diff options
Diffstat (limited to 'drivers/char/random.c')
| -rw-r--r-- | drivers/char/random.c | 29 |
1 files changed, 24 insertions, 5 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 2296ff162316..ed7e283b6cb5 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1038,17 +1038,34 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, /* * This function is the exported kernel interface. It returns some - * number of good random numbers, suitable for seeding TCP sequence - * numbers, etc. + * number of good random numbers, suitable for key generation, seeding + * TCP sequence numbers, etc. It does not use the hw random number + * generator, if available; use get_random_bytes_arch() for that. */ void get_random_bytes(void *buf, int nbytes) { + extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0); +} +EXPORT_SYMBOL(get_random_bytes); + +/* + * This function will use the architecture-specific hardware random + * number generator if it is available. The arch-specific hw RNG will + * almost certainly be faster than what we can do in software, but it + * is impossible to verify that it is implemented securely (as + * opposed, to, say, the AES encryption of a sequence number using a + * 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. + */ +void get_random_bytes_arch(void *buf, int nbytes) +{ char *p = buf; while (nbytes) { unsigned long v; int chunk = min(nbytes, (int)sizeof(unsigned long)); - + if (!arch_get_random_long(&v)) break; @@ -1057,9 +1074,11 @@ void get_random_bytes(void *buf, int nbytes) nbytes -= chunk; } - extract_entropy(&nonblocking_pool, p, nbytes, 0, 0); + if (nbytes) + extract_entropy(&nonblocking_pool, p, nbytes, 0, 0); } -EXPORT_SYMBOL(get_random_bytes); +EXPORT_SYMBOL(get_random_bytes_arch); + /* * init_std_data - initialize pool with system data |