4 ms·
So, what's an embedded system supposed to do when it can't reach its NTP server and needs to validate a cert?
by c3833174 10y ago
So, what's an embedded system supposed to do when it can't reach its NTP server and needs to validate a cert?
- rocqua 10y agoPresume the cert is wrong. If your system can't handle that, a few options: - put a clock in your embedded element - Pin certs - Use a frontend, embedded only connects to authenticated embedded system (say, with ssh Port forwarding). Frontend does connection correctly.
- lvh 10y agoAs usual: it depends. Why does it need to validate a cert? How acceptable is it if you get it wrong? Depending on the answer, perhaps "have a more reliable clock" is the right answer (plenty of embedded devices certainly have a decent idea of what time it is, and if it's already big enough to validate TLS). It seems reasonably probable that the NTP server stops being available for a reasonable amount of time before you have no idea what time it is anymore and can no longer validate certificates; so depending on the device, telemetry might be a good idea too. It doesn't sound like a reason to give up, though :)
- c3833174 10y agoWhat I meant is: - Device is rebooted - Can't reach NTP, no RTC or dead RTC battery, happy that time is January 1st, 1970 - HTTPS breaks
- yjftsjthsd-h 10y agoYou can reach a web host but not NTP? That seems like an edge case.
- Senji 10y agoAsk the user for the time.
- Aldo_MX 10y ago> What time is it? Jan 2nd, 2017 > Sorry, your certificate is expired. Access Denied. Wait, I wrote the wrong date, it's Jan 2nd, 2016 > Ok. Authorized
- tscs37 10y agoI mean, it kinda sounds and looks silly, but if you want to bootstrap security, it should do. Atleast I can't think of a better way to get time from a server with a cert.