PowerShell Remoting in the Enterprise

1. PowerShell Remoting in the Enterprise What you need to know.

2. Speaker • 9+ years experience in Microsoft-based IT • Microsoft System Center 2012 R2 • Windows PowerShell since 2007 • Started writing VBscript in 2005 • Worked in many enterprise environments with 10-70k+ systems

3. Why use remoting? • Fan-out management of Windows Server systems • Desired State Configuration (DSC) in PowerShell v4 • PowerShell Workflow • Interactive remote management (similar to SSH) • Quicker than RDP

4. How does remoting work? Client Server PowerShell Session PowerShell Session PowerShell PowerShell Windows Remote Management Windows Remote Management HTTP TCP 5986 TCP 5985 HTTP Windows Windows

5. Remoting Configuration SSL requires a “Server Authentication” certificate • Enable-PSRemoting -Force; • Set-WsmanQuickConfig -UseSSL; • Use Group Policy Manual Configuration Process

6. WinRM Service GPO Configuration Don’t leave listeners blank!

8. Windows PowerShell GPO Settings • Use either: • Remote Signed • Unrestricted powershell.exe –ExecutionPolicy Bypass –File c:\path\to\script.ps1

9. WinRM Client Configuration • Authentication • Basic • Negotiate • Kerberos • Client certificate mapping • Credential Security Support Provider (CredSSP) • TrustedHosts • DefaultPorts TrustedHosts is useful in multi-forest, multi-domain, or workgroup environments. Special alias “<local>” for hostnames without dots “.”

10. WinRM Client Configuration

11. WinRM Shell Configuration Set-Location –Path wsman:\localhost\shell; Get-ChildItem;

12. Windows Remote Shell GPO Configuration Windows Server 2012 Default Values Quota Management for Remote Shells http://msdn.microsoft.com/en-us/library/windows/desktop/ee309367(v=vs.85).aspx

13. PowerShell Remoting Cmdlets • Enter-PSSession • New-PSSession • Remove-PSSession • Connect-PSSession • Invoke-Command • New-PSSessionConfigurationFile • about_Session_Configuration_Files • about_Session_Configurations

14. CIM Cmdlets Replace the WMI cmdlets in PowerShell v2. • Get-CimAssociatedInstance • Get-CimClass • Get-CimInstance • Get-CimSession • Invoke-CimMethod • New-CimInstance • New-CimSession • New-CimSessionOption • Register-CimIndicationEvent • Remove-CimInstance • Remove-CimSession • Set-CimInstance

15. CIM Session Remoting Protocols

16. Session Configurations • Restrict the commands that can be executed in a remote session • Restrict who can access the session configuration • Default session configurations can be removed or modified • Use Enable-PSRemoting to restore original configurations (after deleting)

17. Credential Security Support Provider (CredSSP) Server01 Server02 • Allows double-hop scenario • Three types of credentials.PowerShell uses one. • Default credential • Saved credential • Fresh credential • Can be configured via GPO Client01 • CredSSP PowerShell Commands • Get-WSManCredSSP • Enable-WSManCredSSP • Disable-WSManCredSSP

18. CredSSP Group Policy Configuration

19. Troubleshooting • Enable-PSWsmanCombinedTrace; • Get-WinEvent –Oldest $PSHome\Traces\pstrace.etl • Enable the Microsoft-Windows-WinRM/Operational event log • Read the error messages • Use Nmap to test ports (http://nmap.org) • nmap.exe –p5985,5986 server.domain.com • Use netstat –aon to ensure port is listening

20. Issues • Missing Service Principal Name (SPN) causes CredSSP connections to fail • Windows Firewall prevents communication (TCP 5985) • Windows Remote Management (WinRM) Listeners are empty in GPO configuration • SSL Certificate is expired or has mismatched DNS name in Subject Name field • Mismatching certificate thumbprints for WinRM“Service” and “Listener” configurations • Get-ChildItem -Path wsman:\localhost\Listeners\<HTTPSListener>; • Get-ChildItem –Path wsman:\localhost\service; • Remove-Item –Path HKLM:\Software\Microsoft\Windows\CurrentVersion\Wsman\Listener\*+HTTPS:certThumbprint • Restart PowerShell after Enable-WSManCredSSP -Role Client; • Incorrect permissions on $env:ProgramData\Microsoft\Crypto\RSA\MachineKeys prevents the WinRM service from reading the SSL certificate • Windows 2008: Missing Microsoft.PowerShell session configuration (use Enable-PSRemoting to resolve) • Use FQDN to connect to remote system with CredSSP or SSL • Certificate Revocation List (CRL) is outdated • Fix with: certutil.exe –CRL

21. Limitations • Starting a remote session from within a remote session • Interactive command-line utilities don’t work well under remotingsessions • diskpart • nslookup • psexec • CredSSP is required to access network resources from a remote session

22. Built-in Variables • $PSSenderInfo – Use this automatic variable to explore the remote session configuration (authentication type, SSL, etc.) • $PSSessionOption – A preference variable that allows you to set the default remote session options

23. TrevorSullivan@projectleadership.net