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libreboot-utils: tidy up the rand code

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Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-25 11:23:49 +00:00
parent 49cc239884
commit 6db9514c95
2 changed files with 26 additions and 60 deletions
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53
util/libreboot-utils/lib/mkhtemp.c
View File

@@ -886,53 +886,30 @@ err:
int
mkhtemp_fill_random(char *p, size_t xc)
{
size_t chx = 0;
int rand_failures = 0;
size_t r;
int saved_rand_error = 0;
static char ch[] =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
size_t chx = 0;
size_t r;
/* clamp rand to prevent modulo bias
* (reduced risk of entropy leak)
*/
size_t limit = ((size_t)-1) - (((size_t)-1) % (sizeof(ch) - 1));
int saved_errno = errno;
if (p == NULL) {
errno = EFAULT;
goto err_mkhtemp_fill_random;
}
if (if_err(p == NULL, EFAULT))
return -1;
for (chx = 0; chx < xc; chx++) {
do {
saved_rand_error = errno;
rand_failures = 0;
retry_rand:
errno = 0;
/* on bsd: uses arc4random
on linux: uses getrandom
on OLD linux: /dev/urandom
on old/other unix: /dev/urandom
*/
r = rlong();
if (errno > 0) {
if (++rand_failures <= 8)
goto retry_rand;
goto err_mkhtemp_fill_random;
}
rand_failures = 0;
errno = saved_rand_error;
} while (r >= limit);
/* on bsd: uses arc4random
on linux: uses getrandom
*never returns error*
*/
r = rlong(); /* always returns successful */
if (r >= limit)
goto retry_rand;
p[chx] = ch[r % (sizeof(ch) - 1)];
}
@@ -940,12 +917,6 @@ retry_rand:
errno = saved_errno;
return 0;
err_mkhtemp_fill_random:
if (errno == saved_errno)
errno = ECANCELED;
return -1;
}
/* WARNING: **ONCE** per file.

33
util/libreboot-utils/lib/rand.c
View File

@@ -59,6 +59,7 @@ rlong(void)
{
size_t rval;
int saved_errno = errno;
errno = 0;
#if (defined(__OpenBSD__) && (OpenBSD) >= 201) || \
defined(__FreeBSD__) || \
@@ -71,30 +72,23 @@ rlong(void)
size_t off = 0;
size_t len = sizeof(rval);
ssize_t rc;
if (!len)
goto err;
retry_rand:
rc = (ssize_t)syscall(SYS_getrandom,
(char *)&rval + off, len - off, 0);
while (off < len) {
if (rc < 0) {
if (errno == EINTR || errno == EAGAIN)
goto retry_rand;
rc = (ssize_t)syscall(SYS_getrandom,
(char *)&rval + off, len - off, 0);
if (rc < 0) {
if (errno == EINTR || errno == EAGAIN)
continue;
goto err; /* possibly unsupported by kernel */
}
off += (size_t)rc;
goto err; /* possibly unsupported by kernel */
}
goto out;
if ((off += (size_t)rc) < len)
goto retry_rand;
return rval;
goto out;
err:
/*
* getrandom can return with error, butt arc4random
@@ -103,8 +97,9 @@ err:
* BSD. So a rand failure is to be interpreted as
* a major systems failure, and we act accordingly.
*/
err_no_cleanup(1, ECANCELED, "Randomisation failure");
exit(1);
err_no_cleanup(1, ECANCELED,
"Randomisation failure, possibly unsupported in your kernel.");
exit(EXIT_FAILURE);
#else
#error Unsupported operating system (possibly unsecure randomisation)