Re: [Teep] My BoF impression

[Tero Kivinen <[e-mail]>]

Michael Richardson writes:
>     > 3) The Secure trusted application marketplace can then encrypt
>     > the trusted application with TEE specific key, so that nobody
>     > else than TEE can decrypt and install it. This will prevent
>     > leaking out confidential material inside the application.
>     > Trusted application instlal package might also be personalized
>     > for the specific TEE. Secure trusted application marketplace
>     > will also sign the trusted application install package, so TEE
>     > can verify it is authentic.
> 
> And yet, this can mean that end-user and even app-writers can not
> verify what code they are actually running.

The end-user and app-writers already both trust the marketplace
provided by the operating system and trusts them. I.e. if marketplace
owner decides to add malware to each application they send to the
customers who would notice that? The connection between the device and
markplace is already encrypted, the software which downloads it from
the OS marketplace is provided by the OS, and they do verify that you
need to log in with your credentials before you can load anything. And
marketplace can provide different versions to different users, so
developer migth always get clean copy of their own app, but other
users could get modified version. Operating system on different
devices sometimes already protects apps from each other, and so on.

So if you do not trust the device OS, and marketplace provided by the
OS, there is nothing you can do.

Have you ever tried to verify for example that the application in your
iPhone is really same as what was given to the apple app store? Can
you even do that in iOS environment?

> I think we need to very carefully seperate signed (and auditable)
> code from encrypted data. And said encrypted data has to be
> non-executable, and the auditable code has to be verified to not
> include a Turing machine.... no (encrypted) data driven programming
> allowed.

That would be another good option. On the other hand, I do think
application developers would like to encrypt the executable also in
some cases. Perhaps this just means that we would need two containers
we are sending from the trusted marketplace to the TEE, one for code
and one for data, and data would always be encrypted, but code only if
requested by the trusted app itself.
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