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Thursday, May 8, 2014

ApiFrame is a simple .NET library that implements the core components required for ASP.NET WEB API development. It's a C# class library with logical separation of Server (Provider), Client (Consumer) and the supporting Framework (An Infrastructure). The Server components provide an interface to implement security (Authentication & Authorization), exception handling and versioning of Web API methods. The security mechanism implemented in this library is HMAC (Hash Message Authentication Code) authentication. One example of HMAC usage is Amazon web service (AWS) and the authentication process in this library uses a HMAC-SHA signature which is the same approach as AWS. The Client part provides a Gateway component that can be referenced by the .NET clients to consume the WEB API.
This article will serve as a simple documentation for ApiFrame that focus on providing a basic description about the class components within the library. The diagram below shows the outline of component architecture.

HMAC authentication provides a simple way to authenticate a HTTP request using a secret key that is known to client and server. Both client and server have access to secret key. Generally, this secret key is a Unique Id which is created at the time of registration and stored in the database. Using the secret key and a message based on request content client generates a signature (MAC) using HMAC algorithm and this signature is attached to the authorization header of HTTP request. When the server receives the request, it extracts the hashed signature (MAC) from the request header and calculates its own version of signature to verify if the received signature matches the calculated signature. If the two signature matches, then the system concludes that the request is valid and should be served. If the two signatures don’t match, then the request is dropped and the system responds with an error message.

The Framework provides token models, configuration class, constant values, helpers, extensions to support the implementation of server and client components. Also, it offers an Interface to integrate with the other applications through dependency injection.

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