/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2003 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by Marshall
 * Kirk McKusick and Network Associates Laboratories, the Security
 * Research Division of Network Associates, Inc. under DARPA/SPAWAR
 * contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA CHATS
 * research program.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The names of the authors may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/mount.h>
#include <sys/stat.h>

#include <ufs/ufs/extattr.h>
#include <ufs/ufs/quota.h>
#include <ufs/ufs/ufsmount.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <limits.h>
#include <mntopts.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

static void
usage(void)
{

        errx(EX_USAGE, "usage: mksnap_ffs snapshot_name");
}

static int
isdir(const char *path, struct stat *stbufp)
{

        if (stat(path, stbufp) < 0)
                return (-1);
        if (!S_ISDIR(stbufp->st_mode))
                return (0);
        return (1);
}

static int
issamefs(const char *path, struct statfs *stfsp)
{
        struct statfs stfsbuf;
        struct stat stbuf;

        if (isdir(path, &stbuf) != 1)
                return (-1);
        if (statfs(path, &stfsbuf) < 0)
                return (-1);
        if (fsidcmp(&stfsbuf.f_fsid, &stfsp->f_fsid) != 0)
                return (0);
        return (1);
}

int
main(int argc, char **argv)
{
        char errmsg[255], path[PATH_MAX];
        char *cp, *snapname;
        struct statfs stfsbuf;
        struct group *grp;
        struct stat stbuf;
        struct iovec *iov;
        int fd, iovlen;

        if (argc == 2)
                snapname = argv[1];
        else if (argc == 3)
                snapname = argv[2];     /* Old usage. */
        else
                usage();

        /*
         * Check that the user running this program has permission
         * to create and remove a snapshot file from the directory
         * in which they have requested to have it made. If the 
         * directory is sticky and not owned by the user, then they
         * will not be able to remove the snapshot when they are
         * done with it.
         */
        if (strlen(snapname) >= PATH_MAX)
                errx(1, "pathname too long %s", snapname);
        cp = strrchr(snapname, '/');
        if (cp == NULL) {
                strlcpy(path, ".", PATH_MAX);
        } else if (cp == snapname) {
                strlcpy(path, "/", PATH_MAX);
        } else {
                strlcpy(path, snapname, cp - snapname + 1);
        }
        if (statfs(path, &stfsbuf) < 0)
                err(1, "%s", path);
        switch (isdir(path, &stbuf)) {
        case -1:
                err(1, "%s", path);
        case 0:
                errx(1, "%s: Not a directory", path);
        default:
                break;
        }
        if (access(path, W_OK) < 0)
                err(1, "Lack write permission in %s", path);
        if ((stbuf.st_mode & S_ISTXT) && stbuf.st_uid != getuid())
                errx(1, "Lack write permission in %s: Sticky bit set", path);

        /*
         * Work around an issue when mksnap_ffs is started in chroot'ed
         * environment and f_mntonname contains absolute path within
         * real root.
         */
        for (cp = stfsbuf.f_mntonname; issamefs(cp, &stfsbuf) != 1;
            cp = strchrnul(cp + 1, '/')) {
                if (cp[0] == '\0')
                        errx(1, "%s: Not a mount point", stfsbuf.f_mntonname);
        }
        if (cp != stfsbuf.f_mntonname)
                memmove(stfsbuf.f_mntonname, cp, strlen(cp) + 1);

        /*
         * Having verified access to the directory in which the
         * snapshot is to be built, proceed with creating it.
         */
        if ((grp = getgrnam("operator")) == NULL)
                errx(1, "Cannot retrieve operator gid");

        iov = NULL;
        iovlen = 0;
        build_iovec(&iov, &iovlen, "fstype", "ffs", 4);
        build_iovec(&iov, &iovlen, "from", snapname, (size_t)-1);
        build_iovec(&iov, &iovlen, "fspath", stfsbuf.f_mntonname, (size_t)-1);
        build_iovec(&iov, &iovlen, "errmsg", errmsg, sizeof(errmsg));
        build_iovec(&iov, &iovlen, "update", NULL, 0);
        build_iovec(&iov, &iovlen, "snapshot", NULL, 0);

        *errmsg = '\0';
        if (nmount(iov, iovlen, stfsbuf.f_flags) < 0) {
                errmsg[sizeof(errmsg) - 1] = '\0';
                err(1, "Cannot create snapshot %s%s%s", snapname,
                    *errmsg != '\0' ? ": " : "", errmsg);
        }
        if ((fd = open(snapname, O_RDONLY)) < 0)
                err(1, "Cannot open %s", snapname);
        if (fstat(fd, &stbuf) != 0)
                err(1, "Cannot stat %s", snapname);
        if ((stbuf.st_flags & SF_SNAPSHOT) == 0)
                errx(1, "File %s is not a snapshot", snapname);
        if (fchown(fd, -1, grp->gr_gid) != 0)
                err(1, "Cannot chown %s", snapname);
        if (fchmod(fd, S_IRUSR | S_IRGRP) != 0)
                err(1, "Cannot chmod %s", snapname);

        exit(EXIT_SUCCESS);
}