API Security Checklist

Found various checks you should put in your API's. Here is a checklist of the most important security countermeasures when designing, testing, and releasing your API.


Authentication

  • [ ] Don't use Basic Auth Use standard authentication (e.g. JWT, OAuth).
  • [ ] Don't reinvent the wheel in Authentication, token generating, password storing use the standards.

JWT (JSON Web Token)

  • [ ] Use random complicated key (JWT Secret) to make brute forcing token very hard.
  • [ ] Don't extract the algorithm from the payload. Force algorithm in the backend (HS256 or RS256).
  • [ ] Make token expiration (TTL, RTTL) as short as possible.
  • [ ] Don't store sensitive data in the JWT payload, it can be decoded easily.

OAuth

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

Access

  • [ ] Limit requests (Throttling) to avoid DDoS / Bruteforce attacks.
  • [ ] Use HTTPS on server side to avoid MITM (Man In The Middle Attack).
  • [ ] Use HSTS header with SSL to avoid SSL Strip attack.

Input

  • [ ] Use proper HTTP method according to operation , GET (read), POST (create), PUT (replace/update) and DELETE (to delete a record).
  • [ ] 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.

Processing

  • [ ] Check if all endpoint protected behind the authentication to avoid broken authentication.
  • [ ] User own resource id should be avoided. Use /me/orders instead of /user/654321/orders
  • [ ] Don't use auto increment id's use UUID instead.
  • [ ] If you are parsing XML files, make sure entity parsing is not enabled to avoid XXE (XML external entity attack).
  • [ ] If you are parsing XML files, make sure entity expansion is not enabled to avoid Billion Laughs/XML bomb via exponential entity expansion attack.
  • [ ] Use CDN for file uploads.
  • [ ] If you are dealing with huge amount of data, use Workers and Queues to return response fast to avoid HTTP Blocking.
  • [ ] Do not forget to turn the DEBUG mode OFF.

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 response content-type is application/json.
  • [ ] Don't return sensitive data like credentials , Passwords, 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).