[Bug 1087915] [NEW] Can't combine -o permissions with -o uid=UUU, gid=GGG

[Dan Muresan]

Public bug reported:

At the moment, it seems that mount.ntfs-3g disables -o permissions if -o
uid=UUU and/or uid=GGG are also specified. This (combined with Ubuntu's
compilation options disallowing user mounts for NTFS-3g) prevents
unprivileged users from easily accessing NTFS systems while preserving
standard Unix permissions.

root# mount -o uid=500,gid=500,umask=000 /dev/sdb1 /vol/exthd/
root# touch /vol/exthd/x
root# ls -al /vol/exthd/x
-rwxrwxrwx 1 muresan muresan 0 Dec 8 00:29 /vol/exthd/x
root# chmod u-x /vol/exthd/x
root# ls -al /vol/exthd/x
-rwxrwxrwx 1 muresan muresan 0 Dec 8 00:29 /vol/exthd/x

So chmod is ignored and all permissions are fixed to rwx.

With "mount -o permissions", permissions ARE preserved, but all files
are owned by root:

root# mount -o permissions /dev/sdb1 /vol/exthd
Using default user mapping
root# touch /vol/exthd/x
root# ls -al /vol/exthd/x
-rw--w--w- 1 root root 0 Dec 8 00:29 /vol/exthd/x
root# chmod u+x /vol/exthd/x
root# ls -al /vol/exthd/x
-rwx-w--w- 1 root root 0 Dec 8 00:29 /vol/exthd/x
root# rm /vol/exthd/x

root# ls -al /bin/bash
-rwxr-xr-x 1 root root 920788 Apr 3 2012 /bin/bash
root# cp -a /bin/bash /vol/exthd/
root# ls -al /vol/exthd/bash
-rwxr-xr-x 1 root root 920788 Apr 3 2012 /vol/exthd/bash
root# umount /vol/exthd

Trying to mount the filesystem as an unprivileged user results in:

Either mount the volume as root, or rebuild NTFS-3G with integrated
FUSE support and make it setuid root. Please see more information at
http://tuxera.com/community/ntfs-3g-faq/#unprivileged

** Affects: ntfs-3g (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1087915

Title:
  Can't combine -o permissions with -o uid=UUU,gid=GGG

Status in “ntfs-3g” package in Ubuntu:
  New

Bug description:
  At the moment, it seems that mount.ntfs-3g disables -o permissions if
  -o uid=UUU and/or uid=GGG are also specified. This (combined with
  Ubuntu's compilation options disallowing user mounts for NTFS-3g)
  prevents unprivileged users from easily accessing NTFS systems while
  preserving standard Unix permissions.

  root# mount -o uid=500,gid=500,umask=000 /dev/sdb1 /vol/exthd/
  root# touch /vol/exthd/x
  root# ls -al /vol/exthd/x
  -rwxrwxrwx 1 muresan muresan 0 Dec 8 00:29 /vol/exthd/x
  root# chmod u-x /vol/exthd/x
  root# ls -al /vol/exthd/x
  -rwxrwxrwx 1 muresan muresan 0 Dec 8 00:29 /vol/exthd/x

  So chmod is ignored and all permissions are fixed to rwx.

  With "mount -o permissions", permissions ARE preserved, but all files
  are owned by root:

  root# mount -o permissions /dev/sdb1 /vol/exthd
  Using default user mapping
  root# touch /vol/exthd/x
  root# ls -al /vol/exthd/x
  -rw--w--w- 1 root root 0 Dec 8 00:29 /vol/exthd/x
  root# chmod u+x /vol/exthd/x
  root# ls -al /vol/exthd/x
  -rwx-w--w- 1 root root 0 Dec 8 00:29 /vol/exthd/x
  root# rm /vol/exthd/x

  root# ls -al /bin/bash
  -rwxr-xr-x 1 root root 920788 Apr 3 2012 /bin/bash
  root# cp -a /bin/bash /vol/exthd/
  root# ls -al /vol/exthd/bash
  -rwxr-xr-x 1 root root 920788 Apr 3 2012 /vol/exthd/bash
  root# umount /vol/exthd

  Trying to mount the filesystem as an unprivileged user results in:

  Either mount the volume as root, or rebuild NTFS-3G with integrated
  FUSE support and make it setuid root. Please see more information at
  http://tuxera.com/community/ntfs-3g-faq/#unprivileged

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