From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Roberto Sassu <roberto.sassu@huawei.com>
Cc: tpmdd-devel@lists.sourceforge.net,
linux-ima-devel@lists.sourceforge.net,
linux-security-module@vger.kernel.org, keyrings@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/5] tpm: introduce tpm_pcr_algo_to_crypto() and tpm_pcr_algo_from_crypto()
Date: Sat, 20 May 2017 16:22:17 +0300 [thread overview]
Message-ID: <20170520132217.t7n7l2pjn7i63hbm@intel.com> (raw)
In-Reply-To: <0deed9be-d0c3-3a69-d510-1c8aa3513ba8@huawei.com>
On Mon, May 15, 2017 at 04:22:22PM +0200, Roberto Sassu wrote:
> On 5/15/2017 1:16 PM, Jarkko Sakkinen wrote:
> > On Fri, May 05, 2017 at 04:21:49PM +0200, Roberto Sassu wrote:
> > > tpm_pcr_algorithms() returns to its callers the IDs of the hash algorithms
> > > supported by the TPM. This patch introduces tpm_pcr_algo_to_crypto(),
> > > so that the callers can use the crypto subsystem to calculate the digest
> > > to be passed to tpm_pcr_extend().
> > >
> > > tpm_pcr_algo_from_crypto(), implemented for completeness, is instead used
> >
> > What do you mean by completeness? Please, never add unused stuff.
> >
> > > by tpm2_seal_trusted() to perform the opposite conversion.
> > >
> > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > > ---
> > > v2
> > >
> > > - fixed return values of tpm2_pcr_algo_to_crypto() and
> > > tpm2_pcr_algo_from_crypto() if TPM support is disabled in the kernel
> >
> > Change Log only to the cover letter.
> >
> > > drivers/char/tpm/tpm-interface.c | 51 ++++++++++++++++++++++++++++++++++++++++
> > > drivers/char/tpm/tpm2-cmd.c | 42 +++++++++------------------------
> > > include/linux/tpm.h | 13 ++++++++++
> > > 3 files changed, 75 insertions(+), 31 deletions(-)
> >
> > This commit is just deadly wrong in so many ways.
> >
> > I would suggest to make extend always just take crypto ID in so you
> > don't have to add these bizarre conversion functions.
>
> The reason of this choice (as I explained in the cover letter)
> is that TPM users might want to produce an event log with
> the TCG format (which includes the TPM algorithm ID). Also,
> TPM IDs should be preferred because, with them, TPM users
> can calculate a digest directly with the TPM.
>
> Taking crypto IDs means relying on the fact that there
> is always a mapping between TPM IDs and crypto IDs.
> Otherwise, tpm_pcr_algorithms() cannot return the algorithms
> to its callers and PCRs cannot be extended. If TPM IDs are used,
> TPM users have two alternatives: calculate the digest with
> the TPM, or pass a SHA1 digest to tpm_pcr_extend(), so that
> it can be padded to extend remanining PCR banks.
>
> However, this second option will work only when the TPM driver
> determines the size of an algorithm without relying on the crypto
> subsystem. At the moment, if a TPM ID is not mapped to a crypto ID,
> tpm2_pcr_extend() ignores the digest.
>
> Roberto
What if tpm_pcr_algorithms would convert TPM IDs to crypto IDs?
Externally other subsystems would have to then deal with only crypto
IDs.
That would favor "memcpy" (or it would become a for loop) for 1/5.
/Jarkko
next prev parent reply other threads:[~2017-05-20 13:22 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-05 14:21 [PATCH v2 0/5] Updated API for TPM 2.0 PCR extend Roberto Sassu
2017-05-05 14:21 ` [PATCH v2 1/5] tpm: introduce tpm_pcr_algorithms() Roberto Sassu
2017-05-15 10:36 ` Jarkko Sakkinen
[not found] ` <20170515103623.sumyo2vyldezual2-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-15 13:18 ` Roberto Sassu
[not found] ` <d2974dd2-e30d-e8f0-a60a-2147f3290670-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-17 8:42 ` Roberto Sassu
2017-05-20 13:18 ` Jarkko Sakkinen
[not found] ` <20170520131846.e3niqiknlrttbdf4-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-22 9:07 ` Roberto Sassu
2017-05-24 17:35 ` Jarkko Sakkinen
[not found] ` <20170524173521.yiiohct7brkcozyk-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-30 8:44 ` Roberto Sassu
[not found] ` <1cf4fbb1-5683-ceb4-2d5b-8ade25a91e83-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-31 11:39 ` Jarkko Sakkinen
2017-05-20 13:00 ` Jarkko Sakkinen
2017-05-05 14:21 ` [PATCH v2 2/5] tpm: introduce tpm_pcr_algo_to_crypto() and tpm_pcr_algo_from_crypto() Roberto Sassu
[not found] ` <20170505142152.29795-3-roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-15 11:16 ` Jarkko Sakkinen
[not found] ` <20170515111629.urjvbhqzohv4vakc-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-15 14:22 ` Roberto Sassu
2017-05-20 13:22 ` Jarkko Sakkinen [this message]
[not found] ` <20170520132217.t7n7l2pjn7i63hbm-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-22 7:21 ` Roberto Sassu
2017-05-24 17:33 ` Jarkko Sakkinen
2017-05-24 20:25 ` Jarkko Sakkinen
2017-05-30 10:24 ` Roberto Sassu
2017-05-31 11:40 ` Jarkko Sakkinen
2017-05-05 14:21 ` [PATCH v2 3/5] tpm: pass multiple digests to tpm_pcr_extend() Roberto Sassu
[not found] ` <20170505142152.29795-4-roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-30 3:29 ` [Linux-ima-devel] " Mimi Zohar
2017-05-30 7:28 ` Roberto Sassu
2017-05-30 11:25 ` Mimi Zohar
[not found] ` <1496143547.3841.517.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-05-30 13:25 ` Roberto Sassu
2017-05-05 14:21 ` [PATCH v2 4/5] keys, trusted: modify arguments of tpm_pcr_extend() Roberto Sassu
2017-05-30 3:35 ` [Linux-ima-devel] " Mimi Zohar
[not found] ` <1496115337.3841.485.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-05-30 7:36 ` Roberto Sassu
2017-05-30 12:06 ` Mimi Zohar
[not found] ` <1496145961.3841.537.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-05-30 13:41 ` Roberto Sassu
2017-05-05 14:21 ` [PATCH v2 5/5] ima: " Roberto Sassu
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