pctx, out, &outlen) <= 0)
/* Error */
.Ed
.Sh SEE ALSO
.Xr EVP_PKEY_CTX_ctrl_str 3 ,
.Xr EVP_PKEY_CTX_new 3 ,
.Xr EVP_PKEY_derive 3
.Sh HISTORY
These functions first appeared in OpenSSL 1.1.0 and have been available since
.Ox 7.6 .
|
