linux-kernel - Re: [PATCH v9 7/8] integrity: Trust MOK keys if MokListTrustedRT found

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Message-ID: <YdoQDjM2aC25M0r7@iki.fi>
Date:   Sun, 9 Jan 2022 00:28:30 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Eric Snowberg <eric.snowberg@...cle.com>
Cc:     dhowells@...hat.com, dwmw2@...radead.org, ardb@...nel.org,
        jmorris@...ei.org, serge@...lyn.com, nayna@...ux.ibm.com,
        zohar@...ux.ibm.com, keescook@...omium.org,
        torvalds@...ux-foundation.org, weiyongjun1@...wei.com,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-security-module@...r.kernel.org,
        James.Bottomley@...senpartnership.com, pjones@...hat.com,
        konrad.wilk@...cle.com
Subject: Re: [PATCH v9 7/8] integrity: Trust MOK keys if MokListTrustedRT
 found

On Wed, Jan 05, 2022 at 06:50:11PM -0500, Eric Snowberg wrote:
> A new Machine Owner Key (MOK) variable called MokListTrustedRT has been
> introduced in shim. When this UEFI variable is set, it indicates the
> end-user has made the decision themselves that they wish to trust MOK keys
> within the Linux trust boundary.  It is not an error if this variable
> does not exist. If it does not exist, the MOK keys should not be trusted
> within the kernel.
> 
> Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>
> ---
> v1: Initial version
> v2: Removed mok_keyring_trust_setup function
> v4: Unmodified from v2
> v5: Rename to machine keyring
> v6: Unmodified from v5
> v7: Use mokvar table instead of EFI var (suggested by Peter Jones)
> v9: Unmodified from v7
> ---
>  .../platform_certs/machine_keyring.c          | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/security/integrity/platform_certs/machine_keyring.c b/security/integrity/platform_certs/machine_keyring.c
> index ea2ac2f9f2b5..09fd8f20c756 100644
> --- a/security/integrity/platform_certs/machine_keyring.c
> +++ b/security/integrity/platform_certs/machine_keyring.c
> @@ -5,6 +5,7 @@
>   * Copyright (c) 2021, Oracle and/or its affiliates.
>   */
>  
> +#include <linux/efi.h>
>  #include "../integrity.h"
>  
>  static __init int machine_keyring_init(void)
> @@ -40,3 +41,21 @@ void __init add_to_machine_keyring(const char *source, const void *data, size_t
>  	if (rc)
>  		pr_info("Error adding keys to machine keyring %s\n", source);
>  }
> +
> +/*
> + * Try to load the MokListTrustedRT MOK variable to see if we should trust
> + * the MOK keys within the kernel. It is not an error if this variable
> + * does not exist.  If it does not exist, MOK keys should not be trusted
> + * within the machine keyring.
> + */
> +static __init bool uefi_check_trust_mok_keys(void)
> +{
> +	struct efi_mokvar_table_entry *mokvar_entry;
> +
> +	mokvar_entry = efi_mokvar_entry_find("MokListTrustedRT");
> +
> +	if (mokvar_entry)
> +		return true;
> +
> +	return false;
> +}
> -- 
> 2.18.4
> 


Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

BR, Jarkko