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Are boot.img, initrd, and vmlinuz adequate or should the entire contents be hashed? I am not familiar enough with the Linux boot process to answer this with confidence myself.

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I'm not qualified to answer, but I'd imagine that you would additionally need to validate the boot sector to prevent an alternative boot sequence being used. I expect that you would ideally want to hash and check everything except the LUKS encrypted partition. Of-course, this won't help if someone can plant a hardware key logger. –  davidgo Aug 4 '13 at 1:53

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The safe bet would be to hash all files on /boot (the kernel, system map, MBR and the boot loader configuration) - however who is to say the evil maid won't simply just replace the hashes? So now you need to implement GPG so you can sign & verify the hash file. But what if the evil maid subverts GPG?? Arghhh ...

So, I suggest if you're really worried about that evil maid, a better solution is to keep /boot on a removable keychain type USB device on your belt. It's only needed to boot after all. I use a nifty one on an elastic tether thingy.

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