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Donenfeld" To: linux-efi@vger.kernel.org, linux-crypto@vger.kernel.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org, ardb@kernel.org Cc: "Jason A. Donenfeld" Subject: [PATCH v3 5/5] efi: random: refresh non-volatile random seed when RNG is initialized Date: Tue, 22 Nov 2022 03:04:04 +0100 Message-Id: <20221122020404.3476063-6-Jason@zx2c4.com> In-Reply-To: <20221122020404.3476063-1-Jason@zx2c4.com> References: <20221122020404.3476063-1-Jason@zx2c4.com> MIME-Version: 1.0 X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1750160162390975416?= X-GMAIL-MSGID: =?utf-8?q?1750160162390975416?= EFI has a rather unique benefit that it has access to some limited non-volatile storage, where the kernel can store a random seed. Register a notification for when the RNG is initialized, and at that point, store a new random seed. Signed-off-by: Jason A. Donenfeld --- drivers/firmware/efi/efi.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index f12cc29bd4b8..b23ec97d68ea 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -337,6 +337,24 @@ static void __init efi_debugfs_init(void) static inline void efi_debugfs_init(void) {} #endif +static void refresh_nv_rng_seed(struct work_struct *work) +{ + u8 seed[EFI_RANDOM_SEED_SIZE]; + + get_random_bytes(seed, sizeof(seed)); + efi.set_variable(L"RandomSeed", &LINUX_EFI_RANDOM_SEED_TABLE_GUID, + EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS, sizeof(seed), seed); + memzero_explicit(seed, sizeof(seed)); +} +static int refresh_nv_rng_seed_notification(struct notifier_block *nb, unsigned long action, void *data) +{ + static DECLARE_WORK(work, refresh_nv_rng_seed); + schedule_work(&work); + return NOTIFY_DONE; +} +static struct notifier_block refresh_nv_rng_seed_nb = { .notifier_call = refresh_nv_rng_seed_notification }; + /* * We register the efi subsystem with the firmware subsystem and the * efivars subsystem with the efi subsystem, if the system was booted with @@ -413,6 +431,7 @@ static int __init efisubsys_init(void) platform_device_register_simple("efi_secret", 0, NULL, 0); #endif + execute_with_initialized_rng(&refresh_nv_rng_seed_nb); return 0; err_remove_group: