1 #include <u.h>
2 #include <libc.h>
3 
4 ulong
5 truerand(void)
6 {
7 	int i, n;
8 	uchar buf[sizeof(ulong)];
9 	static int randfd = -1;
10 	static char *randfile;
11 
12 	if(randfd < 0){
13 		randfd = open(randfile="/dev/random", OREAD);
14 		/* OpenBSD lets you open /dev/random but not read it! */
15 		if(randfd < 0 || read(randfd, buf, 1) != 1)
16 			randfd = open(randfile="/dev/srandom", OREAD);	/* OpenBSD */
17 		if(randfd < 0)
18 			sysfatal("can't open %s: %r", randfile);
19 		fcntl(randfd, F_SETFD, FD_CLOEXEC);
20 	}
21 	for(i=0; i<sizeof(buf); i += n)
22 		if((n = readn(randfd, buf+i, sizeof(buf)-i)) < 0)
23 			sysfatal("can't read %s: %r", randfile);
24 	return *((ulong*)buf);
25 }