hash_pbkdf2

(PHP 5 >= 5.5.0, PHP 7, PHP 8)

hash_pbkdf2 — Генерирует PBKDF2-ключ на основе исходного пароля

Описание

hash_pbkdf2(
    string $algo,
    #[\SensitiveParameter] string $password,
    string $salt,
    int $iterations,
    int $length = 0,
    bool $binary = false,
    array $options = []
): string

Список параметров

algo

Название алгоритма хеширования (например, "sha256"). Список алгоритмов, которые поддерживает функция, приводит описание функции hash_hmac_algos().

Замечание:
Некриптографические хеш-функции не допускаются.

password

Пароль для деривации.

salt

Соль для формирования ключа. Требуется сгенерировать случайное значение.

iterations

Количество внутренних итераций для преобразования исходного пароля в хеш-ключ.

length

Длина строки вывода. Если параметр binary задали как true, значение этого параметра соответствует длине ключа в байтах, если для параметра binary установили значение false — соответствует удвоенной длине ключа в байтах, поскольку каждый байт ключа возвращается в виде двух шестнадцатеричных символов.

Со значением 0 функция вернёт весь вывод заданного алгоритма.

binary

Функция выводит необработанные двоичные данные, если значение параметра равно true. Если false — выводятся шестнадцатеричные строчные буквы в нижнем регистре.

options

Массив опций для алгоритмов хеширования. Пока вариантами функций хеширования MurmurHash поддерживается только параметр "seed".

Возвращаемые значения

Функция возвращает строку, которая содержит сформированный ключ в виде строки шестнадцатеричных чисел в нижнем регистре, если только для параметра binary не установили значение true, тогда возвращаются необработанные двоичные данные.

Ошибки

Функция выбрасывает исключение ValueError, если алгоритм неизвестен, параметр iterations меньше или равен 0, параметр length меньше 0 или параметр salt чрезмерно длинный (больше значения выражения INT_MAX - 4).

Список изменений

Версия	Описание
8.0.0	Теперь выбрасывается исключение ValueError, если возникла ошибка; раньше функция возвращала `false` и выдавала ошибку уровня `E_WARNING`.
7.2.0	Запретили некриптографические хеш-функции (adler32, crc32, crc32b, fnv132, fnv1a32, fnv164, fnv1a64, joaat).

Примеры

Пример #1 Пример базового использования функции hash_pbkdf2()

<?php

$password = "password";
$iterations = 600000;

// Создаём криптографически безопасную случайную соль функцией random_bytes()
$salt = random_bytes(16);

$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 20);
var_dump($hash);

// Для необработанного двоичного файла параметр $length требуется уменьшить вдвое, чтобы получить аналогичные результаты
$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 10, true);
var_dump(bin2hex($hash));

?>

Вывод приведённого примера будет похож на:

string(20) "120fb6cffcf8b32c43e7"
string(20) "120fb6cffcf8b32c43e7"

Примечания

Предостережение

Метод PBKDF2 может использовать для хеширования паролей в целях хранения. Однако следует отметить, что функция password_hash() или функция crypt() с типом хеша CRYPT_BLOWFISH лучше для хранения паролей.

Смотрите также

password_hash() - Создаёт хеш пароля
hash_hkdf() - Формирует HKDF-ключ из исходного ключа
sodium_crypto_pwhash() - Получает ключ из пароля алгоритмом Argon2

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Примечания пользователей 12 notes

down

clarence.pchy(at)gmail.com ¶

8 years ago

Please pay great attention to the **$length** parameter! It is exactly the **return string length**, NOT the length of raw binary hash result.

I had a big problem about this -- 
I thought that `hash_pbkdf2(...false)` should equals to `bin2hex(hash_pbkdf2(...true))` just like `md5($x)` equals `bin2hex(md5($x, true))`. However I was wrong:

hash_pbkdf2('sha256', '123456', 'abc', 10000, 50, false); // returns string(50) "584bc5b41005169f1fa15177edb78d75f9846afc466a4bae05"
hash_pbkdf2('sha256', '123456', 'abc', 10000, 50, true); // returns string(50) "XKŴ��Qw�u��j�FjK���BFW�YpG    �mp.g2�`;N�"
bin2hex(hash_pbkdf2('sha256', '123456', 'abc', 10000, 50, true)); // returns string(100) "584bc5b41005169f1fa15177edb78d75f9846afc466a4bae05119c82424657c81b5970471f098a6d702e6732b7603b194efe"

So I add such a note. Hope it will help someone else like me.

down

does dot not at matter dot org ¶

11 years ago

this snippet was posted over a year ago on a dutch PHP community: (reference/source: http://www.phphulp.nl/php/script/beveiliging/pbkdf2-een-veilige-manier-om-wachtwoorden-op-te-slaan/1956/pbkdf2php/1757/)

<?php

/**
 * @author Chris Horeweg
 * @package Security_Tools
 */

function pbkdf2($password, $salt, $algorithm = 'sha512', $count = 20000, $key_length = 128, $raw_output = false)
{
    if(!in_array($algorithm, hash_algos(), true)) {
        exit('pbkdf2: Hash algoritme is niet geinstalleerd op het systeem.');
    }
    
    if($count <= 0 || $key_length <= 0) {
        $count = 20000;
        $key_length = 128;
    }

    $hash_length = strlen(hash($algorithm, "", true));
    $block_count = ceil($key_length / $hash_length);

    $output = "";
    for($i = 1; $i <= $block_count; $i++) {
        $last = $salt . pack("N", $i);
        $last = $xorsum = hash_hmac($algorithm, $last, $password, true);
        for ($j = 1; $j < $count; $j++) {
            $xorsum ^= ($last = hash_hmac($algorithm, $last, $password, true));
        }
        $output .= $xorsum;
    }

    if($raw_output) {
        return substr($output, 0, $key_length);
    }
    else {
        return base64_encode(substr($output, 0, $key_length));
    }
}

down

Trevor Herselman ¶

9 years ago

This is a light-weight drop-in replacement for PHP's hash_pbkdf2(); written for compatibility with older versions of PHP.
Written, formatted and tested by myself, but using code and ideas based on the following:
https://defuse.ca/php-pbkdf2.htm
https://github.com/rchouinard/hash_pbkdf2-compat/blob/master/src/hash_pbkdf2.php
https://gist.github.com/rsky/5104756

My main goals:
1) Maximum compatibility with PHP hash_pbkdf2(), ie. a drop-in replacement function
2) Minimum code size/bloat
3) Easy to copy/paste
4) No classes, and not encapsulated in a class! Why write a class when a simple function will do?
5) Eliminate calls to sprintf(). (used by other examples for the error reporting)
6) No other dependencies, ie. extra required functions

<?php
if (!function_exists('hash_pbkdf2'))
{
    function hash_pbkdf2($algo, $password, $salt, $count, $length = 0, $raw_output = false)
    {
        if (!in_array(strtolower($algo), hash_algos())) trigger_error(__FUNCTION__ . '(): Unknown hashing algorithm: ' . $algo, E_USER_WARNING);
        if (!is_numeric($count)) trigger_error(__FUNCTION__ . '(): expects parameter 4 to be long, ' . gettype($count) . ' given', E_USER_WARNING);
        if (!is_numeric($length)) trigger_error(__FUNCTION__ . '(): expects parameter 5 to be long, ' . gettype($length) . ' given', E_USER_WARNING);
        if ($count <= 0) trigger_error(__FUNCTION__ . '(): Iterations must be a positive integer: ' . $count, E_USER_WARNING);
        if ($length < 0) trigger_error(__FUNCTION__ . '(): Length must be greater than or equal to 0: ' . $length, E_USER_WARNING);

        $output = '';
        $block_count = $length ? ceil($length / strlen(hash($algo, '', $raw_output))) : 1;
        for ($i = 1; $i <= $block_count; $i++)
        {
            $last = $xorsum = hash_hmac($algo, $salt . pack('N', $i), $password, true);
            for ($j = 1; $j < $count; $j++)
            {
                $xorsum ^= ($last = hash_hmac($algo, $last, $password, true));
            }
            $output .= $xorsum;
        }

        if (!$raw_output) $output = bin2hex($output);
        return $length ? substr($output, 0, $length) : $output;
    }
}

down

Anonymous ¶

11 years ago

Sadly this function was added in PHP 5.5 but many webservers just provide PHP 5.3. But there exists a pure PHP implementation (found here: https://defuse.ca/php-pbkdf2.htm).
I took this implementation, put it into a class with comments for PHPDoc and added a switch so that the native PHP function is used if available.

Feel free to use it!
http://pastebin.com/f5PDq735
(Posted on pastebin.com since the text would have been too long)

down

php . ober-mail . de ¶

3 years ago

If you are wondering what the requirements are for the salt, have a look at the RFC[1]:

"The salt parameter should be a random string containing at least 64 bits of entropy. That means when generated from a function like *mcrypt_create_iv*, at least 8 bytes long. But for salts that consist of only *a-zA-Z0-9* (or are base_64 encoded), the minimum length should be at least 11 characters. It should be generated random for each password that's hashed, and stored along side the generated key."

[1] https://wiki.php.net/rfc/hash_pbkdf2

down

Yahe ¶

5 years ago

On an error hash_pbkdf2() will not just raise an E_WARNING but it will also return FALSE.

down

nimasdj [AT] yahoo [DOT] com ¶

8 years ago

There is a mistake in the class provided by Binod Kumar Luitel (http://php.net/manual/en/function.hash-pbkdf2.php#113488):
this line:
return bin2hex(substr($this->output, 0, $this->key_length));
must be changed to:
return substr(bin2hex($this->output), 0, $this->key_length);

down

Flimm ¶

6 years ago

Note that if $raw_output is false, then the output will be encoded using lowercase hexits. Some other systems (such as Django 2.0) use base64 instead. So if you're trying to generate hash strings that are compatible with those systems, you can use the base64_encode function, like this:

<?php

echo base64_encode( hash_pbkdf2( "sha256", "example password", "BbirbJq1C1G7", 100000, 0, true ) );

?>

down

gfilippakis at sleed dot gr ¶

5 years ago

This is a very basic implementation of Rfc2898DeriveBytes class with only 2 of its constructors in case someone else finds it useful.

class Rfc2898DeriveBytes
{
    private $textToHash;
    private $saltByteSize;
    
    public $salt;
    
    public function __construct($arg1, $arg2)
    {
        if (is_string($arg1) && is_integer($arg2)) {
            $this->textToHash = $arg1;
            $this->saltByteSize = $arg2;
            $this->salt = substr(
                hex2bin(sha1(uniqid('', true))),
                0,
                $this->saltByteSize
            );
        } elseif (is_string($arg1) && is_string($arg2)) {
            $this->textToHash = $arg1;
            $this->salt = $arg2;
        }
    }
    
    public function getBytes($size)
    {
        return hash_pbkdf2(
            "sha1",
            $this->textToHash,
            $this->salt,
            1000,
            $size,
            true
        );
    }
}

down

-1

Binod Kumar Luitel ¶

11 years ago

People who wants pure PHP implementation of the function, i.e. who don't have PHP 5.5 installed within their server, can use the following implementation. Nothing has been modified so far as from reference https://defuse.ca/php-pbkdf2.htm but the OOP lovers might like this.
For more information about PBKDF2 see: http://en.wikipedia.org/wiki/PBKDF2

<?php
/**
 * PBKDF2 key derivation function as defined by RSA's PKCS #5: https://www.ietf.org/rfc/rfc2898.txt
 * $algorithm - The hash algorithm to use. Recommended: SHA256
 * $password - The password.
 * $salt - A salt that is unique to the password.
 * $count - Iteration count. Higher is better, but slower. Recommended: At least 1000.
 * $key_length - The length of the derived key in bytes.
 * $raw_output - If true, the key is returned in raw binary format. Hex encoded otherwise.
 * Returns: A $key_length-byte key derived from the password and salt.
 */
if (!function_exists("hash_pbkdf2")) {
    function hash_pbkdf2($algorithm, $password, $salt, $count, $key_length, $raw_output = false) {

        class pbkdf2 {
            public $algorithm;
            public $password;
            public $salt;
            public $count;
            public $key_length;
            public $raw_output;

            private $hash_length;
            private $output         = "";

            public function __construct($data = null)
            {
                if ($data != null) {
                    $this->init($data);
                }
            }

            public function init($data)
            {
                $this->algorithm  = $data["algorithm"];
                $this->password   = $data["password"];
                $this->salt       = $data["salt"];
                $this->count      = $data["count"];
                $this->key_length = $data["key_length"];
                $this->raw_output = $data["raw_output"];
            }

            public function hash()
            {
                $this->algorithm = strtolower($this->algorithm);
                if(!in_array($this->algorithm, hash_algos(), true))
                    throw new Exception('PBKDF2 ERROR: Invalid hash algorithm.');

                if($this->count <= 0 || $this->key_length <= 0)
                    throw new Exception('PBKDF2 ERROR: Invalid parameters.');

                $this->hash_length = strlen(hash($this->algorithm, "", true));
                $block_count = ceil($this->key_length / $this->hash_length);
                for ($i = 1; $i <= $block_count; $i++) {
                    // $i encoded as 4 bytes, big endian.
                    $last = $this->salt . pack("N", $i);
                    // first iteration
                    $last = $xorsum = hash_hmac($this->algorithm, $last, $this->password, true);
                    // perform the other $this->count - 1 iterations
                    for ($j = 1; $j < $this->count; $j++) {
                        $xorsum ^= ($last = hash_hmac($this->algorithm, $last, $this->password, true));
                    }
                    $this->output .= $xorsum;
                    if($this->raw_output)
                        return substr($this->output, 0, $this->key_length);
                    else
                        return bin2hex(substr($this->output, 0, $this->key_length));
                }
            }
        }

        $data = array('algorithm' => $algorithm, 'password' => $password, 'salt' => $salt, 'count' => $count, 'key_length' => $key_length, 'raw_output' => $raw_output);
        try {
            $pbkdf2 = new pbkdf2($data);
            return $pbkdf2->hash();
        } catch (Exception $e) {
            throw $e;
        }
    }
}

down

-2

php at ober-mail dot de ¶

3 years ago

If you are wondering what the requirements are for the salt, have a look at the RFC[1]:

"The salt parameter should be a random string containing at least 64 bits of entropy. That means when generated from a function like *mcrypt_create_iv*, at least 8 bytes long. But for salts that consist of only *a-zA-Z0-9* (or are base_64 encoded), the minimum length should be at least 11 characters. It should be generated random for each password that's hashed, and stored along side the generated key."

[1] https://wiki.php.net/rfc/hash_pbkdf2

down

-3

php - ober-mail - de ¶

3 years ago

If you are wondering what the requirements are for the salt, have a look at the RFC[1]:

"The salt parameter should be a random string containing at least 64 bits of entropy. That means when generated from a function like *mcrypt_create_iv*, at least 8 bytes long. But for salts that consist of only *a-zA-Z0-9* (or are base_64 encoded), the minimum length should be at least 11 characters. It should be generated random for each password that's hashed, and stored along side the generated key."

[1] https://wiki.php.net/rfc/hash_pbkdf2

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