Securing APIs: Practical Steps to Protecting Your Software

In the dynamic world of software development, Application Programming Interfaces (APIs) serve as essential conduits, facilitating seamless interaction between software components. This intermediary interface not only streamlines development but also empowers software teams to reuse code. However, the increasing prevalence of APIs in modern business comes with security challenges. That’s why we’ve created this blog post - to provide you with actionable steps to enhance the security of your APIs today. 

Understanding API Security

API security extends beyond protecting an application's backend services, including elements such as databases, user management systems, and components interacting with data stores. It involves adopting diverse tools and practices to strengthen the integrity of your tech stack. A strong API security strategy reduces the risk of unauthorized access and malicious actions, ensuring the protection of sensitive information.

Exploring API Vulnerabilities

Despite the integral role APIs play in modern applications, they are frequent targets for attackers seeking to exploit vulnerabilities. This article dives into the risks associated with API vulnerabilities, shedding light on common security best practices to establish a strong security posture.

Risks of API Vulnerabilities

As APIs are publicly accessible, they are common targets for stealing sensitive information, including application logic, user credentials, credit card numbers, etc. In addition, malicious actors can exploit vulnerabilities in an API endpoint to gain unauthorized access to a system or network for other forms of attacks, such as cross-site scripting and code injections. The Online Web Application Security Project (OWASP) issues risk-based recommendations on the top 10 vulnerabilities to secure web APIs.

Best Practices for API Security

To mitigate API attacks and enhance security, the following best practices should be considered:

Uses Throttling and Rate-Limiting

Throttling involves setting a temporary state that allows the API to evaluate every request and is often used as an anti-spam measure or to prevent abuse or denial-of-service attacks. There are two primary considerations when implementing the throttling feature: how much data should be allowed per user, and when should the limit be enforced?

On the other hand, rate-limiting helps administer REST API security by avoiding DoS and Brute force attacks. In some APIs, developers set soft limits, which allow clients to exceed request limits for a brief duration. Setting timeouts is one of the most straightforward API security best practices, as it can handle both synchronous and asynchronous requests. Request queue libraries enable the creation of APIs that accept a maximum number of requests and then put the rest in a waiting queue. Each programming language comes with a queue library directory to implement request queues.

Scan for API Vulnerabilities 

To maintain the continuous security of API services, it is vital to enable API automatic scanning, identify vulnerabilities, and mitigate them across software lifecycle stages. Application security tools autonomously detect security gaps by comparing the application’s configuration against a known vulnerability database. Veracode Dynamic Analysis offers is a dynamic application security testing solution that helps establish a continuous testing process and reduces the risk of being hacked through vulnerabilities of an API.

Veracode Dynamic Analysis runs benchmarks against the OWASP top 10, providing a quick security assessment for a wide range of applications, APIs, and JavaScripts. To know more about how Veracode Dynamic Analysis can help you mitigate security attacks, sign up for a free, 14-day trial.

Use HTTPS/TLS for REST APIs

HTTPS and Transport Layer Security (TLS) offer a secure protocol to transfer encrypted data between web browsers and servers. Apart from other forms of information, HTTPS also helps to protect authentication credentials in transit. As one of the most critical practices, every API should implement HTTPS for integrity, confidentiality, and authenticity. In addition, security teams should consider using mutually authenticated client-side certificates that provide extra protection for sensitive data and services.

When building a secure REST API, developers should avoid redirecting HTTP to HTTPS, which may break API client security. Adequate steps should also be taken to divert Cross-Origin Resource Sharing (CORS) and JSONP requests for their fundamental vulnerabilities for cross-domain calls.

Restrict HTTP Methods to Secure APIs

REST APIs enable web applications that execute various possible HTTP verb operations. Data over HTTP is unencrypted, and using some HTTP methods, may be intercepted and exploited by attack vectors. As a recommended best practice, HTTP methods (GET, PUT, DELETE, POST, etc.) that are inherently insecure should be forbidden.

If a complete forbidding on their usage is not possible, security teams can also apply policies to vet using such methods with a strict allow list, whereby all requests that do not match the list should be rejected. It is also recommended to use RESTful API authentication best practices to ensure that the requesting client can use the specified HTTP method on the action, record, and resource collection.

Implement Sufficient Input Validation

In principle, data supplied by the API client should not be trusted blindly since the authentication server may execute a malicious script from unauthorized users or application services. To avoid this, security teams should implement input validation mechanisms on both the client and server sides to prevent unhealthy input.

While client-side validation involves interactive indication of errors and advice to a user on acceptable inputs, server-side validation additionally checks the data received to avoid the different types of XSS and SQL Injection attacks.

API Security by Using an API Gateway

An API gateway decouples the client interface from the collection of backend APIs, delivering a centralized resource for consistent availability and scalability of API services. Apart from managing various API services, the API management platform also handles standard functions, including telemetry, rate limiting, and user authentication, to maintain security between internal services. The gateway acts as a reverse proxy gatekeeper that accepts all API calls, coordinates the resources required to service them, and returns the appropriate results post-authentication.

Securing Your Web APIs

A proactive approach to API security involves understanding the risks, adopting best practices, and leveraging tools to ensure a resilient defense against evolving threats. That's why we created a hands-on approach to API security. Our Dynamic Application Security Testing (DAST) tool goes beyond theoretical knowledge, offering you a practical solution to identify and mitigate API vulnerabilities throughout your software's lifecycle. Get hands-on access to our DAST solution free today or check out our DevSecOps playbook for practical steps to produce secure software.