Extending Key Validation

In WSO2 API Manager versions prior to 1.9.0, the components were tightly coupled with the Key Manager and token validation was done by directly accessing the databases. However, from WSO2 API Manager 1.9.0 onwards, you can plug different OAuth2 providers to the key validation. When you call an API providing an access token, the execution flows through the handlers specified in the API. Among them, the API authentication handler extracts the token from the header and calls APIKeyValidationService to get the token validated. Upon validating the token, the API Gateway receives APIKeyValidationInforDTO as the response, using which the rest of the operations are performed.

Before decoupling was done, the entire key validation process was executed inside a single method named validateKey(), which performed all the operations by running a single query. After decoupling, that single query was broken down into smaller parts by introducing KeyValidationHandler which runs inside the validateKey() operation, providing a way to extend each step.

The KeyValidationHandler has four main operations that are executed in the following order:

validateToken - Validates the token. The existing implementation should work for most cases.
validateSubscription - Skips/changes the domain validation.
validateScopes - Relaxes/reduces scope restrictions.
GenerateConsumerToken - Creates different types of tokens.

The default implementation of the KeyValidationService was written in a way where you are able to complete the entire key validation flow only by extending the getTokenMetaData() method in KeyManagerInterface.

However, there are situations where you need to customize the default key validation flow according to different requirements. In such situations, API Manager provides the facility to extend the KeyValidationHandler and its methods.

A few examples are listed below.

Requirement	Extension
Domain validation does not add any value and trivial steps such as these need to be skipped	When creating a key via the API Store, the subscriber can specify which domains are allowed to make calls using a token granted against a particular consumer key. If this validation does not add any value, these trivial steps can be ignored and skipped by extending `KeyValidationHandler`. For another example scenario, see Skipping Role Validation for Scopes.
Need to avoid going into detail when validating scopes	Consider a situation where a scope is assigned to a resource and you only need to verify if the token used for access has at least one or more scopes defined for that API without going into much detail. This requirement can be achieved by extending the `validateScope()` method.
Need to send a different type of token instead of JWT to pass details of API invocation to the backend	A JSON Web Token (JWT) is used to pass details of an API invocation to the backend. If a different type of token is required, the `generateConsumerToken()` method can be extended to achieve that.