why can I write to a file I don't have perms to??

[Tobias Speckbacher]

> -----Original Message-----
> From: redhat-list-bounces at redhat.com
> [mailto:redhat-list-bounces at redhat.com]On Behalf Of
> David.Knight at clubcorp.com
> Sent: Thursday, April 14, 2005 2:59 PM
> To: General Red Hat Linux discussion list
> Cc: redhat-list at redhat.com; redhat-list-bounces at redhat.com
> Subject: Re: why can I write to a file I don't have perms to??
> 
> 
> David.Knight at clubcorp.com
> Sent by: redhat-list-bounces at redhat.com
> 04/14/2005 04:56 PM
> Please respond to General Red Hat Linux discussion list
> 
>  
>         To:     redhat-list at redhat.com
>         cc: 
>         Subject:        why can I write to a file I don't own??
> 
> 
> 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. 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. 

This is how it is supposed to work.

>not 
> only that the UID:GID change to that user. I am running ext3 
> file systems 
> with kernel 2.4.21-20.ELsmp. So my question is 
> 
> 1) why is this allowed?
> 2) can I change this?

yes create a directory as root and set the sticky bit on it, deposit the file you want to protect inside this directory.
This should prevent the user from messing with the files.

http://www.linuxdevcenter.com/pub/a/linux/lpt/22_06.html

> 
> # 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
> $vi test.fil
> $ 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......
> Any thoughts on this would be great.
> -David Knight
> 
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