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openssl/crypto/rand/ossl_rand.c
Rich Salz da8fc25a98 Start to overhaul RAND API 
Remove unused rand_hw_xor, MD/EVP indirection
Make rand_pseudo same as rand.
Cleanup formatting and ifdef control
Rename some things:
    - rand_meth to openssl_rand_meth; make it global
    - source file
    - lock/init functions, start per-thread state
    - ossl_meth_init to ossl_rand_init
Put state into RAND_STATE structure
And put OSSL_RAND_STATE into ossl_typ.h
Use "randomness" instead of "entropy"

Reviewed-by: Ben Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/3758)
2017-07-15 01:51:34 -04:00

614 lines
18 KiB
C
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/*
* Copyright 1995-2016 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 <string.h>
#include "e_os.h"
#if !(defined(OPENSSL_SYS_WIN32) || defined(OPENSSL_SYS_VXWORKS) || defined(OPENSSL_SYS_DSPBIOS))
# include <sys/time.h>
#endif
#if defined(OPENSSL_SYS_VXWORKS)
# include <time.h>
#endif
#include <openssl/opensslconf.h>
#include <openssl/crypto.h>
#include <openssl/rand.h>
#include <openssl/async.h>
#include <openssl/err.h>
#include <internal/thread_once.h>
#include "rand_lcl.h"
#if defined(BN_DEBUG) || defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION)
# define PREDICT 1
#endif
#define STATE_SIZE 1023
typedef struct ossl_rand_state_st OSSL_RAND_STATE;
struct ossl_rand_state_st {
size_t num;
size_t index;
unsigned char state[STATE_SIZE + RAND_DIGEST_LENGTH];
unsigned char md[RAND_DIGEST_LENGTH];
long md_count[2];
};
static OSSL_RAND_STATE global_state;
static double randomness = 0;
static int initialized = 0;
static CRYPTO_RWLOCK *rand_lock = NULL;
static CRYPTO_RWLOCK *rand_tmp_lock = NULL;
static CRYPTO_ONCE ossl_rand_init = CRYPTO_ONCE_STATIC_INIT;
static CRYPTO_THREAD_LOCAL key;
/* May be set only when a thread holds rand_lock (to prevent double locking) */
static unsigned int crypto_lock_rand = 0;
/*
* access to locking_threadid is synchronized by rand_tmp_lock;
* valid iff crypto_lock_rand is set
*/
static CRYPTO_THREAD_ID locking_threadid;
#ifdef PREDICT
int rand_predictable = 0;
#endif
static int rand_hw_seed(EVP_MD_CTX *ctx);
static void rand_thread_cleanup(void *arg)
{
OSSL_RAND_STATE *sp = arg;
OPENSSL_clear_free(sp, sizeof(*sp));
}
DEFINE_RUN_ONCE_STATIC(do_ossl_rand_init)
{
int ret = 1;
OPENSSL_init_crypto(0, NULL);
rand_lock = CRYPTO_THREAD_lock_new();
ret &= rand_lock != NULL;
rand_tmp_lock = CRYPTO_THREAD_lock_new();
ret &= rand_tmp_lock != NULL;
ret &= CRYPTO_THREAD_init_local(&key, rand_thread_cleanup) == 1;
return ret;
}
RAND_METHOD *RAND_OpenSSL(void)
{
return &openssl_rand_meth;
}
static void rand_cleanup(void)
{
OPENSSL_cleanse(&global_state, sizeof(global_state));
randomness = 0;
initialized = 0;
CRYPTO_THREAD_lock_free(rand_lock);
CRYPTO_THREAD_lock_free(rand_tmp_lock);
}
static int rand_add(const void *buf, int num, double add)
{
int i, j, k, st_idx;
long md_c[2];
unsigned char local_md[RAND_DIGEST_LENGTH];
EVP_MD_CTX *m;
int do_not_lock;
int rv = 0;
OSSL_RAND_STATE *sp = &global_state;
if (!num)
return 1;
#ifdef PREDICT
if (rand_predictable)
return 1;
#endif
/*
* (Based on the rand(3) manpage)
*
* The input is chopped up into units of 20 bytes (or less for
* the last block). Each of these blocks is run through the hash
* function as follows: The data passed to the hash function
* is the current 'md', the same number of bytes from the 'state'
* (the location determined by in incremented looping index) as
* the current 'block', the new key data 'block', and 'count'
* (which is incremented after each use).
* The result of this is kept in 'md' and also xored into the
* 'state' at the same locations that were used as input into the
* hash function.
*/
m = EVP_MD_CTX_new();
if (m == NULL)
goto err;
if (!RUN_ONCE(&ossl_rand_init, do_ossl_rand_init))
goto err;
/* check if we already have the lock */
if (crypto_lock_rand) {
CRYPTO_THREAD_ID cur = CRYPTO_THREAD_get_current_id();
CRYPTO_THREAD_read_lock(rand_tmp_lock);
do_not_lock = CRYPTO_THREAD_compare_id(locking_threadid, cur);
CRYPTO_THREAD_unlock(rand_tmp_lock);
} else
do_not_lock = 0;
if (!do_not_lock)
CRYPTO_THREAD_write_lock(rand_lock);
st_idx = sp->index;
/*
* use our own copies of the counters so that even if a concurrent thread
* seeds with exactly the same data and uses the same subarray there's
* _some_ difference
*/
md_c[0] = sp->md_count[0];
md_c[1] = sp->md_count[1];
memcpy(local_md, sp->md, sizeof(sp->md));
/* sp->index <= sp->num <= STATE_SIZE */
sp->index += num;
if (sp->index >= STATE_SIZE) {
sp->index %= STATE_SIZE;
sp->num = STATE_SIZE;
} else if (sp->num < STATE_SIZE) {
if (sp->index > sp->num)
sp->num = sp->index;
}
/* sp->index <= sp->num <= STATE_SIZE */
/*
* state[st_idx], ..., state[(st_idx + num - 1) % STATE_SIZE] are what we
* will use now, but other threads may use them as well
*/
sp->md_count[1] += (num / RAND_DIGEST_LENGTH) + (num % RAND_DIGEST_LENGTH > 0);
if (!do_not_lock)
CRYPTO_THREAD_unlock(rand_lock);
for (i = 0; i < num; i += RAND_DIGEST_LENGTH) {
j = (num - i);
j = (j > RAND_DIGEST_LENGTH) ? RAND_DIGEST_LENGTH : j;
if (!EVP_DigestInit_ex(m, RAND_DIGEST, NULL))
goto err;
if (!EVP_DigestUpdate(m, local_md, RAND_DIGEST_LENGTH))
goto err;
k = (st_idx + j) - STATE_SIZE;
if (k > 0) {
if (!EVP_DigestUpdate(m, &sp->state[st_idx], j - k))
goto err;
if (!EVP_DigestUpdate(m, &sp->state[0], k))
goto err;
} else if (!EVP_DigestUpdate(m, &sp->state[st_idx], j))
goto err;
/* DO NOT REMOVE THE FOLLOWING CALL TO EVP_DigestUpdate()! */
if (!EVP_DigestUpdate(m, buf, j))
goto err;
/*
* We know that line may cause programs such as purify and valgrind
* to complain about use of uninitialized data. The problem is not,
* it's with the caller. Removing that line will make sure you get
* really bad randomness and thereby other problems such as very
* insecure keys.
*/
if (!EVP_DigestUpdate(m, (unsigned char *)md_c, sizeof(md_c)))
goto err;
if (!EVP_DigestFinal_ex(m, local_md, NULL))
goto err;
md_c[1]++;
buf = (const char *)buf + j;
for (k = 0; k < j; k++) {
/*
* Parallel threads may interfere with this, but always each byte
* of the new state is the XOR of some previous value of its and
* local_md (intermediate values may be lost). Alway using locking
* could hurt performance more than necessary given that
* conflicts occur only when the total seeding is longer than the
* random state.
*/
sp->state[st_idx++] ^= local_md[k];
if (st_idx >= STATE_SIZE)
st_idx = 0;
}
}
if (!do_not_lock)
CRYPTO_THREAD_write_lock(rand_lock);
/*
* Don't just copy back local_md into md -- this could mean that other
* thread's seeding remains without effect (except for the incremented
* counter). By XORing it we keep at least as much randomness as fits into
* md.
*/
for (k = 0; k < (int)sizeof(sp->md); k++) {
sp->md[k] ^= local_md[k];
}
if (randomness < RANDOMNESS_NEEDED) /* stop counting when we have enough */
randomness += add;
if (!do_not_lock)
CRYPTO_THREAD_unlock(rand_lock);
rv = 1;
err:
EVP_MD_CTX_free(m);
return rv;
}
static int rand_seed(const void *buf, int num)
{
return rand_add(buf, num, (double)num);
}
static int rand_bytes(unsigned char *buf, int num)
{
static volatile int stirred_pool = 0;
int i, j, k;
size_t num_ceil, st_idx, st_num;
int ok;
long md_c[2];
unsigned char local_md[RAND_DIGEST_LENGTH];
EVP_MD_CTX *m;
OSSL_RAND_STATE *sp = &global_state;
#ifndef GETPID_IS_MEANINGLESS
pid_t curr_pid = getpid();
#endif
time_t curr_time = time(NULL);
int do_stir_pool = 0;
/* time value for various platforms */
#ifdef OPENSSL_SYS_WIN32
FILETIME tv;
# ifdef _WIN32_WCE
SYSTEMTIME t;
GetSystemTime(&t);
SystemTimeToFileTime(&t, &tv);
# else
GetSystemTimeAsFileTime(&tv);
# endif
#elif defined(OPENSSL_SYS_VXWORKS)
struct timespec tv;
clock_gettime(CLOCK_REALTIME, &ts);
#elif defined(OPENSSL_SYS_DSPBIOS)
unsigned long long tv, OPENSSL_rdtsc();
tv = OPENSSL_rdtsc();
#else
struct timeval tv;
gettimeofday(&tv, NULL);
#endif
#ifdef PREDICT
if (rand_predictable) {
unsigned char val = 1;
for (i = 0; i < num; i++)
buf[i] = val++;
return (1);
}
#endif
if (num <= 0)
return 1;
m = EVP_MD_CTX_new();
if (m == NULL)
goto err_mem;
/* round upwards to multiple of RAND_DIGEST_LENGTH/2 */
num_ceil =
(1 + (num - 1) / (RAND_DIGEST_LENGTH / 2)) * (RAND_DIGEST_LENGTH / 2);
/*
* (Based on the rand(3) manpage:)
*
* For each group of 10 bytes (or less), we do the following:
*
* Input into the hash function the local 'md' (which is initialized from
* the global 'md' before any bytes are generated), the bytes that are to
* be overwritten by the random bytes, and bytes from the 'state'
* (incrementing looping index). From this digest output (which is kept
* in 'md'), the top (up to) 10 bytes are returned to the caller and the
* bottom 10 bytes are xored into the 'state'.
*
* Finally, after we have finished 'num' random bytes for the
* caller, 'count' (which is incremented) and the local and global 'md'
* are fed into the hash function and the results are kept in the
* global 'md'.
*/
if (!RUN_ONCE(&ossl_rand_init, do_ossl_rand_init))
goto err_mem;
CRYPTO_THREAD_write_lock(rand_lock);
/*
* We could end up in an async engine while holding this lock so ensure
* we don't pause and cause a deadlock
*/
ASYNC_block_pause();
/* prevent rand_bytes() from trying to obtain the lock again */
CRYPTO_THREAD_write_lock(rand_tmp_lock);
locking_threadid = CRYPTO_THREAD_get_current_id();
CRYPTO_THREAD_unlock(rand_tmp_lock);
crypto_lock_rand = 1;
if (!initialized) {
RAND_poll();
initialized = 1;
}
if (!stirred_pool)
do_stir_pool = 1;
ok = (randomness >= RANDOMNESS_NEEDED);
if (!ok) {
/*
* If the PRNG state is not yet unpredictable, then seeing the PRNG
* output may help attackers to determine the new state; thus we have
* to decrease the randomness estimate. Once we've had enough initial
* seeding we don't bother to adjust the randomness count, though,
* because we're not ambitious to provide *information-theoretic*
* randomness. NOTE: This approach fails if the program forks before
* we have enough randomness. Randomness should be collected in a
* separate input pool and be transferred to the output pool only
* when the randomness limit has been reached.
*/
randomness -= num;
if (randomness < 0)
randomness = 0;
}
if (do_stir_pool) {
/*
* In the output function only half of 'md' remains secret, so we
* better make sure that the required randomness gets 'evenly
* distributed' through 'state', our randomness pool. The input
* function (rand_add) chains all of 'md', which makes it more
* suitable for this purpose.
*/
int n = STATE_SIZE; /* so that the complete pool gets accessed */
while (n > 0) {
#if RAND_DIGEST_LENGTH > 20
# error "Please adjust DUMMY_SEED."
#endif
#define DUMMY_SEED "...................." /* at least RAND_DIGEST_LENGTH */
/*
* Note that the seed does not matter, it's just that
* rand_add expects to have something to hash.
*/
rand_add(DUMMY_SEED, RAND_DIGEST_LENGTH, 0.0);
n -= RAND_DIGEST_LENGTH;
}
if (ok)
stirred_pool = 1;
}
st_idx = sp->index;
st_num = sp->num;
md_c[0] = sp->md_count[0];
md_c[1] = sp->md_count[1];
memcpy(local_md, sp->md, sizeof sp->md);
sp->index += num_ceil;
if (sp->index > sp->num)
sp->index %= sp->num;
/*
* state[st_idx], ..., state[(st_idx + num_ceil - 1) % st_num] are now
* ours (but other threads may use them too)
*/
sp->md_count[0] += 1;
/* before unlocking, we must clear 'crypto_lock_rand' */
crypto_lock_rand = 0;
ASYNC_unblock_pause();
CRYPTO_THREAD_unlock(rand_lock);
while (num > 0) {
/* num_ceil -= RAND_DIGEST_LENGTH / 2 */
j = (num >= RAND_DIGEST_LENGTH / 2) ? RAND_DIGEST_LENGTH / 2 : num;
num -= j;
if (!EVP_DigestInit_ex(m, RAND_DIGEST, NULL))
goto err;
#ifndef GETPID_IS_MEANINGLESS
if (curr_pid) { /* just in the first iteration to save time */
if (!EVP_DigestUpdate(m, (unsigned char *)&curr_pid, sizeof curr_pid))
goto err;
curr_pid = 0;
}
#endif
if (curr_time) { /* just in the first iteration to save time */
if (!EVP_DigestUpdate(m, (unsigned char *)&curr_time, sizeof curr_time))
goto err;
if (!EVP_DigestUpdate(m, (unsigned char *)&tv, sizeof tv))
goto err;
curr_time = 0;
if (!rand_hw_seed(m))
goto err;
}
if (!EVP_DigestUpdate(m, local_md, RAND_DIGEST_LENGTH))
goto err;
if (!EVP_DigestUpdate(m, (unsigned char *)md_c, sizeof(md_c)))
goto err;
k = (st_idx + RAND_DIGEST_LENGTH / 2) - st_num;
if (k > 0) {
if (!EVP_DigestUpdate(m, &sp->state[st_idx], RAND_DIGEST_LENGTH / 2 - k))
goto err;
if (!EVP_DigestUpdate(m, &sp->state[0], k))
goto err;
} else if (!EVP_DigestUpdate(m, &sp->state[st_idx], RAND_DIGEST_LENGTH / 2))
goto err;
if (!EVP_DigestFinal_ex(m, local_md, NULL))
goto err;
for (i = 0; i < RAND_DIGEST_LENGTH / 2; i++) {
/* may compete with other threads */
sp->state[st_idx++] ^= local_md[i];
if (st_idx >= st_num)
st_idx = 0;
if (i < j)
*(buf++) = local_md[i + RAND_DIGEST_LENGTH / 2];
}
}
if (!EVP_DigestInit_ex(m, RAND_DIGEST, NULL)
|| !EVP_DigestUpdate(m, (unsigned char *)md_c, sizeof(md_c))
|| !EVP_DigestUpdate(m, local_md, RAND_DIGEST_LENGTH))
goto err;
CRYPTO_THREAD_write_lock(rand_lock);
/*
* Prevent deadlocks if we end up in an async engine
*/
ASYNC_block_pause();
if (!EVP_DigestUpdate(m, sp->md, sizeof(sp->md))
|| !EVP_DigestFinal_ex(m, sp->md, NULL)) {
CRYPTO_THREAD_unlock(rand_lock);
goto err;
}
ASYNC_unblock_pause();
CRYPTO_THREAD_unlock(rand_lock);
EVP_MD_CTX_free(m);
if (ok)
return (1);
RANDerr(RAND_F_RAND_BYTES, RAND_R_PRNG_NOT_SEEDED);
ERR_add_error_data(1, "You need to read the OpenSSL FAQ, "
"https://www.openssl.org/docs/faq.html");
return (0);
err:
RANDerr(RAND_F_RAND_BYTES, ERR_R_EVP_LIB);
EVP_MD_CTX_free(m);
return 0;
err_mem:
RANDerr(RAND_F_RAND_BYTES, ERR_R_MALLOC_FAILURE);
EVP_MD_CTX_free(m);
return 0;
}
static int rand_status(void)
{
CRYPTO_THREAD_ID cur;
int ret;
int do_not_lock;
if (!RUN_ONCE(&ossl_rand_init, do_ossl_rand_init))
return 0;
cur = CRYPTO_THREAD_get_current_id();
/*
* check if we already have the lock (could happen if a RAND_poll()
* implementation calls RAND_status())
*/
if (crypto_lock_rand) {
CRYPTO_THREAD_read_lock(rand_tmp_lock);
do_not_lock = CRYPTO_THREAD_compare_id(locking_threadid, cur);
CRYPTO_THREAD_unlock(rand_tmp_lock);
} else
do_not_lock = 0;
if (!do_not_lock) {
CRYPTO_THREAD_write_lock(rand_lock);
/*
* Prevent deadlocks in case we end up in an async engine
*/
ASYNC_block_pause();
/*
* prevent rand_bytes() from trying to obtain the lock again
*/
CRYPTO_THREAD_write_lock(rand_tmp_lock);
locking_threadid = cur;
CRYPTO_THREAD_unlock(rand_tmp_lock);
crypto_lock_rand = 1;
}
if (!initialized) {
RAND_poll();
initialized = 1;
}
ret = randomness >= RANDOMNESS_NEEDED;
if (!do_not_lock) {
/* before unlocking, we must clear 'crypto_lock_rand' */
crypto_lock_rand = 0;
ASYNC_unblock_pause();
CRYPTO_THREAD_unlock(rand_lock);
}
return ret;
}
/*
* rand_hw_seed: get seed data from any available hardware RNG. only
* currently supports rdrand.
*/
#if (defined(__i386) || defined(__i386__) || defined(_M_IX86) || \
defined(__x86_64) || defined(__x86_64__) || \
defined(_M_AMD64) || defined (_M_X64)) && defined(OPENSSL_CPUID_OBJ) \
&& !defined(OPENSSL_NO_RDRAND)
# define RDRAND_CALLS 4
size_t OPENSSL_ia32_rdrand(void);
extern unsigned int OPENSSL_ia32cap_P[];
static int rand_hw_seed(EVP_MD_CTX *ctx)
{
int i;
if (!(OPENSSL_ia32cap_P[1] & (1 << (62 - 32))))
return 1;
for (i = 0; i < RDRAND_CALLS; i++) {
size_t rnd;
rnd = OPENSSL_ia32_rdrand();
if (rnd == 0)
return 1;
if (!EVP_DigestUpdate(ctx, (unsigned char *)&rnd, sizeof(size_t)))
return 0;
}
return 1;
}
#else
static int rand_hw_seed(EVP_MD_CTX *ctx)
{
return 1;
}
#endif
RAND_METHOD openssl_rand_meth = {
rand_seed,
rand_bytes,
rand_cleanup,
rand_add,
rand_bytes,
rand_status
};
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