Web Application Proxy: Application is using an external certificate that is about to expire

Article
08/31/2016

Applies To: Windows Server 2012 R2

This topic is intended to address a specific issue identified by a Best Practices Analyzer scan. You should apply the information in this topic only to computers that have had the Web Application Proxy Best Practices Analyzer run against them and are experiencing the issue addressed by this topic. For more information about best practices and scans, see Best Practices Analyzer.

Operating System	Windows Server 2012 R2
Product/Feature	Web Application Proxy
Severity	Warning
Category	Configuration

Issue

Application <application_name> that is published by Web Application Proxy is using a certificate that is about to expire.

You will receive this message for applications whose certificates will expire in under 60 days.

Impact

If an application is using a certificate that has expired, users will not be able to secure their access to the application and sensitive data will not be encrypted. Some browsers might block access to such sites.

Resolution

Issue a new certificate for this address and publish this application again with the new certificate.

When you publish an application through Web Application Proxy, a valid certificate with the private key is required to be stored in the Personal certificates store on each Web Application Proxy server. If the certificate used by an application for authentication expires, users will not be able to secure their access to the application and sensitive data will not be encrypted. Some browsers might block access to such sites. To resolve this issue, you must obtain a new certificate for this application. After obtaining the new certificate, you can either change the certificate using the Set-WebApplicationProxyApplication cmdlet with the ExternalCertificateThumbprint parameter, or remove the application and republish it using the new certificate.

Membership in the local Administrators group, or equivalent, is the minimum required to complete this procedure.

To request a certificate for the published application from an internal certification authority

On the Web Application Proxy server, open an MMC console: On the Start screen, click the Apps arrow. On the Apps screen, type mmc.exe, and then press ENTER. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Yes.
In the Console window, on the File menu, click Add/Remove Snap-in.
On the Add or Remove Snap-ins dialog, double-click Certificates.
On the Certificates snap-in dialog, click Computer account, and then click Next.
On the Select Computer dialog, click Local computer, click Finish, and then click OK.
In the Console window, open Certificates/Personal/Certificates.
Right-click in the details pane, click All Tasks, and then click Request New Certificate.
On the Certificate Enrollment dialog, click Next twice.
On the Request Certificates page, select the certificate template that has been configured for website authentication, and click More information is required to enroll for this certificate.
On the Certificate Properties dialog, on the Subject tab, in Subject name, in the Type list, click Common name, and in the Value box, enter a value for this certificate that covers the application that you are attempting to publish, click Add, click OK, and then click Enroll.
After successfully enrolling for this certificate, click Finish.

To remove a published application

On the Web Application Proxy server, open the Remote Access Management console: On the Start screen, click the Apps arrow. On the Apps screen, type RAMgmtUI.exe, and then press ENTER. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Yes.
In the Remote Access Management console, in the navigation pane, click Web Application Proxy.
In the details pane, select the application identified in the BPA, and then in the Tasks pane, click Remove.
On the Remove Applications dialog box, click Yes.

After removing the application, you can republish it.

To publish an application

In the Remote Access Management console, in the Navigation pane, click Web Application Proxy, and then in the Tasks pane, click Publish.
On the Publish New Application Wizard, on the Welcome page, click Next.
On the Preauthentication page, select the required preauthentication, and then click Next.
If you selected Active Directory Federation Services (AD FS), on the Relying Party page, in the list of relying parties select the relying party for the application that you want to publish, and then click Next.
On the Publishing Settings page, do the following, and then click Next:
- In the Name box, enter a friendly name for the application.
- In the External URL box, enter the external URL for this application; for example, https://apps.contoso.com/.
- In the External certificate list, select a certificate whose subject covers the external URL.
- In the Backend server URL box, enter the URL of the backend server. Note that this value is automatically entered when you enter the external URL and you should change it only if the backend server URL is different; for example, https://apps/.
- In the Backend server SPN box, enter the service principal name for the backend server; for example, HTTP/apps.contoso.com.
On the Confirmation page, review the settings, and then click Publish. You can copy the PowerShell command set up additional published applications.
On the Results page, make sure that the application published successfully, and then click Close.

To change the certificate using PowerShell

Obtain a new certificate for the application as described above.
To obtain the application ID of the required application, use the following PowerShell command to show the ID and externalURL of all applications whose name matches the application name. Locate the application ID in the command output of the relevant application:
```
Get-WebApplicationProxyApplication –Name <application_name> | Format-Table ID, ExternalURL
```

Use the following PowerShell command to change the certificate used for the published application:

Set-WebApplicationProxyApplication –ID <application_ID> -ExternalCertificateThumbprint <New_certificate_thumbprint>

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