Re: [Rats] Android comments on EAT draft

[Shawn Willden <[e-mail]>]

Oh, I should also mention that in R I think we're going to add a claim to
present security certifications, for example Common Criteria Secure IC
Profile PP84, probably in multiple assurance levels (though PP84 is EAL4
plus AVA_VAN.5), and perhaps some others.

*From: *Shawn Willden <[e-mail]>
*Date: *Thu, May 16, 2019 at 3:11 PM
*To: *Simon Frost
*Cc: *Laurence Lundblade, [e-mail]

*From: *Simon Frost <[e-mail]>
>
>> As an example, have a look at the draft ‘profile’ we put together for an
>> Arm PSA attestation (
>> https://www.ietf.org/id/draft-tschofenig-rats-psa-token-01.txt) and let
>> us know where that does or doesn’t cover your software needs.
>>
>
> I'll do that.
>
> I would be very interested in reading your set of claims necessary to
>> describe a key as that use case has also been expressed for our usage.
>>
>
> Sure, here's a list of everything currently included in Android key
> attestations (excluding device info items and some elements that are
> redundant, also specified in the enclosing X.509 certificate):
>
>
>    - Purpose:  one or more of SIGN, ENCRYPT and WRAP_KEY.
>    - Digest: one or more of MD5, SHA1, SHA-256, SHA-324, SHA-512; which
>    digest(s) can be used for message digesting (MD5 and SHA1 are only for
>    legacy compatibility).
>    - Padding:  (RSA only) one or more of RSA_PKCS1_1_5_ENCRYPT, RSA_OAEP,
>    RSA_PKCS1_1_5_SIGN and RSA_PSS
>    - Rollback resistance: Boolean, if true, indicates that when the key
>    is deleted it is guaranteed never to be usable again
>    - No auth required:  Indicates key can be used without user
>    authentication.  If this is present, user auth type and auth timeout must
>    not be present.
>    - User auth type:  Indicates type of required user authentication
>    (password/biometric)
>    - Auth timeout: Indicates time in seconds during which key can be used
>    after user authentication (absence indicates key requires authentication
>    for each key usage).
>    - Allow while on body: Applicable only to wearables, and only for keys
>    that require authentication with a timeout.  Indicates that the key
>    immediately becomes unusable when the device is removed from the body, even
>    if timeout has not yet expired.
>    - Origin:  Where the key originated, one of GENERATED (in device;
>    exists nowhere else), DERIVED (in device, but also derivable by some
>    off-device entity), IMPORTED (imported in plaintext), SECURELY_IMPORTED
>    (imported in encrypted form), UNKNOWN
>    - Application ID:  Which Android app created the key
>
> A note about purpose, digest, padding: the idea is that AndroidKeyStore
> only allows keys to be used in the mode(s) that were declared when the key
> was created.  Any attempt to use the keys in any other way (e.g. sign with
> a n RSA key that has only the ENCRYPT purpose) will be rejected by the
> TEE/SE.
>
> I think Android R will add support for ECDH, so that will add some
> associated claims, and we may also add an option for secure export of key
> material, assuming the key was configured to allow it at creation/import
> time.  That will add some associated claims as well, including the public
> key(s) to which exports may be encrypted.
>
> --
> Shawn Willden | Staff Software Engineer | [e-mail] |
>  720-924-6645
>


-- 
Shawn Willden | Staff Software Engineer | [e-mail] | 720-924-6645