if accessKey == "" || !cred.IsTemp() || cred.IsExpired() || cred.ParentUser == "" {
		return time.Time{}, errInvalidArgument
	}

	ttl := int64(cred.Expiration.Sub(UTCNow()).Seconds())

	cache := store.lock()
	defer store.unlock()

	if policyName != "" {
		mp := newMappedPolicy(policyName)
		_, combinedPolicyStmt := filterPolicies(cache, mp.Policies, "")