harbian-audit/bin/hardening/7.7.4.2_ensure_loopback_traffic_is_configured.sh

#!/bin/bash

#
# harbian-audit for Debian GNU/Linux 9/10/11/12 Hardening
#

#
# 7.7.4.2 Ensure loopback traffic is configured (Scored)
# Include ipv4 and ipv6
# Add this feature:Author : Samson wen, Samson <sccxboy@gmail.com>
#

set -e # One error, it's over
set -u # One variable unset, it's over

HARDENING_LEVEL=2

INPUT_ACCEPT=1
OUTPUT_ACCEPT=1
INPUT_DENY=1
IP4VERSION="IPS4"
PACKAGE_NFT='nftables'
		
# This function will be called if the script status is on enabled / audit mode
audit () {
	is_pkg_installed $PACKAGE_NFT
    if [ $FNRET != 0 ]; then
		# Check the loopback interface to accept INPUT traffic.
		ensure_lo_traffic_input_is_accept "$IP4VERSION"
		if [ $FNRET = 0 ]; then
			INPUT_ACCEPT=0
			info "Iptables loopback traffic INPUT has configured!"
		else
			INPUT_ACCEPT=1
			info "Iptables: loopback traffic INPUT is not configured!"
		fi 
		# Check the loopback interface to accept OUTPUT traffic.
		ensure_lo_traffic_output_is_accept "$IP4VERSION"
		if [ $FNRET = 0 ]; then
			OUTPUT_ACCEPT=0
			info "Iptables loopback traffic OUTPUT has configured!"
		else
			OUTPUT_ACCEPT=1
			info "Iptables: loopback traffic OUTPUT is not configured!"
		fi 
		# all other interfaces to deny traffic to the loopback network.
		ensure_lo_traffic_other_if_input_is_deny "$IP4VERSION"
		if [ $FNRET = 0 ]; then
			INPUT_DENY=0
			info "Iptables loopback traffic INPUT deny from other interfaces has configured!"
		else
			INPUT_DENY=1
			info "Iptables: loopback traffic INPUT deny from other interfaces is not configured!"
		fi 
		if [ $INPUT_ACCEPT -eq 0 -a $OUTPUT_ACCEPT -eq 0 -a $INPUT_DENY -eq 0 ]; then
			ok "Loopback traffic rules are configured!"
		else
			crit "Loopback traffic rules are not configured!"
		fi
	else
			if [ $(nft list  chain ip filter INPUT 2>/dev/null | grep -c 'lo.*accept') -gt 0 -a $(nft list  chain ip filter OUTPUT 2>/dev/null | grep -c 'lo.*accept') -gt 0 -a $(nft list  chain ip filter INPUT 2>/dev/null | grep -c 'saddr.*127.0.0.0/8.*drop') -gt 0 ]; then
				ok "nftables loopback traffic INPUT/OUTPUT/deny-other-loopback-interfaces has configured!"
				FNRET=10
			else
				crit "nftables loopback traffic INPUT/OUTPUT/deny-other-loopback-interfaces is not configured!"
				FNRET=11
			fi
	fi
}

# This function will be called if the script status is on enabled mode
apply () {
	if [ $FNRET = 10 ]; then
		ok "nftables loopback traffic INPUT/OUTPUT/deny-other-loopback-interfaces has configured!"
	elif [ $FNRET = 11 ]; then
		warn "nftables loopback traffic INPUT/OUTPUT/deny-other-loopback-interfaces is not configured! Need the administrator to manually add it. "
	else
		if [ $INPUT_ACCEPT = 0 ]; then 
			ok "Iptables loopback traffic INPUT has configured!"
		else
        	warn "Iptables loopback traffic INPUT is not configured! Need the administrator to manually add it. Howto set: iptables -A INPUT -i lo -j ACCEPT"
		fi

		if [ $OUTPUT_ACCEPT = 0 ]; then 
			ok "Iptables loopback traffic OUTPUT has configured!"
		else
        	warn "Iptables loopback traffic OUTPUT is not configured! Need the administrator to manually add it. Howto set: iptables -A OUTPUT -o lo -j ACCEPT"
		fi

		if [ $INPUT_DENY = 0 ]; then 
			ok "Iptables loopback traffic INPUT deny from other interfaces has configured!"
		else
        	warn "Iptables loopback traffic INPUT deny from 127.0.0.0/8 is not configured! Need the administrator to manually add it. Howto set: iptables -A INPUT -s 127.0.0.0/8 -j DROP"
		fi
	fi
}

# This function will check config parameters required
check_config() {
    :
}

# Source Root Dir Parameter
if [ -r /etc/default/cis-hardening ]; then
    . /etc/default/cis-hardening
fi
if [ -z "$CIS_ROOT_DIR" ]; then
     echo "There is no /etc/default/cis-hardening file nor cis-hardening directory in current environment."
     echo "Cannot source CIS_ROOT_DIR variable, aborting."
    exit 128
fi

# Main function, will call the proper functions given the configuration (audit, enabled, disabled)
if [ -r $CIS_ROOT_DIR/lib/main.sh ]; then
    . $CIS_ROOT_DIR/lib/main.sh
else
    echo "Cannot find main.sh, have you correctly defined your root directory? Current value is $CIS_ROOT_DIR in /etc/default/cis-hardening"
    exit 128
fi