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Revision: 1.11
Committed: Wed Sep 3 04:58:46 2008 UTC (15 years, 8 months ago) by pcg
Branch: MAIN
CVS Tags: rel-2_21, rel-2_22
Changes since 1.10: +6 -6 lines
Log Message:
2.21

File Contents

# User Rev Content
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134     .IX Title "GVPE 5"
135 pcg 1.10 .TH GVPE 5 "2008-09-01" "2.2" "GNU Virtual Private Ethernet"
136     .\" For nroff, turn off justification. Always turn off hyphenation; it makes
137     .\" way too many mistakes in technical documents.
138     .if n .ad l
139     .nh
140 pcg 1.1 .SH "NAME"
141     GNU\-VPE \- Overview of the GNU Virtual Private Ethernet suite.
142     .SH "DESCRIPTION"
143     .IX Header "DESCRIPTION"
144     \&\s-1GVPE\s0 is a suite designed to provide a virtual private network for multiple
145 pcg 1.5 nodes over an untrusted network. This document first gives an introduction
146     to VPNs in general and then describes the specific implementation of \s-1GVPE\s0.
147     .Sh "\s-1WHAT\s0 \s-1IS\s0 A \s-1VPN\s0?"
148     .IX Subsection "WHAT IS A VPN?"
149     \&\s-1VPN\s0 is an acronym, it stands for:
150 pcg 1.11 .IP "Virtual" 4
151     .IX Item "Virtual"
152 pcg 1.5 Virtual means that no physical network is created (of course), but a
153     network is \fIemulated\fR by creating multiple tunnels between the member
154     nodes by encapsulating and sending data over another transport network.
155     .Sp
156     Usually the emulated network is a normal \s-1IP\s0 or Ethernet, and the transport
157     network is the Internet. However, using a \s-1VPN\s0 system like \s-1GVPE\s0 to connect
158     nodes over other untrusted networks such as Wireless \s-1LAN\s0 is not uncommon.
159 pcg 1.11 .IP "Private" 4
160     .IX Item "Private"
161 pcg 1.3 Private means that non-participating nodes cannot decode (\*(L"sniff)\*(R" nor
162 pcg 1.5 inject (\*(L"spoof\*(R") packets. This means that nodes can be connected over
163     untrusted networks such as the public Internet without fear of being
164     eavesdropped while at the same time being able to trust data sent by other
165     nodes.
166 pcg 1.3 .Sp
167 pcg 1.5 In the case of \s-1GVPE\s0, even participating nodes cannot sniff packets
168     send to other nodes or spoof packets as if sent from other nodes, so
169     communications between any two nodes is private to those two nodes.
170 pcg 1.11 .IP "Network" 4
171     .IX Item "Network"
172 pcg 1.3 Network means that more than two parties can participate in the network,
173     so for instance it's possible to connect multiple branches of a company
174 pcg 1.10 into a single network. Many so-called \*(L"\s-1VPN\s0\*(R" solutions only create
175 pcg 1.5 point-to-point tunnels, which in turn can be used to build larger
176     networks.
177     .Sp
178 pcg 1.10 \&\s-1GVPE\s0 provides a true multi-point network in which any number of nodes (at
179 pcg 1.5 least a few dozen in practise, the theoretical limit is 4095 nodes) can
180     participate.
181     .Sh "\s-1GVPE\s0 \s-1DESIGN\s0 \s-1GOALS\s0"
182     .IX Subsection "GVPE DESIGN GOALS"
183 pcg 1.1 .IP "\s-1SIMPLE\s0 \s-1DESIGN\s0" 4
184     .IX Item "SIMPLE DESIGN"
185     Cipher, \s-1HMAC\s0 algorithms and other key parameters must be selected
186     at compile time \- this makes it possible to only link in algorithms
187     you actually need. It also makes the crypto part of the source very
188 pcg 1.5 transparent and easy to inspect, and last not least this makes it possible
189     to hardcode the layout of all packets into the binary. \s-1GVPE\s0 goes a step
190     further and internally reserves blocks of the same length for all packets,
191     which virtually removes all possibilities of buffer overflows, as there is
192     only a single type of buffer and it's always of fixed length.
193 pcg 1.1 .IP "\s-1EASY\s0 \s-1TO\s0 \s-1SETUP\s0" 4
194     .IX Item "EASY TO SETUP"
195     A few lines of config (the config file is shared unmodified between all
196     hosts) and a single run of \f(CW\*(C`gvpectrl\*(C'\fR to generate the keys suffices to
197     make it work.
198     .IP "MAC-BASED \s-1SECURITY\s0" 4
199     .IX Item "MAC-BASED SECURITY"
200     Since every host has it's own private key, other hosts cannot spoof
201     traffic from this host. That makes it possible to filter packet by \s-1MAC\s0
202     address, e.g. to ensure that packets from a specific \s-1IP\s0 address come, in
203     fact, from a specific host that is associated with that \s-1IP\s0 and not from
204     another host.
205     .SH "PROGRAMS"
206     .IX Header "PROGRAMS"
207 pcg 1.10 Gvpe comes with two programs: one daemon (\f(CW\*(C`gvpe\*(C'\fR) and one control program
208 pcg 1.1 (\f(CW\*(C`gvpectrl\*(C'\fR).
209     .IP "gvpectrl" 4
210     .IX Item "gvpectrl"
211 pcg 1.10 This program is used to generate the keys, check and give an overview of of the
212     configuration and to control the daemon (restarting etc.).
213 pcg 1.1 .IP "gvpe" 4
214     .IX Item "gvpe"
215 pcg 1.10 This is the daemon used to establish and maintain connections to the other
216     network nodes. It should be run on the gateway of each \s-1VPN\s0 subnet.
217 pcg 1.1 .SH "COMPILETIME CONFIGURATION"
218     .IX Header "COMPILETIME CONFIGURATION"
219     Please have a look at the \f(CW\*(C`gvpe.osdep(5)\*(C'\fR manpage for platform-specific
220     information.
221     .PP
222 pcg 1.10 Gvpe hardcodes most encryption parameters. While this reduces flexibility,
223     it makes the program much simpler and helps making buffer overflows
224     impossible under most circumstances.
225     .PP
226 pcg 1.4 Here are a few recipes for compiling your gvpe, showing the extremes
227 pcg 1.10 (fast, small, insecure \s-1OR\s0 slow, large, more secure), between which you
228     should choose:
229 pcg 1.1 .Sh "\s-1AS\s0 \s-1LOW\s0 \s-1PACKET\s0 \s-1OVERHEAD\s0 \s-1AS\s0 \s-1POSSIBLE\s0"
230     .IX Subsection "AS LOW PACKET OVERHEAD AS POSSIBLE"
231     .Vb 1
232 pcg 1.10 \& ./configure \-\-enable\-hmac\-length=4 \-\-enable\-rand\-length=0
233 pcg 1.1 .Ve
234     .PP
235 pcg 1.4 Minimize the header overhead of \s-1VPN\s0 packets (the above will result in
236     only 4 bytes of overhead over the raw ethernet frame). This is a insecure
237     configuration because a \s-1HMAC\s0 length of 4 makes collision attacks based on
238 pcg 1.10 the birthday paradox pretty easy.
239 pcg 1.1 .Sh "\s-1MINIMIZE\s0 \s-1CPU\s0 \s-1TIME\s0 \s-1REQUIRED\s0"
240     .IX Subsection "MINIMIZE CPU TIME REQUIRED"
241     .Vb 1
242 pcg 1.10 \& ./configure \-\-enable\-cipher=bf \-\-enable\-digest=md4
243 pcg 1.1 .Ve
244     .PP
245 pcg 1.4 Use the fastest cipher and digest algorithms currently available in
246 pcg 1.10 gvpe. \s-1MD4\s0 has been broken and is quite insecure, though, so using another
247     digest algorithm is recommended.
248 pcg 1.1 .Sh "\s-1MAXIMIZE\s0 \s-1SECURITY\s0"
249     .IX Subsection "MAXIMIZE SECURITY"
250     .Vb 1
251 pcg 1.10 \& ./configure \-\-enable\-hmac\-length=16 \-\-enable\-rand\-length=8 \-\-enable\-digest=sha1
252 pcg 1.1 .Ve
253     .PP
254     This uses a 16 byte \s-1HMAC\s0 checksum to authenticate packets (I guess 8\-12
255     would also be pretty secure ;) and will additionally prefix each packet
256 pcg 1.2 with 8 bytes of random data. In the long run, people should move to
257 pcg 1.10 \&\s-1SHA\-256\s0 and beyond).
258 pcg 1.1 .PP
259 pcg 1.10 In general, remember that \s-1AES\-128\s0 seems to be as secure but faster than
260 pcg 1.1 \&\s-1AES\-192\s0 or \s-1AES\-256\s0, more randomness helps against sniffing and a longer
261 pcg 1.10 \&\s-1HMAC\s0 helps against spoofing. \s-1MD4\s0 is a fast digest, \s-1SHA1\s0, \s-1RIPEMD160\s0, \s-1SHA256\s0
262     are consecutively better, and Blowfish is a fast cipher (and also quite
263     secure).
264 pcg 1.1 .SH "HOW TO SET UP A SIMPLE VPN"
265     .IX Header "HOW TO SET UP A SIMPLE VPN"
266     In this section I will describe how to get a simple \s-1VPN\s0 consisting of
267     three hosts up and running.
268     .Sh "\s-1STEP\s0 1: configuration"
269     .IX Subsection "STEP 1: configuration"
270 pcg 1.10 First you have to create a daemon configuration file and put it into the
271 pcg 1.1 configuration directory. This is usually \f(CW\*(C`/etc/gvpe\*(C'\fR, depending on how you
272 pcg 1.10 configured gvpe, and can be overwritten using the \f(CW\*(C`\-c\*(C'\fR command line switch.
273 pcg 1.1 .PP
274     Put the following lines into \f(CW\*(C`/etc/gvpe/gvpe.conf\*(C'\fR:
275     .PP
276     .Vb 3
277 pcg 1.10 \& udp\-port = 50000 # the external port to listen on (configure your firewall)
278 pcg 1.1 \& mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts
279     \& ifname = vpn0 # the local network device name
280 pcg 1.10 \&
281 pcg 1.1 \& node = first # just a nickname
282     \& hostname = first.example.net # the DNS name or IP address of the host
283 pcg 1.10 \&
284 pcg 1.1 \& node = second
285     \& hostname = 133.55.82.9
286 pcg 1.10 \&
287 pcg 1.1 \& node = third
288     \& hostname = third.example.net
289     .Ve
290     .PP
291 pcg 1.10 The only other file necessary is the \f(CW\*(C`if\-up\*(C'\fR script that initializes the
292     virtual ethernet interface on the local host. Put the following lines into
293     \&\f(CW\*(C`/etc/gvpe/if\-up\*(C'\fR and make it executable (\f(CW\*(C`chmod 755 /etc/gvpe/if\-up\*(C'\fR):
294 pcg 1.1 .PP
295     .Vb 6
296     \& #!/bin/sh
297     \& ip link set $IFNAME address $MAC mtu $MTU up
298     \& [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME
299     \& [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
300     \& [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME
301     \& ip route add 10.0.0.0/16 dev $IFNAME
302     .Ve
303     .PP
304     This script will give each node a different \s-1IP\s0 address in the \f(CW\*(C`10.0/16\*(C'\fR
305 pcg 1.10 network. The internal network (if gvpe runs on a router) should then be
306 pcg 1.1 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,
307     \&\f(CW\*(C`10.0.2.0/24\*(C'\fR on node \f(CW\*(C`second\*(C'\fR, and so on.
308     .PP
309     By enabling routing on the gateway host that runs \f(CW\*(C`gvpe\*(C'\fR all nodes will
310 pcg 1.10 be able to reach the other nodes. You can, of course, also use proxy \s-1ARP\s0
311     or other means of pseudo-bridging, or (best) full routing \- the choice is
312     yours.
313 pcg 1.1 .Sh "\s-1STEP\s0 2: create the \s-1RSA\s0 key pairs for all hosts"
314     .IX Subsection "STEP 2: create the RSA key pairs for all hosts"
315 pcg 1.10 Run the following command to generate all key pairs for all nodes (that
316     might take a while):
317 pcg 1.1 .PP
318     .Vb 1
319 pcg 1.10 \& gvpectrl \-c /etc/gvpe \-g
320 pcg 1.1 .Ve
321     .PP
322     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.
323     .Sh "\s-1STEP\s0 3: distribute the config files to all nodes"
324     .IX Subsection "STEP 3: distribute the config files to all nodes"
325 pcg 1.10 Now distribute the config files and private keys to the other nodes. This
326     should be done in two steps, since only the private keys meant for a node
327     should be distributed (so each node has only it's own private key).
328     .PP
329     The example uses rsync-over-ssh
330 pcg 1.1 .PP
331     First all the config files without the hostkeys should be distributed:
332     .PP
333     .Vb 3
334 pcg 1.10 \& rsync \-avzessh /etc/gvpe first.example.net:/etc/. \-\-exclude hostkeys
335     \& rsync \-avzessh /etc/gvpe 133.55.82.9:/etc/. \-\-exclude hostkeys
336     \& rsync \-avzessh /etc/gvpe third.example.net:/etc/. \-\-exclude hostkeys
337 pcg 1.1 .Ve
338     .PP
339     Then the hostkeys should be copied:
340     .PP
341     .Vb 3
342 pcg 1.10 \& rsync \-avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey
343     \& rsync \-avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey
344     \& rsync \-avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey
345 pcg 1.1 .Ve
346     .PP
347 pcg 1.10 You should now check the configuration by issuing the command \f(CW\*(C`gvpectrl \-c
348 pcg 1.1 /etc/gvpe \-s\*(C'\fR on each node and verify it's output.
349     .Sh "\s-1STEP\s0 4: starting gvpe"
350     .IX Subsection "STEP 4: starting gvpe"
351     You should then start gvpe on each node by issuing a command like:
352     .PP
353     .Vb 1
354 pcg 1.10 \& gvpe \-D \-l info first # first is the nodename
355 pcg 1.1 .Ve
356     .PP
357 pcg 1.10 This will make the gvpe daemon stay in foreground. You should then see
358 pcg 1.1 \&\*(L"connection established\*(R" messages. If you don't see them check your
359     firewall and routing (use tcpdump ;).
360     .PP
361     If this works you should check your networking setup by pinging various
362     endpoints.
363     .PP
364 pcg 1.10 To make gvpe run more permanently you can either run it as a daemon (by
365     starting it without the \f(CW\*(C`\-D\*(C'\fR switch), or, much better, from your inittab
366     or equivalent. I use a line like this on all my systems:
367 pcg 1.1 .PP
368     .Vb 1
369 pcg 1.10 \& t1:2345:respawn:/opt/gvpe/sbin/gvpe \-D \-L first >/dev/null 2>&1
370 pcg 1.1 .Ve
371     .Sh "\s-1STEP\s0 5: enjoy"
372     .IX Subsection "STEP 5: enjoy"
373     \&... and play around. Sending a \-HUP (\f(CW\*(C`gvpectrl \-kHUP\*(C'\fR) to the daemon
374     will make it try to connect to all other nodes again. If you run it from
375     inittab, as is recommended, \f(CW\*(C`gvpectrl \-k\*(C'\fR (or simply \f(CW\*(C`killall gvpe\*(C'\fR) will
376     kill the daemon, start it again, making it read it's configuration files
377     again.
378     .SH "SEE ALSO"
379     .IX Header "SEE ALSO"
380 pcg 1.10 \&\fIgvpe.osdep\fR\|(5) for OS-dependent information, \fIgvpe.conf\fR\|(5), \fIgvpectrl\fR\|(8),
381 pcg 1.6 and for a description of the transports, protocol, and routing algorithm,
382     \&\fIgvpe.protocol\fR\|(7).
383 pcg 1.7 .PP
384 pcg 1.10 The \s-1GVPE\s0 mailing list, at <http://lists.schmorp.de/>, or
385 pcg 1.7 \&\f(CW\*(C`gvpe@lists.schmorp.de\*(C'\fR.
386 pcg 1.1 .SH "AUTHOR"
387     .IX Header "AUTHOR"
388 pcg 1.7 Marc Lehmann <gvpe@schmorp.de>
389 pcg 1.1 .SH "COPYRIGHTS AND LICENSES"
390     .IX Header "COPYRIGHTS AND LICENSES"
391     \&\s-1GVPE\s0 itself is distributed under the \s-1GENERAL\s0 \s-1PUBLIC\s0 \s-1LICENSE\s0 (see the file
392     \&\s-1COPYING\s0 that should be part of your distribution).
393     .PP
394     In some configurations it uses modified versions of the tinc vpn suite,
395     which is also available under the \s-1GENERAL\s0 \s-1PUBLIC\s0 \s-1LICENSE\s0.