invisimail.module in Invisimail 5

This module provides a filter that will search content for email addresses and replace them with their ascii equivalents before display. This is not a complete protection from spam harvesters, but it is some help.

File

invisimail.module

<?php

/**
 * @file
 * This module provides a filter that will search content for email addresses
 * and replace them with their ascii equivalents before display. This is not
 * a complete protection from spam harvesters, but it is some help.
 */

/**
 * Implementation of hook_help().
 *
 */
function invisimail_help($section) {
  switch ($section) {
    case 'admin/help#invisimail':
      return t('<p>The invisimail module privides a filter to hide email addresses from email harvesting spam-bots.</p><p>How it works: Invisimail scans content for email addresses and then converts each character of the address to its ASCII-code equivalent. The email address will appear normally on the page, but the source html will not appear as an email address. For even more security, the filter can use a JavaScript write command to further obscure the email address.</p><p>For example:<br /><i>[e-mail]</i> will appear in the html source as: <div style="font-family:courier;border:1px solid #666;padding: 5px">&amp;#121;&amp;#111;&amp;#117;&amp;#64;&amp;#101;&amp;#120;&amp;#97;&amp;#109;&amp;#112;&amp;#108;&amp;#101;&amp;#46;&amp;#99;&amp;#111;&amp;#109;</div></p><p>With the JavaScript and Auto-link options enabled, the source would become: <div style="font-family:courier;border:1px solid #666;padding: 5px">&lt;script type=\'text/javascript\'&gt;&lt;!--<br />
document.write(\'&lt;a href= "&amp;#109;&amp;#97;&amp;#105;&amp;#108;&amp;#116;&amp;#111;&amp;#58;\' + \'&amp;#121;&amp;#111;&amp;#117;&amp;#64;\' + \'&amp;#101;&amp;#120;&amp;#97;&amp;#109;&amp;#112;&amp;#108;&amp;#101;&amp;#46;\' + \'&amp;#99;&amp;#111;&amp;#109;\' + \'"&gt;\' + \'&amp;#121;&amp;#111;&amp;#117;&amp;#64;\' + \'&amp;#101;&amp;#120;&amp;#97;&amp;#109;&amp;#112;&amp;#108;&amp;#101;&amp;#46;\' + \'&amp;#99;&amp;#111;&amp;#109;\' + \'&lt;/a&gt;\');<br />
//--&gt;<br />
&lt;/script&gt;</div></p><p>Doesn\'t look like an email address, does it?</p><p>Of course the best protection against spam-bots is to not publish an email address at all, but on a community site some users are going to publish email addresses. Invisimail provides another level of security to keep them from recieving spam.</p><p>To configure Invisimail, select "configure" next to the <a href="%url">input format</a> you\'d like to use. Enable "Encode Email Addresses" and submit the form. Then select the "configure" tab to choose options for Invisimail.</p>', array(
        '%url' => url('admin/filters'),
      ));
  }
}

/**
 * Implementation of hook_filter_tips().
 *
 */
function invisimail_filter_tips($delta, $format, $long = FALSE) {
  switch ($delta) {
    case 0:
      if ($long) {
        return t('Every email address in the input text will be replaced with its ascii equivalent.');
      }
      break;
  }
}

/**
 * Implementation of hook_filter().
 *
 */
function invisimail_filter($op, $delta = 0, $format = -1, $text = '') {
  if ($op == 'list') {
    return array(
      0 => t('Encode email addresses'),
    );
  }
  switch ($delta) {
    case 0:
      switch ($op) {
        case 'description':
          return t('Hide email addresses from spam-bots.');
        case 'prepare':
          return $text;
        case 'process':
          return invisimail($text, $format);
        case 'settings':
          $form['invisimail_settings'] = array(
            '#type' => 'fieldset',
            '#title' => t('Invisimail email address encoding filter'),
            '#collapsible' => true,
            '#collapsed' => true,
          );
          $form['invisimail_settings']['invisimail_js_' . $format] = array(
            '#type' => 'radios',
            '#title' => t('JavaScript'),
            '#default_value' => variable_get('invisimail_js_' . $format, FALSE),
            '#options' => array(
              FALSE => t('No JavaScript - greater compatibility'),
              TRUE => t('Use JavaScript - greater security'),
            ),
            '#description' => t('Selecting "Use JavaScript" will nearly guarantee protection from spam harvesters. However email addresses will not appear for browsers without JavaScript capability.'),
          );
          $form['invisimail_settings']['invisimail_link_' . $format] = array(
            '#type' => 'radios',
            '#title' => t('Auto-link Emails'),
            '#default_value' => variable_get('invisimail_link_' . $format, FALSE),
            '#options' => array(
              FALSE => t('Do not create links.'),
              TRUE => t('Automatically create links from email addresses.'),
            ),
            '#description' => t('Selecting "Automatically create links" will convert email addresses into a clickable "mailto:" link.'),
          );
          return $form;
      }
      break;
  }
}
function invisimail($string, $format) {
  $pattern = "!(<p>|<li>|<br />|[ \n\r\t\\(])([A-Za-z0-9._-]+@[A-Za-z0-9._-]+\\.[A-Za-z]{2,4})([.,]?)(?=(</p>|</li>|<br />|[ \n\r\t\\)]))!i";

  // the callback needs to know what filter we're using
  // however there's no way to hand off that variable
  // so we'll set a global variable
  $GLOBALS['invisimail_format'] = $format;
  return preg_replace_callback($pattern, 'invisimail_callback', $string);
}
function invisimail_callback($matches) {
  $format = $GLOBALS['invisimail_format'];
  $js = variable_get('invisimail_js_' . $format, FALSE);
  $link = variable_get('invisimail_link_' . $format, FALSE);
  return $matches[1] . invisimail_ascii_encode($matches[2], $js, $link) . $matches[3];
}

/**
 * This function does the actual encoding. 
 *
 * @param $string
 *   A string which contains only an email addres to be encoded. 
 * @param $js
 *   Optional: A boolean which sets whether Javascript is used for encoding.
 * @param $link
 *   Optional: A boolean which set whether the result includes a mailto link.
 * @param $text
 *   Optional: The text to be used for the link.
 * @return
 *   An ascii encoded email address. 
 */
function invisimail_ascii_encode($string, $js = FALSE, $link = FALSE, $text = NULL) {
  if ($text == NULL) {
    $text = $string;
  }
  if ($js) {
    $output = "<script type='text/javascript'><!--\n    document.write('";
  }
  for ($i = 0; $i < strlen($string); $i++) {
    $char = substr($string, $i, 1);
    $encode .= '&#' . ord($char) . ';';
    if ($js) {
      if (in_array($char, array(
        '.',
        '@',
      ))) {

        // break strings after ats and dots
        $encode .= "'+'";
      }
    }
  }
  if ($link && !$js) {

    // ascii in this next line is "mailto:"
    $output .= "<a href=\"&#109;&#97;&#105;&#108;&#116;&#111;&#58;{$encode}\">{$encode}</a>";
  }
  elseif ($link && $js) {
    $output .= "<a href=\"&#109;&#97;&#105;&#108;&#116;&#111;&#58;'+'{$encode}'+'\">'+'{$encode}'+'</a>";
  }
  else {
    $output .= $encode;
  }
  if ($js) {
    $output .= "');\n    //-->\n    </script>";
  }
  return $output;
}

Functions

Name	Description
invisimail
invisimail_ascii_encode	This function does the actual encoding.
invisimail_callback
invisimail_filter	Implementation of hook_filter().
invisimail_filter_tips	Implementation of hook_filter_tips().
invisimail_help	Implementation of hook_help().