1<?php
2
3/**
4 * This module implements a VERY limited parser that finds <link> tags
5 * in the head of HTML or XHTML documents and parses out their
6 * attributes according to the OpenID spec. It is a liberal parser,
7 * but it requires these things from the data in order to work:
8 *
9 * - There must be an open <html> tag
10 *
11 * - There must be an open <head> tag inside of the <html> tag
12 *
13 * - Only <link>s that are found inside of the <head> tag are parsed
14 *   (this is by design)
15 *
16 * - The parser follows the OpenID specification in resolving the
17 *   attributes of the link tags. This means that the attributes DO
18 *   NOT get resolved as they would by an XML or HTML parser. In
19 *   particular, only certain entities get replaced, and href
20 *   attributes do not get resolved relative to a base URL.
21 *
22 * From http://openid.net/specs.bml:
23 *
24 * - The openid.server URL MUST be an absolute URL. OpenID consumers
25 *   MUST NOT attempt to resolve relative URLs.
26 *
27 * - The openid.server URL MUST NOT include entities other than &amp;,
28 *   &lt;, &gt;, and &quot;.
29 *
30 * The parser ignores SGML comments and <![CDATA[blocks]]>. Both kinds
31 * of quoting are allowed for attributes.
32 *
33 * The parser deals with invalid markup in these ways:
34 *
35 * - Tag names are not case-sensitive
36 *
37 * - The <html> tag is accepted even when it is not at the top level
38 *
39 * - The <head> tag is accepted even when it is not a direct child of
40 *   the <html> tag, but a <html> tag must be an ancestor of the
41 *   <head> tag
42 *
43 * - <link> tags are accepted even when they are not direct children
44 *   of the <head> tag, but a <head> tag must be an ancestor of the
45 *   <link> tag
46 *
47 * - If there is no closing tag for an open <html> or <head> tag, the
48 *   remainder of the document is viewed as being inside of the
49 *   tag. If there is no closing tag for a <link> tag, the link tag is
50 *   treated as a short tag. Exceptions to this rule are that <html>
51 *   closes <html> and <body> or <head> closes <head>
52 *
53 * - Attributes of the <link> tag are not required to be quoted.
54 *
55 * - In the case of duplicated attribute names, the attribute coming
56 *   last in the tag will be the value returned.
57 *
58 * - Any text that does not parse as an attribute within a link tag
59 *   will be ignored. (e.g. <link pumpkin rel='openid.server' /> will
60 *   ignore pumpkin)
61 *
62 * - If there are more than one <html> or <head> tag, the parser only
63 *   looks inside of the first one.
64 *
65 * - The contents of <script> tags are ignored entirely, except
66 *   unclosed <script> tags. Unclosed <script> tags are ignored.
67 *
68 * - Any other invalid markup is ignored, including unclosed SGML
69 *   comments and unclosed <![CDATA[blocks.
70 *
71 * PHP versions 4 and 5
72 *
73 * LICENSE: See the COPYING file included in this distribution.
74 *
75 * @access private
76 * @package OpenID
77 * @author JanRain, Inc. <openid@janrain.com>
78 * @copyright 2005-2008 Janrain, Inc.
79 * @license http://www.apache.org/licenses/LICENSE-2.0 Apache
80 */
81
82/**
83 * Require Auth_OpenID::arrayGet().
84 */
85require_once "Auth/OpenID.php";
86
87class Auth_OpenID_Parse {
88
89    /**
90     * Specify some flags for use with regex matching.
91     */
92    var $_re_flags = "si";
93
94    /**
95     * Stuff to remove before we start looking for tags
96     */
97    var $_removed_re =
98           "<!--.*?-->|<!\[CDATA\[.*?\]\]>|<script\b(?!:)[^>]*>.*?<\/script>";
99
100    /**
101     * Starts with the tag name at a word boundary, where the tag name
102     * is not a namespace
103     */
104    var $_tag_expr = "<%s\b(?!:)([^>]*?)(?:\/>|>(.*)(?:<\/?%s\s*>|\Z))";
105
106    var $_attr_find = '\b(\w+)=("[^"]*"|\'[^\']*\'|[^\'"\s\/<>]+)';
107
108    var $_open_tag_expr = "<%s\b";
109    var $_close_tag_expr = "<((\/%s\b)|(%s[^>\/]*\/))>";
110
111    function Auth_OpenID_Parse()
112    {
113        $this->_link_find = sprintf("/<link\b(?!:)([^>]*)(?!<)>/%s",
114                                    $this->_re_flags);
115
116        $this->_entity_replacements = array(
117                                            'amp' => '&',
118                                            'lt' => '<',
119                                            'gt' => '>',
120                                            'quot' => '"'
121                                            );
122
123        $this->_attr_find = sprintf("/%s/%s",
124                                    $this->_attr_find,
125                                    $this->_re_flags);
126
127        $this->_removed_re = sprintf("/%s/%s",
128                                     $this->_removed_re,
129                                     $this->_re_flags);
130
131        $this->_ent_replace =
132            sprintf("&(%s);", implode("|",
133                                      $this->_entity_replacements));
134    }
135
136    /**
137     * Returns a regular expression that will match a given tag in an
138     * SGML string.
139     */
140    function tagMatcher($tag_name, $close_tags = null)
141    {
142        $expr = $this->_tag_expr;
143
144        if ($close_tags) {
145            $options = implode("|", array_merge(array($tag_name), $close_tags));
146            $closer = sprintf("(?:%s)", $options);
147        } else {
148            $closer = $tag_name;
149        }
150
151        $expr = sprintf($expr, $tag_name, $closer);
152        return sprintf("/%s/%s", $expr, $this->_re_flags);
153    }
154
155    function openTag($tag_name)
156    {
157        $expr = sprintf($this->_open_tag_expr, $tag_name);
158        return sprintf("/%s/%s", $expr, $this->_re_flags);
159    }
160
161    function closeTag($tag_name)
162    {
163        $expr = sprintf($this->_close_tag_expr, $tag_name, $tag_name);
164        return sprintf("/%s/%s", $expr, $this->_re_flags);
165    }
166
167    function htmlBegin($s)
168    {
169        $matches = array();
170        $result = preg_match($this->openTag('html'), $s,
171                             $matches, PREG_OFFSET_CAPTURE);
172        if ($result === false || !$matches) {
173            return false;
174        }
175        // Return the offset of the first match.
176        return $matches[0][1];
177    }
178
179    function htmlEnd($s)
180    {
181        $matches = array();
182        $result = preg_match($this->closeTag('html'), $s,
183                             $matches, PREG_OFFSET_CAPTURE);
184        if ($result === false || !$matches) {
185            return false;
186        }
187        // Return the offset of the first match.
188        return $matches[count($matches) - 1][1];
189    }
190
191    function headFind()
192    {
193        return $this->tagMatcher('head', array('body', 'html'));
194    }
195
196    function replaceEntities($str)
197    {
198        foreach ($this->_entity_replacements as $old => $new) {
199            $str = preg_replace(sprintf("/&%s;/", $old), $new, $str);
200        }
201        return $str;
202    }
203
204    function removeQuotes($str)
205    {
206        $matches = array();
207        $double = '/^"(.*)"$/';
208        $single = "/^\'(.*)\'$/";
209
210        if (preg_match($double, $str, $matches)) {
211            return $matches[1];
212        } else if (preg_match($single, $str, $matches)) {
213            return $matches[1];
214        } else {
215            return $str;
216        }
217    }
218
219    function match($regexp, $text, &$match)
220    {
221        if (!is_callable('mb_ereg_search_init')) {
222            return preg_match($regexp, $text, $match);
223        }
224
225        $regexp = substr($regexp, 1, strlen($regexp) - 2 - strlen($this->_re_flags));
226        mb_ereg_search_init($text);
227        if (!mb_ereg_search($regexp)) {
228            return false;
229        }
230        $match = mb_ereg_search_getregs();
231        return true;
232    }
233
234    /**
235     * Find all link tags in a string representing a HTML document and
236     * return a list of their attributes.
237     *
238     * @todo This is quite ineffective and may fail with the default
239     *       pcre.backtrack_limit of 100000 in PHP 5.2, if $html is big.
240     *       It should rather use stripos (in PHP5) or strpos()+strtoupper()
241     *       in PHP4 to manage this.
242     *
243     * @param string $html The text to parse
244     * @return array $list An array of arrays of attributes, one for each
245     * link tag
246     */
247    function parseLinkAttrs($html)
248    {
249        $stripped = preg_replace($this->_removed_re,
250                                 "",
251                                 $html);
252
253        $html_begin = $this->htmlBegin($stripped);
254        $html_end = $this->htmlEnd($stripped);
255
256        if ($html_begin === false) {
257            return array();
258        }
259
260        if ($html_end === false) {
261            $html_end = strlen($stripped);
262        }
263
264        $stripped = substr($stripped, $html_begin,
265                           $html_end - $html_begin);
266
267        // Workaround to prevent PREG_BACKTRACK_LIMIT_ERROR:
268        $old_btlimit = ini_set( 'pcre.backtrack_limit', -1 );
269
270        // Try to find the <HEAD> tag.
271        $head_re = $this->headFind();
272        $head_match = array();
273        if (!$this->match($head_re, $stripped, $head_match)) {
274                     ini_set( 'pcre.backtrack_limit', $old_btlimit );
275                     return array();
276        }
277
278        $link_data = array();
279        $link_matches = array();
280
281        if (!preg_match_all($this->_link_find, $head_match[0],
282                            $link_matches)) {
283            ini_set( 'pcre.backtrack_limit', $old_btlimit );
284            return array();
285        }
286
287        foreach ($link_matches[0] as $link) {
288            $attr_matches = array();
289            preg_match_all($this->_attr_find, $link, $attr_matches);
290            $link_attrs = array();
291            foreach ($attr_matches[0] as $index => $full_match) {
292                $name = $attr_matches[1][$index];
293                $value = $this->replaceEntities(
294                              $this->removeQuotes($attr_matches[2][$index]));
295
296                $link_attrs[strtolower($name)] = $value;
297            }
298            $link_data[] = $link_attrs;
299        }
300
301        ini_set( 'pcre.backtrack_limit', $old_btlimit );
302        return $link_data;
303    }
304
305    function relMatches($rel_attr, $target_rel)
306    {
307        // Does this target_rel appear in the rel_str?
308        // XXX: TESTME
309        $rels = preg_split("/\s+/", trim($rel_attr));
310        foreach ($rels as $rel) {
311            $rel = strtolower($rel);
312            if ($rel == $target_rel) {
313                return 1;
314            }
315        }
316
317        return 0;
318    }
319
320    function linkHasRel($link_attrs, $target_rel)
321    {
322        // Does this link have target_rel as a relationship?
323        // XXX: TESTME
324        $rel_attr = Auth_OpeniD::arrayGet($link_attrs, 'rel', null);
325        return ($rel_attr && $this->relMatches($rel_attr,
326                                               $target_rel));
327    }
328
329    function findLinksRel($link_attrs_list, $target_rel)
330    {
331        // Filter the list of link attributes on whether it has
332        // target_rel as a relationship.
333        // XXX: TESTME
334        $result = array();
335        foreach ($link_attrs_list as $attr) {
336            if ($this->linkHasRel($attr, $target_rel)) {
337                $result[] = $attr;
338            }
339        }
340
341        return $result;
342    }
343
344    function findFirstHref($link_attrs_list, $target_rel)
345    {
346        // Return the value of the href attribute for the first link
347        // tag in the list that has target_rel as a relationship.
348        // XXX: TESTME
349        $matches = $this->findLinksRel($link_attrs_list,
350                                       $target_rel);
351        if (!$matches) {
352            return null;
353        }
354        $first = $matches[0];
355        return Auth_OpenID::arrayGet($first, 'href', null);
356    }
357}
358
359function Auth_OpenID_legacy_discover($html_text, $server_rel,
360                                     $delegate_rel)
361{
362    $p = new Auth_OpenID_Parse();
363
364    $link_attrs = $p->parseLinkAttrs($html_text);
365
366    $server_url = $p->findFirstHref($link_attrs,
367                                    $server_rel);
368
369    if ($server_url === null) {
370        return false;
371    } else {
372        $delegate_url = $p->findFirstHref($link_attrs,
373                                          $delegate_rel);
374        return array($delegate_url, $server_url);
375    }
376}
377
378