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In this article, we discuss how the AWS Private CA Connector for Active Directory simplifies and speeds up the setup of certificate-based authentication (CBA) for Amazon AppStream 2.0 and Amazon WorkSpaces. We provide an overview of AWS Private Certificate Authority and Active Directory Certificate Services within this framework. We also highlight the advantages of utilizing AWS Private CA instead of Active Directory Certificate Services and outline the configuration steps involved.
For those leveraging a SAML 2.0 Identity Provider (IdP) with AppStream 2.0 or WorkSpaces, CBA can enhance the login experience by removing the prompt for an Active Directory domain password. This facilitates single sign-on from the SAML 2.0 IdP directly to the AppStream 2.0 instance or WorkSpace. To learn more about configuring CBA, check out resources like How to Configure CBA for WorkSpaces and How to Configure CBA for AppStream 2.0.
Overview
The Role of AWS Private CA and Active Directory Certificate Services
CBA in AppStream 2.0 and WorkSpaces relies on a combination of user certificates and virtual smart cards, enabling passwordless authentication to Windows machines within an Active Directory domain. Two essential infrastructure components are necessary for this process.
AWS Private CA issues and manages user certificates, which AppStream 2.0 and WorkSpaces services request automatically during session authentication. Users are subsequently authenticated to Active Directory using a virtual smart card provisioned with these certificates. Depending on your needs, AWS Private CA can function as either a root or subordinate CA in the certificate hierarchy.
- DC/Kerberos certificates are automatically issued and installed on all domain controllers through certificate auto-enrollment with AD CS.
- With AWS Private CA configured as a subordinate CA to the AD CS Root CA, the AWS Private CA certificate is manually published to the AD RootCA and NTAuthCA stores.
- The CA certificate chain is replicated automatically to all domain machines via AD.
- Users authenticate through a SAML 2.0 provider.
- Federated users gain access to AppStream 2.0 or WorkSpaces resources.
- Based on the SAML assertion attributes, AppStream 2.0 or WorkSpaces is issued a user certificate signed by AWS Private CA.
- The AppStream 2.0 or WorkSpaces service publishes the user certificate to the Windows machine.
- The AppStream 2.0 or WorkSpaces agent seamlessly authenticates the user to Active Directory utilizing the user certificate.
AWS Private CA Connector for AD as a Substitute for Active Directory Certificate Services
The Connector for AD allows AWS Private CA to function as an integrated Enterprise CA. It deploys Active Directory Certificate Services, providing the necessary certificate templates and enrollment services for machines within your Active Directory. This strategy significantly reduces the implementation effort, eliminating the need for a dedicated Active Directory Certificate Services infrastructure. Additionally, it enhances security by storing CA private keys in FIPS 140-2 Level 3 validated hardware security modules (HSMs).
- AWS Private CA is integrated with AD through the connector and operates as an Enterprise CA, with its CA certificate automatically published to the AD RootCA and NTAuthCA stores.
- DC/Kerberos certificates are issued and installed on domain controllers via certificate auto-enrollment with AWS Private CA.
- The CA certificate chain is replicated to all domain machines via AD.
- Users authenticate through the SAML provider.
- Federated users are authorized for access to AppStream 2.0 or WorkSpaces resources.
- Based on the SAML assertion attributes, AppStream 2.0 or WorkSpaces is issued a user certificate, signed by AWS Private CA.
- The service then publishes this user certificate to the Windows machine.
- The AppStream 2.0 or WorkSpaces agent authentically connects the user to Active Directory using the user certificate.
Walkthrough
This walkthrough guides you through setting up AWS Private CA, the AWS Private CA Connector for Active Directory, and certificate-based authentication for AppStream 2.0 or WorkSpaces.
Prerequisites
- AWS Console with the necessary IAM permissions for the AWS Services involved.
- A functional AppStream 2.0 or WorkSpaces deployment integrated with a SAML 2.0 identity provider.
Ensure you configure the https://aws.amazon.com/SAML/Attributes/PrincipalTag:UserPrincipalName attribute in your SAML assertion. This attribute is crucial for CBA and must align with the User Principal Name (UPN) in Active Directory. More information can be found in the post Create Assertions for the SAML Authentication Response.
Additionally, include the sts:TagSession permission in the IAM role trust policy used with your SAML 2.0 configuration if not already present; this is a requirement for using certificate-based authentication. For further details, check out Create a SAML 2.0 Federation IAM Role.
- Self-Managed Active Directory
AWS Managed Active Directory is not supported. - AWS Directory Service AD Connector
You may utilize an existing connector configured with WorkSpaces directories or set up a new one for this purpose. Note: The Active Directory service account will need additional permissions, as outlined in “Step 3: Create PCA Connector for AD” below. - Plan and Design Your Certificate Authority Hierarchy
It’s important to plan your CA hierarchy according to your specific needs. The configuration steps in this blog presume a one-level CA hierarchy for simplicity. A single AWS Private CA instance is deployed in short-lived mode to act as the Root CA and to issue certificates. For guidance on deploying in production environments where separate administrative controls and a complete trust chain are necessary, refer to AWS Private CA documentation. Short-lived mode is particularly recommended for use with AppStream 2.0 and WorkSpaces CBA.
Configuration Steps
Step 1: Create a Public Repository to Host the Certificate Revocation List (CRL)
Establish an Amazon Simple Storage Service (Amazon S3) bucket, ensuring that ACLs are disabled and all public access is blocked. Next, create a CloudFront distribution:
- Navigate to the Amazon CloudFront console.
- Create a Distribution.
- For the Origin Domain, select the S3 Bucket created in the previous step.
This approach not only streamlines authentication but also enhances security—a vital consideration in today’s digital landscape where implementing effective measures is paramount. If you’re interested in exploring more about enhancing your business strategy, you can check out this insightful blog post on writing a side hustle business plan.
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