/* $OpenBSD: hkdf.h,v 1.2 2018/04/03 13:33:53 tb Exp $ */
/* Copyright (c) 2014, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#ifndef OPENSSL_HEADER_HKDF_H
#define OPENSSL_HEADER_HKDF_H

#include <openssl/evp.h>

#if defined(__cplusplus)
extern "C" {
#endif

/*
 * HKDF computes HKDF (as specified by RFC 5869) of initial keying
 * material |secret| with |salt| and |info| using |digest|, and
 * outputs |out_len| bytes to |out_key|. It returns one on success and
 * zero on error.
 *
 * HKDF is an Extract-and-Expand algorithm. It does not do any key
 * stretching, and as such, is not suited to be used alone to generate
 * a key from a password.
 */

int HKDF(uint8_t *out_key, size_t out_len, const struct env_md_st *digest,
    const uint8_t *secret, size_t secret_len, const uint8_t *salt,
    size_t salt_len, const uint8_t *info, size_t info_len);

/*
 * HKDF_extract computes a HKDF PRK (as specified by RFC 5869) from
 * initial keying material |secret| and salt |salt| using |digest|,
 * and outputs |out_len| bytes to |out_key|. The maximum output size
 * is |EVP_MAX_MD_SIZE|.  It returns one on success and zero on error.
 */
int HKDF_extract(uint8_t *out_key, size_t *out_len,
    const struct env_md_st *digest, const uint8_t *secret,
    size_t secret_len, const uint8_t *salt, size_t salt_len);

/*
 * HKDF_expand computes a HKDF OKM (as specified by RFC 5869) of
 * length |out_len| from the PRK |prk| and info |info| using |digest|,
 * and outputs the result to |out_key|. It returns one on success and
 * zero on error.
 */
int HKDF_expand(uint8_t *out_key, size_t out_len,
    const EVP_MD *digest, const uint8_t *prk, size_t prk_len,
    const uint8_t *info,  size_t info_len);


#if defined(__cplusplus)
}  /* extern C */
#endif

#endif  /* OPENSSL_HEADER_HKDF_H */
