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

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Message-ID: <4b275a33-28ac-78c2-e075-ea2eda4f13a8@canonical.com>
Date:   Fri, 12 Mar 2021 18:39:30 +0000
From:   Dimitri John Ledkov <dimitri.ledkov@...onical.com>
To:     David Howells <dhowells@...hat.com>,
        Eric Snowberg <eric.snowberg@...cle.com>
Cc:     James Bottomley <James.Bottomley@...senPartnership.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Mickaël Salaün <mic@...ikod.net>,
        keyrings@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] integrity: Load mokx variables into the blacklist
 keyring

On 25/02/2021 20:59, David Howells wrote:
> From: Eric Snowberg <eric.snowberg@...cle.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@...cle.com>
> Suggested-by: James Bottomley <James.Bottomley@...senPartnership.com>
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: Jarkko Sakkinen <jarkko@...nel.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.

>  	/* Load the MokListRT certs */
>  	rc = load_moklist_certs();
>  
> 
> 
>