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2.  Architecture

2.1 AppVet System

An AppVet system comprises the AppVet web service and its associated tools and clients. In an AppVet system, the app vetting workflow begins when a client submits an app to AppVet. When AppVet receives an app, it registers the app and performs some pre-processing of the app. Preprocessing is used to extract meta-data about an app and possibly provide additional functionality such as ensuring that the app conforms to specific requirements of the hosting organization. After preprocessing an app, AppVet sends the app and related information to one or more tools for testing and evaluation. When a tool completes its analysis, it returns a report and risk assessment to AppVet which, in turn, makes them available to clients. In addition, AppVet generates an overall risk assessment based on risk assessments from all tools. The AppVet system architecture is shown in Figure 2-1.


Figure 2-1. AppVet System Architecture. (Enlarge)

2.2 Clients

An AppVet system comprises clients that submit apps to the system and consume reports and risk assessments. Clients include users (such as developers and analysts) and applications (such as app stores and continuous integration environments). Using a web browser, users access AppVet via the AppVet App Management Interface (AMI) shown in Figure 2-2.


Figure 2-2. AppVet App Management Interface. (Enlarge)

The AMI provides support for uploading apps, accessing reports and assessing risk. Client applications, on the other hand, access AppVet through the AppVet API.

2.3 Tools

An AppVet system comprises tools that analyze apps for security vulnerabilities. A tool may be provided by a third-party vendor, tool developer, or user that leverages an existing tool. In an AppVet system, tools must be available as online services called tool services. To facilitate integration of a tool service with AppVet, AppVet requires a service to implement a simple REST API for submitting apps to, and receiving reports and risk assessments from, the service. AppVet defines three types of tool services: synchronous, asynchronous, and push tool services.

2.3.1 Synchronous Tool Services

A synchronous tool service is a service that accepts an app from AppVet via an HTTP Request and responds with a report and risk assessment via the corresponding HTTP Response. Because clients will block waiting for a response from a synchronous tool service, such services are aimed at analyses that can be performed relatively quickly. Figure 2-3 shows the AppVet synchronous tool service protocol.


Figure 2-3. AppVet Synchronous Tool Service. (Enlarge)

For more information on synchronous tool services, see the Synchronous Service API. For tool services that take an extended amount of time to analyze an app, an asynchronous tool service may be used.

2.3.2 Asynchronous Tool Services

An asynchronous tool service is a service that accepts an app from AppVet via an HTTP Request and immediately responds with an HTTP 202 Accepted indicating that the app was accepted for processing. After processing the app, the service will then send a report and risk assessment via an HTTP Request to AppVet. Figure 2-4 shows the AppVet asynchronous tool service protocol.


Figure 2-4. AppVet Asynchronous Tool Service. (Enlarge)

For more information on asynchronous services, see the Asynchronous Service API.

2.3.3 Push Tool Services

A push tool service is a service that sends a report and risk assessment to AppVet without first receiving a corresponding request from AppVet. Such cases occur, for example, if the service analyzes an app on behalf of another tool service. After the tool service analyzes the app, it sends the report and risk assessment to AppVet as shown in Figure 2-5. Note that both asynchronous and push tool services serve as clients to AppVet when submitting reports.


Figure 2-5. AppVet Push Tool Service. (Enlarge)

For more information on push tool services, see the Asynchronous and Push Reports API.