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Date:   Wed, 12 Dec 2018 20:27:34 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Roberto Sassu <roberto.sassu@huawei.com>
Cc:     zohar@linux.ibm.com, david.safford@ge.com, monty.wiseman@ge.com,
        linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org, silviu.vlasceanu@huawei.com
Subject: Re: [PATCH v6 7/7] tpm: pass an array of tpm_bank_list structures to
 tpm_pcr_extend()
Message-ID: <20181212182734.GH6333@linux.intel.com>
References: <20181204082138.24600-1-roberto.sassu@huawei.com>
 <20181204082138.24600-8-roberto.sassu@huawei.com>
 <20181205001417.GF1233@linux.intel.com>
 <9d6e47d9-3b88-86f6-1b60-6652dfe8dc00@huawei.com>
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On Thu, Dec 06, 2018 at 07:38:30PM +0100, Roberto Sassu wrote:
> On 12/5/2018 1:14 AM, Jarkko Sakkinen wrote:
> > On Tue, Dec 04, 2018 at 09:21:38AM +0100, Roberto Sassu wrote:
> > > The new tpm_bank_list structure has been preferred to the tpm_digest
> > > structure, to let the caller specify the size of the digest (which may be
> > > unknown to the TPM driver).
> > 
> > Why is that? Didn't previous commit query these?
> 
> Since the TPM driver pads/truncates the first digest passed by the
> caller to extend PCRs for which no digest was provided, it must know
> which amount of data it can use. It is possible that the algorithm of
> the first digest is unknown for the TPM driver, if the caller of
> tpm_pcr_extend() didn't check chip->allocated_banks.
> 
> By requiring that the caller passes also the digest size, this problem
> does not arise. It seems reasonable to me to pass this information, as
> the caller calculated the digest and it should know the digest size.

OK. I noticed something other things that look to alarming:

1. The function does not fail if alg_id is not found. This will go
   silent.
2. The function does not fail if there is a mismatch with the digest
   sizes.

/Jarkko