Missing access control check in shadow copy

Description

All versions of Samba from 3.2.0 to 4.3.2 inclusive are vulnerable to
a missing access control check in the vfs_shadow_copy2 module. When
looking for the shadow copy directory under the share path the current
accessing user should have DIRECTORY_LIST access rights in order to
view the current snapshots.

This was not being checked in the affected versions of Samba.

Patch Availability

Patches addressing this defect have been posted to

https://www.samba.org/samba/history/security.html

Additionally, Samba 4.3.3, 4.2.7 and 4.1.22 have been issued as
security releases to correct the defect.
Samba vendors and administrators running affected versions are
advised to upgrade or apply the patch as soon as possible.

Workarounds

None.

Credits

The problem was found by <[email protected]> who
also provided the fix for the code.