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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;
            $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)
            $connectip =~ /(\d+)\.(\d+)\.(\d+)\.(\d+)/;
            my ($ipbyte1, $ipbyte2, $ipbyte3, $ipbyte4) = ($1, $2, $3, $4);
            my $ipdir1 = "$option{'dir'}/$ipbyte1";
            my $ipdir2 = "$ipdir1/$ipbyte2";
            my $ipdir3 = "$ipdir2/$ipbyte3";
            my $ipdir4;
            my $tupletdir;

            $ipdir4 = "$ipdir3";
            $ipdir4 .= "/$ipbyte4" 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;