if token != "" && cred.AccessKey == "" {
		// x-amz-security-token is not allowed for anonymous access.
		return nil, ErrNoAccessKey
	}

	if token == "" && cred.IsTemp() && !cred.IsServiceAccount() {
		// Temporary credentials should always have x-amz-security-token
		return nil, ErrInvalidToken
	}

	if token != "" && !cred.IsTemp() {
		// x-amz-security-token should not present for static credentials.