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Filename : smtpmailgidonly
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#!/usr/local/cpanel/3rdparty/bin/perl

# cpanel - scripts/smtpmailgidonly                 Copyright 2022 cPanel, L.L.C.
#                                                           All rights reserved.
# copyright@cpanel.net                                         http://cpanel.net
# This code is subject to the cPanel license. Unauthorized copying is prohibited

use strict;
use warnings;

use Cpanel::Exim::Config::Ports ();
use Cpanel::Chkservd            ();
use Cpanel::PwCache             ();

my $version = '2.4';
my $action  = lc( ( grep( m/^-*(?:on|off|status|refresh|start|stop)$/i, @ARGV ) )[0] // '' ) || 0;
$action =~ s/^-*//g;
my $no_run_header = "$0 version $version - Copyright(C) 2020 cPanel, L.L.C.\nThis may be freely redistributed under the terms of the Artistic License.";

if ( !$action ) {
    print STDERR <<"EOM";
$no_run_header

    usage:  $0 <on|off|status|refresh|start|stop>

EOM
    exit 1;
}

my $cpaneluid  = ( Cpanel::PwCache::getpwnam('cpanel') )[2];
my $mailgid    = ( Cpanel::PwCache::getpwnam('mail') )[3];
my $mailmangid = ( Cpanel::PwCache::getpwnam('mailman') )[3];

my $exim_alt_port = Cpanel::Chkservd::geteximport(1);    #first arg allows fetch more then the first port
if ($exim_alt_port) {
    foreach my $port ( split( m/\s*\,\s*/, $exim_alt_port ) ) {
        $Cpanel::Exim::Config::Ports::LISTEN_PORTS{$port} = 1 if ( $port =~ /^[0-9]+$/ && $port < 65535 && $port > 0 );
    }
}

my @PORTS      = sort { $a <=> $b } keys %Cpanel::Exim::Config::Ports::LISTEN_PORTS;
my @RULE_TYPES = (
    { 'table' => 'nat', 'target' => 'RETURN', 'method' => '-I' },
    { 'table' => '',    'target' => 'ACCEPT', 'method' => '-I' }
);
my @RULES = (
    { 'type' => 'uid', 'value' => 0, 'name' => 'root' },    #aka root
    $cpaneluid  ? { 'type' => 'uid', 'value' => $cpaneluid, 'name' => 'cpanel', 'args' => [ '-d', '127.0.0.1' ] } : (),
    $mailgid    ? { 'type' => 'gid', 'value' => $mailgid,    'name' => 'mail' }    : (),
    $mailmangid ? { 'type' => 'gid', 'value' => $mailmangid, 'name' => 'mailman' } : ()
);

# for future expension
if ( -e '/var/cpanel/smtpmailgidonly/conf.yaml' ) {
    print "Loaded custom smtpmailgidonly/conf.yaml\n";
    require Cpanel::YAML::Syck;
    my $cfg = YAML::Syck::LoadFile('/var/cpanel/smtpmailgidonly/conf.yaml');
    push @PORTS, @{ $cfg->{'PORTS'} } if exists $cfg->{'PORTS'};
    push @RULES, @{ $cfg->{'RULES'} } if exists $cfg->{'RULES'};
}

require Cpanel::SafeRun::Errors;

my $enabled = -e '/var/cpanel/smtpgidonlytweak';

if ( $action eq 'status' ) {
    print "Protection is: " . ( $enabled ? 'on' : 'off' ) . "\n";
    exit 0;
}

if ( $action eq 'refresh' ) {
    $action = ( $enabled ? 'on' : 'off' );
    print "Refreshing SMTP Mail protection.\n";
}
remove_firewall_rules( $action =~ /^(?:start|stop)$/ );

if ( $action =~ /^(?:on|start)$/ ) {
    add_firewall_rules( $action eq 'start' );
    print "SMTP Mail protection has been enabled.\n";
    print "All outbound SMTP connections will be redirected to localhost except:\n";
    foreach my $rule (@RULES) {
        print "\t$rule->{'type'} is $rule->{'name'} (ports: " . join( ',', @PORTS ) . ")\n";
    }
}
else {
    print "SMTP Mail protection has been disabled.  All users may make outbound smtp connections.\n";
}

exit;

sub add_firewall_rules {
    my ($start_only) = @_;

    foreach my $type (@RULE_TYPES) {

        foreach my $rule (@RULES) {
            my $result = _iptables( ( $type->{'table'} ? ( '-t', $type->{'table'} ) : () ), $type->{'method'}, 'OUTPUT', '-p', 'tcp', ( ref $rule->{'args'} ? @{ $rule->{'args'} } : () ), '-m', 'multiport', '--dports', join( ',', @PORTS ), '-m', 'owner', '--' . $rule->{'type'} . '-owner', $rule->{'value'}, '-j', $type->{'target'} );
            if ( $result =~ m/(?:No\s+chain|target\s+problem|Unknown\s+error|cannot\s+open\s+shared\s+object\s+file)/i ) {
                remove_firewall_rules();
                print "SMTP Mail protection has been disabled.  All users may make smtp connections.\n";
                print "There was a problem setting up iptables.  You either have an older kernel or a broken iptables install, or ipt_owner could not be loaded.\n";
                exit 1;
            }
        }
    }
    _iptables( '-t', 'nat', '-A', 'OUTPUT', '-p', 'tcp', '-m', 'multiport', '--dports', join( ',', @PORTS ), '-j', 'REDIRECT' );

    return if $start_only;

    require Cpanel::Config::CpConfGuard;

    my $cpconf = Cpanel::Config::CpConfGuard->new();
    $cpconf->{data}->{smtpmailgidonly} = 1;
    $cpconf->save();

    require Cpanel::FileUtils::TouchFile;

    Cpanel::FileUtils::TouchFile::touchfile('/var/cpanel/smtpgidonlytweak');
}

sub remove_firewall_rules {
    my ($stop_only) = @_;

    debug("Removing old rules");
    if ( !-e '/etc/csf' ) {    #case 57565: removing these breaks outbound mail if csf has SMTP_BLOCK=1

        # Old method needs to be removed
        foreach my $rule (@RULES) {
            _iptables( '-D', 'OUTPUT', '--protocol', 'tcp', ( ref $rule->{'args'} ? @{ $rule->{'args'} } : () ), '--dport', '25', '-m', 'owner', '--' . $rule->{'type'} . '-owner', $rule->{'value'}, '-j', 'ACCEPT' );
        }
        _iptables( '-D', 'OUTPUT', '--protocol', 'tcp', '-d', '127.0.0.1', '--dport', '25', '-j', 'ACCEPT' );
        _iptables( '-D', 'OUTPUT', '--protocol', 'tcp', '--dport', '25', '-j', 'REJECT' );
    }
    debug("Removing new type rules");
    {

        # New Method
        foreach my $type (@RULE_TYPES) {

            foreach my $rule (@RULES) {
                _iptables( ( $type->{'table'} ? ( '-t', $type->{'table'} ) : () ), '-D', 'OUTPUT', '-p', 'tcp', ( ref $rule->{'args'} ? @{ $rule->{'args'} } : () ), '-m', 'multiport', '--dports', join( ',', @PORTS ), '-m', 'owner', '--' . $rule->{'type'} . '-owner', $rule->{'value'}, '-j', $type->{'target'} );

            }
        }
        _iptables( '-t', 'nat', '-D', 'OUTPUT', '-p', 'tcp', '-m', 'multiport', '--dports', join( ',', @PORTS ), '-j', 'REDIRECT' );

    }
    debug("Removing multiport rules matching 25...");
    {
        foreach my $type (@RULE_TYPES) {

            # Remove any remaining port 25 rules
            my %port_lists;
            foreach my $line ( split( /\n/, _iptables( ( $type->{'table'} ? ( '-t', $type->{'table'} ) : () ), '-L', '-n' ) ) ) {

                #RETURN     tcp  --  0.0.0.0/0            127.0.0.1           multiport dports 25,26,122,125,232,434,465,587,809,5454 OWNER UID match 32001
                if ( $line =~ m/multiport\s+dports\s+(25,[,0-9]+)\s+(?i:OWNER)\s+[UG]ID\s+match/ ) {
                    $port_lists{$1} = 1;
                }
            }
            foreach my $port_list ( keys %port_lists ) {
                foreach my $rule (@RULES) {
                    _iptables( ( $type->{'table'} ? ( '-t', $type->{'table'} ) : () ), '-D', 'OUTPUT', '-p', 'tcp', ( ref $rule->{'args'} ? @{ $rule->{'args'} } : () ), '-m', 'multiport', '--dports', $port_list, '-m', 'owner', '--' . $rule->{'type'} . '-owner', $rule->{'value'}, '-j', $type->{'target'} );

                }

                if ( $type->{'table'} && $type->{'table'} eq 'nat' ) {
                    _iptables( '-t', 'nat', '-D', 'OUTPUT', '-p', 'tcp', '-m', 'multiport', '--dports', $port_list, '-j', 'REDIRECT' );
                }
            }
        }
    }

    return if $stop_only;

    require Cpanel::Config::CpConfGuard;

    my $cpconf = Cpanel::Config::CpConfGuard->new();
    $cpconf->{data}->{smtpmailgidonly} = 0;
    $cpconf->save();

    unlink '/var/cpanel/smtpgidonlytweak';    # For WHM
}

sub debug {
    print "[$_[0]]\n" if $ENV{'CPANEL_DEBUG'};
}

sub _iptables {
    my @rule_content = @_;
    if ( -x '/sbin/ip6tables' ) {
        my @rule6_content = @rule_content;
        foreach my $part (@rule6_content) {
            $part =~ s/127\.0\.0\.1/\:\:1\/128/g;    # change local host to ipv6 equiv
        }
        debug( "EXEC: " . join( ' ', '/sbin/ip6tables', @rule6_content ) );
        my $result6 = Cpanel::SafeRun::Errors::saferunallerrors( '/sbin/ip6tables', @rule6_content ) . "\n";
        debug("EXEC RESULT: $result6");
    }

    debug( "EXEC: " . join( ' ', '/sbin/iptables', @rule_content ) );
    my $result = Cpanel::SafeRun::Errors::saferunallerrors( '/sbin/iptables', @rule_content ) . "\n";
    debug("EXEC RESULT: $result");
    return $result;
}