[PATCH] efi_loader: update SetVariable attribute check

[Heinrich Schuchardt]

On 2/14/23 10:19, Masahisa Kojima wrote:
> UEFI specification v2.10 says that
> EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS is deprecated and
> EFI_UNSUPPORTED should be returned in SetVariable variable service.
> Current implementation returns EFI_INVALID_PARAMETER,
> let's fix the return value.
>
> Together with above change, this commit also updates the SetVariable
> attribute check to be aligned with the EDK2 reference implementation.
>
> Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
> ---
>   lib/efi_loader/efi_variable.c | 30 +++++++++++++++++++++++-------
>   1 file changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
> index 4c85cfa607..1076ff7585 100644
> --- a/lib/efi_loader/efi_variable.c
> +++ b/lib/efi_loader/efi_variable.c
> @@ -230,9 +230,28 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
>   	u64 time = 0;
>   	enum efi_auth_var_type var_type;
>
> -	if (!variable_name || !*variable_name || !vendor ||
> -	    ((attributes & EFI_VARIABLE_RUNTIME_ACCESS) &&
> -	     !(attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS)))
> +	if (!variable_name || !*variable_name || !vendor)
> +		return EFI_INVALID_PARAMETER;
> +
> +	if (data_size != 0 && !data)

We tend to not use '!= 0' and ' == 0' in logical constraints. You could use

    if (data_size && !data)

instead.

> +		return EFI_INVALID_PARAMETER;
> +
> +	/* EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS is deprecated */
> +	if (attributes & EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS ||
> +	    ((attributes & EFI_VARIABLE_MASK) == 0))

!(attributes & EFI_VARIABLE_MASK)

> +		return EFI_UNSUPPORTED;
> +
> +	/* Make sure if runtime bit is set, boot service bit is set also */
> +	if ((attributes &
> +	     (EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_BOOTSERVICE_ACCESS)) ==
> +	    EFI_VARIABLE_RUNTIME_ACCESS)
> +		return EFI_INVALID_PARAMETER;
> +
> +	/* only EFI_VARIABLE_NON_VOLATILE attribute is invalid */
> +	if ((attributes & EFI_VARIABLE_MASK) == EFI_VARIABLE_NON_VOLATILE)
> +		return EFI_INVALID_PARAMETER;
> +
> +	if (attributes & EFI_VARIABLE_HARDWARE_ERROR_RECORD)
>   		return EFI_INVALID_PARAMETER;

Variables with flags NV, BS, RT, HR, name HwErrRec####, and GUID
EFI_HARDWARE_ERROR_VARIABLE are allowable according to the UEFI spec.
Why do we return EFI_INVALID_PARAMETER here?

Please, sort the checks above such that all EFI_INVALID_PARAMETER are
together followed by EFI_UNSUPPORTED.

Best regards

Heinrich

>
>   	/* check if a variable exists */
> @@ -281,8 +300,6 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
>
>   	/* authenticate a variable */
>   	if (IS_ENABLED(CONFIG_EFI_SECURE_BOOT)) {
> -		if (attributes & EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS)
> -			return EFI_INVALID_PARAMETER;
>   		if (attributes &
>   		    EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) {
>   			u32 env_attr;
> @@ -300,8 +317,7 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
>   		}
>   	} else {
>   		if (attributes &
> -		    (EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS |
> -		     EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS)) {
> +		    EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) {
>   			EFI_PRINT("Secure boot is not configured\n");
>   			return EFI_INVALID_PARAMETER;
>   		}