linux-kernel - Re: [PATCH =v2 3/3] tpm: selftest: cleanup after unseal with wrong auth/policy test

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Date:   Thu, 12 Dec 2019 16:11:42 -0500
From:   James Bottomley <James.Bottomley@...senpartnership.com>
To:     Tadeusz Struk <tadeusz.struk@...el.com>,
        jarkko.sakkinen@...ux.intel.com
CC:     peterz@...radead.org, linux-kernel@...r.kernel.org, jgg@...pe.ca,
        mingo@...hat.com, jeffrin@...agiritech.edu.in,
        linux-integrity@...r.kernel.org, will@...nel.org, peterhuewe@....de
Subject: Re: [PATCH =v2 3/3] tpm: selftest: cleanup after unseal with wrong auth/policy test

On December 12, 2019 4:07:26 PM EST, Tadeusz Struk <tadeusz.struk@...el.com> wrote:
>On 12/12/19 12:54 PM, James Bottomley wrote:
>> Not in the modern kernel resource manager world: anyone who is in the
>> tpm group can access the tpmrm device and we haven't added a
>dangerous
>> command filter like we promised we would, so unless they have
>actually
>> set lockout or platform authorization, they'll find they can execute
>it
>
>The default for the tpm2_* tools with '-T device' switch is to talk to
>/dev/tpm0.
>
>If one would try to run it, by mistake, it would fail with:
>
>$ tpm2_clear -T device
>ERROR:tcti:src/tss2-tcti/tcti-device.c:439:Tss2_Tcti_Device_Init()
>Failed to open device file /dev/tpm0: Permission denied
>
>To point it to /dev/tpmrm0 it would need to be:
>$ tpm2_clear -T device:/dev/tpmrm0

And most other toolkits talk to the tpmrm device because the tpm 1.2 daemon based architecture didn't work so well.  The point is that if tpm2_clear works on your emulator, it likely works on your real tpm, so making the tests safer to run is not unreasonable.

James

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