From: Kees Cook <keescook@chromium.org>
To: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: ard.biesheuvel@linaro.org, hsinyi@chromium.org,
swboyd@chromium.org, robh@kernel.org, tytso@mit.edu,
joeyli.kernel@gmail.com, linux-kernel@vger.kernel.org,
linux-efi@vger.kernel.org
Subject: Re: [RFC] random: UEFI RNG input is bootloader randomness
Date: Sat, 28 Sep 2019 10:09:28 -0700 [thread overview]
Message-ID: <201909281008.C2039DBDB3@keescook> (raw)
In-Reply-To: <20190928101428.GA222453@light.dominikbrodowski.net>
On Sat, Sep 28, 2019 at 12:14:28PM +0200, Dominik Brodowski wrote:
> Depending on RANDOM_TRUST_BOOTLOADER, bootloader-provided randomness
> is credited as entropy. As the UEFI seeding entropy pool is seeded by
> the UEFI firmware/bootloader, add its content as bootloader randomness.
>
> Note that this UEFI (v2.4 or newer) feature is currently only
> implemented for EFI stub booting on ARM, and further note that
> RANDOM_TRUST_BOOTLOADER must only be enabled if there indeed is
> sufficient trust in the bootloader _and_ its source of randomness.
>
> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Hsin-Yi Wang <hsinyi@chromium.org>
> Cc: Stephen Boyd <swboyd@chromium.org>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Theodore Ts'o <tytso@mit.edu>
> Cc: Lee, Chun-Yi <joeyli.kernel@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
-Kees
>
> ---
>
> Untested patch, as efi_random_get_seed() is only hooked up on ARM,
> and the firmware on my old x86 laptop only has UEFI v2.31 anyway.
>
> Thanks,
> Dominik
>
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 8f1ab04f6743..db0bffce754e 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -545,7 +545,7 @@ int __init efi_config_parse_tables(void *config_tables, int count, int sz,
> sizeof(*seed) + size);
> if (seed != NULL) {
> pr_notice("seeding entropy pool\n");
> - add_device_randomness(seed->bits, seed->size);
> + add_bootloader_randomness(seed->bits, seed->size);
> early_memunmap(seed, sizeof(*seed) + size);
> } else {
> pr_err("Could not map UEFI random seed!\n");
--
Kees Cook
next prev parent reply other threads:[~2019-09-28 17:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-28 10:14 [RFC] random: UEFI RNG input is bootloader randomness Dominik Brodowski
2019-09-28 17:09 ` Kees Cook [this message]
2019-09-30 11:11 ` Bhupesh Sharma
2019-09-30 11:57 ` Ard Biesheuvel
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