Re: [PATCH 4/4] integrity: Load mokx variables into the blacklist keyring

From: Eric Snowberg <eric.snowberg@oracle.com>
To: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Cc: "David Howells" <dhowells@redhat.com>,
	"James Bottomley" <James.Bottomley@HansenPartnership.com>,
	"Jarkko Sakkinen" <jarkko@kernel.org>,
	"Mickaël Salaün" <mic@digikod.net>,
	keyrings@vger.kernel.org, linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/4] integrity: Load mokx variables into the blacklist keyring
Date: Fri, 12 Mar 2021 14:49:05 -0700	[thread overview]
Message-ID: <92182F5F-327E-4F1D-A7D9-42355625C84C@oracle.com> (raw)
In-Reply-To: <4b275a33-28ac-78c2-e075-ea2eda4f13a8@canonical.com>

> On Mar 12, 2021, at 11:39 AM, Dimitri John Ledkov <dimitri.ledkov@canonical.com> wrote:
> 
> On 25/02/2021 20:59, David Howells wrote:
>> From: Eric Snowberg <eric.snowberg@oracle.com>
>> 
>> During boot the Secure Boot Forbidden Signature Database, dbx,
>> is loaded into the blacklist keyring.  Systems booted with shim
>> have an equivalent Forbidden Signature Database called mokx.
>> Currently mokx is only used by shim and grub, the contents are
>> ignored by the kernel.
>> 
>> Add the ability to load mokx into the blacklist keyring during boot.
>> 
>> Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
>> Suggested-by: James Bottomley <James.Bottomley@HansenPartnership.com>
>> Signed-off-by: David Howells <dhowells@redhat.com>
>> cc: Jarkko Sakkinen <jarkko@kernel.org>
>> Link: https://lore.kernel.org/r/20210122181054.32635-5-eric.snowberg@oracle.com/ # v5
>> Link: https://lore.kernel.org/r/c33c8e3839a41e9654f41cc92c7231104931b1d7.camel@HansenPartnership.com/
>> ---
>> 
>> security/integrity/platform_certs/load_uefi.c |   20 ++++++++++++++++++--
>> 1 file changed, 18 insertions(+), 2 deletions(-)
>> 
>> diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c
>> index ee4b4c666854..f290f78c3f30 100644
>> --- a/security/integrity/platform_certs/load_uefi.c
>> +++ b/security/integrity/platform_certs/load_uefi.c
>> @@ -132,8 +132,9 @@ static int __init load_moklist_certs(void)
>> static int __init load_uefi_certs(void)
>> {
>> 	efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
>> -	void *db = NULL, *dbx = NULL;
>> -	unsigned long dbsize = 0, dbxsize = 0;
>> +	efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
>> +	void *db = NULL, *dbx = NULL, *mokx = NULL;
>> +	unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0;
>> 	efi_status_t status;
>> 	int rc = 0;
>> 
>> @@ -175,6 +176,21 @@ static int __init load_uefi_certs(void)
>> 		kfree(dbx);
>> 	}
>> 
>> +	mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status);
>> +	if (!mokx) {
>> +		if (status == EFI_NOT_FOUND)
>> +			pr_debug("mokx variable wasn't found\n");
>> +		else
>> +			pr_info("Couldn't get mokx list\n");
>> +	} else {
>> +		rc = parse_efi_signature_list("UEFI:MokListXRT",
>> +					      mokx, mokxsize,
>> +					      get_handler_for_dbx);
>> +		if (rc)
>> +			pr_err("Couldn't parse mokx signatures %d\n", rc);
>> +		kfree(mokx);
>> +	}
>> +
> 
> 
> My preference would be if the above hunk was moved into the
> load_moklist_certs() function which is called just below. Such that
> loading of MokListRT & MOkListXRT are done next to each other.
> 
> And also implement loading the same way it is done for MokListRT -
> specifically via the EFI MOKvar config table & then via a variable.
> 
> See 726bd8965a5f112d9601f7ce68effa1e46e02bf2 otherwise large MokListXRT
> will fail to parse.

Is this support available from shim now?  Previously I thought only
MOK could be loaded from the config table, not MOKx.