Re: [Rats] Dealing with Attestation Roots

Hi Anders,

I think using an X.509 hierarchy with EAT is a fine thing to do, but no one’s done it yet. The two EAT implementations I know of, use other means to find the verification key. One by key ID, another by a combination of claims inside the attestation.

Android’s solution is not standard, it is just used by Android AFAIK.

I think it would be fine to write a draft that says how to use X.509 with EAT. It would involve https://tools.ietf.org/html/draft-ietf-cose-x509-06 and maybe the URL you’ve suggested for finding the root. Would even be interested in adding this functionality to ctoken <https://github.com/laurencelundblade/ctoken>. 

Technically speaking, this is all about endorsements and relates to recent email threads on that subject here.

LL

> On Apr 22, 2020, at 7:54 AM, Anders Rundgren <anders.rundgren.net@gmail.com> wrote:
> 
> On 2020-04-22 16:38, Laurence Lundblade wrote:
>> Hi Anders,
> 
> Hi Laurence,
> Thank you for responding!
> 
>>> On Feb 27, 2020, at 9:51 AM, Anders Rundgren <anders.rundgren.net@gmail.com> wrote:
>>> 
>>> Hi List,
>>> In the https://cyberphone.github.io/openbankingwallet project the idea was to use attestations.  The most recent version of the Android app indeed supports this as well.
>>> 
>>> In an ideal world the root would be provided by Google.  However, since we don't live in an ideal world there are vendors out there who do not follow that "recipe”.
>> Are you referring to Android N Key Attestation that is implemented in the key store?
> 
> This is indeed one possible usage.
> https://developer.android.com/training/articles/security-key-attestation
> 
>>> 
>>> For W3C's PaymentRequest API a simpler solution is used which do not match attestations but is better than nothing.  This scheme builds on publishing a manifest associated with the app.  Here is my particular manifest:  https://mobilepki.org/w3cpay/method
>>> 
>>> But I still would like to use attestations and also not being tied to browsers.
>>> 
>>> What about making attestations optionally contain a URL to the root like https://huawei.com/teeroot ?
>> I don’t know what https://huawei.com/teeroot  is. I can’t get anything from this URL.
> 
> That's correct, I don't even know where to find Huawei's attestation root which is how I came to this idea :)
> 
> 
>> I’m guessing you are after an X.509 root certificate, one that is used for Android-style attestation. Is that right?
> 
> Right.  Is using an X.509 root certificate an unusual way of dealing with attestation verification?
> 
> Anders
> 
>> LL
>>> Since the number of vendors in finite and the Web-PKI is in a fairly good shape these days, this could serve as a workaround for those who don't have any number of cycles to spend on installing arbitrary tee root certificates.  That is, a verifier's "trust registry" would simply hold host names like "huawei.com", "sony.com", "samsung.com", etc.
>>> 
>>> If there is a better method, I'm all ears!
>>> 
>>> thanx,
>>> Anders
>>> 
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> 
> 