hash_pbkdf2

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

    hash_pbkdf2 — Gera uma derivação de chave PBKDF2 de uma senha fornecida

    Descrição

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

    Parâmetros

    algo

    Nome do algoritmo de hash selecionado (por exemplo, "sha256"). Para uma lista de algoritmos suportados, veja hash_hmac_algos().

    Nota:

    Funções de hash não criptográficas não são permitidas.

    password

    A senha a ser usada para a derivação.

    salt

    O salt a ser usado para a derivação. Este valor deve ser gerado aleatoriamente.

    iterations

    O número de iterações internas a serem executadas para a derivação.

    length

    O comprimento da string de saída. Se binary for true isso corresponde ao comprimento em bytes da chave derivada, se binary for false isso corresponde ao dobro do comprimento em bytes da chave derivada (pois cada byte da chave é retornado como dois caracteres hexadecimais).

    Se 0 for passado, toda a saída do algoritmo fornecido será usada.

    binary

    Quando definido como true, gera dados binários brutos. false gera caracteres hexadecimais minúsculos.

    options

    Um array de opções para os vários algoritmos de hash. Atualmente, apenas a chave "seed" é suportada pelas variantes MurmurHash.

    Valor Retornado

    Retorna uma string contendo a chave derivada como hexadecimais minúsculos, a menos que binary esteja definido como true, nesse caso, a representação binária bruta da chave derivada é retornada.

    Erros/Exceções

    Lança uma exceção ValueError se o algoritmo for desconhecido, o parâmetro iterations for menor ou igual a 0, o parâmetro length for menor que 0 ou o parâmetro salt for muito longo (maior que INT_MAX - 4).

    Registro de Alterações

    Versão Descrição
    8.0.0 Agora lança uma exceção ValueError em caso de erro. Anteriormente, false era retornado e uma mensagem E_WARNING era emitida.
    7.2.0 O uso de funções de hash não criptográficas (adler32, crc32, crc32b, fnv132, fnv1a32, fnv164, fnv1a64, joaat) foi desabilitado.

    Exemplos

    Exemplo #1 Exemplo de hash_pbkdf2(), uso básico

    <?php
    $password     = "password";
    $iterations = 600000;

    // Gera um salt aleatório criptograficamente seguro usando random_bytes()
    $salt = random_bytes(16);

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

    // para binário bruto, $length precisa ser reduzido pela metade para resultados equivalentes
    $hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 10, true);
    var_dump(bin2hex($hash));?>

    O exemplo acima produzirá algo semelhante a:

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

    Notas

    Cuidado

    O método PBKDF2 pode ser usado para fazer hash de senhas para armazenamento. No entanto, deve ser notado que password_hash() ou crypt() com CRYPT_BLOWFISH são mais adequados para armazenamento de senhas.

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    Notas Enviadas por Usuários (em inglês) 12 notes

    up
    26
    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.
    up
    7
    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));
    }
    }
    up
    8
    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;
    }
    }
    up
    7
    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)
    up
    2
    php . ober-mail . de
    4 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
    up
    1
    Yahe
    5 years ago
    On an error hash_pbkdf2() will not just raise an E_WARNING but it will also return FALSE.
    up
    1
    nimasdj [AT] yahoo [DOT] com
    9 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);
    up
    1
    Flimm
    7 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 ) );

    ?>
    up
    1
    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
    );
    }
    }
    up
    -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;
    }
    }
    }
    up
    -2
    php at ober-mail dot de
    4 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
    up
    -3
    php - ober-mail - de
    4 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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