lib/cookieless.php

   1 <?php  // $Id$
   2 /**
   3 * Enable cookieless sessions by including $CFG->usesid=true;
   4 * in config.php.
   5 * Based on code from php manual by Richard at postamble.co.uk
   6 * Attempts to use cookies if cookies not present then uses session ids attached to all urls and forms to pass session id from page to page.
   7 * If site is open to google, google is given guest access as usual and there are no sessions. No session ids will be attached to urls for googlebot.
   8 * This doesn't require trans_sid to be turned on but this is recommended for better performance
   9 * you should put :
  10 * session.use_trans_sid = 1
  11 * in your php.ini file and make sure that you don't have a line like this in your php.ini
  12 * session.use_only_cookies = 1
  13 * @author Richard at postamble.co.uk and Jamie Pratt
  14 * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
  15 */
  16 /**
  17 * You won't call this function directly. This function is used to process
  18 * text buffered by php in an output buffer. All output is run through this function
  19 * before it is ouput.
  20 * @param string $buffer is the output sent from php
  21 * @return string the output sent to the browser
  22 */
  23 function sid_ob_rewrite($buffer){
  24     $replacements = array(
  25         '/(<\s*(a|link|script|frame|area)\s[^>]*(href|src)\s*=\s*")([^"]*)(")/i',
  26         '/(<\s*(a|link|script|frame|area)\s[^>]*(href|src)\s*=\s*\')([^\']*)(\')/i');
  27
  28     $buffer = preg_replace_callback($replacements, "sid_rewrite_link_tag", $buffer);
  29     $buffer = preg_replace('/<form\s[^>]*>/i',
  30         '\0<input type="hidden" name="' . session_name() . '" value="' . session_id() . '"/>', $buffer);
  31
  32       return $buffer;
  33 }
  34 /**
  35 * You won't call this function directly. This function is used to process
  36 * text buffered by php in an output buffer. All output is run through this function
  37 * before it is ouput.
  38 * This function only processes absolute urls, it is used when we decide that
  39 * php is processing other urls itself but needs some help with internal absolute urls still.
  40 * @param string $buffer is the output sent from php
  41 * @return string the output sent to the browser
  42 */
  43 function sid_ob_rewrite_absolute($buffer){
  44     $replacements = array(
  45         '/(<\s*(a|link|script|frame|area)\s[^>]*(href|src)\s*=\s*")((?:http|https)[^"]*)(")/i',
  46         '/(<\s*(a|link|script|frame|area)\s[^>]*(href|src)\s*=\s*\')((?:http|https)[^\']*)(\')/i');
  47
  48     $buffer = preg_replace_callback($replacements, "sid_rewrite_link_tag", $buffer);
  49     $buffer = preg_replace('/<form\s[^>]*>/i',
  50         '\0<input type="hidden" name="' . session_name() . '" value="' . session_id() . '"/>', $buffer);
  51     return $buffer;
  52 }
  53 /**
  54 * A function to process link, a and script tags found
  55 * by preg_replace_callback in {@link sid_ob_rewrite($buffer)}.
  56 */
  57 function sid_rewrite_link_tag($matches){
  58     $url = $matches[4];
  59     $url=sid_process_url($url);
  60     return $matches[1]. $url.$matches[5];
  61 }
  62 /**
  63 * You can call this function directly. This function is used to process
  64 * urls to add a moodle session id to the url for internal links.
  65 * @param string $url is a url
  66 * @return string the processed url
  67 */
  68 function sid_process_url($url) {
  69     global $CFG;
  70     if ((preg_match('/^(http|https):/i', $url)) // absolute url
  71         &&  ((stripos($url, $CFG->wwwroot)!==0) && stripos($url, $CFG->httpswwwroot)!==0)) { // and not local one
  72         return $url; //don't attach sessid to non local urls
  73     }
  74     if ($url[0]=='#' || (stripos($url, 'javascript:')===0)) {
  75         return $url; //don't attach sessid to anchors
  76     }
  77     if (strpos($url, session_name())!==FALSE)
  78     {
  79         return $url; //don't attach sessid to url that already has one sessid
  80     }
  81     if (strpos($url, "?")===FALSE){
  82         $append="?".strip_tags(session_name() . '=' . session_id() );
  83     }    else {
  84         $append="&amp;".strip_tags(session_name() . '=' . session_id() );
  85     }
  86     //put sessid before any anchor
  87     $p = strpos($url, "#");
  88     if($p!==FALSE){
  89         $anch = substr($url, $p);
  90         $url = substr($url, 0, $p).$append.$anch ;
  91     } else  {
  92         $url .= $append ;
  93     }
  94     return $url;
  95 }
  96
  97
  98 /**
  99 * Call this function before there has been any output to the browser to
 100 * buffer output and add session ids to all internal links.
 101 */
 102 function sid_start_ob(){
 103     global $CFG;
 104     //don't attach sess id for bots
 105
 106     if (!empty($_SERVER['HTTP_USER_AGENT'])) {
 107         if (!empty($CFG->opentogoogle)) {
 108             if (strpos($_SERVER['HTTP_USER_AGENT'], 'Googlebot') !== false ) {
 109                 @ini_set('session.use_trans_sid', '0'); // try and turn off trans_sid
 110                 $CFG->usesid=false;
 111                 return;
 112             }
 113             if (strpos($_SERVER['HTTP_USER_AGENT'], 'google.com') !== false ) {
 114                 @ini_set('session.use_trans_sid', '0'); // try and turn off trans_sid
 115                 $CFG->usesid=false;
 116                 return;
 117             }
 118         }
 119         if (strpos($_SERVER['HTTP_USER_AGENT'], 'W3C_Validator') !== false ) {
 120             @ini_set('session.use_trans_sid', '0'); // try and turn off trans_sid
 121             $CFG->usesid=false;
 122             return;
 123         }
 124     }
 125     @ini_set('session.use_trans_sid', '1'); // try and turn on trans_sid
 126     if (ini_get('session.use_trans_sid')!=0 ){
 127         // use trans sid as its available
 128         ini_set('url_rewriter.tags', 'a=href,area=href,script=src,link=href,'
 129             . 'frame=src,form=fakeentry');
 130         ob_start('sid_ob_rewrite_absolute');
 131     }else{
 132         //rewrite all links ourselves
 133         ob_start('sid_ob_rewrite');
 134     }
 135 }
 136 ?>