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use HMAC-SHA256 for the cookie string #450

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Merged
briskt merged 4 commits into from
Jul 30, 2026
Merged

use HMAC-SHA256 for the cookie string #450

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c828a3c
use HMAC-SHA256 for the cookie string to bypass bcrypt's 72-char limit
briskt Jul 29, 2026
f6e5d12
the cookie secret doesn't need to be in the hashed string
briskt Jul 29, 2026
39e06b6
Potential fix for pull request finding
briskt Jul 29, 2026
8ef9e79
Format cookie value with separators
briskt Jul 29, 2026
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13 changes: 6 additions & 7 deletions modules/mfa/src/Auth/Process/Mfa.php
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Original file line number Diff line number Diff line change
Expand Up @@ -787,8 +787,9 @@ public static function isRememberMeCookieValid(
if (!empty($cookieHash) && !empty($expireDate) && is_numeric($expireDate)) {
// Check if value of expireDate is in future
if ((int)$expireDate > time()) {
$expectedString = self::generateRememberMeCookieString($rememberSecret, $state['employeeId'], $expireDate, $mfaOptions);
$isValid = password_verify($expectedString, $cookieHash);
$expectedString = self::generateRememberMeCookieString($state['employeeId'], $expireDate, $mfaOptions);
$expectedHash = hash_hmac('sha256', $expectedString, $rememberSecret);
$isValid = hash_equals($expectedHash, $cookieHash);
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briskt marked this conversation as resolved.

if ($isValid) {
$idBrokerClient = self::getIdBrokerClient($state['idBrokerConfig']);
Expand All @@ -804,14 +805,12 @@ public static function isRememberMeCookieValid(

/**
* Generate and return a string to be hashed for remember me cookie
* @param string $rememberSecret
* @param string $employeeId
* @param int $expireDate
* @param array $mfaOptions
* @return string
*/
public static function generateRememberMeCookieString(
string $rememberSecret,
string $employeeId,
int $expireDate,
array $mfaOptions
Expand All @@ -823,7 +822,7 @@ public static function generateRememberMeCookieString(
}
}

return $rememberSecret . $employeeId . $expireDate . $allMfaIds;
return $employeeId . '|' . $expireDate . '|' . $allMfaIds;
}

/**
Expand Down Expand Up @@ -887,8 +886,8 @@ public static function setRememberMeCookies(
$rememberSecret = Env::requireEnv('REMEMBER_ME_SECRET');
$secureCookie = Env::get('SECURE_COOKIE', true);
$expireDate = strtotime($rememberDuration);
$cookieString = self::generateRememberMeCookieString($rememberSecret, $employeeId, $expireDate, $mfaOptions);
$cookieHash = password_hash($cookieString, PASSWORD_DEFAULT);
$cookieString = self::generateRememberMeCookieString($employeeId, $expireDate, $mfaOptions);
$cookieHash = hash_hmac('sha256', $cookieString, $rememberSecret);
setcookie('c1', base64_encode($cookieHash), $expireDate, '/', null, $secureCookie, true);
setcookie('c2', $expireDate, $expireDate, '/', null, $secureCookie, true);
}
Expand Down
3 changes: 1 addition & 2 deletions modules/mfa/tests/MfaTest.php
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Original file line number Diff line number Diff line change
Expand Up @@ -137,12 +137,11 @@ public function testIsRememberMeCookieValid_ValidCookie_UpdatesLastLogin(): void
putenv('REMEMBER_ME_SECRET=test-secret-for-unit-test');
try {
$expectedString = Mfa::generateRememberMeCookieString(
'test-secret-for-unit-test',
$employeeId,
$expireDate,
$mfaOptions
);
$cookieHash = password_hash($expectedString, PASSWORD_DEFAULT);
$cookieHash = hash_hmac('sha256', $expectedString, (string)getenv('REMEMBER_ME_SECRET'));

$isValid = Mfa::isRememberMeCookieValid(
$cookieHash,
Expand Down