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<?php |
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declare(strict_types=1); |
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namespace SimpleSAML\XMLSecurity\Key; |
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use SimpleSAML\XMLSecurity\Utils\Random; |
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use function chr; |
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use function ord; |
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use function strlen; |
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/** |
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* A class to model symmetric key secrets. |
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* |
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* New SymmetricKey objects can be created passing a given secret to the constructor, or using the static method |
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* generate(), which will return a SymmetricKey object with a random secret material. |
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* |
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* Note that random secrets generated by this class will be cryptographically secure. |
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* |
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* @package simplesamlphp/xml-security |
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*/ |
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class SymmetricKey implements KeyInterface |
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{ |
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/** @var string */ |
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protected string $material; |
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/** |
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* Build a new key with $key as its material. |
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* |
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* @param string $key The associated key material. |
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*/ |
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public function __construct(string $key) |
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{ |
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$this->material = $key; |
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} |
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/** |
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* Return the key material associated with this key. |
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* |
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* @return string The key material. |
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*/ |
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public function getMaterial(): string |
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{ |
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return $this->material; |
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} |
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/** |
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* Generate a random, binary secret key of a given length. |
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* |
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* If the key is intended to be used with 3DES in CBC mode, pass true in $parityBits. |
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* |
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* @param positive-int $length The length of the secret we want, in bytes. |
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* @param bool $parityBits Whether the key should be suitable for its use in 3DES in CBC mode or not. |
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* |
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* @return \SimpleSAML\XMLSecurity\Key\SymmetricKey A cryptographically-secure random symmetric key. |
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* |
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* @throws \SimpleSAML\XMLSecurity\Exception\RuntimeException If no appropriate sources of cryptographically-secure |
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* random material are available. |
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*/ |
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public static function generate(int $length, bool $parityBits = false): SymmetricKey |
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{ |
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$key = Random::generateRandomBytes($length); |
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if ($parityBits) { |
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/* |
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* Make sure that the generated key has the proper parity bits set. |
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* Mcrypt doesn't care about the parity bits, but others may care. |
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*/ |
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for ($i = 0; $i < strlen($key); $i++) { |
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$byte = ord($key[$i]) & 0xfe; |
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$parity = 1; |
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for ($j = 1; $j < 8; $j++) { |
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$parity ^= ($byte >> $j) & 1; |
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} |
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$byte |= $parity; |
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$key[$i] = chr($byte); |
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} |
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} |
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return new self($key); |
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} |
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/** |
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* Get the length of this symmetric key, in bytes. |
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* |
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* @return int The length of the key. |
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*/ |
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public function getLength(): int |
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{ |
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return strlen($this->getMaterial()); |
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} |
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} |
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simplesamlphp /
xml-security
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