6 $Safe::VERSION = "2.16_01";
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 $var";
246 *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
247 : ($type eq '&') ? \&{$pkg."::$var"}
248 : ($type eq '$') ? \${$pkg."::$var"}
249 : ($type eq '@') ? \@{$pkg."::$var"}
250 : ($type eq '%') ? \%{$pkg."::$var"}
251 : ($type eq '*') ? *{$pkg."::$var"}
252 : croak(qq(Can't share "$type$var" of unknown type));
254 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
261 my $shares = \%{$obj->{Shares} ||= {}};
262 # Record shares using keys of $obj->{Shares}. See reinit.
263 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
267 my $shares = \%{$obj->{Shares} ||= {}};
269 while(($var, $pkg) = each %$shares) {
270 # warn "share_redo $pkg\:: $var";
271 $obj->share_from($pkg, [ $var ], 1);
275 delete shift->{Shares};
279 my ($obj, $var) = @_;
281 return *{$obj->root()."::$var"};
286 my ($obj, $expr, $strict) = @_;
287 my $root = $obj->{Root};
289 my $evalsub = lexless_anon_sub($root,$strict, $expr);
290 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
294 my ($obj, $file) = @_;
295 my $root = $obj->{Root};
298 sprintf('package %s; sub { @_ = (); do $file }', $root);
299 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
309 Safe - Compile and execute code in restricted compartments
315 $compartment = new Safe;
317 $compartment->permit(qw(time sort :browse));
319 $result = $compartment->reval($unsafe_code);
323 The Safe extension module allows the creation of compartments
324 in which perl code can be evaluated. Each compartment has
328 =item a new namespace
330 The "root" of the namespace (i.e. "main::") is changed to a
331 different package and code evaluated in the compartment cannot
332 refer to variables outside this namespace, even with run-time
333 glob lookups and other tricks.
335 Code which is compiled outside the compartment can choose to place
336 variables into (or I<share> variables with) the compartment's namespace
337 and only that data will be visible to code evaluated in the
340 By default, the only variables shared with compartments are the
341 "underscore" variables $_ and @_ (and, technically, the less frequently
342 used %_, the _ filehandle and so on). This is because otherwise perl
343 operators which default to $_ will not work and neither will the
344 assignment of arguments to @_ on subroutine entry.
346 =item an operator mask
348 Each compartment has an associated "operator mask". Recall that
349 perl code is compiled into an internal format before execution.
350 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
351 the code to be compiled into an internal format and then,
352 provided there was no error in the compilation, executed.
353 Code evaluated in a compartment compiles subject to the
354 compartment's operator mask. Attempting to evaluate code in a
355 compartment which contains a masked operator will cause the
356 compilation to fail with an error. The code will not be executed.
358 The default operator mask for a newly created compartment is
359 the ':default' optag.
361 It is important that you read the L<Opcode> module documentation
362 for more information, especially for detailed definitions of opnames,
365 Since it is only at the compilation stage that the operator mask
366 applies, controlled access to potentially unsafe operations can
367 be achieved by having a handle to a wrapper subroutine (written
368 outside the compartment) placed into the compartment. For example,
372 # vet arguments and perform potentially unsafe operations
374 $cpt->share('&wrapper');
381 The authors make B<no warranty>, implied or otherwise, about the
382 suitability of this software for safety or security purposes.
384 The authors shall not in any case be liable for special, incidental,
385 consequential, indirect or other similar damages arising from the use
388 Your mileage will vary. If in any doubt B<do not use it>.
391 =head2 RECENT CHANGES
393 The interface to the Safe module has changed quite dramatically since
394 version 1 (as supplied with Perl5.002). Study these pages carefully if
395 you have code written to use Safe version 1 because you will need to
399 =head2 Methods in class Safe
401 To create a new compartment, use
405 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
406 to use for the compartment (defaults to "Safe::Root0", incremented for
407 each new compartment).
409 Note that version 1.00 of the Safe module supported a second optional
410 parameter, MASK. That functionality has been withdrawn pending deeper
411 consideration. Use the permit and deny methods described below.
413 The following methods can then be used on the compartment
414 object returned by the above constructor. The object argument
415 is implicit in each case.
420 =item permit (OP, ...)
422 Permit the listed operators to be used when compiling code in the
423 compartment (in I<addition> to any operators already permitted).
425 You can list opcodes by names, or use a tag name; see
426 L<Opcode/"Predefined Opcode Tags">.
428 =item permit_only (OP, ...)
430 Permit I<only> the listed operators to be used when compiling code in
431 the compartment (I<no> other operators are permitted).
435 Deny the listed operators from being used when compiling code in the
436 compartment (other operators may still be permitted).
438 =item deny_only (OP, ...)
440 Deny I<only> the listed operators from being used when compiling code
441 in the compartment (I<all> other operators will be permitted).
445 =item untrap (OP, ...)
447 The trap and untrap methods are synonyms for deny and permit
450 =item share (NAME, ...)
452 This shares the variable(s) in the argument list with the compartment.
453 This is almost identical to exporting variables using the L<Exporter>
456 Each NAME must be the B<name> of a non-lexical variable, typically
457 with the leading type identifier included. A bareword is treated as a
460 Examples of legal names are '$foo' for a scalar, '@foo' for an
461 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
462 for a glob (i.e. all symbol table entries associated with "foo",
463 including scalar, array, hash, sub and filehandle).
465 Each NAME is assumed to be in the calling package. See share_from
466 for an alternative method (which share uses).
468 =item share_from (PACKAGE, ARRAYREF)
470 This method is similar to share() but allows you to explicitly name the
471 package that symbols should be shared from. The symbol names (including
472 type characters) are supplied as an array reference.
474 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
477 =item varglob (VARNAME)
479 This returns a glob reference for the symbol table entry of VARNAME in
480 the package of the compartment. VARNAME must be the B<name> of a
481 variable without any leading type marker. For example,
483 $cpt = new Safe 'Root';
484 $Root::foo = "Hello world";
485 # Equivalent version which doesn't need to know $cpt's package name:
486 ${$cpt->varglob('foo')} = "Hello world";
489 =item reval (STRING, STRICT)
491 This evaluates STRING as perl code inside the compartment.
493 The code can only see the compartment's namespace (as returned by the
494 B<root> method). The compartment's root package appears to be the
495 C<main::> package to the code inside the compartment.
497 Any attempt by the code in STRING to use an operator which is not permitted
498 by the compartment will cause an error (at run-time of the main program
499 but at compile-time for the code in STRING). The error is of the form
500 "'%s' trapped by operation mask...".
502 If an operation is trapped in this way, then the code in STRING will
503 not be executed. If such a trapped operation occurs or any other
504 compile-time or return error, then $@ is set to the error message, just
507 If there is no error, then the method returns the value of the last
508 expression evaluated, or a return statement may be used, just as with
509 subroutines and B<eval()>. The context (list or scalar) is determined
510 by the caller as usual.
512 This behaviour differs from the beta distribution of the Safe extension
513 where earlier versions of perl made it hard to mimic the return
514 behaviour of the eval() command and the context was always scalar.
516 The formerly undocumented STRICT argument sets strictness: if true
517 'use strict;' is used, otherwise it uses 'no strict;'. B<Note>: if
518 STRICT is omitted 'no strict;' is the default.
522 If the entereval op is permitted then the code can use eval "..." to
523 'hide' code which might use denied ops. This is not a major problem
524 since when the code tries to execute the eval it will fail because the
525 opmask is still in effect. However this technique would allow clever,
526 and possibly harmful, code to 'probe' the boundaries of what is
529 Any string eval which is executed by code executing in a compartment,
530 or by code called from code executing in a compartment, will be eval'd
531 in the namespace of the compartment. This is potentially a serious
534 Consider a function foo() in package pkg compiled outside a compartment
535 but shared with it. Assume the compartment has a root package called
536 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
537 normally, $pkg::foo will be set to 1. If foo() is called from the
538 compartment (by whatever means) then instead of setting $pkg::foo, the
539 eval will actually set $Root::pkg::foo.
541 This can easily be demonstrated by using a module, such as the Socket
542 module, which uses eval "..." as part of an AUTOLOAD function. You can
543 'use' the module outside the compartment and share an (autoloaded)
544 function with the compartment. If an autoload is triggered by code in
545 the compartment, or by any code anywhere that is called by any means
546 from the compartment, then the eval in the Socket module's AUTOLOAD
547 function happens in the namespace of the compartment. Any variables
548 created or used by the eval'd code are now under the control of
549 the code in the compartment.
551 A similar effect applies to I<all> runtime symbol lookups in code
552 called from a compartment but not compiled within it.
558 This evaluates the contents of file FILENAME inside the compartment.
559 See above documentation on the B<reval> method for further details.
561 =item root (NAMESPACE)
563 This method returns the name of the package that is the root of the
564 compartment's namespace.
566 Note that this behaviour differs from version 1.00 of the Safe module
567 where the root module could be used to change the namespace. That
568 functionality has been withdrawn pending deeper consideration.
572 This is a get-or-set method for the compartment's operator mask.
574 With no MASK argument present, it returns the current operator mask of
577 With the MASK argument present, it sets the operator mask for the
578 compartment (equivalent to calling the deny_only method).
583 =head2 Some Safety Issues
585 This section is currently just an outline of some of the things code in
586 a compartment might do (intentionally or unintentionally) which can
587 have an effect outside the compartment.
593 Consuming all (or nearly all) available memory.
597 Causing infinite loops etc.
601 Copying private information out of your system. Even something as
602 simple as your user name is of value to others. Much useful information
603 could be gleaned from your environment variables for example.
607 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
609 Setting up a signal handler will need to be carefully considered
610 and controlled. What mask is in effect when a signal handler
611 gets called? If a user can get an imported function to get an
612 exception and call the user's signal handler, does that user's
613 restricted mask get re-instated before the handler is called?
614 Does an imported handler get called with its original mask or
619 Ops such as chdir obviously effect the process as a whole and not just
620 the code in the compartment. Ops such as rand and srand have a similar
621 but more subtle effect.
627 Originally designed and implemented by Malcolm Beattie.
629 Reworked to use the Opcode module and other changes added by Tim Bunce.
631 Currently maintained by the Perl 5 Porters, <perl5-porters@perl.org>.