Re: [PATCH 0/4][RFC v2] Introduce the in-kernel hibernation encryption

Yu Chen
2018-08-06T07:53:51Z

Hi Oliver,
On Thu, Jul 26, 2018 at 09:30:46AM +0200, Oliver Neukum wrote:
> On Di, 2018-07-24 at 00:23 +0800, Yu Chen wrote:
> >
> > Good point, we once tried to generate key in kernel, but people
> > suggest to generate key in userspace and provide it to the
> > kernel, which is what ecryptfs do currently, so it seems this
> > should also be safe for encryption in kernel.
> > https://www.spinics.net/lists/linux-crypto/msg33145.html
> > Thus Chun-Yi's signature can use EFI key and both the key from
> > user space.
>
> Hi,
>
> ecryptfs can trust user space. It is supposed to keep data
> safe while the system is inoperative.
Humm, I did not quite get the point here, let's take fscrypt
for example, the kernel gets user generated key from user space,
and uses per-inode nonce(random bytes) as the master key to
do a KDF(key derivation function) on user provided key, and uses
that key for encryption. We can also added similar mechanism
to generate the key in kernel space but the key should be
original from user's provided key(password derived), because
the security boot/signature mechanism could not cover the case
that, two different users could resume to each other's context
because there isn't any certification during resume if it is
on the same physical hardware.

Best,
Yu
> The whole point of Secure
> Boot is a cryptographic system of trust that does not include
> user space.
>
> I seriously doubt we want to use trusted computing here. So the
> key needs to be generated in kernel space and stored in a safe
> manner. As we have a saolution doing that, can we come to ausable
> synthesis?

>
> Regards
> Oliver
>