/*

 * cryptsetup kernel RNG access functions

 *

 * Copyright (C) 2010-2020 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 <assert.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(struct crypt_device *ctx __attribute__((unused)),

			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 fail;

	/* 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 fail;

	if (crypt_fips_mode())

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

	random_initialised = 1;

	return 0;

fail:

	crypt_random_exit();

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

	return -ENOSYS;

}

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(ctx, buf, len);

		break;

	case CRYPT_RND_SALT:

		if (crypt_fips_mode())

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

		else

			status = _get_urandom(ctx, 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(ctx, 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();

}