program/include/rcube_content_filter.php


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<?php

/*
 +-----------------------------------------------------------------------+
 | program/include/rcube_content_filter.php                              |
 |                                                                       |
 | This file is part of the Roundcube Webmail client                     |
 | Copyright (C) 2011, The Roundcube Dev Team                            |
 | Licensed under the GNU GPL                                            |
 |                                                                       |
 | PURPOSE:                                                              |
 |   PHP stream filter to detect evil content in mail attachments        |
 |                                                                       |
 +-----------------------------------------------------------------------+
 | Author: Thomas Bruederli <roundcube@gmail.com>                        |
 +-----------------------------------------------------------------------+

 $Id$
*/

/**
 * PHP stream filter to detect html/javascript code in attachments
 */
class rcube_content_filter extends php_user_filter
{
  private $buffer = '';
  private $cutoff = 2048;

  function onCreate()
  {
    $this->cutoff = rand(2048, 3027);
    return true;
  }

  function filter($in, $out, &$consumed, $closing)
  {
    while ($bucket = stream_bucket_make_writeable($in)) {
      $this->buffer .= $bucket->data;

      // check for evil content and abort
      if (preg_match('/<(script|iframe|object)/i', $this->buffer))
        return PSFS_ERR_FATAL;

      // keep buffer small enough
      if (strlen($this->buffer) > 4096)
        $this->buffer = substr($this->buffer, $this->cutoff);

      $consumed += $bucket->datalen;
      stream_bucket_append($out, $bucket);
    }

    return PSFS_PASS_ON;
  }
}