Natas teaches the basics of server-side web security. This walkthrough uses cURL so you get used to the command line and useful options.

Each level has access to the password of the next level. Our job is to somehow obtain that next password and level up. All passwords are also stored in /etc/natas_webpass/. E.g. the password for natas5 is stored in the file /etc/natas_webpass/natas5 and only readable by natas4 and natas5.

For the first level we’re given:

cURL is a command-line tool for transferring data to and from a server. To fetch the HTML source for natas0 we need the -u option, which sends the username and password for server authentication:

curl -u user:password URL

So we can request the HTML for natas0 with:

curl -u natas0:natas0 http://natas0.natas.labs.overthewire.org

Example output:

<html>
<head>
<!-- This stuff in the header has nothing to do with the level -->
<link rel="stylesheet" type="text/css" href="http://natas.labs.overthewire.org/css/level.css">
<link rel="stylesheet" href="http://natas.labs.overthewire.org/css/jquery-ui.css" />
<link rel="stylesheet" href="http://natas.labs.overthewire.org/css/wechall.css" />
<script src="http://natas.labs.overthewire.org/js/jquery-1.9.1.js"></script>
<script src="http://natas.labs.overthewire.org/js/jquery-ui.js"></script>
<script src="http://natas.labs.overthewire.org/js/wechall-data.js"></script>
<script src="http://natas.labs.overthewire.org/js/wechall.js"></script>
<script>var wechallinfo = { "level": "natas0", "pass": "natas0" };</script>
</head>
<body>
<h1>natas0</h1>
<div id="content">
You can find the password for the next level on this page.

<!--The password for natas1 is 0nzCigAq7t2iALyvU9xcHlYN4MlkIwlq -->
</div>
</body>
</html>

For this level we only need to look at the body. When you do, you’ll see a comment left for us there: the password for natas1.

Password for natas1: 0nzCigAq7t2iALyvU9xcHlYN4MlkIwlq