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+package Safe;
+
+use 5.003_11;
+use strict;
+
+$Safe::VERSION = "2.12";
+
+# *** Don't declare any lexicals above this point ***
+#
+# This function should return a closure which contains an eval that can't
+# see any lexicals in scope (apart from __ExPr__ which is unavoidable)
+
+sub lexless_anon_sub {
+ # $_[0] is package;
+ # $_[1] is strict flag;
+ my $__ExPr__ = $_[2]; # must be a lexical to create the closure that
+ # can be used to pass the value into the safe
+ # world
+
+ # Create anon sub ref in root of compartment.
+ # Uses a closure (on $__ExPr__) to pass in the code to be executed.
+ # (eval on one line to keep line numbers as expected by caller)
+ eval sprintf
+ 'package %s; %s strict; sub { @_=(); eval q[my $__ExPr__;] . $__ExPr__; }',
+ $_[0], $_[1] ? 'use' : 'no';
+}
+
+use Carp;
+use Carp::Heavy;
+
+use Opcode 1.01, qw(
+ opset opset_to_ops opmask_add
+ empty_opset full_opset invert_opset verify_opset
+ opdesc opcodes opmask define_optag opset_to_hex
+);
+
+*ops_to_opset = \&opset; # Temporary alias for old Penguins
+
+
+my $default_root = 0;
+my $default_share = ['*_']; #, '*main::'];
+
+sub new {
+ my($class, $root, $mask) = @_;
+ my $obj = {};
+ bless $obj, $class;
+
+ if (defined($root)) {
+ croak "Can't use \"$root\" as root name"
+ if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/;
+ $obj->{Root} = $root;
+ $obj->{Erase} = 0;
+ }
+ else {
+ $obj->{Root} = "Safe::Root".$default_root++;
+ $obj->{Erase} = 1;
+ }
+
+ # use permit/deny methods instead till interface issues resolved
+ # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...;
+ croak "Mask parameter to new no longer supported" if defined $mask;
+ $obj->permit_only(':default');
+
+ # We must share $_ and @_ with the compartment or else ops such
+ # as split, length and so on won't default to $_ properly, nor
+ # will passing argument to subroutines work (via @_). In fact,
+ # for reasons I don't completely understand, we need to share
+ # the whole glob *_ rather than $_ and @_ separately, otherwise
+ # @_ in non default packages within the compartment don't work.
+ $obj->share_from('main', $default_share);
+ Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04);
+ return $obj;
+}
+
+sub DESTROY {
+ my $obj = shift;
+ $obj->erase('DESTROY') if $obj->{Erase};
+}
+
+sub erase {
+ my ($obj, $action) = @_;
+ my $pkg = $obj->root();
+ my ($stem, $leaf);
+
+ no strict 'refs';
+ $pkg = "main::$pkg\::"; # expand to full symbol table name
+ ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
+
+ # The 'my $foo' is needed! Without it you get an
+ # 'Attempt to free unreferenced scalar' warning!
+ my $stem_symtab = *{$stem}{HASH};
+
+ #warn "erase($pkg) stem=$stem, leaf=$leaf";
+ #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n";
+ # ", join(', ', %$stem_symtab),"\n";
+
+# delete $stem_symtab->{$leaf};
+
+ my $leaf_glob = $stem_symtab->{$leaf};
+ my $leaf_symtab = *{$leaf_glob}{HASH};
+# warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n";
+ %$leaf_symtab = ();
+ #delete $leaf_symtab->{'__ANON__'};
+ #delete $leaf_symtab->{'foo'};
+ #delete $leaf_symtab->{'main::'};
+# my $foo = undef ${"$stem\::"}{"$leaf\::"};
+
+ if ($action and $action eq 'DESTROY') {
+ delete $stem_symtab->{$leaf};
+ } else {
+ $obj->share_from('main', $default_share);
+ }
+ 1;
+}
+
+
+sub reinit {
+ my $obj= shift;
+ $obj->erase;
+ $obj->share_redo;
+}
+
+sub root {
+ my $obj = shift;
+ croak("Safe root method now read-only") if @_;
+ return $obj->{Root};
+}
+
+
+sub mask {
+ my $obj = shift;
+ return $obj->{Mask} unless @_;
+ $obj->deny_only(@_);
+}
+
+# v1 compatibility methods
+sub trap { shift->deny(@_) }
+sub untrap { shift->permit(@_) }
+
+sub deny {
+ my $obj = shift;
+ $obj->{Mask} |= opset(@_);
+}
+sub deny_only {
+ my $obj = shift;
+ $obj->{Mask} = opset(@_);
+}
+
+sub permit {
+ my $obj = shift;
+ # XXX needs testing
+ $obj->{Mask} &= invert_opset opset(@_);
+}
+sub permit_only {
+ my $obj = shift;
+ $obj->{Mask} = invert_opset opset(@_);
+}
+
+
+sub dump_mask {
+ my $obj = shift;
+ print opset_to_hex($obj->{Mask}),"\n";
+}
+
+
+
+sub share {
+ my($obj, @vars) = @_;
+ $obj->share_from(scalar(caller), \@vars);
+}
+
+sub share_from {
+ my $obj = shift;
+ my $pkg = shift;
+ my $vars = shift;
+ my $no_record = shift || 0;
+ my $root = $obj->root();
+ croak("vars not an array ref") unless ref $vars eq 'ARRAY';
+ no strict 'refs';
+ # Check that 'from' package actually exists
+ croak("Package \"$pkg\" does not exist")
+ unless keys %{"$pkg\::"};
+ my $arg;
+ foreach $arg (@$vars) {
+ # catch some $safe->share($var) errors:
+ croak("'$arg' not a valid symbol table name")
+ unless $arg =~ /^[\$\@%*&]?\w[\w:]*$/
+ or $arg =~ /^\$\W$/;
+ my ($var, $type);
+ $type = $1 if ($var = $arg) =~ s/^(\W)//;
+ # warn "share_from $pkg $type $var";
+ *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"}
+ : ($type eq '&') ? \&{$pkg."::$var"}
+ : ($type eq '$') ? \${$pkg."::$var"}
+ : ($type eq '@') ? \@{$pkg."::$var"}
+ : ($type eq '%') ? \%{$pkg."::$var"}
+ : ($type eq '*') ? *{$pkg."::$var"}
+ : croak(qq(Can't share "$type$var" of unknown type));
+ }
+ $obj->share_record($pkg, $vars) unless $no_record or !$vars;
+}
+
+sub share_record {
+ my $obj = shift;
+ my $pkg = shift;
+ my $vars = shift;
+ my $shares = \%{$obj->{Shares} ||= {}};
+ # Record shares using keys of $obj->{Shares}. See reinit.
+ @{$shares}{@$vars} = ($pkg) x @$vars if @$vars;
+}
+sub share_redo {
+ my $obj = shift;
+ my $shares = \%{$obj->{Shares} ||= {}};
+ my($var, $pkg);
+ while(($var, $pkg) = each %$shares) {
+ # warn "share_redo $pkg\:: $var";
+ $obj->share_from($pkg, [ $var ], 1);
+ }
+}
+sub share_forget {
+ delete shift->{Shares};
+}
+
+sub varglob {
+ my ($obj, $var) = @_;
+ no strict 'refs';
+ return *{$obj->root()."::$var"};
+}
+
+
+sub reval {
+ my ($obj, $expr, $strict) = @_;
+ my $root = $obj->{Root};
+
+ my $evalsub = lexless_anon_sub($root,$strict, $expr);
+ return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
+}
+
+sub rdo {
+ my ($obj, $file) = @_;
+ my $root = $obj->{Root};
+
+ my $evalsub = eval
+ sprintf('package %s; sub { @_ = (); do $file }', $root);
+ return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub);
+}
+
+
+1;
+
+__END__
+
+=head1 NAME
+
+Safe - Compile and execute code in restricted compartments
+
+=head1 SYNOPSIS
+
+ use Safe;
+
+ $compartment = new Safe;
+
+ $compartment->permit(qw(time sort :browse));
+
+ $result = $compartment->reval($unsafe_code);
+
+=head1 DESCRIPTION
+
+The Safe extension module allows the creation of compartments
+in which perl code can be evaluated. Each compartment has
+
+=over 8
+
+=item a new namespace
+
+The "root" of the namespace (i.e. "main::") is changed to a
+different package and code evaluated in the compartment cannot
+refer to variables outside this namespace, even with run-time
+glob lookups and other tricks.
+
+Code which is compiled outside the compartment can choose to place
+variables into (or I<share> variables with) the compartment's namespace
+and only that data will be visible to code evaluated in the
+compartment.
+
+By default, the only variables shared with compartments are the
+"underscore" variables $_ and @_ (and, technically, the less frequently
+used %_, the _ filehandle and so on). This is because otherwise perl
+operators which default to $_ will not work and neither will the
+assignment of arguments to @_ on subroutine entry.
+
+=item an operator mask
+
+Each compartment has an associated "operator mask". Recall that
+perl code is compiled into an internal format before execution.
+Evaluating perl code (e.g. via "eval" or "do 'file'") causes
+the code to be compiled into an internal format and then,
+provided there was no error in the compilation, executed.
+Code evaluated in a compartment compiles subject to the
+compartment's operator mask. Attempting to evaluate code in a
+compartment which contains a masked operator will cause the
+compilation to fail with an error. The code will not be executed.
+
+The default operator mask for a newly created compartment is
+the ':default' optag.
+
+It is important that you read the Opcode(3) module documentation
+for more information, especially for detailed definitions of opnames,
+optags and opsets.
+
+Since it is only at the compilation stage that the operator mask
+applies, controlled access to potentially unsafe operations can
+be achieved by having a handle to a wrapper subroutine (written
+outside the compartment) placed into the compartment. For example,
+
+ $cpt = new Safe;
+ sub wrapper {
+ # vet arguments and perform potentially unsafe operations
+ }
+ $cpt->share('&wrapper');
+
+=back
+
+
+=head1 WARNING
+
+The authors make B<no warranty>, implied or otherwise, about the
+suitability of this software for safety or security purposes.
+
+The authors shall not in any case be liable for special, incidental,
+consequential, indirect or other similar damages arising from the use
+of this software.
+
+Your mileage will vary. If in any doubt B<do not use it>.
+
+
+=head2 RECENT CHANGES
+
+The interface to the Safe module has changed quite dramatically since
+version 1 (as supplied with Perl5.002). Study these pages carefully if
+you have code written to use Safe version 1 because you will need to
+makes changes.
+
+
+=head2 Methods in class Safe
+
+To create a new compartment, use
+
+ $cpt = new Safe;
+
+Optional argument is (NAMESPACE), where NAMESPACE is the root namespace
+to use for the compartment (defaults to "Safe::Root0", incremented for
+each new compartment).
+
+Note that version 1.00 of the Safe module supported a second optional
+parameter, MASK. That functionality has been withdrawn pending deeper
+consideration. Use the permit and deny methods described below.
+
+The following methods can then be used on the compartment
+object returned by the above constructor. The object argument
+is implicit in each case.
+
+
+=over 8
+
+=item permit (OP, ...)
+
+Permit the listed operators to be used when compiling code in the
+compartment (in I<addition> to any operators already permitted).
+
+You can list opcodes by names, or use a tag name; see
+L<Opcode/"Predefined Opcode Tags">.
+
+=item permit_only (OP, ...)
+
+Permit I<only> the listed operators to be used when compiling code in
+the compartment (I<no> other operators are permitted).
+
+=item deny (OP, ...)
+
+Deny the listed operators from being used when compiling code in the
+compartment (other operators may still be permitted).
+
+=item deny_only (OP, ...)
+
+Deny I<only> the listed operators from being used when compiling code
+in the compartment (I<all> other operators will be permitted).
+
+=item trap (OP, ...)
+
+=item untrap (OP, ...)
+
+The trap and untrap methods are synonyms for deny and permit
+respectfully.
+
+=item share (NAME, ...)
+
+This shares the variable(s) in the argument list with the compartment.
+This is almost identical to exporting variables using the L<Exporter>
+module.
+
+Each NAME must be the B<name> of a non-lexical variable, typically
+with the leading type identifier included. A bareword is treated as a
+function name.
+
+Examples of legal names are '$foo' for a scalar, '@foo' for an
+array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo'
+for a glob (i.e. all symbol table entries associated with "foo",
+including scalar, array, hash, sub and filehandle).
+
+Each NAME is assumed to be in the calling package. See share_from
+for an alternative method (which share uses).
+
+=item share_from (PACKAGE, ARRAYREF)
+
+This method is similar to share() but allows you to explicitly name the
+package that symbols should be shared from. The symbol names (including
+type characters) are supplied as an array reference.
+
+ $safe->share_from('main', [ '$foo', '%bar', 'func' ]);
+
+
+=item varglob (VARNAME)
+
+This returns a glob reference for the symbol table entry of VARNAME in
+the package of the compartment. VARNAME must be the B<name> of a
+variable without any leading type marker. For example,
+
+ $cpt = new Safe 'Root';
+ $Root::foo = "Hello world";
+ # Equivalent version which doesn't need to know $cpt's package name:
+ ${$cpt->varglob('foo')} = "Hello world";
+
+
+=item reval (STRING)
+
+This evaluates STRING as perl code inside the compartment.
+
+The code can only see the compartment's namespace (as returned by the
+B<root> method). The compartment's root package appears to be the
+C<main::> package to the code inside the compartment.
+
+Any attempt by the code in STRING to use an operator which is not permitted
+by the compartment will cause an error (at run-time of the main program
+but at compile-time for the code in STRING). The error is of the form
+"'%s' trapped by operation mask...".
+
+If an operation is trapped in this way, then the code in STRING will
+not be executed. If such a trapped operation occurs or any other
+compile-time or return error, then $@ is set to the error message, just
+as with an eval().
+
+If there is no error, then the method returns the value of the last
+expression evaluated, or a return statement may be used, just as with
+subroutines and B<eval()>. The context (list or scalar) is determined
+by the caller as usual.
+
+This behaviour differs from the beta distribution of the Safe extension
+where earlier versions of perl made it hard to mimic the return
+behaviour of the eval() command and the context was always scalar.
+
+Some points to note:
+
+If the entereval op is permitted then the code can use eval "..." to
+'hide' code which might use denied ops. This is not a major problem
+since when the code tries to execute the eval it will fail because the
+opmask is still in effect. However this technique would allow clever,
+and possibly harmful, code to 'probe' the boundaries of what is
+possible.
+
+Any string eval which is executed by code executing in a compartment,
+or by code called from code executing in a compartment, will be eval'd
+in the namespace of the compartment. This is potentially a serious
+problem.
+
+Consider a function foo() in package pkg compiled outside a compartment
+but shared with it. Assume the compartment has a root package called
+'Root'. If foo() contains an eval statement like eval '$foo = 1' then,
+normally, $pkg::foo will be set to 1. If foo() is called from the
+compartment (by whatever means) then instead of setting $pkg::foo, the
+eval will actually set $Root::pkg::foo.
+
+This can easily be demonstrated by using a module, such as the Socket
+module, which uses eval "..." as part of an AUTOLOAD function. You can
+'use' the module outside the compartment and share an (autoloaded)
+function with the compartment. If an autoload is triggered by code in
+the compartment, or by any code anywhere that is called by any means
+from the compartment, then the eval in the Socket module's AUTOLOAD
+function happens in the namespace of the compartment. Any variables
+created or used by the eval'd code are now under the control of
+the code in the compartment.
+
+A similar effect applies to I<all> runtime symbol lookups in code
+called from a compartment but not compiled within it.
+
+
+
+=item rdo (FILENAME)
+
+This evaluates the contents of file FILENAME inside the compartment.
+See above documentation on the B<reval> method for further details.
+
+=item root (NAMESPACE)
+
+This method returns the name of the package that is the root of the
+compartment's namespace.
+
+Note that this behaviour differs from version 1.00 of the Safe module
+where the root module could be used to change the namespace. That
+functionality has been withdrawn pending deeper consideration.
+
+=item mask (MASK)
+
+This is a get-or-set method for the compartment's operator mask.
+
+With no MASK argument present, it returns the current operator mask of
+the compartment.
+
+With the MASK argument present, it sets the operator mask for the
+compartment (equivalent to calling the deny_only method).
+
+=back
+
+
+=head2 Some Safety Issues
+
+This section is currently just an outline of some of the things code in
+a compartment might do (intentionally or unintentionally) which can
+have an effect outside the compartment.
+
+=over 8
+
+=item Memory
+
+Consuming all (or nearly all) available memory.
+
+=item CPU
+
+Causing infinite loops etc.
+
+=item Snooping
+
+Copying private information out of your system. Even something as
+simple as your user name is of value to others. Much useful information
+could be gleaned from your environment variables for example.
+
+=item Signals
+
+Causing signals (especially SIGFPE and SIGALARM) to affect your process.
+
+Setting up a signal handler will need to be carefully considered
+and controlled. What mask is in effect when a signal handler
+gets called? If a user can get an imported function to get an
+exception and call the user's signal handler, does that user's
+restricted mask get re-instated before the handler is called?
+Does an imported handler get called with its original mask or
+the user's one?
+
+=item State Changes
+
+Ops such as chdir obviously effect the process as a whole and not just
+the code in the compartment. Ops such as rand and srand have a similar
+but more subtle effect.
+
+=back
+
+=head2 AUTHOR
+
+Originally designed and implemented by Malcolm Beattie,
+mbeattie@sable.ox.ac.uk.
+
+Reworked to use the Opcode module and other changes added by Tim Bunce
+E<lt>F<Tim.Bunce@ig.co.uk>E<gt>.
+
+=cut
+
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