How scopes affect powershell scripts

The Set-ExecutionPolicy cmdlet changes the user preference for the Windows PowerShell execution policy.

The execution policy is part of the security strategy of Windows PowerShell. It determines whether you can load configuration files (including your Windows PowerShell profile) and run scripts, and it determines which scripts, if any, must be digitally signed before they will run. For more information, see about_Execution_Policies (http://go.microsoft.com/fwlink/?LinkID=135170).

To change the execution policy for the default (LocalMachine) scope, start Windows PowerShell with the “Run as administrator” option.

Parameters
  • Default value isFalse
  • Accepts pipeline input False

Prompts you for confirmation before running the cmdlet.

  • This value is required
  • Default value isNone
  • Accepts pipeline input ByValue

Specifies the new execution policy. The acceptable values for this parameter are:

– Restricted. Does not load configuration files or run scripts. Restricted is the default execution policy. – AllSigned. Requires that all scripts and configuration files be signed by a trusted publisher, including scripts that you write on the local computer. – RemoteSigned. Requires that all scripts and configuration files downloaded from the Internet be signed by a trusted publisher. – Unrestricted. Loads all configuration files and runs all scripts. If you run an unsigned script that was downloaded from the Internet, you are prompted for permission before it runs. – Bypass. Nothing is blocked and there are no warnings or prompts. – Undefined. Removes the currently assigned execution policy from the current scope. This parameter will not remove an execution policy that is set in a Group Policy scope.

  • Default value isFalse
  • Accepts pipeline input False

Suppresses all prompts. By default, Set-ExecutionPolicy displays a warning whenever you change the execution policy.

  • Default value isNone
  • Accepts pipeline input ByPropertyName

Specifies the scope of the execution policy. The default is LocalMachine. The acceptable values for this parameter are:

– Process: The execution policy affects only the current Windows PowerShell process.

– CurrentUser: The execution policy affects only the current user.

– LocalMachine: The execution policy affects all users of the computer.

To remove an execution policy from a particular scope, set the execution policy for that scope to Undefined.When the value of the Scope parameter is Process, the execution policy is saved in the PSExecutionPolicyPreference environment variable ($env:PSExecutionPolicyPreference), instead of the registry, and the variable is deleted when the process is closed. You cannot change the execution policy of the process by editing the variable.

  • Default value isFalse
  • Accepts pipeline input False

Shows what would happen if the cmdlet runs. The cmdlet is not run.

This cmdlet supports the common parameters: Verbose, Debug,ErrorAction, ErrorVariable, WarningAction, WarningVariable,OutBuffer, PipelineVariable, and OutVariable.

Inputs
Outputs
Examples
  1. Set the shell execution policy:

This command sets the user preference for the shell execution policy to RemoteSigned.

This command attempts to set the execution policy for the shell to Restricted. The Restricted setting is written to the registry, but because it conflicts with a group policy, it is not effective, even though it is more restrictive than the group policy.

This command gets the execution policy from a remote computer and applies that execution policy to the local computer.

The command uses the Invoke-Command cmdlet to send the command to the remote computer. Because you can pipe an ExecutionPolicy (Microsoft.PowerShell.ExecutionPolicy) object to Set-ExecutionPolicy , the Set-ExecutionPolicy command does not require an ExecutionPolicy parameter.

The command uses the Force parameter to suppress the user prompt.

The second command uses the *List* parameter of the Get-ExecutionPolicy cmdlet to get the execution policies set in each scope. The results show that the execution policy that is set for the current user differs from the execution policy set for all users of the computer.This example shows how to set an execution policy for a particular scope.

The first command uses the Set-ExecutionPolicy cmdlet to set an execution policy of AllSigned for the current user. It uses the Force parameter to suppress the user prompt.

This command uses an execution policy value of Undefined to effectively remove the execution policy that is set for the current user scope. As a result, the execution policy that is set in Group Policy or in the LocalMachine (all users) scope is effective.

If you set the execution policy in all scopes to Undefined and the Group Policy is not set, the default execution policy, Restricted, is effective for all users of the computer.

This command sets an execution policy of AllSigned for only the current Windows PowerShell session. This execution policy is saved in the PSExecutionPolicyPreference environment variable ($env:PSExecutionPolicyPreference), so it does not affect the value in the registry. The variable and its value are deleted when the current session is closed.

    The first command uses the **Set-ExecutionPolicy** cmdlet to change the execution policy to RemoteSigned.:

The first command uses the **Set-ExecutionPolicy** cmdlet to change the execution policy to RemoteSigned.

The output shows that it is RemoteSigned.

The RemoteSigned policy prevents you from running scripts that are downloaded from the Internet unless they are digitally signed.

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Change the user preference for the execution policy of the shell.

In order to change the Execution policy, you must be running PowerShell As Adminstrator.

ExecutionPolicy is like a baby door. The ExecutionPolicy keeps babies safe but every grown-up surpasses it easily. There are over 20 ways to surpass the ExecutionPolicy as a standard user. Therefore you should set it via GPO as you like it. (e.g. RemoteSigned)
It may prevent some people using PowerShell scripts from the internet but you should not count on it.

System-wide PowerShell Execution Policies have never been a way to prevent the user from doing something they want to do. That job is left to the Windows Account Model, which is a security boundary. [x]

Runing unsigned scripts

Even if the PowerShell execution policy is set to RemoteSigned it is still possible to run unsigned scripts:

Save the script file on your computer, Right-click the file, and click "Properties."
At the bottom of the dialogue box click "Unblock."

Alternatively copy the text into a brand new text file and save it with a .ps1 extension.

Bypass Execution policy completely

Microsoft never intended Execution policies to be a complete security control, so there are several ways to bypass them completely:

Pipe the contents of a script file to PowerShell.exe Std in:
Get-Content .demo.ps1 | PowerShell.exe -noprofile –

Or launch a one liner with invoke-command:
invoke-command -computername Server64 -scriptblock

Several other methods can be found on the NetSPI blog here.

Change Execution policy once only.

To run a single PowerShell session with a different execution policy, use powershell.exe -ExecutionPolicy this will not affect the default policy setting for any future sessions.

64 bit vs 32 bit Execution policies

These will include both the 64bit and 32bit version of PowerShell, they each can have different execution policies, so you may wish to set both.
C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe = 64bit version
C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe = 32bit version

Set the user preference for the shell execution policy to RemoteSigned and then display the effective execution policy. The commands are separated by a semicolon (;)

PS C:\> set-executionpolicy remotesigned; get-executionPolicy

Get the execution policy from a remote computer, server64 and apply that execution policy to the local computer:

PS C:\> invoke-command -computername Server64 -scriptblock | set-executionpolicy -force

Set an execution policy of AllSigned for the current user, then the execution policies set in each scope:

PS C:\> set-executionpolicy -scope CurrentUser -executionPolicy AllSigned -force
PS C:\> get-executionpolicy -list

Set an execution policy value of Undefined to effectively remove the execution policy that is set for the current user scope. As a result, the execution policy that is set in Group Policy or in the LocalMachine (all users) scope is effective:

PS C:\> set-executionpolicy -scope CurrentUser -executionPolicy Undefined

If the execution policy in all scopes is set to Undefined and the Group Policy is not set, the default execution policy, Restricted, is effective for all users of the computer.

“Laughing on the way to your execution is not generally understood by less-advanced life forms, and they call you crazy”

Related PowerShell Cmdlets:

Set-AuthenticodeSignature – Sign a PowerShell script.
Get-ExecutionPolicy – Get the execution policy for the shell.