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.
hash_pbkdf2
(PHP 5 >= 5.5.0, PHP 7, PHP 8)
hash_pbkdf2 — Формирования ключа PBKDF2 для заданных входных данных
Описание
Список параметров
-
algo -
Имя выбранного хеширующего алгоритма (например,
md5,sha256,haval160,4и т.д.) Список поддерживаемых алгоритмов можно посмотреть в описании функции hash_algos(). -
password -
Пароль, используемый для формирования.
-
salt -
Соль, используемая при формировании ключа. Значение необходимо генерировать случайным образом.
-
iterations -
Количество итераций для формирования ключа.
-
length -
Длина генерируемой строки. Если параметр
binaryзадан какtrue, то этот параметр равен количеству байт в генерируемом ключе. Еслиbinaryустановлен какfalse, то длина ключа в байтах будет в два раза меньше, так как каждый байт ключа будет возвращён в виде двух символов шестнадцатеричной системы (0-F).Если задано как
0, то используется весь вывод заданного алгоритма. -
binary -
Если установлено
true, то вывод будет представлять из себя необработанные бинарные данные, а еслиfalse, то вывод будет представлен в виде строки шестнадцатеричных цифр в нижнем регистре.
Возвращаемые значения
Возвращаемая строка содержит сформированный ключ в виде
строки шестнадцатеричных чисел в нижнем регистре. Но если
параметр binary установлен как true,
то будут возвращены сырые бинарные данные.
Ошибки
Выбрасывается исключение ValueError, если
заданный алгоритм некорректен, параметр
iterations меньше или равен
0, параметр length
меньше чем 0 или если salt
очень длинный
(больше чем INT_MAX - 4).
Список изменений
| Версия | Описание |
|---|---|
| 8.0.0 |
Теперь выбрасывается исключение ValueError в случае возникновения ошибки;
ранее возвращалось значение false и выдавалась ошибка уровня E_WARNING.
|
| 7.2.0 | Запрещено использование некриптографических функций (adler32, crc32, crc32b, fnv132, fnv1a32, fnv164, fnv1a64, joaat). |
Примеры
Пример #1 Пример простого использования hash_pbkdf2()
<?php
$password = "password";
$iterations = 600000;
// Создание криптографически безопасной случайной соли с помощью random_bytes()
$salt = random_bytes(16);
$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 20);
var_dump($hash);
// для необработанного двоичного файла параметр $length должен быть уменьшен вдвое для получения аналогичных результатов
$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 быть использован для хеширования паролей в
целях их хранения. Однако стоит помнить, что для этих целей гораздо
лучше использовать password_hash() или
crypt() с CRYPT_BLOWFISH.
Смотрите также
- password_hash() - Создаёт хеш пароля
- hash_hkdf() - Формирования ключа HKDF для заданных входных данных
- sodium_crypto_pwhash() - Получает ключ из пароля, используя Argon2
add a note
User Contributed Notes 13 notes
clarence.pchy(at)gmail.com ¶
8 years ago
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, $key_length));
}
}
Trevor Herselman ¶
9 years ago
This is a light-weight drop-in replacement for PHP's hash_pbkdf2(); written for compatibility with older versions of PHP.
Written, formatted and tested by myself, but using code and ideas based on the following:
https://defuse.ca/php-pbkdf2.htm
https://github.com/rchouinard/hash_pbkdf2-compat/blob/master/src/hash_pbkdf2.php
https://gist.github.com/rsky/5104756
My main goals:
1) Maximum compatibility with PHP hash_pbkdf2(), ie. a drop-in replacement function
2) Minimum code size/bloat
3) Easy to copy/paste
4) No classes, and not encapsulated in a class! Why write a class when a simple function will do?
5) Eliminate calls to sprintf(). (used by other examples for the error reporting)
6) No other dependencies, ie. extra required functions
<?php
if (!function_exists('hash_pbkdf2'))
{
function hash_pbkdf2($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;
}
}
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)
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 ) );
?>
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,
$size,
true
);
}
}
php . ober-mail . de ¶
3 years ago
If you are wondering what the requirements are for the salt, have a look at the RFC[1]:
"The salt parameter should be a random string containing at least 64 bits of entropy. That means when generated from a function like *mcrypt_create_iv*, at least 8 bytes long. But for salts that consist of only *a-zA-Z0-9* (or are base_64 encoded), the minimum length should be at least 11 characters. It should be generated random for each password that's hashed, and stored along side the generated key."
[1] https://wiki.php.net/rfc/hash_pbkdf2
Yahe ¶
5 years ago
On an error hash_pbkdf2() will not just raise an E_WARNING but it will also return FALSE.
php at ober-mail dot de ¶
3 years ago
If you are wondering what the requirements are for the salt, have a look at the RFC[1]:
"The salt parameter should be a random string containing at least 64 bits of entropy. That means when generated from a function like *mcrypt_create_iv*, at least 8 bytes long. But for salts that consist of only *a-zA-Z0-9* (or are base_64 encoded), the minimum length should be at least 11 characters. It should be generated random for each password that's hashed, and stored along side the generated key."
[1] https://wiki.php.net/rfc/hash_pbkdf2
nimasdj [AT] yahoo [DOT] com ¶
8 years ago
There is a mistake in the class provided by Binod Kumar Luitel (http://php.net/manual/en/function.hash-pbkdf2.php#113488):
this line:
return bin2hex(substr($this->output, 0, $this->key_length));
must be changed to:
return substr(bin2hex($this->output), 0, $this->key_length);
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;
}
}
}
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
Peter ¶
11 years ago
See also https://github.com/rchouinard/hash_pbkdf2-compat for a compatibility function
