/*

 * cryptsetup kernel RNG access functions

 *

 * Copyright (C) 2010-2024 Red Hat, Inc. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 2

 * of the License, or (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 */

#include <stdlib.h>

#include <string.h>

#include <errno.h>

#include <sys/select.h>

#include "libcryptsetup.h"

#include "internal.h"

static int random_initialised = 0;

#define URANDOM_DEVICE  "/dev/urandom"

static int urandom_fd = -1;

#define RANDOM_DEVICE "/dev/random"

static int random_fd = -1;

/* Read random chunk - gathered data usually appears with this granularity */

#define RANDOM_DEVICE_CHUNK 8

/* Timeout to print warning if no random data (entropy) */

#define RANDOM_DEVICE_TIMEOUT 5

/* URANDOM_DEVICE access */

static int _get_urandom(char *buf, size_t len)

{

  int r;

  size_t old_len = len;

  char *old_buf = buf;

  assert(urandom_fd != -1);

  while (len) {

    r = read(urandom_fd, buf, len);

    if (r == -1 && errno != EINTR)

      return -EINVAL;

    if (r > 0) {

      len -= r;

      buf += r;

    }

  }

  assert(len == 0);

  assert((size_t)(buf - old_buf) == old_len);

  return 0;

}

static void _get_random_progress(struct crypt_device *ctx, int warn,

         size_t expected_len, size_t read_len)

{

  if (warn)

    log_std(ctx,

      _("System is out of entropy while generating volume key.\n"

        "Please move mouse or type some text in another window "

        "to gather some random events.\n"));

  log_std(ctx, _("Generating key (%d%% done).\n"),

    (int)((expected_len - read_len) * 100 / expected_len));

}

/* RANDOM_DEVICE access */

static int _get_random(struct crypt_device *ctx, char *buf, size_t len)

{

  int r, warn_once = 1;

  size_t n, old_len = len;

  char *old_buf = buf;

  fd_set fds;

  struct timeval tv;

  assert(random_fd != -1);

  while (len) {

    FD_ZERO(&fds);

    FD_SET(random_fd, &fds);

    tv.tv_sec = RANDOM_DEVICE_TIMEOUT;

    tv.tv_usec = 0;

    r = select(random_fd + 1, &fds, NULL, NULL, &tv);

    if(r == -1)

      return -EINVAL;

    if(!r) {

      _get_random_progress(ctx, warn_once, old_len, len);

      warn_once = 0;

      continue;

    }

    do {

      n = RANDOM_DEVICE_CHUNK;

      if (len < RANDOM_DEVICE_CHUNK)

        n = len;

      r = read(random_fd, buf, n);

      if (r == -1 && errno == EINTR) {

        r = 0;

        continue;

      }

      /* bogus read? */

      if(r > (int)n)

        return -EINVAL;

      /* random device is opened with O_NONBLOCK, EAGAIN is expected */

      if (r == -1 && (errno != EAGAIN && errno != EWOULDBLOCK))

        return -EINVAL;

      if (r > 0) {

        len -= r;

        buf += r;

      }

    } while (len && r > 0);

  }

  assert(len == 0);

  assert((size_t)(buf - old_buf) == old_len);

  if (!warn_once)

    _get_random_progress(ctx, 0, old_len, len);

  return 0;

}

/* Initialisation of both RNG file descriptors is mandatory */

int crypt_random_init(struct crypt_device *ctx)

{

  if (random_initialised)

    return 0;

  /* Used for CRYPT_RND_NORMAL */

  if(urandom_fd == -1)

    urandom_fd = open(URANDOM_DEVICE, O_RDONLY | O_CLOEXEC);

  if(urandom_fd == -1)

    goto err;

  /* Used for CRYPT_RND_KEY */

  if(random_fd == -1)

    random_fd = open(RANDOM_DEVICE, O_RDONLY | O_NONBLOCK | O_CLOEXEC);

  if(random_fd == -1)

    goto err;

  if (crypt_fips_mode())

    log_verbose(ctx, _("Running in FIPS mode."));

  random_initialised = 1;

  return 0;

err:

  crypt_random_exit();

  log_err(ctx, _("Fatal error during RNG initialisation."));

  return -ENOSYS;

}

/* coverity[ -taint_source : arg-1 ] */

int crypt_random_get(struct crypt_device *ctx, char *buf, size_t len, int quality)

{

  int status, rng_type;

  switch(quality) {

  case CRYPT_RND_NORMAL:

    status = _get_urandom(buf, len);

    break;

  case CRYPT_RND_SALT:

    if (crypt_fips_mode())

      status = crypt_backend_rng(buf, len, quality, 1);

    else

      status = _get_urandom(buf, len);

    break;

  case CRYPT_RND_KEY:

    if (crypt_fips_mode()) {

      status = crypt_backend_rng(buf, len, quality, 1);

      break;

    }

    rng_type = ctx ? crypt_get_rng_type(ctx) :

         crypt_random_default_key_rng();

    switch (rng_type) {

    case CRYPT_RNG_URANDOM:

      status = _get_urandom(buf, len);

      break;

    case CRYPT_RNG_RANDOM:

      status = _get_random(ctx, buf, len);

      break;

    default:

      abort();

    }

    break;

  default:

    log_err(ctx, _("Unknown RNG quality requested."));

    return -EINVAL;

  }

  if (status)

    log_err(ctx, _("Error reading from RNG."));

  return status;

}

void crypt_random_exit(void)

{

  random_initialised = 0;

  if(random_fd != -1) {

    (void)close(random_fd);

    random_fd = -1;

  }

  if(urandom_fd != -1) {

    (void)close(urandom_fd);

    urandom_fd = -1;

  }

}

int crypt_random_default_key_rng(void)

{

  /* coverity[pointless_string_compare] */

  if (!strcmp(DEFAULT_RNG, RANDOM_DEVICE))

    return CRYPT_RNG_RANDOM;

  /* coverity[pointless_string_compare] */

  if (!strcmp(DEFAULT_RNG, URANDOM_DEVICE))

    return CRYPT_RNG_URANDOM;

  /* RNG misconfiguration is fatal */

  abort();

}