5 use Scalar::Util qw(reftype);
6 use Config qw(%Config);
7 use constant is_usethreads => $Config{usethreads};
9 $Safe::VERSION = "2.21";
11 # *** Don't declare any lexicals above this point ***
13 # This function should return a closure which contains an eval that can't
14 # see any lexicals in scope (apart from __ExPr__ which is unavoidable)
16 sub lexless_anon_sub {
18 # $_[1] is strict flag;
19 my $__ExPr__ = $_[2]; # must be a lexical to create the closure that
20 # can be used to pass the value into the safe
23 # Create anon sub ref in root of compartment.
24 # Uses a closure (on $__ExPr__) to pass in the code to be executed.
25 # (eval on one line to keep line numbers as expected by caller)
27 'package %s; %s strict; sub { @_=(); eval q[my $__ExPr__;] . $__ExPr__; }',
28 $_[0], $_[1] ? 'use' : 'no';
37 opset opset_to_ops opmask_add
38 empty_opset full_opset invert_opset verify_opset
39 opdesc opcodes opmask define_optag opset_to_hex
42 *ops_to_opset = \&opset; # Temporary alias for old Penguins
46 # share *_ and functions defined in universal.c
47 # Don't share stuff like *UNIVERSAL:: otherwise code from the
48 # compartment can 0wn functions in UNIVERSAL
49 my $default_share = [qw[
61 &utf8::native_to_unicode
62 &utf8::unicode_to_native
68 ], ($] >= 5.008001 && qw[
70 ]), ($] >= 5.010 && qw[
75 &Tie::Hash::NamedCapture::FETCH
76 &Tie::Hash::NamedCapture::STORE
77 &Tie::Hash::NamedCapture::DELETE
78 &Tie::Hash::NamedCapture::CLEAR
79 &Tie::Hash::NamedCapture::EXISTS
80 &Tie::Hash::NamedCapture::FIRSTKEY
81 &Tie::Hash::NamedCapture::NEXTKEY
82 &Tie::Hash::NamedCapture::SCALAR
83 &Tie::Hash::NamedCapture::flags
101 ]), ($] >= 5.011 && qw[
106 my($class, $root, $mask) = @_;
110 if (defined($root)) {
111 croak "Can't use \"$root\" as root name"
112 if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/;
113 $obj->{Root} = $root;
117 $obj->{Root} = "Safe::Root".$default_root++;
121 # use permit/deny methods instead till interface issues resolved
122 # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...;
123 croak "Mask parameter to new no longer supported" if defined $mask;
124 $obj->permit_only(':default');
126 # We must share $_ and @_ with the compartment or else ops such
127 # as split, length and so on won't default to $_ properly, nor
128 # will passing argument to subroutines work (via @_). In fact,
129 # for reasons I don't completely understand, we need to share
130 # the whole glob *_ rather than $_ and @_ separately, otherwise
131 # @_ in non default packages within the compartment don't work.
132 $obj->share_from('main', $default_share);
133 Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04);
139 $obj->erase('DESTROY') if $obj->{Erase};
143 my ($obj, $action) = @_;
144 my $pkg = $obj->root();
148 $pkg = "main::$pkg\::"; # expand to full symbol table name
149 ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
151 # The 'my $foo' is needed! Without it you get an
152 # 'Attempt to free unreferenced scalar' warning!
153 my $stem_symtab = *{$stem}{HASH};
155 #warn "erase($pkg) stem=$stem, leaf=$leaf";
156 #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n";
157 # ", join(', ', %$stem_symtab),"\n";
159 # delete $stem_symtab->{$leaf};
161 my $leaf_glob = $stem_symtab->{$leaf};
162 my $leaf_symtab = *{$leaf_glob}{HASH};
163 # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n";
165 #delete $leaf_symtab->{'__ANON__'};
166 #delete $leaf_symtab->{'foo'};
167 #delete $leaf_symtab->{'main::'};
168 # my $foo = undef ${"$stem\::"}{"$leaf\::"};
170 if ($action and $action eq 'DESTROY') {
171 delete $stem_symtab->{$leaf};
173 $obj->share_from('main', $default_share);
187 croak("Safe root method now read-only") if @_;
194 return $obj->{Mask} unless @_;
198 # v1 compatibility methods
199 sub trap { shift->deny(@_) }
200 sub untrap { shift->permit(@_) }
204 $obj->{Mask} |= opset(@_);
208 $obj->{Mask} = opset(@_);
214 $obj->{Mask} &= invert_opset opset(@_);
218 $obj->{Mask} = invert_opset opset(@_);
224 print opset_to_hex($obj->{Mask}),"\n";
230 my($obj, @vars) = @_;
231 $obj->share_from(scalar(caller), \@vars);
238 my $no_record = shift || 0;
239 my $root = $obj->root();
240 croak("vars not an array ref") unless ref $vars eq 'ARRAY';
242 # Check that 'from' package actually exists
243 croak("Package \"$pkg\" does not exist")
244 unless keys %{"$pkg\::"};
246 foreach $arg (@$vars) {
247 # catch some $safe->share($var) errors:
249 $type = $1 if ($var = $arg) =~ s/^(\W)//;
250 # warn "share_from $pkg $type $var";
251 for (1..2) { # assign twice to avoid any 'used once' warnings
252 *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
253 : ($type eq '&') ? \&{$pkg."::$var"}
254 : ($type eq '$') ? \${$pkg."::$var"}
255 : ($type eq '@') ? \@{$pkg."::$var"}
256 : ($type eq '%') ? \%{$pkg."::$var"}
257 : ($type eq '*') ? *{$pkg."::$var"}
258 : croak(qq(Can't share "$type$var" of unknown type));
261 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
268 my $shares = \%{$obj->{Shares} ||= {}};
269 # Record shares using keys of $obj->{Shares}. See reinit.
270 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
274 my $shares = \%{$obj->{Shares} ||= {}};
276 while(($var, $pkg) = each %$shares) {
277 # warn "share_redo $pkg\:: $var";
278 $obj->share_from($pkg, [ $var ], 1);
282 delete shift->{Shares};
286 my ($obj, $var) = @_;
288 return *{$obj->root()."::$var"};
293 my ($obj, $expr, $strict) = @_;
294 my $root = $obj->{Root};
296 my $evalsub = lexless_anon_sub($root, $strict, $expr);
297 my @ret = (wantarray)
298 ? Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub)
299 : scalar Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
301 # RT#60374: Safe.pm sort {} bug with -Dusethreads
302 # If the Safe eval returns a code ref in a perl compiled with usethreads
303 # then wrap code ref with _safe_call_sv so that, when called, the
304 # execution will happen with the compartment fully 'in effect'.
305 # Needed to fix sort blocks that reference $a & $b and
306 # possibly other subtle issues.
307 if (is_usethreads()) {
308 for my $ret (@ret) { # edit (via alias) any CODE refs
309 next unless (reftype($ret)||'') eq 'CODE';
310 my $sub = $ret; # avoid closure problems
312 my @args = @_; # lexical to close over
313 my $sub_with_args = sub { $sub->(@args) };
318 local $@; # needed due to perl_call_sv(sv, G_EVAL|G_KEEPERR)
319 @subret = (wantarray)
320 ? Opcode::_safe_call_sv($root, $obj->{Mask}, $sub_with_args)
321 : scalar Opcode::_safe_call_sv($root, $obj->{Mask}, $sub_with_args);
324 if ($error) { # rethrow exception
325 $error =~ s/\t\(in cleanup\) //; # prefix added by G_KEEPERR
328 return (wantarray) ? @subret : $subret[0];
333 return (wantarray) ? @ret : $ret[0];
337 my ($obj, $file) = @_;
338 my $root = $obj->{Root};
341 sprintf('package %s; sub { @_ = (); do $file }', $root);
342 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
352 Safe - Compile and execute code in restricted compartments
358 $compartment = new Safe;
360 $compartment->permit(qw(time sort :browse));
362 $result = $compartment->reval($unsafe_code);
366 The Safe extension module allows the creation of compartments
367 in which perl code can be evaluated. Each compartment has
371 =item a new namespace
373 The "root" of the namespace (i.e. "main::") is changed to a
374 different package and code evaluated in the compartment cannot
375 refer to variables outside this namespace, even with run-time
376 glob lookups and other tricks.
378 Code which is compiled outside the compartment can choose to place
379 variables into (or I<share> variables with) the compartment's namespace
380 and only that data will be visible to code evaluated in the
383 By default, the only variables shared with compartments are the
384 "underscore" variables $_ and @_ (and, technically, the less frequently
385 used %_, the _ filehandle and so on). This is because otherwise perl
386 operators which default to $_ will not work and neither will the
387 assignment of arguments to @_ on subroutine entry.
389 =item an operator mask
391 Each compartment has an associated "operator mask". Recall that
392 perl code is compiled into an internal format before execution.
393 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
394 the code to be compiled into an internal format and then,
395 provided there was no error in the compilation, executed.
396 Code evaluated in a compartment compiles subject to the
397 compartment's operator mask. Attempting to evaluate code in a
398 compartment which contains a masked operator will cause the
399 compilation to fail with an error. The code will not be executed.
401 The default operator mask for a newly created compartment is
402 the ':default' optag.
404 It is important that you read the L<Opcode> module documentation
405 for more information, especially for detailed definitions of opnames,
408 Since it is only at the compilation stage that the operator mask
409 applies, controlled access to potentially unsafe operations can
410 be achieved by having a handle to a wrapper subroutine (written
411 outside the compartment) placed into the compartment. For example,
415 # vet arguments and perform potentially unsafe operations
417 $cpt->share('&wrapper');
424 The authors make B<no warranty>, implied or otherwise, about the
425 suitability of this software for safety or security purposes.
427 The authors shall not in any case be liable for special, incidental,
428 consequential, indirect or other similar damages arising from the use
431 Your mileage will vary. If in any doubt B<do not use it>.
434 =head2 RECENT CHANGES
436 The interface to the Safe module has changed quite dramatically since
437 version 1 (as supplied with Perl5.002). Study these pages carefully if
438 you have code written to use Safe version 1 because you will need to
442 =head2 Methods in class Safe
444 To create a new compartment, use
448 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
449 to use for the compartment (defaults to "Safe::Root0", incremented for
450 each new compartment).
452 Note that version 1.00 of the Safe module supported a second optional
453 parameter, MASK. That functionality has been withdrawn pending deeper
454 consideration. Use the permit and deny methods described below.
456 The following methods can then be used on the compartment
457 object returned by the above constructor. The object argument
458 is implicit in each case.
463 =item permit (OP, ...)
465 Permit the listed operators to be used when compiling code in the
466 compartment (in I<addition> to any operators already permitted).
468 You can list opcodes by names, or use a tag name; see
469 L<Opcode/"Predefined Opcode Tags">.
471 =item permit_only (OP, ...)
473 Permit I<only> the listed operators to be used when compiling code in
474 the compartment (I<no> other operators are permitted).
478 Deny the listed operators from being used when compiling code in the
479 compartment (other operators may still be permitted).
481 =item deny_only (OP, ...)
483 Deny I<only> the listed operators from being used when compiling code
484 in the compartment (I<all> other operators will be permitted).
488 =item untrap (OP, ...)
490 The trap and untrap methods are synonyms for deny and permit
493 =item share (NAME, ...)
495 This shares the variable(s) in the argument list with the compartment.
496 This is almost identical to exporting variables using the L<Exporter>
499 Each NAME must be the B<name> of a non-lexical variable, typically
500 with the leading type identifier included. A bareword is treated as a
503 Examples of legal names are '$foo' for a scalar, '@foo' for an
504 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
505 for a glob (i.e. all symbol table entries associated with "foo",
506 including scalar, array, hash, sub and filehandle).
508 Each NAME is assumed to be in the calling package. See share_from
509 for an alternative method (which share uses).
511 =item share_from (PACKAGE, ARRAYREF)
513 This method is similar to share() but allows you to explicitly name the
514 package that symbols should be shared from. The symbol names (including
515 type characters) are supplied as an array reference.
517 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
520 =item varglob (VARNAME)
522 This returns a glob reference for the symbol table entry of VARNAME in
523 the package of the compartment. VARNAME must be the B<name> of a
524 variable without any leading type marker. For example,
526 $cpt = new Safe 'Root';
527 $Root::foo = "Hello world";
528 # Equivalent version which doesn't need to know $cpt's package name:
529 ${$cpt->varglob('foo')} = "Hello world";
532 =item reval (STRING, STRICT)
534 This evaluates STRING as perl code inside the compartment.
536 The code can only see the compartment's namespace (as returned by the
537 B<root> method). The compartment's root package appears to be the
538 C<main::> package to the code inside the compartment.
540 Any attempt by the code in STRING to use an operator which is not permitted
541 by the compartment will cause an error (at run-time of the main program
542 but at compile-time for the code in STRING). The error is of the form
543 "'%s' trapped by operation mask...".
545 If an operation is trapped in this way, then the code in STRING will
546 not be executed. If such a trapped operation occurs or any other
547 compile-time or return error, then $@ is set to the error message, just
550 If there is no error, then the method returns the value of the last
551 expression evaluated, or a return statement may be used, just as with
552 subroutines and B<eval()>. The context (list or scalar) is determined
553 by the caller as usual.
555 This behaviour differs from the beta distribution of the Safe extension
556 where earlier versions of perl made it hard to mimic the return
557 behaviour of the eval() command and the context was always scalar.
559 The formerly undocumented STRICT argument sets strictness: if true
560 'use strict;' is used, otherwise it uses 'no strict;'. B<Note>: if
561 STRICT is omitted 'no strict;' is the default.
565 If the entereval op is permitted then the code can use eval "..." to
566 'hide' code which might use denied ops. This is not a major problem
567 since when the code tries to execute the eval it will fail because the
568 opmask is still in effect. However this technique would allow clever,
569 and possibly harmful, code to 'probe' the boundaries of what is
572 Any string eval which is executed by code executing in a compartment,
573 or by code called from code executing in a compartment, will be eval'd
574 in the namespace of the compartment. This is potentially a serious
577 Consider a function foo() in package pkg compiled outside a compartment
578 but shared with it. Assume the compartment has a root package called
579 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
580 normally, $pkg::foo will be set to 1. If foo() is called from the
581 compartment (by whatever means) then instead of setting $pkg::foo, the
582 eval will actually set $Root::pkg::foo.
584 This can easily be demonstrated by using a module, such as the Socket
585 module, which uses eval "..." as part of an AUTOLOAD function. You can
586 'use' the module outside the compartment and share an (autoloaded)
587 function with the compartment. If an autoload is triggered by code in
588 the compartment, or by any code anywhere that is called by any means
589 from the compartment, then the eval in the Socket module's AUTOLOAD
590 function happens in the namespace of the compartment. Any variables
591 created or used by the eval'd code are now under the control of
592 the code in the compartment.
594 A similar effect applies to I<all> runtime symbol lookups in code
595 called from a compartment but not compiled within it.
601 This evaluates the contents of file FILENAME inside the compartment.
602 See above documentation on the B<reval> method for further details.
604 =item root (NAMESPACE)
606 This method returns the name of the package that is the root of the
607 compartment's namespace.
609 Note that this behaviour differs from version 1.00 of the Safe module
610 where the root module could be used to change the namespace. That
611 functionality has been withdrawn pending deeper consideration.
615 This is a get-or-set method for the compartment's operator mask.
617 With no MASK argument present, it returns the current operator mask of
620 With the MASK argument present, it sets the operator mask for the
621 compartment (equivalent to calling the deny_only method).
626 =head2 Some Safety Issues
628 This section is currently just an outline of some of the things code in
629 a compartment might do (intentionally or unintentionally) which can
630 have an effect outside the compartment.
636 Consuming all (or nearly all) available memory.
640 Causing infinite loops etc.
644 Copying private information out of your system. Even something as
645 simple as your user name is of value to others. Much useful information
646 could be gleaned from your environment variables for example.
650 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
652 Setting up a signal handler will need to be carefully considered
653 and controlled. What mask is in effect when a signal handler
654 gets called? If a user can get an imported function to get an
655 exception and call the user's signal handler, does that user's
656 restricted mask get re-instated before the handler is called?
657 Does an imported handler get called with its original mask or
662 Ops such as chdir obviously effect the process as a whole and not just
663 the code in the compartment. Ops such as rand and srand have a similar
664 but more subtle effect.
670 Originally designed and implemented by Malcolm Beattie.
672 Reworked to use the Opcode module and other changes added by Tim Bunce.
674 Currently maintained by the Perl 5 Porters, <perl5-porters@perl.org>.