device: Load/store persistent data from device

New libfprint version from 1.95.0 will support persistent data that
should be stored. Add support to this to fprintd by storing it into a
separate per-device file on disk.

The data is placed into a 0-persistent subdirectory as it needs to
co-exist with arbirary usernames and those are not permitted to start
with a number.

meson.build

@@ -64,7 +64,7 @@ add_project_arguments(common_cflags, language: 'c')
 host_system = host_machine.system()
 # NOTE: Bump gdbus-codegen min version once we can depend on 2.64!
 glib_min_version = '2.56'
-libfprint_min_version = '1.94.0'
+libfprint_min_version = '1.95.0'
 
 glib_version_def = 'GLIB_VERSION_@0@_@1@'.format(
     glib_min_version.split('.')[0], glib_min_version.split('.')[1])

src/device.c

@@ -232,11 +232,15 @@ G_DEFINE_AUTOPTR_CLEANUP_FUNC (FprintDeviceActionUnset, auto_device_action_unset
 static void
 fprint_device_dispose (GObject *object)
 {
+  g_autoptr(GError) error = NULL;
   FprintDevice *self = (FprintDevice *) object;
   FprintDevicePrivate *priv = fprint_device_get_instance_private (self);
 
   g_hash_table_remove_all (priv->clients);
 
+  if (!store.persistent_data_save (priv->dev, &error))
+    g_warning ("Failed to save persistent data: %s", error->message);
+
   G_OBJECT_CLASS (fprint_device_parent_class)->dispose (object);
 }
 
@@ -374,6 +378,7 @@ on_temperature_changed (FprintDevice *rdev,
 static void
 fprint_device_constructed (GObject *object)
 {
+  g_autoptr(GError) error = NULL;
   FprintDevice *rdev = FPRINT_DEVICE (object);
   FprintDBusDevice *dbus_dev = FPRINT_DBUS_DEVICE (rdev);
   FprintDevicePrivate *priv = fprint_device_get_instance_private (rdev);
@@ -400,6 +405,9 @@ fprint_device_constructed (GObject *object)
                            rdev, G_CONNECT_SWAPPED);
   on_temperature_changed (rdev, NULL, priv->dev);
 
+  if (!store.persistent_data_load (priv->dev, &error))
+    g_warning ("Failed to load persistent data: %s", error->message);
+
   G_OBJECT_CLASS (fprint_device_parent_class)->constructed (object);
 }
 

src/file_storage.c

@@ -40,6 +40,8 @@
 #include "file_storage.h"
 
 #define FILE_STORAGE_PATH "/var/lib/fprint"
+/* Starts with a number as that is not valid in a username */
+#define PERSISTENT_DATA_DIR "0-persistent"
 #define DIR_PERMS 0700
 
 static char *storage_path = NULL;
@@ -353,6 +355,74 @@ file_storage_discover_users (void)
   return list;
 }
 
+gboolean
+file_storage_persistent_data_save (FpDevice *dev, GError **error)
+{
+  g_autofree gchar *dir = NULL;
+  g_autofree gchar *path = NULL;
+  g_autofree guint8 *cur_contents = NULL;
+  g_autofree guint8 *new_contents = NULL;
+  gsize cur_length = 0;
+  gsize new_length = 0;
+
+  if (!fp_device_get_persistent_data (dev, &new_contents, &new_length, error))
+    return FALSE;
+
+  dir = g_build_filename (get_storage_path (), PERSISTENT_DATA_DIR, fp_device_get_driver (dev), NULL);
+  path = g_build_filename (dir, fp_device_get_device_id (dev), NULL);
+
+  if (new_length == 0)
+    {
+      if (g_unlink (path) < 0)
+        {
+          if (errno == ENOENT)
+            return TRUE;
+
+          g_set_error (error,
+                       G_IO_ERROR,
+                       g_io_error_from_errno (errno),
+                       "Failed to delete persistent storage for driver/device %s/%s", fp_device_get_driver (dev), fp_device_get_device_id (dev));
+          return FALSE;
+        }
+      return TRUE;
+    }
+
+  if (g_mkdir_with_parents (dir, DIR_PERMS) < 0)
+    {
+      g_set_error (error,
+                   G_IO_ERROR,
+                   g_io_error_from_errno (errno),
+                   "Failed to create directory for persistent data storage");
+      return FALSE;
+    }
+
+  /* Try to load to avoid writing if that is nothing changed (ignore errors) */
+  g_file_get_contents (path, (char **) &cur_contents, &cur_length, NULL);
+
+  /* Nothing needs to be written. */
+  if (new_length == cur_length && memcmp (new_contents, cur_contents, cur_length) == 0)
+    return TRUE;
+
+  /* Pass over to device */
+  return g_file_set_contents (path, new_contents, new_length, error);
+}
+
+gboolean
+file_storage_persistent_data_load (FpDevice *dev, GError **error)
+{
+  g_autofree gchar *path = NULL;
+  g_autofree gchar *contents;
+  gsize length;
+
+  path = g_build_filename (get_storage_path (), PERSISTENT_DATA_DIR, fp_device_get_driver (dev), fp_device_get_device_id (dev), NULL);
+
+  if (!g_file_get_contents (path, &contents, &length, error))
+    return FALSE;
+
+  /* Pass over to device */
+  return fp_device_set_persistent_data (dev, contents, length, error);
+}
+
 int
 file_storage_init (void)
 {

src/file_storage.h

@@ -31,6 +31,11 @@ int file_storage_print_data_delete (FpDevice   *dev,
                                     FpFinger    finger,
                                     const char *username);
 
+gboolean file_storage_persistent_data_save (FpDevice *dev,
+                                            GError  **error);
+gboolean file_storage_persistent_data_load (FpDevice *dev,
+                                            GError  **error);
+
 int file_storage_init (void);
 
 int file_storage_deinit (void);

src/main.c

@@ -49,6 +49,8 @@ set_storage_file (void)
   store.print_data_save = &file_storage_print_data_save;
   store.print_data_load = &file_storage_print_data_load;
   store.print_data_delete = &file_storage_print_data_delete;
+  store.persistent_data_save = &file_storage_persistent_data_save;
+  store.persistent_data_load = &file_storage_persistent_data_load;
   store.discover_prints = &file_storage_discover_prints;
   store.discover_users = &file_storage_discover_users;
 }

src/storage.h

@@ -31,18 +31,26 @@ typedef int (*storage_print_data_delete)(FpDevice   *dev,
 typedef GSList *(*storage_discover_prints)(FpDevice   *dev,
                                            const char *username);
 typedef GSList *(*storage_discover_users)(void);
+
+typedef int (*storage_persistent_data_save)(FpDevice *dev,
+                                            GError  **error);
+typedef int (*storage_persistent_data_load)(FpDevice *dev,
+                                            GError  **error);
+
 typedef int (*storage_init)(void);
 typedef int (*storage_deinit)(void);
 
 struct storage
 {
-  storage_init              init;
-  storage_deinit            deinit;
-  storage_print_data_save   print_data_save;
-  storage_print_data_load   print_data_load;
-  storage_print_data_delete print_data_delete;
-  storage_discover_prints   discover_prints;
-  storage_discover_users    discover_users;
+  storage_init                 init;
+  storage_deinit               deinit;
+  storage_print_data_save      print_data_save;
+  storage_print_data_load      print_data_load;
+  storage_print_data_delete    print_data_delete;
+  storage_persistent_data_save persistent_data_save;
+  storage_persistent_data_load persistent_data_load;
+  storage_discover_prints      discover_prints;
+  storage_discover_users       discover_users;
 };
 
 typedef struct storage fp_storage;