func guessIsLoginSTSReq(req *http.Request) bool {
	if req == nil {
		return false
	}
	return strings.HasPrefix(req.URL.Path, loginPathPrefix) ||
		(req.Method == http.MethodPost && req.URL.Path == SlashSeparator &&
			getRequestAuthType(req) == authTypeSTS)

	}

	vid := r.Form.Get(xhttp.VersionID)
	if vid == "" {
		if u, err := url.Parse(r.Header.Get(xhttp.AmzCopySource)); err == nil {
			vid = u.Query().Get(xhttp.VersionID)
		}
	}

	authType := getRequestAuthType(r)
	var signatureVersion string
	switch authType {
	case authTypeSignedV2, authTypePresignedV2:
		signatureVersion = signV2Algorithm