/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2013-2021, 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
% :- debug(sandbox).
/** <module> 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) :- _), Term) :-
( verify_safe_declaration(Goal)
-> Term = safe_primitive(Goal)
; 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) :- _), Term) :-
\+ current_prolog_flag(xref, true),
( verify_safe_declaration(Goal)
-> Term = sandbox:safe_primitive(Goal)
; 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(_)).
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:'$btree_find_node'(_,_,_,_,_)).
% unification and equivalence
safe_primitive(=(_,_)).
safe_primitive(\=(_,_)).
safe_primitive(system:'?='(_,_)).
safe_primitive(system:unifiable(_,_,_)).
safe_primitive(unify_with_occurs_check(_,_)).
safe_primitive(\==(_,_)).
% arithmetic
safe_primitive(is(_,_)).
safe_primitive(>(_,_)).
safe_primitive(>=(_,_)).
safe_primitive(=:=(_,_)).
safe_primitive(=\=(_,_)).
safe_primitive(=<(_,_)).
safe_primitive(<(_,_)).
:- if(current_prolog_flag(bounded, false)).
safe_primitive(system:nth_integer_root_and_remainder(_,_,_,_)).
:- endif.
% term-handling
safe_primitive(arg(_,_,_)).
safe_primitive(system:setarg(_,_,_)).
safe_primitive(system:nb_setarg(_,_,_)).
safe_primitive(system:nb_linkarg(_,_,_)).
safe_primitive(functor(_,_,_)).
safe_primitive(_ =.. _).
safe_primitive(system:compound_name_arity(_,_,_)).
safe_primitive(system:compound_name_arguments(_,_,_)).
safe_primitive(system:'$filled_array'(_,_,_,_)).
safe_primitive(copy_term(_,_)).
safe_primitive(system: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('$syspreds':term_string(_,_,_)).
% Lists
safe_primitive(length(_,_)).
% exceptions
safe_primitive(throw(_)).
safe_primitive(system:abort).
% misc
safe_primitive(current_prolog_flag(_,_)).
safe_primitive(current_op(_,_,_)).
safe_primitive(system:sleep(_)).
safe_primitive(system:thread_self(_)).
safe_primitive(system:get_time(_)).
safe_primitive(system:statistics(_,_)).
safe_primitive(system:thread_statistics(Id,_,_)) :-
( var(Id)
-> instantiation_error(Id)
; thread_self(Id)
).
safe_primitive(system:thread_property(Id,_)) :-
( var(Id)
-> instantiation_error(Id)
; thread_self(Id)
).
safe_primitive(system:format_time(_,_,_)).
safe_primitive(system:format_time(_,_,_,_)).
safe_primitive(system:date_time_stamp(_,_)).
safe_primitive(system:stamp_date_time(_,_,_)).
safe_primitive(system:strip_module(_,_,_)).
safe_primitive('$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('$dcg':dcg_translate_rule(_,_)).
% We need to do data flow analysis to find the tag of the
% target key before we can conclude that functions on dicts
% are safe.
safe_primitive('$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:'$skip_list'(_,_,_)).
% attributes
safe_primitive(system:get_attr(_,_,_)).
safe_primitive(system:get_attrs(_,_)).
safe_primitive(system:term_attvars(_,_)).
safe_primitive(system:del_attr(_,_)).
safe_primitive(system:del_attrs(_)).
safe_primitive('$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_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) :-
var(Format),
!,
instantiation_error(Format).
format_calls(Format, Args, Calls) :-
format_types(Format, Types),
( format_callables(Types, Args, Calls)
-> true
; throw(error(format_error(Format, Types, Args), _))
).
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, _).
% 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]
].