diff options
Diffstat (limited to 'arch/s390/crypto/arch_random.c')
| -rw-r--r-- | arch/s390/crypto/arch_random.c | 217 |
1 files changed, 0 insertions, 217 deletions
diff --git a/arch/s390/crypto/arch_random.c b/arch/s390/crypto/arch_random.c index 56007c763902..1f2d40993c4d 100644 --- a/arch/s390/crypto/arch_random.c +++ b/arch/s390/crypto/arch_random.c @@ -4,232 +4,15 @@ * * Copyright IBM Corp. 2017, 2020 * Author(s): Harald Freudenberger - * - * The s390_arch_random_generate() function may be called from random.c - * in interrupt context. So this implementation does the best to be very - * fast. There is a buffer of random data which is asynchronously checked - * and filled by a workqueue thread. - * If there are enough bytes in the buffer the s390_arch_random_generate() - * just delivers these bytes. Otherwise false is returned until the - * worker thread refills the buffer. - * The worker fills the rng buffer by pulling fresh entropy from the - * high quality (but slow) true hardware random generator. This entropy - * is then spread over the buffer with an pseudo random generator PRNG. - * As the arch_get_random_seed_long() fetches 8 bytes and the calling - * function add_interrupt_randomness() counts this as 1 bit entropy the - * distribution needs to make sure there is in fact 1 bit entropy contained - * in 8 bytes of the buffer. The current values pull 32 byte entropy - * and scatter this into a 2048 byte buffer. So 8 byte in the buffer - * will contain 1 bit of entropy. - * The worker thread is rescheduled based on the charge level of the - * buffer but at least with 500 ms delay to avoid too much CPU consumption. - * So the max. amount of rng data delivered via arch_get_random_seed is - * limited to 4k bytes per second. */ #include <linux/kernel.h> #include <linux/atomic.h> #include <linux/random.h> -#include <linux/slab.h> #include <linux/static_key.h> -#include <linux/workqueue.h> -#include <linux/moduleparam.h> #include <asm/cpacf.h> DEFINE_STATIC_KEY_FALSE(s390_arch_random_available); atomic64_t s390_arch_random_counter = ATOMIC64_INIT(0); EXPORT_SYMBOL(s390_arch_random_counter); - -#define ARCH_REFILL_TICKS (HZ/2) -#define ARCH_PRNG_SEED_SIZE 32 -#define ARCH_RNG_BUF_SIZE 2048 - -static DEFINE_SPINLOCK(arch_rng_lock); -static u8 *arch_rng_buf; -static unsigned int arch_rng_buf_idx; - -static void arch_rng_refill_buffer(struct work_struct *); -static DECLARE_DELAYED_WORK(arch_rng_work, arch_rng_refill_buffer); - -bool s390_arch_random_generate(u8 *buf, unsigned int nbytes) -{ - /* max hunk is ARCH_RNG_BUF_SIZE */ - if (nbytes > ARCH_RNG_BUF_SIZE) - return false; - - /* lock rng buffer */ - if (!spin_trylock(&arch_rng_lock)) - return false; - - /* try to resolve the requested amount of bytes from the buffer */ - arch_rng_buf_idx -= nbytes; - if (arch_rng_buf_idx < ARCH_RNG_BUF_SIZE) { - memcpy(buf, arch_rng_buf + arch_rng_buf_idx, nbytes); - atomic64_add(nbytes, &s390_arch_random_counter); - spin_unlock(&arch_rng_lock); - return true; - } - - /* not enough bytes in rng buffer, refill is done asynchronously */ - spin_unlock(&arch_rng_lock); - - return false; -} -EXPORT_SYMBOL(s390_arch_random_generate); - -static void arch_rng_refill_buffer(struct work_struct *unused) -{ - unsigned int delay = ARCH_REFILL_TICKS; - - spin_lock(&arch_rng_lock); - if (arch_rng_buf_idx > ARCH_RNG_BUF_SIZE) { - /* buffer is exhausted and needs refill */ - u8 seed[ARCH_PRNG_SEED_SIZE]; - u8 prng_wa[240]; - /* fetch ARCH_PRNG_SEED_SIZE bytes of entropy */ - cpacf_trng(NULL, 0, seed, sizeof(seed)); - /* blow this entropy up to ARCH_RNG_BUF_SIZE with PRNG */ - memset(prng_wa, 0, sizeof(prng_wa)); - cpacf_prno(CPACF_PRNO_SHA512_DRNG_SEED, - &prng_wa, NULL, 0, seed, sizeof(seed)); - cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN, - &prng_wa, arch_rng_buf, ARCH_RNG_BUF_SIZE, NULL, 0); - arch_rng_buf_idx = ARCH_RNG_BUF_SIZE; - } - delay += (ARCH_REFILL_TICKS * arch_rng_buf_idx) / ARCH_RNG_BUF_SIZE; - spin_unlock(&arch_rng_lock); - - /* kick next check */ - queue_delayed_work(system_long_wq, &arch_rng_work, delay); -} - -/* - * Here follows the implementation of s390_arch_get_random_long(). - * - * The random longs to be pulled by arch_get_random_long() are - * prepared in an 4K buffer which is filled from the NIST 800-90 - * compliant s390 drbg. By default the random long buffer is refilled - * 256 times before the drbg itself needs a reseed. The reseed of the - * drbg is done with 32 bytes fetched from the high quality (but slow) - * trng which is assumed to deliver 100% entropy. So the 32 * 8 = 256 - * bits of entropy are spread over 256 * 4KB = 1MB serving 131072 - * arch_get_random_long() invocations before reseeded. - * - * How often the 4K random long buffer is refilled with the drbg - * before the drbg is reseeded can be adjusted. There is a module - * parameter 's390_arch_rnd_long_drbg_reseed' accessible via - * /sys/module/arch_random/parameters/rndlong_drbg_reseed - * or as kernel command line parameter - * arch_random.rndlong_drbg_reseed=<value> - * This parameter tells how often the drbg fills the 4K buffer before - * it is re-seeded by fresh entropy from the trng. - * A value of 16 results in reseeding the drbg at every 16 * 4 KB = 64 - * KB with 32 bytes of fresh entropy pulled from the trng. So a value - * of 16 would result in 256 bits entropy per 64 KB. - * A value of 256 results in 1MB of drbg output before a reseed of the - * drbg is done. So this would spread the 256 bits of entropy among 1MB. - * Setting this parameter to 0 forces the reseed to take place every - * time the 4K buffer is depleted, so the entropy rises to 256 bits - * entropy per 4K or 0.5 bit entropy per arch_get_random_long(). With - * setting this parameter to negative values all this effort is - * disabled, arch_get_random long() returns false and thus indicating - * that the arch_get_random_long() feature is disabled at all. - */ - -static unsigned long rndlong_buf[512]; -static DEFINE_SPINLOCK(rndlong_lock); -static int rndlong_buf_index; - -static int rndlong_drbg_reseed = 256; -module_param_named(rndlong_drbg_reseed, rndlong_drbg_reseed, int, 0600); -MODULE_PARM_DESC(rndlong_drbg_reseed, "s390 arch_get_random_long() drbg reseed"); - -static inline void refill_rndlong_buf(void) -{ - static u8 prng_ws[240]; - static int drbg_counter; - - if (--drbg_counter < 0) { - /* need to re-seed the drbg */ - u8 seed[32]; - - /* fetch seed from trng */ - cpacf_trng(NULL, 0, seed, sizeof(seed)); - /* seed drbg */ - memset(prng_ws, 0, sizeof(prng_ws)); - cpacf_prno(CPACF_PRNO_SHA512_DRNG_SEED, - &prng_ws, NULL, 0, seed, sizeof(seed)); - /* re-init counter for drbg */ - drbg_counter = rndlong_drbg_reseed; - } - - /* fill the arch_get_random_long buffer from drbg */ - cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN, &prng_ws, - (u8 *) rndlong_buf, sizeof(rndlong_buf), - NULL, 0); -} - -bool s390_arch_get_random_long(unsigned long *v) -{ - bool rc = false; - unsigned long flags; - - /* arch_get_random_long() disabled ? */ - if (rndlong_drbg_reseed < 0) - return false; - - /* try to lock the random long lock */ - if (!spin_trylock_irqsave(&rndlong_lock, flags)) - return false; - - if (--rndlong_buf_index >= 0) { - /* deliver next long value from the buffer */ - *v = rndlong_buf[rndlong_buf_index]; - rc = true; - goto out; - } - - /* buffer is depleted and needs refill */ - if (in_interrupt()) { - /* delay refill in interrupt context to next caller */ - rndlong_buf_index = 0; - goto out; - } - - /* refill random long buffer */ - refill_rndlong_buf(); - rndlong_buf_index = ARRAY_SIZE(rndlong_buf); - - /* and provide one random long */ - *v = rndlong_buf[--rndlong_buf_index]; - rc = true; - -out: - spin_unlock_irqrestore(&rndlong_lock, flags); - return rc; -} -EXPORT_SYMBOL(s390_arch_get_random_long); - -static int __init s390_arch_random_init(void) -{ - /* all the needed PRNO subfunctions available ? */ - if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG) && - cpacf_query_func(CPACF_PRNO, CPACF_PRNO_SHA512_DRNG_GEN)) { - - /* alloc arch random working buffer */ - arch_rng_buf = kmalloc(ARCH_RNG_BUF_SIZE, GFP_KERNEL); - if (!arch_rng_buf) - return -ENOMEM; - - /* kick worker queue job to fill the random buffer */ - queue_delayed_work(system_long_wq, - &arch_rng_work, ARCH_REFILL_TICKS); - - /* enable arch random to the outside world */ - static_branch_enable(&s390_arch_random_available); - } - - return 0; -} -arch_initcall(s390_arch_random_init); |