Re: [Umbrella-devel] Re: Getting full path from dentry in LSM hooks

[Horst von Brand]

=?UTF-8?B?S3Jpc3RpYW4gU8O4cmVuc2Vu?= <ks@xxxxxxxxx> said:

[...]

> Umbrella is mostly designed for embedded systems (where selinux is 
> overkill) and also it is very easy to understand. Most restrictions will 
> be made to e.g. stop viruses from spreading, and it is quite easy, yet 
> very effective:

> If an email client receives an malformed email (like the countless 
> attacks on outlook), a simple restriction could be for the process 
> handeling the mail would be "$HOME/.addressbook",

A mail handling process with the adressbook off-limit sounds _real_ useful.

>                                                   furthermore, you could 
> specify that attachments executed _from_ the emailprogram would not have 
> access to the network.

I.e., no child of the email program could access the network, not even to
answer a message. Sounds restrictive.

>                        Thus the virus cannot find mail addresses to send 
> itself to - and it cannot even get network access. Simple and effective.

Right.

> Also simple bufferoverflows in suid-root programs may be avoided.

How?

>                                                                   The 
> simple way would to set the restriction "no fork", and thus if an 
> attacker tries to fork a (root) shell, this would be denied.

A simple exec(2) will do. Or overwriting a file. Or... If you restrict all
potentially dangerous operations, you have nothing useful left.

>                                                              Another way 
> could be to heavily restrict access to the filesystem. If the program is 
> restricted from /var, the root shell spawned by the attack would not 
> have access either. (restrictions are enherited from parent to children).

Just delete /var. Oops, it is there for a purpose...
-- 
Dr. Horst H. von Brand                   User #22616 counter.li.org
Departamento de Informatica                     Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria              +56 32 654239
Casilla 110-V, Valparaiso, Chile                Fax:  +56 32 797513
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