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 "fs-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_and_chown(seed_fd, 0600, 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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