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2ded1cc1 | 1 | package Safe; |
2 | ||
3 | require 5.002; | |
4 | ||
5 | use strict; | |
6 | use Carp; | |
7 | ||
8 | use vars qw($VERSION); | |
9 | ||
10 | $VERSION = "2.06"; | |
11 | ||
12 | use Opcode 1.01, qw( | |
13 | opset opset_to_ops opmask_add | |
14 | empty_opset full_opset invert_opset verify_opset | |
15 | opdesc opcodes opmask define_optag opset_to_hex | |
16 | ); | |
17 | ||
18 | *ops_to_opset = \&opset; # Temporary alias for old Penguins | |
19 | ||
20 | ||
21 | my $default_root = 0; | |
22 | my $default_share = ['*_']; #, '*main::']; | |
23 | ||
24 | sub new { | |
25 | my($class, $root, $mask) = @_; | |
26 | my $obj = {}; | |
27 | bless $obj, $class; | |
28 | ||
29 | if (defined($root)) { | |
30 | croak "Can't use \"$root\" as root name" | |
31 | if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/; | |
32 | $obj->{Root} = $root; | |
33 | $obj->{Erase} = 0; | |
34 | } | |
35 | else { | |
36 | $obj->{Root} = "Safe::Root".$default_root++; | |
37 | $obj->{Erase} = 1; | |
38 | } | |
39 | ||
40 | # use permit/deny methods instead till interface issues resolved | |
41 | # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...; | |
42 | croak "Mask parameter to new no longer supported" if defined $mask; | |
43 | $obj->permit_only(':default'); | |
44 | ||
45 | # We must share $_ and @_ with the compartment or else ops such | |
46 | # as split, length and so on won't default to $_ properly, nor | |
47 | # will passing argument to subroutines work (via @_). In fact, | |
48 | # for reasons I don't completely understand, we need to share | |
49 | # the whole glob *_ rather than $_ and @_ separately, otherwise | |
50 | # @_ in non default packages within the compartment don't work. | |
51 | $obj->share_from('main', $default_share); | |
52 | return $obj; | |
53 | } | |
54 | ||
55 | sub DESTROY { | |
56 | my $obj = shift; | |
57 | $obj->erase if $obj->{Erase}; | |
58 | } | |
59 | ||
60 | sub erase { | |
61 | my $obj= shift; | |
62 | my $pkg = $obj->root(); | |
63 | my ($stem, $leaf); | |
64 | ||
65 | no strict 'refs'; | |
66 | $pkg = "main::$pkg\::"; # expand to full symbol table name | |
67 | ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; | |
68 | ||
69 | # The 'my $foo' is needed! Without it you get an | |
70 | # 'Attempt to free unreferenced scalar' warning! | |
71 | my $stem_symtab = *{$stem}{HASH}; | |
72 | ||
73 | #warn "erase($pkg) stem=$stem, leaf=$leaf"; | |
74 | #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n"; | |
75 | # ", join(', ', %$stem_symtab),"\n"; | |
76 | ||
77 | delete $stem_symtab->{$leaf}; | |
78 | ||
79 | # my $leaf_glob = $stem_symtab->{$leaf}; | |
80 | # my $leaf_symtab = *{$leaf_glob}{HASH}; | |
81 | # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n"; | |
82 | # %$leaf_symtab = (); | |
83 | #delete $leaf_symtab->{'__ANON__'}; | |
84 | #delete $leaf_symtab->{'foo'}; | |
85 | #delete $leaf_symtab->{'main::'}; | |
86 | # my $foo = undef ${"$stem\::"}{"$leaf\::"}; | |
87 | ||
88 | $obj->share_from('main', $default_share); | |
89 | 1; | |
90 | } | |
91 | ||
92 | ||
93 | sub reinit { | |
94 | my $obj= shift; | |
95 | $obj->erase; | |
96 | $obj->share_redo; | |
97 | } | |
98 | ||
99 | sub root { | |
100 | my $obj = shift; | |
101 | croak("Safe root method now read-only") if @_; | |
102 | return $obj->{Root}; | |
103 | } | |
104 | ||
105 | ||
106 | sub mask { | |
107 | my $obj = shift; | |
108 | return $obj->{Mask} unless @_; | |
109 | $obj->deny_only(@_); | |
110 | } | |
111 | ||
112 | # v1 compatibility methods | |
113 | sub trap { shift->deny(@_) } | |
114 | sub untrap { shift->permit(@_) } | |
115 | ||
116 | sub deny { | |
117 | my $obj = shift; | |
118 | $obj->{Mask} |= opset(@_); | |
119 | } | |
120 | sub deny_only { | |
121 | my $obj = shift; | |
122 | $obj->{Mask} = opset(@_); | |
123 | } | |
124 | ||
125 | sub permit { | |
126 | my $obj = shift; | |
127 | # XXX needs testing | |
128 | $obj->{Mask} &= invert_opset opset(@_); | |
129 | } | |
130 | sub permit_only { | |
131 | my $obj = shift; | |
132 | $obj->{Mask} = invert_opset opset(@_); | |
133 | } | |
134 | ||
135 | ||
136 | sub dump_mask { | |
137 | my $obj = shift; | |
138 | print opset_to_hex($obj->{Mask}),"\n"; | |
139 | } | |
140 | ||
141 | ||
142 | ||
143 | sub share { | |
144 | my($obj, @vars) = @_; | |
145 | $obj->share_from(scalar(caller), \@vars); | |
146 | } | |
147 | ||
148 | sub share_from { | |
149 | my $obj = shift; | |
150 | my $pkg = shift; | |
151 | my $vars = shift; | |
152 | my $no_record = shift || 0; | |
153 | my $root = $obj->root(); | |
154 | my ($var, $arg); | |
155 | croak("vars not an array ref") unless ref $vars eq 'ARRAY'; | |
156 | no strict 'refs'; | |
157 | # Check that 'from' package actually exists | |
158 | croak("Package \"$pkg\" does not exist") | |
159 | unless keys %{"$pkg\::"}; | |
160 | foreach $arg (@$vars) { | |
161 | # catch some $safe->share($var) errors: | |
162 | croak("'$arg' not a valid symbol table name") | |
163 | unless $arg =~ /^[\$\@%*&]?\w[\w:]*$/ | |
164 | or $arg =~ /^\$\W$/; | |
165 | ($var = $arg) =~ s/^(\W)//; # get type char | |
166 | # warn "share_from $pkg $1 $var"; | |
167 | *{$root."::$var"} = ($1 eq '$') ? \${$pkg."::$var"} | |
168 | : ($1 eq '@') ? \@{$pkg."::$var"} | |
169 | : ($1 eq '%') ? \%{$pkg."::$var"} | |
170 | : ($1 eq '*') ? *{$pkg."::$var"} | |
171 | : ($1 eq '&') ? \&{$pkg."::$var"} | |
172 | : (!$1) ? \&{$pkg."::$var"} | |
173 | : croak(qq(Can't share "$1$var" of unknown type)); | |
174 | } | |
175 | $obj->share_record($pkg, $vars) unless $no_record or !$vars; | |
176 | } | |
177 | ||
178 | sub share_record { | |
179 | my $obj = shift; | |
180 | my $pkg = shift; | |
181 | my $vars = shift; | |
182 | my $shares = \%{$obj->{Shares} ||= {}}; | |
183 | # Record shares using keys of $obj->{Shares}. See reinit. | |
184 | @{$shares}{@$vars} = ($pkg) x @$vars if @$vars; | |
185 | } | |
186 | sub share_redo { | |
187 | my $obj = shift; | |
188 | my $shares = \%{$obj->{Shares} ||= {}}; | |
189 | my($var, $pkg); | |
190 | while(($var, $pkg) = each %$shares) { | |
191 | # warn "share_redo $pkg\:: $var"; | |
192 | $obj->share_from($pkg, [ $var ], 1); | |
193 | } | |
194 | } | |
195 | sub share_forget { | |
196 | delete shift->{Shares}; | |
197 | } | |
198 | ||
199 | sub varglob { | |
200 | my ($obj, $var) = @_; | |
201 | no strict 'refs'; | |
202 | return *{$obj->root()."::$var"}; | |
203 | } | |
204 | ||
205 | ||
206 | sub reval { | |
207 | my ($obj, $expr, $strict) = @_; | |
208 | my $root = $obj->{Root}; | |
209 | ||
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); | |
214 | my $evalsub; | |
215 | ||
216 | if ($strict) { use strict; $evalsub = eval $evalcode; } | |
217 | else { no strict; $evalsub = eval $evalcode; } | |
218 | ||
219 | return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub); | |
220 | } | |
221 | ||
222 | sub rdo { | |
223 | my ($obj, $file) = @_; | |
224 | my $root = $obj->{Root}; | |
225 | ||
226 | my $evalsub = eval | |
227 | sprintf('package %s; sub { do $file }', $root); | |
228 | return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub); | |
229 | } | |
230 | ||
231 | ||
232 | 1; | |
233 | ||
234 | __DATA__ | |
235 | ||
236 | =head1 NAME | |
237 | ||
238 | Safe - Compile and execute code in restricted compartments | |
239 | ||
240 | =head1 SYNOPSIS | |
241 | ||
242 | use Safe; | |
243 | ||
244 | $compartment = new Safe; | |
245 | ||
246 | $compartment->permit(qw(time sort :browse)); | |
247 | ||
248 | $result = $compartment->reval($unsafe_code); | |
249 | ||
250 | =head1 DESCRIPTION | |
251 | ||
252 | The Safe extension module allows the creation of compartments | |
253 | in which perl code can be evaluated. Each compartment has | |
254 | ||
255 | =over 8 | |
256 | ||
257 | =item a new namespace | |
258 | ||
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. | |
263 | ||
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 | |
267 | compartment. | |
268 | ||
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. | |
274 | ||
275 | =item an operator mask | |
276 | ||
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. | |
286 | ||
287 | The default operator mask for a newly created compartment is | |
288 | the ':default' optag. | |
289 | ||
1fef88e7 JM |
290 | It is important that you read the Opcode(3) module documentation |
291 | for more information, especially for detailed definitions of opnames, | |
2ded1cc1 | 292 | optags and opsets. |
293 | ||
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, | |
298 | ||
299 | $cpt = new Safe; | |
300 | sub wrapper { | |
301 | # vet arguments and perform potentially unsafe operations | |
302 | } | |
303 | $cpt->share('&wrapper'); | |
304 | ||
305 | =back | |
306 | ||
307 | ||
308 | =head1 WARNING | |
309 | ||
310 | The authors make B<no warranty>, implied or otherwise, about the | |
311 | suitability of this software for safety or security purposes. | |
312 | ||
313 | The authors shall not in any case be liable for special, incidental, | |
314 | consequential, indirect or other similar damages arising from the use | |
315 | of this software. | |
316 | ||
317 | Your mileage will vary. If in any doubt B<do not use it>. | |
318 | ||
319 | ||
320 | =head2 RECENT CHANGES | |
321 | ||
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 | |
325 | makes changes. | |
326 | ||
327 | ||
328 | =head2 Methods in class Safe | |
329 | ||
330 | To create a new compartment, use | |
331 | ||
332 | $cpt = new Safe; | |
333 | ||
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). | |
337 | ||
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. | |
341 | ||
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. | |
345 | ||
346 | ||
347 | =over 8 | |
348 | ||
349 | =item permit (OP, ...) | |
350 | ||
351 | Permit the listed operators to be used when compiling code in the | |
352 | compartment (in I<addition> to any operators already permitted). | |
353 | ||
354 | =item permit_only (OP, ...) | |
355 | ||
356 | Permit I<only> the listed operators to be used when compiling code in | |
357 | the compartment (I<no> other operators are permitted). | |
358 | ||
359 | =item deny (OP, ...) | |
360 | ||
361 | Deny the listed operators from being used when compiling code in the | |
362 | compartment (other operators may still be permitted). | |
363 | ||
364 | =item deny_only (OP, ...) | |
365 | ||
366 | Deny I<only> the listed operators from being used when compiling code | |
367 | in the compartment (I<all> other operators will be permitted). | |
368 | ||
369 | =item trap (OP, ...) | |
370 | ||
371 | =item untrap (OP, ...) | |
372 | ||
373 | The trap and untrap methods are synonyms for deny and permit | |
374 | respectfully. | |
375 | ||
376 | =item share (NAME, ...) | |
377 | ||
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)> | |
380 | module. | |
381 | ||
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. | |
384 | ||
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). | |
389 | ||
390 | Each NAME is assumed to be in the calling package. See share_from | |
391 | for an alternative method (which share uses). | |
392 | ||
393 | =item share_from (PACKAGE, ARRAYREF) | |
394 | ||
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. | |
398 | ||
399 | $safe->share_from('main', [ '$foo', '%bar', 'func' ]); | |
400 | ||
401 | ||
402 | =item varglob (VARNAME) | |
403 | ||
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, | |
407 | ||
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"; | |
412 | ||
413 | ||
414 | =item reval (STRING) | |
415 | ||
416 | This evaluates STRING as perl code inside the compartment. | |
417 | ||
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. | |
421 | ||
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...". | |
426 | ||
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 $@ is set to the error message, just | |
430 | as with an eval(). | |
431 | ||
432 | If there is no error, then the method returns the value of the last | |
433 | expression evaluated, or a return statement may be used, just as with | |
434 | subroutines and B<eval()>. The context (list or scalar) is determined | |
435 | by the caller as usual. | |
436 | ||
437 | This behaviour differs from the beta distribution of the Safe extension | |
438 | where earlier versions of perl made it hard to mimic the return | |
439 | behaviour of the eval() command and the context was always scalar. | |
440 | ||
441 | Some points to note: | |
442 | ||
443 | If the entereval op is permitted then the code can use eval "..." to | |
444 | 'hide' code which might use denied ops. This is not a major problem | |
445 | since when the code tries to execute the eval it will fail because the | |
446 | opmask is still in effect. However this technique would allow clever, | |
447 | and possibly harmful, code to 'probe' the boundaries of what is | |
448 | possible. | |
449 | ||
450 | Any string eval which is executed by code executing in a compartment, | |
451 | or by code called from code executing in a compartment, will be eval'd | |
452 | in the namespace of the compartment. This is potentially a serious | |
453 | problem. | |
454 | ||
455 | Consider a function foo() in package pkg compiled outside a compartment | |
456 | but shared with it. Assume the compartment has a root package called | |
1fef88e7 | 457 | 'Root'. If foo() contains an eval statement like eval '$foo = 1' then, |
2ded1cc1 | 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. | |
461 | ||
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. | |
471 | ||
472 | A similar effect applies to I<all> runtime symbol lookups in code | |
473 | called from a compartment but not compiled within it. | |
474 | ||
475 | ||
476 | ||
477 | =item rdo (FILENAME) | |
478 | ||
479 | This evaluates the contents of file FILENAME inside the compartment. | |
480 | See above documentation on the B<reval> method for further details. | |
481 | ||
482 | =item root (NAMESPACE) | |
483 | ||
484 | This method returns the name of the package that is the root of the | |
485 | compartment's namespace. | |
486 | ||
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. | |
490 | ||
491 | =item mask (MASK) | |
492 | ||
493 | This is a get-or-set method for the compartment's operator mask. | |
494 | ||
495 | With no MASK argument present, it returns the current operator mask of | |
496 | the compartment. | |
497 | ||
498 | With the MASK argument present, it sets the operator mask for the | |
499 | compartment (equivalent to calling the deny_only method). | |
500 | ||
501 | =back | |
502 | ||
503 | ||
504 | =head2 Some Safety Issues | |
505 | ||
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. | |
509 | ||
510 | =over 8 | |
511 | ||
512 | =item Memory | |
513 | ||
514 | Consuming all (or nearly all) available memory. | |
515 | ||
516 | =item CPU | |
517 | ||
518 | Causing infinite loops etc. | |
519 | ||
520 | =item Snooping | |
521 | ||
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. | |
525 | ||
526 | =item Signals | |
527 | ||
528 | Causing signals (especially SIGFPE and SIGALARM) to affect your process. | |
529 | ||
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 | |
536 | the user's one? | |
537 | ||
538 | =item State Changes | |
539 | ||
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. | |
543 | ||
544 | =back | |
545 | ||
546 | =head2 AUTHOR | |
547 | ||
548 | Originally designed and implemented by Malcolm Beattie, | |
549 | mbeattie@sable.ox.ac.uk. | |
550 | ||
551 | Reworked to use the Opcode module and other changes added by Tim Bunce | |
1fef88e7 | 552 | E<lt>F<Tim.Bunce@ig.co.uk>E<gt>. |
2ded1cc1 | 553 | |
554 | =cut | |
555 |