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# <@LICENSE>
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to you under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at:
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# </@LICENSE>
package Mail::SpamAssassin::Plugin::RelayEval;
use Mail::SpamAssassin::Plugin;
use Mail::SpamAssassin::Logger;
use Mail::SpamAssassin::Constants qw(:ip);
use strict;
use warnings;
use bytes;
use re 'taint';
use vars qw(@ISA);
@ISA = qw(Mail::SpamAssassin::Plugin);
# constructor: register the eval rule
sub new {
my $class = shift;
my $mailsaobject = shift;
# some boilerplate...
$class = ref($class) || $class;
my $self = $class->SUPER::new($mailsaobject);
bless ($self, $class);
# the important bit!
$self->register_eval_rule("check_for_numeric_helo");
$self->register_eval_rule("check_for_illegal_ip");
$self->register_eval_rule("check_all_trusted");
$self->register_eval_rule("check_no_relays");
$self->register_eval_rule("check_relays_unparseable");
$self->register_eval_rule("check_for_sender_no_reverse");
$self->register_eval_rule("check_for_from_domain_in_received_headers");
$self->register_eval_rule("check_for_forged_received_trail");
$self->register_eval_rule("check_for_forged_received_ip_helo");
$self->register_eval_rule("helo_ip_mismatch");
$self->register_eval_rule("check_for_no_rdns_dotcom_helo");
return $self;
}
# tvd: why isn't this just RegistrarBoundaries ?
sub hostname_to_domain {
my ($hostname) = @_;
if ($hostname !~ /[a-zA-Z]/) { return $hostname; } # IP address
my @parts = split(/\./, $hostname);
if (@parts > 1 && $parts[-1] =~ /(?:\S{3,}|ie|fr|de)/) {
return join('.', @parts[-2..-1]);
}
elsif (@parts > 2) {
return join('.', @parts[-3..-1]);
}
else {
return $hostname;
}
}
sub _helo_forgery_whitelisted {
my ($helo, $rdns) = @_;
if ($helo eq 'msn.com' && $rdns eq 'hotmail.com') { return 1; }
0;
}
sub check_for_numeric_helo {
my ($self, $pms) = @_;
my $rcvd = $pms->{relays_untrusted_str};
if ($rcvd) {
my $IP_ADDRESS = IPV4_ADDRESS;
my $IP_PRIVATE = IP_PRIVATE;
local $1;
if ($rcvd =~ /\bhelo=($IP_ADDRESS)(?=[\000-\040,;\[()<>]|\z)/i # Bug 5878
&& $1 !~ /$IP_PRIVATE/) {
return 1;
}
}
return 0;
}
sub check_for_illegal_ip {
my ($self, $pms) = @_;
# Bug 6295, no longer in use, kept for compatibility with old rules
dbg('eval: the "check_for_illegal_ip" eval rule no longer available, '.
'please update your rules');
return 0;
}
# note using IPv4 addresses for now due to empty strings matching IP_ADDRESS
# due to bug in pure IPv6 address regular expression
sub helo_ip_mismatch {
my ($self, $pms) = @_;
my $IP_ADDRESS = IPV4_ADDRESS;
my $IP_PRIVATE = IP_PRIVATE;
for my $relay (@{$pms->{relays_untrusted}}) {
# is HELO usable?
next unless ($relay->{helo} =~ m/^$IP_ADDRESS$/ &&
$relay->{helo} !~ /$IP_PRIVATE/);
# compare HELO with IP
return 1 if ($relay->{ip} =~ m/^$IP_ADDRESS$/ &&
$relay->{ip} !~ m/$IP_PRIVATE/ &&
$relay->{helo} ne $relay->{ip} &&
# different IP is okay if in same /24
$relay->{helo} =~ /^(\d+\.\d+\.\d+\.)/ &&
index($relay->{ip}, $1) != 0);
}
0;
}
###########################################################################
sub check_all_trusted {
my ($self, $pms) = @_;
return $pms->{num_relays_trusted}
&& !$pms->{num_relays_untrusted}
&& !$pms->{num_relays_unparseable};
}
sub check_no_relays {
my ($self, $pms) = @_;
return !$pms->{num_relays_trusted}
&& !$pms->{num_relays_untrusted}
&& !$pms->{num_relays_unparseable};
}
sub check_relays_unparseable {
my ($self, $pms) = @_;
return $pms->{num_relays_unparseable};
}
# Check if the apparent sender (in the last received header) had
# no reverse lookup for it's IP
#
# Look for headers like:
#
# Received: from mx1.eudoramail.com ([204.32.147.84])
sub check_for_sender_no_reverse {
my ($self, $pms) = @_;
# Sender received header is the last in the sequence
my $srcvd = $pms->{relays_untrusted}->
[$pms->{num_relays_untrusted} - 1];
return 0 unless (defined $srcvd);
# Ignore if the from host is domainless (has no dot)
return 0 unless ($srcvd->{rdns} =~ /\./);
# Ignore if the from host is from a private IP range
return 0 if ($srcvd->{ip_private});
return 1;
} # check_for_sender_no_reverse()
#Received: from dragnet.sjc.ebay.com (dragnet.sjc.ebay.com [10.6.21.14])
# by bashir.ebay.com (8.10.2/8.10.2) with SMTP id g29JpwB10940
# for <rod@begbie.com>; Sat, 9 Mar 2002 11:51:58 -0800
sub check_for_from_domain_in_received_headers {
my ($self, $pms, $domain, $desired) = @_;
if (exists $pms->{from_domain_in_received}) {
if (exists $pms->{from_domain_in_received}->{$domain}) {
if ($desired eq 'true') {
# See use of '0e0' below for why we force int() here:
return int($pms->{from_domain_in_received}->{$domain});
}
else {
# And why we deliberately do NOT use integers here:
return !$pms->{from_domain_in_received}->{$domain};
}
}
} else {
$pms->{from_domain_in_received} = {};
}
my $from = $pms->get('From:addr');
if ($from !~ /\b\Q$domain\E/i) {
# '0e0' is Perl idiom for "true but zero":
$pms->{from_domain_in_received}->{$domain} = '0e0';
return 0;
}
my $rcvd = $pms->{relays_trusted_str}."\n".$pms->{relays_untrusted_str};
if ($rcvd =~ / rdns=\S*\b${domain} [^\]]*by=\S*\b${domain} /) {
$pms->{from_domain_in_received}->{$domain} = 1;
return ($desired eq 'true');
}
$pms->{from_domain_in_received}->{$domain} = 0;
return ($desired ne 'true');
}
sub check_for_no_rdns_dotcom_helo {
my ($self, $pms) = @_;
if (!exists $pms->{no_rdns_dotcom_helo}) { $self->_check_received_helos($pms); }
return $pms->{no_rdns_dotcom_helo};
}
# Bug 1133
# Some spammers will, through HELO, tell the server that their machine
# name *is* the relay; don't know why. An example:
# from mail1.mailwizards.com (m448-mp1.cvx1-b.col.dial.ntli.net
# [213.107.233.192])
# by mail1.mailwizards.com
# When this occurs for real, the from name and HELO name will be the
# same, unless the "helo" name is localhost, or the from and by hostsnames
# themselves are localhost
sub _check_received_helos {
my ($self, $pms) = @_;
for (my $i = 0; $i < $pms->{num_relays_untrusted}; $i++) {
my $rcvd = $pms->{relays_untrusted}->[$i];
# Ignore where IP is in private IP space
next if ($rcvd->{ip_private});
my $from_host = $rcvd->{rdns};
my $helo_host = $rcvd->{helo};
my $by_host = $rcvd->{by};
my $no_rdns = $rcvd->{no_reverse_dns};
next unless defined($helo_host);
# Check for a faked dotcom HELO, e.g.
# Received: from mx02.hotmail.com (www.sucasita.com.mx [148.223.251.99])...
# this can be a stronger spamsign than the normal case, since the
# big dotcoms don't screw up their rDNS normally ;), so less FPs.
# Since spammers like sending out their mails from the dotcoms (esp.
# hotmail and AOL) this will catch those forgeries.
#
# allow stuff before the dot-com for both from-name and HELO-name,
# so HELO="outgoing.aol.com" and from="mx34853495.mx.aol.com" works OK.
#
$pms->{no_rdns_dotcom_helo} = 0;
if ($helo_host =~ /(?:\.|^)(lycos\.com|lycos\.co\.uk|hotmail\.com
|localhost\.com|excite\.com|caramail\.com
|cs\.com|aol\.com|msn\.com|yahoo\.com|drizzle\.com)$/ix)
{
my $dom = $1;
# ok, let's catch the case where there's *no* reverse DNS there either
if ($no_rdns) {
dbg2("eval: Received: no rDNS for dotcom HELO: from=$from_host HELO=$helo_host");
$pms->{no_rdns_dotcom_helo} = 1;
}
}
}
} # _check_received_helos()
# FORGED_RCVD_TRAIL
sub check_for_forged_received_trail {
my ($self, $pms) = @_;
$self->_check_for_forged_received($pms) unless exists $pms->{mismatch_from};
return ($pms->{mismatch_from} > 1);
}
# FORGED_RCVD_IP_HELO
sub check_for_forged_received_ip_helo {
my ($self, $pms) = @_;
$self->_check_for_forged_received($pms) unless exists $pms->{mismatch_ip_helo};
return ($pms->{mismatch_ip_helo} > 0);
}
sub _check_for_forged_received {
my ($self, $pms) = @_;
$pms->{mismatch_from} = 0;
$pms->{mismatch_ip_helo} = 0;
my $IP_PRIVATE = IP_PRIVATE;
my @fromip = map { $_->{ip} } @{$pms->{relays_untrusted}};
# just pick up domains for these
my @by = map {
hostname_to_domain ($_->{lc_by});
} @{$pms->{relays_untrusted}};
my @from = map {
hostname_to_domain ($_->{lc_rdns});
} @{$pms->{relays_untrusted}};
my @helo = map {
hostname_to_domain ($_->{lc_helo});
} @{$pms->{relays_untrusted}};
for (my $i = 0; $i < $pms->{num_relays_untrusted}; $i++) {
next if (!defined $by[$i] || $by[$i] !~ /^\w+(?:[\w.-]+\.)+\w+$/);
if (defined ($from[$i]) && defined($fromip[$i])) {
if ($from[$i] =~ /^localhost(?:\.localdomain)?$/) {
if ($fromip[$i] eq '127.0.0.1') {
# valid: bouncing around inside 1 machine, via the localhost
# interface (freshmeat newsletter does this). TODO: this
# may be obsolete, I think we do this in Received.pm anyway
$from[$i] = undef;
}
}
}
my $frm = $from[$i];
my $hlo = $helo[$i];
my $by = $by[$i];
dbg2("eval: forged-HELO: from=".(defined $frm ? $frm : "(undef)").
" helo=".(defined $hlo ? $hlo : "(undef)").
" by=".(defined $by ? $by : "(undef)"));
# note: this code won't catch IP-address HELOs, but we already have
# a separate rule for that anyway.
next unless ($by =~ /^\w+(?:[\w.-]+\.)+\w+$/);
my $fip = $fromip[$i];
if (defined($hlo) && defined($fip)) {
if ($hlo =~ /^\d+\.\d+\.\d+\.\d+$/
&& $fip =~ /^\d+\.\d+\.\d+\.\d+$/
&& $fip ne $hlo)
{
$hlo =~ /^(\d+\.\d+)\.\d+\.\d+$/; my $hclassb = $1;
$fip =~ /^(\d+\.\d+)\.\d+\.\d+$/; my $fclassb = $1;
# allow private IP addrs here, could be a legit screwup
if ($hclassb && $fclassb &&
$hclassb ne $fclassb &&
!($hlo =~ /$IP_PRIVATE/o))
{
dbg2("eval: forged-HELO: massive mismatch on IP-addr HELO: '$hlo' != '$fip'");
$pms->{mismatch_ip_helo}++;
}
}
}
my $prev = $from[$i-1];
if (defined($prev) && $i > 0
&& $prev =~ /^\w+(?:[\w.-]+\.)+\w+$/
&& $by ne $prev && !_helo_forgery_whitelisted($by, $prev))
{
dbg2("eval: forged-HELO: mismatch on from: '$prev' != '$by'");
$pms->{mismatch_from}++;
}
}
}
###########################################################################
# support eval-test verbose debugs using "-Deval"
sub dbg2 {
if (would_log('dbg', 'eval') == 2) {
dbg(@_);
}
}
1;
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