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>
This commit is contained in:
djm 2022-07-31 05:10:36 +00:00 committed by Corinna Vinschen
parent f5fece2838
commit 52a410f9bd
1 changed files with 14 additions and 3 deletions

View File

@ -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