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4 GNU-VPE - Overview of the GNU 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
14 nodes. 21 member nodes by encapsulating and sending data over another
22 transport network.
15 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
16 "Private" means that non-participating nodes cannot decode ("sniff)" nor 29: Private means that non-participating nodes cannot decode ("sniff)"
17 inject ("spoof") packets. 30 nor inject ("spoof") packets. This means that nodes can be connected
31 over untrusted networks such as the public Internet without fear of
32 being eavesdropped while at the same time being able to trust data
33 sent by other nodes.
18 34
19 In the case of vpe, even participating nodes cannot sniff packets send 35 In the case of GVPE, even participating nodes cannot sniff packets
20 to other nodes or spoof packets as if sent from other nodes. 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.
21 38
22 "Network" means that more than two parties can participate in the 39: Network means that more than two parties can participate in the
23 network, so for instance it's possible to connect multiple branches of a 40 network, so for instance it's possible to connect multiple branches
24 company into a single network. Many so-called "vpn" solutions only 41 of a company into a single network. Many so-called "vpn" solutions
25 create point-to-point tunnels. 42 only create point-to-point tunnels, which in turn can be used to
43 build larger networks.
26 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.
27 48
49
28== DESIGN GOALS == 50== GVPE DESIGN GOALS ==
29 51
30: SIMPLE DESIGN 52: SIMPLE DESIGN
31 Cipher, HMAC algorithms and other key parameters must be selected at 53 Cipher, HMAC algorithms and other key parameters must be selected at
32 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
33 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
34 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.
35 62
36: EASY TO SETUP 63: EASY TO SETUP
37 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
38 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
39 suffices to make it work. 66 suffices to make it work.
40 67
41: MAC-BASED SECURITY 68: MAC-BASED SECURITY
42 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
43 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
44 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
45 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.
46 74
47 75
48==== PROGRAMS ==== 76==== PROGRAMS ====
49 77
50 Vpe comes with two programs: one daemon (``vped'') and one control 78 Vpe comes with two programs: one daemon (``gvpe'') and one control
51 program (``vpectrl''). 79 program (``gvpectrl'').
52 80
53: vpectrl 81: gvpectrl
54 Is used to generate the keys, check and give an overview of of the 82 Is used to generate the keys, check and give an overview of of the
55 configuration and contorl the daemon (restarting etc.). 83 configuration and contorl the daemon (restarting etc.).
56 84
57: vped 85: gvpe
58 Is the daemon used to establish and maintain conenctions to the 86 Is the daemon used to establish and maintain connections to the
59 other network members. It should be run on the gateway machine. 87 other network members. It should be run on the gateway machine.
60 88
61 89
62==== COMPILETIME CONFIGURATION ==== 90==== COMPILETIME CONFIGURATION ====
63 91
64 Please have a look at the ``vpe.osdep(5)'' manpage for platform-specific 92 Please have a look at the ``gvpe.osdep(5)'' manpage for
65 information. 93 platform-specific information.
66 94
67 Here are a few recipes for compiling your vpe: 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:
68 98
69 99
70== AS LOW PACKET OVERHEAD AS POSSIBLE == 100== AS LOW PACKET OVERHEAD AS POSSIBLE ==
71 101
72 ./configure --enable-hmac-length=4 --enable-rand-length=0 102 ./configure --enable-hmac-length=4 --enable-rand-length=0
73 103
74 Minimize the header overhead of VPN packets (the above will result in 104 Minimize the header overhead of VPN packets (the above will result in
75 only 4 bytes of overhead over the raw ethernet frame). 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.
76 108
77 109
78== MINIMIZE CPU TIME REQUIRED == 110== MINIMIZE CPU TIME REQUIRED ==
79 111
80 ./configure --enable-cipher=bf --enable-digest=md4 112 ./configure --enable-cipher=bf --enable-digest=md4
81 113
82 Use the fastest cipher and digest algorithms currently available in vpe. 114 Use the fastest cipher and digest algorithms currently available in
115 gvpe. MD4 has been broken and is quite insecure, though.
83 116
84 117
85== MAXIMIZE SECURITY == 118== MAXIMIZE SECURITY ==
86 119
87 ./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
88 121
89 This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12 122 This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12
90 would also be pretty secure ;) and will additionally prefix each packet 123 would also be pretty secure ;) and will additionally prefix each packet
91 with 8 bytes of random data. 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.
92 127
93 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
94 than AES-192 or AES-256, more randomness helps against sniffing and a 129 than AES-192 or AES-256, more randomness helps against sniffing and a
95 longer HMAC helps against spoofing. MD4 is a fast digest, SHA1 or 130 longer HMAC helps against spoofing. MD4 is a fast digest, SHA1 or
96 RIPEMD160 are better, and Blowfish is a fast cipher (and also quite 131 RIPEMD160 are better, and Blowfish is a fast cipher (and also quite
… …
104 139
105 140
106== STEP 1: configuration == 141== STEP 1: configuration ==
107 142
108 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
109 configuration directory. This is usually ``/etc/vpe'', depending on how 144 configuration directory. This is usually ``/etc/gvpe'', depending on how
110 you configured vpe, and can be overwritten using the ``-c'' commandline 145 you configured gvpe, and can be overwritten using the ``-c'' commandline
111 switch. 146 switch.
112 147
113 Put the following lines into ``/etc/vpe/vped.conf'': 148 Put the following lines into ``/etc/gvpe/gvpe.conf'':
114 149
115 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)
116 mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts 151 mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts
117 ifname = vpn0 # the local network device name 152 ifname = vpn0 # the local network device name
118 153
… …
125 node = third 160 node = third
126 hostname = third.example.net 161 hostname = third.example.net
127 162
128 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
129 the local ethernet interface. Put the following lines into 164 the local ethernet interface. Put the following lines into
130 ``/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''):
131 166
132 #!/bin/sh 167 #!/bin/sh
133 ip link set $IFNAME address $MAC mtu $MTU up 168 ip link set $IFNAME address $MAC mtu $MTU up
134 [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME 169 [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME
135 [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME 170 [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
… …
139 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
140 ``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)
141 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
142 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.
143 178
144 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
145 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
146 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
147 (best) full routing - the choice is yours. 182 (best) full routing - the choice is yours.
148 183
149 184
150== STEP 2: create the RSA key pairs for all hosts == 185== STEP 2: create the RSA key pairs for all hosts ==
151 186
152 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
153 while): 188 while):
154 189
155 vpectrl -c /etc/vpe -g 190 gvpectrl -c /etc/gvpe -g
156 191
157 This command will put the public keys into 192 This command will put the public keys into
158 ``/etc/vpe/pubkeys/*nodename*'' and the private keys into 193 ``/etc/gvpe/pubkeys/*nodename*'' and the private keys into
159 ``/etc/vpe/hostkeys/*nodename*''. 194 ``/etc/gvpe/hostkeys/*nodename*''.
160 195
161 196
162== STEP 3: distribute the config files to all nodes == 197== STEP 3: distribute the config files to all nodes ==
163 198
164 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
165 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
166 example uses rsync-over-ssh 201 example uses rsync-over-ssh
167 202
168 First all the config files without the hostkeys should be distributed: 203 First all the config files without the hostkeys should be distributed:
169 204
170 rsync -avzessh /etc/vpe first.example.net:/etc/. --exclude hostkeys 205 rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys
171 rsync -avzessh /etc/vpe 133.55.82.9:/etc/. --exclude hostkeys 206 rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys
172 rsync -avzessh /etc/vpe third.example.net:/etc/. --exclude hostkeys 207 rsync -avzessh /etc/gvpe third.example.net:/etc/. --exclude hostkeys
173 208
174 Then the hostkeys should be copied: 209 Then the hostkeys should be copied:
175 210
176 rsync -avzessh /etc/vpe/hostkeys/first first.example.net:/etc/hostkey 211 rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey
177 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
178 rsync -avzessh /etc/vpe/hostkeys/third third.example.net:/etc/hostkey 213 rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey
179 214
180 You should now check the configration by issuing the command ``vpectrl 215 You should now check the configration by issuing the command ``gvpectrl
181 -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.
182 217
183 218
184== STEP 4: starting vped == 219== STEP 4: starting gvpe ==
185 220
186 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:
187 222
188 vped -D -linfo first # first is the nodename 223 gvpe -D -linfo first # first is the nodename
189 224
190 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
191 "connection established" messages. If you don't see them check your 226 "connection established" messages. If you don't see them check your
192 firewall and routing (use tcpdump ;). 227 firewall and routing (use tcpdump ;).
193 228
194 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
195 endpoints. 230 endpoints.
196 231
197 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
198 starting it without the ``-D'' switch), or, much better, from your 233 starting it without the ``-D'' switch), or, much better, from your
199 inittab. I use a line like this on my systems: 234 inittab. I use a line like this on my systems:
200 235
201 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
202 237
203 238
204== STEP 5: enjoy == 239== STEP 5: enjoy ==
205 240
206 ... and play around. Sending a -HUP (``vpectrl -kHUP'') to the daemon 241 ... and play around. Sending a -HUP (``gvpectrl -kHUP'') to the daemon
207 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
208 inittab, as is recommended, ``vpectrl -k'' (or simply ``killall vped'') 243 inittab, as is recommended, ``gvpectrl -k'' (or simply ``killall gvpe'')
209 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
210 files again. 245 files again.
211 246
212 247
213==== SEE ALSO ==== 248==== SEE ALSO ====
214 249
215 vpe.osdep(5) for OS-depedendent information, vped.conf(5), vpectrl(8), 250 gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8),
216 and for a description of the protocol and routing algorithms, 251 and for a description of the transports, protocol, and routing
217 vpe.protocol(7). 252 algorithm, gvpe.protocol(7).
253
254 The GVPE mailinglist, at <http://lists.schmorp.de/>, or
255 ``gvpe@lists.schmorp.de''.
218 256
219 257
220==== AUTHOR ==== 258==== AUTHOR ====
221 259
222 Marc Lehmann <vpe@plan9.de> 260 Marc Lehmann <gvpe@schmorp.de>
223 261
224 262
225==== COPYRIGHTS AND LICENSES ==== 263==== COPYRIGHTS AND LICENSES ====
226 264
227 Vpe itself is distributed under the GENERAL PUBLIC LICENSE (see the file 265 GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the
228 COPYING that should be part of your distribution). 266 file COPYING that should be part of your distribution).
229 267
230 In some configurations it uses modified versions of the tinc vpn suite, 268 In some configurations it uses modified versions of the tinc vpn suite,
231 which is also available under the GENERAL PUBLIC LICENSE. 269 which is also available under the GENERAL PUBLIC LICENSE.
232 270
233 In some configurations (notably darwin), it uses a poll emulation
234 library that comes with the following license notice:
235
236 Copyright (c) 1995-2002 Brian M. Clapper
237 All rights reserved.
238
239 Redistribution and use in source and binary forms are permitted
240 provided that: (1) source distributions retain this entire
241 copyright notice and comment; (2) modifications made to the
242 software are prominently mentioned, and a copy of the original
243 software (or a pointer to its location) are included; and (3)
244 distributions including binaries display the following
245 acknowledgement: "This product includes software developed by Brian
246 M. Clapper <bmc@clapper.org>" in the documentation or other
247 materials provided with the distribution. The name of the author
248 may not be used to endorse or promote products derived from this
249 software without specific prior written permission.
250
251 THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
252 IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
253 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
254

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