/*

 * Copyright (C) 2017 Red Hat, Inc.

 *

 * Author: Nikos Mavrogiannopoulos

 *

 * This file is part of GnuTLS.

 *

 * The GnuTLS is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License

 * as published by the Free Software Foundation; either version 2.1 of

 * the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>

 *

 */

/* Functions for the TLS PRF handling.

 */

#if HAVE_CONFIG_H

#include "config.h"

#endif

#include "gnutls_int.h"

#include "fips.h"

#include <stdlib.h>

#include <string.h>

#include <nettle/hmac.h>

#include <nettle/memxor.h>

#include "int/tls1-prf.h"

#include <nettle/sha1.h>

#include <nettle/md5.h>

/* The RFC2246 P_hash() function. The mac_ctx is expected to

 * be initialized and key set to be the secret key.

 */

static void P_hash(void *mac_ctx, nettle_hash_update_func *update,

       nettle_hash_digest_func *digest, size_t digest_size,

       size_t seed_size, const uint8_t *seed, size_t label_size,

       const char *label, size_t dst_length, uint8_t *dst)

{

  uint8_t Atmp[MAX_HASH_SIZE];

  ssize_t left;

  unsigned started = 0;

  /* round up */

  left = dst_length;

  while (left > 0) {

    if (started == 0) { /* A(0) */

      update(mac_ctx, label_size,

             (const uint8_t *)label); /* hash label */

      update(mac_ctx, seed_size, seed);

      started = 1;

    } else {

      update(mac_ctx, digest_size, Atmp);

    }

    digest(mac_ctx, digest_size, Atmp); /* store A(i) */

    update(mac_ctx, digest_size, Atmp); /* hash A(i) */

    update(mac_ctx, label_size,

           (const uint8_t *)label); /* hash label */

    update(mac_ctx, seed_size, seed); /* hash seed */

    if (left < (ssize_t)digest_size)

      digest_size = left;

    digest(mac_ctx, digest_size, dst);

    left -= digest_size;

    dst += digest_size;

  }

  return;

}

int tls10_prf(size_t secret_size, const uint8_t *secret, size_t label_size,

        const char *label, size_t seed_size, const uint8_t *seed,

        size_t length, uint8_t *dst)

{

  int l_s;

  const uint8_t *s1, *s2;

  struct hmac_md5_ctx md5_ctx;

  struct hmac_sha1_ctx sha1_ctx;

  uint8_t o1[MAX_PRF_BYTES];

  if (length > MAX_PRF_BYTES)

    return 0;

  l_s = secret_size / 2;

  s1 = &secret[0];

  s2 = &secret[l_s];

  if (secret_size % 2 != 0) {

    l_s++;

  }

  hmac_md5_set_key(&md5_ctx, l_s, s1);

  P_hash(&md5_ctx, (nettle_hash_update_func *)hmac_md5_update,

         (nettle_hash_digest_func *)hmac_md5_digest, MD5_DIGEST_SIZE,

         seed_size, seed, label_size, label, length, o1);

  hmac_sha1_set_key(&sha1_ctx, l_s, s2);

  P_hash(&sha1_ctx, (nettle_hash_update_func *)hmac_sha1_update,

         (nettle_hash_digest_func *)hmac_sha1_digest, SHA1_DIGEST_SIZE,

         seed_size, seed, label_size, label, length, dst);

  memxor(dst, o1, length);

  return 1;

}

/*-

 * tls12_prf:

 * @mac_ctx: a MAC context initialized with key being the secret

 * @update: a MAC update function

 * @digest: a MAC digest function

 * @digest_size: the MAC output size

 * @label_size: the size of the label

 * @label: the label to apply

 * @seed_size: the seed size

 * @seed: the seed

 * @length: size of desired PRF output

 * @dst: the location to store output

 *

 * The TLS 1.2 Pseudo-Random-Function (PRF).

 *

 * Returns: zero on failure, non zero on success.

 -*/

int tls12_prf(void *mac_ctx, nettle_hash_update_func *update,

        nettle_hash_digest_func *digest, size_t digest_size,

        size_t label_size, const char *label, size_t seed_size,

        const uint8_t *seed, size_t length, uint8_t *dst)

{

#define MASTER_SECRET "master secret"

#define MASTER_SECRET_SIZE (sizeof(MASTER_SECRET) - 1)

  P_hash(mac_ctx, update, digest, digest_size, seed_size, seed,

         label_size, label, length, dst);

  /* Since May 16, 2023, the use of extended master secret is

   * mandatory according to FIPS 140-3 IG D.Q.  Instead of

   * allowing the "extended master secret" label specifically,

   * we mark the use of non-EMS label, i.e., "master secret" as

   * non-approved, because it is still useful to call the

   * gnutls_prf_raw function with arbitrary label, e.g., in

   * self-tests.

   */

  if (label_size == MASTER_SECRET_SIZE &&

      memcmp(label, MASTER_SECRET, MASTER_SECRET_SIZE) == 0) {

    _gnutls_switch_fips_state(GNUTLS_FIPS140_OP_NOT_APPROVED);

  } else {

    _gnutls_switch_fips_state(GNUTLS_FIPS140_OP_APPROVED);

  }

  return 1;

}