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 <terrafrost@php.net>
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
22namespace phpseclib3\Crypt\DSA\Formats\Keys;
23
24use ParagonIE\ConstantTime\Base64;
25use phpseclib3\Common\Functions\Strings;
26use phpseclib3\Exception\BadConfigurationException;
27use phpseclib3\Math\BigInteger;
28
29/**
30 * XML Formatted DSA Key Handler
31 *
32 * @package DSA
33 * @author  Jim Wigginton <terrafrost@php.net>
34 * @access  public
35 */
36abstract 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}
140