1 files changed, 107 insertions, 0 deletions
diff --git a/lib/PublicInbox/SaPlugin/ListMirror.pm b/lib/PublicInbox/SaPlugin/ListMirror.pm
new file mode 100644
index 00000000..10101887
--- /dev/null
+++ b/lib/PublicInbox/SaPlugin/ListMirror.pm
@@ -0,0 +1,107 @@
+# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# Rules useful for running a mailing list mirror.  We want to:
+# * ensure Received: headers are really from the list mail server
+#   users expect.  This is to prevent malicious users from
+#   injecting spam into mirrors without going through the expected
+#   server
+# * flag messages where the mailing list is Bcc:-ed since it is
+#   common for spam to have wrong or non-existent To:/Cc: headers.
+
+package PublicInbox::SaPlugin::ListMirror;
+use strict;
+use warnings;
+use base qw(Mail::SpamAssassin::Plugin);
+
+# constructor: register the eval rules
+sub new {
+        my ($class, $mail) = @_;
+
+        # some boilerplate...
+        $class = ref($class) || $class;
+        my $self = $class->SUPER::new($mail);
+        bless $self, $class;
+        $mail->{conf}->{list_mirror_check} = [];
+        $self->register_eval_rule('check_list_mirror_received');
+        $self->register_eval_rule('check_list_mirror_bcc');
+        $self->set_config($mail->{conf});
+        $self;
+}
+
+sub check_list_mirror_received {
+        my ($self, $pms) = @_;
+        my $recvd = $pms->get('Received') || '';
+        $recvd =~ s/\n.*\z//s;
+
+        foreach my $cfg (@{$pms->{conf}->{list_mirror_check}}) {
+                my ($hdr, $hval, $host_re, $addr_re) = @$cfg;
+                my $v = $pms->get($hdr) or next;
+                chomp $v;
+                next if $v ne $hval;
+                return 1 if $recvd !~ $host_re;
+        }
+
+        0;
+}
+
+sub check_list_mirror_bcc {
+        my ($self, $pms) = @_;
+        my $tocc = $pms->get('ToCc');
+
+        foreach my $cfg (@{$pms->{conf}->{list_mirror_check}}) {
+                my ($hdr, $hval, $host_re, $addr_re) = @$cfg;
+                defined $addr_re or next;
+                my $v = $pms->get($hdr) or next;
+                chomp $v;
+                next if $v ne $hval;
+                return 1 if !$tocc || $tocc !~ $addr_re;
+        }
+
+        0;
+}
+
+# list_mirror HEADER HEADER_VALUE HOSTNAME_GLOB [LIST_ADDRESS]
+# list_mirror X-Mailing-List git@vger.kernel.org *.kernel.org
+# list_mirror List-Id <foo.example.org> *.example.org foo@example.org
+sub config_list_mirror {
+        my ($self, $key, $value, $line) = @_;
+
+        defined $value or
+                return $Mail::SpamAssassin::Conf::MISSING_REQUIRED_VALUE;
+
+        my ($hdr, $hval, $host_glob, @extra) = split(/\s+/, $value);
+        my $addr = shift @extra;
+
+        if (defined $addr) {
+                $addr !~ /\@/ and
+                        return $Mail::SpamAssassin::Conf::INVALID_VALUE;
+                $addr = join('|', map { quotemeta } split(/,/, $addr));
+                $addr = qr/\b$addr\b/i;
+        }
+
+        @extra and return $Mail::SpamAssassin::Conf::INVALID_VALUE;
+
+        defined $host_glob or
+                return $Mail::SpamAssassin::Conf::MISSING_REQUIRED_VALUE;
+
+        my %patmap = ('*' => '\S+', '?' => '.', '[' => '[', ']' => ']');
+        $host_glob =~ s!(.)!$patmap{$1} || "\Q$1"!ge;
+        my $host_re = qr/\A\s*from\s+$host_glob(?:\s|$)/si;
+
+        push @{$self->{list_mirror_check}}, [ $hdr, $hval, $host_re, $addr ];
+}
+
+sub set_config {
+        my ($self, $conf) = @_;
+        my @cmds;
+        push @cmds, {
+                setting => 'list_mirror',
+                default => '',
+                type => $Mail::SpamAssassin::Conf::CONF_TYPE_STRING,
+                code => *config_list_mirror,
+        };
+        $conf->{parser}->register_commands(\@cmds);
+}
+
+1;