Register a client certificate when the client connects to AWS IoT (just-in-time registration) - AWS IoT Core

Register a client certificate when the client connects to AWS IoT (just-in-time registration)

You can configure a CA certificate to enable client certificates it has signed to register with AWS IoT automatically the first time the client connects to AWS IoT.

To register client certificates when a client connects to AWS IoT for the first time, you must enable the CA certificate for automatic registration and configure the first connection by the client to provide the required certificates.

Configure a CA certificate to support automatic registration (console)

To configure a CA certificate to support automatic client certificate registration using the AWS IoT console

  1. Sign in to the AWS Management Console and open the AWS IoT console.

  2. In the left navigation pane, choose Secure, choose CAs.

  3. In the list of certificate authorities, find the one for which you want to enable automatic registration, and open the option menu by using the ellipsis icon.

  4. On the option menu, choose Enable auto-registration.


The auto-registration status is not shown in the list of certificate authorities. To see the auto-registration status of a certificate authority, you must open the Details page of the certificate authority.

Configure a CA certificate to support automatic registration (CLI)

If you have already registered your CA certificate with AWS IoT, use the update-ca-certificate command to set autoRegistrationStatus of the CA certificate to ENABLE.

aws iot update-ca-certificate \ --certificate-idcaCertificateId \ --new-auto-registration-status ENABLE

If you want to enable autoRegistrationStatus when you register the CA certificate, use the register-ca-certificate command.

aws iot register-ca-certificate \ --allow-auto-registration \ --ca-certificate file://root_CA_pem_filename \ --verification-cert file://verification_cert_pem_filename

Use the describe-ca-certificate command to see the status of the CA certificate.

Configure the first connection by a client for automatic registration

When a client attempts to connect to AWS IoT for the first time, it must present a file that contains both your registered CA certificate and the client certificate signed by your CA certificate as part of the TLS handshake. You can combine the two files using a command, such as the following:

cat device_cert_filename ca_certificate_pem_filename > combined_filename

When the client connects to AWS IoT, use the combined_filename file as the certificate file. AWS IoT recognizes the CA certificate as a registered CA certificate, registers the client certificate, and sets its status to PENDING_ACTIVATION. This means that the client certificate was automatically registered and is awaiting activation. The client certificate's state must be ACTIVE before it can be used to connect to AWS IoT.

When AWS IoT automatically registers a certificate or when a client presents a certificate in the PENDING_ACTIVATION status, AWS IoT publishes a message to the following MQTT topic:


Where caCertificateId is the ID of the CA certificate that issued the client certificate.

The message published to this topic has the following structure:

{ "certificateId": "certificateId", "caCertificateId": "caCertificateId", "timestamp": timestamp, "certificateStatus": "PENDING_ACTIVATION", "awsAccountId": "awsAccountId", "certificateRegistrationTimestamp": "certificateRegistrationTimestamp" }

You can create a rule that listens on this topic and performs some actions. We recommend that you create a Lambda rule that verifies the client certificate is not on a certificate revocation list (CRL), activates the certificate, and creates and attaches a policy to the certificate. The policy determines which resources the client can access. For more information about how to create a Lambda rule that listens on the $aws/events/certificates/registered/caCertificateID topic and performs these actions, see Just-in-Time Registration of Client Certificates on AWS IoT.

If any error or exception occurs during the auto-registration of the client certificates, AWS IoT sends events or messages to your logs in CloudWatch Logs. For more information about setting up the logs for your account, see the Amazon CloudWatch documentation.