/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2013-2023, VU University Amsterdam CWI, Amsterdam SWI-Prolog Solutions b.v All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module(sandbox, [ safe_goal/1, % :Goal safe_call/1 % :Goal ]). :- use_module(library(apply_macros),[expand_phrase/2]). :- use_module(library(apply),[maplist/2]). :- use_module(library(assoc),[empty_assoc/1,get_assoc/3,put_assoc/4]). :- use_module(library(debug),[debug/3,debugging/1]). :- use_module(library(error), [ must_be/2, instantiation_error/1, type_error/2, permission_error/3 ]). :- use_module(library(lists),[append/3]). :- use_module(library(prolog_format),[format_types/2]). :- multifile safe_primitive/1, % Goal safe_meta_predicate/1, % Name/Arity safe_meta/2, % Goal, Calls safe_meta/3, % Goal, Context, Calls safe_global_variable/1, % Name safe_directive/1, % Module:Goal safe_prolog_flag/2. % +Name, +Value % :- debug(sandbox). /** Sandboxed Prolog code Prolog is a full-featured Turing complete programming language in which it is easy to write programs that can harm your computer. On the other hand, Prolog is a logic based _query language_ which can be exploited to query data interactively from, e.g., the web. This library provides safe_goal/1, which determines whether it is safe to call its argument. @tbd Handling of ^ and // meta predicates @tbd Complete set of whitelisted predicates @see http://www.swi-prolog.org/pldoc/package/pengines.html */ :- meta_predicate safe_goal(:), safe_call(0). %! safe_call(:Goal) % % Call Goal if it complies with the sandboxing rules. Before % calling Goal, it performs expand_goal/2, followed by % safe_goal/1. Expanding is done explicitly because situations in % which safe_call/1 typically concern goals that are not known at % compile time. % % @see safe_goal/1. safe_call(Goal0) :- expand_goal(Goal0, Goal), safe_goal(Goal), call(Goal). %! safe_goal(:Goal) is det. % % True if calling Goal provides no security risc. This implies % that: % % - The call-graph can be fully expanded. Full expansion *stops* % if a meta-goal is found for which we cannot determine enough % details to know which predicate will be called. % % - All predicates referenced from the fully expanded are % whitelisted by the predicate safe_primitive/1 and safe_meta/2. % % - It is not allowed to make explicitly qualified calls into % modules to predicates that are not exported or declared % public. % % @error instantiation_error if the analysis encounters a term in % a callable position that is insufficiently instantiated % to determine the predicate called. % @error permission_error(call, sandboxed, Goal) if Goal is in % the call-tree and not white-listed. safe_goal(M:Goal) :- empty_assoc(Safe0), catch(safe(Goal, M, [], Safe0, _), E, true), !, nb_delete(sandbox_last_error), ( var(E) -> true ; throw(E) ). safe_goal(_) :- nb_current(sandbox_last_error, E), !, nb_delete(sandbox_last_error), throw(E). safe_goal(G) :- debug(sandbox(fail), 'safe_goal/1 failed for ~p', [G]), throw(error(instantiation_error, sandbox(G, []))). %! safe(+Goal, +Module, +Parents, +Safe0, -Safe) is semidet. % % Is true if Goal can only call safe code. safe(V, _, Parents, _, _) :- var(V), !, Error = error(instantiation_error, sandbox(V, Parents)), nb_setval(sandbox_last_error, Error), throw(Error). safe(M:G, _, Parents, Safe0, Safe) :- !, must_be(atom, M), must_be(callable, G), known_module(M:G, Parents), ( predicate_property(M:G, imported_from(M2)) -> true ; M2 = M ), ( ( safe_primitive(M2:G) ; safe_primitive(G), predicate_property(G, iso) ) -> Safe = Safe0 ; ( predicate_property(M:G, exported) ; predicate_property(M:G, public) ; predicate_property(M:G, multifile) ; predicate_property(M:G, iso) ; memberchk(M:_, Parents) ) -> safe(G, M, Parents, Safe0, Safe) ; throw(error(permission_error(call, sandboxed, M:G), sandbox(M:G, Parents))) ). safe(G, _, Parents, _, _) :- debugging(sandbox(show)), length(Parents, Level), debug(sandbox(show), '[~D] SAFE ~q?', [Level, G]), fail. safe(G, _, Parents, Safe, Safe) :- catch(safe_primitive(G), error(instantiation_error, _), rethrow_instantition_error([G|Parents])), predicate_property(G, iso), !. safe(G, M, Parents, Safe, Safe) :- known_module(M:G, Parents), ( predicate_property(M:G, imported_from(M2)) -> true ; M2 = M ), ( catch(safe_primitive(M2:G), error(instantiation_error, _), rethrow_instantition_error([M2:G|Parents])) ; predicate_property(M2:G, number_of_rules(0)) ), !. safe(G, M, Parents, Safe0, Safe) :- predicate_property(G, iso), safe_meta_call(G, M, Called), !, add_iso_parent(G, Parents, Parents1), safe_list(Called, M, Parents1, Safe0, Safe). safe(G, M, Parents, Safe0, Safe) :- ( predicate_property(M:G, imported_from(M2)) -> true ; M2 = M ), safe_meta_call(M2:G, M, Called), !, safe_list(Called, M, Parents, Safe0, Safe). safe(G, M, Parents, Safe0, Safe) :- goal_id(M:G, Id, Gen), ( get_assoc(Id, Safe0, _) -> Safe = Safe0 ; put_assoc(Id, Safe0, true, Safe1), ( Gen == M:G -> safe_clauses(Gen, M, [Id|Parents], Safe1, Safe) ; catch(safe_clauses(Gen, M, [Id|Parents], Safe1, Safe), error(instantiation_error, Ctx), unsafe(Parents, Ctx)) ) ), !. safe(G, M, Parents, _, _) :- debug(sandbox(fail), 'safe/1 failed for ~p (parents:~p)', [M:G, Parents]), fail. unsafe(Parents, Var) :- var(Var), !, nb_setval(sandbox_last_error, error(instantiation_error, sandbox(_, Parents))), fail. unsafe(_Parents, Ctx) :- Ctx = sandbox(_,_), nb_setval(sandbox_last_error, error(instantiation_error, Ctx)), fail. rethrow_instantition_error(Parents) :- throw(error(instantiation_error, sandbox(_, Parents))). safe_clauses(G, M, Parents, Safe0, Safe) :- predicate_property(M:G, interpreted), def_module(M:G, MD:QG), \+ compiled(MD:QG), !, findall(Ref-Body, clause(MD:QG, Body, Ref), Bodies), safe_bodies(Bodies, MD, Parents, Safe0, Safe). safe_clauses(G, M, [_|Parents], _, _) :- predicate_property(M:G, visible), !, throw(error(permission_error(call, sandboxed, G), sandbox(M:G, Parents))). safe_clauses(_, _, [G|Parents], _, _) :- throw(error(existence_error(procedure, G), sandbox(G, Parents))). compiled(system:(@(_,_))). known_module(M:_, _) :- current_module(M), !. known_module(M:G, Parents) :- throw(error(permission_error(call, sandboxed, M:G), sandbox(M:G, Parents))). add_iso_parent(G, Parents, Parents) :- is_control(G), !. add_iso_parent(G, Parents, [G|Parents]). is_control((_,_)). is_control((_;_)). is_control((_->_)). is_control((_*->_)). is_control(\+(_)). %! safe_bodies(+Bodies, +Module, +Parents, +Safe0, -Safe) % % Verify the safety of bodies. If a clause was compiled with a % qualified module, we consider execution of the body in a % different module _not_ a cross-module call. safe_bodies([], _, _, Safe, Safe). safe_bodies([Ref-H|T], M, Parents, Safe0, Safe) :- ( H = M2:H2, nonvar(M2), clause_property(Ref, module(M2)) -> copy_term(H2, H3), CM = M2 ; copy_term(H, H3), CM = M ), safe(H3, CM, Parents, Safe0, Safe1), safe_bodies(T, M, Parents, Safe1, Safe). def_module(M:G, MD:QG) :- predicate_property(M:G, imported_from(MD)), !, meta_qualify(MD:G, M, QG). def_module(M:G, M:QG) :- meta_qualify(M:G, M, QG). %! safe_list(+Called, +Module, +Parents, +Safe0, -Safe) % % Processed objects called through meta predicates. If the called % object is in our current context we remove the module % qualification to avoid the cross-module check. safe_list([], _, _, Safe, Safe). safe_list([H|T], M, Parents, Safe0, Safe) :- ( H = M2:H2, M == M2 % in our context -> copy_term(H2, H3) ; copy_term(H, H3) % cross-module call ), safe(H3, M, Parents, Safe0, Safe1), safe_list(T, M, Parents, Safe1, Safe). %! meta_qualify(:G, +M, -QG) is det. % % Perform meta-qualification of the goal-argument meta_qualify(MD:G, M, QG) :- predicate_property(MD:G, meta_predicate(Head)), !, G =.. [Name|Args], Head =.. [_|Q], qualify_args(Q, M, Args, QArgs), QG =.. [Name|QArgs]. meta_qualify(_:G, _, G). qualify_args([], _, [], []). qualify_args([H|T], M, [A|AT], [Q|QT]) :- qualify_arg(H, M, A, Q), qualify_args(T, M, AT, QT). qualify_arg(S, M, A, Q) :- q_arg(S), !, qualify(A, M, Q). qualify_arg(_, _, A, A). q_arg(I) :- integer(I), !. q_arg(:). q_arg(^). q_arg(//). qualify(A, M, MZ:Q) :- strip_module(M:A, MZ, Q). %! goal_id(:Goal, -Id, -Gen) is nondet. % % Generate an identifier for the goal proven to be safe. We % first try to prove the most general form of the goal. If % this fails, we try to prove more specific versions. % % @tbd Do step-by-step generalisation instead of the current % two levels (most general and most specific). % @tbd We could also use variant_sha1 for the goal ids. goal_id(M:Goal, M:Id, Gen) :- !, goal_id(Goal, Id, Gen). goal_id(Var, _, _) :- var(Var), !, instantiation_error(Var). goal_id(Atom, Atom, Atom) :- atom(Atom), !. goal_id(Term, _, _) :- \+ compound(Term), !, type_error(callable, Term). goal_id(Term, Skolem, Gen) :- % most general form compound_name_arity(Term, Name, Arity), compound_name_arity(Skolem, Name, Arity), compound_name_arity(Gen, Name, Arity), copy_goal_args(1, Term, Skolem, Gen), ( Gen =@= Term -> ! % No more specific one; we can commit ; true ), numbervars(Skolem, 0, _). goal_id(Term, Skolem, Term) :- % most specific form debug(sandbox(specify), 'Retrying with ~p', [Term]), copy_term(Term, Skolem), numbervars(Skolem, 0, _). %! copy_goal_args(+I, +Term, +Skolem, +Gen) is det. % % Create the most general form, but keep module qualified % arguments because they will likely be called anyway. copy_goal_args(I, Term, Skolem, Gen) :- arg(I, Term, TA), !, arg(I, Skolem, SA), arg(I, Gen, GA), copy_goal_arg(TA, SA, GA), I2 is I + 1, copy_goal_args(I2, Term, Skolem, Gen). copy_goal_args(_, _, _, _). copy_goal_arg(Arg, SArg, Arg) :- copy_goal_arg(Arg), !, copy_term(Arg, SArg). copy_goal_arg(_, _, _). copy_goal_arg(Var) :- var(Var), !, fail. copy_goal_arg(_:_). %! verify_safe_declaration(+Decl) % % See whether a safe declaration makes sense. That is, the % predicate must be defined (such that the attacker cannot define % the predicate), must be sufficiently instantiated and only ISO % declared predicates may omit a module qualification. % % @tbd Verify safe_meta/2 declarations. It is a bit less clear % what the rules are. term_expansion(safe_primitive(Goal), Term) :- ( verify_safe_declaration(Goal) -> Term = safe_primitive(Goal) ; Term = [] ). term_expansion((safe_primitive(Goal) :- Body), Term) :- ( verify_safe_declaration(Goal) -> Term = (safe_primitive(Goal) :- Body) ; Term = [] ). system:term_expansion(sandbox:safe_primitive(Goal), Term) :- \+ current_prolog_flag(xref, true), ( verify_safe_declaration(Goal) -> Term = sandbox:safe_primitive(Goal) ; Term = [] ). system:term_expansion((sandbox:safe_primitive(Goal) :- Body), Term) :- \+ current_prolog_flag(xref, true), ( verify_safe_declaration(Goal) -> Term = (sandbox:safe_primitive(Goal) :- Body) ; Term = [] ). verify_safe_declaration(Var) :- var(Var), !, instantiation_error(Var). verify_safe_declaration(Module:Goal) :- !, must_be(atom, Module), must_be(callable, Goal), ( ok_meta(Module:Goal) -> true ; ( predicate_property(Module:Goal, visible) -> true ; predicate_property(Module:Goal, foreign) ), \+ predicate_property(Module:Goal, imported_from(_)), \+ predicate_property(Module:Goal, meta_predicate(_)) -> true ; permission_error(declare, safe_goal, Module:Goal) ). verify_safe_declaration(Goal) :- must_be(callable, Goal), ( predicate_property(system:Goal, iso), \+ predicate_property(system:Goal, meta_predicate()) -> true ; permission_error(declare, safe_goal, Goal) ). ok_meta(system:assert(_)). ok_meta(system:load_files(_,_)). ok_meta(system:use_module(_,_)). ok_meta(system:use_module(_)). ok_meta('$syspreds':predicate_property(_,_)). verify_predefined_safe_declarations :- forall(clause(safe_primitive(Goal), _Body, Ref), ( E = error(F,_), catch(verify_safe_declaration(Goal), E, true), ( nonvar(F) -> clause_property(Ref, file(File)), clause_property(Ref, line_count(Line)), print_message(error, bad_safe_declaration(Goal, File, Line)) ; true ) )). :- initialization(verify_predefined_safe_declarations, now). %! safe_primitive(?Goal) is nondet. % % True if Goal is safe to call (i.e., cannot access dangerous % system-resources and cannot upset other parts of the Prolog % process). There are two types of facts. ISO built-ins are % declared without a module prefix. This is safe because it is not % allowed to (re-)define these primitives (i.e., give them an % unsafe implementation) and the way around % (redefine_system_predicate/1) is unsafe. The other group are % module-qualified and only match if the system infers that the % predicate is imported from the given module. % First, all ISO system predicates that are considered safe safe_primitive(true). safe_primitive(fail). safe_primitive(system:false). safe_primitive(repeat). safe_primitive(!). % types safe_primitive(var(_)). safe_primitive(nonvar(_)). safe_primitive(system:attvar(_)). safe_primitive(integer(_)). safe_primitive(float(_)). :- if(current_predicate(rational/1)). safe_primitive(system:rational(_)). safe_primitive(system:rational(_,_,_)). :- endif. safe_primitive(number(_)). safe_primitive(atom(_)). safe_primitive(system:blob(_,_)). safe_primitive(system:string(_)). safe_primitive(atomic(_)). safe_primitive(compound(_)). safe_primitive(callable(_)). safe_primitive(ground(_)). safe_primitive(system:nonground(_,_)). safe_primitive(system:cyclic_term(_)). safe_primitive(acyclic_term(_)). safe_primitive(system:is_stream(_)). safe_primitive(system:'$is_char'(_)). safe_primitive(system:'$is_char_code'(_)). safe_primitive(system:'$is_char_list'(_,_)). safe_primitive(system:'$is_code_list'(_,_)). % ordering safe_primitive(@>(_,_)). safe_primitive(@>=(_,_)). safe_primitive(==(_,_)). safe_primitive(@<(_,_)). safe_primitive(@=<(_,_)). safe_primitive(compare(_,_,_)). safe_primitive(sort(_,_)). safe_primitive(keysort(_,_)). safe_primitive(system: =@=(_,_)). safe_primitive(system:'$btree_find_node'(_,_,_,_,_)). % unification and equivalence safe_primitive(=(_,_)). safe_primitive(\=(_,_)). safe_primitive(system:'?='(_,_)). safe_primitive(system:unifiable(_,_,_)). safe_primitive(unify_with_occurs_check(_,_)). safe_primitive(\==(_,_)). % arithmetic safe_primitive(is(_,_)). safe_primitive(>(_,_)). safe_primitive(>=(_,_)). safe_primitive(=:=(_,_)). safe_primitive(=\=(_,_)). safe_primitive(=<(_,_)). safe_primitive(<(_,_)). :- if(current_prolog_flag(bounded, false)). safe_primitive(system:nth_integer_root_and_remainder(_,_,_,_)). :- endif. safe_primitive(system:current_arithmetic_function(_)). safe_primitive(system:bounded_number(_,_,_)). safe_primitive(system:float_class(_,_)). safe_primitive(system:float_parts(_,_,_,_)). % term-handling safe_primitive(arg(_,_,_)). safe_primitive(system:setarg(_,_,_)). safe_primitive(system:nb_setarg(_,_,_)). safe_primitive(system:nb_linkarg(_,_,_)). safe_primitive(functor(_,_,_)). safe_primitive(system:functor(_,_,_,_)). safe_primitive(_ =.. _). safe_primitive(system:compound_name_arity(_,_,_)). safe_primitive(system:compound_name_arguments(_,_,_)). safe_primitive(system:'$filled_array'(_,_,_,_)). safe_primitive(copy_term(_,_)). safe_primitive(system:copy_term(_,_,_,_)). safe_primitive(system:duplicate_term(_,_)). safe_primitive(system:copy_term_nat(_,_)). safe_primitive(system:size_abstract_term(_,_,_)). safe_primitive(numbervars(_,_,_)). safe_primitive(system:numbervars(_,_,_,_)). safe_primitive(subsumes_term(_,_)). safe_primitive(system:term_hash(_,_)). safe_primitive(system:term_hash(_,_,_,_)). safe_primitive(system:variant_sha1(_,_)). safe_primitive(system:variant_hash(_,_)). safe_primitive(system:'$term_size'(_,_,_)). % dicts safe_primitive(system:is_dict(_)). safe_primitive(system:is_dict(_,_)). safe_primitive(system:get_dict(_,_,_)). safe_primitive(system:get_dict(_,_,_,_,_)). safe_primitive(system:'$get_dict_ex'(_,_,_)). safe_primitive(system:dict_create(_,_,_)). safe_primitive(system:dict_pairs(_,_,_)). safe_primitive(system:put_dict(_,_,_)). safe_primitive(system:put_dict(_,_,_,_)). safe_primitive(system:del_dict(_,_,_,_)). safe_primitive(system:select_dict(_,_,_)). safe_primitive(system:b_set_dict(_,_,_)). safe_primitive(system:nb_set_dict(_,_,_)). safe_primitive(system:nb_link_dict(_,_,_)). safe_primitive(system:(:<(_,_))). safe_primitive(system:(>:<(_,_))). % atoms safe_primitive(atom_chars(_, _)). safe_primitive(atom_codes(_, _)). safe_primitive(sub_atom(_,_,_,_,_)). safe_primitive(atom_concat(_,_,_)). safe_primitive(atom_length(_,_)). safe_primitive(char_code(_,_)). safe_primitive(system:name(_,_)). safe_primitive(system:atomic_concat(_,_,_)). safe_primitive(system:atomic_list_concat(_,_)). safe_primitive(system:atomic_list_concat(_,_,_)). safe_primitive(system:downcase_atom(_,_)). safe_primitive(system:upcase_atom(_,_)). safe_primitive(system:char_type(_,_)). safe_primitive(system:normalize_space(_,_)). safe_primitive(system:sub_atom_icasechk(_,_,_)). % numbers safe_primitive(number_codes(_,_)). safe_primitive(number_chars(_,_)). safe_primitive(system:atom_number(_,_)). safe_primitive(system:code_type(_,_)). % strings safe_primitive(system:atom_string(_,_)). safe_primitive(system:number_string(_,_)). safe_primitive(system:string_chars(_, _)). safe_primitive(system:string_codes(_, _)). safe_primitive(system:string_code(_,_,_)). safe_primitive(system:sub_string(_,_,_,_,_)). safe_primitive(system:split_string(_,_,_,_)). safe_primitive(system:atomics_to_string(_,_,_)). safe_primitive(system:atomics_to_string(_,_)). safe_primitive(system:string_concat(_,_,_)). safe_primitive(system:string_length(_,_)). safe_primitive(system:string_lower(_,_)). safe_primitive(system:string_upper(_,_)). safe_primitive(system:term_string(_,_)). safe_primitive('$syspreds':term_string(_,_,_)). % Lists safe_primitive(length(_,_)). % exceptions safe_primitive(throw(_)). safe_primitive(system:abort). % misc safe_primitive(current_prolog_flag(_,_)). safe_primitive(current_op(_,_,_)). safe_primitive(system:sleep(_)). safe_primitive(system:thread_self(_)). safe_primitive(system:get_time(_)). safe_primitive(system:statistics(_,_)). :- if(current_prolog_flag(threads,true)). safe_primitive(system:thread_statistics(Id,_,_)) :- ( var(Id) -> instantiation_error(Id) ; thread_self(Id) ). safe_primitive(system:thread_property(Id,_)) :- ( var(Id) -> instantiation_error(Id) ; thread_self(Id) ). :- endif. safe_primitive(system:format_time(_,_,_)). safe_primitive(system:format_time(_,_,_,_)). safe_primitive(system:date_time_stamp(_,_)). safe_primitive(system:stamp_date_time(_,_,_)). safe_primitive(system:strip_module(_,_,_)). safe_primitive('$messages':message_to_string(_,_)). safe_primitive(system:import_module(_,_)). safe_primitive(system:file_base_name(_,_)). safe_primitive(system:file_directory_name(_,_)). safe_primitive(system:file_name_extension(_,_,_)). safe_primitive(clause(H,_)) :- safe_clause(H). safe_primitive(asserta(X)) :- safe_assert(X). safe_primitive(assertz(X)) :- safe_assert(X). safe_primitive(retract(X)) :- safe_assert(X). safe_primitive(retractall(X)) :- safe_assert(X). safe_primitive(current_predicate(X)) :- safe_current_predicate(X). safe_primitive('$dcg':dcg_translate_rule(_,_)). safe_primitive('$syspreds':predicate_property(Pred, _)) :- nonvar(Pred), Pred \= (_:_). % We need to do data flow analysis to find the tag of the % target key before we can conclude that functions on dicts % are safe. safe_primitive('$dicts':'.'(_,K,_)) :- atom(K). safe_primitive('$dicts':'.'(_,K,_)) :- ( nonvar(K) -> dict_built_in(K) ; instantiation_error(K) ). dict_built_in(get(_)). dict_built_in(put(_)). dict_built_in(put(_,_)). % The non-ISO system predicates. These can be redefined, so we must % be careful to ensure the system ones are used. safe_primitive(system:false). safe_primitive(system:cyclic_term(_)). safe_primitive(system:msort(_,_)). safe_primitive(system:sort(_,_,_,_)). safe_primitive(system:between(_,_,_)). safe_primitive(system:succ(_,_)). safe_primitive(system:plus(_,_,_)). safe_primitive(system:float_class(_,_)). safe_primitive(system:term_variables(_,_)). safe_primitive(system:term_variables(_,_,_)). safe_primitive(system:'$term_size'(_,_,_)). safe_primitive(system:atom_to_term(_,_,_)). safe_primitive(system:term_to_atom(_,_)). safe_primitive(system:atomic_list_concat(_,_,_)). safe_primitive(system:atomic_list_concat(_,_)). safe_primitive(system:downcase_atom(_,_)). safe_primitive(system:upcase_atom(_,_)). safe_primitive(system:is_list(_)). safe_primitive(system:memberchk(_,_)). safe_primitive(system:'$skip_list'(_,_,_)). safe_primitive(system:'$seek_list'(_, _, _, _)). % attributes safe_primitive(system:get_attr(_,_,_)). safe_primitive(system:get_attrs(_,_)). safe_primitive(system:term_attvars(_,_)). safe_primitive(system:del_attr(_,_)). safe_primitive(system:del_attrs(_)). safe_primitive('$attvar':copy_term(_,_,_)). % globals safe_primitive(system:b_getval(_,_)). safe_primitive(system:b_setval(Var,_)) :- safe_global_var(Var). safe_primitive(system:nb_getval(_,_)). safe_primitive('$syspreds':nb_setval(Var,_)) :- safe_global_var(Var). safe_primitive(system:nb_linkval(Var,_)) :- safe_global_var(Var). safe_primitive(system:nb_current(_,_)). % database safe_primitive(system:assert(X)) :- safe_assert(X). % Output safe_primitive(system:writeln(_)). safe_primitive('$messages':print_message(_,_)). % Stack limits (down) safe_primitive('$syspreds':set_prolog_stack(Stack, limit(ByteExpr))) :- nonvar(Stack), stack_name(Stack), catch(Bytes is ByteExpr, _, fail), prolog_stack_property(Stack, limit(Current)), Bytes =< Current. stack_name(global). stack_name(local). stack_name(trail). safe_primitive('$tabling':abolish_all_tables). safe_primitive('$tabling':'$wrap_tabled'(Module:_Head, _Mode)) :- prolog_load_context(module, Module), !. safe_primitive('$tabling':'$moded_wrap_tabled'(Module:_Head,_,_,_,_)) :- prolog_load_context(module, Module), !. % use_module/1. We only allow for .pl files that are loaded from % relative paths that do not contain /../ safe_primitive(system:use_module(Spec, _Import)) :- safe_primitive(system:use_module(Spec)). safe_primitive(system:load_files(Spec, Options)) :- safe_primitive(system:use_module(Spec)), maplist(safe_load_file_option, Options). safe_primitive(system:use_module(Spec)) :- ground(Spec), ( atom(Spec) -> Path = Spec ; Spec =.. [_Alias, Segments], phrase(segments_to_path(Segments), List), atomic_list_concat(List, Path) ), \+ is_absolute_file_name(Path), \+ sub_atom(Path, _, _, _, '/../'), absolute_file_name(Spec, AbsFile, [ access(read), file_type(prolog), file_errors(fail) ]), file_name_extension(_, Ext, AbsFile), save_extension(Ext). % support predicates for safe_primitive, validating the safety of % arguments to certain goals. segments_to_path(A/B) --> !, segments_to_path(A), [/], segments_to_path(B). segments_to_path(X) --> [X]. save_extension(pl). safe_load_file_option(if(changed)). safe_load_file_option(if(not_loaded)). safe_load_file_option(must_be_module(_)). safe_load_file_option(optimise(_)). safe_load_file_option(silent(_)). %! safe_assert(+Term) is semidet. % % True if assert(Term) is safe, which means it asserts in the % current module. Cross-module asserts are considered unsafe. We % only allow for adding facts. In theory, we could also allow for % rules if we prove the safety of the body. safe_assert(C) :- cyclic_term(C), !, fail. safe_assert(X) :- var(X), !, fail. safe_assert(_Head:-_Body) :- !, fail. safe_assert(_:_) :- !, fail. safe_assert(_). %! safe_clause(+Head) is semidet. % % Consider a call to clause safe if it does not try to cross a % module boundary. Cross-module usage of clause/2 can extract % private information from other modules. safe_clause(H) :- var(H), !. safe_clause(_:_) :- !, fail. safe_clause(_). %! safe_global_var(+Name) is semidet. % % True if Name is a global variable to which assertion is % considered safe. safe_global_var(Name) :- var(Name), !, instantiation_error(Name). safe_global_var(Name) :- safe_global_variable(Name). %! safe_global_variable(Name) is semidet. % % Declare the given global variable safe to write to. %! safe_current_predicate(+X) % % current_predicate/1 is safe when not used with qualification. safe_current_predicate(X) :- nonvar(X), X = _:_, !, fail. safe_current_predicate(_). %! safe_meta(+Goal, -Called:list(callable)) is semidet. % % Hook. True if Goal is a meta-predicate that is considered safe % iff all elements in Called are safe. safe_meta(system:put_attr(V,M,A), Called) :- !, ( atom(M) -> attr_hook_predicates([ attr_unify_hook(A, _), attribute_goals(V,_,_), project_attributes(_,_) ], M, Called) ; instantiation_error(M) ). safe_meta(system:with_output_to(Output, G), [G]) :- safe_output(Output), !. safe_meta(system:format(Format, Args), Calls) :- format_calls(Format, Args, Calls). safe_meta(system:format(Output, Format, Args), Calls) :- safe_output(Output), format_calls(Format, Args, Calls). safe_meta(prolog_debug:debug(_Term, Format, Args), Calls) :- format_calls(Format, Args, Calls). safe_meta(system:set_prolog_flag(Flag, Value), []) :- atom(Flag), safe_prolog_flag(Flag, Value). safe_meta('$attvar':freeze(_Var,Goal), [Goal]). safe_meta(phrase(NT,Xs0,Xs), [Goal]) :- % phrase/2,3 and call_dcg/2,3 expand_nt(NT,Xs0,Xs,Goal). safe_meta(phrase(NT,Xs0), [Goal]) :- expand_nt(NT,Xs0,[],Goal). safe_meta('$dcg':call_dcg(NT,Xs0,Xs), [Goal]) :- expand_nt(NT,Xs0,Xs,Goal). safe_meta('$dcg':call_dcg(NT,Xs0), [Goal]) :- expand_nt(NT,Xs0,[],Goal). safe_meta('$tabling':abolish_table_subgoals(V), []) :- \+ qualified(V). safe_meta('$tabling':current_table(V, _), []) :- \+ qualified(V). safe_meta('$tabling':tnot(G), [G]). safe_meta('$tabling':not_exists(G), [G]). qualified(V) :- nonvar(V), V = _:_. %! attr_hook_predicates(+Hooks0, +Module, -Hooks) is det. % % Filter the defined hook implementations. This is safe because % (1) calling an undefined predicate is not a safety issue, (2) % the user an only assert in the current module and only % predicates that have a safe body. This avoids the need to define % attribute hooks solely for the purpose of making them safe. attr_hook_predicates([], _, []). attr_hook_predicates([H|T], M, Called) :- ( predicate_property(M:H, defined) -> Called = [M:H|Rest] ; Called = Rest ), attr_hook_predicates(T, M, Rest). %! expand_nt(+NT, ?Xs0, ?Xs, -NewGoal) % % Similar to expand_phrase/2, but we do throw errors instead of % failing if NT is not sufficiently instantiated. expand_nt(NT, _Xs0, _Xs, _NewGoal) :- strip_module(NT, _, Plain), var(Plain), !, instantiation_error(Plain). expand_nt(NT, Xs0, Xs, NewGoal) :- dcg_translate_rule((pseudo_nt --> NT), (pseudo_nt(Xs0c,Xsc) :- NewGoal0)), ( var(Xsc), Xsc \== Xs0c -> Xs = Xsc, NewGoal1 = NewGoal0 ; NewGoal1 = (NewGoal0, Xsc = Xs) ), ( var(Xs0c) -> Xs0 = Xs0c, NewGoal = NewGoal1 ; NewGoal = ( Xs0 = Xs0c, NewGoal1 ) ). %! safe_meta_call(+Goal, +Context, -Called:list(callable)) is semidet. % % True if Goal is a meta-predicate that is considered safe % iff all elements in Called are safe. safe_meta_call(Goal, _, _Called) :- debug(sandbox(meta), 'Safe meta ~p?', [Goal]), fail. safe_meta_call(Goal, Context, Called) :- ( safe_meta(Goal, Called) -> true ; safe_meta(Goal, Context, Called) ), !. % call hook safe_meta_call(Goal, _, Called) :- Goal = M:Plain, compound(Plain), compound_name_arity(Plain, Name, Arity), safe_meta_predicate(M:Name/Arity), predicate_property(Goal, meta_predicate(Spec)), !, called(Spec, Plain, Called). safe_meta_call(M:Goal, _, Called) :- !, generic_goal(Goal, Gen), safe_meta(M:Gen), called(Gen, Goal, Called). safe_meta_call(Goal, _, Called) :- generic_goal(Goal, Gen), safe_meta(Gen), called(Gen, Goal, Called). called(Gen, Goal, Called) :- compound_name_arity(Goal, _, Arity), called(1, Arity, Gen, Goal, Called). called(I, Arity, Gen, Goal, Called) :- I =< Arity, !, arg(I, Gen, Spec), ( calling_meta_spec(Spec) -> arg(I, Goal, Called0), extend(Spec, Called0, G), Called = [G|Rest] ; Called = Rest ), I2 is I+1, called(I2, Arity, Gen, Goal, Rest). called(_, _, _, _, []). generic_goal(G, Gen) :- functor(G, Name, Arity), functor(Gen, Name, Arity). calling_meta_spec(V) :- var(V), !, fail. calling_meta_spec(I) :- integer(I), !. calling_meta_spec(^). calling_meta_spec(//). extend(^, G, Plain) :- !, strip_existential(G, Plain). extend(//, DCG, Goal) :- !, ( expand_phrase(call_dcg(DCG,_,_), Goal) -> true ; instantiation_error(DCG) % Ask more instantiation. ). % might not help, but does not harm. extend(0, G, G) :- !. extend(I, M:G0, M:G) :- !, G0 =.. List, length(Extra, I), append(List, Extra, All), G =.. All. extend(I, G0, G) :- G0 =.. List, length(Extra, I), append(List, Extra, All), G =.. All. strip_existential(Var, Var) :- var(Var), !. strip_existential(M:G0, M:G) :- !, strip_existential(G0, G). strip_existential(_^G0, G) :- !, strip_existential(G0, G). strip_existential(G, G). %! safe_meta(?Template). safe_meta((0,0)). safe_meta((0;0)). safe_meta((0->0)). safe_meta(system:(0*->0)). safe_meta(catch(0,*,0)). safe_meta(findall(*,0,*)). safe_meta('$bags':findall(*,0,*,*)). safe_meta(setof(*,^,*)). safe_meta(bagof(*,^,*)). safe_meta('$bags':findnsols(*,*,0,*)). safe_meta('$bags':findnsols(*,*,0,*,*)). safe_meta(system:call_cleanup(0,0)). safe_meta(system:setup_call_cleanup(0,0,0)). safe_meta(system:setup_call_catcher_cleanup(0,0,*,0)). safe_meta('$attvar':call_residue_vars(0,*)). safe_meta('$syspreds':call_with_inference_limit(0,*,*)). safe_meta('$syspreds':call_with_depth_limit(0,*,*)). safe_meta('$syspreds':undo(0)). safe_meta(^(*,0)). safe_meta(\+(0)). safe_meta(call(0)). safe_meta(call(1,*)). safe_meta(call(2,*,*)). safe_meta(call(3,*,*,*)). safe_meta(call(4,*,*,*,*)). safe_meta(call(5,*,*,*,*,*)). safe_meta(call(6,*,*,*,*,*,*)). safe_meta('$tabling':start_tabling(*,0)). safe_meta('$tabling':start_tabling(*,0,*,*)). safe_meta(wfs:call_delays(0,*)). %! safe_output(+Output) % % True if something is a safe output argument for with_output_to/2 % and friends. We do not want writing to streams. safe_output(Output) :- var(Output), !, instantiation_error(Output). safe_output(atom(_)). safe_output(string(_)). safe_output(codes(_)). safe_output(codes(_,_)). safe_output(chars(_)). safe_output(chars(_,_)). safe_output(current_output). safe_output(current_error). %! format_calls(+Format, +FormatArgs, -Calls) % % Find ~@ calls from Format and Args. :- public format_calls/3. % used in pengines_io format_calls(Format, Args, Calls) :- is_list(Args), !, format_types(Format, Types), ( format_callables(Types, Args, Calls) -> true ; throw(error(format_error(Format, Types, Args), _)) ). format_calls(Format, Arg, Calls) :- format_calls(Format, [Arg], Calls). format_callables([], [], []). format_callables([callable|TT], [G|TA], [G|TG]) :- !, format_callables(TT, TA, TG). format_callables([_|TT], [_|TA], TG) :- !, format_callables(TT, TA, TG). /******************************* * SAFE COMPILATION HOOKS * *******************************/ :- multifile prolog:sandbox_allowed_directive/1, prolog:sandbox_allowed_goal/1, prolog:sandbox_allowed_expansion/1. %! prolog:sandbox_allowed_directive(:G) is det. % % Throws an exception if G is not considered a safe directive. prolog:sandbox_allowed_directive(Directive) :- debug(sandbox(directive), 'Directive: ~p', [Directive]), fail. prolog:sandbox_allowed_directive(Directive) :- safe_directive(Directive), !. prolog:sandbox_allowed_directive(M:PredAttr) :- \+ prolog_load_context(module, M), !, debug(sandbox(directive), 'Cross-module directive', []), permission_error(execute, sandboxed_directive, (:- M:PredAttr)). prolog:sandbox_allowed_directive(M:PredAttr) :- safe_pattr(PredAttr), !, PredAttr =.. [Attr, Preds], ( safe_pattr(Preds, Attr) -> true ; permission_error(execute, sandboxed_directive, (:- M:PredAttr)) ). prolog:sandbox_allowed_directive(_:Directive) :- safe_source_directive(Directive), !. prolog:sandbox_allowed_directive(_:Directive) :- directive_loads_file(Directive, File), !, safe_path(File). prolog:sandbox_allowed_directive(G) :- safe_goal(G). %! safe_directive(:Directive) is semidet. % % Hook to declare additional directives as safe. The argument is a % term `Module:Directive` (without =|:-|= wrapper). In almost all % cases, the implementation must verify that the `Module` is the % current load context as illustrated below. This check is not % performed by the system to allow for cases where particular % cross-module directives are allowed. % % == % sandbox:safe_directive(M:Directive) :- % prolog_load_context(module, M), % ... % == safe_pattr(dynamic(_)). safe_pattr(thread_local(_)). safe_pattr(volatile(_)). safe_pattr(discontiguous(_)). safe_pattr(multifile(_)). safe_pattr(public(_)). safe_pattr(meta_predicate(_)). safe_pattr(table(_)). safe_pattr(non_terminal(_)). safe_pattr(Var, _) :- var(Var), !, instantiation_error(Var). safe_pattr((A,B), Attr) :- !, safe_pattr(A, Attr), safe_pattr(B, Attr). safe_pattr(M:G, Attr) :- !, ( atom(M), prolog_load_context(module, M) -> true ; Goal =.. [Attr,M:G], permission_error(directive, sandboxed, (:- Goal)) ). safe_pattr(_, _). safe_source_directive(op(_,_,Name)) :- !, ( atom(Name) -> true ; is_list(Name), maplist(atom, Name) ). safe_source_directive(set_prolog_flag(Flag, Value)) :- !, atom(Flag), ground(Value), safe_prolog_flag(Flag, Value). safe_source_directive(style_check(_)). safe_source_directive(initialization(_)). % Checked at runtime safe_source_directive(initialization(_,_)). % Checked at runtime directive_loads_file(use_module(library(X)), X). directive_loads_file(use_module(library(X), _Imports), X). directive_loads_file(load_files(library(X), _Options), X). directive_loads_file(ensure_loaded(library(X)), X). directive_loads_file(include(X), X). safe_path(X) :- var(X), !, instantiation_error(X). safe_path(X) :- ( atom(X) ; string(X) ), !, \+ sub_atom(X, 0, _, 0, '..'), \+ sub_atom(X, 0, _, _, '/'), \+ sub_atom(X, 0, _, _, '../'), \+ sub_atom(X, _, _, 0, '/..'), \+ sub_atom(X, _, _, _, '/../'). safe_path(A/B) :- !, safe_path(A), safe_path(B). %! safe_prolog_flag(+Flag, +Value) is det. % % True if it is safe to set the flag Flag to Value. % % @tbd If we can avoid that files are loaded after changing % this flag, we can allow for more flags. The syntax % flags are safe because they are registered with the % module. % misc safe_prolog_flag(generate_debug_info, _). safe_prolog_flag(optimise, _). safe_prolog_flag(occurs_check, _). safe_prolog_flag(write_attributes, _). % syntax safe_prolog_flag(var_prefix, _). safe_prolog_flag(double_quotes, _). safe_prolog_flag(back_quotes, _). safe_prolog_flag(rational_syntax, _). % arithmetic safe_prolog_flag(prefer_rationals, _). safe_prolog_flag(float_overflow, _). safe_prolog_flag(float_zero_div, _). safe_prolog_flag(float_undefined, _). safe_prolog_flag(float_underflow, _). safe_prolog_flag(float_rounding, _). safe_prolog_flag(float_rounding, _). safe_prolog_flag(max_rational_size, _). safe_prolog_flag(max_rational_size_action, _). % tabling safe_prolog_flag(max_answers_for_subgoal,_). safe_prolog_flag(max_answers_for_subgoal_action,_). safe_prolog_flag(max_table_answer_size,_). safe_prolog_flag(max_table_answer_size_action,_). safe_prolog_flag(max_table_subgoal_size,_). safe_prolog_flag(max_table_subgoal_size_action,_). %! prolog:sandbox_allowed_expansion(:G) is det. % % Throws an exception if G is not considered a safe expansion % goal. This deals with call-backs from the compiler for % % - goal_expansion/2 % - term_expansion/2 % - Quasi quotations. % % Our assumption is that external expansion rules are coded safely % and we only need to be careful if the sandboxed code defines % expansion rules. prolog:sandbox_allowed_expansion(M:G) :- prolog_load_context(module, M), !, debug(sandbox(expansion), 'Expand in ~p: ~p', [M, G]), safe_goal(M:G). prolog:sandbox_allowed_expansion(_,_). %! prolog:sandbox_allowed_goal(:G) is det. % % Throw an exception if it is not safe to call G prolog:sandbox_allowed_goal(G) :- safe_goal(G). /******************************* * MESSAGES * *******************************/ :- multifile prolog:message//1, prolog:message_context//1, prolog:error_message//1. prolog:message(error(instantiation_error, Context)) --> { nonvar(Context), Context = sandbox(_Goal,Parents), numbervars(Context, 1, _) }, [ 'Sandbox restriction!'-[], nl, 'Could not derive which predicate may be called from'-[] ], ( { Parents == [] } -> [ 'Search space too large'-[] ] ; callers(Parents, 10) ). prolog:message_context(sandbox(_G, [])) --> !. prolog:message_context(sandbox(_G, Parents)) --> [ nl, 'Reachable from:'-[] ], callers(Parents, 10). callers([], _) --> !. callers(_, 0) --> !. callers([G|Parents], Level) --> { NextLevel is Level-1 }, [ nl, '\t ~p'-[G] ], callers(Parents, NextLevel). prolog:message(bad_safe_declaration(Goal, File, Line)) --> [ '~w:~d: Invalid safe_primitive/1 declaration: ~p'- [File, Line, Goal] ]. prolog:error_message(format_error(Format, Types, Args)) --> format_error(Format, Types, Args). format_error(Format, Types, Args) --> { length(Types, TypeLen), length(Args, ArgsLen), ( TypeLen > ArgsLen -> Problem = 'not enough' ; Problem = 'too many' ) }, [ 'format(~q): ~w arguments (found ~w, need ~w)'- [Format, Problem, ArgsLen, TypeLen] ].