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<?php
/**
* XML Formatted DSA Key Handler
*
* While XKMS defines a private key format for RSA it does not do so for DSA. Quoting that standard:
*
* "[XKMS] does not specify private key parameters for the DSA signature algorithm since the algorithm only
* supports signature modes and so the application of server generated keys and key recovery is of limited
* value"
*
* PHP version 5
*
* @author Jim Wigginton <[email protected]>
* @copyright 2015 Jim Wigginton
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @link http://phpseclib.sourceforge.net
*/
namespace phpseclib3\Crypt\DSA\Formats\Keys;
use phpseclib3\Common\Functions\Strings;
use phpseclib3\Exception\BadConfigurationException;
use phpseclib3\Math\BigInteger;
/**
* XML Formatted DSA Key Handler
*
* @author Jim Wigginton <[email protected]>
*/
abstract class XML
{
/**
* Break a public or private key down into its constituent components
*
* @param string $key
* @param string $password optional
* @return array
*/
public static function load($key, $password = '')
{
if (!Strings::is_stringable($key)) {
throw new \UnexpectedValueException('Key should be a string - not a ' . gettype($key));
}
if (!class_exists('DOMDocument')) {
throw new BadConfigurationException('The dom extension is not setup correctly on this system');
}
$use_errors = libxml_use_internal_errors(true);
$dom = new \DOMDocument();
if (substr($key, 0, 5) != '<?xml') {
$key = '<xml>' . $key . '</xml>';
}
if (!$dom->loadXML($key)) {
libxml_use_internal_errors($use_errors);
throw new \UnexpectedValueException('Key does not appear to contain XML');
}
$xpath = new \DOMXPath($dom);
$keys = ['p', 'q', 'g', 'y', 'j', 'seed', 'pgencounter'];
foreach ($keys as $key) {
// $dom->getElementsByTagName($key) is case-sensitive
$temp = $xpath->query("//*[translate(local-name(), 'ABCDEFGHIJKLMNOPQRSTUVWXYZ','abcdefghijklmnopqrstuvwxyz')='$key']");
if (!$temp->length) {
continue;
}
$value = new BigInteger(Strings::base64_decode($temp->item(0)->nodeValue), 256);
switch ($key) {
case 'p': // a prime modulus meeting the [DSS] requirements
// Parameters P, Q, and G can be public and common to a group of users. They might be known
// from application context. As such, they are optional but P and Q must either both appear
// or both be absent
$components['p'] = $value;
break;
case 'q': // an integer in the range 2**159 < Q < 2**160 which is a prime divisor of P-1
$components['q'] = $value;
break;
case 'g': // an integer with certain properties with respect to P and Q
$components['g'] = $value;
break;
case 'y': // G**X mod P (where X is part of the private key and not made public)
$components['y'] = $value;
// the remaining options do not do anything
case 'j': // (P - 1) / Q
// Parameter J is available for inclusion solely for efficiency as it is calculatable from
// P and Q
case 'seed': // a DSA prime generation seed
// Parameters seed and pgenCounter are used in the DSA prime number generation algorithm
// specified in [DSS]. As such, they are optional but must either both be present or both
// be absent
case 'pgencounter': // a DSA prime generation counter
}
}
libxml_use_internal_errors($use_errors);
if (!isset($components['y'])) {
throw new \UnexpectedValueException('Key is missing y component');
}
switch (true) {
case !isset($components['p']):
case !isset($components['q']):
case !isset($components['g']):
return ['y' => $components['y']];
}
return $components;
}
/**
* Convert a public key to the appropriate format
*
* See https://www.w3.org/TR/xmldsig-core/#sec-DSAKeyValue
*
* @param \phpseclib3\Math\BigInteger $p
* @param \phpseclib3\Math\BigInteger $q
* @param \phpseclib3\Math\BigInteger $g
* @param \phpseclib3\Math\BigInteger $y
* @return string
*/
public static function savePublicKey(BigInteger $p, BigInteger $q, BigInteger $g, BigInteger $y)
{
return "<DSAKeyValue>\r\n" .
' <P>' . Strings::base64_encode($p->toBytes()) . "</P>\r\n" .
' <Q>' . Strings::base64_encode($q->toBytes()) . "</Q>\r\n" .
' <G>' . Strings::base64_encode($g->toBytes()) . "</G>\r\n" .
' <Y>' . Strings::base64_encode($y->toBytes()) . "</Y>\r\n" .
'</DSAKeyValue>';
}
}
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