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Add key size validation #609

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Add key size validation #609

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a9eb44a
Add key size validation
mariusklocke Oct 29, 2025
9beaed7
Adjust tests for minimum key length requirements
mariusklocke Oct 29, 2025
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42 changes: 42 additions & 0 deletions src/JWT.php
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Original file line number Diff line number Diff line change
Expand Up @@ -259,12 +259,16 @@ public static function sign(
if (!\is_string($key)) {
throw new InvalidArgumentException('key must be a string when using hmac');
}
self::validateHmacKeyLength($key, $algorithm);
return \hash_hmac($algorithm, $msg, $key, true);
case 'openssl':
$signature = '';
if (!\is_resource($key) && !openssl_pkey_get_private($key)) {
throw new DomainException('OpenSSL unable to validate key');
}
if (str_starts_with($algorithm, 'RS')) {
self::validateRsaKeyLength($key);
}
$success = \openssl_sign($msg, $signature, $key, $algorithm); // @phpstan-ignore-line
if (!$success) {
throw new DomainException('OpenSSL unable to sign data');
Expand Down Expand Up @@ -324,6 +328,9 @@ private static function verify(
list($function, $algorithm) = static::$supported_algs[$alg];
switch ($function) {
case 'openssl':
if (str_starts_with($algorithm, 'RS')) {
self::validateRsaKeyLength($keyMaterial);
}
$success = \openssl_verify($msg, $signature, $keyMaterial, $algorithm); // @phpstan-ignore-line
if ($success === 1) {
return true;
Expand Down Expand Up @@ -361,6 +368,7 @@ private static function verify(
if (!\is_string($keyMaterial)) {
throw new InvalidArgumentException('key must be a string when using hmac');
}
self::validateHmacKeyLength($keyMaterial, $algorithm);
$hash = \hash_hmac($algorithm, $msg, $keyMaterial, true);
return self::constantTimeEquals($hash, $signature);
}
Expand Down Expand Up @@ -675,4 +683,38 @@ private static function readDER(string $der, int $offset = 0): array

return [$pos, $data];
}

/**
* Validate HMAC key length
*
* @param string $key HMAC key material
* @param string $algorithm The algorithm
*
* @throws DomainException Provided key is too short
*/
private static function validateHmacKeyLength(string $key, string $algorithm): void
{
$keyLength = strlen($key) * 8;
$minKeyLength = (int)str_replace($algorithm, 'SHA', '');
if ($keyLength < $minKeyLength) {
throw new DomainException('Provided key is too short');
}
}

/**
* Validate RSA key length
*
* @param OpenSSLAsymmetricKey|OpenSSLCertificate $key RSA key material
*
* @throws DomainException Provided key is too short
*/
private static function validateRsaKeyLength(OpenSSLAsymmetricKey|OpenSSLCertificate $key): void
{
$keyDetails = openssl_pkey_get_details(openssl_pkey_get_private($key));
$keyLength = $keyDetails['bits'];
$minKeyLength = 2048;
if ($keyLength < $minKeyLength) {
throw new DomainException('Provided key is too short');
}
}
}
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