lib/randutils: Do not block on getrandom()

In Endless we have hit a problem when using 'sfdisk' on the really first boot to automatically expand the rootfs partition. On this platform 'sfdisk' is blocking on getrandom() because not enough random bytes are available. This is an ARM platform without a hwrng. We fix this passing GRND_NONBLOCK to getrandom(). 'sfdisk' will use the best entropy it has available and fallback only as necessary. Signed-off-by: Carlo Caione <[email protected]>
NordMike · Mar 19, 2018 · a9cf659 · a9cf659
1 parent 655776a
commit a9cf659
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/lib/randutils.c b/lib/randutils.c
@@ -36,6 +36,8 @@
 
 #if !defined(HAVE_GETRANDOM) && defined(SYS_getrandom)
 /* libc without function, but we have syscal */
+#define GRND_NONBLOCK 0x01
+#define GRND_RANDOM 0x02
 static int getrandom(void *buf, size_t buflen, unsigned int flags)
 {
 	return (syscall(SYS_getrandom, buf, buflen, flags));
@@ -104,13 +106,15 @@ void random_get_bytes(void *buf, size_t nbytes)
 		int x;
 
 		errno = 0;
-		x = getrandom(cp, n, 0);
+		x = getrandom(cp, n, GRND_NONBLOCK);
 		if (x > 0) {			/* success */
 		       n -= x;
 		       cp += x;
 		       lose_counter = 0;
 		} else if (errno == ENOSYS)	/* kernel without getrandom() */
 			break;
+		else if (errno == EAGAIN)
+			break;
 		else if (lose_counter++ > 16)	/* entropy problem? */
 			break;
 	}