#261: Allow 'Generic' as serial valueu

doc/CONFIGURATION

@@ -103,7 +103,7 @@ The syntax is the following:
 | `volume_uuid` | Element   | UUID of the device's volume used to store pads | `6F6B-42FC`            |
 
 ### Note:
-Some cheap devices don't report a vendor and/or model. To use these devices you can use "Generic" for these values, then it won't be checked.
+Some cheap devices don't report a vendor and/or model, some not even a serial (see https://github.com/mcdope/pam_usb/issues/261). To use these devices you can use "Generic" for these values, then it won't be checked.
 Be aware that this reduces security if you have `one_time_pads` disabled since the device containing the volume won't be checked anymore (but these attributes could be faked with a custom firmware anyway).
 
 ### Example:

src/device.c

@@ -50,7 +50,11 @@ static int pusb_device_connected(t_pusb_options *opts, UDisksClient *udisks)
 			if (udisks_object_peek_drive(object))
 			{
 				drive = udisks_object_get_drive(object);
-				retval = strcmp(udisks_drive_get_serial(drive), opts->device_list[currentDevice].serial) == 0;
+
+				if (strcmp(opts->device_list[currentDevice].serial, "Generic") != 0)
+				{
+					retval = strcmp(udisks_drive_get_serial(drive), opts->device_list[currentDevice].serial) == 0;
+				}
 
 				if (strcmp(opts->device_list[currentDevice].vendor, "Generic") != 0)
 				{