API Security Checklist: README

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# API Security Checklist

Checklist of the most important security countermeasures when designing, testing, and releasing your API.

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## Authentication

- [ ] Don't use `Basic Auth`. Use standard authentication instead.
- [ ] Don't reinvent the wheel in `Authentication`, `token generation`, `password storage`. Use the standards.
- [ ] Use `Max Retry` and jail features in Login.
- [ ] Use encryption on all sensitive data.

## Access

- [ ] Limit requests (Throttling) to avoid DDoS / brute-force attacks.
- [ ] Use HTTPS on server side with TLS 1.2+ and secure ciphers to avoid MITM (Man in the Middle Attack) and ensure `Host` header matches the SNI.
- [ ] Use `HSTS` header with SSL to avoid SSL Strip attacks.
- [ ] Turn off directory listings.
- [ ] For private APIs, allow access only from safelisted IPs/hosts.

## Authorization

### OAuth

- [ ] Always validate `redirect_uri` server-side to allow only safelisted URLs.
- [ ] Always try to exchange for code and not tokens (don't allow `response_type=token`).
- [ ] Use `state` parameter with a random hash to prevent CSRF on the OAuth authorization process.
- [ ] Define the default scope, and validate scope parameters for each application.

## Input

- [ ] Use the proper HTTP method according to the operation: `GET (read)`, `POST (create)`, `PUT/PATCH (replace/update)`, and `DELETE (to delete a record)`, and respond with `405 Method Not Allowed` if the requested method isn't appropriate for the requested resource.
- [ ] Validate `content-type` on request Accept header (Content Negotiation) to allow only your supported format (e.g., `application/xml`, `application/json`, etc.) and respond with `406 Not Acceptable` response if not matched.
- [ ] Validate `content-type` of posted data as you accept (e.g., `application/x-www-form-urlencoded`, `multipart/form-data`, `application/json`, etc.).
- [ ] Validate user input to avoid common vulnerabilities (e.g., `XSS`, `SQL-Injection`, `Remote Code Execution`, etc.).
- [ ] Don't use any sensitive data (`credentials`, `Passwords`, `security tokens`, or `API keys`) in the URL, but use standard Authorization header.
- [ ] Use only server-side encryption.
- [ ] Use an API Gateway service to enable caching, Rate Limit policies (e.g., `Quota`, `Spike Arrest`, or `Concurrent Rate Limit`) and deploy APIs resources dynamically.

## Processing

- [ ] Check if all the endpoints are protected behind authentication to avoid broken authentication process.
- [ ] User own resource ID should be avoided. Use `/me/orders` instead of `/user/654321/orders`.
- [ ] Don't auto-increment IDs. Use `UUID` instead.
- [ ] If you are parsing XML data, make sure entity parsing is not enabled to avoid `XXE` (XML external entity attack).
- [ ] If you are parsing XML, YAML or any other language with anchors and refs, make sure entity expansion is not enabled to avoid `Billion Laughs/XML bomb` via exponential entity expansion attack.
- [ ] Use a CDN for file uploads.
- [ ] If you are dealing with huge amount of data, use Workers and Queues to process as much as possible in background and return response fast to avoid HTTP Blocking.
- [ ] Do not forget to turn the DEBUG mode OFF.
- [ ] Use non-executable stacks when available.

## Output

- [ ] Send `X-Content-Type-Options: nosniff` header.
- [ ] Send `X-Frame-Options: deny` header.
- [ ] Send `Content-Security-Policy: default-src 'none'` header.
- [ ] Remove fingerprinting headers - `X-Powered-By`, `Server`, `X-AspNet-Version`, etc.
- [ ] Force `content-type` for your response. If you return `application/json`, then your `content-type` response is `application/json`.
- [ ] Do not return overly specific error messages to the client that could reveal implementation details, use generic messages instead, and log detailed information only on the server side.
- [ ] Don't return sensitive data like `credentials`, `passwords`, or `security tokens`.
- [ ] Return the proper status code according to the operation completed. (e.g., `200 OK`, `400 Bad Request`, `401 Unauthorized`, `405 Method Not Allowed`, etc.).

## CI & CD

- [ ] Audit your design and implementation with unit/integration tests coverage.
- [ ] Use a code review process and disregard self-approval.
- [ ] Ensure that all components of your services are statically scanned by AV software before pushing to production, including vendor libraries and other dependencies.
- [ ] Continuously run security tests (static/dynamic analysis) on your code.
- [ ] Check your dependencies (both software and OS) for known vulnerabilities.
- [ ] Design a rollback solution for deployments.

## Monitoring

- [ ] Use centralized logins for all services and components.
- [ ] Use agents to monitor all traffic, errors, requests, and responses.
- [ ] Use alerts for SMS, Slack, Email, Telegram, Kibana, Cloudwatch, etc.
- [ ] Ensure that you aren't logging any sensitive data like credit cards, passwords, PINs, etc.
- [ ] Use an IDS and/or IPS system to monitor your API requests and instances.

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## See also:

- [yosriady/api-development-tools](https://github.com/yosriady/api-development-tools) - A collection of useful resources for building RESTful HTTP+JSON APIs.
- You don't need JWT, just use a randomly generated API key. If you need asymmetric encryption or tamper prevention, [here are some alternatives to JWT](https://kevin.burke.dev/kevin/things-to-use-instead-of-jwt/).

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## API Security Best Practices (Advanced)

### Rate Limiting & Abuse Prevention
- [ ] Implement sliding window rate limiting per API key and IP.
- [ ] Use exponential backoff for repeated failed authentication attempts.
- [ ] Implement CAPTCHA or proof-of-work challenges after suspicious activity.
- [ ] Monitor and alert on unusual API usage patterns (time, volume, endpoints).

### GraphQL-Specific Security
- [ ] Disable introspection in production environments.
- [ ] Implement query depth limiting to prevent nested query attacks.
- [ ] Use query cost analysis to prevent resource exhaustion.
- [ ] Whitelist allowed queries in production when possible.

### Secrets Management
- [ ] Rotate API keys and secrets on a regular schedule.
-