59 lines
1.7 KiB
C
59 lines
1.7 KiB
C
/*
|
|
* Copyright (C) 2016 Etienne Champetier <champetier.etienne@gmail.com>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*/
|
|
#define _GNU_SOURCE
|
|
#include <errno.h>
|
|
#include <linux/random.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <sys/syscall.h>
|
|
#include <unistd.h>
|
|
|
|
#define ERROR_EXIT(fmt, ...) do { \
|
|
fprintf(stderr, fmt, ## __VA_ARGS__); \
|
|
return EXIT_FAILURE; \
|
|
} while (0)
|
|
|
|
static int usage(char *name)
|
|
{
|
|
fprintf(stderr, "Usage: %s <nb>\n", name);
|
|
fprintf(stderr, " => return <nb> bytes from getrandom()\n");
|
|
return EXIT_FAILURE;
|
|
}
|
|
|
|
int main(int argc, char *argv[])
|
|
{
|
|
if (argc != 2)
|
|
return usage(argv[0]);
|
|
|
|
if (isatty(STDOUT_FILENO))
|
|
ERROR_EXIT("Not outputting random to a tty\n");
|
|
|
|
int nbtot = atoi(argv[1]);
|
|
if (nbtot < 1)
|
|
ERROR_EXIT("Invalid <nb> param (must be > 0)\n");
|
|
|
|
char buf[256];
|
|
int len = sizeof(buf);
|
|
while (nbtot > 0) {
|
|
if (nbtot <= sizeof(buf))
|
|
len = nbtot;
|
|
if (syscall(SYS_getrandom, buf, len, 0) == -1)
|
|
ERROR_EXIT("getrandom() failed: %s\n", strerror(errno));
|
|
if (write(STDOUT_FILENO, buf, len) != len)
|
|
ERROR_EXIT("write() failed: %s\n", strerror(errno));
|
|
nbtot -= sizeof(buf);
|
|
}
|
|
}
|