engine: improve robustness of profile parsing

Checking for 'u' or 's' is really insanely silly from a robustness
standpoint.  Ensure that we properly have "user-db:" or "system-db:" and
that a non-empty database name is given, warning if not.

This was specifically causing annoying problems with the profile file
that gdm was installing, so add a copy of that file to our testcases.

2 files changed, 43 insertions, 20 deletions

diff --git a/engine/dconf-engine-profile.c b/engine/dconf-engine-profile.c
index 0413f32..7415406 100644
--- a/engine/dconf-engine-profile.c
+++ b/engine/dconf-engine-profile.c
@@ -100,6 +100,7 @@ dconf_engine_default_profile (gint *n_sources)
 static DConfEngineSource *
 dconf_engine_profile_handle_line (gchar *line)
 {
+  DConfEngineSource *source;
   gchar *end;
 
   /* remove whitespace at the front */
@@ -119,7 +120,12 @@ dconf_engine_profile_handle_line (gchar *line)
 
   *end = '\0';
 
-  return dconf_engine_source_new (line);
+  source = dconf_engine_source_new (line);
+
+  if (source == NULL)
+    g_warning ("unknown dconf database description: %s", line);
+
+  return source;
 }
 
 static DConfEngineSource **
diff --git a/engine/dconf-engine-source.c b/engine/dconf-engine-source.c
index 834644c..2fe58f4 100644
--- a/engine/dconf-engine-source.c
+++ b/engine/dconf-engine-source.c
@@ -76,27 +76,44 @@ dconf_engine_source_new (const gchar *description)
 {
   const DConfEngineSourceVTable *vtable;
   DConfEngineSource *source;
-
-  switch (description[0])
-    {
-    case 's':
-      vtable = &dconf_engine_source_system_vtable;
-      break;
-
-    case 'u':
-      vtable = &dconf_engine_source_user_vtable;
-      break;
-
-    default:
-      g_warning ("unknown dconf database description: %s", description);
-      return NULL;
-    }
-
+  const gchar *colon;
+
+  /* Source descriptions are of the form
+   *
+   *   type:name
+   *
+   * Where type must currently be one of "user-db" or "system-db".
+   *
+   * We first find the colon.
+   */
+  colon = strchr (description, ':');
+
+  /* Ensure that we have a colon and that a database name follows it. */
+  if (colon == NULL || colon[1] == '\0')
+    return NULL;
+
+  /* Check if the part before the colon is "user-db"... */
+  if ((colon == description + 7) && memcmp (description, "user-db", 7) == 0)
+    vtable = &dconf_engine_source_user_vtable;
+
+  /* ...or "system-db" */
+  else if ((colon == description + 9) && memcmp (description, "system-db", 9) == 0)
+    vtable = &dconf_engine_source_system_vtable;
+
+  /* If it's not either of those, we have failed. */
+  else
+    return NULL;
+
+  /* We have had a successful parse.
+   *
+   *  - either user-db: or system-db:
+   *  - non-NULL and non-empty database name
+   *
+   * Create the source.
+   */
   source = g_malloc0 (vtable->instance_size);
   source->vtable = vtable;
-  source->name = strchr (description, ':');
-  if (source->name)
-    source->name = g_strdup (source->name + 1);
+  source->name = g_strdup (colon + 1);
   source->vtable->init (source);
 
   return source;