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SubjectRe: [kernel-hardening] Re: [PATCH 0/2] sysctl: allow CLONE_NEWUSER to be disabled
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On Tue, Jan 26, 2016 at 9:15 AM, Serge Hallyn <serge.hallyn@ubuntu.com> wrote:
> Quoting Josh Boyer (jwboyer@fedoraproject.org):
>> What you're saying is true for the "oh crap" case of a new userns
>> related CVE being found. However, there is the case where sysadmins
>> know for a fact that a set of machines should not allow user
>> namespaces to be enabled. Currently they have 2 choices, 1) use their
>
> Hi - can you give a specific example of this? (Where users really should
> not be able to use them - not where they might not need them) I think
> it'll help the discussion tremendously. Because so far the only good
> arguments I've seen have been about actual bugs in the user namespaces,
> which would not warrant a designed-in permanent disable switch. If
> there are good use cases where such a disable switch will always be
> needed (and compiling out can't satisfy) that'd be helpful.

My example is a machine in a colo rack serving web pages. A site gets
attacked, and www-data uses user namespaces to continue their attack
to gain root privileges.

The admin of such a machine could have disabled userns months earlier
and limited the scope of the attack.

-Kees

--
Kees Cook
Chrome OS & Brillo Security

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