synaptics: Encode metadata into userid string

This allows us to properly extract metadata for prints that are stored
on the device. We could for example delete the oldest prints first with
this information.

libfprint/drivers/synaptics/synaptics.c

@@ -34,25 +34,6 @@ static const FpIdEntry id_table [ ] = {
 };
 
 
-static gboolean rand_string(char *str, size_t size)
-{
-    const char charset[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
-	srand(time(NULL));
-    if (size) {
-        --size;
-        for (size_t n = 0; n < size; n++) {
-            int key = rand() % (int) (sizeof charset - 1);
-            str[n] = charset[key];
-        }
-        str[size] = '\0';
-    }
-	else
-		return FALSE;
-    return TRUE;
-}
-
-
-
 static void
 cmd_recieve_cb (FpiUsbTransfer *transfer,
 		FpDevice *device,
@@ -470,6 +451,7 @@ list_msg_cb(FpiDeviceSynaptics *self,
 				GVariant *data = NULL;
 				GVariant *uid = NULL;
 				FpPrint *print;
+				gchar *userid;
 
 				if (get_enroll_templates_resp->templates[n].user_id_len == 0)
 					continue;
@@ -482,6 +464,8 @@ list_msg_cb(FpiDeviceSynaptics *self,
 					get_enroll_templates_resp->templates[n].user_id,
 					get_enroll_templates_resp->templates[n].finger_id);
 
+				userid = get_enroll_templates_resp->templates[n].user_id;
+
 				print = fp_print_new (FP_DEVICE (self));
 				uid = g_variant_new_fixed_array (G_VARIANT_TYPE_BYTE,
 								 get_enroll_templates_resp->templates[n].user_id,
@@ -494,6 +478,41 @@ list_msg_cb(FpiDeviceSynaptics *self,
 				fpi_print_set_type (print, FP_PRINT_RAW);
 				g_object_set (print, "fp-data", data, NULL);
 				g_object_set (print, "description", get_enroll_templates_resp->templates[n].user_id, NULL);
+
+				/* The format has 24 bytes at the start and some dashes in the right places */
+				if (g_str_has_prefix (userid, "FP1-") && strlen(userid) >= 24 &&
+				    userid[12] == '-' && userid[14] == '-' && userid[23] == '-') {
+					g_autofree gchar *copy = g_strdup(userid);
+					gint32 date_ymd;
+					GDate *date = NULL;
+					gint32 finger;
+					gchar *username;
+					/* Try to parse information from the string. */
+
+					copy[12] = '\0';
+					date_ymd = g_ascii_strtod (copy + 4, NULL);
+					if (date_ymd > 0)
+						date = g_date_new_dmy (date_ymd % 100,
+						                       (date_ymd / 100) % 100,
+						                       date_ymd / 10000);
+					else
+						date = g_date_new ();
+
+					fp_print_set_enroll_date (print, date);
+					g_date_free (date);
+
+					copy[14] = '\0';
+					finger = g_ascii_strtoll (copy + 13, NULL, 16);
+					fp_print_set_finger (print, finger);
+
+					/* We ignore the next chunk, it is just random data.
+					 * Then comes the username; nobody is the default if the metadata
+					 * is unknown */
+					username = copy + 24;
+					if (strlen(username) > 0 && g_strcmp0 (username, "nobody") != 0)
+						fp_print_set_username (print, username);
+				}
+
 				g_ptr_array_add (self->list_result, g_object_ref_sink (print));
 			}
 
@@ -709,18 +728,50 @@ enroll(FpDevice *device)
 	FpPrint *print = NULL;
 	GVariant *data = NULL;
 	GVariant *uid = NULL;
-	guint8 finger;
-	char user_id[TEMPLATE_ID_SIZE + 1];
+	const gchar *username;
+	guint finger;
+	g_autofree gchar *user_id;
 	gssize user_id_len;
-	guint8 payload[TEMPLATE_ID_SIZE + 1 + 2];
+	g_autofree guint8 *payload = NULL;
+	const GDate *date;
+	gint y, m, d;
+	gint32 rand_id = 0;
 
 	fpi_device_get_enroll_data (device, &print);
 
 	G_DEBUG_HERE();
 
-	finger = 1;
-	rand_string (user_id, TEMPLATE_ID_SIZE);
+	date = fp_print_get_enroll_date (print);
+	if (date && g_date_valid (date)) {
+		y = date->year;
+		m = date->month;
+		d = date->day;
+	} else {
+		y = 0;
+		m = 0;
+		d = 0;
+	}
+
+	username = fp_print_get_username (print);
+	if (!username)
+		username = "nobody";
+
+	if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+		rand_id = 0;
+	else
+		rand_id = g_random_int();
+
+	user_id = g_strdup_printf ("FP1-%04d%02d%02d-%X-%08X-%s",
+	                           y, m, d,
+	                           fp_print_get_finger (print),
+	                           rand_id,
+	                           username);
+
 	user_id_len = strlen (user_id);
+	user_id_len = MIN(BMKT_MAX_USER_ID_LEN, user_id_len);
+
+	/* We currently always use finger 1 from the devices piont of view */
+	finger = 1;
 
 	uid = g_variant_new_fixed_array (G_VARIANT_TYPE_BYTE,
 					 user_id,
@@ -736,6 +787,8 @@ enroll(FpDevice *device)
 
 	g_debug("user_id: %s, finger: %d", user_id, finger);
 
+	payload = g_malloc0(user_id_len + 2);
+
 	/* Backup options are not supported for Prometheus */
 	payload[0] = 0;
 	payload[1] = finger;