// perform strict type conversion using reflection.
	var rawPolicy struct {
		Expiration string        `json:"expiration"`
		Conditions []interface{} `json:"conditions"`
	}

	d.DisallowUnknownFields()
	if err := d.Decode(&rawPolicy); err != nil {
		return PostPolicyForm{}, err
	}

	parsedPolicy := PostPolicyForm{}

	// Parse expiry time.