fix: validate cached property access

device.go

@@ -498,7 +498,24 @@ type cacheMethod struct {
 
 type propertyCache struct {
 	PropertySpec
-	Method cacheMethod `json:"method"`
+	Method    cacheMethod `json:"method"`
+	rwPresent bool
+}
+
+func (cache *propertyCache) UnmarshalJSON(data []byte) error {
+	type propertyCacheAlias propertyCache
+	decoded := struct {
+		*propertyCacheAlias
+		RW *string `json:"rw"`
+	}{propertyCacheAlias: (*propertyCacheAlias)(cache)}
+	if err := json.Unmarshal(data, &decoded); err != nil {
+		return err
+	}
+	cache.rwPresent = decoded.RW != nil
+	if decoded.RW != nil {
+		cache.RW = *decoded.RW
+	}
+	return nil
 }
 
 type actionCache struct {
@@ -536,6 +553,9 @@ func decodeDeviceInfo(data []byte, model string) (DeviceInfo, error) {
 
 	info := DeviceInfo{Name: cache.Name, Model: cache.Model}
 	for _, cachedProperty := range cache.Properties {
+		if !cachedProperty.rwPresent {
+			return DeviceInfo{}, fmt.Errorf("property %q is missing access metadata", cachedProperty.Name)
+		}
 		property := cachedProperty.PropertySpec
 		if property.SIID == 0 {
 			property.SIID = cachedProperty.Method.SIID
@@ -572,7 +592,7 @@ func validateDeviceInfo(info *DeviceInfo, model string) error {
 	properties := make(map[propertyID]PropertySpec, len(info.Properties))
 	for index, property := range info.Properties {
 		if strings.TrimSpace(property.Name) == "" || !validPropertyType(property.Type) ||
-			(property.RW != "r" && property.RW != "w" && property.RW != "rw") || property.SIID <= 0 || property.PIID <= 0 {
+			(property.RW != "" && property.RW != "r" && property.RW != "w" && property.RW != "rw") || property.SIID <= 0 || property.PIID <= 0 {
 			return fmt.Errorf("property %d is invalid", index)
 		}
 		properties[propertyID{siid: property.SIID, piid: property.PIID}] = property