commit b25cd5cfe168b85500c160ca538a44d9adba52c1 Author: Nick Mathewson nickm@torproject.org Date: Tue Feb 19 15:23:31 2019 -0500
Implement code to manage a per-thread instance of crypto_fast_rng()
The subsystems API makes this really simple, fortunately.
Closes ticket 29536 --- changes/ticket29536 | 9 +++++ src/lib/crypt_ops/crypto_init.c | 7 ++++ src/lib/crypt_ops/crypto_rand.h | 9 +++++ src/lib/crypt_ops/crypto_rand_fast.c | 67 +++++++++++++++++++++++++++++++++++- 4 files changed, 91 insertions(+), 1 deletion(-)
diff --git a/changes/ticket29536 b/changes/ticket29536 new file mode 100644 index 000000000..a5ae26b70 --- /dev/null +++ b/changes/ticket29536 @@ -0,0 +1,9 @@ + o Minor features (performance, RNG): + - Tor now constructs a fast secure pseudorandom number generator for + each thread, to use for cases where performance is critical. This PRNG + is based on AES-CTR, using a buffering construction similar to + libottery and the (newer) OpenBSD arc4random() code. It outperforms + OpenSSL 1.1.1a's CSPRNG by roughly a factor of 100 for small outputs. + Although we believe it to be cryptographically strong, we are only + using it when necessary for reasonable performance. Implements tickets + 29023 and 29536. diff --git a/src/lib/crypt_ops/crypto_init.c b/src/lib/crypt_ops/crypto_init.c index 4040085c7..cf491f32d 100644 --- a/src/lib/crypt_ops/crypto_init.c +++ b/src/lib/crypt_ops/crypto_init.c @@ -12,6 +12,8 @@
#include "orconfig.h"
+#define CRYPTO_PRIVATE + #include "lib/crypt_ops/crypto_init.h"
#include "lib/crypt_ops/crypto_curve25519.h" @@ -69,6 +71,8 @@ crypto_early_init(void) if (crypto_init_siphash_key() < 0) return -1;
+ crypto_rand_fast_init(); + curve25519_init(); ed25519_init(); } @@ -111,6 +115,7 @@ crypto_thread_cleanup(void) #ifdef ENABLE_OPENSSL crypto_openssl_thread_cleanup(); #endif + destroy_thread_fast_rng(); }
/** @@ -129,6 +134,8 @@ crypto_global_cleanup(void) crypto_nss_global_cleanup(); #endif
+ crypto_rand_fast_shutdown(); + crypto_early_initialized_ = 0; crypto_global_initialized_ = 0; have_seeded_siphash = 0; diff --git a/src/lib/crypt_ops/crypto_rand.h b/src/lib/crypt_ops/crypto_rand.h index 8a81a4acd..6eef22ed4 100644 --- a/src/lib/crypt_ops/crypto_rand.h +++ b/src/lib/crypt_ops/crypto_rand.h @@ -68,6 +68,15 @@ unsigned crypto_fast_rng_get_uint(crypto_fast_rng_t *rng, unsigned limit); uint64_t crypto_fast_rng_get_uint64(crypto_fast_rng_t *rng, uint64_t limit); double crypto_fast_rng_get_double(crypto_fast_rng_t *rng);
+crypto_fast_rng_t *get_thread_fast_rng(void); + +#ifdef CRYPTO_PRIVATE +/* These are only used from crypto_init.c */ +void destroy_thread_fast_rng(void); +void crypto_rand_fast_init(void); +void crypto_rand_fast_shutdown(void); +#endif + #if defined(TOR_UNIT_TESTS) /* Used for white-box testing */ size_t crypto_fast_rng_get_bytes_used_per_stream(void); diff --git a/src/lib/crypt_ops/crypto_rand_fast.c b/src/lib/crypt_ops/crypto_rand_fast.c index 34e763bf5..760e1025e 100644 --- a/src/lib/crypt_ops/crypto_rand_fast.c +++ b/src/lib/crypt_ops/crypto_rand_fast.c @@ -33,6 +33,7 @@ */
#define CRYPTO_RAND_FAST_PRIVATE +#define CRYPTO_PRIVATE
#include "lib/crypt_ops/crypto_rand.h" #include "lib/crypt_ops/crypto_cipher.h" @@ -41,6 +42,7 @@ #include "lib/intmath/cmp.h" #include "lib/cc/ctassert.h" #include "lib/malloc/map_anon.h" +#include "lib/thread/threads.h"
#include "lib/log/util_bug.h"
@@ -122,7 +124,8 @@ crypto_fast_rng_new(void) * long. * * Note that this object is NOT thread-safe. If you need a thread-safe - * prng, use crypto_rand(), or wrap this in a mutex. + * prng, you should probably look at get_thread_fast_rng(). Alternatively, + * use crypto_rand(), wrap this in a mutex. **/ crypto_fast_rng_t * crypto_fast_rng_new_from_seed(const uint8_t *seed) @@ -261,3 +264,65 @@ crypto_fast_rng_get_bytes_used_per_stream(void) return BUFLEN; } #endif + +/** + * Thread-local instance for our fast RNG. + **/ +static tor_threadlocal_t thread_rng; + +/** + * Return a per-thread fast RNG, initializing it if necessary. + * + * You do not need to free this yourself. + * + * It is NOT safe to share this value across threads. + **/ +crypto_fast_rng_t * +get_thread_fast_rng(void) +{ + crypto_fast_rng_t *rng = tor_threadlocal_get(&thread_rng); + + if (PREDICT_UNLIKELY(rng == NULL)) { + rng = crypto_fast_rng_new(); + tor_threadlocal_set(&thread_rng, rng); + } + + return rng; +} + +/** + * Used when a thread is exiting: free the per-thread fast RNG if needed. + * Invoked from the crypto subsystem's thread-cleanup code. + **/ +void +destroy_thread_fast_rng(void) +{ + crypto_fast_rng_t *rng = tor_threadlocal_get(&thread_rng); + if (!rng) + return; + crypto_fast_rng_free(rng); + tor_threadlocal_set(&thread_rng, NULL); +} + +/** + * Initialize the global thread-local key that will be used to keep track + * of per-thread fast RNG instances. Called from the crypto subsystem's + * initialization code. + **/ +void +crypto_rand_fast_init(void) +{ + tor_threadlocal_init(&thread_rng); +} + +/** + * Initialize the global thread-local key that will be used to keep track + * of per-thread fast RNG instances. Called from the crypto subsystem's + * shutdown code. + **/ +void +crypto_rand_fast_shutdown(void) +{ + destroy_thread_fast_rng(); + tor_threadlocal_destroy(&thread_rng); +}