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Revision 1.10 by root, Wed Jul 10 01:51:40 2013 UTC

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12 12
13VPN is an acronym, it stands for: 13VPN is an acronym, it stands for:
14 14
15=over 4 15=over 4
16 16
17=item X<Virtual> 17=item Virtual
18 18
19Virtual means that no physical network is created (of course), but a 19Virtual means that no physical network is created (of course), but a
20network is I<emulated> by creating multiple tunnels between the member 20network is I<emulated> by creating multiple tunnels between the member
21nodes by encapsulating and sending data over another transport network. 21nodes by encapsulating and sending data over another transport network.
22 22
23Usually the emulated network is a normal IP or Ethernet, and the transport 23Usually the emulated network is a normal IP or Ethernet, and the transport
24network is the Internet. However, using a VPN system like GVPE to connect 24network is the Internet. However, using a VPN system like GVPE to connect
25nodes over other untrusted networks such as Wireless LAN is not uncommon. 25nodes over other untrusted networks such as Wireless LAN is not uncommon.
26 26
27=item X<Private> 27=item Private
28 28
29Private means that non-participating nodes cannot decode ("sniff)" nor 29Private means that non-participating nodes cannot decode ("sniff)" nor
30inject ("spoof") packets. This means that nodes can be connected over 30inject ("spoof") packets. This means that nodes can be connected over
31untrusted networks such as the public Internet without fear of being 31untrusted networks such as the public Internet without fear of being
32eavesdropped while at the same time being able to trust data sent by other 32eavesdropped while at the same time being able to trust data sent by other
… …
34 34
35In the case of GVPE, even participating nodes cannot sniff packets 35In the case of GVPE, even participating nodes cannot sniff packets
36send to other nodes or spoof packets as if sent from other nodes, so 36send to other nodes or spoof packets as if sent from other nodes, so
37communications between any two nodes is private to those two nodes. 37communications between any two nodes is private to those two nodes.
38 38
39=item X<Network> 39=item Network
40 40
41Network means that more than two parties can participate in the network, 41Network means that more than two parties can participate in the network,
42so for instance it's possible to connect multiple branches of a company 42so for instance it's possible to connect multiple branches of a company
43into a single network. Many so-called "vpn" solutions only create 43into a single network. Many so-called "VPN" solutions only create
44point-to-point tunnels, which in turn can be used to build larger 44point-to-point tunnels, which in turn can be used to build larger
45networks. 45networks.
46 46
47GVPE provides a true multi-point network in wich any number of nodes (at 47GVPE provides a true multi-point network in which any number of nodes (at
48least a few dozen in practise, the theoretical limit is 4095 nodes) can 48least a few dozen in practise, the theoretical limit is 4095 nodes) can
49participate. 49participate.
50 50
51=back 51=back
52 52
53=head2 GVPE DESIGN GOALS 53=head2 GVPE DESIGN GOALS
54 54
55=over 4 55=over 4
56 56
57=item SIMPLE DESIGN 57=item SIMPLE DESIGN
58 58
59Cipher, HMAC algorithms and other key parameters must be selected 59Cipher, HMAC algorithms and other key parameters must be selected
60at compile time - this makes it possible to only link in algorithms 60at compile time - this makes it possible to only link in algorithms
… …
81 81
82=back 82=back
83 83
84=head1 PROGRAMS 84=head1 PROGRAMS
85 85
86Vpe comes with two programs: one daemon (C<gvpe>) and one control program 86Gvpe comes with two programs: one daemon (C<gvpe>) and one control program
87(C<gvpectrl>). 87(C<gvpectrl>).
88 88
89=over 4 89=over 4
90 90
91=item gvpectrl 91=item gvpectrl
92 92
93Is used to generate the keys, check and give an overview of of the 93This program is used to generate the keys, check and give an overview of of the
94configuration and contorl the daemon (restarting etc.). 94configuration and to control the daemon (restarting etc.).
95 95
96=item gvpe 96=item gvpe
97 97
98Is the daemon used to establish and maintain connections to the other 98This is the daemon used to establish and maintain connections to the other
99network members. It should be run on the gateway machine. 99network nodes. It should be run on the gateway of each VPN subnet.
100 100
101=back 101=back
102 102
103=head1 COMPILETIME CONFIGURATION 103=head1 COMPILETIME CONFIGURATION
104 104
105Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific 105Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific
106information. 106information.
107 107
108Gvpe hardcodes most encryption parameters. While this reduces flexibility,
109it makes the program much simpler and helps making buffer overflows
110impossible under most circumstances.
111
108Here are a few recipes for compiling your gvpe, showing the extremes 112Here are a few recipes for compiling your gvpe, showing the extremes
109(fast, small, insecure OR slow, large, more secure), between you should 113(fast, small, insecure OR slow, large, more secure), between which you
110choose: 114should choose:
111 115
112=head2 AS LOW PACKET OVERHEAD AS POSSIBLE 116=head2 AS LOW PACKET OVERHEAD AS POSSIBLE
113 117
114 ./configure --enable-hmac-length=4 --enable-rand-length=0 118 ./configure --enable-hmac-length=4 --enable-rand-length=0
115 119
116Minimize the header overhead of VPN packets (the above will result in 120Minimize the header overhead of VPN packets (the above will result in
117only 4 bytes of overhead over the raw ethernet frame). This is a insecure 121only 4 bytes of overhead over the raw ethernet frame). This is a insecure
118configuration because a HMAC length of 4 makes collision attacks based on 122configuration because a HMAC length of 4 makes collision attacks based on
119the birthday paradox easy, though. 123the birthday paradox pretty easy.
120 124
121=head2 MINIMIZE CPU TIME REQUIRED 125=head2 MINIMIZE CPU TIME REQUIRED
122 126
123 ./configure --enable-cipher=bf --enable-digest=md4 127 ./configure --enable-cipher=bf --enable-digest=md4
124 128
125Use the fastest cipher and digest algorithms currently available in 129Use the fastest cipher and digest algorithms currently available in
126gvpe. MD4 has been broken and is quite insecure, though. 130gvpe. MD4 has been broken and is quite insecure, though, so using another
131digest algorithm is recommended.
127 132
128=head2 MAXIMIZE SECURITY 133=head2 MAXIMIZE SECURITY
129 134
130 ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1 135 ./configure --enable-hmac-length=16 --enable-rand-length=16 --enable-digest=sha384
131 136
132This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12 137This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12
133would also be pretty secure ;) and will additionally prefix each packet 138would also be pretty secure ;) and will additionally prefix each packet
134with 8 bytes of random data. In the long run, people should move to 139with 16 bytes of random data.
135SHA-224 and beyond, but support in openssl is missing as of writing this
136document.
137 140
138In general, remember that AES-128 seems to be more secure and faster than 141In general, remember that AES-128 seems to be as secure but faster than
139AES-192 or AES-256, more randomness helps against sniffing and a longer 142AES-192 or AES-256, more randomness helps against sniffing and a longer
140HMAC helps against spoofing. MD4 is a fast digest, SHA1 or RIPEMD160 are 143HMAC helps against spoofing. MD4 is a fast digest, SHA1, RIPEMD160, SHA256
141better, and Blowfish is a fast cipher (and also quite secure). 144are consecutively better, and Blowfish is a fast cipher (and also quite
145secure).
142 146
143=head1 HOW TO SET UP A SIMPLE VPN 147=head1 HOW TO SET UP A SIMPLE VPN
144 148
145In this section I will describe how to get a simple VPN consisting of 149In this section I will describe how to get a simple VPN consisting of
146three hosts up and running. 150three hosts up and running.
147 151
148=head2 STEP 1: configuration 152=head2 STEP 1: configuration
149 153
150First you have to create a daemon configuation file and put it into the 154First you have to create a daemon configuration file and put it into the
151configuration directory. This is usually C</etc/gvpe>, depending on how you 155configuration directory. This is usually C</etc/gvpe>, depending on how you
152configured gvpe, and can be overwritten using the C<-c> commandline switch. 156configured gvpe, and can be overwritten using the C<-c> command line switch.
153 157
154Put the following lines into C</etc/gvpe/gvpe.conf>: 158Put the following lines into C</etc/gvpe/gvpe.conf>:
155 159
156 udp-port = 50000 # the external port to listen on (configure your firewall) 160 udp-port = 50000 # the external port to listen on (configure your firewall)
157 mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts 161 mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts
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164 hostname = 133.55.82.9 168 hostname = 133.55.82.9
165 169
166 node = third 170 node = third
167 hostname = third.example.net 171 hostname = third.example.net
168 172
169The only other file neccessary if the C<if-up> script that initializes the 173The only other file necessary is the C<if-up> script that initializes the
170local ethernet interface. Put the following lines into C</etc/gvpe/if-up> 174virtual ethernet interface on the local host. Put the following lines into
171and make it execute (C<chmod 755 /etc/gvpe/if-up>): 175C</etc/gvpe/if-up> and make it executable (C<chmod 755 /etc/gvpe/if-up>):
172 176
173 #!/bin/sh 177 #!/bin/sh
174 ip link set $IFNAME address $MAC mtu $MTU up 178 ip link set $IFNAME address $MAC mtu $MTU up
175 [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME 179 [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME
176 [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME 180 [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
177 [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME 181 [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME
178 ip route add 10.0.0.0/16 dev $IFNAME 182 ip route add 10.0.0.0/16 dev $IFNAME
179 183
180This script will give each node a different IP address in the C<10.0/16> 184This script will give each node a different IP address in the C<10.0/16>
181network. The internal network (e.g. the C<eth0> interface) should then be 185network. The internal network (if gvpe runs on a router) should then be
182set to a subset of that network, e.g. C<10.0.1.0/24> on node C<first>, 186set to a subset of that network, e.g. C<10.0.1.0/24> on node C<first>,
183C<10.0.2.0/24> on node C<second>, and so on. 187C<10.0.2.0/24> on node C<second>, and so on.
184 188
185By enabling routing on the gateway host that runs C<gvpe> all nodes will 189By enabling routing on the gateway host that runs C<gvpe> all nodes will
186be able to reach the other nodes. You can, of course, also use proxy arp 190be able to reach the other nodes. You can, of course, also use proxy ARP
187or other means of pseudo-bridging (or even real briding), or (best) full 191or other means of pseudo-bridging, or (best) full routing - the choice is
188routing - the choice is yours. 192yours.
189 193
190=head2 STEP 2: create the RSA key pairs for all hosts 194=head2 STEP 2: create the RSA key pairs for all hosts
191 195
192Run the following command to generate all key pairs (that might take a 196Run the following command to generate all key pairs for all nodes (that
193while): 197might take a while):
194 198
195 gvpectrl -c /etc/gvpe -g 199 gvpectrl -c /etc/gvpe -g
196 200
197This command will put the public keys into C<< 201This command will put the public keys into C<<
198/etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<< 202/etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<<
199/etc/gvpe/hostkeys/I<nodename> >>. 203/etc/gvpe/hostkeys/I<nodename> >>.
200 204
201=head2 STEP 3: distribute the config files to all nodes 205=head2 STEP 3: distribute the config files to all nodes
202 206
203Now distribute the config files to the other nodes. This should be done in two steps, since the 207Now distribute the config files and private keys to the other nodes. This
204private keys should not be distributed. The example uses rsync-over-ssh 208should be done in two steps, since only the private keys meant for a node
209should be distributed (so each node has only it's own private key).
210
211The example uses rsync-over-ssh
205 212
206First all the config files without the hostkeys should be distributed: 213First all the config files without the hostkeys should be distributed:
207 214
208 rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys 215 rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys
209 rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys 216 rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys
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213 220
214 rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey 221 rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey
215 rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey 222 rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey
216 rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey 223 rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey
217 224
218You should now check the configration by issuing the command C<gvpectrl -c 225You should now check the configuration by issuing the command C<gvpectrl -c
219/etc/gvpe -s> on each node and verify it's output. 226/etc/gvpe -s> on each node and verify it's output.
220 227
221=head2 STEP 4: starting gvpe 228=head2 STEP 4: starting gvpe
222 229
223You should then start gvpe on each node by issuing a command like: 230You should then start gvpe on each node by issuing a command like:
224 231
225 gvpe -D -linfo first # first is the nodename 232 gvpe -D -l info first # first is the nodename
226 233
227This will make the gvpe stay in foreground. You should then see 234This will make the gvpe daemon stay in foreground. You should then see
228"connection established" messages. If you don't see them check your 235"connection established" messages. If you don't see them check your
229firewall and routing (use tcpdump ;). 236firewall and routing (use tcpdump ;).
230 237
231If this works you should check your networking setup by pinging various 238If this works you should check your networking setup by pinging various
232endpoints. 239endpoints.
233 240
234To make gvpe run more permanently you can either run it as a daemon 241To make gvpe run more permanently you can either run it as a daemon (by
235(by starting it without the C<-D> switch), or, much better, from your 242starting it without the C<-D> switch), or, much better, from your inittab
236inittab. I use a line like this on my systems: 243or equivalent. I use a line like this on all my systems:
237 244
238 t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1 245 t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1
239 246
240=head2 STEP 5: enjoy 247=head2 STEP 5: enjoy
241 248
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245kill the daemon, start it again, making it read it's configuration files 252kill the daemon, start it again, making it read it's configuration files
246again. 253again.
247 254
248=head1 SEE ALSO 255=head1 SEE ALSO
249 256
250gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), and 257gvpe.osdep(5) for OS-dependent information, gvpe.conf(5), gvpectrl(8),
251for a description of the protocol and routing algorithms, gvpe.protocol(7). 258and for a description of the transports, protocol, and routing algorithm,
259gvpe.protocol(7).
260
261The GVPE mailing list, at L<http://lists.schmorp.de/>, or
262C<gvpe@lists.schmorp.de>.
252 263
253=head1 AUTHOR 264=head1 AUTHOR
254 265
255Marc Lehmann <gvpe@plan9.de> 266Marc Lehmann <gvpe@schmorp.de>
256 267
257=head1 COPYRIGHTS AND LICENSES 268=head1 COPYRIGHTS AND LICENSES
258 269
259GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file 270GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file
260COPYING that should be part of your distribution). 271COPYING that should be part of your distribution).

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