tree 5939aad61d19c7d3981939925863881077d11ecb
parent 8feb3063d6be53554534010b12484db4b3b77369
author Asim Shankar <ashankar@google.com> 1408497516 -0700
committer Asim Shankar <ashankar@google.com> 1408497517 -0700

veyron2/security,veyron/runtimes/google/ipc: Provide context to a discharger.

(Originally done by andreser@, I took over the change since he's left after
completing his internship)

This commit adds the interfaces and plumbing to:
(a) Allow ThirdPartyCaveats to specify what information should be reported
    to the third-party issuing discharges
(b) Sending that information and making it available to the Discharger
    RPC service so that implementations can make decisions on whether or
    not to discharge and to bind the discharge to a specific use.

Consider the following use-case:
- I provide a blessing to my child's device that allows the device to
  watch movies from my content provider.
  This blessing includes a ThirdPartyCaveat that requires a discharge
  from me (i.e., a Discharger service running on my device)
- When my child tries to view a movie, the context pops up on my device
  asking for permission. Based on the context (which movie is being
  requested for example), I issue a discharge with caveats, for example:
  (a) Discharge is valid for any G rated movie
  (b) Discharge is valid only for a specific movie otherwise.

Without this additional context, I had no useful information other than
the fact that a "discharge is being requested" in order to guide my
decision on whether or not to issue a discharge and what caveats to put
on it.

Change-Id: I079fba0d3848b4f630bccde719f50047e81d9008