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random-seed: avoid errors when we cannot write random-seed file

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When we call 'systemd-random-seed load' with a read-only /var/lib/systemd,
the cleanup code (which rewrites the random-seed file) will fail and exit.

Arguably, if the filesystem is read-only and the random-seed file exists
then this will be possibly be quite bad for entroy on subsequent reboots
but it should still not make the unit fail.
This commit is contained in:
Colin Guthrie 2015-01-12 20:40:14 +00:00 committed by David Herrmann
parent f299e3e430
commit 352e209804
1 changed files with 17 additions and 13 deletions
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30
src/random-seed/random-seed.c
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@ -38,6 +38,7 @@ int main(int argc, char *argv[]) {
ssize_t k;
int r;
FILE *f;
bool cleanup_seed_file = true;
if (argc != 2) {
log_error("This program requires one argument.");
@ -90,6 +91,7 @@ int main(int argc, char *argv[]) {
r = -errno;
goto finish;
}
cleanup_seed_file = false;
}
random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY, 0600);
@ -140,20 +142,22 @@ int main(int argc, char *argv[]) {
goto finish;
}
/* This is just a safety measure. Given that we are root and
* most likely created the file ourselves the mode and owner
* should be correct anyway. */
fchmod(seed_fd, 0600);
fchown(seed_fd, 0, 0);
if (cleanup_seed_file) {
/* This is just a safety measure. Given that we are root and
* most likely created the file ourselves the mode and owner
* should be correct anyway. */
fchmod(seed_fd, 0600);
fchown(seed_fd, 0, 0);
k = loop_read(random_fd, buf, buf_size, false);
if (k <= 0) {
log_error("Failed to read new seed from /dev/urandom: %s", r < 0 ? strerror(-r) : "EOF");
r = k == 0 ? -EIO : (int) k;
} else {
r = loop_write(seed_fd, buf, (size_t) k, false);
if (r < 0)
log_error_errno(r, "Failed to write new random seed file: %m");
k = loop_read(random_fd, buf, buf_size, false);
if (k <= 0) {
log_error("Failed to read new seed from /dev/urandom: %s", r < 0 ? strerror(-r) : "EOF");
r = k == 0 ? -EIO : (int) k;
} else {
r = loop_write(seed_fd, buf, (size_t) k, false);
if (r < 0)
log_error_errno(r, "Failed to write new random seed file: %m");
}
}
finish: