From 2edc017a6e0cb92b72b768aaa46c6d336ad84eff Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Mon, 28 Mar 2022 00:25:56 -0400 Subject: [PATCH] urandom-seed: use seedrng for seeding the random number generator MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The RNG can't actually be seeded from a shell script, due to the reliance on ioctls. For this reason, the seedrng project provides a basic script meant to be copy and pasted into projects like OpenWRT and tweaked as needed: . This commit imports it into the urandom-seed package and wires up the init scripts to call it. This also is a significant improvement over the current init script, which does not robustly handle cleaning up of seeds and syncing to prevent reuse. Additionally, the existing script creates a new seed immediately after writing an old one, which means that the amount of entropy might actually regress, due to failing to credit the old seed. Closes: https://github.com/openwrt/openwrt/issues/9570 Signed-off-by: Jason A. Donenfeld Signed-off-by: Petr Å tetiar [fixed missing INSTALL_DIR] --- package/system/urandom-seed/Makefile | 5 +- .../files/etc/init.d/urandom_seed | 2 +- .../files/lib/preinit/81_urandom_seed | 16 +- .../urandom-seed/files/sbin/urandom_seed | 20 - package/system/urandom-seed/seedrng.c | 434 ++++++++++++++++++ 5 files changed, 442 insertions(+), 35 deletions(-) delete mode 100755 package/system/urandom-seed/files/sbin/urandom_seed create mode 100644 package/system/urandom-seed/seedrng.c diff --git a/package/system/urandom-seed/Makefile b/package/system/urandom-seed/Makefile index 7c5524a9db89..0c8d77f445ee 100644 --- a/package/system/urandom-seed/Makefile +++ b/package/system/urandom-seed/Makefile @@ -9,7 +9,6 @@ include $(INCLUDE_DIR)/package.mk define Package/urandom-seed SECTION:=base CATEGORY:=Base system - DEPENDS:=+getrandom TITLE:=/etc/urandom.seed handling for OpenWrt URL:=https://openwrt.org/ endef @@ -19,11 +18,15 @@ define Build/Prepare endef define Build/Compile/Default + $(TARGET_CC) $(TARGET_CFLAGS) $(TARGET_CPPFLAGS) $(TARGET_LDFLAGS) \ + -std=gnu99 -o $(PKG_BUILD_DIR)/seedrng seedrng.c endef Build/Compile = $(Build/Compile/Default) define Package/urandom-seed/install $(CP) ./files/* $(1)/ + $(INSTALL_DIR) $(1)/sbin + $(CP) $(PKG_BUILD_DIR)/seedrng $(1)/sbin/ endef $(eval $(call BuildPackage,urandom-seed)) diff --git a/package/system/urandom-seed/files/etc/init.d/urandom_seed b/package/system/urandom-seed/files/etc/init.d/urandom_seed index 17d9c1340078..d6e81c6079fb 100755 --- a/package/system/urandom-seed/files/etc/init.d/urandom_seed +++ b/package/system/urandom-seed/files/etc/init.d/urandom_seed @@ -5,7 +5,7 @@ USE_PROCD=1 start_service() { procd_open_instance "urandom_seed" - procd_set_param command "/sbin/urandom_seed" + procd_set_param command "/sbin/seedrng" procd_set_param stdout 1 procd_set_param stderr 1 procd_close_instance diff --git a/package/system/urandom-seed/files/lib/preinit/81_urandom_seed b/package/system/urandom-seed/files/lib/preinit/81_urandom_seed index 2adc6c47f050..b3014daeafb1 100644 --- a/package/system/urandom-seed/files/lib/preinit/81_urandom_seed +++ b/package/system/urandom-seed/files/lib/preinit/81_urandom_seed @@ -2,21 +2,11 @@ log_urandom_seed() { echo "urandom-seed: $1" > /dev/kmsg } -_do_urandom_seed() { - [ -f "$1" ] || { log_urandom_seed "Seed file not found ($1)"; return; } - [ -O "$1" -a -G "$1" -a ! -x "$1" ] || { log_urandom_seed "Wrong owner / permissions for $1"; return; } - - log_urandom_seed "Seeding with $1" - cat "$1" > /dev/urandom -} - do_urandom_seed() { [ -c /dev/urandom ] || { log_urandom_seed "Something is wrong with /dev/urandom"; return; } - - _do_urandom_seed "/etc/urandom.seed" - - SEED="$(uci -q get system.@system[0].urandom_seed)" - [ "${SEED:0:1}" = "/" -a "$SEED" != "/etc/urandom.seed" ] && _do_urandom_seed "$SEED" + seedrng 2>&1 | while read -r line; do + log_urandom_seed "$line" + done } boot_hook_add preinit_main do_urandom_seed diff --git a/package/system/urandom-seed/files/sbin/urandom_seed b/package/system/urandom-seed/files/sbin/urandom_seed deleted file mode 100755 index 7043e8af4e6a..000000000000 --- a/package/system/urandom-seed/files/sbin/urandom_seed +++ /dev/null @@ -1,20 +0,0 @@ -#!/bin/sh -set -e - -trap '[ "$?" -eq 0 ] || echo "An error occured" >&2' EXIT - -save() { - touch "$1.tmp" - chown root:root "$1.tmp" - chmod 600 "$1.tmp" - getrandom 512 > "$1.tmp" - mv "$1.tmp" "$1" - echo "Seed saved ($1)" -} - -SEED="$(uci -q get system.@system[0].urandom_seed || true)" -[ "${SEED:0:1}" = "/" ] && save "$SEED" - -SEED=/etc/urandom.seed -[ ! -f $SEED ] && save "$SEED" -true diff --git a/package/system/urandom-seed/seedrng.c b/package/system/urandom-seed/seedrng.c new file mode 100644 index 000000000000..9a2cb10f55af --- /dev/null +++ b/package/system/urandom-seed/seedrng.c @@ -0,0 +1,434 @@ +// SPDX-License-Identifier: (GPL-2.0 OR MIT OR Apache-2.0) +/* + * Copyright (C) 2022 Jason A. Donenfeld . All Rights Reserved. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define SEED_DIR "/etc/seedrng" +#define CREDITABLE_SEED SEED_DIR "/seed.credit" +#define NON_CREDITABLE_SEED SEED_DIR "/seed.no-credit" +#define LOCK_FILE "/tmp/run/seedrng.lock" + +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) { + fprintf(stderr, "WARNING: Unable to determine pool size, falling back to %u bits: %s\n", 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; + } else if (ret < 0 && 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; + fprintf(stderr, "ERROR: Unable to open seed file: %s\n", strerror(errno)); + return ret; + } + dfd = open(SEED_DIR, O_DIRECTORY | O_RDONLY); + if (dfd < 0) { + ret = -errno; + close(fd); + fprintf(stderr, "ERROR: Unable to open seed directory: %s\n", strerror(errno)); + return ret; + } + seed_len = read(fd, seed, sizeof(seed)); + if (seed_len < 0) { + ret = -errno; + fprintf(stderr, "ERROR: Unable to read seed file: %s\n", strerror(errno)); + } + close(fd); + if (ret) { + close(dfd); + return ret; + } + if ((unlink(filename) < 0 || fsync(dfd) < 0) && seed_len) { + ret = -errno; + fprintf(stderr, "ERROR: Unable to remove seed after reading, so not seeding: %s\n", 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); + + fprintf(stdout, "Seeding %zd bits %s crediting\n", seed_len * 8, credit ? "and" : "without"); + ret = seed_rng(seed, seed_len, credit); + if (ret < 0) + fprintf(stderr, "ERROR: Unable to seed: %s\n", strerror(-ret)); + return ret; +} + +static bool skip_credit(void) +{ + const char *skip = getenv("SEEDRNG_SKIP_CREDIT"); + return skip && (!strcmp(skip, "1") || !strcasecmp(skip, "true") || + !strcasecmp(skip, "yes") || !strcasecmp(skip, "y")); +} + +int main(int argc __attribute__((unused)), char *argv[] __attribute__((unused))) +{ + 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; + + umask(0077); + if (getuid()) { + fprintf(stderr, "ERROR: This program requires root\n"); + return 1; + } + + 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) { + fprintf(stderr, "ERROR: Unable to create \"%s\" directory: %s\n", SEED_DIR, strerror(errno)); + return 1; + } + + lock = open(LOCK_FILE, O_WRONLY | O_CREAT, 0000); + if (lock < 0 || flock(lock, LOCK_EX) < 0) { + fprintf(stderr, "ERROR: Unable to open lock file: %s\n", 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) { + fprintf(stderr, "ERROR: Unable to read new seed: %s\n", 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); + + fprintf(stdout, "Saving %zu bits of %s seed for next boot\n", 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) { + fprintf(stderr, "ERROR: Unable to open seed file for writing: %s\n", strerror(errno)); + program_ret |= 1 << 4; + goto out; + } + if (write(fd, new_seed, new_seed_len) != (ssize_t)new_seed_len || fsync(fd) < 0) { + fprintf(stderr, "ERROR: Unable to write seed file: %s\n", strerror(errno)); + program_ret |= 1 << 5; + goto out; + } + if (new_seed_creditable && rename(NON_CREDITABLE_SEED, CREDITABLE_SEED) < 0) { + fprintf(stderr, "WARNING: Unable to make new seed creditable: %s\n", strerror(errno)); + program_ret |= 1 << 6; + } +out: + if (fd >= 0) + close(fd); + if (lock >= 0) + close(lock); + return program_ret; +} -- 2.30.2