Designing a Secure REST API
A backend security scenario focused on authentication, authorization, validation, error handling and protecting sensitive business operations.
This technical case study explores how a modern REST API can be designed with security built into the backend architecture instead of treating security as an afterthought.
The Problem
The application needed to expose multiple business operations through REST APIs.
Different users required different levels of access to resources and operations.
The backend needed to prevent unauthorized access to sensitive resources.
Client-provided data could not be blindly trusted by the server.
Architecture
Technical Challenges
Designing authentication correctly
Enforcing authorization at the resource level
Protecting object ownership
Validating incoming data
Handling sensitive API operations
Investigation
Solution
Validate authentication before processing protected operations.
Perform authorization checks at the resource and action level.
Verify resource ownership instead of trusting client-provided identifiers.
Validate and normalize incoming API data.
Apply rate limiting to sensitive operations.
Keep security decisions on the server.
Results
Clear separation between authentication and authorization.
Better protection of sensitive backend resources.
More predictable authorization behavior.
Improved API security architecture.
Security controls became part of the backend design.
Lessons Learned
Authentication is not authorization.
The server must never blindly trust the client.
Authorization should be enforced close to the resource being accessed.
Security should be considered during architecture rather than after development.