From: Roberto Sassu <roberto.sassu@huawei.com>
To: "jejb@linux.ibm.com" <jejb@linux.ibm.com>,
Maurizio Drocco <maurizio.drocco@ibm.com>,
"zohar@linux.ibm.com" <zohar@linux.ibm.com>
Cc: "dmitry.kasatkin@gmail.com" <dmitry.kasatkin@gmail.com>,
"jmorris@namei.org" <jmorris@namei.org>,
"linux-integrity@vger.kernel.org"
<linux-integrity@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-security-module@vger.kernel.org"
<linux-security-module@vger.kernel.org>,
"serge@hallyn.com" <serge@hallyn.com>,
Silviu Vlasceanu <Silviu.Vlasceanu@huawei.com>
Subject: RE: [PATCH] extend IMA boot_aggregate with kernel measurements
Date: Tue, 16 Jun 2020 17:29:21 +0000 [thread overview]
Message-ID: <8c44ed75fb884cad9f33c86c2d4e8a27@huawei.com> (raw)
In-Reply-To: <1591982059.7235.29.camel@linux.ibm.com>
> From: James Bottomley [mailto:jejb@linux.ibm.com]
> Sent: Friday, June 12, 2020 7:14 PM
> On Fri, 2020-06-12 at 15:11 +0000, Roberto Sassu wrote:
> > with recent patches, boot_aggregate can be calculated from non-SHA1
> > PCR banks. I would replace with:
> >
> > Extend cumulative digest over ...
> >
> > Given that with this patch boot_aggregate is calculated differently,
> > shouldn't we call it boot_aggregate_v2 and enable it with a new
> > option?
>
> So here's the problem: if your current grub doesn't do any TPM
> extensions (as most don't), then the two boot aggregates are the same
> because PCRs 8 and 9 are zero and there's a test that doesn't add them
> to the aggregate if they are zero. For these people its a nop so we
> shouldn't force them to choose a different version of the same thing.
>
> If, however, you're on a distribution where grub is automatically
> measuring the kernel and command line into PCRs 8 and 9 (I think Fedora
> 32 does this), your boot aggregate will change. It strikes me in that
> case we can call this a bug fix, since the boot aggregate isn't
> properly binding to the previous measurements without PCRs 8 and 9. In
> this case, do we want to allow people to select an option which doesn't
> properly bind the IMA log to the boot measurements? That sounds like a
> security hole to me.
>
> However, since it causes a user visible difference in the grub already
> measures case, do you have a current use case that would be affected?
> As in are lots of people already running a distro with the TPM grub
> updates and relying on the old boot aggregate?
I don't know how many people would be affected. However, if an
attestation tool processes both measurement lists from unpatched kernels
and patched kernels, keeping the same name would be a problem as it
cannot be determined from the measurement list how boot_aggregate
was calculated.
Anyway, I agree this should be fixed. At least, I suggest to add a Fixes tag,
to ensure that this patch is applied to all stable kernels.
Roberto
HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Li Jian, Shi Yanli
next prev parent reply other threads:[~2020-06-16 17:29 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-11 19:54 [PATCH] extend IMA boot_aggregate with kernel measurements Maurizio Drocco
2020-06-12 0:29 ` Mimi Zohar
2020-06-12 14:38 ` Maurizio Drocco
2020-06-12 15:11 ` Roberto Sassu
2020-06-12 17:14 ` James Bottomley
2020-06-16 17:29 ` Roberto Sassu [this message]
2020-06-16 18:11 ` Mimi Zohar
2020-06-18 12:38 ` Roberto Sassu
2020-06-18 20:11 ` Maurizio Drocco
2020-06-18 20:11 ` [PATCH] ima_evm_utils: extended calc_bootaggr to PCRs 8 - 9 Maurizio Drocco
2020-06-22 20:14 ` Mimi Zohar
2020-06-22 4:50 ` [PATCH] ima: extend boot_aggregate with kernel measurements Maurizio Drocco
2020-06-23 14:03 ` Mimi Zohar
2020-06-23 15:57 ` [PATCH v4] " Maurizio Drocco
2020-06-23 18:53 ` Bruno Meneguele
2020-06-23 18:01 ` [PATCH v2] ima_evm_utils: extended calc_bootaggr to PCRs 8 - 9 Maurizio Drocco
2020-06-23 18:13 ` Bruno Meneguele
2020-06-24 21:17 ` Stefan Berger
2020-06-24 21:33 ` [PATCH] " Maurizio Drocco
2020-06-24 21:33 ` [PATCH v2] " Bruno Meneguele
2020-06-24 21:35 ` [PATCH v3] " Maurizio Drocco
2020-06-24 21:50 ` Bruno Meneguele
2020-06-12 4:47 ` [PATCH] extend IMA boot_aggregate with kernel measurements kernel test robot
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