about_Execution_Policies

TOPIC
	about_Execution_Policies

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

LONG DESCRIPTION
	Windows PowerShell execution policies let you determine the
	conditions under which Windows PowerShell loads configuration files
	and runs scripts.

	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 policy for computers and users.

	Execution policies for the local computer and current user are stored
	in the registry. You do not need to set execution policies in your
	Windows 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 is not a security system that restricts user actions.
	For example, users can easily circumvent a policy by typing the script 
	contents at the command line when they cannot run a script. Instead, the
	execution policy helps users to set basic rules and prevents them from 
	violating them unintentionally.


 WINDOWS POWERSHELL EXECUTION POLICIES
 -------------------------------------

	The Windows PowerShell execution policies are as follows:

	"Restricted" is the default policy.

		Restricted
			- Default execution policy.

			- Permits individual commands, but will not run
			scripts. 

			- Prevents running of all script files, including
			formatting and configuration files (.ps1xml), module
			script files (.psm1), and Windows PowerShell
			profiles (.ps1).  

		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 have not yet classified as trusted or
			untrusted.

			- Risks running unsigned scripts from sources other
			than the Internet and signed, but malicious, scripts.

		RemoteSigned
			- Scripts can run.

			- Requires a digital signature from a trusted
			publisher on scripts and configuration files that
			are downloaded from the Internet (including
			e-mail and instant messaging programs).

			- Does not require digital signatures on scripts that you have run
			and that you have written on the local computer (not
			downloaded from the Internet).

			- Risks running signed, but malicious, scripts.

		Unrestricted
			- Unsigned scripts can run. (This risks running malicious
			scripts.)

			- Warns the user before running srcipts and configuration
			files that are downloaded from the Internet.  

		Bypass
			- Nothing is blocked and there are no warnings or
			prompts.

			- This execution policy is designed for configurations
			in which a Windows PowerShell script is built in to a
			a larger application or for configurations in which
			Windows PowerShell is the foundation for a program
			that has its own security model.

		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, which is the
			default execution policy.


	Note: On systems that do not 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
 ----------------------
	You can set an execution policy that is effective only in a 
	particular scope. 

	The valid values for Scope are Process, CurrentUser, and
	LocalMachine. LocalMachine is the default when setting an
	execution policy. 

	The Scope values are listed in precedence order.

		- Process 
			 The execution policy affects only the current session
			 (the current Windows PowerShell process). The execution
			 policy is stored in the $PSExecutionPolicyPreference
			 environment variable. This value is deleted when the
			 session in which the policy is set is closed.

		- CurrentUser 
			 The execution policy affects only the current user. It
			 is stored in the HKEY_CURRENT_USER registry subkey. 

		- LocalMachine
			 The execution policy affects all users on the current
			 computer. It is stored in the HKEY_LOCAL_MACHINE
			 registry subkey.

	The policy that takes precedence is effective in the current
	session, even if a more restrictive policy was set at a lower
	level of precedence.

	For more information, see Set-ExecutionPolicy.



 GET YOUR EXECUTION POLICY
 ------------------------------
	To get the Windows PowerShell execution policy that is in
	effect in the current session, use the Get-ExecutionPolicy cmdlet. 

	The following command gets the current execution policy:

		get-executionpolicy


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

		get-executionpolicy -list

	The result will look 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 current user scope.

		get-executionpolicy -scope CurrentUser  
	




 CHANGE YOUR EXECUTION POLICY
 ------------------------------
	To change the Windows PowerShell execution policy on your
	computer, use the Set-ExecutionPolicy cmdlet. 

	The change is effective immediately; you do not need to restart
	Windows PowerShell. 

	If you set the execution policy for the local computer (the default)
	or the current user, the change is saved in the registry and remains
	effective until you change it again.

	If you set the execution policy for the current process, it is 
	not saved in the registry. It is retained until the current
	process and any child processes are closed. 


	Note: In Windows Vista and later versions of Windows, to run
		commands that change the execution policy for the local
		computer (the default), start Windows PowerShell with the
		"Run as administrator" option.


	To change your execution policy, type:
 
		Set-ExecutionPolicy <policy-name>

	For example: 

		Set-ExecutionPolicy RemoteSigned



	To set the execution policy in a particular scope, type:

		Set-ExecutionPolicy <policy-name> -scope <scope>

	For example: 

		Set-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 YOUR EXECUTION POLICY
 ----------------------------
	To remove the execution policy for a particular scope, set
	the value of the value of the execution policy to Undefined.

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

		set-executionpolicy Undefined

	Or, type:

		set-executionpolicy Undefined -scope LocalMachine

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



 SET AN EXECUTION POLICY IN POWERSHELL.EXE
 -----------------------------------------
	You can use the ExecutionPolicy parameter of PowerShell.exe to
	set an execution policy for a new Windows PowerShell session.
	The policy affects only the current session and child sessions.

	To set the execution policy for a new session, start Windows PowerShell
	at the command line (such as Cmd.exe or Windows PowerShell), and then use
	the ExecutionPolicy parameter of PowerShell.exe to set the execution
	policy.

	For example:

		powershell.exe -executionpolicy -allsigned


	The execution policy that you set is not stored in the registry.
	Instead, it is stored in the $PSExecutionPolicyPreference environment
	variable. The variable is deleted when you close the session in which the
	policy is set.
	 
	During the session, the execution policy that is set for the session takes
	precedence over an execution policy that is set in the registry for the 
	local computer or current user. However, it does not take precedence over 
	the execution policy set by using a Group Policy setting (discussed below).

		 

 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 Windows
	PowerShell in all scopes. 

	The "Turn on Script Execution" policy settings are as follows:

	-- If you disable "Turn on Script Execution", scripts do not 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		 RemoteSigned
		and remote signed
		scripts. 

		Allow only signed		 AllSigned
		scripts. 

	-- If "Turn on Script Execution" is not configured, it has no
	 effect. The execution policy set in Windows PowerShell is
	 effective.


	The PowerShellExecutionPolicy.adm file adds the 
	"Turn on Script Execution" policy to the Computer Configuration
	and User Configuration nodes in Group Policy Editor in the following
	paths.

		For Windows XP and Windows Server 2003:
		Administrative Templates\Windows Components\Windows PowerShell

		For Windows Vista and later versions of Windows:
		Administrative Templates\Classic Administrative Templates\
		Windows Components\Windows PowerShell

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

	The PowerShellExecutionPolicy.adm file is available on the 
	Microsoft Download Center. For more information, see "Administrative 
	Templates for Windows PowerShell" at 
	http://go.microsoft.com/fwlink/?LinkId=131786.


 EXECUTION POLICY PRECEDENCE
 ---------------------------
	When determining the effective execution policy for a 
	session, Windows PowerShell evaluates the execution policies
	in the following precedence order:

		- Group Policy: Computer Configuration
		- Group Policy: User Configuration
		- Execution Policy: Process (or PowerShell.exe -ExecutionPolicy)
		- Execution Policy: CurrentUser
		- Execution Policy: LocalMachine


 MANAGE SIGNED AND UNSIGNED SCRIPTS
 ----------------------------------
	If your Windows PowerShell execution policy is RemoteSigned,
	Windows PowerShell will not run unsigned scripts that are
	downloaded from the Internet (including e-mail and instant
	messaging programs).
 
	You can sign the script or elect to run an unsigned script
	without changing the execution policy.

	For more information, see about_Signing.


SEE ALSO
	Get-ExecutionPolicy
	Set-ExecutionPolicy
	about_Signing
	"Administrative Templates for Windows PowerShell" 
		(http://go.microsoft.com/fwlink/?LinkId=131786)