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authorTheodore Ts'o <tytso@mit.edu>2018-07-17 18:24:27 -0400
committerTheodore Ts'o <tytso@mit.edu>2018-07-24 15:43:24 -0400
commit39a8883a2b989d1d21bd8dd99f5557f0c5e89694 (patch)
tree9e86c920e258b8ca73ffa3955cd82c6c1ee84cea /drivers/char/random.c
parent3672476edaa0660eb833f54fa9edeb505417b75c (diff)
random: add a config option to trust the CPU's hwrng
This gives the user building their own kernel (or a Linux distribution) the option of deciding whether or not to trust the CPU's hardware random number generator (e.g., RDRAND for x86 CPU's) as being correctly implemented and not having a back door introduced (perhaps courtesy of a Nation State's law enforcement or intelligence agencies). This will prevent getrandom(2) from blocking, if there is a willingness to trust the CPU manufacturer. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'drivers/char/random.c')
-rw-r--r--drivers/char/random.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 34ddfd57419b..f4013b8a711b 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -782,6 +782,7 @@ static void invalidate_batched_entropy(void);
static void crng_initialize(struct crng_state *crng)
{
int i;
+ int arch_init = 1;
unsigned long rv;
memcpy(&crng->state[0], "expand 32-byte k", 16);
@@ -792,10 +793,18 @@ static void crng_initialize(struct crng_state *crng)
_get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
for (i = 4; i < 16; i++) {
if (!arch_get_random_seed_long(&rv) &&
- !arch_get_random_long(&rv))
+ !arch_get_random_long(&rv)) {
rv = random_get_entropy();
+ arch_init = 0;
+ }
crng->state[i] ^= rv;
}
+#ifdef CONFIG_RANDOM_TRUST_CPU
+ if (arch_init) {
+ crng_init = 2;
+ pr_notice("random: crng done (trusting CPU's manufacturer)\n");
+ }
+#endif
crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
}