Shield your API and safeguard your data: Embrace security best practices for unbeatable protection!

In today's digital landscape, Application Programming Interfaces (APIs) are becoming increasingly crucial for businesses to connect with customers and partners. However, as the use of APIs grows, so does the potential for security breaches and vulnerabilities. That's why implementing security best practices for API is vital for protecting sensitive data and maintaining user trust.

By combining all the various best practices from the vast pool of API security knowledge, experts have created a simple yet effective list of practices that can be easily applied in an API context. By following these guidelines, businesses can significantly reduce their API vulnerabilities and prevent potentially devastating security breaches.

Applying these best practices involves identifying and authenticating users, encrypting data, implementing strict access controls, and constantly monitoring and updating the API's security measures. Ultimately, these practices provide a strong shield of protection against security threats, ensuring businesses can confidently deliver high-quality services to their users without fear of compromise.

In conclusion, implementing security best practices for APIs is a must for all businesses that use APIs. It ensures the protection of sensitive data and helps build trust with users, ultimately leading to long-term success. So, take the time to review and implement these practices and enjoy the peace of mind that comes with knowing your API is secure.

Step 1: Lock down your API by restricting HTTP methods with a safe list.

HTTP methods like GET, DELETE, PUT, and POST are the building blocks of APIs, but they also pose a significant security risk if not adequately secured. That's why implementing a 'Safe List' of allowed HTTP methods is crucial in safeguarding your API from malicious attacks.

By creating a 'Safe List', you can easily verify if incoming HTTP methods are allowed or not. If the request matches an approved method, it's allowed to continue, but if it's not on the list, it's immediately rejected with a 405 Method Not Allowed HTTP return code.

This simple yet powerful step can significantly reduce the risk of API vulnerabilities and keep your data safe from unauthorized access. So, start securing your API today by implementing a 'Safe List'.

Step 2: Validate all your API input against a safe list.

When it comes to APIs, input validation is one of the most crucial steps you can take to safeguard against security breaches. By not trusting any inbound parameters or objects, you can ensure that your API is protected from malicious attacks.

The best way to do this is by creating an input 'Safe List' that includes all the approved types of input for your API endpoint. This list can include rules for length, range format, and type of data, ensuring that any input that doesn't meet these criteria is dropped immediately.

For instance, if you're dealing with a Boolean value, you could set a specific rule on the safe input list that requires a length of fewer than 400 bytes, a range value from one to 512, and a data type of Boolean. Any input that doesn't match these criteria is rejected, ensuring that your API processes only safe, validated requests.

If you're using strong types, you can further define the structure of your data, allowing your API to work even more securely. By throwing exceptions when a request doesn't meet your defined data structure, you can ensure that your API is only processing requests that meet your strict input validation rules.

So, fortify your API today by implementing input validation and take the first step towards creating an impenetrable security shield for your data!

Step 3: Always validate incoming request Content Types against a safe list.

One of the critical steps in securing your API is validating the content types of incoming requests. By creating a safe list of approved content types, you can ensure that your API only processes requests with safe, valid content types.

In our example, we have a request with a content type of text/plain. By applying the safe list principle, we create a safe list for content types, which specifies the approved types of content that we accept. In our example, we only accept content types of text/plain or image/jpeg. Any requests with a different content type are rejected, ensuring that your API only processes valid content types.

It's also crucial to document all the supported content types within your API and reject any requests with unexpected or missing content-type headers. This can be achieved by responding with an HTTP 406 Unacceptable or 415 Unsupported Media Type error code.

For instance, if an attacker sends a request with a content type of font otf, which isn't on the approved safe list, your API should respond with either a 406 Unacceptable or a 415 Unsupported Media Type error code, alerting you to the potential security breach.

So, tighten up your API's security today by implementing strict content type validation and safeguarding your API against potential security threats.

Step 4: Enhance security with Validation and Sanitisation Libraries, Parsers and Logging.

It is highly recommended to utilise validation and sanitisation libraries or frameworks as a best practice. While it's technically possible to create your own input validation code, why would you go through the hassle? There are already established libraries available for all the programming languages you're using. You can use those well-tested validation and sanitisation libraries or even the ones already included in your specific code framework.

In the example shown above, incoming requests from users are being validated using a library, which ensures that the requests meet the predetermined safe list of accepted input types. It's crucial to log all input validation failures to detect any security threats, such as an attacker probing for vulnerabilities in your API by sending thousands of requests for different data types.

It's also essential to use a secure parser for parsing incoming messages, such as JSON or XML. Attempting to do this manually can be extremely complicated and error-prone. Instead, you can use the secure parsers already available in your chosen programming language or included via a trusted library.

Step 5: Send Safe Response Content Types

To ensure the security of API responses, it is crucial to follow best practices for sending safe content types. The client can specify the desired format for receiving the response data using the accept header, which is particularly relevant when an API endpoint returns various types of data, such as XML or JSON.

Therefore, when a request is received, the accept header should be checked to ensure that it aligns with the allowable types that the API endpoint can provide. If the header does not match, the request should be rejected outright to avoid security threats.

It is also essential to be cautious when including JavaScript in a response, as header injection attacks can occur. This type of attack can lead to the exposure of sensitive data or the execution of malicious code.

When sending back the response content, it is necessary to match the headers' intended content type with the prepared body content to be sent back to the user. To avoid the application of JavaScript as a content type, it is critical to use appropriate headers and ensure that the content type is not mistakenly set to JavaScript.

Step 6: Return the Correct HTTP Status Codes

It is a best practice to return the semantically correct HTTP status code to ensure effective communication between the API and its users. Although there are numerous HTTP status codes available in the standard, many APIs tend to use only 200 for "OK" and 404 for "Not Found" for every response, which is not ideal.

In reality, different conditions could apply to an API, and using the appropriate error code can help convey to the user what is happening behind the scenes in the API. It is recommended to use the correct error code for communicating the status of the API accurately. Using the correct error code also helps to prevent any information disclosure since none of these error codes reveals any critical information.

To make the API as robust as possible, it is essential to communicate the underlying status by returning the correct error codes. This way, the API can effectively communicate with its users, making it easier for them to identify and address any issues.

Step 7: Secure Management Endpoints

It is considered a best practice to protect any API management endpoints used for administering an API solution. When an attacker gains access to these endpoints, it can compromise the entire system. Therefore, it is crucial to implement proper security measures to prevent such attacks.

To begin, it is recommended to avoid exposing management endpoints via the internet. It is ideal to have a control network with a backchannel network for management and administration, which can help prevent attackers from accessing the API directly.

Additionally, restricting access to management endpoints via firewall rules or access control lists can be an effective way to enhance security. Implementing specific API security firewalls can also be considered to provide an added layer of protection.

In cases where management endpoints are accessible via the internet, it is recommended to use multi-factor authentication to ensure that only authorized users can access the endpoints.

It is essential to use the API security best practice list as a checklist to assess the API's security measures thoroughly. Each of the conditions should be evaluated, and if any measures are missing, they should be added to enhance the security of the API

Step 8: Perform Error Handling and Auditing

It's essential to ensure that API endpoints respond with generic error messages without any technical details or information that could expose how your API works. This is crucial to maintaining the security of your API. It's best practice to use the correct HTTP error codes to communicate the appropriate error to the client.

Additionally, never pass technical details, such as call stacks or internal hints, back to the client in the API response. This information should be kept internal to your API.

Audit logging is a critical part of API security. Always ensure you write audit logs before and after any security-related events, such as authentication attempts. This helps to detect potential attacks by providing information about any failed authentication attempts.

In particular, it's essential to log token validation errors to assist with attack detection. If you're using an API key or a JWT for authentication, make sure that any validation errors are audited and logged.

When logging data, it's essential to sanitise the data to prevent log injection attacks. Attackers may attempt to inject JavaScript into log messages with the hope that the log message will be opened in a browser-based console, leading to the compromise of your local administration station.

Step 9: Use Security Tools to Identify API Vulnerabilities

To ensure API security, it is crucial to identify vulnerabilities in your API before its release. Various third-party and open-source tools are available for this purpose. As APIs can be written in multiple languages, such as .NET, Node JS, and Ruby on Rails, it's important to choose tools that support your language. Popular tools like Snyk, Karate, Postman, and Sauce Labs API Testing and Monitoring can be used to detect vulnerabilities and automate API testing. It's recommended to use a tool to identify third-party and open-source vulnerabilities in the API code, regardless of its programming language. Some of these are:

1. Snyk: A developer security platform that integrates directly into development tools and workflows, making it easy to find vulnerabilities in your code.
2. Karate: An open-source framework for API testing, performance testing, and mocking. It uses a behaviour-driven development approach and Gherkin syntax to create test scripts.
3. Postman: A widely used platform for building and testing APIs with over 17 million users across 500,000 organizations. It is available as a SaaS platform or a desktop app and is compatible with Windows, Linux, and macOS.
4. Sauce Labs API Testing and Monitoring: A comprehensive platform for web services and REST API testing, monitoring, error reporting, and debugging. It allows for the auto-generation of tests from payloads or specification files and editing them in either an IDE or a drag-and-drop test composer.

Step 10: Implement HTTPS and TLS for API Endpoints

Enforcing HTTPS and TLS usage for API endpoints is a crucial best practice. HTTPS is essential because it encrypts the data that is transmitted between the client and the server, ensuring that no third party can intercept or tamper with it. Without HTTPS, attackers can easily intercept and read sensitive information transmitted by an API, such as authentication tokens or user data.

TLS, or Transport Layer Security, is the protocol that is used to establish secure connections between the client and the server. It ensures that the data transmitted over HTTPS is encrypted and that the server being communicated with is authentic. It is essential to enforce only the latest versions of TLS in order to ensure that the API uses the most secure and up-to-date encryption protocols.

In the diagram above, TLS version 1.3 is being enforced, which is the latest version at the time of writing. As newer versions of TLS are released, it is essential to migrate to them in order to take advantage of the latest security improvements. By keeping up-to-date with the latest TLS versions, API developers can ensure that their endpoints are as secure as possible.

Step 11: Secure Sensitive Information in HTTP requests

As developers, we must take every precaution to safeguard sensitive information in HTTP requests. Accidental information leakage in API requests is a common occurrence and can result in severe security breaches. To prevent this, we must ensure that sensitive data is transferred only in the request body or headers, not in the URL when using POST or PUT requests. For GET requests, we should transfer sensitive data only in the HTTP header.

It's essential to be aware of the risks posed by intermediary proxy servers when transmitting sensitive data. Since we have no way of knowing whether a proxy server is malicious or not, we must assume that it is untrusted. Exposing an API key in the URL, for example, would allow the proxy server to see the key and log it, potentially resulting in the abuse of this compromised key.

In the "NOT OKAY" section of our example, as shown above, the apiKey is exposed in the URL, which a proxy server could log. Instead, we should encrypt the API key, considered sensitive data and transmit it in the header to keep it hidden from potential attackers. This type of attack is prevalent in public places such as airports and internet cafes, where attackers set up free public wifi to exploit security flaws in API design.

Protecting sensitive information in HTTP requests is crucial to API security. As developers, we must make every effort to follow this best practice and ensure the safe transmission of sensitive data.

Step 12: Secure your API using Standard Security Headers

API security is a critical aspect of modern software development, and it's essential to implement standard security headers to ensure the best possible protection for your API endpoints and clients. In addition to the common security headers used in web applications, there are some specific headers that you should implement in your API deployment.

One of the standard security headers you should send is the Content-Type header, which specifies the type of content you are sending back in your API response. By continuously sending this header with the correct content type, you can help prevent certain types of attacks that target the interpretation of the content.

Another important header to include is the X-Frame-Options header, recommended by OWASP. By setting this header to DENY, you can prevent your API from being embedded in an iframe on another site, which can help protect against clickjacking attacks.

You should also send the X-Content-Type-Options header with the value nosniff to prevent the browser from detecting a different content type from the one sent, which can help prevent cross-site scripting attacks.

Finally, it's essential to consider the Access-Control-Allow-Origin header, which is part of the CORS mechanism used by browsers to allow the loading of resources from origins other than the server's own. By configuring this header, you can prevent unauthorized cross-origin requests to your API.

By implementing these standard security headers, you can help protect your API from various common attacks and ensure the security of your users' sensitive data.

Step 13: Implement Quotas, Rate Limiting, and Throttling.

When developing an API, it's crucial to ensure that one user doesn't consume all the available resources and cause a denial of service for others. That's where quotas, rate limiting, and throttling come into play.

Quotas allow you to limit how many requests a user can make within a specific time frame. This ensures that a single user doesn't use all the API's resources. Rate limiting is another technique used to prevent resource starvation. It enables you to limit the number of requests a user can make per second or minute.

In the diagram above, you can see how the rate limit policy works with the quota. If a user sends more requests than allowed, the API can either deny those requests or send a 429 Too Many Requests HTTP status code to notify the user that they have exceeded the limit.

Throttling is a mechanism that queues rejected requests until the next time window. This ensures that users don't experience a poor user experience due to the rejection of their requests. Once users pass their rate limit, the API can keep their requests until they're no longer over the limit.

It's crucial to have a uniform approach to how all users access your API. You can implement global, per-role, or per-user policies based on your requirements. Be aware of what your API is used for and ensure that out-of-bounds behaviour isn't allowed.

By implementing quotas, rate limiting, and throttling in your API, you can prevent resource starvation, avoid a denial of service condition, and ensure a seamless experience for all users.

Step 14: Deploy Filtering to Control Access to API Endpoints

One crucial best practice to implement is deploying filtering to control who can connect to your API endpoints. By filtering, you can restrict access to your endpoints, thereby preventing unauthorized or malicious use.

There are various filtering methods you can use to achieve this. For instance, you can filter based on IP address, geographic range, or country. Filtering by IP address involves allowing only specific IP addresses to access your API endpoints. In contrast, geographic filtering restricts access to users within a specific geographic region or country.

It's essential to note that relying on a single filtering method may not be sufficient to achieve optimal protection. For example, a user who should have been filtered by one of the previous filters could bypass it by using an anonymous proxy to access your API endpoint. To counter this, you could also choose to block anonymous proxies.

To ensure maximum security, you should apply multiple filters based on your API's security policy. By doing this, you can control and lock down who can connect to your API endpoints, thereby preventing unauthorized access or malicious use.

In conclusion, implementing these fourteen best practices may seem like a daunting task, but it is crucial to secure your API from potential threats. Starting with input validation, which is a relatively simple step, is an excellent place to begin your security journey. From there, you can build on top of the other security best practices to establish a robust and secure API. By implementing measures such as authentication, authorization, encryption, and rate limiting, you can significantly reduce the risk of malicious attacks on your API. Remember, security should be a top priority for any API, and by following these best practices, you can ensure that your API is protected against potential threats.