#!/usr/bin/perl -T -w

# Postgrey: a Postfix Greylisting Policy Server
# Copyright (c) 2004-2007 ETH Zurich
# Copyright (c) 2007 Open Systems AG, Switzerland
# released under the GNU General Public License

# see the documentation with 'perldoc postgrey'

package postgrey;
use strict;
use Pod::Usage;
use Getopt::Long 2.25 qw(:config posix_default no_ignore_case);
use Net::Server; # used only to find out which version we use
use Net::Server::Multiplex;
use BerkeleyDB;
use Fcntl ':flock'; # import LOCK_* constants
use Sys::Hostname;
use Sys::Syslog; # used only to find out which version we use
use POSIX qw(strftime setlocale LC_ALL);

use vars qw(@ISA);
@ISA = qw(Net::Server::Multiplex);

my $VERSION = '1.31';
my $DEFAULT_DBDIR = '/var/spool/postfix/postgrey';
my $CONFIG_DIR = '/usr/local/etc/postfix';

sub cidr_parse($)
{
    defined $_[0] or return undef;
    $_[0] =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)\/(\d+)$/ or return undef;
    $1 < 256 and $2 < 256 and $3 < 256 and $4 < 256 and $5 <= 32 and $5 > 0
    	or return undef;
    my $net = ($1<<24)+($2<<16)+($3<<8)+$4;
    my $mask = ~((1<<(32-$5))-1);
    return ($net & $mask, $mask);
}

sub cidr_match($$$)
{
    my ($net, $mask, $addr) = @_;
    return undef unless defined $net and defined $mask and defined $addr;
    if($addr =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/) {
        $addr =  ($1<<24)+($2<<16)+($3<<8)+$4;
    }
    return ($addr & $mask) == $net;
}

sub read_clients_whitelists($)
{
    my ($self) = @_;

    my @whitelist_clients = ();
    my @whitelist_ips = ();
    my @whitelist_cidr = ();
    for my $f (@{$self->{postgrey}{whitelist_clients_files}}) {
        if(open(CLIENTS, $f)) {
            while(<CLIENTS>) {
                s/#.*$//; s/^\s+//; s/\s+$//; next if $_ eq '';
                if(/^\/(\S+)\/$/) {
                    # regular expression
                    push @whitelist_clients, qr{$1}i;
                }
                elsif(/^\d{1,3}(?:\.\d{1,3}){0,3}$/) {
                    # IP address or part of it
                    push @whitelist_ips, qr{^\Q$_\E\b};
                }
                elsif(/^.*\:.*\:.*$/) {
                    # IPv6?
                    push @whitelist_ips, qr{^\Q$_\E\b};
                }
                elsif(/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\/\d{1,2}$/) {
                    my ($net, $mask) = cidr_parse($_);
                    if(defined $mask) {
                        push @whitelist_cidr, [ $net, $mask ];
                    }
                    else {
                        warn "$f line $.: invalid cidr address\n";
                    }
                }
                # note: we had ^[^\s\/]+$ but it triggers a bug in perl 5.8.0
                elsif(/^\S+$/) {
                    push @whitelist_clients, qr{(?:^|\.)\Q$_\E$}i;
                }
                else {
                    warn "$f line $.: doesn't look like a hostname\n";
                }
            }
        }
        else {
            # do not warn about .local file: maybe the user just doesn't have one
            warn "can't open $f: $!\n" unless $f =~ /\.local$/;
        }
        close(CLIENTS);
    }
    $self->{postgrey}{whitelist_clients} = \@whitelist_clients;
    $self->{postgrey}{whitelist_ips}     = \@whitelist_ips;
    $self->{postgrey}{whitelist_cidr}    = \@whitelist_cidr;
}

sub read_recipients_whitelists($)
{
    my ($self) = @_;

    my @whitelist_recipients = ();
    for my $f (@{$self->{postgrey}{whitelist_recipients_files}}) {
        if(open(RECIPIENTS, $f)) {
            while(<RECIPIENTS>) {
                s/#.*$//; s/^\s+//; s/\s+$//; next if $_ eq '';
                my ($user, $domain) = split(/\@/, $_, 2);
                if(/^\/(\S+)\/$/) {
                    # regular expression
                    push @whitelist_recipients, qr{$1}i;
                }
                elsif(!/^\S+$/) {
                    warn "$f line $.: doesn't look like an address\n";
                }
                # postfix access(5) syntax:
                elsif(defined $domain and $domain ne '') {
                    # user@domain (match also user+extension@domain)
                    push @whitelist_recipients, qr{^\Q$user\E(?:\+[^@]+)?\@\Q$domain\E$}i;
                }
                elsif(defined $domain) {
                    # user@
                    push @whitelist_recipients, qr{^\Q$user\E(?:\+[^@]+)?\@}i;
                }
                else {
                    # domain ($user is the domain)
                    push @whitelist_recipients, qr{(?:^|\.)\Q$user\E$}i;
                }
            }
        }
        else {
            # do not warn about .local file: maybe the user just doesn't have one
            warn "can't open $f: $!\n" unless $f =~ /\.local$/;
        }
        close(RECIPIENTS);
    }
    $self->{postgrey}{whitelist_recipients} = \@whitelist_recipients;
}

sub do_sender_substitutions($$)
{
    my ($self, $addr) = @_;

    my ($user, $domain) = split(/@/, $addr, 2);
    defined $domain or return $addr;
    # strip extension, used sometimes for mailing-list VERP
    $user =~ s/\+.*//;
    # replace numbers in VERP addresses with '#' so that
    # we don't create a new key for each mail
    $user =~ s/\b\d+\b/#/g;
    return "$user\@$domain";
}

# split network and host part and return both
sub do_client_substitutions($$$)
{
    my ($self, $ip, $revdns) = @_;

    if($self->{postgrey}{lookup_by_host}) {
        return ($ip, undef);
    }

    my @ip=split(/\./, $ip);
    return ($ip, undef) unless defined $ip[3];
    # skip if it contains the last two IP numbers in the hostname
    # (we assume it is a pool of dialup addresses of a provider)
    return ($ip, undef) if $revdns =~ /$ip[2]/ and $revdns =~ /$ip[3]/;
    return (join('.', @ip[0..2], '0'), $ip[3]);
}

sub mylog($$$)
{
    my ($self, $level, $string) = @_;
    $string =~ s/\%/%%/g; # for Net::Server <= 0.87
    if(!defined $Sys::Syslog::VERSION or $Sys::Syslog::VERSION lt '0.15'
    or !defined $Net::Server::VERSION or $Net::Server::VERSION lt '0.94') {
        # Workaround for a crash when syslog daemon is temporarily not
        # present (for example on syslog rotation).
        # Note that this is not necessary with Sys::Syslog >= 0.15 and
        # Net::Server >= 0.94 thanks to the nofatal Option.
        eval {
            local $SIG{"__DIE__"} = sub { };
            $self->log($level, $string);
        };
    }
    else {
        $self->log($level, $string);
    }
}

sub mylog_action($$$;$$)
{
    my ($self, $attr, $action, $reason, $additional_info) = @_;

    my $str;
    $str .= $attr->{queue_id} . ': ' if $attr->{queue_id};
    my @info = ("action=$action");
    push @info, "reason=$reason" if defined $reason;
    push @info, $additional_info if defined $additional_info;
    for my $a (qw(client_name client_address sender recipient)) {
        push @info, "$a=$attr->{$a}" if $attr->{$a};
    }
    $str .= join(', ', @info);
    $self->mylog(2, $str);
}

sub do_maintenance($$)
{
    my ($self, $now) = @_;
    my $db     = $self->{postgrey}{db};
    my $db_env = $self->{postgrey}{db_env};

    # remove old db logs

    $self->mylog(1, "cleaning up old logs...");
    $db_env->txn_checkpoint(0, 0) and
        warn "can't checkpoint !? $BerkeleyDB::Error";
    for my $l ($db_env->log_archive(DB_ARCH_ABS)) {
        $self->mylog(1, "rm $l");
        unlink $l or warn "can't remove db log $l: $!\n";
    }

    # remove old keys
    # this is very expensive:  We might refuse to speak to postfix for too
    # long, after which clients will start getting "450 Server configuration
    # problem" errors... do it only during the night and only if at least one
    # day has passed
    my $hour = (localtime($now))[2];
    if($hour > 1 and $hour < 7 and
        $now - $self->{postgrey}{last_maint_keys} >= 82800)
    {
        $self->mylog(1, "cleaning up old entries...");
        my $max_age = $self->{postgrey}{max_age};
        my $retry_window = $self->{postgrey}{retry_window};
        my ($nr_keys_before, $nr_keys_after) = (0,0);
        # note: deleteing hash elements in a 'each'-loop isn't supported
        # that's why we first put them in @old_keys and then delete them
        my @old_keys = ();
        while (my ($key, $value) = each %$db) {
            $nr_keys_before++;
            my ($first, $last) = split(/,/,$value);
            if(not defined $last) {
                # shouldn't happen
                push @old_keys, $key;
            }
            elsif($now - $last > $max_age) {
                # last-seen passed max-age
                push @old_keys, $key;
            }
            elsif($last-$first < $self->{postgrey}{delay} and $now-$last > $retry_window) {
                # no successful entry yet and last seen passed retry-window
                push @old_keys, $key;
            }
            else {
                $nr_keys_after++;
            }
        }
        my $db_obj = $self->{postgrey}{db_obj};
        my $txn = $db_env->txn_begin();
        $db_obj->Txn($txn);
        for my $key (@old_keys) { delete $db->{$key}; }
        $txn->txn_commit();
        
        $self->mylog(1, "cleaning main database finished. before: $nr_keys_before, after: $nr_keys_after");

        if($self->{postgrey}{awl_clients}) {
            # cleanup clients auto-whitelist database
            my $cawl_db  = $self->{postgrey}{db_cawl};
            ($nr_keys_before, $nr_keys_after) = (0, 0);
            $nr_keys_after=0;
            my @old_keys_cawl = ();
            while (my ($key, $value) = each %$cawl_db) {
                my $cawl_last_seen = (split(/,/, $value))[1];
                $nr_keys_before++;
                if($now - $cawl_last_seen > $max_age) {
                    push @old_keys_cawl, $key;
                }
                else {
                    $nr_keys_after++;
                }
            }
            my $db_cawl_obj = $self->{postgrey}{db_cawl_obj};
            $txn = $db_env->txn_begin();
            $db_cawl_obj->Txn($txn);
            for my $key (@old_keys_cawl) { delete $cawl_db->{$key}; }
            $txn->txn_commit();

            $self->mylog(1, "cleaning clients database finished. before: $nr_keys_before, after: $nr_keys_after");
        }

        $self->{postgrey}{last_maint_keys}=$now;
    }
}

sub is_new_instance($$)
{
    my ($self, $inst) = @_;
    return 1 if not defined $inst; # in case the 'instance' parameter
                                   # was not supplied by the client (Exim)

    # we keep a list of the last 20 "instances", which identify unique messages
    # so that for example we only put one X-Greylist header per message.
    $self->{postgrey}{instances} = [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ]
        unless defined $self->{postgrey}{instances};

    my $i = $self->{postgrey}{instances};
    return 0 if scalar grep { $_ eq $inst } @$i;
    
    # put new value into the array
    unshift @$i, $inst;
    pop @$i;

    return 1;
}

# main routine: based on attributes specified as argument, return policy decision
sub smtpd_access_policy($$)
{
    my ($self, $now, $attr) = @_;
    my $db  = $self->{postgrey}{db};
    # This attribute occurs in connections from the policy-test script,
    # not in a regular postfix query connection
    if(defined $attr->{policy_test_time}) { $now = $attr->{policy_test_time} }

    # whitelists
    for my $w (@{$self->{postgrey}{whitelist_clients}}) {
        if($attr->{client_name} =~ $w) {
            $self->mylog_action($attr, 'pass', 'client whitelist');
            return 'DUNNO';
        }
    }
    for my $w (@{$self->{postgrey}{whitelist_ips}}) {
        if($attr->{client_address} =~ $w) {
            $self->mylog_action($attr, 'pass', 'client whitelist');
            return 'DUNNO';
        }
    }
    for my $w (@{$self->{postgrey}{whitelist_cidr}}) {
        if(cidr_match($w->[0], $w->[1], $attr->{client_address})) {
            $self->mylog_action($attr, 'pass', 'client whitelist');
            return 'DUNNO';
        }
    }
    for my $w (@{$self->{postgrey}{whitelist_recipients}}) {
        if($attr->{recipient} =~ $w) {
            $self->mylog_action($attr, 'pass', 'recipient whitelist');
            return 'DUNNO';
        }
    }

    # auto whitelist clients (see below for explanation)
    my ($cawl_db, $cawl_key, $cawl_count, $cawl_last);
    if($self->{postgrey}{awl_clients}) {
        $cawl_db  = $self->{postgrey}{db_cawl};
        $cawl_key = $attr->{client_address};
        if ($self->{postgrey}{privacy}) {
             $cawl_key = Digest::SHA1::sha1_hex($cawl_key);
        }
        my $cawl_val = $cawl_db->{$cawl_key};
        ($cawl_count, $cawl_last) = split(/,/,$cawl_val) if defined $cawl_val;
        
        # whitelist if count is enough
        if(defined $cawl_count and $cawl_count >= $self->{postgrey}{awl_clients})
        {
            if($now >= $cawl_last+3600) {
                $cawl_count++; # for statistics
                $cawl_db->{$cawl_key}=$cawl_count.','.$now;
            }
            $self->mylog_action($attr, 'pass', 'client AWL');
            return 'DUNNO';
        }
    }

    # lookup
    my $sender = $self->do_sender_substitutions($attr->{sender});
    my ($client_net, $client_host) =
        $self->do_client_substitutions($attr->{client_address}, $attr->{client_name});
    my $key    = lc "$client_net/$sender/$attr->{recipient}";
    if ($self->{postgrey}{privacy}) {
        $key = Digest::SHA1::sha1_hex($key);
    }
    my $val    = $db->{$key};
    my $first;
    my $last_was_successful=0;
    if(defined $val) {
        my $last;
        ($first, $last) = split(/,/,$val);
        # find out if the last time was unsuccessful, so that we can add a header
        # to say how much had to be waited
        if($last - $first >= $self->{postgrey}{delay}) {
            $last_was_successful=1;
        }
        else {
            # discard stored first-seen if it is the first retrial and
            # it is beyond the retry_window
            $first = $now if $now-$first > $self->{postgrey}{retry_window};
        }
    }
    else {
        $first = $now;
    }

    # update (put as last element stripped host-part if it was stripped)
    if(defined $client_host) {
        $db->{$key}="$first,$now,$client_host";
    }
    else {
        $db->{$key}="$first,$now";
    }

    my $diff = $self->{postgrey}{delay} - ($now - $first);

    # auto whitelist clients
    # algorithm:
    # - on successful entry in the greylist db of a triplet:
    #   - client not whitelisted yet? -> increase count, whitelist if count > 10 or so
    #   - client whitelisted already? -> update last-seen timestamp
    if($self->{postgrey}{awl_clients}) {
        # greylisting succeeded
        if($diff <= 0 and !$last_was_successful) {
            # enough time has passed (record only one attempt per hour)
            if(! defined $cawl_last or $now >= $cawl_last + 3600) {
                # ok, increase count
                $cawl_count++;
                $cawl_db->{$cawl_key}=$cawl_count.','.$now;
                my $client = $attr->{client_name} ?
                    $attr->{client_name}.'['.$attr->{client_address}.']' :
                    $attr->{client_address};
                $self->mylog(1, "whitelisted: $client")
                    if $cawl_count==$self->{postgrey}{awl_clients};
            }
        }
    }

    # not enough waited? -> greylist
    if ($diff > 0 ) {
        my $msg = $self->{postgrey}{greylist_text};
        # Workaround for an Exchange bug related to Greylisting:
        # use DSN 4.2.0 instead of the default 4.7.1. This works
        # only with Postfix 2.3 though and we know that Postfix >= 2.3
        # always defines the etrn_domain attribute (is this really true and
        # guaranteed in future versions? I don't know...)
        $msg = '4.2.0 ' . $msg if defined $attr->{etrn_domain} and
                          $msg !~ /^\d/;
        $msg =~ s/\%s/$diff/;
        my $recip_domain = $attr->{recipient}; $recip_domain =~ s/.*\@//;
        $msg =~ s/\%r/$recip_domain/;
        $self->mylog_action($attr, 'greylist',
            $now != $first ? "early-retry (${diff}s missing)" : "new"
            );
        return "$self->{postgrey}{greylist_action} $msg";
    }

    # X-Greylist header:
    if(!$last_was_successful and $self->is_new_instance($attr->{instance})) {
        # syslog
        my $client = ($attr->{client_name} and $attr->{client_name} ne 'unknown') ?
                     $attr->{client_name} : $attr->{client_address};

        # add X-Greylist header
        my $date = strftime("%a, %d %b %Y %T %Z", localtime);
        $self->mylog_action($attr, 'pass', 'triplet found', 'delay='.($now-$first));
        return 'PREPEND X-Greylist: delayed '.($now-$first).
            " seconds by postgrey-$VERSION at $self->{postgrey}{hostname}; $date";
    }

    $self->mylog_action($attr, 'pass', 'triplet found');
    return 'DUNNO';
}

sub main()
{
    # save arguments for Net:Server HUP restart
    my @ARGV_saved = @ARGV;

    # do not output any localized texts!
    setlocale(LC_ALL, 'C');

    # parse options
    my %opt = ();
    GetOptions(\%opt, 'help|h', 'man', 'version', 'noaction|no-action|n',
        'verbose|v', 'quiet|q', 'daemonize|d', 'unix|u=s', 'inet|i=s',
        'user=s', 'group=s', 'dbdir=s', 'pidfile=s', 'delay=i', 'max-age=i',
        'lookup-by-subnet', 'lookup-by-host', 'auto-whitelist-clients:s', 
        'whitelist-clients=s@', 'whitelist-recipients=s@',
        'retry-window=s', 'greylist-action=s', 'greylist-text=s', 'privacy',
        'hostname=s', 'exim', 'listen-queue-size=i'
    ) or exit(1);
    # note: lookup-by-subnet can be given for compatibility, but it is default
    # so do not do nothing with it...
    # note: auto-whitelist-clients:s and not auto-whitelist-clients:n so that
    # we can differentiate between --auto-whitelist-clients=0 and
    # auto-whitelist-clients

    if($opt{help})     { pod2usage(1) }
    if($opt{man})      { pod2usage(-exitstatus => 0, -verbose => 2) }
    if($opt{version})  { print "postgrey $VERSION\n"; exit(0) }
    if($opt{noaction}) { die "ERROR: don't know how to \"no-action\".\n" }

    defined $opt{unix} or defined $opt{inet} or
        die "ERROR: --unix or --inet must be specified\n";

    # bind only localhost if no host is specified
    if(defined $opt{inet} and $opt{inet}=~/^\d+$/) {
        $opt{inet} = "localhost:$opt{inet}";
    }

    # retry window
    my $retry_window = 24*3600*2; # default: 2 days
    if(defined $opt{'retry-window'}) {
        if($opt{'retry-window'} =~ /^(\d+)h$/i) {
            $retry_window = $1 * 3600;
        }
        elsif($opt{'retry-window'} =~ /^\d+$/) {
            $retry_window = $opt{'retry-window'} * 24 * 3600;
        }
        else {
            die "ERROR: --retry-window must be either a number of days or a number\n",
                "       followed by 'h' for hours ('6h' for example).\n";
        }
    }

    # untaint what is given on --dbdir. It is not security sensitive since
    # it is provided by the admin
    if($opt{dbdir}) {
        $opt{dbdir} =~ /^(.*)$/; $opt{dbdir} = $1;
    }

    # determine proper "logsock" for Sys::Syslog
    my $syslog_logsock;
    if(defined $Sys::Syslog::VERSION and $Sys::Syslog::VERSION ge '0.15'
    and defined $Net::Server::VERSION and $Net::Server::VERSION ge '0.97') {
        # use 'native' when Sys::Syslog >= 0.15
        $syslog_logsock = 'native';
    }
    elsif($^O eq 'solaris') {
        # 'stream' is broken and 'unix' doesn't work on Solaris: only 'inet'
        # seems to be useable with Sys::Syslog < 0.15
        $syslog_logsock = 'inet';
    }
    else {
        $syslog_logsock = 'unix';
    }

    # Workaround: Net::Server doesn't allow for a value of 'listen' higher than 999
    if(defined $opt{'listen-queue-size'} and $opt{'listen-queue-size'} > 999) {
        $opt{'listen-queue-size'} = 999;
    }

    # create Net::Server object and run it
    my $server = bless {
        server => {
            commandline      => [ $0, @ARGV_saved ],
            port             => [ $opt{inet} ? $opt{inet} : $opt{unix}."|unix" ],
            proto            => $opt{inet} ? 'tcp' : 'unix',
            user             => $opt{user} || 'postgrey',
            group            => $opt{group} || 'nogroup',
            dbdir            => $opt{dbdir} || $DEFAULT_DBDIR,
            setsid           => $opt{daemonize} ? 1 : undef,
            pid_file         => $opt{daemonize} ? $opt{pidfile} : undef,
            log_level        => $opt{quiet} ? 1 : ($opt{verbose} ? 3 : 2),
            log_file         => $opt{daemonize} ? 'Sys::Syslog' : undef,
            syslog_logsock   => $syslog_logsock,
            syslog_facility  => 'mail',
            syslog_ident     => 'postgrey',
            listen           => $opt{'listen-queue-size'} ? $opt{'listen-queue-size'} : undef,
        },
        postgrey => {
            delay            => $opt{delay}     || 300,
            max_age          => $opt{'max-age'} || 35,
            last_maint       => time,
            last_maint_keys  => 0, # do it on the first night
            lookup_by_host   => $opt{'lookup-by-host'},
            awl_clients      => defined $opt{'auto-whitelist-clients'} ?
                ($opt{'auto-whitelist-clients'} ne '' ?
                    $opt{'auto-whitelist-clients'} : 5) : 5,
            retry_window     => $retry_window,
            greylist_action  => $opt{'greylist-action'} || 'DEFER_IF_PERMIT',
            greylist_text    => $opt{'greylist-text'} || 'Greylisted, see http://postgrey.schweikert.ch/help/%r.html',
            whitelist_clients_files    => $opt{'whitelist-clients'} ||
                [ "$CONFIG_DIR/postgrey_whitelist_clients" ,
                  "$CONFIG_DIR/postgrey_whitelist_clients.local" ],
            whitelist_recipients_files => $opt{'whitelist-recipients'} ||
                [ "$CONFIG_DIR/postgrey_whitelist_recipients" ],
            privacy => defined $opt{'privacy'},
            hostname => defined $opt{hostname} ? $opt{hostname} : hostname,
            exim => defined $opt{'exim'},
        },
    }, 'postgrey';

    # max_age is in days
    $server->{postgrey}{max_age}*=3600*24;

    # read whitelist
    $server->read_clients_whitelists();
    $server->read_recipients_whitelists();

    # --privacy requires Digest::SHA1
    if($opt{'privacy'}) {
        require Digest::SHA1;
    }

    $0 = join(' ', @{$server->{server}{commandline}});
    $server->run;

    # shouldn't get here
    $server->mylog(1, "Exiting!");
    exit 1;
}

##### Net::Server::Multiplex methods:

# reload whitelists on HUP
sub sig_hup {
    my $self = shift;
    $self->mylog(1, "HUP received: reloading whitelists...");
    $self->read_clients_whitelists();
    $self->read_recipients_whitelists();
}

sub post_bind_hook()
{
    my ($self) = @_;

    # unix socket permissions should be 666
    if($self->{server}{port}[0] =~ /^(.*)\|unix$/) {
        chmod 0666, $1;
    }
}

sub pre_loop_hook()
{
    my ($self) = @_;

    # be sure to put in syslog any warnings / fatal errors
    if($self->{server}{log_file} eq 'Sys::Syslog') {
        $SIG{__WARN__} = sub { Sys::Syslog::syslog('warning', '%s', "WARNING: $_[0]") };
        $SIG{__DIE__}  = sub { Sys::Syslog::syslog('crit', '%s', "FATAL: $_[0]"); die @_; };
    }

    # write files with mode 600
    umask 0077;

    # ensure that only one instance of postgrey is running
    my $lock = "$self->{server}{dbdir}/postgrey.lock";
    open(LOCK, ">>$lock") or die "ERROR: can't open lock file: $lock\n";
    flock(LOCK, LOCK_EX|LOCK_NB) or die "ERROR: locked: $lock\n";

    # my $setflags = DB_TXN_NOSYNC;
    my $setflags = 0; # see http://bugs.debian.org/334430
    if($BerkeleyDB::db_version >= 4.1) {
        $setflags |= BerkeleyDB::DB_AUTO_COMMIT;
    }
    else {
        warn "disabling DB_AUTO_COMMIT because you are using BerkeleyDB version $BerkeleyDB::db_version. Version 4.1 is required for DB_AUTO_COMMIT. You might have problems in case of system failures to recover the database.\n";
    }

    # open database with transactions, logging and auto-commit to make it as
    # safe as possible. Note that locking is not required since only one
    # process is running
    $self->{postgrey}{db_env} = BerkeleyDB::Env->new(
        -Home     => $self->{server}{dbdir},
        -Flags    => DB_CREATE|DB_RECOVER|DB_INIT_TXN|DB_INIT_MPOOL|DB_INIT_LOG,
        -SetFlags => $setflags,
    ) or die "ERROR: can't create DB environment: $! (" .
             "dbdir: ".$self->{server}{dbdir}." uid/gid: $<,$>)\n";

    $self->{postgrey}{db_obj} = tie(%{$self->{postgrey}{db}}, 'BerkeleyDB::Btree',
        -Filename => 'postgrey.db',
        -Flags    => DB_CREATE,
        -Env      => $self->{postgrey}{db_env}
    ) or die "ERROR: can't create database $self->{server}{dbdir}/postgrey.db: $!\n";

    if($self->{postgrey}{awl_clients}) {
        $self->{postgrey}{db_cawl_obj} = tie(%{$self->{postgrey}{db_cawl}}, 'BerkeleyDB::Btree',
            -Filename => 'postgrey_clients.db',
            -Flags    => DB_CREATE,
            -Env      => $self->{postgrey}{db_env}
        ) or die "ERROR: can't create database $self->{server}{dbdir}/postgrey_clients.db: $!\n";
    }
}

sub mux_input()
{
    my ($self, $mux, $fh, $in_ref) = @_;
    defined $self->{postgrey_attr} or $self->{postgrey_attr} = {};
    my $attr = $self->{postgrey_attr};

    # consume entire lines
    while ($$in_ref =~ s/^([^\r\n]*)\r?\n//) {
        next unless defined $1;
        my $in = $1;
        if($in =~ /([^=]+)=(.*)/) {
            # read attributes
            $attr->{substr($1, 0, 512)} = substr($2, 0, 512);
        }
        elsif($in eq '') {
            defined $attr->{request} or $attr->{request}='';
            if($attr->{request} ne 'smtpd_access_policy') {
                $self->{net_server}->mylog(0, "unrecognized request type: '$attr->{request}'");
            }
            else {
                my $now = time;

                # decide
                my $action = $self->{net_server}->smtpd_access_policy($now, $attr);

                # give answer
                print $fh "action=$action\n\n";

                # attempt maintenance if one hour has passed since the last one
                my $server = $self->{net_server};
                if($server->{postgrey}{last_maint} && 
                    $now-$server->{postgrey}{last_maint} >= 3600)
                {
                    $server->{postgrey}{last_maint} = $now;
                    $server->do_maintenance($now);
                }

                # close the filehandle if --exim is set
                if ($self->{net_server}->{postgrey}{exim}) {
                    close($fh);
                    last;
                } 
            }
            $self->{postgrey_attr} = {};
        }
        else {
            $self->{net_server}->mylog(1, "ignoring garbage: <".substr($in, 0, 100).">");
        }
    }
}

sub fatal_hook()
{
    my ($self, $error, $package, $file, $line) = @_;
    # Net::Server calls $self->server_close but, unfortunately,
    # it does exit(0) (with Net::Server 0.97)...
    # It is however useful for init-script to detect non-zero exit codes
    die('ERROR: ' . $error);
}

main;

__END__

=head1 NAME

postgrey - Postfix Greylisting Policy Server

=head1 SYNOPSIS

B<postgrey> [I<options>...]

 -h, --help              display this help and exit
     --version           output version information and exit
 -v, --verbose           increase verbosity level
 -q, --quiet             decrease verbosity level
 -u, --unix=PATH         listen on unix socket PATH
 -i, --inet=[HOST:]PORT  listen on PORT, localhost if HOST is not specified
 -d, --daemonize         run in the background
     --pidfile=PATH      put daemon pid into this file
     --user=USER         run as USER (default: postgrey)
     --group=GROUP       run as group GROUP (default: nogroup)
     --dbdir=PATH        put db files in PATH (default: /var/spool/postfix/postgrey)
     --delay=N           greylist for N seconds (default: 300)
     --max-age=N         delete entries older than N days since the last time
                         that they have been seen (default: 35)
     --retry-window=N    allow only N days for the first retrial (default: 2)
                         append 'h' if you want to specify it in hours
     --greylist-action=A if greylisted, return A to Postfix (default: DEFER_IF_PERMIT)
     --greylist-text=TXT response when a mail is greylisted
                         (default: Greylisted + help url, see below)
     --lookup-by-subnet  strip the last 8 bits from IP addresses (default)
     --lookup-by-host    do not strip the last 8 bits from IP addresses
     --privacy           store data using one-way hash functions
     --hostname=NAME     set the hostname (default: `hostname`)
     --exim              don't reuse a socket for more than one query (exim compatible)
     --whitelist-clients=FILE     default: /usr/local/etc/postfix/postgrey_whitelist_clients
     --whitelist-recipients=FILE  default: /usr/local/etc/postfix/postgrey_whitelist_recipients
     --auto-whitelist-clients=N   whitelist host after first successful delivery
                                  N is the minimal count of mails before a client is 
                                  whitelisted (turned on by default with value 5)
                                  specify N=0 to disable.
     --listen-queue-size=N        allow for N waiting connections to our socket

 Note that the --whitelist-x options can be specified multiple times,
 and that per default /usr/local/etc/postfix/postgrey_whitelist_clients.local is
 also read, so that you can put there local entries.

=head1 DESCRIPTION

Postgrey is a Postfix policy server implementing greylisting.

When a request for delivery of a mail is received by Postfix via SMTP, the
triplet C<CLIENT_IP> / C<SENDER> / C<RECIPIENT> is built. If it is the first
time that this triplet is seen, or if the triplet was first seen less than
I<delay> seconds (300 is the default), then the mail gets rejected with a
temporary error. Hopefully spammers or viruses will not try again later, as it
is however required per RFC.

Note that you shouldn't use the --lookup-by-host option unless you know what
you are doing: there are a lot of mail servers that use a pool of addresses to
send emails, so that they can change IP every time they try again. That's why
without this option postgrey will strip the last byte of the IP address when
doing lookups in the database.

=head2 Installation

=over 4

=item *

Create a C<postgrey> user and the directory where to put the database I<dbdir>
(default: C</var/spool/postfix/postgrey>)

=item *

Write an init script to start postgrey at boot and start it. Like this for example:

 postgrey --inet=10023 -d

=item *

Put something like this in /usr/local/etc/main.cf:

 smtpd_recipient_restrictions =
               permit_mynetworks
               ...
               reject_unauth_destination
               check_policy_service inet:127.0.0.1:10023

=item *

Install the provided postgrey_whitelist_clients and
postgrey_whitelist_recipients in /usr/local/etc/postfix.

=item *

Put in /usr/local/etc/postfix/postgrey_whitelist_recipients users that do not want
greylisting.

=back

=head2 Whitelists

Whitelists allow you to specify client addresses or recipient address, for
which no greylisting should be done. Per default postgrey will read the
following files:

 /usr/local/etc/postfix/postgrey_whitelist_clients
 /usr/local/etc/postfix/postgrey_whitelist_clients.local
 /usr/local/etc/postfix/postgrey_whitelist_recipients

You can specify alternative paths with the --whitelist-x options.

Postgrey whitelists follow similar syntax rules as Postfix access tables.
The following can be specified for B<recipient addresses>:

=over 10

=item domain.addr

C<domain.addr> domain and subdomains.

=item name@

C<name@.*> and extended addresses C<name+blabla@.*>.

=item name@domain.addr

C<name@domain.addr> and extended addresses.

=item /regexp/

anything that matches C<regexp> (the full address is matched).

=back

The following can be specified for B<client addresses>:

=over 10

=item domain.addr

C<domain.addr> domain and subdomains.

=item IP1.IP2.IP3.IP4

IP address IP1.IP2.IP3.IP4. You can also leave off one number, in
which case only the first specified numbers will be checked.

=item IP1.IP2.IP3.IP4/MASK

CIDR-syle network. Example: 192.168.1.0/24

=item /regexp/

anything that matches C<regexp> (the full address is matched).

=back

=head2 Auto-whitelisting clients

With the option --auto-whitelist-clients a client IP address will be
automatically whitelisted if the following conditions are met:

=over 4

=item *

At least 5 successfull attempts of delivering a mail (after greylisting was
done). That number can be changed by specifying a number after the
--auto-whitelist-clients argument. Only one attempt per hour counts.

=item *

The client was last seen before --max-age days (35 per default).

=back

=head2 Greylist Action

To set the action to be returned to postfix when a message fails
postgrey's tests and should be deferred, use the
--greylist-action=ACTION option.

By default, postgrey returns DEFER_IF_PERMIT, which causes postfix to
check the rest of the restrictions and defer the message only if it
would otherwise be accepted.  A delay action of 451 causes postfix to
always defer the message with an SMTP reply code of 451 (temp fail).

See the postfix manual page access(5) for a discussion of the actions
allowed.

=head2 Greylist Text

When a message is greylisted, an error message like this will be sent at the
SMTP-level:

 Greylisted, see http://postgrey.schweikert.ch/help/example.com.html

Usually no user should see that error message and the idea of that URL is to
provide some help to system administrators seeing that message or users of
broken mail clients which try to send mails directly and get a greylisting
error. Note that the default help-URL contains the original recipient domain
(example.com), so that domain-specific help can be presented to the user (on
the default page it is said to contact postmaster@example.com)

You can change the text (and URL) with the B<--greylist-text> parameter. The
following special variables will be replaced in the text:

=over 4

=item %s

How many seconds left until the greylisting is over (300).

=item %r

Mail-domain of the recipient (example.com).

=back

=head2 Privacy

The --privacy option enable the use of a SHA1 hash function to store
IPs and emails in the greylisting database.  This will defeat straight
forward attempts to retrieve mail user behaviours.

=head2 SEE ALSO

See L<http://www.greylisting.org/> for a description of what
greylisting is and L<http://www.postfix.org/SMTPD_POLICY_README.html>
for a description of how Postfix policy servers work.

=head1 COPYRIGHT

Copyright (c) 2004-2007 by ETH Zurich. All rights reserved.
Copyright (c) 2007 by Open Systems AG. All rights reserved.

=head1 LICENSE

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

=head1 AUTHOR

S<David Schweikert E<lt>david@schweikert.chE<gt>>

=cut

# vi: sw=4 et