diff --git a/src/random-seed/random-seed.c b/src/random-seed/random-seed.c index 82c29d0d7f..22ddf659ae 100644 --- a/src/random-seed/random-seed.c +++ b/src/random-seed/random-seed.c @@ -2,6 +2,7 @@ #include #include +#include #include #include #if USE_SYS_RANDOM_H @@ -22,20 +23,34 @@ #include "missing_random.h" #include "missing_syscall.h" #include "mkdir.h" +#include "parse-argument.h" #include "parse-util.h" +#include "pretty-print.h" #include "random-util.h" +#include "string-table.h" #include "string-util.h" +#include "strv.h" #include "sync-util.h" #include "sha256.h" +#include "terminal-util.h" #include "util.h" #include "xattr-util.h" +typedef enum SeedAction { + ACTION_LOAD, + ACTION_SAVE, + _ACTION_MAX, + _ACTION_INVALID = -EINVAL, +} SeedAction; + typedef enum CreditEntropy { CREDIT_ENTROPY_NO_WAY, CREDIT_ENTROPY_YES_PLEASE, CREDIT_ENTROPY_YES_FORCED, } CreditEntropy; +static SeedAction arg_action = _ACTION_INVALID; + static CreditEntropy may_credit(int seed_fd) { _cleanup_free_ char *creditable = NULL; const char *e; @@ -87,51 +102,306 @@ static CreditEntropy may_credit(int seed_fd) { /* Don't credit the random seed if we are in first-boot mode, because we are supposed to start from * scratch. This is a safety precaution for cases where we people ship "golden" images with empty * /etc but populated /var that contains a random seed. */ - if (access("/run/systemd/first-boot", F_OK) < 0) { - - if (errno != ENOENT) { - log_warning_errno(errno, "Failed to check whether we are in first-boot mode, not crediting entropy: %m"); - return CREDIT_ENTROPY_NO_WAY; - } - - /* If ENOENT all is good, we are not in first-boot mode. */ - } else { - log_debug("Not crediting entropy, since booted in first-boot mode."); + r = RET_NERRNO(access("/run/systemd/first-boot", F_OK)); + if (r == -ENOENT) + /* All is good, we are not in first-boot mode. */ + return CREDIT_ENTROPY_YES_PLEASE; + if (r < 0) { + log_warning_errno(r, "Failed to check whether we are in first-boot mode, not crediting entropy: %m"); return CREDIT_ENTROPY_NO_WAY; } - return CREDIT_ENTROPY_YES_PLEASE; + log_debug("Not crediting entropy, since booted in first-boot mode."); + return CREDIT_ENTROPY_NO_WAY; +} + +static int random_seed_size(int seed_fd, size_t *ret_size) { + struct stat st; + + assert(ret_size); + assert(seed_fd >= 0); + + if (fstat(seed_fd, &st) < 0) + return log_error_errno(errno, "Failed to stat() seed file " RANDOM_SEED ": %m"); + + /* If the seed file is larger than what the kernel expects, then honour the existing size and + * save/restore as much as it says */ + + *ret_size = CLAMP((uint64_t)st.st_size, random_pool_size(), RANDOM_POOL_SIZE_MAX); + return 0; +} + +static int load_seed_file( + int seed_fd, + int urandom_fd, + size_t seed_size, + struct sha256_ctx **ret_hash_state) { + + _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(); + + k = loop_read(seed_fd, buf, seed_size, false); + if (k < 0) { + log_warning_errno(k, "Failed to read seed from " RANDOM_SEED ": %m"); + return 0; + } + if (k == 0) { + log_debug("Seed file " RANDOM_SEED " not yet initialized, proceeding."); + return 0; + } + + /* If we're going to later write out a seed file, initialize a hash state with the contents of the + * seed file we just read, so that the new one can't regress in entropy. */ + if (ret_hash_state) { + struct sha256_ctx *hash_state; + + hash_state = malloc(sizeof(struct sha256_ctx)); + if (!hash_state) + return log_oom(); + + sha256_init_ctx(hash_state); + sha256_process_bytes(&k, sizeof(k), hash_state); /* Hash length to distinguish from new seed. */ + sha256_process_bytes(buf, k, hash_state); + + *ret_hash_state = hash_state; + } + + (void) lseek(seed_fd, 0, SEEK_SET); + + lets_credit = may_credit(seed_fd); + + /* Before we credit or use the entropy, let's make sure to securely drop the creditable xattr from + * the file, so that we never credit the same random seed again. Note that further down we'll write a + * new seed again, and likely mark it as credible again, hence this is just paranoia to close the + * short time window between the time we upload the random seed into the kernel and download the new + * one from it. */ + + if (fremovexattr(seed_fd, "user.random-seed-creditable") < 0) { + if (!ERRNO_IS_XATTR_ABSENT(errno)) + log_warning_errno(errno, "Failed to remove extended attribute, ignoring: %m"); + + /* Otherwise, there was no creditable flag set, which is OK. */ + } else { + r = fsync_full(seed_fd); + if (r < 0) { + log_warning_errno(r, "Failed to synchronize seed to disk, not crediting entropy: %m"); + + if (lets_credit == CREDIT_ENTROPY_YES_PLEASE) + lets_credit = CREDIT_ENTROPY_NO_WAY; + } + } + + r = random_write_entropy(urandom_fd, buf, k, + IN_SET(lets_credit, CREDIT_ENTROPY_YES_PLEASE, CREDIT_ENTROPY_YES_FORCED)); + if (r < 0) + log_warning_errno(r, "Failed to write seed to /dev/urandom: %m"); + + return 0; +} + +static int save_seed_file( + int seed_fd, + int urandom_fd, + size_t seed_size, + bool synchronous, + struct sha256_ctx *hash_state) { + + _cleanup_free_ void *buf = NULL; + bool getrandom_worked = false; + ssize_t k, l; + int r; + + assert(seed_fd >= 0); + assert(urandom_fd >= 0); + + /* 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. */ + r = fchmod_and_chown(seed_fd, 0600, 0, 0); + if (r < 0) + return log_error_errno(r, "Failed to adjust seed file ownership and access mode: %m"); + + buf = malloc(seed_size); + if (!buf) + return log_oom(); + + k = getrandom(buf, seed_size, GRND_NONBLOCK); + if (k < 0 && errno == EAGAIN && synchronous) { + /* If we're asked to make ourselves a barrier for proper initialization of the random pool + * make this whole job synchronous by asking getrandom() to wait until the requested number + * of random bytes is available. */ + log_notice("Kernel entropy pool is not initialized yet, waiting until it is."); + k = getrandom(buf, seed_size, 0); + } + if (k < 0) + log_debug_errno(errno, "Failed to read random data with getrandom(), falling back to /dev/urandom: %m"); + else if ((size_t) k < seed_size) + log_debug("Short read from getrandom(), falling back to /dev/urandom."); + else + getrandom_worked = true; + + if (!getrandom_worked) { + /* Retry with classic /dev/urandom */ + k = loop_read(urandom_fd, buf, seed_size, false); + if (k < 0) + return log_error_errno(k, "Failed to read new seed from /dev/urandom: %m"); + if (k == 0) + return log_error_errno(SYNTHETIC_ERRNO(EIO), "Got EOF while reading from /dev/urandom."); + } + + /* If we previously read in a seed file, then hash the new seed into the old one, and replace the + * last 32 bytes of the seed with the hash output, so that the new seed file can't regress in + * entropy. */ + if (hash_state) { + uint8_t hash[SHA256_DIGEST_SIZE]; + + sha256_process_bytes(&k, sizeof(k), hash_state); /* Hash length to distinguish from old seed. */ + sha256_process_bytes(buf, k, hash_state); + sha256_finish_ctx(hash_state, hash); + l = MIN((size_t)k, sizeof(hash)); + memcpy((uint8_t *)buf + k - l, hash, l); + } + + r = loop_write(seed_fd, buf, (size_t) k, false); + if (r < 0) + return log_error_errno(r, "Failed to write new random seed file: %m"); + + if (ftruncate(seed_fd, k) < 0) + return log_error_errno(r, "Failed to truncate random seed file: %m"); + + r = fsync_full(seed_fd); + if (r < 0) + return log_error_errno(r, "Failed to synchronize seed file: %m"); + + /* If we got this random seed data from getrandom() the data is suitable for crediting entropy later + * on. Let's keep that in mind by setting an extended attribute. on the file */ + if (getrandom_worked) + if (fsetxattr(seed_fd, "user.random-seed-creditable", "1", 1, 0) < 0) + log_full_errno(ERRNO_IS_NOT_SUPPORTED(errno) ? LOG_DEBUG : LOG_WARNING, errno, + "Failed to mark seed file as creditable, ignoring: %m"); + return 0; +} + +static int help(int argc, char *argv[], void *userdata) { + _cleanup_free_ char *link = NULL; + int r; + + r = terminal_urlify_man("systemd-random-seed", "8", &link); + if (r < 0) + return log_oom(); + + printf("%1$s [OPTIONS...] COMMAND\n" + "\n%5$sLoad and save the system random seed at boot and shutdown.%6$s\n" + "\n%3$sCommands:%4$s\n" + " load Load a random seed saved on disk into the kernel entropy pool\n" + " save Save a new random seed on disk\n" + "\n%3$sOptions:%4$s\n" + " -h --help Show this help\n" + " --version Show package version\n" + "\nSee the %2$s for details.\n", + program_invocation_short_name, + link, + ansi_underline(), + ansi_normal(), + ansi_highlight(), + ansi_normal()); + + return 0; +} + +static const char* const seed_action_table[_ACTION_MAX] = { + [ACTION_LOAD] = "load", + [ACTION_SAVE] = "save", +}; + +DEFINE_PRIVATE_STRING_TABLE_LOOKUP_FROM_STRING(seed_action, SeedAction); + +static int parse_argv(int argc, char *argv[]) { + enum { + ARG_VERSION = 0x100, + }; + + static const struct option options[] = { + { "help", no_argument, NULL, 'h' }, + { "version", no_argument, NULL, ARG_VERSION }, + }; + + int c; + + assert(argc >= 0); + assert(argv); + + while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0) + switch (c) { + case 'h': + return help(0, NULL, NULL); + case ARG_VERSION: + return version(); + case '?': + return -EINVAL; + + default: + assert_not_reached(); + } + + if (optind + 1 != argc) + return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "This program requires one argument."); + + arg_action = seed_action_from_string(argv[optind]); + if (arg_action < 0) + return log_error_errno(arg_action, "Unknown action '%s'", argv[optind]); + + return 1; } static int run(int argc, char *argv[]) { - bool read_seed_file, write_seed_file, synchronous, hashed_old_seed = false; + _cleanup_free_ struct sha256_ctx *hash_state = NULL; _cleanup_close_ int seed_fd = -1, random_fd = -1; - _cleanup_free_ void* buf = NULL; - struct sha256_ctx hash_state; - size_t buf_size; - struct stat st; - ssize_t k, l; + bool read_seed_file, write_seed_file, synchronous; + size_t seed_size; int r; log_setup(); - if (argc != 2) - return log_error_errno(SYNTHETIC_ERRNO(EINVAL), - "This program requires one argument."); + r = parse_argv(argc, argv); + if (r <= 0) + return r; umask(0022); - buf_size = random_pool_size(); - r = mkdir_parents(RANDOM_SEED, 0755); if (r < 0) return log_error_errno(r, "Failed to create directory " RANDOM_SEED_DIR ": %m"); - /* When we load the seed we read it and write it to the device and then immediately update the saved seed with - * new data, to make sure the next boot gets seeded differently. */ - - if (streq(argv[1], "load")) { + /* When we load the seed we read it and write it to the device and then immediately update the saved + * seed with new data, to make sure the next boot gets seeded differently. */ + switch (arg_action) { + case ACTION_LOAD: seed_fd = open(RANDOM_SEED, O_RDWR|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600); if (seed_fd < 0) { int open_rw_error = -errno; @@ -141,25 +411,25 @@ static int run(int argc, char *argv[]) { seed_fd = open(RANDOM_SEED, O_RDONLY|O_CLOEXEC|O_NOCTTY); if (seed_fd < 0) { bool missing = errno == ENOENT; + int level = missing ? LOG_DEBUG : LOG_ERR; - log_full_errno(missing ? LOG_DEBUG : LOG_ERR, - open_rw_error, "Failed to open " RANDOM_SEED " for writing: %m"); - r = log_full_errno(missing ? LOG_DEBUG : LOG_ERR, - errno, "Failed to open " RANDOM_SEED " for reading: %m"); - return missing ? 0 : r; + log_full_errno(level, open_rw_error, "Failed to open " RANDOM_SEED " for writing: %m"); + log_full_errno(level, errno, "Failed to open " RANDOM_SEED " for reading: %m"); + + return missing ? 0 : -errno; } } else write_seed_file = true; - random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY, 0600); + 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; - } else if (streq(argv[1], "save")) { - + case ACTION_SAVE: random_fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY); if (random_fd < 0) return log_error_errno(errno, "Failed to open /dev/urandom: %m"); @@ -171,156 +441,24 @@ static int run(int argc, char *argv[]) { read_seed_file = false; write_seed_file = true; synchronous = false; - } else - return log_error_errno(SYNTHETIC_ERRNO(EINVAL), - "Unknown verb '%s'.", argv[1]); + break; - if (fstat(seed_fd, &st) < 0) - return log_error_errno(errno, "Failed to stat() seed file " RANDOM_SEED ": %m"); - - /* If the seed file is larger than what we expect, then honour the existing size and save/restore as much as it says */ - if ((uint64_t) st.st_size > buf_size) - buf_size = MIN(st.st_size, RANDOM_POOL_SIZE_MAX); - - buf = malloc(buf_size); - if (!buf) - return log_oom(); - - if (read_seed_file) { - sd_id128_t mid; - - /* 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 = loop_write(random_fd, &mid, sizeof(mid), false); - if (r < 0) - log_debug_errno(r, "Failed to write machine ID to /dev/urandom, ignoring: %m"); - } - - k = loop_read(seed_fd, buf, buf_size, false); - if (k < 0) - log_error_errno(k, "Failed to read seed from " RANDOM_SEED ": %m"); - else if (k == 0) - log_debug("Seed file " RANDOM_SEED " not yet initialized, proceeding."); - else { - CreditEntropy lets_credit; - - /* If we're going to later write out a seed file, initialize a hash state with - * the contents of the seed file we just read, so that the new one can't regress - * in entropy. */ - if (write_seed_file) { - sha256_init_ctx(&hash_state); - sha256_process_bytes(&k, sizeof(k), &hash_state); /* Hash length to distinguish from new seed. */ - sha256_process_bytes(buf, k, &hash_state); - hashed_old_seed = true; - } - - (void) lseek(seed_fd, 0, SEEK_SET); - - lets_credit = may_credit(seed_fd); - - /* Before we credit or use the entropy, let's make sure to securely drop the - * creditable xattr from the file, so that we never credit the same random seed - * again. Note that further down we'll write a new seed again, and likely mark it as - * credible again, hence this is just paranoia to close the short time window between - * the time we upload the random seed into the kernel and download the new one from - * it. */ - - if (fremovexattr(seed_fd, "user.random-seed-creditable") < 0) { - if (!ERRNO_IS_XATTR_ABSENT(errno)) - log_warning_errno(errno, "Failed to remove extended attribute, ignoring: %m"); - - /* Otherwise, there was no creditable flag set, which is OK. */ - } else { - r = fsync_full(seed_fd); - if (r < 0) { - log_warning_errno(r, "Failed to synchronize seed to disk, not crediting entropy: %m"); - - if (lets_credit == CREDIT_ENTROPY_YES_PLEASE) - lets_credit = CREDIT_ENTROPY_NO_WAY; - } - } - - r = random_write_entropy(random_fd, buf, k, - IN_SET(lets_credit, CREDIT_ENTROPY_YES_PLEASE, CREDIT_ENTROPY_YES_FORCED)); - if (r < 0) - log_error_errno(r, "Failed to write seed to /dev/urandom: %m"); - } + default: + assert_not_reached(); } - if (write_seed_file) { - bool getrandom_worked = false; + r = random_seed_size(seed_fd, &seed_size); + if (r < 0) + return r; - /* 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. */ - r = fchmod_and_chown(seed_fd, 0600, 0, 0); - if (r < 0) - return log_error_errno(r, "Failed to adjust seed file ownership and access mode: %m"); + if (read_seed_file) + r = load_seed_file(seed_fd, random_fd, seed_size, + write_seed_file ? &hash_state : NULL); - /* Let's make this whole job asynchronous, i.e. let's make ourselves a barrier for - * proper initialization of the random pool. */ - k = getrandom(buf, buf_size, GRND_NONBLOCK); - if (k < 0 && errno == EAGAIN && synchronous) { - log_notice("Kernel entropy pool is not initialized yet, waiting until it is."); - k = getrandom(buf, buf_size, 0); /* retry synchronously */ - } - if (k < 0) - log_debug_errno(errno, "Failed to read random data with getrandom(), falling back to /dev/urandom: %m"); - else if ((size_t) k < buf_size) - log_debug("Short read from getrandom(), falling back to /dev/urandom."); - else - getrandom_worked = true; + if (r >= 0 && write_seed_file) + r = save_seed_file(seed_fd, random_fd, seed_size, synchronous, hash_state); - if (!getrandom_worked) { - /* Retry with classic /dev/urandom */ - k = loop_read(random_fd, buf, buf_size, false); - if (k < 0) - return log_error_errno(k, "Failed to read new seed from /dev/urandom: %m"); - if (k == 0) - return log_error_errno(SYNTHETIC_ERRNO(EIO), - "Got EOF while reading from /dev/urandom."); - } - - /* If we previously read in a seed file, then hash the new seed into the old one, - * and replace the last 32 bytes of the seed with the hash output, so that the - * new seed file can't regress in entropy. */ - if (hashed_old_seed) { - uint8_t hash[SHA256_DIGEST_SIZE]; - sha256_process_bytes(&k, sizeof(k), &hash_state); /* Hash length to distinguish from old seed. */ - sha256_process_bytes(buf, k, &hash_state); - sha256_finish_ctx(&hash_state, hash); - l = MIN((size_t)k, sizeof(hash)); - memcpy((uint8_t *)buf + k - l, hash, l); - } - - r = loop_write(seed_fd, buf, (size_t) k, false); - if (r < 0) - return log_error_errno(r, "Failed to write new random seed file: %m"); - - if (ftruncate(seed_fd, k) < 0) - return log_error_errno(r, "Failed to truncate random seed file: %m"); - - r = fsync_full(seed_fd); - if (r < 0) - return log_error_errno(r, "Failed to synchronize seed file: %m"); - - /* If we got this random seed data from getrandom() the data is suitable for crediting - * entropy later on. Let's keep that in mind by setting an extended attribute. on the file */ - if (getrandom_worked) - if (fsetxattr(seed_fd, "user.random-seed-creditable", "1", 1, 0) < 0) - log_full_errno(ERRNO_IS_NOT_SUPPORTED(errno) ? LOG_DEBUG : LOG_WARNING, errno, - "Failed to mark seed file as creditable, ignoring: %m"); - } - - return 0; + return r; } DEFINE_MAIN_FUNCTION(run);