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    1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2017, VU University Amsterdam
    7    All rights reserved.
    8
    9    Redistribution and use in source and binary forms, with or without
   10    modification, are permitted provided that the following conditions
   11    are met:
   12
   13    1. Redistributions of source code must retain the above copyright
   14       notice, this list of conditions and the following disclaimer.
   15
   16    2. Redistributions in binary form must reproduce the above copyright
   17       notice, this list of conditions and the following disclaimer in
   18       the documentation and/or other materials provided with the
   19       distribution.
   20
   21    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   25    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   29    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   31    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   32    POSSIBILITY OF SUCH DAMAGE.
   33*/
   34
   35:- module(pengines_sandbox, []).   36:- use_module(library(pengines), []).   37:- use_module(library(lists)).   38:- use_module(library(error)).

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. */

   50                 /*******************************
   51                 *    PENGINE SANDBOX SUPPORT   *
   52                 *******************************/
   53
   54:- multifile
   55    sandbox:safe_primitive/1,               % Goal
   56    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.
To be done
- If at some point we allow for `unsafe' pengines, we must reconsider this.
   67sandbox:safe_primitive(pengines:pengine_destroy(_,_)).
   68sandbox:safe_primitive(pengines:pengine_event(_, _)).
   69sandbox:safe_primitive(pengines:pengine_send(_, _, _)).
   70sandbox:safe_primitive(pengines:pengine_ask(_, _, _)).
   71sandbox:safe_primitive(pengines:pengine_pull_response(_,_)).
   72sandbox:safe_primitive(pengines:pengine_user(_)).
   73sandbox: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.
   81sandbox:safe_meta(pengines:pengine_create(_), []).
   82sandbox:safe_meta(pengines:pengine_rpc(_, _, _), []).
   83sandbox:safe_meta(pengines:pengine_event_loop(_,Closure,_,_), [Closure1]) :-
   84    extend_goal(Closure, [_], Closure1).
   85
   86extend_goal(Var, _, _) :-
   87    var(Var),
   88    !,
   89    instantiation_error(Var).
   90extend_goal(M:Term0, Extra, M:Term) :-
   91    extend_goal(Term0, Extra, Term).
   92extend_goal(Atom, Extra, Goal) :-
   93    atom(Atom),
   94    !,
   95    Goal =.. [Atom|Extra].
   96extend_goal(Compound, Extra, Goal) :-
   97    compound(Compound),
   98    !,
   99    compound_name_arguments(Compound, Name, Args0),
  100    append(Args0, Extra, Args),
  101    compound_name_arguments(Goal, Name, Args)