With a timestamp, as long as the signing date was within the signing cert's validity period, the signed driver continues to be trusted beyond the signing certificate expiration.
If the driver was valid when it was signed, then revoking it will break the system. Not installing it is another story.
how so? it merely limits which dates you can sign code, after which the code you signed remain valid, but you can't sign any more code.
The whole problem here is that the code that was signed is not being treated as valid code beyond the expiration date.
Ideally it's not used except by the timestamp service, but it seems like a fairly reasonable fallback.
The fact that the driver was installed locally before the expiration should be taken as proof that the driver was signed before expiration.
You could look at the system clock but that was not designed to be secure for this purpose.
If you think I'm proposing any changes to how drivers are installed, then you have misread me. I'm proposing a change to how already-installed drivers are handled: absent any new information, the code that was trusted yesterday should be trusted today, and be allowed to keep running.
You could say that any damage has already been done which is most likely true. But I can't fault them from mitigating it as much as possible.
I suppose you could modify the system to get external attestation of the time while the driver is installed and use that as a sticky bit - but its a big complication and its much better if the driver is securely timestamped in the first place.
The only way that the system "knows better" is by acquiring something like a certificate revocation list. The system does not know whether it was powered down for five minutes while the network outage was fixed, or for five years. When the system is powered back on with a working internet connection, it does not have any reliable way to tell whether the offline installation of the network driver occurred prior to the expiration, or after the expiration with a properly backdated driver and backdated system clock. There is no way to justify suddenly de-trusting a driver that's already been running simply by observing that you're in the future.
I guess I don’t know the time when Microsoft has their code and heir contact information and is doing some kind of preflight check, or if that ever actually happens, and there are already so many ways to be very dumb with drivers...