UbuntuHelp:VPNServer
来自Ubuntu中文
 |
点击翻译: |
English |
请不要直接编辑翻译本页，本页将定期与来源同步。 |
Parent page: Internet and Networking
Securing a small Wireless network using VPN
TODO: this document should be split into VPN and wireless specific parts.
Summary
While Wifi encryption generally provides a first protective layer for a wireless network, it is far from being perfect:
- WEP is still widely used and must be considered as very insecure
- WPA can also be broken (it requires more efforts), and many devices are still not WPA-enabled
This document intends to provide a complementary approach to secure a wireless network, by using an additional encryption level using a Virtual Private Network (VPN). It is assumed that the reader understands basic IP networks routing and Linux system administration. However, in an attempt to widen the audience to non-experts, this document will not cover many technical aspects of VPN.
This document contains instructions to setup a routed VPN using a static key, which will work with one client only. Multiple-clients setup requires a public key infrastructure (PKI), which is slightly more complex, and is not treated here.
Routing
Ideally, the wireless access point, as well as the Wifi machine, have no direct Internet access. It should be connected to the VPN server, so that all the routing can be handled by the router. In practice, the VPN server would be connected to the LAN_SUBNET with one network interface, and to the wireless access point with another network interface. It is highly recommended to configure different subnets for these two interfaces.
In the document, the network topology is expected to look like:
[WIFI_MACHINE]----(WIFI)---->[WIRELESS_ACCESS_POINT]----(LAN)---->[VPN_SERVER]----->INTERNET (potentially via a local gateway)
Example:
- The Internet gateway: eth0 inet adr:192.168.0.10 bcast:192.168.0.255 (LAN_SUBNET)
- The VPN server: eth0 inet adr:192.168.0.1 bcast:192.168.0.255 (LAN_SUBNET)
- The VPN server: eth1 inet adr:192.168.1.1 bcast:192.168.1.255 (WIFI_SUBNET)
- The wireless access point: eth0 inet adr:192.168.1.2 bcast:192.168.1.255 (WIFI_SUBNET)
- Wifi machine (SYSTEM): eth0 inet adr:192.168.1.3 bcast:192.168.1.255 (WIFI_SUBNET)
The following iptables configuration could be installed on the VPN server to route the traffic:
*filter :INPUT DROP [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -i lo -p all -j ACCEPT -A INPUT -p all -m state --state RELATED,ESTABLISHED -j ACCEPT -A FORWARD -d LAN_SUBNET -j DROP -A INPUT -i tun+ -j ACCEPT -A FORWARD -i tun+ -j ACCEPT -A INPUT -p udp --dport 1194 -j ACCEPT -A INPUT -s LAN_SUBNET -p all -j ACCEPT -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT COMMIT
Configuring OpenVPN
Setting up the server
- Install OpenVPN
Install the following package: openvpn (see InstallingSoftware).
- Generate a shared static key
cd /etc/openvpn/ && /usr/sbin/openvpn --genkey --secret static.key
- Comment all the lines from /etc/default/openvpn, and add:
AUTOSTART="openvpn"
- Populate the configuration file /etc/openvpn/openvpn.conf with:
dev tun local 192.168.1.1 ifconfig 10.1.0.1 10.1.0.2 up ./office.up secret static.key ping 15 tun-mtu 1200 mssfix 1400 verb 3
- /etc/openvpn/office.up should be executable and contain:
route add -net 10.0.1.0 netmask 255.255.255.0 gw $5
- Finally, we can complete the routing for the wireless network in the iptables configuration:
*nat
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A POSTROUTING -s VPN_CLIENT -o eth0 -j MASQUERADE
COMMIT
- Start the OpenVPN service:
/etc/init.d/openvpn start
Setting up the client
- Install OpenVPN
apt-get install openvpn
- Copy the static key /etc/openvpn/static.key to the client system in /etc/openvpn.
- Comment all the lines from /etc/default/openvpn, and add:
AUTOSTART="openvpn"
- Populate the configuration file /etc/openvpn/openvpn.conf with:
dev tun local 192.168.1.3 remote 192.168.1.1 nobind ifconfig 10.1.0.2 10.1.0.1 up ./home.up down ./home.down secret static.key ping 15 tun-mtu 1200 mssfix 1400 verb 3
- /etc/openvpn/home.up should be executable and contain:
route add -net 10.0.0.0 netmask 255.255.255.0 gw $5 route add -net 0.0.0.0 netmask 0.0.0.0 dev tun0 route del -net 0.0.0.0 netmask 0.0.0.0 dev eth0
- /etc/openvpn/home.down should be executable and contain:
route add -net 0.0.0.0 netmask 0.0.0.0 dev eth0
- Start the OpenVPN service:
/etc/init.d/openvpn start
- If the following ping commands do not return an error, it worked!
ping 10.1.0.1 ping 10.1.0.2
