Fix and feat

[T1anjiu]

Summary

This PR removes insecure hash algorithms (MD5 and SHA1) and fixes resource leaks in the file upload and zip download
functionality.

Changes

Security Improvements

• Remove MD5 and SHA1: These algorithms are no longer considered secure and have been removed from the RPC hash
  function
• Enhanced path validation: Use filepath.Clean() to sanitize paths and prevent directory traversal attacks
• Directory existence check: Validate that the target directory exists and is accessible on startup

Bug Fixes

• Fix file handle leak in upload: Added defer dst.Close() to ensure uploaded files are properly closed
• Fix file handle leak in zipRPC: Changed from defer file.Close() to explicit file.Close() to avoid
  accumulating file handles in the filepath.Walk loop

Code Quality

• Enhanced error logging: Improved error messages in verbose mode for better debugging
• Replace deprecated imports: Updated io/ioutil to io in test code (Go 1.16+)

Testing

• Existing tests pass (note: TestNormal has a pre-existing failure unrelated to these changes)
• Manual testing confirms:
  • File upload works correctly
  • Zip download works correctly
  • Directory validation prevents invalid paths
  • Error messages are more informative in verbose mode

Breaking Changes

• Hash algorithm changes: RPC calls using md5 or sha1 will now return an error. Users should update to use
  sha256 or sha512.

Checklist

• Code follows project style
• No new files added
• Cross-platform compatible
• Tests pass (pre-existing failures unrelated)

[pldubouilh]

Can you keep md5 and sha1 ? It's cryptographically insecure, but still widely used by other systems for file stamping.

[pldubouilh]

Thank you for your PR ! I'm ready to accept it - just please bring back md5 and sha1, I know it's used by some users.

[T1anjiu]

Thank you for your PR ! I'm ready to accept it - just please bring back md5 and sha1, I know it's used by some users.

Done. I've restored MD5 and SHA1 as suggested.

[pldubouilh]

Thank you ! I'll test it out a bit on my side and merge it later on !