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

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Message-ID: <2b5b1722-7934-045e-1807-075278041ae7@pengutronix.de>
Date:   Wed, 25 Aug 2021 11:34:00 +0200
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Tim Harvey <tharvey@...eworks.com>
Cc:     David Gstir <david@...ma-star.at>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Jan Luebbe <j.luebbe@...gutronix.de>, keyrings@...r.kernel.org,
        Steffen Trumtrar <s.trumtrar@...gutronix.de>,
        linux-security-module@...r.kernel.org,
        Udit Agarwal <udit.agarwal@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Horia Geantă <horia.geanta@....com>,
        Richard Weinberger <richard@....at>,
        James Morris <jmorris@...ei.org>,
        Eric Biggers <ebiggers@...nel.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Sumit Garg <sumit.garg@...aro.org>,
        James Bottomley <jejb@...ux.ibm.com>,
        Franck LENORMAND <franck.lenormand@....com>,
        David Howells <dhowells@...hat.com>,
        open list <linux-kernel@...r.kernel.org>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        linux-crypto@...r.kernel.org, Sascha Hauer <kernel@...gutronix.de>,
        linux-integrity@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 0/4] KEYS: trusted: Introduce support for NXP CAAM-based
 trusted keys

On 24.08.21 17:23, Tim Harvey wrote:
> On Tue, Aug 24, 2021 at 12:33 AM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
>>
>> On 23.08.21 19:50, Tim Harvey wrote:
>>> On Mon, Aug 23, 2021 at 6:29 AM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
>>>> On 20.08.21 23:19, Tim Harvey wrote:
>>>>> On Fri, Aug 20, 2021 at 1:36 PM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
>>>>>> On 20.08.21 22:20, Tim Harvey wrote:
>>>>> It works for a user keyring but not a session keyring... does that
>>>>> explain anything?
>>>>> # keyctl add trusted mykey 'new 32' @u
>>>>> 941210782
>>>>> # keyctl print 941210782
>>>>> 83b7845cb45216496aead9ee2c6a406f587d64aad47bddc539d8947a247e618798d9306b36398b5dc2722a4c3f220a3a763ee175f6bd64758fdd49ca4db597e8ce328121b60edbba9b8d8d55056be896
>>>>> # keyctl add trusted mykey 'new 32' @s
>>>>> 310571960
>>>>> # keyctl print 310571960
>>>>> keyctl_read_alloc: Unknown error 126
>>>>
>>>> Both sequences work for me.
>>>>
>>>> My getty is started by systemd. I think systemd allocates a new session
>>>> keyring for the getty that's inherited by the shell and the commands I run
>>>> it in. If you don't do that, each command will get its own session key.
>>>>
>>>>> Sorry, I'm still trying to wrap my head around the differences in
>>>>> keyrings and trusted vs user keys.
>>>>
>>>> No problem. HTH.
>>>
>>> Ahmad,
>>>
>>> Ok that explains it - my testing is using a very basic buildroot
>>> ramdisk rootfs. If I do a 'keyctl new_session' first I can use the
>>> system keyring fine as well.
>>
>> Great. Does this mean I can get your Tested-by: ? :)
>>
> 
> Absolutely,
> 
> For the series:
> 
> I tested this series on top of v5.14.rc-7 on a Gateworks
> imx8mm-venice-gw73xx board with kernel param trusted.source=caam and
> keyutils-1.6:
> # keyctl new_session
> 22544757
> # keyctl add trusted mykey 'new 32' @s
> 160701809
> # keyctl print 160701809
> 990e03aa4515aee420eede17e26a58d0c5568c8bd2c9c2ee2f22a0583181d20d4f65cf9cb1f944a3cc92c0e3184a44a29a7e511f0a55a6af11a70ac2b2924514002475e73ae09820042896b9ee00a5ec
> 
> Tested-By: Tim Harvey <tharvey@...eworks.com>

Thanks. I'll apply it to the whole series then.

> One more question: I've got a user that wants to blob/deblob generic
> data. They can use the caam_encap_blob/caam_decap_blob functions in
> kernel code but could you give me a suggestion for how they could use
> this in:
> a) userspace code (using the keyctl syscall I assume)
> b) userspace cmdline (via keyutils I assume)

Trusted keys aren't disclosed to userspace in plain text, only in sealed
form (bar vulnerabilities of course).

Cheers,
Ahmad

> 
> Many thanks,
> 
> Tim
> 


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