package Crypt::RSA::Key::Private;
use strict;
use warnings;

## Crypt::RSA::Key::Private
##
## 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.

use vars qw($AUTOLOAD $VERSION);
use base 'Crypt::RSA::Errorhandler';
use Tie::EncryptedHash;
use Data::Dumper;
use Math::BigInt try => 'GMP, Pari';
use Math::Prime::Util qw/is_prime/;
use Carp;

$Crypt::RSA::Key::Private::VERSION = '1.99';

sub new {

    my ($class, %params) = @_;
    my $self    = { Version => $Crypt::RSA::Key::Private::VERSION };
    if ($params{Filename}) {
        bless $self, $class;
        $self = $self->read (%params);
        return bless $self, $class;
    } else {
        bless $self, $class;
        $self->Identity ($params{Identity}) if $params{Identity};
        $self->Cipher   ($params{Cipher}||"Blowfish");
        $self->Password ($params{Password}) if $params{Password};
        return $self;
    }

}


sub AUTOLOAD {

    my ($self, $value) = @_;
    my $key = $AUTOLOAD; $key =~ s/.*:://;
    if ($key =~ /^(e|n|d|p|q|dp|dq|u|phi)$/) {
        my $prikey = \$self->{private}{"_$key"};
        if (defined $value) {
          $self->{Checked} = 0;
          if (ref $value eq 'Math::BigInt') {
            $$prikey = $value;
          } elsif (ref $value eq 'Math::Pari') {
            $$prikey = Math::BigInt->new($value->pari2pv);
          } else {
            $$prikey = Math::BigInt->new("$value");
          }
        }
        if (defined $$prikey) {
          $$prikey = Math::BigInt->new("$$prikey") unless ref($$prikey) eq 'Math::BigInt';
          return $$prikey;
        }
        return $self->{private_encrypted}{"_$key"} if defined $self->{private_encrypted}{"_$key"};
        return;
    } elsif ($key =~ /^Identity|Cipher|Password$/) {
        $self->{$key} = $value if $value;
        return $self->{$key};
    } elsif ($key =~ /^Checked$/) {
        my ($package) = caller();
        $self->{Checked} = $value if ($value && $package eq "Crypt::RSA::Key::Private") ;
        return $self->{Checked};
    }
}


sub hide {

    my ($self) = @_;

    return unless $$self{Password};

    $self->{private_encrypted} = new Tie::EncryptedHash
            __password => $self->{Password},
            __cipher   => $self->{Cipher};

    for (keys %{$$self{private}}) {
        $$self{private_encrypted}{$_} = $$self{private}{$_}->bstr;
    }

    my $private = $self->{private_encrypted};
    delete $private->{__password};
    delete $$self{private};
    delete $$self{Password};

    # Mark ourselves as hidden
    $self->{Hidden} = 1;
}


sub reveal {

    my ($self, %params) = @_;
    $$self{Password} = $params{Password} if $params{Password};
    return unless $$self{Password};
    $$self{private_encrypted}{__password} = $params{Password};
    for (keys %{$$self{private_encrypted}}) {
        $$self{private}{$_} = Math::BigInt->new("$$self{private_encrypted}{$_}");
    }
    $self->{Hidden} = 0;

}


sub check {

    my ($self) = @_;

    return 1 if $self->{Checked};

    return $self->error ("Cannot check hidden key - call reveal first.")
        if $self->{Hidden};

    return $self->error ("Incomplete key.") unless
        ($self->n && $self->d) || ($self->n && $self->p && $self->q);

    if ($self->p && $self->q) {
        return $self->error ("n is not a number.") if $self->n =~ /\D/;
        return $self->error ("p is not a number.") if $self->p =~ /\D/;
        return $self->error ("q is not a number.") if $self->q =~ /\D/;
        return $self->error ("n is not p*q."  ) unless $self->n == $self->p * $self->q;
        return $self->error ("p is not prime.") unless is_prime( $self->p );
        return $self->error ("q is not prime.") unless is_prime( $self->q );
    }

    if ($self->e) {
        # d * e == 1 mod lcm(p-1, q-1)
        return $self->error ("e is not a number.") if $self->e =~ /\D/;
        my $k = Math::BigInt::blcm($self->p-1, $self->q-1);
        my $KI = ($self->e)->copy->bmul($self->d)->bmodinv($k);
        return $self->error ("Bad `d'.") unless $KI == 1;
    }

    if ($self->dp) {
        # dp == d mod (p-1)
        return $self->error ("Bad `dp'.") unless $self->dp == $self->d % ($self->p - 1);
    }

    if ($self->dq) {
        # dq == d mod (q-1)
        return $self->error ("Bad `dq'.") unless $self->dq == $self->d % ($self->q - 1);
    }

    if ($self->u && $self->q && $self->p) {
        my $m = ($self->p)->copy->bmodinv($self->q);
        return $self->error ("Bad `u'.") unless $self->u == $m;
    }

    $self->Checked(1);
    return 1;

}


sub DESTROY {

    my $self = shift;
    delete $$self{private_encrypted}{__password};
    delete $$self{private_encrypted};
    delete $$self{private};
    delete $$self{Password};
    undef $self;

}


sub write {

    my ($self, %params) = @_;
    $self->hide();
    my $string = $self->serialize (%params);
    open(my $disk, '>', $params{Filename}) or
        croak "Can't open $params{Filename} for writing.";
    binmode $disk;
    print $disk $string;
    close $disk;

}


sub read {
    my ($self, %params) = @_;
    open(my $disk, '<', $params{Filename}) or
        croak "Can't open $params{Filename} to read.";
    binmode $disk;
    my @key = <$disk>;
    close $disk;
    $self = $self->deserialize (String => \@key);
    $self->reveal(%params);
    return $self;
}


sub serialize {

    my ($self, %params) = @_;
    if ($$self{private}) {   # this is an unencrypted key
        for (keys %{$$self{private}}) {
            $$self{private}{$_} = ($$self{private}{$_})->bstr;
        }
    }
    return Dumper $self;

}


sub deserialize {

    my ($self, %params) = @_;
    my $string = join'', @{$params{String}};
    $string =~ s/\$VAR1 =//;
    $self = eval $string;
    if ($$self{private}) { # the key is unencrypted
        for (keys %{$$self{private}}) {
            $$self{private}{$_} = Math::BigInt->new("$$self{private}{$_}");
        }
        return $self;
    }
    my $private = new Tie::EncryptedHash;
    %$private = %{$$self{private_encrypted}};
    $self->{private_encrypted} = $private;
    return $self;

}


1;

=head1 NAME

Crypt::RSA::Key::Private -- RSA Private Key Management.

=head1 SYNOPSIS

    $key = new Crypt::RSA::Key::Private (
                Identity => 'Lord Banquo <banquo@lochaber.com>',
                Password => 'The earth hath bubbles',
           );

    $key->hide();

    $key->write( Filename => 'rsakeys/banquo.private'  );

    $akey = new Crypt::RSA::Key::Private (
                 Filename => 'rsakeys/banquo.private'
                );

    $akey->reveal ( Password => 'The earth hath bubbles' );

=head1 DESCRIPTION

Crypt::RSA::Key::Private provides basic private key management
functionality for Crypt::RSA private keys. Following methods are
available:

=over 4

=item B<new()>

The constructor. Takes a hash, usually with two arguments: C<Filename> and
C<Password>. C<Filename> indicates a file from which the private key
should be read. More often than not, private keys are kept encrypted with
a symmetric cipher and MUST be decrypted before use. When a C<Password>
argument is provided, the key is also decrypted before it is returned by
C<new()>. Here's a complete list of arguments accepted by C<new()> (all of
which are optional):

=over 4

=item Identity

A string identifying the owner of the key. Canonically, a name and
email address.

=item Filename

Name of the file that contains the private key.

=item Password

Password with which the private key is encrypted, or should be encrypted
(in case of a new key).

=item Cipher

Name of the symmetric cipher in which the private key is encrypted (or
should be encrypted). The default is "Blowfish" and possible values
include DES, IDEA, Twofish and other ciphers supported by Crypt::CBC.

=back

=item B<reveal()>

If the key is not decrypted at C<new()>, it can be decrypted by
calling C<reveal()> with a C<Password> argument.

=item B<hide()>

C<hide()> causes the key to be encrypted by the chosen symmetric cipher
and password.

=item B<write()>

Causes the key to be written to a disk file specified by the
C<Filename> argument. C<write()> will call C<hide()> before
writing the key to disk. If you wish to store the key in plain,
don't specify a password at C<new()>.

=item B<read()>

Causes the key to be read from a disk file specified by
C<Filename> into the object. If C<Password> is provided, the
method automatically calls reveal() to decrypt the key.

=item B<serialize()>

Creates a Data::Dumper(3) serialization of the private key and
returns the string representation.

=item B<deserialize()>

Accepts a serialized key under the C<String> parameter and
coverts it into the perl representation stored in the object.

=item C<check()>

Check the consistency of the key. If the key checks out, it sets
$self->{Checked} = 1. Returns undef on failure.

=back

=head1 AUTHOR

Vipul Ved Prakash, E<lt>mail@vipul.netE<gt>

=head1 SEE ALSO

Crypt::RSA::Key(3), Crypt::RSA::Public(3)

=cut