Securing .NET Microservices with Entra ID on AWS

This article explains how to secure .NET microservices running on AWS using Microsoft Entra ID and OAuth 2.0 client credentials flow for service-to-service authentication.

• Implement enterprise-grade service-to-service authentication using OAuth 2.0 client credentials
• Register each microservice as an application in Microsoft Entra ID with unique credentials
• Services obtain access tokens from Entra ID before calling other services
• Token caching improves performance by reusing valid tokens until near expiration
• Service B validates incoming tokens with Entra ID before processing requests
• Use [Authorize] attribute to enforce token validation on protected endpoints
• Store client IDs and secrets in AWS Secrets Manager for secure credential management
• Configure API permissions in Entra ID to grant services access to specific APIs

This approach provides secure, passwordless authentication between microservices with clear security boundaries and audit trails, deployable on AWS container services like ECS and EKS.