6 $Safe::VERSION = "2.15";
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 $default_share = [qw[
59 &utf8::native_to_unicode
60 &utf8::unicode_to_native
64 ], ($] >= 5.010 && qw[
69 &Tie::Hash::NamedCapture::FETCH
70 &Tie::Hash::NamedCapture::STORE
71 &Tie::Hash::NamedCapture::DELETE
72 &Tie::Hash::NamedCapture::CLEAR
73 &Tie::Hash::NamedCapture::EXISTS
74 &Tie::Hash::NamedCapture::FIRSTKEY
75 &Tie::Hash::NamedCapture::NEXTKEY
76 &Tie::Hash::NamedCapture::SCALAR
77 &Tie::Hash::NamedCapture::flags
95 ]), ($] >= 5.011 && qw[
100 my($class, $root, $mask) = @_;
104 if (defined($root)) {
105 croak "Can't use \"$root\" as root name"
106 if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/;
107 $obj->{Root} = $root;
111 $obj->{Root} = "Safe::Root".$default_root++;
115 # use permit/deny methods instead till interface issues resolved
116 # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...;
117 croak "Mask parameter to new no longer supported" if defined $mask;
118 $obj->permit_only(':default');
120 # We must share $_ and @_ with the compartment or else ops such
121 # as split, length and so on won't default to $_ properly, nor
122 # will passing argument to subroutines work (via @_). In fact,
123 # for reasons I don't completely understand, we need to share
124 # the whole glob *_ rather than $_ and @_ separately, otherwise
125 # @_ in non default packages within the compartment don't work.
126 $obj->share_from('main', $default_share);
127 Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04);
133 $obj->erase('DESTROY') if $obj->{Erase};
137 my ($obj, $action) = @_;
138 my $pkg = $obj->root();
142 $pkg = "main::$pkg\::"; # expand to full symbol table name
143 ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
145 # The 'my $foo' is needed! Without it you get an
146 # 'Attempt to free unreferenced scalar' warning!
147 my $stem_symtab = *{$stem}{HASH};
149 #warn "erase($pkg) stem=$stem, leaf=$leaf";
150 #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n";
151 # ", join(', ', %$stem_symtab),"\n";
153 # delete $stem_symtab->{$leaf};
155 my $leaf_glob = $stem_symtab->{$leaf};
156 my $leaf_symtab = *{$leaf_glob}{HASH};
157 # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n";
159 #delete $leaf_symtab->{'__ANON__'};
160 #delete $leaf_symtab->{'foo'};
161 #delete $leaf_symtab->{'main::'};
162 # my $foo = undef ${"$stem\::"}{"$leaf\::"};
164 if ($action and $action eq 'DESTROY') {
165 delete $stem_symtab->{$leaf};
167 $obj->share_from('main', $default_share);
181 croak("Safe root method now read-only") if @_;
188 return $obj->{Mask} unless @_;
192 # v1 compatibility methods
193 sub trap { shift->deny(@_) }
194 sub untrap { shift->permit(@_) }
198 $obj->{Mask} |= opset(@_);
202 $obj->{Mask} = opset(@_);
208 $obj->{Mask} &= invert_opset opset(@_);
212 $obj->{Mask} = invert_opset opset(@_);
218 print opset_to_hex($obj->{Mask}),"\n";
224 my($obj, @vars) = @_;
225 $obj->share_from(scalar(caller), \@vars);
232 my $no_record = shift || 0;
233 my $root = $obj->root();
234 croak("vars not an array ref") unless ref $vars eq 'ARRAY';
236 # Check that 'from' package actually exists
237 croak("Package \"$pkg\" does not exist")
238 unless keys %{"$pkg\::"};
240 foreach $arg (@$vars) {
241 # catch some $safe->share($var) errors:
243 $type = $1 if ($var = $arg) =~ s/^(\W)//;
244 # warn "share_from $pkg $type $var";
245 *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
246 : ($type eq '&') ? \&{$pkg."::$var"}
247 : ($type eq '$') ? \${$pkg."::$var"}
248 : ($type eq '@') ? \@{$pkg."::$var"}
249 : ($type eq '%') ? \%{$pkg."::$var"}
250 : ($type eq '*') ? *{$pkg."::$var"}
251 : croak(qq(Can't share "$type$var" of unknown type));
253 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
260 my $shares = \%{$obj->{Shares} ||= {}};
261 # Record shares using keys of $obj->{Shares}. See reinit.
262 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
266 my $shares = \%{$obj->{Shares} ||= {}};
268 while(($var, $pkg) = each %$shares) {
269 # warn "share_redo $pkg\:: $var";
270 $obj->share_from($pkg, [ $var ], 1);
274 delete shift->{Shares};
278 my ($obj, $var) = @_;
280 return *{$obj->root()."::$var"};
285 my ($obj, $expr, $strict) = @_;
286 my $root = $obj->{Root};
288 my $evalsub = lexless_anon_sub($root,$strict, $expr);
289 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
293 my ($obj, $file) = @_;
294 my $root = $obj->{Root};
297 sprintf('package %s; sub { @_ = (); do $file }', $root);
298 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
308 Safe - Compile and execute code in restricted compartments
314 $compartment = new Safe;
316 $compartment->permit(qw(time sort :browse));
318 $result = $compartment->reval($unsafe_code);
322 The Safe extension module allows the creation of compartments
323 in which perl code can be evaluated. Each compartment has
327 =item a new namespace
329 The "root" of the namespace (i.e. "main::") is changed to a
330 different package and code evaluated in the compartment cannot
331 refer to variables outside this namespace, even with run-time
332 glob lookups and other tricks.
334 Code which is compiled outside the compartment can choose to place
335 variables into (or I<share> variables with) the compartment's namespace
336 and only that data will be visible to code evaluated in the
339 By default, the only variables shared with compartments are the
340 "underscore" variables $_ and @_ (and, technically, the less frequently
341 used %_, the _ filehandle and so on). This is because otherwise perl
342 operators which default to $_ will not work and neither will the
343 assignment of arguments to @_ on subroutine entry.
345 =item an operator mask
347 Each compartment has an associated "operator mask". Recall that
348 perl code is compiled into an internal format before execution.
349 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
350 the code to be compiled into an internal format and then,
351 provided there was no error in the compilation, executed.
352 Code evaluated in a compartment compiles subject to the
353 compartment's operator mask. Attempting to evaluate code in a
354 compartment which contains a masked operator will cause the
355 compilation to fail with an error. The code will not be executed.
357 The default operator mask for a newly created compartment is
358 the ':default' optag.
360 It is important that you read the L<Opcode> module documentation
361 for more information, especially for detailed definitions of opnames,
364 Since it is only at the compilation stage that the operator mask
365 applies, controlled access to potentially unsafe operations can
366 be achieved by having a handle to a wrapper subroutine (written
367 outside the compartment) placed into the compartment. For example,
371 # vet arguments and perform potentially unsafe operations
373 $cpt->share('&wrapper');
380 The authors make B<no warranty>, implied or otherwise, about the
381 suitability of this software for safety or security purposes.
383 The authors shall not in any case be liable for special, incidental,
384 consequential, indirect or other similar damages arising from the use
387 Your mileage will vary. If in any doubt B<do not use it>.
390 =head2 RECENT CHANGES
392 The interface to the Safe module has changed quite dramatically since
393 version 1 (as supplied with Perl5.002). Study these pages carefully if
394 you have code written to use Safe version 1 because you will need to
398 =head2 Methods in class Safe
400 To create a new compartment, use
404 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
405 to use for the compartment (defaults to "Safe::Root0", incremented for
406 each new compartment).
408 Note that version 1.00 of the Safe module supported a second optional
409 parameter, MASK. That functionality has been withdrawn pending deeper
410 consideration. Use the permit and deny methods described below.
412 The following methods can then be used on the compartment
413 object returned by the above constructor. The object argument
414 is implicit in each case.
419 =item permit (OP, ...)
421 Permit the listed operators to be used when compiling code in the
422 compartment (in I<addition> to any operators already permitted).
424 You can list opcodes by names, or use a tag name; see
425 L<Opcode/"Predefined Opcode Tags">.
427 =item permit_only (OP, ...)
429 Permit I<only> the listed operators to be used when compiling code in
430 the compartment (I<no> other operators are permitted).
434 Deny the listed operators from being used when compiling code in the
435 compartment (other operators may still be permitted).
437 =item deny_only (OP, ...)
439 Deny I<only> the listed operators from being used when compiling code
440 in the compartment (I<all> other operators will be permitted).
444 =item untrap (OP, ...)
446 The trap and untrap methods are synonyms for deny and permit
449 =item share (NAME, ...)
451 This shares the variable(s) in the argument list with the compartment.
452 This is almost identical to exporting variables using the L<Exporter>
455 Each NAME must be the B<name> of a non-lexical variable, typically
456 with the leading type identifier included. A bareword is treated as a
459 Examples of legal names are '$foo' for a scalar, '@foo' for an
460 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
461 for a glob (i.e. all symbol table entries associated with "foo",
462 including scalar, array, hash, sub and filehandle).
464 Each NAME is assumed to be in the calling package. See share_from
465 for an alternative method (which share uses).
467 =item share_from (PACKAGE, ARRAYREF)
469 This method is similar to share() but allows you to explicitly name the
470 package that symbols should be shared from. The symbol names (including
471 type characters) are supplied as an array reference.
473 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
476 =item varglob (VARNAME)
478 This returns a glob reference for the symbol table entry of VARNAME in
479 the package of the compartment. VARNAME must be the B<name> of a
480 variable without any leading type marker. For example,
482 $cpt = new Safe 'Root';
483 $Root::foo = "Hello world";
484 # Equivalent version which doesn't need to know $cpt's package name:
485 ${$cpt->varglob('foo')} = "Hello world";
490 This evaluates STRING as perl code inside the compartment.
492 The code can only see the compartment's namespace (as returned by the
493 B<root> method). The compartment's root package appears to be the
494 C<main::> package to the code inside the compartment.
496 Any attempt by the code in STRING to use an operator which is not permitted
497 by the compartment will cause an error (at run-time of the main program
498 but at compile-time for the code in STRING). The error is of the form
499 "'%s' trapped by operation mask...".
501 If an operation is trapped in this way, then the code in STRING will
502 not be executed. If such a trapped operation occurs or any other
503 compile-time or return error, then $@ is set to the error message, just
506 If there is no error, then the method returns the value of the last
507 expression evaluated, or a return statement may be used, just as with
508 subroutines and B<eval()>. The context (list or scalar) is determined
509 by the caller as usual.
511 This behaviour differs from the beta distribution of the Safe extension
512 where earlier versions of perl made it hard to mimic the return
513 behaviour of the eval() command and the context was always scalar.
517 If the entereval op is permitted then the code can use eval "..." to
518 'hide' code which might use denied ops. This is not a major problem
519 since when the code tries to execute the eval it will fail because the
520 opmask is still in effect. However this technique would allow clever,
521 and possibly harmful, code to 'probe' the boundaries of what is
524 Any string eval which is executed by code executing in a compartment,
525 or by code called from code executing in a compartment, will be eval'd
526 in the namespace of the compartment. This is potentially a serious
529 Consider a function foo() in package pkg compiled outside a compartment
530 but shared with it. Assume the compartment has a root package called
531 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
532 normally, $pkg::foo will be set to 1. If foo() is called from the
533 compartment (by whatever means) then instead of setting $pkg::foo, the
534 eval will actually set $Root::pkg::foo.
536 This can easily be demonstrated by using a module, such as the Socket
537 module, which uses eval "..." as part of an AUTOLOAD function. You can
538 'use' the module outside the compartment and share an (autoloaded)
539 function with the compartment. If an autoload is triggered by code in
540 the compartment, or by any code anywhere that is called by any means
541 from the compartment, then the eval in the Socket module's AUTOLOAD
542 function happens in the namespace of the compartment. Any variables
543 created or used by the eval'd code are now under the control of
544 the code in the compartment.
546 A similar effect applies to I<all> runtime symbol lookups in code
547 called from a compartment but not compiled within it.
553 This evaluates the contents of file FILENAME inside the compartment.
554 See above documentation on the B<reval> method for further details.
556 =item root (NAMESPACE)
558 This method returns the name of the package that is the root of the
559 compartment's namespace.
561 Note that this behaviour differs from version 1.00 of the Safe module
562 where the root module could be used to change the namespace. That
563 functionality has been withdrawn pending deeper consideration.
567 This is a get-or-set method for the compartment's operator mask.
569 With no MASK argument present, it returns the current operator mask of
572 With the MASK argument present, it sets the operator mask for the
573 compartment (equivalent to calling the deny_only method).
578 =head2 Some Safety Issues
580 This section is currently just an outline of some of the things code in
581 a compartment might do (intentionally or unintentionally) which can
582 have an effect outside the compartment.
588 Consuming all (or nearly all) available memory.
592 Causing infinite loops etc.
596 Copying private information out of your system. Even something as
597 simple as your user name is of value to others. Much useful information
598 could be gleaned from your environment variables for example.
602 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
604 Setting up a signal handler will need to be carefully considered
605 and controlled. What mask is in effect when a signal handler
606 gets called? If a user can get an imported function to get an
607 exception and call the user's signal handler, does that user's
608 restricted mask get re-instated before the handler is called?
609 Does an imported handler get called with its original mask or
614 Ops such as chdir obviously effect the process as a whole and not just
615 the code in the compartment. Ops such as rand and srand have a similar
616 but more subtle effect.
622 Originally designed and implemented by Malcolm Beattie.
624 Reworked to use the Opcode module and other changes added by Tim Bunce.
626 Currently maintained by the Perl 5 Porters, <perl5-porters@perl.org>.