this post was submitted on 20 Sep 2023
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Privacy
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From what I read in the article, there is still one part of the boot sequence that does require some sort of storage: the part where the bootloader fetches the network boot image and verifies it against the checksum signature. But I think that can be performed by booting from a pendrive and then removing it. The problem will come if law enforcement gets a hold of said pendrive...
Why would that be a problem? A boot image should only contain the commands to get the main system started after POST. It shouldn't contain any kind of logs, traffic data, or user data. In fact it should be read-only.
PXE boot will TFTP the boot image into RAM and carry on from there. You shouldn't need any storage on your device.
I'm aware of PXE, but in order to do so you need either of:
Since the first mode is probably too unsafe, that leaves us with the second mode. Either the operator memorizes a specific IP address and types it into the BIOS each time the server is rebooted, or the IP address (and possibly the checksum of the image) are stored in a single-use pendrive that the operator carries. I wonder which of these two methods is used in this case.
PXE is automagic being basically kind of hacky extension to DHCP stuff.
If PXE is enabled the machine will automatically find it via a DHCP relay on the network.
Why do you think that's unsafe?
I’ve never done this, but I believe server network cards can be configured for PXE automatically so
Bios -> network card -> PXE over network
So the storage is in the bios config, and then I guess the network card has its own kind of bios?
So there is still one single damning piece of information stored in the servers after all - the IP address to fetch the PXE boot image from. But hey, if Mullvad finds a way to strip even that out of the servers, that'd be great
Why is it damning?
Because by knowing which IP is the boot image stored from, law enforcement can locate the source of the unencrypted image, thus making the scheme lose its privacy. The only way to bypass the issue is by manually configuring the IP after every reboot and keeping it a secret.
Why does being able to access the unencrypted image pose such a problem?
Because by doing so, law enforcement can manipulate the image from the source by:
Unless, of course, the BIOS stores the checksum of the untainted image. (Which adds its own can of worms, because that would make legitimate image upgrades require writing the new proper checksum on each server)
Boot Drive could be immutable and not contain any form of log?
Destroy the drive. That’s what Apple does and how they get around the whole “we need a backdoor” problem. When no one can access the server, no more problems.
Something tells me that they have a stack of single-use drives so that each time a server needs to reboot for some reason, they write a boot loader in one from their central headquarters, walk back to the server room, use the device to boot the server, and finally hammer the everliving bejeezus out of the thumb drive juuuuust in case. Hopefully they don't have to reboot that often!
What tells you that?
something