OpenWRT: Setup PPTP VPN Server

Sumber: http://wiki.openwrt.org/doc/howto/vpn.server.pptpd

Paket yang Dibutuhkan

opkg install pptpd kmod-mppe
/etc/init.d/pptpd enable
/etc/init.d/pptpd start

pptpd akan jalan, dan akan jangan saat boot. Tambahkan user ke /etc/ppp/chap-secrets (caranya di terangkan di bawah). Pilihan lain, tambahkan proxyarp ke /etc/ppp/options.pptpd. Kemudian coba connect dari client.

Kernel module kmod-mppe dibutuhkan untuk enkripsi. Jika kita menggunakan source code trunk, kita perlu mengupdate firmware ke yang paling akhir sebelum menginstalasi kernel module. Karena kernel kadang berubah, sehingga module reposirory di trunk tidak cocok dengan kernel yang lama.

OpenWrt Generic

Instruksi ini berlaku umum untuk semua versi OpenWRT.

Konfigurasi

Default IP address dari ujung server dari tunnel adalah 172.16.1.1, ini di set di file /etc/ppp/options.pptpd, dengan diakhiri titik dua , seperti:

172.16.1.1:

Ubah ini menjadi IP address LAN anda jika kita ingin menggunakan IP VPN yang berbeda. Tidak perlu me-restart pptpd jika kita mengubah parameter ini.

Set agar client menggunakan DNS Server tertentu

ms-dns 8.8.8.8   
ms-dns 8.8.4.4

Untuk mengalokasikan lokal IP adress pada sisi server dari tunnel, gunakan opsi localip di /etc/pptpd.conf. Contoh :

localip 172.16.1.1

Cara paling mudah untuk mengakses LAN adalah memastikan localip dalam range IP LAN. Untuk memberikan IP address secara dinamik ke client, kita dapat menambahkan kalimat berikut :

remoteip 172.16.1.100-109

Tunnel Remote IP Address

Tambahkan kalimat ke /etc/ppp/chap-secrets untuk setiap client. Formatnya adalah:

username provider password ipaddress

Tambahkan IP address untuk setiap client. Contoh chap-secrets sebagai berikut :

vpnuser pptp-server vpnpassword 172.16.1.2

Agar user VPN memperoleh IP dinamik, gunakan

vpnuser pptp-server vpnpassword *

Ketik man pppd di shell untuk memperoleh informasi lebih lanjut tentang file ini. Perhatikan bahwa nama provider ada di /etc/ppp/options.pptpd. default adalah pptp-server.

/!\ If you have x-wrt installed and use it to edit the chap-secrets file, it will create every entry with the provider of pptpd. Also, every time the router is rebooted the file will be rewritten so that the provider is pptpd. The easiest way to deal with this is to set the default provider in /etc/ppp/options.pptpd to pptpd.

/!\ For the bin and pptp builds of OpenWrt, the file will start out being a symbolic link to a template in /rom, so remove the link, copy the template, and make sure it is chmod 600.

/!\ It is important to set an IP address rather than use the default asterisk. If you use an asterisk, the peer may propose it's own address, which could cause a routing loop. This results in very large transmit counters on ifconfig ppp0 and a badly performing router, as it spends all it's time trying to move packets through the loop.

Firewall

For your security OpenWrt will ignore connections on the WAN interface, but accept connection from a client on the LAN or wireless interfaces. If your client is to connect on the WAN interface, edit the /etc/firewall.user file and add the following:

iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 1723 -j ACCEPT
iptables        -A input_rule      -i $WAN -p tcp --dport 1723 -j ACCEPT
iptables        -A output_rule             -p 47               -j ACCEPT
iptables        -A input_rule              -p 47               -j ACCEPT

See the firewall for help. Be aware that $WAN might not be defined. If that is the case, insert the interface name instead. I.e. replace $WAN by eth1.

Alternatif lain, kita dapat mengkonfigurasi firewall menggunakan UCI di "/etc/config/firewall":

config 'rule'
	option 'target' 'ACCEPT'
	option '_name' 'pptpd'
	option 'proto' 'tcp'
	option 'dest_port' '1723'
	option 'family' 'ipv4'
	option 'src' 'wan'

/sbin/iptables -t nat -A POSTROUTING -s 172.16.1.0/24 -o eth1 -j MASQUERADE
/sbin/iptables -I FORWARD -p tcp --syn -i ppp+ -j TCPMSS -set-mss 1356

Test Connection

Tell a client to connect to the PPTP server, using the username and password you set in chap-secrets.

The connection should work, ping between the client and the server should work, but you may have to do some more configuring to let the client use your PPTP server as a gateway to the internet, or to see inside your LAN. See the routing section below.

Konfigurasi Routing

Sampai titik ini, client sudah bisa tersambung dengan VPN ke OpenWRT router. Untuk memberikan ijin agar client dapat tersambung ke LAN akan sangat mudah jika kita tambahkan pada /etc/ppp/options.pptpd:

proxyarp

Jika client tersambung maka akan terlihat pada log

found interface vlan0 for proxy arp

Kita perlu menambahkan rule iptables :

# Allow all traffic in and out of the ppp interface. No reason to specify nets.
/usr/sbin/iptables -A input_rule -i ppp+ -j ACCEPT
/usr/sbin/iptables -A output_rule -o ppp+ -j ACCEPT
# This rule will allow traffic towards internet
/usr/sbin/iptables -A forwarding_rule -i ppp+ -j ACCEPT

Setup for Windows filesharing

If you have Windows PPTP clients and you want them to be able to access file shares on the LAN, you need to set the IP addresses of the PPTP clients to be on the same subnet as the LAN. This is because of a limitation in proxyarp. They also cannot be on the same subnet as the local addresses of the PPTP clients. For example, if your PPTP clients have addresses in the 192.168.0.0/24 subnet, you can set you LAN to be 192.168.30.0/24 with DCHP assigning 192.168.30.50-192.168.30.100, but be careful that your PPTP clients' subnets are not in the 192.168.0.0 range. You would be better off selecting something in the 172.16.0.0/12 range (such as 172.18 for your LAN and 172.19 for the VPN clients with a bitmask of 16, i.e. 255.255.0.0). You can set the IP address of the PPTP server to be 192.168.30.200 by adding the following line to /etc/ppp/options.pptpd:

192.168.30.200:

You can then assign the client IP address beginning with 192.168.30.201. Use the following settings for VPN in /etc/firewall.user.

iptables        -A forwarding_rule -s 192.168.30.0/24 -d 192.168.30.0/24 -j ACCEPT
iptables        -A output_rule     -o ppp+ -s 192.168.30.0/24 -d 192.168.30.0/24 -j ACCEPT
iptables        -A input_rule      -i ppp+ -s 192.168.30.0/24 -d 192.168.30.0/24 -j ACCEPT
# allow VPN connections to get out WAN interface (to internet)
iptables        -A forwarding_rule -i ppp+ -o $WAN -j ACCEPT

You will now be able to access file shares by IP address. For example, you can type

\\192.168.30.50

into the address bar of Windows Explorer. Network neighborhood still doesn't detect available computers. If anyone knows how to make this work please post the instructions here. The desired configuration would have automatic detection and population, so there is no need to edit host files. I tried following instructions for setting up samba to run as a WINS server but I couldn't get it to work. Perhaps this is because OpenWrt is running an older version of samba that was selected because it has a smaller memory footprint.

⇒ In general the way for computers to appear in Net-Hood is to have server (master browser) to populate browse list across networks + have hosts or lmhosts file setup on client machines(that is only way I discovered so far). For samba servers you need to have config options in smb.conf: (ip address of router/name of workgroup), but I'm not sure how it works on wrt (as it only have cups I couldn't get them installed due to space limitation) remote announce = 192.168.11.1/UR-WG-NAME and hosts file in windoze (c:\Windows\System32\drivers\etc\hosts) like 192.168.11.10 mypc mypc.behind-wrt54g.org ..

⇒ Other way way for computers to appear in Net-Hood is to use on router side utility called bcrelay. Bcrelay turns on broadcast relay mode, sending all broadcasts received on the server's internal interface to the clients. Default pptpd package on WhiteRussian 0.9 contains pptpd version 1.3.0 compiled without bcrelay support. Good discussion about this problem can be found at http://forum.openwrt.org/viewtopic.php?pid=56890

Decision:

1. Recompile pptpd with bcrelay support or get compiled by simba87 package from http://rapidshare.com/files/59421121/pptpd_1.3.4-1_mipsel.ipk.html. 2. Backup /etc/pptpd.conf and all files in /etc/ppp/. Uninstall old pptpd package. 3. I put pptpd_1.3.4-1_mipsel.ipk to my hosting, then use wget on the router and use ipkg install pptpd_1.3.4-1_mipsel.ipk. 4. Add bcrelay br0 to /etc/pptpd.conf and proxyarp to /etc/ppp/options.pptpd. Troubleshooting

If you can connect to the pptpd and can ping the client from the server and vice versa but are not able to ping anything else refer to this checklist for diagnosis

There is a Windows XP client HOWTO that may help.

There is also the PPTP Client for Linux or check the OpenWrt vpn.pptp.client.

If the PPTP clients are behind an Actiontec DSL Modem/Router, only one of them will be able to connect. This is do to a bug in the Actiontec. Apparently it locks the connection to one client. If the router is rebooted the first client to reconnect is locked in. Putting the Actiontec into bridged mode and using a different router will probably bypass the problem. Does anyone else have any experience with this?

Referensi

• http://wiki.openwrt.org/doc/howto/vpn.server.pptpd