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   1  <?php  // $Id: cookieless.php,v 1.4 2007/01/03 15:00:13 moodler Exp $
   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  ?>