Re: Security & UID, GID?

[Jens Ritter <Jens.Ritter@weh.rwth-aachen.de>]

Art Lemasters <alemas@rmi.net> writes:

>      One account on my system (e.g., one user in the /home directory)
> has had its group permission changed to from x to s without my doing
> so, a couple of times.  For example, in the /home directory, one user
> directory permission looked thusly:
> 
> drwxr-sr-x   16 user  user  1024  Sep 29 18:00  user
> 
>      I did not manually chmod the permissions that way.  What
> might have caused this, and what are the implications, anyone?
> Thanks for any leads on this, and yes, I have changed that group
> permission back to "x" each time this occured.

s permission on directories make up for the following behaviour:

$ ls -ld test
drwx------   2 jens     jens         1024 Sep 30 10:16 test
$ cd test 
$ su
Password: 
# mkdir test2
# exit
exit
$ chmod g+s .
hilbert [~/test] $ su
Password: 
# mkdir test3
# exit
exit
$ ls -la 
total 8
drwx--S---   4 jens     jens         1024 Sep 30 10:19 .
drwx------  46 jens     jens         5120 Sep 30 10:16 ..
drwxr-xr-x   2 root     root         1024 Sep 30 10:17 test2
drwxr-sr-x   2 root     jens         1024 Sep 30 10:19 test3

The uppercase letter indicates that the group x right is not set. 
All files and directories created in a directory with group s set,
will automatically set the group to the group of the parent
directory. 

See info "file utilities"

HTH,

Jens

---
Jens.Ritter@weh.rwth-aachen.de   grimaldi@debian.org
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