<?php

/**
 * @file
 * Secure password hashing functions for user authentication.
 *
 * 
 * Please NOTE:  This file was taken largely from the open source Drupal 7 CMS project,
 * and is used here in compliance with the GNU GPL v.3+ license.
 * 
 * For more documentation, see:
 * https://api.drupal.org/api/drupal/includes%21password.inc/7
 * 
 * 
 * 
 * 
 * Based on the Portable PHP password hashing framework.
 * @see http://www.openwall.com/phpass/
 *
 * An alternative or custom version of this password hashing API may be
 * used by setting the variable password_inc to the name of the PHP file
 * containing replacement user_hash_password(), user_check_password(), and
 * user_needs_new_hash() functions.
 */

/**
 * The standard log2 number of iterations for password stretching. This should
 * increase by 1 every major FlightPath version in order to counteract increases in the
 * speed and power of computers available to crack the hashes.
 */
define('FP_HASH_COUNT', 15);

/**
 * The minimum allowed log2 number of iterations for password stretching.
 */
define('FP_MIN_HASH_COUNT', 7);

/**
 * The maximum allowed log2 number of iterations for password stretching.
 */
define('FP_MAX_HASH_COUNT', 30);

/**
 * The expected (and maximum) number of characters in a hashed password.
 */
define('FP_HASH_LENGTH', 55);

/**
 * Returns a string for mapping an int to the corresponding base 64 character.
 */
function _password_itoa64() {
  return './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
}

/**
 * Encodes bytes into printable base 64 using the *nix standard from crypt().
 *
 * @param $input
 *   The string containing bytes to encode.
 * @param $count
 *   The number of characters (bytes) to encode.
 *
 * @return
 *   Encoded string
 */
function _password_base64_encode($input, $count) {
  $output = '';
  $i = 0;
  $itoa64 = _password_itoa64();
  do {
    $value = ord($input[$i++]);
    $output .= $itoa64[$value & 0x3f];
    if ($i < $count) {
      $value |= ord($input[$i]) << 8;
    }
    $output .= $itoa64[($value >> 6) & 0x3f];
    if ($i++ >= $count) {
      break;
    }
    if ($i < $count) {
      $value |= ord($input[$i]) << 16;
    }
    $output .= $itoa64[($value >> 12) & 0x3f];
    if ($i++ >= $count) {
      break;
    }
    $output .= $itoa64[($value >> 18) & 0x3f];
  } while ($i < $count);

  return $output;
}

/**
 * Generates a random base 64-encoded salt prefixed with settings for the hash.
 *
 * Proper use of salts may defeat a number of attacks, including:
 *  - The ability to try candidate passwords against multiple hashes at once.
 *  - The ability to use pre-hashed lists of candidate passwords.
 *  - The ability to determine whether two users have the same (or different)
 *    password without actually having to guess one of the passwords.
 *
 * @param $count_log2
 *   Integer that determines the number of iterations used in the hashing
 *   process. A larger value is more secure, but takes more time to complete.
 *
 * @return
 *   A 12 character string containing the iteration count and a random salt.
 */
function _password_generate_salt($count_log2) {
  $output = '$S$';
  // Ensure that $count_log2 is within set bounds.
  $count_log2 = _password_enforce_log2_boundaries($count_log2);
  // We encode the final log2 iteration count in base 64.
  $itoa64 = _password_itoa64();
  $output .= $itoa64[$count_log2];
  // 6 bytes is the standard salt for a portable phpass hash.
  $output .= _password_base64_encode(fp_random_bytes(6), 6);
  //$output .= _password_base64_encode("123456", 6);
    
  return $output;
}

function fp_random_bytes($count) {
  // $random_state does not use drupal_static as it stores random bytes.
  static $random_state, $bytes, $has_openssl;

  $missing_bytes = $count - strlen($bytes);

  if ($missing_bytes > 0) {
    // PHP versions prior 5.3.4 experienced openssl_random_pseudo_bytes()
    // locking on Windows and rendered it unusable.
    if (!isset($has_openssl)) {
      $has_openssl = version_compare(PHP_VERSION, '5.3.4', '>=') && function_exists('openssl_random_pseudo_bytes');
    }

    // openssl_random_pseudo_bytes() will find entropy in a system-dependent
    // way.
    if ($has_openssl) {
      $bytes .= openssl_random_pseudo_bytes($missing_bytes);
    }

    // Else, read directly from /dev/urandom, which is available on many *nix
    // systems and is considered cryptographically secure.
    elseif ($fh = @fopen('/dev/urandom', 'rb')) {
      // PHP only performs buffered reads, so in reality it will always read
      // at least 4096 bytes. Thus, it costs nothing extra to read and store
      // that much so as to speed any additional invocations.
      $bytes .= fread($fh, max(4096, $missing_bytes));
      fclose($fh);
    }

    // If we couldn't get enough entropy, this simple hash-based PRNG will
    // generate a good set of pseudo-random bytes on any system.
    // Note that it may be important that our $random_state is passed
    // through hash() prior to being rolled into $output, that the two hash()
    // invocations are different, and that the extra input into the first one -
    // the microtime() - is prepended rather than appended. This is to avoid
    // directly leaking $random_state via the $output stream, which could
    // allow for trivial prediction of further "random" numbers.
    if (strlen($bytes) < $count) {
      // Initialize on the first call. The contents of $_SERVER includes a mix of
      // user-specific and system information that varies a little with each page.
      if (!isset($random_state)) {
        $random_state = print_r($_SERVER, TRUE);
        if (function_exists('getmypid')) {
          // Further initialize with the somewhat random PHP process ID.
          $random_state .= getmypid();
        }
        $bytes = '';
      }

      do {
        $random_state = hash('sha256', microtime() . mt_rand() . $random_state);
        $bytes .= hash('sha256', mt_rand() . $random_state, TRUE);
      } 
       while (strlen($bytes) < $count);
    }
  }
  $output = substr($bytes, 0, $count);
  $bytes = substr($bytes, $count);
  return $output;
}




/**
 * Ensures that $count_log2 is within set bounds.
 *
 * @param $count_log2
 *   Integer that determines the number of iterations used in the hashing
 *   process. A larger value is more secure, but takes more time to complete.
 *
 * @return
 *   Integer within set bounds that is closest to $count_log2.
 */
function _password_enforce_log2_boundaries($count_log2) {
  if ($count_log2 < FP_MIN_HASH_COUNT) {
    return FP_MIN_HASH_COUNT;
  }
  elseif ($count_log2 > FP_MAX_HASH_COUNT) {
    return FP_MAX_HASH_COUNT;
  }

  return (int) $count_log2;
}

/**
 * Hash a password using a secure stretched hash.
 *
 * By using a salt and repeated hashing the password is "stretched". Its
 * security is increased because it becomes much more computationally costly
 * for an attacker to try to break the hash by brute-force computation of the
 * hashes of a large number of plain-text words or strings to find a match.
 *
 * @param $algo
 *   The string name of a hashing algorithm usable by hash(), like 'sha256'.
 * @param $password
 *   The plain-text password to hash.
 * @param $setting
 *   An existing hash or the output of _password_generate_salt().  Must be
 *   at least 12 characters (the settings and salt).
 *
 * @return
 *   A string containing the hashed password (and salt) or FALSE on failure.
 *   The return string will be truncated at FP_HASH_LENGTH characters max.
 */
function _password_crypt($algo, $password, $setting) {
  // The first 12 characters of an existing hash are its setting string.
  $setting = substr($setting, 0, 12);

  if ($setting[0] != '$' || $setting[2] != '$') {
    return FALSE;
  }
  $count_log2 = _password_get_count_log2($setting);
  // Hashes may be imported from elsewhere, so we allow != FP_HASH_COUNT
  if ($count_log2 < FP_MIN_HASH_COUNT || $count_log2 > FP_MAX_HASH_COUNT) {
    return FALSE;
  }
  $salt = substr($setting, 4, 8);
  // Hashes must have an 8 character salt.
  if (strlen($salt) != 8) {
    return FALSE;
  }

  // Convert the base 2 logarithm into an integer.
  $count = 1 << $count_log2;

  // We rely on the hash() function being available in PHP 5.2+.
  $hash = hash($algo, $salt . $password, TRUE);
  do {
    $hash = hash($algo, $hash . $password, TRUE);
  } while (--$count);

  $len = strlen($hash);
  $output =  $setting . _password_base64_encode($hash, $len);
  // _password_base64_encode() of a 16 byte MD5 will always be 22 characters.
  // _password_base64_encode() of a 64 byte sha512 will always be 86 characters.
  $expected = 12 + ceil((8 * $len) / 6);
  return (strlen($output) == $expected) ? substr($output, 0, FP_HASH_LENGTH) : FALSE;
}

/**
 * Parse the log2 iteration count from a stored hash or setting string.
 */
function _password_get_count_log2($setting) {
  $itoa64 = _password_itoa64();
  return strpos($itoa64, $setting[3]);
}

/**
 * Hash a password using a secure hash.
 *
 * @param $password
 *   A plain-text password.
 * @param $count_log2
 *   Optional integer to specify the iteration count. Generally used only during
 *   mass operations where a value less than the default is needed for speed.
 *
 * @return
 *   A string containing the hashed password (and a salt), or FALSE on failure.
 */
function user_hash_password($password, $count_log2 = 0) {
  if (empty($count_log2)) {
    // Use the standard iteration count.
    $count_log2 = variable_get('password_count_log2', FP_HASH_COUNT);
  }
  return _password_crypt('sha512', $password, _password_generate_salt($count_log2));
}

/**
 * Check whether a plain text password matches a stored hashed password.
 *
 * Alternative implementations of this function may use other data in the
 * $account object, for example the uid to look up the hash in a custom table
 * or remote database.
 *
 * @param $password
 *   A plain-text password
 * @param $stored_hash
 *   The password hash for a user from the database.
 * 
 * @return
 *   TRUE or FALSE.
 */
function user_check_password($password, $stored_hash) {


  $type = substr($stored_hash, 0, 3);  
  switch ($type) {
    case '$S$':
      // A normal FlightPath password using sha512.
      $hash = _password_crypt('sha512', $password, $stored_hash);      
      break;
    case '$H$':
      // phpBB3 uses "$H$" for the same thing as "$P$".
    case '$P$':
      // A phpass password generated using md5.  This is an
      // imported password or from an earlier FlightPath version.
      $hash = _password_crypt('md5', $password, $stored_hash);
      break;
    default:
      return FALSE;
  }
  return ($hash && $stored_hash == $hash);
}

/**
 * NOTE:  This function is from Drupal 7, but at the moment is not being used by FlightPath.
 * 
 * 
 */
 /* Check whether a user's hashed password needs to be replaced with a new hash.
 *
 * This is typically called during the login process when the plain text
 * password is available. A new hash is needed when the desired iteration count
 * has changed through a change in the variable password_count_log2 or
 * FP_HASH_COUNT or if the user's password hash was generated in an update
 * like user_update_7000().
 *
 * Alternative implementations of this function might use other criteria based
 * on the fields in $account.
 *
 * @param $account
 *   A user object with at least the fields from the {users} table.
 *
 * @return
 *   TRUE or FALSE.
 */
function user_needs_new_hash($account) {
  // Check whether this was an updated password.
  if ((substr($account->password, 0, 3) != '$S$') || (strlen($account->password) != FP_HASH_LENGTH)) {
    return TRUE;
  }
  // Ensure that $count_log2 is within set bounds.
  $count_log2 = _password_enforce_log2_boundaries(variable_get('password_count_log2', FP_HASH_COUNT));
  // Check whether the iteration count used differs from the standard number.
  return (_password_get_count_log2($account->password) !== $count_log2);
}