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From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Roberto Sassu <roberto.sassu@huawei.com>
Cc: jejb@linux.ibm.com, zohar@linux.ibm.com, jgg@ziepe.ca,
	tyhicks@canonical.com, linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org, keyrings@vger.kernel.org,
	linux-kernel@vger.kernel.org, crazyt2019+lml@gmail.com,
	nayna@linux.vnet.ibm.com, silviu.vlasceanu@huawei.com
Subject: Re: [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated
Date: Tue, 6 Aug 2019 01:12:43 +0300	[thread overview]
Message-ID: <20190805221243.chp4x5h2ow76nmz4@linux.intel.com> (raw)
In-Reply-To: <20190805164427.17408-1-roberto.sassu@huawei.com>

On Mon, Aug 05, 2019 at 06:44:27PM +0200, Roberto Sassu wrote:
> Commit c78719203fc6 ("KEYS: trusted: allow trusted.ko to initialize w/o a
> TPM") allows the trusted module to be loaded even if a TPM is not found, to
> avoid module dependency problems.
> 
> However, trusted module initialization can still fail if the TPM is
> inactive or deactivated. tpm_get_random() returns an error.
> 
> This patch removes the call to tpm_get_random() and instead extends the PCR
> specified by the user with zeros. The security of this alternative is
> equivalent to the previous one, as either option prevents with a PCR update
> unsealing and misuse of sealed data by a user space process.
> 
> Even if a PCR is extended with zeros, instead of random data, it is still
> computationally infeasible to find a value as input for a new PCR extend
> operation, to obtain again the PCR value that would allow unsealing.
> 
> Fixes: 240730437deb ("KEYS: trusted: explicitly use tpm_chip structure...")
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

/Jarkko

  parent reply	other threads:[~2019-08-05 22:12 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-05 16:44 [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated Roberto Sassu
2019-08-05 17:20 ` Tyler Hicks
2019-08-05 22:12 ` Jarkko Sakkinen [this message]
2019-08-09 15:50 ` Jarkko Sakkinen

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