Enabling mTLS authentication in AD Connector for use with smart cards - Amazon Directory Service
PrerequisitesEnabling smart card authentication
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Enabling mTLS authentication in AD Connector for use with smart cards

You can use certificate-based mutual Transport Layer Security (mTLS) authentication with smart cards to authenticate users into Amazon WorkSpaces through your self-managed Active Directory (AD) and AD Connector. When enabled, users select their smart card at the WorkSpaces login screen and enter a PIN to authenticate, instead of using a username and password. From there, the Windows or Linux virtual desktop uses the smart card to authenticate into AD from the native desktop OS.

Note

Smart card authentication in AD Connector is only available in the following Amazon Web Services Regions, and only with WorkSpaces. Other Amazon applications are not supported at this time.

  • US East (N. Virginia)

  • US West (Oregon)

  • Asia Pacific (Sydney)

  • Asia Pacific (Tokyo)

  • Europe (Ireland)

  • Amazon GovCloud (US-West)

  • Amazon GovCloud (US-East)

You can also deregister and disable the certificates.

Topics

Prerequisites

To enable certificate-based mutual Transport Layer Security (mTLS) authentication using smart cards for the Amazon WorkSpaces client, you need an operational smart card infrastructure integrated with your self-managed Active Directory. For more information on how to set up smart card authentication with Amazon WorkSpaces and Active Directory, see the Amazon WorkSpaces Administration Guide.

Before you enable smart card authentication for WorkSpaces, please review the following prerequisites:

CA certificate requirements

AD Connector requires a certificate authority (CA) certificate, which represents the issuer of your user certificates, for smart card authentication. AD Connector matches CA certificates with the certificates presented by your users with their smart cards. Note the following CA certificate requirements:

  • Before you can register a CA certificate, it must be more than 90 days away from expiration.

  • CA certificates must be in Privacy-Enhanced Mail (PEM) format. If you export CA certificates from inside Active Directory, choose Base64-encoded X.509 (.CER) as the export file format.

  • All root and intermediary CA certificates that chain from an issuing CA to user certificates must be uploaded for smart card authentication to succeed.

  • A maximum of 100 CA certificates can be stored per AD Connector directory

  • AD Connector does not support the RSASSA-PSS signature algorithm for CA certificates.

  • Verify the Certificate Propagation Service is set to Automatic and running.

User certificate requirements

The following are some of the requirements for the user certificate:

  • The user’s smart card certificate has a Subject Alternative Name (SAN) of the user’s userPrincipalName (UPN).

  • The user’s smart card certificate has Enhanced Key Usage as the smart card log-on (1.3.6.1.4.1.311.20.2.2) Client Authentication (1.3.6.1.5.5.7.3.2).

  • The Online Certificate Status Protocol (OCSP) information for the user’s smart card certificate should be Access Method=On-line Certificate Status Protocol (1.3.6.1.5.5.7.48.1) in the Authority Information Access.

For more information on AD Connector and smart card authentication requirements, see Requirements in Amazon WorkSpaces Administration Guide. For help troubleshooting Amazon WorkSpaces issues, like logging into WorkSpaces, resetting password, or connecting to WorkSpaces, see Troubleshoot WorkSpaces client issues in Amazon WorkSpaces User Guide.

Certificate revocation checking process

In order to perform smart card authentication, AD Connector must check the revocation status of user certificates using Online Certificate Status Protocol (OCSP). To perform certificate revocation checking, an OCSP responder URL must be internet-accessible. If using a DNS name, an OCSP responder URL must use a top-level domain found in the Internet Assigned Numbers Authority (IANA) Root Zone Database.

AD Connector certificate revocation checking uses the following process:

  • AD Connector must check the Authority Information Access (AIA) extension in the user certificate for an OCSP responder URL, then AD Connector uses the URL to check for revocation.

  • If AD Connector cannot resolve the URL found in the user certificate AIA extension, or find an OCSP responder URL in the user certificate, then AD Connector uses the optional OCSP URL provided during root CA certificate registration.

    If the URL in the user certificate AIA extension resolves but is unresponsive, then user authentication fails.

  • If the OCSP responder URL provided during root CA certificate registration cannot resolve, is unresponsive, or no OCSP responder URL was provided, user authentication fails.

  • The OCSP server must be compliant with RFC 6960. Additionally, the OCSP server must support requests using the GET method for requests that are less than or equal to 255 bytes in total.

Note

AD Connector requires an HTTP URL for the OCSP responder URL.

Considerations

Before enabling smart card authentication in AD Connector, consider the following items:

  • AD Connector uses certificate-based mutual Transport Layer Security authentication (mutual TLS) to authenticate users to Active Directory using hardware or software-based smart card certificates. Only common access cards (CAC) and personal identity verification (PIV) cards are supported at this time. Other types of hardware or software-based smart cards might work but have not been tested for use with the WorkSpaces Streaming Protocol.

  • Smart card authentication replaces username and password authentication to WorkSpaces.

    If you have other Amazon applications configured on your AD Connector directory with smart card authentication enabled, those applications still present the username and password input screen.

  • Enabling smart card authentication limits the user session length to the maximum lifetime for Kerberos service tickets. You can configure this setting using a Group Policy, and is set to 10 hours by default. For more information on this setting, see Microsoft documentation.

  • The AD Connector service account's supported Kerberos encryption type should match each of the domain controller's supported Kerberos encryption type.

Enabling smart card authentication

To enable smart card authentication for WorkSpaces on your AD Connector, first you need to import your certificate authority (CA) certificates into AD Connector. You can import your CA certificates into AD Connector using Amazon Directory Service console, API or CLI. Use the following steps to import your CA certificates and subsequently enable smart card authentication.

Enabling Kerberos constrained delegation for the AD Connector service account

To use smart card authentication with AD Connector, you must enable Kerberos Constrained Delegation (KCD) for the AD Connector Service account to the LDAP service in the self-managed AD directory.

Kerberos Constrained Delegation is a feature in Windows Server. This feature enables administrators to specify and enforce application trust boundaries by limiting the scope where application services can act on a user’s behalf. For more information, see Kerberos constrained delegation.

Note

Kerberos Constrained Delegation (KCD) requires the username portion of the AD Connector service account to match the sAMAccountName of the same user. The sAMAccountName is restricted to 20 characters. sAMAccountName is a Microsoft Active Directory attribute used as a sign in name for prior versions of Windows clients and servers.

  1. Use the SetSpn command to set a Service Principal Name (SPN) for the AD Connector service account in the self-managed AD. This enables the service account for delegation configuration.

    The SPN can be any service or name combination but not a duplicate of an existing SPN. The -s checks for duplicates.

    setspn -s my/spn service_account

  2. In AD Users and Computers, open the context (right-click) menu and choose the AD Connector service account and choose Properties.

  3. Choose the Delegation tab.

  4. Choose the Trust this user for delegation to specified service only and Use any authentication protocol options.

  5. Choose Add and then Users or Computers to locate the domain controller.

  6. Choose OK to display a list of available services used for delegation.

  7. Choose the ldap service type and choose OK.

  8. Choose OK again to save the configuration.

  9. Repeat this process for other domain controllers in the Active Directory. Alternatively you can automate the process using PowerShell.

Registering the CA certificate in AD Connector

Use either of the following methods to register a CA certificate for your AD Connector directory.

Method 1: To register your CA certificate in AD Connector (Amazon Web Services Management Console)

  1. In the Amazon Directory Service console navigation pane, select Directories.

  2. Choose the directory ID link for your directory.

  3. On the Directory details page, choose the Networking & security tab.

  4. In the Smart card authentication section, choose Actions, and then choose Register certificate.

  5. In the Register a certificate dialog box, select Choose file, and then choose a certificate and choose Open. You can optionally choose to perform revocation checking for this certificate by providing an Online Certificate Status Protocol (OCSP) responder URL. For more information about OCSP, see Certificate revocation checking process.

  6. Choose Register certificate. When you see the certificate status change to Registered, the registration process has completed successfully.

Method 2: To register your CA certificate in AD Connector (Amazon CLI)

  • Run the following command. For the certificate data, point to the location of your CA certificate file. To provide a secondary OCSP responder address, use the optional ClientCertAuthSettings object. 

    aws ds register-certificate --directory-id your_directory_id --certificate-data file://your_file_path --type ClientCertAuth --client-cert-auth-settings OCSPUrl=http://your_OCSP_address

    If successful, the response provides a certificate ID. You can also verify your CA certificate registered successfully by running the following CLI command:

    aws ds list-certificates --directory-id your_directory_id

    If the status value returns Registered, you have successfully registered your certificate.

Enabling smart card authentication for supported Amazon applications and services

Use either of the following methods to register a CA certificate for your AD Connector directory.

Method 1: To enable smart card authentication in AD Connector (Amazon Web Services Management Console)

  1. Navigate to the Smart card authentication section on the Directory details page, and choose Enable. If this option is not available, verify that a valid certificate has been successfully registered, and then try again.

  2. In the Enable smart card authentication dialog box, select Enable.

Method 2: To enable smart card authentication in AD Connector (Amazon CLI)

  • Run the following command.

    aws ds enable-client-authentication --directory-id your_directory_id --type SmartCard

    If successful, AD Connector returns an HTTP 200 response with an empty HTTP body.

For more information on viewing your certificate, deregistering or disabling your certificate, see Managing smart card authentication settings.