linux-kernel - Re: [PATCH v7 1/2] fTPM: firmware TPM running in TEE

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Message-ID: <CAFA6WYMvd1BVGppYM230Bd1XjO11uU4WQf-F+ZtmtpasP4AjxQ@mail.gmail.com>
Date:   Wed, 3 Jul 2019 15:33:14 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Thirupathaiah Annapureddy <thiruan@...rosoft.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Sasha Levin <sashal@...nel.org>,
        "peterhuewe@....de" <peterhuewe@....de>,
        "jgg@...pe.ca" <jgg@...pe.ca>, "corbet@....net" <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        Microsoft Linux Kernel List <linux-kernel@...rosoft.com>,
        "Bryan Kelly (CSI)" <bryankel@...rosoft.com>,
        "tee-dev@...ts.linaro.org" <tee-dev@...ts.linaro.org>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        Joakim Bech <joakim.bech@...aro.org>
Subject: Re: [PATCH v7 1/2] fTPM: firmware TPM running in TEE

On Wed, 3 Jul 2019 at 13:42, Ilias Apalodimas
<ilias.apalodimas@...aro.org> wrote:
>
> Hi Thirupathaiah,
>
> (+Joakim)
>
> On Wed, 3 Jul 2019 at 09:58, Ilias Apalodimas
> <ilias.apalodimas@...aro.org> wrote:
> >
> > Hi Thirupathaiah,
> > >
> > > First of all, Thanks a lot for trying to test the driver.
> > >
> > np
> >
> > [...]
> > > > I managed to do some quick testing in QEMU.
> > > > Everything works fine when i build this as a module (using IBM's TPM 2.0
> > > > TSS)
> > > >
> > > > - As module
> > > > # insmod /lib/modules/5.2.0-rc1/kernel/drivers/char/tpm/tpm_ftpm_tee.ko
> > > > # getrandom -by 8
> > > > randomBytes length 8
> > > > 23 b9 3d c3 90 13 d9 6b
> > > >
> > > > - Built-in
> > > > # dmesg | grep optee
> > > > ftpm-tee firmware:optee: ftpm_tee_probe:tee_client_open_session failed,
> > > > err=ffff0008
> > > This (0xffff0008) translates to TEE_ERROR_ITEM_NOT_FOUND.
> > >
> > > Where is fTPM TA located in the your test setup?
> > > Is it stitched into TEE binary as an EARLY_TA or
> > > Is it expected to be loaded during run-time with the help of user mode OP-TEE supplicant?
> > >
> > > My guess is that you are trying to load fTPM TA through user mode OP-TEE supplicant.
> > > Can you confirm?
> > I tried both
> >
>
> Ok apparently there was a failure with my built-in binary which i
> didn't notice. I did a full rebuilt and checked the elf this time :)
>
> Built as an earlyTA my error now is:
> ftpm-tee firmware:optee: ftpm_tee_probe:tee_client_open_session
> failed, err=ffff3024 (translates to TEE_ERROR_TARGET_DEAD)
> Since you tested it on real hardware i guess you tried both
> module/built-in. Which TEE version are you using?
>

> > > U-boot and Linux driver stacks work seamlessly without dependency on supplicant.

Is this true?

It looks like this fTPM driver can't work as a built-in driver. The
reason seems to be secure storage access required by OP-TEE fTPM TA
that is provided via OP-TEE supplicant that's not available during
kernel boot.

Snippet from ms-tpm-20-ref/Samples/ARM32-FirmwareTPM/optee_ta/fTPM/fTPM.c +145:

    // If we fail to open fTPM storage we cannot continue.
    if (_plat__NVEnable(NULL) == 0) {
        TEE_Panic(TEE_ERROR_BAD_STATE);
    }

So it seems like this module will work as a loadable module only after
OP-TEE supplicant is up.

-Sumit

> Thanks
> /Ilias