Re: [PATCH v2 05/16] x86/efi: Get entropy through EFI random number generator protocol

[Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>]

On Tue, 11 Aug, at 02:16:25PM, Lee, Chun-Yi wrote:
> +
> +static unsigned long efi_get_rng64(efi_system_table_t *sys_table,
> +				   void **rng_handle)
> +{
> +	const struct efi_config *efi_early = __efi_early();
> +	efi_rng_protocol_64 *rng = NULL;
> +	efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
> +	u64 *handles = (u64 *)(unsigned long)rng_handle;
> +	efi_status_t status;
> +	unsigned long rng_number;
> +
> +	status = efi_call_early(handle_protocol, handles[0],
> +				&rng_proto, (void **)&rng);
> +	if (status != EFI_SUCCESS)
> +		efi_printk(sys_table, "Failed to get EFI_RNG_PROTOCOL handles\n");
> +
> +	if (status == EFI_SUCCESS && rng) {
> +		status = efi_early->call((unsigned long)rng->get_rng, rng, NULL,
> +					sizeof(rng_number), &rng_number);

Actually, one thing just occurred to me - you're not passing an
RNGAlgorithm value and are relying upon the firmware's default
implementation.

I don't think that's a safe bet, the default could be anything and
might vary across implementations.

Can we do a little better here and pick a "preferred" algorithm
instead of the default?

-- 
Matt Fleming, Intel Open Source Technology Center