linux-kernel - Re: [PATCH 07/24] hibernate: Disable when the kernel is locked down

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Message-ID: <CALCETrWnucpY8VueVh==ZGo8LpvVBpppoK6MLwW188A89TwzQQ@mail.gmail.com>
Date:   Sun, 22 Apr 2018 07:34:43 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Pavel Machek <pavel@....cz>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-man <linux-man@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        LKML <linux-kernel@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH 07/24] hibernate: Disable when the kernel is locked down

On Thu, Apr 19, 2018 at 7:38 AM, David Howells <dhowells@...hat.com> wrote:
> Pavel Machek <pavel@....cz> wrote:
>
>> > There is currently no way to verify the resume image when returning
>> > from hibernate.  This might compromise the signed modules trust model,
>> > so until we can work with signed hibernate images we disable it when the
>> > kernel is locked down.
>>
>> I'd rather see hibernation fixed than disabled like this.
>
> The problem is that you have to store the hibernated kernel image encrypted,
> but you can't store the decryption key on disk unencrypted or you've just
> wasted the effort.
>
> So the firmware has to unlock the image, asking the user for a password to
> unlock the key.

Why firmware?

Either the boot kernel could figure out how to ask for a password (or
unseal using the TPM) or we could defer this to userspace.  The latter
should already work using kexec-jump, no?