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();
154 croak("vars not an array ref") unless ref $vars eq 'ARRAY';
156 # Check that 'from' package actually exists
157 croak("Package \"$pkg\" does not exist")
158 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 $arg =~ /^[\$\@%*&]?\w[\w:]*$/
164 ($var = $arg) =~ s/^(\W)//; # get type char
165 # warn "share_from $pkg $1 $var";
166 *{$root."::$var"} = ($1 eq '$') ? \${$pkg."::$var"}
167 : ($1 eq '@') ? \@{$pkg."::$var"}
168 : ($1 eq '%') ? \%{$pkg."::$var"}
169 : ($1 eq '*') ? *{$pkg."::$var"}
170 : ($1 eq '&') ? \&{$pkg."::$var"}
171 : (!$1) ? \&{$pkg."::$var"}
172 : croak(qq(Can't share "$1$var" of unknown type));
174 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
181 my $shares = \%{$obj->{Shares} ||= {}};
182 # Record shares using keys of $obj->{Shares}. See reinit.
183 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
187 my $shares = \%{$obj->{Shares} ||= {}};
189 while(($var, $pkg) = each %$shares) {
190 # warn "share_redo $pkg\:: $var";
191 $obj->share_from($pkg, [ $var ], 1);
195 delete shift->{Shares};
199 my ($obj, $var) = @_;
201 return *{$obj->root()."::$var"};
206 my ($obj, $expr, $strict) = @_;
207 my $root = $obj->{Root};
209 # Create anon sub ref in root of compartment.
210 # Uses a closure (on $expr) to pass in the code to be executed.
211 # (eval on one line to keep line numbers as expected by caller)
212 my $evalcode = sprintf('package %s; sub { eval $expr; }', $root);
215 if ($strict) { use strict; $evalsub = eval $evalcode; }
216 else { no strict; $evalsub = eval $evalcode; }
218 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
222 my ($obj, $file) = @_;
223 my $root = $obj->{Root};
226 sprintf('package %s; sub { do $file }', $root);
227 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
237 Safe - Compile and execute code in restricted compartments
243 $compartment = new Safe;
245 $compartment->permit(qw(time sort :browse));
247 $result = $compartment->reval($unsafe_code);
251 The Safe extension module allows the creation of compartments
252 in which perl code can be evaluated. Each compartment has
256 =item a new namespace
258 The "root" of the namespace (i.e. "main::") is changed to a
259 different package and code evaluated in the compartment cannot
260 refer to variables outside this namespace, even with run-time
261 glob lookups and other tricks.
263 Code which is compiled outside the compartment can choose to place
264 variables into (or I<share> variables with) the compartment's namespace
265 and only that data will be visible to code evaluated in the
268 By default, the only variables shared with compartments are the
269 "underscore" variables $_ and @_ (and, technically, the less frequently
270 used %_, the _ filehandle and so on). This is because otherwise perl
271 operators which default to $_ will not work and neither will the
272 assignment of arguments to @_ on subroutine entry.
274 =item an operator mask
276 Each compartment has an associated "operator mask". Recall that
277 perl code is compiled into an internal format before execution.
278 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
279 the code to be compiled into an internal format and then,
280 provided there was no error in the compilation, executed.
281 Code evaulated in a compartment compiles subject to the
282 compartment's operator mask. Attempting to evaulate code in a
283 compartment which contains a masked operator will cause the
284 compilation to fail with an error. The code will not be executed.
286 The default operator mask for a newly created compartment is
287 the ':default' optag.
289 It is important that you read the Opcode(3) module documentation
290 for more information, especially for detailed definitions of opnames,
293 Since it is only at the compilation stage that the operator mask
294 applies, controlled access to potentially unsafe operations can
295 be achieved by having a handle to a wrapper subroutine (written
296 outside the compartment) placed into the compartment. For example,
300 # vet arguments and perform potentially unsafe operations
302 $cpt->share('&wrapper');
309 The authors make B<no warranty>, implied or otherwise, about the
310 suitability of this software for safety or security purposes.
312 The authors shall not in any case be liable for special, incidental,
313 consequential, indirect or other similar damages arising from the use
316 Your mileage will vary. If in any doubt B<do not use it>.
319 =head2 RECENT CHANGES
321 The interface to the Safe module has changed quite dramatically since
322 version 1 (as supplied with Perl5.002). Study these pages carefully if
323 you have code written to use Safe version 1 because you will need to
327 =head2 Methods in class Safe
329 To create a new compartment, use
333 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
334 to use for the compartment (defaults to "Safe::Root0", incremented for
335 each new compartment).
337 Note that version 1.00 of the Safe module supported a second optional
338 parameter, MASK. That functionality has been withdrawn pending deeper
339 consideration. Use the permit and deny methods described below.
341 The following methods can then be used on the compartment
342 object returned by the above constructor. The object argument
343 is implicit in each case.
348 =item permit (OP, ...)
350 Permit the listed operators to be used when compiling code in the
351 compartment (in I<addition> to any operators already permitted).
353 =item permit_only (OP, ...)
355 Permit I<only> the listed operators to be used when compiling code in
356 the compartment (I<no> other operators are permitted).
360 Deny the listed operators from being used when compiling code in the
361 compartment (other operators may still be permitted).
363 =item deny_only (OP, ...)
365 Deny I<only> the listed operators from being used when compiling code
366 in the compartment (I<all> other operators will be permitted).
370 =item untrap (OP, ...)
372 The trap and untrap methods are synonyms for deny and permit
375 =item share (NAME, ...)
377 This shares the variable(s) in the argument list with the compartment.
378 This is almost identical to exporting variables using the L<Exporter(3)>
381 Each NAME must be the B<name> of a variable, typically with the leading
382 type identifier included. A bareword is treated as a function name.
384 Examples of legal names are '$foo' for a scalar, '@foo' for an
385 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
386 for a glob (i.e. all symbol table entries associated with "foo",
387 including scalar, array, hash, sub and filehandle).
389 Each NAME is assumed to be in the calling package. See share_from
390 for an alternative method (which share uses).
392 =item share_from (PACKAGE, ARRAYREF)
394 This method is similar to share() but allows you to explicitly name the
395 package that symbols should be shared from. The symbol names (including
396 type characters) are supplied as an array reference.
398 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
401 =item varglob (VARNAME)
403 This returns a glob reference for the symbol table entry of VARNAME in
404 the package of the compartment. VARNAME must be the B<name> of a
405 variable without any leading type marker. For example,
407 $cpt = new Safe 'Root';
408 $Root::foo = "Hello world";
409 # Equivalent version which doesn't need to know $cpt's package name:
410 ${$cpt->varglob('foo')} = "Hello world";
415 This evaluates STRING as perl code inside the compartment.
417 The code can only see the compartment's namespace (as returned by the
418 B<root> method). The compartment's root package appears to be the
419 C<main::> package to the code inside the compartment.
421 Any attempt by the code in STRING to use an operator which is not permitted
422 by the compartment will cause an error (at run-time of the main program
423 but at compile-time for the code in STRING). The error is of the form
424 "%s trapped by operation mask operation...".
426 If an operation is trapped in this way, then the code in STRING will
427 not be executed. If such a trapped operation occurs or any other
428 compile-time or return error, then $@ is set to the error message, just
431 If there is no error, then the method returns the value of the last
432 expression evaluated, or a return statement may be used, just as with
433 subroutines and B<eval()>. The context (list or scalar) is determined
434 by the caller as usual.
436 This behaviour differs from the beta distribution of the Safe extension
437 where earlier versions of perl made it hard to mimic the return
438 behaviour of the eval() command and the context was always scalar.
442 If the entereval op is permitted then the code can use eval "..." to
443 'hide' code which might use denied ops. This is not a major problem
444 since when the code tries to execute the eval it will fail because the
445 opmask is still in effect. However this technique would allow clever,
446 and possibly harmful, code to 'probe' the boundaries of what is
449 Any string eval which is executed by code executing in a compartment,
450 or by code called from code executing in a compartment, will be eval'd
451 in the namespace of the compartment. This is potentially a serious
454 Consider a function foo() in package pkg compiled outside a compartment
455 but shared with it. Assume the compartment has a root package called
456 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
457 normally, $pkg::foo will be set to 1. If foo() is called from the
458 compartment (by whatever means) then instead of setting $pkg::foo, the
459 eval will actually set $Root::pkg::foo.
461 This can easily be demonstrated by using a module, such as the Socket
462 module, which uses eval "..." as part of an AUTOLOAD function. You can
463 'use' the module outside the compartment and share an (autoloaded)
464 function with the compartment. If an autoload is triggered by code in
465 the compartment, or by any code anywhere that is called by any means
466 from the compartment, then the eval in the Socket module's AUTOLOAD
467 function happens in the namespace of the compartment. Any variables
468 created or used by the eval'd code are now under the control of
469 the code in the compartment.
471 A similar effect applies to I<all> runtime symbol lookups in code
472 called from a compartment but not compiled within it.
478 This evaluates the contents of file FILENAME inside the compartment.
479 See above documentation on the B<reval> method for further details.
481 =item root (NAMESPACE)
483 This method returns the name of the package that is the root of the
484 compartment's namespace.
486 Note that this behaviour differs from version 1.00 of the Safe module
487 where the root module could be used to change the namespace. That
488 functionality has been withdrawn pending deeper consideration.
492 This is a get-or-set method for the compartment's operator mask.
494 With no MASK argument present, it returns the current operator mask of
497 With the MASK argument present, it sets the operator mask for the
498 compartment (equivalent to calling the deny_only method).
503 =head2 Some Safety Issues
505 This section is currently just an outline of some of the things code in
506 a compartment might do (intentionally or unintentionally) which can
507 have an effect outside the compartment.
513 Consuming all (or nearly all) available memory.
517 Causing infinite loops etc.
521 Copying private information out of your system. Even something as
522 simple as your user name is of value to others. Much useful information
523 could be gleaned from your environment variables for example.
527 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
529 Setting up a signal handler will need to be carefully considered
530 and controlled. What mask is in effect when a signal handler
531 gets called? If a user can get an imported function to get an
532 exception and call the user's signal handler, does that user's
533 restricted mask get re-instated before the handler is called?
534 Does an imported handler get called with its original mask or
539 Ops such as chdir obviously effect the process as a whole and not just
540 the code in the compartment. Ops such as rand and srand have a similar
541 but more subtle effect.
547 Originally designed and implemented by Malcolm Beattie,
548 mbeattie@sable.ox.ac.uk.
550 Reworked to use the Opcode module and other changes added by Tim Bunce
551 E<lt>F<Tim.Bunce@ig.co.uk>E<gt>.