AccessPoint

Revision as of 06:59, 5 June 2008

Introduction

FreeBSD is very well suited for use as a wifi access point as it has 'master mode' support for a variety of wifi network cards, out of the box. Some of these include ralink and Atheros cards.

There are many difficulties setting up a wireless network access point on linux. Some of the problems(with non madwifi cards) include:

• You must use a kernel that is yet-to-be released (2.6.26-rc4).
• You must patch the kernel. Download Patch
• You must compile a recent libnl(I used libnl-1.1-r1, on Gentoo) against the custom kernel.
• On Gentoo you need to copy nl80211.h from your kenrel directory to /usr/include/linux
• Finally, you need to compile a git version of hostapd...

All of the above steps must be completed for maximum support of various wireless network cards. Most other sets are fairly similar to those on FreeBSD.

On this Howto we will assume that your modem gives you a dhcp address,see AccessPoint using pppoe if you need to setup PPPOE

The hardware

For my setup, and the instructions included here, I used:

• 2 Realtech PCI 10/100 cards, on FreeBSD. These cards are recognized as rl0 and rl1. (Perhaps there is the possibility to use interfaces aliasing, but as i had 2 cards...)
• 1 Ralink rt2500 PCI card, on FreeBSD. This card is recognized as ral0.

Installation and Configuration

• Install FreeBSD as usual. This example uses FreeBSD 7.0.
• Enable ssh logins during the installation, or add the following line to your /etc/rc.conf:

sshd_enable="YES"

• If you have a DHCP-enabled modem, you can add the following to your /etc/rc.conf:

ifconfig_rl0="DHCP"

Note, make certain you replace rl0 with your wired network interface name.

Wireless

To configure the wireless card, the following commands need to be executed:

ifconfig ral0 inet 192.168.1.1 netmask 255.255.255.0 ssid freebsdap mediaopt hostap channel 4

Note that, in the FreeBSD Handbook, inet is placed incorrectly. Also, make certain to include a channel number. Without it, I was unable to get this working.

Next, try to associate to the new AP from a client. If something goes wrong (i.e. ping doesn't work), look to dmesg for debugging output. Specifically, look for association messages.

Finally, if you can see the wireless network, and can ping it, simply add the following to /etc/rc.conf:

ifconfig_ral0="inet 192.168.1.1 netmask 255.255.255.0 ssid freebsdap mediaopt hostap channel 4"

Useful Association Commands

Under GNU/Linux type as root(remplacing wlan0 by your wifi card interface name):

ifconfig wlan0 up
 iwlist wlan0 scan
 iwconfig wlan0 essid "freebsdap"
 ifconfig wlan0 192.168.1.100 netmask 255.255.255.0
 ping 192.168.1.1

Under FreeBSD type as root(remplacing ral0 by your wifi card interface name):

ifconfig ral0 up
 ifconfig ral0 list scan
 ifconfig ral0 inet 192.168.1.100 netmask 255.255.255.0 ssid freebsdap
 ping 192.168.1.1

DNS and DHCP

Once the wireless AP is working, we can install DNS and DHCP servers. For simplicity, we will use dnsmasq. As root, execute the following command:

cd /usr/ports/dns/dnsmasq && make config && make install

On the configuration menu, deselect the followingn options:

• ipv6
• dbus

Once installed, we need to configure dnsmasq:

Edit /usr/local/etc/dnsmasq.conf with your favorite editor and add the following:

# filter what we send upstream
domain-needed
bogus-priv
filterwin2k
localise-queries
 
# allow /etc/hosts and dhcp lookups via *.lan
local=/lan/
domain=workgroup
expand-hosts
#resolv-file=/tmp/resolv.conf.auto
 
dhcp-authoritative
#dhcp-leasefile=/tmp/dhcp.leases
 
# use /etc/ethers for static hosts; same format as --dhcp-host
# <hwaddr> <ipaddr>
read-ethers
 
# other useful options:
# default route(s):
dhcp-option=3,192.168.1.1
#    dns server(s):
dhcp-option=6,192.168.1.1

dhcp-range=192.168.1.100,192.168.1.255,255.255.255.0,12h

The option, read-ethers, permits you to assign statics IPs to certain MAC addresses. Edit /etc/ethers with entries as follows:

00:14:85:11:EF:02 192.168.1.106

In order to give a DNS name to this entry, edit /etc/hosts and add an entry like this:

192.168.1.106 Ralink

To start your dnsmasq server at boot, add the following to /etc/rc.conf:

dnsmasq_enable="YES"

You can now test the wifi connection with any graphical tool (like NetworkManager in GNU/linux or even test it with a windows computer) you can even try to ping a website... but you will only get his ip and no response...that's because we didn't set up the NAT yet...

Nat and firewall

in order to set the nat we will add this to /etc/rc.conf:(remplacing ral0 by your wired card(that is connected to the internet) interface name)::

gateway_enable="YES"
firewall_enable="YES"
firewall_type="OPEN"
natd_enable="YES"
natd_interface="rl0"
natd_flags=""

if you wish to redirect ports add this to natd_flags="" in /etc/rc.conf:

-redirect_port tcp 192.168.0.6:80 80

now normally the access point should work...

OpenVPN

Introduction

now that we have wireless we could choose between theses choices:

• having a full open wireless(not great for security)
• having a wpa wireless(not compatible with all drivers,devices doesn't always work),no guests...
• having an open wireless while encrypting the data sent to to wireless access point...yes that is possible...with the help of openvpn

i chose the third possibility.

installation

here the commands to run in order to install openvpn:

cd /usr/ports/security/openvpn
make
make install

configuration

EasyRsa

install bash:

cd /usr/ports/shells/bash
make
make install
ln -s /usr/local/bin/bash /bin/bash 

run theses commands:

cp -r /usr/local/share/doc/openvpn/easy-rsa/2.0/ /root/easy-rsa-2.0

here we will copy it in order not to have our keys erased by an update... then we will need bash run:

/bin/bash
cd /root/easy-rsa-2.0

then we will make the certificates: modify the vars script in order to suit your needs,then run:

source ./vars
./clean all
./build-ca ca

then we will build the server key:

./build-key-server server

then we will build the clients key:

./build-key client1
./build-key client2

then we genreate diffie helman parameters:

./build-dh

in order to build a new client just do:

source ./vars
./build-key client2

then copy the keys at the keys location:

cp -r keys /usr/local/etc/openvpn/keys

alternatively you can do the following:

mkdir /usr/local/etc/openvpn/keys/
cd /root/easy-rsa-2.0/keys
cp ca.crt /usr/local/etc/openvpn/keys/ca.crt
cp server.crt /usr/local/etc/openvpn/keys/server.crt
cp server.key /usr/local/etc/openvpn/keys/server.key
cp dh1024.pem /usr/local/etc/openvpn/keys/dh1024.pem

OpenVpn configuration

We will first install all in test-mode that is to say not runnning at the boot,not running as daemon etc... we will run theses commands:

ifconfig tap0 destroy
ifconfig bridge0 destroy
ifconfig tun0 destroy
ifconfig bridge0 create
ifconfig tap0 create
#remplace ral0 by your card interface name
ifconfig bridge0 addm ral0 addm tap0 up
ifconfig br0 192.168.1.1

then here's my server configuration for openvpn:

ca /usr/local/etc/openvpn/keys/ca.crt
cert /usr/local/etc/openvpn/keys/server.crt
key /usr/local/etc/openvpn/keys/server.key
dh /usr/local/etc/openvpn/keys/dh1024.pem
dev tap
# replace 10.0.0.1 with the VPN IP
server-bridge 10.0.0.1 255.255.255.0 10.0.0.2 10.0.0.250
keepalive 10 120
client-to-client
verb 3
duplicate-cn
push "route-gateway 10.0.0.1"
push "dhcp-option DNS 10.0.0.1" # push DNS entries to openvpn client

here we push the gateway to the client...i also tried to push the dns in /etc/resolv.conf but it didn't work and here's my client configuration(ubuntu GNU/Linux):

remote 192.168.1.1
client
dev tap
nobind
tls-client
ca /home/ubu/ca.crt
cert /home/ubu/ubu.crt
key /home/ubu/ubu.key
pull
verb 4
remote-cert-tls server
#auth-user-pass

in order to make it work do this on the server:

/usr/loca/sbin/openvpn server.conf
ifconfig tap0 10.0.0.1

on the client:

openvpn client.conf
route del default
route add default gw 10.0.0.1 tap0
redirect-gateway

here redirect-gateway pull the default gateway from the openvpn server if you put wireshark on the client's wireless interface you'll see only udp packet from and to the openvpn port...so it works...

in order to make our openvpn start at boot we will add this to /etc/rc.conf:

#openvpn
cloned_interfaces="bridge0 tap0"
autobridge_interfaces="bridge0"
autobridge_bridge0="tap0 ral0"
openvpn_if="tap"
openvpn_enable="YES"
openvpn_configfile="/usr/local/etc/openvpn/openvpn.conf"
ifconfig_tap0="inet 10.0.0.1 netmask 255.255.255.0"
ifconfig_bridge0="inet 192.168.1.1 netmask 255.255.255.0"

so here's our final rc.conf:

# -- sysinstall generated deltas -- # Mon Oct  6 04:45:53 2008
# Created: Mon Oct  6 04:45:53 2008
# Enable network daemons for user convenience.
# Please make all changes to this file, not to /etc/defaults/rc.conf.
# This file now contains just the overrides from /etc/defaults/rc.conf.
keymap="us.iso"
sshd_enable="YES"
ifconfig_rl0="DHCP"
ifconfig_ral0="inet 192.168.1.1 netmask 255.255.255.0 ssid freebsdap mediaopt hostap channel 4"
gateway_enable="YES"
firewall_enable="YES"
firewall_type="OPEN"
natd_enable="YES"
natd_interface="rl0"
natd_flags=""
#defaultrouter="192.168.1.1"
dnsmasq_enable="YES" 

#openvpn
cloned_interfaces="bridge0 tap0"
autobridge_interfaces="bridge0"
autobridge_bridge0="tap0 ral0"
openvpn_if="tap"
openvpn_enable="YES"
openvpn_configfile="/usr/local/etc/openvpn/openvpn.conf"
ifconfig_tap0="inet 10.0.0.1 netmask 255.255.255.0"
ifconfig_bridge0="inet 192.168.1.1 netmask 255.255.255.0"