linux-kernel - Re: [PATCH v2 1/6] KEYS: trusted: allow use of TEE as backend without TCG

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Date:   Mon, 19 Jul 2021 11:09:29 +0200
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Sumit Garg <sumit.garg@...aro.org>
Cc:     James Bottomley <jejb@...ux.ibm.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        kernel <kernel@...gutronix.de>, James Morris <jmorris@...ei.org>,
        Eric Biggers <ebiggers@...nel.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Horia Geantă <horia.geanta@....com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Udit Agarwal <udit.agarwal@....com>,
        Jan Luebbe <j.luebbe@...gutronix.de>,
        David Gstir <david@...ma-star.at>,
        Richard Weinberger <richard@....at>,
        Franck LENORMAND <franck.lenormand@....com>,
        "open list:ASYMMETRIC KEYS" <keyrings@...r.kernel.org>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:SECURITY SUBSYSTEM" 
        <linux-security-module@...r.kernel.org>,
        Andreas Rammhold <andreas@...mhold.de>
Subject: Re: [PATCH v2 1/6] KEYS: trusted: allow use of TEE as backend without
 TCG_TPM support

Hello Sumit,

On 19.07.21 10:04, Sumit Garg wrote:
> Hi Ahmad,
> 
> On Tue, 22 Jun 2021 at 18:08, Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
>>
>> With recent rework, trusted keys are no longer limited to TPM as trust
>> source. The Kconfig symbol is unchanged however leading to a few issues:
>>
>>  - TCG_TPM is required, even if only TEE is to be used
>>  - Enabling TCG_TPM, but excluding it from available trusted sources
>>    is not possible
>>  - TEE=m && TRUSTED_KEYS=y will lead to TEE support being silently
>>    dropped, which is not the best user experience
>>
>> Remedy these issues by introducing two new Kconfig symbols:
>> TRUSTED_KEYS_TPM and TRUSTED_KEYS_TEE with the appropriate
>> dependencies.
>>
> 
> This should include a fixes tag to the rework commit.

Yes. I wasn't aware of the regression that Andreas (CC'd) recently
reported. Knowing, it now indeed warrants a backport. Will add in v2.

>> diff --git a/security/keys/Kconfig b/security/keys/Kconfig
>> index 64b81abd087e..6fdb953b319f 100644
>> --- a/security/keys/Kconfig
>> +++ b/security/keys/Kconfig
>> @@ -70,23 +70,23 @@ config BIG_KEYS
>>
>>  config TRUSTED_KEYS
>>         tristate "TRUSTED KEYS"
>> -       depends on KEYS && TCG_TPM
>> +       depends on KEYS
> 
>>         select CRYPTO
>>         select CRYPTO_HMAC
>>         select CRYPTO_SHA1
>>         select CRYPTO_HASH_INFO
> 
> Should move these as well to TRUSTED_KEYS_TPM as the core code doesn't
> mandate their need.

Ok, will test and change appropriately.

> 
>> -       select ASN1_ENCODER
>> -       select OID_REGISTRY
>> -       select ASN1

>>  $(obj)/trusted_tpm2.o: $(obj)/tpm2key.asn1.h
>> -trusted-y += trusted_tpm2.o
>> -trusted-y += tpm2key.asn1.o
>> +trusted-$(CONFIG_TRUSTED_KEYS_TPM) += trusted_tpm2.o
>> +trusted-$(CONFIG_TRUSTED_KEYS_TPM) += tpm2key.asn1.o
>> +
>> +trusted-$(CONFIG_TRUSTED_KEYS_TEE) += trusted_tee.o
>>
>>  trusted-$(CONFIG_TEE) += trusted_tee.o
> 
> This should be dropped.

Right..

Thanks for the review. I'll isolate this patch for v2.

Cheers,
Ahmad


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