i API security checklist – All things in moderation

API security checklist

API Security Checklist

Authentication

  • Dont’t use Basic Auth Use standard authentication(e.g. JWT, OAth).
  • 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). For examples: https://example/api/v1/users/create/
    https://example/api/v1/users/124/update
    https://example/api/v1/users/123/delete/

  • 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 ntity 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).
    Below is the source, I just folk it and push some examples. Hope it helpful for you guys. Feel free to contribute for this repository.
    Source on github API security checklist

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