/*
* 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)
{
size_t ret = 0;
size_t entropy_available = 0;
RAND_POOL *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.
*/
if (drbg->parent->lock)
CRYPTO_THREAD_write_lock(drbg->parent->lock);
if (RAND_DRBG_generate(drbg->parent,
buffer, bytes_needed,
0,
(unsigned char *)drbg, sizeof(*drbg)) != 0)
bytes = bytes_needed;
if (drbg->parent->lock)
CRYPTO_THREAD_unlock(drbg->parent->lock);
entropy_available = RAND_POOL_add_end(pool, bytes, 8 * bytes);
}
} else {
/* 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;
}
/*
* 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;
CRYPTO_THREAD_write_lock(drbg->lock);
ret = rand_drbg_restart(drbg, NULL, 0, 0);
CRYPTO_THREAD_unlock(drbg->lock);
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;
}
/*
* 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;
}
/*
* Restart |drbg|, using the specified entropy or additional input
*
* Tries its best to get the drbg instantiated by all means,
* regardless of its current state.
*
* Optionally, a |buffer| of |len| random bytes can be passed,
* which is assumed to contain at least |entropy| bits of entropy.
*
* If |entropy| > 0, the buffer content is used as entropy input.
*
* If |entropy| == 0, the buffer content is used as additional input
*
* Returns 1 on success, 0 on failure.
*
* This function is used internally only.
*/
int rand_drbg_restart(RAND_DRBG *drbg,
const unsigned char *buffer, size_t len, size_t entropy)
{
int reseeded = 0;
const unsigned char *adin = NULL;
size_t adinlen = 0;
if (drbg->pool != NULL) {
RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
RAND_POOL_free(drbg->pool);
drbg->pool = NULL;
}
if (buffer != NULL) {
if (entropy > 0) {
if (drbg->max_entropylen < len) {
RANDerr(RAND_F_RAND_DRBG_RESTART,
RAND_R_ENTROPY_INPUT_TOO_LONG);
return 0;
}
if (entropy > 8 * len) {
RANDerr(RAND_F_RAND_DRBG_RESTART, RAND_R_ENTROPY_OUT_OF_RANGE);
return 0;
}
/* will be picked up by the rand_drbg_get_entropy() callback */
drbg->pool = RAND_POOL_new(entropy, len, len);
if (drbg->pool == NULL)
return 0;
RAND_POOL_add(drbg->pool, buffer, len, entropy);
} else {
if (drbg->max_adinlen < len) {
RANDerr(RAND_F_RAND_DRBG_RESTART,
RAND_R_ADDITIONAL_INPUT_TOO_LONG);
return 0;
}
adin = buffer;
adinlen = len;
}
}
/* repair error state */
if (drbg->state == DRBG_ERROR)
RAND_DRBG_uninstantiate(drbg);
/* repair uninitialized state */
if (drbg->state == DRBG_UNINITIALISED) {
/* reinstantiate drbg */
RAND_DRBG_instantiate(drbg,
(const unsigned char *) ossl_pers_string,
sizeof(ossl_pers_string) - 1);
/* already reseeded. prevent second reseeding below */
reseeded = (drbg->state == DRBG_READY);
}
/* refresh current state if entropy or additional input has been provided */
if (drbg->state == DRBG_READY) {
if (adin != NULL) {
/*
* mix in additional input without reseeding
*
* Similar to RAND_DRBG_reseed(), but the provided additional
* data |adin| is mixed into the current state without pulling
* entropy from the trusted entropy source using get_entropy().
* This is not a reseeding in the strict sense of NIST SP 800-90A.
*/
drbg->meth->reseed(drbg, adin, adinlen, NULL, 0);
} else if (reseeded == 0) {
/* do a full reseeding if it has not been done yet above */
RAND_DRBG_reseed(drbg, NULL, 0);
}
}
/* check whether a given entropy pool was cleared properly during reseed */
if (drbg->pool != NULL) {
drbg->state = DRBG_ERROR;
RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
RAND_POOL_free(drbg->pool);
drbg->pool = NULL;
return 0;
}
return drbg->state == DRBG_READY;
}
