[Devel] Re: [patch -mm 08/17] nsproxy: add hashtable

[Serge E. Hallyn]

Quoting Eric W. Biederman (ebiederm at xmission.com):
> "Serge E. Hallyn" <serue at us.ibm.com> writes:
> 
> > Quoting Eric W. Biederman (ebiederm at xmission.com):
> >
> > Yeah, that occurred to me, but it doesn't seem like we can possibly make
> > sufficient guarantees to the client to make this worthwhile.
> >
> > I'd love to be wrong about that, but if nothing else we can't prove to
> > the client that they're running on an unhacked host.  So the host admin
> > will always have to be trusted.
> 
> To some extent that is true.  Although all security models we have
> currently fall down if you hack the kernel, or run your kernel
> in a hacked virtual environment.  It would be nice if under normal
> conditions you could mount an encrypted filesystem only in a container
> and not have concerns of those files escaping.

Hmm, well perhaps I'm being overly pessimistic - IBM research did have a
demo based on TPM of remote attestation, which may be usable for
ensuring that you're connecting to a service on your virtual machine on
a certain (unhacked) kernel on particular hardware, in which case what
you're talking about may be possible - given a stringent initial
environment (i.e. not the 'gimme $20/month for a hosted partition in
arizona' environment).

Given that, perhaps having a virtual machine with access to encrypted
storage - safe from the host machine admins - may not be unattainable
after all.  And given that, it would be worth designing the ns_enter()
system call so that a parent cannot enter some child namespace.

> Which would probably be a matter of having a separate uid_ns and not
> allowing process outside of your container to have any permissions in
> that filesystem.

Yup.  Or even just a separate uid_ns and an ecryptfs partition, so
that the host can back up the encrypted data incrementally (per file,
i.e. not just the whole dmcrypted loop file).

-serge
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