/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005 Jean-Sebastien Pedron
 * Copyright (c) 2005 Csaba Henk 
 * All rights reserved.
 *
 * Copyright (c) 2019 The FreeBSD Foundation
 *
 * Portions of this software were developed by BFF Storage Systems under
 * sponsorship from the FreeBSD Foundation.
 *
 * 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.
 *
 * 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/uio.h>
#include <sys/stat.h>
#include <sys/sysctl.h>

#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <getopt.h>
#include <limits.h>
#include <mntopts.h>
#include <osreldate.h>
#include <paths.h>

#ifndef FUSE4BSD_VERSION
#define FUSE4BSD_VERSION        "0.3.9-pre1"
#endif

void    __usage_short(void);
void    usage(void);
void    helpmsg(void);
void    showversion(void);

static struct mntopt mopts[] = {
        #define ALTF_PRIVATE 0x01
        { "private",             0, ALTF_PRIVATE, 1 },
        { "neglect_shares",      0, 0x02, 1 },
        { "push_symlinks_in",    0, 0x04, 1 },
        { "allow_other",         0, 0x08, 1 },
        { "default_permissions", 0, 0x10, 1 },
        #define ALTF_MAXREAD 0x20
        { "max_read=",           0, ALTF_MAXREAD, 1 },
        #define ALTF_SUBTYPE 0x40
        { "subtype=",            0, ALTF_SUBTYPE, 1 },
        #define ALTF_FSNAME 0x80
        { "fsname=",             0, ALTF_FSNAME, 1 },
        /*
         * MOPT_AUTOMOUNTED, included by MOPT_STDOPTS, does not fit into
         * the 'flags' argument to nmount(2).  We have to abuse altflags
         * to pass it, as string, via iovec.
         */
        #define ALTF_AUTOMOUNTED 0x100
        { "automounted",        0, ALTF_AUTOMOUNTED, 1 },
        #define ALTF_INTR 0x200
        { "intr",               0, ALTF_INTR, 1 },
        #define ALTF_AUTOUNMOUNT 0x400
        { "auto_unmount",               0, ALTF_AUTOUNMOUNT, 1 },
        /* Linux specific options, we silently ignore them */
        { "fd=",                 0, 0x00, 1 },
        { "rootmode=",           0, 0x00, 1 },
        { "user_id=",            0, 0x00, 1 },
        { "group_id=",           0, 0x00, 1 },
        { "large_read",          0, 0x00, 1 },
        /* "nonempty", just the first two chars are stripped off during parsing */
        { "nempty",              0, 0x00, 1 },
        { "async",               0, MNT_ASYNC, 0},
        { "noasync",             1, MNT_ASYNC, 0},
        MOPT_STDOPTS,
        MOPT_END
};

struct mntval {
        int mv_flag;
        void *mv_value;
        int mv_len;
};

static struct mntval mvals[] = {
        { ALTF_MAXREAD, NULL, 0 },
        { ALTF_SUBTYPE, NULL, 0 },
        { ALTF_FSNAME, NULL, 0 },
        { 0, NULL, 0 }
};

#define DEFAULT_MOUNT_FLAGS ALTF_PRIVATE

int
main(int argc, char *argv[])
{
        struct iovec *iov;
        int mntflags, iovlen, verbose = 0;
        char *dev = NULL, *dir = NULL, mntpath[MAXPATHLEN];
        char *devo = NULL, *diro = NULL;
        char ndev[128], fdstr[15];
        int i, done = 0, reject_allow_other = 0, safe_level = 0;
        int altflags = DEFAULT_MOUNT_FLAGS;
        int __altflags = DEFAULT_MOUNT_FLAGS;
        int ch = 0;
        struct mntopt *mo;
        struct mntval *mv;
        static struct option longopts[] = {
                {"reject-allow_other", no_argument, NULL, 'A'},
                {"safe", no_argument, NULL, 'S'},
                {"daemon", required_argument, NULL, 'D'},
                {"daemon_opts", required_argument, NULL, 'O'},
                {"special", required_argument, NULL, 's'},
                {"mountpath", required_argument, NULL, 'm'},
                {"version", no_argument, NULL, 'V'},
                {"help", no_argument, NULL, 'h'},
                {0,0,0,0}
        };
        int pid = 0;
        int fd = -1, fdx;
        char *ep;
        char *daemon_str = NULL, *daemon_opts = NULL;

        /*
         * We want a parsing routine which is not sensitive to
         * the position of args/opts; it should extract the
         * first two args and stop at the beginning of the rest.
         * (This makes it easier to call mount_fusefs from external
         * utils than it is with a strict "util flags args" syntax.)
         */

        iov = NULL;
        iovlen = 0;
        mntflags = 0;
        /* All in all, I feel it more robust this way... */
        unsetenv("POSIXLY_CORRECT");
        if (getenv("MOUNT_FUSEFS_IGNORE_UNKNOWN"))
                getmnt_silent = 1;
        if (getenv("MOUNT_FUSEFS_VERBOSE"))
                verbose = 1;

        do {
                for (i = 0; i < 3; i++) {
                        if (optind < argc && argv[optind][0] != '-') {
                                if (dir) {
                                        done = 1;
                                        break;
                                }
                                if (dev)
                                        dir = argv[optind];
                                else
                                        dev = argv[optind];
                                optind++;
                        }
                }
                switch(ch) {
                case 'A':
                        reject_allow_other = 1;
                        break;
                case 'S':
                        safe_level = 1;
                        break;
                case 'D':
                        if (daemon_str)
                                errx(1, "daemon specified inconsistently");
                        daemon_str = optarg;
                        break;
                case 'O':
                        if (daemon_opts)
                                errx(1, "daemon opts specified inconsistently");
                        daemon_opts = optarg;
                        break;
                case 'o':
                        getmntopts(optarg, mopts, &mntflags, &altflags);
                        for (mv = mvals; mv->mv_flag; ++mv) {
                                if (! (altflags & mv->mv_flag))
                                        continue;
                                for (mo = mopts; mo->m_flag; ++mo) {
                                        char *p, *q;

                                        if (mo->m_flag != mv->mv_flag)
                                                continue;
                                        p = strstr(optarg, mo->m_option);
                                        if (p) {
                                                p += strlen(mo->m_option);
                                                q = p;
                                                while (*q != '\0' && *q != ',')
                                                        q++;
                                                mv->mv_len = q - p + 1;
                                                mv->mv_value = malloc(mv->mv_len);
                                                if (mv->mv_value == NULL)
                                                        err(1, "malloc");
                                                memcpy(mv->mv_value, p, mv->mv_len - 1);
                                                ((char *)mv->mv_value)[mv->mv_len - 1] = '\0';
                                                break;
                                        }
                                }
                        }
                        break;
                case 's':
                        if (devo)
                                errx(1, "special specified inconsistently");
                        devo = optarg;
                        break;
                case 'm':
                        if (diro)
                                errx(1, "mount path specified inconsistently");
                        diro = optarg;
                        break;
                case 'v': 
                        verbose = 1;
                        break;
                case 'h':
                        helpmsg();
                        break;
                case 'V':
                        showversion();
                        break;
                case '\0':
                        break;
                case '?':
                default:
                        usage();
                }
                if (done)
                        break;
        } while ((ch = getopt_long(argc, argv, "AvVho:SD:O:s:m:", longopts, NULL)) != -1);

        argc -= optind;
        argv += optind;

        if (devo) {
                if (dev)
                        errx(1, "special specified inconsistently");
                dev = devo;
        } else if (diro)
                errx(1, "if mountpoint is given via an option, special should also be given via an option"); 

        if (diro) {
                if (dir)
                        errx(1, "mount path specified inconsistently");
                dir = diro;
        }

        if ((! dev) && argc > 0) {
                dev = *argv++;
                argc--;
        }

        if ((! dir) && argc > 0) {
                dir = *argv++;
                argc--;
        }

        if (! (dev && dir))
                errx(1, "missing special and/or mountpoint");

        for (mo = mopts; mo->m_flag; ++mo) {
                if (altflags & mo->m_flag) {
                        int iov_done = 0;

                        if (reject_allow_other &&
                            strcmp(mo->m_option, "allow_other") == 0)
                                /*
                                 * reject_allow_other is stronger than a
                                 * negative of allow_other: if this is set,
                                 * allow_other is blocked, period.
                                 */
                                errx(1, "\"allow_other\" usage is banned by respective option");

                        for (mv = mvals; mv->mv_flag; ++mv) {
                                if (mo->m_flag != mv->mv_flag)
                                        continue;
                                if (mv->mv_value) {
                                        build_iovec(&iov, &iovlen, mo->m_option, mv->mv_value, mv->mv_len);
                                        iov_done = 1;
                                        break;
                                }
                        }
                        if (! iov_done)
                                build_iovec(&iov, &iovlen, mo->m_option,
                                    __DECONST(void *, ""), -1);
                }
                if (__altflags & mo->m_flag) {
                        char *uscore_opt;

                        if (asprintf(&uscore_opt, "__%s", mo->m_option) == -1)
                                err(1, "failed to allocate memory");
                        build_iovec(&iov, &iovlen, uscore_opt,
                            __DECONST(void *, ""), -1);
                        free(uscore_opt);
                }
        }

        if (getenv("MOUNT_FUSEFS_SAFE"))
                safe_level = 1;

        if (safe_level > 0 && (argc > 0 || daemon_str || daemon_opts))
                errx(1, "safe mode, spawning daemon not allowed");

        if ((argc > 0 && (daemon_str || daemon_opts)) ||
            (daemon_opts && ! daemon_str))
                errx(1, "daemon specified inconsistently");

        /*
         * Resolve the mountpoint with realpath(3) and remove unnecessary
         * slashes from the devicename if there are any.
         */
        if (checkpath(dir, mntpath) != 0)
                err(1, "%s", mntpath);
        (void)rmslashes(dev, dev);

        if (strcmp(dev, "auto") == 0)
                dev = __DECONST(char *, "/dev/fuse");

        if (strcmp(dev, "/dev/fuse") == 0) {
                if (! (argc > 0 || daemon_str)) {
                        fprintf(stderr, "Please also specify the fuse daemon to run when mounting via the multiplexer!\n");
                        usage();
                }
                if ((fd = open(dev, O_RDWR)) < 0)
                        err(1, "failed to open fuse device");
        } else {
                fdx = strtol(dev, &ep, 10);
                if (*ep == '\0')
                        fd = fdx;
        }

        /* Identifying device */
        if (fd >= 0) {
                struct stat sbuf;
                char *ndevbas, *lep;

                if (fstat(fd, &sbuf) == -1)
                        err(1, "cannot stat device file descriptor");

                strcpy(ndev, _PATH_DEV);
                ndevbas = ndev + strlen(_PATH_DEV);
                devname_r(sbuf.st_rdev, S_IFCHR, ndevbas,
                          sizeof(ndev) - strlen(_PATH_DEV));

                if (strncmp(ndevbas, "fuse", 4))
                        errx(1, "mounting inappropriate device");

                strtol(ndevbas + 4, &lep, 10);
                if (*lep != '\0')
                        errx(1, "mounting inappropriate device");

                dev = ndev;
        }

        if (argc > 0 || daemon_str) {
                char *fds;

                if (fd < 0 && (fd = open(dev, O_RDWR)) < 0)
                        err(1, "failed to open fuse device");
        
                if (asprintf(&fds, "%d", fd) == -1)
                        err(1, "failed to allocate memory");
                setenv("FUSE_DEV_FD", fds, 1);
                free(fds);
                setenv("FUSE_NO_MOUNT", "1", 1);

                if (daemon_str) {
                        char *bgdaemon;
                        int len;

                        if (! daemon_opts)
                                daemon_opts = __DECONST(char *, "");

                        len =  strlen(daemon_str) + 1 + strlen(daemon_opts) +
                            2 + 1;
                        bgdaemon = calloc(1, len);

                        if (! bgdaemon)
                                err(1, "failed to allocate memory");

                        strlcpy(bgdaemon, daemon_str, len);
                        strlcat(bgdaemon, " ", len);
                        strlcat(bgdaemon, daemon_opts, len);
                        strlcat(bgdaemon, " &", len);

                        if (system(bgdaemon))
                                err(1, "failed to call fuse daemon");
                } else {
                        if ((pid = fork()) < 0)
                                err(1, "failed to fork for fuse daemon");

                        if (pid == 0) {
                                execvp(argv[0], argv);
                                err(1, "failed to exec fuse daemon");
                        }
                }
        }

        /* Prepare the options vector for nmount(). build_iovec() is declared
         * in mntopts.h. */
        sprintf(fdstr, "%d", fd);
        build_iovec(&iov, &iovlen, "fstype", __DECONST(void *, "fusefs"), -1);
        build_iovec(&iov, &iovlen, "fspath", mntpath, -1);
        build_iovec(&iov, &iovlen, "from", dev, -1);
        build_iovec(&iov, &iovlen, "fd", fdstr, -1);

        if (verbose)
                fprintf(stderr, "mounting fuse daemon on device %s\n", dev);

        if (nmount(iov, iovlen, mntflags) < 0)
                err(EX_OSERR, "%s on %s", dev, mntpath);

        exit(0);
}

void
__usage_short(void) {
        fprintf(stderr,
            "usage:\n%s [-A|-S|-v|-V|-h|-D daemon|-O args|-s special|-m node|-o option...] special node [daemon args...]\n\n",
            getprogname());
}

void
usage(void)
{
        struct mntopt *mo;

        __usage_short();

        fprintf(stderr, "known options:\n");
        for (mo = mopts; mo->m_flag; ++mo)
                fprintf(stderr, "\t%s\n", mo->m_option);

        fprintf(stderr, "\n(use -h for a detailed description of these options)\n");
        exit(EX_USAGE);
}

void
helpmsg(void)
{
        if (! getenv("MOUNT_FUSEFS_CALL_BY_LIB")) {
                __usage_short();
                fprintf(stderr, "description of options:\n");
        }

        /*
         * The main use case of this function is giving info embedded in general
         * FUSE lib help output. Therefore the style and the content of the output
         * tries to fit there as much as possible.
         */
        fprintf(stderr,
                "    -o allow_other         allow access to other users\n"
                /* "    -o nonempty            allow mounts over non-empty file/dir\n" */
                "    -o default_permissions enable permission checking by kernel\n"
                "    -o intr                interruptible mount\n"
                "    -o fsname=NAME         set filesystem name\n"
                /*
                "    -o large_read          issue large read requests (2.4 only)\n"
                 */
                "    -o subtype=NAME        set filesystem type\n"
                "    -o max_read=N          set maximum size of read requests\n"
                "    -o noprivate           allow secondary mounting of the filesystem\n"
                "    -o neglect_shares      don't report EBUSY when unmount attempted\n"
                "                           in presence of secondary mounts\n" 
                "    -o push_symlinks_in    prefix absolute symlinks with mountpoint\n"
                );
        exit(EX_USAGE);
}

void
showversion(void)
{
        puts("mount_fusefs [fuse4bsd] version: " FUSE4BSD_VERSION);
        exit(EX_USAGE);
}