Perl-Critic-Policy-RegularExpressions-RequireDefault

Always use the /a or /aa modifier with regular expressions.


Keywords
perl, perl-critic, perl5, policy
License
Artistic-2.0

Documentation

NAME

Perl::Critic::Policy::RegularExpressions::RequireDefault - Always use the /a or /aa modifier with regular expressions.

VERSION

This documentation describes version 1.00

AFFILIATION

This policy has no affiliation

DESCRIPTION

This poliy aims to help enforce using Perl's protective measures against security vulnerabilities related to Unicode, such as:

  • Visual Spoofing
  • Character and String Transformation Vulnerabilities

The /a and /aa modifiers standing for ASCII-restrict or ASCII-safe, provides protection for applications that do not need to be exposed to all of Unicode and possible security issues with Unicode.

/a causes the sequences \d, \s, \w, and the Posix character classes to match only in the ASCII range. Meaning:

  • \d means the digits 0 to 9

      my $ascii_letters =~ m/[A-Z]*/i;  # not ok
      my $ascii_letters =~ m/[A-Z]*/a;  # ok
      my $ascii_letters =~ m/[A-Z]*/aa; # ok
    
  • \s means the five characters [ \f\n\r\t], and starting in Perl v5.18, also the vertical tab

      my $characters =~ m/[ \f\n\r\t]*/;   # not ok
      my $characters =~ m/[ \f\n\r\t]*/a;  # ok
      my $characters =~ m/[ \f\n\r\t]*/aa; # ok
    
  • \w means the 63 characters [A-Za-z0-9_] and all the Posix classes such as [[:print:]] match only the appropriate ASCII-range characters

      my $letters =~ m/[A-Za-z0-9_]*/;   # not ok
      my $letters =~ m/[A-Za-z0-9_]*/a;  # ok
      my $letters =~ m/[A-Za-z0-9_]*/aa; # ok
    

The policy also supports the pragma:

use re 'a';

and:

use re 'aa';

Which mean it will not evaluate the regular expressions any further:

use re 'a';
my $letters =~ m/[A-Za-z0-9_]*/;   # ok

Do note that the /a and /aa modifiers require Perl 5.14, so by using the recommended modifiers you indirectly introduct a requirement for Perl 5.14.

This policy is inspired by Perl::Critic::Policy::RegularExpressions::RequireExtendedFormatting and many implementation details was lifted from this particular distribution.

CONFIGURATION AND ENVIRONMENT

This policy is not configurable at this time. Please see the TODO "section".

INCOMPATIBILITIES

This distribution holds no known incompatibilities at this time, please see "DEPENDENCIES AND REQUIREMENTS" for details on version requirements.

BUGS AND LIMITATIONS

  • The pragma handling does not take into consideration of a pragma is disabled.
  • The pragma handling does not take lexical scope into consideration properly and only detects the definition once

This distribution holds no other known limitations or bugs at this time, please refer to the the issue listing on GitHub for more up to date information.

BUG REPORTING

Please report bugs via GitHub.

TEST AND QUALITY

This distribution aims to adhere to the Perl::Critic::Policy standards and Perl best practices and recommendations.

DEPENDENCIES AND REQUIREMENTS

This distribution requires:

  • Perl 5.14
  • Carp
  • Readonly
  • Perl::Critic::Policy
  • Perl::Critic::Utils

Please see the listing in the file: cpanfile, included with the distribution for a complete listing and description for configuration, test and development.

TODO

Ideas and suggestions for improvements and new features are listed in GitHub and are marked as enhancement.

SEE ALSO

MOTIVATION

The motivation for this Perl::Critic policy came from a tweet by @joel

| Perl folk: Looking for a PR challenge task? Check for \d in regexes
| that really should be [0-9] or should have the /a regex modifier.
| Perl is multinational by default! #TPCiSLC

AUTHOR

ACKNOWLEDGEMENTS

LICENSE AND COPYRIGHT

Perl::Critic::Policy::RegularExpressions::RequireDefault is (C) by jonasbn 2018

Perl::Critic::Policy::RegularExpressions::RequireDefault is released under the Artistic License 2.0

Please see the LICENSE file included with the distribution of this module