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util/nvmutil: re-add fallback timer rand

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for 1989

enabled via ifdef. not enabled by default.

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-19 19:02:59 +00:00
parent 0229e84539
commit e55f7ea081
2 changed files with 103 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
util/nvmutil/include/common.h
View File

@@ -337,12 +337,18 @@ void set_mac_nib(unsigned long mac_str_pos,
unsigned long mac_byte_pos, unsigned long mac_nib_pos);
unsigned short hextonum(char ch_s);
unsigned long rlong(void);
#if !(defined(FALLBACK_RAND_1989) && \
((FALLBACK_RAND_1989) > 0))
#if defined(__linux__)
#if defined(HAVE_GETRANDOM) || \
defined(HAVE_GETRANDOM_SYSCALL)
int fallback_rand_getrandom(void *buf, size_t len);
#endif
#endif
#else
unsigned long fallback_rand_1989(void);
unsigned long entropy_jitter(void);
#endif
void write_mac_part(unsigned long partnum);
/* Helper functions for command: dump

102
util/nvmutil/lib/num.c
View File

@@ -8,6 +8,10 @@
#include <sys/param.h>
#endif
#include <sys/types.h>
#if defined(FALLBACK_RAND_1989) && \
(FALLBACK_RAND_1989) > 0
#include <sys/time.h>
#endif
#include <errno.h>
#if !((defined(__OpenBSD__) && (OpenBSD) >= 201) || \
@@ -18,6 +22,10 @@
#include <limits.h>
#include <stddef.h>
#include <string.h>
#if defined(FALLBACK_RAND_1989) && \
(FALLBACK_RAND_1989) > 0
#include <time.h>
#endif
#include <unistd.h>
#include "../include/common.h"
@@ -49,6 +57,8 @@ hextonum(char ch_s)
unsigned long
rlong(void)
{
#if !(defined(FALLBACK_RAND_1989) && \
((FALLBACK_RAND_1989) > 0))
#if (defined(__OpenBSD__) && (OpenBSD) >= 201) || \
defined(__FreeBSD__) || \
defined(__NetBSD__) || defined(__APPLE__)
@@ -131,8 +141,8 @@ retry_urandom_read:
O_RDONLY | O_BINARY | O_NOFOLLOW |
O_CLOEXEC);
#ifdef PORTABLE_RAND_DEV
#if (PORTABLE_RAND_DEV) > 0
#ifdef USE_OLD_DEV_RANDOM
#if (USE_OLD_DEV_RANDOM) > 0
/* WARNING:
* /dev/random may block
* forever and does **NOT**
@@ -190,15 +200,29 @@ rlong_next:
off = 0;
nr = -1;
/* TODO: will re-add timer-based fallback here #if defined(PORTABLE) */
err(EIO, "Can't read from /dev/[ua]random");
return 0;
/* add portable timers here */
#endif
#else /* FALLBACK_RAND_1989 */
/* your computer is from a museum
*/
unsigned long mix = 0;
int nr;
/* 100 times, for entropy
*/
for (nr = 0; nr < 100; nr++)
mix ^= fallback_rand_1989();
/* 101 times ;)
*/
return fallback_rand_1989();
#endif
}
#if !(defined(FALLBACK_RAND_1989) && \
((FALLBACK_RAND_1989) > 0))
#if defined(__linux__)
#if defined(HAVE_GETRANDOM) || \
defined(HAVE_GETRANDOM_SYSCALL)
@@ -243,6 +267,74 @@ fallback_rand_getrandom(void *buf, size_t len)
}
#endif
#endif
#else
/* nobody should use this
* (not crypto-safe)
*/
unsigned long
fallback_rand_1989(void)
{
static unsigned long mix = 0;
static unsigned long counter = 0;
struct timeval tv;
gettimeofday(&tv, NULL);
mix ^= (unsigned long)tv.tv_sec
^ (unsigned long)tv.tv_usec
^ (unsigned long)getpid()
^ (unsigned long)&mix
^ counter++
^ entropy_jitter();
/*
* Stack addresses can vary between
* calls, thus increasing entropy.
*/
mix ^= (unsigned long)&mix;
mix ^= (unsigned long)&tv;
mix ^= (unsigned long)&counter;
return mix;
}
unsigned long
entropy_jitter(void)
{
unsigned long mix;
struct timeval a, b;
long mix_diff;
int c;
mix = 0;
gettimeofday(&a, NULL);
for (c = 0; c < 32; c++) {
getpid();
gettimeofday(&b, NULL);
/*
* prevent negative numbers to prevent overflow,
* which would bias rand to large numbers
*/
mix_diff = (long)(b.tv_usec - a.tv_usec);
if (mix_diff < 0)
mix_diff = -mix_diff;
mix ^= (unsigned long)(mix_diff);
mix ^= (unsigned long)&mix;
}
return mix;
}
#endif
void
check_bin(unsigned long a, const char *a_name)