Api Security

# API Security Best Practices

Implement secure API design patterns including authentication, authorization, input validation, rate limiting, and protection against common API vulnerabilities.

## Description

USE WHEN:
- Designing new API endpoints
- Securing existing APIs
- Implementing authentication and authorization (JWT, OAuth 2.0, API keys)
- Setting up rate limiting and throttling
- Protecting against injection attacks (SQL, XSS, command)
- Conducting API security reviews or preparing for audits
- Handling sensitive data in APIs
- Building REST, GraphQL, or WebSocket APIs

DON'T USE WHEN:
- Need vulnerability scanning (use `vulnerability-scanner` skill)
- Building frontend-only apps with no API
- Need network-level security (firewalls, WAF config)

OUTPUTS:
- Secure authentication implementations (JWT, refresh tokens)
- Input validation schemas (Zod, Joi)
- Rate limiting configurations
- Security middleware examples
- OWASP API Top 10 compliance guidance

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## How It Works

### Step 1: Authentication & Authorization

- Choose authentication method (JWT, OAuth 2.0, API keys)
- Implement token-based authentication
- Set up role-based access control (RBAC)
- Secure session management
- Implement multi-factor authentication (MFA)

### Step 2: Input Validation & Sanitization

- Validate all input data
- Sanitize user inputs
- Use parameterized queries
- Implement request schema validation
- Prevent SQL injection, XSS, and command injection

### Step 3: Rate Limiting & Throttling

- Implement rate limiting per user/IP
- Set up API throttling
- Configure request quotas
- Handle rate limit errors gracefully
- Monitor for suspicious activity

### Step 4: Data Protection

- Encrypt data in transit (HTTPS/TLS)
- Encrypt sensitive data at rest
- Implement proper error handling (no data leaks)
- Sanitize error messages
- Use secure headers

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## JWT Authentication Implementation

### Generate Secure JWT Tokens

```javascript
// auth.js
const jwt = require('jsonwebt...