linux-security-module November 2007 archive
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linux-security-module: Re: [Apparmor-dev] Re: AppArmor Security

Re: [Apparmor-dev] Re: AppArmor Security Goal

From: Crispin Cowan <crispin_at_nospam>
Date: Tue Nov 13 2007 - 08:21:20 GMT

Rob Meijer wrote: >> The >> system is "defended" in that the worst the attacker can do to corrupt >> the system is limited to the transitive closure of what the confined >> processes are allowed to access. >>
> The damage the atacker can do would be defined by the authority not the
> permissions the process has.

As far as I can tall, the transitive closure of permissions is precisely authority. >> * AppArmor confines processes if they are children of a confined >> process, or if the name of the exec'd child matches the name of an >> AppArmor profile. >>
> What is left unspecified here is 'how' a child 'with its own profile' is
> confined here. Are it is confined to just its own profile, it may that
> the "complicit process" communication may need to be wider specified to
> include this.

It is deliberately unspecified in this document, because it is a matter of policy. And this item that you've excerpted is just one of a list of specific disclaimers that were put here in response to criticisms and misunderstandings of AppArmor in the past.

Remember, the purpose of *this* document is to define the security goals that AppArmor has to live up to. It is fine to use it as a jumping off point for design ideas that some system might employ some day, or even proposed enhancements to AppArmor itself, but don't over-burden the "security goal" document, it needs to be short & comprehensible. >> * A confined process can operate on a file descriptor passed to it >> by an unconfined process, even if it manipulates a file not in the >> confined process's profile. To block this attack, confine the >> process that passed the file descriptor. >>
> This should not count as an 'attack' given that the unconfined process
> would either be trusted, or be mallicious and fall inside the "influence"
> of the confined process anyway.

It counts as a surprising result, and so is specifically disclaimed. I can tell it is surprising, because it surprised Andi Kleen :)

Crispin -- Crispin Cowan, Ph.D. CEO, Mercenary Linux Itanium. Vista. GPLv3. Complexity at work - To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to More majordomo info at