fusermount.c

FUSE文件系统开发工具,将内核层面的文件系统开发过程平移到应用层面上来。

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <[e-mail]>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
*/
/* This program does the mounting and unmounting of FUSE filesystems */

#include <config.h>

#include "mount_util.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <getopt.h>
#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <mntent.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <sys/fsuid.h>
#include <sys/socket.h>
#include <sys/utsname.h>

#define FUSE_COMMFD_ENV		"_FUSE_COMMFD"

#define FUSE_DEV_OLD "/proc/fs/fuse/dev"
#define FUSE_DEV_NEW "/dev/fuse"
#define FUSE_VERSION_FILE_OLD "/proc/fs/fuse/version"
#define FUSE_CONF "/etc/fuse.conf"

#ifndef MS_DIRSYNC
#define MS_DIRSYNC 128
#endif

static const char *progname;

static int user_allow_other = 0;
static int mount_max = 1000;

static const char *get_user_name(void)
{
	struct passwd *pw = getpwuid(getuid());
	if (pw != NULL && pw->pw_name != NULL)
		return pw->pw_name;
	else {
		fprintf(stderr, "%s: could not determine username\n", progname);
		return NULL;
	}
}

static uid_t oldfsuid;
static gid_t oldfsgid;

static void drop_privs(void)
{
	if (getuid() != 0) {
		oldfsuid = setfsuid(getuid());
		oldfsgid = setfsgid(getgid());
	}
}

static void restore_privs(void)
{
	if (getuid() != 0) {
		setfsuid(oldfsuid);
		setfsgid(oldfsgid);
	}
}

#ifndef IGNORE_MTAB
static int add_mount(const char *source, const char *mnt, const char *type,
		     const char *opts)
{
	return fuse_mnt_add_mount(progname, source, mnt, type, opts);
}

static int unmount_fuse(const char *mnt, int quiet, int lazy)
{
	if (getuid() != 0) {
		struct mntent *entp;
		FILE *fp;
		const char *user = NULL;
		char uidstr[32];
		unsigned uidlen = 0;
		int found;
		const char *mtab = _PATH_MOUNTED;

		user = get_user_name();
		if (user == NULL)
			return -1;

		fp = setmntent(mtab, "r");
		if (fp == NULL) {
			fprintf(stderr,
				"%s: failed to open %s: %s\n", progname, mtab,
				strerror(errno));
			return -1;
		}

		uidlen = sprintf(uidstr, "%u", getuid());

		found = 0;
		while ((entp = getmntent(fp)) != NULL) {
			if (!found && strcmp(entp->mnt_dir, mnt) == 0 &&
			    (strcmp(entp->mnt_type, "fuse") == 0 ||
			     strcmp(entp->mnt_type, "fuseblk") == 0 ||
			     strncmp(entp->mnt_type, "fuse.", 5) == 0 ||
			     strncmp(entp->mnt_type, "fuseblk.", 8) == 0)) {
				char *p = strstr(entp->mnt_opts, "user=");
				if (p &&
				    (p == entp->mnt_opts || *(p-1) == ',') &&
				    strcmp(p + 5, user) == 0) {
					found = 1;
					break;
				}
				/* /etc/mtab is a link pointing to
				   /proc/mounts: */
				else if ((p =
					  strstr(entp->mnt_opts, "user_id=")) &&
					 (p == entp->mnt_opts ||
					  *(p-1) == ',') &&
					 strncmp(p + 8, uidstr, uidlen) == 0 &&
					 (*(p+8+uidlen) == ',' ||
					  *(p+8+uidlen) == '\0')) {
					found = 1;
					break;
				}
			}
		}
		endmntent(fp);

		if (!found) {
			if (!quiet)
				fprintf(stderr,
					"%s: entry for %s not found in %s\n",
					progname, mnt, mtab);
			return -1;
		}
	}

	return fuse_mnt_umount(progname, mnt, lazy);
}

static int count_fuse_fs(void)
{
	struct mntent *entp;
	int count = 0;
	const char *mtab = _PATH_MOUNTED;
	FILE *fp = setmntent(mtab, "r");
	if (fp == NULL) {
		fprintf(stderr, "%s: failed to open %s: %s\n", progname, mtab,
			strerror(errno));
		return -1;
	}
	while ((entp = getmntent(fp)) != NULL) {
		if (strcmp(entp->mnt_type, "fuse") == 0 ||
		    strncmp(entp->mnt_type, "fuse.", 5) == 0)
			count ++;
	}
	endmntent(fp);
	return count;
}


#else /* IGNORE_MTAB */
static int count_fuse_fs()
{
	return 0;
}

static int add_mount(const char *source, const char *mnt, const char *type,
		     const char *opts)
{
	(void) source;
	(void) mnt;
	(void) type;
	(void) opts;
	return 0;
}

static int unmount_fuse(const char *mnt, int quiet, int lazy)
{
	return fuse_mnt_umount(progname, mnt, lazy);
}
#endif /* IGNORE_MTAB */

static void strip_line(char *line)
{
	char *s = strchr(line, '#');
	if (s != NULL)
		s[0] = '\0';
	for (s = line + strlen(line) - 1;
	     s >= line && isspace((unsigned char) *s); s--);
	s[1] = '\0';
	for (s = line; isspace((unsigned char) *s); s++);
	if (s != line)
		memmove(line, s, strlen(s)+1);
}

static void parse_line(char *line, int linenum)
{
	int tmp;
	if (strcmp(line, "user_allow_other") == 0)
		user_allow_other = 1;
	else if (sscanf(line, "mount_max = %i", &tmp) == 1)
		mount_max = tmp;
	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 get_string_opt(const char *s, unsigned len, const char *opt,
			  char **val)
{
	unsigned opt_len = strlen(opt);

	if (*val)
		free(*val);
	*val = (char *) malloc(len - opt_len + 1);
	if (!*val) {
		fprintf(stderr, "%s: failed to allocate memory\n", progname);
		return 0;
	}

	memcpy(*val, s + opt_len, len - opt_len);
	(*val)[len - opt_len] = '\0';
	return 1;
}

static int do_mount(const char *mnt, char **typep, mode_t rootmode,
		    int fd, const char *opts, const char *dev, char **sourcep,
		    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;
	char *subtype = NULL;
	char *source = NULL;
	char *type = 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=";
		const char *subtype_str = "subtype=";
		for (len = 0; s[len] && s[len] != ','; len++);
		if (begins_with(s, fsname_str)) {
			if (!get_string_opt(s, len, fsname_str, &fsname))
				goto err;
		} else if (begins_with(s, subtype_str)) {
			if (!get_string_opt(s, len, subtype_str, &subtype))
				goto err;
		} 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 (check_empty &&
	    fuse_mnt_check_empty(progname, mnt, rootmode, rootsize) == -1)
		goto err;

	source = malloc((fsname ? strlen(fsname) : 0) +
			(subtype ? strlen(subtype) : 0) + strlen(dev) + 32);