[PATCH v8 16/17] integrity: Trust MOK keys if MokListTrustedRT found

[Darren Kenny]

On Tuesday, 2021-11-23 at 23:41:23 -05, 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 at oracle.com>

Reviewed-by: Darren Kenny <darren.kenny at oracle.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)
> v8: 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