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<?php
/**
* @file
* Secure password hashing functions for user authentication.
*
* 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 Drupal version in order to counteract increases in the
* speed and power of computers available to crack the hashes.
*/
define('DRUPAL_HASH_COUNT', 15);
/**
* The minimum allowed log2 number of iterations for password stretching.
*/
define('DRUPAL_MIN_HASH_COUNT', 7);
/**
* The maximum allowed log2 number of iterations for password stretching.
*/
define('DRUPAL_MAX_HASH_COUNT', 30);
/**
* The expected (and maximum) number of characters in a hashed password.
*/
define('DRUPAL_HASH_LENGTH', 55);
/**
* Returns a string for mapping an int to the corresponding base 64 character.
*/
function _password_itoa64() {
return './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
}
/**
* Encode 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(drupal_random_bytes(6), 6);
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 ($count_log2 < DRUPAL_MIN_HASH_COUNT) {
return DRUPAL_MIN_HASH_COUNT;
}
elseif ($count_log2 > DRUPAL_MAX_HASH_COUNT) {
return DRUPAL_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 $setting
* An existing hash or the output of _password_generate_salt(). Must be
* at least 12 characters (the settings and salt).
*
* @return
* A string containing the hashed password (and salt) or FALSE on failure.
* The return string will be truncated at DRUPAL_HASH_LENGTH characters max.
*/
function _password_crypt($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 != DRUPAL_HASH_COUNT
if ($count_log2 < DRUPAL_MIN_HASH_COUNT || $count_log2 > DRUPAL_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, DRUPAL_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', DRUPAL_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 $account
* A user object with at least the fields from the {users} table.
*
* @return
* TRUE or FALSE.
*/
function user_check_password($password, $account) {
if (substr($account->pass, 0, 2) == 'U$') {
// This may be an updated password from user_update_7000(). Such hashes
// have 'U' added as the first character and need an extra md5().
$stored_hash = substr($account->pass, 1);
$password = md5($password);
}
else {
$stored_hash = $account->pass;
}
$type = substr($stored_hash, 0, 3);
switch ($type) {
case '$S$':
// A normal Drupal 7 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 Drupal version.
$hash = _password_crypt('md5', $password, $stored_hash);
break;
default:
return FALSE;
}
return ($hash && $stored_hash == $hash);
}
/**
* 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
* DRUPAL_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($account->pass, 0, 3) != '$S$') || (strlen($account->pass) != DRUPAL_HASH_LENGTH)) {
return TRUE;
}
// Ensure that $count_log2 is within set bounds.
$count_log2 = _password_enforce_log2_boundaries(variable_get('password_count_log2', DRUPAL_HASH_COUNT));
// Check whether the iteration count used differs from the standard number.
return (_password_get_count_log2($account->pass) !== $count_log2);
}
