Perl::Critic::Policy::InputOutput::RequireEncodingWithUTF8Layer - Write open $fh, q{<:encoding(UTF-8)}, $filename; instead of open $fh, q{{<:utf8}, $filename;.
open $fh, q{<:encoding(UTF-8)}, $filename;
open $fh, q{{<:utf8}, $filename;
This Policy is part of the core Perl::Critic distribution.
Use of the :utf8 I/O layer (as opposed to :encoding(UTF8) or :encoding(UTF-8)) was suggested in the Perl documentation up to version 5.8.8. This may be OK for output, but on input :utf8 does not validate the input, leading to unexpected results.
:utf8
:encoding(UTF8)
:encoding(UTF-8)
An exploit based on this behavior of :utf8 is exhibited on PerlMonks at http://www.perlmonks.org/?node_id=644786. The exploit involves a string read from an external file and sanitized with m/^(\w+)$/, where $1 nonetheless ends up containing shell meta-characters.
m/^(\w+)$/
$1
To summarize:
open $fh, '<:utf8', 'foo.txt'; # BAD open $fh, '<:encoding(UTF8)', 'foo.txt'; # GOOD open $fh, '<:encoding(UTF-8)', 'foo.txt'; # BETTER
See the Encode documentation for the difference between UTF8 and UTF-8. The short version is that UTF-8 implements the Unicode standard, and UTF8 is liberalized.
UTF8
UTF-8
For consistency's sake, this policy checks files opened for output as well as input, For complete coverage it also checks binmode() calls, where the direction the operation can not be determined.
binmode()
This Policy is not configurable except for the standard options.
Because Perl::Critic does a static analysis, this policy can not detect cases like
Perl::Critic
my $encoding = ':utf8'; binmode $fh, $encoding;
where the encoding is computed.
PerlIO
Encode
perldoc -f binmode
http://www.socialtext.net/perl5/index.cgi?the_utf8_perlio_layer
http://www.perlmonks.org/?node_id=644786
Thomas R. Wyant, III wyant at cpan dot org
Copyright (c) 2010-2011 Thomas R. Wyant, III
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
To install Perl::Critic, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Perl::Critic
CPAN shell
perl -MCPAN -e shell install Perl::Critic
For more information on module installation, please visit the detailed CPAN module installation guide.