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Authorization Rules and Security Features of Windows PowerShell Web Access

Published: June 24, 2013

Updated: June 24, 2013

Applies To: Windows Server 2012, Windows Server 2012 R2



Windows PowerShell® Web Access in Windows Server® 2012 R2 and Windows Server® 2012 has a restrictive security model. Users must explicitly be granted access before they can sign in to the Windows PowerShell Web Access gateway and use the web-based Windows PowerShell console.

After Windows PowerShell Web Access is installed and the gateway is configured, users can open the sign-in page in a browser, but they cannot sign in until the Windows PowerShell Web Access administrator grants users access explicitly. Windows PowerShell Web Access access control is managed by using the set of Windows PowerShell cmdlets described in the following table. There is no comparable GUI for adding or managing authorization rules. For more detailed information about Windows PowerShell Web Access cmdlets, see the cmdlet reference topics, Windows PowerShell Web Access Cmdlets.

Administrators can define 0-n authentication rules for Windows PowerShell Web Access. The default security is restrictive rather than permissive; zero authentication rules means no users have access to anything.

Add-PswaAuthorizationRule and Test-PswaAuthorizationRule in Windows Server 2012 R2 include a Credential parameter that allows you to add and test Windows PowerShell Web Access authorization rules from a remote computer, or from within an active Windows PowerShell Web Access session. As with other Windows PowerShell cmdlets that have a Credential parameter, you can specify a PSCredential object as the value of the parameter. To create a PSCredential object that contains credentials you want to pass to a remote computer, run the Get-Credential cmdlet.

Windows PowerShell Web Access authentication rules are whitelist rules. Each rule is a definition of an allowed connection between users, target computers, and particular Windows PowerShell session configurations (also referred to as endpoints or runspaces) on specified target computers.

securitySecurity Note
A user needs only one rule to be true to get access. If a user is given access to one computer with either full language access or access only to Windows PowerShell remote management cmdlets, from the web-based console, the user can log on (or hop) to other computers that are connected to the first target computer. The most secure way to configure Windows PowerShell Web Access is to allow users access only to constrained session configurations (also called endpoints or runspaces) that allow them to accomplish specific tasks that they normally need to perform remotely.

 

Name Description Parameters

Add-PswaAuthorizationRule

Adds a new authorization rule to the Windows PowerShell Web Access authorization rule set.

  • ComputerGroupName

  • ComputerName

  • ConfigurationName

  • RuleName

  • UserGroupName

  • UserName

  • Credential (Windows Server 2012 R2 and later)

Remove-PswaAuthorizationRule

Removes a specified authorization rule from Windows PowerShell Web Access.

  • Id

  • RuleName

Get-PswaAuthorizationRule

Returns a set of Windows PowerShell Web Access authorization rules. When it is used without parameters, the cmdlet returns all rules.

  • Id

  • RuleName

Test-PswaAuthorizationRule

Evaluates authorization rules to determine if a specific user, computer, or session configuration access request is authorized. By default, if no parameters are added, the cmdlet evaluates all authorization rules. By adding parameters, administrators can specify an authorization rule or a subset of rules to test.

  • ComputerName

  • ConfigurationName

  • RuleName

  • UserName

  • Credential (Windows Server 2012 R2 and later)

The preceding cmdlets create a set of access rules which are used to authorize a user on the Windows PowerShell Web Access gateway. The rules are different from the access control lists (ACLs) on the destination computer, and provide an additional layer of security for web access. More details about security are described in the following section.

If users cannot pass any of the preceding security layers, they receive a generic “access denied” message in their browser windows. Although security details are logged on the gateway server, end users are not shown information about how many security layers they passed, or at which layer the sign-in or authentication failure occurred.

For more information about configuring authorization rules, see Configuring authorization rules in this topic.

The Windows PowerShell Web Access security model has four layers between an end user of the web-based console, and a target computer. Windows PowerShell Web Access administrators can add security layers through additional configuration in the IIS Manager console. For more information about securing websites in the IIS Manager console, see Configure Web Server Security (IIS 7). For more information about IIS best practices and preventing denial-of-service attacks, see Best Practices for Preventing DoS/Denial of Service Attacks. An administrator can also buy and install additional, retail authentication software.

The following table describes the four layers of security between end users and target computers.

 

Order Layer Description

1

Web Server (IIS) security features, such as client certificate authentication

Windows PowerShell Web Access users must always provide a user name and password to authenticate their accounts on the gateway. However, Windows PowerShell Web Access administrators can also turn optional client certificate authentication on or off (see step 10 of “To use IIS Manager to configure the gateway in an existing website” in Install and Use Windows PowerShell Web Access). The optional client certificate feature requires end users to have a valid client certificate, in addition to their user names and passwords, and is part of Web Server (IIS) configuration. When the client certificate layer is enabled, the Windows PowerShell Web Access sign-in page prompts users to provide valid certificates before their sign-in credentials are evaluated. Client certificate authentication automatically checks for the client certificate.

If a valid certificate is not found, Windows PowerShell Web Access informs users, so they can provide the certificate. If a valid client certificate is found, Windows PowerShell Web Access opens the sign-in page for users to provide their user names and passwords.

This is one example of additional security settings that are offered by Web Server (IIS). For more information about other IIS security features, see Configure Web Server Security (IIS 7).

2

Windows PowerShell Web Access forms-based gateway authentication

The Windows PowerShell Web Access sign-in page requires a set of credentials (user name and password) and offers users the option of providing different credentials for the target computer. If the user does not provide alternate credentials, the primary user name and password that are used to connect to the gateway are also used to connect to the target computer.

The required credentials are authenticated on the Windows PowerShell Web Access gateway. These credentials must be valid user accounts on either the local Windows PowerShell Web Access gateway server, or in Active Directory®.

After a user is authenticated at the gateway, Windows PowerShell Web Access checks authorization rules to verify if the user has access to the requested target computer. After successful authorization, the user’s credentials are passed along to the target computer.

3

Windows PowerShell Web Access authorization rules

After a user is authenticated at the gateway, Windows PowerShell Web Access checks authorization rules to verify if the user has access to the requested target computer. After successful authorization, the user’s credentials are passed along to the target computer.

These rules are evaluated only after a user has been authenticated by the gateway, and before a user can be authenticated on a target computer.

4

Target authentication and authorization rules

The final layer of security for Windows PowerShell Web Access is the target computer’s own security configuration. Users must have the appropriate access rights configured on the target computer, and also in the Windows PowerShell Web Access authorization rules, to run a Windows PowerShell web-based console that affects a target computer through Windows PowerShell Web Access.

This layer offers the same security mechanisms that would evaluate connection attempts if users tried to create a remote Windows PowerShell session to a target computer from within Windows PowerShell by running the Enter-PSSession or New-PSSession cmdlets.

By default, Windows PowerShell Web Access uses the primary user name and password for authentication on both the gateway and the target computer. The web-based sign-in page, in a section titled Optional connection settings, offers users the option of providing different credentials for the target computer, if they are required. If the user does not provide alternate credentials, the primary user name and password that are used to connect to the gateway are also used to connect to the target computer.

Authorization rules can be used to allow users access to a particular session configuration. You can create restricted runspaces or session configurations for Windows PowerShell Web Access, and allow specific users to connect only to specific session configurations when they sign in to Windows PowerShell Web Access. You can use access control lists (ACLs) to determine which users have access to specific endpoints, and further restrict access to the endpoint for a specific set of users by using authorization rules described in this section. For more information about restricted runspaces, see Constrained Runspaces on MSDN.

Administrators likely want the same authorization rule for Windows PowerShell Web Access users that is already defined in their environment for Windows PowerShell remote management. The first procedure in this section describes how to add a secure authorization rule that grants access to one user, signing in to manage one computer, and within a single session configuration. The second procedure describes how to remove an authorization rule that is no longer needed.

If you plan to use custom session configurations to allow specific users to work only within restricted runspaces in Windows PowerShell Web Access, create your custom session configurations before you add authorization rules that refer to them. You cannot use the Windows PowerShell Web Access cmdlets to create custom session configurations. For more information about creating custom session configurations, see about_Session_Configuration_Files on MSDN.

Windows PowerShell Web Access cmdlets support one wildcard character, an asterisk ( * ). Wildcard characters within strings are not supported; use a single asterisk per property (users, computers, or session configurations).

noteNote
For more ways you can use authorization rules to grant access to users and help secure the Windows PowerShell Web Access environment, see Other authorization rule scenario examples in this topic.

  1. Do one of the following to open a Windows PowerShell session with elevated user rights.

    • On the Windows desktop, right-click Windows PowerShell on the taskbar, and then click Run as Administrator.

    • On the Windows Start screen, right-click Windows PowerShell, and then click Run as Administrator.

  2. Optional step for restricting user access by using session configurations: Verify that session configurations that you want to use in your rules already exist. If they have not yet been created, use instructions for creating session configurations in about_Session_Configuration_Files on MSDN.

  3. Type the following, and then press Enter.

    Add-PswaAuthorizationRule –UserName <domain\user | computer\user> -ComputerName <computer_name> -ConfigurationName <session_configuration_name>
    

    This authorization rule allows a specific user access to one computer on the network to which they typically have access, with access to a specific session configuration that is scoped to the user’s typical scripting and cmdlet needs. In the following example, a user named JSmith in the Contoso domain is granted access to manage the computer Contoso_214, and use a session configuration named NewAdminsOnly.

    Add-PswaAuthorizationRule –UserName Contoso\JSmith -ComputerName Contoso_214 -ConfigurationName NewAdminsOnly
    
  4. Verify that the rule has been created by running either the Get-PswaAuthorizationRule cmdlet, or Test-PswaAuthorizationRule -UserName <domain\user | computer\user> -ComputerName <computer_name>. For example, Test-PswaAuthorizationRule –UserName Contoso\JSmith –ComputerName Contoso_214.

  1. If a Windows PowerShell session is not already open, see step 1 of To add a restrictive authorization rule in this section.

  2. Type the following, and then press Enter, where rule ID represents the unique ID number of the rule that you want to remove.

    Remove-PswaAuthorizationRule -ID <rule ID>
    

    Alternatively, if you do not know the ID number, but know the friendly name of the rule you want to remove, you can get the name of the rule, and pipe it to the Remove-PswaAuthorizationRule cmdlet to remove the rule, as shown in the following example: Get-PswaAuthorizationRule -RuleName <rule name> | Remove-PswaAuthorizationRule.

    noteNote
    You are not prompted to confirm whether you want to delete the specified authorization rule; the rule is deleted when you press Enter. Be sure that you want to remove the authorization rule before running the Remove-PswaAuthorizationRule cmdlet.

Every Windows PowerShell session uses a session configuration; if one is not specified for a session, Windows PowerShell uses the default, built-in Windows PowerShell session configuration, called Microsoft.PowerShell. The default session configuration includes all cmdlets that are available on a computer. Administrators can restrict access to all computers by defining a session configuration with a restricted runspace (a limited range of cmdlets and tasks that their end users could perform). A user who is granted access to one computer with either full language access or only the Windows PowerShell remote management cmdlets can connect to other computers that are connected to the first computer. Defining a restricted runspace can prevent users from accessing other computers from their allowed Windows PowerShell runspace, and improves the security of your Windows PowerShell Web Access environment. The session configuration can be distributed (by using Group Policy) to all computers that administrators want to make accessible through Windows PowerShell Web Access. For more information about session configurations, see about_Session_Configurations. The following are some examples of this scenario.

  • An administrator creates an endpoint, called PswaEndpoint, with a restricted runspace. Then, the administrator creates a rule, *,*,PswaEndpoint, and distributes the endpoint to other computers. The rule allows all users to access all computers with the endpoint PswaEndpoint. If this is the only authorization rule defined in the rule set, computers without that endpoint would not be accessible.

  • The administrator created an endpoint with a restricted runspace called PswaEndpoint,and wants to restrict access to specific users. The administrator creates a group of users called Level1Support, and defines the following rule: Level1Support,*,PswaEndpoint. The rule grants any users in the group Level1Support access to all computers with the PswaEndpoint configuration. Similarly, access can be restricted to a specific set of computers.

  • Some administrators provide certain users more access than others. For example, an administrator creates two user groups, Admins and BasicSupport. The administrator also creates an endpoint with a restricted runspace called PswaEndpoint, and defines the following two rules: Admins,*,* and BasicSupport,*,PswaEndpoint. The first rule provides all users in the Admin group access to all computers, and the second rule provides all users in the BasicSupport group access only to those computers with PswaEndpoint.

  • An administrator has set up a private test environment, and wants to allow all authorized network users access to all computers on the network to which they typically have access, with access to all session configurations to which they typically have access. Because this is a private test environment, the administrator creates an authorization rule that is not secure. The administrator runs the cmdlet Add-PswaAuthorizationRule * * *, which uses the wildcard character * to represent all users, all computers, and all configurations. This rule is the equivalent of the following: Add-PswaAuthorizationRule –UserName * -ComputerName * -ConfigurationName *.

    securitySecurity Note
    This rule is not recommended in a secure environment, and bypasses the authorization rule layer of security provided by Windows PowerShell Web Access.

  • An administrator must allow users to connect to target computers in an environment that includes both workgroups and domains, where workgroup computers are occasionally used to connect to target computers in domains, and computers in domains are occasionally used to connect to target computers in workgroups. The administrator has a gateway server, PswaServer, in a workgroup; and target computer srv1.contoso.com is in a domain. User Chris is an authorized local user on both the workgroup gateway server and the target computer. His user name on the workgroup server is chrisLocal; and his user name on the target computer is contoso\chris. To authorize access to srv1.contoso.com for Chris, the administrator adds the following rule.

    Add-PswaAuthorizationRule –userName PswaServer\chrisLocal –computerName srv1.contoso.com –configurationName Microsoft.PowerShell
    
    The preceding rule example authenticates Chris on the gateway server, and then authorizes his access to srv1. On the sign-in page, Chris must provide a second set of credentials in the Optional connection settings area (contoso\chris). The gateway server uses the additional set of credentials to authenticate him on the target computer, srv1.contoso.com.

    In the preceding scenario, Windows PowerShell Web Access establishes a successful connection to the target computer only after the following have been successful, and allowed by at least one authorization rule.

    1. Authentication on the workgroup gateway server by adding a user name in the format server_name\user_name to the authorization rule

    2. Authentication on the target computer by using alternate credentials provided on the sign-in page, in the Optional connection settings area

    noteNote
    If gateway and target computers are in different workgroups or domains, a trust relationship must be established between the two workgroup computers, the two domains, or between the workgroup and the domain. This relationship cannot be configured by using Windows PowerShell Web Access authorization rule cmdlets. Authorization rules do not define a trust relationship between computers; they can only authorize users to connect to specific target computers and session configurations. For more information about how to configure a trust relationship between different domains, see Creating Domain and Forest Trusts. For more information about how to add workgroup computers to a trusted hosts list, see Remote Management with Server Manager.

Authorization rules are stored in an XML file. By default, the path name of the XML file is %windir%\Web\PowershellWebAccess\data\AuthorizationRules.xml.

The path to the authorization rules XML file is stored in the powwa.config file, which is found in %windir%\Web\PowershellWebAccess\data. The administrator has the flexibility to change the reference to the default path in powwa.config to suit preferences or requirements. Allowing the administrator to change the location of the file lets multiple Windows PowerShell Web Access gateways use the same authorization rules, if such a configuration is desired.

By default, Windows PowerShell Web Access limits a user to three sessions at one time. You can edit the web application’s web.config file in IIS Manager to support a different number of sessions per user. The path to the web.config file is $Env:Windir\Web\PowerShellWebAccess\wwwroot\Web.config.

By default, Web Server (IIS) is configured to restart the application pool if any settings are edited. For example, the application pool is restarted if changes are made to the web.config file. Because Windows PowerShell Web Access uses in-memory session states, users signed in to Windows PowerShell Web Access sessions lose their sessions when the application pool is restarted.

If your Windows PowerShell Web Access gateway is running on Windows Server 2012 R2, you can configure default values for the settings that are displayed on the Windows PowerShell Web Access sign-in page. You can configure values in the web.config file that is described in the preceding paragraph. Default values for the sign-in page settings are found in the appSettings section of the web.config file; the following is an example of the appSettings section. Valid values for many of these settings are the same as those for the corresponding parameters of the New-PSSession cmdlet in Windows PowerShell. For example, the defaultApplicationName key, as shown in the following code block, is the value of the $PSSessionApplicationName preference variable on the target computer.

<appSettings>
        <add key="maxSessionsAllowedPerUser" value="3"/>
        <add key="defaultPortNumber" value="5985"/>
        <add key="defaultSSLPortNumber" value="5986"/>
        <add key="defaultApplicationName" value="WSMAN"/>
        <add key="defaultUseSslSelection" value="0"/>
        <add key="defaultAuthenticationType" value="0"/>
        <add key="defaultAllowRedirection" value="0"/>
        <add key="defaultConfigurationName" value="Microsoft.PowerShell"/>
</appSettings>

Windows PowerShell Web Access sessions time out. In Windows PowerShell Web Access running on Windows Server 2012, A time-out message is displayed to signed-in users after 15 minutes of session inactivity. If the user does not respond within five minutes after the time-out message is displayed, the session is ended, and the user is signed out. You can change time-out periods for sessions in the website settings in IIS Manager.

In Windows PowerShell Web Access running on Windows Server 2012 R2, sessions time out, by default, after 20 minutes of inactivity. If users are disconnected from sessions in the web-based console because of network errors or other unplanned shutdowns or failures, and not because they have closed the sessions themselves, the Windows PowerShell Web Access sessions continue to run, connected to target computers, until the time-out period on the client side lapses. The session is disconnected after either the default 20 minutes, or after the time-out period specified by the gateway administrator, whichever is shorter.

If the gateway server is running Windows Server 2012 R2, Windows PowerShell Web Access lets users reconnect to saved sessions at a later time, but when network errors, unplanned shutdowns, or other failures disconnect sessions, users cannot see or reconnect to saved sessions until after the time-out period specified by the gateway administrator has lapsed.

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