linux-kernel - Re: [RFC PATCH] tpm: Allow the TPM2 pcr_extend HMAC capability to be disabled on boot

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <D5FHSOW7V440.36E1YDA8Q2698@kernel.org>
Date: Thu, 07 Nov 2024 01:42:28 +0200
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Jarkko Sakkinen" <jarkko@...nel.org>, "James Bottomley"
 <James.Bottomley@...senPartnership.com>, "Mimi Zohar"
 <zohar@...ux.ibm.com>, <linux-integrity@...r.kernel.org>
Cc: <roberto.sassu@...wei.com>, <mapengyu@...il.com>, "Paul Moore"
 <paul@...l-moore.com>, <linux-kernel@...r.kernel.org>,
 <christian@...sel.eu>
Subject: Re: [RFC PATCH] tpm: Allow the TPM2 pcr_extend HMAC capability to
 be disabled on boot

On Thu Nov 7, 2024 at 1:40 AM EET, Jarkko Sakkinen wrote:
> On Thu Nov 7, 2024 at 1:22 AM EET, Jarkko Sakkinen wrote:
> > > I'm a bit confused here.  It's TPM2_PCR_Extend we have the trouble with
> > > (as Mimi says in her email that you quoted) not TPM2_GetRandom.
> > >
> > > The random number generator reseed occurs in a kernel thread that fires
> > > about once a minute, so it doesn't show up in really any of the boot
> > > timings.  Plus even with sessions added, what there now isn't a
> > > significant overhead even to the running kernel given it's asynchronous
> > > and called infrequently.
> >
> > Ah, right then we need the boot flag, and my earlier comments to the
> > parameter apply. I've never used IMA so I don't actually even know in
> > detail how it is using TPM.
> >
> > Now that I did some seek I mixed this up with the report:
> >
> > https://chaos.social/@gromit/113345582873908273
> >
> > Anyway concerning this issue and patch, my earlier comments still apply.
>
> Makes me wonder tho why do we then export tpm_get_random() in the first
> place? HWRNG does not needed that export, and the code does not have any
> of the mentioned features.

I mean specifically the code for tpm_get_random() and tpm2_get_random().

BR, Jarkko