linux-kernel - Re: [PATCH 2/2] dm crypt: support using trusted keys

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Date:   Fri, 22 Jan 2021 20:04:46 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Song Liu <song@...nel.org>, kernel@...gutronix.de,
        Jan Lübbe <jlu@...gutronix.de>,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        Dmitry Baryshkov <dbaryshkov@...il.com>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        Sumit Garg <sumit.garg@...aro.org>
Subject: Re: [PATCH 2/2] dm crypt: support using trusted keys

Hello Jarkko,

On 22.01.21 19:18, Jarkko Sakkinen wrote:
> On Fri, Jan 22, 2021 at 08:05:51PM +0200, Jarkko Sakkinen wrote:
>> On Fri, Jan 22, 2021 at 09:43:21AM +0100, Ahmad Fatoum wrote:
>>> Commit 27f5411a718c ("dm crypt: support using encrypted keys") extended
>>> dm-crypt to allow use of "encrypted" keys along with "user" and "logon".
>>>
>>> Along the same lines, teach dm-crypt to support "trusted" keys as well.
>>>
>>> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
>>> ---
>>
>> Is it possible to test run this with tmpfs? Would be a good test
>> target for Sumit's ARM-TEE trusted keys patches.

I tested these on top of Sumit's patches with TPM and a CAAM blobifier
backend, I am preparing. The system I am developing these patches against
doesn't have a TEE.  Steps to test these changes:

#!/bin/sh

DEV=/dev/loop0
ALGO=aes-cbc-essiv:sha256
KEYNAME=kmk
BLOCKS=20

fallocate -l $((BLOCKS*512)) /tmp/loop0.img
losetup -P $DEV /tmp/loop0.img
mount -o remount,rw /
KEY="$(keyctl add trusted $KEYNAME 'new 32' @s)"
keyctl pipe $KEY >$HOME/kmk.blob

TABLE="0 $BLOCKS crypt $ALGO :32:trusted:$KEYNAME 0 $DEV 0 1 allow_discards"
echo $TABLE | dmsetup create mydev
echo $TABLE | dmsetup load mydev
dd if=/dev/zero of=/dev/mapper/mydev
echo "It works!" 1<> /dev/mapper/mydev
cryptsetup close mydev

reboot

DEV=/dev/loop0
ALGO=aes-cbc-essiv:sha256
KEYNAME=kmk
BLOCKS=20

losetup -P $DEV $HOME/loop0.img
keyctl add trusted $KEYNAME "load $(cat $HOME/kmk.blob)" @s
TABLE="0 $BLOCKS crypt $ALGO :32:trusted:$KEYNAME 0 $DEV 0 1 allow_discards"
echo $TABLE | dmsetup create mydev
echo $TABLE | dmsetup load mydev

# should print that It works!
hexdump -C /dev/mapper/mydev

>> https://lore.kernel.org/linux-integrity/1604419306-26105-1-git-send-email-sumit.garg@linaro.org/
> 
> Also, I would hold merging *this* patch up until we are able to
> test TEE trusted keys with TEE trusted keys.

Which blocks which? I tested this with TPM-Trusted keys, so it's usable
as is. For convenient usage, it would be nice to have cryptsetup
support for trusted and encrypted keys. I intended to look at this next week.

Cheers,
Ahmad

> 
> /Jarkko
> 

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