On Mon, 2018-10-22 at 11:50 -0400, Ken Goldman wrote:

On 10/22/2018 10:18 AM, James Bottomley wrote:

quoted

quoted

1 - Any policy that requires a password (policypassword) can
substitute
an HMAC (policyauthvalue) at the callers discretion.  They result
in the same policy digest.

Right but this requires the co-operation of the policy handle
creator, so it's an API change.

In case it wasn't clear:  The choice is not made at the time the
policy is calculated, nor is it made at startauthsession (when
the policy is created).

The choice is made when the policy is being satisfied.

policypassword tells the TPM to expect a plaintext password, while
policyauthvalue tells the TPM to expect an HMAC.

It's subtle that either policy command results in the same policy
digest.

I understand, but the API just has a policy handle from a fully
constructed policy passed in.  There's no way to deconstruct this even
to know if it has auth requirements and what type.  To get that info we
 have to see the policy commands that go into building up the policy
session ... this means the API needs to change.

James