6 $Safe::VERSION = "2.12";
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';
32 opset opset_to_ops opmask_add
33 empty_opset full_opset invert_opset verify_opset
34 opdesc opcodes opmask define_optag opset_to_hex
37 *ops_to_opset = \&opset; # Temporary alias for old Penguins
41 my $default_share = ['*_']; #, '*main::'];
44 my($class, $root, $mask) = @_;
49 croak "Can't use \"$root\" as root name"
50 if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/;
55 $obj->{Root} = "Safe::Root".$default_root++;
59 # use permit/deny methods instead till interface issues resolved
60 # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...;
61 croak "Mask parameter to new no longer supported" if defined $mask;
62 $obj->permit_only(':default');
64 # We must share $_ and @_ with the compartment or else ops such
65 # as split, length and so on won't default to $_ properly, nor
66 # will passing argument to subroutines work (via @_). In fact,
67 # for reasons I don't completely understand, we need to share
68 # the whole glob *_ rather than $_ and @_ separately, otherwise
69 # @_ in non default packages within the compartment don't work.
70 $obj->share_from('main', $default_share);
71 Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04);
77 $obj->erase('DESTROY') if $obj->{Erase};
81 my ($obj, $action) = @_;
82 my $pkg = $obj->root();
86 $pkg = "main::$pkg\::"; # expand to full symbol table name
87 ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
89 # The 'my $foo' is needed! Without it you get an
90 # 'Attempt to free unreferenced scalar' warning!
91 my $stem_symtab = *{$stem}{HASH};
93 #warn "erase($pkg) stem=$stem, leaf=$leaf";
94 #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n";
95 # ", join(', ', %$stem_symtab),"\n";
97 # delete $stem_symtab->{$leaf};
99 my $leaf_glob = $stem_symtab->{$leaf};
100 my $leaf_symtab = *{$leaf_glob}{HASH};
101 # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n";
103 #delete $leaf_symtab->{'__ANON__'};
104 #delete $leaf_symtab->{'foo'};
105 #delete $leaf_symtab->{'main::'};
106 # my $foo = undef ${"$stem\::"}{"$leaf\::"};
108 if ($action and $action eq 'DESTROY') {
109 delete $stem_symtab->{$leaf};
111 $obj->share_from('main', $default_share);
125 croak("Safe root method now read-only") if @_;
132 return $obj->{Mask} unless @_;
136 # v1 compatibility methods
137 sub trap { shift->deny(@_) }
138 sub untrap { shift->permit(@_) }
142 $obj->{Mask} |= opset(@_);
146 $obj->{Mask} = opset(@_);
152 $obj->{Mask} &= invert_opset opset(@_);
156 $obj->{Mask} = invert_opset opset(@_);
162 print opset_to_hex($obj->{Mask}),"\n";
168 my($obj, @vars) = @_;
169 $obj->share_from(scalar(caller), \@vars);
176 my $no_record = shift || 0;
177 my $root = $obj->root();
178 croak("vars not an array ref") unless ref $vars eq 'ARRAY';
180 # Check that 'from' package actually exists
181 croak("Package \"$pkg\" does not exist")
182 unless keys %{"$pkg\::"};
184 foreach $arg (@$vars) {
185 # catch some $safe->share($var) errors:
186 croak("'$arg' not a valid symbol table name")
187 unless $arg =~ /^[\$\@%*&]?\w[\w:]*$/
190 $type = $1 if ($var = $arg) =~ s/^(\W)//;
191 # warn "share_from $pkg $type $var";
192 *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
193 : ($type eq '&') ? \&{$pkg."::$var"}
194 : ($type eq '$') ? \${$pkg."::$var"}
195 : ($type eq '@') ? \@{$pkg."::$var"}
196 : ($type eq '%') ? \%{$pkg."::$var"}
197 : ($type eq '*') ? *{$pkg."::$var"}
198 : croak(qq(Can't share "$type$var" of unknown type));
200 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
207 my $shares = \%{$obj->{Shares} ||= {}};
208 # Record shares using keys of $obj->{Shares}. See reinit.
209 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
213 my $shares = \%{$obj->{Shares} ||= {}};
215 while(($var, $pkg) = each %$shares) {
216 # warn "share_redo $pkg\:: $var";
217 $obj->share_from($pkg, [ $var ], 1);
221 delete shift->{Shares};
225 my ($obj, $var) = @_;
227 return *{$obj->root()."::$var"};
232 my ($obj, $expr, $strict) = @_;
233 my $root = $obj->{Root};
235 my $evalsub = lexless_anon_sub($root,$strict, $expr);
236 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
240 my ($obj, $file) = @_;
241 my $root = $obj->{Root};
244 sprintf('package %s; sub { @_ = (); do $file }', $root);
245 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
255 Safe - Compile and execute code in restricted compartments
261 $compartment = new Safe;
263 $compartment->permit(qw(time sort :browse));
265 $result = $compartment->reval($unsafe_code);
269 The Safe extension module allows the creation of compartments
270 in which perl code can be evaluated. Each compartment has
274 =item a new namespace
276 The "root" of the namespace (i.e. "main::") is changed to a
277 different package and code evaluated in the compartment cannot
278 refer to variables outside this namespace, even with run-time
279 glob lookups and other tricks.
281 Code which is compiled outside the compartment can choose to place
282 variables into (or I<share> variables with) the compartment's namespace
283 and only that data will be visible to code evaluated in the
286 By default, the only variables shared with compartments are the
287 "underscore" variables $_ and @_ (and, technically, the less frequently
288 used %_, the _ filehandle and so on). This is because otherwise perl
289 operators which default to $_ will not work and neither will the
290 assignment of arguments to @_ on subroutine entry.
292 =item an operator mask
294 Each compartment has an associated "operator mask". Recall that
295 perl code is compiled into an internal format before execution.
296 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
297 the code to be compiled into an internal format and then,
298 provided there was no error in the compilation, executed.
299 Code evaluated in a compartment compiles subject to the
300 compartment's operator mask. Attempting to evaluate code in a
301 compartment which contains a masked operator will cause the
302 compilation to fail with an error. The code will not be executed.
304 The default operator mask for a newly created compartment is
305 the ':default' optag.
307 It is important that you read the Opcode(3) module documentation
308 for more information, especially for detailed definitions of opnames,
311 Since it is only at the compilation stage that the operator mask
312 applies, controlled access to potentially unsafe operations can
313 be achieved by having a handle to a wrapper subroutine (written
314 outside the compartment) placed into the compartment. For example,
318 # vet arguments and perform potentially unsafe operations
320 $cpt->share('&wrapper');
327 The authors make B<no warranty>, implied or otherwise, about the
328 suitability of this software for safety or security purposes.
330 The authors shall not in any case be liable for special, incidental,
331 consequential, indirect or other similar damages arising from the use
334 Your mileage will vary. If in any doubt B<do not use it>.
337 =head2 RECENT CHANGES
339 The interface to the Safe module has changed quite dramatically since
340 version 1 (as supplied with Perl5.002). Study these pages carefully if
341 you have code written to use Safe version 1 because you will need to
345 =head2 Methods in class Safe
347 To create a new compartment, use
351 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
352 to use for the compartment (defaults to "Safe::Root0", incremented for
353 each new compartment).
355 Note that version 1.00 of the Safe module supported a second optional
356 parameter, MASK. That functionality has been withdrawn pending deeper
357 consideration. Use the permit and deny methods described below.
359 The following methods can then be used on the compartment
360 object returned by the above constructor. The object argument
361 is implicit in each case.
366 =item permit (OP, ...)
368 Permit the listed operators to be used when compiling code in the
369 compartment (in I<addition> to any operators already permitted).
371 You can list opcodes by names, or use a tag name; see
372 L<Opcode/"Predefined Opcode Tags">.
374 =item permit_only (OP, ...)
376 Permit I<only> the listed operators to be used when compiling code in
377 the compartment (I<no> other operators are permitted).
381 Deny the listed operators from being used when compiling code in the
382 compartment (other operators may still be permitted).
384 =item deny_only (OP, ...)
386 Deny I<only> the listed operators from being used when compiling code
387 in the compartment (I<all> other operators will be permitted).
391 =item untrap (OP, ...)
393 The trap and untrap methods are synonyms for deny and permit
396 =item share (NAME, ...)
398 This shares the variable(s) in the argument list with the compartment.
399 This is almost identical to exporting variables using the L<Exporter>
402 Each NAME must be the B<name> of a non-lexical variable, typically
403 with the leading type identifier included. A bareword is treated as a
406 Examples of legal names are '$foo' for a scalar, '@foo' for an
407 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
408 for a glob (i.e. all symbol table entries associated with "foo",
409 including scalar, array, hash, sub and filehandle).
411 Each NAME is assumed to be in the calling package. See share_from
412 for an alternative method (which share uses).
414 =item share_from (PACKAGE, ARRAYREF)
416 This method is similar to share() but allows you to explicitly name the
417 package that symbols should be shared from. The symbol names (including
418 type characters) are supplied as an array reference.
420 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
423 =item varglob (VARNAME)
425 This returns a glob reference for the symbol table entry of VARNAME in
426 the package of the compartment. VARNAME must be the B<name> of a
427 variable without any leading type marker. For example,
429 $cpt = new Safe 'Root';
430 $Root::foo = "Hello world";
431 # Equivalent version which doesn't need to know $cpt's package name:
432 ${$cpt->varglob('foo')} = "Hello world";
437 This evaluates STRING as perl code inside the compartment.
439 The code can only see the compartment's namespace (as returned by the
440 B<root> method). The compartment's root package appears to be the
441 C<main::> package to the code inside the compartment.
443 Any attempt by the code in STRING to use an operator which is not permitted
444 by the compartment will cause an error (at run-time of the main program
445 but at compile-time for the code in STRING). The error is of the form
446 "'%s' trapped by operation mask...".
448 If an operation is trapped in this way, then the code in STRING will
449 not be executed. If such a trapped operation occurs or any other
450 compile-time or return error, then $@ is set to the error message, just
453 If there is no error, then the method returns the value of the last
454 expression evaluated, or a return statement may be used, just as with
455 subroutines and B<eval()>. The context (list or scalar) is determined
456 by the caller as usual.
458 This behaviour differs from the beta distribution of the Safe extension
459 where earlier versions of perl made it hard to mimic the return
460 behaviour of the eval() command and the context was always scalar.
464 If the entereval op is permitted then the code can use eval "..." to
465 'hide' code which might use denied ops. This is not a major problem
466 since when the code tries to execute the eval it will fail because the
467 opmask is still in effect. However this technique would allow clever,
468 and possibly harmful, code to 'probe' the boundaries of what is
471 Any string eval which is executed by code executing in a compartment,
472 or by code called from code executing in a compartment, will be eval'd
473 in the namespace of the compartment. This is potentially a serious
476 Consider a function foo() in package pkg compiled outside a compartment
477 but shared with it. Assume the compartment has a root package called
478 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
479 normally, $pkg::foo will be set to 1. If foo() is called from the
480 compartment (by whatever means) then instead of setting $pkg::foo, the
481 eval will actually set $Root::pkg::foo.
483 This can easily be demonstrated by using a module, such as the Socket
484 module, which uses eval "..." as part of an AUTOLOAD function. You can
485 'use' the module outside the compartment and share an (autoloaded)
486 function with the compartment. If an autoload is triggered by code in
487 the compartment, or by any code anywhere that is called by any means
488 from the compartment, then the eval in the Socket module's AUTOLOAD
489 function happens in the namespace of the compartment. Any variables
490 created or used by the eval'd code are now under the control of
491 the code in the compartment.
493 A similar effect applies to I<all> runtime symbol lookups in code
494 called from a compartment but not compiled within it.
500 This evaluates the contents of file FILENAME inside the compartment.
501 See above documentation on the B<reval> method for further details.
503 =item root (NAMESPACE)
505 This method returns the name of the package that is the root of the
506 compartment's namespace.
508 Note that this behaviour differs from version 1.00 of the Safe module
509 where the root module could be used to change the namespace. That
510 functionality has been withdrawn pending deeper consideration.
514 This is a get-or-set method for the compartment's operator mask.
516 With no MASK argument present, it returns the current operator mask of
519 With the MASK argument present, it sets the operator mask for the
520 compartment (equivalent to calling the deny_only method).
525 =head2 Some Safety Issues
527 This section is currently just an outline of some of the things code in
528 a compartment might do (intentionally or unintentionally) which can
529 have an effect outside the compartment.
535 Consuming all (or nearly all) available memory.
539 Causing infinite loops etc.
543 Copying private information out of your system. Even something as
544 simple as your user name is of value to others. Much useful information
545 could be gleaned from your environment variables for example.
549 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
551 Setting up a signal handler will need to be carefully considered
552 and controlled. What mask is in effect when a signal handler
553 gets called? If a user can get an imported function to get an
554 exception and call the user's signal handler, does that user's
555 restricted mask get re-instated before the handler is called?
556 Does an imported handler get called with its original mask or
561 Ops such as chdir obviously effect the process as a whole and not just
562 the code in the compartment. Ops such as rand and srand have a similar
563 but more subtle effect.
569 Originally designed and implemented by Malcolm Beattie,
570 mbeattie@sable.ox.ac.uk.
572 Reworked to use the Opcode module and other changes added by Tim Bunce
573 E<lt>F<Tim.Bunce@ig.co.uk>E<gt>.