mirror of
https://github.com/openssl/openssl.git
synced 2024-12-15 06:01:37 +08:00
99d63d4662
Move manpages to manX directories Add Windows/VMS install fix from Richard Levitte Update README Fix typo's Remove some duplicates Reviewed-by: Richard Levitte <levitte@openssl.org>
129 lines
4.1 KiB
Plaintext
129 lines
4.1 KiB
Plaintext
=pod
|
|
|
|
=head1 NAME
|
|
|
|
EVP_PKEY_CTX_set_hkdf_md, EVP_PKEY_CTX_set1_hkdf_salt,
|
|
EVP_PKEY_CTX_set1_hkdf_key, EVP_PKEY_CTX_add1_hkdf_info -
|
|
HMAC-based Extract-and-Expand key derivation algorithm
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#include <openssl/kdf.h>
|
|
|
|
int EVP_PKEY_CTX_set_hkdf_md(EVP_PKEY_CTX *pctx, const EVP_MD *md);
|
|
|
|
int EVP_PKEY_CTX_set1_hkdf_salt(EVP_PKEY_CTX *pctx, unsigned char *salt,
|
|
int saltlen);
|
|
|
|
int EVP_PKEY_CTX_set1_hkdf_key(EVP_PKEY_CTX *pctx, unsigned char *key,
|
|
int keylen);
|
|
|
|
int EVP_PKEY_CTX_add1_hkdf_info(EVP_PKEY_CTX *pctx, unsigned char *info,
|
|
int infolen);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
The EVP_PKEY_HKDF algorithm implements the HKDF key derivation function.
|
|
HKDF follows the "extract-then-expand" paradigm, where the KDF logically
|
|
consists of two modules. The first stage takes the input keying material
|
|
and "extracts" from it a fixed-length pseudorandom key K. The second stage
|
|
"expands" the key K into several additional pseudorandom keys (the output
|
|
of the KDF).
|
|
|
|
EVP_PKEY_set_hkdf_md() sets the message digest associated with the HKDF.
|
|
|
|
EVP_PKEY_CTX_set1_hkdf_salt() sets the salt to B<saltlen> bytes of the
|
|
buffer B<salt>. Any existing value is replaced.
|
|
|
|
EVP_PKEY_CTX_set_hkdf_key() sets the key to B<keylen> bytes of the buffer
|
|
B<key>. Any existing value is replaced.
|
|
|
|
EVP_PKEY_CTX_add1_hkdf_info() sets the info value to B<infolen> bytes of the
|
|
buffer B<info>. If a value is already set, it is appended to the existing
|
|
value.
|
|
|
|
=head1 STRING CTRLS
|
|
|
|
HKDF also supports string based control operations via
|
|
L<EVP_PKEY_CTX_ctrl_str(3)>.
|
|
The B<type> parameter "md" uses the supplied B<value> as the name of the digest
|
|
algorithm to use.
|
|
The B<type> parameters "salt", "key" and "info" use the supplied B<value>
|
|
parameter as a B<seed>, B<key> or B<info> value.
|
|
The names "hexsalt", "hexkey" and "hexinfo" are similar except they take a hex
|
|
string which is converted to binary.
|
|
|
|
=head1 NOTES
|
|
|
|
All these functions are implemented as macros.
|
|
|
|
A context for HKDF can be obtained by calling:
|
|
|
|
EVP_PKEY_CTX *pctx = EVP_PKEY_new_id(EVP_PKEY_HKDF, NULL);
|
|
|
|
The digest, key, salt and info values must be set before a key is derived or
|
|
an error occurs.
|
|
|
|
The total length of the info buffer cannot exceed 1024 bytes in length: this
|
|
should be more than enough for any normal use of HKDF.
|
|
|
|
The output length of the KDF is specified via the length parameter to the
|
|
L<EVP_PKEY_derive(3)> function.
|
|
Since the HKDF output length is variable, passing a B<NULL> buffer as a means
|
|
to obtain the requisite length is not meaningful with HKDF.
|
|
Instead, the caller must allocate a buffer of the desired length, and pass that
|
|
buffer to L<EVP_PKEY_derive(3)> along with (a pointer initialized to) the
|
|
desired length.
|
|
|
|
Optimised versions of HKDF can be implemented in an ENGINE.
|
|
|
|
=head1 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.
|
|
|
|
=head1 EXAMPLE
|
|
|
|
This example derives 10 bytes using SHA-256 with the secret key "secret",
|
|
salt value "salt" and info value "label":
|
|
|
|
EVP_PKEY_CTX *pctx;
|
|
unsigned char out[10];
|
|
size_t outlen = sizeof(out);
|
|
pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
|
|
|
|
if (EVP_PKEY_derive_init(pctx) <= 0)
|
|
/* Error */
|
|
if (EVP_PKEY_CTX_set_hkdf_md(pctx, EVP_sha256()) <= 0)
|
|
/* Error */
|
|
if (EVP_PKEY_CTX_set1_salt(pctx, "salt", 4) <= 0)
|
|
/* Error */
|
|
if (EVP_PKEY_CTX_set1_key(pctx, "secret", 6) <= 0)
|
|
/* Error */
|
|
if (EVP_PKEY_CTX_add1_hkdf_info(pctx, "label", 6) <= 0)
|
|
/* Error */
|
|
if (EVP_PKEY_derive(pctx, out, &outlen) <= 0)
|
|
/* Error */
|
|
|
|
=head1 CONFORMING TO
|
|
|
|
RFC 5869
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<EVP_PKEY_CTX_new(3)>,
|
|
L<EVP_PKEY_CTX_ctrl_str(3)>,
|
|
L<EVP_PKEY_derive(3)>
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2016 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
|