Securing Microservices: mTLS within Kubernetes

Zero Trust security means we shouldn’t trust network traffic even inside our cluster. Mutual TLS (mTLS) ensures that not only is traffic encrypted, but both the client and server verify each other’s identity.

The Sidecar Approach

Implementing certificate rotation in every microservice is a nightmare. This is where Service Meshes (like Linkerd or Istio) or Dapr shine. They run a sidecar that handles the handshake transparency.

flowchart LR
    subgraph PodA [Service A]
        AppA[App Code] <--> ProxyA[Sidecar Proxy]
    end
    
    subgraph PodB [Service B]
        ProxyB[Sidecar Proxy] <--> AppB[App Code]
    end
    
    ProxyA <-->|mTLS Encrypted| ProxyB
    
    style ProxyA fill:#FFF3E0,stroke:#E65100
    style ProxyB fill:#FFF3E0,stroke:#E65100

With Linkerd, it’s literally one command to enable this across your cluster. No code changes required. The sidecar intercepts the HTTP call, upgrades it to mTLS, and forwards it.