linux-kernel - Re: [PATCH v2 1/3] keys, trusted: select the hash algorithm

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Date:	Wed, 4 Nov 2015 15:13:26 +0200
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	Peter Huewe <peterhuewe@....de>,
	Marcel Selhorst <tpmdd@...horst.net>,
	David Howells <dhowells@...hat.com>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
	chris.j.arges@...onical.com, seth.forshee@...onical.com,
	colin.king@...onical.com, josh@...htriplett.org,
	Jonathan Corbet <corbet@....net>,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] keys, trusted: select the hash algorithm

On Tue, Nov 03, 2015 at 06:12:17PM +0200, Jarkko Sakkinen wrote:
> On Tue, Nov 03, 2015 at 10:39:11AM -0500, Mimi Zohar wrote:
> > On Tue, 2015-11-03 at 09:39 +0200, Jarkko Sakkinen wrote:
> > > On Mon, Nov 02, 2015 at 07:16:49AM -0500, Mimi Zohar wrote:
> > > > On Fri, 2015-10-30 at 13:35 +0200, Jarkko Sakkinen wrote:
> > > > 
> > > > > @@ -787,6 +791,20 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
> > > > >  				return -EINVAL;
> > > > >  			opt->pcrlock = lock;
> > > > >  			break;
> > > > > +		case Opt_hash:
> > > > > +			for (i = 0; i < HASH_ALGO__LAST; i++) {
> > > > > +				if (!strcmp(args[0].from, hash_algo_name[i])) {
> > > > > +					opt->hash = i;
> > > > > +					break;
> > > > > +				}
> > > > > +			}
> > > > > +			res = tpm_is_tpm2(TPM_ANY_NUM);
> > > > 
> > > > While looking at this, I wanted to verify that chips are still added to
> > > > the tail of the tpm_chip_list.  Unfortunately, commit "afb5abc tpm:
> > > > two-phase chip management functions" reverted David Howell's commit
> > > > "770ab65 TPM: Add new TPMs to the tail of the list to prevent
> > > > inadvertent change of dev".
> > > > 
> > > > > +			if (res < 0)
> > > > > +				return res;
> > > > > +			if (i == HASH_ALGO__LAST ||
> > > > > +			    (!res && i != HASH_ALGO_SHA1))
> > > > > +				return -EINVAL;
> > > > > +			break;
> > > > 
> > > > If the first TPM registered is a TPM 1.2, then changing the default TPM
> > > > 2.0 hash algorithm will fail.
> > > 
> > > Now that we are going fix this issue in 4.3 and 4.4 do you find this
> > > patch otherwise acceptable?
> > > 
> > > PS. In other options that we don't support in TPM2 I'm planning to
> > > submit a fix that they will return -EINVAL (like pcrinfo).
> > 
> > I don't have a problem failing the request, but I do suggest adding some
> > sort of error message.  Different systems might behavior differently
> > without any explanation.
> 
> Something like the pr_info("trusted_key: TPM 1.x supports only sha1")?

I've started to think that maybe it was a bad idea to break this into
patch set as the changes are small and they make sense only together.
What do you think? Should quash everything into single patch?

> > Mimi

/Jarkko
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