1<?php
2
3/**
4 * Validates a host according to the IPv4, IPv6 and DNS (future) specifications.
5 */
6class HTMLPurifier_AttrDef_URI_Host extends HTMLPurifier_AttrDef
7{
8
9    /**
10     * IPv4 sub-validator.
11     * @type HTMLPurifier_AttrDef_URI_IPv4
12     */
13    protected $ipv4;
14
15    /**
16     * IPv6 sub-validator.
17     * @type HTMLPurifier_AttrDef_URI_IPv6
18     */
19    protected $ipv6;
20
21    public function __construct()
22    {
23        $this->ipv4 = new HTMLPurifier_AttrDef_URI_IPv4();
24        $this->ipv6 = new HTMLPurifier_AttrDef_URI_IPv6();
25    }
26
27    /**
28     * @param string $string
29     * @param HTMLPurifier_Config $config
30     * @param HTMLPurifier_Context $context
31     * @return bool|string
32     */
33    public function validate($string, $config, $context)
34    {
35        $length = strlen($string);
36        // empty hostname is OK; it's usually semantically equivalent:
37        // the default host as defined by a URI scheme is used:
38        //
39        //      If the URI scheme defines a default for host, then that
40        //      default applies when the host subcomponent is undefined
41        //      or when the registered name is empty (zero length).
42        if ($string === '') {
43            return '';
44        }
45        if ($length > 1 && $string[0] === '[' && $string[$length - 1] === ']') {
46            //IPv6
47            $ip = substr($string, 1, $length - 2);
48            $valid = $this->ipv6->validate($ip, $config, $context);
49            if ($valid === false) {
50                return false;
51            }
52            return '[' . $valid . ']';
53        }
54
55        // need to do checks on unusual encodings too
56        $ipv4 = $this->ipv4->validate($string, $config, $context);
57        if ($ipv4 !== false) {
58            return $ipv4;
59        }
60
61        // A regular domain name.
62
63        // This doesn't match I18N domain names, but we don't have proper IRI support,
64        // so force users to insert Punycode.
65
66        // There is not a good sense in which underscores should be
67        // allowed, since it's technically not! (And if you go as
68        // far to allow everything as specified by the DNS spec...
69        // well, that's literally everything, modulo some space limits
70        // for the components and the overall name (which, by the way,
71        // we are NOT checking!).  So we (arbitrarily) decide this:
72        // let's allow underscores wherever we would have allowed
73        // hyphens, if they are enabled.  This is a pretty good match
74        // for browser behavior, for example, a large number of browsers
75        // cannot handle foo_.example.com, but foo_bar.example.com is
76        // fairly well supported.
77        $underscore = $config->get('Core.AllowHostnameUnderscore') ? '_' : '';
78
79        // Based off of RFC 1738, but amended so that
80        // as per RFC 3696, the top label need only not be all numeric.
81        // The productions describing this are:
82        $a   = '[a-z]';     // alpha
83        $an  = '[a-z0-9]';  // alphanum
84        $and = "[a-z0-9-$underscore]"; // alphanum | "-"
85        // domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum
86        $domainlabel = "$an(?:$and*$an)?";
87        // AMENDED as per RFC 3696
88        // toplabel    = alphanum | alphanum *( alphanum | "-" ) alphanum
89        //      side condition: not all numeric
90        $toplabel = "$an(?:$and*$an)?";
91        // hostname    = *( domainlabel "." ) toplabel [ "." ]
92        if (preg_match("/^(?:$domainlabel\.)*($toplabel)\.?$/i", $string, $matches)) {
93            if (!ctype_digit($matches[1])) {
94                return $string;
95            }
96        }
97
98        // PHP 5.3 and later support this functionality natively
99        if (function_exists('idn_to_ascii')) {
100            if (defined('IDNA_NONTRANSITIONAL_TO_ASCII') && defined('INTL_IDNA_VARIANT_UTS46')) {
101                $string = idn_to_ascii($string, IDNA_NONTRANSITIONAL_TO_ASCII, INTL_IDNA_VARIANT_UTS46);
102            } else {
103                $string = idn_to_ascii($string);
104            }
105
106        // If we have Net_IDNA2 support, we can support IRIs by
107        // punycoding them. (This is the most portable thing to do,
108        // since otherwise we have to assume browsers support
109        } elseif ($config->get('Core.EnableIDNA')) {
110            $idna = new Net_IDNA2(array('encoding' => 'utf8', 'overlong' => false, 'strict' => true));
111            // we need to encode each period separately
112            $parts = explode('.', $string);
113            try {
114                $new_parts = array();
115                foreach ($parts as $part) {
116                    $encodable = false;
117                    for ($i = 0, $c = strlen($part); $i < $c; $i++) {
118                        if (ord($part[$i]) > 0x7a) {
119                            $encodable = true;
120                            break;
121                        }
122                    }
123                    if (!$encodable) {
124                        $new_parts[] = $part;
125                    } else {
126                        $new_parts[] = $idna->encode($part);
127                    }
128                }
129                $string = implode('.', $new_parts);
130            } catch (Exception $e) {
131                // XXX error reporting
132            }
133        }
134        // Try again
135        if (preg_match("/^($domainlabel\.)*$toplabel\.?$/i", $string)) {
136            return $string;
137        }
138        return false;
139    }
140}
141
142// vim: et sw=4 sts=4
143