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#!/usr/bin/perl -sw
##
## Convert::ASCII::Armour
##
## Copyright (c) 2001, Vipul Ved Prakash. All rights reserved.
## This code is free software; you can redistribute it and/or modify
## it under the same terms as Perl itself.
##
## $Id: Armour.pm,v 1.4 2001/03/19 23:15:09 vipul Exp $
package Convert::ASCII::Armour;
use strict;
use Digest::MD5 qw(md5);
use MIME::Base64;
use Compress::Zlib qw(compress uncompress);
use vars qw($VERSION);
($VERSION) = '$Revision: 1.4 $' =~ /\s(\d+\.\d+)\s/;
sub new {
return bless {}, shift;
}
sub error {
my ($self, $errstr) = @_;
$$self{errstr} = "$errstr\n";
return;
}
sub errstr {
my $self = shift;
return $$self{errstr};
}
sub armour {
my ($self, %params) = @_;
my $compress = $params{Compress} ? "COMPRESSED " : "";
return undef unless $params{Content};
$params{Object} = "UNKNOWN $compress DATA" unless $params{Object};
my $head = "-"x5 . "BEGIN $compress$params{Object}" . "-"x5;
my $tail = "-"x5 . "END $compress$params{Object}" . "-"x5;
my $content = $self->encode_content (%{$params{Content}});
$content = compress($content) if $compress;
my $checksum = encode_base64 (md5 ($content));
my $econtent = encode_base64 ($content);
my $eheaders = "";
for my $key (keys %{$params{Headers}}) {
$eheaders .= "$key: $params{Headers}->{$key}\n";
}
my $message = "$head\n$eheaders\n$econtent=$checksum$tail\n";
return $message;
}
sub unarmour {
my ($self, $message) = @_;
my ($head, $object, $headers, $content, $tail) = $message =~
m:(-----BEGIN ([^\n\-]+)-----)\n(.*?\n\n)?(.+)(-----END .*?-----)$:s
or return $self->error ("Breached Armour.");
my ($compress, $obj) = $object =~ /^(COMPRESSED )(.*)$/;
$object = $obj if $obj;
$content =~ s:=([^\n]+)$::s or return $self->error ("Breached Armour.");
my $checksum = $1; $content = decode_base64 ($content);
my $ncheck = encode_base64 (md5 ($content)); $ncheck =~ s/\n//;
return $self->error ("Checksum Failed.") unless $ncheck eq $checksum;
$content = uncompress ($content) if $compress;
my $dcontent = $self->decode_content ($content) || return;
my $dheaders;
if ($headers) {
my @pairs = split /\n/, $headers;
for (@pairs) {
my ($key, $value) = split /: /, $_, 2;
$$dheaders{$key} = $value if $key;
}
}
my %return = ( Content => $dcontent,
Object => $object,
Headers => $dheaders );
return \%return;
}
sub encode_content {
my ($self, %data) = @_;
my $encoded = "";
for my $key (keys %data) {
$encoded .= length ($key) . chr(0) . length ($data{$key}) .
chr(0) . "$key$data{$key}";
}
return $encoded;
}
sub decode_content {
my ($self, $content) = @_;
my %data;
while ($content) {
$content =~ s/^(\d+)\x00(\d+)\x00// ||
return $self->error ("Inconsistent content.");
my $keylen = $1; my $valuelen = $2;
my $key = substr $content, 0, $keylen;
my $value = substr $content, $keylen, $valuelen;
substr ($content, 0, $keylen + $valuelen) = "";
$data{$key} = $value;
}
return \%data;
}
sub armor { armour (@_) }
sub unarmor { unarmour (@_) }
1;
=head1 NAME
Convert::ASCII::Armour - Convert binary octets into ASCII armoured messages.
=head1 SYNOPSIS
my $converter = new Convert::ASCII::Armour;
my $message = $converter->armour(
Object => "FOO RECORD",
Headers => {
Table => "FooBar",
Version => "1.23",
},
Content => {
Key => "0x8738FA7382",
Name => "Zoya Hall",
Pic => "....", # gif
},
Compress => 1,
);
print $message;
-----BEGIN COMPRESSED FOO RECORD-----
Version: 1.23
Table: FooBar
eJwzZzA0Z/BNLS5OTE8NycgsVgCiRIVciIAJg6EJg0tiSaqhsYJvYlFy...
XnpOZl5qYlJySmpaekZmVnZObl5+QWFRcUlpWXlFZRWXAk7g6OTs4urm...
Fh4VGaWAR5ehkbGJqZm5hSUeNXWKDsoGcWpaGpq68bba0dWxtTVmDOYM...
NzuZ
=MxpZvjkrv5XyhkVCuXmsBQ==
-----END COMPRESSED FOO RECORD-----
my $decoded = $converter->unarmour( $message )
|| die $converter->errstr();
=head1 DESCRIPTION
This module converts hashes of binary octets into ASCII messages suitable
for transfer over 6-bit clean transport channels. The encoded ASCII
resembles PGP's armoured messages, but are in no way compatible with PGP.
=head1 METHODS
=head2 B<new()>
Constructor.
=head2 B<armour()>
Converts a hash of binary octets into an ASCII encoded message. The
encoded message has 4 parts: head and tail strings that act as identifiers
and delimiters, a cluster of headers at top of the message, Base64 encoded
message body and a Base64 encoded MD5 digest of the message body. armour()
takes a hash as argument with following keys:
=over 4
=item B<Object>
An identification string embedded in head and tail strings.
=item B<Content>
Content is a hashref that contains the binary octets to be encoded. This
hash is serialized, compressed (if specified) and encoded into ASCII with
MIME::Base64. The result is the body of the encoded message.
=item B<Headers>
Headers is a hashref that contains ASCII headers that are placed at top of
the encoded message. Headers are encoded as RFC822 headers.
=item B<Compress>
A boolean parameter that forces armour() to compress the message body.
=back
=head2 B<unarmour()>
Decodes an armoured ASCII message into the hash provided as argument
to armour(). The hash contains Content, Object, and Headers.
unarmour() performs several consistency checks and returns a non-true
value on failure.
=head2 B<errstr()>
Returns the error message set by unarmour() on failure.
=head1 AUTHOR
Vipul Ved Prakash, E<lt>mail@vipul.netE<gt>
=head1 LICENSE
Copyright (c) 2001, Vipul Ved Prakash. All rights reserved. This code is
free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
=head1 SEE ALSO
MIME::Base64(3), Compress::Zlib(3), Digest::MD5(3)
=cut
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