qpsmtpd/plugins/virus/clamdscan

#!perl -Tw

=head1 NAME

clamdscan

=head1 DESCRIPTION

A qpsmtpd plugin for virus scanning using the ClamAV scan daemon, clamd.

=head1 RESTRICTIONS

The ClamAV scan daemon, clamd, must have at least execute access to the qpsmtpd
spool directory in order to sucessfully scan the messages.  You can ensure this
by running clamd as the same user as qpsmtpd does, or by doing the following: 

=over 4

=item * Change the group ownership of the spool directory to be a group 
of which clamav is a member or add clamav to the same group as the qpsmtpd
user.

=item * Enable the "AllowSupplementaryGroups" option in clamd.conf.

=item * Add group-execute permissions to the qpsmtpd spool directory.

=item * Make sure that all directories above the spool directory (to the
root) are g+x so that the group has directory traversal rights; it is not
necessary for the group to have any read rights.

=back

It may be helpful to temporary grant the clamav user a shell and test to
make sure you can cd into the spool directory and read files located there.
Remember to remove the shell from the clamav user when you are done
testing.

=head1 INSTALL AND CONFIG

Place this plugin in the plugin/virus directory beneath the standard
qpsmtpd installation.  If you installed clamd with the default path, you
can use this plugin with default options (nothing specified):

You must have the ClamAV::Client module installed to use the plugin.

=over 4

=item B<clamd_socket>

Full path to the clamd socket (the recommended mode), if different from the
ClamAV::Client defaults.

=item B<clamd_port>

If present, must be the TCP port where the clamd service is running,
typically 3310; default disabled.  If present, overrides the clamd_socket.

=item B<deny_viruses>

Whether the scanner will automatically delete messages which have viruses.
Takes either 'yes' or 'no' (defaults to 'yes').  If set to 'no' it will add
a header to the message with the virus results.

=item B<defer_on_error>

Whether to defer the mail (with a soft-failure error, which will incur a retry)
if an unrecoverable error occurs during the scan.   The default is to accept
the mail under these conditions.  This can permit viruses to be accepted when
the clamd daemon is malfunctioning or unreadable, but will not allow mail to
backlog or be lost if the condition persists.

=item B<max_size>

The maximum size, in kilobytes, of messages to scan; defaults to 128k.

=item B<scan_all>

Scan all messages, even if there are no attachments

=back

=head1 REQUIREMENTS

This module requires the ClamAV::Client module, found on CPAN here:

L<http://search.cpan.org/dist/ClamAV-Client/>

=head1 AUTHOR

Originally written for the Clamd module by John Peacock <jpeacock@cpan.org>;
adjusted for ClamAV::Client by Devin Carraway <qpsmtpd/@/devin.com>.

=head1 COPYRIGHT AND LICENSE

Copyright (c) 2005 John Peacock,
Copyright (c) 2007 Devin Carraway

Based heavily on the clamav plugin

This plugin is licensed under the same terms as the qpsmtpd package itself.
Please see the LICENSE file included with qpsmtpd for details.

=cut

use strict;
use warnings;

use ClamAV::Client;
use Qpsmtpd::Constants;

sub register {
    my ( $self, $qp, @args ) = @_;

    $self->log(LOGERROR, "Bad parameters for the clamdscan plugin") if @_ % 2;
    %{ $self->{"_clamd"} } = @args;

    # Set some sensible defaults
    $self->{"_clamd"}->{"deny_viruses"} ||= "yes";
    $self->{"_clamd"}->{"max_size"}     ||= 128;
    $self->{"_clamd"}->{"scan_all"}     ||= 0;
    for my $setting ('deny_viruses', 'defer_on_error') {
        next unless $self->{"_clamd"}->{$setting};
        $self->{"_clamd"}->{$setting} = 0
            if lc $self->{"_clamd"}->{$setting} eq 'no';
    }
}

sub hook_data_post {
    my ( $self, $transaction ) = @_;
    $DB::single = 1;

    if ( $transaction->data_size > $self->{"_clamd"}->{"max_size"} * 1024 ) {
        $self->log( LOGNOTICE, "Declining due to data_size" );
        return (DECLINED);
    }

    # Ignore non-multipart emails
    my $content_type = $transaction->header->get('Content-Type');
    $content_type =~ s/\s/ /g if defined $content_type;
    unless ( $self->{"_clamd"}->{"scan_all"}
        || $content_type
        && $content_type =~ m!\bmultipart/.*\bboundary="?([^"]+)!i )
    {
        $self->log( LOGNOTICE, "non-multipart mail - skipping" );
        return DECLINED;
    }

    my $filename = $transaction->body_filename;
    unless ($filename) {
        $self->log( LOGWARN, "Cannot process due to lack of filename" );
        return (DECLINED);    # unless $filename;
    }

    # the spool directory must be readable and executable by the scanner;
    # this generally means either group or world exec; if
    # neither of these is set, issue a warning but try to proceed anyway
    my $mode = ( stat( $self->spool_dir() ) )[2];
    if ( $mode & 0010 || $mode & 0001 ) {
        # match the spool file mode with the mode of the directory -- add
        # the read bit for group, world, or both, depending on what the
        # spool dir had, and strip all other bits, especially the sticky bit
        my $fmode = ($mode & 0044) |
                    ($mode & 0010 ? 0040 : 0) |
                    ($mode & 0001 ? 0004 : 0);
        unless ( chmod $fmode, $filename ) {
            $self->log( LOGERROR, "chmod: $filename: $!" );
            return DECLINED;
        }
    } else {
        $self->log( LOGWARN,
            "Permission on spool directory do not permit scanner access" );
    }

    my $clamd;

    if ( ($self->{"_clamd"}->{"clamd_port"} || '') =~ /^(\d+)/ ) {
        $clamd = new ClamAV::Client( socket_host =>
                                     $self->{_clamd}->{clamd_host},
                                     socket_port => $1 );
    }
    elsif ( ($self->{"_clamd"}->{"clamd_socket"} || '') =~ /([\w\/.]+)/ ) {
        $clamd = new ClamAV::Client( socket_name => $1 );
    }
    else {
        $clamd = new ClamAV::Client;
    }

    unless ( $clamd ) {
        $self->log( LOGERROR, "Cannot instantiate ClamAV::Client" );
        return (DENYSOFT, "Unable to scan for viruses")
            if $self->{"_clamd"}->{"defer_on_error"};
        return DECLINED;
    }

    unless ( eval { $clamd->ping() } ) {
        $self->log( LOGERROR, "Cannot ping clamd server:  $@" );
        return (DENYSOFT, "Unable to scan for viruses")
            if $self->{"_clamd"}->{"defer_on_error"};
        return DECLINED;
    }

    my @clamd_version = split(/\//, $clamd->version);
    $self->{"_clamd"}->{'version'} = $clamd_version[0] || 'ClamAV';

    my ( $path, $found ) = eval { $clamd->scan_path( $filename ) };
    if ($@) {
        $self->log( LOGERROR, "Error scanning mail: $@" );
        return (DENYSOFT, "Unable to scan for viruses")
            if $self->{"_clamd"}->{"defer_on_error"};
        return DECLINED;
    }
    elsif ( $found ) {
        $self->log( LOGERROR, "Virus found: $found" );

        if ( $self->{"_clamd"}->{"deny_viruses"} ) {
            return ( DENY, "Virus found: $found" );
        }
        else {
            $transaction->header->add( 'X-Virus-Found',   'Yes' );
            $transaction->header->add( 'X-Virus-Details', $found );
            return (DECLINED);
        }
    }
    else {
        $transaction->header->add( 'X-Virus-Found',   'No' );
        $self->log( LOGINFO, "ClamAV scan reports clean");
    }

    $transaction->header->add( 'X-Virus-Checked',
        "Checked by $self->{'_clamd'}->{'version'} on " . $self->qp->config("me") );

    return (DECLINED);
}