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#include "secure_random.h"
#include "condition_variable.h"
#include "mersenne_twister_64.h"
#include "mutex.h"
#include "time.h"
#include <assert.h>
#include <stdio.h>
#if defined(_WIN32) && !defined(__CYGWIN__)
# ifndef WIN32_LEAN_AND_MEAN
# define WIN32_LEAN_AND_MEAN 1
# endif
# include <Windows.h>
#else
# include <unistd.h>
#endif
static uint64_t get_available_memory() {
#if defined(_WIN32) && !defined(__CYGWIN__)
MEMORYSTATUSEX status;
status.dwLength = sizeof(status);
GlobalMemoryStatusEx(&status);
return (uint64_t) status.ullTotalPhys;
#else
uint64_t pages = (uint64_t) sysconf(_SC_PHYS_PAGES);
uint64_t page_size = (uint64_t) sysconf(_SC_PAGE_SIZE);
return pages * page_size;
#endif
}
#ifndef KIT_DISABLE_SYSTEM_THREADS
static once_flag kit_secure_random_fallback_flag;
static mtx_t kit_secure_random_fallback_mutex;
static void secure_random_fallback_init() {
mtx_init(&kit_secure_random_fallback_mutex, mtx_plain);
}
#endif
static void secure_random_fallback(ptrdiff_t const size,
void *const data) {
#ifndef KIT_DISABLE_SYSTEM_THREADS
call_once(&kit_secure_random_fallback_flag,
secure_random_fallback_init);
mtx_lock(&kit_secure_random_fallback_mutex);
#endif
/* Try to get some unpredictable system properties and use them to
* seed the pseudo random number generator.
*/
static uint64_t n = 0;
static uint64_t time_sec = 0;
static uint64_t time_nsec = 0;
struct timespec t;
ptrdiff_t i;
timespec_get(&t, TIME_UTC);
kit_mt64_state_t state;
if (time_sec == 0 && time_nsec == 0) {
uint64_t const seed[] = { n, get_available_memory(),
(uint64_t) t.tv_sec,
(uint64_t) t.tv_nsec };
kit_mt64_init_array(&state, sizeof seed / sizeof *seed, seed);
} else {
uint64_t const seed[] = { n,
get_available_memory(),
(uint64_t) t.tv_sec,
(uint64_t) t.tv_nsec,
(uint64_t) t.tv_sec - time_sec,
(uint64_t) t.tv_nsec - time_nsec };
kit_mt64_init_array(&state, sizeof seed / sizeof *seed, seed);
}
kit_mt64_rotate(&state);
n = kit_mt64_generate(&state);
time_sec = (uint64_t) t.tv_sec;
time_nsec = (uint64_t) t.tv_nsec;
for (i = 0; i < size; i++)
((uint8_t *) data)[i] = (uint8_t) (kit_mt64_generate(&state) >>
56);
#ifndef KIT_DISABLE_SYSTEM_THREADS
mtx_unlock(&kit_secure_random_fallback_mutex);
#endif
}
void kit_secure_random(ptrdiff_t const size, void *const data) {
assert(size > 0);
assert(data != NULL);
if (size <= 0 || data == NULL)
return;
#if defined(_WIN32) && !defined(__CYGWIN__)
secure_random_fallback(size, data);
#else
FILE *f = fopen("/dev/urandom", "rb");
assert(f != NULL);
if (f == NULL) {
secure_random_fallback(size, data);
return;
}
size_t const n = fread(data, 1, size, f);
fclose(f);
assert(n == size);
if (n != size)
secure_random_fallback(size, data);
#endif
}
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