6 $Safe::VERSION = "2.19";
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 strict; sub { @_=(); eval q[my $__ExPr__;] . $__ExPr__; }',
25 $_[0], $_[1] ? 'use' : 'no';
34 opset opset_to_ops opmask_add
35 empty_opset full_opset invert_opset verify_opset
36 opdesc opcodes opmask define_optag opset_to_hex
39 *ops_to_opset = \&opset; # Temporary alias for old Penguins
43 # share *_ and functions defined in universal.c
44 # Don't share stuff like *UNIVERSAL:: otherwise code from the
45 # compartment can 0wn functions in UNIVERSAL
46 my $default_share = [qw[
58 &utf8::native_to_unicode
59 &utf8::unicode_to_native
63 ], ($] >= 5.008001 && qw[
65 ]), ($] >= 5.010 && qw[
70 &Tie::Hash::NamedCapture::FETCH
71 &Tie::Hash::NamedCapture::STORE
72 &Tie::Hash::NamedCapture::DELETE
73 &Tie::Hash::NamedCapture::CLEAR
74 &Tie::Hash::NamedCapture::EXISTS
75 &Tie::Hash::NamedCapture::FIRSTKEY
76 &Tie::Hash::NamedCapture::NEXTKEY
77 &Tie::Hash::NamedCapture::SCALAR
78 &Tie::Hash::NamedCapture::flags
96 ]), ($] >= 5.011 && qw[
101 my($class, $root, $mask) = @_;
105 if (defined($root)) {
106 croak "Can't use \"$root\" as root name"
107 if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/;
108 $obj->{Root} = $root;
112 $obj->{Root} = "Safe::Root".$default_root++;
116 # use permit/deny methods instead till interface issues resolved
117 # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...;
118 croak "Mask parameter to new no longer supported" if defined $mask;
119 $obj->permit_only(':default');
121 # We must share $_ and @_ with the compartment or else ops such
122 # as split, length and so on won't default to $_ properly, nor
123 # will passing argument to subroutines work (via @_). In fact,
124 # for reasons I don't completely understand, we need to share
125 # the whole glob *_ rather than $_ and @_ separately, otherwise
126 # @_ in non default packages within the compartment don't work.
127 $obj->share_from('main', $default_share);
128 Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04);
134 $obj->erase('DESTROY') if $obj->{Erase};
138 my ($obj, $action) = @_;
139 my $pkg = $obj->root();
143 $pkg = "main::$pkg\::"; # expand to full symbol table name
144 ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
146 # The 'my $foo' is needed! Without it you get an
147 # 'Attempt to free unreferenced scalar' warning!
148 my $stem_symtab = *{$stem}{HASH};
150 #warn "erase($pkg) stem=$stem, leaf=$leaf";
151 #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n";
152 # ", join(', ', %$stem_symtab),"\n";
154 # delete $stem_symtab->{$leaf};
156 my $leaf_glob = $stem_symtab->{$leaf};
157 my $leaf_symtab = *{$leaf_glob}{HASH};
158 # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n";
160 #delete $leaf_symtab->{'__ANON__'};
161 #delete $leaf_symtab->{'foo'};
162 #delete $leaf_symtab->{'main::'};
163 # my $foo = undef ${"$stem\::"}{"$leaf\::"};
165 if ($action and $action eq 'DESTROY') {
166 delete $stem_symtab->{$leaf};
168 $obj->share_from('main', $default_share);
182 croak("Safe root method now read-only") if @_;
189 return $obj->{Mask} unless @_;
193 # v1 compatibility methods
194 sub trap { shift->deny(@_) }
195 sub untrap { shift->permit(@_) }
199 $obj->{Mask} |= opset(@_);
203 $obj->{Mask} = opset(@_);
209 $obj->{Mask} &= invert_opset opset(@_);
213 $obj->{Mask} = invert_opset opset(@_);
219 print opset_to_hex($obj->{Mask}),"\n";
225 my($obj, @vars) = @_;
226 $obj->share_from(scalar(caller), \@vars);
233 my $no_record = shift || 0;
234 my $root = $obj->root();
235 croak("vars not an array ref") unless ref $vars eq 'ARRAY';
237 # Check that 'from' package actually exists
238 croak("Package \"$pkg\" does not exist")
239 unless keys %{"$pkg\::"};
241 foreach $arg (@$vars) {
242 # catch some $safe->share($var) errors:
244 $type = $1 if ($var = $arg) =~ s/^(\W)//;
245 # warn "share_from $pkg $type $var";
246 for (1..2) { # assign twice to avoid any 'used once' warnings
247 *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
248 : ($type eq '&') ? \&{$pkg."::$var"}
249 : ($type eq '$') ? \${$pkg."::$var"}
250 : ($type eq '@') ? \@{$pkg."::$var"}
251 : ($type eq '%') ? \%{$pkg."::$var"}
252 : ($type eq '*') ? *{$pkg."::$var"}
253 : croak(qq(Can't share "$type$var" of unknown type));
256 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
263 my $shares = \%{$obj->{Shares} ||= {}};
264 # Record shares using keys of $obj->{Shares}. See reinit.
265 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
269 my $shares = \%{$obj->{Shares} ||= {}};
271 while(($var, $pkg) = each %$shares) {
272 # warn "share_redo $pkg\:: $var";
273 $obj->share_from($pkg, [ $var ], 1);
277 delete shift->{Shares};
281 my ($obj, $var) = @_;
283 return *{$obj->root()."::$var"};
288 my ($obj, $expr, $strict) = @_;
289 my $root = $obj->{Root};
291 my $evalsub = lexless_anon_sub($root,$strict, $expr);
292 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
296 my ($obj, $file) = @_;
297 my $root = $obj->{Root};
300 sprintf('package %s; sub { @_ = (); do $file }', $root);
301 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
311 Safe - Compile and execute code in restricted compartments
317 $compartment = new Safe;
319 $compartment->permit(qw(time sort :browse));
321 $result = $compartment->reval($unsafe_code);
325 The Safe extension module allows the creation of compartments
326 in which perl code can be evaluated. Each compartment has
330 =item a new namespace
332 The "root" of the namespace (i.e. "main::") is changed to a
333 different package and code evaluated in the compartment cannot
334 refer to variables outside this namespace, even with run-time
335 glob lookups and other tricks.
337 Code which is compiled outside the compartment can choose to place
338 variables into (or I<share> variables with) the compartment's namespace
339 and only that data will be visible to code evaluated in the
342 By default, the only variables shared with compartments are the
343 "underscore" variables $_ and @_ (and, technically, the less frequently
344 used %_, the _ filehandle and so on). This is because otherwise perl
345 operators which default to $_ will not work and neither will the
346 assignment of arguments to @_ on subroutine entry.
348 =item an operator mask
350 Each compartment has an associated "operator mask". Recall that
351 perl code is compiled into an internal format before execution.
352 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
353 the code to be compiled into an internal format and then,
354 provided there was no error in the compilation, executed.
355 Code evaluated in a compartment compiles subject to the
356 compartment's operator mask. Attempting to evaluate code in a
357 compartment which contains a masked operator will cause the
358 compilation to fail with an error. The code will not be executed.
360 The default operator mask for a newly created compartment is
361 the ':default' optag.
363 It is important that you read the L<Opcode> module documentation
364 for more information, especially for detailed definitions of opnames,
367 Since it is only at the compilation stage that the operator mask
368 applies, controlled access to potentially unsafe operations can
369 be achieved by having a handle to a wrapper subroutine (written
370 outside the compartment) placed into the compartment. For example,
374 # vet arguments and perform potentially unsafe operations
376 $cpt->share('&wrapper');
383 The authors make B<no warranty>, implied or otherwise, about the
384 suitability of this software for safety or security purposes.
386 The authors shall not in any case be liable for special, incidental,
387 consequential, indirect or other similar damages arising from the use
390 Your mileage will vary. If in any doubt B<do not use it>.
393 =head2 RECENT CHANGES
395 The interface to the Safe module has changed quite dramatically since
396 version 1 (as supplied with Perl5.002). Study these pages carefully if
397 you have code written to use Safe version 1 because you will need to
401 =head2 Methods in class Safe
403 To create a new compartment, use
407 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
408 to use for the compartment (defaults to "Safe::Root0", incremented for
409 each new compartment).
411 Note that version 1.00 of the Safe module supported a second optional
412 parameter, MASK. That functionality has been withdrawn pending deeper
413 consideration. Use the permit and deny methods described below.
415 The following methods can then be used on the compartment
416 object returned by the above constructor. The object argument
417 is implicit in each case.
422 =item permit (OP, ...)
424 Permit the listed operators to be used when compiling code in the
425 compartment (in I<addition> to any operators already permitted).
427 You can list opcodes by names, or use a tag name; see
428 L<Opcode/"Predefined Opcode Tags">.
430 =item permit_only (OP, ...)
432 Permit I<only> the listed operators to be used when compiling code in
433 the compartment (I<no> other operators are permitted).
437 Deny the listed operators from being used when compiling code in the
438 compartment (other operators may still be permitted).
440 =item deny_only (OP, ...)
442 Deny I<only> the listed operators from being used when compiling code
443 in the compartment (I<all> other operators will be permitted).
447 =item untrap (OP, ...)
449 The trap and untrap methods are synonyms for deny and permit
452 =item share (NAME, ...)
454 This shares the variable(s) in the argument list with the compartment.
455 This is almost identical to exporting variables using the L<Exporter>
458 Each NAME must be the B<name> of a non-lexical variable, typically
459 with the leading type identifier included. A bareword is treated as a
462 Examples of legal names are '$foo' for a scalar, '@foo' for an
463 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
464 for a glob (i.e. all symbol table entries associated with "foo",
465 including scalar, array, hash, sub and filehandle).
467 Each NAME is assumed to be in the calling package. See share_from
468 for an alternative method (which share uses).
470 =item share_from (PACKAGE, ARRAYREF)
472 This method is similar to share() but allows you to explicitly name the
473 package that symbols should be shared from. The symbol names (including
474 type characters) are supplied as an array reference.
476 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
479 =item varglob (VARNAME)
481 This returns a glob reference for the symbol table entry of VARNAME in
482 the package of the compartment. VARNAME must be the B<name> of a
483 variable without any leading type marker. For example,
485 $cpt = new Safe 'Root';
486 $Root::foo = "Hello world";
487 # Equivalent version which doesn't need to know $cpt's package name:
488 ${$cpt->varglob('foo')} = "Hello world";
491 =item reval (STRING, STRICT)
493 This evaluates STRING as perl code inside the compartment.
495 The code can only see the compartment's namespace (as returned by the
496 B<root> method). The compartment's root package appears to be the
497 C<main::> package to the code inside the compartment.
499 Any attempt by the code in STRING to use an operator which is not permitted
500 by the compartment will cause an error (at run-time of the main program
501 but at compile-time for the code in STRING). The error is of the form
502 "'%s' trapped by operation mask...".
504 If an operation is trapped in this way, then the code in STRING will
505 not be executed. If such a trapped operation occurs or any other
506 compile-time or return error, then $@ is set to the error message, just
509 If there is no error, then the method returns the value of the last
510 expression evaluated, or a return statement may be used, just as with
511 subroutines and B<eval()>. The context (list or scalar) is determined
512 by the caller as usual.
514 This behaviour differs from the beta distribution of the Safe extension
515 where earlier versions of perl made it hard to mimic the return
516 behaviour of the eval() command and the context was always scalar.
518 The formerly undocumented STRICT argument sets strictness: if true
519 'use strict;' is used, otherwise it uses 'no strict;'. B<Note>: if
520 STRICT is omitted 'no strict;' is the default.
524 If the entereval op is permitted then the code can use eval "..." to
525 'hide' code which might use denied ops. This is not a major problem
526 since when the code tries to execute the eval it will fail because the
527 opmask is still in effect. However this technique would allow clever,
528 and possibly harmful, code to 'probe' the boundaries of what is
531 Any string eval which is executed by code executing in a compartment,
532 or by code called from code executing in a compartment, will be eval'd
533 in the namespace of the compartment. This is potentially a serious
536 Consider a function foo() in package pkg compiled outside a compartment
537 but shared with it. Assume the compartment has a root package called
538 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
539 normally, $pkg::foo will be set to 1. If foo() is called from the
540 compartment (by whatever means) then instead of setting $pkg::foo, the
541 eval will actually set $Root::pkg::foo.
543 This can easily be demonstrated by using a module, such as the Socket
544 module, which uses eval "..." as part of an AUTOLOAD function. You can
545 'use' the module outside the compartment and share an (autoloaded)
546 function with the compartment. If an autoload is triggered by code in
547 the compartment, or by any code anywhere that is called by any means
548 from the compartment, then the eval in the Socket module's AUTOLOAD
549 function happens in the namespace of the compartment. Any variables
550 created or used by the eval'd code are now under the control of
551 the code in the compartment.
553 A similar effect applies to I<all> runtime symbol lookups in code
554 called from a compartment but not compiled within it.
560 This evaluates the contents of file FILENAME inside the compartment.
561 See above documentation on the B<reval> method for further details.
563 =item root (NAMESPACE)
565 This method returns the name of the package that is the root of the
566 compartment's namespace.
568 Note that this behaviour differs from version 1.00 of the Safe module
569 where the root module could be used to change the namespace. That
570 functionality has been withdrawn pending deeper consideration.
574 This is a get-or-set method for the compartment's operator mask.
576 With no MASK argument present, it returns the current operator mask of
579 With the MASK argument present, it sets the operator mask for the
580 compartment (equivalent to calling the deny_only method).
585 =head2 Some Safety Issues
587 This section is currently just an outline of some of the things code in
588 a compartment might do (intentionally or unintentionally) which can
589 have an effect outside the compartment.
595 Consuming all (or nearly all) available memory.
599 Causing infinite loops etc.
603 Copying private information out of your system. Even something as
604 simple as your user name is of value to others. Much useful information
605 could be gleaned from your environment variables for example.
609 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
611 Setting up a signal handler will need to be carefully considered
612 and controlled. What mask is in effect when a signal handler
613 gets called? If a user can get an imported function to get an
614 exception and call the user's signal handler, does that user's
615 restricted mask get re-instated before the handler is called?
616 Does an imported handler get called with its original mask or
621 Ops such as chdir obviously effect the process as a whole and not just
622 the code in the compartment. Ops such as rand and srand have a similar
623 but more subtle effect.
629 Originally designed and implemented by Malcolm Beattie.
631 Reworked to use the Opcode module and other changes added by Tim Bunce.
633 Currently maintained by the Perl 5 Porters, <perl5-porters@perl.org>.