Messages in this thread | | | Date | Tue, 26 Jan 2016 15:13:29 -0800 | Subject | Re: [kernel-hardening] Re: [PATCH 0/2] sysctl: allow CLONE_NEWUSER to be disabled | From | Kees Cook <> |
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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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