fusermount.c

file system in user space ! It s very good!

    else if(line[0])
        fprintf(stderr, "%s: unknown parameter in %s at line %i: '%s'\n",
                progname, FUSE_CONF, linenum, line);
}

static void read_conf(void)
{
    FILE *fp = fopen(FUSE_CONF, "r");
    if (fp != NULL) {
        int linenum = 1;
        char line[256];
        int isnewline = 1;
        while (fgets(line, sizeof(line), fp) != NULL) {
            if (isnewline) {
                if (line[strlen(line)-1] == '\n') {
                    strip_line(line);
                    parse_line(line, linenum);
                } else {
                    fprintf(stderr, "%s: reading %s: line %i too long\n",
                            progname, FUSE_CONF, linenum);
                    isnewline = 0;
                }
            } else if(line[strlen(line)-1] == '\n')
                isnewline = 1;
            if (isnewline)
                linenum ++;
        }
        fclose(fp);
    } else if (errno != ENOENT) {
        fprintf(stderr, "%s: failed to open %s: %s\n", progname, FUSE_CONF,
                strerror(errno));
    }
}

static int begins_with(const char *s, const char *beg)
{
    if (strncmp(s, beg, strlen(beg)) == 0)
        return 1;
    else
        return 0;
}

struct mount_flags {
    const char *opt;
    unsigned long flag;
    int on;
    int safe;
};

static struct mount_flags mount_flags[] = {
    {"rw",      MS_RDONLY,      0, 1},
    {"ro",      MS_RDONLY,      1, 1},
    {"suid",    MS_NOSUID,      0, 0},
    {"nosuid",  MS_NOSUID,      1, 1},
    {"dev",     MS_NODEV,       0, 0},
    {"nodev",   MS_NODEV,       1, 1},
    {"exec",    MS_NOEXEC,      0, 1},
    {"noexec",  MS_NOEXEC,      1, 1},
    {"async",   MS_SYNCHRONOUS, 0, 1},
    {"sync",    MS_SYNCHRONOUS, 1, 1},
    {"atime",   MS_NOATIME,     0, 1},
    {"noatime", MS_NOATIME,     1, 1},
    {"dirsync", MS_DIRSYNC,     1, 1},
    {NULL,      0,              0, 0}
};

static int find_mount_flag(const char *s, unsigned len, int *on, int *flag)
{
    int i;

    for (i = 0; mount_flags[i].opt != NULL; i++) {
        const char *opt = mount_flags[i].opt;
        if (strlen(opt) == len && strncmp(opt, s, len) == 0) {
            *on = mount_flags[i].on;
            *flag = mount_flags[i].flag;
            if (!mount_flags[i].safe && getuid() != 0) {
                *flag = 0;
                fprintf(stderr, "%s: unsafe option %s ignored\n",
                        progname, opt);
            }
            return 1;
        }
    }
    return 0;
}

static int add_option(char **optsp, const char *opt, unsigned expand)
{
    char *newopts;
    if (*optsp == NULL)
        newopts = strdup(opt);
    else {
        unsigned oldsize = strlen(*optsp);
        unsigned newsize = oldsize + 1 + strlen(opt) + expand + 1;
        newopts = (char *) realloc(*optsp, newsize);
        if (newopts)
            sprintf(newopts + oldsize, ",%s", opt);
    }
    if (newopts == NULL) {
        fprintf(stderr, "%s: failed to allocate memory\n", progname);
        return -1;
    }
    *optsp = newopts;
    return 0;
}

static int get_mnt_opts(int flags, char *opts, char **mnt_optsp)
{
    int i;
    int l;

    if (!(flags & MS_RDONLY) && add_option(mnt_optsp, "rw", 0) == -1)
        return -1;

    for (i = 0; mount_flags[i].opt != NULL; i++) {
        if (mount_flags[i].on && (flags & mount_flags[i].flag) &&
            add_option(mnt_optsp, mount_flags[i].opt, 0) == -1)
            return -1;
    }

    if (add_option(mnt_optsp, opts, 0) == -1)
        return -1;
    /* remove comma from end of opts*/
    l = strlen(*mnt_optsp);
    if ((*mnt_optsp)[l-1] == ',')
        (*mnt_optsp)[l-1] = '\0';
    if (getuid() != 0) {
        const char *user = get_user_name();
        if (user == NULL)
            return -1;

        if (add_option(mnt_optsp, "user=", strlen(user)) == -1)
            return -1;
        strcat(*mnt_optsp, user);
    }
    return 0;
}

static int opt_eq(const char *s, unsigned len, const char *opt)
{
    if(strlen(opt) == len && strncmp(s, opt, len) == 0)
        return 1;
    else
        return 0;
}

static int check_mountpoint_empty(const char *mnt, mode_t rootmode,
                                  off_t rootsize)
{
    int isempty = 1;

    if (S_ISDIR(rootmode)) {
        struct dirent *ent;
        DIR *dp = opendir(mnt);
        if (dp == NULL) {
            fprintf(stderr, "%s: failed to open mountpoint for reading: %s\n",
                    progname, strerror(errno));
            return -1;
        }
        while ((ent = readdir(dp)) != NULL) {
            if (strcmp(ent->d_name, ".") != 0 &&
                strcmp(ent->d_name, "..") != 0) {
                isempty = 0;
                break;
            }
        }
        closedir(dp);
    } else if (rootsize)
        isempty = 0;

    if (!isempty) {
        fprintf(stderr, "%s: mountpoint is not empty\n", progname);
        fprintf(stderr, "%s: if you are sure this is safe, use the 'nonempty' mount option\n", progname);
        return -1;
    }
    return 0;
}

static int has_fuseblk(void)
{
    char buf[256];
    FILE *f = fopen("/proc/filesystems", "r");
    if (!f)
        return 1;

    while (fgets(buf, sizeof(buf), f))
        if (strstr(buf, "fuseblk\n")) {
            fclose(f);
            return 1;
        }

    fclose(f);
    return 0;
}

static int do_mount(const char *mnt, const char **type, mode_t rootmode,
                    int fd, const char *opts, const char *dev, char **fsnamep,
                    char **mnt_optsp, off_t rootsize)
{
    int res;
    int flags = MS_NOSUID | MS_NODEV;
    char *optbuf;
    char *mnt_opts = NULL;
    const char *s;
    char *d;
    char *fsname = NULL;
    int check_empty = 1;
    int blkdev = 0;

    optbuf = (char *) malloc(strlen(opts) + 128);
    if (!optbuf) {
        fprintf(stderr, "%s: failed to allocate memory\n", progname);
        return -1;
    }

    for (s = opts, d = optbuf; *s;) {
        unsigned len;
        const char *fsname_str = "fsname=";
        for (len = 0; s[len] && s[len] != ','; len++);
        if (begins_with(s, fsname_str)) {
            unsigned fsname_str_len = strlen(fsname_str);
            if (fsname)
                free(fsname);
            fsname = (char *) malloc(len - fsname_str_len + 1);
            if (!fsname) {
                fprintf(stderr, "%s: failed to allocate memory\n", progname);
                goto err;
            }
            memcpy(fsname, s + fsname_str_len, len - fsname_str_len);
            fsname[len - fsname_str_len] = '\0';
        } else if (opt_eq(s, len, "blkdev")) {
            if (getuid() != 0) {
                fprintf(stderr, "%s: option blkdev is privileged\n", progname);
                goto err;
            }
            blkdev = 1;
        } else if (opt_eq(s, len, "nonempty")) {
            check_empty = 0;
        } else if (!begins_with(s, "fd=") &&
                   !begins_with(s, "rootmode=") &&
                   !begins_with(s, "user_id=") &&
                   !begins_with(s, "group_id=")) {
            int on;
            int flag;
            int skip_option = 0;
            if (opt_eq(s, len, "large_read")) {
                struct utsname utsname;
                unsigned kmaj, kmin;
                res = uname(&utsname);
                if (res == 0 &&
                    sscanf(utsname.release, "%u.%u", &kmaj, &kmin) == 2 &&
                    (kmaj > 2 || (kmaj == 2 && kmin > 4))) {
                    fprintf(stderr, "%s: note: 'large_read' mount option is deprecated for %i.%i kernels\n", progname, kmaj, kmin);
                    skip_option = 1;
                }
            }
            if (getuid() != 0 && !user_allow_other &&
                (opt_eq(s, len, "allow_other") ||
                 opt_eq(s, len, "allow_root"))) {
                fprintf(stderr, "%s: option %.*s only allowed if 'user_allow_other' is set in /etc/fuse.conf\n", progname, len, s);
                goto err;
            }
            if (!skip_option) {
                if (find_mount_flag(s, len, &on, &flag)) {
                    if (on)
                        flags |= flag;
                    else
                        flags  &= ~flag;
                } else {
                    memcpy(d, s, len);
                    d += len;
                    *d++ = ',';
                }
            }
        }
        s += len;
        if (*s)
            s++;
    }
    *d = '\0';
    res = get_mnt_opts(flags, optbuf, &mnt_opts);
    if (res == -1)
        goto err;

    sprintf(d, "fd=%i,rootmode=%o,user_id=%i,group_id=%i",
            fd, rootmode, getuid(), getgid());
    if (fsname == NULL) {
        fsname = strdup(dev);
        if (!fsname) {
            fprintf(stderr, "%s: failed to allocate memory\n", progname);
            goto err;
        }
    }

    if (check_empty && check_mountpoint_empty(mnt, rootmode, rootsize) == -1)
        goto err;

    if (blkdev)
        *type = "fuseblk";
    res = mount(fsname, mnt, *type, flags, optbuf);
    if (res == -1 && errno == EINVAL) {
        /* It could be an old version not supporting group_id */
        sprintf(d, "fd=%i,rootmode=%o,user_id=%i", fd, rootmode, getuid());
        res = mount(fsname, mnt, *type, flags, optbuf);
    }
    if (res == -1) {
        int errno_save = errno;
        if (blkdev && errno == ENODEV && !has_fuseblk())
            fprintf(stderr, "%s: 'fuseblk' support missing; try the kernel module from fuse-2.6.0 or later\n", progname);
        else
            fprintf(stderr, "%s: mount failed: %s\n", progname, strerror(errno_save));
        goto err;
    } else {
        *fsnamep = fsname;
        *mnt_optsp = mnt_opts;
    }
    free(optbuf);

    return res;

 err:
    free(fsname);
    free(mnt_opts);
    free(optbuf);
    return -1;
}

static int check_version(const char *dev)
{
    int res;
    int majorver;
    int minorver;
    const char *version_file;
    FILE *vf;

    if (strcmp(dev, FUSE_DEV_OLD) != 0)
        return 0;

    version_file = FUSE_VERSION_FILE_OLD;
    vf = fopen(version_file, "r");
    if (vf == NULL) {
        fprintf(stderr, "%s: kernel interface too old\n", progname);
        return -1;
    }
    res = fscanf(vf, "%i.%i", &majorver, &minorver);
    fclose(vf);
    if (res != 2) {
        fprintf(stderr, "%s: error reading %s\n", progname, version_file);
        return -1;
    }
     if (majorver < 3) {
        fprintf(stderr, "%s: kernel interface too old\n", progname);
        return -1;
    }
    return 0;
}

static int check_perm(const char **mntp, struct stat *stbuf, int *currdir_fd,
                      int *mountpoint_fd)
{
    int res;
    const char *mnt = *mntp;
    const char *origmnt = mnt;

    res = lstat(mnt, stbuf);
    if (res == -1) {
        fprintf(stderr, "%s: failed to access mountpoint %s: %s\n",
                progname, mnt, strerror(errno));
        return -1;
    }

    /* No permission checking is done for root */
    if (getuid() == 0)
        return 0;

    if (S_ISDIR(stbuf->st_mode)) {
        *currdir_fd = open(".", O_RDONLY);
        if (*currdir_fd == -1) {
            fprintf(stderr, "%s: failed to open current directory: %s\n",
                    progname, strerror(errno));
            return -1;
        }
        res = chdir(mnt);
        if (res == -1) {
            fprintf(stderr, "%s: failed to chdir to mountpoint: %s\n",
                    progname, strerror(errno));
            return -1;
        }
        mnt = *mntp = ".";
        res = lstat(mnt, stbuf);
        if (res == -1) {
            fprintf(stderr, "%s: failed to access mountpoint %s: %s\n",
                    progname, origmnt, strerror(errno));
            return -1;
        }

        if ((stbuf->st_mode & S_ISVTX) && stbuf->st_uid != getuid()) {
            fprintf(stderr, "%s: mountpoint %s not owned by user\n",
                    progname, origmnt);