why can I write to a file I don't own??

[Bill Medland]

On April 14, 2005 02:56 pm, David.Knight at clubcorp.com wrote:
> RedHat List,
>         I was working on a script the other day and ran into
> an anomaly with the file permission's on files. I have checked
> this on several ES servers and all produce the same results.

Makes sense to me, as a weird behaviour of vi.

> Say a file has the following perms: 644  and it is owner and
> group are root:root. as long as a user has write permission's
> to the directory it is in they can write to it.

Not quite; they can delete it and then create a new one.

> not only that
> the UID:GID change to that user.

Not quite; the new one correctly has the user as owner, since the 
user created it.

(Interesting; it gets the same inode)

>
 I am running ext3 file
> systems with kernel 2.4.21-20.ELsmp. So my question is
>
> 1) why is this allowed?

Standard Unix file permissions

> 2) can I change this?

Don't override vi's decision when it tells you that you are 
overriding a readonly file.

>
> # pwd
> /home/test_dir
> # rm test.fil
> # pwd
> /home/test_dir
> # ls -ld .
> drwxr-xr-x    2 user7  root         4096 Apr 14 16:56 .
> # id
> uid=0(root) gid=0(root)
> groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel
>) # echo "test from root" > test.fil
> # ls -l test.fil
> -rw-r--r--    1 root     root           15 Apr 14 16:57
> test.fil # su - user7

So I presume /home/test_dir is user7's home directory

> $vi test.fil

And presumably vi told you it was a readonly file.

> $ ls -l test.fil
> -rw-r--r--    1 user7  user7        31 Apr 14 16:57 test.fil
> $ cat test.fil
> test from root
> test from uset7
>
> However it doesn't let you echo "test from user7" >
> ./test.fil. it responds correctly......
because that would truly be trying to modify the file rather than 
replace it.
> Any thoughts on this would be great.
> -David Knight

-- 
Bill Medland
mailto:billmedland at mercuryspeed.com
http://webhome.idirect.com/~kbmed