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.\" ======================================================================== |
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.\" |
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.IX Title "GVPE 5" |
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.TH GVPE 5 "2005-03-17" "1.8" "GNU Virtual Private Ethernet" |
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.SH "NAME" |
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GNU\-VPE \- Overview of the GNU Virtual Private Ethernet suite. |
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.SH "DESCRIPTION" |
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.IX Header "DESCRIPTION" |
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\&\s-1GVPE\s0 is a suite designed to provide a virtual private network for multiple |
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nodes over an untrusted network. This document first gives an introduction |
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to VPNs in general and then describes the specific implementation of \s-1GVPE\s0. |
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.Sh "\s-1WHAT\s0 \s-1IS\s0 A \s-1VPN\s0?" |
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.IX Subsection "WHAT IS A VPN?" |
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\&\s-1VPN\s0 is an acronym, it stands for: |
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.IP "\(bu" 4 |
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.IX Xref "Virtual" |
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Virtual means that no physical network is created (of course), but a |
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network is \fIemulated\fR by creating multiple tunnels between the member |
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nodes by encapsulating and sending data over another transport network. |
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.Sp |
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Usually the emulated network is a normal \s-1IP\s0 or Ethernet, and the transport |
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network is the Internet. However, using a \s-1VPN\s0 system like \s-1GVPE\s0 to connect |
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nodes over other untrusted networks such as Wireless \s-1LAN\s0 is not uncommon. |
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.IP "\(bu" 4 |
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.IX Xref "Private" |
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Private means that non-participating nodes cannot decode (\*(L"sniff)\*(R" nor |
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inject (\*(L"spoof\*(R") packets. This means that nodes can be connected over |
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untrusted networks such as the public Internet without fear of being |
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eavesdropped while at the same time being able to trust data sent by other |
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nodes. |
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.Sp |
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In the case of \s-1GVPE\s0, even participating nodes cannot sniff packets |
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send to other nodes or spoof packets as if sent from other nodes, so |
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communications between any two nodes is private to those two nodes. |
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.IP "\(bu" 4 |
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.IX Xref "Network" |
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Network means that more than two parties can participate in the network, |
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so for instance it's possible to connect multiple branches of a company |
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into a single network. Many so-called \*(L"vpn\*(R" solutions only create |
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point-to-point tunnels, which in turn can be used to build larger |
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networks. |
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.Sp |
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\&\s-1GVPE\s0 provides a true multi-point network in wich any number of nodes (at |
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least a few dozen in practise, the theoretical limit is 4095 nodes) can |
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participate. |
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.Sh "\s-1GVPE\s0 \s-1DESIGN\s0 \s-1GOALS\s0" |
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.IX Subsection "GVPE DESIGN GOALS" |
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.IP "\s-1SIMPLE\s0 \s-1DESIGN\s0" 4 |
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.IX Item "SIMPLE DESIGN" |
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Cipher, \s-1HMAC\s0 algorithms and other key parameters must be selected |
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at compile time \- this makes it possible to only link in algorithms |
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you actually need. It also makes the crypto part of the source very |
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transparent and easy to inspect, and last not least this makes it possible |
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to hardcode the layout of all packets into the binary. \s-1GVPE\s0 goes a step |
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further and internally reserves blocks of the same length for all packets, |
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which virtually removes all possibilities of buffer overflows, as there is |
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only a single type of buffer and it's always of fixed length. |
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.IP "\s-1EASY\s0 \s-1TO\s0 \s-1SETUP\s0" 4 |
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.IX Item "EASY TO SETUP" |
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A few lines of config (the config file is shared unmodified between all |
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hosts) and a single run of \f(CW\*(C`gvpectrl\*(C'\fR to generate the keys suffices to |
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make it work. |
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.IP "MAC-BASED \s-1SECURITY\s0" 4 |
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.IX Item "MAC-BASED SECURITY" |
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Since every host has it's own private key, other hosts cannot spoof |
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traffic from this host. That makes it possible to filter packet by \s-1MAC\s0 |
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address, e.g. to ensure that packets from a specific \s-1IP\s0 address come, in |
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fact, from a specific host that is associated with that \s-1IP\s0 and not from |
| 197 |
another host. |
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.SH "PROGRAMS" |
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.IX Header "PROGRAMS" |
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Vpe comes with two programs: one daemon (\f(CW\*(C`gvpe\*(C'\fR) and one control program |
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(\f(CW\*(C`gvpectrl\*(C'\fR). |
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.IP "gvpectrl" 4 |
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.IX Item "gvpectrl" |
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Is used to generate the keys, check and give an overview of of the |
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configuration and contorl the daemon (restarting etc.). |
| 206 |
.IP "gvpe" 4 |
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.IX Item "gvpe" |
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Is the daemon used to establish and maintain connections to the other |
| 209 |
network members. It should be run on the gateway machine. |
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.SH "COMPILETIME CONFIGURATION" |
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.IX Header "COMPILETIME CONFIGURATION" |
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Please have a look at the \f(CW\*(C`gvpe.osdep(5)\*(C'\fR manpage for platform-specific |
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information. |
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.PP |
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Here are a few recipes for compiling your gvpe, showing the extremes |
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(fast, small, insecure \s-1OR\s0 slow, large, more secure), between you should |
| 217 |
choose: |
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.Sh "\s-1AS\s0 \s-1LOW\s0 \s-1PACKET\s0 \s-1OVERHEAD\s0 \s-1AS\s0 \s-1POSSIBLE\s0" |
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.IX Subsection "AS LOW PACKET OVERHEAD AS POSSIBLE" |
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.Vb 1 |
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\& ./configure --enable-hmac-length=4 --enable-rand-length=0 |
| 222 |
.Ve |
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.PP |
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Minimize the header overhead of \s-1VPN\s0 packets (the above will result in |
| 225 |
only 4 bytes of overhead over the raw ethernet frame). This is a insecure |
| 226 |
configuration because a \s-1HMAC\s0 length of 4 makes collision attacks based on |
| 227 |
the birthday paradox easy, though. |
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.Sh "\s-1MINIMIZE\s0 \s-1CPU\s0 \s-1TIME\s0 \s-1REQUIRED\s0" |
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.IX Subsection "MINIMIZE CPU TIME REQUIRED" |
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.Vb 1 |
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\& ./configure --enable-cipher=bf --enable-digest=md4 |
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.Ve |
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.PP |
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Use the fastest cipher and digest algorithms currently available in |
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gvpe. \s-1MD4\s0 has been broken and is quite insecure, though. |
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.Sh "\s-1MAXIMIZE\s0 \s-1SECURITY\s0" |
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.IX Subsection "MAXIMIZE SECURITY" |
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.Vb 1 |
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\& ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1 |
| 240 |
.Ve |
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.PP |
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This uses a 16 byte \s-1HMAC\s0 checksum to authenticate packets (I guess 8\-12 |
| 243 |
would also be pretty secure ;) and will additionally prefix each packet |
| 244 |
with 8 bytes of random data. In the long run, people should move to |
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\&\s-1SHA\-224\s0 and beyond, but support in openssl is missing as of writing this |
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document. |
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.PP |
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In general, remember that \s-1AES\-128\s0 seems to be more secure and faster than |
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\&\s-1AES\-192\s0 or \s-1AES\-256\s0, more randomness helps against sniffing and a longer |
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\&\s-1HMAC\s0 helps against spoofing. \s-1MD4\s0 is a fast digest, \s-1SHA1\s0 or \s-1RIPEMD160\s0 are |
| 251 |
better, and Blowfish is a fast cipher (and also quite secure). |
| 252 |
.SH "HOW TO SET UP A SIMPLE VPN" |
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.IX Header "HOW TO SET UP A SIMPLE VPN" |
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In this section I will describe how to get a simple \s-1VPN\s0 consisting of |
| 255 |
three hosts up and running. |
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.Sh "\s-1STEP\s0 1: configuration" |
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.IX Subsection "STEP 1: configuration" |
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First you have to create a daemon configuation file and put it into the |
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configuration directory. This is usually \f(CW\*(C`/etc/gvpe\*(C'\fR, depending on how you |
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configured gvpe, and can be overwritten using the \f(CW\*(C`\-c\*(C'\fR commandline switch. |
| 261 |
.PP |
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Put the following lines into \f(CW\*(C`/etc/gvpe/gvpe.conf\*(C'\fR: |
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.PP |
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.Vb 3 |
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\& udp-port = 50000 # the external port to listen on (configure your firewall) |
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\& mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts |
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\& ifname = vpn0 # the local network device name |
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.Ve |
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.PP |
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.Vb 2 |
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\& node = first # just a nickname |
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\& hostname = first.example.net # the DNS name or IP address of the host |
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.Ve |
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.PP |
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.Vb 2 |
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\& node = second |
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\& hostname = 133.55.82.9 |
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.Ve |
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.PP |
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.Vb 2 |
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\& node = third |
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\& hostname = third.example.net |
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.Ve |
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.PP |
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The only other file neccessary if the \f(CW\*(C`if\-up\*(C'\fR script that initializes the |
| 286 |
local ethernet interface. Put the following lines into \f(CW\*(C`/etc/gvpe/if\-up\*(C'\fR |
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and make it execute (\f(CW\*(C`chmod 755 /etc/gvpe/if\-up\*(C'\fR): |
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.PP |
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.Vb 6 |
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\& #!/bin/sh |
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\& ip link set $IFNAME address $MAC mtu $MTU up |
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\& [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME |
| 293 |
\& [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME |
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\& [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME |
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\& ip route add 10.0.0.0/16 dev $IFNAME |
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.Ve |
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.PP |
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This script will give each node a different \s-1IP\s0 address in the \f(CW\*(C`10.0/16\*(C'\fR |
| 299 |
network. The internal network (e.g. the \f(CW\*(C`eth0\*(C'\fR interface) should then be |
| 300 |
set to a subset of that network, e.g. \f(CW\*(C`10.0.1.0/24\*(C'\fR on node \f(CW\*(C`first\*(C'\fR, |
| 301 |
\&\f(CW\*(C`10.0.2.0/24\*(C'\fR on node \f(CW\*(C`second\*(C'\fR, and so on. |
| 302 |
.PP |
| 303 |
By enabling routing on the gateway host that runs \f(CW\*(C`gvpe\*(C'\fR all nodes will |
| 304 |
be able to reach the other nodes. You can, of course, also use proxy arp |
| 305 |
or other means of pseudo-bridging (or even real briding), or (best) full |
| 306 |
routing \- the choice is yours. |
| 307 |
.Sh "\s-1STEP\s0 2: create the \s-1RSA\s0 key pairs for all hosts" |
| 308 |
.IX Subsection "STEP 2: create the RSA key pairs for all hosts" |
| 309 |
Run the following command to generate all key pairs (that might take a |
| 310 |
while): |
| 311 |
.PP |
| 312 |
.Vb 1 |
| 313 |
\& gvpectrl -c /etc/gvpe -g |
| 314 |
.Ve |
| 315 |
.PP |
| 316 |
This command will put the public keys into \f(CW\*(C`/etc/gvpe/pubkeys/\f(CInodename\f(CW\*(C'\fR and the private keys into \f(CW\*(C`/etc/gvpe/hostkeys/\f(CInodename\f(CW\*(C'\fR. |
| 317 |
.Sh "\s-1STEP\s0 3: distribute the config files to all nodes" |
| 318 |
.IX Subsection "STEP 3: distribute the config files to all nodes" |
| 319 |
Now distribute the config files to the other nodes. This should be done in two steps, since the |
| 320 |
private keys should not be distributed. The example uses rsync-over-ssh |
| 321 |
.PP |
| 322 |
First all the config files without the hostkeys should be distributed: |
| 323 |
.PP |
| 324 |
.Vb 3 |
| 325 |
\& rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys |
| 326 |
\& rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys |
| 327 |
\& rsync -avzessh /etc/gvpe third.example.net:/etc/. --exclude hostkeys |
| 328 |
.Ve |
| 329 |
.PP |
| 330 |
Then the hostkeys should be copied: |
| 331 |
.PP |
| 332 |
.Vb 3 |
| 333 |
\& rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey |
| 334 |
\& rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey |
| 335 |
\& rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey |
| 336 |
.Ve |
| 337 |
.PP |
| 338 |
You should now check the configration by issuing the command \f(CW\*(C`gvpectrl \-c |
| 339 |
/etc/gvpe \-s\*(C'\fR on each node and verify it's output. |
| 340 |
.Sh "\s-1STEP\s0 4: starting gvpe" |
| 341 |
.IX Subsection "STEP 4: starting gvpe" |
| 342 |
You should then start gvpe on each node by issuing a command like: |
| 343 |
.PP |
| 344 |
.Vb 1 |
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\& gvpe -D -linfo first # first is the nodename |
| 346 |
.Ve |
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.PP |
| 348 |
This will make the gvpe stay in foreground. You should then see |
| 349 |
\&\*(L"connection established\*(R" messages. If you don't see them check your |
| 350 |
firewall and routing (use tcpdump ;). |
| 351 |
.PP |
| 352 |
If this works you should check your networking setup by pinging various |
| 353 |
endpoints. |
| 354 |
.PP |
| 355 |
To make gvpe run more permanently you can either run it as a daemon |
| 356 |
(by starting it without the \f(CW\*(C`\-D\*(C'\fR switch), or, much better, from your |
| 357 |
inittab. I use a line like this on my systems: |
| 358 |
.PP |
| 359 |
.Vb 1 |
| 360 |
\& t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1 |
| 361 |
.Ve |
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.Sh "\s-1STEP\s0 5: enjoy" |
| 363 |
.IX Subsection "STEP 5: enjoy" |
| 364 |
\&... and play around. Sending a \-HUP (\f(CW\*(C`gvpectrl \-kHUP\*(C'\fR) to the daemon |
| 365 |
will make it try to connect to all other nodes again. If you run it from |
| 366 |
inittab, as is recommended, \f(CW\*(C`gvpectrl \-k\*(C'\fR (or simply \f(CW\*(C`killall gvpe\*(C'\fR) will |
| 367 |
kill the daemon, start it again, making it read it's configuration files |
| 368 |
again. |
| 369 |
.SH "SEE ALSO" |
| 370 |
.IX Header "SEE ALSO" |
| 371 |
\&\fIgvpe.osdep\fR\|(5) for OS-depedendent information, \fIgvpe.conf\fR\|(5), \fIgvpectrl\fR\|(8), |
| 372 |
and for a description of the transports, protocol, and routing algorithm, |
| 373 |
\&\fIgvpe.protocol\fR\|(7). |
| 374 |
.SH "AUTHOR" |
| 375 |
.IX Header "AUTHOR" |
| 376 |
Marc Lehmann <gvpe@plan9.de> |
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.SH "COPYRIGHTS AND LICENSES" |
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.IX Header "COPYRIGHTS AND LICENSES" |
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\&\s-1GVPE\s0 itself is distributed under the \s-1GENERAL\s0 \s-1PUBLIC\s0 \s-1LICENSE\s0 (see the file |
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\&\s-1COPYING\s0 that should be part of your distribution). |
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.PP |
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In some configurations it uses modified versions of the tinc vpn suite, |
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which is also available under the \s-1GENERAL\s0 \s-1PUBLIC\s0 \s-1LICENSE\s0. |
