From: Eric Snowberg <eric.snowberg@oracle.com>
To: Mimi Zohar <zohar@linux.ibm.com>,
David Howells <dhowells@redhat.com>,
Jarkko Sakkinen <jarkko@kernel.org>
Cc: linux-integrity <linux-integrity@vger.kernel.org>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
dwmw2@infradead.org, herbert@gondor.apana.org.au,
davem@davemloft.net, jmorris@namei.org, serge@hallyn.com,
nayna@linux.ibm.com, erichte@linux.ibm.com, mpe@ellerman.id.au,
keyrings@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-crypto@vger.kernel.org,
linux-security-module@vger.kernel.org,
James.Bottomley@hansenpartnership.com,
Eric Snowberg <eric.snowberg@oracle.com>
Subject: Re: [PATCH v4] certs: Add EFI_CERT_X509_GUID support for dbx entries
Date: Wed, 27 Jan 2021 08:41:29 -0700 [thread overview]
Message-ID: <86CE3924-E36F-44FD-A259-3CC7E69D3EAC@oracle.com> (raw)
In-Reply-To: <61a0420790250807837b5a701bb52f3d63ff0c84.camel@linux.ibm.com>
> On Jan 27, 2021, at 7:03 AM, Mimi Zohar <zohar@linux.ibm.com> wrote:
>
> [Cc'ing linux-integrity]
>
> On Wed, 2021-01-27 at 11:46 +0000, David Howells wrote:
>> Jarkko Sakkinen <jarkko@kernel.org> wrote:
>>
>>>> I suppose a user space tool could be created. But wouldn’t what is
>>>> currently done in the kernel in this area need to be removed?
>>>
>>> Right. I don't think this was a great idea in the first place to
>>> do to the kernel but since it exists, I guess the patch does make
>>> sense.
>>
>> This information needs to be loaded from the UEFI tables before the system
>> starts loading any kernel modules or running any programs (if we do
>> verification of such, which I think IMA can do).
>
> There needs to a clear distinction between the pre-boot and post-boot
> keys. UEFI has its own trust model, which should be limited to UEFI.
> The .platform keyring was upstreamed and limited to verifying the kexec
> kernel image. Any other usage of the .platform keyring keys is
> abusing its intended purpose.
>
> The cover letter says, "Anytime the .platform keyring is used, the
> keys in the .blacklist keyring are referenced, if a matching key is
> found, the key will be rejected." I don't have a problem with loading
> the UEFI X509 dbx entries as long as its usage is limited to verifying
> the kexec kernel image.
Correct, with my patch, when EFI_CERT_X509_GUID entries are found in the
dbx, they will only be used during kexec. I believe the latest dbx file on
uefi.org contains three of these entires.
Based on my understanding of why the platform keyring was introduced,
I intentionally only used these for kexec. I do question the current
upstream mainline code though. Currently, when EFI_CERT_X509_SHA256_GUID
or EFI_CERT_SHA256_GUID entries are found in the dbx, they are applied
everywhere. It seems like there should be a dbx revocation keyring
equivalent to the current platform keyring that is only used for pre-boot.
If that is a direction you would like to see this go in the future, let
me know, I’d be happy to work on it.
next prev parent reply other threads:[~2021-01-27 15:46 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-16 0:49 [PATCH v4] certs: Add EFI_CERT_X509_GUID support for dbx entries Eric Snowberg
2020-09-16 18:09 ` Jarkko Sakkinen
2020-12-10 9:49 ` David Howells
2020-12-10 18:56 ` Eric Snowberg
2021-01-12 14:57 ` David Howells
2021-01-13 20:41 ` Jarkko Sakkinen
2021-01-14 0:11 ` Eric Snowberg
2021-01-15 9:15 ` Jarkko Sakkinen
2021-01-15 16:49 ` Eric Snowberg
2021-01-20 11:26 ` Jarkko Sakkinen
2021-01-20 22:13 ` Eric Snowberg
2021-01-21 0:36 ` Jarkko Sakkinen
2021-01-27 11:46 ` David Howells
2021-01-27 14:03 ` Mimi Zohar
2021-01-27 15:41 ` Eric Snowberg [this message]
2021-01-28 4:13 ` Nayna
2021-01-30 10:24 ` Jarkko Sakkinen
2021-01-29 23:27 ` Jarkko Sakkinen
2021-01-12 17:10 ` David Howells
2021-01-12 19:13 ` Eric Snowberg
2021-01-15 17:21 ` James Bottomley
2021-01-15 23:01 ` Eric Snowberg
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