PHP call of undefined function hash_equals()

Question

any one can help me out of this problem? i'm getting error of 'call of undefined function hash_equals()' here is my code:

$username = 'Admin';
$password = 'sample1Pasword';

$dbh = new PDO('mysql:host=localhost;dbname=test', $USER, $PASSWORD);

$sth = $dbh->prepare('
  SELECT
    hash
  FROM users
  WHERE
    username = :username
  LIMIT 1
  ');

$sth->bindParam(':username', $username);

$sth->execute();

$user = $sth->fetch(PDO::FETCH_OBJ);

// Hashing the password with its hash as the salt returns the same hash
if ( hash_equals($user->hash, crypt($password, $user->hash)) ) {
  // Ok!
}else{
  //user not found
}

I dont know what's going on, i just search for this function but it givin me a problem instead. sorry for my bad english. Thank you!

Answer 1

In php.net docs we can find a replacement function for older php versions :

if(!function_exists('hash_equals'))
{
    function hash_equals($str1, $str2)
    {
        if(strlen($str1) != strlen($str2))
        {
            return false;
        }
        else
        {
            $res = $str1 ^ $str2;
            $ret = 0;
            for($i = strlen($res) - 1; $i >= 0; $i--)
            {
                $ret |= ord($res[$i]);
            }
            return !$ret;
        }
    }
}

Otherwise, you could use this library : https://github.com/ircmaxell/password_compat

Answer 2

Use phpinfo() and check your PHP version. PHP versions prior to 5.6 don't have hash_equals function built-in. Upgrade to the latest version of PHP (or at least to 5.6) to use this function.

Answer 3

Solution taken from Facebook sdk: https://github.com/facebook/php-graph-sdk/blob/5.x/src/Facebook/polyfills.php

/**
 * Copyright 2017 Facebook, Inc.
 *
 * You are hereby granted a non-exclusive, worldwide, royalty-free license to
 * use, copy, modify, and distribute this software in source code or binary
 * form for use in connection with the web services and APIs provided by
 * Facebook.
 *
 * As with any software that integrates with the Facebook platform, your use
 * of this software is subject to the Facebook Developer Principles and
 * Policies [http://developers.facebook.com/policy/]. This copyright notice
 * shall be included in all copies or substantial portions of the software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 */
/**
 * @see https://github.com/sarciszewski/php-future/blob/master/src/Security.php#L37-L51
 */
if (!function_exists('hash_equals')) {
    function hash_equals($knownString, $userString)
    {
        if (function_exists('mb_strlen')) {
            $kLen = mb_strlen($knownString, '8bit');
            $uLen = mb_strlen($userString, '8bit');
        } else {
            $kLen = strlen($knownString);
            $uLen = strlen($userString);
        }
        if ($kLen !== $uLen) {
            return false;
        }
        $result = 0;
        for ($i = 0; $i < $kLen; $i++) {
            $result |= (ord($knownString[$i]) ^ ord($userString[$i]));
        }
        // They are only identical strings if $result is exactly 0...
        return 0 === $result;
    }
}