pengines_sandbox.pl

/*  Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (c)  2017, VU University Amsterdam
    All rights reserved.

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*/

:- module(pengines_sandbox, []).
:- use_module(library(pengines), []).
:- autoload(library(error),[instantiation_error/1]).
:- autoload(library(lists),[append/3]).

/** <module> Declare Pengine interaction sandbox-safe

This module can be  loaded  alongside   library(pengines)  to  allow for
calling remote pengines from a sandboxed environment. This is disallowed
by default because one of the  use-cases   of  sandboxed  pengines is to
provide a generic application interface. In such   cases you do not want
the application to act as a proxy, in particular not to other systems in
a protected network.
*/

                 /*******************************
                 *    PENGINE SANDBOX SUPPORT   *
                 *******************************/

:- multifile
    sandbox:safe_primitive/1,               % Goal
    sandbox:safe_meta/2.                    % Goal, Calls

%!  sandbox:safe_primitive(+Goal) is semidet.
%
%   Declare the core pengine operations as   safe. If we are talking
%   about  local  pengines,  their  safety   is  guaranteed  by  the
%   sandboxing done for all pengines.
%
%   @tbd    If at some point we allow for `unsafe' pengines, we must
%           reconsider this.

sandbox:safe_primitive(pengines:pengine_destroy(_,_)).
sandbox:safe_primitive(pengines:pengine_event(_, _)).
sandbox:safe_primitive(pengines:pengine_send(_, _, _)).
sandbox:safe_primitive(pengines:pengine_ask(_, _, _)).
sandbox:safe_primitive(pengines:pengine_pull_response(_,_)).
sandbox:safe_primitive(pengines:pengine_user(_)).
sandbox:safe_primitive(system:'#file'(_,_)).

%!  sandbox:safe_meta(+Goal, -Called) is semidet.
%
%   Declare the pengine  meta-predicates  as   safe.  Note  that the
%   pengine calling predicates  are  safe   because  the  safety  is
%   guaranteed by the recieving pengine.

sandbox:safe_meta(pengines:pengine_create(_), []).
sandbox:safe_meta(pengines:pengine_rpc(_, _, _), []).
sandbox:safe_meta(pengines:pengine_event_loop(_,Closure,_,_), [Closure1]) :-
    extend_goal(Closure, [_], Closure1).

extend_goal(Var, _, _) :-
    var(Var),
    !,
    instantiation_error(Var).
extend_goal(M:Term0, Extra, M:Term) :-
    extend_goal(Term0, Extra, Term).
extend_goal(Atom, Extra, Goal) :-
    atom(Atom),
    !,
    Goal =.. [Atom|Extra].
extend_goal(Compound, Extra, Goal) :-
    compound(Compound),
    !,
    compound_name_arguments(Compound, Name, Args0),
    append(Args0, Extra, Args),
    compound_name_arguments(Goal, Name, Args).