feed-random.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/ioctl.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <linux/random.h>

#define BUFSIZE 256

typedef struct {
    int             entropy_count;
    int             buf_size;
    unsigned int    buf[0];
} entropy_t;

int main(void) {
    entropy_t *en = malloc(sizeof(*en) + sizeof(unsigned int[BUFSIZE]));
    // for (int i = 0 ; i < BUFSIZE; i++) {
    //     en->buf[i] = i;
    // }
    // for (int i = 0 ; i < BUFSIZE; i++) {
    //     printf("(%d) => %d\n", i, en->buf[i]);
    // }
    // printf("sizeof(*en): %zu\n", sizeof(*en));
    // printf("sizeof(en): %zu\n", sizeof(en));
    // printf("sizeof(unsigned int[%d]): %zu\n", BUFSIZE, sizeof(unsigned int[BUFSIZE]));
    int fd = open("/dev/random", O_WRONLY);
    int rc = ioctl(fd, RNDADDENTROPY, en);
    if (rc != 0) {
        perror("ioctl()");
    }
}