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package Net::DNS::Domain;
#
# $Id: Domain.pm 1561 2017-04-19 13:08:13Z willem $
#
our $VERSION = (qw$LastChangedRevision: 1561 $)[1];
=head1 NAME
Net::DNS::Domain - DNS domains
=head1 SYNOPSIS
use Net::DNS::Domain;
$domain = new Net::DNS::Domain('example.com');
$name = $domain->name;
=head1 DESCRIPTION
The Net::DNS::Domain module implements a class of abstract DNS
domain objects with associated class and instance methods.
Each domain object instance represents a single DNS domain which
has a fixed identity throughout its lifetime.
Internally, the primary representation is a (possibly empty) list
of ASCII domain name labels, and optional link to an arbitrary
origin domain object topologically closer to the DNS root.
The computational expense of Unicode character-set conversion is
partially mitigated by use of caches.
=cut
use strict;
use warnings;
use integer;
use Carp;
use constant ASCII => ref eval {
require Encode;
Encode::find_encoding('ascii');
};
use constant UTF8 => scalar eval { ## not UTF-EBCDIC [see UTR#16 3.6]
Encode::encode_utf8( chr(182) ) eq pack( 'H*', 'C2B6' );
};
use constant LIBIDN => defined eval { require Net::LibIDN; };
# perlcc: address of encoding objects must be determined at runtime
my $ascii = ASCII ? Encode::find_encoding('ascii') : undef; # Osborn's Law:
my $utf8 = UTF8 ? Encode::find_encoding('utf8') : undef; # Variables won't; constants aren't.
=head1 METHODS
=head2 new
$object = new Net::DNS::Domain('example.com');
Creates a domain object which represents the DNS domain specified
by the character string argument. The argument consists of a
sequence of labels delimited by dots.
A character preceded by \ represents itself, without any special
interpretation.
Arbitrary 8-bit codes can be represented by \ followed by exactly
three decimal digits.
Character code points are ASCII, irrespective of the character
coding scheme employed by the underlying platform.
Argument string literals should be delimited by single quotes to
avoid escape sequences being interpreted as octal character codes
by the Perl compiler.
The character string presentation format follows the conventions
for zone files described in RFC1035.
=cut
my ( %escape, %unescape ); ## precalculated ASCII escape tables
our $ORIGIN;
my ( $cache1, $cache2, $limit ) = ( {}, {}, 100 );
sub new {
my ( $class, $s ) = @_;
croak 'domain identifier undefined' unless defined $s;
my $k = join '', $s, $class, $ORIGIN || ''; # cache key
my $cache = $$cache1{$k} ||= $$cache2{$k}; # two layer cache
return $cache if defined $cache;
( $cache1, $cache2, $limit ) = ( {}, $cache1, 500 ) unless $limit--; # recycle cache
my $self = bless {}, $class;
local $_ = _encode_ascii($s);
s/\134\134/\134\060\071\062/g; # disguise escaped escape
s/\134\056/\134\060\064\066/g; # disguise escaped dot
my $label = $self->{label} = $_ eq "\100" ? [] : [split /\056/];
foreach (@$label) {
s/\134([\060-\071]{3})/$unescape{$1}/eg; # numeric escape
s/\134(.)/$1/g; # character escape
croak 'empty domain label' unless length;
next unless length > 63;
substr( $_, 63 ) = '';
carp 'domain label truncated';
}
$$cache1{$k} = $self; # cache object reference
return $self if /\056$/; # fully qualified name
$self->{origin} = $ORIGIN || return $self; # dynamically scoped $ORIGIN
return $self;
}
=head2 name
$name = $domain->name;
Returns the domain name as a character string corresponding to the
"common interpretation" to which RFC1034, 3.1, paragraph 9 alludes.
Character escape sequences are used to represent a dot inside a
domain name label and the escape character itself.
Any non-printable code point is represented using the appropriate
numerical escape sequence.
=cut
sub name {
my ($self) = @_;
return $self->{name} if defined $self->{name};
return unless defined wantarray;
my @label = map { s/([^\055\101-\132\141-\172\060-\071])/$escape{$1}/eg; $_ } $self->_wire;
return $self->{name} = '.' unless scalar @label;
$self->{name} = _decode_ascii( join chr(46), @label );
}
=head2 fqdn
@fqdn = $domain->fqdn;
Returns a character string containing the fully qualified domain
name, including the trailing dot.
=cut
sub fqdn {
my $name = &name;
return $name =~ /[.]$/ ? $name : $name . '.'; # append trailing dot
}
=head2 xname
$xname = $domain->xname;
Interprets an extended name containing Unicode domain name labels
encoded as Punycode A-labels.
Domain names containing Unicode characters are supported if the
Net::LibIDN module is installed.
=cut
sub xname {
my $name = &name;
if ( LIBIDN && UTF8 && $name =~ /xn--/ ) {
my $self = shift;
return $self->{xname} if defined $self->{xname};
return $self->{xname} = $utf8->decode( Net::LibIDN::idn_to_unicode $name, 'utf-8' );
}
return $name;
}
=head2 label
@label = $domain->label;
Identifies the domain by means of a list of domain labels.
=cut
sub label {
map {
s/([^\055\101-\132\141-\172\060-\071])/$escape{$1}/eg;
_decode_ascii($_)
} shift->_wire;
}
sub _wire {
my $self = shift;
my $label = $self->{label};
my $origin = $self->{origin} || return (@$label);
return ( @$label, $origin->_wire );
}
=head2 string
$string = $object->string;
Returns a character string containing the fully qualified domain
name as it appears in a zone file.
Characters which are recognised by RFC1035 zone file syntax are
represented by the appropriate escape sequence.
=cut
sub string {
( my $name = &name ) =~ s/(["'\$();@])/\\$1/; # escape special char
return $name =~ /[.]$/ ? $name : $name . '.'; # append trailing dot
}
=head2 origin
$create = origin Net::DNS::Domain( $ORIGIN );
$result = &$create( sub{ new Net::DNS::RR( 'mx MX 10 a' ); } );
$expect = new Net::DNS::RR( "mx.$ORIGIN. MX 10 a.$ORIGIN." );
Class method which returns a reference to a subroutine wrapper
which executes a given constructor in a dynamically scoped context
where relative names become descendents of the specified $ORIGIN.
=cut
my $placebo = sub { my $constructor = shift; &$constructor; };
sub origin {
my ( $class, $name ) = @_;
my $domain = defined $name ? new Net::DNS::Domain($name) : return $placebo;
return sub { # closure w.r.t. $domain
my $constructor = shift;
local $ORIGIN = $domain; # dynamically scoped $ORIGIN
&$constructor;
}
}
########################################
sub _decode_ascii { ## translate ASCII to perl string
my $s = shift;
# partial transliteration for non-ASCII character encodings
$s =~ tr
[\040-\176\000-\377]
[ !"#$%&'()*+,\-./0-9:;<=>?@A-Z\[\\\]^_`a-z{|}~?] unless ASCII;
my $z = length substr $s, 0, 0; # pre-5.18 taint workaround
return ASCII ? pack( "a* x$z", $ascii->decode($s) ) : $s;
}
sub _encode_ascii { ## translate perl string to ASCII
my $s = shift;
my $z = length substr $s, 0, 0; # pre-5.18 taint workaround
if ( LIBIDN && UTF8 && $s =~ /[^\000-\177]/ ) {
my $xn = Net::LibIDN::idn_to_ascii( $s, 'utf-8' );
croak 'invalid name' unless $xn;
return pack "a* x$z", $xn;
}
# partial transliteration for non-ASCII character encodings
$s =~ tr
[ !"#$%&'()*+,\-./0-9:;<=>?@A-Z\[\\\]^_`a-z{|}~\000-\377]
[\040-\176\077] unless ASCII;
return ASCII ? pack( "a* x$z", $ascii->encode($s) ) : $s;
}
%escape = eval { ## precalculated ASCII escape table
my %table;
foreach ( 33 .. 126 ) { # ASCII printable
$table{pack( 'C', $_ )} = pack 'C', $_;
}
# minimal character escapes
foreach ( 46, 92 ) { # \. \\
$table{pack( 'C', $_ )} = pack 'C*', 92, $_;
}
foreach my $n ( 0 .. 32, 127 .. 255 ) { # \ddd
my $codepoint = sprintf( '%03u', $n );
# partial transliteration for non-ASCII character encodings
$codepoint =~ tr [0-9] [\060-\071];
$table{pack( 'C', $n )} = pack 'C a3', 92, $codepoint;
}
return %table;
};
%unescape = eval { ## precalculated numeric escape table
my %table;
foreach my $n ( 0 .. 255 ) {
my $key = sprintf( '%03u', $n );
# partial transliteration for non-ASCII character encodings
$key =~ tr [0-9] [\060-\071];
$table{$key} = pack 'C', $n;
$table{$key} = pack 'C2', 92, $n if $n == 92; # escaped escape
}
return %table;
};
1;
__END__
########################################
=head1 BUGS
Coding strategy is intended to avoid creating unnecessary argument
lists and stack frames. This improves efficiency at the expense of
code readability.
Platform specific character coding features are conditionally
compiled into the code.
=head1 COPYRIGHT
Copyright (c)2009-2011,2017 Dick Franks.
All rights reserved.
=head1 LICENSE
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation, and that the name of the author not be used in advertising
or publicity pertaining to distribution of the software without specific
prior written permission.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
=head1 SEE ALSO
L<perl>, L<Net::LibIDN>, L<Net::DNS>, RFC1034, RFC1035, RFC5891,
Unicode Technical Report #16
=cut
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