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AWS Certificate Manager

1. Introduction​

AWS Certificate Manager is a fully managed service that simplifies the provisioning, management, and deployment of SSL/TLS certificates to secure network communications in the cloud. At its core, ACM addresses one of the most challenging aspects of SSL certificate management—manual certificate renewal and installation. By automating certificate issuance and renewal, ACM alleviates the operational overhead traditionally associated with maintaining secure connections, while integrating seamlessly with many AWS services.

The service supports both public certificates, trusted by browsers and external clients, and private certificates for internal communications. ACM leverages the principles of authenticity, integrity, and privacy by providing certificates that are cryptographically signed by AWS Trust Services CA or issued by a private CA that you manage, ensuring that clients can securely verify the identity of your servers.

2. Core Features & Integrations​

ACM’s functionality is built around key features and deep integration with AWS managed services, ensuring streamlined deployment and security.

2.1. Public vs. Private Certificates​

  • Public Certificates:
    ACM can automatically provision public SSL/TLS certificates that are issued by a trusted certificate authority (CA) maintained by AWS. These certificates are inherently trusted by most modern browsers and client devices, making them ideal for securing internet-facing applications.

  • Private Certificates:
    In addition to public certificates, ACM supports private certificates for internal applications. Using AWS Private CA, organizations can issue internal X.509 certificates that are only trusted within a controlled environment. These certificates allow enterprises to build a robust public key infrastructure (PKI) for internal communications, API security, IoT device authentication, and client VPN access.

2.2. SSL Termination​

SSL termination refers to the process where an intermediary device (typically a load balancer) decrypts incoming SSL/TLS traffic before passing unencrypted requests to backend servers. ACM-provisioned certificates are deployed on services such as Application Load Balancers (ALB), where they facilitate SSL termination. This offloads the computational overhead from backend instances and optimizes overall performance by ensuring that the CPU-intensive encryption and decryption processes are handled at the edge of the network.

2.3. Supported Services​

ACM integrates with a wide range of AWS services to simplify certificate deployment. Key integrations include:

  • Elastic Load Balancing (ELB):
    Certificates can be directly associated with load balancers, which then perform SSL termination.

  • CloudFront Distributions:
    For global content delivery, CloudFront uses ACM certificates (typically provisioned in the US East [N. Virginia] region) to secure HTTPS traffic.

  • API Gateway and Elastic Beanstalk:
    These services can leverage ACM for secure communication endpoints, ensuring that all external requests are encrypted and trusted.

ACM’s integration with these services means that once a certificate is issued, it can be automatically applied to the target AWS resources, thereby simplifying deployment and management across the environment.

3. Certificate Provisioning​

ACM supports multiple certificate provisioning approaches, each suited to different operational scenarios.

3.1. Public Certificates​

Requesting a public certificate from ACM is streamlined through an automated process. When you request a public certificate, ACM validates your ownership or control of the domain via DNS or email. Once validated, ACM issues the certificate, which is automatically maintained and renewed (subject to validation method) and is valid for 13 months. This automated process eliminates the need for manual renewal and reduces the risk of downtime due to expired certificates.

3.2. Private Certificates​

For internal or non-public use cases, private certificates can be issued using AWS Private CA. This capability allows you to create and manage your own certificate authority hierarchy, including root and subordinate CAs, to generate end-entity X.509 certificates. Private certificates are used within enterprise environments to secure internal applications, APIs, and IoT communications. Unlike public certificates, the trust chain for private certificates is established within your organization, requiring that all internal systems explicitly trust your private CA.

3.3. Importing External Certificates​

ACM also allows the importation of externally acquired certificates. If you obtain a certificate from another well-known CA, you can upload it along with its associated private key to ACM. However, externally imported certificates do not benefit from automatic renewal. Instead, they require manual renewal and re-importation once they approach expiration. This option is useful when organizations have existing relationships with external certificate authorities or require custom certificate properties not provided by ACM’s automated issuance process.

4. Validation & Renewal​

The process of validating domain ownership and renewing certificates is critical to maintaining secure communications. ACM supports two primary validation methods along with distinct renewal processes.

4.1. DNS Validation​

DNS validation is the preferred method for public certificates in ACM. During this process, ACM provides a unique CNAME record that must be added to the domain’s DNS configuration. When the DNS record is detected, ACM confirms domain ownership and proceeds to issue the certificate. DNS validation is highly automated, reducing administrative overhead and enabling seamless certificate renewals.

4.2. Email Validation​

Alternatively, ACM can validate domain ownership by sending a confirmation email to the domain’s registered contact address (as found in WHOIS records). The recipient must follow a link to confirm ownership, after which ACM issues the certificate. Although effective, this method requires manual intervention during initial issuance and subsequent renewals, making it less desirable for environments that benefit from full automation.

4.3. Automatic vs. Manual Renewal​

  • Automatic Renewal:
    Certificates provisioned directly by ACM using DNS validation are automatically renewed. ACM monitors the certificate’s validity period and initiates the renewal process—typically starting 45 days prior to expiration—to ensure continuous security without human intervention.

  • Manual Renewal:
    For certificates that are either imported from external sources or validated via email, the renewal process requires manual steps. Administrators must respond to renewal notifications and take the necessary actions (such as updating DNS records or confirming via email) to ensure that the certificate is reissued and remains valid. EventBridge and AWS Config can be configured to generate alerts or trigger automated workflows for monitoring certificate expiration and renewal compliance.

5. Regional Deployment​

ACM is inherently a regional service, and understanding its deployment model is essential for global applications.

5.1. Multi-Region Strategies​

Since ACM certificates are bound to the AWS region in which they are issued, organizations deploying applications in multiple regions must provision certificates in each region. This means that for an application spanning several regions, each regional endpoint (for example, load balancers) requires its own ACM-issued certificate. Adopting a multi-region strategy ensures that every deployment is secured in compliance with regional service boundaries.

5.2. CloudFront Global Exception​

CloudFront is an exception to the regional constraint imposed by ACM. As a global content delivery network, CloudFront requires that certificates used to secure its distributions be provisioned in the US East (N. Virginia) region. This exception allows CloudFront to utilize ACM certificates globally, while other AWS services continue to adhere to regional limitations.

6. Private Certificate Authority (CA)​

Beyond managing public certificates, AWS offers the AWS Private CA service—a dedicated solution for organizations needing a private PKI. With AWS Private CA, you can:

  • Establish a Certificate Hierarchy:
    Create and manage your own root and subordinate CAs, allowing you to issue and revoke certificates within your organization.

  • Issue End-Entity Certificates:
    Deploy certificates to authenticate internal users, applications, APIs, and IoT devices. These end-entity certificates ensure secure TLS communication within your controlled environment.

  • Custom PKI Management:
    Enjoy granular control over certificate properties, such as validity periods, revocation lists, and custom extensions, which are crucial for meeting enterprise compliance and security requirements.

The AWS Private CA service is especially beneficial for scenarios where public trust is not required, but a robust internal security infrastructure is necessary.

7. Monitoring & Best Practices​

To ensure the continued security and operational efficiency of your ACM deployments, it is essential to implement proper monitoring and adhere to best practices.

7.1. Expiration Alerts​

ACM provides proactive alerts regarding certificate expiration. For certificates managed by ACM, renewal notifications are typically issued 45 days prior to expiration. For imported certificates, administrators should set up monitoring—using EventBridge, Lambda functions, or SNS notifications—to receive timely alerts and prevent service disruptions caused by expired certificates.

7.2. Avoiding CNAME/TXT Conflicts​

DNS configuration plays a pivotal role in the successful issuance and renewal of certificates. When using DNS validation, ensure that the provided CNAME record is correctly inserted without modifications by your DNS provider. Conflicts may occur if duplicate records (such as TXT records with the same name) are present. It is crucial to verify and, if necessary, remove conflicting records to maintain proper validation and issuance workflows.

7.3. SSL Termination Cost Optimization​

By offloading SSL termination to load balancers and other AWS-managed services, you can reduce the CPU burden on backend EC2 instances. This not only enhances performance but also lowers operational costs by leveraging ACM’s integration with services like ALB and CloudFront. Ensuring that SSL termination is managed at the edge of your network maximizes efficiency and scalability, particularly in high-traffic environments.

8. Conclusion​

AWS Certificate Manager significantly simplifies the management of SSL/TLS certificates by automating certificate issuance, renewal, and deployment across a wide range of AWS services. Whether you are securing public-facing applications or internal communications, ACM provides a robust framework for managing digital certificates. Its integration with load balancers, CloudFront, API Gateway, and other AWS services, combined with support for both public and private certificates, makes it an essential tool for maintaining secure network communications.