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API Gateways: Developer Tools

By Adrian Lane

Our previous post discussed the first step in the development process: getting access to the API gateway through access provisioning. Now that you have access it’s time to discuss how the gateway supports your code development and deployment processes. An API gateway must accomplish two primary functions: help developers build, test, and deploy applications; and help companies control use of their API. They are part development environment and part operational security tool.

API Catalog

The APIs catalog is basically a menu of APIs, services, and support services that provide developers front-end integration to access back-office applications, external APIs (for mashups), data and related services, along with all the supporting tools to build and deploy applications. Catalogs typically include APIs, documentation, coding help, build tools, configuration requirements, testing tools, guidance, and sample code for each supported function. They offer other relevant details such as network controls, access controls, integration options, orchestration, brokering and messaging options – all bundled into a management interface for selecting and configuring the services you want. Developer time is expensive so anything that streamlines this process is a win. Security controls such as identity protocols are notoriously difficult to fully grasp and implement. If your security architects want developers to “do it right”, this is the place to invest time to show them how.

Traditionally security tools are bolted onto – or in front of – applications, generating howls of displeasure from developers who don’t want the added complexity nor performance impact. With third-party APIs things are different, as security is part of the core value. API gateways offer features than enable network, interface, and data security as part of the core feature set. For example it is faster and easier to enable built-in SAML or OAuth identity services than to build them from scratch – or worse to build a password management system. Even better, the features are available at design time, before you assemble the application, so they can be bundled into the development process.

Reference implementations are extremely helpful. For example, consider OAuth: if you look at 10 different companies’ OAuth implementations you will probably find a dozen different implementations. Don’t assume developers will just figure it all out – connect the dots. To have a chance at a secure deployment developers need concrete guidance for security services – especially for things as abstract as identity protocols. Reference implementations show end-to-end examples of the identity protocol in practice. For a developer trying to “do it right” this is like finding diamonds in the backyard. The reference implementation is even more effective if it is backed up by testing tools that can verify developer implementations.

Access management is a principal feature of API gateways. The gateway helps you enforce access controls, building in authentication and authorization services into the API set. Gateways typically rely on token-based security services, and support one or more token services such as SAML and OAuth. All API gateways offer authentication support, and most integrate with other identity sources to support federation. Gateways provide basic role-based authorization support, sometimes with fine-grained authorization to constrain data access by user identity or endpoint device.

Beyond identity protocols, some gateways offer services to defend against attacks such as replay attacks and other forms of session hijacking. API gateways provide dynamic filtering of requests, allowing policy-based routing and response to API calls. Developers get tools to parse incoming calls, filter or transform messages, and then route to appropriate services. This facilitates modification of application function, debugging of application functions, and application of different security or compliance controls in response to user requests. Filters also provide a mechanism for sending requests to different locations, workflow modification, or even sending requests to different applications. This flexibility is a powerful security capability, particularly for analysis of and protection against suspect clients – access to services and data can be dynamically adjusted.

API gateway providers offer a range of pre-deployment tools to validate applications prior to deployment. Sandbox testing and runtime simulators both validate correct API usage, and can also verify that the application developer properly handles input variables and simulated attacks. Some test harnesses are provided with gateways and others are custom implementations by API service owners. Pre-deployment validation is good a way to ensure all third-party developers meet a minimum security standard, and no single user becomes the proverbial weak link. If possible, tests should be executed as part of the normal integration process, (i.e., Jenkins) so implementation quality can be continually tested.

Deployment Support

The API catalog provides options for how to build security into your application, but API gateways also offer deployment support. When you are push APIs that connect the world to internal systems you need to account for a myriad of different threats at multiple network, protocol, application, and data layers. Denial of service, parser attacks, code injection, replay attacks, HTTP protocol abuse, network sniffing, and denial of service attacks are all things to consider.

API gateways can optionally provide privacy and security for network sessions through SSL. Most also offer network firewall capabilities such as IP whitelisting, blacklisting, and signature-based detection. While network security is a must have for many, it’s not really their core value to security. The key security features are overall security of the API and message-level filtering. API gateways provide capabilities to detect code injection, cross-site scripting, and various encoding attacks; most also offer off-the-shelf filters for input validation and sanitization.

Logging, Monitoring, and Reporting

As an application platform API gateways capture activity and generate audit logs. Sitting between developer applications and the API, they are perfectly positioned to capture API usage – useful for throttling, billing, and metering API access, as well as security. Log files are essential for security, operations, and compliance, so these teams all rely upon gateway audit trails. Most API gateways provide flexible configuration of which audit events are collected, record format, and record destination.

Audit capabilities are mostly designed for the gateway owner rather than developers. But the audit trail captures sessions of all users across all third-party code to provide an overview of all activity. Logs generally go into a supplementary SIEM or log management tool for event storage and parsing, using syslog or an equivalent format. API gateways provide extensibility to format, tag, and enrich events – with information from the network and API layers, as well as context from the application session – to help SIEM or log management leverage them.

Most API gateways provide rudimentary extensibility to alert on both usage patterns and suspicious behavior. This type of event monitoring can be used to provide basic security and intrusion detection capabilities out-of-the-box. As described above, message filtering is a more advanced and effective way to detect malicious events, but filtering requires careful development and selection of which capabilities to deploy.

Client Integration

“In my beginning is my end.” – T.S. Eliot

The API is only as useful as the clients it supports. API development in most cases is the art of the possible: supporting all your different kinds of clients. Your API could be called by iOS & Android apps, web service clients, .NET and Windows desktop applications, other APIs, and so on. The fully deployed API gateway is the starting point for client integration. Client integration becomes a game of adapters, wrappers, and domain or technology specific ways to use your API … in iOS, from mashup APIs, and so on.

As always, developers want simple tools to get things working across a broad range of environments. The security challenge is to offer domain-specific guidance suited to the integration context. At a basic level, can you even support the same protocols across all environments? The answer is often ‘no’. If not, what does “safe API consumption” look like for each client environment? From there, what kinds of data can be accessed, and where should it reside? How are keys managed and stored? How will you implement SSL and verify the gateway’s hostname from each supported client? Unpacking and answering each of these questions and more shows developers how to use and consume the API and data safely.

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