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Diffstat (limited to 'lib/randutils.c')
| -rw-r--r-- | lib/randutils.c | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/lib/randutils.c b/lib/randutils.c new file mode 100644 index 0000000..bf81933 --- /dev/null +++ b/lib/randutils.c @@ -0,0 +1,238 @@ +/* + * 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 __linux__ +#include <sys/syscall.h> +#endif +#include "c.h" +#include "randutils.h" +#include "nls.h" + +#ifdef HAVE_TLS +#define THREAD_LOCAL static __thread +#else +#define THREAD_LOCAL static +#endif + +#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 syscal */ +#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 i, fd; + + fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC); + if (fd == -1) + fd = open("/dev/random", O_RDONLY | O_NONBLOCK | O_CLOEXEC); + if (fd >= 0) { + i = fcntl(fd, F_GETFD); + if (i >= 0) + fcntl(fd, F_SETFD, i | FD_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 */ + +void 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; + + } 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 +} + + +/* + * Tell source of randomness. + */ +const char *random_tell_source(void) +{ +#ifdef HAVE_GETRANDOM + return _("getrandom() function"); +#else + size_t i; + static const char *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 */ |