Re: Why Ext2/3 needs immutable attribute?

[Willy TARREAU <willy@w.ods.org>]

On Sun, Apr 17, 2005 at 12:12:13PM -0400, Xin Zhao wrote:
> Thanks for your reply. 
> 
> Yes. I know,  with immutable,  even root cannot modify sensitive
> files. What I am curious is if an intruder has root access, he may
> have many ways to turn off the immutable protection and modify files. 
> So immutable is designed just to prevent a valid root from making
> silly mistakes?

Probably yes, but it also provides a first level of security :
  - if the intruder launches programs blindly, he will not systematically
    get write access. Eg: if he abuses a CGI to call things like
      echo r00t::0:0::/:/bin/sh >>/etc/passwd
    it will not work.

  - if you give root access to other people on your file-system but you
    don't give them the CAP_LINUX_IMMUTABLE capability, they will not be
    able to modify the protected files. Useful when those files are the
    ones you use to grant them access ;-)

Regards,
Willy