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util/nvmutil: use arc4random when available

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fall back to urandom.

also add a /dev/random fallback, for older unices.

with the posix compatibility changes, combined with
this change as above, the code should be portable
now. i expect it to compile on *many* unix systems!

pretty much everything from the last 30 years.

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-06 14:40:23 +00:00
parent 95b294db05
commit e7cbd9441c
1 changed files with 48 additions and 4 deletions
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52
util/nvmutil/nvmutil.c
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@@ -51,6 +51,13 @@ static void err(int, const char *, ...);
static const char *getnvmprogname(void);
static void set_err(int);
#if defined(__OpenBSD__) || defined(__FreeBSD__) || \
defined(__NetBSD__) || defined(__APPLE__)
#ifndef HAVE_ARC4RANDOM
#define HAVE_ARC4RANDOM
#endif
#endif
#define NVM_CHECKSUM 0xBABA
#define NVM_CHECKSUM_WORD 0x3F
#define NVM_SIZE 128
@@ -64,12 +71,20 @@ static void set_err(int);
#define items(x) (sizeof((x)) / sizeof((x)[0]))
static const char newrandom[] = "/dev/urandom";
static const char oldrandom[] = "/dev/random"; /* fallback on OLD unix */
#ifndef HAVE_ARC4RANDOM
static const char *rname = NULL;
#endif
static uint8_t buf[SIZE_8KB];
static uint16_t macbuf[3];
static off_t partsize;
static int flags;
#ifndef HAVE_ARC4RANDOM
static int rfd = -1;
#endif
static int fd = -1;
static int part;
static int invert;
@@ -109,8 +124,22 @@ main(int argc, char *argv[])
#ifdef __OpenBSD__
if (pledge("stdio rpath wpath unveil", NULL) == -1)
err(ECANCELED, "pledge");
/*
* For restricted filesystem access on early error.
*
* Unveiling the random device early, regardless of
* whether we will use it, prevents operations on any
* GbE files until we permit it, while performing the
* prerequisite error checks.
*
* We don't actually use the random device on platforms
* that have arc4random, which includes OpenBSD.
*/
if (unveil("/dev/urandom", "r") == -1)
err(ECANCELED, "unveil '/dev/urandom'");
if (unveil("/dev/random", "r") == -1)
err(ECANCELED, "unveil '/dev/random'");
#endif
set_cmd(argc, argv);
@@ -148,8 +177,10 @@ main(int argc, char *argv[])
if (close(fd) == -1)
err(ECANCELED, "close '%s'", fname);
#ifndef HAVE_ARC4RANDOM
if (close(rfd) == -1)
err(ECANCELED, "close '/dev/urandom'");
err(ECANCELED, "close '%s'", rname);
#endif
if (cmd != cmd_dump) {
if (errno)
@@ -241,9 +272,18 @@ static void
open_files(void)
{
struct stat st;
#ifndef HAVE_ARC4RANDOM
struct stat st_rfd;
xopen(&rfd, "/dev/urandom", O_RDONLY, &st_rfd);
rname = newrandom;
if ((rfd = open(rname, O_RDONLY)) == -1) {
/*
* Fall back to /dev/random on old platforms
* where /dev/urandom does not exist.
*/
rname = oldrandom;
xopen(&rfd, rname, O_RDONLY, &st_rfd);
}
#endif
xopen(&fd, fname, flags, &st);
switch(st.st_size) {
@@ -397,8 +437,12 @@ rhex(void)
if (n == -1) {
n = sizeof(rnum) - 1;
#ifdef HAVE_ARC4RANDOM
arc4random_buf(rnum, sizeof(rnum));
#else
read_file_PERFECTLY_or_die(rfd, rnum, sizeof(rnum),
0, "/dev/urandom", NULL);
0, rname, NULL);
#endif
}
return rnum[n--] & 0xf;