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/* Generate sizeof(uint32_t) bytes of as random data as possible to seed
the hash function.
*/
#ifdef HAVE_CONFIG_H
#include <jansson_private_config.h>
#endif
#include <stdio.h>
#include <time.h>
#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#ifdef HAVE_SCHED_H
#include <sched.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#if defined(_WIN32)
/* For _getpid() */
#include <process.h>
#endif
#include "jansson.h"
static uint32_t buf_to_uint32(char *data) {
size_t i;
uint32_t result = 0;
for (i = 0; i < sizeof(uint32_t); i++)
result = (result << 8) | (unsigned char)data[i];
return result;
}
/* /dev/urandom */
#if !defined(_WIN32) && defined(USE_URANDOM)
static int seed_from_urandom(uint32_t *seed) {
/* Use unbuffered I/O if we have open(), close() and read(). Otherwise
fall back to fopen() */
char data[sizeof(uint32_t)];
int ok;
#if defined(HAVE_OPEN) && defined(HAVE_CLOSE) && defined(HAVE_READ)
int urandom;
urandom = open("/dev/urandom", O_RDONLY);
if (urandom == -1)
return 1;
ok = read(urandom, data, sizeof(uint32_t)) == sizeof(uint32_t);
close(urandom);
#else
FILE *urandom;
urandom = fopen("/dev/urandom", "rb");
if (!urandom)
return 1;
ok = fread(data, 1, sizeof(uint32_t), urandom) == sizeof(uint32_t);
fclose(urandom);
#endif
if (!ok)
return 1;
*seed = buf_to_uint32(data);
return 0;
}
#endif
/* Windows Crypto API */
#if defined(_WIN32) && defined(USE_WINDOWS_CRYPTOAPI)
#include <windows.h>
#include <wincrypt.h>
typedef BOOL (WINAPI *CRYPTACQUIRECONTEXTA)(HCRYPTPROV *phProv, LPCSTR pszContainer, LPCSTR pszProvider, DWORD dwProvType, DWORD dwFlags);
typedef BOOL (WINAPI *CRYPTGENRANDOM)(HCRYPTPROV hProv, DWORD dwLen, BYTE *pbBuffer);
typedef BOOL (WINAPI *CRYPTRELEASECONTEXT)(HCRYPTPROV hProv, DWORD dwFlags);
static int seed_from_windows_cryptoapi(uint32_t *seed)
{
HINSTANCE hAdvAPI32 = NULL;
CRYPTACQUIRECONTEXTA pCryptAcquireContext = NULL;
CRYPTGENRANDOM pCryptGenRandom = NULL;
CRYPTRELEASECONTEXT pCryptReleaseContext = NULL;
HCRYPTPROV hCryptProv = 0;
BYTE data[sizeof(uint32_t)];
int ok;
hAdvAPI32 = GetModuleHandle("advapi32.dll");
if(hAdvAPI32 == NULL)
return 1;
pCryptAcquireContext = (CRYPTACQUIRECONTEXTA)GetProcAddress(hAdvAPI32, "CryptAcquireContextA");
if (!pCryptAcquireContext)
return 1;
pCryptGenRandom = (CRYPTGENRANDOM)GetProcAddress(hAdvAPI32, "CryptGenRandom");
if (!pCryptGenRandom)
return 1;
pCryptReleaseContext = (CRYPTRELEASECONTEXT)GetProcAddress(hAdvAPI32, "CryptReleaseContext");
if (!pCryptReleaseContext)
return 1;
if (!pCryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
return 1;
ok = CryptGenRandom(hCryptProv, sizeof(uint32_t), data);
pCryptReleaseContext(hCryptProv, 0);
if (!ok)
return 1;
*seed = buf_to_uint32((char *)data);
return 0;
}
#endif
/* gettimeofday() and getpid() */
static int seed_from_timestamp_and_pid(uint32_t *seed) {
#ifdef HAVE_GETTIMEOFDAY
/* XOR of seconds and microseconds */
struct timeval tv;
gettimeofday(&tv, NULL);
*seed = (uint32_t)tv.tv_sec ^ (uint32_t)tv.tv_usec;
#else
/* Seconds only */
*seed = (uint32_t)time(NULL);
#endif
/* XOR with PID for more randomness */
#if defined(_WIN32)
*seed ^= (uint32_t)_getpid();
#elif defined(HAVE_GETPID)
*seed ^= (uint32_t)getpid();
#endif
return 0;
}
static uint32_t generate_seed() {
uint32_t seed;
int done = 0;
#if !defined(_WIN32) && defined(USE_URANDOM)
if (!done && seed_from_urandom(&seed) == 0)
done = 1;
#endif
#if defined(_WIN32) && defined(USE_WINDOWS_CRYPTOAPI)
if (!done && seed_from_windows_cryptoapi(&seed) == 0)
done = 1;
#endif
if (!done) {
/* Fall back to timestamp and PID if no better randomness is
available */
seed_from_timestamp_and_pid(&seed);
}
/* Make sure the seed is never zero */
if (seed == 0)
seed = 1;
return seed;
}
volatile uint32_t hashtable_seed = 0;
#if defined(HAVE_ATOMIC_BUILTINS) && (defined(HAVE_SCHED_YIELD) || !defined(_WIN32))
static volatile char seed_initialized = 0;
void json_object_seed(size_t seed) {
uint32_t new_seed = (uint32_t)seed;
if (hashtable_seed == 0) {
if (__atomic_test_and_set(&seed_initialized, __ATOMIC_RELAXED) == 0) {
/* Do the seeding ourselves */
if (new_seed == 0)
new_seed = generate_seed();
__atomic_store_n(&hashtable_seed, new_seed, __ATOMIC_ACQ_REL);
} else {
/* Wait for another thread to do the seeding */
do {
#ifdef HAVE_SCHED_YIELD
sched_yield();
#endif
} while(__atomic_load_n(&hashtable_seed, __ATOMIC_ACQUIRE) == 0);
}
}
}
#elif defined(HAVE_SYNC_BUILTINS) && (defined(HAVE_SCHED_YIELD) || !defined(_WIN32))
void json_object_seed(size_t seed) {
uint32_t new_seed = (uint32_t)seed;
if (hashtable_seed == 0) {
if (new_seed == 0) {
/* Explicit synchronization fences are not supported by the
__sync builtins, so every thread getting here has to
generate the seed value.
*/
new_seed = generate_seed();
}
do {
if (__sync_bool_compare_and_swap(&hashtable_seed, 0, new_seed)) {
/* We were the first to seed */
break;
} else {
/* Wait for another thread to do the seeding */
#ifdef HAVE_SCHED_YIELD
sched_yield();
#endif
}
} while(hashtable_seed == 0);
}
}
#elif defined(_WIN32)
static long seed_initialized = 0;
void json_object_seed(size_t seed) {
uint32_t new_seed = (uint32_t)seed;
if (hashtable_seed == 0) {
if (InterlockedIncrement(&seed_initialized) == 1) {
/* Do the seeding ourselves */
if (new_seed == 0)
new_seed = generate_seed();
hashtable_seed = new_seed;
} else {
/* Wait for another thread to do the seeding */
do {
SwitchToThread();
} while (hashtable_seed == 0);
}
}
}
#else
/* Fall back to a thread-unsafe version */
void json_object_seed(size_t seed) {
uint32_t new_seed = (uint32_t)seed;
if (hashtable_seed == 0) {
if (new_seed == 0)
new_seed = generate_seed();
hashtable_seed = new_seed;
}
}
#endif
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