MinIO information disclosure vulnerability

Impact

If-Modified-Since
If-Unmodified-Since

Headers when used with anonymous requests by sending a random object name requests you can figure
out if the object exists or not on the server on a specific bucket and also gain access to some amount of
information such as

Last-Modified (of the latest version)
Etag (of the latest version) 
x-amz-version-id (of the latest version)
Expires (metadata value of the latest version)
Cache-Control (metadata value of the latest version)

This conditional check was being honored before validating if the anonymous
access is indeed allowed on the metadata of an object.

Patches

Yes this issue has been already fixed in

commit e0fe7cc391724fc5baa85b45508f425020fe4272 (HEAD -> master, origin/master)
Author: Harshavardhana <harsha@minio.io>
Date:   Mon May 27 12:17:46 2024 -0700

    fix: information disclosure bug in preconditions GET (#19810)
    
    precondition check was being honored before, validating
    if anonymous access is allowed on the metadata of an
    object, leading to metadata disclosure of the following
    headers.
    
    ```
    Last-Modified
    Etag
    x-amz-version-id
    Expires:
    Cache-Control:
    ```
    
    although the information presented is minimal in nature,
    and of opaque nature. It still simply discloses that an
    object by a specific name exists or not without even having
    enough permissions.

Users must upgrade to RELEASE.2024-05-27T19-17-46Z for the fix

Workarounds

There are no workarounds.

References

Refer to the pull request #19810 for more information on the fix.