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/*
FUSE: Filesystem in Userspace
Copyright (C) 2001 Miklos Szeredi (mszeredi@inf.bme.hu)
This program can be distributed under the terms of the GNU GPL.
See the file COPYING.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <linux/fuse.h>
#include <sys/capability.h>
#define FUSE_DEV "/proc/fs/fuse/dev"
const char *progname;
static int do_mount(const char *dev, const char *mnt, const char *type,
mode_t rootmode, int fd)
{
int res;
struct fuse_mount_data data;
data.version = FUSE_KERNEL_VERSION;
data.fd = fd;
data.rootmode = rootmode;
res = mount(dev, mnt, type, MS_MGC_VAL | MS_NOSUID | MS_NODEV, &data);
if(res == -1) {
fprintf(stderr, "%s: mount failed: %s\n", progname, strerror(errno));
return -1;
}
return 0;
}
static int check_perm(const char *mnt, struct stat *stbuf)
{
int res;
res = lstat(mnt, stbuf);
if(res == -1) {
fprintf(stderr, "%s: failed to access mountpoint %s: %s\n",
progname, mnt, strerror(errno));
return -1;
}
if(!S_ISDIR(stbuf->st_mode) && !S_ISREG(stbuf->st_mode)) {
fprintf(stderr, "%s: mountpoint %s is a special file\n",
progname, mnt);
return -1;
}
if(getuid() != 0) {
if(stbuf->st_uid != getuid()) {
fprintf(stderr, "%s: mountpoint %s not owned by user\n",
progname, mnt);
return -1;
}
res = access(mnt, R_OK | W_OK | (S_ISDIR(stbuf->st_mode) ? X_OK : 0));
if(res == -1) {
fprintf(stderr, "%s: user has no full access to mountpoint %s\n",
progname, mnt);
return -1;
}
}
return 0;
}
static int mount_fuse(const char *mnt)
{
int res;
int fd;
const char *dev = FUSE_DEV;
const char *type = "fuse";
struct stat stbuf;
res = check_perm(mnt, &stbuf);
if(res == -1)
return -1;
fd = open(dev, O_RDWR);
if(fd == -1) {
fprintf(stderr, "%s: unable to open fuse device %s: %s\n", progname,
dev, strerror(errno));
return -1;
}
res = do_mount(dev, mnt, type, stbuf.st_mode & S_IFMT, fd);
if(res == -1)
return -1;
return fd;
}
static void usage()
{
fprintf(stderr,
"%s: [options] mountpoint program [args ...]\n"
"Options:\n"
" -h print help\n",
progname);
exit(1);
}
int main(int argc, char *argv[])
{
int a;
const char *mnt = NULL;
char **userprog;
pid_t pid;
int fd;
int status;
int res;
progname = argv[0];
for(a = 1; a < argc; a++) {
if(argv[a][0] != '-')
break;
switch(argv[a][1]) {
case 'h':
usage();
break;
default:
fprintf(stderr, "%s: Unknown option %s\n", progname, argv[a]);
exit(1);
}
}
if(a == argc) {
fprintf(stderr, "%s: Missing mountpoint argument\n", progname);
exit(1);
}
mnt = argv[a++];
if(a == argc) {
fprintf(stderr, "%s: Missing program argument\n", progname);
exit(1);
}
userprog = argv + a;
fd = mount_fuse(mnt);
if(fd == -1)
exit(1);
/* Dup the file descriptor to stdin */
if(fd != 0) {
dup2(fd, 0);
close(fd);
}
pid = fork();
if(pid == -1) {
fprintf(stderr, "%s: Unable to fork: %s\n", progname, strerror(errno));
umount(mnt);
exit(1);
}
if(pid == 0) {
/* Drop setuid/setgid permissions */
setuid(getuid());
setgid(getgid());
execv(userprog[0], userprog);
fprintf(stderr, "%s: failed to exec %s: %s\n", progname, userprog[0],
strerror(errno));
exit(1);
}
close(0);
res = waitpid(pid, &status, 0);
if(res == -1) {
fprintf(stderr, "%s: failed to wait for child: %s\n", progname,
strerror(errno));
exit(1);
}
res = umount(mnt);
if(res == -1) {
fprintf(stderr, "%s: failed to unmount %s: %s\n", progname, mnt,
strerror(errno));
exit(1);
}
return 0;
}
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