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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)  2013-2022, VU University Amsterdam
    7                              CWI, Amsterdam
    8                              SWI-Prolog Solutions b.v
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   29    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   30    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module(sandbox,
   38          [ safe_goal/1,                % :Goal
   39            safe_call/1                 % :Goal
   40          ]).   41:- use_module(library(apply_macros),[expand_phrase/2]).   42:- use_module(library(apply),[maplist/2]).   43:- use_module(library(assoc),[empty_assoc/1,get_assoc/3,put_assoc/4]).   44:- use_module(library(debug),[debug/3,debugging/1]).   45:- use_module(library(error),
   46              [ must_be/2,
   47                instantiation_error/1,
   48                type_error/2,
   49                permission_error/3
   50              ]).   51:- use_module(library(lists),[append/3]).   52:- use_module(library(prolog_format),[format_types/2]).   53
   54:- multifile
   55    safe_primitive/1,               % Goal
   56    safe_meta_predicate/1,          % Name/Arity
   57    safe_meta/2,                    % Goal, Calls
   58    safe_meta/3,                    % Goal, Context, Calls
   59    safe_global_variable/1,         % Name
   60    safe_directive/1,               % Module:Goal
   61    safe_prolog_flag/2.             % +Name, +Value
   62
   63% :- debug(sandbox).
   64
   65/** <module> Sandboxed Prolog code
   66
   67Prolog is a full-featured Turing complete  programming language in which
   68it is easy to write programs that can   harm your computer. On the other
   69hand, Prolog is a logic based _query language_ which can be exploited to
   70query data interactively from, e.g.,  the   web.  This  library provides
   71safe_goal/1, which determines whether it is safe to call its argument.
   72
   73@tbd    Handling of ^ and // meta predicates
   74@tbd    Complete set of whitelisted predicates
   75@see    http://www.swi-prolog.org/pldoc/package/pengines.html
   76*/
   77
   78
   79:- meta_predicate
   80    safe_goal(:),
   81    safe_call(0).   82
   83%!  safe_call(:Goal)
   84%
   85%   Call Goal if it  complies  with   the  sandboxing  rules. Before
   86%   calling   Goal,   it   performs   expand_goal/2,   followed   by
   87%   safe_goal/1. Expanding is done explicitly  because situations in
   88%   which safe_call/1 typically concern goals that  are not known at
   89%   compile time.
   90%
   91%   @see safe_goal/1.
   92
   93safe_call(Goal0) :-
   94    expand_goal(Goal0, Goal),
   95    safe_goal(Goal),
   96    call(Goal).
   97
   98%!  safe_goal(:Goal) is det.
   99%
  100%   True if calling Goal provides  no   security  risc. This implies
  101%   that:
  102%
  103%     - The call-graph can be fully expanded. Full expansion *stops*
  104%     if a meta-goal is found for   which we cannot determine enough
  105%     details to know which predicate will be called.
  106%
  107%     - All predicates  referenced  from   the  fully  expanded  are
  108%     whitelisted by the predicate safe_primitive/1 and safe_meta/2.
  109%
  110%     - It is not allowed to make explicitly qualified calls into
  111%     modules to predicates that are not exported or declared
  112%     public.
  113%
  114%   @error  instantiation_error if the analysis encounters a term in
  115%           a callable position that is insufficiently instantiated
  116%           to determine the predicate called.
  117%   @error  permission_error(call, sandboxed, Goal) if Goal is in
  118%           the call-tree and not white-listed.
  119
  120safe_goal(M:Goal) :-
  121    empty_assoc(Safe0),
  122    catch(safe(Goal, M, [], Safe0, _), E, true),
  123    !,
  124    nb_delete(sandbox_last_error),
  125    (   var(E)
  126    ->  true
  127    ;   throw(E)
  128    ).
  129safe_goal(_) :-
  130    nb_current(sandbox_last_error, E),
  131    !,
  132    nb_delete(sandbox_last_error),
  133    throw(E).
  134safe_goal(G) :-
  135    debug(sandbox(fail), 'safe_goal/1 failed for ~p', [G]),
  136    throw(error(instantiation_error, sandbox(G, []))).
  137
  138
  139%!  safe(+Goal, +Module, +Parents, +Safe0, -Safe) is semidet.
  140%
  141%   Is true if Goal can only call safe code.
  142
  143safe(V, _, Parents, _, _) :-
  144    var(V),
  145    !,
  146    Error = error(instantiation_error, sandbox(V, Parents)),
  147    nb_setval(sandbox_last_error, Error),
  148    throw(Error).
  149safe(M:G, _, Parents, Safe0, Safe) :-
  150    !,
  151    must_be(atom, M),
  152    must_be(callable, G),
  153    known_module(M:G, Parents),
  154    (   predicate_property(M:G, imported_from(M2))
  155    ->  true
  156    ;   M2 = M
  157    ),
  158    (   (   safe_primitive(M2:G)
  159        ;   safe_primitive(G),
  160            predicate_property(G, iso)
  161        )
  162    ->  Safe = Safe0
  163    ;   (   predicate_property(M:G, exported)
  164        ;   predicate_property(M:G, public)
  165        ;   predicate_property(M:G, multifile)
  166        ;   predicate_property(M:G, iso)
  167        ;   memberchk(M:_, Parents)
  168        )
  169    ->  safe(G, M, Parents, Safe0, Safe)
  170    ;   throw(error(permission_error(call, sandboxed, M:G),
  171                    sandbox(M:G, Parents)))
  172    ).
  173safe(G, _, Parents, _, _) :-
  174    debugging(sandbox(show)),
  175    length(Parents, Level),
  176    debug(sandbox(show), '[~D] SAFE ~q?', [Level, G]),
  177    fail.
  178safe(G, _, Parents, Safe, Safe) :-
  179    catch(safe_primitive(G),
  180          error(instantiation_error, _),
  181          rethrow_instantition_error([G|Parents])),
  182    predicate_property(G, iso),
  183    !.
  184safe(G, M, Parents, Safe, Safe) :-
  185    known_module(M:G, Parents),
  186    (   predicate_property(M:G, imported_from(M2))
  187    ->  true
  188    ;   M2 = M
  189    ),
  190    (   catch(safe_primitive(M2:G),
  191              error(instantiation_error, _),
  192              rethrow_instantition_error([M2:G|Parents]))
  193    ;   predicate_property(M2:G, number_of_rules(0))
  194    ),
  195    !.
  196safe(G, M, Parents, Safe0, Safe) :-
  197    predicate_property(G, iso),
  198    safe_meta_call(G, M, Called),
  199    !,
  200    add_iso_parent(G, Parents, Parents1),
  201    safe_list(Called, M, Parents1, Safe0, Safe).
  202safe(G, M, Parents, Safe0, Safe) :-
  203    (   predicate_property(M:G, imported_from(M2))
  204    ->  true
  205    ;   M2 = M
  206    ),
  207    safe_meta_call(M2:G, M, Called),
  208    !,
  209    safe_list(Called, M, Parents, Safe0, Safe).
  210safe(G, M, Parents, Safe0, Safe) :-
  211    goal_id(M:G, Id, Gen),
  212    (   get_assoc(Id, Safe0, _)
  213    ->  Safe = Safe0
  214    ;   put_assoc(Id, Safe0, true, Safe1),
  215        (   Gen == M:G
  216        ->  safe_clauses(Gen, M, [Id|Parents], Safe1, Safe)
  217        ;   catch(safe_clauses(Gen, M, [Id|Parents], Safe1, Safe),
  218                  error(instantiation_error, Ctx),
  219                  unsafe(Parents, Ctx))
  220        )
  221    ),
  222    !.
  223safe(G, M, Parents, _, _) :-
  224    debug(sandbox(fail),
  225          'safe/1 failed for ~p (parents:~p)', [M:G, Parents]),
  226    fail.
  227
  228unsafe(Parents, Var) :-
  229    var(Var),
  230    !,
  231    nb_setval(sandbox_last_error,
  232              error(instantiation_error, sandbox(_, Parents))),
  233    fail.
  234unsafe(_Parents, Ctx) :-
  235    Ctx = sandbox(_,_),
  236    nb_setval(sandbox_last_error,
  237              error(instantiation_error, Ctx)),
  238    fail.
  239
  240rethrow_instantition_error(Parents) :-
  241    throw(error(instantiation_error, sandbox(_, Parents))).
  242
  243safe_clauses(G, M, Parents, Safe0, Safe) :-
  244    predicate_property(M:G, interpreted),
  245    def_module(M:G, MD:QG),
  246    \+ compiled(MD:QG),
  247    !,
  248    findall(Ref-Body, clause(MD:QG, Body, Ref), Bodies),
  249    safe_bodies(Bodies, MD, Parents, Safe0, Safe).
  250safe_clauses(G, M, [_|Parents], _, _) :-
  251    predicate_property(M:G, visible),
  252    !,
  253    throw(error(permission_error(call, sandboxed, G),
  254                sandbox(M:G, Parents))).
  255safe_clauses(_, _, [G|Parents], _, _) :-
  256    throw(error(existence_error(procedure, G),
  257                sandbox(G, Parents))).
  258
  259compiled(system:(@(_,_))).
  260
  261known_module(M:_, _) :-
  262    current_module(M),
  263    !.
  264known_module(M:G, Parents) :-
  265    throw(error(permission_error(call, sandboxed, M:G),
  266                sandbox(M:G, Parents))).
  267
  268add_iso_parent(G, Parents, Parents) :-
  269    is_control(G),
  270    !.
  271add_iso_parent(G, Parents, [G|Parents]).
  272
  273is_control((_,_)).
  274is_control((_;_)).
  275is_control((_->_)).
  276is_control((_*->_)).
  277is_control(\+(_)).
  278
  279
  280%!  safe_bodies(+Bodies, +Module, +Parents, +Safe0, -Safe)
  281%
  282%   Verify the safety of bodies. If  a   clause  was compiled with a
  283%   qualified module, we  consider  execution  of   the  body  in  a
  284%   different module _not_ a cross-module call.
  285
  286safe_bodies([], _, _, Safe, Safe).
  287safe_bodies([Ref-H|T], M, Parents, Safe0, Safe) :-
  288    (   H = M2:H2, nonvar(M2),
  289        clause_property(Ref, module(M2))
  290    ->  copy_term(H2, H3),
  291        CM = M2
  292    ;   copy_term(H, H3),
  293        CM = M
  294    ),
  295    safe(H3, CM, Parents, Safe0, Safe1),
  296    safe_bodies(T, M, Parents, Safe1, Safe).
  297
  298def_module(M:G, MD:QG) :-
  299    predicate_property(M:G, imported_from(MD)),
  300    !,
  301    meta_qualify(MD:G, M, QG).
  302def_module(M:G, M:QG) :-
  303    meta_qualify(M:G, M, QG).
  304
  305%!  safe_list(+Called, +Module, +Parents, +Safe0, -Safe)
  306%
  307%   Processed objects called through meta  predicates. If the called
  308%   object  is  in  our  current  context    we  remove  the  module
  309%   qualification to avoid the cross-module check.
  310
  311safe_list([], _, _, Safe, Safe).
  312safe_list([H|T], M, Parents, Safe0, Safe) :-
  313    (   H = M2:H2,
  314        M == M2                             % in our context
  315    ->  copy_term(H2, H3)
  316    ;   copy_term(H, H3)                    % cross-module call
  317    ),
  318    safe(H3, M, Parents, Safe0, Safe1),
  319    safe_list(T, M, Parents, Safe1, Safe).
  320
  321%!  meta_qualify(:G, +M, -QG) is det.
  322%
  323%   Perform meta-qualification of the goal-argument
  324
  325meta_qualify(MD:G, M, QG) :-
  326    predicate_property(MD:G, meta_predicate(Head)),
  327    !,
  328    G =.. [Name|Args],
  329    Head =.. [_|Q],
  330    qualify_args(Q, M, Args, QArgs),
  331    QG =.. [Name|QArgs].
  332meta_qualify(_:G, _, G).
  333
  334qualify_args([], _, [], []).
  335qualify_args([H|T], M, [A|AT], [Q|QT]) :-
  336    qualify_arg(H, M, A, Q),
  337    qualify_args(T, M, AT, QT).
  338
  339qualify_arg(S, M, A, Q) :-
  340    q_arg(S),
  341    !,
  342    qualify(A, M, Q).
  343qualify_arg(_, _, A, A).
  344
  345q_arg(I) :- integer(I), !.
  346q_arg(:).
  347q_arg(^).
  348q_arg(//).
  349
  350qualify(A, M, MZ:Q) :-
  351    strip_module(M:A, MZ, Q).
  352
  353%!  goal_id(:Goal, -Id, -Gen) is nondet.
  354%
  355%   Generate an identifier for the goal proven to be safe. We
  356%   first try to prove the most general form of the goal.  If
  357%   this fails, we try to prove more specific versions.
  358%
  359%   @tbd    Do step-by-step generalisation instead of the current
  360%           two levels (most general and most specific).
  361%   @tbd    We could also use variant_sha1 for the goal ids.
  362
  363goal_id(M:Goal, M:Id, Gen) :-
  364    !,
  365    goal_id(Goal, Id, Gen).
  366goal_id(Var, _, _) :-
  367    var(Var),
  368    !,
  369    instantiation_error(Var).
  370goal_id(Atom, Atom, Atom) :-
  371    atom(Atom),
  372    !.
  373goal_id(Term, _, _) :-
  374    \+ compound(Term),
  375    !,
  376    type_error(callable, Term).
  377goal_id(Term, Skolem, Gen) :-           % most general form
  378    compound_name_arity(Term, Name, Arity),
  379    compound_name_arity(Skolem, Name, Arity),
  380    compound_name_arity(Gen, Name, Arity),
  381    copy_goal_args(1, Term, Skolem, Gen),
  382    (   Gen =@= Term
  383    ->  !                           % No more specific one; we can commit
  384    ;   true
  385    ),
  386    numbervars(Skolem, 0, _).
  387goal_id(Term, Skolem, Term) :-          % most specific form
  388    debug(sandbox(specify), 'Retrying with ~p', [Term]),
  389    copy_term(Term, Skolem),
  390    numbervars(Skolem, 0, _).
  391
  392%!  copy_goal_args(+I, +Term, +Skolem, +Gen) is det.
  393%
  394%   Create  the  most  general  form,   but  keep  module  qualified
  395%   arguments because they will likely be called anyway.
  396
  397copy_goal_args(I, Term, Skolem, Gen) :-
  398    arg(I, Term, TA),
  399    !,
  400    arg(I, Skolem, SA),
  401    arg(I, Gen, GA),
  402    copy_goal_arg(TA, SA, GA),
  403    I2 is I + 1,
  404    copy_goal_args(I2, Term, Skolem, Gen).
  405copy_goal_args(_, _, _, _).
  406
  407copy_goal_arg(Arg, SArg, Arg) :-
  408    copy_goal_arg(Arg),
  409    !,
  410    copy_term(Arg, SArg).
  411copy_goal_arg(_, _, _).
  412
  413copy_goal_arg(Var) :- var(Var), !, fail.
  414copy_goal_arg(_:_).
  415
  416%!  verify_safe_declaration(+Decl)
  417%
  418%   See whether a  safe  declaration  makes   sense.  That  is,  the
  419%   predicate must be defined (such that  the attacker cannot define
  420%   the predicate), must be sufficiently   instantiated and only ISO
  421%   declared predicates may omit a module qualification.
  422%
  423%   @tbd    Verify safe_meta/2 declarations.  It is a bit less clear
  424%           what the rules are.
  425
  426term_expansion(safe_primitive(Goal), Term) :-
  427    (   verify_safe_declaration(Goal)
  428    ->  Term = safe_primitive(Goal)
  429    ;   Term = []
  430    ).
  431term_expansion((safe_primitive(Goal) :- Body), Term) :-
  432    (   verify_safe_declaration(Goal)
  433    ->  Term = (safe_primitive(Goal) :- Body)
  434    ;   Term = []
  435    ).
  436
  437system:term_expansion(sandbox:safe_primitive(Goal), Term) :-
  438    \+ current_prolog_flag(xref, true),
  439    (   verify_safe_declaration(Goal)
  440    ->  Term = sandbox:safe_primitive(Goal)
  441    ;   Term = []
  442    ).
  443system:term_expansion((sandbox:safe_primitive(Goal) :- Body), Term) :-
  444    \+ current_prolog_flag(xref, true),
  445    (   verify_safe_declaration(Goal)
  446    ->  Term = (sandbox:safe_primitive(Goal) :- Body)
  447    ;   Term = []
  448    ).
  449
  450verify_safe_declaration(Var) :-
  451    var(Var),
  452    !,
  453    instantiation_error(Var).
  454verify_safe_declaration(Module:Goal) :-
  455    !,
  456    must_be(atom, Module),
  457    must_be(callable, Goal),
  458    (   ok_meta(Module:Goal)
  459    ->  true
  460    ;   (   predicate_property(Module:Goal, visible)
  461        ->  true
  462        ;   predicate_property(Module:Goal, foreign)
  463        ),
  464        \+ predicate_property(Module:Goal, imported_from(_)),
  465        \+ predicate_property(Module:Goal, meta_predicate(_))
  466    ->  true
  467    ;   permission_error(declare, safe_goal, Module:Goal)
  468    ).
  469verify_safe_declaration(Goal) :-
  470    must_be(callable, Goal),
  471    (   predicate_property(system:Goal, iso),
  472        \+ predicate_property(system:Goal, meta_predicate())
  473    ->  true
  474    ;   permission_error(declare, safe_goal, Goal)
  475    ).
  476
  477ok_meta(system:assert(_)).
  478ok_meta(system:load_files(_,_)).
  479ok_meta(system:use_module(_,_)).
  480ok_meta(system:use_module(_)).
  481ok_meta('$syspreds':predicate_property(_,_)).
  482
  483verify_predefined_safe_declarations :-
  484    forall(clause(safe_primitive(Goal), _Body, Ref),
  485           ( E = error(F,_),
  486             catch(verify_safe_declaration(Goal), E, true),
  487             (   nonvar(F)
  488             ->  clause_property(Ref, file(File)),
  489                 clause_property(Ref, line_count(Line)),
  490                 print_message(error, bad_safe_declaration(Goal, File, Line))
  491             ;   true
  492             )
  493           )).
  494
  495:- initialization(verify_predefined_safe_declarations, now).  496
  497%!  safe_primitive(?Goal) is nondet.
  498%
  499%   True if Goal is safe  to   call  (i.e.,  cannot access dangerous
  500%   system-resources and cannot upset  other   parts  of  the Prolog
  501%   process). There are two  types  of   facts.  ISO  built-ins  are
  502%   declared without a module prefix. This is safe because it is not
  503%   allowed to (re-)define these  primitives   (i.e.,  give  them an
  504%   unsafe     implementation)     and     the       way      around
  505%   (redefine_system_predicate/1) is unsafe.  The   other  group are
  506%   module-qualified and only match if the   system  infers that the
  507%   predicate is imported from the given module.
  508
  509% First, all ISO system predicates that are considered safe
  510
  511safe_primitive(true).
  512safe_primitive(fail).
  513safe_primitive(system:false).
  514safe_primitive(repeat).
  515safe_primitive(!).
  516                                        % types
  517safe_primitive(var(_)).
  518safe_primitive(nonvar(_)).
  519safe_primitive(system:attvar(_)).
  520safe_primitive(integer(_)).
  521safe_primitive(float(_)).
  522:- if(current_predicate(rational/1)).  523safe_primitive(system:rational(_)).
  524safe_primitive(system:rational(_,_,_)).
  525:- endif.  526safe_primitive(number(_)).
  527safe_primitive(atom(_)).
  528safe_primitive(system:blob(_,_)).
  529safe_primitive(system:string(_)).
  530safe_primitive(atomic(_)).
  531safe_primitive(compound(_)).
  532safe_primitive(callable(_)).
  533safe_primitive(ground(_)).
  534safe_primitive(system:nonground(_,_)).
  535safe_primitive(system:cyclic_term(_)).
  536safe_primitive(acyclic_term(_)).
  537safe_primitive(system:is_stream(_)).
  538safe_primitive(system:'$is_char'(_)).
  539safe_primitive(system:'$is_char_code'(_)).
  540safe_primitive(system:'$is_char_list'(_,_)).
  541safe_primitive(system:'$is_code_list'(_,_)).
  542                                        % ordering
  543safe_primitive(@>(_,_)).
  544safe_primitive(@>=(_,_)).
  545safe_primitive(==(_,_)).
  546safe_primitive(@<(_,_)).
  547safe_primitive(@=<(_,_)).
  548safe_primitive(compare(_,_,_)).
  549safe_primitive(sort(_,_)).
  550safe_primitive(keysort(_,_)).
  551safe_primitive(system: =@=(_,_)).
  552safe_primitive(system:'$btree_find_node'(_,_,_,_,_)).
  553
  554                                        % unification and equivalence
  555safe_primitive(=(_,_)).
  556safe_primitive(\=(_,_)).
  557safe_primitive(system:'?='(_,_)).
  558safe_primitive(system:unifiable(_,_,_)).
  559safe_primitive(unify_with_occurs_check(_,_)).
  560safe_primitive(\==(_,_)).
  561                                        % arithmetic
  562safe_primitive(is(_,_)).
  563safe_primitive(>(_,_)).
  564safe_primitive(>=(_,_)).
  565safe_primitive(=:=(_,_)).
  566safe_primitive(=\=(_,_)).
  567safe_primitive(=<(_,_)).
  568safe_primitive(<(_,_)).
  569:- if(current_prolog_flag(bounded, false)).  570safe_primitive(system:nth_integer_root_and_remainder(_,_,_,_)).
  571:- endif.  572
  573                                        % term-handling
  574safe_primitive(arg(_,_,_)).
  575safe_primitive(system:setarg(_,_,_)).
  576safe_primitive(system:nb_setarg(_,_,_)).
  577safe_primitive(system:nb_linkarg(_,_,_)).
  578safe_primitive(functor(_,_,_)).
  579safe_primitive(system:functor(_,_,_,_)).
  580safe_primitive(_ =.. _).
  581safe_primitive(system:compound_name_arity(_,_,_)).
  582safe_primitive(system:compound_name_arguments(_,_,_)).
  583safe_primitive(system:'$filled_array'(_,_,_,_)).
  584safe_primitive(copy_term(_,_)).
  585safe_primitive(system:copy_term(_,_,_,_)).
  586safe_primitive(system:duplicate_term(_,_)).
  587safe_primitive(system:copy_term_nat(_,_)).
  588safe_primitive(system:size_abstract_term(_,_,_)).
  589safe_primitive(numbervars(_,_,_)).
  590safe_primitive(system:numbervars(_,_,_,_)).
  591safe_primitive(subsumes_term(_,_)).
  592safe_primitive(system:term_hash(_,_)).
  593safe_primitive(system:term_hash(_,_,_,_)).
  594safe_primitive(system:variant_sha1(_,_)).
  595safe_primitive(system:variant_hash(_,_)).
  596safe_primitive(system:'$term_size'(_,_,_)).
  597
  598                                        % dicts
  599safe_primitive(system:is_dict(_)).
  600safe_primitive(system:is_dict(_,_)).
  601safe_primitive(system:get_dict(_,_,_)).
  602safe_primitive(system:get_dict(_,_,_,_,_)).
  603safe_primitive(system:'$get_dict_ex'(_,_,_)).
  604safe_primitive(system:dict_create(_,_,_)).
  605safe_primitive(system:dict_pairs(_,_,_)).
  606safe_primitive(system:put_dict(_,_,_)).
  607safe_primitive(system:put_dict(_,_,_,_)).
  608safe_primitive(system:del_dict(_,_,_,_)).
  609safe_primitive(system:select_dict(_,_,_)).
  610safe_primitive(system:b_set_dict(_,_,_)).
  611safe_primitive(system:nb_set_dict(_,_,_)).
  612safe_primitive(system:nb_link_dict(_,_,_)).
  613safe_primitive(system:(:<(_,_))).
  614safe_primitive(system:(>:<(_,_))).
  615                                        % atoms
  616safe_primitive(atom_chars(_, _)).
  617safe_primitive(atom_codes(_, _)).
  618safe_primitive(sub_atom(_,_,_,_,_)).
  619safe_primitive(atom_concat(_,_,_)).
  620safe_primitive(atom_length(_,_)).
  621safe_primitive(char_code(_,_)).
  622safe_primitive(system:name(_,_)).
  623safe_primitive(system:atomic_concat(_,_,_)).
  624safe_primitive(system:atomic_list_concat(_,_)).
  625safe_primitive(system:atomic_list_concat(_,_,_)).
  626safe_primitive(system:downcase_atom(_,_)).
  627safe_primitive(system:upcase_atom(_,_)).
  628safe_primitive(system:char_type(_,_)).
  629safe_primitive(system:normalize_space(_,_)).
  630safe_primitive(system:sub_atom_icasechk(_,_,_)).
  631                                        % numbers
  632safe_primitive(number_codes(_,_)).
  633safe_primitive(number_chars(_,_)).
  634safe_primitive(system:atom_number(_,_)).
  635safe_primitive(system:code_type(_,_)).
  636                                        % strings
  637safe_primitive(system:atom_string(_,_)).
  638safe_primitive(system:number_string(_,_)).
  639safe_primitive(system:string_chars(_, _)).
  640safe_primitive(system:string_codes(_, _)).
  641safe_primitive(system:string_code(_,_,_)).
  642safe_primitive(system:sub_string(_,_,_,_,_)).
  643safe_primitive(system:split_string(_,_,_,_)).
  644safe_primitive(system:atomics_to_string(_,_,_)).
  645safe_primitive(system:atomics_to_string(_,_)).
  646safe_primitive(system:string_concat(_,_,_)).
  647safe_primitive(system:string_length(_,_)).
  648safe_primitive(system:string_lower(_,_)).
  649safe_primitive(system:string_upper(_,_)).
  650safe_primitive(system:term_string(_,_)).
  651safe_primitive('$syspreds':term_string(_,_,_)).
  652                                        % Lists
  653safe_primitive(length(_,_)).
  654                                        % exceptions
  655safe_primitive(throw(_)).
  656safe_primitive(system:abort).
  657                                        % misc
  658safe_primitive(current_prolog_flag(_,_)).
  659safe_primitive(current_op(_,_,_)).
  660safe_primitive(system:sleep(_)).
  661safe_primitive(system:thread_self(_)).
  662safe_primitive(system:get_time(_)).
  663safe_primitive(system:statistics(_,_)).
  664safe_primitive(system:thread_statistics(Id,_,_)) :-
  665    (   var(Id)
  666    ->  instantiation_error(Id)
  667    ;   thread_self(Id)
  668    ).
  669safe_primitive(system:thread_property(Id,_)) :-
  670    (   var(Id)
  671    ->  instantiation_error(Id)
  672    ;   thread_self(Id)
  673    ).
  674safe_primitive(system:format_time(_,_,_)).
  675safe_primitive(system:format_time(_,_,_,_)).
  676safe_primitive(system:date_time_stamp(_,_)).
  677safe_primitive(system:stamp_date_time(_,_,_)).
  678safe_primitive(system:strip_module(_,_,_)).
  679safe_primitive('$messages':message_to_string(_,_)).
  680safe_primitive(system:import_module(_,_)).
  681safe_primitive(system:file_base_name(_,_)).
  682safe_primitive(system:file_directory_name(_,_)).
  683safe_primitive(system:file_name_extension(_,_,_)).
  684
  685safe_primitive(clause(H,_)) :- safe_clause(H).
  686safe_primitive(asserta(X)) :- safe_assert(X).
  687safe_primitive(assertz(X)) :- safe_assert(X).
  688safe_primitive(retract(X)) :- safe_assert(X).
  689safe_primitive(retractall(X)) :- safe_assert(X).
  690safe_primitive('$dcg':dcg_translate_rule(_,_)).
  691safe_primitive('$syspreds':predicate_property(Pred, _)) :-
  692    nonvar(Pred),
  693    Pred \= (_:_).
  694
  695% We need to do data flow analysis to find the tag of the
  696% target key before we can conclude that functions on dicts
  697% are safe.
  698safe_primitive('$dicts':'.'(_,K,_)) :- atom(K).
  699safe_primitive('$dicts':'.'(_,K,_)) :-
  700    (   nonvar(K)
  701    ->  dict_built_in(K)
  702    ;   instantiation_error(K)
  703    ).
  704
  705dict_built_in(get(_)).
  706dict_built_in(put(_)).
  707dict_built_in(put(_,_)).
  708
  709% The non-ISO system predicates.  These can be redefined, so we must
  710% be careful to ensure the system ones are used.
  711
  712safe_primitive(system:false).
  713safe_primitive(system:cyclic_term(_)).
  714safe_primitive(system:msort(_,_)).
  715safe_primitive(system:sort(_,_,_,_)).
  716safe_primitive(system:between(_,_,_)).
  717safe_primitive(system:succ(_,_)).
  718safe_primitive(system:plus(_,_,_)).
  719safe_primitive(system:float_class(_,_)).
  720safe_primitive(system:term_variables(_,_)).
  721safe_primitive(system:term_variables(_,_,_)).
  722safe_primitive(system:'$term_size'(_,_,_)).
  723safe_primitive(system:atom_to_term(_,_,_)).
  724safe_primitive(system:term_to_atom(_,_)).
  725safe_primitive(system:atomic_list_concat(_,_,_)).
  726safe_primitive(system:atomic_list_concat(_,_)).
  727safe_primitive(system:downcase_atom(_,_)).
  728safe_primitive(system:upcase_atom(_,_)).
  729safe_primitive(system:is_list(_)).
  730safe_primitive(system:memberchk(_,_)).
  731safe_primitive(system:'$skip_list'(_,_,_)).
  732                                        % attributes
  733safe_primitive(system:get_attr(_,_,_)).
  734safe_primitive(system:get_attrs(_,_)).
  735safe_primitive(system:term_attvars(_,_)).
  736safe_primitive(system:del_attr(_,_)).
  737safe_primitive(system:del_attrs(_)).
  738safe_primitive('$attvar':copy_term(_,_,_)).
  739                                        % globals
  740safe_primitive(system:b_getval(_,_)).
  741safe_primitive(system:b_setval(Var,_)) :-
  742    safe_global_var(Var).
  743safe_primitive(system:nb_getval(_,_)).
  744safe_primitive('$syspreds':nb_setval(Var,_)) :-
  745    safe_global_var(Var).
  746safe_primitive(system:nb_linkval(Var,_)) :-
  747    safe_global_var(Var).
  748safe_primitive(system:nb_current(_,_)).
  749                                        % database
  750safe_primitive(system:assert(X)) :-
  751    safe_assert(X).
  752                                        % Output
  753safe_primitive(system:writeln(_)).
  754safe_primitive('$messages':print_message(_,_)).
  755
  756                                        % Stack limits (down)
  757safe_primitive('$syspreds':set_prolog_stack(Stack, limit(ByteExpr))) :-
  758    nonvar(Stack),
  759    stack_name(Stack),
  760    catch(Bytes is ByteExpr, _, fail),
  761    prolog_stack_property(Stack, limit(Current)),
  762    Bytes =< Current.
  763
  764stack_name(global).
  765stack_name(local).
  766stack_name(trail).
  767
  768safe_primitive('$tabling':abolish_all_tables).
  769safe_primitive('$tabling':'$wrap_tabled'(Module:_Head, _Mode)) :-
  770    prolog_load_context(module, Module),
  771    !.
  772safe_primitive('$tabling':'$moded_wrap_tabled'(Module:_Head,_,_,_,_)) :-
  773    prolog_load_context(module, Module),
  774    !.
  775
  776
  777% use_module/1.  We only allow for .pl files that are loaded from
  778% relative paths that do not contain /../
  779
  780safe_primitive(system:use_module(Spec, _Import)) :-
  781    safe_primitive(system:use_module(Spec)).
  782safe_primitive(system:load_files(Spec, Options)) :-
  783    safe_primitive(system:use_module(Spec)),
  784    maplist(safe_load_file_option, Options).
  785safe_primitive(system:use_module(Spec)) :-
  786    ground(Spec),
  787    (   atom(Spec)
  788    ->  Path = Spec
  789    ;   Spec =.. [_Alias, Segments],
  790        phrase(segments_to_path(Segments), List),
  791        atomic_list_concat(List, Path)
  792    ),
  793    \+ is_absolute_file_name(Path),
  794    \+ sub_atom(Path, _, _, _, '/../'),
  795    absolute_file_name(Spec, AbsFile,
  796                       [ access(read),
  797                         file_type(prolog),
  798                         file_errors(fail)
  799                       ]),
  800    file_name_extension(_, Ext, AbsFile),
  801    save_extension(Ext).
  802
  803% support predicates for safe_primitive, validating the safety of
  804% arguments to certain goals.
  805
  806segments_to_path(A/B) -->
  807    !,
  808    segments_to_path(A),
  809    [/],
  810    segments_to_path(B).
  811segments_to_path(X) -->
  812    [X].
  813
  814save_extension(pl).
  815
  816safe_load_file_option(if(changed)).
  817safe_load_file_option(if(not_loaded)).
  818safe_load_file_option(must_be_module(_)).
  819safe_load_file_option(optimise(_)).
  820safe_load_file_option(silent(_)).
  821
  822%!  safe_assert(+Term) is semidet.
  823%
  824%   True if assert(Term) is safe,  which   means  it  asserts in the
  825%   current module. Cross-module asserts are   considered unsafe. We
  826%   only allow for adding facts. In theory,  we could also allow for
  827%   rules if we prove the safety of the body.
  828
  829safe_assert(C) :- cyclic_term(C), !, fail.
  830safe_assert(X) :- var(X), !, fail.
  831safe_assert(_Head:-_Body) :- !, fail.
  832safe_assert(_:_) :- !, fail.
  833safe_assert(_).
  834
  835%!  safe_clause(+Head) is semidet.
  836%
  837%   Consider a call to clause safe if  it   does  not try to cross a
  838%   module boundary. Cross-module usage  of   clause/2  can  extract
  839%   private information from other modules.
  840
  841safe_clause(H) :- var(H), !.
  842safe_clause(_:_) :- !, fail.
  843safe_clause(_).
  844
  845
  846%!  safe_global_var(+Name) is semidet.
  847%
  848%   True if Name  is  a  global   variable  to  which  assertion  is
  849%   considered safe.
  850
  851safe_global_var(Name) :-
  852    var(Name),
  853    !,
  854    instantiation_error(Name).
  855safe_global_var(Name) :-
  856    safe_global_variable(Name).
  857
  858%!  safe_global_variable(Name) is semidet.
  859%
  860%   Declare the given global variable safe to write to.
  861
  862
  863%!  safe_meta(+Goal, -Called:list(callable)) is semidet.
  864%
  865%   Hook. True if Goal is a   meta-predicate that is considered safe
  866%   iff all elements in Called are safe.
  867
  868safe_meta(system:put_attr(V,M,A), Called) :-
  869    !,
  870    (   atom(M)
  871    ->  attr_hook_predicates([ attr_unify_hook(A, _),
  872                               attribute_goals(V,_,_),
  873                               project_attributes(_,_)
  874                             ], M, Called)
  875    ;   instantiation_error(M)
  876    ).
  877safe_meta(system:with_output_to(Output, G), [G]) :-
  878    safe_output(Output),
  879    !.
  880safe_meta(system:format(Format, Args), Calls) :-
  881    format_calls(Format, Args, Calls).
  882safe_meta(system:format(Output, Format, Args), Calls) :-
  883    safe_output(Output),
  884    format_calls(Format, Args, Calls).
  885safe_meta(prolog_debug:debug(_Term, Format, Args), Calls) :-
  886    format_calls(Format, Args, Calls).
  887safe_meta(system:set_prolog_flag(Flag, Value), []) :-
  888    atom(Flag),
  889    safe_prolog_flag(Flag, Value).
  890safe_meta('$attvar':freeze(_Var,Goal), [Goal]).
  891safe_meta(phrase(NT,Xs0,Xs), [Goal]) :- % phrase/2,3 and call_dcg/2,3
  892    expand_nt(NT,Xs0,Xs,Goal).
  893safe_meta(phrase(NT,Xs0), [Goal]) :-
  894    expand_nt(NT,Xs0,[],Goal).
  895safe_meta('$dcg':call_dcg(NT,Xs0,Xs), [Goal]) :-
  896    expand_nt(NT,Xs0,Xs,Goal).
  897safe_meta('$dcg':call_dcg(NT,Xs0), [Goal]) :-
  898    expand_nt(NT,Xs0,[],Goal).
  899safe_meta('$tabling':abolish_table_subgoals(V), []) :-
  900    \+ qualified(V).
  901safe_meta('$tabling':current_table(V, _), []) :-
  902    \+ qualified(V).
  903safe_meta('$tabling':tnot(G), [G]).
  904safe_meta('$tabling':not_exists(G), [G]).
  905
  906qualified(V) :-
  907    nonvar(V),
  908    V = _:_.
  909
  910%!  attr_hook_predicates(+Hooks0, +Module, -Hooks) is det.
  911%
  912%   Filter the defined hook implementations.   This  is safe because
  913%   (1) calling an undefined predicate is   not  a safety issue, (2)
  914%   the  user  an  only  assert  in  the  current  module  and  only
  915%   predicates that have a safe body. This avoids the need to define
  916%   attribute hooks solely for the purpose of making them safe.
  917
  918attr_hook_predicates([], _, []).
  919attr_hook_predicates([H|T], M, Called) :-
  920    (   predicate_property(M:H, defined)
  921    ->  Called = [M:H|Rest]
  922    ;   Called = Rest
  923    ),
  924    attr_hook_predicates(T, M, Rest).
  925
  926
  927%!  expand_nt(+NT, ?Xs0, ?Xs, -NewGoal)
  928%
  929%   Similar to expand_phrase/2, but we do   throw  errors instead of
  930%   failing if NT is not sufficiently instantiated.
  931
  932expand_nt(NT, _Xs0, _Xs, _NewGoal) :-
  933    strip_module(NT, _, Plain),
  934    var(Plain),
  935    !,
  936    instantiation_error(Plain).
  937expand_nt(NT, Xs0, Xs, NewGoal) :-
  938    dcg_translate_rule((pseudo_nt --> NT),
  939                       (pseudo_nt(Xs0c,Xsc) :- NewGoal0)),
  940    (   var(Xsc), Xsc \== Xs0c
  941    ->  Xs = Xsc, NewGoal1 = NewGoal0
  942    ;   NewGoal1 = (NewGoal0, Xsc = Xs)
  943    ),
  944    (   var(Xs0c)
  945    ->  Xs0 = Xs0c,
  946        NewGoal = NewGoal1
  947    ;   NewGoal = ( Xs0 = Xs0c, NewGoal1 )
  948    ).
  949
  950%!  safe_meta_call(+Goal, +Context, -Called:list(callable)) is semidet.
  951%
  952%   True if Goal is a   meta-predicate that is considered safe
  953%   iff all elements in Called are safe.
  954
  955safe_meta_call(Goal, _, _Called) :-
  956    debug(sandbox(meta), 'Safe meta ~p?', [Goal]),
  957    fail.
  958safe_meta_call(Goal, Context, Called) :-
  959    (   safe_meta(Goal, Called)
  960    ->  true
  961    ;   safe_meta(Goal, Context, Called)
  962    ),
  963    !.     % call hook
  964safe_meta_call(Goal, _, Called) :-
  965    Goal = M:Plain,
  966    compound(Plain),
  967    compound_name_arity(Plain, Name, Arity),
  968    safe_meta_predicate(M:Name/Arity),
  969    predicate_property(Goal, meta_predicate(Spec)),
  970    !,
  971    called(Spec, Plain, Called).
  972safe_meta_call(M:Goal, _, Called) :-
  973    !,
  974    generic_goal(Goal, Gen),
  975    safe_meta(M:Gen),
  976    called(Gen, Goal, Called).
  977safe_meta_call(Goal, _, Called) :-
  978    generic_goal(Goal, Gen),
  979    safe_meta(Gen),
  980    called(Gen, Goal, Called).
  981
  982called(Gen, Goal, Called) :-
  983    compound_name_arity(Goal, _, Arity),
  984    called(1, Arity, Gen, Goal, Called).
  985
  986called(I, Arity, Gen, Goal, Called) :-
  987    I =< Arity,
  988    !,
  989    arg(I, Gen, Spec),
  990    (   calling_meta_spec(Spec)
  991    ->  arg(I, Goal, Called0),
  992        extend(Spec, Called0, G),
  993        Called = [G|Rest]
  994    ;   Called = Rest
  995    ),
  996    I2 is I+1,
  997    called(I2, Arity, Gen, Goal, Rest).
  998called(_, _, _, _, []).
  999
 1000generic_goal(G, Gen) :-
 1001    functor(G, Name, Arity),
 1002    functor(Gen, Name, Arity).
 1003
 1004calling_meta_spec(V) :- var(V), !, fail.
 1005calling_meta_spec(I) :- integer(I), !.
 1006calling_meta_spec(^).
 1007calling_meta_spec(//).
 1008
 1009
 1010extend(^, G, Plain) :-
 1011    !,
 1012    strip_existential(G, Plain).
 1013extend(//, DCG, Goal) :-
 1014    !,
 1015    (   expand_phrase(call_dcg(DCG,_,_), Goal)
 1016    ->  true
 1017    ;   instantiation_error(DCG)    % Ask more instantiation.
 1018    ).                              % might not help, but does not harm.
 1019extend(0, G, G) :- !.
 1020extend(I, M:G0, M:G) :-
 1021    !,
 1022    G0 =.. List,
 1023    length(Extra, I),
 1024    append(List, Extra, All),
 1025    G =.. All.
 1026extend(I, G0, G) :-
 1027    G0 =.. List,
 1028    length(Extra, I),
 1029    append(List, Extra, All),
 1030    G =.. All.
 1031
 1032strip_existential(Var, Var) :-
 1033    var(Var),
 1034    !.
 1035strip_existential(M:G0, M:G) :-
 1036    !,
 1037    strip_existential(G0, G).
 1038strip_existential(_^G0, G) :-
 1039    !,
 1040    strip_existential(G0, G).
 1041strip_existential(G, G).
 1042
 1043%!  safe_meta(?Template).
 1044
 1045safe_meta((0,0)).
 1046safe_meta((0;0)).
 1047safe_meta((0->0)).
 1048safe_meta(system:(0*->0)).
 1049safe_meta(catch(0,*,0)).
 1050safe_meta(findall(*,0,*)).
 1051safe_meta('$bags':findall(*,0,*,*)).
 1052safe_meta(setof(*,^,*)).
 1053safe_meta(bagof(*,^,*)).
 1054safe_meta('$bags':findnsols(*,*,0,*)).
 1055safe_meta('$bags':findnsols(*,*,0,*,*)).
 1056safe_meta(system:call_cleanup(0,0)).
 1057safe_meta(system:setup_call_cleanup(0,0,0)).
 1058safe_meta(system:setup_call_catcher_cleanup(0,0,*,0)).
 1059safe_meta('$attvar':call_residue_vars(0,*)).
 1060safe_meta('$syspreds':call_with_inference_limit(0,*,*)).
 1061safe_meta('$syspreds':call_with_depth_limit(0,*,*)).
 1062safe_meta('$syspreds':undo(0)).
 1063safe_meta(^(*,0)).
 1064safe_meta(\+(0)).
 1065safe_meta(call(0)).
 1066safe_meta(call(1,*)).
 1067safe_meta(call(2,*,*)).
 1068safe_meta(call(3,*,*,*)).
 1069safe_meta(call(4,*,*,*,*)).
 1070safe_meta(call(5,*,*,*,*,*)).
 1071safe_meta(call(6,*,*,*,*,*,*)).
 1072safe_meta('$tabling':start_tabling(*,0)).
 1073safe_meta('$tabling':start_tabling(*,0,*,*)).
 1074safe_meta(wfs:call_delays(0,*)).
 1075
 1076%!  safe_output(+Output)
 1077%
 1078%   True if something is a safe output argument for with_output_to/2
 1079%   and friends. We do not want writing to streams.
 1080
 1081safe_output(Output) :-
 1082    var(Output),
 1083    !,
 1084    instantiation_error(Output).
 1085safe_output(atom(_)).
 1086safe_output(string(_)).
 1087safe_output(codes(_)).
 1088safe_output(codes(_,_)).
 1089safe_output(chars(_)).
 1090safe_output(chars(_,_)).
 1091safe_output(current_output).
 1092safe_output(current_error).
 1093
 1094%!  format_calls(+Format, +FormatArgs, -Calls)
 1095%
 1096%   Find ~@ calls from Format and Args.
 1097
 1098:- public format_calls/3.                       % used in pengines_io
 1099
 1100format_calls(Format, _Args, _Calls) :-
 1101    var(Format),
 1102    !,
 1103    instantiation_error(Format).
 1104format_calls(Format, Args, Calls) :-
 1105    format_types(Format, Types),
 1106    (   format_callables(Types, Args, Calls)
 1107    ->  true
 1108    ;   throw(error(format_error(Format, Types, Args), _))
 1109    ).
 1110
 1111format_callables([], [], []).
 1112format_callables([callable|TT], [G|TA], [G|TG]) :-
 1113    !,
 1114    format_callables(TT, TA, TG).
 1115format_callables([_|TT], [_|TA], TG) :-
 1116    !,
 1117    format_callables(TT, TA, TG).
 1118
 1119
 1120                 /*******************************
 1121                 *    SAFE COMPILATION HOOKS    *
 1122                 *******************************/
 1123
 1124:- multifile
 1125    prolog:sandbox_allowed_directive/1,
 1126    prolog:sandbox_allowed_goal/1,
 1127    prolog:sandbox_allowed_expansion/1. 1128
 1129%!  prolog:sandbox_allowed_directive(:G) is det.
 1130%
 1131%   Throws an exception if G is not considered a safe directive.
 1132
 1133prolog:sandbox_allowed_directive(Directive) :-
 1134    debug(sandbox(directive), 'Directive: ~p', [Directive]),
 1135    fail.
 1136prolog:sandbox_allowed_directive(Directive) :-
 1137    safe_directive(Directive),
 1138    !.
 1139prolog:sandbox_allowed_directive(M:PredAttr) :-
 1140    \+ prolog_load_context(module, M),
 1141    !,
 1142    debug(sandbox(directive), 'Cross-module directive', []),
 1143    permission_error(execute, sandboxed_directive, (:- M:PredAttr)).
 1144prolog:sandbox_allowed_directive(M:PredAttr) :-
 1145    safe_pattr(PredAttr),
 1146    !,
 1147    PredAttr =.. [Attr, Preds],
 1148    (   safe_pattr(Preds, Attr)
 1149    ->  true
 1150    ;   permission_error(execute, sandboxed_directive, (:- M:PredAttr))
 1151    ).
 1152prolog:sandbox_allowed_directive(_:Directive) :-
 1153    safe_source_directive(Directive),
 1154    !.
 1155prolog:sandbox_allowed_directive(_:Directive) :-
 1156    directive_loads_file(Directive, File),
 1157    !,
 1158    safe_path(File).
 1159prolog:sandbox_allowed_directive(G) :-
 1160    safe_goal(G).
 1161
 1162%!  safe_directive(:Directive) is semidet.
 1163%
 1164%   Hook to declare additional directives as safe. The argument is a
 1165%   term `Module:Directive` (without =|:-|= wrapper).  In almost all
 1166%   cases, the implementation must verify that   the `Module` is the
 1167%   current load context as illustrated  below.   This  check is not
 1168%   performed by the system to  allow   for  cases  where particular
 1169%   cross-module directives are allowed.
 1170%
 1171%     ==
 1172%     sandbox:safe_directive(M:Directive) :-
 1173%         prolog_load_context(module, M),
 1174%         ...
 1175%     ==
 1176
 1177
 1178safe_pattr(dynamic(_)).
 1179safe_pattr(thread_local(_)).
 1180safe_pattr(volatile(_)).
 1181safe_pattr(discontiguous(_)).
 1182safe_pattr(multifile(_)).
 1183safe_pattr(public(_)).
 1184safe_pattr(meta_predicate(_)).
 1185safe_pattr(table(_)).
 1186safe_pattr(non_terminal(_)).
 1187
 1188safe_pattr(Var, _) :-
 1189    var(Var),
 1190    !,
 1191    instantiation_error(Var).
 1192safe_pattr((A,B), Attr) :-
 1193    !,
 1194    safe_pattr(A, Attr),
 1195    safe_pattr(B, Attr).
 1196safe_pattr(M:G, Attr) :-
 1197    !,
 1198    (   atom(M),
 1199        prolog_load_context(module, M)
 1200    ->  true
 1201    ;   Goal =.. [Attr,M:G],
 1202        permission_error(directive, sandboxed, (:- Goal))
 1203    ).
 1204safe_pattr(_, _).
 1205
 1206safe_source_directive(op(_,_,Name)) :-
 1207    !,
 1208    (   atom(Name)
 1209    ->  true
 1210    ;   is_list(Name),
 1211        maplist(atom, Name)
 1212    ).
 1213safe_source_directive(set_prolog_flag(Flag, Value)) :-
 1214    !,
 1215    atom(Flag), ground(Value),
 1216    safe_prolog_flag(Flag, Value).
 1217safe_source_directive(style_check(_)).
 1218safe_source_directive(initialization(_)).   % Checked at runtime
 1219safe_source_directive(initialization(_,_)). % Checked at runtime
 1220
 1221directive_loads_file(use_module(library(X)), X).
 1222directive_loads_file(use_module(library(X), _Imports), X).
 1223directive_loads_file(load_files(library(X), _Options), X).
 1224directive_loads_file(ensure_loaded(library(X)), X).
 1225directive_loads_file(include(X), X).
 1226
 1227safe_path(X) :-
 1228    var(X),
 1229    !,
 1230    instantiation_error(X).
 1231safe_path(X) :-
 1232    (   atom(X)
 1233    ;   string(X)
 1234    ),
 1235    !,
 1236    \+ sub_atom(X, 0, _, 0, '..'),
 1237    \+ sub_atom(X, 0, _, _, '/'),
 1238    \+ sub_atom(X, 0, _, _, '../'),
 1239    \+ sub_atom(X, _, _, 0, '/..'),
 1240    \+ sub_atom(X, _, _, _, '/../').
 1241safe_path(A/B) :-
 1242    !,
 1243    safe_path(A),
 1244    safe_path(B).
 1245
 1246
 1247%!  safe_prolog_flag(+Flag, +Value) is det.
 1248%
 1249%   True if it is safe to set the flag Flag to Value.
 1250%
 1251%   @tbd    If we can avoid that files are loaded after changing
 1252%           this flag, we can allow for more flags.  The syntax
 1253%           flags are safe because they are registered with the
 1254%           module.
 1255
 1256% misc
 1257safe_prolog_flag(generate_debug_info, _).
 1258safe_prolog_flag(optimise, _).
 1259safe_prolog_flag(occurs_check, _).
 1260% syntax
 1261safe_prolog_flag(var_prefix, _).
 1262safe_prolog_flag(double_quotes, _).
 1263safe_prolog_flag(back_quotes, _).
 1264safe_prolog_flag(rational_syntax, _).
 1265% arithmetic
 1266safe_prolog_flag(prefer_rationals, _).
 1267safe_prolog_flag(float_overflow, _).
 1268safe_prolog_flag(float_zero_div, _).
 1269safe_prolog_flag(float_undefined, _).
 1270safe_prolog_flag(float_underflow, _).
 1271safe_prolog_flag(float_rounding, _).
 1272safe_prolog_flag(float_rounding, _).
 1273safe_prolog_flag(max_rational_size, _).
 1274safe_prolog_flag(max_rational_size_action, _).
 1275% tabling
 1276safe_prolog_flag(max_answers_for_subgoal,_).
 1277safe_prolog_flag(max_answers_for_subgoal_action,_).
 1278safe_prolog_flag(max_table_answer_size,_).
 1279safe_prolog_flag(max_table_answer_size_action,_).
 1280safe_prolog_flag(max_table_subgoal_size,_).
 1281safe_prolog_flag(max_table_subgoal_size_action,_).
 1282
 1283
 1284%!  prolog:sandbox_allowed_expansion(:G) is det.
 1285%
 1286%   Throws an exception if G  is   not  considered  a safe expansion
 1287%   goal. This deals with call-backs from the compiler for
 1288%
 1289%     - goal_expansion/2
 1290%     - term_expansion/2
 1291%     - Quasi quotations.
 1292%
 1293%   Our assumption is that external expansion rules are coded safely
 1294%   and we only need to be  careful   if  the sandboxed code defines
 1295%   expansion rules.
 1296
 1297prolog:sandbox_allowed_expansion(M:G) :-
 1298    prolog_load_context(module, M),
 1299    !,
 1300    debug(sandbox(expansion), 'Expand in ~p: ~p', [M, G]),
 1301    safe_goal(M:G).
 1302prolog:sandbox_allowed_expansion(_,_).
 1303
 1304%!  prolog:sandbox_allowed_goal(:G) is det.
 1305%
 1306%   Throw an exception if it is not safe to call G
 1307
 1308prolog:sandbox_allowed_goal(G) :-
 1309    safe_goal(G).
 1310
 1311
 1312                 /*******************************
 1313                 *            MESSAGES          *
 1314                 *******************************/
 1315
 1316:- multifile
 1317    prolog:message//1,
 1318    prolog:message_context//1,
 1319    prolog:error_message//1. 1320
 1321prolog:message(error(instantiation_error, Context)) -->
 1322    { nonvar(Context),
 1323      Context = sandbox(_Goal,Parents),
 1324      numbervars(Context, 1, _)
 1325    },
 1326    [ 'Sandbox restriction!'-[], nl,
 1327      'Could not derive which predicate may be called from'-[]
 1328    ],
 1329    (   { Parents == [] }
 1330    ->  [ 'Search space too large'-[] ]
 1331    ;   callers(Parents, 10)
 1332    ).
 1333
 1334prolog:message_context(sandbox(_G, [])) --> !.
 1335prolog:message_context(sandbox(_G, Parents)) -->
 1336    [ nl, 'Reachable from:'-[] ],
 1337    callers(Parents, 10).
 1338
 1339callers([], _) --> !.
 1340callers(_,  0) --> !.
 1341callers([G|Parents], Level) -->
 1342    { NextLevel is Level-1
 1343    },
 1344    [ nl, '\t  ~p'-[G] ],
 1345    callers(Parents, NextLevel).
 1346
 1347prolog:message(bad_safe_declaration(Goal, File, Line)) -->
 1348    [ '~w:~d: Invalid safe_primitive/1 declaration: ~p'-
 1349      [File, Line, Goal] ].
 1350
 1351prolog:error_message(format_error(Format, Types, Args)) -->
 1352    format_error(Format, Types, Args).
 1353
 1354format_error(Format, Types, Args) -->
 1355    { length(Types, TypeLen),
 1356      length(Args, ArgsLen),
 1357      (   TypeLen > ArgsLen
 1358      ->  Problem = 'not enough'
 1359      ;   Problem = 'too many'
 1360      )
 1361    },
 1362    [ 'format(~q): ~w arguments (found ~w, need ~w)'-
 1363      [Format, Problem, ArgsLen, TypeLen]
 1364    ]