Securing Your Spring WebFlux REST API with HMAC Authentication

Learn how to use HMAC verification for securing REST APIs with Spring WebFlux and Spring Security in this step-by-step guide.
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Securing Your Spring WebFlux REST API with HMAC Authentication

In a world where security breaches are becoming increasingly common, it's vital to secure your APIs effectively. If you're using Spring Boot with WebFlux and Spring Security, one powerful method of securing your REST API is through HMAC (Hash-based Message Authentication Code) of the request body. This article will guide you through implementing this security feature step-by-step.

The Challenge

Suppose you want to secure a REST API where the client sends a request with a header containing a hashed value of the request body. Your task is to read the header, calculate a hash of the body, and compare it with the hashed value sent in the request.

However, the challenge arises due to the reactive nature of Spring WebFlux: accessing the request body can be tricky since it can only be consumed once. You need to find a way to read the body multiple times without causing an error.

The Solution

To successfully implement HMAC authentication for your REST API, you will need two core components:

A WebFilter to cache the request body, allowing multiple reads.

A ServerAuthenticationConverter that will compute the hash from the body and validate the signature.

Creating the WebFilter

The WebFilter will read the request body and cache it so that it can be read multiple times by the application. Here’s the code example for the HttpRequestBodyCachingFilter:

[[See Video to Reveal this Text or Code Snippet]]

Creating the ServerAuthenticationConverter

Next, create a ServerAuthenticationConverter to handle the logic for verifying the HMAC. Below is the code snippet for the HttpJwsAuthenticationConverter:

[[See Video to Reveal this Text or Code Snippet]]

Wiring Up Your Configuration

Finally, you need to integrate both components into your Spring Security configuration. Here's how to wire everything up:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By implementing both a WebFilter and a ServerAuthenticationConverter, you can secure your Spring WebFlux REST API with HMAC of the request body efficiently. This method not only prevents unauthorized access but also ensures that the data integrity remains intact.

For further improvements, consider adding error handling and logging to monitor authentication requests and responses. With these components effectively wired together, your API should be robust against common security threats.