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From: Roberto Sassu <roberto.sassu@huawei.com>
To: Mimi Zohar <zohar@linux.ibm.com>,
	"jarkko.sakkinen@linux.intel.com"
	<jarkko.sakkinen@linux.intel.com>,
	"james.bottomley@hansenpartnership.com" 
	<james.bottomley@hansenpartnership.com>,
	"linux-integrity@vger.kernel.org"
	<linux-integrity@vger.kernel.org>
Cc: "linux-security-module@vger.kernel.org" 
	<linux-security-module@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Silviu Vlasceanu <Silviu.Vlasceanu@huawei.com>
Subject: RE: [PATCH 7/8] ima: use ima_hash_algo for collision detection in the measurement list
Date: Fri, 31 Jan 2020 14:02:36 +0000
Message-ID: <44c1b3f6d3fe414e914317ef8e5c6f8f@huawei.com> (raw)
In-Reply-To: <1580423169.6104.18.camel@linux.ibm.com>

> -----Original Message-----
> From: linux-integrity-owner@vger.kernel.org [mailto:linux-integrity-
> owner@vger.kernel.org] On Behalf Of Mimi Zohar
> Sent: Thursday, January 30, 2020 11:26 PM
> To: Roberto Sassu <roberto.sassu@huawei.com>;
> jarkko.sakkinen@linux.intel.com;
> james.bottomley@hansenpartnership.com; linux-integrity@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org; linux-kernel@vger.kernel.org;
> Silviu Vlasceanu <Silviu.Vlasceanu@huawei.com>
> Subject: Re: [PATCH 7/8] ima: use ima_hash_algo for collision detection in
> the measurement list
> 
> On Mon, 2020-01-27 at 18:04 +0100, Roberto Sassu wrote:
> > Before calculating a digest for each PCR bank, collisions were detected
> > with a SHA1 digest. This patch includes ima_hash_algo among the
> algorithms
> > used to calculate the template digest and checks collisions on that digest.
> >
> > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> 
> Definitely needed to protect against a sha1 collision attack.
> 
> <snip>
> 
> >
> > diff --git a/security/integrity/ima/ima_api.c
> b/security/integrity/ima/ima_api.c
> > index ebaf0056735c..a9bb45de6db9 100644
> > --- a/security/integrity/ima/ima_api.c
> > +++ b/security/integrity/ima/ima_api.c
> > @@ -51,7 +51,7 @@ int ima_alloc_init_template(struct ima_event_data
> *event_data,
> >  	if (!*entry)
> >  		return -ENOMEM;
> >
> > -	(*entry)->digests = kcalloc(ima_tpm_chip->nr_allocated_banks + 1,
> > +	(*entry)->digests = kcalloc(ima_tpm_chip->nr_allocated_banks + 2,
> >  				    sizeof(*(*entry)->digests), GFP_NOFS);
> >  	if (!(*entry)->digests) {
> >  		result = -ENOMEM;
> 
> I would prefer not having to allocate and use "nr_allocated_banks + 1"
> everywhere, but I understand the need for it.  I'm not sure this patch
> warrants allocating +2.  Perhaps, if a TPM bank doesn't exist for the
> IMA default hash algorithm, use a different algorithm or, worst case,
> continue using the ima_sha1_idx.

We could introduce a new option called ima_hash_algo_tpm to specify
the algorithm of an allocated bank. We can use this for boot_aggregate
and hash collision detection.

Roberto

HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Li Jian, Shi Yanli

  reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-27 17:04 [PATCH 0/8] ima: support stronger algorithms for attestation Roberto Sassu
2020-01-27 17:04 ` [PATCH 1/8] tpm: initialize crypto_id of allocated_banks to HASH_ALGO__LAST Roberto Sassu
2020-01-29  8:39   ` Petr Vorel
2020-01-30  8:47   ` Jarkko Sakkinen
2020-01-30 16:11     ` Roberto Sassu
2020-01-31 13:33       ` Mimi Zohar
2020-02-01 17:10         ` Jarkko Sakkinen
2020-01-27 17:04 ` [PATCH 2/8] ima: evaluate error in init_ima() Roberto Sassu
2020-01-31 13:33   ` Mimi Zohar
2020-01-27 17:04 ` [PATCH 3/8] ima: store template digest directly in ima_template_entry Roberto Sassu
2020-01-27 17:04 ` [PATCH 4/8] ima: switch to dynamically allocated buffer for template digests Roberto Sassu
2020-01-27 17:04 ` [PATCH 5/8] ima: allocate and initialize tfm for each PCR bank Roberto Sassu
2020-01-31 12:18   ` Mimi Zohar
2020-01-31 13:42     ` Roberto Sassu
2020-01-31 13:58       ` Mimi Zohar
2020-01-27 17:04 ` [PATCH 6/8] ima: calculate and extend PCR with digests in ima_template_entry Roberto Sassu
2020-01-27 17:29   ` Roberto Sassu
2020-01-27 17:04 ` [PATCH 7/8] ima: use ima_hash_algo for collision detection in the measurement list Roberto Sassu
2020-01-30 22:26   ` Mimi Zohar
2020-01-31 14:02     ` Roberto Sassu [this message]
2020-01-31 14:22       ` Mimi Zohar
2020-01-31 14:41         ` Roberto Sassu
2020-01-31 14:50           ` Mimi Zohar
2020-01-27 17:04 ` [PATCH 8/8] ima: switch to ima_hash_algo for boot aggregate Roberto Sassu
2020-01-31 15:21   ` Roberto Sassu
2020-01-30 22:26 ` [PATCH 0/8] ima: support stronger algorithms for attestation Mimi Zohar

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