crypto_rand_fast.c File Reference

A fast strong PRNG for use when our underlying cryptographic library's PRNG isn't fast enough. More...

#include "lib/crypt_ops/crypto_rand.h"
#include "lib/crypt_ops/crypto_cipher.h"
#include "lib/crypt_ops/crypto_digest.h"
#include "lib/crypt_ops/crypto_util.h"
#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"
#include <string.h>

Go to the source code of this file.

Data Structures
struct	crypto_fast_rng_t
struct	crypto_fast_rng_t::cbuf_t

Macros
#define	CRYPTO_PRIVATE
#define	PID_FIELD_LEN   0
#define	SEED_LEN   (CRYPTO_FAST_RNG_SEED_LEN)
#define	MAPLEN   4096
#define	BUFLEN   (MAPLEN - 2*sizeof(uint16_t) - SEED_LEN - PID_FIELD_LEN)
#define	RESEED_AFTER   16
#define	KEY_LEN   (CRYPTO_FAST_RNG_SEED_LEN - CIPHER_IV_LEN)
#define	KEY_BITS   (KEY_LEN * 8)

Functions
	CTASSERT (KEY_BITS==128||KEY_BITS==192||KEY_BITS==256)
	CTASSERT (sizeof(struct cbuf_t)==BUFLEN+SEED_LEN)
	CTASSERT (sizeof(crypto_fast_rng_t)<=MAPLEN)
crypto_fast_rng_t *	crypto_fast_rng_new (void)
crypto_fast_rng_t *	crypto_fast_rng_new_from_seed (const uint8_t *seed)
static crypto_cipher_t *	cipher_from_seed (const uint8_t *seed)
static void	crypto_fast_rng_add_entopy (crypto_fast_rng_t *rng)
static void	crypto_fast_rng_refill (crypto_fast_rng_t *rng)
void	crypto_fast_rng_free_ (crypto_fast_rng_t *rng)
static void	crypto_fast_rng_getbytes_impl (crypto_fast_rng_t *rng, uint8_t *out, const size_t n)
void	crypto_fast_rng_getbytes (crypto_fast_rng_t *rng, uint8_t *out, size_t n)
crypto_fast_rng_t *	get_thread_fast_rng (void)
void	destroy_thread_fast_rng (void)
void	crypto_rand_fast_init (void)
void	crypto_rand_fast_shutdown (void)

Variables
static tor_threadlocal_t	thread_rng

Detailed Description

A fast strong PRNG for use when our underlying cryptographic library's PRNG isn't fast enough.

Definition in file crypto_rand_fast.c.

Function Documentation

cipher_from_seed()

static crypto_cipher_t* cipher_from_seed ( const uint8_t *  seed )

inlinestatic

Helper: create a crypto_cipher_t object from SEED_LEN bytes of input. The first KEY_LEN bytes are used as the stream cipher's key, and the remaining CIPHER_IV_LEN bytes are used as its IV.

Definition at line 210 of file crypto_rand_fast.c.

crypto_fast_rng_add_entopy()

static void crypto_fast_rng_add_entopy ( crypto_fast_rng_t *  rng )

static

Helper: mix additional entropy into rng by using our XOF to mix the old value for the seed with some additional bytes from crypto_strongest_rand().

Definition at line 221 of file crypto_rand_fast.c.

Referenced by crypto_fast_rng_refill().

crypto_fast_rng_free_()

void crypto_fast_rng_free_

(

crypto_fast_rng_t *

rng

)

Release all storage held by rng.

Definition at line 273 of file crypto_rand_fast.c.

crypto_fast_rng_getbytes()

void crypto_fast_rng_getbytes	(	crypto_fast_rng_t *	rng,
		uint8_t *	out,
		size_t	n
	)

Extract n bytes from rng into the buffer at out.

Definition at line 334 of file crypto_rand_fast.c.

Referenced by crypto_fast_rng_get_double(), crypto_fast_rng_get_u32(), crypto_fast_rng_get_uint(), and crypto_fast_rng_get_uint64().

crypto_fast_rng_getbytes_impl()

static void crypto_fast_rng_getbytes_impl ( crypto_fast_rng_t *  rng, uint8_t *  out, const size_t  n  )

static

Helper: extract bytes from the PRNG, refilling it as necessary. Does not optimize the case when the user has asked for a huge output.

Definition at line 286 of file crypto_rand_fast.c.

crypto_fast_rng_new()

crypto_fast_rng_t* crypto_fast_rng_new

(

void

)

Initialize and return a new fast PRNG, using a strong random seed.

Note that this object is NOT thread-safe. If you need a thread-safe prng, use crypto_rand(), or wrap this in a mutex.

Definition at line 138 of file crypto_rand_fast.c.

crypto_fast_rng_new_from_seed()

crypto_fast_rng_t* crypto_fast_rng_new_from_seed

(

const uint8_t *

seed

)

Initialize and return a new fast PRNG, using a seed value specified in seed. This value must be CRYPTO_FAST_RNG_SEED_LEN bytes long.

Note that this object is NOT thread-safe. If you need a thread-safe prng, you should probably look at get_thread_fast_rng(). Alternatively, use crypto_rand(), wrap this in a mutex.

Definition at line 157 of file crypto_rand_fast.c.

crypto_fast_rng_refill()

static void crypto_fast_rng_refill ( crypto_fast_rng_t *  rng )

static

Helper: refill the seed bytes and output buffer of rng, using the input seed bytes as input (key and IV) for the stream cipher.

If the n_till_reseed counter has reached zero, mix more random bytes into the seed before refilling the buffer.

Definition at line 243 of file crypto_rand_fast.c.

Referenced by crypto_fast_rng_getbytes_impl().

crypto_rand_fast_init()

void crypto_rand_fast_init

(

void

)

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.

Definition at line 423 of file crypto_rand_fast.c.

crypto_rand_fast_shutdown()

void crypto_rand_fast_shutdown

(

void

)

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.

Definition at line 434 of file crypto_rand_fast.c.

destroy_thread_fast_rng()

void destroy_thread_fast_rng

(

void

)

Used when a thread is exiting: free the per-thread fast RNG if needed. Invoked from the crypto subsystem's thread-cleanup code.

Definition at line 394 of file crypto_rand_fast.c.

Referenced by crypto_rand_fast_shutdown(), and crypto_thread_cleanup().

get_thread_fast_rng()

crypto_fast_rng_t* get_thread_fast_rng

(

void

)

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.

Definition at line 377 of file crypto_rand_fast.c.

Referenced by circuit_reset_sendme_randomness(), circuit_resume_edge_reading_helper(), extend_info_pick_orport(), genpareto_sample(), geometric_sample(), log_logistic_sample(), logistic_sample(), random_uniform_01(), and weibull_sample().

Variable Documentation

thread_rng

tor_threadlocal_t thread_rng

static

Thread-local instance for our fast RNG.

Definition at line 367 of file crypto_rand_fast.c.

Referenced by crypto_rand_fast_init(), crypto_rand_fast_shutdown(), destroy_thread_fast_rng(), and get_thread_fast_rng().