Commit | Line | Data |
2ded1cc1 |
1 | package Safe; |
2 | |
5f05dabc |
3 | use 5.003_11; |
2ded1cc1 |
4 | use strict; |
2ded1cc1 |
5 | |
fad23372 |
6 | $Safe::VERSION = "2.14"; |
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; |
bda6a610 |
29 | BEGIN { eval q{ |
30 | use Carp::Heavy; |
31 | } } |
5f05dabc |
32 | |
2ded1cc1 |
33 | use Opcode 1.01, qw( |
34 | opset opset_to_ops opmask_add |
35 | empty_opset full_opset invert_opset verify_opset |
36 | opdesc opcodes opmask define_optag opset_to_hex |
37 | ); |
38 | |
39 | *ops_to_opset = \&opset; # Temporary alias for old Penguins |
40 | |
41 | |
42 | my $default_root = 0; |
096e1543 |
43 | # share *_ and functions defined in universal.c |
44 | # Don't share stuff like *UNIVERSAL:: otherwise code from the |
45 | # compartment can 0wn functions in UNIVERSAL |
46 | my $default_share = [qw[ |
47 | *_ |
48 | &PerlIO::get_layers |
49 | &Regexp::DESTROY |
50 | &re::is_regexp |
51 | &re::regname |
52 | &re::regnames |
53 | &re::regnames_count |
54 | &Tie::Hash::NamedCapture::FETCH |
55 | &Tie::Hash::NamedCapture::STORE |
56 | &Tie::Hash::NamedCapture::DELETE |
57 | &Tie::Hash::NamedCapture::CLEAR |
58 | &Tie::Hash::NamedCapture::EXISTS |
59 | &Tie::Hash::NamedCapture::FIRSTKEY |
60 | &Tie::Hash::NamedCapture::NEXTKEY |
61 | &Tie::Hash::NamedCapture::SCALAR |
62 | &Tie::Hash::NamedCapture::flags |
63 | &UNIVERSAL::isa |
64 | &UNIVERSAL::can |
65 | &UNIVERSAL::DOES |
66 | &UNIVERSAL::VERSION |
67 | &utf8::is_utf8 |
68 | &utf8::valid |
69 | &utf8::encode |
70 | &utf8::decode |
71 | &utf8::upgrade |
72 | &utf8::downgrade |
73 | &utf8::native_to_unicode |
74 | &utf8::unicode_to_native |
75 | &version::() |
76 | &version::new |
77 | &version::("" |
78 | &version::stringify |
79 | &version::(0+ |
80 | &version::numify |
81 | &version::normal |
82 | &version::(cmp |
83 | &version::(<=> |
84 | &version::vcmp |
85 | &version::(bool |
86 | &version::boolean |
87 | &version::(nomethod |
88 | &version::noop |
89 | &version::is_alpha |
90 | &version::qv |
91 | ]]; |
2ded1cc1 |
92 | |
93 | sub new { |
94 | my($class, $root, $mask) = @_; |
95 | my $obj = {}; |
96 | bless $obj, $class; |
97 | |
98 | if (defined($root)) { |
99 | croak "Can't use \"$root\" as root name" |
100 | if $root =~ /^main\b/ or $root !~ /^\w[:\w]*$/; |
101 | $obj->{Root} = $root; |
102 | $obj->{Erase} = 0; |
103 | } |
104 | else { |
105 | $obj->{Root} = "Safe::Root".$default_root++; |
106 | $obj->{Erase} = 1; |
107 | } |
108 | |
109 | # use permit/deny methods instead till interface issues resolved |
110 | # XXX perhaps new Safe 'Root', mask => $mask, foo => bar, ...; |
111 | croak "Mask parameter to new no longer supported" if defined $mask; |
112 | $obj->permit_only(':default'); |
113 | |
114 | # We must share $_ and @_ with the compartment or else ops such |
115 | # as split, length and so on won't default to $_ properly, nor |
116 | # will passing argument to subroutines work (via @_). In fact, |
117 | # for reasons I don't completely understand, we need to share |
118 | # the whole glob *_ rather than $_ and @_ separately, otherwise |
119 | # @_ in non default packages within the compartment don't work. |
120 | $obj->share_from('main', $default_share); |
ac5e3691 |
121 | Opcode::_safe_pkg_prep($obj->{Root}) if($Opcode::VERSION > 1.04); |
2ded1cc1 |
122 | return $obj; |
123 | } |
124 | |
125 | sub DESTROY { |
126 | my $obj = shift; |
4d8e9581 |
127 | $obj->erase('DESTROY') if $obj->{Erase}; |
2ded1cc1 |
128 | } |
129 | |
130 | sub erase { |
4d8e9581 |
131 | my ($obj, $action) = @_; |
2ded1cc1 |
132 | my $pkg = $obj->root(); |
133 | my ($stem, $leaf); |
134 | |
135 | no strict 'refs'; |
136 | $pkg = "main::$pkg\::"; # expand to full symbol table name |
137 | ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/; |
138 | |
139 | # The 'my $foo' is needed! Without it you get an |
140 | # 'Attempt to free unreferenced scalar' warning! |
141 | my $stem_symtab = *{$stem}{HASH}; |
142 | |
143 | #warn "erase($pkg) stem=$stem, leaf=$leaf"; |
144 | #warn " stem_symtab hash ".scalar(%$stem_symtab)."\n"; |
145 | # ", join(', ', %$stem_symtab),"\n"; |
146 | |
4d8e9581 |
147 | # delete $stem_symtab->{$leaf}; |
2ded1cc1 |
148 | |
4d8e9581 |
149 | my $leaf_glob = $stem_symtab->{$leaf}; |
150 | my $leaf_symtab = *{$leaf_glob}{HASH}; |
2ded1cc1 |
151 | # warn " leaf_symtab ", join(', ', %$leaf_symtab),"\n"; |
4d8e9581 |
152 | %$leaf_symtab = (); |
2ded1cc1 |
153 | #delete $leaf_symtab->{'__ANON__'}; |
154 | #delete $leaf_symtab->{'foo'}; |
155 | #delete $leaf_symtab->{'main::'}; |
156 | # my $foo = undef ${"$stem\::"}{"$leaf\::"}; |
157 | |
4d8e9581 |
158 | if ($action and $action eq 'DESTROY') { |
159 | delete $stem_symtab->{$leaf}; |
160 | } else { |
161 | $obj->share_from('main', $default_share); |
162 | } |
2ded1cc1 |
163 | 1; |
164 | } |
165 | |
166 | |
167 | sub reinit { |
168 | my $obj= shift; |
169 | $obj->erase; |
170 | $obj->share_redo; |
171 | } |
172 | |
173 | sub root { |
174 | my $obj = shift; |
175 | croak("Safe root method now read-only") if @_; |
176 | return $obj->{Root}; |
177 | } |
178 | |
179 | |
180 | sub mask { |
181 | my $obj = shift; |
182 | return $obj->{Mask} unless @_; |
183 | $obj->deny_only(@_); |
184 | } |
185 | |
186 | # v1 compatibility methods |
187 | sub trap { shift->deny(@_) } |
188 | sub untrap { shift->permit(@_) } |
189 | |
190 | sub deny { |
191 | my $obj = shift; |
192 | $obj->{Mask} |= opset(@_); |
193 | } |
194 | sub deny_only { |
195 | my $obj = shift; |
196 | $obj->{Mask} = opset(@_); |
197 | } |
198 | |
199 | sub permit { |
200 | my $obj = shift; |
201 | # XXX needs testing |
202 | $obj->{Mask} &= invert_opset opset(@_); |
203 | } |
204 | sub permit_only { |
205 | my $obj = shift; |
206 | $obj->{Mask} = invert_opset opset(@_); |
207 | } |
208 | |
209 | |
210 | sub dump_mask { |
211 | my $obj = shift; |
212 | print opset_to_hex($obj->{Mask}),"\n"; |
213 | } |
214 | |
215 | |
216 | |
217 | sub share { |
218 | my($obj, @vars) = @_; |
219 | $obj->share_from(scalar(caller), \@vars); |
220 | } |
221 | |
222 | sub share_from { |
223 | my $obj = shift; |
224 | my $pkg = shift; |
225 | my $vars = shift; |
226 | my $no_record = shift || 0; |
50fc18f7 |
227 | my $root = $obj->root(); |
2ded1cc1 |
228 | croak("vars not an array ref") unless ref $vars eq 'ARRAY'; |
d00660f4 |
229 | no strict 'refs'; |
2ded1cc1 |
230 | # Check that 'from' package actually exists |
231 | croak("Package \"$pkg\" does not exist") |
232 | unless keys %{"$pkg\::"}; |
3fe9a6f1 |
233 | my $arg; |
2ded1cc1 |
234 | foreach $arg (@$vars) { |
235 | # catch some $safe->share($var) errors: |
3fe9a6f1 |
236 | my ($var, $type); |
237 | $type = $1 if ($var = $arg) =~ s/^(\W)//; |
238 | # warn "share_from $pkg $type $var"; |
50fc18f7 |
239 | *{$root."::$var"} = (!$type) ? \&{$pkg."::$var"} |
3fe9a6f1 |
240 | : ($type eq '&') ? \&{$pkg."::$var"} |
241 | : ($type eq '$') ? \${$pkg."::$var"} |
242 | : ($type eq '@') ? \@{$pkg."::$var"} |
243 | : ($type eq '%') ? \%{$pkg."::$var"} |
244 | : ($type eq '*') ? *{$pkg."::$var"} |
245 | : croak(qq(Can't share "$type$var" of unknown type)); |
2ded1cc1 |
246 | } |
247 | $obj->share_record($pkg, $vars) unless $no_record or !$vars; |
248 | } |
249 | |
250 | sub share_record { |
251 | my $obj = shift; |
252 | my $pkg = shift; |
253 | my $vars = shift; |
254 | my $shares = \%{$obj->{Shares} ||= {}}; |
255 | # Record shares using keys of $obj->{Shares}. See reinit. |
256 | @{$shares}{@$vars} = ($pkg) x @$vars if @$vars; |
257 | } |
258 | sub share_redo { |
259 | my $obj = shift; |
260 | my $shares = \%{$obj->{Shares} ||= {}}; |
d00660f4 |
261 | my($var, $pkg); |
2ded1cc1 |
262 | while(($var, $pkg) = each %$shares) { |
263 | # warn "share_redo $pkg\:: $var"; |
264 | $obj->share_from($pkg, [ $var ], 1); |
265 | } |
266 | } |
267 | sub share_forget { |
268 | delete shift->{Shares}; |
269 | } |
270 | |
271 | sub varglob { |
272 | my ($obj, $var) = @_; |
273 | no strict 'refs'; |
274 | return *{$obj->root()."::$var"}; |
275 | } |
276 | |
277 | |
278 | sub reval { |
279 | my ($obj, $expr, $strict) = @_; |
50fc18f7 |
280 | my $root = $obj->{Root}; |
2ded1cc1 |
281 | |
35ed0d3c |
282 | my $evalsub = lexless_anon_sub($root,$strict, $expr); |
50fc18f7 |
283 | return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub); |
2ded1cc1 |
284 | } |
285 | |
286 | sub rdo { |
287 | my ($obj, $file) = @_; |
50fc18f7 |
288 | my $root = $obj->{Root}; |
289 | |
290 | my $evalsub = eval |
d00660f4 |
291 | sprintf('package %s; sub { @_ = (); do $file }', $root); |
50fc18f7 |
292 | return Opcode::_safe_call_sv($root, $obj->{Mask}, $evalsub); |
2ded1cc1 |
293 | } |
294 | |
295 | |
296 | 1; |
297 | |
3e92a254 |
298 | __END__ |
2ded1cc1 |
299 | |
300 | =head1 NAME |
301 | |
302 | Safe - Compile and execute code in restricted compartments |
303 | |
304 | =head1 SYNOPSIS |
305 | |
306 | use Safe; |
307 | |
308 | $compartment = new Safe; |
309 | |
310 | $compartment->permit(qw(time sort :browse)); |
311 | |
312 | $result = $compartment->reval($unsafe_code); |
313 | |
314 | =head1 DESCRIPTION |
315 | |
316 | The Safe extension module allows the creation of compartments |
317 | in which perl code can be evaluated. Each compartment has |
318 | |
319 | =over 8 |
320 | |
321 | =item a new namespace |
322 | |
323 | The "root" of the namespace (i.e. "main::") is changed to a |
324 | different package and code evaluated in the compartment cannot |
325 | refer to variables outside this namespace, even with run-time |
326 | glob lookups and other tricks. |
327 | |
328 | Code which is compiled outside the compartment can choose to place |
329 | variables into (or I<share> variables with) the compartment's namespace |
330 | and only that data will be visible to code evaluated in the |
331 | compartment. |
332 | |
333 | By default, the only variables shared with compartments are the |
334 | "underscore" variables $_ and @_ (and, technically, the less frequently |
335 | used %_, the _ filehandle and so on). This is because otherwise perl |
336 | operators which default to $_ will not work and neither will the |
337 | assignment of arguments to @_ on subroutine entry. |
338 | |
339 | =item an operator mask |
340 | |
341 | Each compartment has an associated "operator mask". Recall that |
342 | perl code is compiled into an internal format before execution. |
343 | Evaluating perl code (e.g. via "eval" or "do 'file'") causes |
344 | the code to be compiled into an internal format and then, |
345 | provided there was no error in the compilation, executed. |
f610777f |
346 | Code evaluated in a compartment compiles subject to the |
347 | compartment's operator mask. Attempting to evaluate code in a |
2ded1cc1 |
348 | compartment which contains a masked operator will cause the |
349 | compilation to fail with an error. The code will not be executed. |
350 | |
351 | The default operator mask for a newly created compartment is |
352 | the ':default' optag. |
353 | |
86780939 |
354 | It is important that you read the L<Opcode> module documentation |
1fef88e7 |
355 | for more information, especially for detailed definitions of opnames, |
2ded1cc1 |
356 | optags and opsets. |
357 | |
358 | Since it is only at the compilation stage that the operator mask |
359 | applies, controlled access to potentially unsafe operations can |
360 | be achieved by having a handle to a wrapper subroutine (written |
361 | outside the compartment) placed into the compartment. For example, |
362 | |
363 | $cpt = new Safe; |
364 | sub wrapper { |
365 | # vet arguments and perform potentially unsafe operations |
366 | } |
367 | $cpt->share('&wrapper'); |
368 | |
369 | =back |
370 | |
371 | |
372 | =head1 WARNING |
373 | |
374 | The authors make B<no warranty>, implied or otherwise, about the |
375 | suitability of this software for safety or security purposes. |
376 | |
377 | The authors shall not in any case be liable for special, incidental, |
378 | consequential, indirect or other similar damages arising from the use |
379 | of this software. |
380 | |
381 | Your mileage will vary. If in any doubt B<do not use it>. |
382 | |
383 | |
384 | =head2 RECENT CHANGES |
385 | |
386 | The interface to the Safe module has changed quite dramatically since |
387 | version 1 (as supplied with Perl5.002). Study these pages carefully if |
388 | you have code written to use Safe version 1 because you will need to |
389 | makes changes. |
390 | |
391 | |
392 | =head2 Methods in class Safe |
393 | |
394 | To create a new compartment, use |
395 | |
396 | $cpt = new Safe; |
397 | |
398 | Optional argument is (NAMESPACE), where NAMESPACE is the root namespace |
399 | to use for the compartment (defaults to "Safe::Root0", incremented for |
400 | each new compartment). |
401 | |
402 | Note that version 1.00 of the Safe module supported a second optional |
403 | parameter, MASK. That functionality has been withdrawn pending deeper |
404 | consideration. Use the permit and deny methods described below. |
405 | |
406 | The following methods can then be used on the compartment |
407 | object returned by the above constructor. The object argument |
408 | is implicit in each case. |
409 | |
410 | |
411 | =over 8 |
412 | |
413 | =item permit (OP, ...) |
414 | |
415 | Permit the listed operators to be used when compiling code in the |
416 | compartment (in I<addition> to any operators already permitted). |
417 | |
86f9b3f5 |
418 | You can list opcodes by names, or use a tag name; see |
419 | L<Opcode/"Predefined Opcode Tags">. |
420 | |
2ded1cc1 |
421 | =item permit_only (OP, ...) |
422 | |
423 | Permit I<only> the listed operators to be used when compiling code in |
424 | the compartment (I<no> other operators are permitted). |
425 | |
426 | =item deny (OP, ...) |
427 | |
428 | Deny the listed operators from being used when compiling code in the |
429 | compartment (other operators may still be permitted). |
430 | |
431 | =item deny_only (OP, ...) |
432 | |
433 | Deny I<only> the listed operators from being used when compiling code |
434 | in the compartment (I<all> other operators will be permitted). |
435 | |
436 | =item trap (OP, ...) |
437 | |
438 | =item untrap (OP, ...) |
439 | |
440 | The trap and untrap methods are synonyms for deny and permit |
441 | respectfully. |
442 | |
443 | =item share (NAME, ...) |
444 | |
445 | This shares the variable(s) in the argument list with the compartment. |
5f944aa8 |
446 | This is almost identical to exporting variables using the L<Exporter> |
2ded1cc1 |
447 | module. |
448 | |
5c3cfe29 |
449 | Each NAME must be the B<name> of a non-lexical variable, typically |
450 | with the leading type identifier included. A bareword is treated as a |
451 | function name. |
2ded1cc1 |
452 | |
453 | Examples of legal names are '$foo' for a scalar, '@foo' for an |
454 | array, '%foo' for a hash, '&foo' or 'foo' for a subroutine and '*foo' |
455 | for a glob (i.e. all symbol table entries associated with "foo", |
456 | including scalar, array, hash, sub and filehandle). |
457 | |
458 | Each NAME is assumed to be in the calling package. See share_from |
459 | for an alternative method (which share uses). |
460 | |
461 | =item share_from (PACKAGE, ARRAYREF) |
462 | |
463 | This method is similar to share() but allows you to explicitly name the |
464 | package that symbols should be shared from. The symbol names (including |
465 | type characters) are supplied as an array reference. |
466 | |
467 | $safe->share_from('main', [ '$foo', '%bar', 'func' ]); |
468 | |
469 | |
470 | =item varglob (VARNAME) |
471 | |
472 | This returns a glob reference for the symbol table entry of VARNAME in |
473 | the package of the compartment. VARNAME must be the B<name> of a |
474 | variable without any leading type marker. For example, |
475 | |
476 | $cpt = new Safe 'Root'; |
477 | $Root::foo = "Hello world"; |
478 | # Equivalent version which doesn't need to know $cpt's package name: |
479 | ${$cpt->varglob('foo')} = "Hello world"; |
480 | |
481 | |
482 | =item reval (STRING) |
483 | |
484 | This evaluates STRING as perl code inside the compartment. |
485 | |
486 | The code can only see the compartment's namespace (as returned by the |
487 | B<root> method). The compartment's root package appears to be the |
488 | C<main::> package to the code inside the compartment. |
489 | |
490 | Any attempt by the code in STRING to use an operator which is not permitted |
491 | by the compartment will cause an error (at run-time of the main program |
492 | but at compile-time for the code in STRING). The error is of the form |
cb77fdf0 |
493 | "'%s' trapped by operation mask...". |
2ded1cc1 |
494 | |
495 | If an operation is trapped in this way, then the code in STRING will |
496 | not be executed. If such a trapped operation occurs or any other |
497 | compile-time or return error, then $@ is set to the error message, just |
498 | as with an eval(). |
499 | |
500 | If there is no error, then the method returns the value of the last |
501 | expression evaluated, or a return statement may be used, just as with |
502 | subroutines and B<eval()>. The context (list or scalar) is determined |
503 | by the caller as usual. |
504 | |
505 | This behaviour differs from the beta distribution of the Safe extension |
506 | where earlier versions of perl made it hard to mimic the return |
507 | behaviour of the eval() command and the context was always scalar. |
508 | |
509 | Some points to note: |
510 | |
511 | If the entereval op is permitted then the code can use eval "..." to |
512 | 'hide' code which might use denied ops. This is not a major problem |
513 | since when the code tries to execute the eval it will fail because the |
514 | opmask is still in effect. However this technique would allow clever, |
515 | and possibly harmful, code to 'probe' the boundaries of what is |
516 | possible. |
517 | |
518 | Any string eval which is executed by code executing in a compartment, |
519 | or by code called from code executing in a compartment, will be eval'd |
520 | in the namespace of the compartment. This is potentially a serious |
521 | problem. |
522 | |
523 | Consider a function foo() in package pkg compiled outside a compartment |
524 | but shared with it. Assume the compartment has a root package called |
1fef88e7 |
525 | 'Root'. If foo() contains an eval statement like eval '$foo = 1' then, |
2ded1cc1 |
526 | normally, $pkg::foo will be set to 1. If foo() is called from the |
527 | compartment (by whatever means) then instead of setting $pkg::foo, the |
528 | eval will actually set $Root::pkg::foo. |
529 | |
530 | This can easily be demonstrated by using a module, such as the Socket |
531 | module, which uses eval "..." as part of an AUTOLOAD function. You can |
532 | 'use' the module outside the compartment and share an (autoloaded) |
533 | function with the compartment. If an autoload is triggered by code in |
534 | the compartment, or by any code anywhere that is called by any means |
535 | from the compartment, then the eval in the Socket module's AUTOLOAD |
536 | function happens in the namespace of the compartment. Any variables |
537 | created or used by the eval'd code are now under the control of |
538 | the code in the compartment. |
539 | |
540 | A similar effect applies to I<all> runtime symbol lookups in code |
541 | called from a compartment but not compiled within it. |
542 | |
543 | |
544 | |
545 | =item rdo (FILENAME) |
546 | |
547 | This evaluates the contents of file FILENAME inside the compartment. |
548 | See above documentation on the B<reval> method for further details. |
549 | |
550 | =item root (NAMESPACE) |
551 | |
552 | This method returns the name of the package that is the root of the |
553 | compartment's namespace. |
554 | |
555 | Note that this behaviour differs from version 1.00 of the Safe module |
556 | where the root module could be used to change the namespace. That |
557 | functionality has been withdrawn pending deeper consideration. |
558 | |
559 | =item mask (MASK) |
560 | |
561 | This is a get-or-set method for the compartment's operator mask. |
562 | |
563 | With no MASK argument present, it returns the current operator mask of |
564 | the compartment. |
565 | |
566 | With the MASK argument present, it sets the operator mask for the |
567 | compartment (equivalent to calling the deny_only method). |
568 | |
569 | =back |
570 | |
571 | |
572 | =head2 Some Safety Issues |
573 | |
574 | This section is currently just an outline of some of the things code in |
575 | a compartment might do (intentionally or unintentionally) which can |
576 | have an effect outside the compartment. |
577 | |
578 | =over 8 |
579 | |
580 | =item Memory |
581 | |
582 | Consuming all (or nearly all) available memory. |
583 | |
584 | =item CPU |
585 | |
586 | Causing infinite loops etc. |
587 | |
588 | =item Snooping |
589 | |
590 | Copying private information out of your system. Even something as |
591 | simple as your user name is of value to others. Much useful information |
592 | could be gleaned from your environment variables for example. |
593 | |
594 | =item Signals |
595 | |
596 | Causing signals (especially SIGFPE and SIGALARM) to affect your process. |
597 | |
598 | Setting up a signal handler will need to be carefully considered |
599 | and controlled. What mask is in effect when a signal handler |
600 | gets called? If a user can get an imported function to get an |
601 | exception and call the user's signal handler, does that user's |
602 | restricted mask get re-instated before the handler is called? |
603 | Does an imported handler get called with its original mask or |
604 | the user's one? |
605 | |
606 | =item State Changes |
607 | |
608 | Ops such as chdir obviously effect the process as a whole and not just |
609 | the code in the compartment. Ops such as rand and srand have a similar |
610 | but more subtle effect. |
611 | |
612 | =back |
613 | |
614 | =head2 AUTHOR |
615 | |
25ff8439 |
616 | Originally designed and implemented by Malcolm Beattie. |
2ded1cc1 |
617 | |
25ff8439 |
618 | Reworked to use the Opcode module and other changes added by Tim Bunce. |
619 | |
620 | Currently maintained by the Perl 5 Porters, <perl5-porters@perl.org>. |
2ded1cc1 |
621 | |
622 | =cut |
623 | |