secret-file-collection: Check for file changes and reload when needed

When some other process changes the underlying file, the collection
should reload its in-memory content, to reflect the changes.

Closes https://gitlab.gnome.org/GNOME/libsecret/-/issues/62

libsecret/secret-file-collection.c

@@ -54,6 +54,7 @@ struct _SecretFileCollection
 	guint64 usage_count;
 	GBytes *key;
 	GVariant *items;
+	guint64 file_last_modified;
 };
 
 static void secret_file_collection_async_initable_iface (GAsyncInitableIface *iface);
@@ -68,6 +69,22 @@ enum {
 	PROP_PASSWORD
 };
 
+static guint64
+get_file_last_modified (SecretFileCollection *self)
+{
+	GFileInfo *info;
+	guint64 res;
+
+	info = g_file_query_info (self->file, G_FILE_ATTRIBUTE_TIME_MODIFIED, G_FILE_QUERY_INFO_NONE, NULL, NULL);
+	if (info == NULL)
+		return 0;
+
+	res = g_file_info_get_attribute_uint64 (info, G_FILE_ATTRIBUTE_TIME_MODIFIED);
+	g_object_unref (info);
+
+	return res;
+}
+
 static gboolean
 do_derive_key (SecretFileCollection *self)
 {
@@ -296,17 +313,13 @@ secret_file_collection_class_init (SecretFileCollectionClass *klass)
 	egg_libgcrypt_initialize ();
 }
 
-static void
+static gboolean
-on_load_contents (GObject *source_object,
+load_contents (SecretFileCollection *self,
-		  GAsyncResult *result,
+	       gchar *contents, /* takes ownership */
-		  gpointer user_data)
+	       gsize length,
+	       GError **error)
 {
-	GFile *file = G_FILE (source_object);
-	GTask *task = G_TASK (user_data);
-	SecretFileCollection *self = g_task_get_source_object (task);
-	gchar *contents;
 	gchar *p;
-	gsize length;
 	GVariant *variant;
 	GVariant *salt_array;
 	guint32 salt_size;
@@ -315,70 +328,25 @@ on_load_contents (GObject *source_object,
 	guint64 usage_count;
 	gconstpointer data;
 	gsize n_data;
-	GError *error = NULL;
-	gboolean ret;
-
-	ret = g_file_load_contents_finish (file, result,
-					   &contents, &length,
-					   &self->etag,
-					   &error);
-
-	if (!ret) {
-		if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND)) {
-			GVariantBuilder builder;
-			guint8 salt[SALT_SIZE];
-
-			g_clear_error (&error);
-
-			gcry_create_nonce (salt, sizeof(salt));
-			self->salt = g_bytes_new (salt, sizeof(salt));
-			self->iteration_count = ITERATION_COUNT;
-			self->modified = g_date_time_new_now_utc ();
-			self->usage_count = 0;
-
-			if (!do_derive_key (self)) {
-				g_task_return_new_error (task,
-							 SECRET_ERROR,
-							 SECRET_ERROR_PROTOCOL,
-							 "couldn't derive key");
-				g_object_unref (task);
-				return;
-			}
-
-			g_variant_builder_init (&builder,
-						G_VARIANT_TYPE ("a(a{say}ay)"));
-			self->items = g_variant_builder_end (&builder);
-			g_variant_ref_sink (self->items);
-			g_task_return_boolean (task, TRUE);
-			g_object_unref (task);
-			return;
-		}
-
-		g_task_return_error (task, error);
-		g_object_unref (task);
-		return;
-	}
 
 	p = contents;
 	if (length < KEYRING_FILE_HEADER_LEN ||
 	    memcmp (p, KEYRING_FILE_HEADER, KEYRING_FILE_HEADER_LEN) != 0) {
-		g_task_return_new_error (task,
+		g_set_error_literal (error,
-					 SECRET_ERROR,
+				     SECRET_ERROR,
-					 SECRET_ERROR_INVALID_FILE_FORMAT,
+				     SECRET_ERROR_INVALID_FILE_FORMAT,
-					 "file header mismatch");
+				     "file header mismatch");
-		g_object_unref (task);
+		return FALSE;
-		return;
 	}
 	p += KEYRING_FILE_HEADER_LEN;
 	length -= KEYRING_FILE_HEADER_LEN;
 
 	if (length < 2 || *p != MAJOR_VERSION || *(p + 1) != MINOR_VERSION) {
-		g_task_return_new_error (task,
+		g_set_error_literal (error,
-					 SECRET_ERROR,
+				     SECRET_ERROR,
-					 SECRET_ERROR_INVALID_FILE_FORMAT,
+				     SECRET_ERROR_INVALID_FILE_FORMAT,
-					 "version mismatch");
+				     "version mismatch");
-		g_object_unref (task);
+		return FALSE;
-		return;
 	}
 	p += 2;
 	length -= 2;
@@ -407,19 +375,125 @@ on_load_contents (GObject *source_object,
 	g_assert (n_data == salt_size);
 
 	self->salt = g_bytes_new (data, n_data);
-	if (!do_derive_key (self)) {
-		g_task_return_new_error (task,
-					 SECRET_ERROR,
-					 SECRET_ERROR_PROTOCOL,
-					 "couldn't derive key");
-		goto out;
-	}
 
-	g_task_return_boolean (task, TRUE);
-
- out:
 	g_variant_unref (salt_array);
 	g_variant_unref (variant);
+
+	if (!do_derive_key (self)) {
+		g_set_error_literal (error,
+				     SECRET_ERROR,
+				     SECRET_ERROR_PROTOCOL,
+				     "couldn't derive key");
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
+static gboolean
+init_empty_file (SecretFileCollection *self,
+		 GError **error)
+{
+	GVariantBuilder builder;
+	guint8 salt[SALT_SIZE];
+
+	gcry_create_nonce (salt, sizeof(salt));
+	self->salt = g_bytes_new (salt, sizeof(salt));
+	self->iteration_count = ITERATION_COUNT;
+	self->modified = g_date_time_new_now_utc ();
+	self->usage_count = 0;
+
+	if (!do_derive_key (self)) {
+		g_set_error_literal (error,
+				     SECRET_ERROR,
+				     SECRET_ERROR_PROTOCOL,
+				     "couldn't derive key");
+		return FALSE;
+	}
+
+	g_variant_builder_init (&builder,
+				G_VARIANT_TYPE ("a(a{say}ay)"));
+	self->items = g_variant_builder_end (&builder);
+	g_variant_ref_sink (self->items);
+
+	return TRUE;
+}
+
+static void
+ensure_up_to_date (SecretFileCollection *self)
+{
+	guint64 last_modified;
+
+	last_modified = get_file_last_modified (self);
+	if (last_modified != self->file_last_modified) {
+		gchar *contents = NULL;
+		gsize length = 0;
+		gboolean success;
+		GError *error = NULL;
+
+		self->file_last_modified = last_modified;
+		g_clear_pointer (&self->etag, g_free);
+
+		success = g_file_load_contents (self->file, NULL, &contents, &length, &self->etag, &error);
+
+		if (!success && g_error_matches (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND)) {
+			g_clear_error (&error);
+
+			success = init_empty_file (self, &error);
+		}
+
+		if (success)
+			success = load_contents (self, contents, length, &error);
+
+		if (!success)
+			g_debug ("Failed to load file contents: %s", error ? error->message : "Unknown error");
+
+		g_clear_error (&error);
+	}
+}
+
+static void
+on_load_contents (GObject *source_object,
+		  GAsyncResult *result,
+		  gpointer user_data)
+{
+	GFile *file = G_FILE (source_object);
+	GTask *task = G_TASK (user_data);
+	SecretFileCollection *self = g_task_get_source_object (task);
+	gchar *contents;
+	gsize length;
+	GError *error = NULL;
+	gboolean ret;
+
+	self->file_last_modified = get_file_last_modified (self);
+
+	ret = g_file_load_contents_finish (file, result,
+					   &contents, &length,
+					   &self->etag,
+					   &error);
+
+	if (!ret) {
+		if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND)) {
+			g_clear_error (&error);
+
+			if (init_empty_file (self, &error)) {
+				g_task_return_boolean (task, TRUE);
+				g_object_unref (task);
+				return;
+			}
+		}
+
+		g_task_return_error (task, error);
+		g_object_unref (task);
+		return;
+	}
+
+	ret = load_contents (self, contents, length, &error);
+	if (ret)
+		g_task_return_boolean (task, ret);
+	else
+		g_task_return_error (task, error);
+
 	g_object_unref (task);
 }
 
@@ -546,6 +620,8 @@ secret_file_collection_replace (SecretFileCollection *self,
 	GDateTime *created = NULL;
 	GDateTime *modified;
 
+	ensure_up_to_date (self);
+
 	hashed_attributes = hash_attributes (self, attributes);
 	if (!hashed_attributes) {
 		g_set_error (error,
@@ -657,6 +733,8 @@ secret_file_collection_search (SecretFileCollection *self,
 	GVariant *child;
 	GList *result = NULL;
 
+	ensure_up_to_date (self);
+
 	g_variant_iter_init (&iter, self->items);
 	while ((child = g_variant_iter_next_value (&iter)) != NULL) {
 		GVariant *hashed_attributes;
@@ -750,6 +828,8 @@ secret_file_collection_clear (SecretFileCollection *self,
 	GVariant *child;
 	gboolean removed = FALSE;
 
+	ensure_up_to_date (self);
+
 	g_variant_builder_init (&builder, G_VARIANT_TYPE ("a(a{say}ay)"));
 	g_variant_iter_init (&items, self->items);
 	while ((child = g_variant_iter_next_value (&items)) != NULL) {
@@ -791,6 +871,8 @@ on_replace_contents (GObject *source_object,
 		return;
 	}
 
+	self->file_last_modified = get_file_last_modified (self);
+
 	g_task_return_boolean (task, TRUE);
 	g_object_unref (task);
 }