return auth.Credentials{}, time.Time{}, auth.ErrNoAccessKeyWithSecretKey
	}

	var policyBuf []byte
	if opts.sessionPolicy != nil {
		err := opts.sessionPolicy.Validate()
		if err != nil {
			return auth.Credentials{}, time.Time{}, err
		}
		policyBuf, err = json.Marshal(opts.sessionPolicy)
		if err != nil {
			return auth.Credentials{}, time.Time{}, err
		}
		if len(policyBuf) > maxSVCSessionPolicySize {