diff options
| author |   Kees Cook <keescook@chromium.org> | 2018-08-27 14:51:54 -0700 |
|---|---|---|
| committer |   Theodore Ts'o <tytso@mit.edu> | 2018-09-01 12:51:54 -0400 |
| commit | 9b25436662d5fb4c66eb527ead53cab15f596ee0 (patch) | |
| tree | f81de29079d0cd3e4816cae947a0a3b0b3c4767a | |
| parent | random: Make crng state queryable (diff) | |
| download | linux-dev-9b25436662d5fb4c66eb527ead53cab15f596ee0.tar.xz linux-dev-9b25436662d5fb4c66eb527ead53cab15f596ee0.zip | |
random: make CPU trust a boot parameter
Instead of forcing a distro or other system builder to choose
at build time whether the CPU is trusted for CRNG seeding via
CONFIG_RANDOM_TRUST_CPU, provide a boot-time parameter for end users to
control the choice. The CONFIG will set the default state instead.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 6 | ||||
| -rw-r--r-- | drivers/char/Kconfig | 4 | ||||
| -rw-r--r-- | drivers/char/random.c | 11 |
3 files changed, 16 insertions, 5 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0c8f7889efa1..227c5c6fa4c1 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3390,6 +3390,12 @@ ramdisk_size= [RAM] Sizes of RAM disks in kilobytes See Documentation/blockdev/ramdisk.txt. + random.trust_cpu={on,off} + [KNL] Enable or disable trusting the use of the + CPU's random number generator (if available) to + fully seed the kernel's CRNG. Default is controlled + by CONFIG_RANDOM_TRUST_CPU. + ras=option[,option,...] [KNL] RAS-specific options cec_disable [X86] diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig index ce277ee0a28a..40728491f37b 100644 --- a/drivers/char/Kconfig +++ b/drivers/char/Kconfig @@ -566,5 +566,5 @@ config RANDOM_TRUST_CPU that CPU manufacturer (perhaps with the insistence or mandate of a Nation State's intelligence or law enforcement agencies) has not installed a hidden back door to compromise the CPU's - random number generation facilities. - + random number generation facilities. This can also be configured + at boot with "random.trust_cpu=on/off". diff --git a/drivers/char/random.c b/drivers/char/random.c index bf5f99fc36f1..c75b6cdf0053 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -779,6 +779,13 @@ static struct crng_state **crng_node_pool __read_mostly; static void invalidate_batched_entropy(void); +static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); +static int __init parse_trust_cpu(char *arg) +{ + return kstrtobool(arg, &trust_cpu); +} +early_param("random.trust_cpu", parse_trust_cpu); + static void crng_initialize(struct crng_state *crng) { int i; @@ -799,12 +806,10 @@ static void crng_initialize(struct crng_state *crng) } crng->state[i] ^= rv; } -#ifdef CONFIG_RANDOM_TRUST_CPU - if (arch_init) { + if (trust_cpu && arch_init) { crng_init = 2; pr_notice("random: crng done (trusting CPU's manufacturer)\n"); } -#endif crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1; } |