12 opset opset_to_ops opmask_add
13 empty_opset full_opset invert_opset verify_opset
14 opdesc opcodes opmask define_optag opset_to_hex
17 *ops_to_opset = \&opset; # Temporary alias for old Penguins
21 my $default_share = ['*_']; #, '*main::'];
24 my($class, $root, $mask) = @_;
29 croak "Can't use \"$root\" as root name"
30 if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/;
35 $obj->{Root} = "Safe::Root".$default_root++;
39 # use permit/deny methods instead till interface issues resolved
40 # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...;
41 croak "Mask parameter to new no longer supported" if defined $mask;
42 $obj->permit_only(':default');
44 # We must share $_ and @_ with the compartment or else ops such
45 # as split, length and so on won't default to $_ properly, nor
46 # will passing argument to subroutines work (via @_). In fact,
47 # for reasons I don't completely understand, we need to share
48 # the whole glob *_ rather than $_ and @_ separately, otherwise
49 # @_ in non default packages within the compartment don't work.
50 $obj->share_from('main', $default_share);
56 $obj->erase if $obj->{Erase};
61 my $pkg = $obj->root();
65 $pkg = "main::$pkg\::"; # expand to full symbol table name
66 ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
68 # The 'my $foo' is needed! Without it you get an
69 # 'Attempt to free unreferenced scalar' warning!
70 my $stem_symtab = *{$stem}{HASH};
72 #warn "erase($pkg) stem=$stem, leaf=$leaf";
73 #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n";
74 # ", join(', ', %$stem_symtab),"\n";
76 delete $stem_symtab->{$leaf};
78 # my $leaf_glob = $stem_symtab->{$leaf};
79 # my $leaf_symtab = *{$leaf_glob}{HASH};
80 # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n";
82 #delete $leaf_symtab->{'__ANON__'};
83 #delete $leaf_symtab->{'foo'};
84 #delete $leaf_symtab->{'main::'};
85 # my $foo = undef ${"$stem\::"}{"$leaf\::"};
87 $obj->share_from('main', $default_share);
100 croak("Safe root method now read-only") if @_;
107 return $obj->{Mask} unless @_;
111 # v1 compatibility methods
112 sub trap { shift->deny(@_) }
113 sub untrap { shift->permit(@_) }
117 $obj->{Mask} |= opset(@_);
121 $obj->{Mask} = opset(@_);
127 $obj->{Mask} &= invert_opset opset(@_);
131 $obj->{Mask} = invert_opset opset(@_);
137 print opset_to_hex($obj->{Mask}),"\n";
143 my($obj, @vars) = @_;
144 $obj->share_from(scalar(caller), \@vars);
151 my $no_record = shift || 0;
152 my $root = $obj->root();
153 croak("vars not an array ref") unless ref $vars eq 'ARRAY';
155 # Check that 'from' package actually exists
156 croak("Package \"$pkg\" does not exist")
157 unless keys %{"$pkg\::"};
159 foreach $arg (@$vars) {
160 # catch some $safe->share($var) errors:
161 croak("'$arg' not a valid symbol table name")
162 unless $arg =~ /^[\$\@%*&]?\w[\w:]*$/
165 $type = $1 if ($var = $arg) =~ s/^(\W)//;
166 # warn "share_from $pkg $type $var";
167 *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
168 : ($type eq '&') ? \&{$pkg."::$var"}
169 : ($type eq '$') ? \${$pkg."::$var"}
170 : ($type eq '@') ? \@{$pkg."::$var"}
171 : ($type eq '%') ? \%{$pkg."::$var"}
172 : ($type eq '*') ? *{$pkg."::$var"}
173 : croak(qq(Can't share "$type$var" of unknown type));
175 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
182 my $shares = \%{$obj->{Shares} ||= {}};
183 # Record shares using keys of $obj->{Shares}. See reinit.
184 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
188 my $shares = \%{$obj->{Shares} ||= {}};
190 while(($var, $pkg) = each %$shares) {
191 # warn "share_redo $pkg\:: $var";
192 $obj->share_from($pkg, [ $var ], 1);
196 delete shift->{Shares};
200 my ($obj, $var) = @_;
202 return *{$obj->root()."::$var"};
207 my ($obj, $expr, $strict) = @_;
208 my $root = $obj->{Root};
210 # Create anon sub ref in root of compartment.
211 # Uses a closure (on $expr) to pass in the code to be executed.
212 # (eval on one line to keep line numbers as expected by caller)
213 my $evalcode = sprintf('package %s; sub { eval $expr; }', $root);
216 if ($strict) { use strict; $evalsub = eval $evalcode; }
217 else { no strict; $evalsub = eval $evalcode; }
219 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
223 my ($obj, $file) = @_;
224 my $root = $obj->{Root};
227 sprintf('package %s; sub { do $file }', $root);
228 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
238 Safe - Compile and execute code in restricted compartments
244 $compartment = new Safe;
246 $compartment->permit(qw(time sort :browse));
248 $result = $compartment->reval($unsafe_code);
252 The Safe extension module allows the creation of compartments
253 in which perl code can be evaluated. Each compartment has
257 =item a new namespace
259 The "root" of the namespace (i.e. "main::") is changed to a
260 different package and code evaluated in the compartment cannot
261 refer to variables outside this namespace, even with run-time
262 glob lookups and other tricks.
264 Code which is compiled outside the compartment can choose to place
265 variables into (or I<share> variables with) the compartment's namespace
266 and only that data will be visible to code evaluated in the
269 By default, the only variables shared with compartments are the
270 "underscore" variables $_ and @_ (and, technically, the less frequently
271 used %_, the _ filehandle and so on). This is because otherwise perl
272 operators which default to $_ will not work and neither will the
273 assignment of arguments to @_ on subroutine entry.
275 =item an operator mask
277 Each compartment has an associated "operator mask". Recall that
278 perl code is compiled into an internal format before execution.
279 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
280 the code to be compiled into an internal format and then,
281 provided there was no error in the compilation, executed.
282 Code evaulated in a compartment compiles subject to the
283 compartment's operator mask. Attempting to evaulate code in a
284 compartment which contains a masked operator will cause the
285 compilation to fail with an error. The code will not be executed.
287 The default operator mask for a newly created compartment is
288 the ':default' optag.
290 It is important that you read the Opcode(3) module documentation
291 for more information, especially for detailed definitions of opnames,
294 Since it is only at the compilation stage that the operator mask
295 applies, controlled access to potentially unsafe operations can
296 be achieved by having a handle to a wrapper subroutine (written
297 outside the compartment) placed into the compartment. For example,
301 # vet arguments and perform potentially unsafe operations
303 $cpt->share('&wrapper');
310 The authors make B<no warranty>, implied or otherwise, about the
311 suitability of this software for safety or security purposes.
313 The authors shall not in any case be liable for special, incidental,
314 consequential, indirect or other similar damages arising from the use
317 Your mileage will vary. If in any doubt B<do not use it>.
320 =head2 RECENT CHANGES
322 The interface to the Safe module has changed quite dramatically since
323 version 1 (as supplied with Perl5.002). Study these pages carefully if
324 you have code written to use Safe version 1 because you will need to
328 =head2 Methods in class Safe
330 To create a new compartment, use
334 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
335 to use for the compartment (defaults to "Safe::Root0", incremented for
336 each new compartment).
338 Note that version 1.00 of the Safe module supported a second optional
339 parameter, MASK. That functionality has been withdrawn pending deeper
340 consideration. Use the permit and deny methods described below.
342 The following methods can then be used on the compartment
343 object returned by the above constructor. The object argument
344 is implicit in each case.
349 =item permit (OP, ...)
351 Permit the listed operators to be used when compiling code in the
352 compartment (in I<addition> to any operators already permitted).
354 =item permit_only (OP, ...)
356 Permit I<only> the listed operators to be used when compiling code in
357 the compartment (I<no> other operators are permitted).
361 Deny the listed operators from being used when compiling code in the
362 compartment (other operators may still be permitted).
364 =item deny_only (OP, ...)
366 Deny I<only> the listed operators from being used when compiling code
367 in the compartment (I<all> other operators will be permitted).
371 =item untrap (OP, ...)
373 The trap and untrap methods are synonyms for deny and permit
376 =item share (NAME, ...)
378 This shares the variable(s) in the argument list with the compartment.
379 This is almost identical to exporting variables using the L<Exporter(3)>
382 Each NAME must be the B<name> of a variable, typically with the leading
383 type identifier included. A bareword is treated as a function name.
385 Examples of legal names are '$foo' for a scalar, '@foo' for an
386 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
387 for a glob (i.e. all symbol table entries associated with "foo",
388 including scalar, array, hash, sub and filehandle).
390 Each NAME is assumed to be in the calling package. See share_from
391 for an alternative method (which share uses).
393 =item share_from (PACKAGE, ARRAYREF)
395 This method is similar to share() but allows you to explicitly name the
396 package that symbols should be shared from. The symbol names (including
397 type characters) are supplied as an array reference.
399 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
402 =item varglob (VARNAME)
404 This returns a glob reference for the symbol table entry of VARNAME in
405 the package of the compartment. VARNAME must be the B<name> of a
406 variable without any leading type marker. For example,
408 $cpt = new Safe 'Root';
409 $Root::foo = "Hello world";
410 # Equivalent version which doesn't need to know $cpt's package name:
411 ${$cpt->varglob('foo')} = "Hello world";
416 This evaluates STRING as perl code inside the compartment.
418 The code can only see the compartment's namespace (as returned by the
419 B<root> method). The compartment's root package appears to be the
420 C<main::> package to the code inside the compartment.
422 Any attempt by the code in STRING to use an operator which is not permitted
423 by the compartment will cause an error (at run-time of the main program
424 but at compile-time for the code in STRING). The error is of the form
425 "%s trapped by operation mask operation...".
427 If an operation is trapped in this way, then the code in STRING will
428 not be executed. If such a trapped operation occurs or any other
429 compile-time or return error, then $@ is set to the error message, just
432 If there is no error, then the method returns the value of the last
433 expression evaluated, or a return statement may be used, just as with
434 subroutines and B<eval()>. The context (list or scalar) is determined
435 by the caller as usual.
437 This behaviour differs from the beta distribution of the Safe extension
438 where earlier versions of perl made it hard to mimic the return
439 behaviour of the eval() command and the context was always scalar.
443 If the entereval op is permitted then the code can use eval "..." to
444 'hide' code which might use denied ops. This is not a major problem
445 since when the code tries to execute the eval it will fail because the
446 opmask is still in effect. However this technique would allow clever,
447 and possibly harmful, code to 'probe' the boundaries of what is
450 Any string eval which is executed by code executing in a compartment,
451 or by code called from code executing in a compartment, will be eval'd
452 in the namespace of the compartment. This is potentially a serious
455 Consider a function foo() in package pkg compiled outside a compartment
456 but shared with it. Assume the compartment has a root package called
457 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
458 normally, $pkg::foo will be set to 1. If foo() is called from the
459 compartment (by whatever means) then instead of setting $pkg::foo, the
460 eval will actually set $Root::pkg::foo.
462 This can easily be demonstrated by using a module, such as the Socket
463 module, which uses eval "..." as part of an AUTOLOAD function. You can
464 'use' the module outside the compartment and share an (autoloaded)
465 function with the compartment. If an autoload is triggered by code in
466 the compartment, or by any code anywhere that is called by any means
467 from the compartment, then the eval in the Socket module's AUTOLOAD
468 function happens in the namespace of the compartment. Any variables
469 created or used by the eval'd code are now under the control of
470 the code in the compartment.
472 A similar effect applies to I<all> runtime symbol lookups in code
473 called from a compartment but not compiled within it.
479 This evaluates the contents of file FILENAME inside the compartment.
480 See above documentation on the B<reval> method for further details.
482 =item root (NAMESPACE)
484 This method returns the name of the package that is the root of the
485 compartment's namespace.
487 Note that this behaviour differs from version 1.00 of the Safe module
488 where the root module could be used to change the namespace. That
489 functionality has been withdrawn pending deeper consideration.
493 This is a get-or-set method for the compartment's operator mask.
495 With no MASK argument present, it returns the current operator mask of
498 With the MASK argument present, it sets the operator mask for the
499 compartment (equivalent to calling the deny_only method).
504 =head2 Some Safety Issues
506 This section is currently just an outline of some of the things code in
507 a compartment might do (intentionally or unintentionally) which can
508 have an effect outside the compartment.
514 Consuming all (or nearly all) available memory.
518 Causing infinite loops etc.
522 Copying private information out of your system. Even something as
523 simple as your user name is of value to others. Much useful information
524 could be gleaned from your environment variables for example.
528 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
530 Setting up a signal handler will need to be carefully considered
531 and controlled. What mask is in effect when a signal handler
532 gets called? If a user can get an imported function to get an
533 exception and call the user's signal handler, does that user's
534 restricted mask get re-instated before the handler is called?
535 Does an imported handler get called with its original mask or
540 Ops such as chdir obviously effect the process as a whole and not just
541 the code in the compartment. Ops such as rand and srand have a similar
542 but more subtle effect.
548 Originally designed and implemented by Malcolm Beattie,
549 mbeattie@sable.ox.ac.uk.
551 Reworked to use the Opcode module and other changes added by Tim Bunce
552 E<lt>F<Tim.Bunce@ig.co.uk>E<gt>.