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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: Ard 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ard Biesheuvel 2017-08-25 16:50:16 +01:00 committed by Ingo Molnar
parent ccc829ba36
commit c2ceb5fd4e
3 changed files with 8 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/firmware/efi/efi.c
View File

@ -541,6 +541,7 @@ int __init efi_config_parse_tables(void *config_tables, int count, int sz,
if (seed != NULL) {
add_device_randomness(seed->bits, seed->size);
early_memunmap(seed, sizeof(*seed) + size);
pr_notice("seeding entropy pool\n");
} else {
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);
if (seed != NULL) {
size = min(seed->size, 32U);
size = min(seed->size, EFI_RANDOM_SEED_SIZE);
memunmap(seed);
} else {
pr_err("Could not map UEFI random seed!\n");

10
drivers/firmware/efi/libstub/random.c
View File

@ -145,8 +145,6 @@ efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg,
return status;
}
#define RANDOM_SEED_SIZE 32
efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg)
{
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;
status = efi_call_early(allocate_pool, EFI_RUNTIME_SERVICES_DATA,
sizeof(*seed) + RANDOM_SEED_SIZE,
sizeof(*seed) + EFI_RANDOM_SEED_SIZE,
(void **)&seed);
if (status != EFI_SUCCESS)
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);
if (status == EFI_UNSUPPORTED)
/*
* Use whatever algorithm we have available if the raw algorithm
* is not implemented.
*/
status = rng->get_rng(rng, NULL, RANDOM_SEED_SIZE,
status = rng->get_rng(rng, NULL, EFI_RANDOM_SEED_SIZE,
seed->bits);
if (status != EFI_SUCCESS)
goto err_freepool;
seed->size = RANDOM_SEED_SIZE;
seed->size = EFI_RANDOM_SEED_SIZE;
status = efi_call_early(install_configuration_table, &rng_table_guid,
seed);
if (status != EFI_SUCCESS)

2
include/linux/efi.h
View File

@ -1571,6 +1571,8 @@ efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table,
void *priv,
efi_exit_boot_map_processing priv_func);
#define EFI_RANDOM_SEED_SIZE 64U
struct linux_efi_random_seed {
u32 size;
u8 bits[];