The Challenges of OAuth Client Broker Tooling
In terms of OAuth enterprise tooling, a lot of focus is given to OAuth-enabling APIs exposed by the enterprise itself. Naturally, the demand for this reflects today’s reality where the enterprise is increasingly playing the role of an api provider. However, many enterprise integration use cases involving cloud-based services puts the enterprise in the role of API consumer, rather than provider. And as the number of enterprise applications consuming these external APIs grows, and the number of such external APIs themselves grows, point-to-point OAuth handshakes become problematic.
Another challenge relating to consuming these external APIs is that OAuth handshakes are geared towards a client application driven by a user. The protocol involves a redirection of that user to the API provider in order to authenticate and express authorization. Many enterprise integration (EI) applications do not function in this way. Instead their behavior follows a machine-to-machine transaction type; they operate at runtime without being driven by a user. Wouldn’t it be great if these EI apps could benefit from the OAuth capabilities of the APIs and still operate in headless mode? The so-called ‘two-legged’ OAuth pattern provides a work around for this challenge but requires the client app to hold resource owner credentials, which is problematic, especially when replicated across every client app.
To illustrate how an enterprise API management solution can help manage this challenge, I demonstrate an OAuth tooling geared towards brokering a client-side OAuth session with the Salesforce API using the Layer 7 Gateway. By proxying the Salesforce API at the perimeter using the Layer 7 Gateway, my EI apps do not have to worry about the API provider OAuth handshake. Instead, these EI apps can be authenticated and authorized locally using the Enterprise identity solution of choice and the Layer 7 Gateway manages the OAuth session on behalf of these applications. The benefits of this outbound API proxy are numerous. First, the OAuth handshake is completely abstracted out of the EI apps. In addition, the enterprise now has an easy way to manage control of which applications and enterprise identities can consume the external API, control of the rates of consumption and monitor usage over time. The API can itself be abstracted and the proxy can transform API calls at runtime to protect the consuming apps from version changes at the hosted API side.
To set this up on the Layer 7 Gateway, you first need to register a remote access to your Salesforce instance. Log into your Salesforce instance and navigate to Setup -> App Setup -> Develop -> Remote Access. From there, you define your remote access application. The callback URL must match the URL used by the Layer 7 Gateway administrator at setup time in the Layer 7 Gateway. Make sure you note the Consumer Key and Consumer Secret as they will be used during the OAuth handshake setup; these values will be used by your Layer 7 OAuth broker setup policy.
Using the Layer 7 Policy Manager, you publish your broker setup policies to manage the OAuth handshake between the Gateway and your Salesforce instance. Note that the OAuth callback handling must listen at a URL matching the URL defined in Salesforce. These policies use the consumer key and consumer secret associated with the registered remote access in your Salesforce instance. The secret should be stored in the Gateway’s secure password store for added security. Use templates from Layer 7 to simplify the process of setting up these policies.
Once these two policies are in place, you are ready to initiate the OAuth handshake between the Layer 7 Gateway and the Salesforce instance. Using your favorite browser, navigate to the entry point defined in the admin policy above. Click the ‘Reset Handshake’ button. This will redirect you to your Salesforce instance. If you do not have a session in place on this browser, you will be asked to authenticate to the instance, then you are asked to authorize the client app (in this case, your Layer 7 Gateway). Finally, you are redirected back to the Layer 7 Gateway admin policy which now shows the current OAuth handshake in place. The admin policy stores the OAuth access token so that it can be used by the api proxy at runtime.
Your Layer 7 Gateway is now ready to act as an OAuth broker for your EI apps consuming the Salesforce API. You can publish a simple policy to act as this proxy. This policy should authenticate and authorize the EI app and inject the stored OAuth access token on the way out. Note that this policy can be enhanced to perform additional tasks such as transformation, rate limiting, caching, etc.
Although this use case focuses on the Salesforce API, it is generally applicable to any external API you consume. You can maintain an OAuth session for each API you want to proxy in this Gateway as well as perform identity mapping for other external access control mechanism, for example AWS HMAC signatures.
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