On Sun, Jan 8, 2017 at 10:23 PM, <[email protected]> wrote:

> My tongue in cheek response would be to say that you are doing this
> backwards and you should be wanting to run Xen on seL4.
>

At a previous job I was interested in the potential of seL4 as a secure
enclave providing cryptographic services to a Linux-based guest. That is
not applicable to my current job though. So yes, that's great, and makes
more sense than what I'm describing and it's something I've been a fan of,
but not applicable to what I'm working on right now.

Long-term I am considering the possibility of shipping seL4 on dedicated
hardware devices as the only OS with no Linux host or guest. Deploying
these services on EC2 would allow us a way to ship seL4 in a production
capacity before we have a full hardware solution in place.


> More seriously though, what is the value that seL4 is providing in this
> setup? What are the specific threat scenarios that seL4 is mitigating
> against? If you are using seL4 to provide isolation of two applications,
> then since you are already relying on the isolation provided by Xen, why
> not cut out seL4 and run those two applications directly on Xen?
>

A "unikernel" deployment of these applications is definitely another
option. Explaining exactly what I'd like to do is a bit involved as it
requires knowledge of several AWS features including KMS and EC2
roles/instance metadata. I've been talking about it on the Robigalia IRC
channel if you'd like to discuss it there. I will say that shipping these
services in separate Xen instance would require e.g. a TLS encrypted
channel between them. While that's doable, I'd probably prefer for them to
just run on the same OS, and would probably just fold them into the same
unikernel were I not to use seL4.

I agree having a reasonable threat model in place before moving forward on
seL4 is a must, and I also understand there's much work to do re: Robigalia
and things like capability spaces.

-- 
Tony Arcieri
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