source/client/smbumount.c

   1 /*
   2  *  smbumount.c
   3  *
   4  *  Copyright (C) 1995-1998 by Volker Lendecke
   5  *
   6  */
   7
   8 #define SMBMOUNT_MALLOC 1
   9
  10 #include "includes.h"
  11
  12 #include <mntent.h>
  13
  14 #include <asm/types.h>
  15 #include <asm/posix_types.h>
  16 #include <linux/smb.h>
  17 #include <linux/smb_mount.h>
  18 #include <linux/smb_fs.h>
  19
  20 /* This is a (hopefully) temporary hack due to the fact that
  21         sizeof( uid_t ) != sizeof( __kernel_uid_t ) under glibc.
  22         This may change in the future and smb.h may get fixed in the
  23         future.  In the mean time, it's ugly hack time - get over it.
  24 */
  25 #undef SMB_IOC_GETMOUNTUID
  26 #define SMB_IOC_GETMOUNTUID             _IOR('u', 1, __kernel_uid_t)
  27
  28 #ifndef O_NOFOLLOW
  29 #define O_NOFOLLOW     0400000
  30 #endif
  31
  32 static void
  33 usage(void)
  34 {
  35         printf("usage: smbumount mountpoint\n");
  36 }
  37
  38 static int
  39 umount_ok(const char *mount_point)
  40 {
  41         /* we set O_NOFOLLOW to prevent users playing games with symlinks to
  42            umount filesystems they don't own */
  43         int fid = open(mount_point, O_RDONLY|O_NOFOLLOW, 0);
  44         __kernel_uid32_t mount_uid;
  45
  46         if (fid == -1) {
  47                 fprintf(stderr, "Could not open %s: %s\n",
  48                         mount_point, strerror(errno));
  49                 return -1;
  50         }
  51
  52         if (ioctl(fid, SMB_IOC_GETMOUNTUID32, &mount_uid) != 0) {
  53                 __kernel_uid_t mount_uid16;
  54                 if (ioctl(fid, SMB_IOC_GETMOUNTUID, &mount_uid16) != 0) {
  55                         fprintf(stderr, "%s probably not smb-filesystem\n",
  56                                 mount_point);
  57                         return -1;
  58                 }
  59                 mount_uid = mount_uid16;
  60         }
  61
  62         if ((getuid() != 0)
  63             && (mount_uid != getuid())) {
  64                 fprintf(stderr, "You are not allowed to umount %s\n",
  65                         mount_point);
  66                 return -1;
  67         }
  68
  69         close(fid);
  70         return 0;
  71 }
  72
  73 /* Make a canonical pathname from PATH.  Returns a freshly malloced string.
  74    It is up the *caller* to ensure that the PATH is sensible.  i.e.
  75    canonicalize ("/dev/fd0/.") returns "/dev/fd0" even though ``/dev/fd0/.''
  76    is not a legal pathname for ``/dev/fd0''  Anything we cannot parse
  77    we return unmodified.   */
  78 static char *
  79 canonicalize (char *path)
  80 {
  81         char *canonical = malloc (PATH_MAX + 1);
  82
  83         if (!canonical) {
  84                 fprintf(stderr, "Error! Not enough memory!\n");
  85                 return NULL;
  86         }
  87
  88         if (strlen(path) > PATH_MAX) {
  89                 fprintf(stderr, "Mount point string too long\n");
  90                 return NULL;
  91         }
  92
  93         if (path == NULL)
  94                 return NULL;
  95
  96         if (realpath (path, canonical))
  97                 return canonical;
  98
  99         strncpy (canonical, path, PATH_MAX);
 100         canonical[PATH_MAX] = '\0';
 101         return canonical;
 102 }
 103
 104
 105 int
 106 main(int argc, char *argv[])
 107 {
 108         int fd;
 109         char* mount_point;
 110         struct mntent *mnt;
 111         FILE* mtab;
 112         FILE* new_mtab;
 113
 114         if (argc != 2) {
 115                 usage();
 116                 exit(1);
 117         }
 118
 119         if (geteuid() != 0) {
 120                 fprintf(stderr, "smbumount must be installed suid root\n");
 121                 exit(1);
 122         }
 123
 124         mount_point = canonicalize(argv[1]);
 125
 126         if (mount_point == NULL)
 127         {
 128                 exit(1);
 129         }
 130
 131         if (umount_ok(mount_point) != 0) {
 132                 exit(1);
 133         }
 134
 135         if (umount(mount_point) != 0) {
 136                 fprintf(stderr, "Could not umount %s: %s\n",
 137                         mount_point, strerror(errno));
 138                 exit(1);
 139         }
 140
 141         if ((fd = open(MOUNTED"~", O_RDWR|O_CREAT|O_EXCL, 0600)) == -1)
 142         {
 143                 fprintf(stderr, "Can't get "MOUNTED"~ lock file");
 144                 return 1;
 145         }
 146         close(fd);
 147
 148         if ((mtab = setmntent(MOUNTED, "r")) == NULL) {
 149                 fprintf(stderr, "Can't open " MOUNTED ": %s\n",
 150                         strerror(errno));
 151                 return 1;
 152         }
 153
 154 #define MOUNTED_TMP MOUNTED".tmp"
 155
 156         if ((new_mtab = setmntent(MOUNTED_TMP, "w")) == NULL) {
 157                 fprintf(stderr, "Can't open " MOUNTED_TMP ": %s\n",
 158                         strerror(errno));
 159                 endmntent(mtab);
 160                 return 1;
 161         }
 162
 163         while ((mnt = getmntent(mtab)) != NULL) {
 164                 if (strcmp(mnt->mnt_dir, mount_point) != 0) {
 165                         addmntent(new_mtab, mnt);
 166                 }
 167         }
 168
 169         endmntent(mtab);
 170
 171         if (fchmod (fileno (new_mtab), S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH) < 0) {
 172                 fprintf(stderr, "Error changing mode of %s: %s\n",
 173                         MOUNTED_TMP, strerror(errno));
 174                 exit(1);
 175         }
 176
 177         endmntent(new_mtab);
 178
 179         if (rename(MOUNTED_TMP, MOUNTED) < 0) {
 180                 fprintf(stderr, "Cannot rename %s to %s: %s\n",
 181                         MOUNTED, MOUNTED_TMP, strerror(errno));
 182                 exit(1);
 183         }
 184
 185         if (unlink(MOUNTED"~") == -1)
 186         {
 187                 fprintf(stderr, "Can't remove "MOUNTED"~");
 188                 return 1;
 189         }
 190
 191         return 0;
 192 }