<?php
namespace Defuse\Crypto;
use Defuse\Crypto\Exception as Ex;
final class KeyOrPassword
{
const PBKDF2_ITERATIONS = 100000;
const SECRET_TYPE_KEY = 1;
const SECRET_TYPE_PASSWORD = 2;
/**
* @var int
*/
private $secret_type = 0;
/**
* @var Key|string
*/
private $secret;
/**
* Initializes an instance of KeyOrPassword from a key.
*
* @param Key $key
*
* @return KeyOrPassword
*/
public static function createFromKey(Key $key)
{
return new KeyOrPassword(self::SECRET_TYPE_KEY, $key);
}
/**
* Initializes an instance of KeyOrPassword from a password.
*
* @param string $password
*
* @return KeyOrPassword
*/
public static function createFromPassword(
#[\SensitiveParameter]
$password
)
{
return new KeyOrPassword(self::SECRET_TYPE_PASSWORD, $password);
}
/**
* Derives authentication and encryption keys from the secret, using a slow
* key derivation function if the secret is a password.
*
* @param string $salt
*
* @throws Ex\CryptoException
* @throws Ex\EnvironmentIsBrokenException
*
* @return DerivedKeys
*/
public function deriveKeys($salt)
{
Core::ensureTrue(
Core::ourStrlen($salt) === Core::SALT_BYTE_SIZE,
'Bad salt.'
);
if ($this->secret_type === self::SECRET_TYPE_KEY) {
Core::ensureTrue($this->secret instanceof Key);
/**
* @psalm-suppress PossiblyInvalidMethodCall
*/
$akey = Core::HKDF(
Core::HASH_FUNCTION_NAME,
$this->secret->getRawBytes(),
Core::KEY_BYTE_SIZE,
Core::AUTHENTICATION_INFO_STRING,
$salt
);
/**
* @psalm-suppress PossiblyInvalidMethodCall
*/
$ekey = Core::HKDF(
Core::HASH_FUNCTION_NAME,
$this->secret->getRawBytes(),
Core::KEY_BYTE_SIZE,
Core::ENCRYPTION_INFO_STRING,
$salt
);
return new DerivedKeys($akey, $ekey);
} elseif ($this->secret_type === self::SECRET_TYPE_PASSWORD) {
Core::ensureTrue(\is_string($this->secret));
/* Our PBKDF2 polyfill is vulnerable to a DoS attack documented in
* GitHub issue #230. The fix is to pre-hash the password to ensure
* it is short. We do the prehashing here instead of in pbkdf2() so
* that pbkdf2() still computes the function as defined by the
* standard. */
/**
* @psalm-suppress PossiblyInvalidArgument
*/
$prehash = \hash(Core::HASH_FUNCTION_NAME, $this->secret, true);
$prekey = Core::pbkdf2(
Core::HASH_FUNCTION_NAME,
$prehash,
$salt,
self::PBKDF2_ITERATIONS,
Core::KEY_BYTE_SIZE,
true
);
$akey = Core::HKDF(
Core::HASH_FUNCTION_NAME,
$prekey,
Core::KEY_BYTE_SIZE,
Core::AUTHENTICATION_INFO_STRING,
$salt
);
/* Note the cryptographic re-use of $salt here. */
$ekey = Core::HKDF(
Core::HASH_FUNCTION_NAME,
$prekey,
Core::KEY_BYTE_SIZE,
Core::ENCRYPTION_INFO_STRING,
$salt
);
return new DerivedKeys($akey, $ekey);
} else {
throw new Ex\EnvironmentIsBrokenException('Bad secret type.');
}
}
/**
* Constructor for KeyOrPassword.
*
* @param int $secret_type
* @param mixed $secret (either a Key or a password string)
*/
private function __construct(
$secret_type,
#[\SensitiveParameter]
$secret
)
{
// The constructor is private, so these should never throw.
if ($secret_type === self::SECRET_TYPE_KEY) {
Core::ensureTrue($secret instanceof Key);
} elseif ($secret_type === self::SECRET_TYPE_PASSWORD) {
Core::ensureTrue(\is_string($secret));
} else {
throw new Ex\EnvironmentIsBrokenException('Bad secret type.');
}
$this->secret_type = $secret_type;
$this->secret = $secret;
}
}
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