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squarooticus / efi-measured-boot

Measured Boot for TPM 2.0-enabled UEFI Debian Systems
MIT License
17 stars 2 forks source link

Further idiot-proof the kernel update process #8

Open squarooticus opened 2 years ago

squarooticus commented 2 years ago

Use a two-phase commit to update the token for a particular loader without crippling the automated boot after some common classes of errors by: preserving the old token while creating a new token from the new loader written to a different filename; moving the new loader over the original loader, ensuring both are bootable regardless of which "wins"; and then deleting the old token once the new loader is definitely in place.

squarooticus commented 2 years ago

Similarly, seal a loader to counter+1 and put it in place prior to actually incrementing the counter.

squarooticus commented 2 years ago

Keep in mind that +1 doesn't actually work because for a TPM "increment" really means "highest value of any counter + 1", and could be arbitrarily higher.