| Description: |
Crypt::OpenPGP provides no overt mechanism to interrogate a self-signed key to determine the owner's preferred encryption mechanisms. After pointers in Crypt::OpenPGP - determining which cipher to use I came up with this sample code that shows how you can do that.
Caveats: delves into object innards, provided for education only, tested only with modern (v4) signatures, assumption that code is self-documenting may be dubious. |
#!/usr/bin/perl -w
use Crypt::OpenPGP;
use Crypt::OpenPGP::KeyRing;
my($keyfile, $email) = @ARGV;
my $ring = Crypt::OpenPGP::KeyRing->new(Filename => $keyfile);
my $pgp = Crypt::OpenPGP->new(PubRing => $ring);
my $kb = $ring->find_keyblock_by_uid($email);
my $alg = $kb->preferred_sk_alg;
my $crypt = $pgp->encrypt(
Data => 'squeamish ossifrage',
Recipients => [ $email ],
Armour => 1,
($alg ? (Cipher => $alg) : ()), # use default if no preference loc
+ated
);
print $crypt;
exit 0;
{
package Crypt::OpenPGP::KeyBlock;
sub preferred_sk_alg {
my $self = shift;
use Crypt::OpenPGP::Cipher;
my $supported = Crypt::OpenPGP::Cipher->supported;
my @prefs;
for my $sig (@{ $self->get('Crypt::OpenPGP::Signature') }) {
if ($sig->is_primary) {
unshift @prefs, @{ $sig->preferred_sk_alg };
} else {
push @prefs, @{ $sig->preferred_sk_alg };
}
}
for (@prefs) {
return $_ if $supported->{$_};
}
return;
}
}
{
package Crypt::OpenPGP::Signature;
sub is_primary {
my $self = shift;
my $packet = $self->find_subpacket(25); # primary user id
($packet && $packet->{data}) || 0;
}
sub preferred_sk_alg {
my $self = shift;
my $packet = $self->find_subpacket(11); # preferred SK algorit
+hms
$packet ? $packet->{data} : [];
}
}
|
