feat(authentication): enhance logging and integrate Fail2Ban configuration (#187)

[jiongxuan]

This PR includes several improvements to the authentication system's logging, along with a guide to integrating Fail2Ban to enhance the overall security of the WebDAV server.

Key Changes:

1. Improve IP Logging for Real Client IP Address:

   • Commit: feat(authentication): improve IP logging by extracting real client IP from X-Forwarded-For header
   • Added the getRealRemoteIP function to correctly extract the client's real IP address when requests come through a reverse proxy.
   • Updated authentication logging to use the extracted IP instead of r.RemoteAddr.
   • Ensured fallback to r.RemoteAddr if X-Forwarded-For header is not present, maintaining compatibility with both proxy and non-proxy environments.

2. Authentication Logging Enhancements:

   • Commit: feat(authentication): enhance login failure logging and reduce log volume
   • Added logging for failed login attempts specifically indicating invalid usernames, enhancing the detail in logs.
   • Removed redundant "login attempt" logs, focusing only on final validation results, which helps reduce log volume.
   • Retained detailed logging for invalid passwords and successful authorizations for greater clarity and auditability.

3. Fail2Ban Integration Guide:

   • Commit: docs: add Fail2Ban configuration guide to README
   • Added a section in README.md to guide users on how to configure Fail2Ban with WebDAV.
   • Included examples for filter.d and jail.d configurations, allowing users to automatically ban IP addresses that exceed the allowed number of failed login attempts.

Issue Reference:

This PR closes #187, which requested improvements in logging details and Fail2Ban integration for better security.

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Additional Context:

• Real Client IP Address Extraction:

  • The addition of getRealRemoteIP helps to accurately log the IP address of the actual client, especially when the server is behind a reverse proxy. This is crucial for accurate logging and security analysis.

• Fail2Ban Configuration:

  • The integration of Fail2Ban helps protect the WebDAV server from brute-force attacks by banning IP addresses that repeatedly fail to authenticate. This increases server resilience against malicious attempts.

• Log Volume Optimization:

  • Reducing log entries to only include validation outcomes (i.e., success or failure) instead of every login attempt will help maintain clean logs that are easier to monitor and analyze.

Feel free to review the changes. Let me know if any further adjustments are needed or if there are additional requirements!

[hacdias]

Thanks for the contribution. I will merge this once the comment above is tackled.

[jiongxuan]

Thanks for the feedback! I’ve removed the commented line as requested.

I initially left it there for comparison purposes, to highlight the change in log volume, but I agree that removing it entirely makes the code cleaner and more focused. Thanks again!