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   1  <?php
   2  
   3  /**
   4   * XML Formatted DSA Key Handler
   5   *
   6   * While XKMS defines a private key format for RSA it does not do so for DSA. Quoting that standard:
   7   *
   8   * "[XKMS] does not specify private key parameters for the DSA signature algorithm since the algorithm only
   9   *  supports signature modes and so the application of server generated keys and key recovery is of limited
  10   *  value"
  11   *
  12   * PHP version 5
  13   *
  14   * @author    Jim Wigginton <terrafrost@php.net>
  15   * @copyright 2015 Jim Wigginton
  16   * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
  17   * @link      http://phpseclib.sourceforge.net
  18   */
  19  
  20  namespace phpseclib3\Crypt\DSA\Formats\Keys;
  21  
  22  use phpseclib3\Common\Functions\Strings;
  23  use phpseclib3\Exception\BadConfigurationException;
  24  use phpseclib3\Math\BigInteger;
  25  
  26  /**
  27   * XML Formatted DSA Key Handler
  28   *
  29   * @author  Jim Wigginton <terrafrost@php.net>
  30   */
  31  abstract class XML
  32  {
  33      /**
  34       * Break a public or private key down into its constituent components
  35       *
  36       * @param string $key
  37       * @param string $password optional
  38       * @return array
  39       */
  40      public static function load($key, $password = '')
  41      {
  42          if (!Strings::is_stringable($key)) {
  43              throw new \UnexpectedValueException('Key should be a string - not a ' . gettype($key));
  44          }
  45  
  46          if (!class_exists('DOMDocument')) {
  47              throw new BadConfigurationException('The dom extension is not setup correctly on this system');
  48          }
  49  
  50          $use_errors = libxml_use_internal_errors(true);
  51  
  52          $dom = new \DOMDocument();
  53          if (substr($key, 0, 5) != '<?xml') {
  54              $key = '<xml>' . $key . '</xml>';
  55          }
  56          if (!$dom->loadXML($key)) {
  57              libxml_use_internal_errors($use_errors);
  58              throw new \UnexpectedValueException('Key does not appear to contain XML');
  59          }
  60          $xpath = new \DOMXPath($dom);
  61          $keys = ['p', 'q', 'g', 'y', 'j', 'seed', 'pgencounter'];
  62          foreach ($keys as $key) {
  63              // $dom->getElementsByTagName($key) is case-sensitive
  64              $temp = $xpath->query("//*[translate(local-name(), 'ABCDEFGHIJKLMNOPQRSTUVWXYZ','abcdefghijklmnopqrstuvwxyz')='$key']");
  65              if (!$temp->length) {
  66                  continue;
  67              }
  68              $value = new BigInteger(Strings::base64_decode($temp->item(0)->nodeValue), 256);
  69              switch ($key) {
  70                  case 'p': // a prime modulus meeting the [DSS] requirements
  71                      // Parameters P, Q, and G can be public and common to a group of users. They might be known
  72                      // from application context. As such, they are optional but P and Q must either both appear
  73                      // or both be absent
  74                      $components['p'] = $value;
  75                      break;
  76                  case 'q': // an integer in the range 2**159 < Q < 2**160 which is a prime divisor of P-1
  77                      $components['q'] = $value;
  78                      break;
  79                  case 'g': // an integer with certain properties with respect to P and Q
  80                      $components['g'] = $value;
  81                      break;
  82                  case 'y': // G**X mod P (where X is part of the private key and not made public)
  83                      $components['y'] = $value;
  84                      // the remaining options do not do anything
  85                  case 'j': // (P - 1) / Q
  86                      // Parameter J is available for inclusion solely for efficiency as it is calculatable from
  87                      // P and Q
  88                  case 'seed': // a DSA prime generation seed
  89                      // Parameters seed and pgenCounter are used in the DSA prime number generation algorithm
  90                      // specified in [DSS]. As such, they are optional but must either both be present or both
  91                      // be absent
  92                  case 'pgencounter': // a DSA prime generation counter
  93              }
  94          }
  95  
  96          libxml_use_internal_errors($use_errors);
  97  
  98          if (!isset($components['y'])) {
  99              throw new \UnexpectedValueException('Key is missing y component');
 100          }
 101  
 102          switch (true) {
 103              case !isset($components['p']):
 104              case !isset($components['q']):
 105              case !isset($components['g']):
 106                  return ['y' => $components['y']];
 107          }
 108  
 109          return $components;
 110      }
 111  
 112      /**
 113       * Convert a public key to the appropriate format
 114       *
 115       * See https://www.w3.org/TR/xmldsig-core/#sec-DSAKeyValue
 116       *
 117       * @param \phpseclib3\Math\BigInteger $p
 118       * @param \phpseclib3\Math\BigInteger $q
 119       * @param \phpseclib3\Math\BigInteger $g
 120       * @param \phpseclib3\Math\BigInteger $y
 121       * @return string
 122       */
 123      public static function savePublicKey(BigInteger $p, BigInteger $q, BigInteger $g, BigInteger $y)
 124      {
 125          return "<DSAKeyValue>\r\n" .
 126                 '  <P>' . Strings::base64_encode($p->toBytes()) . "</P>\r\n" .
 127                 '  <Q>' . Strings::base64_encode($q->toBytes()) . "</Q>\r\n" .
 128                 '  <G>' . Strings::base64_encode($g->toBytes()) . "</G>\r\n" .
 129                 '  <Y>' . Strings::base64_encode($y->toBytes()) . "</Y>\r\n" .
 130                 '</DSAKeyValue>';
 131      }
 132  }