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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   * @category  Crypt
  15   * @package   DSA
  16   * @author    Jim Wigginton <[email protected]>
  17   * @copyright 2015 Jim Wigginton
  18   * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
  19   * @link      http://phpseclib.sourceforge.net
  20   */
  21  
  22  namespace phpseclib3\Crypt\DSA\Formats\Keys;
  23  
  24  use ParagonIE\ConstantTime\Base64;
  25  use phpseclib3\Common\Functions\Strings;
  26  use phpseclib3\Exception\BadConfigurationException;
  27  use phpseclib3\Math\BigInteger;
  28  
  29  /**
  30   * XML Formatted DSA Key Handler
  31   *
  32   * @package DSA
  33   * @author  Jim Wigginton <[email protected]>
  34   * @access  public
  35   */
  36  abstract class XML
  37  {
  38      /**
  39       * Break a public or private key down into its constituent components
  40       *
  41       * @access public
  42       * @param string $key
  43       * @param string $password optional
  44       * @return array
  45       */
  46      public static function load($key, $password = '')
  47      {
  48          if (!Strings::is_stringable($key)) {
  49              throw new \UnexpectedValueException('Key should be a string - not a ' . gettype($key));
  50          }
  51  
  52          if (!class_exists('DOMDocument')) {
  53              throw new BadConfigurationException('The dom extension is not setup correctly on this system');
  54          }
  55  
  56          $use_errors = libxml_use_internal_errors(true);
  57  
  58          $dom = new \DOMDocument();
  59          if (substr($key, 0, 5) != '<?xml') {
  60              $key = '<xml>' . $key . '</xml>';
  61          }
  62          if (!$dom->loadXML($key)) {
  63              libxml_use_internal_errors($use_errors);
  64              throw new \UnexpectedValueException('Key does not appear to contain XML');
  65          }
  66          $xpath = new \DOMXPath($dom);
  67          $keys = ['p', 'q', 'g', 'y', 'j', 'seed', 'pgencounter'];
  68          foreach ($keys as $key) {
  69              // $dom->getElementsByTagName($key) is case-sensitive
  70              $temp = $xpath->query("//*[translate(local-name(), 'ABCDEFGHIJKLMNOPQRSTUVWXYZ','abcdefghijklmnopqrstuvwxyz')='$key']");
  71              if (!$temp->length) {
  72                  continue;
  73              }
  74              $value = new BigInteger(Base64::decode($temp->item(0)->nodeValue), 256);
  75              switch ($key) {
  76                  case 'p': // a prime modulus meeting the [DSS] requirements
  77                      // Parameters P, Q, and G can be public and common to a group of users. They might be known
  78                      // from application context. As such, they are optional but P and Q must either both appear
  79                      // or both be absent
  80                      $components['p'] = $value;
  81                      break;
  82                  case 'q': // an integer in the range 2**159 < Q < 2**160 which is a prime divisor of P-1
  83                      $components['q'] = $value;
  84                      break;
  85                  case 'g': // an integer with certain properties with respect to P and Q
  86                      $components['g'] = $value;
  87                      break;
  88                  case 'y': // G**X mod P (where X is part of the private key and not made public)
  89                      $components['y'] = $value;
  90                      // the remaining options do not do anything
  91                  case 'j': // (P - 1) / Q
  92                      // Parameter J is available for inclusion solely for efficiency as it is calculatable from
  93                      // P and Q
  94                  case 'seed': // a DSA prime generation seed
  95                      // Parameters seed and pgenCounter are used in the DSA prime number generation algorithm
  96                      // specified in [DSS]. As such, they are optional but must either both be present or both
  97                      // be absent
  98                  case 'pgencounter': // a DSA prime generation counter
  99              }
 100          }
 101  
 102          libxml_use_internal_errors($use_errors);
 103  
 104          if (!isset($components['y'])) {
 105              throw new \UnexpectedValueException('Key is missing y component');
 106          }
 107  
 108          switch (true) {
 109              case !isset($components['p']):
 110              case !isset($components['q']):
 111              case !isset($components['g']):
 112                  return ['y' => $components['y']];
 113          }
 114  
 115          return $components;
 116      }
 117  
 118      /**
 119       * Convert a public key to the appropriate format
 120       *
 121       * See https://www.w3.org/TR/xmldsig-core/#sec-DSAKeyValue
 122       *
 123       * @access public
 124       * @param \phpseclib3\Math\BigInteger $p
 125       * @param \phpseclib3\Math\BigInteger $q
 126       * @param \phpseclib3\Math\BigInteger $g
 127       * @param \phpseclib3\Math\BigInteger $y
 128       * @return string
 129       */
 130      public static function savePublicKey(BigInteger $p, BigInteger $q, BigInteger $g, BigInteger $y)
 131      {
 132          return "<DSAKeyValue>\r\n" .
 133                 '  <P>' . Base64::encode($p->toBytes()) . "</P>\r\n" .
 134                 '  <Q>' . Base64::encode($q->toBytes()) . "</Q>\r\n" .
 135                 '  <G>' . Base64::encode($g->toBytes()) . "</G>\r\n" .
 136                 '  <Y>' . Base64::encode($y->toBytes()) . "</Y>\r\n" .
 137                 '</DSAKeyValue>';
 138      }
 139  }