rand_lib.c
/*
* Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdio.h>
#include <time.h>
#include "internal/cryptlib.h"
#include <openssl/opensslconf.h>
#include "internal/rand_int.h"
#include <openssl/engine.h>
#include "internal/thread_once.h"
#include "rand_lcl.h"
#ifdef OPENSSL_SYS_UNIX
# include <sys/types.h>
# include <unistd.h>
# include <sys/time.h>
#endif
#include "e_os.h"
/* Macro to convert two thirty two bit values into a sixty four bit one */
#define TWO32TO64(a, b) ((((uint64_t)(a)) << 32) + (b))
/*
* Check for the existence and support of POSIX timers. The standard
* says that the _POSIX_TIMERS macro will have a positive value if they
* are available.
*
* However, we want an additional constraint: that the timer support does
* not require an extra library dependency. Early versions of glibc
* require -lrt to be specified on the link line to access the timers,
* so this needs to be checked for.
*
* It is worse because some libraries define __GLIBC__ but don't
* support the version testing macro (e.g. uClibc). This means
* an extra check is needed.
*
* The final condition is:
* "have posix timers and either not glibc or glibc without -lrt"
*
* The nested #if sequences are required to avoid using a parameterised
* macro that might be undefined.
*/
#undef OSSL_POSIX_TIMER_OKAY
#if defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0
# if defined(__GLIBC__)
# if defined(__GLIBC_PREREQ)
# if __GLIBC_PREREQ(2, 17)
# define OSSL_POSIX_TIMER_OKAY
# endif
# endif
# else
# define OSSL_POSIX_TIMER_OKAY
# endif
#endif
#ifndef OPENSSL_NO_ENGINE
/* non-NULL if default_RAND_meth is ENGINE-provided */
static ENGINE *funct_ref;
static CRYPTO_RWLOCK *rand_engine_lock;
#endif
static CRYPTO_RWLOCK *rand_meth_lock;
static const RAND_METHOD *default_RAND_meth;
static CRYPTO_ONCE rand_init = CRYPTO_ONCE_STATIC_INIT;
int rand_fork_count;
#ifdef OPENSSL_RAND_SEED_RDTSC
/*
* IMPORTANT NOTE: It is not currently possible to use this code
* because we are not sure about the amount of randomness it provides.
* Some SP900 tests have been run, but there is internal skepticism.
* So for now this code is not used.
*/
# error "RDTSC enabled? Should not be possible!"
/*
* Acquire entropy from high-speed clock
*
* Since we get some randomness from the low-order bits of the
* high-speed clock, it can help.
*
* Returns the total entropy count, if it exceeds the requested
* entropy count. Otherwise, returns an entropy count of 0.
*/
size_t rand_acquire_entropy_from_tsc(RAND_POOL *pool)
{
unsigned char c;
int i;
if ((OPENSSL_ia32cap_P[0] & (1 << 4)) != 0) {
for (i = 0; i < TSC_READ_COUNT; i++) {
c = (unsigned char)(OPENSSL_rdtsc() & 0xFF);
rand_pool_add(pool, &c, 1, 4);
}
}
return rand_pool_entropy_available(pool);
}
#endif
#ifdef OPENSSL_RAND_SEED_RDCPU
size_t OPENSSL_ia32_rdseed_bytes(unsigned char *buf, size_t len);
size_t OPENSSL_ia32_rdrand_bytes(unsigned char *buf, size_t len);
extern unsigned int OPENSSL_ia32cap_P[];
/*
* Acquire entropy using Intel-specific cpu instructions
*
* Uses the RDSEED instruction if available, otherwise uses
* RDRAND if available.
*
* For the differences between RDSEED and RDRAND, and why RDSEED
* is the preferred choice, see https://goo.gl/oK3KcN
*
* Returns the total entropy count, if it exceeds the requested
* entropy count. Otherwise, returns an entropy count of 0.
*/
size_t rand_acquire_entropy_from_cpu(RAND_POOL *pool)
{
size_t bytes_needed;
unsigned char *buffer;
bytes_needed = rand_pool_bytes_needed(pool, 8 /*entropy_per_byte*/);
if (bytes_needed > 0) {
buffer = rand_pool_add_begin(pool, bytes_needed);
if (buffer != NULL) {
/* If RDSEED is available, use that. */
if ((OPENSSL_ia32cap_P[2] & (1 << 18)) != 0) {
if (OPENSSL_ia32_rdseed_bytes(buffer, bytes_needed)
== bytes_needed)
return rand_pool_add_end(pool,
bytes_needed,
8 * bytes_needed);
}
/* Second choice is RDRAND. */
if ((OPENSSL_ia32cap_P[1] & (1 << (62 - 32))) != 0) {
if (OPENSSL_ia32_rdrand_bytes(buffer, bytes_needed)
== bytes_needed)
return rand_pool_add_end(pool,
bytes_needed,
8 * bytes_needed);
}
return rand_pool_add_end(pool, 0, 0);
}
}
return rand_pool_entropy_available(pool);
}
#endif
/*
* Implements the get_entropy() callback (see RAND_DRBG_set_callbacks())
*
* If the DRBG has a parent, then the required amount of entropy input
* is fetched using the parent's RAND_DRBG_generate().
*
* Otherwise, the entropy is polled from the system entropy sources
* using rand_pool_acquire_entropy().
*
* If a random pool has been added to the DRBG using RAND_add(), then
* its entropy will be used up first.
*/
size_t rand_drbg_get_entropy(RAND_DRBG *drbg,
unsigned char **pout,
int entropy, size_t min_len, size_t max_len,
int prediction_resistance)
{
size_t ret = 0;
size_t entropy_available = 0;
RAND_POOL *pool;
if (drbg->parent && drbg->strength > drbg->parent->strength) {
/*
* We currently don't support the algorithm from NIST SP 800-90C
* 10.1.2 to use a weaker DRBG as source
*/
RANDerr(RAND_F_RAND_DRBG_GET_ENTROPY, RAND_R_PARENT_STRENGTH_TOO_WEAK);
return 0;
}
pool = rand_pool_new(entropy, min_len, max_len);
if (pool == NULL)
return 0;
if (drbg->pool) {
rand_pool_add(pool,
rand_pool_buffer(drbg->pool),
rand_pool_length(drbg->pool),
rand_pool_entropy(drbg->pool));
rand_pool_free(drbg->pool);
drbg->pool = NULL;
}
if (drbg->parent) {
size_t bytes_needed = rand_pool_bytes_needed(pool, 8);
unsigned char *buffer = rand_pool_add_begin(pool, bytes_needed);
if (buffer != NULL) {
size_t bytes = 0;
/*
* Get random from parent, include our state as additional input.
* Our lock is already held, but we need to lock our parent before
* generating bits from it. (Note: taking the lock will be a no-op
* if locking if drbg->parent->lock == NULL.)
*/
rand_drbg_lock(drbg->parent);
if (RAND_DRBG_generate(drbg->parent,
buffer, bytes_needed,
prediction_resistance,
(unsigned char *)drbg, sizeof(*drbg)) != 0)
bytes = bytes_needed;
rand_drbg_unlock(drbg->parent);
entropy_available = rand_pool_add_end(pool, bytes, 8 * bytes);
}
} else {
if (prediction_resistance) {
/*
* We don't have any entropy sources that comply with the NIST
* standard to provide prediction resistance (see NIST SP 800-90C,
* Section 5.4).
*/
RANDerr(RAND_F_RAND_DRBG_GET_ENTROPY,
RAND_R_PREDICTION_RESISTANCE_NOT_SUPPORTED);
return 0;
}
/* Get entropy by polling system entropy sources. */
entropy_available = rand_pool_acquire_entropy(pool);
}
if (entropy_available > 0) {
ret = rand_pool_length(pool);
*pout = rand_pool_detach(pool);
}
rand_pool_free(pool);
return ret;
}
/*
* Find a suitable source of time. Start with the highest resolution source
* and work down to the slower ones. This is added as additional data and
* isn't counted as randomness, so any result is acceptable.
*
* Returns 0 when we weren't able to find any time source
*/
static uint64_t get_timer_bits(void)
{
uint64_t res = OPENSSL_rdtsc();
if (res != 0)
return res;
#if defined(_WIN32)
{
LARGE_INTEGER t;
FILETIME ft;
if (QueryPerformanceCounter(&t) != 0)
return t.QuadPart;
GetSystemTimeAsFileTime(&ft);
return TWO32TO64(ft.dwHighDateTime, ft.dwLowDateTime);
}
#elif defined(__sun) || defined(__hpux)
return gethrtime();
#elif defined(_AIX)
{
timebasestruct_t t;
read_wall_time(&t, TIMEBASE_SZ);
return TWO32TO64(t.tb_high, t.tb_low);
}
#else
# if defined(OSSL_POSIX_TIMER_OKAY)
{
struct timespec ts;
clockid_t cid;
# ifdef CLOCK_BOOTTIME
cid = CLOCK_BOOTTIME;
# elif defined(_POSIX_MONOTONIC_CLOCK)
cid = CLOCK_MONOTONIC;
# else
cid = CLOCK_REALTIME;
# endif
if (clock_gettime(cid, &ts) == 0)
return TWO32TO64(ts.tv_sec, ts.tv_nsec);
}
# endif
# if defined(__unix__) \
|| (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
{
struct timeval tv;
if (gettimeofday(&tv, NULL) == 0)
return TWO32TO64(tv.tv_sec, tv.tv_usec);
}
# endif
{
time_t t = time(NULL);
if (t == (time_t)-1)
return 0;
return t;
}
#endif
}
/*
* Generate additional data that can be used for the drbg. The data does
* not need to contain entropy, but it's useful if it contains at least
* some bits that are unpredictable.
*
* Returns 0 on failure.
*
* On success it allocates a buffer at |*pout| and returns the length of
* the data. The buffer should get freed using OPENSSL_secure_clear_free().
*/
size_t rand_drbg_get_additional_data(unsigned char **pout, size_t max_len)
{
RAND_POOL *pool;
CRYPTO_THREAD_ID thread_id;
size_t len;
#ifdef OPENSSL_SYS_UNIX
pid_t pid;
#elif defined(OPENSSL_SYS_WIN32)
DWORD pid;
#endif
uint64_t tbits;
pool = rand_pool_new(0, 0, max_len);
if (pool == NULL)
return 0;
#ifdef OPENSSL_SYS_UNIX
pid = getpid();
rand_pool_add(pool, (unsigned char *)&pid, sizeof(pid), 0);
#elif defined(OPENSSL_SYS_WIN32)
pid = GetCurrentProcessId();
rand_pool_add(pool, (unsigned char *)&pid, sizeof(pid), 0);
#endif
thread_id = CRYPTO_THREAD_get_current_id();
if (thread_id != 0)
rand_pool_add(pool, (unsigned char *)&thread_id, sizeof(thread_id), 0);
tbits = get_timer_bits();
if (tbits != 0)
rand_pool_add(pool, (unsigned char *)&tbits, sizeof(tbits), 0);
/* TODO: Use RDSEED? */
len = rand_pool_length(pool);
if (len != 0)
*pout = rand_pool_detach(pool);
rand_pool_free(pool);
return len;
}
/*
* Implements the cleanup_entropy() callback (see RAND_DRBG_set_callbacks())
*
*/
void rand_drbg_cleanup_entropy(RAND_DRBG *drbg,
unsigned char *out, size_t outlen)
{
OPENSSL_secure_clear_free(out, outlen);
}
void rand_fork()
{
rand_fork_count++;
}
DEFINE_RUN_ONCE_STATIC(do_rand_init)
{
int ret = 1;
#ifndef OPENSSL_NO_ENGINE
rand_engine_lock = CRYPTO_THREAD_lock_new();
ret &= rand_engine_lock != NULL;
#endif
rand_meth_lock = CRYPTO_THREAD_lock_new();
ret &= rand_meth_lock != NULL;
return ret;
}
void rand_cleanup_int(void)
{
const RAND_METHOD *meth = default_RAND_meth;
if (meth != NULL && meth->cleanup != NULL)
meth->cleanup();
RAND_set_rand_method(NULL);
#ifndef OPENSSL_NO_ENGINE
CRYPTO_THREAD_lock_free(rand_engine_lock);
#endif
CRYPTO_THREAD_lock_free(rand_meth_lock);
}
/*
* RAND_poll() reseeds the default RNG using random input
*
* The random input is obtained from polling various entropy
* sources which depend on the operating system and are
* configurable via the --with-rand-seed configure option.
*/
int RAND_poll(void)
{
int ret = 0;
RAND_POOL *pool = NULL;
const RAND_METHOD *meth = RAND_get_rand_method();
if (meth == RAND_OpenSSL()) {
/* fill random pool and seed the master DRBG */
RAND_DRBG *drbg = RAND_DRBG_get0_master();
if (drbg == NULL)
return 0;
rand_drbg_lock(drbg);
ret = rand_drbg_restart(drbg, NULL, 0, 0);
rand_drbg_unlock(drbg);
return ret;
} else {
/* fill random pool and seed the current legacy RNG */
pool = rand_pool_new(RAND_DRBG_STRENGTH,
RAND_DRBG_STRENGTH / 8,
DRBG_MINMAX_FACTOR * (RAND_DRBG_STRENGTH / 8));
if (pool == NULL)
return 0;
if (rand_pool_acquire_entropy(pool) == 0)
goto err;
if (meth->add == NULL
|| meth->add(rand_pool_buffer(pool),
rand_pool_length(pool),
(rand_pool_entropy(pool) / 8.0)) == 0)
goto err;
ret = 1;
}
err:
rand_pool_free(pool);
return ret;
}
/*
* Allocate memory and initialize a new random pool
*/
RAND_POOL *rand_pool_new(int entropy, size_t min_len, size_t max_len)
{
RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));
if (pool == NULL) {
RANDerr(RAND_F_RAND_POOL_NEW, ERR_R_MALLOC_FAILURE);
goto err;
}
pool->min_len = min_len;
pool->max_len = max_len;
pool->buffer = OPENSSL_secure_zalloc(pool->max_len);
if (pool->buffer == NULL) {
RANDerr(RAND_F_RAND_POOL_NEW, ERR_R_MALLOC_FAILURE);
goto err;
}
pool->requested_entropy = entropy;
return pool;
err:
OPENSSL_free(pool);
return NULL;
}
/*
* Free |pool|, securely erasing its buffer.
*/
void rand_pool_free(RAND_POOL *pool)
{
if (pool == NULL)
return;
OPENSSL_secure_clear_free(pool->buffer, pool->max_len);
OPENSSL_free(pool);
}
/*
* Return the |pool|'s buffer to the caller (readonly).
*/
const unsigned char *rand_pool_buffer(RAND_POOL *pool)
{
return pool->buffer;
}
/*
* Return the |pool|'s entropy to the caller.
*/
size_t rand_pool_entropy(RAND_POOL *pool)
{
return pool->entropy;
}
/*
* Return the |pool|'s buffer length to the caller.
*/
size_t rand_pool_length(RAND_POOL *pool)
{
return pool->len;
}
/*
* Detach the |pool| buffer and return it to the caller.
* It's the responsibility of the caller to free the buffer
* using OPENSSL_secure_clear_free().
*/
unsigned char *rand_pool_detach(RAND_POOL *pool)
{
unsigned char *ret = pool->buffer;
pool->buffer = NULL;
return ret;
}
/*
* If every byte of the input contains |entropy_per_bytes| bits of entropy,
* how many bytes does one need to obtain at least |bits| bits of entropy?
*/
#define ENTROPY_TO_BYTES(bits, entropy_per_bytes) \
(((bits) + ((entropy_per_bytes) - 1))/(entropy_per_bytes))
/*
* Checks whether the |pool|'s entropy is available to the caller.
* This is the case when entropy count and buffer length are high enough.
* Returns
*
* |entropy| if the entropy count and buffer size is large enough
* 0 otherwise
*/
size_t rand_pool_entropy_available(RAND_POOL *pool)
{
if (pool->entropy < pool->requested_entropy)
return 0;
if (pool->len < pool->min_len)
return 0;
return pool->entropy;
}
/*
* Returns the (remaining) amount of entropy needed to fill
* the random pool.
*/
size_t rand_pool_entropy_needed(RAND_POOL *pool)
{
if (pool->entropy < pool->requested_entropy)
return pool->requested_entropy - pool->entropy;
return 0;
}
/*
* Returns the number of bytes needed to fill the pool, assuming
* the input has 'entropy_per_byte' entropy bits per byte.
* In case of an error, 0 is returned.
*/
size_t rand_pool_bytes_needed(RAND_POOL *pool, unsigned int entropy_per_byte)
{
size_t bytes_needed;
size_t entropy_needed = rand_pool_entropy_needed(pool);
if (entropy_per_byte < 1 || entropy_per_byte > 8) {
RANDerr(RAND_F_RAND_POOL_BYTES_NEEDED, RAND_R_ARGUMENT_OUT_OF_RANGE);
return 0;
}
bytes_needed = ENTROPY_TO_BYTES(entropy_needed, entropy_per_byte);
if (bytes_needed > pool->max_len - pool->len) {
/* not enough space left */
RANDerr(RAND_F_RAND_POOL_BYTES_NEEDED, RAND_R_RANDOM_POOL_OVERFLOW);
return 0;
}
if (pool->len < pool->min_len &&
bytes_needed < pool->min_len - pool->len)
/* to meet the min_len requirement */
bytes_needed = pool->min_len - pool->len;
return bytes_needed;
}
/* Returns the remaining number of bytes available */
size_t rand_pool_bytes_remaining(RAND_POOL *pool)
{
return pool->max_len - pool->len;
}
/*
* Add random bytes to the random pool.
*
* It is expected that the |buffer| contains |len| bytes of
* random input which contains at least |entropy| bits of
* randomness.
*
* Return available amount of entropy after this operation.
* (see rand_pool_entropy_available(pool))
*/
size_t rand_pool_add(RAND_POOL *pool,
const unsigned char *buffer, size_t len, size_t entropy)
{
if (len > pool->max_len - pool->len) {
RANDerr(RAND_F_RAND_POOL_ADD, RAND_R_ENTROPY_INPUT_TOO_LONG);
return 0;
}
if (len > 0) {
memcpy(pool->buffer + pool->len, buffer, len);
pool->len += len;
pool->entropy += entropy;
}
return rand_pool_entropy_available(pool);
}
/*
* Start to add random bytes to the random pool in-place.
*
* Reserves the next |len| bytes for adding random bytes in-place
* and returns a pointer to the buffer.
* The caller is allowed to copy up to |len| bytes into the buffer.
* If |len| == 0 this is considered a no-op and a NULL pointer
* is returned without producing an error message.
*
* After updating the buffer, rand_pool_add_end() needs to be called
* to finish the udpate operation (see next comment).
*/
unsigned char *rand_pool_add_begin(RAND_POOL *pool, size_t len)
{
if (len == 0)
return NULL;
if (len > pool->max_len - pool->len) {
RANDerr(RAND_F_RAND_POOL_ADD_BEGIN, RAND_R_RANDOM_POOL_OVERFLOW);
return NULL;
}
return pool->buffer + pool->len;
}
/*
* Finish to add random bytes to the random pool in-place.
*
* Finishes an in-place update of the random pool started by
* rand_pool_add_begin() (see previous comment).
* It is expected that |len| bytes of random input have been added
* to the buffer which contain at least |entropy| bits of randomness.
* It is allowed to add less bytes than originally reserved.
*/
size_t rand_pool_add_end(RAND_POOL *pool, size_t len, size_t entropy)
{
if (len > pool->max_len - pool->len) {
RANDerr(RAND_F_RAND_POOL_ADD_END, RAND_R_RANDOM_POOL_OVERFLOW);
return 0;
}
if (len > 0) {
pool->len += len;
pool->entropy += entropy;
}
return rand_pool_entropy_available(pool);
}
int RAND_set_rand_method(const RAND_METHOD *meth)
{
if (!RUN_ONCE(&rand_init, do_rand_init))
return 0;
CRYPTO_THREAD_write_lock(rand_meth_lock);
#ifndef OPENSSL_NO_ENGINE
ENGINE_finish(funct_ref);
funct_ref = NULL;
#endif
default_RAND_meth = meth;
CRYPTO_THREAD_unlock(rand_meth_lock);
return 1;
}
const RAND_METHOD *RAND_get_rand_method(void)
{
const RAND_METHOD *tmp_meth = NULL;
if (!RUN_ONCE(&rand_init, do_rand_init))
return NULL;
CRYPTO_THREAD_write_lock(rand_meth_lock);
if (default_RAND_meth == NULL) {
#ifndef OPENSSL_NO_ENGINE
ENGINE *e;
/* If we have an engine that can do RAND, use it. */
if ((e = ENGINE_get_default_RAND()) != NULL
&& (tmp_meth = ENGINE_get_RAND(e)) != NULL) {
funct_ref = e;
default_RAND_meth = tmp_meth;
} else {
ENGINE_finish(e);
default_RAND_meth = &rand_meth;
}
#else
default_RAND_meth = &rand_meth;
#endif
}
tmp_meth = default_RAND_meth;
CRYPTO_THREAD_unlock(rand_meth_lock);
return tmp_meth;
}
#ifndef OPENSSL_NO_ENGINE
int RAND_set_rand_engine(ENGINE *engine)
{
const RAND_METHOD *tmp_meth = NULL;
if (!RUN_ONCE(&rand_init, do_rand_init))
return 0;
if (engine != NULL) {
if (!ENGINE_init(engine))
return 0;
tmp_meth = ENGINE_get_RAND(engine);
if (tmp_meth == NULL) {
ENGINE_finish(engine);
return 0;
}
}
CRYPTO_THREAD_write_lock(rand_engine_lock);
/* This function releases any prior ENGINE so call it first */
RAND_set_rand_method(tmp_meth);
funct_ref = engine;
CRYPTO_THREAD_unlock(rand_engine_lock);
return 1;
}
#endif
void RAND_seed(const void *buf, int num)
{
const RAND_METHOD *meth = RAND_get_rand_method();
if (meth->seed != NULL)
meth->seed(buf, num);
}
void RAND_add(const void *buf, int num, double randomness)
{
const RAND_METHOD *meth = RAND_get_rand_method();
if (meth->add != NULL)
meth->add(buf, num, randomness);
}
/*
* This function is not part of RAND_METHOD, so if we're not using
* the default method, then just call RAND_bytes(). Otherwise make
* sure we're instantiated and use the private DRBG.
*/
int RAND_priv_bytes(unsigned char *buf, int num)
{
const RAND_METHOD *meth = RAND_get_rand_method();
RAND_DRBG *drbg;
int ret;
if (meth != RAND_OpenSSL())
return RAND_bytes(buf, num);
drbg = RAND_DRBG_get0_private();
if (drbg == NULL)
return 0;
ret = RAND_DRBG_bytes(drbg, buf, num);
return ret;
}
int RAND_bytes(unsigned char *buf, int num)
{
const RAND_METHOD *meth = RAND_get_rand_method();
if (meth->bytes != NULL)
return meth->bytes(buf, num);
RANDerr(RAND_F_RAND_BYTES, RAND_R_FUNC_NOT_IMPLEMENTED);
return -1;
}
#if OPENSSL_API_COMPAT < 0x10100000L
int RAND_pseudo_bytes(unsigned char *buf, int num)
{
const RAND_METHOD *meth = RAND_get_rand_method();
if (meth->pseudorand != NULL)
return meth->pseudorand(buf, num);
return -1;
}
#endif
int RAND_status(void)
{
const RAND_METHOD *meth = RAND_get_rand_method();
if (meth->status != NULL)
return meth->status();
return 0;
}
