diff options
Diffstat (limited to 'src/seedrng/seedrng.c')
| -rw-r--r-- | src/seedrng/seedrng.c | 522 |
1 files changed, 522 insertions, 0 deletions
diff --git a/src/seedrng/seedrng.c b/src/seedrng/seedrng.c new file mode 100644 index 00000000..95fb947d --- /dev/null +++ b/src/seedrng/seedrng.c @@ -0,0 +1,522 @@ +/* + * seedrng.c + * Seed kernel RNG from seed file, based on code from: + * https://git.zx2c4.com/seedrng/about/ + */ + +/* + * Copyright (c) 2022 The OpenRC Authors. + * See the Authors file at the top-level directory of this distribution and + * https://github.com/OpenRC/openrc/blob/HEAD/AUTHORS + * + * This file is part of OpenRC. It is subject to the license terms in + * the LICENSE file found in the top-level directory of this + * distribution and at https://github.com/OpenRC/openrc/blob/HEAD/LICENSE + * This file may not be copied, modified, propagated, or distributed + * except according to the terms contained in the LICENSE file. + */ + +#include <linux/random.h> +#include <sys/random.h> +#include <sys/ioctl.h> +#include <sys/file.h> +#include <sys/stat.h> +#include <sys/types.h> +#include <fcntl.h> +#include <getopt.h> +#include <poll.h> +#include <unistd.h> +#include <time.h> +#include <errno.h> +#include <endian.h> +#include <stdbool.h> +#include <stdint.h> +#include <string.h> +#include <stdio.h> +#include <stdlib.h> + +#include "rc.h" +#include "einfo.h" +#include "helpers.h" +#include "_usage.h" + +#ifndef GRND_INSECURE +#define GRND_INSECURE 0x0004 /* Apparently some headers don't ship with this yet. */ +#endif + +/* Use long option value that is out of range for 8 bit getopt values. + * The exact enum value is internal and can freely change, so we keep the + * options sorted. + */ +enum long_opts { + /* This has to come first so following values stay in the 0x100+ range. */ + LONGOPT_BASE = 0x100, + LONGOPT_LOCK_FILE, + LONGOPT_SEED_DIR, + LONGOPT_SKIP_CREDIT, +}; + +const char *applet = NULL; +const char *extraopts =NULL; +const char getoptstring[] = getoptstring_COMMON; +const struct option longopts[] = { + { "lock-file", 1, NULL, LONGOPT_LOCK_FILE }, + { "seed-dir", 1, NULL, LONGOPT_SEED_DIR }, + { "skip-credit", 0, NULL, LONGOPT_SKIP_CREDIT }, + longopts_COMMON +}; +const char * const longopts_help[] = { + "lock file", + "directory for seed files", + "skip credit", + longopts_help_COMMON +}; +const char *usagestring = NULL; + +static char *lock_file = NULL; +static char *seed_dir = NULL; +static char *creditable_seed = NULL; +static char *non_creditable_seed = NULL; + +enum blake2s_lengths { + BLAKE2S_BLOCK_LEN = 64, + BLAKE2S_HASH_LEN = 32, + BLAKE2S_KEY_LEN = 32 +}; + +enum seedrng_lengths { + MAX_SEED_LEN = 512, + MIN_SEED_LEN = BLAKE2S_HASH_LEN +}; + +struct blake2s_state { + uint32_t h[8]; + uint32_t t[2]; + uint32_t f[2]; + uint8_t buf[BLAKE2S_BLOCK_LEN]; + unsigned int buflen; + unsigned int outlen; +}; + +#define le32_to_cpup(a) le32toh(*(a)) +#define cpu_to_le32(a) htole32(a) +#ifndef ARRAY_SIZE +#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) +#endif +#ifndef DIV_ROUND_UP +#define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d)) +#endif + +static inline void cpu_to_le32_array(uint32_t *buf, unsigned int words) +{ + while (words--) { + *buf = cpu_to_le32(*buf); + ++buf; + } +} + +static inline void le32_to_cpu_array(uint32_t *buf, unsigned int words) +{ + while (words--) { + *buf = le32_to_cpup(buf); + ++buf; + } +} + +static inline uint32_t ror32(uint32_t word, unsigned int shift) +{ + return (word >> (shift & 31)) | (word << ((-shift) & 31)); +} + +static const uint32_t blake2s_iv[8] = { + 0x6A09E667UL, 0xBB67AE85UL, 0x3C6EF372UL, 0xA54FF53AUL, + 0x510E527FUL, 0x9B05688CUL, 0x1F83D9ABUL, 0x5BE0CD19UL +}; + +static const uint8_t blake2s_sigma[10][16] = { + { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 }, + { 14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3 }, + { 11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4 }, + { 7, 9, 3, 1, 13, 12, 11, 14, 2, 6, 5, 10, 4, 0, 15, 8 }, + { 9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13 }, + { 2, 12, 6, 10, 0, 11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9 }, + { 12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11 }, + { 13, 11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10 }, + { 6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4, 10, 5 }, + { 10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0 }, +}; + +static void blake2s_set_lastblock(struct blake2s_state *state) +{ + state->f[0] = -1; +} + +static void blake2s_increment_counter(struct blake2s_state *state, const uint32_t inc) +{ + state->t[0] += inc; + state->t[1] += (state->t[0] < inc); +} + +static void blake2s_init_param(struct blake2s_state *state, const uint32_t param) +{ + int i; + + memset(state, 0, sizeof(*state)); + for (i = 0; i < 8; ++i) + state->h[i] = blake2s_iv[i]; + state->h[0] ^= param; +} + +static void blake2s_init(struct blake2s_state *state, const size_t outlen) +{ + blake2s_init_param(state, 0x01010000 | outlen); + state->outlen = outlen; +} + +static void blake2s_compress(struct blake2s_state *state, const uint8_t *block, size_t nblocks, const uint32_t inc) +{ + uint32_t m[16]; + uint32_t v[16]; + int i; + + while (nblocks > 0) { + blake2s_increment_counter(state, inc); + memcpy(m, block, BLAKE2S_BLOCK_LEN); + le32_to_cpu_array(m, ARRAY_SIZE(m)); + memcpy(v, state->h, 32); + v[ 8] = blake2s_iv[0]; + v[ 9] = blake2s_iv[1]; + v[10] = blake2s_iv[2]; + v[11] = blake2s_iv[3]; + v[12] = blake2s_iv[4] ^ state->t[0]; + v[13] = blake2s_iv[5] ^ state->t[1]; + v[14] = blake2s_iv[6] ^ state->f[0]; + v[15] = blake2s_iv[7] ^ state->f[1]; + +#define G(r, i, a, b, c, d) do { \ + a += b + m[blake2s_sigma[r][2 * i + 0]]; \ + d = ror32(d ^ a, 16); \ + c += d; \ + b = ror32(b ^ c, 12); \ + a += b + m[blake2s_sigma[r][2 * i + 1]]; \ + d = ror32(d ^ a, 8); \ + c += d; \ + b = ror32(b ^ c, 7); \ +} while (0) + +#define ROUND(r) do { \ + G(r, 0, v[0], v[ 4], v[ 8], v[12]); \ + G(r, 1, v[1], v[ 5], v[ 9], v[13]); \ + G(r, 2, v[2], v[ 6], v[10], v[14]); \ + G(r, 3, v[3], v[ 7], v[11], v[15]); \ + G(r, 4, v[0], v[ 5], v[10], v[15]); \ + G(r, 5, v[1], v[ 6], v[11], v[12]); \ + G(r, 6, v[2], v[ 7], v[ 8], v[13]); \ + G(r, 7, v[3], v[ 4], v[ 9], v[14]); \ +} while (0) + ROUND(0); + ROUND(1); + ROUND(2); + ROUND(3); + ROUND(4); + ROUND(5); + ROUND(6); + ROUND(7); + ROUND(8); + ROUND(9); + +#undef G +#undef ROUND + + for (i = 0; i < 8; ++i) + state->h[i] ^= v[i] ^ v[i + 8]; + + block += BLAKE2S_BLOCK_LEN; + --nblocks; + } +} + +static void blake2s_update(struct blake2s_state *state, const void *inp, size_t inlen) +{ + const size_t fill = BLAKE2S_BLOCK_LEN - state->buflen; + const uint8_t *in = inp; + + if (!inlen) + return; + if (inlen > fill) { + memcpy(state->buf + state->buflen, in, fill); + blake2s_compress(state, state->buf, 1, BLAKE2S_BLOCK_LEN); + state->buflen = 0; + in += fill; + inlen -= fill; + } + if (inlen > BLAKE2S_BLOCK_LEN) { + const size_t nblocks = DIV_ROUND_UP(inlen, BLAKE2S_BLOCK_LEN); + blake2s_compress(state, in, nblocks - 1, BLAKE2S_BLOCK_LEN); + in += BLAKE2S_BLOCK_LEN * (nblocks - 1); + inlen -= BLAKE2S_BLOCK_LEN * (nblocks - 1); + } + memcpy(state->buf + state->buflen, in, inlen); + state->buflen += inlen; +} + +static void blake2s_final(struct blake2s_state *state, uint8_t *out) +{ + blake2s_set_lastblock(state); + memset(state->buf + state->buflen, 0, BLAKE2S_BLOCK_LEN - state->buflen); + blake2s_compress(state, state->buf, 1, state->buflen); + cpu_to_le32_array(state->h, ARRAY_SIZE(state->h)); + memcpy(out, state->h, state->outlen); +} + +static size_t determine_optimal_seed_len(void) +{ + size_t ret = 0; + char poolsize_str[11] = { 0 }; + int fd = open("/proc/sys/kernel/random/poolsize", O_RDONLY); + + if (fd < 0 || read(fd, poolsize_str, sizeof(poolsize_str) - 1) < 0) { + ewarn("%s: Unable to determine pool size, falling back to %u bits: %s", + applet, MIN_SEED_LEN * 8, strerror(errno)); + ret = MIN_SEED_LEN; + } else + ret = DIV_ROUND_UP(strtoul(poolsize_str, NULL, 10), 8); + if (fd >= 0) + close(fd); + if (ret < MIN_SEED_LEN) + ret = MIN_SEED_LEN; + else if (ret > MAX_SEED_LEN) + ret = MAX_SEED_LEN; + return ret; +} + +static int read_new_seed(uint8_t *seed, size_t len, bool *is_creditable) +{ + ssize_t ret; + int urandom_fd; + + *is_creditable = false; + ret = getrandom(seed, len, GRND_NONBLOCK); + if (ret == (ssize_t)len) { + *is_creditable = true; + return 0; + } + if (ret == -1 && errno == ENOSYS) { + struct pollfd random_fd = { + .fd = open("/dev/random", O_RDONLY), + .events = POLLIN + }; + if (random_fd.fd < 0) + return -errno; + *is_creditable = poll(&random_fd, 1, 0) == 1; + close(random_fd.fd); + } else if (getrandom(seed, len, GRND_INSECURE) == (ssize_t)len) + return 0; + urandom_fd = open("/dev/urandom", O_RDONLY); + if (urandom_fd < 0) + return -errno; + ret = read(urandom_fd, seed, len); + if (ret == (ssize_t)len) + ret = 0; + else + ret = -errno ? -errno : -EIO; + close(urandom_fd); + return ret; +} + +static int seed_rng(uint8_t *seed, size_t len, bool credit) +{ + struct { + int entropy_count; + int buf_size; + uint8_t buffer[MAX_SEED_LEN]; + } req = { + .entropy_count = credit ? len * 8 : 0, + .buf_size = len + }; + int random_fd, ret; + + if (len > sizeof(req.buffer)) + return -EFBIG; + memcpy(req.buffer, seed, len); + + random_fd = open("/dev/random", O_RDWR); + if (random_fd < 0) + return -errno; + ret = ioctl(random_fd, RNDADDENTROPY, &req); + if (ret) + ret = -errno ? -errno : -EIO; + close(random_fd); + return ret; +} + +static int seed_from_file_if_exists(const char *filename, bool credit, struct blake2s_state *hash) +{ + uint8_t seed[MAX_SEED_LEN]; + ssize_t seed_len; + int fd, dfd, ret = 0; + + fd = open(filename, O_RDONLY); + if (fd < 0 && errno == ENOENT) + return 0; + else if (fd < 0) { + ret = -errno; + eerror("%s: Unable to open seed file: %s", applet, strerror(errno)); + return ret; + } + dfd = open(seed_dir, O_DIRECTORY | O_RDONLY); + if (dfd < 0) { + ret = -errno; + close(fd); + eerror("%s: Unable to open seed directory: %s", applet, strerror(errno)); + return ret; + } + seed_len = read(fd, seed, sizeof(seed)); + if (seed_len < 0) { + ret = -errno; + eerror("%s: Unable to read seed file: %s", applet, strerror(errno)); + } + close(fd); + if (ret) { + close(dfd); + return ret; + } + if ((unlink(filename) < 0 || fsync(dfd) < 0) && seed_len) { + ret = -errno; + eerror("%s: Unable to remove seed after reading, so not seeding: %s", + applet, strerror(errno)); + } + close(dfd); + if (ret) + return ret; + if (!seed_len) + return 0; + + blake2s_update(hash, &seed_len, sizeof(seed_len)); + blake2s_update(hash, seed, seed_len); + + einfo("Seeding %zd bits %s crediting", seed_len * 8, credit ? "and" : "without"); + ret = seed_rng(seed, seed_len, credit); + if (ret < 0) + eerror("%s: Unable to seed: %s", applet, strerror(-ret)); + return ret; +} + +static void populate_global_paths(void) +{ + if (!lock_file) + lock_file = xstrdup("/var/run/seedrng.lock"); + if (!seed_dir) + seed_dir = xstrdup("/var/lib/seedrng"); + xasprintf(&creditable_seed, "%s/seed.credit", seed_dir); + xasprintf(&non_creditable_seed, "%s/seed.no-credit", seed_dir); +} + +static void cleanup(void) +{ + free(lock_file); + free(seed_dir); + free(creditable_seed); + free(non_creditable_seed); +} + +int main(int argc, char **argv) +{ + int opt; + static const char seedrng_prefix[] = "SeedRNG v1 Old+New Prefix"; + static const char seedrng_failure[] = "SeedRNG v1 No New Seed Failure"; + int ret, fd = -1, lock, program_ret = 0; + uint8_t new_seed[MAX_SEED_LEN]; + size_t new_seed_len; + bool new_seed_creditable; + struct timespec realtime = { 0 }, boottime = { 0 }; + struct blake2s_state hash; + bool skip_credit = false; + + atexit(cleanup); + applet = basename_c(argv[0]); + if (geteuid()) + eerrorx("%s: superuser access is required", applet); + umask(0077); + + while ((opt = getopt_long(argc, argv, getoptstring, + longopts, (int *) 0)) != -1) + { + switch (opt) { + case LONGOPT_LOCK_FILE: + if (!lock_file) + lock_file = xstrdup(optarg); + break; + case LONGOPT_SEED_DIR: + if (!seed_dir) + seed_dir = xstrdup(optarg); + break; + case LONGOPT_SKIP_CREDIT: + skip_credit = true; + break; + case_RC_COMMON_GETOPT + } + } + populate_global_paths(); + blake2s_init(&hash, BLAKE2S_HASH_LEN); + blake2s_update(&hash, seedrng_prefix, strlen(seedrng_prefix)); + clock_gettime(CLOCK_REALTIME, &realtime); + clock_gettime(CLOCK_BOOTTIME, &boottime); + blake2s_update(&hash, &realtime, sizeof(realtime)); + blake2s_update(&hash, &boottime, sizeof(boottime)); + + if (mkdir(seed_dir, 0700) < 0 && errno != EEXIST) + eerrorx("%s: Unable to create \"%s\" directory: %s", + applet, seed_dir, strerror(errno)); + + lock = open(lock_file, O_WRONLY | O_CREAT, 0000); + if (lock < 0 || flock(lock, LOCK_EX) < 0) { + eerror("%s: Unable to open lock file: %s", applet, strerror(errno)); + program_ret = 1; + goto out; + } + + ret = seed_from_file_if_exists(non_creditable_seed, false, &hash); + if (ret < 0) + program_ret |= 1 << 1; + ret = seed_from_file_if_exists(creditable_seed, !skip_credit, &hash); + if (ret < 0) + program_ret |= 1 << 2; + + new_seed_len = determine_optimal_seed_len(); + ret = read_new_seed(new_seed, new_seed_len, &new_seed_creditable); + if (ret < 0) { + eerror("%s: Unable to read new seed: %s", applet, strerror(-ret)); + new_seed_len = BLAKE2S_HASH_LEN; + strncpy((char *)new_seed, seedrng_failure, new_seed_len); + program_ret |= 1 << 3; + } + blake2s_update(&hash, &new_seed_len, sizeof(new_seed_len)); + blake2s_update(&hash, new_seed, new_seed_len); + blake2s_final(&hash, new_seed + new_seed_len - BLAKE2S_HASH_LEN); + + einfo("Saving %zu bits of %s seed for next boot", new_seed_len * 8, new_seed_creditable ? "creditable" : "non-creditable"); + fd = open(non_creditable_seed, O_WRONLY | O_CREAT | O_TRUNC, 0400); + if (fd < 0) { + eerror("%s: Unable to open seed file for writing: %s", + applet, strerror(errno)); + program_ret |= 1 << 4; + goto out; + } + if (write(fd, new_seed, new_seed_len) != (ssize_t)new_seed_len || fsync(fd) < 0) { + eerror("%s: Unable to write seed file: %s", applet, strerror(errno)); + program_ret |= 1 << 5; + goto out; + } + if (new_seed_creditable && rename(non_creditable_seed, creditable_seed) < 0) { + ewarn("%s: Unable to make new seed creditable: %s", + applet, strerror(errno)); + program_ret |= 1 << 6; + } +out: + if (fd >= 0) + close(fd); + if (lock >= 0) + close(lock); + return program_ret; +} |