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random-seed: make sure to load machine id even if the seed file is missing

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This commit is contained in:
Franck Bui
2022-11-09 18:41:30 +01:00
committed by Luca Boccassi
parent 718e5d3f60
commit a2f0dbb810
1 changed files with 29 additions and 20 deletions
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src/random-seed/random-seed.c
+29 -20
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@@ -131,6 +131,27 @@ static int random_seed_size(int seed_fd, size_t *ret_size) {
return 0;
}
static void load_machine_id(int urandom_fd) {
sd_id128_t mid;
int r;
assert(urandom_fd >= 0);
/* As an extra protection against "golden images" that are put together sloppily, i.e. images which
* are duplicated on multiple systems but where the random seed file is not properly
* reset. Frequently the machine ID is properly reset on those systems however (simply because it's
* easier to notice, if it isn't due to address clashes and so on, while random seed equivalence is
* generally not noticed easily), hence let's simply write the machined ID into the random pool
* too. */
r = sd_id128_get_machine(&mid);
if (r < 0)
return (void) log_debug_errno(r, "Failed to get machine ID, ignoring: %m");
r = random_write_entropy(urandom_fd, &mid, sizeof(mid), /* credit= */ false);
if (r < 0)
log_debug_errno(r, "Failed to write machine ID to /dev/urandom, ignoring: %m");
}
static int load_seed_file(
int seed_fd,
int urandom_fd,
@@ -139,28 +160,12 @@ static int load_seed_file(
_cleanup_free_ void *buf = NULL;
CreditEntropy lets_credit;
sd_id128_t mid;
ssize_t k;
int r;
assert(seed_fd >= 0);
assert(urandom_fd >= 0);
/* First, let's write the machine ID into /dev/urandom, not crediting entropy. Why? As an extra
* protection against "golden images" that are put together sloppily, i.e. images which are
* duplicated on multiple systems but where the random seed file is not properly reset. Frequently
* the machine ID is properly reset on those systems however (simply because it's easier to notice,
* if it isn't due to address clashes and so on, while random seed equivalence is generally not
* noticed easily), hence let's simply write the machined ID into the random pool too. */
r = sd_id128_get_machine(&mid);
if (r < 0)
log_debug_errno(r, "Failed to get machine ID, ignoring: %m");
else {
r = random_write_entropy(urandom_fd, &mid, sizeof(mid), /* credit= */ false);
if (r < 0)
log_debug_errno(r, "Failed to write machine ID to /dev/urandom, ignoring: %m");
}
buf = malloc(seed_size);
if (!buf)
return log_oom();
@@ -402,6 +407,14 @@ static int run(int argc, char *argv[]) {
switch (arg_action) {
case ACTION_LOAD:
random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY);
if (random_fd < 0)
return log_error_errno(errno, "Failed to open /dev/urandom: %m");
/* First, let's write the machine ID into /dev/urandom, not crediting entropy. See
* load_machine_id() for an explanation why. */
load_machine_id(random_fd);
seed_fd = open(RANDOM_SEED, O_RDWR|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600);
if (seed_fd < 0) {
int open_rw_error = -errno;
@@ -421,10 +434,6 @@ static int run(int argc, char *argv[]) {
} else
write_seed_file = true;
random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY);
if (random_fd < 0)
return log_error_errno(errno, "Failed to open /dev/urandom: %m");
read_seed_file = true;
synchronous = true; /* make this invocation a synchronous barrier for random pool initialization */
break;