5 use Scalar::Util qw(reftype);
6 use Config qw(%Config);
7 use constant is_usethreads => $Config{usethreads};
9 $Safe::VERSION = "2.20";
11 # *** Don't declare any lexicals above this point ***
13 # This function should return a closure which contains an eval that can't
14 # see any lexicals in scope (apart from __ExPr__ which is unavoidable)
16 sub lexless_anon_sub {
18 # $_[1] is strict flag;
19 my $__ExPr__ = $_[2]; # must be a lexical to create the closure that
20 # can be used to pass the value into the safe
23 # Create anon sub ref in root of compartment.
24 # Uses a closure (on $__ExPr__) to pass in the code to be executed.
25 # (eval on one line to keep line numbers as expected by caller)
27 'package %s; %s strict; sub { @_=(); eval q[my $__ExPr__;] . $__ExPr__; }',
28 $_[0], $_[1] ? 'use' : 'no';
37 opset opset_to_ops opmask_add
38 empty_opset full_opset invert_opset verify_opset
39 opdesc opcodes opmask define_optag opset_to_hex
42 *ops_to_opset = \&opset; # Temporary alias for old Penguins
46 # share *_ and functions defined in universal.c
47 # Don't share stuff like *UNIVERSAL:: otherwise code from the
48 # compartment can 0wn functions in UNIVERSAL
49 my $default_share = [qw[
61 &utf8::native_to_unicode
62 &utf8::unicode_to_native
68 ], ($] >= 5.008001 && qw[
70 ]), ($] >= 5.010 && qw[
75 &Tie::Hash::NamedCapture::FETCH
76 &Tie::Hash::NamedCapture::STORE
77 &Tie::Hash::NamedCapture::DELETE
78 &Tie::Hash::NamedCapture::CLEAR
79 &Tie::Hash::NamedCapture::EXISTS
80 &Tie::Hash::NamedCapture::FIRSTKEY
81 &Tie::Hash::NamedCapture::NEXTKEY
82 &Tie::Hash::NamedCapture::SCALAR
83 &Tie::Hash::NamedCapture::flags
101 ]), ($] >= 5.011 && qw[
106 my($class, $root, $mask) = @_;
110 if (defined($root)) {
111 croak "Can't use \"$root\" as root name"
112 if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/;
113 $obj->{Root} = $root;
117 $obj->{Root} = "Safe::Root".$default_root++;
121 # use permit/deny methods instead till interface issues resolved
122 # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...;
123 croak "Mask parameter to new no longer supported" if defined $mask;
124 $obj->permit_only(':default');
126 # We must share $_ and @_ with the compartment or else ops such
127 # as split, length and so on won't default to $_ properly, nor
128 # will passing argument to subroutines work (via @_). In fact,
129 # for reasons I don't completely understand, we need to share
130 # the whole glob *_ rather than $_ and @_ separately, otherwise
131 # @_ in non default packages within the compartment don't work.
132 $obj->share_from('main', $default_share);
133 Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04);
139 $obj->erase('DESTROY') if $obj->{Erase};
143 my ($obj, $action) = @_;
144 my $pkg = $obj->root();
148 $pkg = "main::$pkg\::"; # expand to full symbol table name
149 ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
151 # The 'my $foo' is needed! Without it you get an
152 # 'Attempt to free unreferenced scalar' warning!
153 my $stem_symtab = *{$stem}{HASH};
155 #warn "erase($pkg) stem=$stem, leaf=$leaf";
156 #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n";
157 # ", join(', ', %$stem_symtab),"\n";
159 # delete $stem_symtab->{$leaf};
161 my $leaf_glob = $stem_symtab->{$leaf};
162 my $leaf_symtab = *{$leaf_glob}{HASH};
163 # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n";
165 #delete $leaf_symtab->{'__ANON__'};
166 #delete $leaf_symtab->{'foo'};
167 #delete $leaf_symtab->{'main::'};
168 # my $foo = undef ${"$stem\::"}{"$leaf\::"};
170 if ($action and $action eq 'DESTROY') {
171 delete $stem_symtab->{$leaf};
173 $obj->share_from('main', $default_share);
187 croak("Safe root method now read-only") if @_;
194 return $obj->{Mask} unless @_;
198 # v1 compatibility methods
199 sub trap { shift->deny(@_) }
200 sub untrap { shift->permit(@_) }
204 $obj->{Mask} |= opset(@_);
208 $obj->{Mask} = opset(@_);
214 $obj->{Mask} &= invert_opset opset(@_);
218 $obj->{Mask} = invert_opset opset(@_);
224 print opset_to_hex($obj->{Mask}),"\n";
230 my($obj, @vars) = @_;
231 $obj->share_from(scalar(caller), \@vars);
238 my $no_record = shift || 0;
239 my $root = $obj->root();
240 croak("vars not an array ref") unless ref $vars eq 'ARRAY';
242 # Check that 'from' package actually exists
243 croak("Package \"$pkg\" does not exist")
244 unless keys %{"$pkg\::"};
246 foreach $arg (@$vars) {
247 # catch some $safe->share($var) errors:
249 $type = $1 if ($var = $arg) =~ s/^(\W)//;
250 # warn "share_from $pkg $type $var";
251 for (1..2) { # assign twice to avoid any 'used once' warnings
252 *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
253 : ($type eq '&') ? \&{$pkg."::$var"}
254 : ($type eq '$') ? \${$pkg."::$var"}
255 : ($type eq '@') ? \@{$pkg."::$var"}
256 : ($type eq '%') ? \%{$pkg."::$var"}
257 : ($type eq '*') ? *{$pkg."::$var"}
258 : croak(qq(Can't share "$type$var" of unknown type));
261 $obj->share_record($pkg, $vars) unless $no_record or !$vars;
268 my $shares = \%{$obj->{Shares} ||= {}};
269 # Record shares using keys of $obj->{Shares}. See reinit.
270 @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
274 my $shares = \%{$obj->{Shares} ||= {}};
276 while(($var, $pkg) = each %$shares) {
277 # warn "share_redo $pkg\:: $var";
278 $obj->share_from($pkg, [ $var ], 1);
282 delete shift->{Shares};
286 my ($obj, $var) = @_;
288 return *{$obj->root()."::$var"};
293 my ($obj, $expr, $strict) = @_;
294 my $root = $obj->{Root};
296 my $evalsub = lexless_anon_sub($root, $strict, $expr);
297 my @ret = (wantarray)
298 ? Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub)
299 : scalar Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
301 # RT#60374: Safe.pm sort {} bug with -Dusethreads
302 # If the Safe eval returns a code ref in a perl compiled with usethreads
303 # then wrap code ref with _safe_call_sv so that, when called, the
304 # execution will happen with the compartment fully 'in effect'.
305 # Needed to fix sort blocks that reference $a & $b and
306 # possibly other subtle issues.
307 if (is_usethreads()) {
308 for my $ret (@ret) { # edit (via alias) any CODE refs
309 next unless (reftype($ret)||'') eq 'CODE';
310 my $sub = $ret; # avoid closure problems
311 $ret = sub { Opcode::_safe_call_sv($root, $obj->{Mask}, $sub) };
315 return (wantarray) ? @ret : $ret[0];
319 my ($obj, $file) = @_;
320 my $root = $obj->{Root};
323 sprintf('package %s; sub { @_ = (); do $file }', $root);
324 return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
334 Safe - Compile and execute code in restricted compartments
340 $compartment = new Safe;
342 $compartment->permit(qw(time sort :browse));
344 $result = $compartment->reval($unsafe_code);
348 The Safe extension module allows the creation of compartments
349 in which perl code can be evaluated. Each compartment has
353 =item a new namespace
355 The "root" of the namespace (i.e. "main::") is changed to a
356 different package and code evaluated in the compartment cannot
357 refer to variables outside this namespace, even with run-time
358 glob lookups and other tricks.
360 Code which is compiled outside the compartment can choose to place
361 variables into (or I<share> variables with) the compartment's namespace
362 and only that data will be visible to code evaluated in the
365 By default, the only variables shared with compartments are the
366 "underscore" variables $_ and @_ (and, technically, the less frequently
367 used %_, the _ filehandle and so on). This is because otherwise perl
368 operators which default to $_ will not work and neither will the
369 assignment of arguments to @_ on subroutine entry.
371 =item an operator mask
373 Each compartment has an associated "operator mask". Recall that
374 perl code is compiled into an internal format before execution.
375 Evaluating perl code (e.g. via "eval" or "do 'file'") causes
376 the code to be compiled into an internal format and then,
377 provided there was no error in the compilation, executed.
378 Code evaluated in a compartment compiles subject to the
379 compartment's operator mask. Attempting to evaluate code in a
380 compartment which contains a masked operator will cause the
381 compilation to fail with an error. The code will not be executed.
383 The default operator mask for a newly created compartment is
384 the ':default' optag.
386 It is important that you read the L<Opcode> module documentation
387 for more information, especially for detailed definitions of opnames,
390 Since it is only at the compilation stage that the operator mask
391 applies, controlled access to potentially unsafe operations can
392 be achieved by having a handle to a wrapper subroutine (written
393 outside the compartment) placed into the compartment. For example,
397 # vet arguments and perform potentially unsafe operations
399 $cpt->share('&wrapper');
406 The authors make B<no warranty>, implied or otherwise, about the
407 suitability of this software for safety or security purposes.
409 The authors shall not in any case be liable for special, incidental,
410 consequential, indirect or other similar damages arising from the use
413 Your mileage will vary. If in any doubt B<do not use it>.
416 =head2 RECENT CHANGES
418 The interface to the Safe module has changed quite dramatically since
419 version 1 (as supplied with Perl5.002). Study these pages carefully if
420 you have code written to use Safe version 1 because you will need to
424 =head2 Methods in class Safe
426 To create a new compartment, use
430 Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
431 to use for the compartment (defaults to "Safe::Root0", incremented for
432 each new compartment).
434 Note that version 1.00 of the Safe module supported a second optional
435 parameter, MASK. That functionality has been withdrawn pending deeper
436 consideration. Use the permit and deny methods described below.
438 The following methods can then be used on the compartment
439 object returned by the above constructor. The object argument
440 is implicit in each case.
445 =item permit (OP, ...)
447 Permit the listed operators to be used when compiling code in the
448 compartment (in I<addition> to any operators already permitted).
450 You can list opcodes by names, or use a tag name; see
451 L<Opcode/"Predefined Opcode Tags">.
453 =item permit_only (OP, ...)
455 Permit I<only> the listed operators to be used when compiling code in
456 the compartment (I<no> other operators are permitted).
460 Deny the listed operators from being used when compiling code in the
461 compartment (other operators may still be permitted).
463 =item deny_only (OP, ...)
465 Deny I<only> the listed operators from being used when compiling code
466 in the compartment (I<all> other operators will be permitted).
470 =item untrap (OP, ...)
472 The trap and untrap methods are synonyms for deny and permit
475 =item share (NAME, ...)
477 This shares the variable(s) in the argument list with the compartment.
478 This is almost identical to exporting variables using the L<Exporter>
481 Each NAME must be the B<name> of a non-lexical variable, typically
482 with the leading type identifier included. A bareword is treated as a
485 Examples of legal names are '$foo' for a scalar, '@foo' for an
486 array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
487 for a glob (i.e. all symbol table entries associated with "foo",
488 including scalar, array, hash, sub and filehandle).
490 Each NAME is assumed to be in the calling package. See share_from
491 for an alternative method (which share uses).
493 =item share_from (PACKAGE, ARRAYREF)
495 This method is similar to share() but allows you to explicitly name the
496 package that symbols should be shared from. The symbol names (including
497 type characters) are supplied as an array reference.
499 $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
502 =item varglob (VARNAME)
504 This returns a glob reference for the symbol table entry of VARNAME in
505 the package of the compartment. VARNAME must be the B<name> of a
506 variable without any leading type marker. For example,
508 $cpt = new Safe 'Root';
509 $Root::foo = "Hello world";
510 # Equivalent version which doesn't need to know $cpt's package name:
511 ${$cpt->varglob('foo')} = "Hello world";
514 =item reval (STRING, STRICT)
516 This evaluates STRING as perl code inside the compartment.
518 The code can only see the compartment's namespace (as returned by the
519 B<root> method). The compartment's root package appears to be the
520 C<main::> package to the code inside the compartment.
522 Any attempt by the code in STRING to use an operator which is not permitted
523 by the compartment will cause an error (at run-time of the main program
524 but at compile-time for the code in STRING). The error is of the form
525 "'%s' trapped by operation mask...".
527 If an operation is trapped in this way, then the code in STRING will
528 not be executed. If such a trapped operation occurs or any other
529 compile-time or return error, then $@ is set to the error message, just
532 If there is no error, then the method returns the value of the last
533 expression evaluated, or a return statement may be used, just as with
534 subroutines and B<eval()>. The context (list or scalar) is determined
535 by the caller as usual.
537 This behaviour differs from the beta distribution of the Safe extension
538 where earlier versions of perl made it hard to mimic the return
539 behaviour of the eval() command and the context was always scalar.
541 The formerly undocumented STRICT argument sets strictness: if true
542 'use strict;' is used, otherwise it uses 'no strict;'. B<Note>: if
543 STRICT is omitted 'no strict;' is the default.
547 If the entereval op is permitted then the code can use eval "..." to
548 'hide' code which might use denied ops. This is not a major problem
549 since when the code tries to execute the eval it will fail because the
550 opmask is still in effect. However this technique would allow clever,
551 and possibly harmful, code to 'probe' the boundaries of what is
554 Any string eval which is executed by code executing in a compartment,
555 or by code called from code executing in a compartment, will be eval'd
556 in the namespace of the compartment. This is potentially a serious
559 Consider a function foo() in package pkg compiled outside a compartment
560 but shared with it. Assume the compartment has a root package called
561 'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
562 normally, $pkg::foo will be set to 1. If foo() is called from the
563 compartment (by whatever means) then instead of setting $pkg::foo, the
564 eval will actually set $Root::pkg::foo.
566 This can easily be demonstrated by using a module, such as the Socket
567 module, which uses eval "..." as part of an AUTOLOAD function. You can
568 'use' the module outside the compartment and share an (autoloaded)
569 function with the compartment. If an autoload is triggered by code in
570 the compartment, or by any code anywhere that is called by any means
571 from the compartment, then the eval in the Socket module's AUTOLOAD
572 function happens in the namespace of the compartment. Any variables
573 created or used by the eval'd code are now under the control of
574 the code in the compartment.
576 A similar effect applies to I<all> runtime symbol lookups in code
577 called from a compartment but not compiled within it.
583 This evaluates the contents of file FILENAME inside the compartment.
584 See above documentation on the B<reval> method for further details.
586 =item root (NAMESPACE)
588 This method returns the name of the package that is the root of the
589 compartment's namespace.
591 Note that this behaviour differs from version 1.00 of the Safe module
592 where the root module could be used to change the namespace. That
593 functionality has been withdrawn pending deeper consideration.
597 This is a get-or-set method for the compartment's operator mask.
599 With no MASK argument present, it returns the current operator mask of
602 With the MASK argument present, it sets the operator mask for the
603 compartment (equivalent to calling the deny_only method).
608 =head2 Some Safety Issues
610 This section is currently just an outline of some of the things code in
611 a compartment might do (intentionally or unintentionally) which can
612 have an effect outside the compartment.
618 Consuming all (or nearly all) available memory.
622 Causing infinite loops etc.
626 Copying private information out of your system. Even something as
627 simple as your user name is of value to others. Much useful information
628 could be gleaned from your environment variables for example.
632 Causing signals (especially SIGFPE and SIGALARM) to affect your process.
634 Setting up a signal handler will need to be carefully considered
635 and controlled. What mask is in effect when a signal handler
636 gets called? If a user can get an imported function to get an
637 exception and call the user's signal handler, does that user's
638 restricted mask get re-instated before the handler is called?
639 Does an imported handler get called with its original mask or
644 Ops such as chdir obviously effect the process as a whole and not just
645 the code in the compartment. Ops such as rand and srand have a similar
646 but more subtle effect.
652 Originally designed and implemented by Malcolm Beattie.
654 Reworked to use the Opcode module and other changes added by Tim Bunce.
656 Currently maintained by the Perl 5 Porters, <perl5-porters@perl.org>.