1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235
|
/*
* SPDX-License-Identifier: BSD-3-Clause
*
* General purpose random utilities. Based on libuuid code.
*
* This code is free software; you can redistribute it and/or modify it under
* the terms of the Modified BSD License. The complete text of the license is
* available in the Documentation/licenses/COPYING.BSD-3-Clause file.
*/
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#ifdef HAVE_SYS_SYSCALL_H
#include <sys/syscall.h>
#endif
#include "c.h"
#include "randutils.h"
#include "nls.h"
#ifdef HAVE_GETRANDOM
# include <sys/random.h>
#elif defined (__linux__)
# if !defined(SYS_getrandom) && defined(__NR_getrandom)
/* usable kernel-headers, but old glibc-headers */
# define SYS_getrandom __NR_getrandom
# endif
#endif
#if !defined(HAVE_GETRANDOM) && defined(SYS_getrandom)
/* libc without function, but we have syscall */
#define GRND_NONBLOCK 0x01
#define GRND_RANDOM 0x02
static int getrandom(void *buf, size_t buflen, unsigned int flags)
{
return (syscall(SYS_getrandom, buf, buflen, flags));
}
# define HAVE_GETRANDOM
#endif
#if defined(__linux__) && defined(__NR_gettid) && defined(HAVE_JRAND48)
#define DO_JRAND_MIX
THREAD_LOCAL unsigned short ul_jrand_seed[3];
#endif
int rand_get_number(int low_n, int high_n)
{
return rand() % (high_n - low_n + 1) + low_n;
}
static void crank_random(void)
{
int i;
struct timeval tv;
unsigned int n_pid, n_uid;
gettimeofday(&tv, NULL);
n_pid = getpid();
n_uid = getuid();
srand((n_pid << 16) ^ n_uid ^ tv.tv_sec ^ tv.tv_usec);
#ifdef DO_JRAND_MIX
ul_jrand_seed[0] = getpid() ^ (tv.tv_sec & 0xFFFF);
ul_jrand_seed[1] = getppid() ^ (tv.tv_usec & 0xFFFF);
ul_jrand_seed[2] = (tv.tv_sec ^ tv.tv_usec) >> 16;
#endif
/* Crank the random number generator a few times */
gettimeofday(&tv, NULL);
for (i = (tv.tv_sec ^ tv.tv_usec) & 0x1F; i > 0; i--)
rand();
}
int random_get_fd(void)
{
int fd;
fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
if (fd == -1)
fd = open("/dev/random", O_RDONLY | O_NONBLOCK | O_CLOEXEC);
crank_random();
return fd;
}
/*
* Generate a stream of random nbytes into buf.
* Use /dev/urandom if possible, and if not,
* use glibc pseudo-random functions.
*/
#define UL_RAND_READ_ATTEMPTS 8
#define UL_RAND_READ_DELAY 125000 /* microseconds */
/*
* Write @nbytes random bytes into @buf.
*
* Returns 0 for good quality of random bytes or 1 for weak quality.
*/
int ul_random_get_bytes(void *buf, size_t nbytes)
{
unsigned char *cp = (unsigned char *)buf;
size_t i, n = nbytes;
int lose_counter = 0;
#ifdef HAVE_GETRANDOM
while (n > 0) {
int x;
errno = 0;
x = getrandom(cp, n, GRND_NONBLOCK);
if (x > 0) { /* success */
n -= x;
cp += x;
lose_counter = 0;
errno = 0;
} else if (errno == ENOSYS) { /* kernel without getrandom() */
break;
} else if (errno == EAGAIN && lose_counter < UL_RAND_READ_ATTEMPTS) {
xusleep(UL_RAND_READ_DELAY); /* no entropy, wait and try again */
lose_counter++;
} else
break;
}
if (errno == ENOSYS)
#endif
/*
* We've been built against headers that support getrandom, but the
* running kernel does not. Fallback to reading from /dev/{u,}random
* as before
*/
{
int fd = random_get_fd();
lose_counter = 0;
if (fd >= 0) {
while (n > 0) {
ssize_t x = read(fd, cp, n);
if (x <= 0) {
if (lose_counter++ > UL_RAND_READ_ATTEMPTS)
break;
xusleep(UL_RAND_READ_DELAY);
continue;
}
n -= x;
cp += x;
lose_counter = 0;
}
close(fd);
}
}
/*
* We do this all the time, but this is the only source of
* randomness if /dev/random/urandom is out to lunch.
*/
crank_random();
for (cp = buf, i = 0; i < nbytes; i++)
*cp++ ^= (rand() >> 7) & 0xFF;
#ifdef DO_JRAND_MIX
{
unsigned short tmp_seed[3];
memcpy(tmp_seed, ul_jrand_seed, sizeof(tmp_seed));
ul_jrand_seed[2] = ul_jrand_seed[2] ^ syscall(__NR_gettid);
for (cp = buf, i = 0; i < nbytes; i++)
*cp++ ^= (jrand48(tmp_seed) >> 7) & 0xFF;
memcpy(ul_jrand_seed, tmp_seed,
sizeof(ul_jrand_seed)-sizeof(unsigned short));
}
#endif
return n != 0;
}
/*
* Tell source of randomness.
*/
const char *random_tell_source(void)
{
#ifdef HAVE_GETRANDOM
return _("getrandom() function");
#else
size_t i;
static const char *const random_sources[] = {
"/dev/urandom",
"/dev/random"
};
for (i = 0; i < ARRAY_SIZE(random_sources); i++) {
if (!access(random_sources[i], R_OK))
return random_sources[i];
}
#endif
return _("libc pseudo-random functions");
}
#ifdef TEST_PROGRAM_RANDUTILS
#include <inttypes.h>
int main(int argc, char *argv[])
{
size_t i, n;
int64_t *vp, v;
char *buf;
size_t bufsz;
n = argc == 1 ? 16 : atoi(argv[1]);
printf("Multiple random calls:\n");
for (i = 0; i < n; i++) {
ul_random_get_bytes(&v, sizeof(v));
printf("#%02zu: %25"PRIu64"\n", i, v);
}
printf("One random call:\n");
bufsz = n * sizeof(*vp);
buf = malloc(bufsz);
if (!buf)
err(EXIT_FAILURE, "failed to allocate buffer");
ul_random_get_bytes(buf, bufsz);
for (i = 0; i < n; i++) {
vp = (int64_t *) (buf + (i * sizeof(*vp)));
printf("#%02zu: %25"PRIu64"\n", i, *vp);
}
return EXIT_SUCCESS;
}
#endif /* TEST_PROGRAM_RANDUTILS */
|