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package Greylisting;

#

# $Id: Greylisting.pm,v 1.4 2006/01/11 17:17:28 marcmerlin Exp $

#

# General Greylisting Plugin, written by Marc MERLIN <marc_soft@merlins.org>

# (Kristopher Austin gets the credit for the original port to an SA 3.0 plugin)

#

# This was originally written to implement greylisting in SA-Exim, although

# I have tried to make it more general and allow for reuse in other MTAs

# (although they will need to

# 1) be running SA at SMTP time

# 2) Provide the list of rcpt to and env from in some headers for SA to read

# 3) Provide the IP of the connecting host )

#

# This rule should get a negative score so that if we've already seen the

# greylisting tuplet before, we lower the score, which hopefully brings us from

# a tempreject to an accept (at least that's how sa-exim does it)

# 

# -- Marc 2004/01/19

use strict;

use Mail::SpamAssassin::Plugin;

our @ISA = qw(Mail::SpamAssassin::Plugin);

sub new

{

    my ($class, $mailsa) = @_;

    $class = ref($class) || $class;

    my $self = $class->SUPER::new($mailsa);

    bless ($self, $class);

    $self->register_eval_rule ("greylisting");

    return $self;

}

sub check_end

{

    my ($self, $permsgstatus) = @_;

    if (not $self->{'rangreylisting'})

    {

        Mail::SpamAssassin::Plugin::dbg("GREYLISTING: greylisting didn't run since the configuration wasn't setup to call us");

    }

}

# Greylisting happens depending on the SA score, so we want to run it last,

# which is why we give it a high priority

sub greylisting

{

    my ($self, $permsgstatus, $optionhash) = @_;

    my $connectip;

    my $envfrom;

    my $rcptto;

    my @rcptto;

    my $iswhitelisted=0;

    my $err;

    my $mesgid = $permsgstatus->get('Message-Id')."\n";

    my $mesgidfn;

    my $tuplet;

    my $sascore = $permsgstatus->get_score();

    my $dontcheckscore;

    my %option;

    Mail::SpamAssassin::Plugin::dbg("GREYLISTING: called function");

    $optionhash  =~ s/;/,/g;

    # This is safe, right? (users shouldn't be able to set it in their config)

    %option=eval $optionhash;

    $self->{'rangreylisting'}=1;

    foreach my $reqoption (qw ( method greylistsecs dontgreylistthreshold

        connectiphdr envfromhdr rcpttohdr greylistnullfrom greylistfourthbyte ))

    {

        die "Greylist option $reqoption missing from SA config" unless (defined $option{$reqoption});

    }

    $dontcheckscore = $option{'dontgreylistthreshold'};

    # No newlines, thank you (yes, you need this twice apparently)

    chomp ($mesgid);

    chomp ($mesgid);

    # Newline in the middle mesgids, are you serious? Get rid of them here

    $mesgid =~ s/\012/|/g;

    # For stuff that we know is spam, don't greylist the host

    # (that might help later spam with a lower score to come in)

    if ($sascore >= $dontcheckscore)

    {

        Mail::SpamAssassin::Plugin::dbg("GREYLISTING: skipping greylisting on $mesgid, since score is already $sascore and you configured greylisting not to bother with anything above $dontcheckscore");

        return 0;

    }

    else

    {

        Mail::SpamAssassin::Plugin::dbg("GREYLISTING: running greylisting on $mesgid, since score is too low ($sascore) and you configured greylisting to greylist anything under $dontcheckscore");

    }

    if (not $connectip = $permsgstatus->get($option{'connectiphdr'}))

    {

        warn "Couldn't get Connecting IP header $option{'connectiphdr'} for message $mesgid, skipping greylisting call\n";

        return 0;

    }

    chomp($connectip);

    # Clean up input (for security, if you use files/dirs)

    $connectip =~ /([\d.:]+)/;

    $connectip = ($1 or "");

    # Account for a null envelope from

    if (not defined ($envfrom = $permsgstatus->get($option{'envfromhdr'})))

    {

        warn "Couldn't get Envelope From header $option{'envfromhdr'} for message $mesgid, skipping greylisting call\n";

        return 0;

    }

    chomp($envfrom);

    # Clean up input (for security, if you use files/dirs)

    $envfrom =~ s#/#-#g;

    if (not $envfrom)

    {

        $envfrom="<>";

        return 0 if (not $option{'greylistnullfrom'});

    }

    if (not $rcptto = $permsgstatus->get($option{'rcpttohdr'}))

    {

        warn "Couldn't get Rcpt To header $option{'rcpttohdr'} for message $mesgid, skipping greylisting call\n";

        return 0;

    }

    chomp($rcptto);

    # Clean up input (for security, if you use files/dirs)

    $rcptto =~ s#/#-#g;

    @rcptto = split(/, /, $rcptto);

    umask 0007;

    foreach $rcptto (@rcptto)

    {

        # The dir method is easy to fiddle with and expire records in (with

        # a find | rm) but it's probably more I/O extensive than a real DB

        # and suffers from directory size problems if a specific IP is sending

        # generating tens of thousands of tuplets. -- Marc

        # That said, I prefer formats I can easily tinker with, and not having

        # to worry about buggy locking and so forth

        if ($option{'method'} eq "dir")

        {

            my $tmpvar;

            # The clean strings are hardcoded because it's hard to do a variable

            # substitution within a tr (and using the eval solution is too

            # resource expensive)

            # envfrom could be cleaned outside of the loop, but the other method 

            # options might now want that

            $envfrom =~ tr/!#%()*+,-.0123456789:<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_abcdefghijklmnopqrstuvwxyz{|}~/_/c;

            # clean variables to run properly under -T

            $envfrom =~ /(.+)/;

            $tmpvar = ($1 or "");

            # work around bug in perl untaint in perl 5.8

            $envfrom=undef;

            $envfrom=$tmpvar;

            $envfrom =~ s/^([a-z0-9._]*)[^@]*/$1/i;

            $rcptto  =~ tr/!#%()*+,-.0123456789:<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_abcdefghijklmnopqrstuvwxyz{|}~/_/c;

            $rcptto =~ /(.+)/;

            $tmpvar = ($1 or "");

            $rcptto=undef;

            $rcptto=$tmpvar;

            die "greylist option dir not passed, even though method was set to dir" unless ($option{'dir'});

            # connectip is supposed to be untainted now, but I was still getting

            # some insecure dependecy error messages sometimes (perl 5.8 problem apparently)

            unless ($connectip =~ /(\d+)\.(\d+)\.(\d+)\.(\d+)/) {

                warn "Can only handle IPv4 addresses; skipping greylisting call for message $mesgid\n";

                return 0;

            }

            my $ipdir1 = "$option{'dir'}/$1";

            my $ipdir2 = "$ipdir1/$2";

            my $ipdir3 = "$ipdir2/$3";

            my $ipdir4;

            my $tupletdir;

            $ipdir4 = "$ipdir3";

            $ipdir4 .= "/$4" if ($option{'greylistfourthbyte'});

            $tupletdir = "$ipdir4/$envfrom";

            $tuplet = "$tupletdir/$rcptto";

            # make directory whether it's there or not (faster than test and set)

            mkdir $ipdir1;

            mkdir $ipdir2;

            mkdir $ipdir3;

            mkdir $ipdir4;

            mkdir $tupletdir;

            if (not -e $tuplet)

            {

                # If the tuplets aren't there, we create them and continue in

                # case there are other ones (one of them might be whitelisted

                # already)

                $err="creating $tuplet";

                open (TUPLET, ">$tuplet") or goto greylisterror;

                print TUPLET time."\n";

                print TUPLET "Status: Greylisted\n";

                print TUPLET "Last Message-Id: $mesgid\n";

                print TUPLET "Whitelisted Count: 0\n";

                print TUPLET "Query Count: 1\n";

                print TUPLET "SA Score: $sascore\n";

                $err="closing first-written $tuplet";

                close TUPLET or goto greylisterror;

            }

            else

            {

                my $time;

                my $status;

                my $whitelistcount;

                my $querycount;

                # Take into account race condition of expiring deletes and us

                # running

                $err="reading $tuplet";

                open (TUPLET, "<$tuplet") or goto greylisterror;

                $err="Couldn't read time";

                defined ($time=<TUPLET>) or goto greylisterror;

                chomp ($time);

                $err="Couldn't read status";

                defined ($status=<TUPLET>) or goto greylisterror;

                chomp ($status);

                $err="Couldn't extract Status from $status";

                $status =~ s/^Status: // or goto greylisterror;

                # Skip Mesg-Id

                $err="Couldn't skip Mesg-Id";

                defined ($_=<TUPLET>) or goto greylisterror;

                $err="Couldn't read whitelistcount";

                defined ($whitelistcount=<TUPLET>) or goto greylisterror;

                chomp ($whitelistcount);

                $err="Couldn't extract Whitelisted Count from $whitelistcount";

                $whitelistcount =~ s/^Whitelisted Count: // or goto greylisterror;

                $err="Couldn't read querycount";

                defined ($querycount=<TUPLET>) or goto greylisterror;

                chomp ($querycount);

                $err="Couldn't extract Query Count from $querycount";

                $querycount =~ s/^Query Count: // or goto greylisterror;

                close (TUPLET);

                $querycount++;

                if ((time - $time) > $option{'greylistsecs'})

                {

                    $status="Whitelisted";

                    $whitelistcount++;

                }

                $err="re-writing $tuplet";

                open (TUPLET, ">$tuplet") or goto greylisterror;

                print TUPLET "$time\n";

                print TUPLET "Status: $status\n";

                print TUPLET "Last Message-Id: $mesgid\n";

                print TUPLET "Whitelisted Count: $whitelistcount\n";

                print TUPLET "Query Count: $querycount\n";

                print TUPLET "SA Score: $sascore\n";

                $err="closing re-written $tuplet";

                close TUPLET or goto greylisterror;

                # We continue processing the other recipients, to setup or

                # update their counters

                if ($status eq "Whitelisted")

                {

                    $iswhitelisted=1;

                }

            }

        }

        elsif ($option{'method'} eq "file")

        {

            warn "codeme (file greylisting)\n";

        }

        elsif ($option{'method'} eq "db")

        {

            warn "codeme (db greylisting)\n";

        }

    }

    Mail::SpamAssassin::Plugin::dbg("GREYLISTING: computed greylisting on tuplet, saved info in $tuplet and whitelist status is $iswhitelisted");

    return $iswhitelisted;

    greylisterror:

    warn "Reached greylisterror: $err / $!";

    # delete tuplet since it apparently had issues but don't check for errors

    # in case it was a permission denied on write

    unlink ($tuplet);

    return $iswhitelisted;

}

1;