[tip:efi/core] efi/random: Increase size of firmware supplied randomness

tip-bot for Ard Biesheuvel
2017-08-26T08:03:15Z

Commit-ID: c2ceb5fd4e921506e86208b82fca716a2c3aad59
Gitweb: http://git.kernel.org/tip/c2ceb5fd4e921506e86208b82fca716a2c3aad59
Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
AuthorDate: Fri, 25 Aug 2017 16:50:16 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 26 Aug 2017 09:20:33 +0200

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>
---
drivers/firmware/efi/efi.c | 3 ++-
drivers/firmware/efi/libstub/random.c | 10 ++++------
include/linux/efi.h | 2 ++
3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index a32e146..c8a27a2 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -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");
diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c
index 7e72954..e0e603a 100644
--- a/drivers/firmware/efi/libstub/random.c
+++ b/drivers/firmware/efi/libstub/random.c
@@ -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)
diff --git a/include/linux/efi.h b/include/linux/efi.h
index c241acc..33d41df 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -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[];