Re: [Buildroot] [PATCH] package/urandom-scripts: actually credit seed files via seedrng

[James Hilliard <james.hilliard1@gmail.com>]

On Sat, Mar 26, 2022 at 11:48 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> 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 buildroot
> and tweaked as needed: <https://git.zx2c4.com/seedrng/about/>.
>
> This commit imports it into buildroot and wires up the init scripts to
> call it. This also is a significant improvement over the current init
> script, which doesn't credit entropy and whose hashing in shell scripts
> is sort of fragile.
>
> As seedrng.c is a short tiny C program, we include this here in the
> package, like a few other packages do. Later we'll investigate adding
> this to busybox, but for now, this is a good start and a positive step
> in the right direction.
>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
>  package/urandom-scripts/Config.in          |   4 -
>  package/urandom-scripts/S20urandom         |  55 +--
>  package/urandom-scripts/seedrng.c          | 445 +++++++++++++++++++++
>  package/urandom-scripts/urandom-scripts.mk |  10 +
>  4 files changed, 464 insertions(+), 50 deletions(-)
>  create mode 100644 package/urandom-scripts/seedrng.c
>
> diff --git a/package/urandom-scripts/Config.in b/package/urandom-scripts/Config.in
> index 987e442e22..070ffa5e9a 100644
> --- a/package/urandom-scripts/Config.in
> +++ b/package/urandom-scripts/Config.in
> @@ -4,7 +4,3 @@ config BR2_PACKAGE_URANDOM_SCRIPTS
>         depends on !BR2_PACKAGE_SYSTEMD
>         help
>           Initscript to preserve the random seed between reboots.
> -
> -         WARNING: this is a poor fit to try and get high-quality
> -         entropy at boot. There are better ways, like haveged, or
> -         rng-tools.
> diff --git a/package/urandom-scripts/S20urandom b/package/urandom-scripts/S20urandom
> index c6b2ebd48f..f248089a0f 100644
> --- a/package/urandom-scripts/S20urandom
> +++ b/package/urandom-scripts/S20urandom
> @@ -6,63 +6,26 @@
>  # Quietly do nothing if /dev/urandom does not exist
>  [ -c /dev/urandom ] || exit 0
>
> -URANDOM_SEED="/var/lib/random-seed"
> +# Set this to true only if you do not want seed files to actually credit the
> +# RNG, for example if you plan to replicate this file system image and do not
> +# have the wherewithal to first delete the contents of /var/lib/seedrng.
> +#export SEEDRNG_SKIP_CREDIT=false
> +# You can also place this line into /etc/default/urandom.
>
>  # shellcheck source=/dev/null
>  [ -r "/etc/default/urandom" ] && . "/etc/default/urandom"
>
> -if pool_bits=$(cat /proc/sys/kernel/random/poolsize 2> /dev/null); then
> -       pool_size=$((pool_bits/8))
> -else
> -       pool_size=512
> -fi
> -
> -init_rng() {
> -       printf 'Initializing random number generator: '
> -       dd if="$URANDOM_SEED" bs="$pool_size" of=/dev/urandom count=1 2> /dev/null
> -       status=$?
> -       if [ "$status" -eq 0 ]; then
> -               echo "OK"
> -       else
> -               echo "FAIL"
> -       fi
> -       return "$status"
> -}
> -
> -save_random_seed() {
> -       printf 'Saving random seed: '
> -       status=1
> -       if touch "$URANDOM_SEED.new" 2> /dev/null; then
> -               old_umask=$(umask)
> -               umask 077
> -               dd if=/dev/urandom of="$URANDOM_SEED.tmp" bs="$pool_size" count=1 2> /dev/null
> -               cat "$URANDOM_SEED" "$URANDOM_SEED.tmp" 2>/dev/null \
> -                       | sha256sum \
> -                       | cut -d ' ' -f 1 > "$URANDOM_SEED.new" && \
> -               mv "$URANDOM_SEED.new" "$URANDOM_SEED" && status=0
> -               rm -f "$URANDOM_SEED.tmp"
> -               umask "$old_umask"
> -               if [ "$status" -eq 0 ]; then
> -                       echo "OK"
> -               else
> -                       echo "FAIL"
> -               fi
> -
> -       else
> -               echo "SKIP (read-only file system detected)"
> -       fi
> -       return "$status"
> -}
> -
>  case "$1" in
>         start|restart|reload)
>                 # Carry a random seed from start-up to start-up
>                 # Load and then save the whole entropy pool
> -               init_rng && save_random_seed;;
> +               # Never fail, as this isn't worth making a fuss
> +               # over if it doesn't go as planned.
> +               seedrng || true;;
>         stop)
>                 # Carry a random seed from shut-down to start-up
>                 # Save the whole entropy pool
> -               save_random_seed;;
> +               seedrng;;
>         *)
>                 echo "Usage: $0 {start|stop|restart|reload}"
>                 exit 1
> diff --git a/package/urandom-scripts/seedrng.c b/package/urandom-scripts/seedrng.c
> new file mode 100644
> index 0000000000..a77365d406
> --- /dev/null
> +++ b/package/urandom-scripts/seedrng.c
> @@ -0,0 +1,445 @@
> +// SPDX-License-Identifier: (GPL-2.0 OR MIT OR Apache-2.0)
> +/*
> + * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
> + *
> + * This is based on code from <https://git.zx2c4.com/seedrng/about/>.
> + */
> +
> +#define _GNU_SOURCE
> +#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 <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>
> +
> +#ifndef GRND_INSECURE
> +#define GRND_INSECURE 0x0004 /* Apparently some headers don't ship with this yet. */
> +#endif
> +
> +#ifndef LOCALSTATEDIR
> +#define LOCALSTATEDIR "/var/lib"
> +#endif
> +#ifndef RUNSTATEDIR
> +#define RUNSTATEDIR "/var/run"
> +#endif

Might be a good idea to have runtime env overrides for these to allow easier
path customization by only having to override the init script in a
rootfs overlay:
https://buildroot.org/downloads/manual/manual.html#rootfs-custom

Maybe something similar to the SEEDRNG_SKIP_CREDIT env override would
make sense for these paths.

> +
> +#define SEED_DIR LOCALSTATEDIR "/seedrng"
> +#define CREDITABLE_SEED SEED_DIR "/seed.credit"
> +#define NON_CREDITABLE_SEED SEED_DIR "/seed.no-credit"
> +#define LOCK_FILE RUNSTATEDIR "/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, 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));
> +               return 1;
> +       }
> +
> +       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:
> +       close(fd);
> +       close(lock);
> +       return program_ret;
> +}
> diff --git a/package/urandom-scripts/urandom-scripts.mk b/package/urandom-scripts/urandom-scripts.mk
> index 2c09728c46..a5cbb95feb 100644
> --- a/package/urandom-scripts/urandom-scripts.mk
> +++ b/package/urandom-scripts/urandom-scripts.mk
> @@ -4,7 +4,17 @@
>  #
>  ################################################################################
>
> +define URANDOM_SCRIPTS_EXTRACT_CMDS
> +       cp $(URANDOM_SCRIPTS_PKGDIR)/seedrng.c $(@D)
> +endef
> +
> +define URANDOM_SCRIPTS_BUILD_CMDS
> +       $(TARGET_CC) $(TARGET_CFLAGS) -std=gnu99 $(TARGET_LDFLAGS) \
> +               $(@D)/seedrng.c -o $(@D)/seedrng
> +endef
> +
>  define URANDOM_SCRIPTS_INSTALL_INIT_SYSV
> +       $(INSTALL) -D -m 0755 $(@D)/seedrng $(TARGET_DIR)/sbin/seedrng
>         $(INSTALL) -D -m 0755 $(URANDOM_SCRIPTS_PKGDIR)/S20urandom \
>                 $(TARGET_DIR)/etc/init.d/S20urandom
>  endef
> --
> 2.35.1
>
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