qpsmtpd/plugins/tls

#!perl -w

=head1 NAME

tls - plugin to support STARTTLS

=head1 SYNOPSIS

# in config/plugins

  tls ssl/cert.pem ssl/privkey.pem

=head1 DESCRIPTION

This plugin implements basic TLS support.

If TLS is successfully negotiated then the C<tls_enabled> field in the
Connection notes is set. If you wish to make TLS mandatory you should check
that field and take appropriate action. Note that you can only do that from
MAIL FROM onwards.

=cut

use IO::Socket::SSL qw(debug1 debug2 debug3 debug4);

sub init {
    my ($self, $qp, $cert, $key) = @_;
    $cert ||= 'ssl/cert.pem';
    $key  ||= 'ssl/privkey.pem';
    $self->tls_cert($cert);
    $self->tls_key($key);
    
    local $^W; # this bit is very noisy...
    my $ssl_ctx = IO::Socket::SSL::SSL_Context->new(
        SSL_use_cert => 1,
        SSL_cert_file => $self->tls_cert,
        SSL_key_file => $self->tls_key,
        SSL_cipher_list => 'HIGH',
        SSL_server => 1
    ) or die "Could not create SSL context: $!";
    # now extract the password...
    
    $self->ssl_context($ssl_ctx);
    
    # Check for possible AUTH mechanisms
HOOK: foreach my $hook ( keys %{$qp->{hooks}} ) {
        if ( $hook =~ m/^auth-?(.+)?$/ ) {
            if ( defined $1 ) {
                my $hooksub = "hook_$hook";
                $hooksub =~ s/\W/_/g;
                *$hooksub = \&bad_ssl_hook;
            }
            else { # at least one polymorphous auth provider
                *hook_auth = \&bad_ssl_hook;
            }
        }
    }
    
}

sub hook_ehlo {
    my ($self, $transaction) = @_;
    return DECLINED unless $self->can_do_tls;
    return DECLINED if $self->connection->notes('tls_enabled');
    return DENY, "Command refused due to lack of security" if $transaction->notes('ssl_failed');
    my $cap = $transaction->notes('capabilities');
    $cap ||= [];
    push @$cap, 'STARTTLS';
    $transaction->notes('tls_enabled', 1);
    $transaction->notes('capabilities', $cap);
    return DECLINED;
}

sub hook_unrecognized_command {
    my ($self, $transaction, $cmd, @args) = @_;
    return DECLINED unless $cmd eq 'starttls';
    return DECLINED unless $transaction->notes('tls_enabled');
    return DENY, "Syntax error (no parameters allowed)" if @args;
    
    # OK, now we setup TLS
    $self->qp->respond (220, "Go ahead with TLS");
    
    eval {
        my $tlssocket = IO::Socket::SSL->new_from_fd(
            fileno(STDIN), '+>',
            SSL_use_cert => 1,
            SSL_cert_file => $self->tls_cert,
            SSL_key_file => $self->tls_key,
            SSL_cipher_list => 'HIGH',
            SSL_server => 1,
            SSL_reuse_ctx => $self->ssl_context,
        ) or die "Could not create SSL socket: $!";
    
        my $conn = $self->connection;
        # Create a new connection object with subset of information collected thus far
        $self->qp->connection(Qpsmtpd::Connection->new(
           map { $_ => $conn->$_ }
                qw(
                    local_ip
                    local_port
                    remote_ip
                    remote_port
                    remote_host
                    remote_info
                ),
            ));
        $self->qp->reset_transaction;
        *STDIN = *STDOUT = $self->connection->notes('tls_socket', $tlssocket);
        $self->connection->notes('tls_enabled', 1);
    };
    if ($@) {
        # SSL setup failed. Now we must respond to every command with 5XX
        warn("TLS failed: $@\n");
        $transaction->notes('ssl_failed', 1);
        return DENY, "TLS Negotiation Failed";
    }
    
    warn("TLS setup returning\n");
    return DONE;
}

sub can_do_tls {
    my ($self) = @_;
    $self->tls_cert && -r $self->tls_cert;
}

sub tls_cert {
    my $self = shift;
    @_ and $self->{_tls_cert} = shift;
    $self->{_tls_cert};
}

sub tls_key {
    my $self = shift;
    @_ and $self->{_tls_key} = shift;
    $self->{_tls_key};
}

sub ssl_context {
    my $self = shift;
    @_ and $self->{_ssl_ctx} = shift;
    $self->{_ssl_ctx};
}

# Fulfill RFC 2487 secn 5.1
sub bad_ssl_hook {
    my ($self, $transaction) = @_;
    return DENY, "Command refused due to lack of security" if $transaction->notes('ssl_failed');
    return DECLINED;
}
*hook_helo = *hook_data = *hook_rcpt = *hook_mail = \&bad_ssl_hook;