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:
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)