5468d9af77
We don't load the selinux label database anyway, hence this is not going to do anything at all. Let's simplify this hence and drop the explicit request. Also note that today SELinux can take the filename into account when automatically deducing the label for a new file, hence even if this code actually would have done something it is redundant today.
178 lines
6.9 KiB
C
178 lines
6.9 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#include <errno.h>
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#include <fcntl.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "sd-id128.h"
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "io-util.h"
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#include "log.h"
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#include "main-func.h"
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#include "mkdir.h"
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#include "string-util.h"
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#include "util.h"
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#define POOL_SIZE_MIN 512
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#define POOL_SIZE_MAX (10*1024*1024)
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static int run(int argc, char *argv[]) {
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_cleanup_close_ int seed_fd = -1, random_fd = -1;
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bool read_seed_file, write_seed_file;
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_cleanup_free_ void* buf = NULL;
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size_t buf_size = 0;
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struct stat st;
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ssize_t k;
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FILE *f;
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int r;
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log_setup_service();
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if (argc != 2)
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return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
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"This program requires one argument.");
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umask(0022);
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/* Read pool size, if possible */
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f = fopen("/proc/sys/kernel/random/poolsize", "re");
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if (f) {
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if (fscanf(f, "%zu", &buf_size) > 0)
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/* poolsize is in bits on 2.6, but we want bytes */
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buf_size /= 8;
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fclose(f);
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}
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if (buf_size < POOL_SIZE_MIN)
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buf_size = POOL_SIZE_MIN;
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r = mkdir_parents(RANDOM_SEED, 0755);
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if (r < 0)
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return log_error_errno(r, "Failed to create directory " RANDOM_SEED_DIR ": %m");
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/* When we load the seed we read it and write it to the device and then immediately update the saved seed with
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* new data, to make sure the next boot gets seeded differently. */
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if (streq(argv[1], "load")) {
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int open_rw_error;
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seed_fd = open(RANDOM_SEED, O_RDWR|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600);
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open_rw_error = -errno;
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if (seed_fd < 0) {
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write_seed_file = false;
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seed_fd = open(RANDOM_SEED, O_RDONLY|O_CLOEXEC|O_NOCTTY);
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if (seed_fd < 0) {
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bool missing = errno == ENOENT;
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log_full_errno(missing ? LOG_DEBUG : LOG_ERR,
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open_rw_error, "Failed to open " RANDOM_SEED " for writing: %m");
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r = log_full_errno(missing ? LOG_DEBUG : LOG_ERR,
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errno, "Failed to open " RANDOM_SEED " for reading: %m");
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return missing ? 0 : r;
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}
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} else
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write_seed_file = true;
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random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY, 0600);
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if (random_fd < 0) {
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write_seed_file = false;
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random_fd = open("/dev/urandom", O_WRONLY|O_CLOEXEC|O_NOCTTY, 0600);
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if (random_fd < 0)
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return log_error_errno(errno, "Failed to open /dev/urandom: %m");
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}
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read_seed_file = true;
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} else if (streq(argv[1], "save")) {
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random_fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
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if (random_fd < 0)
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return log_error_errno(errno, "Failed to open /dev/urandom: %m");
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seed_fd = open(RANDOM_SEED, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600);
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if (seed_fd < 0)
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return log_error_errno(errno, "Failed to open " RANDOM_SEED ": %m");
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read_seed_file = false;
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write_seed_file = true;
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} else
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return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
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"Unknown verb '%s'.", argv[1]);
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if (fstat(seed_fd, &st) < 0)
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return log_error_errno(errno, "Failed to stat() seed file " RANDOM_SEED ": %m");
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/* If the seed file is larger than what we expect, then honour the existing size and save/restore as much as it says */
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if ((uint64_t) st.st_size > buf_size)
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buf_size = MIN(st.st_size, POOL_SIZE_MAX);
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buf = malloc(buf_size);
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if (!buf)
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return log_oom();
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if (read_seed_file) {
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sd_id128_t mid;
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int z;
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k = loop_read(seed_fd, buf, buf_size, false);
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if (k < 0)
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r = log_error_errno(k, "Failed to read seed from " RANDOM_SEED ": %m");
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else if (k == 0) {
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r = 0;
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log_debug("Seed file " RANDOM_SEED " not yet initialized, proceeding.");
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} else {
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(void) lseek(seed_fd, 0, SEEK_SET);
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r = loop_write(random_fd, buf, (size_t) k, false);
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if (r < 0)
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log_error_errno(r, "Failed to write seed to /dev/urandom: %m");
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}
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/* Let's also write the machine ID into the random seed. Why? As an extra protection against "golden
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* images" that are put together sloppily, i.e. images which are duplicated on multiple systems but
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* where the random seed file is not properly reset. Frequently the machine ID is properly reset on
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* those systems however (simply because it's easier to notice, if it isn't due to address clashes and
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* so on, while random seed equivalence is generally not noticed easily), hence let's simply write the
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* machined ID into the random pool too. */
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z = sd_id128_get_machine(&mid);
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if (z < 0)
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log_debug_errno(z, "Failed to get machine ID, ignoring: %m");
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else {
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z = loop_write(random_fd, &mid, sizeof(mid), false);
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if (z < 0)
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log_debug_errno(z, "Failed to write machine ID to /dev/urandom, ignoring: %m");
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}
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}
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if (write_seed_file) {
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/* This is just a safety measure. Given that we are root and
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* most likely created the file ourselves the mode and owner
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* should be correct anyway. */
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(void) fchmod(seed_fd, 0600);
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(void) fchown(seed_fd, 0, 0);
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k = loop_read(random_fd, buf, buf_size, false);
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if (k < 0)
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return log_error_errno(k, "Failed to read new seed from /dev/urandom: %m");
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if (k == 0)
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return log_error_errno(SYNTHETIC_ERRNO(EIO),
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"Got EOF while reading from /dev/urandom.");
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r = loop_write(seed_fd, buf, (size_t) k, false);
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if (r < 0)
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return log_error_errno(r, "Failed to write new random seed file: %m");
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}
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return r;
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}
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DEFINE_MAIN_FUNCTION(run);
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