Date:	Thu, 27 Dec 2007 22:00:04 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	serue@...ibm.com
Cc:	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: TOMOYO Linux Security Goal

Hello.

Thank you for feedback.

Serge E. Hallyn wrote:
> > TOMOYO Linux is a DIY tool for understanding and protecting your system.
> > TOMOYO Linux policy definitions are absolutely readable to Linux users, and
> > TOMOYO Linux supports unique policy learning mechanism which automatically
> 
> Are they in fact unique?
> 
Yes, at least we believe so.

Have you ever heard an implementation that can automatically generate PIH
and restrict the behavior based on PIH?
Adding permissions to policy is not new because there is audit2allow
that can do it. But adding domains (or PIH) to policy is new.

Here's our version of Linux security comparison table.
http://tomoyo.sourceforge.jp/wiki-e/?WhatIs#comparison

> What kernel resources does TOMOYO authorize?  All those which SELinux
> does?
TOMOYO can authorize part of kernel resources which SELinux can
and part of other resources which SELinux can't.

Currently, TOMOYO can authorize

  * execve() of programs.
  * open() of files for reading/writing.
  * creat()/link()/rename()/unlink()/symlink()/mkfifo()/mksock()/mkblock()/
    mkchar()/truncate()/mkdir()/rmdir() of files and directries
    that are visible to userland process's namespace.
  * namespace manipulation. (i.e. mount()/umount()/pivot_root())
  * TCP/IP networking operations based on IPv4/v6 addresses and port numbers.
    (Need to add LSM hooks for incoming connections/packets.)
  * booleans for some operations. (Part of POSIX capability and TOMOYO's
    original capability.)
  * signal transmissions. (Needs to add LSM hooks.)
  * argv[0] passed to execve().
  * environment variables' names passed to execve().

> So your point was that your main goal is simplicity?
Yes. Keep it understandable and customizable so that end users
(i.e. administrators) can configure policy for their systems.

> 1. Tomoyo provide no sort of information flow control.
Yes. TOMOYO is not intended to provide information flow control.
Controlling information flow is not the region of interest for TOMOYO.
(I'm not a security architect. I don't understand the definition and
coverage of "information flow" in security field.
I'm using "information flow" as "how information propagates".)

I think no access control can guarantee regarding information flow.
No access control can prevent attackers from leaking information
which are caused by means granted to attackers.
Even if some implementation can prevent attackers from leaking information
regarding an atomic operation, it does not guarantee that the implementation
can prevent attackers from leaking information as a whole system.
Attackers can still do nasty requests within given permissions.
But without these permissions, the system can't work properly.
So, the region of interest for TOMOYO is how to minimize means granted to
each PIH, although not all permissions TOMOYO can authorize.

> 2. TOMOYO is purely restrictive.
Excuse me. What models are there other than "restrictive"?
I'm not sure whether what TOMOYO is doing are categorized to
"restrictive" model.

> 3. Learning mode is primary source of policy so you
>    depend on change of behavior to detect intruders.
>
> 4. but any intruder who attempts to do something which
>    the compomised sftware wouldn't have done should be
>    stopped and detected.
Yes. TOMOYO's power comes from "know all and understand what requests
can happen within this system".

Regards.
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