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From: Roberto Sassu <roberto.sassu@huawei.com>
To: Mimi Zohar <zohar@linux.ibm.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: <david.safford@ge.com>, <monty.wiseman@ge.com>,
	<linux-integrity@vger.kernel.org>,
	<linux-security-module@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <silviu.vlasceanu@huawei.com>
Subject: Re: [PATCH v5 7/7] tpm: pass an array of tpm_bank_list structures to tpm_pcr_extend()
Date: Mon, 19 Nov 2018 09:16:45 +0100	[thread overview]
Message-ID: <26519f33-b5d6-c2c6-5179-c43f197f2cbd@huawei.com> (raw)
In-Reply-To: <1542603470.4914.55.camel@linux.ibm.com>

On 11/19/2018 5:57 AM, Mimi Zohar wrote:
> On Sun, 2018-11-18 at 09:27 +0200, Jarkko Sakkinen wrote:
>> On Fri, Nov 16, 2018 at 04:55:36PM +0100, Roberto Sassu wrote:
>>> On 11/16/2018 4:03 PM, Jarkko Sakkinen wrote:
>>>> On Wed, Nov 14, 2018 at 04:31:08PM +0100, Roberto Sassu wrote:
>>>>> Currently, tpm_pcr_extend() accepts as an input only a SHA1 digest.
>>>>>
>>>>> This patch modifies the definition of tpm_pcr_extend() to allow other
>>>>> kernel subsystems to pass a digest for each algorithm supported by the TPM.
>>>>> All digests are processed by the TPM in one operation.
>>>>>
>>>>> If a tpm_pcr_extend() caller provides a subset of the supported algorithms,
>>>>> the TPM driver extends the remaining PCR banks with the first digest
>>>>> passed as an argument to the function.
>>>>
>>>> What is the legit use case for this?
>>>
>>> A subset could be chosen for better performance, or when a TPM algorithm
>>> is not supported by the crypto subsystem.
>>
>> Doesn't extending a subset a security concern?
> 
> Right, so instead of extending a subset of the allocated banks, all of
> the allocated banks need to be extended, even for those banks that a
> digest was not included.  This is no different than what is being done
> today.  IMA is currently only calculating the SHA1 hash, padding the
> digest with 0's, and extending the padded value(s) into all of the
> allocated banks.

The caller of tpm_pcr_extend() could pass a subset of the allocated
banks, but the TPM driver extends all banks as before.

Roberto


> If there is a vulnerability with the hash algorithm, then any bank
> extended with the padded/truncated digest would be susceptible.
> 
> IMA will need to become TPM 2.0 aware, calculating and extending
> multiple banks and define a new measurement list format containing the
> multiple digests.
> 
> Mimi
> 

-- 
HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Bo PENG, Jian LI, Yanli SHI

  reply	other threads:[~2018-11-19  8:16 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-14 15:31 [PATCH v5 0/7] tpm: retrieve digest size of unknown algorithms from TPM Roberto Sassu
2018-11-14 15:31 ` [PATCH v5 1/7] tpm: dynamically allocate the allocated_banks array Roberto Sassu
2018-11-16 13:36   ` Jarkko Sakkinen
2018-11-14 15:31 ` [PATCH v5 2/7] tpm: remove definition of TPM2_ACTIVE_PCR_BANKS Roberto Sassu
2018-11-16 13:38   ` Jarkko Sakkinen
2018-11-28  7:50     ` Roberto Sassu
2018-11-28 12:17     ` Roberto Sassu
2018-11-29 12:04       ` Roberto Sassu
2018-11-30 19:41         ` Jarkko Sakkinen
2018-11-30 19:45           ` Jarkko Sakkinen
2018-11-30 22:18             ` Jarkko Sakkinen
2018-12-03  9:59             ` Roberto Sassu
2018-12-03 17:31               ` Jarkko Sakkinen
2018-11-14 15:31 ` [PATCH v5 3/7] tpm: rename and export tpm2_digest and tpm2_algorithms Roberto Sassu
2018-11-14 15:31 ` [PATCH v5 4/7] tpm: modify tpm_pcr_read() definition to pass a TPM hash algorithm Roberto Sassu
2018-11-16 13:41   ` Jarkko Sakkinen
2018-11-14 15:31 ` [PATCH v5 5/7] tpm: retrieve digest size of unknown algorithms with PCR read Roberto Sassu
2018-11-14 15:31 ` [PATCH v5 6/7] tpm: ensure that the output of PCR read contains the correct digest size Roberto Sassu
2018-11-16 13:41   ` Jarkko Sakkinen
2018-11-16 16:06     ` Roberto Sassu
2018-11-18  7:32       ` Jarkko Sakkinen
2018-11-19  8:14         ` Roberto Sassu
2018-11-19 14:33           ` Jarkko Sakkinen
2018-11-19 15:09             ` Roberto Sassu
2018-11-19 16:07               ` Jarkko Sakkinen
2018-11-28  8:40                 ` Roberto Sassu
2018-11-28 19:19                   ` Jarkko Sakkinen
2018-11-14 15:31 ` [PATCH v5 7/7] tpm: pass an array of tpm_bank_list structures to tpm_pcr_extend() Roberto Sassu
2018-11-16 15:03   ` Jarkko Sakkinen
2018-11-16 15:55     ` Roberto Sassu
2018-11-18  7:27       ` Jarkko Sakkinen
2018-11-19  4:57         ` Mimi Zohar
2018-11-19  8:16           ` Roberto Sassu [this message]
2018-11-19 14:33             ` Mimi Zohar
2018-11-19 14:39             ` Jarkko Sakkinen
2018-11-18  7:29       ` Jarkko Sakkinen
2018-11-19  8:22         ` Roberto Sassu
2018-11-19 14:42           ` Jarkko Sakkinen

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