lib/commit: reject empty metadata keys

This adds one more check to the metadata validation logic in order
to reject empty metadata keys.

src/libostree/ostree-core.c

@@ -2197,6 +2197,19 @@ ostree_validate_structureof_commit (GVariant      *commit,
   if (!validate_variant (commit, OSTREE_COMMIT_GVARIANT_FORMAT, error))
     return FALSE;
 
+  g_autoptr(GVariant) metadata = NULL;
+  g_variant_get_child (commit, 0, "@a{sv}", &metadata);
+  g_assert (metadata != NULL);
+  g_autoptr(GVariantIter) metadata_iter = g_variant_iter_new (metadata);
+  g_assert (metadata_iter != NULL);
+  g_autoptr(GVariant) metadata_entry = NULL;
+  const gchar *metadata_key = NULL;
+  while (g_variant_iter_loop (metadata_iter, "{sv}", &metadata_key, NULL))
+    {
+      if (metadata_key == NULL || strlen (metadata_key) == 0)
+        return glnx_throw (error, "Empty metadata key");
+    }
+
   g_autoptr(GVariant) parent_csum_v = NULL;
   g_variant_get_child (commit, 1, "@ay", &parent_csum_v);
   gsize n_elts;

src/ostree/ot-builtin-commit.c

@@ -335,17 +335,18 @@ parse_keyvalue_strings (GVariantBuilder   *builder,
       if (!eq)
         return glnx_throw (error, "Missing '=' in KEY=VALUE metadata '%s'", s);
       g_autofree char *key = g_strndup (s, eq - s);
+      const char *value = eq + 1;
       if (is_gvariant_print)
         {
-          g_autoptr(GVariant) value = g_variant_parse (NULL, eq + 1, NULL, NULL, error);
-          if (!value)
+          g_autoptr(GVariant) variant = g_variant_parse (NULL, value, NULL, NULL, error);
+          if (!variant)
             return glnx_prefix_error (error, "Parsing %s", s);
 
-          g_variant_builder_add (builder, "{sv}", key, value);
+          g_variant_builder_add (builder, "{sv}", key, variant);
         }
       else
         g_variant_builder_add (builder, "{sv}", key,
-                               g_variant_new_string (eq + 1));
+                               g_variant_new_string (value));
     }
 
   return TRUE;