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/*
* Copyright (C) Igor Sysoev
* Copyright (C) NGINX, Inc.
*/
#include <nxt_main.h>
/*
* The pseudorandom generator based on OpenBSD arc4random. Although it is
* usually stated that arc4random uses RC4 pseudorandom generation algorithm
* they are actually different in nxt_random_add().
*/
#define NXT_RANDOM_KEY_SIZE 128
nxt_inline void nxt_random_start_schedule(nxt_random_t *r);
static void nxt_random_stir(nxt_random_t *r);
static void nxt_random_add(nxt_random_t *r, const u_char *key, uint32_t len);
nxt_inline uint8_t nxt_random_byte(nxt_random_t *r);
void
nxt_random_init(nxt_random_t *r)
{
nxt_random_start_schedule(r);
nxt_random_stir(r);
}
nxt_inline void
nxt_random_start_schedule(nxt_random_t *r)
{
nxt_uint_t i;
r->i = 0;
r->j = 0;
for (i = 0; i < 256; i++) {
r->s[i] = i;
}
}
static void
nxt_random_stir(nxt_random_t *r)
{
int fd;
ssize_t n;
struct timeval tv;
union {
uint32_t value[4];
u_char bytes[NXT_RANDOM_KEY_SIZE];
} key;
#if (NXT_HAVE_GETRANDOM)
n = getrandom(&key, NXT_RANDOM_KEY_SIZE, 0);
#elif (NXT_HAVE_LINUX_SYS_GETRANDOM)
/* Linux 3.17 SYS_getrandom. */
n = syscall(SYS_getrandom, &key, NXT_RANDOM_KEY_SIZE, 0);
#elif (NXT_HAVE_GETENTROPY || NXT_HAVE_GETENTROPY_SYS_RANDOM)
n = 0;
if (getentropy(&key, NXT_RANDOM_KEY_SIZE) == 0) {
n = NXT_RANDOM_KEY_SIZE;
}
#else
n = 0;
#endif
if (n != NXT_RANDOM_KEY_SIZE) {
fd = open("/dev/urandom", O_RDONLY);
if (fd >= 0) {
n = read(fd, &key, NXT_RANDOM_KEY_SIZE);
(void) close(fd);
}
}
if (n != NXT_RANDOM_KEY_SIZE) {
(void) gettimeofday(&tv, NULL);
/* XOR with stack garbage. */
key.value[0] ^= tv.tv_usec;
key.value[1] ^= tv.tv_sec;
key.value[2] ^= nxt_pid;
key.value[3] ^= (uintptr_t) nxt_thread_tid(nxt_thread());
}
nxt_random_add(r, key.bytes, NXT_RANDOM_KEY_SIZE);
/* Drop the first 3072 bytes. */
for (n = 3072; n != 0; n--) {
(void) nxt_random_byte(r);
}
/* Stir again after 1,600,000 bytes. */
r->count = 400000;
}
static void
nxt_random_add(nxt_random_t *r, const u_char *key, uint32_t len)
{
uint8_t val;
uint32_t n;
for (n = 0; n < 256; n++) {
val = r->s[r->i];
r->j += val + key[n % len];
r->s[r->i] = r->s[r->j];
r->s[r->j] = val;
r->i++;
}
/* This index is not decremented in RC4 algorithm. */
r->i--;
r->j = r->i;
}
uint32_t
nxt_random(nxt_random_t *r)
{
uint32_t val;
r->count--;
if (r->count <= 0) {
nxt_random_stir(r);
}
val = (uint32_t) nxt_random_byte(r) << 24;
val |= (uint32_t) nxt_random_byte(r) << 16;
val |= (uint32_t) nxt_random_byte(r) << 8;
val |= (uint32_t) nxt_random_byte(r);
return val;
}
nxt_inline uint8_t
nxt_random_byte(nxt_random_t *r)
{
uint8_t si, sj;
r->i++;
si = r->s[r->i];
r->j += si;
sj = r->s[r->j];
r->s[r->i] = sj;
r->s[r->j] = si;
si += sj;
return r->s[si];
}
#if (NXT_TESTS)
nxt_int_t
nxt_random_test(nxt_thread_t *thr)
{
nxt_uint_t n;
nxt_random_t r;
nxt_random_start_schedule(&r);
r.count = 400000;
nxt_random_add(&r, (u_char *) "arc4random", nxt_length("arc4random"));
/*
* Test arc4random() numbers.
* RC4 pseudorandom numbers would be 0x4642AFC3 and 0xBAF0FFF0.
*/
if (nxt_random(&r) == 0xD6270B27) {
for (n = 100000; n != 0; n--) {
(void) nxt_random(&r);
}
if (nxt_random(&r) == 0x6FCAE186) {
nxt_log_error(NXT_LOG_NOTICE, thr->log, "arc4random test passed");
return NXT_OK;
}
}
nxt_log_error(NXT_LOG_NOTICE, thr->log, "arc4random test failed");
return NXT_ERROR;
}
#endif
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