Cis AWS Foundations 2.17

Ensure that all expired SSL/TLS certificates stored in AWS IAM are removed

Description

To enable HTTPS connections to your website or application in AWS, you need an SSL/TLS server certificate. You should use AWS Certificate Manager (ACM) to store and deploy server certificates, as storing certificates in IAM is no longer recommended. Use IAM only when you must support HTTPS connections in a region or service that is not supported by ACM. IAM securely encrypts your private keys and stores the encrypted version in IAM SSL certificate storage. IAM supports deploying server certificates in all regions, but you must obtain your certificate from an external provider for use with AWS. You cannot upload an ACM certificate to IAM. Additionally, you cannot manage your certificates from the IAM Console.

Rationale

Removing expired SSL/TLS certificates eliminates the risk that an invalid certificate will be deployed accidentally to a resource such as AWS Elastic Load Balancer (ELB), which can damage the credibility of the application or website behind the ELB. As a best practice, it is recommended to delete expired certificates and migrate certificate management to AWS Certificate Manager (ACM) where supported.

Impact

Deleting certificates may impact applications if expired certificates are still in use by services such as Elastic Load Balancing or CloudFront. Ensure services are updated to use valid certificates before removal. Migrating certificates from IAM to ACM may require updates to associated resources.

Audit Procedure

Using AWS Console

Getting certificate expiration information via the AWS Management Console is not currently supported for IAM-stored certificates. To request information about SSL/TLS certificates stored in IAM, use the Command Line Interface (CLI).

Using AWS CLI

1. Run the following command to list all IAM-stored server certificates:

aws iam list-server-certificates

2. The command output returns an array containing all SSL/TLS certificates and their metadata:

{
  "ServerCertificateMetadataList": [
    {
      "ServerCertificateId": "EHDGFRW7EJFYTE88D",
      "ServerCertificateName": "MyServerCertificate",
      "Expiration": "2018-07-10T23:59:59Z",
      "Path": "/",
      "Arn": "arn:aws:iam::012345678910:server-certificate/MySSLCertificate",
      "UploadDate": "2018-06-10T11:56:08Z"
    }
  ]
}

3. Review the Expiration value for each certificate and determine if any certificates are expired
4. If expired certificates are identified, they should be removed
5. If the command returns:

{ "ServerCertificateMetadataList": [] }

This indicates that no certificates are currently stored in IAM

Expected Result

No expired SSL/TLS certificates should be stored in AWS IAM. The ServerCertificateMetadataList should either be empty or contain only certificates with Expiration dates in the future.

Remediation

Using AWS Console

Removing expired certificates via the AWS Management Console is not currently supported. Use the CLI to delete IAM-stored certificates.

Using AWS CLI

1. Run the following command to delete an expired certificate:

aws iam delete-server-certificate --server-certificate-name <CERTIFICATE_NAME>

2. A successful command returns no output

Default Value

By default, expired SSL/TLS certificates stored in AWS IAM are not automatically deleted. Certificates remain in IAM until manually removed. ACM-managed certificates are automatically renewed when possible.

References

1. https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_server-certs.html
2. https://awscli.amazonaws.com/v2/documentation/api/latest/reference/iam/delete-server-certificate.html

CIS Controls

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Level 1 | Automated