/*
* Try the various seeding methods in turn, exit when successful.
*
* TODO(DRBG): If more than one entropy source is available, is it
* preferable to stop as soon as enough entropy has been collected
* (as favored by @rsalz) or should one rather be defensive and add
* more entropy than requested and/or from different sources?
*
* Currently, the user can select multiple entropy sources in the
* configure step, yet in practice only the first available source
* will be used. A more flexible solution has been requested, but
* currently it is not clear how this can be achieved without
* overengineering the problem. There are many parameters which
* could be taken into account when selecting the order and amount
* of input from the different entropy sources (trust, quality,
* possibility of blocking).
*/
size_t rand_pool_acquire_entropy(RAND_POOL *pool)
{
# ifdef OPENSSL_RAND_SEED_NONE
return rand_pool_entropy_available(pool);
# else
size_t bytes_needed;
size_t entropy_available = 0;
unsigned char *buffer;
# ifdef OPENSSL_RAND_SEED_GETRANDOM
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
buffer = rand_pool_add_begin(pool, bytes_needed);
if (buffer != NULL) {
size_t bytes = 0;
if (syscall_random(buffer, bytes_needed) == (int)bytes_needed)
bytes = bytes_needed;
rand_pool_add_end(pool, bytes, 8 * bytes);
entropy_available = rand_pool_entropy_available(pool);
}
if (entropy_available > 0)
return entropy_available;
# endif
# if defined(OPENSSL_RAND_SEED_LIBRANDOM)
{
/* Not yet implemented. */
}
# endif
# ifdef OPENSSL_RAND_SEED_DEVRANDOM
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
{
size_t i;
for (i = 0; bytes_needed > 0 && i < OSSL_NELEM(random_device_paths); i++) {
const int fd = get_random_device(i);
if (fd == -1)
continue;
buffer = rand_pool_add_begin(pool, bytes_needed);
if (buffer != NULL) {
const ssize_t n = read(fd, buffer, bytes_needed);
if (n <= 0) {
close_random_device(i);
continue;
}
rand_pool_add_end(pool, n, 8 * n);
}
if (!keep_random_devices_open)
close_random_device(i);
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
}
entropy_available = rand_pool_entropy_available(pool);
if (entropy_available > 0)
return entropy_available;
}
# endif
# ifdef OPENSSL_RAND_SEED_RDTSC
entropy_available = rand_acquire_entropy_from_tsc(pool);
if (entropy_available > 0)
return entropy_available;
# endif
# ifdef OPENSSL_RAND_SEED_RDCPU
entropy_available = rand_acquire_entropy_from_cpu(pool);
if (entropy_available > 0)
return entropy_available;
# endif
# ifdef OPENSSL_RAND_SEED_EGD
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
if (bytes_needed > 0) {
static const char *paths[] = { DEVRANDOM_EGD, NULL };
int i;
for (i = 0; paths[i] != NULL; i++) {
buffer = rand_pool_add_begin(pool, bytes_needed);
if (buffer != NULL) {
size_t bytes = 0;
int num = RAND_query_egd_bytes(paths[i],
buffer, (int)bytes_needed);
if (num == (int)bytes_needed)
bytes = bytes_needed;
rand_pool_add_end(pool, bytes, 8 * bytes);
entropy_available = rand_pool_entropy_available(pool);
}
if (entropy_available > 0)
return entropy_available;
}
}
# endif
return rand_pool_entropy_available(pool);
# endif
}
/*
* Try the various seeding methods in turn, exit when successful.
*
* TODO(DRBG): If more than one entropy source is available, is it
* preferable to stop as soon as enough entropy has been collected
* (as favored by @rsalz) or should one rather be defensive and add
* more entropy than requested and/or from different sources?
*
* Currently, the user can select multiple entropy sources in the
* configure step, yet in practice only the first available source
* will be used. A more flexible solution has been requested, but
* currently it is not clear how this can be achieved without
* overengineering the problem. There are many parameters which
* could be taken into account when selecting the order and amount
* of input from the different entropy sources (trust, quality,
* possibility of blocking).
*/
size_t rand_pool_acquire_entropy(RAND_POOL *pool)
{
# if defined(OPENSSL_RAND_SEED_NONE)
return rand_pool_entropy_available(pool);
# else
size_t bytes_needed;
size_t entropy_available = 0;
unsigned char *buffer;
# if defined(OPENSSL_RAND_SEED_GETRANDOM)
{
ssize_t bytes;
/* Maximum allowed number of consecutive unsuccessful attempts */
int attempts = 3;
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
while (bytes_needed != 0 && attempts-- > 0) {
buffer = rand_pool_add_begin(pool, bytes_needed);
bytes = syscall_random(buffer, bytes_needed);
if (bytes > 0) {
rand_pool_add_end(pool, bytes, 8 * bytes);
bytes_needed -= bytes;
attempts = 3; /* reset counter after successful attempt */
} else if (bytes < 0 && errno != EINTR) {
break;
}
}
}
entropy_available = rand_pool_entropy_available(pool);
if (entropy_available > 0)
return entropy_available;
# endif
# if defined(OPENSSL_RAND_SEED_LIBRANDOM)
{
/* Not yet implemented. */
}
# endif
# if defined(OPENSSL_RAND_SEED_DEVRANDOM)
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
{
size_t i;
for (i = 0; bytes_needed > 0 && i < OSSL_NELEM(random_device_paths); i++) {
ssize_t bytes = 0;
/* Maximum allowed number of consecutive unsuccessful attempts */
int attempts = 3;
const int fd = get_random_device(i);
if (fd == -1)
continue;
while (bytes_needed != 0 && attempts-- > 0) {
buffer = rand_pool_add_begin(pool, bytes_needed);
bytes = read(fd, buffer, bytes_needed);
if (bytes > 0) {
rand_pool_add_end(pool, bytes, 8 * bytes);
bytes_needed -= bytes;
attempts = 3; /* reset counter after successful attempt */
} else if (bytes < 0 && errno != EINTR) {
break;
}
}
if (bytes < 0 || !keep_random_devices_open)
close_random_device(i);
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
}
entropy_available = rand_pool_entropy_available(pool);
if (entropy_available > 0)
return entropy_available;
}
# endif
# if defined(OPENSSL_RAND_SEED_RDTSC)
entropy_available = rand_acquire_entropy_from_tsc(pool);
if (entropy_available > 0)
return entropy_available;
# endif
# if defined(OPENSSL_RAND_SEED_RDCPU)
entropy_available = rand_acquire_entropy_from_cpu(pool);
if (entropy_available > 0)
return entropy_available;
# endif
# if defined(OPENSSL_RAND_SEED_EGD)
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
if (bytes_needed > 0) {
static const char *paths[] = { DEVRANDOM_EGD, NULL };
int i;
for (i = 0; paths[i] != NULL; i++) {
buffer = rand_pool_add_begin(pool, bytes_needed);
if (buffer != NULL) {
size_t bytes = 0;
int num = RAND_query_egd_bytes(paths[i],
buffer, (int)bytes_needed);
if (num == (int)bytes_needed)
bytes = bytes_needed;
rand_pool_add_end(pool, bytes, 8 * bytes);
entropy_available = rand_pool_entropy_available(pool);
}
if (entropy_available > 0)
return entropy_available;
}
}
# endif
return rand_pool_entropy_available(pool);
# endif
}
