added dspam plugin
This commit is contained in:
Matt Simerson
Ask Bjørn Hansen
parent
318c9ed4f2
commit
102e068297
@ -57,6 +57,8 @@ spamassassin
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#
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# spamassassin reject_threshold 20 munge_subject_threshold 10
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# dspam must run after spamassassin for the learn_from_sa feature to work
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dspam learn_from_sa 7 reject 1
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# run the clamav virus checking plugin
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# virus/clamav
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341
plugins/dspam
Normal file
341
plugins/dspam
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@ -0,0 +1,341 @@
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#!perl -Tw
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=head1 NAME
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dspam - dspam integration for qpsmtpd
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=head1 DESCRIPTION
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qpsmtpd plugin that uses dspam to classify messages. Can use SpamAssassin to
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train dspam.
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Adds the X-DSPAM-Result and X-DSPAM-Signature headers to messages. The latter is essential for
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training dspam and the former is useful to MDAs, MUAs, and humans.
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=head1 TRAINING DSPAM
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To get dspam into a useful state, it must be trained. The best method way to
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train dspam is to feed it two large equal sized corpuses of spam and ham from
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your mail server. The dspam authors suggest avoiding public corpuses. I do
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this as follows:
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=over 4
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=item learn from SpamAssassin
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See the docs on the learn_from_sa feature in the CONFIG section.
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=item daily training
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I have a script that crawls the contents of every users maildir each night.
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The script builds two lists of messages: ham and spam.
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The spam message list consists of all read messages in folders named Spam
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that have changed since the last spam learning run (normally 1 day).
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The ham message list consists of read messages in any folder not named like
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Spam, Junk, Trash, or Deleted. This catches messages that users have read
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and left in their inbox, filed away into subfolders, and
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=item on-the-fly training
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=back
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=head1 CONFIG
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=over 4
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=item dspam_bin
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The path to the dspam binary. If yours is installed somewhere other
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than /usr/local/bin/dspam, you'll need to set this.
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=item learn_from_sa
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Dspam can be trained by SpamAssassin. This relationship between them requires
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attention to several important details:
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=over 4
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=item 1
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dspam must be listed B<after> spamassassin in the config/plugins file.
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Because SA runs first, I crank the SA reject_threshold up above 100 so that
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all spam messages will be used to train dspam.
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Once dspam is trained and errors are rare, I plan to run dspam first and
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reduce the SA load.
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=item 2
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Autolearn must be enabled and configured in SpamAssassin. SA autolearn
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preferences will determine whether a message is learned as spam or innocent
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by dspam. The settings to pay careful attention to in your SA local.cf file
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are bayes_auto_learn_threshold_spam and bayes_auto_learn_threshold_nonspam.
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Make sure they are both set to conservative values that are certain to
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yield no false positives.
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If you are using learn_from_sa and reject, then messages that exceed the SA
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threshholds will cause dspam to reject them. Again I say, make sure them SA
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autolearn threshholds are set high enough to avoid false positives.
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=item 3
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dspam must be configured and working properly. I have modified the following
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dspam values on my system:
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=over 4
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=item mysql storage
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=item Trust smtpd
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=item TrainingMode tum
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=item Tokenizer osb
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=item Preference "trainingMode=TOE"
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=item Preference "spamAction=deliver"
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=item Preference "signatureLocation=headers"
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=item TrainPristine off
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=item ParseToHeaders off
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=back
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Of those changes, the most important is the signature location. This plugin
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only supports storing the signature in the headers. If you want to train dspam
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after delivery (ie, users moving messages to/from spam folders), then the
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dspam signature must be in the headers.
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=back
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=item reject
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Set to a floating point value between 0 and 1.00 where 0 is no confidence
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and 1.0 is 100% confidence.
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If dspam's confidence is greater than or equal to this threshold, the
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message will be rejected.
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=back
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=head1 MULTIPLE RECIPIENT BEHAVIOR
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For messages with multiple recipients, the user that dspam is running as will
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be the dspam username.
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When messages have a single recipient, the recipient address is used as the
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dspam username. For dspam to trust qpsmtpd with modifying the username, you
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B<must> add the username that qpsmtpd is running to to the dspamd.conf file.
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ie, (Trust smtpd).
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=head1 CHANGES
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=cut
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use strict;
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use Qpsmtpd::Constants;
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use Qpsmtpd::DSN;
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use IO::Handle;
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use Socket qw(:DEFAULT :crlf);
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sub register {
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my ($self, $qp, @args) = @_;
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$self->log(LOGERROR, "Bad parameters for the dspam plugin") if @_ % 2;
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%{$self->{_args}} = @args;
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$self->register_hook('data_post', 'dspam_reject')
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if $self->{_args}->{reject};
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}
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sub hook_data_post {
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my ($self, $transaction) = @_;
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$self->log(LOGDEBUG, "check_dspam");
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return (DECLINED) if $transaction->data_size > 500_000;
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my $username = $self->select_username( $transaction );
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my $message = $self->assemble_message($transaction);
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my $filtercmd = $self->get_filter_cmd( $transaction, $username );
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$self->log(LOGWARN, $filtercmd);
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my $response = $self->dspam_process( $filtercmd, $message );
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if ( ! $response ) {
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$self->log(LOGWARN, "No response received from dspam. Check your logs for errors.");
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return (DECLINED);
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};
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$self->log(LOGWARN, $response);
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# X-DSPAM-Result: user@example.com; result="Spam"; class="Spam"; probability=1.0000; confidence=1.00; signature=N/A
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# X-DSPAM-Result: smtpd; result="Innocent"; class="Innocent"; probability=0.0023; confidence=1.00; signature=4f8dae6a446008399211546
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my ($result,$prob,$conf,$sig) = $response =~ /result=\"(Spam|Innocent)\";.*?probability=([\d\.]+); confidence=([\d\.]+); signature=(.*)/;
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my $header_str = "$result, probability=$prob, confidence=$conf";
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$self->log(LOGWARN, $header_str);
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$transaction->header->add('X-DSPAM-Result', $header_str, 0);
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# the signature header is required if you intend to train dspam later
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# you must set Preference "signatureLocation=headers" in dspam.conf
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$transaction->header->add('X-DSPAM-Signature', $sig, 0);
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return (DECLINED);
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};
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sub select_username {
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my ($self, $transaction) = @_;
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my $recipient_count = scalar $transaction->recipients;
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$self->log(LOGDEBUG, "Message has $recipient_count recipients");
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if ( $recipient_count > 1 ) {
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$self->log(LOGINFO, "skipping user prefs, $recipient_count recipients detected.");
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return getpwuid($>);
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};
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# use the recipients email address as username. This enables user prefs
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my $username = ($transaction->recipients)[0]->address;
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return lc($username);
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};
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sub assemble_message {
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my ($self, $transaction) = @_;
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$transaction->body_resetpos;
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my $message = "X-Envelope-From: "
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. $transaction->sender->format . "\n"
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. $transaction->header->as_string . "\n\n";
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while (my $line = $transaction->body_getline) { $message .= $line; };
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$message = join(CRLF, split/\n/, $message);
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return $message . CRLF;
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};
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sub dspam_process {
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my ( $self, $filtercmd, $message ) = @_;
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#return $self->dspam_process_open2( $filtercmd, $message );
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my ($in_fh, $out_fh);
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if (! open($in_fh, "-|")) {
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open($out_fh, "|$filtercmd") or die "Can't run $filtercmd: $!\n";
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print $out_fh $message;
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close $out_fh;
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exit(0);
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};
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my $response = join('', <$in_fh>);
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close $in_fh;
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chomp $response;
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return $response;
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};
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sub dspam_process_open2 {
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my ( $self, $filtercmd, $message ) = @_;
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# not sure why, but this is not as reliable as I'd like. What's a dspam
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# error -5 mean anyway?
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use FileHandle;
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use IPC::Open2;
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my ($dspam_in, $dspam_out);
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my $pid = open2($dspam_out, $dspam_in, $filtercmd);
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print $dspam_in $message;
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close $dspam_in;
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my $response = join('', <$dspam_out>);
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waitpid $pid, 0;
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chomp $response;
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return $response;
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};
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sub dspam_reject {
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my ($self, $transaction) = @_;
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return (DECLINED) if ! $self->{_args}->{reject};
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my $status = $transaction->header->get('X-DSPAM-Result') or do {
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$self->log(LOGWARN, "dspam_reject: failed to find the dspam header");
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return (DECLINED);
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};
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my ($clas,$probability,$confidence) = $status =~ m/^(Spam|Innocent), probability=([\d\.]+), confidence=([\d\.]+)/i;
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$self->log(LOGDEBUG, "dspam $clas, prob: $probability, conf: $confidence");
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if ( $clas eq 'Spam' && $probability == 1 && $confidence == 1 ) {
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# default of media_unsupported is DENY, so just change the message
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if ( $self->qp->connection->relay_client ) {
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$self->log(LOGWARN, "allowing spam since user authenticated");
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return DECLINED;
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};
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return Qpsmtpd::DSN->media_unsupported('dspam says, no spam please');
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};
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return DECLINED;
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}
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sub get_filter_cmd {
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my ($self, $transaction, $user) = @_;
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my $dspam_bin = $self->{_args}->{dspam_bin} || '/usr/local/bin/dspam';
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my $default = "$dspam_bin --user $user --mode=tum --process --deliver=summary --stdout";
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my $min_score = $self->{_args}->{learn_from_sa} or return $default;
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#$self->log(LOGDEBUG, "attempting to learn from SA");
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my $sa_status = $transaction->header->get('X-Spam-Status');
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if ( ! $sa_status ) {
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$self->log(LOGERROR, "dspam learn_from_sa was set but no X-Spam-Status header detected");
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return $default;
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};
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chomp $sa_status;
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my ($is_spam,$score,$autolearn) = $sa_status =~ /^(yes|no), score=([\d\.\-]+)\s.*?autolearn=([\w]+)/i;
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$self->log(LOGINFO, "sa_status: $sa_status; $is_spam; $autolearn");
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$is_spam = lc($is_spam);
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$autolearn = lc($autolearn);
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if ( $is_spam eq 'yes' && $score < $min_score ) {
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$self->log(LOGWARN, "SA spam score of $score is less than $min_score, skipping autolearn");
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return $default;
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};
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if ( $is_spam eq 'yes' && $autolearn eq 'spam' ) {
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return "$dspam_bin --user $user --mode=tum --source=corpus --class=spam --deliver=summary --stdout";
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}
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elsif ( $is_spam eq 'no' && $autolearn eq 'ham' ) {
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return "$dspam_bin --user $user --mode=tum --source=corpus --class=innocent --deliver=summary --stdout";
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};
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return $default;
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};
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sub _cleanup_spam_header {
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my ($self, $transaction, $header_name) = @_;
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my $action = 'rename';
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if ( $self->{_args}->{leave_old_headers} ) {
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$action = lc($self->{_args}->{leave_old_headers});
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};
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return unless $action eq 'drop' || $action eq 'rename';
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my $old_header_name = $header_name;
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$old_header_name = ($old_header_name =~ s/^X-//) ? "X-Old-$old_header_name" : "Old-$old_header_name";
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for my $header ( $transaction->header->get($header_name) ) {
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$transaction->header->add($old_header_name, $header) if $action eq 'rename';
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$transaction->header->delete($header_name);
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}
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}
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