Commit c2ceb5fd authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Ingo Molnar
Browse files

efi/random: Increase size of firmware supplied randomness 



The crng code requires at least 64 bytes (2 * CHACHA20_BLOCK_SIZE)
to complete the fast boot-time init, so provide that many bytes
when invoking UEFI protocols to seed the entropy pool. Also, add
a notice so we can tell from the boot log when the seeding actually
took place.

Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20170825155019.6740-3-ard.biesheuvel@linaro.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ccc829ba

drivers/firmware/efi/efi.c

+2 −1
Original line number Original line Diff line number Diff line
@@ -541,6 +541,7 @@ int __init efi_config_parse_tables(void *config_tables, int count, int sz, 
			if (seed != NULL) {

			if (seed != NULL) {

				add_device_randomness(seed->bits, seed->size);

				add_device_randomness(seed->bits, seed->size);

				early_memunmap(seed, sizeof(*seed) + size);

				early_memunmap(seed, sizeof(*seed) + size);

				pr_notice("seeding entropy pool\n");

			} else {

			} else {

				pr_err("Could not map UEFI random seed!\n");

				pr_err("Could not map UEFI random seed!\n");

			}

			}
@@ -900,7 +901,7 @@ static int update_efi_random_seed(struct notifier_block *nb, 




	seed = memremap(efi.rng_seed, sizeof(*seed), MEMREMAP_WB);

	seed = memremap(efi.rng_seed, sizeof(*seed), MEMREMAP_WB);

	if (seed != NULL) {

	if (seed != NULL) {

		size = min(seed->size, 32U);

		size = min(seed->size, EFI_RANDOM_SEED_SIZE);

		memunmap(seed);

		memunmap(seed);

	} else {

	} else {

		pr_err("Could not map UEFI random seed!\n");

		pr_err("Could not map UEFI random seed!\n");

drivers/firmware/efi/libstub/random.c

+4 −6
Original line number Original line Diff line number Diff line
@@ -145,8 +145,6 @@ efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg, 
	return status;

	return status;

}

}





#define RANDOM_SEED_SIZE	32



efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg)

efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg)

{

{

	efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;

	efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
@@ -162,25 +160,25 @@ efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg) 
		return status;

		return status;





	status = efi_call_early(allocate_pool, EFI_RUNTIME_SERVICES_DATA,

	status = efi_call_early(allocate_pool, EFI_RUNTIME_SERVICES_DATA,

				sizeof(*seed) + RANDOM_SEED_SIZE,

				sizeof(*seed) + EFI_RANDOM_SEED_SIZE,

				(void **)&seed);

				(void **)&seed);

	if (status != EFI_SUCCESS)

	if (status != EFI_SUCCESS)

		return status;

		return status;





	status = rng->get_rng(rng, &rng_algo_raw, RANDOM_SEED_SIZE,

	status = rng->get_rng(rng, &rng_algo_raw, EFI_RANDOM_SEED_SIZE,

			      seed->bits);

			      seed->bits);

	if (status == EFI_UNSUPPORTED)

	if (status == EFI_UNSUPPORTED)

		/*

		/*

		 * Use whatever algorithm we have available if the raw algorithm

		 * Use whatever algorithm we have available if the raw algorithm

		 * is not implemented.

		 * is not implemented.

		 */

		 */

		status = rng->get_rng(rng, NULL, RANDOM_SEED_SIZE,

		status = rng->get_rng(rng, NULL, EFI_RANDOM_SEED_SIZE,

				      seed->bits);

				      seed->bits);





	if (status != EFI_SUCCESS)

	if (status != EFI_SUCCESS)

		goto err_freepool;

		goto err_freepool;





	seed->size = RANDOM_SEED_SIZE;

	seed->size = EFI_RANDOM_SEED_SIZE;

	status = efi_call_early(install_configuration_table, &rng_table_guid,

	status = efi_call_early(install_configuration_table, &rng_table_guid,

				seed);

				seed);

	if (status != EFI_SUCCESS)

	if (status != EFI_SUCCESS)

include/linux/efi.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -1571,6 +1571,8 @@ efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table, 
				    void *priv,

				    void *priv,

				    efi_exit_boot_map_processing priv_func);

				    efi_exit_boot_map_processing priv_func);





#define EFI_RANDOM_SEED_SIZE		64U



struct linux_efi_random_seed {

struct linux_efi_random_seed {

	u32	size;

	u32	size;

	u8	bits[];

	u8	bits[];

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