[type/__uci] Check __object_id for syntax errors

cdist/conf/type/__uci/gencode-local

@@ -48,8 +48,53 @@ uci_cmd() {
 	printf ' >>%s\n' "$(quote "${tmpfile}")"
 }
 
+uci_validate_name() {
+	# like util.c uci_validate_name()
+	test -n "$*" && test -z "$(echo "$*" | tr -d '[:alnum:]_')"
+}
+
+uci_validate_tuple() (
+	tok=${1:?}
+	case $tok
+	in
+		(*.*.*)
+			# check option
+			option=${tok##*.}
+			uci_validate_name "${option}" || {
+				printf 'Invalid option: %s\n' "${option}" >&2
+				return 1
+			}
+			tok=${tok%.*}
+			;;
+		(*.*)
+			# no option (section definition)
+			;;
+		(*)
+			printf 'Invalid tuple: %s\n' "$1" >&2
+			return 1
+			;;
+	esac
+
+	case ${tok#*.}
+	in
+		(@*) section=$(expr "${tok#*.}" : '@\(.*\)\[-*[0-9]*\]$') ;;
+		(*)  section=${tok#*.} ;;
+	esac
+	uci_validate_name "${section}" || {
+		printf 'Invalid section: %s\n' "${1#*.}" >&2
+		return 1
+	}
+
+	config=${tok%%.*}
+	uci_validate_name "${config}" || {
+		printf 'Invalid config: %s\n' "${config}" >&2
+		return 1
+	}
+)
+
 
 config=${__object_id:?}
+uci_validate_tuple "${config}"
 
 state_is=$(cat "${__object:?}/explorer/state")
 state_should=$(cat "${__object:?}/parameter/state")