I agree that secure boot is not a good protection against malware. Even if we consider just dom0 protection, without considering AppVMs:
With systems allowing a limited level of customization (e.g., ChromeOS or Android), this might provide a limited level of protection. It can guarantee that you boot a signed image with a signed root filesystem (see dm-verity). On Android (and probably also on ChromeOS), writable (and thus unverifiable) partitions are usually mounted with nosuid and nothing seems to be executed from them with root privileges, so you are *theoretically* protected. But don't overrate this protection: As soon as some suitable vulnerability is found in the kernel or other privileged component, the malware can root the phone on every boot and even take full control and prevent kernel update (blue pill or chainloading). And even if some vulnerability is impractical for rooting on boot (e.g. it takes hours until winning a race condition), the malware could downgrade the kernel to an older version that has more known vulnerabilities. With system allowing you to install any driver, the first driver that is loaded can contain malware and so on. Qubes is today the latter case. Maybe ITL with some partner could sell laptops restricted to boot some restricted QubesOS only, so one would not be easily able to run unauthorized software in dom0. This would be essentially the first case where secure boot offers a limited security advantage. But I don't think it is worth the work and the restrictions. QubesOS tries to prevent the attacker from getting into dom0 in the first place, which has better benefit than we can get from secure boot. When protecting against evil maid, the situation is different a bit. We assume that the attacker has some limited physical access (e.g., she cannot replace your CPU with some backdoored version), maybe she is just able to boot some custom OS image. So the can modify any content on your HDD/SSD. However: * If she modifies grub or some similar component, she should be caught by AEM. * If she wants to modify something else (e.g., some bash script in dom0), she will need to alter the encrypted drive. While encryption is not generally a good protection against modification (see malleablity of stream ciphers or CBC mode or some other ciphers), it can provide a poor man's authentication if the cipher is not malleable in a much practical way and/or the attacker does not know the position of the file to alter. Worth to mention, this is the main difference from malware running in dom0 that has also access to a mounted filesystem. The problem is: 1. The AEM is not perfect. Various vulnerabilities have been published and I am unsure what level of real protection (i.e., not just obscurity) can it provide. 2. AEM is not for free. When filtering only laptops with TXT+TPM, you have quite limited options, selection will take more time and it will probably result in a more expensive laptop. It is really worth the limited protection? Regards, Vít Šesták 'v6ak' -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/99581bcf-e80b-49c4-9f71-befa1e0b6139%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
