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Add compatibility for PHP 5.6's hash_equals function #61

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Add compatibility for PHP 5.6's hash_equals function #61

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2d4129a
Add compatibility for PHP 5.6's `hash_equals` function
timemachine3030 Sep 2, 2014
7a89894
Attempting to use the testSuiteLoaderFile directly in phpunit
timemachine3030 Sep 2, 2014
a2d54a9
Return false if the input hash is not a string
timemachine3030 Sep 2, 2014
510d3da
Checking the hash str length
timemachine3030 Sep 3, 2014
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61 changes: 56 additions & 5 deletions lib/password.php
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Original file line number Diff line number Diff line change
Expand Up @@ -222,16 +222,67 @@ function password_verify($password, $hash) {
return false;
}
$ret = crypt($password, $hash);
if (!is_string($ret) || PasswordCompat\binary\_strlen($ret) != PasswordCompat\binary\_strlen($hash) || PasswordCompat\binary\_strlen($ret) <= 13) {
if (!is_string($hash) || !is_string($ret) || PasswordCompat\binary\_strlen($ret) <= 13) {
return false;
}

$status = 0;
for ($i = 0; $i < PasswordCompat\binary\_strlen($ret); $i++) {
$status |= (ord($ret[$i]) ^ ord($hash[$i]));
return hash_equals($hash, $ret);
}

}

if (!function_exists('hash_equals')) {

/**
* Timing attack safe string comparison
*
* @param string $known_string The string of known length to compare against
* @param string $user_string The user-supplied hash
*
* @return boolean or null
*/
function hash_equals($known_string, $user_string) {
$argc = func_num_args();
$eq = true;
$result = 0;

if ($argc < 2) {
trigger_error("hash_equals() expects at least 2 parameters, {$argc} given", E_USER_WARNING);
return null;
}

if (!is_string($known_string)) {
trigger_error("hash_equals(): Expected known_string to be a string, " . gettype($known_string) . " given", E_USER_WARNING);
$eq = false;
}

if (!is_string($user_string)) {
trigger_error("hash_equals(): Expected user_string to be a string, " . gettype($user_string) . " given", E_USER_WARNING);
$eq = false;
}

if (!is_string($known_string) || !is_string($user_string)) {
$eq = false;
}

$known_len = PasswordCompat\binary\_strlen($known_string);
$user_len = PasswordCompat\binary\_strlen($user_string);

if ($known_len != $user_len) {
$eq = false;
}

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I'm not sure the following block of code is equivalent to the xor + or loop e.g.

for($i = 0; $i < $user_len && $i < $known_len; ++$i)
{
    $diff |= ord($known_string[$i]) ^ ord($user_string[$i]);
}
return $diff === 0;

However, it appears to still resolve the side-channel. Just worth examining before merging, I suspect. 😄

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I originally left out the ord diff as it is not UTF-8 safe and I wanted to stay future compatible. But it doesn't matter as bcrypt, scrypt, PBKDF2, and SHA2x all generate ASCII safe hashes. Updated.

for ($i = 0; $i < $known_len; $i++) {
if ($known_len > $i && $user_len > $i) {
$result |= ord($known_string[$i]) ^ ord($user_string[$i]);
}
}

if ($result !== 0) {
$eq = false;
}

return $status === 0;
return $eq;
}
}

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2 changes: 1 addition & 1 deletion phpunit.xml.dist
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@
stopOnFailure="false"
stopOnIncomplete="false"
stopOnSkipped="false"
testSuiteLoaderClass="PHPUnit_Runner_StandardTestSuiteLoader"
testSuiteLoaderFile="vendor/phpunit/phpunit/src/Runner/StandardTestSuiteLoader.php"
strict="false"
verbose="false">
<testsuites>
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55 changes: 55 additions & 0 deletions test/Unit/HashEquals.php
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Original file line number Diff line number Diff line change
@@ -0,0 +1,55 @@
<?php

class HashEquals extends PHPUnit_Framework_TestCase {

public function testFuncExists() {
$this->assertTrue(function_exists('hash_equals'));
}
public function testExamples() {
$expected = crypt('12345', '$2a$07$usesomesillystringforsalt$');
$correct = crypt('12345', '$2a$07$usesomesillystringforsalt$');
$incorrect = crypt('apple', '$2a$07$usesomesillystringforsalt$');

$this->assertTrue(hash_equals($expected, $correct));
$this->assertFalse(hash_equals($expected, $incorrect));
}

public function testProvider() {
return array(
array("same", "same", true),
array("not1same", "not2same", false),
array("short", "longer", false),
array("longer", "short", false),
array("", "notempty", false),
array("notempty", "", false),
array("", "", true),
);
}

public function warningProvider() {
return array(
array(123, "NaN", true),
array("NaN", 123, true),
array(123, 123, true),
array(null, "", true),
array(null, 123, true),
array(null, null, true),
);
}

/**
* @dataProvider testProvider
*/
public function testHashEquals($knownString, $userString, $result) {
$this->assertSame($result, hash_equals($knownString, $userString));
}

/**
* @expectedException PHPUnit_Framework_Error_Warning
* @dataProvider warningProvider
*/
public function testHashEqualsWarning($knownString, $userString, $result) {
$this->assertSame($result, hash_equals($knownString, $userString));
}

}