Module Name: src
Committed By: riastradh
Date: Thu Apr 30 03:42:23 UTC 2020
Modified Files:
src/sys/kern: kern_entropy.c
Log Message:
Accept both byte orders for random seed in the kernel.
The file format was defined with a machine-dependent 32-bit integer
field (the estimated number of bits of entropy in the process that
generated it). Fortunately we have a checksum to verify the order.
This way you can use `rndctl -S' on a little-endian machine to
generate a seed when installing NetBSD on a big-endian machine, and
the kernel will accept it on boot.
To generate a diff of this commit:
cvs rdiff -u -r1.1 -r1.2 src/sys/kern/kern_entropy.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/kern_entropy.c
diff -u src/sys/kern/kern_entropy.c:1.1 src/sys/kern/kern_entropy.c:1.2
--- src/sys/kern/kern_entropy.c:1.1 Thu Apr 30 03:28:18 2020
+++ src/sys/kern/kern_entropy.c Thu Apr 30 03:42:23 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_entropy.c,v 1.1 2020/04/30 03:28:18 riastradh Exp $ */
+/* $NetBSD: kern_entropy.c,v 1.2 2020/04/30 03:42:23 riastradh Exp $ */
/*-
* Copyright (c) 2019 The NetBSD Foundation, Inc.
@@ -77,7 +77,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_entropy.c,v 1.1 2020/04/30 03:28:18 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_entropy.c,v 1.2 2020/04/30 03:42:23 riastradh Exp $");
#include <sys/param.h>
#include <sys/types.h>
@@ -514,8 +514,6 @@ entropy_seed(rndsave_t *seed)
* but ignore the entropy estimate -- the file may have been
* incompletely written with garbage, which is harmless to add
* but may not be as unpredictable as alleged.
- *
- * XXX There is a byte order dependency here...
*/
SHA1Init(&ctx);
SHA1Update(&ctx, (const void *)&seed->entropy, sizeof(seed->entropy));
@@ -526,9 +524,20 @@ entropy_seed(rndsave_t *seed)
printf("entropy: invalid seed checksum\n");
seed->entropy = 0;
}
- explicit_memset(&ctx, 0, sizeof &ctx);
+ explicit_memset(&ctx, 0, sizeof ctx);
explicit_memset(digest, 0, sizeof digest);
+ /*
+ * If the entropy is insensibly large, try byte-swapping.
+ * Otherwise assume the file is corrupted and act as though it
+ * has zero entropy.
+ */
+ if (howmany(seed->entropy, NBBY) > sizeof(seed->data)) {
+ seed->entropy = bswap32(seed->entropy);
+ if (howmany(seed->entropy, NBBY) > sizeof(seed->data))
+ seed->entropy = 0;
+ }
+
/* Make sure the seed source is attached. */
attach_seed_rndsource();
