class.cryptography.php

<?php
/**
 * @package toolkit
 */
/**
 * Cryptography is a utility class that offers a number of general purpose cryptography-
 * related functions for message digestation as well as (backwards-)compatibility
 * checking. The message digestation algorithms are placed in the subclasses
 * `MD5`, `SHA1` and `PBKDF2`.
 *
 * @since Symphony 2.3.1
 * @see cryptography.MD5
 * @see cryptography.SHA1
 * @see cryptography.PBKDF2
 */

class Cryptography
{
    /**
     * Uses an instance of `PBKDF2` to create a hash. If you require other
     * hashes, see the related functions of the `MD5` or `SHA1` classes
     *
     * @see cryptography.MD5#hash()
     * @see cryptography.SHA1#hash()
     * @see cryptography.PBKDF2#hash()
     *
     * @param string $input
     * the string to be hashed
     * @return string
     * the hashed string
     */
    public static function hash($input)
    {
        return PBKDF2::hash($input);
    }

    /**
     * Compares a given hash with a clean text password by figuring out the
     * algorithm that has been used and then calling the appropriate sub-class
     *
     * @see cryptography.MD5#compare()
     * @see cryptography.SHA1#compare()
     * @see cryptography.PBKDF2#compare()
     *
     * @param string $input
     *  the cleartext password
     * @param string $hash
     *  the hash the password should be checked against
     * @param boolean $isHash
     * @return boolean
     *  the result of the comparison
     */
    public static function compare($input, $hash, $isHash = false)
    {
        $version = substr($hash, 0, 8);

        if ($isHash == true) {
            return $input == $hash;
        } elseif ($version == 'PBKDF2v1') { // salted PBKDF2
            return PBKDF2::compare($input, $hash);
        } elseif (strlen($hash) == 40) { // legacy, unsalted SHA1
            return SHA1::compare($input, $hash);
        } elseif (strlen($hash) == 32) { // legacy, unsalted MD5
            return MD5::compare($input, $hash);
        } else { // the hash provided doesn't make any sense
            return false;
        }
    }

    /**
     * Checks if provided hash has been computed by most recent algorithm
     * returns true if otherwise
     *
     * @param string $hash
     * the hash to be checked
     * @return boolean
     * whether the hash should be re-computed
     */
    public static function requiresMigration($hash)
    {
        $version = substr($hash, 0, 8);

        if ($version == PBKDF2::PREFIX) { // salted PBKDF2, let the responsible class decide
            return PBKDF2::requiresMigration($hash);
        } else { // everything else
            return true;
        }
    }

    /**
     * Generates a salt to be used in message digestation.
     *
     * @param integer $length
     * the length of the salt
     * @return string
     * a hexadecimal string
     */
    public static function generateSalt($length)
    {
        mt_srand(microtime(true)*100000 + memory_get_usage(true));
        return substr(sha1(uniqid(mt_rand(), true)), 0, $length);
    }
}