source/client/smbumount.c

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