5 use Scalar::Util qw(reftype);
6 use Config qw(%Config);
7 use constant is_usethreads => $Config{usethreads};
9 $Safe::VERSION = "2.19";
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 $default_share = [qw[
61 &utf8::native_to_unicode
62 &utf8::unicode_to_native
66 ], ($] >= 5.008001 && qw[
68 ]), ($] >= 5.010 && qw[
73 &Tie::Hash::NamedCapture::FETCH
74 &Tie::Hash::NamedCapture::STORE
75 &Tie::Hash::NamedCapture::DELETE
76 &Tie::Hash::NamedCapture::CLEAR
77 &Tie::Hash::NamedCapture::EXISTS
78 &Tie::Hash::NamedCapture::FIRSTKEY
79 &Tie::Hash::NamedCapture::NEXTKEY
80 &Tie::Hash::NamedCapture::SCALAR
81 &Tie::Hash::NamedCapture::flags
99 ]), ($] >= 5.011 && qw[
104 my($class, $root, $mask) = @_;
108 if (defined($root)) {
109 croak "Can't use \"$root\" as root name"
110 if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/;
111 $obj->{Root} = $root;
115 $obj->{Root} = "Safe::Root".$default_root++;
119 # use permit/deny methods instead till interface issues resolved
120 # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...;
121 croak "Mask parameter to new no longer supported" if defined $mask;
122 $obj->permit_only(':default');
124 # We must share $_ and @_ with the compartment or else ops such
125 # as split, length and so on won't default to $_ properly, nor
126 # will passing argument to subroutines work (via @_). In fact,
127 # for reasons I don't completely understand, we need to share
128 # the whole glob *_ rather than $_ and @_ separately, otherwise
129 # @_ in non default packages within the compartment don't work.
130 $obj->share_from('main', $default_share);
131 Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04);
137 $obj->erase('DESTROY') if $obj->{Erase};
141 my ($obj, $action) = @_;
142 my $pkg = $obj->root();
146 $pkg = "main::$pkg\::"; # expand to full symbol table name
147 ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
149 # The 'my $foo' is needed! Without it you get an
150 # 'Attempt to free unreferenced scalar' warning!
151 my $stem_symtab = *{$stem}{HASH};
153 #warn "erase($pkg) stem=$stem, leaf=$leaf";
154 #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n";
155 # ", join(', ', %$stem_symtab),"\n";
157 # delete $stem_symtab->{$leaf};
159 my $leaf_glob = $stem_symtab->{$leaf};
160 my $leaf_symtab = *{$leaf_glob}{HASH};
161 # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n";
163 #delete $leaf_symtab->{'__ANON__'};
164 #delete $leaf_symtab->{'foo'};
165 #delete $leaf_symtab->{'main::'};
166 # my $foo = undef ${"$stem\::"}{"$leaf\::"};
168 if ($action and $action eq 'DESTROY') {
169 delete $stem_symtab->{$leaf};
171 $obj->share_from('main', $default_share);
185 croak("Safe root method now read-only") if @_;
192 return $obj->{Mask} unless @_;
196 # v1 compatibility methods
197 sub trap { shift->deny(@_) }
198 sub untrap { shift->permit(@_) }
202 $obj->{Mask} |= opset(@_);
206 $obj->{Mask} = opset(@_);
212 $obj->{Mask} &= invert_opset opset(@_);
216 $obj->{Mask} = invert_opset opset(@_);
222 print opset_to_hex($obj->{Mask}),"\n";
228 my($obj, @vars) = @_;
229 $obj->share_from(scalar(caller), \@vars);
236 my $no_record = shift || 0;
237 my $root = $obj->root();
238 croak("vars not an array ref") unless ref $vars eq 'ARRAY';
240 # Check that 'from' package actually exists
241 croak("Package \"$pkg\" does not exist")
242 unless keys %{"$pkg\::"};
244 foreach $arg (@$vars) {
245 # catch some $safe->share($var) errors:
247 $type = $1 if ($var = $arg) =~ s/^(\W)//;
248 # warn "share_from $pkg $type $var";
249 for (1..2) { # assign twice to avoid any 'used once' warnings
250 *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
251 : ($type eq '&') ? \&{$pkg."::$var"}
252 : ($type eq '$') ? \${$pkg."::$var"}
253 : ($type eq '@') ? \@{$pkg."::$var"}
254 : ($type eq '%') ? \%{$pkg."::$var"}
255 : ($type eq '*') ? *{$pkg."::$var"}
256 : croak(qq(Can't share "$type$var" of unknown type));
259 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
266 my $shares = \%{$obj->{Shares} ||= {}};
267 # Record shares using keys of $obj->{Shares}. See reinit.
268 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
272 my $shares = \%{$obj->{Shares} ||= {}};
274 while(($var, $pkg) = each %$shares) {
275 # warn "share_redo $pkg\:: $var";
276 $obj->share_from($pkg, [ $var ], 1);
280 delete shift->{Shares};
284 my ($obj, $var) = @_;
286 return *{$obj->root()."::$var"};
291 my ($obj, $expr, $strict) = @_;
292 my $root = $obj->{Root};
294 my $evalsub = lexless_anon_sub($root, $strict, $expr);
295 my @ret = (wantarray)
296 ? Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub)
297 : scalar Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
299 # RT#60374: Safe.pm sort {} bug with -Dusethreads
300 # If the Safe eval returns a code ref in a perl compiled with usethreads
301 # then wrap code ref with _safe_call_sv so that, when called, the
302 # execution will happen with the compartment fully 'in effect'.
303 # Needed to fix sort blocks that reference $a & $b and
304 # possibly other subtle issues.
305 if (is_usethreads()) {
306 for my $ret (@ret) { # edit (via alias) any CODE refs
307 next unless (reftype($ret)||'') eq 'CODE';
308 my $sub = $ret; # avoid closure problems
309 $ret = sub { Opcode::_safe_call_sv($root, $obj->{Mask}, $sub) };
313 return (wantarray) ? @ret : $ret[0];
317 my ($obj, $file) = @_;
318 my $root = $obj->{Root};
321 sprintf('package %s; sub { @_ = (); do $file }', $root);
322 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
332 Safe - Compile and execute code in restricted compartments
338 $compartment = new Safe;
340 $compartment->permit(qw(time sort :browse));
342 $result = $compartment->reval($unsafe_code);
346 The Safe extension module allows the creation of compartments
347 in which perl code can be evaluated. Each compartment has
351 =item a new namespace
353 The "root" of the namespace (i.e. "main::") is changed to a
354 different package and code evaluated in the compartment cannot
355 refer to variables outside this namespace, even with run-time
356 glob lookups and other tricks.
358 Code which is compiled outside the compartment can choose to place
359 variables into (or I<share> variables with) the compartment's namespace
360 and only that data will be visible to code evaluated in the
363 By default, the only variables shared with compartments are the
364 "underscore" variables $_ and @_ (and, technically, the less frequently
365 used %_, the _ filehandle and so on). This is because otherwise perl
366 operators which default to $_ will not work and neither will the
367 assignment of arguments to @_ on subroutine entry.
369 =item an operator mask
371 Each compartment has an associated "operator mask". Recall that
372 perl code is compiled into an internal format before execution.
373 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
374 the code to be compiled into an internal format and then,
375 provided there was no error in the compilation, executed.
376 Code evaluated in a compartment compiles subject to the
377 compartment's operator mask. Attempting to evaluate code in a
378 compartment which contains a masked operator will cause the
379 compilation to fail with an error. The code will not be executed.
381 The default operator mask for a newly created compartment is
382 the ':default' optag.
384 It is important that you read the L<Opcode> module documentation
385 for more information, especially for detailed definitions of opnames,
388 Since it is only at the compilation stage that the operator mask
389 applies, controlled access to potentially unsafe operations can
390 be achieved by having a handle to a wrapper subroutine (written
391 outside the compartment) placed into the compartment. For example,
395 # vet arguments and perform potentially unsafe operations
397 $cpt->share('&wrapper');
404 The authors make B<no warranty>, implied or otherwise, about the
405 suitability of this software for safety or security purposes.
407 The authors shall not in any case be liable for special, incidental,
408 consequential, indirect or other similar damages arising from the use
411 Your mileage will vary. If in any doubt B<do not use it>.
414 =head2 RECENT CHANGES
416 The interface to the Safe module has changed quite dramatically since
417 version 1 (as supplied with Perl5.002). Study these pages carefully if
418 you have code written to use Safe version 1 because you will need to
422 =head2 Methods in class Safe
424 To create a new compartment, use
428 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
429 to use for the compartment (defaults to "Safe::Root0", incremented for
430 each new compartment).
432 Note that version 1.00 of the Safe module supported a second optional
433 parameter, MASK. That functionality has been withdrawn pending deeper
434 consideration. Use the permit and deny methods described below.
436 The following methods can then be used on the compartment
437 object returned by the above constructor. The object argument
438 is implicit in each case.
443 =item permit (OP, ...)
445 Permit the listed operators to be used when compiling code in the
446 compartment (in I<addition> to any operators already permitted).
448 You can list opcodes by names, or use a tag name; see
449 L<Opcode/"Predefined Opcode Tags">.
451 =item permit_only (OP, ...)
453 Permit I<only> the listed operators to be used when compiling code in
454 the compartment (I<no> other operators are permitted).
458 Deny the listed operators from being used when compiling code in the
459 compartment (other operators may still be permitted).
461 =item deny_only (OP, ...)
463 Deny I<only> the listed operators from being used when compiling code
464 in the compartment (I<all> other operators will be permitted).
468 =item untrap (OP, ...)
470 The trap and untrap methods are synonyms for deny and permit
473 =item share (NAME, ...)
475 This shares the variable(s) in the argument list with the compartment.
476 This is almost identical to exporting variables using the L<Exporter>
479 Each NAME must be the B<name> of a non-lexical variable, typically
480 with the leading type identifier included. A bareword is treated as a
483 Examples of legal names are '$foo' for a scalar, '@foo' for an
484 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
485 for a glob (i.e. all symbol table entries associated with "foo",
486 including scalar, array, hash, sub and filehandle).
488 Each NAME is assumed to be in the calling package. See share_from
489 for an alternative method (which share uses).
491 =item share_from (PACKAGE, ARRAYREF)
493 This method is similar to share() but allows you to explicitly name the
494 package that symbols should be shared from. The symbol names (including
495 type characters) are supplied as an array reference.
497 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
500 =item varglob (VARNAME)
502 This returns a glob reference for the symbol table entry of VARNAME in
503 the package of the compartment. VARNAME must be the B<name> of a
504 variable without any leading type marker. For example,
506 $cpt = new Safe 'Root';
507 $Root::foo = "Hello world";
508 # Equivalent version which doesn't need to know $cpt's package name:
509 ${$cpt->varglob('foo')} = "Hello world";
512 =item reval (STRING, STRICT)
514 This evaluates STRING as perl code inside the compartment.
516 The code can only see the compartment's namespace (as returned by the
517 B<root> method). The compartment's root package appears to be the
518 C<main::> package to the code inside the compartment.
520 Any attempt by the code in STRING to use an operator which is not permitted
521 by the compartment will cause an error (at run-time of the main program
522 but at compile-time for the code in STRING). The error is of the form
523 "'%s' trapped by operation mask...".
525 If an operation is trapped in this way, then the code in STRING will
526 not be executed. If such a trapped operation occurs or any other
527 compile-time or return error, then $@ is set to the error message, just
530 If there is no error, then the method returns the value of the last
531 expression evaluated, or a return statement may be used, just as with
532 subroutines and B<eval()>. The context (list or scalar) is determined
533 by the caller as usual.
535 This behaviour differs from the beta distribution of the Safe extension
536 where earlier versions of perl made it hard to mimic the return
537 behaviour of the eval() command and the context was always scalar.
539 The formerly undocumented STRICT argument sets strictness: if true
540 'use strict;' is used, otherwise it uses 'no strict;'. B<Note>: if
541 STRICT is omitted 'no strict;' is the default.
545 If the entereval op is permitted then the code can use eval "..." to
546 'hide' code which might use denied ops. This is not a major problem
547 since when the code tries to execute the eval it will fail because the
548 opmask is still in effect. However this technique would allow clever,
549 and possibly harmful, code to 'probe' the boundaries of what is
552 Any string eval which is executed by code executing in a compartment,
553 or by code called from code executing in a compartment, will be eval'd
554 in the namespace of the compartment. This is potentially a serious
557 Consider a function foo() in package pkg compiled outside a compartment
558 but shared with it. Assume the compartment has a root package called
559 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
560 normally, $pkg::foo will be set to 1. If foo() is called from the
561 compartment (by whatever means) then instead of setting $pkg::foo, the
562 eval will actually set $Root::pkg::foo.
564 This can easily be demonstrated by using a module, such as the Socket
565 module, which uses eval "..." as part of an AUTOLOAD function. You can
566 'use' the module outside the compartment and share an (autoloaded)
567 function with the compartment. If an autoload is triggered by code in
568 the compartment, or by any code anywhere that is called by any means
569 from the compartment, then the eval in the Socket module's AUTOLOAD
570 function happens in the namespace of the compartment. Any variables
571 created or used by the eval'd code are now under the control of
572 the code in the compartment.
574 A similar effect applies to I<all> runtime symbol lookups in code
575 called from a compartment but not compiled within it.
581 This evaluates the contents of file FILENAME inside the compartment.
582 See above documentation on the B<reval> method for further details.
584 =item root (NAMESPACE)
586 This method returns the name of the package that is the root of the
587 compartment's namespace.
589 Note that this behaviour differs from version 1.00 of the Safe module
590 where the root module could be used to change the namespace. That
591 functionality has been withdrawn pending deeper consideration.
595 This is a get-or-set method for the compartment's operator mask.
597 With no MASK argument present, it returns the current operator mask of
600 With the MASK argument present, it sets the operator mask for the
601 compartment (equivalent to calling the deny_only method).
606 =head2 Some Safety Issues
608 This section is currently just an outline of some of the things code in
609 a compartment might do (intentionally or unintentionally) which can
610 have an effect outside the compartment.
616 Consuming all (or nearly all) available memory.
620 Causing infinite loops etc.
624 Copying private information out of your system. Even something as
625 simple as your user name is of value to others. Much useful information
626 could be gleaned from your environment variables for example.
630 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
632 Setting up a signal handler will need to be carefully considered
633 and controlled. What mask is in effect when a signal handler
634 gets called? If a user can get an imported function to get an
635 exception and call the user's signal handler, does that user's
636 restricted mask get re-instated before the handler is called?
637 Does an imported handler get called with its original mask or
642 Ops such as chdir obviously effect the process as a whole and not just
643 the code in the compartment. Ops such as rand and srand have a similar
644 but more subtle effect.
650 Originally designed and implemented by Malcolm Beattie.
652 Reworked to use the Opcode module and other changes added by Tim Bunce.
654 Currently maintained by the Perl 5 Porters, <perl5-porters@perl.org>.