about_Execution_Policies

Short description

Describes the PowerShell execution policies and explains how to manage them.

Long description

PowerShell's execution policy is a safety feature that controls the conditions under which PowerShell loads configuration files and runs scripts. This feature helps prevent the execution of malicious scripts.

On a Windows computer you can set an execution policy for the local computer, for the current user, or for a particular session. You can also use a Group Policy setting to set execution policies for computers and users.

Execution policies for the local computer and current user are stored in the PowerShell configuration files. You don't need to set execution policies in your PowerShell profile. The execution policy for a particular session is stored only in memory and is lost when the session is closed.

The execution policy isn't a security boundary, it's defense in depth. For example, users can easily bypass a policy by typing the script contents at the command line when they can't run a script. Instead, the execution policy helps users to set basic rules and prevents them from violating them unintentionally.

For more information about security boundaries, see the Security service criteria section of PowerShell security features.

On non-Windows computers, the default execution policy is Unrestricted and can't be changed. The Set-ExecutionPolicy cmdlet is available, but PowerShell displays a console message that it's not supported. While Get-ExecutionPolicy returns Unrestricted on non-Windows platforms, the behavior really matches Bypass because those platforms don't implement the Windows Security Zones.

PowerShell execution policies

Enforcement of these policies only occurs on Windows platforms. The PowerShell execution policies are as follows:

• AllSigned

  • Scripts can run.
  • Requires that all scripts and configuration files be signed by a trusted publisher, including scripts that you write on the local computer.
  • Prompts you before running scripts from publishers that you haven't yet classified as trusted or untrusted.
  • Risks running signed, but malicious, scripts.

• Bypass

  • Nothing is blocked and there are no warnings or prompts.
  • This execution policy is designed for configurations in which a PowerShell script is built into a larger application or for configurations in which PowerShell is the foundation for a program that has its own security model.

• Default

  • Sets the default execution policy.
  • RemoteSigned for Windows clients and servers.

• RemoteSigned

  • The default execution policy for Windows computers.
  • Scripts can run.
  • Requires a digital signature from a trusted publisher on scripts and configuration files that are downloaded from the internet which includes email and instant messaging programs.
  • Doesn't require digital signatures on scripts that are written on the local computer and not downloaded from the internet.
  • Runs scripts that are downloaded from the internet and not signed, if the scripts are unblocked, such as by using the Unblock-File cmdlet.
  • Risks running unsigned scripts from sources other than the internet and signed scripts that could be malicious.

• Restricted

  • Permits individual commands, but doesn't allow scripts.
  • Prevents running of all script files, including formatting and configuration files (.ps1xml), module script files (.psm1), and PowerShell profiles (.ps1).

• Undefined

  • There is no execution policy set in the current scope.
  • If the execution policy in all scopes is Undefined, the effective execution policy is Restricted for Windows clients and RemoteSigned for Windows Server.

• Unrestricted

  • The default execution policy for non-Windows computers and can't be changed.
  • Unsigned scripts can run. There is a risk of running malicious scripts.
  • Warns the user before running scripts and configuration files that are not from the local intranet zone.

  Note

  On systems that don't distinguish Universal Naming Convention (UNC) paths from internet paths, scripts that are identified by a UNC path might not be permitted to run with the RemoteSigned execution policy.

Execution policy scope and precedence

You can set an execution policy that's effective only in a particular scope. The parameter accepts the following values:

• MachinePolicy - Set by a Group Policy for all users of the computer
• UserPolicy - Set by a Group Policy for the current user of the computer
• Process - Affects only the current PowerShell session
• CurrentUser - Affects only the current user
• LocalMachine - Default scope that affects all users of the computer

If the Execution Policy isn't defined by Group Policy, the effective execution policy is determined by the order of precedence as follows:

• Process - Highest precedence. The Process scope only affects the current PowerShell session. The execution policy is saved in the environment variable $Env:PSExecutionPolicyPreference, rather than the registry. When the PowerShell session is closed, the variable and value are deleted.
• CurrentUser - Second highest precedence. The setting is stored in the user-specific powershell.config.json file.
• LocalMachine - Lowest precedence. The setting is stored in the $PSHOME/powershell.config.json file.

For more information about the powershell.config.json file, see about_PowerShell_Config.

Managing the execution policy with PowerShell

To get the effective execution policy for the current PowerShell session, use the Get-ExecutionPolicy cmdlet.

The following command gets the effective execution policy:

Get-ExecutionPolicy

To get all of the execution policies that affect the current session and display them in precedence order:

Get-ExecutionPolicy -List

The result looks similar to the following sample output:

        Scope ExecutionPolicy
        ----- ---------------
MachinePolicy       Undefined
   UserPolicy       Undefined
      Process       Undefined
  CurrentUser    RemoteSigned
 LocalMachine       AllSigned

In this case, the effective execution policy is RemoteSigned because the execution policy for the current user takes precedence over the execution policy set for the local computer.

To get the execution policy set for a particular scope, use the Scope parameter of Get-ExecutionPolicy.

For example, the following command gets the execution policy for the CurrentUser scope:

Get-ExecutionPolicy -Scope CurrentUser

Change the execution policy

To change the PowerShell execution policy on your Windows computer, use the Set-ExecutionPolicy cmdlet. The change is effective immediately. You don't need to restart PowerShell.

If you set the execution policy for the scopes LocalMachine or the CurrentUser, the change is saved in the configuration file and remains effective until you change it again.

If you set the execution policy for the Process scope, it's not saved in the configuration file. The execution policy is retained until the current process and any child processes are closed.

To change your execution policy:

Set-ExecutionPolicy -ExecutionPolicy <PolicyName>

For example:

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned

To set the execution policy in a particular scope:

Set-ExecutionPolicy -ExecutionPolicy <PolicyName> -Scope <scope>

For example:

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

A command to change an execution policy can succeed but still not change the effective execution policy.

For example, a command that sets the execution policy for the local computer can succeed but be overridden by the execution policy for the current user.

Remove the execution policy

To remove the execution policy for a particular scope, set the execution policy to Undefined.

For example, to remove the execution policy for all the users of the local computer:

Set-ExecutionPolicy -ExecutionPolicy Undefined -Scope LocalMachine

To remove the execution policy for a Scope:

Set-ExecutionPolicy -ExecutionPolicy Undefined -Scope CurrentUser

If no execution policy is set in any scope, the effective execution policy is Restricted, which is the default for Windows clients.

Set a different policy for one session

You can use the ExecutionPolicy parameter of pwsh.exe to set an execution policy for a new PowerShell session. The policy affects only the current session and child sessions.

To set the execution policy for a new session, start PowerShell at the command line, such as cmd.exe or from PowerShell, and then use the ExecutionPolicy parameter of pwsh.exe to set the execution policy.

For example:

pwsh.exe -ExecutionPolicy AllSigned

The execution policy that you set isn't stored in the configuration file. Instead, it's stored in the $Env:PSExecutionPolicyPreference environment variable. The variable is deleted when you close the session in which the policy is set. You can't change the policy by editing the variable value.

During the session, the execution policy that's set for the session takes precedence over an execution policy that's set in the configuration file for the local computer or current user. However, it doesn't take precedence over the execution policy set by using a Group Policy.

Use Group Policy to manage execution policy

You can use the Turn on Script Execution Group Policy setting to manage the execution policy of computers in your enterprise. The Group Policy setting overrides the execution policies set in PowerShell in all scopes.

The Turn on Script Execution policy settings are as follows:

• If you disable Turn on Script Execution, scripts don't run. This is equivalent to the Restricted execution policy.

• If you enable Turn on Script Execution, you can select an execution policy. The Group Policy settings are equivalent to the following execution policy settings:

  Group Policy	Execution Policy
  Allow all scripts	Unrestricted
  Allow local scripts and remote signed scripts	RemoteSigned
  Allow only signed scripts	AllSigned

• If Turn on Script Execution isn't configured, it has no effect. The execution policy set in PowerShell is effective.

The PowerShellCoreExecutionPolicy.adm and PowerShellCoreExecutionPolicy.admx files add the Turn on Script Execution policy to the Computer Configuration and User Configuration nodes in Group Policy Editor in the following path:

Administrative Templates\Windows Components\Windows PowerShell

Policies set in the Computer Configuration node take precedence over policies set in the User Configuration node.

For more information, see about_Group_Policy_Settings.

Manage signed and unsigned scripts

In Windows, programs like Internet Explorer and Microsoft Edge add an alternate data stream to files that are downloaded. This marks the file as "coming from the Internet". If your PowerShell execution policy is RemoteSigned, PowerShell won't run unsigned scripts that are downloaded from the internet which includes email and instant messaging programs.

You can sign the script or elect to run an unsigned script without changing the execution policy.

Beginning in PowerShell 3.0, you can use the Stream parameter of the Get-Item cmdlet to detect files that are blocked because they were downloaded from the internet. Use the Unblock-File cmdlet to unblock the scripts so that you can run them in PowerShell.

For more information, see about_Signing, Get-Item, and Unblock-File.

Execution policy on Windows Server Core and Windows Nano Server

When PowerShell 6 is run on Windows Server Core or Windows Nano Server under certain conditions, execution policies can fail with the following error:

AuthorizationManager check failed.
At line:1 char:1
+ C:\scriptpath\scriptname.ps1
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : SecurityError: (:) [], PSSecurityException
    + FullyQualifiedErrorId : UnauthorizedAccess

PowerShell uses APIs in the Windows Desktop Shell (explorer.exe) to validate the Zone of a script file. The Windows Shell isn't available on Windows Server Core and Windows Nano Server.

You could also get this error on any Windows system if the Windows Desktop Shell is unavailable or unresponsive. For example, during sign on, a PowerShell logon script could start execution before the Windows Desktop is ready, resulting in failure.

Using an execution policy of ByPass or AllSigned doesn't require a Zone check which avoids the problem.

See also

• about_Environment_Variables
• about_Group_Policy_Settings
• about_Pwsh
• about_Signing
• Get-ExecutionPolicy
• Set-ExecutionPolicy
• Get-Item
• Unblock-File