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* [newlib-cygwin] upstream OpenBSD: arc4random: Randomise the rekey interval a little.
@ 2022-09-10 19:01 Corinna Vinschen
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From: Corinna Vinschen @ 2022-09-10 19:01 UTC (permalink / raw)
To: newlib-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=52a410f9bdd504d94f1e5711ecbf096eaaf9af97
commit 52a410f9bdd504d94f1e5711ecbf096eaaf9af97
Author: djm <djm@openbsd.org>
Date: Sun Jul 31 05:10:36 2022 +0000
upstream OpenBSD: arc4random: Randomise the rekey interval a little.
Previously, the chacha20 instance would be rekeyed every 1.6MB. This
makes it happen at a random point somewhere in the 1-2MB range.
Feedback deraadt@ visa@, ok tb@ visa@
newlib port: Make REKEY_BASE depend on SIZE_MAX
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Diff:
---
newlib/libc/stdlib/arc4random.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/newlib/libc/stdlib/arc4random.c b/newlib/libc/stdlib/arc4random.c
index c394f984a..7b6ac8a7a 100644
--- a/newlib/libc/stdlib/arc4random.c
+++ b/newlib/libc/stdlib/arc4random.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: arc4random.c,v 1.56 2022/02/28 21:56:29 dtucker Exp $ */
+/* $OpenBSD: arc4random.c,v 1.57 2022/07/31 05:10:36 djm Exp $ */
/*
* Copyright (c) 1996, David Mazieres <dm@uun.org>
@@ -49,6 +49,14 @@
#define BLOCKSZ 64
#define RSBUFSZ (16*BLOCKSZ)
+#if SIZE_MAX <= 65535
+#define REKEY_BASE ( 32*1024) /* NB. should be a power of 2 */
+#elif SIZE_MAX <= 1048575
+#define REKEY_BASE ( 512*1024) /* NB. should be a power of 2 */
+#else
+#define REKEY_BASE (1024*1024) /* NB. should be a power of 2 */
+#endif
+
/* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */
static struct _rs {
size_t rs_have; /* valid bytes at end of rs_buf */
@@ -86,6 +94,7 @@ static void
_rs_stir(void)
{
u_char rnd[KEYSZ + IVSZ];
+ uint32_t rekey_fuzz = 0;
memset(rnd, 0, (KEYSZ + IVSZ) * sizeof(u_char));
@@ -102,8 +111,10 @@ _rs_stir(void)
rs->rs_have = 0;
memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
- rs->rs_count = (SIZE_MAX <= 65535) ? 65000
- : (SIZE_MAX <= 1048575 ? 1048000 : 1600000);
+ /* rekey interval should not be predictable */
+ chacha_encrypt_bytes(&rsx->rs_chacha, (uint8_t *)&rekey_fuzz,
+ (uint8_t *)&rekey_fuzz, sizeof(rekey_fuzz));
+ rs->rs_count = REKEY_BASE + (rekey_fuzz % REKEY_BASE);
}
static inline void
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2022-09-10 19:01 [newlib-cygwin] upstream OpenBSD: arc4random: Randomise the rekey interval a little Corinna Vinschen
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