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util/nvmutil: remove randomness fallback

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not secure. i'll just re-add arc4random

and use urandom as the fallback

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-18 04:26:10 +00:00
parent 1ecea3247d
commit 1d1f721d85
2 changed files with 13 additions and 120 deletions
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111
util/nvmutil/nvmutil.c
View File

@@ -989,56 +989,12 @@ hextonum(char ch_s)
unsigned long
rlong(void)
{
static unsigned long mix = 0;
static unsigned long counter = 0;
int fd = -1;
struct x_st_timeval tv;
int fd;
long nr;
unsigned long rval;
rval = 0;
nr = -1;
x_i_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;
/*
* Now, we won't use this mix
* immediately. We'll try to
* read urandom first, which is
* likely safer, and pass that,
* falling back to the mixture
* if urandom fails.
*
* Since urandom is likely
* reliable, the number of
* times it will fail is
* likely extremely random,
* thus, building more than
* sufficient entropy by the
* time we do eventually use
* the fallback code
*/
if (fd < 0)
fd = open("/dev/urandom", O_RDONLY | O_BINARY | O_NONBLOCK);
#if !(defined(__OpenBSD__) && defined(OpenBSD)) || \
@@ -1051,7 +1007,8 @@ rlong(void)
if (fd < 0)
fd = open("/dev/random", O_RDONLY | O_BINARY | O_NONBLOCK);
if (fd > -1) {
if (fd < 0)
err(errno, "can't open random device");
nr = rw_file_exact(fd, (unsigned char *)&rval,
sizeof(unsigned long), 0, IO_READ, LOOP_EAGAIN,
@@ -1060,66 +1017,12 @@ rlong(void)
if (x_i_close(fd) < 0)
err(errno, "Can't close randomness fd");
if (nr == sizeof(unsigned long))
if (nr != sizeof(unsigned long))
err(errno, "Incomplete read from random device");
return rval;
}
return mix;
}
unsigned long
entropy_jitter(void)
{
unsigned long mix;
struct x_st_timeval a, b;
long mix_diff;
int c;
mix = 0;
x_i_gettimeofday(&a, NULL);
for (c = 0; c < 32; c++) {
getpid();
x_i_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;
}
int
x_i_gettimeofday(struct x_st_timeval *tv, void *tz)
{
time_t t;
(void)tz;
t = time(NULL);
tv->tv_sec = t;
tv->tv_usec = (long)((unsigned long)clock() % 1000000UL);
return 0;
}
void
write_mac_part(unsigned long partnum)
{

10
util/nvmutil/nvmutil.h
View File

@@ -215,14 +215,6 @@
#define SKIP_CHECKSUM_WRITE 0
#define CHECKSUM_WRITE 1
/*
* portable timeval
*/
struct x_st_timeval {
long tv_sec;
long tv_usec;
};
struct commands {
unsigned long chk;
char *str;
@@ -357,8 +349,6 @@ 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);
unsigned long entropy_jitter(void);
int x_i_gettimeofday(struct x_st_timeval *tv, void *tz);
void write_mac_part(unsigned long partnum);
/*