File permissions are incorrect during file copy

[Till Ulen]

Binary package hint: nautilus

From http://bugzilla.gnome.org/show_bug.cgi?id=458397
reported by Roberto Zunino:

When copying files, files are created with the default umask permissions
instead of using the permissions of the file being copied. Permissions are then
"fixed" after the copy has been completed. This however leaves a window of
vulnerability.

Real world example: I just copyed my old home (perms=700) to a new disk. This
took quite a long time, during which my home had permissions 775.

Steps to reproduce:
1. Create a folder and put some large files inside
2. chmod 700 folder
3. Nautilus-copy it somewhere else

Actual results:
while copying, ls -d folder_copy shows 775 perms, and other users can go in and
read inside the folders

Expected results:
folder_copy should be created with 700 perms

Does this happen every time?
yes

Other information:
The Right Thing would be to pass the correct permissions to open()/mkdir() etc.

Failing that, a good enough easier fix would be to set umask to 700&old_umask
for the copying stuff.

-----[ End of bug report by Roberto Zunino ]-------------------------------------------

I can reproduce this bug now with nautilus version 1:2.20.0-0ubuntu7.1 under Ubuntu 7.10 (Gutsy). I tried to copy a single regular file with the permissions set to 600, so the problem is not limited to copying directories.

I'm marking this as a security vulnerability because under appropriate circumstances it can allow local users to read other's files effectively bypassing the permissions set by the owner. It is true that many users won't be affected by this but that's not a valid reason to ignore the problem.

[Sebastien Bacher (seb128)]

Confirmed on hardy

[Rashkae (rashkae)]

This behaviour also has a non-security annoyance.. on systems that use ACL, when a file is copied to a location where it should (and does) get default permissions, Nautilus then removes the needed MASK bits, rendering those default ineffective.

[Valentin Crone (va-crone)]

The cp command use umask permission by default, it seem logic that nautilus do the same thing. cp don't preserve chmod and chown by default.
This fake bug can be resolved by adding a new feature that purpose to preserve permissions, or by choosing new permissions on a Window before copy.
Example by adding a "Advanced paste" option in the menu, under the normal "Paste" option.

Advanced paste can be a Window that purpose to preserve or not permissions, or/and define new permission for files and for folders copied.
I think it's the best way to solve this problem...