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1 1
2==== NAME ==== 2==== NAME ====
3 3
4 vpe - Overview of the virtual private ethernet suite. 4 GNU-VPE - Overview of the GNU Virtual Private Ethernet suite.
5 5
6 6
7==== DESCRIPTION ==== 7==== DESCRIPTION ====
8 8
9 Vpe is a suite designed to provide a virtual private network for 9 GVPE is a suite designed to provide a virtual private network for
10 multiple nodes over an untrusted network. 10 multiple nodes over an untrusted network. This document first gives an
11 introduction to VPNs in general and then describes the specific
12 implementation of GVPE.
11 13
14
15== WHAT IS A VPN? ==
16
17 VPN is an acronym, it stands for:
18
12 "Virtual" means that no physical network is created (of course), but an 19: Virtual means that no physical network is created (of course), but a
13 ethernet is emulated by creating multiple tunnels between the member 20 network is *emulated* by creating multiple tunnels between the
21 member nodes by encapsulating and sending data over another
22 transport network.
23
24 Usually the emulated network is a normal IP or Ethernet, and the
25 transport network is the Internet. However, using a VPN system like
26 GVPE to connect nodes over other untrusted networks such as Wireless
27 LAN is not uncommon.
28
14 nodes. "Private" means that non-participating nodes cannot decode 29: Private means that non-participating nodes cannot decode ("sniff)"
15 ("sniff)" nor inject ("spoof") packets. In the case of vpe, even 30 nor inject ("spoof") packets. This means that nodes can be connected
16 participating nodes cannot spoof packets from other nodes. And "network" 31 over untrusted networks such as the public Internet without fear of
17 means that more than two parties - many so-called vpn solutions only 32 being eavesdropped while at the same time being able to trust data
18 create point-to-point tunnels - can participate in the network, so it's 33 sent by other nodes.
19 possible to connect multiple branches of a company into a single
20 network.
21 34
35 In the case of GVPE, even participating nodes cannot sniff packets
36 send to other nodes or spoof packets as if sent from other nodes, so
37 communications between any two nodes is private to those two nodes.
22 38
39: Network means that more than two parties can participate in the
40 network, so for instance it's possible to connect multiple branches
41 of a company into a single network. Many so-called "vpn" solutions
42 only create point-to-point tunnels, which in turn can be used to
43 build larger networks.
44
45 GVPE provides a true multi-point network in wich any number of nodes
46 (at least a few dozen in practise, the theoretical limit is 4095
47 nodes) can participate.
48
49
23== DESIGN GOALS == 50== GVPE DESIGN GOALS ==
24 51
25: SIMPLE DESIGN 52: SIMPLE DESIGN
26 Cipher, HMAC algorithms and other key parameters must be selected at 53 Cipher, HMAC algorithms and other key parameters must be selected at
27 compile time - this makes it possible to only link in algorithms you 54 compile time - this makes it possible to only link in algorithms you
28 actually need. It also makes the crypto part of the source very 55 actually need. It also makes the crypto part of the source very
29 transparent and easy to inspect. 56 transparent and easy to inspect, and last not least this makes it
57 possible to hardcode the layout of all packets into the binary. GVPE
58 goes a step further and internally reserves blocks of the same
59 length for all packets, which virtually removes all possibilities of
60 buffer overflows, as there is only a single type of buffer and it's
61 always of fixed length.
30 62
31: EASY TO SETUP 63: EASY TO SETUP
32 A few lines of config (the config file is shared unmodified between 64 A few lines of config (the config file is shared unmodified between
33 all hosts) and a single run of ``vpectrl'' to generate the keys 65 all hosts) and a single run of ``gvpectrl'' to generate the keys
34 suffices to make it work. 66 suffices to make it work.
35 67
36: MAC-BASED SECURITY 68: MAC-BASED SECURITY
37 Since every host has it's own private key, other hosts cannot spoof 69 Since every host has it's own private key, other hosts cannot spoof
38 traffic from this host. That makes it possible to filter packest by 70 traffic from this host. That makes it possible to filter packet by
39 MAC address, e.g. to ensure that packets from a specific IP address 71 MAC address, e.g. to ensure that packets from a specific IP address
40 come, in fact, from a specific host. 72 come, in fact, from a specific host that is associated with that IP
73 and not from another host.
41 74
42 75
43==== PROGRAMS ==== 76==== PROGRAMS ====
44 77
45 Vpe comes with two programs: one daemon (``vped'') and one control 78 Vpe comes with two programs: one daemon (``gvpe'') and one control
46 program ``vpectrl''). 79 program (``gvpectrl'').
47 80
48: vpectrl 81: gvpectrl
49 Is used to generate the keys and give an overview of the 82 Is used to generate the keys, check and give an overview of of the
50 configuration. 83 configuration and contorl the daemon (restarting etc.).
51 84
52: vped 85: gvpe
53 Is the daemon used to establish and maintain conenctions to the 86 Is the daemon used to establish and maintain connections to the
54 other network members. It should be run on the gateway machine. 87 other network members. It should be run on the gateway machine.
55 88
56 89
57==== CONFIGURING VPE ==== 90==== COMPILETIME CONFIGURATION ====
58 91
59 Here are a few recipes for configuring your vpe: 92 Please have a look at the ``gvpe.osdep(5)'' manpage for
93 platform-specific information.
94
95 Here are a few recipes for compiling your gvpe, showing the extremes
96 (fast, small, insecure OR slow, large, more secure), between you should
97 choose:
60 98
61 99
62== AS LOW PACKET OVERHEAD AS POSSIBLE == 100== AS LOW PACKET OVERHEAD AS POSSIBLE ==
63 101
64 ./configure --enable-hmac-length=4 --enable-rand-length=0 102 ./configure --enable-hmac-length=4 --enable-rand-length=0
65 103
66 Minimize the header overhead of VPN packets. 104 Minimize the header overhead of VPN packets (the above will result in
105 only 4 bytes of overhead over the raw ethernet frame). This is a
106 insecure configuration because a HMAC length of 4 makes collision
107 attacks based on the birthday paradox easy, though.
67 108
68 109
69== MINIMIZE CPU TIME REQUIRED == 110== MINIMIZE CPU TIME REQUIRED ==
70 111
71 ./configure --enable-cipher=bf --enable-digest=md4 112 ./configure --enable-cipher=bf --enable-digest=md4
72 113
73 Use the fastest cipher and digest algorithms. 114 Use the fastest cipher and digest algorithms currently available in
115 gvpe. MD4 has been broken and is quite insecure, though.
74 116
75 117
76== MAXIMIZE SECURITY == 118== MAXIMIZE SECURITY ==
77 119
78 ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1 120 ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1
121
122 This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12
123 would also be pretty secure ;) and will additionally prefix each packet
124 with 8 bytes of random data. In the long run, people should move to
125 SHA-224 and beyond, but support in openssl is missing as of writing this
126 document.
79 127
80 In general, remember that AES-128 seems to be more secure and faster 128 In general, remember that AES-128 seems to be more secure and faster
81 than AES-192 or AES-256, more randomness and longer hmac is more secure, 129 than AES-192 or AES-256, more randomness helps against sniffing and a
82 MD4 is a fast digest, SHA1 or RIPEMD160 are better, and Blowfish is a 130 longer HMAC helps against spoofing. MD4 is a fast digest, SHA1 or
83 fast and so-far quite secure cipher. 131 RIPEMD160 are better, and Blowfish is a fast cipher (and also quite
132 secure).
84 133
85 134
86==== HOW TO SET UP A SIMPLE VPN ==== 135==== HOW TO SET UP A SIMPLE VPN ====
87 136
88 In this section I will describe how to get a simple VPN consisting of 137 In this section I will describe how to get a simple VPN consisting of
… …
90 139
91 140
92== STEP 1: configuration == 141== STEP 1: configuration ==
93 142
94 First you have to create a daemon configuation file and put it into the 143 First you have to create a daemon configuation file and put it into the
95 configuration directory. This is usually ``/etc/vpe'', depending on how 144 configuration directory. This is usually ``/etc/gvpe'', depending on how
96 you configured vpe, and can be overwritten using the ``-c'' commandline 145 you configured gvpe, and can be overwritten using the ``-c'' commandline
97 switch. 146 switch.
98 147
99 Put the following lines into ``/etc/vpe/vped.conf'': 148 Put the following lines into ``/etc/gvpe/gvpe.conf'':
100 149
101 udp-port = 50000 # the external port to listen on (configure your firewall) 150 udp-port = 50000 # the external port to listen on (configure your firewall)
102 mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts 151 mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts
103 ifname = vpn0 # the local network device name 152 ifname = vpn0 # the local network device name
104 153
105 node = first # just a nickname 154 node = first # just a nickname
106 hostname = first.example.net # the DNS name or IP address of the host 155 hostname = first.example.net # the DNS name or IP address of the host
107 156
108 node = second 157 node = second
109 hostname = 133.55.82.9 158 hostname = 133.55.82.9
110 159
111 node = third 160 node = third
112 hostname = third.example.net 161 hostname = third.example.net
113 162
114 The only other file neccessary if the ``if-up'' script that initializes 163 The only other file neccessary if the ``if-up'' script that initializes
115 the local ethernet interface. Put the following lines into 164 the local ethernet interface. Put the following lines into
116 ``/etc/vpe/if-up'' and make it execute (``chmod 755 /etc/vpe/if-up''): 165 ``/etc/gvpe/if-up'' and make it execute (``chmod 755 /etc/gvpe/if-up''):
117 166
118 #!/bin/sh 167 #!/bin/sh
119 ip link set $IFNAME address $MAC mtu $MTU up 168 ip link set $IFNAME address $MAC mtu $MTU up
120 [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME 169 [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME
121 [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME 170 [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
122 [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME 171 [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME
123 ip route add 10.0.0.0/16 dev $IFNAME 172 ip route add 10.0.0.0/16 dev $IFNAME
124 173
125 This script will give each node a different IP address in the 174 This script will give each node a different IP address in the
126 ``10.0/16'' network. The internal network (e.g. the ``eth0'' interface) 175 ``10.0/16'' network. The internal network (e.g. the ``eth0'' interface)
127 should then be set to a subset of that network, e.g. ``10.0.1.0/24'' on 176 should then be set to a subset of that network, e.g. ``10.0.1.0/24'' on
128 node ``first'', ``10.0.2.0/24'' on node ``second'', and so on. 177 node ``first'', ``10.0.2.0/24'' on node ``second'', and so on.
129 178
130 By enabling routing on the gateway host that runs ``vped'' all nodes 179 By enabling routing on the gateway host that runs ``gvpe'' all nodes
131 will be able to reach the other nodes. You can, of course, also use 180 will be able to reach the other nodes. You can, of course, also use
132 proxy arp or other means of pseudo-bridging (or even real briding), or 181 proxy arp or other means of pseudo-bridging (or even real briding), or
133 (best) full routing - the choice is yours. 182 (best) full routing - the choice is yours.
134 183
135 184
136== STEP 2: create the RSA key pairs for all hosts == 185== STEP 2: create the RSA key pairs for all hosts ==
137 186
138 Run the following command to generate all key pairs (that might take a 187 Run the following command to generate all key pairs (that might take a
139 while): 188 while):
140 189
141 vpectrl -c /etc/vpe -g 190 gvpectrl -c /etc/gvpe -g
142 191
143 This command will put the public keys into 192 This command will put the public keys into
144 ``/etc/vpe/pubkeys/*nodename*'' and the private keys into 193 ``/etc/gvpe/pubkeys/*nodename*'' and the private keys into
145 ``/etc/vpe/hostkeys/*nodename*''. 194 ``/etc/gvpe/hostkeys/*nodename*''.
146 195
147 196
148== STEP 3: distribute the config files to all nodes == 197== STEP 3: distribute the config files to all nodes ==
149 198
150 Now distribute the config files to the other nodes. This should be done 199 Now distribute the config files to the other nodes. This should be done
151 in two steps, since the private keys should not be distributed. The 200 in two steps, since the private keys should not be distributed. The
152 example uses rsync-over-ssh 201 example uses rsync-over-ssh
153 202
154 First all the config files without the hostkeys should be distributed: 203 First all the config files without the hostkeys should be distributed:
155 204
156 rsync -avzessh /etc/vpe first.example.net:/etc/. --exclude hostkeys 205 rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys
157 rsync -avzessh /etc/vpe 133.55.82.9:/etc/. --exclude hostkeys 206 rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys
158 rsync -avzessh /etc/vpe third.example.net:/etc/. --exclude hostkeys 207 rsync -avzessh /etc/gvpe third.example.net:/etc/. --exclude hostkeys
159 208
160 Then the hostkeys should be copied: 209 Then the hostkeys should be copied:
161 210
162 rsync -avzessh /etc/vpe/hostkeys/first first.example.net:/etc/hostkey 211 rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey
163 rsync -avzessh /etc/vpe/hostkeys/second 133.55.82.9:/etc/hostkey 212 rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey
164 rsync -avzessh /etc/vpe/hostkeys/third third.example.net:/etc/hostkey 213 rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey
165 214
166 You should now check the configration by issuing the command ``vpectrl 215 You should now check the configration by issuing the command ``gvpectrl
167 -c /etc/vpe -s'' on each node and verify it's output. 216 -c /etc/gvpe -s'' on each node and verify it's output.
168 217
169 218
170== STEP 4: starting vped == 219== STEP 4: starting gvpe ==
171 220
172 You should then start vped on each node by issuing a command like: 221 You should then start gvpe on each node by issuing a command like:
173 222
174 vped -D -linfo first # first is the nodename 223 gvpe -D -linfo first # first is the nodename
175 224
176 This will make the vped stay in foreground. You should then see 225 This will make the gvpe stay in foreground. You should then see
177 "connection established" messages. If you don't see them check your 226 "connection established" messages. If you don't see them check your
178 firewall and routing (use tcpdump ;). 227 firewall and routing (use tcpdump ;).
179 228
180 If this works you should check your networking setup by pinging various 229 If this works you should check your networking setup by pinging various
181 endpoints. 230 endpoints.
182 231
183 To make vped run more permanently you can either run it as a daemon (by 232 To make gvpe run more permanently you can either run it as a daemon (by
184 starting it without the ``-D'' switch), or, much better, from your 233 starting it without the ``-D'' switch), or, much better, from your
185 inittab. I use a line like this on my systems: 234 inittab. I use a line like this on my systems:
186 235
187 t1:2345:respawn:/opt/vpe/sbin/vped -D -L first >/dev/null 2>&1 236 t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1
188 237
189 238
190== STEP 5: enjoy == 239== STEP 5: enjoy ==
191 240
192 ... and play around. Sending a -HUP (``vpectrl -kHUP'') to the daemon 241 ... and play around. Sending a -HUP (``gvpectrl -kHUP'') to the daemon
193 will make it try to connect to all other nodes again. If you run it from 242 will make it try to connect to all other nodes again. If you run it from
194 inittab, as is recommended, ``vpectrl -k'' (or simply ``killall vped'') 243 inittab, as is recommended, ``gvpectrl -k'' (or simply ``killall gvpe'')
195 will kill the daemon, start it again, making it read it's configuration 244 will kill the daemon, start it again, making it read it's configuration
196 files again. 245 files again.
197 246
198 247
199==== SEE ALSO ==== 248==== SEE ALSO ====
200 249
201 vpe(8), vpectrl(8), vped.conf(5). 250 gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8),
251 and for a description of the transports, protocol, and routing
252 algorithm, gvpe.protocol(7).
253
254 The GVPE mailinglist, at <http://lists.schmorp.de/>, or
255 ``gvpe@lists.schmorp.de''.
202 256
203 257
204==== AUTHOR ==== 258==== AUTHOR ====
205 259
206 Marc Lehmann <vpe@plan9.de> 260 Marc Lehmann <gvpe@schmorp.de>
207 261
262
263==== COPYRIGHTS AND LICENSES ====
264
265 GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the
266 file COPYING that should be part of your distribution).
267
268 In some configurations it uses modified versions of the tinc vpn suite,
269 which is also available under the GENERAL PUBLIC LICENSE.
270

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