Blog Inforeseau.com – Alexandre Blanc Cyber Security

Using raspberry pi 3 as wifi bridge and repeater and firewall

Hi again,

following my raspberry 3 router project (https://blog.inforeseau.com/2018/06/raspberry-3-point-dacces-wifi-avec-filtrage-pub-tracking-access-point-add-tracking-filtering) and the repeater project (https://blog.inforeseau.com/2019/01/raspberry-3-create-a-wifi-repeater-with-usb-wifi-dongle) , i decided to fork these into a wifi repeater and bridge.

The goal is to use this approach in hotels or public wifi, where you wish to use your own router with its pi-hole and firewall. Any device connected behind the raspberry, will be hidden behind a totally blocking firewall.

So, let’s make it simple, i assume you took the image of the router project : https://blog.inforeseau.com/2018/06/raspberry-3-point-dacces-wifi-avec-filtrage-pub-tracking-access-point-add-tracking-filtering
I also assume you have the needed hardware ( a raspberry 3 and a wifi adapter like the canakit or panda as recommended into the linked original post)

You then replace the file /etc/rc.local (available as zip file here rc.local ) in the SD CARD rootfs partition, by the following one, in which you customize the following values :
wifissid which is your access point name, the SSID on which you will connect
wifipass which is the password you’ll have to use to this access point
existingwifissid which is the existing wifi on which the raspberry will connect to (the hotel or public wifi SSID)
existingwifipass which is the existing password of the wifi on which the raspberry will connect to (the hotel or public wifi password)

[bash]#!/bin/sh
# removed -e option above, because below command returns some warnings that must be ignored
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
printf "My IP address is %s\n" "$_IP"
fi

# Create Access point wifi raspap other USB adapter
#/usr/bin/create_ap --isolate-clients --daemon --ieee80211n --ht_capab '[HT40+]' -c 44 -w 2 wlxe84e0651e6f6 enxb827eb9446d8 raspappriv welcomepriv2

#in this version, we connect to wan through wifi, so the onboard ethernet will be another LAN
onboardlan=`/root/get-nic.sh`
#since we'll connect to an existing wifi
#if using panda wifi, device is called wlan1, if using canakit, device is called wlx......
#we need to know if we have a wlan1
iswlan1=`/sbin/ifconfig -a|/bin/grep wlan1`;
#defining USB wifi interface name
if [ ! -z "${iswlan1}" ]; then
onboardwan="wlan1"
else
#we need to extract it
onboardwan=`/sbin/ifconfig -a|/bin/grep wlx|/usr/bin/awk -F ":" '{print $1}'`;
fi

#using the canakit wifi, only 2.4Ghz is supported, check before entering SSID in here
existingwifissid="my-wifi-ssid"
existingwifipass="my-wifi-password"
#we make sure default wpa-supplicant is empty
/bin/echo "" > /etc/wpa_supplicant/wpa_supplicant.conf
#we now create the one we need to be used with wlan1
#cleanup of the file
/bin/echo "" > /home/pi/wpa_supplicant.conf
#Populate the file
/bin/echo "ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev" > /home/pi/wpa_supplicant.conf
/bin/echo "update_config=1" >> /home/pi/wpa_supplicant.conf
/bin/echo "network={" >> /home/pi/wpa_supplicant.conf
/bin/echo 'ssid="'${existingwifissid}'"' >> /home/pi/wpa_supplicant.conf
/bin/echo 'psk="'${existingwifipass}'"' >> /home/pi/wpa_supplicant.conf
/bin/echo "}" >> /home/pi/wpa_supplicant.conf
#initiate wifi connection
/bin/echo "" > /home/pi/start-wifi.sh
/bin/echo "#!/bin/bash" >> /home/pi/start-wifi.sh
/bin/echo "/sbin/wpa_supplicant -B -c/home/pi/wpa_supplicant.conf -i${onboardwan} -Dnl80211,wext" >> /home/pi/start-wifi.sh
/bin/chmod +x /home/pi/start-wifi.sh;
/home/pi/start-wifi.sh &

#Identify an other NIC in the raspberry (USB plugged one, to be used as LAN, aside of wifi)
usbnic=`/root/get-2nd-nic.sh`

#Force dhcp on interface
/sbin/dhclient ${onboardwan}

#update the NIC interface in the pi-hole config
#drop interface (last line)
/bin/cat /etc/dnsmasq.d/01-pihole.conf| grep -v interface > /root/01-pihole.conf.tmp
#update file without interface
/bin/cat /root/01-pihole.conf.tmp > /etc/dnsmasq.d/01-pihole.conf
#Add interface
/bin/echo "interface="${onboardwan} >> /etc/dnsmasq.d/01-pihole.conf

#restart the service
#systemctl restart dnsmasq

#Define wifi SSID
wifissid="raspappriv"

#Define wifi password
wifipass="welcomepriv2"

#Define wifi ip-net /24 by default
wifinetip="192.168.12.1"
# For home we keep subnet isolated (no bridge) to be able to force web filtering via pi-hole and we allow communication between devices (default IP for the AP is 192.168.12.1 and we run a pi-hole on it for DNS fo we force DNS server to be itself) using embedded wifi
/usr/bin/create_ap --daemon --dhcp-dns ${wifinetip} --ieee80211n --ht_capab '[HT20+]' -c 11 -w 2 wlan0 ${onboardwan} ${wifissid} ${wifipass}

#Now we want to protect the connected interface assuming this is WAN, and nothing from there should come in
#create_ap brings its own rules already
#I accept only packets that were initiated by the device
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
#If you want to allow ping from outside to your device, uncomment below
#iptables -A INPUT -p icmp -j ACCEPT
#We fix slowlyness due to pi-hole as explained here : https://pi-hole.net/2018/02/02/why-some-pages-load-slow-when-using-pi-hole-and-how-to-fix-it/
iptables -A INPUT -p tcp --destination-port 443 -j REJECT --reject-with tcp-reset
iptables -A INPUT -p udp --destination-port 80 -j REJECT --reject-with icmp-port-unreachable
iptables -A INPUT -p udp --destination-port 443 -j REJECT --reject-with icmp-port-unreachable
#If you want to route/NAT a port from outside to an internal machine (which has static IP or reserved IP in /root/udhcpd.conf.master like 192.168.12.200 for the example below) to export a service (if you host nextcloud on a machine in your lan and want to make it available) :
#iptables -t nat -A PREROUTING -j DNAT -i ${onboardwan} -p tcp --dport 9443 --to-destination 192.168.12.200:9443

#now, while your service above is available from outside, like https://your-public-ip:9443, it is sadly not responding from internal wifi, so we allow it as well this way
#iptables -t nat -A PREROUTING -j DNAT -i wlan0 -p tcp --deport 9443 --to-destination 192.168.12.200:9443

#if you want to allow SSH to your device from outside (be careful, you'll get a lot of dictionary attacks and hacking attempts), you may want to uncomment below to open port 22 from outside
#iptables -A INPUT -p tcp -m state --state NEW -m tcp --deport 22 -j ACCEPT

#If we have a second interface (usbnic) then, we assign an IP to it, and we start dhcp server, and add propoer firewall rules
if [ ! -z "${usbnic}" ]; then
#we have an USB NIC, we set it up to handle the LAN connections as well
#defining IP
/sbin/ifconfig ${usbnic} 192.168.13.1 netmask 255.255.255.0 broadcast 192.168.13.255
#starting dhcp server on it
#copy the master config file as base (no interface designed)
/bin/cp /root/udhcpd.conf.master /root/udhcpd.conf
#adding the proper interface
/bin/echo "interface ${usbnic}">>/root/udhcpd.conf
#sending DNS request to the pi-hole on pi-hole proper IP
iptables -t nat -A PREROUTING -j DNAT -i ${usbnic} -p tcp --dport 53 --to-destination ${wifinetip}:5353
iptables -t nat -A PREROUTING -j DNAT -i ${usbnic} -p udp --dport 53 --to-destination ${wifinetip}:5353
#Assuming you opened the port 9443 above on wan and wifi, you also want, if connected your LAN machines to be able to access the service, so you would uncomment
#iptables -t nat -A PREROUTING -j DNAT -i ${usbnic} -p tcp --dport 9443 --to-destination 192.168.12.200:9443
#allow ip forward from this LAN
iptables -A FORWARD -s 192.168.13.0/24 -i ${usbnic} -j ACCEPT
#We NAT the traffic from this LAN
iptables -t nat -A POSTROUTING -s 192.168.13.0/24 -j MASQUERADE
#starting udhcpd
/usr/sbin/udhcpd -S /root/udhcpd.conf

fi

####################
#Because we use the WIFI as WAN, we can use the onbard NIC ($onboardlan) as second LAN CARD
####################
#configure onboard LAN IP
/sbin/ifconfig ${onboardlan} 192.168.15.1 netmask 255.255.255.0 broadcast 192.168.15.255
#create dedicated dhcp server config file
/bin/echo "" > /root/udhcpd2.conf
/bin/echo "start		192.168.15.10" >> /root/udhcpd2.conf
/bin/echo "end		192.168.15.254" >> /root/udhcpd2.conf
/bin/echo "lease_file	/var/lib/misc/udhcpd2.leases" >> /root/udhcpd2.conf
/bin/echo "pidfile	/var/run/udhcpd2.pid" >> /root/udhcpd2.conf
/bin/echo "opt	dns	192.168.15.1" >> /root/udhcpd2.conf
/bin/echo "option	subnet	255.255.255.0" >> /root/udhcpd2.conf
/bin/echo "opt	router	192.168.15.1" >> /root/udhcpd2.conf
/bin/echo "option	domain	local" >> /root/udhcpd2.conf
/bin/echo "option	lease	864000" >> /root/udhcpd2.conf
/bin/echo "# Static leases map" >> /root/udhcpd2.conf
/bin/echo "#static_lease 00:60:08:11:CE:4E 192.168.15.54" >> /root/udhcpd2.conf
/bin/echo "#static_lease 00:60:08:11:CE:3E 192.168.15.44" >> /root/udhcpd2.conf
/bin/echo "interface ${onboardlan}" >> /root/udhcpd2.conf
iptables -t nat -A PREROUTING -j DNAT -i ${onboardlan} -p tcp --dport 53 --to-destination ${wifinetip}:5353
iptables -t nat -A PREROUTING -j DNAT -i ${onboardlan} -p udp --dport 53 --to-destination ${wifinetip}:5353
iptables -A FORWARD -s 192.168.15.0/24 -i ${onboardlan} -j ACCEPT
iptables -t nat -A POSTROUTING -s 192.168.15.0/24 -j MASQUERADE
/usr/sbin/udhcpd -S /root/udhcpd2.conf

#If you decided to open the port for your service on 9443 above (NAT), you need to accept it on the router too, so uncomment below
#iptables -A INPUT -p tcp -m tcp --dport 9443 -j ACCEPT

#I refuse any connection otherwise
iptables -A INPUT -i ${onboardwan} -j DROP

#We also load all the iptables helpers modules
/sbin/modprobe ip_nat_ftp nf_conntrack_netbios_ns xt_conntrack xt_multiport ip_nat_sip ip_conntrack_sip nf_conntrack_ftp nf_nat_ftp

exit 0[/bash]

Then, when the raspberry boots, it will connect to the existing wifi with the information you’ve configure in the file, and will broadcast your own SSID.
You’ll also be able to connect a device on the LAN port, AND the USB LAN adapter if you have the one used for the router project. It means, 2 clients in ethernet (or more if using a switch) and wifi.

From there, you may consider the use of a VPN on the raspberry itself, yet to be tested, i’ll add comments later on, planning to test sshuttle, openvpn (compatibles with protonvpn), and potentially expressvpn. All are working, just to be tested against existing iptables rules basically.

As usual, this is a post to keep a track, and it should work for you as well.

Raspberry 3 – create a wifi repeater with USB wifi dongle

Updated on 2019 Jan 11 – tested and working from scratch

What you need to do this :

You need a raspberry pi 3 or raspberry pi 3 B+ if you want to handle wifi 5Ghz.
We need an extra wifi adapter (panda 005 or canakit wifi or any kernel supported adapter) – listed below are 2.4Ghz only
https://www.amazon.ca/gp/product/B00EQT0YK2/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
https://www.amazon.ca/CanaKit-Raspberry-Wireless-Adapter-Dongle/dp/B00GFAN498/ref=sr_1_4?s=electronics&ie=UTF8&qid=1546365634&sr=1-4&keywords=raspberry+pi+wifi
or that
https://www.canakit.com/raspberry-pi-wifi.html

What you need to do then

Deploy original raspbian lite on it (this is a network management device, we don’t want or need a GUI on it). SSH to it or connect on the raspberri pi itself. User pi, password raspberry, sudo bash to be root.

Update the system and install requirements as follow :

apt-get update
apt upgrade
apt-get update
 apt-get install git bash util-linux procps hostapd iproute2 iw haveged dnsmasq iptables vim
 git clone https://github.com/oblique/create_ap
 cd create_ap/
 make install
 cd ..

The above does apply all the latest updates, and clone the create_ap script that allows easy wifi access point creation.

You might want to change keyboard layout, which by default is UK. I do use US layout, so to change, run « raspi-config » -> « 4 – Localisation Options » -> « I3 – change keyboard layout » -> »Generic 103… » -> « Other » -> « English (US) » -> « ok » -> « default » -> « ok » -> « no compose key » -> « ok » -> « finish »
(use TAB to switch between buttons)

We want to handle wpa_supplicant manually, because otherwise we can’t assign proper interface. There is a configuration menu on the raspi-config command, but this is NOT what we want. The default wpa_supplicant use any of the wifi adapters to connect, sometime both. But in our case, we want 1 connected, and 1 access point.

mv /etc/wpa_supplicant/wpa_supplicant.conf /home/pi/wpa_supplicant.conf

Content of wpa_supplicant.conf have to be :

 ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
 update_config=1

network={
     ssid="yourexistingwifi"
     psk="existingwifipassword"
 }

In the above, you have to put the SSID of your main / existing wifi, and the password of it as psk. This will allow the raspberry to connect to this network with 1 of its adapters.

We then create a little script that will do what wee need. Create the file /home/pi/start-relaywifi.sh with the following content :

#!/bin/bash
wpa_supplicant -B -c/home/pi/wpa_supplicant.conf -iwlan0 -Dnl80211,wext
 create_ap -g 172.20.0.1 -c 10 -w 2 wlan1 wlan0 relaywifi relaywifipassword

The above use the wlan0 interface to connect to your existing wifi (using most likely the onboard wifi of the raspberry), and the second line create an access point on the second wifi adapter (the USB one) that shares the connection of the first one.

We then set this to be called at boot from /etc/rc.local by adding the following lines before the last line of rc.local :

 /home/pi/start-relaywifi.sh

We then set the executable bit on our little script :

chmod +x /home/pi/start-relaywifi.sh

All good. Reboot the pi, and it should :

Boot raspbian, execute rc.local which call our script, connect to existing wifi, and appear as access point.

Sidenote : The onboard wifi driver does not support full A/P or bridging mode. Therefore, the extended wifi is using its own IP range, which must be different from the main one.
The IP range used in this example is 172.20.0.x, but you can pick any private IP range and adjust the create_ap command accordingly.
Device on extended wifi can speak to the main wifi, but main most likely won’t be able to see the devices on extended. If you have a printer, or so, it should be on the one.
If you want this to happen you should :
– reserve an IP on your main wifi for the raspberry MAC, so as it always gets the same IP
– add a route on your main router, that state, network 172.20.0.x can be reached via IP-YOU-RESERVED for the raspberry
I won’t go more in details, since the point was to get wifi network extended, and connect your wifi devices from bigger range.

I might add french later one, and will test this and adjust if need be, as i said, i have it running, but did not redo everything from scratch :D

Happy new year 2019 :D