auditing access to directories with restricted access

[jon.bird at generaldynamics.uk.com]

Hi,

I am trying to set up some audit rules to monitor failed accesses to a given folder - here is the basics:

-a exit,always -S open -k fk_open -F dir=/recorder/ -F success=0

Here are the permissions on the folder:

drwxrwx---    3 red      red           4096 Jun  4 10:39 recorder

and the contents:

drwxrwx---    3 red      red           4096 Jun  4 12:05 .
drwxr-xr-x   21 root     root          1024 Jun  4 10:38 ..
drwx------    2 root     root         16384 Apr 24 15:49 lost+found
-rw-rw----    1 root     root             6 Jun  4 12:05 test.txt

If I run as user "red" ie. Who does have permission to write to this folder but then try and replace the "text.txt" file (which is owned by root) I get:

reduser at unit:~ echo test >test.txt 
-sh: can't create test.txt: Permission denied

Along with a corresponding entry in the audit log which is what I'm expected.

However if I run as another use which does not have permission to access this folder and try the same thing:

blackuser at unit:~ echo test >/recorder/test.txt
-sh: can't create /recorder/test.txt: Permission denied

But I don't get anything captured in the audit log. I've tried a few incarnations of the rule, including setting up similar arrangements and having the daemon monitor the parent folder (thinking the access will show up there) but I can't get this scenario to be detected by the audit daemon. If I remove the file system filter (ie. So I see all failed accesses) then it does get logged but this generates way too much traffic to be of much use. I've also done an strace call around the command and verified that (in this latter scenario) is it definitely the open call which is generating the permission denied error and it is.

This is using audit-2.3.6 on a 3.2.55 kernel. 

Any help appreciated,


Jon.

--
Jon Bird, CEng MBCS
Software Engineer
Electronic Systems  
General Dynamics United Kingdom Ltd.
Castleham Road, St Leonards on Sea, East Sussex, TN38 9NJ

Telephone: +441424798278  
Email: jon.bird at generaldynamics.uk.com
Website: www.generaldynamics.uk.com      




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