core: disallow using '-.service' as a service name

-.service.d will become a special top level drop in so don't let it be a
usable service name (otherwise the interaction gets complicated).

3 files changed, 31 insertions, 0 deletions

diff --git a/src/basic/special.h b/src/basic/special.h
index add1c1d507..6475501078 100644
--- a/src/basic/special.h
+++ b/src/basic/special.h
@@ -105,3 +105,7 @@
 
 /* The root directory. */
 #define SPECIAL_ROOT_MOUNT "-.mount"
+
+/* Used to apply settings to all services through drop-ins.
+ * Should not exist as an actual service. */
+#define SPECIAL_ROOT_SERVICE "-.service"
diff --git a/src/basic/unit-name.c b/src/basic/unit-name.c
index 4226f3014d..ecbf5ae7f5 100644
--- a/src/basic/unit-name.c
+++ b/src/basic/unit-name.c
@@ -665,6 +665,31 @@ good:
         return 0;
 }
 
+bool service_unit_name_is_valid(const char *name) {
+        _cleanup_free_ char *prefix = NULL, *s = NULL;
+        const char *e, *service_name = name;
+
+        if (!unit_name_is_valid(name, UNIT_NAME_ANY))
+                return false;
+
+        e = endswith(name, ".service");
+        if (!e)
+                return false;
+
+        /* If it's a template or instance, get the prefix as a service name. */
+        if (unit_name_is_valid(name, UNIT_NAME_INSTANCE|UNIT_NAME_TEMPLATE)) {
+                assert_se(unit_name_to_prefix(name, &prefix) == 0);
+                assert_se(s = strjoin(prefix, ".service"));
+                service_name = s;
+        }
+
+        /* Reject reserved service name(s). */
+        if (streq(service_name, SPECIAL_ROOT_SERVICE))
+                return false;
+
+        return true;
+}
+
 int slice_build_parent_slice(const char *slice, char **ret) {
         char *s, *dash;
         int r;
diff --git a/src/basic/unit-name.h b/src/basic/unit-name.h
index 2e060ff3e8..ddcfc1b349 100644
--- a/src/basic/unit-name.h
+++ b/src/basic/unit-name.h
@@ -58,6 +58,8 @@ static inline int unit_name_mangle(const char *name, UnitNameMangle flags, char
         return unit_name_mangle_with_suffix(name, flags, ".service", ret);
 }
 
+bool service_unit_name_is_valid(const char *name);
+
 int slice_build_parent_slice(const char *slice, char **ret);
 int slice_build_subslice(const char *slice, const char *name, char **subslice);
 bool slice_name_is_valid(const char *name);