Difference between revisions of "Linux Router with VPN on a Raspberry Pi"

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(Rationale)
m (Installation: Added link to Raspberry Pi installation article)
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= Installation =
 
= Installation =
This guide assumes you're using AlpineLinux from a micro sdcard in ramdisk mode. It assumes you've read the basics of how to use [[Alpine local backup]] First format the sdcard as described, stop when you get to the end of the [[Create a Bootable USB#Format_USB_stick]]
+
This guide assumes you're using Alpine Linux from a micro SD card in ramdisk mode. It assumes you've read the basics of how to use [[Alpine local backup]].  The [[Raspberry Pi]] article contains information on how to install Alpine Linux on a Raspberry Pi.
 
 
Download armhf.rpi.tar.gz archive and extract into FAT32 partition. You will need version 3.2.0 or greater if you have a Raspberry Pi 2.
 
  
 
= Modem in full bridge mode =
 
= Modem in full bridge mode =

Revision as of 17:23, 1 October 2015

Contents

Rationale

This guide demonstrates how to set up a Raspberry Pi as an open source Linux router with a VPN tunnel. You will need a USB ethernet adaptor. I chose the Apple USB Ethernet Adapter as it contains a ASIX AX88772 which has good Linux support. Be sure to not buy a cheap counterfeit one as they do exist. You may choose to also buy an RTC clock. If you don't have an RTC clock, the time is lost when your Pi is shut down. When it is rebooted, the time will be set back to Thursday, 1 January 1970. As this is earlier than the creation time of your VPN certificates OpenVPN will refuse to start, which may mean you cannot do DNS lookups over VPN.

For wireless, a separate access point was purchased (Ubiquiti UniFi AP) because it contains a Atheros AR9287 which is supported by ath9k and I was keen to avoid blob drivers.

You could choose to use an old x86/amd64 system instead. This may be a more attractive option if you want to route high speeds. If you want to route speeds above 100 Mbit/s you'll want to make use of hardware encryption like AES-NI.

The network in this tutorial looks like this:

Network Diagram

Installation

This guide assumes you're using Alpine Linux from a micro SD card in ramdisk mode. It assumes you've read the basics of how to use Alpine local backup. The Raspberry Pi article contains information on how to install Alpine Linux on a Raspberry Pi.

Modem in full bridge mode

Your modem will need to be configured in "full bridge mode". The method for doing this varies depending on the interface on your device and is out of the scope of this tutorial.

The modem I am using is a Cisco 877 Integrated Services Router. It has no web interface and is controlled over SSH. More information can be found Configuring a Cisco 877 in full bridge mode.

Configuring PPP

Next up we need to configure our router to be able to dial a PPP connection with our modem.

apk add ppp-pppoe

Check that the interface between your router and modem is eth1, or change it. Enter your credentials at the bottom of the file or use /etc/ppp/chap-secrets

/etc/ppp/peers/yourISP

nolog

# Try to get the IP address from the ISP
noipdefault

# Try to get the name server addresses from the ISP
usepeerdns

# Use this connection as the default route.
defaultroute

defaultroute-metric 300

# detatch after ppp0 interface is created
updetach

# Replace previous default route
#replacedefaultroute

# rp-pppoe plug-in makes PPPoE connection so rp-pppoe package is not needed
#  Possibly, you may need to change interface according your configuration
plugin rp-pppoe.so eth1

# Uncomment if you need on-demand connection
#demand

# Disconnect after 300 seconds (5 minutes) of idle time.
#idle 300

# Hide password from log entries
hide-password

# Send echo requests
lcp-echo-interval 20
lcp-echo-failure 3

# Do not authenticate ISP peer
noauth

# Control connection consistency
persist
maxfail 0

# Control MTU size if your ISP does not force it
#mtu 1492

# Set your credentials
#  Alternatively you may use /etc/ppp/pap-secrets or /etc/ppp/chap-secrets files
user username@yourISP.tld
password <SECRET>

/etc/modules

Update modules to include pppoe:

pppoe

Network

/etc/hostname

Set this to your hostname eg:

<HOST_NAME>

/etc/hosts

Set your host and hostname

127.0.0.1	<HOST_NAME> <HOST_NAME>.<DOMAIN_NAME>

::1		<HOST_NAME> ipv6-gateway ipv6-loopback
ff00::0		ipv6-localnet
ff00::0		ipv6-mcastprefix
ff02::1		ipv6-allnodes
ff02::2		ipv6-allrouters
ff02::3		ipv6-allhosts

/etc/network/interfaces

Configure your network interfaces:

auto lo
    iface lo inet loopback

# internal interface
auto eth0
iface eth0 inet static
	address 192.168.1.1
	netmask 255.255.255.0

# external interface
auto eth1
iface eth1 inet static
	address 192.168.0.2
	netmask 255.255.255.252

# internet connection
auto ppp0
iface ppp0 inet ppp
	pre-up ip link set dev eth1 up
	provider <yourISP> # Make sure this is the same as /etc/ppp/peers/yourISP

Basic IPtables firewall with routing

This demonstrates how to set up basic routing with a permissive outgoing firewall. Incoming packets are blocked. The rest is commented in the rule set.

First install iptables:

apk add iptables ip6tables

#################################
# Basic iptables routing rule set
#################################

#
# Mangle Table
# We leave this empty for the moment.
#
*mangle
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
COMMIT

#
# Filter Table
# This is where we decide to ACCEPT, DROP or REJECT things
#
*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
*filter

# Create rule chain per input interface for forwarding packets
:FWD_ETH0 - [0:0]
:FWD_ETH1 - [0:0]
:FWD_PPP0 - [0:0]

# Create rule chain per input interface for input packets (for host itself)
:IN_ETH0 - [0:0]
:IN_ETH1 - [0:0]
:IN_PPP0 - [0:0]

# Create a log drop chain
:LOG_DROP - [0:0]

# Pass input packet to corresponding rule chain
-A INPUT -i lo -j ACCEPT
-A INPUT -i eth0 -j IN_ETH0
-A INPUT -i eth1 -j IN_ETH1
-A INPUT -i ppp0 -j IN_PPP0

# Pass forwarded packet to corresponding rule chain
-A FORWARD -i eth0 -j FWD_ETH0
-A FORWARD -i eth1 -j FWD_ETH1
-A FORWARD -i ppp0 -j FWD_PPP0

# Forward LAN traffic out
-A FWD_ETH0 -s 192.168.1.0/24 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Forward SSH packets from network to modem
-A FWD_ETH1 -s 192.168.0.0/30 -d 192.168.1.0/24 -p tcp -m tcp --sport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Forward HTTP to modem's webserver
-A FWD_ETH1 -s 192.168.0.0/30 -d 192.168.1.0/24 -p tcp -m tcp --sport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Forward traffic to ISP
-A FWD_PPP0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

# SSH to Router
-A IN_ETH0 -s 192.168.1.0/24 -p tcp -m tcp --dport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# DNS to Router
-A IN_ETH0 -s 192.168.1.0/24 -p tcp -m tcp --dport 1812 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# FreeRadius Client (eg a UniFi AP)
-A IN_ETH0 -s 192.168.1.0/24 -p udp -m udp --dport 1812 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# NTP to Router
-A IN_ETH0 -s 192.168.1.0/24 -p udp -m udp --dport 123 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Accept traffic
-A IN_ETH0 -s 192.168.1.0/24 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# SSH To Modem from Router
-A IN_ETH1 -s 192.168.0.1/32 -d 192.168.0.0/30 -p tcp -m tcp --sport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# HTTP to modem
-A IN_ETH1 -s 192.168.0.1/32 -d 192.168.0.0/30 -p tcp -m tcp --sport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Accept incoming tracked PPP0 connection
-A IN_PPP0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
COMMIT

#
# NAT Table
# This is where translation of packets happens and "forwarding" of ports
# to specific hosts.
#
*nat
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]

# Port forwarding for Bittorrent
-A PREROUTING -i ppp0 -p tcp -m tcp --dport 6881:6889 -j DNAT --to-destination 192.168.1.20
-A PREROUTING -i ppp0 -p udp -m udp --dport 6881:6889 -j DNAT --to-destination 192.168.1.20

# Allows routing to our modem subnet so we can access the web interface or SSH
-A POSTROUTING -s 192.168.1.0/24 -d 192.168.0.1/32 -o eth1 -p tcp -m tcp --dport 22 -j MASQUERADE
-A POSTROUTING -s 192.168.1.0/24 -d 192.168.0.1/32 -o eth1 -p tcp -m tcp --dport 80 -j MASQUERADE

# Allows hosts of the network to use the PPP tunnel
-A POSTROUTING -s 192.168.1.0/24 -o ppp0 -j MASQUERADE
COMMIT

I'd also highly suggest reading these resources if you are new to iptables:

/etc/sysctl.conf

These sysctl settings harden a few things and were mostly borrowed from the ArchLinux wiki.

net.ipv4.ip_forward = 1
net.ipv4.conf.default.rp_filter = 1
kernel.panic = 120

#### ipv4 networking and equivalent ipv6 parameters ####

## TCP SYN cookie protection (default)
## helps protect against SYN flood attacks
## only kicks in when net.ipv4.tcp_max_syn_backlog is reached
net.ipv4.tcp_syncookies = 1

## protect against tcp time-wait assassination hazards
## drop RST packets for sockets in the time-wait state
## (not widely supported outside of linux, but conforms to RFC)
net.ipv4.tcp_rfc1337 = 1

## sets the kernels reverse path filtering mechanism to value 1(on)
## will do source validation of the packet's recieved from all the interfaces on the machine
## protects from attackers that are using ip spoofing methods to do harm
net.ipv4.conf.all.rp_filter = 1
net.ipv6.conf.all.rp_filter = 1

## tcp timestamps
## + protect against wrapping sequence numbers (at gigabit speeds)
## + round trip time calculation implemented in TCP
## - causes extra overhead and allows uptime detection by scanners like nmap
## enable @ gigabit speeds
net.ipv4.tcp_timestamps = 0
#net.ipv4.tcp_timestamps = 1

## log martian packets
net.ipv4.conf.all.log_martians = 1

## ignore echo broadcast requests to prevent being part of smurf attacks (default)
net.ipv4.icmp_echo_ignore_broadcasts = 1

## ignore bogus icmp errors (default)
net.ipv4.icmp_ignore_bogus_error_responses = 1

## send redirects (not a router, disable it)
net.ipv4.conf.all.send_redirects = 0

## ICMP routing redirects (only secure)
#net.ipv4.conf.all.secure_redirects = 1 (default)
net/ipv4/conf/default/accept_redirects=0
net/ipv4/conf/all/accept_redirects=0
net/ipv6/conf/default/accept_redirects=0
net/ipv6/conf/all/accept_redirects=0

# Disable ipv6
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

DHCP

apk add dhcp

/etc/conf.d/dhcpd

Change DHCPD_IFACE="eth0" to the interface you want DHCP to run on.

/etc/dhcp/dhcpd.conf

Configure your DHCP configuration server. For my DHCP server I'm going to have three subnets. Each has a specific purpose. You may choose to have any number of subnets like below. The broadcast-address would be different if you used VLANs. However in this case we are not.

authoritative;
ddns-update-style interim;

shared-network home {
    # Subnet for regular nodes that require direct Internet access
    subnet 192.168.1.0 netmask 255.255.255.0 {
        range 192.168.1.10 192.168.1.240;
	default-lease-time 259200;
	max-lease-time 518400;
	option subnet-mask 255.255.255.0;
	option broadcast-address 192.168.1.255;
	option routers 192.168.1.1;
	option ntp-servers 192.168.1.1;
	option domain-name-servers 192.168.1.1;
	allow unknown-clients;

        host Gaming_Computer {
            hardware ethernet XX:XX:XX:XX:XX:XX;
            fixed-address 192.168.1.20;
            option subnet-mask 255.255.255.0;
            option routers 192.168.1.1;
	}
    }

    # Subnet for regular nodes that require VPN access
    subnet 192.168.2.0 netmask 255.255.255.0 {
        range 192.168.2.10 192.168.2.240;
	default-lease-time 259200;
	max-lease-time 518400;
	option subnet-mask 255.255.255.0;
	option broadcast-address 192.168.1.255;
	option routers 192.168.2.1;
        option ntp-servers 192.168.2.1;
	option domain-name-servers 192.168.1.1;
	ignore unknown-clients;

        host Linux_Workstation {
            hardware ethernet YY:YY:YY:YY:YY:YY;
            fixed-address 192.168.2.20;
            option subnet-mask 255.255.255.0;
            option routers 192.168.2.1;
	}
    }

    # Subnet for regular nodes that require no Internet access
    subnet 192.168.3.0 netmask 255.255.255.0 {
        range 192.168.3.10 192.168.3.240;
	default-lease-time 259200;
	max-lease-time 518400;
	option subnet-mask 255.255.255.0;
	option broadcast-address 192.168.1.255;
	option routers 192.168.3.1;
        option ntp-servers 192.168.3.1;
	option domain-name-servers 192.168.1.1;
	ignore unknown-clients;

        host printer {
            hardware ethernet ZZ:ZZ:ZZ:ZZ:ZZ:ZZ;
            fixed-address 192.168.3.9;
            option subnet-mask 255.255.255.0;
            option routers 192.168.3.1;
	}
    }
}

Make sure to add this to the default run level once configured:

rc-update add dhcp default

Synchronizing the clock

You can choose to use BusyBox's ntpd or you can choose a more fully fledged option like OpenNTPD

Busybox /etc/conf.d/ntpd

Allow clients to synchronize their clocks with the router.

# By default ntpd runs as a client. Add -l to run as a server on port 123.
NTPD_OPTS="-l -N -p <REMOTE TIME SERVER>"

Make sure to add this to the default run level once configured:

rc-update add ntpd default

Or if you prefer to synchronize with multiple servers...

OpenNTPD /etc/ntpd.conf

Install OpenNTPD

apk add openntpd

Add to default run level.

rc-update add openntpd default

/etc/ntpd.conf

# sample ntpd configuration file, see ntpd.conf(5)

# Addresses to listen on (ntpd does not listen by default)
listen on 192.168.1.1
listen on 192.168.2.1

# sync to a single server
#server ntp.example.org

# use a random selection of NTP Pool Time Servers
# see http://support.ntp.org/bin/view/Servers/NTPPoolServers
server 0.pool.ntp.org
server 1.pool.ntp.org
server 2.pool.ntp.org
server 3.pool.ntp.org

tlsdate

The time can also be extracted from a https handshake. If the certificate is self-signed you will need to use skip-verification:

apk add tlsdate

tlsdate -V --skip-verification -p 80 -H example.com

timezone

You might also want to set a timezone, see Setting the timezone.

Saving Time

There are two ways to do this. If you didn't buy an RTC clock see Saving time with Software Clock. If you did like the PiFace Real Time Clock see Saving time with Hardware Clock

Unbound DNS forwarder with dnscrypt

We want to be able to do our lookups using dnscrypt without installing dnscrypt on every client on the network. Therefore the router will also run a DNS forwarder and request unknown domains over dnscrypt for our clients.

Unbound

First install

apk add unbound

/etc/unbound/unbound.conf

# unbound.conf(5) man page.
#
# See /usr/share/doc/unbound/examples/unbound.conf for a commented
# reference config file.

server:
    # The following line will configure unbound to perform cryptographic
    # DNSSEC validation using the root trust anchor.
    # auto-trust-anchor-file: "/var/lib/unbound/root.key"
server:
verbosity: 1
num-threads: 4                                                        
interface: 192.168.1.1
 do-ip4: yes
 do-udp: yes
 do-tcp: yes
 access-control: 192.168.1.0/24 allow  # Specify the subnets you want to listen on
 access-control: 192.168.2.0/24 allow
 do-not-query-localhost: no
 chroot: ""       
 logfile: "/var/log/unbound.log"             
 use-syslog: no 
 hide-identity: yes
 hide-version: yes 
 harden-glue: yes
 harden-dnssec-stripped: yes
 use-caps-for-id: yes       
 private-domain: "<HOSTNAME>"      
 #local-zone: "localhost." static
 #local-data: "freebox.localhost. IN A 192.168.0.254"                                              
 #local-data-ptr: "192.168.0.254 freebox.localhost"
python:
remote-control:
forward-zone:
  name: "."
  forward-addr: 127.0.0.2@53

/etc/network/interfaces

You'll need a second loopback device, put it under the already existing one.

auto lo
    iface lo inet loopback

auto lo:1
iface lo:1 inet static
	address 127.0.0.2
	netmask 255.0.0.0

Blocking nasties on the network by domain

It seems Microsoft has added a whole bunch of telemetry (spyware) analytics to Windows itself, whereby the OS now calls home with various information regarding it's usage. Back porting to previous versions of Windows is not an option, because the telemetry patches have also been back ported to 7/8.1.

Changing the knobs in Windows to stop this activity doesn't silence it completely, and they can always be reset with another update from Microsoft. It is however unlikely they will change the domains that are looked up. More information about that can be found here. You should also consider ditching Windows entirely and using a proper operating system that does not contain intrusive malware here are a few choices to consider.

As this is a network router, it might be prudent to block those domains.

This script takes in a list of domains and produces a filter file. We are directing all lookups to "0.0.0.1" which is an invalid IP and should fail immediately, unlike localhost. There are lists of the addresses in various places such as here and in this script.

You could also use this to block advertising, but that's probably easier to do in a web browser with something like UBlock/UBlock Origin.

/etc/unbound/unbound.conf

In your main unbound configuration add

include: /etc/unbound/filter.conf

Script to prepare/sort domains for Unbound

#!/bin/sh

##################################################
# Script taken from http://npr.me.uk/unbound.html
# Note you need GNU sed
##################################################

# Remove "#" comments
# Remove space and tab
# Remove blank lines
# Remove localhost and broadcasthost lines
# Keep just the hosts
# Remove leading and trailing space and tab (again)
# Make everything lower case

sed -e "s/#.*//" \
    -e "s/[ \x09]*$//"\
    -e "/^$/ d" \
    -e "/^.*local.*/ d" \
    -e "/^.*broadcasthost.*/ d" \
    -e "s/\(^.*\) \([a-zA-Z0-9\.\-]*\)/\2/" \
    -e "s/^[ \x09]*//;s/[ \x09]*$//" $1 \
    -e "s/\(.*\)/\L\1/" hosts.txt > temp1.txt

# Remove any duplicate hosts

sort temp1.txt | uniq >temp2.txt

# Remove any hosts starting with "."
# Create the two required lines for each host.

sed -e "/^\..*/ d" \
    -e "s/\(^.*\)/local-zone: \x22\1\x22 redirect\nlocal-data: \x22\1 A 0.0.0.1\x22/" \
       temp2.txt > filter.conf

# Clean up
rm temp1.txt
rm temp2.txt

/etc/unbound/filter.conf

local-zone: "a-0001.a-msedge.net" redirect
local-data: "a-0001.a-msedge.net A 0.0.0.1"
local-zone: "a-0002.a-msedge.net" redirect
local-data: "a-0002.a-msedge.net A 0.0.0.1"
local-zone: "a-0003.a-msedge.net" redirect
local-data: "a-0003.a-msedge.net A 0.0.0.1"
local-zone: "a-0004.a-msedge.net" redirect
local-data: "a-0004.a-msedge.net A 0.0.0.1"
local-zone: "a-0005.a-msedge.net" redirect
local-data: "a-0005.a-msedge.net A 0.0.0.1"
local-zone: "a-0006.a-msedge.net" redirect
local-data: "a-0006.a-msedge.net A 0.0.0.1"
local-zone: "a-0007.a-msedge.net" redirect
local-data: "a-0007.a-msedge.net A 0.0.0.1"
local-zone: "a-0008.a-msedge.net" redirect
local-data: "a-0008.a-msedge.net A 0.0.0.1"
local-zone: "a-0009.a-msedge.net" redirect
local-data: "a-0009.a-msedge.net A 0.0.0.1"
local-zone: "a-msedge.net" redirect
local-data: "a-msedge.net A 0.0.0.1"
local-zone: "a.ads1.msn.com" redirect
local-data: "a.ads1.msn.com A 0.0.0.1"
local-zone: "a.ads2.msads.net" redirect
local-data: "a.ads2.msads.net A 0.0.0.1"
local-zone: "a.ads2.msn.com" redirect
local-data: "a.ads2.msn.com A 0.0.0.1"
local-zone: "a.rad.msn.com" redirect
local-data: "a.rad.msn.com A 0.0.0.1"
local-zone: "ac3.msn.com" redirect
local-data: "ac3.msn.com A 0.0.0.1"
local-zone: "ad.doubleclick.net" redirect
local-data: "ad.doubleclick.net A 0.0.0.1"
local-zone: "adnexus.net" redirect
local-data: "adnexus.net A 0.0.0.1"
local-zone: "adnxs.com" redirect
local-data: "adnxs.com A 0.0.0.1"
local-zone: "ads.msn.com" redirect
local-data: "ads.msn.com A 0.0.0.1"
local-zone: "ads1.msads.net" redirect
local-data: "ads1.msads.net A 0.0.0.1"
local-zone: "ads1.msn.com" redirect
local-data: "ads1.msn.com A 0.0.0.1"
local-zone: "aidps.atdmt.com" redirect
local-data: "aidps.atdmt.com A 0.0.0.1"
local-zone: "aka-cdn-ns.adtech.de" redirect
local-data: "aka-cdn-ns.adtech.de A 0.0.0.1"
local-zone: "apps.skype.com" redirect
local-data: "apps.skype.com A 0.0.0.1"
local-zone: "az361816.vo.msecnd.net" redirect
local-data: "az361816.vo.msecnd.net A 0.0.0.1"
local-zone: "az512334.vo.msecnd.net" redirect
local-data: "az512334.vo.msecnd.net A 0.0.0.1"
local-zone: "b.ads1.msn.com" redirect
local-data: "b.ads1.msn.com A 0.0.0.1"
local-zone: "b.ads2.msads.net" redirect
local-data: "b.ads2.msads.net A 0.0.0.1"
local-zone: "b.rad.msn.com" redirect
local-data: "b.rad.msn.com A 0.0.0.1"
local-zone: "bs.serving-sys.com" redirect
local-data: "bs.serving-sys.com A 0.0.0.1"
local-zone: "c.atdmt.com" redirect
local-data: "c.atdmt.com A 0.0.0.1"
local-zone: "c.msn.com" redirect
local-data: "c.msn.com A 0.0.0.1"
local-zone: "cdn.atdmt.com" redirect
local-data: "cdn.atdmt.com A 0.0.0.1"
local-zone: "cds26.ams9.msecn.net" redirect
local-data: "cds26.ams9.msecn.net A 0.0.0.1"
local-zone: "choice.microsoft.com" redirect
local-data: "choice.microsoft.com A 0.0.0.1"
local-zone: "choice.microsoft.com.nsatc.net" redirect
local-data: "choice.microsoft.com.nsatc.net A 0.0.0.1"
local-zone: "compatexchange.cloudapp.net" redirect
local-data: "compatexchange.cloudapp.net A 0.0.0.1"
local-zone: "corp.sts.microsoft.com" redirect
local-data: "corp.sts.microsoft.com A 0.0.0.1"
local-zone: "corpext.msitadfs.glbdns2.microsoft.com" redirect
local-data: "corpext.msitadfs.glbdns2.microsoft.com A 0.0.0.1"
local-zone: "cs1.wpc.v0cdn.net" redirect
local-data: "cs1.wpc.v0cdn.net A 0.0.0.1"
local-zone: "db3aqu.atdmt.com" redirect
local-data: "db3aqu.atdmt.com A 0.0.0.1"
local-zone: "df.telemetry.microsoft.com" redirect
local-data: "df.telemetry.microsoft.com A 0.0.0.1"
local-zone: "diagnostics.support.microsoft.com" redirect
local-data: "diagnostics.support.microsoft.com A 0.0.0.1"
local-zone: "ec.atdmt.com" redirect
local-data: "ec.atdmt.com A 0.0.0.1"
local-zone: "fe2.update.microsoft.com.akadns.net" redirect
local-data: "fe2.update.microsoft.com.akadns.net A 0.0.0.1"
local-zone: "feedback.microsoft-hohm.com" redirect
local-data: "feedback.microsoft-hohm.com A 0.0.0.1"
local-zone: "feedback.search.microsoft.com" redirect
local-data: "feedback.search.microsoft.com A 0.0.0.1"
local-zone: "feedback.windows.com" redirect
local-data: "feedback.windows.com A 0.0.0.1"
local-zone: "flex.msn.com" redirect
local-data: "flex.msn.com A 0.0.0.1"
local-zone: "g.msn.com" redirect
local-data: "g.msn.com A 0.0.0.1"
local-zone: "h1.msn.com" redirect
local-data: "h1.msn.com A 0.0.0.1"
local-zone: "h2.msn.com" redirect
local-data: "h2.msn.com A 0.0.0.1"
local-zone: "i1.services.social.microsoft.com" redirect
local-data: "i1.services.social.microsoft.com A 0.0.0.1"
local-zone: "i1.services.social.microsoft.com.nsatc.net" redirect
local-data: "i1.services.social.microsoft.com.nsatc.net A 0.0.0.1"
local-zone: "lb1.www.ms.akadns.net" redirect
local-data: "lb1.www.ms.akadns.net A 0.0.0.1"
local-zone: "live.rads.msn.com" redirect
local-data: "live.rads.msn.com A 0.0.0.1"
local-zone: "m.adnxs.com" redirect
local-data: "m.adnxs.com A 0.0.0.1"
local-zone: "m.hotmail.com" redirect
local-data: "m.hotmail.com A 0.0.0.1"
local-zone: "msedge.net" redirect
local-data: "msedge.net A 0.0.0.1"
local-zone: "msftncsi.com" redirect
local-data: "msftncsi.com A 0.0.0.1"
local-zone: "msnbot-65-55-108-23.search.msn.com" redirect
local-data: "msnbot-65-55-108-23.search.msn.com A 0.0.0.1"
local-zone: "msntest.serving-sys.com" redirect
local-data: "msntest.serving-sys.com A 0.0.0.1"
local-zone: "oca.telemetry.microsoft.com" redirect
local-data: "oca.telemetry.microsoft.com A 0.0.0.1"
local-zone: "oca.telemetry.microsoft.com.nsatc.net" redirect
local-data: "oca.telemetry.microsoft.com.nsatc.net A 0.0.0.1"
local-zone: "pre.footprintpredict.com" redirect
local-data: "pre.footprintpredict.com A 0.0.0.1"
local-zone: "preview.msn.com" redirect
local-data: "preview.msn.com A 0.0.0.1"
local-zone: "pricelist.skype.com" redirect
local-data: "pricelist.skype.com A 0.0.0.1"
local-zone: "rad.live.com" redirect
local-data: "rad.live.com A 0.0.0.1"
local-zone: "rad.msn.com" redirect
local-data: "rad.msn.com A 0.0.0.1"
local-zone: "redir.metaservices.microsoft.com" redirect
local-data: "redir.metaservices.microsoft.com A 0.0.0.1"
local-zone: "reports.wes.df.telemetry.microsoft.com" redirect
local-data: "reports.wes.df.telemetry.microsoft.com A 0.0.0.1"
local-zone: "s.gateway.messenger.live.com" redirect
local-data: "s.gateway.messenger.live.com A 0.0.0.1"
local-zone: "s0.2mdn.net" redirect
local-data: "s0.2mdn.net A 0.0.0.1"
local-zone: "schemas.microsoft.akadns.net" redirect
local-data: "schemas.microsoft.akadns.net A 0.0.0.1"
local-zone: "secure.adnxs.com" redirect
local-data: "secure.adnxs.com A 0.0.0.1"
local-zone: "secure.flashtalking.com" redirect
local-data: "secure.flashtalking.com A 0.0.0.1"
local-zone: "services.wes.df.telemetry.microsoft.com" redirect
local-data: "services.wes.df.telemetry.microsoft.com A 0.0.0.1"
local-zone: "settings-sandbox.data.microsoft.com" redirect
local-data: "settings-sandbox.data.microsoft.com A 0.0.0.1"
local-zone: "settings-win.data.microsoft.com" redirect
local-data: "settings-win.data.microsoft.com A 0.0.0.1"
local-zone: "sls.update.microsoft.com.akadns.net" redirect
local-data: "sls.update.microsoft.com.akadns.net A 0.0.0.1"
local-zone: "so.2mdn.net" redirect
local-data: "so.2mdn.net A 0.0.0.1"
local-zone: "sqm.df.telemetry.microsoft.com" redirect
local-data: "sqm.df.telemetry.microsoft.com A 0.0.0.1"
local-zone: "sqm.telemetry.microsoft.com" redirect
local-data: "sqm.telemetry.microsoft.com A 0.0.0.1"
local-zone: "sqm.telemetry.microsoft.com.nsatc.net" redirect
local-data: "sqm.telemetry.microsoft.com.nsatc.net A 0.0.0.1"
local-zone: "static.2mdn.net" redirect
local-data: "static.2mdn.net A 0.0.0.1"
local-zone: "statsfe1.ws.microsoft.com" redirect
local-data: "statsfe1.ws.microsoft.com A 0.0.0.1"
local-zone: "statsfe2.update.microsoft.com.akadns.net" redirect
local-data: "statsfe2.update.microsoft.com.akadns.net A 0.0.0.1"
local-zone: "statsfe2.ws.microsoft.com" redirect
local-data: "statsfe2.ws.microsoft.com A 0.0.0.1"
local-zone: "survey.watson.microsoft.com" redirect
local-data: "survey.watson.microsoft.com A 0.0.0.1"
local-zone: "telecommand.telemetry.microsoft.com" redirect
local-data: "telecommand.telemetry.microsoft.com A 0.0.0.1"
local-zone: "telecommand.telemetry.microsoft.com.nsatc.net" redirect
local-data: "telecommand.telemetry.microsoft.com.nsatc.net A 0.0.0.1"
local-zone: "telemetry.appex.bing.net" redirect
local-data: "telemetry.appex.bing.net A 0.0.0.1"
local-zone: "telemetry.appex.bing.net:443" redirect
local-data: "telemetry.appex.bing.net:443 A 0.0.0.1"
local-zone: "telemetry.microsoft.com" redirect
local-data: "telemetry.microsoft.com A 0.0.0.1"
local-zone: "telemetry.urs.microsoft.com" redirect
local-data: "telemetry.urs.microsoft.com A 0.0.0.1"
local-zone: "ui.skype.com" redirect
local-data: "ui.skype.com A 0.0.0.1"
local-zone: "view.atdmt.com" redirect
local-data: "view.atdmt.com A 0.0.0.1"
local-zone: "vortex-bn2.metron.live.com.nsatc.net" redirect
local-data: "vortex-bn2.metron.live.com.nsatc.net A 0.0.0.1"
local-zone: "vortex-cy2.metron.live.com.nsatc.net" redirect
local-data: "vortex-cy2.metron.live.com.nsatc.net A 0.0.0.1"
local-zone: "vortex-sandbox.data.microsoft.com" redirect
local-data: "vortex-sandbox.data.microsoft.com A 0.0.0.1"
local-zone: "vortex-win.data.microsoft.com" redirect
local-data: "vortex-win.data.microsoft.com A 0.0.0.1"
local-zone: "vortex.data.microsoft.com" redirect
local-data: "vortex.data.microsoft.com A 0.0.0.1"
local-zone: "watson.live.com" redirect
local-data: "watson.live.com A 0.0.0.1"
local-zone: "watson.microsoft.com" redirect
local-data: "watson.microsoft.com A 0.0.0.1"
local-zone: "watson.ppe.telemetry.microsoft.com" redirect
local-data: "watson.ppe.telemetry.microsoft.com A 0.0.0.1"
local-zone: "watson.telemetry.microsoft.com" redirect
local-data: "watson.telemetry.microsoft.com A 0.0.0.1"
local-zone: "watson.telemetry.microsoft.com.nsatc.net" redirect
local-data: "watson.telemetry.microsoft.com.nsatc.net A 0.0.0.1"
local-zone: "wes.df.telemetry.microsoft.com" redirect
local-data: "wes.df.telemetry.microsoft.com A 0.0.0.1"
local-zone: "www.msftncsi.com" redirect
local-data: "www.msftncsi.com A 0.0.0.1"

DNSCrypt

You'll need to pin the testing repository. See: Alpine Linux package management#Repository pinning

Then install:

apk add dnscrypt-proxy@testing

/etc/conf.d/dnscrypt-proxy

Enter a dnscrypt server, it should look something like this:

# DNSCRYPT_LOGFILE=/var/log/dnscrypt-proxy/dnscrypt-proxy.log

# override listen address where DNSCRYPT listen
DNSCRYPT_LOCALIP=127.0.0.2:53

RESOLVER=208.67.220.220:443                                                        
PROVIDER=2.dnscrypt-cert.opendns.com                                               
PUBKEY=B735:1140:206F:225D:3E2B:D822:D7FD:691E:A1C3:3CC8:D666:8D0C:BE04:BFAB:CA43:FB79

Finally add both to the default run level

rc-update add unbound default

rc-update add dnscrypt-proxy default

WiFi 802.1x EAP and FreeRadius

A more secure way than using pre-shared keys (WPA2) is to use EAP-TLS and use separate certificates for each device. See FreeRadius EAP-TLS configuration

VPN Tunnel on specific subnet

As mentioned earlier in this article it might be useful to have a VPN subnet and a non-VPN subnet. Typically gaming consoles or computers might want low-latency connections. For this exercise we use fwmark.

Install the necessary packages:

apk add openvpn iproute2 iputils

/etc/modules

You'll want to add the tun module

tun

/etc/iproute2/rt_tables

Add the two routing tables to the bottom of rt_tables. It should look something like this:

#
# reserved values
#
255	local
254	main
253	default
0	unspec
#
# local
#
#1	inr.ruhep
1 ISP
2 VPN

/etc/network/interfaces

Next up add the virtual interface: eth0:2, just under eth0 will do:

auto eth0
iface eth0 inet static
	address 192.168.1.1
	netmask 255.255.255.0

# Virtual interface
auto eth0:2
iface eth0:2 inet static
	address 192.168.2.1
	netmask 255.255.255.0
        post-up /etc/network/fwmark_rules

/etc/sysctl.conf

If you want to use fwmark rules you need to change this setting. It causes the router to still do source validation.

net.ipv4.conf.all.rp_filter = 2

fwmark won't work if you have this set to 1.

/etc/network/fwmark_rules

In this file we want to put the fwmark rules and set the correct priorities.

#!/bin/sh

# Normal packets to go direct out WAN
/sbin/ip rule add fwmark 1 table ISP prio 100

# Put packets destined into VPN when VPN is up
/sbin/ip rule add fwmark 2 table VPN prio 200

# Prevent packets from being routed out when VPN is down.
# This prevents packets from falling back to the main table
# that has a priority of 32766
/sbin/ip rule add prohibit fwmark 2 prio 300

/etc/ppp/ip-up

Next up we want to create the routes that should be run when PPP comes online. There are special hooks we can use in ip-up and ip-down to refer to the IP address, ppp man file - Scripts You can also read about them in your man file if you have ppp-doc installed.

#!/bin/sh
#
# This script is run by pppd when there's a successful ppp connection.
#

# Flush out any old rules that might be there
/sbin/ip route flush table ISP

# Add route to table from subnets on LAN
/sbin/ip route add 192.168.1.0/24 dev eth0 table ISP
/sbin/ip route add 192.168.2.0/24 dev eth0 table ISP

# Add route from IP given by ISP to the table
/sbin/ip rule add from ${IPLOCAL} table ISP prio 100

# Add a default route
/sbin/ip route add table ISP default via ${IPLOCAL}

/etc/ppp/ip-down

#!/bin/sh
#
# This script is run by pppd after the connection has ended.
#

# Delete the rules when we take the interface down
/sbin/ip rule del from ${IPLOCAL} table ISP prio 100

/etc/openvpn/route-up-fwmark.sh

OpenVPN needs similar routing scripts and it also has it's own special hooks that allow you to specify particular values. A full list is here OpenVPN man file - Environmental Variables

#!/bin/sh
#
# This script is run by OpenVPN when there's a successful VPN connection.
#

# Flush out any old rules that might be there
/sbin/ip route flush table VPN

# Add route to table from 192.168.2.0/24 subnet on LAN
/sbin/ip route add 192.168.2.0/24 dev eth0 table VPN

# Add route from VPN interface IP to the VPN table
/sbin/ip rule add from ${ifconfig_local} table VPN prio 200

# Add a default route
/sbin/ip route add default via ${ifconfig_local} dev ${dev} table VPN

/etc/openvpn/route-pre-down-fwmark.sh

#!/bin/sh
#
# This script is run by OpenVPN after the connection has ended
#

# Delete the rules when we take the interface down
/sbin/ip rule del from ${ifconfig_local} table VPN prio 200

What I did find was when starting and stopping the OpenVPN service if you used:

service openvpn stop

The rules in route-pre-down-fwmark.sh were not executed.

However:

/etc/init.d/openvpn stop

seemed to work correctly.

Advanced IPtables rules that allow us to route into our two routing tables

This is an expansion of the previous set of rules. It sets up NAT masquerading for the 192.168.2.0 to go through the VPN using marked packets.

I used these guides to write complete this:

#########################################################################
# Advanced routing rule set
# Uses 192.168.1.0 via ISP
#      192.168.2.0 via VPN
#
# Packets to/from 192.168.1.0/24 are marked with 0x1 and routed to ISP
# Packets to/from 192.168.2.0/24 are marked with 0x2 and routed to VPN
#
#########################################################################

#
# NAT Table
# This is where translation of packets happens and "forwarding" of ports
# to specific hosts.
#
*nat

# Set default policies for table
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]

# Port forwarding for Bittorrent
-A PREROUTING -i tun0 -p tcp -m tcp --dport 6881:6889 -j DNAT --to-destination 192.168.2.20
-A PREROUTING -i tun0 -p udp -m udp --dport 6881:6889 -j DNAT --to-destination 192.168.2.20

# Allows routing to our modem subnet so we can access the web interface
-A POSTROUTING -s 192.168.1.0/24 -d 192.168.0.1/32 -o eth1 -p tcp -m tcp --dport 80 -j MASQUERADE
-A POSTROUTING -s 192.168.2.0/24 -d 192.168.0.1/32 -o eth1 -p tcp -m tcp --dport 80 -j MASQUERADE

# Allows hosts of the network to use the VPN tunnel
-A POSTROUTING -o tun0 -j MASQUERADE

# Allows hosts of the network to use the PPP tunnel
-A POSTROUTING -o ppp0 -j MASQUERADE
COMMIT

#
# Filter Table
# This is where we decide to ACCEPT, DROP or REJECT things
#
*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]

# Create rule chain per input interface for forwarding packets
:FWD_ETH0 - [0:0]
:FWD_ETH1 - [0:0]
:FWD_PPP0 - [0:0]
:FWD_TUN0 - [0:0]

# Create rule chain per input interface for input packets (for host itself)
:IN_ETH0 - [0:0]
:IN_ETH1 - [0:0]
:IN_PPP0 - [0:0]
:IN_TUN0 - [0:0]

# Create a log drop chain
:LOG_DROP - [0:0]

# Create a reject chain
:LOG_REJECT - [0:0]

# Pass input packet to corresponding rule chain
-A INPUT -i lo -j ACCEPT
-A INPUT -i eth0 -j IN_ETH0
-A INPUT -i eth1 -j IN_ETH1
-A INPUT -i ppp0 -j IN_PPP0
-A INPUT -i tun0 -j IN_TUN0

# Track forwarded packets
-A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

# Pass forwarded packet to corresponding rule chain
-A FORWARD -i eth0 -j FWD_ETH0
-A FORWARD -i eth1 -j FWD_ETH1
-A FORWARD -i ppp0 -j FWD_PPP0
-A FORWARD -i tun0 -j FWD_TUN0

# Forward traffic to ISP
-A FWD_ETH0 -s 192.168.1.0/24 -j ACCEPT

# Forward traffic to VPN
-A FWD_ETH0 -s 192.168.2.0/24 -j ACCEPT

# Allow excepted server to be FORWARD to ppp0
#-A FWD_ETH0 -s 192.168.2.0/24 -d <IP_OF_EXCEPTED_SERVER>/32 -o ppp0 -j ACCEPT

# Forward SSH packets from network to modem
-A FWD_ETH1 -s 192.168.0.1/32 -d 192.168.1.0/24 -p tcp -m tcp --sport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A FWD_ETH1 -s 192.168.0.1/32 -d 192.168.2.0/24 -p tcp -m tcp --sport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Forward HTTP packets from network to modem
-A FWD_ETH1 -s 192.168.0.1/32 -d 192.168.1.0/24 -p tcp -m tcp --sport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A FWD_ETH1 -s 192.168.0.1/32 -d 192.168.2.0/24 -p tcp -m tcp --sport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Forward Bittorrent Port to workstation
-A FWD_TUN0 -d 192.168.2.20/32 -p tcp -m tcp --dport 6881:6889 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A FWD_TUN0 -d 192.168.2.20/32 -p udp -m udp --dport 6881:6889 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# SSH to Router
-A IN_ETH0 -s 192.168.1.0/24 -p tcp -m tcp --dport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A IN_ETH0 -s 192.168.2.0/24 -p tcp -m tcp --dport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# DNS to Router
-A IN_ETH0 -s 192.168.1.0/24 -p udp -m udp --dport 53 -m conntrack --ctstate NEW -j ACCEPT
-A IN_ETH0 -s 192.168.2.0/24 -p udp -m udp --dport 53 -m conntrack --ctstate NEW -j ACCEPT

# FreeRadius Client (eg a UniFi AP)
-A IN_ETH0 -s 192.168.1.0/24 -p tcp -m tcp --dport 1812 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A IN_ETH0 -s 192.168.1.0/24 -p udp -m udp --dport 1812 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Ubiquiti UAP Device Discovery Broadcast
-A IN_ETH0 -s 192.168.1.0/24 -p udp -m udp --dport 10001 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# NTP to Router
-A IN_ETH0 -s 192.168.1.0/24 -p udp -m udp --dport 123 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A IN_ETH0 -s 192.168.2.0/24 -p udp -m udp --dport 123 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Accept traffic to router on both subnets
-A IN_ETH0 -s 192.168.1.0/24 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A IN_ETH0 -s 192.168.2.0/24 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Allow excepted server to be INPUT to eth0 from LAN
#-A IN_ETH0 -s 192.168.2.0/24 -d <IP_OF_EXCEPTED_SERVER>/32 -o ppp0 -j ACCEPT

# SSH To Modem from Router
-A IN_ETH1 -s 192.168.0.1/32 -d 192.168.0.0/30 -p tcp -m tcp --sport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# HTTP To Modem from Router
-A IN_ETH1 -s 192.168.0.1/32 -d 192.168.0.0/30 -p tcp -m tcp --sport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Accept incoming tracked PPP0 connection
-A IN_PPP0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

# Log dropped packets coming in on PPP0
-A IN_PPP0 -j LOG --log-prefix "DROP:INPUT " --log-level 6
-A IN_PPP0 -j LOG_DROP

# Accept incoming tracked TUN0 connection
-A IN_TUN0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

# Log dropped packets coming in on TUN0
-A IN_TUN0 -j LOG --log-prefix "DROP:INPUT " --log-level 6
-A IN_TUN0 -j LOG_DROP
COMMIT

#
# Mangle Table
# This is the place where our markings happen, whether they be 0x1 or 0x2
#
*mangle

# Set default policies for table
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]

# Restore CONNMARK to the MARK (If one doesn't exist then no mark is set)
-A PREROUTING -j CONNMARK --restore-mark --nfmask 0xffffffff --ctmask 0xffffffff

# If packet MARK is 2, then it means there is already a connection mark and the
# original packet came in on VPN
-A PREROUTING -s 192.168.2.0/24 -m mark --mark 0x2 -j ACCEPT

# Check exception (this is a server which when accessed on a 192.168.2.0/24 address will go out the ISP table) are 0x1
#-A PREROUTING -s 192.168.2.0/24 -d <IP_OF_EXCEPTED_SERVER>/32 -m mark --mark 0x1 -j ACCEPT

# Mark packets coming from 192.168.2.0/24 are 0x2
-A PREROUTING -s 192.168.2.0/24 -j MARK --set-xmark 0x2/0xffffffff

# If packet MARK is 1, then it means there is already a connection mark and the
# original packet came in on ISP
-A PREROUTING -s 192.168.1.0/24 -m mark --mark 0x1 -j ACCEPT

# Mark packets 192.168.1.0/24 are 0x1
-A PREROUTING -s 192.168.1.0/24 -j MARK --set-xmark 0x1/0xffffffff

# Mark exception (this is a server which when accessed on a 192.168.2.0/24 address will go out the ISP table) as 0x1
#-A PREROUTING -s 192.168.2.0/24 -d <IP_OF_EXCEPTED_SERVER>/32 -j MARK --set-xmark 0x1/0xffffffff

# Set mark to 0 - This is for the modem. Otherwise it will mark with 0x1 or 0x2
-A PREROUTING -d 192.168.0.1/32 -j MARK --set-xmark 0x0/0xffffffff

# Save MARK to CONNMARK (remember iproute can't see CONNMARKs)
-A PREROUTING -j CONNMARK --save-mark --nfmask 0xffffffff --ctmask 0xffffffff
COMMIT

You may want to delete certain rules here that do not apply to you, eg the FreeRadius rules. That is covered later in this article.

OpenVPN Routing

Usually when you connect with OpenVPN the remote VPN server will push routes down to your system. We don't want this as we still want to be able to access the internet without the VPN. We have also created our own routes that we want to use earlier in this guide.

You'll need to add this to the bottom of your OpenVPN configuration file:

# Prevents default gateway from being set on the default routing table
route-noexec

# Allows route-up script to be executed
script-security 2

# Calls custom shell script after connection to add necessary routes
route-up /etc/openvpn/route-up-fwmark.sh
route-pre-down /etc/openvpn/route-pre-down-fwmark.sh

My VPNs are arranged like this in /etc/openvpn:

OpenVPN configuration file for that server:

countrycode.serverNumber.openvpn.conf

OpenVPN certs for that server:

countrycode.serverNumber.openvpn/countrycode.serverNumber.openvpn.crt
countrycode.serverNumber.openvpn/countrycode.serverNumber.openvpn.key
countrycode.serverNumber.openvpn/myKey.crt
countrycode.serverNumber.openvpn/myKey.key

So I use this helpful script to automate the process of changing between servers:

#!/bin/sh

vpn_server_filename=$1

rm /etc/openvpn/openvpn.conf
ln -s $vpn_server_filename /etc/openvpn/openvpn.conf
chown -R openvpn:openvpn /etc/openvpn
chmod -R a=-rwx,u=+rX /etc/openvpn
chmod u=x /etc/openvpn/*.sh*


if grep -Fxq "#CustomStuffHere" openvpn.conf
then
    echo "Not adding custom routes, this server has been used previously"
else
    echo "Adding custom route rules"
    
    echo -e "#CustomStuffHere\
\n# Prevents default gateway from being set on the default routing table\
\nroute-noexec\
\n# Allows route-up script to be executed\
\nscript-security 2 \
\n# Calls custom shell script after connection to add necessary routes\
\nroute-up /etc/openvpn/route-up-fwmark.sh\
\nroute-pre-down /etc/openvpn/route-pre-down-fwmark.sh\
\n# Logging of OpenVPN to file\
\n#log /etc/openvpn/openvpn.log"\
>> /etc/openvpn/openvpn.conf
fi

echo "Remember to set BitTorrent port forward in vcp.ovpn.to control panel"

That way I can simply change between servers by running:

changevpn.sh countrycode.serverNumber.openvpn

and then restart openvpn. I am also reminded to put the port forward through on the VPN control panel so my BitTorrent client is connectable:

service openvpn restart

Finally add openvpn to the default run level

rc-update add openvpn default

Creating a LAN only Subnet

In this section, we'll be creating a LAN only subnet. This subnet will be 192.168.3.0/24. The idea of this subnet is nodes in it cannot have their packets forwarded to the Internet, however they can be accessed via the other LAN subnets 192.168.1.0/24 and 192.168.2.0/24. This approach doesn't use VLANs although that would be recommended if you had a managed switch. The idea of this subnet is for things like WiFi access points, IP Phones which contact a local Asterisk server and of course printers.

At the end of this section we will have something like:

Network Diagram

/etc/iproute2/rt_tables

First up we'll add a third routing table:

3 LAN

/etc/network/interfaces

Add a an extra interface.

auto eth0:3
iface eth0:3 inet static
	address 192.168.3.1
	netmask 255.255.255.0
        post-up /etc/network/route_LAN

/etc/network/route_LAN

This file will have our route added to it

#!/bin/sh

# Add routes from ISP to LAN
/sbin/ip route add 192.168.1.0/24 dev eth0 table LAN

# Add route from VPN to LAN
/sbin/ip route add 192.168.2.0/24 dev eth0 table LAN

# Add route from LAN to it's own table
/sbin/ip route add 192.168.3.0/24 dev eth0 table LAN

/etc/ppp/ip-up

Append a route from the LAN subnet to the ISP table

# Add route to LAN subnet
/sbin/ip route add 192.168.3.0/24 dev eth0 table ISP

/etc/openvpn/route-up-fwmark.sh

Append a route from the LAN subnet to the VPN table

# Add route to LAN only subnet
/sbin/ip route add 192.168.3.0/24 dev eth0 table VPN

/etc/ntpd.conf

Add a listen address for ntp (OpenNTPD).

You should now have:

# Addresses to listen on (ntpd does not listen by default)
listen on 192.168.1.1
listen on 192.168.2.1
listen on 192.168.3.1

Devices needing the correct time will need to use this NTP server because they will not be able to get it from the Internet.

Blocking bogons

Our LAN now has 4 subnets in total that are possible:

  • 192.168.0.0/30 (connection between modem and router)
  • 192.168.1.0/24 (ISP table, directly routed out WAN)
  • 192.168.2.0/24 (VPN table, routed out VPN)
  • 192.168.3.0/24 (Null routed subnet for LAN only hosts)
  • 172.16.32.0/20 (VPN provider's network, so we can access things on the VPN's network).

Everything else should be rejected. No packets should ever be forwarded on 192.168.5.2 or 10.0.0.5 for example.

Installing ipset

Install ipset:

apk add ipset

Add it to start up:

rc-update add ipset default

Now we need to load the lists of addresses into ipset Securing Your Server using IPset and Dynamic Blocklists mentions a script which was particularly useful. This script could be run on a cron job if you wanted to regularly update it and for the full bogon list you should as they change when that address space has been allocated.

For the purpose of this we will be using just the bogon-bn-nonagg.txt list.

0.0.0.0/8
10.0.0.0/8
100.64.0.0/10
127.0.0.0/8
169.254.0.0/16
172.16.0.0/12
192.0.0.0/24
192.0.2.0/24
192.168.0.0/16
198.18.0.0/15
198.51.100.0/24
203.0.113.0/24
224.0.0.0/4
240.0.0.0/4

This is unlikely to change as it's the IPV4 Reserved IP addresses space. The script:

#! /bin/bash

# /usr/local/sbin/fullbogons-ipv4
# BoneKracker
# Rev. 11 October 2012
# Tested with ipset 6.13

# Purpose: Periodically update an ipset used in a running firewall to block
# bogons. Bogons are addresses that nobody should be using on the public
# Internet because they are either private, not to be assigned, or have
# not yet been assigned.
#
# Notes: Call this from crontab. Feed updated every 4 hours.

# target="http://www.team-cymru.org/Services/Bogons/fullbogons-ipv4.txt"
# Use alternative URL from pfSense, due to 404 error with URL above
target="https://files.pfsense.org/lists/bogon-bn-nonagg.txt"
ipset_params="hash:net"

filename=$(basename ${target})
firewall_ipset=${filename%.*}           # ipset will be filename minus ext
data_dir="/var/tmp/${firewall_ipset}"   # data directory will be same
data_file="${data_dir}/${filename}"

# if data directory does not exist, create it
mkdir -pm 0750 ${data_dir}

# function to get modification time of the file in log-friendly format
get_timestamp() {
    date -r $1 +%m/%d' '%R
}

# file modification time on server is preserved during wget download
[ -w ${data_file} ] && old_timestamp=$(get_timestamp ${data_file})

# fetch file only if newer than the version we already have
wget -qNP ${data_dir} ${target}

if [ "$?" -ne "0" ]; then
    logger -p cron.err "IPSet: ${firewall_ipset} wget failed."
    exit 1
fi

timestamp=$(get_timestamp ${data_file})

# compare timestamps because wget returns success even if no newer file
if [ "${timestamp}" != "${old_timestamp}" ]; then

    temp_ipset="${firewall_ipset}_temp"
    ipset create ${temp_ipset} ${ipset_params}

    #sed -i '/^#/d' ${data_file}            # strip comments
    sed -ri '/^[#< \t]|^$/d' ${data_file}   # occasionally the file has been xhtml

    while read network; do
        ipset add ${temp_ipset} ${network}
    done < ${data_file}

    # if ipset does not exist, create it
    ipset create -exist ${firewall_ipset} ${ipset_params}

    # swap the temp ipset for the live one
    ipset swap ${temp_ipset} ${firewall_ipset}
    ipset destroy ${temp_ipset}

    # log the file modification time for use in minimizing lag in cron schedule
    logger -p cron.notice "IPSet: ${firewall_ipset} updated (as of: ${timestamp})."

fi

Now you should see the list loaded into memory when you do:

ipset list

We want to save it so our router can refer to it next time it starts up so for that:

/etc/init.d/ipset save

Restricting our LAN subnet with iptables, and blocking the bogons

Finally we can apply our iptables rules, to filter both 192.168.3.0/24 and make sure that subnets like 192.168.5.0/24 are not forwarded or accessible by our router. You will need to review these rules, and remove the ones that do not apply to you.

Don't forget to change your RADIUS rules if you moved your WiFi APs into the 192.168.3.0/24 subnet. You'll also need to edit /etc/raddb/clients.conf

#########################################################################
# Advanced routing rule set
# Uses 192.168.1.0 via ISP
#      192.168.2.0 via VPN
#      192.168.3.0 via LAN
#
# Packets to/from 192.168.1.0/24 are marked with 0x1 and routed to ISP
# Packets to/from 192.168.2.0/24 are marked with 0x2 and routed to VPN
# Packets to/from 192.168.3.0/24 are routed to LAN and not forwarded onto
#                                    the internet
# 
#########################################################################

#
# Mangle Table
# This is the place where our markings happen, whether they be 0x1 or 0x2
#
*mangle

# Set default policies for table
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]

# Restore CONNMARK to the MARK (If one doesn't exist then no mark is set)
-A PREROUTING -j CONNMARK --restore-mark --nfmask 0xffffffff --ctmask 0xffffffff

# If packet MARK is 2, then it means there is already a connection mark and the
# original packet came in on VPN
-A PREROUTING -s 192.168.2.0/24 -m mark --mark 0x2 -j ACCEPT

# Check exception (this is a server which when accessed on a 192.168.2.0/24 address will go out the ISP table) are 0x1
#-A PREROUTING -s 192.168.2.0/24 -d <IP_OF_EXCEPTED_SERVER>/32 -m mark --mark 0x1 -j ACCEPT

# Mark packets coming from 192.168.2.0/24 are 0x2
-A PREROUTING -s 192.168.2.0/24 -j MARK --set-xmark 0x2/0xffffffff

# If packet MARK is 1, then it means there is already a connection mark and the
# original packet came in on ISP
-A PREROUTING -s 192.168.1.0/24 -m mark --mark 0x1 -j ACCEPT

# Mark packets 192.168.1.0/24 are 0x1
-A PREROUTING -s 192.168.1.0/24 -j MARK --set-xmark 0x1/0xffffffff

# Mark exception (this is a server which when accessed on a 192.168.2.0/24 address will go out the ISP table) as 0x1
#-A PREROUTING -s 192.168.2.0/24 -d <IP_OF_EXCEPTED_SERVER>/32 -j MARK --set-xmark 0x1/0xffffff

# Strip mark if packet is destined for modem.
-A PREROUTING -d 192.168.0.1/32 -j MARK --set-xmark 0x0/0xffffffff

# Strip mark if unknown bogon range to be blocked
-A PREROUTING -m set --match-set bogon-bn-nonagg dst -j MARK --set-xmark 0x0/0xffffffff

# Save MARK to CONNMARK (remember iproute can't see CONNMARKs)
-A PREROUTING -j CONNMARK --save-mark --nfmask 0xffffffff --ctmask 0xffffffff
COMMIT

#
# Filter Table
# This is where we decide to ACCEPT, DROP or REJECT things
#
*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]

# Create rule chain per input interface for forwarding packets
:FWD_ETH0 - [0:0]
:FWD_ETH1 - [0:0]
:FWD_PPP0 - [0:0]
:FWD_TUN0 - [0:0]

# Create rule chain per input interface for input packets (for host itself)
:IN_ETH0 - [0:0]
:IN_ETH1 - [0:0]
:IN_PPP0 - [0:0]
:IN_TUN0 - [0:0]

# Create a drop chain
:LOG_DROP - [0:0]

# Create a reject chain
:LOG_REJECT - [0:0]

# Create an output chain
:OUT_PPP0 - [0:0]
:OUT_TUN0 - [0:0]

# Pass input packet to corresponding rule chain
-A INPUT -i lo -j ACCEPT
-A INPUT -i eth0 -j IN_ETH0
-A INPUT -i eth1 -j IN_ETH1
-A INPUT -i ppp0 -j IN_PPP0
-A INPUT -i tun0 -j IN_TUN0

# Track forwarded packets
-A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

# Pass forwarded packet to corresponding rule chain
-A FORWARD -i eth0 -j FWD_ETH0
-A FORWARD -i eth1 -j FWD_ETH1
-A FORWARD -i ppp0 -j FWD_PPP0
-A FORWARD -i tun0 -j FWD_TUN0

# Pass output interface to corresponding chain
-A OUTPUT -o ppp0 -j OUT_PPP0
-A OUTPUT -o tun0 -j OUT_TUN0

# Forward traffic to Modem
-A FWD_ETH0 -d 192.168.0.1/32 -j ACCEPT

# Allow routing to remote address on VPN
-A FWD_ETH0 -s 192.168.1.0/24 -d 172.16.32.1/32 -o tun0 -j ACCEPT
-A FWD_ETH0 -s 192.168.2.0/24 -d 172.16.32.1/32 -o tun0 -j ACCEPT

# Allow forwarding from LAN hosts to LAN ONLY subnet
-A FWD_ETH0 -s 192.168.1.0/24 -d 192.168.3.0/24 -j ACCEPT
-A FWD_ETH0 -s 192.168.2.0/24 -d 192.168.3.0/24 -j ACCEPT

# Allow LAN ONLY subnet to contact other LAN hosts
-A FWD_ETH0 -s 192.168.3.0/24 -d 192.168.1.0/24 -j ACCEPT
-A FWD_ETH0 -s 192.168.3.0/24 -d 192.168.2.0/24 -j ACCEPT

# Refuse to forward bogons to the internet! eg 192.168.9.0/24 or 10.0.0.0
# or any other range which we are not using on our LAN
-A FWD_ETH0 -m set --match-set bogon-bn-nonagg dst -j LOG_REJECT

# Forward traffic to ISP
-A FWD_ETH0 -s 192.168.1.0/24 -j ACCEPT

# Forward traffic to VPN
-A FWD_ETH0 -s 192.168.2.0/24 -j ACCEPT

# Prevent 192.168.3.0/24 from accessing internet
-A FWD_ETH0 -s 192.168.3.0/24 -j LOG_REJECT

# Allow excepted server to be FORWARD to ppp0
#-A FWD_ETH0 -s 192.168.2.0/24 -d <IP_OF_EXCEPTED_SERVER>/32 -o ppp0 -j ACCEPT

# Forward SSH packets from network to modem
-A FWD_ETH1 -s 192.168.0.1/32 -d 192.168.1.0/24 -p tcp -m tcp --sport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A FWD_ETH1 -s 192.168.0.1/32 -d 192.168.2.0/24 -p tcp -m tcp --sport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Forward HTTP packets from network to mode
-A FWD_ETH1 -s 192.168.0.1/32 -d 192.168.1.0/24 -p tcp -m tcp --sport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A FWD_ETH1 -s 192.168.0.1/32 -d 192.168.2.0/24 -p tcp -m tcp --sport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Forward Bittorrent Port to workstation
-A FWD_TUN0 -d 192.168.2.30/32 -p tcp -m tcp --dport 6881:6889 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A FWD_TUN0 -d 192.168.2.30/32 -p udp -m udp --dport 6881:6889 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# SSH to Router
-A IN_ETH0 -s 192.168.1.0/24 -p tcp -m tcp --dport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A IN_ETH0 -s 192.168.2.0/24 -p tcp -m tcp --dport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# DNS to Router
-A IN_ETH0 -s 192.168.1.0/24 -p udp -m udp --dport 53 -m conntrack --ctstate NEW -j ACCEPT
-A IN_ETH0 -s 192.168.2.0/24 -p udp -m udp --dport 53 -m conntrack --ctstate NEW -j ACCEPT

# FreeRadius Client (eg a UniFi AP)
-A IN_ETH0 -s 192.168.3.10/32 -p tcp -m tcp --dport 1812 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A IN_ETH0 -s 192.168.3.10/32 -p udp -m udp --dport 1812 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Ubiquiti UAP Device Discovery Broadcast
-A IN_ETH0 -s 192.168.3.10/32 -p udp -m udp --dport 10001 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# NTP to Router
-A IN_ETH0 -s 192.168.1.0/24 -p udp -m udp --dport 123 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A IN_ETH0 -s 192.168.2.0/24 -p udp -m udp --dport 123 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A IN_ETH0 -s 192.168.3.0/24 -p udp -m udp --dport 123 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Accept traffic to router on both subnets
-A IN_ETH0 -s 192.168.1.0/24 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
-A IN_ETH0 -s 192.168.2.0/24 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Allow excepted server to be INPUT to eth0 from LAN
#-A IN_ETH0 -s 192.168.2.0/24 -d <IP_OF_EXCEPTED_SERVER>/32 -o ppp0 -j ACCEPT

# SSH To Modem from Router
-A IN_ETH1 -s 192.168.0.1/32 -d 192.168.0.0/30 -p tcp -m tcp --sport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# HTTP To Modem from Router
-A IN_ETH1 -s 192.168.0.1/32 -d 192.168.0.0/30 -p tcp -m tcp --sport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

# Deny bogons from ISP
-A IN_PPP0 -m set --match-set bogon-bn-nonagg src -j LOG_REJECT

# Accept incoming tracked PPP0 connection
-A IN_PPP0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

# Log dropped packets coming in on PPP0
-A IN_PPP0 -j LOG --log-prefix "DROP:INPUT " --log-level 6
-A IN_PPP0 -j LOG_DROP

# Accept traffic from IP on VPN (exception not a bogon)
-A IN_TUN0 -d 172.16.32.0/20 -j ACCEPT

# Accept incoming tracked TUN0 connection
-A IN_TUN0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

# Log dropped packets coming in on TUN0
-A IN_TUN0 -j LOG --log-prefix "DROP:INPUT " --log-level 6
-A IN_TUN0 -j LOG_DROP

# Log rejected packets
-A LOG_REJECT -j LOG --log-prefix "Rejected Bogon: " --log-level 6
-A LOG_REJECT -j REJECT --reject-with icmp-port-unreachable

# Deny bogons to ISP
-A OUT_PPP0 -m set --match-set bogon-bn-nonagg dst -j LOG_REJECT

# Allow traffic to IP on VPN (exception not a bogon)
-A OUT_TUN0 -d 172.16.32.0/20 -j ACCEPT

# Deny bogons to VPN
-A OUT_TUN0 -m set --match-set bogon-bn-nonagg dst -j LOG_REJECT
COMMIT

#
# NAT Table
# This is where translation of packets happens and "forwarding" of ports
# to specific hosts.
#
*nat
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]

# Port forwarding for Bittorrent
-A PREROUTING -i tun0 -p tcp -m tcp --dport 6881:6889 -j DNAT --to-destination 192.168.2.20
-A PREROUTING -i tun0 -p udp -m udp --dport 6881:6889 -j DNAT --to-destination 192.168.2.20

# Allows routing to our modem subnet so we can access the web interface
-A POSTROUTING -s 192.168.1.0/24 -d 192.168.0.1/32 -o eth1 -p tcp -m tcp --dport 80 -j MASQUERADE
-A POSTROUTING -s 192.168.2.0/24 -d 192.168.0.1/32 -o eth1 -p tcp -m tcp --dport 80 -j MASQUERADE

# Allows hosts of the network to use the VPN tunnel
-A POSTROUTING -o tun0 -j MASQUERADE

# Allows hosts of the network to use the PPP tunnel
-A POSTROUTING -o ppp0 -j MASQUERADE
COMMIT

Other Tips

lbu cache

Configure lbu cache so that you don't need to download packages when you restart your router eg Local APK cache

This is particularly important as some of the images do not contain ppp-pppoe. This might mean you're unable to get an internet connection to download the other packages on boot.

lbu encryption /etc/lbu/lbu.conf

In /etc/lbu/lbu.conf you might want to enable encryption to protect your VPN keys.

# what cipher to use with -e option
DEFAULT_CIPHER=aes-256-cbc

# Uncomment the row below to encrypt config by default
ENCRYPTION=$DEFAULT_CIPHER

# Uncomment below to avoid <media> option to 'lbu commit'
# Can also be set to 'floppy'
LBU_MEDIA=mmcblk0p1

# Set the LBU_BACKUPDIR variable in case you prefer to save the apkovls
# in a normal directory instead of mounting an external media.
# LBU_BACKUPDIR=/root/config-backups

# Uncomment below to let lbu make up to 3 backups
# BACKUP_LIMIT=3

Remember to set a root password, by default Alpine Linux's root account is passwordless.

passwd root

Backup apkprov

It's a good idea to back up your apk provision file. You can pull it off your router to your local workstation with:

scp -r root@192.168.2.1:/media/mmcblk0p1/<YOUR HOST NAME>.apkovl.tar.gz.aes-256-cbc ./

And decrypt it with:

openssl enc -d -aes-256-cbc -in <YOUR HOST NAME>.apkovl.tar.gz.aes-256-cbc -out <YOUR HOST NAME>.apkovl.tar.gz

It can be encrypted with:

openssl aes-256-cbc -salt -in <YOUR HOST NAME>.apkovl.tar.gz -out <YOUR HOST NAME>.apkovl.tar.gz.aes-256-cbc

Harden SSH

Generate a SSH key

ssh-keygen -t rsa -b 4096

You will want to put the contents of id_rsa.pub in /etc/ssh/authorized_keys

You can put multiple public keys on multiple lines if more than one person has access to the router.

/etc/ssh/sshd_config

A couple of good options to set in here can be:

ListenAddress 192.168.1.1
ListenAddress 192.168.2.1

While this isn't usually a good idea, a router doesn't need more than one user.

PermitRootLogin yes

The most important options:

RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile  /etc/ssh/authorized_keys
PasswordAuthentication no
PermitEmptyPasswords no
AllowTcpForwarding no
X11Forwarding no

/etc/conf.d/sshd

You will want to add

rc_need="net"

This instructs OpenRC to make sure the network is up before starting ssh.


Finally add sshd to the default run level

rc-update add sshd default

References