clientETag, err := etag.FromContentMD5(r.Header)
	if err != nil {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrInvalidDigest), r.URL)
		return
	}

	// if Content-Length is unknown/missing, deny the request
	size := r.ContentLength
	rAuthType := getRequestAuthType(r)
	switch rAuthType {
	// Check signature types that must have content length