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Re: Protection of boot sector and embedded area

From: Vladimir 'phcoder' Serbinenko
Subject: Re: Protection of boot sector and embedded area
Date: Sun, 27 Sep 2009 14:41:33 +0200
User-agent: Mozilla-Thunderbird (X11/20090701)

James Courtier-Dutton wrote:
> 2009/9/27 Michal Suchanek <address@hidden>:
>> Obviously your encryption solution does not encrypt the linux volume
>> which you boot using the USB stick so it has no reason to be loaded
>> when loading Linux, it can only cause harm by trying to decrypt what
>> is not encrypted.
> You make a assumption that the encryption program would cause harm. It does 
> not.
> One specifies which partitions to encrypt/decrypt and it leaves the rest 
> alone.
It's loaded uselessly. Actually normally there is no reason to encrypt
any of the files grub accesses. But authenticating files is needed.
(encryption doesn't prevent attacker from modifying files)
Encrypting is to keep secret
MAC or signatures is to keep unmodified.
GRUB and most OSes we support are free software so there is no reason to
keep them secret. Even proprietary for kernels you have, the binaries
aren't secret.
There are two reason full disk encryption exists:
1) "I have everything encrypted" is a good confidence-giving sentence
and good for marketing
2) If you encrypt everything you have no risk of forgetting encrypting
something (typical examples: swap, /tmp, /var/tmp). This renders the
approach fool-proof and easy to configure
>> Also as Grub can access the disk drives by various means (BIOS, PCI
>> device driver, ...) the encryption software would have to hijack all
>> these access paths transparently which I can't imagine happening.
> One would obviously need grub to only use BIOS calls and no direct PCI
> device access for it to work together with the whole disc encryption
> program in pre-boot stages. 
The only reason we keep BIOS calls by default is that our own drivers
don't work in all configurations.
> Alternatively, one would have to add
> encryption support into grub itself that is not a good idea.
We have patches to do so. While encrypting a part of bootloader and a
kernel isn't security-improving, it renders encrypted configuration
easier (no need for separate /boot). So I'm favorable to it. Why do you
say it's a bad idea?
Signatures in grub are on todo list.
> I think that maybe being able to install grub into it's own small
> partition instead of the embedded area would be all I would need.
I explained why this "all I need" is problematic
> Kind Regards
> James
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