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<?php
/**
* This module implements a VERY limited parser that finds <link> tags
* in the head of HTML or XHTML documents and parses out their
* attributes according to the OpenID spec. It is a liberal parser,
* but it requires these things from the data in order to work:
*
* - There must be an open <html> tag
*
* - There must be an open <head> tag inside of the <html> tag
*
* - Only <link>s that are found inside of the <head> tag are parsed
* (this is by design)
*
* - The parser follows the OpenID specification in resolving the
* attributes of the link tags. This means that the attributes DO
* NOT get resolved as they would by an XML or HTML parser. In
* particular, only certain entities get replaced, and href
* attributes do not get resolved relative to a base URL.
*
* From http://openid.net/specs.bml:
*
* - The openid.server URL MUST be an absolute URL. OpenID consumers
* MUST NOT attempt to resolve relative URLs.
*
* - The openid.server URL MUST NOT include entities other than &,
* <, >, and ".
*
* The parser ignores SGML comments and <![CDATA[blocks]]>. Both kinds
* of quoting are allowed for attributes.
*
* The parser deals with invalid markup in these ways:
*
* - Tag names are not case-sensitive
*
* - The <html> tag is accepted even when it is not at the top level
*
* - The <head> tag is accepted even when it is not a direct child of
* the <html> tag, but a <html> tag must be an ancestor of the
* <head> tag
*
* - <link> tags are accepted even when they are not direct children
* of the <head> tag, but a <head> tag must be an ancestor of the
* <link> tag
*
* - If there is no closing tag for an open <html> or <head> tag, the
* remainder of the document is viewed as being inside of the
* tag. If there is no closing tag for a <link> tag, the link tag is
* treated as a short tag. Exceptions to this rule are that <html>
* closes <html> and <body> or <head> closes <head>
*
* - Attributes of the <link> tag are not required to be quoted.
*
* - In the case of duplicated attribute names, the attribute coming
* last in the tag will be the value returned.
*
* - Any text that does not parse as an attribute within a link tag
* will be ignored. (e.g. <link pumpkin rel='openid.server' /> will
* ignore pumpkin)
*
* - If there are more than one <html> or <head> tag, the parser only
* looks inside of the first one.
*
* - The contents of <script> tags are ignored entirely, except
* unclosed <script> tags. Unclosed <script> tags are ignored.
*
* - Any other invalid markup is ignored, including unclosed SGML
* comments and unclosed <![CDATA[blocks.
*
* PHP versions 4 and 5
*
* LICENSE: See the COPYING file included in this distribution.
*
* @access private
* @package OpenID
* @author JanRain, Inc. <openid@janrain.com>
* @copyright 2005-2008 Janrain, Inc.
* @license http://www.apache.org/licenses/LICENSE-2.0 Apache
*/
/**
* Require Auth_OpenID::arrayGet().
*/
require_once "Auth/OpenID.php";
class Auth_OpenID_Parse {
/**
* Specify some flags for use with regex matching.
*/
var $_re_flags = "si";
/**
* Stuff to remove before we start looking for tags
*/
var $_removed_re =
"<!--.*?-->|<!\[CDATA\[.*?\]\]>|<script\b(?!:)[^>]*>.*?<\/script>";
/**
* Starts with the tag name at a word boundary, where the tag name
* is not a namespace
*/
var $_tag_expr = "<%s\b(?!:)([^>]*?)(?:\/>|>(.*)(?:<\/?%s\s*>|\Z))";
var $_attr_find = '\b(\w+)=("[^"]*"|\'[^\']*\'|[^\'"\s\/<>]+)';
var $_open_tag_expr = "<%s\b";
var $_close_tag_expr = "<((\/%s\b)|(%s[^>\/]*\/))>";
function Auth_OpenID_Parse()
{
$this->_link_find = sprintf("/<link\b(?!:)([^>]*)(?!<)>/%s",
$this->_re_flags);
$this->_entity_replacements = array(
'amp' => '&',
'lt' => '<',
'gt' => '>',
'quot' => '"'
);
$this->_attr_find = sprintf("/%s/%s",
$this->_attr_find,
$this->_re_flags);
$this->_removed_re = sprintf("/%s/%s",
$this->_removed_re,
$this->_re_flags);
$this->_ent_replace =
sprintf("&(%s);", implode("|",
$this->_entity_replacements));
}
/**
* Returns a regular expression that will match a given tag in an
* SGML string.
*/
function tagMatcher($tag_name, $close_tags = null)
{
$expr = $this->_tag_expr;
if ($close_tags) {
$options = implode("|", array_merge(array($tag_name), $close_tags));
$closer = sprintf("(?:%s)", $options);
} else {
$closer = $tag_name;
}
$expr = sprintf($expr, $tag_name, $closer);
return sprintf("/%s/%s", $expr, $this->_re_flags);
}
function openTag($tag_name)
{
$expr = sprintf($this->_open_tag_expr, $tag_name);
return sprintf("/%s/%s", $expr, $this->_re_flags);
}
function closeTag($tag_name)
{
$expr = sprintf($this->_close_tag_expr, $tag_name, $tag_name);
return sprintf("/%s/%s", $expr, $this->_re_flags);
}
function htmlBegin($s)
{
$matches = array();
$result = preg_match($this->openTag('html'), $s,
$matches, PREG_OFFSET_CAPTURE);
if ($result === false || !$matches) {
return false;
}
// Return the offset of the first match.
return $matches[0][1];
}
function htmlEnd($s)
{
$matches = array();
$result = preg_match($this->closeTag('html'), $s,
$matches, PREG_OFFSET_CAPTURE);
if ($result === false || !$matches) {
return false;
}
// Return the offset of the first match.
return $matches[count($matches) - 1][1];
}
function headFind()
{
return $this->tagMatcher('head', array('body', 'html'));
}
function replaceEntities($str)
{
foreach ($this->_entity_replacements as $old => $new) {
$str = preg_replace(sprintf("/&%s;/", $old), $new, $str);
}
return $str;
}
function removeQuotes($str)
{
$matches = array();
$double = '/^"(.*)"$/';
$single = "/^\'(.*)\'$/";
if (preg_match($double, $str, $matches)) {
return $matches[1];
} else if (preg_match($single, $str, $matches)) {
return $matches[1];
} else {
return $str;
}
}
function match($regexp, $text, &$match)
{
if (!is_callable('mb_ereg_search_init')) {
if (!preg_match($regexp, $text, $match)) {
return false;
}
$match = $match[0];
return true;
}
$regexp = substr($regexp, 1, strlen($regexp) - 2 - strlen($this->_re_flags));
mb_ereg_search_init($text);
if (!mb_ereg_search($regexp)) {
return false;
}
$match = mb_ereg_search_getregs();
return true;
}
/**
* Find all link tags in a string representing a HTML document and
* return a list of their attributes.
*
* @todo This is quite ineffective and may fail with the default
* pcre.backtrack_limit of 100000 in PHP 5.2, if $html is big.
* It should rather use stripos (in PHP5) or strpos()+strtoupper()
* in PHP4 to manage this.
*
* @param string $html The text to parse
* @return array $list An array of arrays of attributes, one for each
* link tag
*/
function parseLinkAttrs($html)
{
$stripped = preg_replace($this->_removed_re,
"",
$html);
$html_begin = $this->htmlBegin($stripped);
$html_end = $this->htmlEnd($stripped);
if ($html_begin === false) {
return array();
}
if ($html_end === false) {
$html_end = strlen($stripped);
}
$stripped = substr($stripped, $html_begin,
$html_end - $html_begin);
// Workaround to prevent PREG_BACKTRACK_LIMIT_ERROR:
$old_btlimit = ini_set( 'pcre.backtrack_limit', -1 );
// Try to find the <HEAD> tag.
$head_re = $this->headFind();
$head_match = array();
if (!$this->match($head_re, $stripped, $head_match)) {
ini_set( 'pcre.backtrack_limit', $old_btlimit );
return array();
}
$link_data = array();
$link_matches = array();
if (!preg_match_all($this->_link_find, $head_match[0],
$link_matches)) {
ini_set( 'pcre.backtrack_limit', $old_btlimit );
return array();
}
foreach ($link_matches[0] as $link) {
$attr_matches = array();
preg_match_all($this->_attr_find, $link, $attr_matches);
$link_attrs = array();
foreach ($attr_matches[0] as $index => $full_match) {
$name = $attr_matches[1][$index];
$value = $this->replaceEntities(
$this->removeQuotes($attr_matches[2][$index]));
$link_attrs[strtolower($name)] = $value;
}
$link_data[] = $link_attrs;
}
ini_set( 'pcre.backtrack_limit', $old_btlimit );
return $link_data;
}
function relMatches($rel_attr, $target_rel)
{
// Does this target_rel appear in the rel_str?
// XXX: TESTME
$rels = preg_split("/\s+/", trim($rel_attr));
foreach ($rels as $rel) {
$rel = strtolower($rel);
if ($rel == $target_rel) {
return 1;
}
}
return 0;
}
function linkHasRel($link_attrs, $target_rel)
{
// Does this link have target_rel as a relationship?
// XXX: TESTME
$rel_attr = Auth_OpeniD::arrayGet($link_attrs, 'rel', null);
return ($rel_attr && $this->relMatches($rel_attr,
$target_rel));
}
function findLinksRel($link_attrs_list, $target_rel)
{
// Filter the list of link attributes on whether it has
// target_rel as a relationship.
// XXX: TESTME
$result = array();
foreach ($link_attrs_list as $attr) {
if ($this->linkHasRel($attr, $target_rel)) {
$result[] = $attr;
}
}
return $result;
}
function findFirstHref($link_attrs_list, $target_rel)
{
// Return the value of the href attribute for the first link
// tag in the list that has target_rel as a relationship.
// XXX: TESTME
$matches = $this->findLinksRel($link_attrs_list,
$target_rel);
if (!$matches) {
return null;
}
$first = $matches[0];
return Auth_OpenID::arrayGet($first, 'href', null);
}
}
function Auth_OpenID_legacy_discover($html_text, $server_rel,
$delegate_rel)
{
$p = new Auth_OpenID_Parse();
$link_attrs = $p->parseLinkAttrs($html_text);
$server_url = $p->findFirstHref($link_attrs,
$server_rel);
if ($server_url === null) {
return false;
} else {
$delegate_url = $p->findFirstHref($link_attrs,
$delegate_rel);
return array($delegate_url, $server_url);
}
}
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