/*

 * SHA1-based key derivation function (PBKDF2) for IEEE 802.11i

 * 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"

static int pbkdf2_sha1_f(const char *passphrase, const u8 *ssid,

       size_t ssid_len, int iterations, unsigned int count,

       u8 *digest)

{

  unsigned char tmp[SHA1_MAC_LEN], tmp2[SHA1_MAC_LEN];

  int i, j;

  unsigned char count_buf[4];

  const u8 *addr[2];

  size_t len[2];

  size_t passphrase_len = os_strlen(passphrase);

  addr[0] = ssid;

  len[0] = ssid_len;

  addr[1] = count_buf;

  len[1] = 4;

  /* F(P, S, c, i) = U1 xor U2 xor ... Uc

   * U1 = PRF(P, S || i)

   * U2 = PRF(P, U1)

   * Uc = PRF(P, Uc-1)

   */

  count_buf[0] = (count >> 24) & 0xff;

  count_buf[1] = (count >> 16) & 0xff;

  count_buf[2] = (count >> 8) & 0xff;

  count_buf[3] = count & 0xff;

  if (hmac_sha1_vector((u8 *) passphrase, passphrase_len, 2, addr, len,

           tmp))

    return -1;

  os_memcpy(digest, tmp, SHA1_MAC_LEN);

  for (i = 1; i < iterations; i++) {

    if (hmac_sha1((u8 *) passphrase, passphrase_len, tmp,

            SHA1_MAC_LEN, tmp2))

      return -1;

    os_memcpy(tmp, tmp2, SHA1_MAC_LEN);

    for (j = 0; j < SHA1_MAC_LEN; j++)

      digest[j] ^= tmp2[j];

  }

  forced_memzero(tmp, SHA1_MAC_LEN);

  forced_memzero(tmp2, SHA1_MAC_LEN);

  return 0;

}

/**

 * pbkdf2_sha1 - SHA1-based key derivation function (PBKDF2) for IEEE 802.11i

 * @passphrase: ASCII passphrase

 * @ssid: SSID

 * @ssid_len: SSID length in bytes

 * @iterations: Number of iterations to run

 * @buf: Buffer for the generated key

 * @buflen: Length of the buffer in bytes

 * Returns: 0 on success, -1 of failure

 *

 * This function is used to derive PSK for WPA-PSK. For this protocol,

 * iterations is set to 4096 and buflen to 32. This function is described in

 * IEEE Std 802.11-2004, Clause H.4. The main construction is from PKCS#5 v2.0.

 */

int pbkdf2_sha1(const char *passphrase, const u8 *ssid, size_t ssid_len,

    int iterations, u8 *buf, size_t buflen)

{

  unsigned int count = 0;

  unsigned char *pos = buf;

  size_t left = buflen, plen;

  unsigned char digest[SHA1_MAC_LEN];

  while (left > 0) {

    count++;

    if (pbkdf2_sha1_f(passphrase, ssid, ssid_len, iterations,

          count, digest))

      return -1;

    plen = left > SHA1_MAC_LEN ? SHA1_MAC_LEN : left;

    os_memcpy(pos, digest, plen);

    pos += plen;

    left -= plen;

  }

  forced_memzero(digest, SHA1_MAC_LEN);

  return 0;

}