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From: Roberto Sassu <roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
To: Jarkko Sakkinen
	<jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: linux-ima-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
	linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
	keyrings-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v2 2/5] tpm: introduce tpm_pcr_algo_to_crypto() and tpm_pcr_algo_from_crypto()
Date: Mon, 22 May 2017 09:21:28 +0200	[thread overview]
Message-ID: <0b04a33c-248b-6597-473f-c5bc4ccaba62@huawei.com> (raw)
In-Reply-To: <20170520132217.t7n7l2pjn7i63hbm-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

On 5/20/2017 3:22 PM, Jarkko Sakkinen wrote:
> 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-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
>>>> ---
>>>> 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.

Then, other subsystems cannot:

- use the TPM to calculate a digest
- create an event log with the TCG format

Roberto

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  parent reply	other threads:[~2017-05-22  7:21 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
     [not found]             ` <20170520132217.t7n7l2pjn7i63hbm-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-22  7:21               ` Roberto Sassu [this message]
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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