完美扫描PHP特殊一句话后门

在我们进行渗透测试的最后阶段，入侵到内网里，无论是想要浏览网站结构，还是抓取数据库，或者是挂个木马等等，到最后最常用的就是执行一句话木马，从客户端轻松连接服务器。

一句话木马的原理很简单，造型也很简单，所以造成了它理解起来容易，抵御起来也容易。于是黑白的较量变成了黑帽不断的构造变形的后门，去隐蔽特征，而白帽则不断的更新过滤方法，建起更高的城墙。

原理简述

对于不同的语言有不同的构造方法。

• 基本构造：最开头构造的是脚本开始的标记
• 核心部分：获取并执行得到的内容，通常类似eval、execute等
• 被执行内容：一般是http等协议接受的值，通常类似request、$_POST等

如果我们通过客户端向服务器发送被执行内容，那么就会让服务器执行我们发送的脚本，挂马就实现了。

code：

<?php
/**********************
作者 Spider
网上公布的各种PHP后门全军覆没
针对一些特殊变形的后门需要自己添加特征
误报率不到百分之一
**********************/
error_reporting(E_ERROR);
ini_set('max_execution_time',20000);
ini_set('memory_limit','512M');
header("content-Type: text/html; charset=gb2312");
 
$matches = array(
        '/function\_exists\s*\(\s*[\'|\"](popen|exec|proc\_open|system|passthru)+[\'|\"]\s*\)/i',
        '/(exec|shell\_exec|system|passthru)+\s*\(\s*\$\_(\w+)\[(.*)\]\s*\)/i',
        '/((udp|tcp)\:\/\/(.*)\;)+/i',
        '/preg\_replace\s*\((.*)\/e(.*)\,\s*\$\_(.*)\,(.*)\)/i',
        '/preg\_replace\s*\((.*)\(base64\_decode\(\$/i',
        '/(eval|assert|include|require|include\_once|require\_once)+\s*\(\s*(base64\_decode|str\_rot13|gz(\w+)|file\_(\w+)\_contents|(.*)php\:\/\/input)+/i',
        '/(eval|assert|include|require|include\_once|require\_once|array\_map|array\_walk)+\s*\(\s*\$\_(GET|POST|REQUEST|COOKIE|SERVER|SESSION)+\[(.*)\]\s*\)/i',
        '/eval\s*\(\s*\(\s*\$\$(\w+)/i',
        '/(include|require|include\_once|require\_once)+\s*\(\s*[\'|\"](\w+)\.(jpg|gif|ico|bmp|png|txt|zip|rar|htm|css|js)+[\'|\"]\s*\)/i',
        '/\$\_(\w+)(.*)(eval|assert|include|require|include\_once|require\_once)+\s*\(\s*\$(\w+)\s*\)/i',
        '/\(\s*\$\_FILES\[(.*)\]\[(.*)\]\s*\,\s*\$\_(GET|POST|REQUEST|FILES)+\[(.*)\]\[(.*)\]\s*\)/i',
        '/(fopen|fwrite|fputs|file\_put\_contents)+\s*\((.*)\$\_(GET|POST|REQUEST|COOKIE|SERVER)+\[(.*)\](.*)\)/i',
        '/echo\s*curl\_exec\s*\(\s*\$(\w+)\s*\)/i',
        '/new com\s*\(\s*[\'|\"]shell(.*)[\'|\"]\s*\)/i',
        '/\$(.*)\s*\((.*)\/e(.*)\,\s*\$\_(.*)\,(.*)\)/i',
        '/\$\_\=(.*)\$\_/i',
        '/\$\_(GET|POST|REQUEST|COOKIE|SERVER)+\[(.*)\]\(\s*\$(.*)\)/i',
        '/\$(\w+)\s*\(\s*\$\_(GET|POST|REQUEST|COOKIE|SERVER)+\[(.*)\]\s*\)/i',
        '/\$(\w+)\s*\(\s*\$\{(.*)\}/i',
        '/\$(\w+)\s*\(\s*chr\(\d+\)/i'
);
 
function antivirus($dir,$exs,$matches) {
        if(($handle = @opendir($dir)) == NULL) return false;
        while(false !== ($name = readdir($handle))) {
                if($name == '.' || $name == '..') continue;
                $path = $dir.$name;
                if(is_dir($path)) {
                        //chmod($path,0777);/*主要针对一些0111的目录*/
                        if(is_readable($path)) antivirus($path.'/',$exs,$matches);
                } elseif(strpos($name,';') > -1 || strpos($name,'%00') > -1 || strpos($name,'/') > -1) {
                        echo '特征 <input type="text" style="width:218px;" value="解析漏洞"> '.$path.'<div></div>'; flush(); ob_flush();
                } else {
                        if(!preg_match($exs,$name)) continue;
                        if(filesize($path) > 10000000) continue;
                        $fp = fopen($path,'r');
                        $code = fread($fp,filesize($path));
                        fclose($fp);
                        if(empty($code)) continue;
                        foreach($matches as $matche) {
                                $array = array();
                                preg_match($matche,$code,$array);
                                if(!$array) continue;
                                if(strpos($array[0],"\x24\x74\x68\x69\x73\x2d\x3e")) continue;
                                $len = strlen($array[0]);
                                if($len > 6 && $len < 200) {
                                        echo '特征 <input type="text" style="width:218px;" value="'.htmlspecialchars($array[0]).'"> '.$path.'<div></div>';
                                        flush(); ob_flush(); break;
                                }
                        }
                        unset($code,$array);
                }
        }
        closedir($handle);
        return true;
}
 
function strdir($str) { return str_replace(array('\\','//','//'),array('/','/','/'),chop($str)); }
 
echo '<form method="POST">';
echo '路径: <input type="text" name="dir" value="'.($_POST['dir'] ? strdir($_POST['dir'].'/') : strdir($_SERVER['DOCUMENT_ROOT'].'/')).'" style="width:398px;"><div></div>';
echo '后缀: <input type="text" name="exs" value="'.($_POST['exs'] ? $_POST['exs'] : '.php|.inc|.phtml').'" style="width:398px;"><div></div>';
echo '操作: <input type="submit" style="width:80px;" value="scan"><div></div>';
echo '</form>';
 
if(file_exists($_POST['dir']) && $_POST['exs']) {
        $dir = strdir($_POST['dir'].'/');
        $exs = '/('.str_replace('.','\\.',$_POST['exs']).')/i';
        echo antivirus($dir,$exs,$matches) ? '<div></div>扫描完毕' : '<div></div>扫描中断';
}
?>

另外一个版本：

<!DOCTYPE html>
<html>
<head>
        <meta charset='gb2312'>
        <title>PHP web shell scan</title>
</head>
<body>
 
</body>
 
<?php
error_reporting(E_ERROR);
ini_set('max_execution_time',20000);
ini_set('memory_limit','512M');
header("content-Type: text/html; charset=gb2312");
 
function weevelyshell($file){
        $content=file_get_contents($file);
        if(
                (
                preg_match('#(\$\w{2,4}\s?=\s?str_replace\("\w+","","[\w\_]+"\);\s?)+#s',$content)&&
            preg_match('#(\$\w{2,4}\s?=\s?"[\w\d\+\/\=]+";\s?)+#',$content)&&                             preg_match('#\$[\w]{2,4}\s?=\s\$[\w]{2,4}\(\'\',\s?\$\w{2,4}\(\$\w{2,4}\("\w{2,4}",\s?"",\s?\$\w{2,4}\.\$\w{2,4}\.\$\w{2,4}\.\$\w{2,4}\)\)\);\s+?\$\w{2,4}\(\)\;#',$content))
                    ||
                    (preg_match('#\$\w+\d\s?=\s?str_replace\(\"[\w\d]+\",\"\",\"[\w\d]+\"\);#s',$content)&&
                preg_match('#\$\w+\s?=\s?\$[\w\d]+\(\'\',\s?\$[\w\d]+\(\$\w+\(\$\w+\(\"[[:punct:]]+\",\s?\"\",\s?\$\w+\.\$\w+\.\$\w+\.\$\w+\)\)\)\);\s?\$\w+\(\);#s',$content))
                ){
                return true;
        }
}
 
 
 
$matches = array(
        '/preg_replace\(.*?e.*?\',[eval\.\'\"]+\(/',
        '/function\_exists\s*\(\s*[\'|\"](popen|exec|proc\_open|system|passthru)+[\'|\"]\s*\)/i',
        '/(exec|shell\_exec|system|passthru)+\s*\(\s*\$\_(\w+)\[(.*)\]\s*\)/i',
        '/(exec|shell\_exec|system|passthru)+\s*\(\$\w+\)/i',
            '/john\.barker446@gmail\.com/i',
        '/((udp|tcp)\:\/\/(.*)\;)+/i',
        '/preg\_replace\s*\((.*)\/e(.*)\,\s*\$\_(.*)\,(.*)\)/i',
        '/preg\_replace\s*\((.*)\(base64\_decode\(\$/i',
        '/(eval|assert|include|require|include\_once|require\_once)+\s*\(\s*(base64\_decode|str\_rot13|gz(\w+)|file\_(\w+)\_contents|(.*)php\:\/\/input)+/i',
        '/(eval|assert|include|require|include\_once|require\_once|array\_map|array\_walk)+\s*\(\s*\$\_(GET|POST|REQUEST|COOKIE|SERVER|SESSION)+\[(.*)\]\s*\)/i',
        '/eval\s*\(\s*\(\s*\$\$(\w+)/i',
        '/(include|require|include\_once|require\_once)+\s*\(\s*[\'|\"](\w+)\.(jpg|gif|ico|bmp|png|txt|zip|rar|htm|css|js)+[\'|\"]\s*\)/i',
        '/\$\_(\w+)(.*)(eval|assert|include|require|include\_once|require\_once)+\s*\(\s*\$(\w+)\s*\)/i',
        '/\(\s*\$\_FILES\[(.*)\]\[(.*)\]\s*\,\s*\$\_(GET|POST|REQUEST|FILES)+\[(.*)\]\[(.*)\]\s*\)/i',
        '/(fopen|fwrite|fputs|file\_put\_contents)+\s*\((.*)\$\_(GET|POST|REQUEST|COOKIE|SERVER)+\[(.*)\](.*)\)/i',
        '/echo\s*curl\_exec\s*\(\s*\$(\w+)\s*\)/i',
        '/new com\s*\(\s*[\'|\"]shell(.*)[\'|\"]\s*\)/i',
        '/\$(.*)\s*\((.*)\/e(.*)\,\s*\$\_(.*)\,(.*)\)/i',
        '/\$\_\=(.*)\$\_/i',
        '/\$\_(GET|POST|REQUEST|COOKIE|SERVER)+\[(.*)\]\(\s*\$(.*)\)/i',
        '/\$(\w+)\s*\(\s*\$\_(GET|POST|REQUEST|COOKIE|SERVER)+\[(.*)\]\s*\)/i',
        '/\$(\w+)\s*\(\s*\$\{(.*)\}/i',
        '/\$(\w+)\s*\(\s*chr\(\d+\)/i'
);
 
function antivirus($dir,$exs,$matches) {
        if(($handle = @opendir($dir)) == NULL) return false;
        while(false !== ($name = readdir($handle))) {
                if($name == '.' || $name == '..') continue;
                $path = $dir.$name;
                //$path=iconv("UTF-8","gb2312",$path);
                if(is_dir($path)) {
                        //chmod($path,0777);/*主要针对一些0111的目录*/
                        if(is_readable($path)) antivirus($path.'/',$exs,$matches);
                } elseif(strpos($name,';') > -1 || strpos($name,'%00') > -1 || strpos($name,'/') > -1) {
                        echo '特征 <input type="text" style="width:218px;" value="解析漏洞"> '.$path.'<div></div>'; flush(); ob_flush();
                }elseif(weevelyshell($path)){
                        echo '特征 <input type="text" style="width:218px;" value="weevely 加密shell"> '.$path.'<div></div>'; flush(); ob_flush();
 
                } else {
                        if(!preg_match($exs,$name)) continue;
                        if(filesize($path) > 10000000) continue;
                        $fp = fopen($path,'r');
                        $code = fread($fp,filesize($path));
                        fclose($fp);
                        if(empty($code)) continue;
                        foreach($matches as $matche) {
                                $array = array();
                                preg_match($matche,$code,$array);
                                if(!$array) continue;
                                if(strpos($array[0],"\x24\x74\x68\x69\x73\x2d\x3e")) continue;
                                $len = strlen($array[0]);
                                if($len > 6 && $len < 200) {
                                        echo '特征 <input type="text" style="width:218px;" value="'.htmlspecialchars($array[0]).'"> '.$path.'<div></div>';
                                        flush(); ob_flush(); break;
                                }
                        }
                        unset($code,$array);
                }
        }
        closedir($handle);
        return true;
}
 
function strdir($str) { return str_replace(array('\\','//','//'),array('/','/','/'),chop($str)); }
 
echo '<form method="POST">';
echo '路径: <input type="text" name="dir" value="'.($_POST['dir'] ? strdir($_POST['dir'].'/') : strdir($_SERVER['DOCUMENT_ROOT'].'/')).'" style="width:398px;"><div></div>';
echo '后缀: <input type="text" name="exs" value="'.($_POST['exs'] ? $_POST['exs'] : '.php|.inc|.phtml').'" style="width:398px;"><div></div>';
echo '操作: <input type="submit" style="width:80px;" value="scan"><div></div>';
echo '</form>';
 
if(file_exists($_POST['dir']) && $_POST['exs']) {
        $dir = strdir($_POST['dir'].'/');
        $exs = '/('.str_replace('.','\\.',$_POST['exs']).')/i';
        echo antivirus($dir,$exs,$matches) ? '<div></div>扫描完毕' : '<div></div>扫描中断';
}
?>
</html>