lkml.org 
[lkml]   [2021]   [Feb]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: Migration to trusted keys: sealing user-provided key?
From
Date
On Mon, 2021-02-01 at 11:36 +0000, David Howells wrote:
> Jan Lübbe <jlu@pengutronix.de> wrote:
>
> > ... But at this point, you can still do 'keyctl read' on that key, exposing
> > the key material to user space.
>
> I wonder if it would help to provide a keyctl function to mark a key as being
> permanently unreadable - so that it overrides the READ permission bit.
>
> Alternatively, you can disable READ and SETATTR permission - but that then
> prevents you from removing other perms if you want to :-/

That would mean using user type keys, right? Then we'd still have the core
problem how a master key can be protected against simply reading it from
flash/disk, as it would be unencrypted in this scenario.


Maybe a bit of background:

We're looking at the trusted/encrypted keys because we want to store the key
material in an encrypted format, only loadable into the same system where they
were generated and only if that's in a trusted state (to solve the master key
problem above).

This binding can be done with trusted keys via a TPM (and soon with Sumit's OP-
TEE backend, or later based on SoC-specific hardware like NXP's CAAM). In the
OP-TEE/CAAM case, the bootloader would ensure that the backend can only be used
when booting a correctly authenticated kernel.

Of course, that's not as flexible as TPMs with a custom policy, but much simpler
and a good fit for many embedded use-cases.

Best regards,
Jan Lübbe
--
Pengutronix e.K. | |
Steuerwalder Str. 21 | http://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |

\
 
 \ /
  Last update: 2021-02-01 16:55    [W:0.115 / U:0.416 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site