Enabling Client Certificate Authentication for an Application Inside Default Web Site

Enabling Client Certificate Authentication for an Application Inside Default Web Site

In this blog, we will explore how to enable client certificate authentication for a specific application hosted inside the Web Site in IIS, while keeping client certificate authentication disabled at the Web Site level. This configuration is useful when you want to secure only a particular application with client certificates, without affecting the entire site.

Understanding the Scenario

Imagine you have a Web Site in IIS that hosts multiple applications. You want to enable client certificate authentication for one specific application, but not for the entire Web Site. This setup ensures that only the designated application requires client certificates for access, while the rest of the site remains accessible without this additional layer of security.

Step-by-Step Configuration

1. Install IIS Client Certificate Mapping Authentication:
• Open Server Manager.
• Click on Manage and then Add Roles and Features.
• In the Add Roles and Features Wizard, click Next until you reach the Server Roles page.
• Expand Web Server (IIS), then Web Server, then Security.
• Select IIS Client Certificate Mapping Authentication and click Next.
• Complete the wizard and click Install
2. Configure SSL Settings at the Application Level:
• Launch IIS Manager and navigate to your Default Web Site.
• Select the specific application for which you want to enable client certificate authentication.
• In the Features View, double-click on SSL Settings.
• Check Require SSL and Require under Client Certificates
3. Disable Client Certificate Authentication at the Web Site Level:
• In IIS Manager, select the Default Web Site.
• Go to SSL Settings.
• Ensure that Require SSL and Client Certificates are not checked
4. Configure Client Certificate Mapping Authentication:
• Select the specific application in IIS Manager.
• In the Features View, select Configuration Editor under the Management section.
• Navigate to system.webServer/security/authentication/iisClientCertificateMappingAuthentication.
• Set the enabled field to true.
• Set the oneToOneCertificateMappingsEnabled property to true.
• Click on Edit Items under the oneToOneMappings property.
• Add a new mapping by providing the BLOB of the client certificate

Common Mistakes and Solutions

1. Configuring at the Sub-Application Level:
• A common mistake is configuring client certificate authentication at the sub-application level. This approach does not work as expected and should be avoided. Instead, configure it at the server and site level to ensure proper authentication
2. Fallback Mechanism Issue:
• Ensure that all other authentication methods are disabled for the application that requires client certificate authentication. This prevents fallback mechanisms from allowing access without the correct certificate.

Conclusion

By following these steps, you can successfully enable client certificate authentication for a specific application within the Default Web Site in IIS. This configuration ensures that only the designated application requires client certificates for access, while the rest of the site remains accessible without this additional layer of security. If you encounter any issues or need further assistance, feel free to reach out.