linux-kernel - Re: [PATCH v3 2/8] ima: Switch to ima_hash

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Date:   Mon, 02 Mar 2020 12:33:01 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>,
        "James.Bottomley@...senPartnership.com" 
        <James.Bottomley@...senPartnership.com>,
        "jarkko.sakkinen@...ux.intel.com" <jarkko.sakkinen@...ux.intel.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>
Cc:     "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Silviu Vlasceanu <Silviu.Vlasceanu@...wei.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v3 2/8] ima: Switch to ima_hash_algo for boot aggregate

On Mon, 2020-03-02 at 15:11 +0000, Roberto Sassu wrote:


> > Yes, preference is given to the IMA default algorithm, but it should
> > fall back to using SHA256 or SHA1, based on the TPM.
> 
> Ok. The patch already does it even if the TPM version is not checked.
> For TPM 1.2, if the default algorithm is not SHA1 the patch will select
> the first PCR bank (SHA1).
> 
> Should I send a new patch which explicitly checks the TPM version?

Checking the TPM version shouldn't be necessary.  The code currently
sets bank_idx to the HASH_ALGO_SHA256.  If instead of initializing
bank_idx to 0, initialize it to the nr_allocated_banks or -1.  As long
as the bank_idx value is the same as the initialized value, set the
bank_idx to HASH_ALGO_SHA1.

The subsequent bank_idx would then be limited to testing for the
initialized value.

Mimi