MinIO performs incomplete signature validation for unsigned-trailer uploads

Impact

This is a high priority vulnerability and users must upgrade ASAP.

The signature component of the authorization may be invalid, which would mean that as a client you can use any arbitrary secret to upload objects given the user already has prior WRITE permissions on the bucket,

Prior knowledge of access-key, and bucket name this user might have access to - and an access-key with a WRITE permissions is necessary.

However with relevant information in place, uploading random objects to buckets is trivial and easy via curl

Patches

Yes https://github.com/minio/minio/pull/21103

Workarounds

Reject requests with x-amz-content-sha256: STREAMING-UNSIGNED-PAYLOAD-TRAILER for now at LB layer, ask application users to use STREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER