80 lines
1.8 KiB
C
80 lines
1.8 KiB
C
#include <errno.h>
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#include <string.h>
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#include "random.h"
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#include "util.h"
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#if __has_include(<sys/random.h>)
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// glibc 2.25 and later
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#include <sys/random.h>
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#else
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#include <unistd.h>
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#include <sys/syscall.h>
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static ssize_t getrandom(void *buf, size_t buflen, unsigned int flags) {
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return syscall(SYS_getrandom, buf, buflen, flags);
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}
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#endif
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void get_random_seed(void *buf, size_t size) {
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while (size > 0) {
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ssize_t r;
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do {
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r = getrandom(buf, size, 0);
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} while (r == -1 && errno == EINTR);
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if (r <= 0) {
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fatal_error("getrandom failed");
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}
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buf = (char *)buf + r;
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size -= r;
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}
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}
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void random_state_init(struct random_state *state) {
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state->index = RANDOM_CACHE_SIZE;
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}
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void get_random_bytes(struct random_state *state, void *buf, size_t size) {
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if (size > RANDOM_CACHE_SIZE / 2) {
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get_random_seed(buf, size);
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return;
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}
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while (size) {
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if (state->index == RANDOM_CACHE_SIZE) {
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state->index = 0;
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get_random_seed(state->cache, RANDOM_CACHE_SIZE);
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}
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size_t remaining = RANDOM_CACHE_SIZE - state->index;
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size_t copy_size = size < remaining ? size : remaining;
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memcpy(buf, state->cache + state->index, copy_size);
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state->index += copy_size;
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size -= copy_size;
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}
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}
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size_t get_random_size(struct random_state *state) {
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size_t size;
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get_random_bytes(state, &size, sizeof(size));
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return size;
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}
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// based on OpenBSD arc4random_uniform
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size_t get_random_size_uniform(struct random_state *state, size_t bound) {
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if (bound < 2) {
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return 0;
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}
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size_t min = -bound % bound;
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size_t r;
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do {
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r = get_random_size(state);
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} while (r < min);
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return r % bound;
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}
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