Those using Global Positioning System (GPS) appliances and the open source daemon, GPSD, to obtain time information from these GPS appliances could have experienced problems on Oct. 24, 2021. However, they were warned. On October 21, 2021, the Cybersecurity & Infrastructure Security Agency (CISA) released a warning to Critical Infrastructure (CI) owners and operators, and other users who obtain Coordinated Universal Time (UTC) from GPS devices. A bug in GPSD versions 3.20 (released December 31, 2019) through 3.22 (released January 8, 2021) was identified to possibly rollback the date 1,024 weeks to March 2002. To prevent this, CISA urged users to upgrade to GPSD version 3.23 (released August 8, 2021) or newer.
In addition to GPSD’s extensive use in mobile embedded systems, including the map service on Android phones, it is used in drones, robot submarines, driverless cars and it is increasingly popular in newer generations of manned aircraft, marine navigation systems and military vehicles.
The GPS Week Number Roll Over (WNRO) problem was previously identified as an issue in 2019. Since the week counter in GPS that enables receivers to calculate the appropriate date uses 10 bits, it needs to be reset every 1,024 weeks—about every 20 years. On April 6, 2019, the GPS week counter reset to zero and users were warned. The next predicted occurrence should have been in November 2038. However, earlier in 2021, a bug was discovered in the GPSD code that would cause it to subtract 1024 from the week number on October 24, 2021. When the GPS week number counter is increased to 13 bits, the possibility of another rollover event will not occur for approximately 157 years – unless another bug occurs.
To prevent network timekeeping issues arising from events like the GPS WNRO, Duke Buckner, Director, Strategic Marketing and Business Development in Microchip Technology’s frequency and timing systems business unit, suggests avoiding systems utilizing GPS daemon open-source software. “Microchip’s timekeeping servers are not GPSD-reliant, therefore provide a resilient source of timing for critical networking systems,” says Buckner.
While open source software allows many sensor applications to be easily and inexpensively implemented, one of its drawbacks can be a system bug such as the one encountered in GPSD.