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1 | package Safe; |
2 | |
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3 | use 5.003_11; |
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4 | use strict; |
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5 | |
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6 | $Safe::VERSION = "2.12"; |
35ed0d3c |
7 | |
8 | # *** Don't declare any lexicals above this point *** |
9 | # |
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) |
12 | |
13 | sub lexless_anon_sub { |
14 | # $_[0] is package; |
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 |
18 | # world |
19 | |
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) |
23 | eval sprintf |
24 | 'package %s; %s strict; sub { @_=(); eval q[my $__ExPr__;] . $__ExPr__; }', |
25 | $_[0], $_[1] ? 'use' : 'no'; |
26 | } |
2ded1cc1 |
27 | |
5f05dabc |
28 | use Carp; |
b27d3831 |
29 | use Carp::Heavy; |
5f05dabc |
30 | |
2ded1cc1 |
31 | use Opcode 1.01, qw( |
32 | opset opset_to_ops opmask_add |
33 | empty_opset full_opset invert_opset verify_opset |
34 | opdesc opcodes opmask define_optag opset_to_hex |
35 | ); |
36 | |
37 | *ops_to_opset = \&opset; # Temporary alias for old Penguins |
38 | |
39 | |
40 | my $default_root = 0; |
096e1543 |
41 | # share *_ and functions defined in universal.c |
42 | # Don't share stuff like *UNIVERSAL:: otherwise code from the |
43 | # compartment can 0wn functions in UNIVERSAL |
44 | my $default_share = [qw[ |
45 | *_ |
46 | &PerlIO::get_layers |
47 | &Regexp::DESTROY |
48 | &re::is_regexp |
49 | &re::regname |
50 | &re::regnames |
51 | &re::regnames_count |
52 | &Tie::Hash::NamedCapture::FETCH |
53 | &Tie::Hash::NamedCapture::STORE |
54 | &Tie::Hash::NamedCapture::DELETE |
55 | &Tie::Hash::NamedCapture::CLEAR |
56 | &Tie::Hash::NamedCapture::EXISTS |
57 | &Tie::Hash::NamedCapture::FIRSTKEY |
58 | &Tie::Hash::NamedCapture::NEXTKEY |
59 | &Tie::Hash::NamedCapture::SCALAR |
60 | &Tie::Hash::NamedCapture::flags |
61 | &UNIVERSAL::isa |
62 | &UNIVERSAL::can |
63 | &UNIVERSAL::DOES |
64 | &UNIVERSAL::VERSION |
65 | &utf8::is_utf8 |
66 | &utf8::valid |
67 | &utf8::encode |
68 | &utf8::decode |
69 | &utf8::upgrade |
70 | &utf8::downgrade |
71 | &utf8::native_to_unicode |
72 | &utf8::unicode_to_native |
73 | &version::() |
74 | &version::new |
75 | &version::("" |
76 | &version::stringify |
77 | &version::(0+ |
78 | &version::numify |
79 | &version::normal |
80 | &version::(cmp |
81 | &version::(<=> |
82 | &version::vcmp |
83 | &version::(bool |
84 | &version::boolean |
85 | &version::(nomethod |
86 | &version::noop |
87 | &version::is_alpha |
88 | &version::qv |
89 | ]]; |
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90 | |
91 | sub new { |
92 | my($class, $root, $mask) = @_; |
93 | my $obj = {}; |
94 | bless $obj, $class; |
95 | |
96 | if (defined($root)) { |
97 | croak "Can't use \"$root\" as root name" |
98 | if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/; |
99 | $obj->{Root} = $root; |
100 | $obj->{Erase} = 0; |
101 | } |
102 | else { |
103 | $obj->{Root} = "Safe::Root".$default_root++; |
104 | $obj->{Erase} = 1; |
105 | } |
106 | |
107 | # use permit/deny methods instead till interface issues resolved |
108 | # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...; |
109 | croak "Mask parameter to new no longer supported" if defined $mask; |
110 | $obj->permit_only(':default'); |
111 | |
112 | # We must share $_ and @_ with the compartment or else ops such |
113 | # as split, length and so on won't default to $_ properly, nor |
114 | # will passing argument to subroutines work (via @_). In fact, |
115 | # for reasons I don't completely understand, we need to share |
116 | # the whole glob *_ rather than $_ and @_ separately, otherwise |
117 | # @_ in non default packages within the compartment don't work. |
118 | $obj->share_from('main', $default_share); |
ac5e3691 |
119 | Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04); |
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120 | return $obj; |
121 | } |
122 | |
123 | sub DESTROY { |
124 | my $obj = shift; |
4d8e9581 |
125 | $obj->erase('DESTROY') if $obj->{Erase}; |
2ded1cc1 |
126 | } |
127 | |
128 | sub erase { |
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129 | my ($obj, $action) = @_; |
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130 | my $pkg = $obj->root(); |
131 | my ($stem, $leaf); |
132 | |
133 | no strict 'refs'; |
134 | $pkg = "main::$pkg\::"; # expand to full symbol table name |
135 | ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; |
136 | |
137 | # The 'my $foo' is needed! Without it you get an |
138 | # 'Attempt to free unreferenced scalar' warning! |
139 | my $stem_symtab = *{$stem}{HASH}; |
140 | |
141 | #warn "erase($pkg) stem=$stem, leaf=$leaf"; |
142 | #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n"; |
143 | # ", join(', ', %$stem_symtab),"\n"; |
144 | |
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145 | # delete $stem_symtab->{$leaf}; |
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146 | |
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147 | my $leaf_glob = $stem_symtab->{$leaf}; |
148 | my $leaf_symtab = *{$leaf_glob}{HASH}; |
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149 | # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n"; |
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150 | %$leaf_symtab = (); |
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151 | #delete $leaf_symtab->{'__ANON__'}; |
152 | #delete $leaf_symtab->{'foo'}; |
153 | #delete $leaf_symtab->{'main::'}; |
154 | # my $foo = undef ${"$stem\::"}{"$leaf\::"}; |
155 | |
4d8e9581 |
156 | if ($action and $action eq 'DESTROY') { |
157 | delete $stem_symtab->{$leaf}; |
158 | } else { |
159 | $obj->share_from('main', $default_share); |
160 | } |
2ded1cc1 |
161 | 1; |
162 | } |
163 | |
164 | |
165 | sub reinit { |
166 | my $obj= shift; |
167 | $obj->erase; |
168 | $obj->share_redo; |
169 | } |
170 | |
171 | sub root { |
172 | my $obj = shift; |
173 | croak("Safe root method now read-only") if @_; |
174 | return $obj->{Root}; |
175 | } |
176 | |
177 | |
178 | sub mask { |
179 | my $obj = shift; |
180 | return $obj->{Mask} unless @_; |
181 | $obj->deny_only(@_); |
182 | } |
183 | |
184 | # v1 compatibility methods |
185 | sub trap { shift->deny(@_) } |
186 | sub untrap { shift->permit(@_) } |
187 | |
188 | sub deny { |
189 | my $obj = shift; |
190 | $obj->{Mask} |= opset(@_); |
191 | } |
192 | sub deny_only { |
193 | my $obj = shift; |
194 | $obj->{Mask} = opset(@_); |
195 | } |
196 | |
197 | sub permit { |
198 | my $obj = shift; |
199 | # XXX needs testing |
200 | $obj->{Mask} &= invert_opset opset(@_); |
201 | } |
202 | sub permit_only { |
203 | my $obj = shift; |
204 | $obj->{Mask} = invert_opset opset(@_); |
205 | } |
206 | |
207 | |
208 | sub dump_mask { |
209 | my $obj = shift; |
210 | print opset_to_hex($obj->{Mask}),"\n"; |
211 | } |
212 | |
213 | |
214 | |
215 | sub share { |
216 | my($obj, @vars) = @_; |
217 | $obj->share_from(scalar(caller), \@vars); |
218 | } |
219 | |
220 | sub share_from { |
221 | my $obj = shift; |
222 | my $pkg = shift; |
223 | my $vars = shift; |
224 | my $no_record = shift || 0; |
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225 | my $root = $obj->root(); |
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226 | croak("vars not an array ref") unless ref $vars eq 'ARRAY'; |
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227 | no strict 'refs'; |
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228 | # Check that 'from' package actually exists |
229 | croak("Package \"$pkg\" does not exist") |
230 | unless keys %{"$pkg\::"}; |
3fe9a6f1 |
231 | my $arg; |
2ded1cc1 |
232 | foreach $arg (@$vars) { |
233 | # catch some $safe->share($var) errors: |
3fe9a6f1 |
234 | my ($var, $type); |
235 | $type = $1 if ($var = $arg) =~ s/^(\W)//; |
236 | # warn "share_from $pkg $type $var"; |
50fc18f7 |
237 | *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"} |
3fe9a6f1 |
238 | : ($type eq '&') ? \&{$pkg."::$var"} |
239 | : ($type eq '$') ? \${$pkg."::$var"} |
240 | : ($type eq '@') ? \@{$pkg."::$var"} |
241 | : ($type eq '%') ? \%{$pkg."::$var"} |
242 | : ($type eq '*') ? *{$pkg."::$var"} |
243 | : croak(qq(Can't share "$type$var" of unknown type)); |
2ded1cc1 |
244 | } |
245 | $obj->share_record($pkg, $vars) unless $no_record or !$vars; |
246 | } |
247 | |
248 | sub share_record { |
249 | my $obj = shift; |
250 | my $pkg = shift; |
251 | my $vars = shift; |
252 | my $shares = \%{$obj->{Shares} ||= {}}; |
253 | # Record shares using keys of $obj->{Shares}. See reinit. |
254 | @{$shares}{@$vars} = ($pkg) x @$vars if @$vars; |
255 | } |
256 | sub share_redo { |
257 | my $obj = shift; |
258 | my $shares = \%{$obj->{Shares} ||= {}}; |
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259 | my($var, $pkg); |
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260 | while(($var, $pkg) = each %$shares) { |
261 | # warn "share_redo $pkg\:: $var"; |
262 | $obj->share_from($pkg, [ $var ], 1); |
263 | } |
264 | } |
265 | sub share_forget { |
266 | delete shift->{Shares}; |
267 | } |
268 | |
269 | sub varglob { |
270 | my ($obj, $var) = @_; |
271 | no strict 'refs'; |
272 | return *{$obj->root()."::$var"}; |
273 | } |
274 | |
275 | |
276 | sub reval { |
277 | my ($obj, $expr, $strict) = @_; |
50fc18f7 |
278 | my $root = $obj->{Root}; |
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279 | |
35ed0d3c |
280 | my $evalsub = lexless_anon_sub($root,$strict, $expr); |
50fc18f7 |
281 | return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub); |
2ded1cc1 |
282 | } |
283 | |
284 | sub rdo { |
285 | my ($obj, $file) = @_; |
50fc18f7 |
286 | my $root = $obj->{Root}; |
287 | |
288 | my $evalsub = eval |
d00660f4 |
289 | sprintf('package %s; sub { @_ = (); do $file }', $root); |
50fc18f7 |
290 | return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub); |
2ded1cc1 |
291 | } |
292 | |
293 | |
294 | 1; |
295 | |
3e92a254 |
296 | __END__ |
2ded1cc1 |
297 | |
298 | =head1 NAME |
299 | |
300 | Safe - Compile and execute code in restricted compartments |
301 | |
302 | =head1 SYNOPSIS |
303 | |
304 | use Safe; |
305 | |
306 | $compartment = new Safe; |
307 | |
308 | $compartment->permit(qw(time sort :browse)); |
309 | |
310 | $result = $compartment->reval($unsafe_code); |
311 | |
312 | =head1 DESCRIPTION |
313 | |
314 | The Safe extension module allows the creation of compartments |
315 | in which perl code can be evaluated. Each compartment has |
316 | |
317 | =over 8 |
318 | |
319 | =item a new namespace |
320 | |
321 | The "root" of the namespace (i.e. "main::") is changed to a |
322 | different package and code evaluated in the compartment cannot |
323 | refer to variables outside this namespace, even with run-time |
324 | glob lookups and other tricks. |
325 | |
326 | Code which is compiled outside the compartment can choose to place |
327 | variables into (or I<share> variables with) the compartment's namespace |
328 | and only that data will be visible to code evaluated in the |
329 | compartment. |
330 | |
331 | By default, the only variables shared with compartments are the |
332 | "underscore" variables $_ and @_ (and, technically, the less frequently |
333 | used %_, the _ filehandle and so on). This is because otherwise perl |
334 | operators which default to $_ will not work and neither will the |
335 | assignment of arguments to @_ on subroutine entry. |
336 | |
337 | =item an operator mask |
338 | |
339 | Each compartment has an associated "operator mask". Recall that |
340 | perl code is compiled into an internal format before execution. |
341 | Evaluating perl code (e.g. via "eval" or "do 'file'") causes |
342 | the code to be compiled into an internal format and then, |
343 | provided there was no error in the compilation, executed. |
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344 | Code evaluated in a compartment compiles subject to the |
345 | compartment's operator mask. Attempting to evaluate code in a |
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346 | compartment which contains a masked operator will cause the |
347 | compilation to fail with an error. The code will not be executed. |
348 | |
349 | The default operator mask for a newly created compartment is |
350 | the ':default' optag. |
351 | |
86780939 |
352 | It is important that you read the L<Opcode> module documentation |
1fef88e7 |
353 | for more information, especially for detailed definitions of opnames, |
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354 | optags and opsets. |
355 | |
356 | Since it is only at the compilation stage that the operator mask |
357 | applies, controlled access to potentially unsafe operations can |
358 | be achieved by having a handle to a wrapper subroutine (written |
359 | outside the compartment) placed into the compartment. For example, |
360 | |
361 | $cpt = new Safe; |
362 | sub wrapper { |
363 | # vet arguments and perform potentially unsafe operations |
364 | } |
365 | $cpt->share('&wrapper'); |
366 | |
367 | =back |
368 | |
369 | |
370 | =head1 WARNING |
371 | |
372 | The authors make B<no warranty>, implied or otherwise, about the |
373 | suitability of this software for safety or security purposes. |
374 | |
375 | The authors shall not in any case be liable for special, incidental, |
376 | consequential, indirect or other similar damages arising from the use |
377 | of this software. |
378 | |
379 | Your mileage will vary. If in any doubt B<do not use it>. |
380 | |
381 | |
382 | =head2 RECENT CHANGES |
383 | |
384 | The interface to the Safe module has changed quite dramatically since |
385 | version 1 (as supplied with Perl5.002). Study these pages carefully if |
386 | you have code written to use Safe version 1 because you will need to |
387 | makes changes. |
388 | |
389 | |
390 | =head2 Methods in class Safe |
391 | |
392 | To create a new compartment, use |
393 | |
394 | $cpt = new Safe; |
395 | |
396 | Optional argument is (NAMESPACE), where NAMESPACE is the root namespace |
397 | to use for the compartment (defaults to "Safe::Root0", incremented for |
398 | each new compartment). |
399 | |
400 | Note that version 1.00 of the Safe module supported a second optional |
401 | parameter, MASK. That functionality has been withdrawn pending deeper |
402 | consideration. Use the permit and deny methods described below. |
403 | |
404 | The following methods can then be used on the compartment |
405 | object returned by the above constructor. The object argument |
406 | is implicit in each case. |
407 | |
408 | |
409 | =over 8 |
410 | |
411 | =item permit (OP, ...) |
412 | |
413 | Permit the listed operators to be used when compiling code in the |
414 | compartment (in I<addition> to any operators already permitted). |
415 | |
86f9b3f5 |
416 | You can list opcodes by names, or use a tag name; see |
417 | L<Opcode/"Predefined Opcode Tags">. |
418 | |
2ded1cc1 |
419 | =item permit_only (OP, ...) |
420 | |
421 | Permit I<only> the listed operators to be used when compiling code in |
422 | the compartment (I<no> other operators are permitted). |
423 | |
424 | =item deny (OP, ...) |
425 | |
426 | Deny the listed operators from being used when compiling code in the |
427 | compartment (other operators may still be permitted). |
428 | |
429 | =item deny_only (OP, ...) |
430 | |
431 | Deny I<only> the listed operators from being used when compiling code |
432 | in the compartment (I<all> other operators will be permitted). |
433 | |
434 | =item trap (OP, ...) |
435 | |
436 | =item untrap (OP, ...) |
437 | |
438 | The trap and untrap methods are synonyms for deny and permit |
439 | respectfully. |
440 | |
441 | =item share (NAME, ...) |
442 | |
443 | This shares the variable(s) in the argument list with the compartment. |
5f944aa8 |
444 | This is almost identical to exporting variables using the L<Exporter> |
2ded1cc1 |
445 | module. |
446 | |
5c3cfe29 |
447 | Each NAME must be the B<name> of a non-lexical variable, typically |
448 | with the leading type identifier included. A bareword is treated as a |
449 | function name. |
2ded1cc1 |
450 | |
451 | Examples of legal names are '$foo' for a scalar, '@foo' for an |
452 | array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo' |
453 | for a glob (i.e. all symbol table entries associated with "foo", |
454 | including scalar, array, hash, sub and filehandle). |
455 | |
456 | Each NAME is assumed to be in the calling package. See share_from |
457 | for an alternative method (which share uses). |
458 | |
459 | =item share_from (PACKAGE, ARRAYREF) |
460 | |
461 | This method is similar to share() but allows you to explicitly name the |
462 | package that symbols should be shared from. The symbol names (including |
463 | type characters) are supplied as an array reference. |
464 | |
465 | $safe->share_from('main', [ '$foo', '%bar', 'func' ]); |
466 | |
467 | |
468 | =item varglob (VARNAME) |
469 | |
470 | This returns a glob reference for the symbol table entry of VARNAME in |
471 | the package of the compartment. VARNAME must be the B<name> of a |
472 | variable without any leading type marker. For example, |
473 | |
474 | $cpt = new Safe 'Root'; |
475 | $Root::foo = "Hello world"; |
476 | # Equivalent version which doesn't need to know $cpt's package name: |
477 | ${$cpt->varglob('foo')} = "Hello world"; |
478 | |
479 | |
480 | =item reval (STRING) |
481 | |
482 | This evaluates STRING as perl code inside the compartment. |
483 | |
484 | The code can only see the compartment's namespace (as returned by the |
485 | B<root> method). The compartment's root package appears to be the |
486 | C<main::> package to the code inside the compartment. |
487 | |
488 | Any attempt by the code in STRING to use an operator which is not permitted |
489 | by the compartment will cause an error (at run-time of the main program |
490 | but at compile-time for the code in STRING). The error is of the form |
cb77fdf0 |
491 | "'%s' trapped by operation mask...". |
2ded1cc1 |
492 | |
493 | If an operation is trapped in this way, then the code in STRING will |
494 | not be executed. If such a trapped operation occurs or any other |
495 | compile-time or return error, then $@ is set to the error message, just |
496 | as with an eval(). |
497 | |
498 | If there is no error, then the method returns the value of the last |
499 | expression evaluated, or a return statement may be used, just as with |
500 | subroutines and B<eval()>. The context (list or scalar) is determined |
501 | by the caller as usual. |
502 | |
503 | This behaviour differs from the beta distribution of the Safe extension |
504 | where earlier versions of perl made it hard to mimic the return |
505 | behaviour of the eval() command and the context was always scalar. |
506 | |
507 | Some points to note: |
508 | |
509 | If the entereval op is permitted then the code can use eval "..." to |
510 | 'hide' code which might use denied ops. This is not a major problem |
511 | since when the code tries to execute the eval it will fail because the |
512 | opmask is still in effect. However this technique would allow clever, |
513 | and possibly harmful, code to 'probe' the boundaries of what is |
514 | possible. |
515 | |
516 | Any string eval which is executed by code executing in a compartment, |
517 | or by code called from code executing in a compartment, will be eval'd |
518 | in the namespace of the compartment. This is potentially a serious |
519 | problem. |
520 | |
521 | Consider a function foo() in package pkg compiled outside a compartment |
522 | but shared with it. Assume the compartment has a root package called |
1fef88e7 |
523 | 'Root'. If foo() contains an eval statement like eval '$foo = 1' then, |
2ded1cc1 |
524 | normally, $pkg::foo will be set to 1. If foo() is called from the |
525 | compartment (by whatever means) then instead of setting $pkg::foo, the |
526 | eval will actually set $Root::pkg::foo. |
527 | |
528 | This can easily be demonstrated by using a module, such as the Socket |
529 | module, which uses eval "..." as part of an AUTOLOAD function. You can |
530 | 'use' the module outside the compartment and share an (autoloaded) |
531 | function with the compartment. If an autoload is triggered by code in |
532 | the compartment, or by any code anywhere that is called by any means |
533 | from the compartment, then the eval in the Socket module's AUTOLOAD |
534 | function happens in the namespace of the compartment. Any variables |
535 | created or used by the eval'd code are now under the control of |
536 | the code in the compartment. |
537 | |
538 | A similar effect applies to I<all> runtime symbol lookups in code |
539 | called from a compartment but not compiled within it. |
540 | |
541 | |
542 | |
543 | =item rdo (FILENAME) |
544 | |
545 | This evaluates the contents of file FILENAME inside the compartment. |
546 | See above documentation on the B<reval> method for further details. |
547 | |
548 | =item root (NAMESPACE) |
549 | |
550 | This method returns the name of the package that is the root of the |
551 | compartment's namespace. |
552 | |
553 | Note that this behaviour differs from version 1.00 of the Safe module |
554 | where the root module could be used to change the namespace. That |
555 | functionality has been withdrawn pending deeper consideration. |
556 | |
557 | =item mask (MASK) |
558 | |
559 | This is a get-or-set method for the compartment's operator mask. |
560 | |
561 | With no MASK argument present, it returns the current operator mask of |
562 | the compartment. |
563 | |
564 | With the MASK argument present, it sets the operator mask for the |
565 | compartment (equivalent to calling the deny_only method). |
566 | |
567 | =back |
568 | |
569 | |
570 | =head2 Some Safety Issues |
571 | |
572 | This section is currently just an outline of some of the things code in |
573 | a compartment might do (intentionally or unintentionally) which can |
574 | have an effect outside the compartment. |
575 | |
576 | =over 8 |
577 | |
578 | =item Memory |
579 | |
580 | Consuming all (or nearly all) available memory. |
581 | |
582 | =item CPU |
583 | |
584 | Causing infinite loops etc. |
585 | |
586 | =item Snooping |
587 | |
588 | Copying private information out of your system. Even something as |
589 | simple as your user name is of value to others. Much useful information |
590 | could be gleaned from your environment variables for example. |
591 | |
592 | =item Signals |
593 | |
594 | Causing signals (especially SIGFPE and SIGALARM) to affect your process. |
595 | |
596 | Setting up a signal handler will need to be carefully considered |
597 | and controlled. What mask is in effect when a signal handler |
598 | gets called? If a user can get an imported function to get an |
599 | exception and call the user's signal handler, does that user's |
600 | restricted mask get re-instated before the handler is called? |
601 | Does an imported handler get called with its original mask or |
602 | the user's one? |
603 | |
604 | =item State Changes |
605 | |
606 | Ops such as chdir obviously effect the process as a whole and not just |
607 | the code in the compartment. Ops such as rand and srand have a similar |
608 | but more subtle effect. |
609 | |
610 | =back |
611 | |
612 | =head2 AUTHOR |
613 | |
25ff8439 |
614 | Originally designed and implemented by Malcolm Beattie. |
2ded1cc1 |
615 | |
25ff8439 |
616 | Reworked to use the Opcode module and other changes added by Tim Bunce. |
617 | |
618 | Currently maintained by the Perl 5 Porters, <perl5-porters@perl.org>. |
2ded1cc1 |
619 | |
620 | =cut |
621 | |