From: "Jason A. Donenfeld" Jason@zx2c4.com
commit a5ed7cb1a7732ef11959332d507889fbc39ebbb4 upstream.
This pulls all of the entropy extraction-focused functions into the third labeled section.
No functional changes.
Cc: Theodore Ts'o tytso@mit.edu Reviewed-by: Eric Biggers ebiggers@google.com Reviewed-by: Dominik Brodowski linux@dominikbrodowski.net Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 216 +++++++++++++++++++++++++------------------------- 1 file changed, 109 insertions(+), 107 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -891,23 +891,36 @@ size_t __must_check get_random_bytes_arc } EXPORT_SYMBOL(get_random_bytes_arch);
+ +/********************************************************************** + * + * Entropy accumulation and extraction routines. + * + * Callers may add entropy via: + * + * static void mix_pool_bytes(const void *in, size_t nbytes) + * + * After which, if added entropy should be credited: + * + * static void credit_entropy_bits(size_t nbits) + * + * Finally, extract entropy via these two, with the latter one + * setting the entropy count to zero and extracting only if there + * is POOL_MIN_BITS entropy credited prior: + * + * static void extract_entropy(void *buf, size_t nbytes) + * static bool drain_entropy(void *buf, size_t nbytes) + * + **********************************************************************/ + enum { POOL_BITS = BLAKE2S_HASH_SIZE * 8, POOL_MIN_BITS = POOL_BITS /* No point in settling for less. */ };
-/* - * Static global variables - */ +/* For notifying userspace should write into /dev/random. */ static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
-/********************************************************************** - * - * OS independent entropy store. Here are the functions which handle - * storing entropy in an entropy pool. - * - **********************************************************************/ - static struct { struct blake2s_state hash; spinlock_t lock; @@ -920,28 +933,106 @@ static struct { .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), };
-static void extract_entropy(void *buf, size_t nbytes); -static bool drain_entropy(void *buf, size_t nbytes); - -static void crng_reseed(void); +static void _mix_pool_bytes(const void *in, size_t nbytes) +{ + blake2s_update(&input_pool.hash, in, nbytes); +}
/* * This function adds bytes into the entropy "pool". It does not * update the entropy estimate. The caller should call * credit_entropy_bits if this is appropriate. */ -static void _mix_pool_bytes(const void *in, size_t nbytes) +static void mix_pool_bytes(const void *in, size_t nbytes) { - blake2s_update(&input_pool.hash, in, nbytes); + unsigned long flags; + + spin_lock_irqsave(&input_pool.lock, flags); + _mix_pool_bytes(in, nbytes); + spin_unlock_irqrestore(&input_pool.lock, flags); }
-static void mix_pool_bytes(const void *in, size_t nbytes) +static void credit_entropy_bits(size_t nbits) +{ + unsigned int entropy_count, orig, add; + + if (!nbits) + return; + + add = min_t(size_t, nbits, POOL_BITS); + + do { + orig = READ_ONCE(input_pool.entropy_count); + entropy_count = min_t(unsigned int, POOL_BITS, orig + add); + } while (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig); + + if (crng_init < 2 && entropy_count >= POOL_MIN_BITS) + crng_reseed(); +} + +/* + * This is an HKDF-like construction for using the hashed collected entropy + * as a PRF key, that's then expanded block-by-block. + */ +static void extract_entropy(void *buf, size_t nbytes) { unsigned long flags; + u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE]; + struct { + unsigned long rdseed[32 / sizeof(long)]; + size_t counter; + } block; + size_t i; + + for (i = 0; i < ARRAY_SIZE(block.rdseed); ++i) { + if (!arch_get_random_seed_long(&block.rdseed[i]) && + !arch_get_random_long(&block.rdseed[i])) + block.rdseed[i] = random_get_entropy(); + }
spin_lock_irqsave(&input_pool.lock, flags); - _mix_pool_bytes(in, nbytes); + + /* seed = HASHPRF(last_key, entropy_input) */ + blake2s_final(&input_pool.hash, seed); + + /* next_key = HASHPRF(seed, RDSEED || 0) */ + block.counter = 0; + blake2s(next_key, (u8 *)&block, seed, sizeof(next_key), sizeof(block), sizeof(seed)); + blake2s_init_key(&input_pool.hash, BLAKE2S_HASH_SIZE, next_key, sizeof(next_key)); + spin_unlock_irqrestore(&input_pool.lock, flags); + memzero_explicit(next_key, sizeof(next_key)); + + while (nbytes) { + i = min_t(size_t, nbytes, BLAKE2S_HASH_SIZE); + /* output = HASHPRF(seed, RDSEED || ++counter) */ + ++block.counter; + blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed)); + nbytes -= i; + buf += i; + } + + memzero_explicit(seed, sizeof(seed)); + memzero_explicit(&block, sizeof(block)); +} + +/* + * First we make sure we have POOL_MIN_BITS of entropy in the pool, and then we + * set the entropy count to zero (but don't actually touch any data). Only then + * can we extract a new key with extract_entropy(). + */ +static bool drain_entropy(void *buf, size_t nbytes) +{ + unsigned int entropy_count; + do { + entropy_count = READ_ONCE(input_pool.entropy_count); + if (entropy_count < POOL_MIN_BITS) + return false; + } while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count); + extract_entropy(buf, nbytes); + wake_up_interruptible(&random_write_wait); + kill_fasync(&fasync, SIGIO, POLL_OUT); + return true; }
struct fast_pool { @@ -984,24 +1075,6 @@ static void fast_mix(u32 pool[4]) pool[2] = c; pool[3] = d; }
-static void credit_entropy_bits(size_t nbits) -{ - unsigned int entropy_count, orig, add; - - if (!nbits) - return; - - add = min_t(size_t, nbits, POOL_BITS); - - do { - orig = READ_ONCE(input_pool.entropy_count); - entropy_count = min_t(unsigned int, POOL_BITS, orig + add); - } while (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig); - - if (crng_init < 2 && entropy_count >= POOL_MIN_BITS) - crng_reseed(); -} - /********************************************************************* * * Entropy input management @@ -1198,77 +1271,6 @@ void add_disk_randomness(struct gendisk EXPORT_SYMBOL_GPL(add_disk_randomness); #endif
-/********************************************************************* - * - * Entropy extraction routines - * - *********************************************************************/ - -/* - * This is an HKDF-like construction for using the hashed collected entropy - * as a PRF key, that's then expanded block-by-block. - */ -static void extract_entropy(void *buf, size_t nbytes) -{ - unsigned long flags; - u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE]; - struct { - unsigned long rdseed[32 / sizeof(long)]; - size_t counter; - } block; - size_t i; - - for (i = 0; i < ARRAY_SIZE(block.rdseed); ++i) { - if (!arch_get_random_seed_long(&block.rdseed[i]) && - !arch_get_random_long(&block.rdseed[i])) - block.rdseed[i] = random_get_entropy(); - } - - spin_lock_irqsave(&input_pool.lock, flags); - - /* seed = HASHPRF(last_key, entropy_input) */ - blake2s_final(&input_pool.hash, seed); - - /* next_key = HASHPRF(seed, RDSEED || 0) */ - block.counter = 0; - blake2s(next_key, (u8 *)&block, seed, sizeof(next_key), sizeof(block), sizeof(seed)); - blake2s_init_key(&input_pool.hash, BLAKE2S_HASH_SIZE, next_key, sizeof(next_key)); - - spin_unlock_irqrestore(&input_pool.lock, flags); - memzero_explicit(next_key, sizeof(next_key)); - - while (nbytes) { - i = min_t(size_t, nbytes, BLAKE2S_HASH_SIZE); - /* output = HASHPRF(seed, RDSEED || ++counter) */ - ++block.counter; - blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed)); - nbytes -= i; - buf += i; - } - - memzero_explicit(seed, sizeof(seed)); - memzero_explicit(&block, sizeof(block)); -} - -/* - * First we make sure we have POOL_MIN_BITS of entropy in the pool, and then we - * set the entropy count to zero (but don't actually touch any data). Only then - * can we extract a new key with extract_entropy(). - */ -static bool drain_entropy(void *buf, size_t nbytes) -{ - unsigned int entropy_count; - do { - entropy_count = READ_ONCE(input_pool.entropy_count); - if (entropy_count < POOL_MIN_BITS) - return false; - } while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count); - extract_entropy(buf, nbytes); - wake_up_interruptible(&random_write_wait); - kill_fasync(&fasync, SIGIO, POLL_OUT); - return true; -} - /* * Each time the timer fires, we expect that we got an unpredictable * jump in the cycle counter. Even if the timer is running on another