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authorLinus Torvalds <torvalds@linux-foundation.org>2018-08-16 07:16:02 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-16 07:16:02 +0300
commit99a2c789ddeb703cf7b0a3d889ab1a25cf4cbbaf (patch)
tree3a653ba4bfb2db0c8fc52fbb5a2f0dc2e817e513 /drivers
parentfa3b39cdafbfd5d9b1d064f5cf63cf0314f1d070 (diff)
parent9a47249d444d344051c7c0e909fad0e88515a5c2 (diff)
downloadlinux-99a2c789ddeb703cf7b0a3d889ab1a25cf4cbbaf.tar.xz
Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random
Pull random updates from Ted Ts'o: "Some changes to trust cpu-based hwrng (such as RDRAND) for initializing hashed pointers and (optionally, controlled by a config option) to initialize the CRNG to avoid boot hangs" * tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random: random: Make crng state queryable random: remove preempt disabled region random: add a config option to trust the CPU's hwrng vsprintf: Add command line option debug_boot_weak_hash vsprintf: Use hw RNG for ptr_key random: Return nbytes filled from hw RNG random: Fix whitespace pre random-bytes work
Diffstat (limited to 'drivers')
-rw-r--r--drivers/char/Kconfig14
-rw-r--r--drivers/char/random.c49
2 files changed, 49 insertions, 14 deletions
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 212f447938ae..ce277ee0a28a 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -554,3 +554,17 @@ config ADI
endmenu
+config RANDOM_TRUST_CPU
+ bool "Trust the CPU manufacturer to initialize Linux's CRNG"
+ depends on X86 || S390 || PPC
+ default n
+ help
+ Assume that CPU manufacturer (e.g., Intel or AMD for RDSEED or
+ RDRAND, IBM for the S390 and Power PC architectures) is trustworthy
+ for the purposes of initializing Linux's CRNG. Since this is not
+ something that can be independently audited, this amounts to trusting
+ 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.
+
diff --git a/drivers/char/random.c b/drivers/char/random.c
index bd449ad52442..bf5f99fc36f1 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;
}
@@ -1122,8 +1131,6 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
} sample;
long delta, delta2, delta3;
- preempt_disable();
-
sample.jiffies = jiffies;
sample.cycles = random_get_entropy();
sample.num = num;
@@ -1161,8 +1168,6 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
* and limit entropy entimate to 12 bits.
*/
credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
-
- preempt_enable();
}
void add_input_randomness(unsigned int type, unsigned int code,
@@ -1659,6 +1664,21 @@ int wait_for_random_bytes(void)
EXPORT_SYMBOL(wait_for_random_bytes);
/*
+ * Returns whether or not the urandom pool has been seeded and thus guaranteed
+ * to supply cryptographically secure random numbers. This applies to: the
+ * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
+ * ,u64,int,long} family of functions.
+ *
+ * Returns: true if the urandom pool has been seeded.
+ * false if the urandom pool has not been seeded.
+ */
+bool rng_is_initialized(void)
+{
+ return crng_ready();
+}
+EXPORT_SYMBOL(rng_is_initialized);
+
+/*
* Add a callback function that will be invoked when the nonblocking
* pool is initialised.
*
@@ -1725,30 +1745,31 @@ EXPORT_SYMBOL(del_random_ready_callback);
* key known by the NSA). So it's useful if we need the speed, but
* only if we're willing to trust the hardware manufacturer not to
* have put in a back door.
+ *
+ * Return number of bytes filled in.
*/
-void get_random_bytes_arch(void *buf, int nbytes)
+int __must_check get_random_bytes_arch(void *buf, int nbytes)
{
+ int left = nbytes;
char *p = buf;
- trace_get_random_bytes_arch(nbytes, _RET_IP_);
- while (nbytes) {
+ trace_get_random_bytes_arch(left, _RET_IP_);
+ while (left) {
unsigned long v;
- int chunk = min(nbytes, (int)sizeof(unsigned long));
+ int chunk = min_t(int, left, sizeof(unsigned long));
if (!arch_get_random_long(&v))
break;
-
+
memcpy(p, &v, chunk);
p += chunk;
- nbytes -= chunk;
+ left -= chunk;
}
- if (nbytes)
- get_random_bytes(p, nbytes);
+ return nbytes - left;
}
EXPORT_SYMBOL(get_random_bytes_arch);
-
/*
* init_std_data - initialize pool with system data
*