What is API security?

An application programming interface (API) serves as a means for software systems to communicate and interact with each other. When a program or application possesses an API, external clients can make requests for services from it.

API security encompasses the measures taken to safeguard APIs from potential attacks. Just like applications, networks, and servers can be targeted, APIs are also susceptible to various threats.

API security plays a crucial role in ensuring web application security. The majority of modern web applications heavily rely on APIs for their functionality. However, APIs introduce additional risks to an application as they enable external entities to access it. To draw a parallel, it is akin to a business opening its doors to the public. With more people entering the premises, including those unfamiliar to the business’s employees, the level of risk escalates. Similarly, an API permits external users to utilize a program, thereby increasing the vulnerability of the API service’s infrastructure.

What are some common API security risks?

Exploiting Vulnerabilities: When an attacker sends specifically crafted data to a target, taking advantage of flaws in its design, it is referred to as a vulnerability exploit. These flaws, known as “vulnerabilities,” can grant the attacker unintended access to an API or its corresponding application. The Open Web Application Security Project (OWASP) maintains a list of the top 10 API vulnerabilities, including SQL injection, security misconfiguration, and others. Exploits that target previously unknown vulnerabilities are known as zero-day threats, which are highly challenging to prevent.

Authentication-Based Attacks: Clients must authenticate themselves before making API requests to ensure that the API server only accepts requests from known and legitimate sources. However, different authentication methods are susceptible to compromise. For example, an attacker may acquire legitimate client credentials, steal an API key, or intercept and use an authentication token.

Authorization Errors: Authorization determines the level of access granted to each user. If authorization is not properly managed, an API client may gain access to data that should be restricted, significantly increasing the risk of a data breach.

DoS and DDoS Attacks: An API can be overwhelmed by a large number of requests, causing a slowdown or complete halt in service for other clients. Some attackers intentionally flood an API with excessive requests in what is known as a denial-of-service (DoS) or distributed denial-of-service (DDoS) attack.

To mitigate these and other risks, implementing effective API security strategies is crucial.

Strong authentication and authorization measures are essential to prevent data leakage and ensure that only authorized clients can make API requests. Employing DDoS protection mechanisms and rate limiting can effectively thwart DDoS attacks. Additionally, performing schema validation and utilizing a web application firewall (WAF) can effectively block vulnerability exploits.

How do rate limiting and DDoS mitigation help protect APIs?

Rate limiting establishes a restriction on the frequency with which an individual can repeat a specific action within a defined time period. When an API client surpasses the permissible number of requests, any additional requests from them are either discarded or blocked for a designated duration.

DDoS mitigation plays a critical role in thwarting DoS and DDoS attacks. In a DDoS attack, an assailant endeavors to inundate an API with an excessive volume of requests within a limited timeframe, often originating from numerous distinct sources.

The significance of rate limiting and DDoS mitigation for APIs can be attributed to the following factors:

Preventing DoS and DDoS attacks: By impeding or disregarding superfluous requests, rate limiting and DDoS mitigation safeguard the API against overwhelming onslaughts. While rate limiting alone may not be sufficient to halt low and slow DDoS attacks, DDoS mitigation possesses the capacity to absorb the surplus traffic effectively.

Mitigating excessive usage: Apart from deliberate attacks, certain clients may unintentionally place an excessive burden on an API by excessively utilizing its resources. This imposes significant compute power costs on the API service and may impede service delivery for other clients. Rate limiting serves as a preventive measure, ensuring that the API server does not become overloaded.

How are vulnerability exploits blocked?

To ensure the effectiveness of a vulnerability exploit, it is necessary to structure malicious API requests in a manner that causes unintended responses from the API’s architects. However, API developers have multiple approaches to counter such malicious attempts, with two key methods being:

• Schema Validation: API schemas define the expected behavior of an API, encompassing the types of requests it should receive and the corresponding responses it should provide. When incoming requests fail to adhere to this predefined schema, the API may exhibit unexpected behavior, potentially leading to data leaks. Schema validation is employed to identify and block invalid requests and responses. By preventing invalid responses, API developers can mitigate certain types of attacks and protect against data leaks.

• Web Application Firewall (WAF) Rules: Similar to traditional firewalls, WAFs intercept and regulate network requests and responses. They achieve this by utilizing a set of predefined rules that determine whether to block or allow specific requests and responses. WAFs are typically deployed in front of APIs or web applications to monitor HTTP traffic. By configuring WAF rules, it becomes possible to obstruct request and response patterns targeting vulnerabilities. Moreover, WAF rules can be leveraged to block requests originating from specific IP addresses, thereby countering bot attacks and other forms of malicious activity.

Why are authentication and authorization so important for API security?

API authentication ensures the origin and legitimacy of requests, while authorization determines whether a client has permission to access requested data.

Let’s consider an example where Alice develops an API, and Bob creates a web application that utilizes Alice’s API. When Bob’s application sends an API request to Alice’s API, he includes an identifier indicating that the request is from Bob. This authentication step allows Alice’s API server to recognize and validate Bob’s request as genuine.

Alice’s API server also evaluates Bob’s privileges. If Bob’s request pertains to data labeled as “accessible to Bob,” the server fulfills the request. However, if the data is labeled as “not for Bob,” the server rejects Bob’s request as he lacks authorization. This highlights the significance of authorization in the process.

(In practice, Bob would attach an authentication key or similar mechanism to API requests, rather than a simple identifier like “this is from Bob.”)

Several authentication methods exist for APIs, with the most common ones being:

1. API key: The client receives a unique string of characters known only to them and the API service. This key is included with each API request. The API server verifies the key’s presence to ensure that the client is authenticated. However, if the key gets compromised, an attacker could exploit it to impersonate the client and carry out malicious activities. To mitigate this risk, it is crucial to encrypt API requests and responses using Transport Layer Security (TLS) or a similar encryption protocol. This prevents the exposure of the key as it traverses the internet.

2. Username and password: API requests can use conventional username and password credentials for authentication, employing a method called HTTP authentication. The username and password are encoded and added to the HTTP header of all API requests. The server validates these credentials against an approved client list to authenticate the requests. However, this approach inherits the typical challenges associated with passwords, including the risk of loss, leakage, theft, guessing, or sharing with untrusted parties. It is also susceptible to credential stuffing and brute force attacks.

3. OAuth token: Rather than directly authenticating the client, an API server can obtain an authentication token from a trusted authentication server using the OAuth protocol. To use the API, a user logs in to a third-party service instead of directly authenticating with the API. Similar to the username-and-password approach, this authentication method remains vulnerable to credential stuffing and other attacks.

4. Mutual TLS (mTLS): Transport Layer Security (TLS) establishes an encrypted and authenticated connection between the client and server while loading webpages. TLS can also verify and authenticate both ends of an API connection. In mutual TLS (mTLS), both the client and server possess TLS certificates. They authenticate each other using these certificates, ensuring that both parties are who they claim to be without relying on passwords or other authentication methods. Implementing mTLS can be challenging since all API endpoints and clients must possess valid TLS certificates, which might be difficult to enforce and maintain.

What is API Shield?

Toffs API Gateway provides a unified dashboard to access a range of API security features, safeguarding against prevalent API security risks. With API Gateway, you gain access to the following capabilities:

• mTLS for API endpoint authentication: Ensures secure authentication of API endpoints by utilizing mutual Transport Layer Security (mTLS) protocols.

• Schema validation: Implements a positive security model to exclusively permit requests that adhere to the designated schema of the API, thus bolstering protection.

• Data loss prevention (DLP): Scans outgoing API traffic to detect any sensitive data, preventing inadvertent leaks or breaches.

• Rate limiting and DDoS mitigation: Guards APIs against overload and potential Distributed Denial of Service (DDoS) attacks, guaranteeing uninterrupted service availability.

To explore further details about API Gateway and its comprehensive features, you can refer to additional resources.