/*

 * SHA1-based PRF

 * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>

 *

 * This software may be distributed under the terms of the BSD license.

 * See README for more details.

 */

#include "includes.h"

#include "common.h"

#include "sha1.h"

#include "crypto.h"

/**

 * sha1_prf - SHA1-based Pseudo-Random Function (PRF) (IEEE 802.11i, 8.5.1.1)

 * @key: Key for PRF

 * @key_len: Length of the key in bytes

 * @label: A unique label for each purpose of the PRF

 * @data: Extra data to bind into the key

 * @data_len: Length of the data

 * @buf: Buffer for the generated pseudo-random key

 * @buf_len: Number of bytes of key to generate

 * Returns: 0 on success, -1 of failure

 *

 * This function is used to derive new, cryptographically separate keys from a

 * given key (e.g., PMK in IEEE 802.11i).

 */

int sha1_prf(const u8 *key, size_t key_len, const char *label,

       const u8 *data, size_t data_len, u8 *buf, size_t buf_len)

{

  u8 counter = 0;

  size_t pos, plen;

  u8 hash[SHA1_MAC_LEN];

  size_t label_len = os_strlen(label) + 1;

  const unsigned char *addr[3];

  size_t len[3];

  addr[0] = (u8 *) label;

  len[0] = label_len;

  addr[1] = data;

  len[1] = data_len;

  addr[2] = &counter;

  len[2] = 1;

  pos = 0;

  while (pos < buf_len) {

    plen = buf_len - pos;

    if (plen >= SHA1_MAC_LEN) {

      if (hmac_sha1_vector(key, key_len, 3, addr, len,

               &buf[pos]))

        return -1;

      pos += SHA1_MAC_LEN;

    } else {

      if (hmac_sha1_vector(key, key_len, 3, addr, len,

               hash))

        return -1;

      os_memcpy(&buf[pos], hash, plen);

      break;

    }

    counter++;

  }

  forced_memzero(hash, sizeof(hash));

  return 0;

}