From: Jarkko Sakkinen <jarkko@kernel.org>
To: Eric Snowberg <eric.snowberg@oracle.com>,
keyrings@vger.kernel.org, linux-integrity@vger.kernel.org,
zohar@linux.ibm.com, dhowells@redhat.com, dwmw2@infradead.org,
herbert@gondor.apana.org.au, davem@davemloft.net,
jmorris@namei.org, serge@hallyn.com
Cc: keescook@chromium.org, gregkh@linuxfoundation.org,
torvalds@linux-foundation.org, scott.branden@broadcom.com,
weiyongjun1@huawei.com, nayna@linux.ibm.com, ebiggers@google.com,
ardb@kernel.org, nramas@linux.microsoft.com, lszubowi@redhat.com,
linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
linux-security-module@vger.kernel.org,
James.Bottomley@HansenPartnership.com, pjones@redhat.com,
konrad.wilk@oracle.com
Subject: Re: [PATCH v5 00/12] Enroll kernel keys thru MOK
Date: Wed, 08 Sep 2021 19:49:06 +0300 [thread overview]
Message-ID: <b44726f2d71960d53b4860ccab71f02186295da9.camel@kernel.org> (raw)
In-Reply-To: <7f9fb65a4ee20c337646a1fc887cd24365c2c59e.camel@kernel.org>
On Wed, 2021-09-08 at 19:03 +0300, Jarkko Sakkinen wrote:
> On Tue, 2021-09-07 at 12:00 -0400, Eric Snowberg wrote:
> > Many UEFI Linux distributions boot using shim. The UEFI shim provides
> > what is called Machine Owner Keys (MOK). Shim uses both the UEFI Secure
> > Boot DB and MOK keys to validate the next step in the boot chain. The
> > MOK facility can be used to import user generated keys. These keys can
> > be used to sign an end-user development kernel build. When Linux boots,
> > pre-boot keys (both UEFI Secure Boot DB and MOK keys) get loaded in the
> > Linux .platform keyring.
> >
> > Currently, pre-boot keys are not trusted within the Linux trust boundary
> > [1]. These platform keys can only be used for kexec. If an end-user
>
> What exactly is "trust boundary"? And what do you mean when you say that
> Linux "trusts" something? AFAIK, software does not have feelings. Please,
> just speak about exact things.
>
> That's the whole point of the cover letter. It's better to not have cover
> letter at all, than a confusing cover letter that reads like a white paper.
> Code changes at least tell the exact story, and not speak about feelings.
>
> > wants to use their own key within the Linux trust boundary, they must
> > either compile it into the kernel themselves or use the insert-sys-cert
> > script. Both options present a problem. Many end-users do not want to
> > compile their own kernels. With the insert-sys-cert option, there are
> > missing upstream changes [2]. Also, with the insert-sys-cert option,
> > the end-user must re-sign their kernel again with their own key, and
> > then insert that key into the MOK db. Another problem with
> > insert-sys-cert is that only a single key can be inserted into a
> > compressed kernel.
>
> I use a pre-compiled kernel in my desktop: https://liquorix.net/. When
> a new version comes up it requires a sbsign one-liner to sign it for
> secure boot. I'm wondering what is the problem I'm facing because I do
> not see it.
>
> If there are something missing changes that you use as a rationale for
> this large patch set, you should at least broadly explain what we are
> missing. How I conclude this paragraph is that, since there is only an
> xref, they are not really "that important" changes, which are missing.
>
> > Having the ability to insert a key into the Linux trust boundary opens
> > up various possibilities. The end-user can use a pre-built kernel and
> > sign their own kernel modules. It also opens up the ability for an
>
> Which both can be done by end-user as of today, or I'm misreading this.
>
> > end-user to more easily use digital signature based IMA-appraisal. To
> > get a key into the ima keyring, it must be signed by a key within the
> > Linux trust boundary.
>
> What is IMA appraisal? I just don't know it because I don't use IMA.
> Again, this trust boundary is really something I do not. Looking at
> code changes, you could just speak about exact assets in the kernel.
>
> > Downstream Linux distros try to have a single signed kernel for each
> > architecture. Each end-user may use this kernel in entirely different
> > ways. Some downstream kernels have chosen to always trust platform keys
> > within the Linux trust boundary for kernel module signing. These
> > kernels have no way of using digital signature base IMA appraisal.
> >
> > This series introduces a new Linux kernel keyring containing the Machine
> > Owner Keys (MOK) called .machine. It also adds a new MOK variable to shim.
> > This variable allows the end-user to decide if they want to trust keys
> > enrolled in the MOK within the Linux trust boundary. By default,
> > nothing changes; MOK keys are not trusted within the Linux kernel. They
> > are only trusted after the end-user makes the decision themselves. The
> > end-user would set this through mokutil using a new --trust-mok option
> > [3]. This would work similar to how the kernel uses MOK variables to
> > enable/disable signature validation as well as use/ignore the db.
>
> OK, changes are described here (again speaking about trusting tho). The
> motivation part is missing. The text before this is more like confusion
> part. When you describe motivation to do something you should really be in
> grass roots, e.g. "when you have this feature in the kernel, look, I can
> do now this". It's not that hard. E.g. with an usage example it is quite
> quick accomplish this.
The code changes overally make sense but this motivotional part is the
problem. E.g. if you do a pull request, it is completely *unusable* in
that context. In that case I would have to write something that should
have been the cover letter. It's 12 patches, so it is perfectly sensible
to ask a better one.
/Jarkko
next prev parent reply other threads:[~2021-09-08 16:49 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-07 16:00 [PATCH v5 00/12] Enroll kernel keys thru MOK Eric Snowberg
2021-09-07 16:00 ` [PATCH v5 01/12] integrity: Introduce a Linux keyring called machine Eric Snowberg
2021-09-09 13:55 ` Jarkko Sakkinen
2021-09-09 15:19 ` Mimi Zohar
2021-09-09 17:32 ` Eric Snowberg
2021-09-07 16:01 ` [PATCH v5 02/12] integrity: Do not allow machine keyring updates following init Eric Snowberg
2021-09-09 13:43 ` Jarkko Sakkinen
2021-09-07 16:01 ` [PATCH v5 03/12] KEYS: CA link restriction Eric Snowberg
2021-09-07 16:01 ` [PATCH v5 04/12] integrity: restrict INTEGRITY_KEYRING_MACHINE to restrict_link_by_ca Eric Snowberg
2021-09-09 13:49 ` Jarkko Sakkinen
2021-09-09 17:25 ` Mimi Zohar
2021-09-09 17:53 ` Eric Snowberg
2021-09-09 18:19 ` Mimi Zohar
2021-09-07 16:01 ` [PATCH v5 05/12] integrity: add new keyring handler for mok keys Eric Snowberg
2021-09-07 16:01 ` [PATCH v5 06/12] KEYS: add a reference to machine keyring Eric Snowberg
2021-09-07 16:01 ` [PATCH v5 07/12] KEYS: Introduce link restriction to include builtin, secondary and machine keys Eric Snowberg
2021-09-09 17:26 ` Mimi Zohar
2021-09-09 18:03 ` Eric Snowberg
2021-09-09 18:19 ` Mimi Zohar
2021-09-07 16:01 ` [PATCH v5 08/12] KEYS: integrity: change link restriction to trust the machine keyring Eric Snowberg
2021-09-09 17:27 ` Mimi Zohar
2021-09-07 16:01 ` [PATCH v5 09/12] KEYS: link secondary_trusted_keys to machine trusted keys Eric Snowberg
2021-09-07 16:01 ` [PATCH v5 10/12] integrity: store reference to machine keyring Eric Snowberg
2021-09-07 16:01 ` [PATCH v5 11/12] integrity: Trust MOK keys if MokListTrustedRT found Eric Snowberg
2021-09-07 16:01 ` [PATCH v5 12/12] integrity: Only use machine keyring when uefi_check_trust_mok_keys is true Eric Snowberg
2021-09-09 13:58 ` Jarkko Sakkinen
2021-09-08 16:03 ` [PATCH v5 00/12] Enroll kernel keys thru MOK Jarkko Sakkinen
2021-09-08 16:49 ` Jarkko Sakkinen [this message]
2021-09-08 22:25 ` Eric Snowberg
2021-09-09 13:02 ` Mimi Zohar
2021-09-08 17:09 ` Eric Snowberg
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