fabaccess-bffh/schema/api.capnp

# Copyright © 2020 Gregor Reitzenstein
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@0xfd92ce9be2369b8e;

interface Diflouroborane {
    # Upon initial connection this is the interface a program is presented with, serving as the
    # common point to access specific subsystems. Keep in mind that one can use pipelining to make this
    # just as efficient as direct calls — e.g. access the authentication system and call
    # `initializeAuthentication` on it in one roundtrip, provided one gets granted access to the
    # Authentication subsystem (which in all fairness is a reasonable assumption)

    authentication @0 () -> ( auth :Authentication );
    # Then authentication subsystem handles authentication of clients and servers. Multiple
    # authentication is possible, see the `Authentication` interface for details.

    permissions @1 () -> ( perm :Permissions );
    # Permission subsystem to manage permissions and systems underlying the authorization process

    machines @2 () -> ( mach :Machines );
    # Diflouroborane stores machine¹ information in an opaque internal database. This interface is
    # the only stable process of modifying that information

    # TODO Capability transfer system, required for machine takeover, session resumption.
}

struct UUID {
    # UUID type used to identify machines.
    # Since the exact value has no meaning the encoding rules are not too relevant, but it is
    # paramount that you are consistent when encoding and decoding this type.
    #
    # Consider using this algorithm for assembling the 128-bit integer:
    #   uint128_t uuid = (uuid1 << 64) + uuid0;
    # And then respectively this code for deconstructing it:
    #   uint64_t uuid0 = (uint64_t num);
    #   uint64_t uuid1 = (uint64_t (num >> 64));

    uuid0 @0 :UInt64;
    uuid1 @1 :UInt64;
}

interface Machines {
    interface Manage {
        setBlocked @0 ( blocked :Bool ) -> ();
        # Block or Unblock the machine. A blocked machine can not be used.

        return @1 () -> ();
        # Forcefully marking a machine as `returned` — i.e. not used.
    }

    interface Return {
        # The only way of getting a `return` interface is by successfully calling `use`. This means
        # only the user that marked a machine as `used` can return it again. (Baring force override)
        return @0 () -> ();
    }

    manage @0 ( uuid :UUID ) -> ( manage :Manage );

    use @1 ( uuid :UUID ) -> ( return :Return );
    # Use a machine, identified by its UUID. If the caller is allowed to and the machine is
    # available to being used a `return` Capability will be returned — the person using a machine is
    # after all the only person that can return the machine after use.
}

interface Permissions {
    getAllSubjects @0 () -> ( subjects :List(Text) );
    getAllObjects @1 () -> ( objects :List(Text) );
    getAllAction @2 () -> ( actions :List(Text) );
    getAllRoles @3 () -> ( roles :List(Text) );

    removePolicy @4 ( p :List(Text) ) -> ();
    addPolicy @5 ( p :List(Text) ) -> ();
}

interface Authentication {
    # List all SASL mechs the server is willing to use
    availableMechanisms @0 () -> ( mechanisms :List(Text) );

    # Start authentication using the given mechanism and optional initial data
    initializeAuthentication @1 ( mechanism :Text, initialData :MaybeData )
        -> (response :StepResult );

    getAuthzid @2 () -> ( authzid :Text );

    struct StepResult {
        union {
            challenge @0 :Challenge;
            outcome @1 :Outcome;
        }
    }

    struct MaybeData {
        union {
            some @0 :Data;
            none @1 :Void;
        }
    }

    interface Challenge {
        # Access the challenge data
        read @0 () -> ( data :MaybeData );

        respond @1 ( data :MaybeData ) 
            -> ( response :StepResult );
    }

    interface Outcome {
        # Outcomes may contain additional data
        read @0 () -> ( data :MaybeData );
        # The actual outcome.
        value @1 () -> ( granted :Bool );
    }
}