#!/usr/bin/env bash
{
    l_output="" l_output2=""
    l_parlist="net.ipv4.ip_forward=0 net.ipv6.conf.all.forwarding=0"
    l_searchloc="/run/sysctl.d/*.conf /etc/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf $([ -f /etc/default/ufw ] && awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)"
    KPC() {
        l_krp="$(sysctl "$l_kpname" | awk -F= '{print $2}' | xargs)"
        l_pafile="$(grep -Psl -- "^\h*$l_kpname\h*=\h*$l_kpvalue\b\h*(#.*)?$" $l_searchloc)"
        l_fafile="$(grep -s -- "^\s*$l_kpname" $l_searchloc | grep -Pv -- "\h*=\h*$l_kpvalue\b\h*" | awk -F: '{print $1}'  )"
        if [ "$l_krp" = "$l_kpvalue" ]; then
            l_output="$l_output\n - \"$l_kpname\" is set to \"$l_kpvalue\" in the running configuration"
        else
            l_output2="$l_output2\n - \"$l_kpname\" is set to \"$l_krp\" in the running configuration"
        fi
        if [ -n "$l_pafile" ]; then
            l_output="$l_output\n - \"$l_kpname\" is set to \"$l_kpvalue\" in \"$l_pafile\""
        else
            l_output2="$l_output2\n - \"$l_kpname = $l_kpvalue\" is not set in a kernel parameter configuration file"
        fi
        [ -n "$l_fafile" ] && l_output2="$l_output2\n - \"$l_kpname\" is set incorrectly in \"$l_fafile\""
    }
    ipv6_chk() {
        l_ipv6s=""
        grubfile=$(find /boot -type f \( -name 'grubenv' -o -name 'grub.conf' -o -name 'grub.cfg' \) -exec grep -Pl -- '^\h*(kernelopts=|linux|kernel)' {} \; )
        if [ -s "$grubfile" ]; then
            ! grep -P -- "^\h*(kernelopts=|linux|kernel)" "$grubfile" | grep -vq -- ipv6.disable=1 && l_ipv6s="disabled"
        fi
        if
            grep -Pqs -- "^\h*net\.ipv6\.conf\.all\.disable_ipv6\h*=\h*1\h*(#.*)?$" $l_searchloc && grep -Pqs -- "^\h*net\.ipv6\.conf\.default\.disable_ipv6\h*=\h*1\h*(#.*)?$" $l_searchloc && sysctl net.ipv6.conf.all.disable_ipv6 | grep -Pqs -- "^\h*net\.ipv6\.conf\.all\.disable_ipv6\h*=\h*1\h*(#.*)?$" && sysctl net.ipv6.conf.default.disable_ipv6 | grep -Pqs -- "^\h*net\.ipv6\.conf\.default\.disable_ipv6\h*=\h*1\h*(#.*)?$"
        then
            l_ipv6s="disabled"
        fi
        if [ -n "$l_ipv6s" ]; then
            l_output="$l_output\n - IPv6 is disabled on the system, \"$l_kpname\" is not applicable"
        else
            KPC
        fi
    }
    for l_kpe in $l_parlist; do
        l_kpname="$(awk -F= '{print $1}' <<<"$l_kpe")"
        l_kpvalue="$(awk -F= '{print $2}' <<<"$l_kpe")"
        if grep -q '^net.ipv6.' <<<"$l_kpe"; then
            ipv6_chk
        else
            KPC
        fi
    done
    if [ -z "$l_output2" ]; then
        echo -e "\n- Audit Result:\n ** PASS **\n$l_output\n"
    else
        echo -e "\n- Audit Result:\n ** FAIL **\n - Reason(s) for audit failure:\n$l_output2\n"
        [ -n "$l_output" ] && echo -e "\n- Correctly set:\n$l_output\n"
    fi
}