hash_hmac
(PHP 5 >= 5.1.2, PHP 7, PECL hash >= 1.1)
hash_hmac — Генерация хеш-кода на основе ключа, используя метод HMAC
Описание
$algo
, string $data
, string $key
[, bool $raw_output = false
] )Список параметров
-
algo -
Имя выбранного алгоритма хеширования (например, "md5", "sha256", "haval160,4" и т.д.) Смотрите hash_algos() для получения списка поддерживаемых алгоритмов.
-
data -
Сообщение для хеширования.
-
key -
Общий секретный ключ, используемый для генерации HMAC хеш кода.
-
raw_output -
Когда установлено в
TRUE, выводит необработанные двоичные данные. ПриFALSEвыводит данные в шестнадцатеричной кодировке в нижнем регистре.
Возвращаемые значения
Возвращает строку содержащую вычисленный хеш-код в шестнадцатеричной кодировке
в нижнем регистре. Если raw_output задан как TRUE,
то возвращается хеш-код в виде бинарных данных.
Возвращает FALSE, если algo неизвестен.
Примеры
Пример #1 Пример использования hash_hmac()
<?php
echo hash_hmac('ripemd160', 'Наглый коричневый лисёнок прыгает вокруг ленивой собаки.', 'secret');
?>
Результат выполнения данного примера:
b95d4abec7c27ec87fb54da1621f9942948879e4
Смотрите также
- hash() - Генерирует хеш-код (дайджест сообщения)
- hash_algos() - Возвращает список зарегистрированных алгоритмов хеширования
- hash_init() - Инициализация инкрементального контекста хеширования
- hash_hmac_file() - Генерация хэш-кода на основе ключа, используя метод HMAC и содержимое полученного файла
Коментарии
Generating OATH-compliant OTP (one time passwords) results in PHP:
<?php
$otp = oath_truncate (oath_hotp ($key, $counter), $length);
function oath_hotp ($key, $counter) {
// Counter
$bin_counter = pack ('C*', $counter);
// Pad to 8 chars
if (strlen ($bin_counter) < 8) {
$bin_counter = str_repeat (chr(0), 8 - strlen ($bin_counter)) . $bin_counter;
}
// HMAC
$hash = hash_hmac ('sha1', $bin_counter, $key);
return $hash;
}
function oath_truncate ($hash, $length = 6) {
// The last byte is used as an offset
$offset = hexdec (substr ($hash, 38)) & 0xf;
// Extract the relevant part, and clear the first bit
$hex_truncated = substr ($hash, $offset * 2, 8);
$bin_truncated = decbin (hexdec ($hex_truncated));
$bin_truncated[0] = '0';
$dec_truncated = bindec ($bin_truncated);
return substr ($dec_truncated, 0 - $length);
}
?>
HOTP Algorithm that works according to the RCF http://tools.ietf.org/html/draft-mraihi-oath-hmac-otp-04
The test cases from the RCF document the ASCII string as "123456787901234567890".
But the hex decoded to a string is "12345678901234567890".
Secret="12345678901234567890";
Count:
0 755224
1 287082
<?php
function oath_hotp($key,$counter) {
// Convert to padded binary string
$data = pack ('C*', $counter);
$data = str_pad($data,8,chr(0),STR_PAD_LEFT);
// HMAC
return hash_hmac('sha1',$data,$key);
}
function oath_truncate($hash, $length = 6) {
// Convert to dec
foreach(str_split($hash,2) as $hex) {
$hmac_result[]=hexdec($hex);
}
// Find offset
$offset = $hmac_result[19] & 0xf;
// Algorithm from RFC
return (
(($hmac_result[$offset+0] & 0x7f) << 24 ) |
(($hmac_result[$offset+1] & 0xff) << 16 ) |
(($hmac_result[$offset+2] & 0xff) << 8 ) |
($hmac_result[$offset+3] & 0xff)
) % pow(10,$length);
}
print "<pre>";
print "Compare results with:"
print " http://tools.ietf.org/html/draft-mraihi-oath-hmac-otp-04\n";
print "Count\tHash\t\t\t\t\t\tPin\n";
for($i=0;$i<10;$i++)
print $i."\t".($a=oath_hotp("12345678901234567890",$i))
print "\t".oath_truncate($a)."\n";
The hotp algorithms above work with counter values less than 256, but since the counter can be larger, it's necessary to iterate through all the bytes of the counter:
<?php
function oath_hotp ($key, $counter)
{
// Counter
//the counter value can be more than one byte long, so we need to go multiple times
$cur_counter = array(0,0,0,0,0,0,0,0);
for($i=7;$i>=0;$i--)
{
$cur_counter[$i] = pack ('C*', $counter);
$counter = $counter >> 8;
}
$bin_counter = implode($cur_counter);
// Pad to 8 chars
if (strlen ($bin_counter) < 8)
{
$bin_counter = str_repeat (chr(0), 8 - strlen ($bin_counter)) . $bin_counter;
}
// HMAC
$hash = hash_hmac ('sha1', $bin_counter, $key);
return $hash;
}
function oath_truncate($hash, $length = 6)
{
// Convert to dec
foreach(str_split($hash,2) as $hex)
{
$hmac_result[]=hexdec($hex);
}
// Find offset
$offset = $hmac_result[19] & 0xf;
// Algorithm from RFC
return
(
(($hmac_result[$offset+0] & 0x7f) << 24 ) |
(($hmac_result[$offset+1] & 0xff) << 16 ) |
(($hmac_result[$offset+2] & 0xff) << 8 ) |
($hmac_result[$offset+3] & 0xff)
) % pow(10,$length);
}
print "<pre>";
print "Compare results with:";
print " http://tools.ietf.org/html/draft-mraihi-oath-hmac-otp-04\n";
print "Count\tHash\t\t\t\t\t\tPin\n";
for($i=0;$i<=1024;$i=$i+128)
{
print $i."\t".($a=oath_hotp("12345678901234567890",$i));
print "\t".oath_truncate($a)."\n";
}
?>
Sometimes a hosting provider doesn't provide access to the Hash extension. Here is a clone of the hash_hmac function you can use in the event you need an HMAC generator and Hash is not available. It's only usable with MD5 and SHA1 encryption algorithms, but its output is identical to the official hash_hmac function (so far at least).
<?php
function custom_hmac($algo, $data, $key, $raw_output = false)
{
$algo = strtolower($algo);
$pack = 'H'.strlen($algo('test'));
$size = 64;
$opad = str_repeat(chr(0x5C), $size);
$ipad = str_repeat(chr(0x36), $size);
if (strlen($key) > $size) {
$key = str_pad(pack($pack, $algo($key)), $size, chr(0x00));
} else {
$key = str_pad($key, $size, chr(0x00));
}
for ($i = 0; $i < strlen($key) - 1; $i++) {
$opad[$i] = $opad[$i] ^ $key[$i];
$ipad[$i] = $ipad[$i] ^ $key[$i];
}
$output = $algo($opad.pack($pack, $algo($ipad.$data)));
return ($raw_output) ? pack($pack, $output) : $output;
}
?>
Example Use:
<?php
custom_hmac('sha1', 'Hello, world!', 'secret', true);
?>
For signing an Amazon AWS query, base64-encode the binary value:
<?php
$Sig = base64_encode(hash_hmac('sha256', $Request, $AmazonSecretKey, true));
?>
The Implementation of the PBKDF2 key derivation function as described in RFC 2898 can be used to not only get the hashed KEY but also a specific IV.
To use, one would use it as follows:-
<?php
$p = str_hash_pbkdf2($pw, $salt, 10, 32, 'sha1');
$p = base64_encode($p);
$iv = str_hash_pbkdf2($pw, $salt, 10, 16, 'sha1', 32);
$iv = base64_encode($iv);
?>
The function should be:-
<?php
// PBKDF2 Implementation (described in RFC 2898)
//
// @param string p password
// @param string s salt
// @param int c iteration count (use 1000 or higher)
// @param int kl derived key length
// @param string a hash algorithm
// @param int st start position of result
//
// @return string derived key
function str_hash_pbkdf2($p, $s, $c, $kl, $a = 'sha256', $st=0)
{
$kb = $start+$kl; // Key blocks to compute
$dk = ''; // Derived key
// Create key
for ($block=1; $block<=$kb; $block++)
{
// Initial hash for this block
$ib = $h = hash_hmac($a, $s . pack('N', $block), $p, true);
// Perform block iterations
for ($i=1; $i<$c; $i++)
{
// XOR each iterate
$ib ^= ($h = hash_hmac($a, $h, $p, true));
}
$dk .= $ib; // Append iterated block
}
// Return derived key of correct length
return substr($dk, $start, $kl);
}
?>
Simple implementation of hmac sha1
<?php
function hmac_sha1($key, $data)
{
// Adjust key to exactly 64 bytes
if (strlen($key) > 64) {
$key = str_pad(sha1($key, true), 64, chr(0));
}
if (strlen($key) < 64) {
$key = str_pad($key, 64, chr(0));
}
// Outter and Inner pad
$opad = str_repeat(chr(0x5C), 64);
$ipad = str_repeat(chr(0x36), 64);
// Xor key with opad & ipad
for ($i = 0; $i < strlen($key); $i++) {
$opad[$i] = $opad[$i] ^ $key[$i];
$ipad[$i] = $ipad[$i] ^ $key[$i];
}
return sha1($opad.sha1($ipad.$data, true));
}
Yet another OATH HOTP function. Has a 64 bit counter and is a lot shorter. Enjoy.
<?php
function oath_hotp ($secret, $ctr, $len=6) {
$binctr = pack ('NNC*', $ctr>>32, $ctr & 0xFFFFFFFF);
$hash = hash_hmac ("sha1", $binctr, $secret);
// This is where hashing stops and truncation begins
$ofs = 2*hexdec (substr ($hash, 39, 1));
$int = hexdec (substr ($hash, $ofs, 8)) & 0x7FFFFFFF;
$pin = substr ($int, -$len);
$pin = str_pad ($pin, $len, "0", STR_PAD_LEFT);
return $pin;
}
?>
Here is an efficient PBDKF2 implementation:
<?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 1024.
* $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 $key_length-byte key derived from the password and salt.
*
* Test vectors can be found here: https://www.ietf.org/rfc/rfc6070.txt
*
* This implementation of PBKDF2 was originally created by defuse.ca
* With improvements by variations-of-shadow.com
*/
function pbkdf2($algorithm, $password, $salt, $count, $key_length, $raw_output = false)
{
$algorithm = strtolower($algorithm);
if(!in_array($algorithm, hash_algos(), true))
die('PBKDF2 ERROR: Invalid hash algorithm.');
if($count <= 0 || $key_length <= 0)
die('PBKDF2 ERROR: Invalid parameters.');
$hash_length = strlen(hash($algorithm, "", true));
$block_count = ceil($key_length / $hash_length);
$output = "";
for($i = 1; $i <= $block_count; $i++) {
// $i encoded as 4 bytes, big endian.
$last = $salt . pack("N", $i);
// first iteration
$last = $xorsum = hash_hmac($algorithm, $last, $password, true);
// perform the other $count - 1 iterations
for ($j = 1; $j < $count; $j++) {
$xorsum ^= ($last = hash_hmac($algorithm, $last, $password, true));
}
$output .= $xorsum;
}
if($raw_output)
return substr($output, 0, $key_length);
else
return bin2hex(substr($output, 0, $key_length));
}
?>
<?php
/* Here is a solution for those who used hash_hmac
with Tiger algorithm in PHP 5.1 - 5.3
and want to upgrade to PHP 5.4 (or newer?).
The problem occured because the order of bytes for Tiger
was changed to big endian since PHP 5.4.0.
The two functions below assert $algo is one of Tiger algorithms,
for example tiger160,4.
*/
# replaces hash('tiger...
function hash_tiger_rev($algo, $data, $raw_output = false) {
$len = intval(substr($algo, 5, 3)); # 128, 160 or 192 bits
$times = substr($algo, 9, 1); # 3 or 4
$revhash = implode("", array_map("strrev",
str_split(hash('tiger192,'.$times, $data, true), 8)));
if ($len < 192) $revhash = substr($revhash, 0, $len >> 3);
return $raw_output? $revhash: bin2hex($revhash);
}
# replaces hash_hmac('tiger...
function hash_hmac_tiger_rev($algo, $data, $key, $raw_output = false) {
if (strlen($key) > 64) $key = hash_tiger_rev($algo, $key);
$key = str_pad($key, 64, chr(0));
$o_pad = str_repeat("\\", 64) ^ $key; # "\" = chr(0x5C)
$i_pad = str_repeat("6", 64) ^ $key; # "6" = chr(0x36)
return hash_tiger_rev($algo, $o_pad .
hash_tiger_rev($algo, $i_pad . $data, true), $raw_output);
}
# always the new version of tiger
function hash_hmac_new($algo, $data, $key, $raw_output = false) {
if (phpversion() > '5.4' || !preg_match('/^tiger(128|160|192),(3|4)$/', $algo))
return hash_hmac($algo, $data, $key, $raw_output);
else
return hash_hmac_tiger_rev($algo, $data, $key, $raw_output);
}
# always the old version of tiger
function hash_hmac_old($algo, $data, $key, $raw_output = false) {
if (phpversion() < '5.4' || !preg_match('/^tiger(128|160|192),(3|4)$/', $algo))
return hash_hmac($algo, $data, $key, $raw_output);
else
return hash_hmac_tiger_rev($algo, $data, $key, $raw_output);
}
# let's test it
$algo = 'tiger160,4'; $pwd = 'foo'; $key = 'bar';
echo hash_hmac($algo, $pwd, $key), "<br>";
echo hash_hmac_tiger_rev($algo, $pwd, $key), "<br>";
echo "<br>";
echo hash_hmac_old($algo, $pwd, $key), "<br>";
echo hash_hmac_new($algo, $pwd, $key), "<br>";
/* With PHP 5.4 output would be
590546d9f425188da35e5dfa53306ba3953571cc
bd6664330ed96b9b39ee063241b62e43f546a49d
bd6664330ed96b9b39ee063241b62e43f546a49d
590546d9f425188da35e5dfa53306ba3953571cc
With PHP 5.3
bd6664330ed96b9b39ee063241b62e43f546a49d
590546d9f425188da35e5dfa53306ba3953571cc
bd6664330ed96b9b39ee063241b62e43f546a49d
590546d9f425188da35e5dfa53306ba3953571cc
*/
?>
A function implementing the algorithm outlined in RFC 6238 (http://tools.ietf.org/html/rfc6238)
<?php
/**
* This function implements the algorithm outlined
* in RFC 6238 for Time-Based One-Time Passwords
*
* @link http://tools.ietf.org/html/rfc6238
* @param string $key the string to use for the HMAC key
* @param mixed $time a value that reflects a time (unix
* time in the example)
* @param int $digits the desired length of the OTP
* @param string $crypto the desired HMAC crypto algorithm
* @return string the generated OTP
*/
function oauth_totp($key, $time, $digits=8, $crypto='sha256')
{
$digits = intval($digits);
$result = null;
// Convert counter to binary (64-bit)
$data = pack('NNC*', $time >> 32, $time & 0xFFFFFFFF);
// Pad to 8 chars (if necessary)
if (strlen ($data) < 8) {
$data = str_pad($data, 8, chr(0), STR_PAD_LEFT);
}
// Get the hash
$hash = hash_hmac($crypto, $data, $key);
// Grab the offset
$offset = 2 * hexdec(substr($hash, strlen($hash) - 1, 1));
// Grab the portion we're interested in
$binary = hexdec(substr($hash, $offset, 8)) & 0x7fffffff;
// Modulus
$result = $binary % pow(10, $digits);
// Pad (if necessary)
$result = str_pad($result, $digits, "0", STR_PAD_LEFT);
return $result;
}
?>
Please be careful when comparing hashes. In certain cases, information can be leaked by using a timing attack. It takes advantage of the == operator only comparing until it finds a difference in the two strings. To prevent it, you have two options.
Option 1: hash both hashed strings first - this doesn't stop the timing difference, but it makes the information useless.
<?php
if (md5($hashed_value) === md5($hashed_expected)) {
echo "hashes match!";
}
?>
Option 2: always compare the whole string.
<?php
if (hash_compare($hashed_value, $hashed_expected)) {
echo "hashes match!";
}
function hash_compare($a, $b) {
if (!is_string($a) || !is_string($b)) {
return false;
}
$len = strlen($a);
if ($len !== strlen($b)) {
return false;
}
$status = 0;
for ($i = 0; $i < $len; $i++) {
$status |= ord($a[$i]) ^ ord($b[$i]);
}
return $status === 0;
}
?>
For signing an Amazon AWS query, base64-encode the binary value:
<?php
echo base64_encode(hash_hmac("sha1", $Request, $AmazonSecretKey, true));
?>
As Michael uggests we should take care not to compare the hash using == (or ===). Since PHP version 5.6 we can now use hash_equals().
So the example will be:
<?php
if (hash_equals($hashed_expected, $hashed_value) ) {
echo "hashes match!";
}
?>
This Is The Most Secure Way To Hash Your Data,
It Will Be Almost Impossible To Retrieve Your Data.
--------------------------------------------------------
--- Create Two Random Keys And Save Them In Your Configuration File ---
<?php
// Create A Random Key
echo base64_encode(openssl_random_pseudo_bytes(64));
?>
--------------------------------------------------------
<?php
// Save The Keys In Your Configuration File
define('FIRSTKEY','TNYazlbZ1Mq3HDMiEFDLrRMZBftFqpU2Ipytgytsc+jmQysE8lmigKtmGK+exB337ZOcAgwPpWmoPHL5niO3jA==');
define('SECONDKEY','z5hh/Kax4+HKZ8exOlvGlrHev/6ZynOEn904yiiIcWo/qLXWSfLkzm4NSJiGXu4uR7xxUowOkO26VqAi2p2DYQ==');
?>
--------------------------------------------------------
<?php
function secured_hash($data)
{
$first_key = base64_decode(FIRSTKEY);
$second_key = base64_decode(SECONDKEY);
$first_hashed = hash_hmac('sha3-512', $data, $first_key, TRUE);
$second_hashed = hash_hmac('sha3-512', $first_hashed, $second_key);
return $second_hashed;
}
?>
Very important notice, if you pass array to $data, php will generate a Warning, return a NULL and continue your application. Which I think is critical vulnerability as this function used to check authorisation typically.
Example:
<?php
var_dump(hash_hmac('sha256', [], 'secret'));
WARNING hash_hmac() expects parameter 2 to be string, array given on line number 3
NULL
?>
Of course not documented feature.
Function for those, who really need to use crc32 algorithm in PHP>7.1
<?php
function hash_hmac_crc32(string $key, string $data): string
{
$b = 4;
if (strlen($key) > $b) {
$key = pack("H*", hash('crc32', $key));
}
$key = str_pad($key, $b, chr(0x00));
$ipad = str_pad('', $b, chr(0x36));
$opad = str_pad('', $b, chr(0x5c));
$k_ipad = $key ^ $ipad;
$k_opad = $key ^ $opad;
return hash('crc32', $k_opad . hash('crc32', $k_ipad . $data, true));
}
?>
While implementing a TOTP application, please note that hash_hmac() must receive data in binary, not in a hexadecimal string, to generate a valid OTP across platforms.
This problem can be easily fixed by converting a hexadecimal string to its binary form before passing it to hash_hmac().
<?php
$time = hex2bin('0000000003523f77'); // time must be in this "hexadecimal and padded" form
$key = hex2bin('bb57d1...'); // 160-bits = 40-digit hexadecimal (4 bits) = 32-digit base32 (5 bits)
hash_hmac('sha1', $time, $key);
?>