/*

 * loopback block device utilities

 *

 * Copyright (C) 2009-2020 Red Hat, Inc. All rights reserved.

 * Copyright (C) 2009-2020 Milan Broz

 *

 * 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 <stdio.h>

#include <unistd.h>

#include <fcntl.h>

#include <errno.h>

#include <limits.h>

#include <sys/ioctl.h>

#include <sys/stat.h>

#include <sys/types.h>

#ifdef HAVE_SYS_SYSMACROS_H

# include <sys/sysmacros.h>     /* for major, minor */

#endif

#include <linux/loop.h>

#include "utils_loop.h"

#define LOOP_DEV_MAJOR 7

#ifndef LO_FLAGS_AUTOCLEAR

#define LO_FLAGS_AUTOCLEAR 4

#endif

#ifndef LOOP_CTL_GET_FREE

#define LOOP_CTL_GET_FREE 0x4C82

#endif

#ifndef LOOP_SET_CAPACITY

#define LOOP_SET_CAPACITY 0x4C07

#endif

static char *crypt_loop_get_device_old(void)

{

	char dev[20];

	int i, loop_fd;

	struct loop_info64 lo64 = {0};

	for (i = 0; i < 256; i++) {

		sprintf(dev, "/dev/loop%d", i);

		loop_fd = open(dev, O_RDONLY);

		if (loop_fd < 0)

			return NULL;

		if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) &&

		    errno == ENXIO) {

			close(loop_fd);

			return strdup(dev);

		}

		close(loop_fd);

	}

	return NULL;

}

static char *crypt_loop_get_device(void)

{

	char dev[64];

	int i, loop_fd;

	struct stat st;

	loop_fd = open("/dev/loop-control", O_RDONLY);

	if (loop_fd < 0)

		return crypt_loop_get_device_old();

	i = ioctl(loop_fd, LOOP_CTL_GET_FREE);

	if (i < 0) {

		close(loop_fd);

		return NULL;

	}

	close(loop_fd);

	if (sprintf(dev, "/dev/loop%d", i) < 0)

		return NULL;

	if (stat(dev, &st) || !S_ISBLK(st.st_mode))

		return NULL;

	return strdup(dev);

}

int crypt_loop_attach(char **loop, const char *file, int offset,

		      int autoclear, int *readonly)

{

	struct loop_info64 lo64 = {0};

	char *lo_file_name;

	int loop_fd = -1, file_fd = -1, r = 1;

	*loop = NULL;

	file_fd = open(file, (*readonly ? O_RDONLY : O_RDWR) | O_EXCL);

	if (file_fd < 0 && (errno == EROFS || errno == EACCES) && !*readonly) {

		*readonly = 1;

		file_fd = open(file, O_RDONLY | O_EXCL);

	}

	if (file_fd < 0)

		goto out;

	while (loop_fd < 0)  {

		*loop = crypt_loop_get_device();

		if (!*loop)

			goto out;

		loop_fd = open(*loop, *readonly ? O_RDONLY : O_RDWR);

		if (loop_fd < 0)

			goto out;

		if (ioctl(loop_fd, LOOP_SET_FD, file_fd) < 0) {

			if (errno != EBUSY)

				goto out;

			free(*loop);

			*loop = NULL;

			close(loop_fd);

			loop_fd = -1;

		}

	}

	lo_file_name = (char*)lo64.lo_file_name;

	lo_file_name[LO_NAME_SIZE-1] = '\0';

	strncpy(lo_file_name, file, LO_NAME_SIZE-1);

	lo64.lo_offset = offset;

	if (autoclear)

		lo64.lo_flags |= LO_FLAGS_AUTOCLEAR;

	if (ioctl(loop_fd, LOOP_SET_STATUS64, &lo64) < 0) {

		(void)ioctl(loop_fd, LOOP_CLR_FD, 0);

		goto out;

	}

	/* Verify that autoclear is really set */

	if (autoclear) {

		memset(&lo64, 0, sizeof(lo64));

		if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) < 0 ||

		   !(lo64.lo_flags & LO_FLAGS_AUTOCLEAR)) {

		(void)ioctl(loop_fd, LOOP_CLR_FD, 0);

			goto out;

		}

	}

	r = 0;

out:

	if (r && loop_fd >= 0)

		close(loop_fd);

	if (file_fd >= 0)

		close(file_fd);

	if (r && *loop) {

		free(*loop);

		*loop = NULL;

	}

	return r ? -1 : loop_fd;

}

int crypt_loop_detach(const char *loop)

{

	int loop_fd = -1, r = 1;

	loop_fd = open(loop, O_RDONLY);

	if (loop_fd < 0)

                return 1;

	if (!ioctl(loop_fd, LOOP_CLR_FD, 0))

		r = 0;

	close(loop_fd);

	return r;

}

int crypt_loop_resize(const char *loop)

{

	int loop_fd = -1, r = 1;

	loop_fd = open(loop, O_RDONLY);

	if (loop_fd < 0)

                return 1;

	if (!ioctl(loop_fd, LOOP_SET_CAPACITY, 0))

		r = 0;

	close(loop_fd);

	return r;

}

static char *_ioctl_backing_file(const char *loop)

{

	struct loop_info64 lo64 = {0};

	int loop_fd;

	loop_fd = open(loop, O_RDONLY);

	if (loop_fd < 0)

		return NULL;

	if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) < 0) {

		close(loop_fd);

		return NULL;

	}

	lo64.lo_file_name[LO_NAME_SIZE-2] = '*';

	lo64.lo_file_name[LO_NAME_SIZE-1] = 0;

	close(loop_fd);

	return strdup((char*)lo64.lo_file_name);

}

static char *_sysfs_backing_file(const char *loop)

{

	struct stat st;

	char buf[PATH_MAX];

	size_t len;

	int fd;

	if (stat(loop, &st) || !S_ISBLK(st.st_mode))

		return NULL;

	snprintf(buf, sizeof(buf), "/sys/dev/block/%d:%d/loop/backing_file",

		 major(st.st_rdev), minor(st.st_rdev));

	fd = open(buf, O_RDONLY);

	if (fd < 0)

		return NULL;

	len = read(fd, buf, PATH_MAX);

	close(fd);

	if (len < 2)

		return NULL;

	buf[len - 1] = '\0';

	return strdup(buf);

}

char *crypt_loop_backing_file(const char *loop)

{

	char *bf;

	if (!crypt_loop_device(loop))

		return NULL;

	bf = _sysfs_backing_file(loop);

	return bf ?: _ioctl_backing_file(loop);

}

int crypt_loop_device(const char *loop)

{

	struct stat st;

	if (!loop)

		return 0;

	if (stat(loop, &st) || !S_ISBLK(st.st_mode) ||

	    major(st.st_rdev) != LOOP_DEV_MAJOR)

		return 0;

	return 1;

}