Three Considerations for Implementing Mutual TLS with AWS App Mesh

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Mutual Transport Layer Security (mTLS) expands on traditional TLS by requiring both the client and server to authenticate each other through X.509 digital certificates before establishing communication. In this setup, clients present their certificates to the server, which must validate them, thereby granting access similarly to how servers operate in standard TLS interactions. This dual validation process is essential in scenarios where client authenticity is paramount, such as in zero trust networks or highly regulated environments. Common applications include communication between IoT devices and central servers, like AWS IoT Core, or interactions among microservices.

When planning for Mutual TLS, several critical design choices must be made upfront. These decisions encompass the management of client certificates, their validity duration, and the secure storage of sensitive certificate data. This blog focuses on the microservices context within container platforms like Amazon Elastic Container Service (ECS) or Amazon Elastic Kubernetes Service (EKS), exploring key design considerations while leveraging AWS App Mesh for workload security and authentication.

Understanding AWS App Mesh

In container environments, mutual authentication typically involves a network proxy operating within a sidecar container, standardizing processes and alleviating certificate management burdens from development teams. However, maintaining numerous network proxy configurations and certificates can become burdensome operationally. This is where service meshes, like AWS App Mesh, come into play, simplifying the management of network proxies across containerized applications.

AWS App Mesh offers application-level networking, facilitating communication among services on various AWS compute infrastructures. To establish an mTLS-enabled service mesh with AWS App Mesh, it’s essential to grasp its core concepts. The first step is creating a Mesh, which serves as a logical boundary for service network traffic. Subsequent components include virtual gateways, virtual services, virtual routers, routes, and virtual nodes. For further details on AWS App Mesh concepts, refer to the Getting Started Guide in the AWS App Mesh documentation.

The diagram below illustrates how AWS App Mesh components can route external traffic to container workloads:

• Virtual Gateway: Enables communication between external resources and those within the mesh.
• Virtual Service: Represents an abstraction of a real service, which is provided directly or indirectly via a virtual node or router.
• Virtual Node: Acts as a logical reference to a specific task group, such as an ECS service or Kubernetes deployment. It specifies the expected inbound traffic as a listener.

With AWS App Mesh, mutual TLS authentication can be enabled for all supported protocols, including TCP, HTTP/1.1, HTTP/2, and gRPC. Mesh endpoints like VirtualNode and VirtualGateway are where the certificates for session negotiation and trusted authorities for client certificate validation are specified. So, how should you approach designing an mTLS-enabled App Mesh?

Key Design Decisions for mTLS in AWS App Mesh

Before deploying mutual TLS, it’s crucial to establish three key aspects:

1. Certificate Generation: Define a centralized certificate authority (CA) for your organization, which can be your own management system or a service like AWS Certificate Manager (ACM) Private CA. A couple of factors often overlooked are the certificates’ expiration duration—internal certificates for service-to-service communication generally have shorter lifespans than external ones. Additionally, ensure that access to certificates is restricted to authorized parties.
2. Certificate Delivery and Management: Understand how your certificate management system will deliver certificates to the network proxy containers, and establish processes for certificate rotation and revocation. Depending on your chosen system, you may need to manually manage certificate lifecycles, which can add significant operational overhead, so thorough planning is essential.
3. Service Onboarding: One of the most complex aspects of implementing mutual TLS is ensuring that enabling it doesn’t disrupt service functionality. Identifying all internal and external clients can be challenging, so it’s advisable to initially run network proxies in permissive mode. This allows services to communicate with or without client certificates during the transition. With proper monitoring and policies, you can verify whether all services within the mesh are mTLS-enabled and if clients comply with mutual TLS requirements.

For a more detailed exploration of these considerations in the context of Amazon ECS, including certificate sourcing and lifecycle management, check out this authoritative resource on the topic. Additionally, if you’re looking for excellent resources on related topics, this job opportunity could be beneficial.

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