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From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: Roberto Sassu <roberto.sassu@huawei.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-ima-devel@lists.sourceforge.net,
	linux-security-module@vger.kernel.org,
	tpmdd-devel@lists.sourceforge.net, keyrings@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Kenneth Goldman <kgoldman@us.ibm.com>
Subject: Re: [Linux-ima-devel] [PATCH v3 0/6] Updated API for TPM 2.0 PCR extend
Date: Mon, 26 Jun 2017 13:12:15 -0400	[thread overview]
Message-ID: <1498497135.3387.69.camel@linux.vnet.ibm.com> (raw)
In-Reply-To: <03e70c05-5127-5c95-de8b-fedf90a23d7e@huawei.com>

On Mon, 2017-06-26 at 16:56 +0200, Roberto Sassu wrote:
> On 6/26/2017 2:33 PM, Mimi Zohar wrote:
> > On Sat, 2017-06-24 at 11:03 +0200, Jarkko Sakkinen wrote:
> >> On Wed, Jun 21, 2017 at 04:29:35PM +0200, Roberto Sassu wrote:
> >
> >
> >> To move this forward and be more constructive here's how I see it
> >> should be done (along the lines, draft):
> >>
> >> int tpm_pcr_extend(u32 chip_num, int pcr_idx, unsigned int alg,
> >> 		   const u8 *hash);
> >>
> >> The paramater 'alg' is crypto ID as specified by crypto subsystem.
> >
> > Based on Kenneth Goldman's input, the new IMA TPM-2.0 crypto hash
> > agile measurement list will contain the TPM crypto hash algorithm ids
> > (TPM crypto-ID).
> >
> >> TPM driver must have a precompiled table of mappings for crypto IDs
> >> and TPM algorithm IDs.
> >
> > We could map the TPM crypto-IDs to the crypto subsystem IDs and then
> > map them back, but is that necessary?
> >
> >>
> >> In addition it must have dynamically acquired list of TPM alg IDs.
> >> For those algs that static mapping does not exist it must extend
> >> them like we do now everything else except SHA-1 (Naynas changes).
> >
> > Padding/truncating an unknown bank using SHA1 is fine, but at some
> > point, as Roberto pointed out to me, TPM 2.0's might not support SHA-
> > 1.  So for the record, we're hard coding the use of SHA1 for the
> > unknown algorithms whether or not the TPM supports SHA1.
> 
> This solution requires that SHA1 digests are always calculated
> and included in the event log, even if SHA1 has not been selected
> by the user. I think this is not acceptable in the scenarios where
> saving power and memory is important.
> 
> I would instead use the first digest passed to tpm_pcr_extend()
> (it must be the first also in the event log) to extend banks
> for which the digest is missing.

As long as we don't break the existing userspace/kernel IMA
measurement list ABI, then I'm Ok with this.

Mimi

> If TPM users want to pad/truncate a different digest, they can
> pass to tpm_pcr_extend() a digest for each TPM algorithm.
> This is possible with the patches I sent because TPM users
> receive the TPM algorithm IDs and the digest size for each
> algorithm.
> 
> Regarding the possibility that SHA1 could not be supported,
> for now this shouldn't happen because, according to TCG,
> SHA1 support is mandatory for TPM 2.0:
> 
> https://trustedcomputinggroup.org/wp-content/uploads/TCG_Algorithm_Registry_Rev_1.24.pdf
> 
> I don't know if SHA1 can be marked as Legacy in a next
> revision of the document.
> 
> Roberto
> 
> 
> >> There's absolutely no need to pass digest size like you do BTW as it is
> >> defined by the standard.
> >
> > For algorithms known to the crypto subsystem, that is fine, but for
> > the unknown TPM crypto algorithms, we would need to somehow query the
> > TPM for the digest sizes to create the mapping.
> >
> > Mimi
> >
> >> I also except that where ever this interleaves with trusted keys there
> >> won't be duplicate structures and code.
> >>
> >> /Jarkko
> >>
> >
> 


  reply	other threads:[~2017-06-26 17:12 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-21 14:29 [PATCH v3 0/6] Updated API for TPM 2.0 PCR extend Roberto Sassu
2017-06-21 14:29 ` [PATCH v3 4/6] tpm: replace TPM algorithms IDs with tpm_pcr_bank_info structs in tpm_chip Roberto Sassu
2017-06-23 10:32   ` Jarkko Sakkinen
2017-06-21 14:29 ` [PATCH v3 5/6] tpm: introduce tpm_get_pcr_banks_info() Roberto Sassu
2017-06-23 10:35   ` Jarkko Sakkinen
2017-06-21 14:29 ` [PATCH v3 6/6] tpm: pass multiple digests to tpm_pcr_extend() Roberto Sassu
     [not found]   ` <20170621142941.32674-7-roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-06-23 10:37     ` Jarkko Sakkinen
     [not found] ` <20170621142941.32674-1-roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-06-21 14:29   ` [PATCH v3 1/6] tpm: use tpm_buf functions to perform a PCR read Roberto Sassu
2017-06-22 10:14     ` [tpmdd-devel] " Jarkko Sakkinen
     [not found]       ` <20170622101404.blfpqcryrbe35ha4-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-06-22 11:54         ` Roberto Sassu
2017-06-23 10:56           ` [tpmdd-devel] " Jarkko Sakkinen
2017-06-21 14:29   ` [PATCH v3 2/6] tpm: use tpm2_pcr_read_tpm_buf() in tpm2_do_selftest() Roberto Sassu
2017-06-23  9:55     ` [tpmdd-devel] " Jarkko Sakkinen
2017-06-23 10:22       ` Roberto Sassu
2017-06-21 14:29   ` [PATCH v3 3/6] tpm: introduce tpm_pcr_bank_info structure with digest_size from TPM Roberto Sassu
2017-06-23 10:26     ` Jarkko Sakkinen
     [not found]       ` <20170623102606.3xkuqbslr3g3o22s-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-06-23 11:25         ` Roberto Sassu
     [not found]     ` <20170621142941.32674-4-roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-06-27 15:24       ` Mimi Zohar
2017-06-24  9:03   ` [PATCH v3 0/6] Updated API for TPM 2.0 PCR extend Jarkko Sakkinen
     [not found]     ` <20170624090325.kbqhwkrx5qvtxveg-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-06-26  6:58       ` Roberto Sassu
2017-06-26  7:21       ` Roberto Sassu
2017-06-28 17:10         ` Jarkko Sakkinen
2017-06-26 12:33     ` [Linux-ima-devel] " Mimi Zohar
2017-06-26 14:56       ` Roberto Sassu
2017-06-26 17:12         ` Mimi Zohar [this message]
2017-06-28 17:28       ` Jarkko Sakkinen
2017-06-28 22:28         ` Mimi Zohar
2017-07-05 15:18         ` [tpmdd-devel] " Ken Goldman
2017-07-05 16:06           ` Mimi Zohar

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