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#include <fcntl.h>
#include <limits.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>
// musl forbids include/linux
#define RNDADDENTROPY _IOW( 'R', 0x03, int [2] )
#define RAND_POOL_SIZE 512
int main(int argc, char *argv[]) {
if (argc != 2) {
fputs("usage: load-random-seed FILE\n", stderr);
exit(1);
}
int seed_fd = open(argv[1], O_RDONLY);
if (seed_fd == -1) {
perror("error opening seed file");
exit(1);
}
struct {
int entropy_count;
int buf_size;
char buf[RAND_POOL_SIZE];
} rpi = {
.entropy_count = RAND_POOL_SIZE * CHAR_BIT,
.buf_size = RAND_POOL_SIZE
};
size_t sz = 0;
do {
ssize_t r = read(seed_fd, &rpi.buf[sz], RAND_POOL_SIZE - sz);
if (r == -1) {
perror("error reading seed file");
exit(1);
}
sz += r;
} while (sz < RAND_POOL_SIZE);
if (close(seed_fd) == -1) {
perror("error closing seed file");
exit(1);
}
int urandom_fd = open("/dev/urandom", O_RDWR);
if (urandom_fd == -1) {
perror("error opening /dev/urandom");
exit(1);
}
if (ioctl(urandom_fd, RNDADDENTROPY, &rpi) == -1) {
perror("error adding entropy");
exit(1);
}
if (close(urandom_fd) == -1) {
perror("error closing /dev/urandom");
exit(1);
}
return 0;
}
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