package Crypt::OpenPGP::Util;
use strict;
# For some reason, FastCalc causes problems. Restrict to one of these 3 backends
use Math::BigInt only => 'Pari,GMP,Calc';
use vars qw( @EXPORT_OK @ISA );
use Exporter;
@EXPORT_OK = qw( bitsize bin2bigint bin2mp bigint2bin mp2bin mod_exp mod_inverse
dash_escape dash_unescape canonical_text );
@ISA = qw( Exporter );
sub bitsize {
my $bigint = Math::BigInt->new($_[0]);
return $bigint->bfloor($bigint->blog(2)) + 1;
}
sub bin2bigint { $_[0] ? Math::BigInt->new('0x' . unpack 'H*', $_[0]) : 0 }
*bin2mp = \&bin2bigint;
sub bigint2bin {
my($p) = @_;
$p = _ensure_bigint($p);
my $base = _ensure_bigint(1) << _ensure_bigint(4*8);
my $res = '';
while ($p != 0) {
my $r = $p % $base;
$p = ($p-$r) / $base;
my $buf = pack 'N', $r;
if ($p == 0) {
$buf = $r >= 16777216 ? $buf :
$r >= 65536 ? substr($buf, -3, 3) :
$r >= 256 ? substr($buf, -2, 2) :
substr($buf, -1, 1);
}
$res = $buf . $res;
}
$res;
}
*mp2bin = \&bigint2bin;
sub mod_exp {
my($a, $exp, $n) = @_;
$a = _ensure_bigint($a);
$a->copy->bmodpow($exp, $n);
}
sub mod_inverse {
my($a, $n) = @_;
$a = _ensure_bigint($a);
$a->copy->bmodinv($n);
}
sub dash_escape {
my($data) = @_;
$data =~ s/^-/- -/mg;
$data;
}
sub dash_unescape {
my($data) = @_;
$data =~ s/^-\s//mg;
$data;
}
sub canonical_text {
my($text) = @_;
my @lines = split /\n/, $text, -1;
for my $l (@lines) {
## pgp2 and pgp5 do not trim trailing whitespace from "canonical text"
## signatures, only from cleartext signatures.
## See:
## http://cert.uni-stuttgart.de/archive/ietf-openpgp/2000/01/msg00033.html
if ($Crypt::OpenPGP::Globals::Trim_trailing_ws) {
$l =~ s/[ \t\r\n]*$//;
} else {
$l =~ s/[\r\n]*$//;
}
}
join "\r\n", @lines;
}
sub _ensure_bigint {
my $num = shift;
if ($num && (! ref $num || ! $num->isa('Math::BigInt'))) {
$num = Math::BigInt->new($num);
}
return $num;
}
1;
__END__
=head1 NAME
Crypt::OpenPGP::Util - Miscellaneous utility functions
=head1 DESCRIPTION
I<Crypt::OpenPGP::Util> contains a set of exportable utility functions
used through the I<Crypt::OpenPGP> set of libraries.
=head2 bitsize($n)
Returns the number of bits in the I<Math::BigInt> integer object
I<$n>.
=head2 bin2bigint($string)
Given a string I<$string> of any length, treats the string as a
base-256 representation of an integer, and returns that integer,
a I<Math::BigInt> object.
I<bin2mp> is an alias for this function, for backwards
compatibility reasons.
=head2 bigint2bin($int)
Given a biginteger I<$int> (a I<Math::BigInt> object), linearizes
the integer into an octet string, and returns the octet string.
I<mp2bin> is an alias for this function, for backwards
compatibility reasons.
=head2 mod_exp($a, $exp, $n)
Computes $a ^ $exp mod $n and returns the value. The calculations
are done using I<Math::BigInt>, and the return value is a I<Math::BigInt>
object.
=head2 mod_inverse($a, $n)
Computes the multiplicative inverse of $a mod $n and returns the
value. The calculations are done using I<Math::BigInt>, and the
return value is a I<Math::BigInt> object.
=head2 canonical_text($text)
Takes a piece of text content I<$text> and formats it into PGP canonical
text, where: 1) all whitespace at the end of lines is stripped, and
2) all line endings are made up of a carriage return followed by a line
feed. Returns the canonical form of the text.
=head2 dash_escape($text)
Escapes I<$text> for use in a cleartext signature; the escaping looks
for any line starting with a dash, and on such lines prepends a dash
('-') followed by a space (' '). Returns the escaped text.
=head1 AUTHOR & COPYRIGHTS
Please see the Crypt::OpenPGP manpage for author, copyright, and
license information.
=cut