Try to gather entropy from /dev/random.

src/lib9/truerand.c

@@ -0,0 +1,21 @@
+#include <u.h>
+#include <libc.h>
+
+ulong
+truerand(void)
+{
+	int i, n;
+	uchar buf[sizeof(ulong)];
+	static int randfd = -1;
+
+	if(randfd < 0){
+		randfd = open("/dev/random", OREAD);
+		fcntl(randfd, F_SETFD, FD_CLOEXEC);
+	}
+	if(randfd < 0)
+		sysfatal("can't open /dev/random: %r");
+	for(i=0; i<sizeof(buf); i += n)
+		if((n = readn(randfd, buf+i, sizeof(buf)-i)) < 0)
+			sysfatal("can't read /dev/random: %r");
+	return *((ulong*)buf);
+}