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# Content
1 =head1 NAME
2
3 GNU-VPE - Overview of the GNU Virtual Private Ethernet suite.
4
5 =head1 DESCRIPTION
6
7 GVPE is a suite designed to provide a virtual private network for multiple
8 nodes over an untrusted network.
9
10 =over 4
11
12 =item X<Virtual>
13
14 Virtual means that no physical network is created (of course), but an
15 ethernet is emulated by creating multiple tunnels between the member
16 nodes.
17
18 =item X<Private>
19
20 Private means that non-participating nodes cannot decode ("sniff)" nor
21 inject ("spoof") packets.
22
23 In the case of gvpe, even participating nodes cannot sniff packets send to
24 other nodes or spoof packets as if sent from other nodes.
25
26 =item X<Network>
27
28 Network means that more than two parties can participate in the network,
29 so for instance it's possible to connect multiple branches of a company
30 into a single network. Many so-called "vpn" solutions only create
31 point-to-point tunnels.
32
33 =back
34
35 =head2 DESIGN GOALS
36
37 =over 4
38
39 =item SIMPLE DESIGN
40
41 Cipher, HMAC algorithms and other key parameters must be selected
42 at compile time - this makes it possible to only link in algorithms
43 you actually need. It also makes the crypto part of the source very
44 transparent and easy to inspect.
45
46 =item EASY TO SETUP
47
48 A few lines of config (the config file is shared unmodified between all
49 hosts) and a single run of C<gvpectrl> to generate the keys suffices to
50 make it work.
51
52 =item MAC-BASED SECURITY
53
54 Since every host has it's own private key, other hosts cannot spoof
55 traffic from this host. That makes it possible to filter packet by MAC
56 address, e.g. to ensure that packets from a specific IP address come, in
57 fact, from a specific host that is associated with that IP and not from
58 another host.
59
60 =back
61
62 =head1 PROGRAMS
63
64 Vpe comes with two programs: one daemon (C<gvpe>) and one control program
65 (C<gvpectrl>).
66
67 =over 4
68
69 =item gvpectrl
70
71 Is used to generate the keys, check and give an overview of of the
72 configuration and contorl the daemon (restarting etc.).
73
74 =item gvpe
75
76 Is the daemon used to establish and maintain connections to the other
77 network members. It should be run on the gateway machine.
78
79 =back
80
81 =head1 COMPILETIME CONFIGURATION
82
83 Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific
84 information.
85
86 Here are a few recipes for compiling your gvpe, showing the extremes
87 (fast, small, insecure OR slow, large, more secure), between you should
88 choose:
89
90 =head2 AS LOW PACKET OVERHEAD AS POSSIBLE
91
92 ./configure --enable-hmac-length=4 --enable-rand-length=0
93
94 Minimize the header overhead of VPN packets (the above will result in
95 only 4 bytes of overhead over the raw ethernet frame). This is a insecure
96 configuration because a HMAC length of 4 makes collision attacks based on
97 the birthday paradox easy, though.
98
99 =head2 MINIMIZE CPU TIME REQUIRED
100
101 ./configure --enable-cipher=bf --enable-digest=md4
102
103 Use the fastest cipher and digest algorithms currently available in
104 gvpe. MD4 has been broken and is quite insecure, though.
105
106 =head2 MAXIMIZE SECURITY
107
108 ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1
109
110 This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12
111 would also be pretty secure ;) and will additionally prefix each packet
112 with 8 bytes of random data. In the long run, people should move to
113 SHA-224 and beyond, but support in openssl is missing as of writing this
114 document.
115
116 In general, remember that AES-128 seems to be more secure and faster than
117 AES-192 or AES-256, more randomness helps against sniffing and a longer
118 HMAC helps against spoofing. MD4 is a fast digest, SHA1 or RIPEMD160 are
119 better, and Blowfish is a fast cipher (and also quite secure).
120
121 =head1 HOW TO SET UP A SIMPLE VPN
122
123 In this section I will describe how to get a simple VPN consisting of
124 three hosts up and running.
125
126 =head2 STEP 1: configuration
127
128 First you have to create a daemon configuation file and put it into the
129 configuration directory. This is usually C</etc/gvpe>, depending on how you
130 configured gvpe, and can be overwritten using the C<-c> commandline switch.
131
132 Put the following lines into C</etc/gvpe/gvpe.conf>:
133
134 udp-port = 50000 # the external port to listen on (configure your firewall)
135 mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts
136 ifname = vpn0 # the local network device name
137
138 node = first # just a nickname
139 hostname = first.example.net # the DNS name or IP address of the host
140
141 node = second
142 hostname = 133.55.82.9
143
144 node = third
145 hostname = third.example.net
146
147 The only other file neccessary if the C<if-up> script that initializes the
148 local ethernet interface. Put the following lines into C</etc/gvpe/if-up>
149 and make it execute (C<chmod 755 /etc/gvpe/if-up>):
150
151 #!/bin/sh
152 ip link set $IFNAME address $MAC mtu $MTU up
153 [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME
154 [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
155 [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME
156 ip route add 10.0.0.0/16 dev $IFNAME
157
158 This script will give each node a different IP address in the C<10.0/16>
159 network. The internal network (e.g. the C<eth0> interface) should then be
160 set to a subset of that network, e.g. C<10.0.1.0/24> on node C<first>,
161 C<10.0.2.0/24> on node C<second>, and so on.
162
163 By enabling routing on the gateway host that runs C<gvpe> all nodes will
164 be able to reach the other nodes. You can, of course, also use proxy arp
165 or other means of pseudo-bridging (or even real briding), or (best) full
166 routing - the choice is yours.
167
168 =head2 STEP 2: create the RSA key pairs for all hosts
169
170 Run the following command to generate all key pairs (that might take a
171 while):
172
173 gvpectrl -c /etc/gvpe -g
174
175 This command will put the public keys into C<<
176 /etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<<
177 /etc/gvpe/hostkeys/I<nodename> >>.
178
179 =head2 STEP 3: distribute the config files to all nodes
180
181 Now distribute the config files to the other nodes. This should be done in two steps, since the
182 private keys should not be distributed. The example uses rsync-over-ssh
183
184 First all the config files without the hostkeys should be distributed:
185
186 rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys
187 rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys
188 rsync -avzessh /etc/gvpe third.example.net:/etc/. --exclude hostkeys
189
190 Then the hostkeys should be copied:
191
192 rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey
193 rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey
194 rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey
195
196 You should now check the configration by issuing the command C<gvpectrl -c
197 /etc/gvpe -s> on each node and verify it's output.
198
199 =head2 STEP 4: starting gvpe
200
201 You should then start gvpe on each node by issuing a command like:
202
203 gvpe -D -linfo first # first is the nodename
204
205 This will make the gvpe stay in foreground. You should then see
206 "connection established" messages. If you don't see them check your
207 firewall and routing (use tcpdump ;).
208
209 If this works you should check your networking setup by pinging various
210 endpoints.
211
212 To make gvpe run more permanently you can either run it as a daemon
213 (by starting it without the C<-D> switch), or, much better, from your
214 inittab. I use a line like this on my systems:
215
216 t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1
217
218 =head2 STEP 5: enjoy
219
220 ... and play around. Sending a -HUP (C<gvpectrl -kHUP>) to the daemon
221 will make it try to connect to all other nodes again. If you run it from
222 inittab, as is recommended, C<gvpectrl -k> (or simply C<killall gvpe>) will
223 kill the daemon, start it again, making it read it's configuration files
224 again.
225
226 =head1 SEE ALSO
227
228 gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), and
229 for a description of the protocol and routing algorithms, gvpe.protocol(7).
230
231 =head1 AUTHOR
232
233 Marc Lehmann <gvpe@plan9.de>
234
235 =head1 COPYRIGHTS AND LICENSES
236
237 GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file
238 COPYING that should be part of your distribution).
239
240 In some configurations it uses modified versions of the tinc vpn suite,
241 which is also available under the GENERAL PUBLIC LICENSE.
242