neysx 07/05/23 08:50:13 Added: vpnc-howto.xml Log: #97760 updated and moved to /doc/en/
Revision Changes Path 1.1 xml/htdocs/doc/en/vpnc-howto.xml file : http://sources.gentoo.org/viewcvs.py/gentoo/xml/htdocs/doc/en/vpnc-howto.xml?rev=1.1&view=markup plain: http://sources.gentoo.org/viewcvs.py/gentoo/xml/htdocs/doc/en/vpnc-howto.xml?rev=1.1&content-type=text/plain Index: vpnc-howto.xml =================================================================== <?xml version='1.0' encoding='UTF-8'?> <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/vpnc-howto.xml,v 1.1 2007/05/23 08:50:13 neysx Exp $ --> <!DOCTYPE guide SYSTEM "/dtd/guide.dtd"> <guide link="/doc/en/vpnc-howto.xml" disclaimer="draft"> <title>Gentoo vpnc HOWTO</title> <author title="Author"> <mail link="[EMAIL PROTECTED]">David H. Askew</mail> </author> <author title="Contributor"> <mail link="[EMAIL PROTECTED]">Sven Vermeulen</mail> </author> <author title="Contributor"> <mail link="[EMAIL PROTECTED]">Christian Faulhammer</mail> </author> <abstract> This document details how to connect your workstation to a Cisco VPN concentrator utilizing vpnc to manage the connection. </abstract> <!-- The content of this document is licensed under the CC-BY-SA license --> <!-- See http://creativecommons.org/licenses/by-sa/2.5 --> <license/> <version>0.14</version> <date>2007-05-23</date> <chapter> <title>Introduction</title> <section> <body> <p> If you're reading this, then you likely need to connect to your office network from home or during travel. Many companies utilize Cisco 3000 VPN concentrators for their VPN needs, and I am willing to bet that most Linux newbies think that they are forced to use Windows to connect to them. Well this document informs you that connecting to a Cisco VPN is very possible and will hopefully enable you to setup a working tunnel using your Gentoo workstation or laptop. </p> </body> </section> <section> <title>What this document is</title> <body> <ul> <li>A guide to the basic workings of <c>vpnc</c></li> <li>A discussion of DNS and routing issues that relate to VPNs</li> <li>Examples of managing VPN sessions</li> <li>Useful tips and tricks (hopefully)</li> </ul> </body> </section> <section> <title>What this document is not</title> <body> <ul> <li>An in-depth guide to VPN/encryption technologies</li> <li>A feature by feature explanation of <c>vpnc</c></li> </ul> </body> </section> <section> <title>Assumptions</title> <body> <p> The assumptions made at this point are: </p> <ul> <li>You have Gentoo installed</li> <li>You have Internet access</li> <li>You want to connect to a Cisco 3000 VPN concentrator</li> <li>You know how to configure, build and install a new kernel</li> </ul> </body> </section> </chapter> <chapter> <title>Kernel Configuration</title> <section> <body> <p> In order for Linux to be able to open a VPN connection <e>Universal TUN/TAP device driver support</e> must be enabled in the kernel. What is it and why do you need it? Below is a relatively straight forward explanation from the kernel configuration dialog: </p> <pre caption="CONFIG_TUN"> TUN/TAP provides packet reception and transmission for user space programs. It can be viewed as a simple Point-to-Point or Ethernet device, which instead of receiving packets from a physical media, receives them from user space program and instead of sending packets via physical media writes them to the user space program. When a program opens /dev/net/tun, driver creates and registers corresponding net device tunX or tapX. After a program closed above devices, driver will automatically delete tunXX or tapXX device and all routes corresponding to it. </pre> <p> >From the vpnc ebuild 0.4.0-r1 on, it is tested wether TUN/TAP support is enabled. If not, enable it in your kernel config either as module or built-in, recompile and reboot. </p> <p> You can verify yourself if your kernel has TUN/TAP support with the following command: </p> <pre caption="Checking the kernel config"> # <i> grep "TUN" /usr/src/linux/.config</i> CONFIG_INET_TUNNEL=m # CONFIG_INET6_TUNNEL is not set # CONFIG_IPV6_TUNNEL is not set <comment>(TUN/TAP enabled as a module)</comment> CONFIG_TUN=m # CONFIG_8139TOO_TUNE_TWISTER is not set </pre> <p> As you can see above, <c>CONFIG_TUN=m</c> is compiled as a module. If it is disabled in your setup, enable it in your kernel of choice, rebuild, install, reboot and return to this document before continuing with the next steps. </p> <pre caption="Configuration location in the kernel configuration dialog"> Device Drivers ---> Networking support ---> [*] Universal TUN/TAP device driver support </pre> <p> If you built TUN/TAP support directly into the kernel, you should see information from <c>dmesg</c> output like the following: </p> <pre caption="Checking dmesg output"> # <i>dmesg | grep TUN</i> Universal TUN/TAP device driver 1.5 (C)1999-2002 Maxim Krasnyansky </pre> <p> If you build TUN/TAP support as a module, you first must load the <c>tun</c> module: </p> <pre caption="Load tun module"> # <i>modprobe tun</i> # <i>lsmod</i> Module Size Used by tun 7296 0 nvidia 4050204 12 </pre> <p> Now that the <c>tun</c> module is loaded, check <c>dmesg</c> output. You should see something like the following: </p> <pre caption="Checking dmesg output"> # <i>dmesg | grep TUN</i> Universal TUN/TAP device driver 1.5 (C)1999-2002 Maxim Krasnyansky </pre> </body> </section> </chapter> <chapter> <title>Install Needed Software</title> <section> <body> <p> Now that you have a working kernel setup, you need to install <c>net-misc/vpnc</c>: </p> <pre caption="Installing vpnc"> # <i>emerge -av net-misc/vpnc</i> </pre> </body> </section> </chapter> <chapter> <title>Example Setup</title> <section> <body> <p> In order to make the following sections more clear, we need an example setup to work from. For the purposes of this exercise, we will assume that you have a home network of several computers. All computers are on the 192.168.0.0 / 255.255.255.0 network. The LAN in question is run by a Gentoo box using an iptables firewall, DHCP, caching DNS, etc ... and it masquerades the LAN behind the public IP address it receives from an ISP. You also have a workstation on the LAN from which you want to be able to VPN into your office with. </p> <p> Our example workstation configuration looks like the following: </p> <pre caption="Our workstation configuration"> <comment>(Name server configuration)</comment> # <i>cat /etc/resolv.conf</i> nameserver 192.168.0.1 <comment>(Network configuration)</comment> # <i>cat /etc/hosts</i> 127.0.0.1 desktop localhost 192.168.0.1 router 192.168.2.2 mediacenter <comment>(Interface configuration)</comment> # <i>ifconfig -a</i> eth0 Link encap:Ethernet HWaddr 00:11:2F:8D:08:08 inet addr:192.168.0.2 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::211:2fff:fe8d:808/64 Scope:Link UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1 RX packets:3657889 errors:0 dropped:0 overruns:0 frame:0 TX packets:2305893 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2193722103 (2092.0 Mb) TX bytes:1415104432 (1349.5 Mb) Interrupt:185 Memory:fac00000-0 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:35510 errors:0 dropped:0 overruns:0 frame:0 TX packets:35510 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:16023838 (15.2 Mb) TX bytes:16023838 (15.2 Mb) <comment>(Routing information)</comment> # <i>netstat -r</i> Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.0.0 * 255.255.255.0 U 0 0 0 eth0 loopback desktop 255.0.0.0 UG 0 0 0 lo default router 0.0.0.0 UG 0 0 0 eth0 </pre> </body> </section> </chapter> <chapter> <title>Configuring vpnc</title> <section> <body> <p> Now that you have <c>vpnc</c> installed and we have an example to work from, let's discuss the basics of setting up <c>vpnc</c>. The configuration file for <c>vpnc</c> connection settings can be located in a couple places, depending on how many profiles you want to setup. By default, <c>vpnc</c> looks first for <path>/etc/vpnc/default.conf</path> for its connection settings. If it doesn't find that file, then it looks for <path>/etc/vpnc.conf</path>. This setup will only address a single profile example and will use the configuration file location <path>/etc/vpnc.conf</path>. Make sure you do not have a <path>/etc/vpnc/default.conf</path> file. </p> <pre caption="Example /etc/vpnc.conf file"> IPSec gateway vpngateway.domain.org IPSec ID group_id IPSec secret group_password Xauth username network_signon Xauth password network_password </pre> <p> The configuration file example above should be modified to reflect the appropriate values for your setup. The gateway option <c>vpngateway.domain.org</c> can be a fully qualified domain name or an IP address. The ID and secret options should be given to you by a network administrator. If they are hesitant about giving you this info and you currently have a working setup on a Windows box which utilizes the official Cisco VPN client, then all you have to do is export your profile. The user name and password options are for your normal network sign-on, such as a Windows NT domain account. </p> <p> If you are forced to export your profile from a Windows machine, then what you will likely have is a file ending in <path>.pcf</path>. This file will have all the information you need. Below is an example: </p> <pre caption="Example profile.pcf file"> [main] Description= Host=VPNGATEWAY.DOMAIN.ORG AuthType=1 GroupName=group_id GroupPwd= enc_GroupPwd=F3256220AA200A1D532556024F4F314B0388D48B0FBF2DB12 EnableISPConnect=0 ISPConnectType=0 ISPConnect=FOOBAR ISPCommand= Username= SaveUserPassword=0 UserPassword= enc_UserPassword= NTDomain= EnableBackup=0 BackupServer= EnableMSLogon=1 MSLogonType=0 EnableNat=1 TunnelingMode=0 TcpTunnelingPort=10000 CertStore=0 CertName= CertPath= CertSubjectName= CertSerialHash=00000000000000000000000000000000 SendCertChain=0 VerifyCertDN= DHGroup=2 ForceKeepAlives=0 PeerTimeout=90 EnableLocalLAN=0 EnableSplitDNS=1 ForceNetLogin=0 </pre> <p> In the above example, we can see entries for <c>Host</c>, <c>GroupName</c> and <c>enc_GroupPwd</c>. Your <c>Username</c> and <c>UserPassword</c> may or may not be exported depending on the setup. To generate a working vpnc configuration out of it, you can use <c>pcf2vpnc</c>, included with vpnc. </p> <note> You can decrypt the password with the help from the <c>cisco-decrypt</c> program, shipped with the latest vpnc. </note> </body> </section> <section> <title>Testing your setup</title> <body> <p> Now that you have a configuration in place, it's time to test your setup. To start <c>vpnc</c> you do the following: </p> <pre caption="Example vpnc usage"> # <i>vpnc</i> Enter password for [EMAIL PROTECTED]: VPNC started in background (pid: 14788)... </pre> <p> As you can see from the above command output, once you type <c>vpnc</c> (as root), you are prompted for your password. After entering your password, which will not be echoed back to you, the <c>vpnc</c> process will automatically become a background process. </p> <note> If you specified the <c>Xauth password</c> option in your <c>vpnc</c> config file, then you will not be prompted for your password at <c>vpnc</c> startup. Additionally, if <c>vpnc</c> needs some extra options not specified in the configuration file, or if you have forgotten something, don't worry, it will ask you for it. </note> <pre caption="Sample interface configuration changes made by vpnc"> # <i> ifconfig -a</i> eth1 Link encap:Ethernet HWaddr 00:11:2F:8D:08:08 inet addr:192.168.0.2 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::211:2fff:fe8d:808/64 Scope:Link UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1 RX packets:2101119 errors:0 dropped:0 overruns:0 frame:0 TX packets:1577559 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1757862627 (1676.4 Mb) TX bytes:732200131 (698.2 Mb) Interrupt:177 Memory:faa00000-0 sit0 Link encap:IPv6-in-IPv4 NOARP MTU:1480 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:192.168.160.42 P-t-P:192.168.160.42 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1412 Metric:1 RX packets:1 errors:0 dropped:0 overruns:0 frame:0 TX packets:9 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:60 (60.0 b) TX bytes:616 (616.0 b) </pre> <pre caption="Sample routing modifications made by vpnc"> # <i>netstat -r</i> Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface vpn01.domain.or router 255.255.255.255 UGH 1500 0 0 eth1 192.168.0.0 * 255.255.255.0 U 0 0 0 eth1 loopback desktop 255.0.0.0 UG 0 0 0 lo default * 0.0.0.0 U 0 0 0 tun0 </pre> <p> As you can see from the above command output(s), <c>vpnc</c> has done the following: </p> <ul> <li> Created the tun0 network interface, a virtual interface to handle the traffic across your VPN tunnel </li> <li>Obtained the IP address for the tun0 device from your VPN provider</li> <li>Set the default route to your VPN gateway</li> </ul> <p> At this point, your workstation is capable of communicating with hosts via the VPN, but only by IP address. As you might have noticed, <c>vpnc</c> did not alter your <path>/etc/resolv.conf</path>, thus not setting up DNS services for the virtual link. Also, because <c>vpnc</c> sets your default route to your VPN gateway, all network traffic will travel across the VPN, even if it destined for the Internet or elsewhere not specifically specified by additional routes. For some, this basic type of connection may be satisfactory, but for most, additional steps need to be taken. </p> <p> Additional things you might want to have: </p> <ul> <li>DNS for the VPN</li> <li> A routing setup that will only send traffic destined for the VPN down the virtual tunnel. This way, you can browse the Internet while connected to the VPN, without your personal web/p2p etc ... traffic going across the tunnel. </li> <li> A script to manage all this, because <c>vpnc</c> just doesn't do enough by default. </li> </ul> <p> When you are ready to end the VPN session, execute <c>vpnc-disconnect</c>. An example is shown below. </p> <note> Don't disconnect yet, because we have additional things to test. The example below is just for informational purposes. </note> <pre caption="vpnc-disconnect"> # <i>vpnc-disconnect</i> Terminating vpnc daemon (pid: 26250) </pre> </body> </section> </chapter> <chapter> <title>Set up DNS</title> <section> <body> <p> Unfortunately, <c>vpnc</c> doesn't handle the setup and management of DNS for your newly established tunnel. The user is left to decide how DNS should be handled. You could just overwrite <path>/etc/resolv.conf</path> when you connect, but that would utilize your VPN DNS for all DNS queries regardless of whether or not the traffic is destined for your VPN tunnel. This is a very functional solution and if you simply need to connect to the tunnel, do your work, and then disconnect, read no further. But, if you want to be able to leave your tunnel connected for lengthy periods of time and don't want your work DNS servers handling requests for your personal traffic, read on. </p> <p> The ideal setup would allow you to separate your DNS queries into two categories: VPN-related and other. Under this setup, all VPN-related DNS queries would be answered by DNS servers located at the other end of your VPN tunnel and all other queries would continue to be answered by local or ISP supplied DNS servers. This is the setup that will be demonstrated here. </p> <note> We will consider VPN-related DNS queries to be any query belonging to the example.org domain, such as host1.example.org or server1.example.org. </note> <p> So how do you set things up, so that only requests made to hosts on the example.org domain get sent to VPN supplied DNS servers? Well, you're going to need to install a local DNS server, but don't worry, it's much easier than you think. There are several software packages that can handle the type of setup we desire, but for the purposes of this demonstration, <c>dnsmasq</c> will be utilized. Let's emerge it now: </p> <note> This DNS server software will not be available to the network, and will only answer requests from localhost, <c>127.0.0.1</c>. </note> <pre caption="Install dnsmasq"> # <i> emerge dnsmasq</i> </pre> <p> Now you need to add an option to your <c>dnsmasq</c> startup options. Edit the following option to suit your needs. Substitute .example.org with the appropriate domain and the IP address with a valid DNS server that belongs to the VPN tunnel. </p> <pre caption="/etc/conf.d/dnsmasq"> Config file for /etc/init.d/dnsmasq # See the dnsmasq(8) man page for possible options to put here. DNSMASQ_OPTS="-S /.example.org/192.168.125.10" </pre> <p> Next, make sure that the first entry in <path>/etc/resolv.conf</path> is your local host <c>127.0.0.1</c>, followed by the location of the backup DNS servers that should handle the DNS traffic in case dnsmasq fails to start, or if it needs to forward a DNS query it doesn't currently have in its cache. An example <path>/etc/resolv.conf</path> is shown below. </p> <pre caption="/etc/resolv.conf"> nameserver 127.0.0.1 nameserver 192.168.0.1 </pre> <p> Now that you have setup a rule for your VPN tunnel DNS, you need to start <c>dnsmasq</c>. </p> <pre caption="Starting up dnsmasq"> # <i>/etc/init.d/dnsmasq start</i> # <i>rc-update add dnsmasq default</i> </pre> </body> </section> </chapter> <chapter> <title>Configuring the routing table</title> <section> <body> <p> The ideal scenario would be if only the traffic destined for VPN tunnel would travel across the link. At this point, you have a VPN tunnel setup and all traffic will travel across the tunnel, unless you specify additional routes. In order to fix this situation you need to know what networks are available to you on your VPN. The easiest way to find out the needed information is to ask a network administrator, but sometimes they are reluctant to answer such questions. If your local network admin wont provide the needed information, some trial and error experiments will be required. </p> <p> When the VPN tunnel was started, <c>vpnc</c> set the default route to the tunnel. So you must set your default route back to normal, so that things work as expected. </p> <pre caption="Resetting your default route"> # <i>route add default gw 192.168.0.1</i> </pre> <p> Earlier, when DNS services were being configured for your VPN, you specified a DNS server to handle your example.org domain. You need to add a route for the 192.168.125.0 subnet so that DNS queries will work. </p> <pre caption="Adding a route for dns"> # <i>route add -net 192.168.160.0 netmask 255.255.255.0 dev tun0</i> </pre> <p> At this point, you should add any additional routes for known networks. If your friendly network administrator gave you the required info, great. Otherwise, you might need to ping hosts you will be connecting to frequently, to give yourself an idea about what your routing table should look like. </p> <note> Due to your setup, when using VPN network services by name, you must specify the fully qualified domain name, for instance: webserver1.example.org </note> <pre caption="Ping example"> # <i>ping intranet1.example.org</i> PING intranet1.example.org (172.25.230.29) 56(84) bytes of data. --- intranet.example.org ping statistics --- 18 packets transmitted, 0 received, 100% packet loss, time 16997ms </pre> <p> As you can see from the above example, the ping probes to <c>intranet1.example.org</c> were unsuccessful. So we need to add a route for that subnet. </p> <pre caption="another route command example"> # <i>route add -net 172.25.230.0 netmask 255.255.255.0 dev tun0</i> </pre> <p> A few ping and route commands later, you should be well on your way to a well working routing table. </p> </body> </section> </chapter> <chapter> <title>Manage the connection</title> <section> <title>Calling vpnc when needed</title> <body> <p> Next is an example script to manage the VPN connection. You could execute it (as root) from an xterm to start a connection to your VPN. Then all you have to do is press return to disconnect the VPN. Obviously you will need to modify this for your setup, remembering to add all the additional routes that you may need. </p> <pre caption="Example session management script"> #!/bin/bash source /sbin/functions.sh ebegin "Connecting to the VPN" vpnc eend ebegin "Modifying the routing table" route add default gw 192.168.0.1 route add -net 172.25.230.0 netmask 255.255.255.0 dev tun0 route add -net 192.168.160.0 netmask 255.255.255.0 dev tun0 route add -net 192.168.125.0 netmask 255.255.255.0 dev tun0 eend einfo "Press any key to disconnect ..." read $disconnect ebegin "Disconnecting from the VPN" vpnc-disconnect eend ebegin "Reconfiguring the default routing table" route add default gw 192.168.0.1 eend einfo "VPN should now be disconnected" </pre> </body> </section> <section> <title>Start vpnc on boot</title> <body> <p> Version 0.4.0-r1 of vpnc brings an init file for Gentoo which even can handle multiple configurations. You will find a file <path>/etc/init.d/vpnc</path> which can be handled by the usual means of init scripts. The default looks for <path>/etc/vpnc/vpnc.conf</path>, the scheme is sketched in the following table. </p> <table> <tr> <th>init script name</th> <th>needed configuration file</th> </tr> <tr> <ti>/etc/init.d/vpnc</ti> <ti>/etc/vpnc/vpnc.conf</ti> </tr> <tr> <ti>/etc/init.d/vpnc.work</ti> <ti>/etc/vpnc/work.conf</ti> </tr> </table> <p> Add vpnc to default runlevel with the following commands (in this case for the standard configuration). Don't forget to add the tun module (if you have built it that way) to the kernels autoload mechanism at startup. </p> <pre caption="Adding vpnc to startup scripts"> # <i>rc-update add vpnc default</i> </pre> <note> The init scripts don't handle DNS separation. </note> </body> </section> </chapter> <chapter> <title>Tips and Tricks</title> <section> <body> <p> If you are looking for a linux application that supports RDP (Remote Desktop Protocol) then give <c>grdesktop</c> a try. It's a GUI app written in Gtk that fits in well with a gnome desktop, but doesn't require it. If you don't want the GUI configuration dialogs that grdesktop provides, then just install <c>rdesktop</c>. Ultimately, grdesktop is just a frontend for rdesktop. </p> <p> If you are a KDE user, you might want to try <c>kvpnc</c>. It a appears to be a very mature VPN management GUI. </p> <p> If you need to connect to a windows machine which doesn't have a DNS entry, and you know the address of an available WINS server, you can use a tool called <c>nmblookup</c> to query the WINS server for the host name of the machine you want to connect to. Unfortunately, you have to install samba to get it, but if you are going to be working with boxes running Windows you might as well want to install samba, because it includes several other useful tools. </p> <pre caption="Installing samba"> # <i>emerge -av samba</i> </pre> <p> When you have samba and its tools installed, test <c>nmblookup</c> by asking the WINS server at IP address 192.168.125.11 about a host named wintelbox1. </p> <pre caption="nmblookup example"> # <i>nmblookup -U 192.168.125.11 -R 'wintelbox1'</i> querying wintelbox1 on 192.168.125.11 172.25.230.76 wintelbox1 </pre> </body> </section> </chapter> <chapter> <title>Useful Links</title> <section> <body> <ul> <li> <uri link="http://www.unix-ag.uni-kl.de/~massar/vpnc/";>vpnc homepage</uri> </li> <li> <uri link="http://home.gna.org/kvpnc/en/index.html";>kvpnc homepage</uri> </li> <li> <uri link="http://www.nongnu.org/grdesktop/";>grdesktop homepage</uri> </li> </ul> </body> </section> </chapter> <chapter> <title>Final Notes</title> <section> <body> <p> Hopefully by now you have been able to connect to your VPN of choice and are well on your way to remote office work. Feel free to file a bug at <uri link="http://bugs.gentoo.org";>bugs.gentoo.org</uri> should you find a mistake or wish to make an addition or recommendation regarding this document. </p> </body> </section> </chapter> </guide> -- [EMAIL PROTECTED] mailing list
