HTTP - API Design Considerations

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API(Application Programming Interface) allows applications to communicate over the web. Designing an effective API allows smooth communication between clients and servers. HTTP APIs operates over the HTTP protocol, and forms the core of web-based interactions. This chapter covers about RESTful API principles, API Security considerations and Versioning APIs.

RESTful API Principles

REST (Representational State Transfer) is used to design networked applications. It is a stateless, client-server communication model which focuses on scalability, simplicity, and resource oriented communication. The key principles of RESTful API design are mentioned below:

• Resources Identification: Resources can be any objects or entities such as users, products. The client should use clear URLs to identify resources.
• HTTP Methods: RESTful API uses HTTP methods such as GET, POST, PUT, DELETE and PATCH for performing operations on resources.
• Representation: Representation of resources is in standard formats such as JSON or XML. It can be specified in Content-Type header.
• Hypermedia: APIs can provide links of related resources in the responses which helps clients to discover actions dynamically.
• Error Handling: Uses standard HTTP status codes for indicating the response of a request such as 200 OK, 404 NOT FOUND, 400 Bad Request.

API Security Considerations

API security is an important aspect as APIs handles the sensitive data. It also acts as gateways between various systems. APIs may become vulnerable to various threats without proper security. It protects the integrity and confidentiality. We have mentioned below few techniques for API security.

Authentication and Authorization

• Authentication and Authorization allows only authenticated and authorized users to access API resources.
• OAuth 2.0, RBAC(Role-Based Access Control), and JWT can be used for better authentication and authorization.
• We can use IP Whitelisting for restricting the access and allow only trusted IP addresses for sensitive APIs.

Rate Limiting

• We can limit or control the number of API requests a client can make within a specific time period. It will help in avoiding abuse, server overload, and DDoS attacks.
• We can use exponential backoff strategies for delaying the requests after hitting limits.
• Implement burst control to handle sudden traffic spikes within acceptable limits.

Cross-Origin Resource Sharing (CORS)

• By configuring headers, we can manage which origins are allowed to access APIs, restrict untrusted domains, and control access methods.
• User need to specify allowed HTTP methods and headers in the CORS policy.

Encryption

• Encryption can help in securing data during transmission and at rest using HTTPS.
• Use HTTPS for the API traffic to secure data during transmission.
• For securing sensitive data at rest, use strong encryption algorithms such as AES-256.
• One should implement certificate pinning. It prevents use of fraudulent certificates.
• Keep rotating encryption keys periodically for maintaining the security.

Input Validation

• Input validation protects APIs from malicious attacks. It validates and sanitizes the incoming data. enforcing strict schemas, and rejecting unexpected payloads.
• All the incoming data should be Validated against a strict schema such as JSON Schema.
• Sanitize input data to remove malicious characters that could lead to injection attacks.
• The payload sizes can be limited in order to prevent denial-of-service (DoS) attacks.
• Reject the requests which has missing fields in the payload.

Versioning APIs

API versioning refers to managing the changes made to an API over time by maintaining multiple versions. It ensures backward compatibility and allows developers to introduce new features or changes without disrupting existing clients.

Types of API Versioning

• URI Versioning: It is path based API versioning where version number is directly included into the URL path. Example: /v1/users, /v2/users.
• Header Versioning: In Header Versioning, we include the version number in custom HTTP header. Example: X-API-Version: 1.
• Query Parameter Versioning: In Query Parameter Versioning, we append the version number as a query parameter to the URL. Example: /products?version=2
• Media Type Versioning: In Media Type Versioning, we include the version number in the Content-Type header.