Perl::Critic::Policy::InputOutput::RequireEncodingWithUTF8Layer - Write
$filename; instead of
This Policy is part of the core Perl::Critic distribution.
Use of the
:utf8 I/O layer (as opposed to
: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.
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
$1 nonetheless ends up containing shell meta-characters.
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
UTF-8. The short version is that
UTF-8 implements the Unicode standard, and
UTF8 is liberalized.
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.
This Policy is not configurable except for the standard options.
Perl::Critic does a static analysis, this policy can not detect cases like
my $encoding = ':utf8'; binmode $fh, $encoding;
where the encoding is computed.
perldoc -f binmode
Thomas R. Wyant, III wyant at cpan dot org
Copyright (c) 2010-2011 Thomas R. Wyant, III