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1 | #!/usr/bin/perl |
2 | package evil; | |
3 | ||
4 | use 5.008009; | |
5 | use strict; | |
6 | use warnings; | |
7 | ||
8 | use Carp; | |
9 | ||
10 | our $VERSION = 0.001; | |
11 | ||
12 | our %tainted; | |
13 | our $strict; | |
14 | ||
15 | sub import { | |
16 | $tainted{caller()} = 1; | |
17 | croak "Cannot load evil module when \"no evil ':strict'\" is in effect" if $strict; | |
18 | } | |
19 | ||
20 | sub unimport { | |
21 | my $strict_arg = grep /^:strict$/, @_; | |
22 | carp 'no evil; interpreted as no evil ":strict". This will change in a future version of Acme::Evil' unless $strict_arg; | |
23 | $strict = 1; # To be changed when other modes are implemented | |
24 | if ($strict && %tainted) { | |
25 | croak "Evil module already loaded. Cannot enforce \"no evil ':strict'\""; | |
26 | } | |
27 | } | |
28 | ||
29 | 1; | |
30 | __END__ | |
31 | ||
32 | =encoding utf-8 | |
33 | ||
34 | =head1 NAME | |
35 | ||
36 | evil - RFC 3514 (evil bit) implementation for Perl modules | |
37 | ||
38 | =head1 SYNOPSIS | |
39 | ||
40 | # in A.pm | |
41 | package A; | |
42 | use evil; | |
43 | ... | |
44 | ||
45 | # in B.pm | |
46 | package B; | |
47 | no evil ':strict'; | |
48 | use A; # <dies> | |
49 | ... | |
50 | ||
51 | ||
52 | =head1 DESCRIPTION | |
53 | ||
54 | L<RFC3514|https://www.ietf.org/rfc/rfc3514.txt> introduces a new flag | |
55 | called the "evil bit" in all IP packets. The intention is to simplify | |
56 | the work of firewalls. Software that sends IP packets with malicious | |
57 | intent must set the evil bit to true, and firewalls can simply drop | |
58 | such packets. | |
59 | ||
60 | The evil pragma is a Perl implementation of the same concept. With | |
61 | this pragma malicious modules can declare their evil intent while | |
62 | critical modules can request that they will only use / run alongside | |
63 | non-evil code. | |
64 | ||
65 | The pragma can be used in the following ways: | |
66 | ||
67 | =over | |
68 | ||
69 | =item use B<evil>; | |
70 | ||
71 | Marks the current package as evil. All malicious modules MUST use this | |
72 | directive to ensure the full functionality of this module. | |
73 | ||
74 | =item no B<evil> ':strict'; | |
75 | ||
76 | The calling module function properly if malignant code is loaded | |
77 | anywhere in the program. Throws an exception if an evil module is | |
78 | loaded, whether at the moment of calling this pragma or in the future. | |
79 | ||
80 | =item no B<evil> ':intermediate'; (TODO) | |
81 | ||
82 | Not yet implemented. The calling module cannot function properly if it | |
83 | is using evil code, whether directly or indirectly. Throws an | |
84 | exception if an evil module is loaded by the calling module or by one | |
85 | of the children modules (or by one of their children modules, etc). | |
86 | ||
87 | =item no B<evil> ':lax'; (TODO) | |
88 | ||
89 | Not yet implemented. The calling module cannot function properly if it | |
90 | is using evil code direcly. Throws an exception if the calling module | |
91 | loads an evil module. | |
92 | ||
93 | =item no B<evil>; | |
94 | ||
95 | This would normally be equivalent to C<no evil ':intermediate';> but | |
96 | since that mode is not yet implemented this call does the same as | |
97 | C<no evil ':strict';> while also emitting a warning saying that this | |
98 | behaviour will change in a future version. | |
99 | ||
100 | =back | |
101 | ||
102 | =head1 AUTHOR | |
103 | ||
104 | Marius Gavrilescu, E<lt>marius@ieval.roE<gt> | |
105 | ||
106 | =head1 COPYRIGHT AND LICENSE | |
107 | ||
108 | Copyright (C) 2016 by Marius Gavrilescu | |
109 | ||
110 | This library is free software; you can redistribute it and/or modify | |
111 | it under the same terms as Perl itself, either Perl version 5.22.2 or, | |
112 | at your option, any later version of Perl 5 you may have available. | |
113 | ||
114 | ||
115 | =cut |