Welcome back! Today, I continue with part 2 of my series on building custom applications on SAS Viya. The goal of this series is to discuss securely integrating custom-written applications into your SAS Viya platform.
In the first installment of this series, I outlined my experiences on a recent project. In that example, our team worked with a pre-owned auto mall to create a custom application for their buyers to use at auction, facilitating data-driven decisions and maximizing potential profits. Buyers use the app's UI to select/enter the characteristics of the specific car on which they'd like to bid. Those details are then sent via an HTTP REST call to a specific API endpoint in the customer's SAS Viya environment which exposes a packaged version of a detailed decision flow. Business rules and analytic models evaluate the car details as part of that flow. The endpoint returns a maximum bid recommendation and other helpful information via the custom applications's UI.
If you haven't already, I encourage you to read part 1 for more details.
If the concept of exposing endpoints to custom applications elicits some alarming thoughts for you, fear not. The goal of this post is to introduce the security-related considerations when integrating custom applications into your SAS Viya environment. In fact, that is the topic of the next two sections. Today we'll take a look at the security underpinnings of SAS Viya so we can start to flesh out how that integration works. In part 3, we'll dive into more specific decision points. To round things out, the series finishes with some examples of the concepts discussed in parts 1-3.
Looking a little deeper
So how does SAS Viya know it can trust your custom app? How does it know your app should have the authority to call specific API endpoints in your SAS Viya environment and what HTTP methods it should allow? Moreover, who should be able to make those REST calls, the app itself or only individual logged-in users of that app? To answer these questions, we need to understand the foundation of the security frameworks in SAS Viya.
Security in SAS Viya is built around OAuth 2.0 (authorization) and OpenID Connect (authentication), both of which are industry-standard frameworks. The details of how they work, separately and together, are out of the scope of this post. We will, however, delve into a few key things to be aware of within their implementation context for SAS Viya.
First, SAS Logon Manager is the centerpiece. When a client (application) requests access to endpoints and resources, they must first communicate with SAS Logon Manager which returns a scoped access token if it was a valid request. This is true both within SAS Viya (like when internal services hosting APIs communicate with each other) and for external applications like we’re talking about here. The client/application subsequently hands that token in with their request to the desired endpoint.
The long and short of it is that we don’t want users of our custom applications to see or manipulate anything they shouldn’t, so these tokens need to be scoped. The authorization systems in SAS Viya need to be able to understand what the bearer of that specific token should be able to do. For a detailed overview of how SAS Viya services leverage OAuth and OpenID Connect tokens for authentication, I'd recommend reading the SAS Global Forum paper OpenID Connect Opens the Door to SAS Viya APIs by SAS' Mike Roda.
Later in this series, we'll see examples of obtaining a scoped token and then using it to make REST calls to SAS Viya API endpoints, like the auto mall's custom app does to return recommendations for its users. For now, suffice it to say the scope of the token is the critical component to answering our questions regarding how SAS Viya returns specific responses to our custom application.
The glue that binds the two
We've established that native SAS Viya applications and services register themselves as clients to SAS Logon Manager. When a client requests access to an endpoint and/or resource, they must first communicate with SAS Logon Manager which returns a scoped access token if it was a valid request. If the request was unauthorized, it receives a
403 unauthorized (sometimes 401) response. Your SAS Viya environment's administrator has complete control over the rules that determine the authorization decision. We can register additional custom applications, like the auto mall's auction bidding app, to SAS Logon Manager so they too can request scoped tokens. This provides our custom applications with fine-grained access to endpoints and content within SAS Viya. But we’ve already hit a fork in the road. We need to understand the purpose of the application we’re looking to build, so we can decide if the access should be user-scoped or general-scoped.
In the pre-owned auto mall's custom application, a decision and modeling flow is exposed by way of a SAS Micro Analytics Score (MAS) module at a specific HTTP REST API endpoint. All the users of the application have the same level of access to the same endpoint by design; there was no need for differentiated access levels. This is considered an instance of general-scoped access. Abiding by a least-privilege approach, the app should only access certain data and endpoints in SAS Viya, that is, only what it needs to rather than having free reign. In this case, the appropriate level of access can be granted to the registered client (custom application) itself. The result is an access token from SAS Logon Manager scoped within the context of the application.
In other applications you might find it necessary to make more sensitive, or user-specific resources available. In this instance, you'll want to make all authorization decisions within the context of the individual logged-in user. For these situations, it is more prudent to redirect the user directly to SAS Logon Manager to log in and then redirect them back to your application. This results in SAS Logon Manager returning an access token scoped within the context of the logged-in user.
Once you've decided which of these two scenarios most closely fits your custom application's needs, the next step is to decide on a flow (or grant) to provide the associated type of access token, general- or user-scoped. Here “flow” is a term used to describe the process for accessing a protected resource within the OAuth framework and that's what I'll cover in the next post in this series.