Re: [PATCH v6 5/7] tpm: retrieve digest size of unknown algorithms with PCR read

[Roberto Sassu]

On 12/5/2018 12:53 AM, Jarkko Sakkinen wrote:
> On Tue, Dec 04, 2018 at 09:21:36AM +0100, Roberto Sassu wrote:
> > +	for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
> > +		enum hash_algo crypto_algo = tpm2_hash_map[i].crypto_id;
> > +
> > +		if (bank->alg_id != tpm2_hash_map[i].tpm_id)
> > +			continue;
> > +
> > +		bank->digest_size = hash_digest_size[crypto_algo];
> > +		bank->crypto_id = crypto_algo;
> > +		return 0;
> > +	}
> > +
> > +	return tpm2_pcr_read(chip, 0, &digest, &bank->digest_size);
> > +}
>
> This is a part that I don't get. Coud you just always call
> tpm2_pcr_read() instead of this complexity

First, we avoid operations that may increase the boot time. Second, the
loop is necessary to obtain the crypto subsystem identifier from a TPM
algorithm identifier.

Roberto


> /Jarkko

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