[PATCH 0/4] KEYS: trusted: Introduce support for NXP CAAM-based trusted keys

Ahmad Fatoum a.fatoum at pengutronix.de
Fri Aug 20 20:36:30 UTC 2021

On 20.08.21 22:20, Tim Harvey wrote:
> On Fri, Aug 20, 2021 at 9:20 AM Ahmad Fatoum <a.fatoum at pengutronix.de> wrote:
>> On 20.08.21 17:39, Tim Harvey wrote:
>>> Thanks for your work!
>>> I've been asked to integrate the capability of using CAAM to
>>> blob/deblob data to an older 5.4 kernel such as NXP's downstream
>>> vendor kernel does [1] and I'm trying to understand how your series
>>> works. I'm not at all familiar with the Linux Key Management API's or
>>> trusted keys. Can you provide an example of how this can be used for
>>> such a thing?
>> Here's an example with dm-crypt:
>>   https://lore.kernel.org/linux-integrity/5d44e50e-4309-830b-79f6-f5d888b1ef69@pengutronix.de/
>> dm-crypt is a bit special at the moment, because it has direct support for
>> trusted keys. For interfacing with other parts of the kernel like ecryptfs
>> or EVM, you have to create encrypted keys rooted to the trusted keys and use
>> those. The kernel documentation has an example:
>>   https://www.kernel.org/doc/html/v5.13/security/keys/trusted-encrypted.html
>> If you backport this series, you can include the typo fix spotted by David.
>> I'll send out a revised series, but given that a regression fix I want to
>> rebase on hasn't been picked up for 3 weeks now, I am not in a hurry.
> Thanks for the reference.
> I'm still trying to understand the keyctl integration with caam. For
> the 'data' param to keyctl you are using tings like 'new <len>' and
> 'load <data>'. Where are these 'commands' identified?

Search for match_table_t in security/keys/trusted-keys/trusted_core.c

> I may still be missing something. I'm using 4.14-rc6 with your series
> and seeing the following:

That's an odd version to backport stuff to..

> # cat /proc/cmdline
> trusted.source=caam
> # keyctl add trusted mykey 'new 32' @s)# create new trusted key named
> 'mykey' of 32 bytes in the session keyring
> 480104283
> # keyctl print 480104283 # dump the key
> keyctl_read_alloc: Unknown error 126
> ^^^ not clear what this is

Not sure what returns -ENOKEY for you. I haven't been using trusted
keys on v4.14, but you can try tracing the keyctl syscall.


> Best regards,
> Tim

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