6 $Safe::VERSION = "2.11";
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 =item permit_only (OP, ...)
373 Permit I<only> the listed operators to be used when compiling code in
374 the compartment (I<no> other operators are permitted).
378 Deny the listed operators from being used when compiling code in the
379 compartment (other operators may still be permitted).
381 =item deny_only (OP, ...)
383 Deny I<only> the listed operators from being used when compiling code
384 in the compartment (I<all> other operators will be permitted).
388 =item untrap (OP, ...)
390 The trap and untrap methods are synonyms for deny and permit
393 =item share (NAME, ...)
395 This shares the variable(s) in the argument list with the compartment.
396 This is almost identical to exporting variables using the L<Exporter>
399 Each NAME must be the B<name> of a non-lexical variable, typically
400 with the leading type identifier included. A bareword is treated as a
403 Examples of legal names are '$foo' for a scalar, '@foo' for an
404 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
405 for a glob (i.e. all symbol table entries associated with "foo",
406 including scalar, array, hash, sub and filehandle).
408 Each NAME is assumed to be in the calling package. See share_from
409 for an alternative method (which share uses).
411 =item share_from (PACKAGE, ARRAYREF)
413 This method is similar to share() but allows you to explicitly name the
414 package that symbols should be shared from. The symbol names (including
415 type characters) are supplied as an array reference.
417 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
420 =item varglob (VARNAME)
422 This returns a glob reference for the symbol table entry of VARNAME in
423 the package of the compartment. VARNAME must be the B<name> of a
424 variable without any leading type marker. For example,
426 $cpt = new Safe 'Root';
427 $Root::foo = "Hello world";
428 # Equivalent version which doesn't need to know $cpt's package name:
429 ${$cpt->varglob('foo')} = "Hello world";
434 This evaluates STRING as perl code inside the compartment.
436 The code can only see the compartment's namespace (as returned by the
437 B<root> method). The compartment's root package appears to be the
438 C<main::> package to the code inside the compartment.
440 Any attempt by the code in STRING to use an operator which is not permitted
441 by the compartment will cause an error (at run-time of the main program
442 but at compile-time for the code in STRING). The error is of the form
443 "'%s' trapped by operation mask...".
445 If an operation is trapped in this way, then the code in STRING will
446 not be executed. If such a trapped operation occurs or any other
447 compile-time or return error, then $@ is set to the error message, just
450 If there is no error, then the method returns the value of the last
451 expression evaluated, or a return statement may be used, just as with
452 subroutines and B<eval()>. The context (list or scalar) is determined
453 by the caller as usual.
455 This behaviour differs from the beta distribution of the Safe extension
456 where earlier versions of perl made it hard to mimic the return
457 behaviour of the eval() command and the context was always scalar.
461 If the entereval op is permitted then the code can use eval "..." to
462 'hide' code which might use denied ops. This is not a major problem
463 since when the code tries to execute the eval it will fail because the
464 opmask is still in effect. However this technique would allow clever,
465 and possibly harmful, code to 'probe' the boundaries of what is
468 Any string eval which is executed by code executing in a compartment,
469 or by code called from code executing in a compartment, will be eval'd
470 in the namespace of the compartment. This is potentially a serious
473 Consider a function foo() in package pkg compiled outside a compartment
474 but shared with it. Assume the compartment has a root package called
475 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
476 normally, $pkg::foo will be set to 1. If foo() is called from the
477 compartment (by whatever means) then instead of setting $pkg::foo, the
478 eval will actually set $Root::pkg::foo.
480 This can easily be demonstrated by using a module, such as the Socket
481 module, which uses eval "..." as part of an AUTOLOAD function. You can
482 'use' the module outside the compartment and share an (autoloaded)
483 function with the compartment. If an autoload is triggered by code in
484 the compartment, or by any code anywhere that is called by any means
485 from the compartment, then the eval in the Socket module's AUTOLOAD
486 function happens in the namespace of the compartment. Any variables
487 created or used by the eval'd code are now under the control of
488 the code in the compartment.
490 A similar effect applies to I<all> runtime symbol lookups in code
491 called from a compartment but not compiled within it.
497 This evaluates the contents of file FILENAME inside the compartment.
498 See above documentation on the B<reval> method for further details.
500 =item root (NAMESPACE)
502 This method returns the name of the package that is the root of the
503 compartment's namespace.
505 Note that this behaviour differs from version 1.00 of the Safe module
506 where the root module could be used to change the namespace. That
507 functionality has been withdrawn pending deeper consideration.
511 This is a get-or-set method for the compartment's operator mask.
513 With no MASK argument present, it returns the current operator mask of
516 With the MASK argument present, it sets the operator mask for the
517 compartment (equivalent to calling the deny_only method).
522 =head2 Some Safety Issues
524 This section is currently just an outline of some of the things code in
525 a compartment might do (intentionally or unintentionally) which can
526 have an effect outside the compartment.
532 Consuming all (or nearly all) available memory.
536 Causing infinite loops etc.
540 Copying private information out of your system. Even something as
541 simple as your user name is of value to others. Much useful information
542 could be gleaned from your environment variables for example.
546 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
548 Setting up a signal handler will need to be carefully considered
549 and controlled. What mask is in effect when a signal handler
550 gets called? If a user can get an imported function to get an
551 exception and call the user's signal handler, does that user's
552 restricted mask get re-instated before the handler is called?
553 Does an imported handler get called with its original mask or
558 Ops such as chdir obviously effect the process as a whole and not just
559 the code in the compartment. Ops such as rand and srand have a similar
560 but more subtle effect.
566 Originally designed and implemented by Malcolm Beattie,
567 mbeattie@sable.ox.ac.uk.
569 Reworked to use the Opcode module and other changes added by Tim Bunce
570 E<lt>F<Tim.Bunce@ig.co.uk>E<gt>.