4 use Scalar::Util qw(reftype refaddr);
6 $Safe::VERSION = "2.39";
8 # *** Don't declare any lexicals above this point ***
10 # This function should return a closure which contains an eval that can't
11 # see any lexicals in scope (apart from __ExPr__ which is unavoidable)
13 sub lexless_anon_sub {
15 # $_[1] is strict flag;
16 my $__ExPr__ = $_[2]; # must be a lexical to create the closure that
17 # can be used to pass the value into the safe
20 # Create anon sub ref in root of compartment.
21 # Uses a closure (on $__ExPr__) to pass in the code to be executed.
22 # (eval on one line to keep line numbers as expected by caller)
24 'package %s; %s sub { @_=(); eval q[local *SIG; my $__ExPr__;] . $__ExPr__; }',
25 $_[0], $_[1] ? 'use strict;' : '';
37 if (defined &B::sub_generation) {
38 *sub_generation = \&B::sub_generation;
41 # fake sub generation changing for perls < 5.8.9
42 my $sg; *sub_generation = sub { ++$sg };
47 opset opset_to_ops opmask_add
48 empty_opset full_opset invert_opset verify_opset
49 opdesc opcodes opmask define_optag opset_to_hex
52 *ops_to_opset = \&opset; # Temporary alias for old Penguins
54 # Regular expressions and other unicode-aware code may need to call
55 # utf8->SWASHNEW (via perl's utf8.c). That will fail unless we share the
57 # Sadly we can't just add utf8::SWASHNEW to $default_share because perl's
58 # utf8.c code does a fetchmethod on SWASHNEW to check if utf8.pm is loaded,
59 # and sharing makes it look like the method exists.
60 # The simplest and most robust fix is to ensure the utf8 module is loaded when
61 # Safe is loaded. Then we can add utf8::SWASHNEW to $default_share.
63 # we must ensure that utf8_heavy.pl, where SWASHNEW is defined, is loaded
64 # but without depending on too much knowledge of that implementation detail.
65 # This code (//i on a unicode string) should ensure utf8 is fully loaded
66 # and also loads the ToFold SWASH, unless things change so that these
67 # particular code points don't cause it to load.
68 # (Swashes are cached internally by perl in PL_utf8_* variables
69 # independent of being inside/outside of Safe. So once loaded they can be)
70 do { my $a = pack('U',0x100); my $b = chr 0x101; utf8::upgrade $b; $a =~ /$b/i };
71 # now we can safely include utf8::SWASHNEW in $default_share defined below.
74 # share *_ and functions defined in universal.c
75 # Don't share stuff like *UNIVERSAL:: otherwise code from the
76 # compartment can 0wn functions in UNIVERSAL
77 my $default_share = [qw[
89 &utf8::native_to_unicode
90 &utf8::unicode_to_native
99 ]), ($] >= 5.008001 && qw[
101 ]), ($] >= 5.010 && qw[
123 &version::vxs::declare
125 &version::vxs::_VERSION
126 &version::vxs::stringify
130 ]), ($] >= 5.011 && qw[
132 ]), ($] >= 5.010 && $] < 5.014 && qw[
133 &Tie::Hash::NamedCapture::FETCH
134 &Tie::Hash::NamedCapture::STORE
135 &Tie::Hash::NamedCapture::DELETE
136 &Tie::Hash::NamedCapture::CLEAR
137 &Tie::Hash::NamedCapture::EXISTS
138 &Tie::Hash::NamedCapture::FIRSTKEY
139 &Tie::Hash::NamedCapture::NEXTKEY
140 &Tie::Hash::NamedCapture::SCALAR
141 &Tie::Hash::NamedCapture::flags
143 if (defined $Devel::Cover::VERSION) {
144 push @$default_share, '&Devel::Cover::use_file';
148 my($class, $root, $mask) = @_;
152 if (defined($root)) {
153 croak "Can't use \"$root\" as root name"
154 if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/;
155 $obj->{Root} = $root;
159 $obj->{Root} = "Safe::Root".$default_root++;
163 # use permit/deny methods instead till interface issues resolved
164 # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...;
165 croak "Mask parameter to new no longer supported" if defined $mask;
166 $obj->permit_only(':default');
168 # We must share $_ and @_ with the compartment or else ops such
169 # as split, length and so on won't default to $_ properly, nor
170 # will passing argument to subroutines work (via @_). In fact,
171 # for reasons I don't completely understand, we need to share
172 # the whole glob *_ rather than $_ and @_ separately, otherwise
173 # @_ in non default packages within the compartment don't work.
174 $obj->share_from('main', $default_share);
176 Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04);
183 $obj->erase('DESTROY') if $obj->{Erase};
187 my ($obj, $action) = @_;
188 my $pkg = $obj->root();
192 $pkg = "main::$pkg\::"; # expand to full symbol table name
193 ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
195 # The 'my $foo' is needed! Without it you get an
196 # 'Attempt to free unreferenced scalar' warning!
197 my $stem_symtab = *{$stem}{HASH};
199 #warn "erase($pkg) stem=$stem, leaf=$leaf";
200 #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n";
201 # ", join(', ', %$stem_symtab),"\n";
203 # delete $stem_symtab->{$leaf};
205 my $leaf_glob = $stem_symtab->{$leaf};
206 my $leaf_symtab = *{$leaf_glob}{HASH};
207 # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n";
209 #delete $leaf_symtab->{'__ANON__'};
210 #delete $leaf_symtab->{'foo'};
211 #delete $leaf_symtab->{'main::'};
212 # my $foo = undef ${"$stem\::"}{"$leaf\::"};
214 if ($action and $action eq 'DESTROY') {
215 delete $stem_symtab->{$leaf};
217 $obj->share_from('main', $default_share);
231 croak("Safe root method now read-only") if @_;
238 return $obj->{Mask} unless @_;
242 # v1 compatibility methods
243 sub trap { shift->deny(@_) }
244 sub untrap { shift->permit(@_) }
248 $obj->{Mask} |= opset(@_);
252 $obj->{Mask} = opset(@_);
258 $obj->{Mask} &= invert_opset opset(@_);
262 $obj->{Mask} = invert_opset opset(@_);
268 print opset_to_hex($obj->{Mask}),"\n";
273 my($obj, @vars) = @_;
274 $obj->share_from(scalar(caller), \@vars);
282 my $no_record = shift || 0;
283 my $root = $obj->root();
284 croak("vars not an array ref") unless ref $vars eq 'ARRAY';
286 # Check that 'from' package actually exists
287 croak("Package \"$pkg\" does not exist")
288 unless keys %{"$pkg\::"};
290 foreach $arg (@$vars) {
291 # catch some $safe->share($var) errors:
293 $type = $1 if ($var = $arg) =~ s/^(\W)//;
294 # warn "share_from $pkg $type $var";
295 for (1..2) { # assign twice to avoid any 'used once' warnings
296 *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
297 : ($type eq '&') ? \&{$pkg."::$var"}
298 : ($type eq '$') ? \${$pkg."::$var"}
299 : ($type eq '@') ? \@{$pkg."::$var"}
300 : ($type eq '%') ? \%{$pkg."::$var"}
301 : ($type eq '*') ? *{$pkg."::$var"}
302 : croak(qq(Can't share "$type$var" of unknown type));
305 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
313 my $shares = \%{$obj->{Shares} ||= {}};
314 # Record shares using keys of $obj->{Shares}. See reinit.
315 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
321 my $shares = \%{$obj->{Shares} ||= {}};
323 while(($var, $pkg) = each %$shares) {
324 # warn "share_redo $pkg\:: $var";
325 $obj->share_from($pkg, [ $var ], 1);
331 delete shift->{Shares};
336 my ($obj, $var) = @_;
338 return *{$obj->root()."::$var"};
342 my ($root, $saved_refs) = @_;
345 foreach my $hook (qw(DESTROY AUTOLOAD), grep /^\(/, keys %$root) {
346 push @$saved_refs, \*{$root.$hook};
347 delete ${$root}{$hook};
350 for (grep /::$/, keys %$root) {
351 next if \%{$root.$_} eq \%$root;
352 _clean_stash($root.$_, $saved_refs);
357 my ($obj, $expr, $strict) = @_;
358 die "Bad Safe object" unless $obj->isa('Safe');
360 my $root = $obj->{Root};
362 my $evalsub = lexless_anon_sub($root, $strict, $expr);
364 my $sg = sub_generation();
366 if (defined wantarray) {
367 @subret = (wantarray)
368 ? Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub)
369 : scalar Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
372 Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
374 _clean_stash($root.'::') if $sg != sub_generation();
375 $obj->wrap_code_refs_within(@subret);
376 return (wantarray) ? @subret : $subret[0];
381 sub wrap_code_refs_within {
385 $obj->_find_code_refs('wrap_code_ref', @_);
389 sub _find_code_refs {
394 my $reftype = $item && reftype $item
397 # skip references already seen
398 next if ++$OID{refaddr $item} > 1;
400 if ($reftype eq 'ARRAY') {
401 $obj->_find_code_refs($visitor, @$item);
403 elsif ($reftype eq 'HASH') {
404 $obj->_find_code_refs($visitor, values %$item);
407 elsif ($reftype eq 'CODE') {
408 $item = $obj->$visitor($item);
415 my ($obj, $sub) = @_;
416 die "Bad safe object" unless $obj->isa('Safe');
418 # wrap code ref $sub with _safe_call_sv so that, when called, the
419 # execution will happen with the compartment fully 'in effect'.
421 croak "Not a CODE reference"
422 if reftype $sub ne 'CODE';
425 my @args = @_; # lexical to close over
426 my $sub_with_args = sub { $sub->(@args) };
431 local $@; # needed due to perl_call_sv(sv, G_EVAL|G_KEEPERR)
432 my $sg = sub_generation();
433 @subret = (wantarray)
434 ? Opcode::_safe_call_sv($obj->{Root}, $obj->{Mask}, $sub_with_args)
435 : scalar Opcode::_safe_call_sv($obj->{Root}, $obj->{Mask}, $sub_with_args);
437 _clean_stash($obj->{Root}.'::') if $sg != sub_generation();
439 if ($error) { # rethrow exception
440 $error =~ s/\t\(in cleanup\) //; # prefix added by G_KEEPERR
443 return (wantarray) ? @subret : $subret[0];
451 my ($obj, $file) = @_;
452 die "Bad Safe object" unless $obj->isa('Safe');
454 my $root = $obj->{Root};
456 my $sg = sub_generation();
458 sprintf('package %s; sub { @_ = (); do $file }', $root);
459 my @subret = (wantarray)
460 ? Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub)
461 : scalar Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
462 _clean_stash($root.'::') if $sg != sub_generation();
463 $obj->wrap_code_refs_within(@subret);
464 return (wantarray) ? @subret : $subret[0];
474 Safe - Compile and execute code in restricted compartments
480 $compartment = new Safe;
482 $compartment->permit(qw(time sort :browse));
484 $result = $compartment->reval($unsafe_code);
488 The Safe extension module allows the creation of compartments
489 in which perl code can be evaluated. Each compartment has
493 =item a new namespace
495 The "root" of the namespace (i.e. "main::") is changed to a
496 different package and code evaluated in the compartment cannot
497 refer to variables outside this namespace, even with run-time
498 glob lookups and other tricks.
500 Code which is compiled outside the compartment can choose to place
501 variables into (or I<share> variables with) the compartment's namespace
502 and only that data will be visible to code evaluated in the
505 By default, the only variables shared with compartments are the
506 "underscore" variables $_ and @_ (and, technically, the less frequently
507 used %_, the _ filehandle and so on). This is because otherwise perl
508 operators which default to $_ will not work and neither will the
509 assignment of arguments to @_ on subroutine entry.
511 =item an operator mask
513 Each compartment has an associated "operator mask". Recall that
514 perl code is compiled into an internal format before execution.
515 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
516 the code to be compiled into an internal format and then,
517 provided there was no error in the compilation, executed.
518 Code evaluated in a compartment compiles subject to the
519 compartment's operator mask. Attempting to evaluate code in a
520 compartment which contains a masked operator will cause the
521 compilation to fail with an error. The code will not be executed.
523 The default operator mask for a newly created compartment is
524 the ':default' optag.
526 It is important that you read the L<Opcode> module documentation
527 for more information, especially for detailed definitions of opnames,
530 Since it is only at the compilation stage that the operator mask
531 applies, controlled access to potentially unsafe operations can
532 be achieved by having a handle to a wrapper subroutine (written
533 outside the compartment) placed into the compartment. For example,
537 # vet arguments and perform potentially unsafe operations
539 $cpt->share('&wrapper');
546 The authors make B<no warranty>, implied or otherwise, about the
547 suitability of this software for safety or security purposes.
549 The authors shall not in any case be liable for special, incidental,
550 consequential, indirect or other similar damages arising from the use
553 Your mileage will vary. If in any doubt B<do not use it>.
558 To create a new compartment, use
562 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
563 to use for the compartment (defaults to "Safe::Root0", incremented for
564 each new compartment).
566 Note that version 1.00 of the Safe module supported a second optional
567 parameter, MASK. That functionality has been withdrawn pending deeper
568 consideration. Use the permit and deny methods described below.
570 The following methods can then be used on the compartment
571 object returned by the above constructor. The object argument
572 is implicit in each case.
575 =head2 permit (OP, ...)
577 Permit the listed operators to be used when compiling code in the
578 compartment (in I<addition> to any operators already permitted).
580 You can list opcodes by names, or use a tag name; see
581 L<Opcode/"Predefined Opcode Tags">.
583 =head2 permit_only (OP, ...)
585 Permit I<only> the listed operators to be used when compiling code in
586 the compartment (I<no> other operators are permitted).
588 =head2 deny (OP, ...)
590 Deny the listed operators from being used when compiling code in the
591 compartment (other operators may still be permitted).
593 =head2 deny_only (OP, ...)
595 Deny I<only> the listed operators from being used when compiling code
596 in the compartment (I<all> other operators will be permitted, so you probably
597 don't want to use this method).
599 =head2 trap (OP, ...), untrap (OP, ...)
601 The trap and untrap methods are synonyms for deny and permit
604 =head2 share (NAME, ...)
606 This shares the variable(s) in the argument list with the compartment.
607 This is almost identical to exporting variables using the L<Exporter>
610 Each NAME must be the B<name> of a non-lexical variable, typically
611 with the leading type identifier included. A bareword is treated as a
614 Examples of legal names are '$foo' for a scalar, '@foo' for an
615 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
616 for a glob (i.e. all symbol table entries associated with "foo",
617 including scalar, array, hash, sub and filehandle).
619 Each NAME is assumed to be in the calling package. See share_from
620 for an alternative method (which C<share> uses).
622 =head2 share_from (PACKAGE, ARRAYREF)
624 This method is similar to share() but allows you to explicitly name the
625 package that symbols should be shared from. The symbol names (including
626 type characters) are supplied as an array reference.
628 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
630 Names can include package names, which are relative to the specified PACKAGE.
631 So these two calls have the same effect:
633 $safe->share_from('Scalar::Util', [ 'reftype' ]);
634 $safe->share_from('main', [ 'Scalar::Util::reftype' ]);
636 =head2 varglob (VARNAME)
638 This returns a glob reference for the symbol table entry of VARNAME in
639 the package of the compartment. VARNAME must be the B<name> of a
640 variable without any leading type marker. For example:
642 ${$cpt->varglob('foo')} = "Hello world";
644 has the same effect as:
646 $cpt = new Safe 'Root';
647 $Root::foo = "Hello world";
649 but avoids the need to know $cpt's package name.
652 =head2 reval (STRING, STRICT)
654 This evaluates STRING as perl code inside the compartment.
656 The code can only see the compartment's namespace (as returned by the
657 B<root> method). The compartment's root package appears to be the
658 C<main::> package to the code inside the compartment.
660 Any attempt by the code in STRING to use an operator which is not permitted
661 by the compartment will cause an error (at run-time of the main program
662 but at compile-time for the code in STRING). The error is of the form
663 "'%s' trapped by operation mask...".
665 If an operation is trapped in this way, then the code in STRING will
666 not be executed. If such a trapped operation occurs or any other
667 compile-time or return error, then $@ is set to the error message, just
670 If there is no error, then the method returns the value of the last
671 expression evaluated, or a return statement may be used, just as with
672 subroutines and B<eval()>. The context (list or scalar) is determined
673 by the caller as usual.
675 If the return value of reval() is (or contains) any code reference,
676 those code references are wrapped to be themselves executed always
677 in the compartment. See L</wrap_code_refs_within>.
679 The formerly undocumented STRICT argument sets strictness: if true
680 'use strict;' is used, otherwise it uses 'no strict;'. B<Note>: if
681 STRICT is omitted 'no strict;' is the default.
685 If the entereval op is permitted then the code can use eval "..." to
686 'hide' code which might use denied ops. This is not a major problem
687 since when the code tries to execute the eval it will fail because the
688 opmask is still in effect. However this technique would allow clever,
689 and possibly harmful, code to 'probe' the boundaries of what is
692 Any string eval which is executed by code executing in a compartment,
693 or by code called from code executing in a compartment, will be eval'd
694 in the namespace of the compartment. This is potentially a serious
697 Consider a function foo() in package pkg compiled outside a compartment
698 but shared with it. Assume the compartment has a root package called
699 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
700 normally, $pkg::foo will be set to 1. If foo() is called from the
701 compartment (by whatever means) then instead of setting $pkg::foo, the
702 eval will actually set $Root::pkg::foo.
704 This can easily be demonstrated by using a module, such as the Socket
705 module, which uses eval "..." as part of an AUTOLOAD function. You can
706 'use' the module outside the compartment and share an (autoloaded)
707 function with the compartment. If an autoload is triggered by code in
708 the compartment, or by any code anywhere that is called by any means
709 from the compartment, then the eval in the Socket module's AUTOLOAD
710 function happens in the namespace of the compartment. Any variables
711 created or used by the eval'd code are now under the control of
712 the code in the compartment.
714 A similar effect applies to I<all> runtime symbol lookups in code
715 called from a compartment but not compiled within it.
717 =head2 rdo (FILENAME)
719 This evaluates the contents of file FILENAME inside the compartment.
720 See above documentation on the B<reval> method for further details.
722 =head2 root (NAMESPACE)
724 This method returns the name of the package that is the root of the
725 compartment's namespace.
727 Note that this behaviour differs from version 1.00 of the Safe module
728 where the root module could be used to change the namespace. That
729 functionality has been withdrawn pending deeper consideration.
733 This is a get-or-set method for the compartment's operator mask.
735 With no MASK argument present, it returns the current operator mask of
738 With the MASK argument present, it sets the operator mask for the
739 compartment (equivalent to calling the deny_only method).
741 =head2 wrap_code_ref (CODEREF)
743 Returns a reference to an anonymous subroutine that, when executed, will call
744 CODEREF with the Safe compartment 'in effect'. In other words, with the
745 package namespace adjusted and the opmask enabled.
747 Note that the opmask doesn't affect the already compiled code, it only affects
748 any I<further> compilation that the already compiled code may try to perform.
750 This is particularly useful when applied to code references returned from reval().
752 (It also provides a kind of workaround for RT#60374: "Safe.pm sort {} bug with
753 -Dusethreads". See L<http://rt.perl.org/rt3//Public/Bug/Display.html?id=60374>
754 for I<much> more detail.)
756 =head2 wrap_code_refs_within (...)
758 Wraps any CODE references found within the arguments by replacing each with the
759 result of calling L</wrap_code_ref> on the CODE reference. Any ARRAY or HASH
760 references in the arguments are inspected recursively.
766 This section is just an outline of some of the things code in a compartment
767 might do (intentionally or unintentionally) which can have an effect outside
774 Consuming all (or nearly all) available memory.
778 Causing infinite loops etc.
782 Copying private information out of your system. Even something as
783 simple as your user name is of value to others. Much useful information
784 could be gleaned from your environment variables for example.
788 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
790 Setting up a signal handler will need to be carefully considered
791 and controlled. What mask is in effect when a signal handler
792 gets called? If a user can get an imported function to get an
793 exception and call the user's signal handler, does that user's
794 restricted mask get re-instated before the handler is called?
795 Does an imported handler get called with its original mask or
800 Ops such as chdir obviously effect the process as a whole and not just
801 the code in the compartment. Ops such as rand and srand have a similar
802 but more subtle effect.
808 Originally designed and implemented by Malcolm Beattie.
810 Reworked to use the Opcode module and other changes added by Tim Bunce.
812 Currently maintained by the Perl 5 Porters, <perl5-porters@perl.org>.