| Message ID | 20221118133239.2515648-6-Jason@zx2c4.com |
|---|---|
| State | New |
| Headers | show |
| Series | Use EFI variables for random seed | expand |
On Fri, 18 Nov 2022 at 14:34, Jason A. Donenfeld <Jason@zx2c4.com> wrote: > > 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 <Jason@zx2c4.com> > --- > drivers/firmware/efi/efi.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > Not sure why I don't see v3 in my inbox. In any case, Reviewed-by: Ard Biesheuvel <ardb@kernel.org> for this patch, or the one with the varname wide string literal used in place instead of via a CPP macro. > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c > index f12cc29bd4b8..f8edf6164833 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(LINUX_EFI_RANDOM_NV_SEED_VAR, &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 0; > +} > +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: > -- > 2.38.1 >
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index f12cc29bd4b8..f8edf6164833 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(LINUX_EFI_RANDOM_NV_SEED_VAR, &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 0; +} +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:
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 <Jason@zx2c4.com> --- drivers/firmware/efi/efi.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)