qpsmtpd/plugins/count_unrecognized_commands

#!perl -w

=head1 NAME

count_unrecognized_commands - Count unrecognized commands and disconnect when we have too many

=head1 DESCRIPTION

Disconnect the client if it sends too many unrecognized commands.
Good for rejecting spam sent through open HTTP proxies.

=head1 CONFIGURATION

Takes one parameter, the number of allowed unrecognized commands
before we disconnect the client.  Defaults to 4.

=cut

use strict;
use warnings;

use Qpsmtpd::Constants;

sub register {
    my ($self, $qp ) = shift, shift;

    $self->{_unrec_cmd_max} = shift || 4;

    if ( scalar @_ ) {
        $self->log(LOGWARN, "Ignoring additional arguments.");
    }
}

sub hook_connect {
  my $self = shift;

  $self->qp->connection->notes('unrec_cmd_count', 0);
  return DECLINED;
}

sub hook_unrecognized_command {
  my ($self, $cmd) = @_[0,2];
  
  $self->log(LOGINFO, "Unrecognized command '$cmd'");

  my $badcmdcount = 
    $self->qp->connection->notes( 'unrec_cmd_count',
        ($self->qp->connection->notes('unrec_cmd_count') || 0) + 1
    );

  if ($badcmdcount >= $self->{_unrec_cmd_max}) {
    my $msg = "Closing connection, $badcmdcount unrecognized commands.";
    $self->log(LOGINFO, "fail: $msg");
    return (DENY_DISCONNECT, "$msg Perhaps you should read RFC 2821?");
  }

  return DECLINED;
}