samba - Aug 2010 - Project: writing a vfs module to preverse permissions with MS Office

Hello list,


Short introduction: I'm Pierre, on my non-free time I work for Red Hat
in Farnborough, UK. I'm not really using Samba extensively myself, but
how could one not love a source tree containing torture.c and weird.c?

About that, if anyone can explain what the latter is for, I'd be very
interested... "Add the weird charset in 3_0 and build it by default
for ./configure --enable-developer" in the git repodidn't hit me.

Problem
-------

I'd like to write a workaround for "MS Word with Samba Changes Owner of
File"
http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/AccessControls.html#id2615334

A university is using relatively complex POSIX ACLs and the currently
provided workaround wouldn't be enough.

Approach
--------
A VFS module seems like the best way to go:
1) If a file is renamed to a MS Office temporary file, we store its
permissions incl. POSIX ACLs
2) If a MS Office temporary file is renamed, we restore the
permissions of the corresponding file in 1) if any

Given both the renames were made by the same user, I assume no
security checks are necessary.

Obviously this means I should match the filenames for both MS Office
documents and temporary files.
A good reason to avoid such this procedure when MS Office is not
involved is for example to avoid losing the SUID bit on binaries, even
though it's far-fetched.

Why this E-mail
---------------
I found http://support.microsoft.com/kb/211632 which doesn't cover
matching patterns but give examples.
However I just reproduced the problem with Microsoft Office 2010
installation on Windows XP (cf logs extracts after my signature) and:
- I got filenames without the "~wrd"-like part they always show
- It also applies to non-Microsoft file formats, making the list too long

At the current stage I therefore intend:
- To only rely on the .tmp extension for temporary files
- Not to match any pattern for documents MS Office manipulates

I'd rather:
- Find some clever way to only store permissions of documents renamed
by MS Office
- Get better patterns to match temporary files

How to help
-----------
If you want to see this happen, mailing me to mention you could use
this vfs module will motivate me :)

If you are willing to help,?you can do so by providing data from your
environment:
- Enabling "vfs objects = extd_audit:2" for a share
- Provide me with the corresponding logs when you save an existing
file on this share
?"grep vfs_extd_audit" through your recent logs would be enough, no
need to prepare them further

Ideally, I'd like to get covered:
- All versions of Microsoft Office
- All versions of Microsoft Windows
- All supported file formats?

Moreover I'll be targeting/testing on Linux only, so other OSes users
will be welcome.


Thank you for your time,

--
Pierre Carrier

log.pierre-a3ca0284.1: ?vfs_extd_audit: rename old: ./s.docx newname:
./5D1CA1C1.tmp
log.pierre-a3ca0284.1: ?vfs_extd_audit: rename old: ./86A278C0.tmp
newname: ./s.docx
log.pierre-a3ca0284.2: ?vfs_extd_audit: rename old: ./Classeur1.xls
newname: ./F7C49255.tmp
log.pierre-a3ca0284.2: ?vfs_extd_audit: rename old: ./9E117AA4.tmp
newname: ./Classeur1.xls
log.pierre-a3ca0284.2: ?vfs_extd_audit: rename old: ./Classeur1.xls
newname: ./CFAF4030.tmp
log.pierre-a3ca0284.2: ?vfs_extd_audit: rename old: ./DB0C8C2B.tmp
newname: ./Classeur1.xls
log.pierre-a3ca0284.3: ?vfs_extd_audit: rename old: ./a.odt newname:
./DD33EC9A.tmp
log.pierre-a3ca0284.3: ?vfs_extd_audit: rename old: ./E629A9BD.tmp
newname: ./a.odt
log.pierre-a3ca0284.3: ?vfs_extd_audit: rename old: ./a.odt newname:
./4817EFB8.tmp
log.pierre-a3ca0284.3: ?vfs_extd_audit: rename old: ./6F25FD3.tmp
newname: ./a.odt