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.\" ======================================================================== |
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.\" |
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.IX Title "GVPE 5" |
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.TH GVPE 5 "2016-11-02" "2.25" "GNU Virtual Private Ethernet" |
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes |
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.\" way too many mistakes in technical documents. |
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.if n .ad l |
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.nh |
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.SH "NAME" |
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GNU\-VPE \- Overview of the GNU Virtual Private Ethernet suite. |
143 |
.SH "DESCRIPTION" |
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.IX Header "DESCRIPTION" |
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\&\s-1GVPE\s0 is a suite designed to provide a virtual private network for multiple |
146 |
nodes over an untrusted network. This document first gives an introduction |
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to VPNs in general and then describes the specific implementation of \s-1GVPE.\s0 |
148 |
.SS "\s-1WHAT IS A VPN\s0?" |
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.IX Subsection "WHAT IS A VPN?" |
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\&\s-1VPN\s0 is an acronym, it stands for: |
151 |
.IP "Virtual" 4 |
152 |
.IX Item "Virtual" |
153 |
Virtual means that no physical network is created (of course), but a |
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network is \fIemulated\fR by creating multiple tunnels between the member |
155 |
nodes by encapsulating and sending data over another transport network. |
156 |
.Sp |
157 |
Usually the emulated network is a normal \s-1IP\s0 or Ethernet, and the transport |
158 |
network is the Internet. However, using a \s-1VPN\s0 system like \s-1GVPE\s0 to connect |
159 |
nodes over other untrusted networks such as Wireless \s-1LAN\s0 is not uncommon. |
160 |
.IP "Private" 4 |
161 |
.IX Item "Private" |
162 |
Private means that non-participating nodes cannot decode (\*(L"sniff)\*(R" nor |
163 |
inject (\*(L"spoof\*(R") packets. This means that nodes can be connected over |
164 |
untrusted networks such as the public Internet without fear of being |
165 |
eavesdropped while at the same time being able to trust data sent by other |
166 |
nodes. |
167 |
.Sp |
168 |
In the case of \s-1GVPE,\s0 even participating nodes cannot sniff packets |
169 |
send to other nodes or spoof packets as if sent from other nodes, so |
170 |
communications between any two nodes is private to those two nodes. |
171 |
.IP "Network" 4 |
172 |
.IX Item "Network" |
173 |
Network means that more than two parties can participate in the network, |
174 |
so for instance it's possible to connect multiple branches of a company |
175 |
into a single network. Many so-called \*(L"\s-1VPN\*(R"\s0 solutions only create |
176 |
point-to-point tunnels, which in turn can be used to build larger |
177 |
networks. |
178 |
.Sp |
179 |
\&\s-1GVPE\s0 provides a true multi-point network in which any number of nodes (at |
180 |
least a few dozen in practise, the theoretical limit is 4095 nodes) can |
181 |
participate. |
182 |
.SS "\s-1GVPE DESIGN GOALS\s0" |
183 |
.IX Subsection "GVPE DESIGN GOALS" |
184 |
.IP "\s-1SIMPLE DESIGN\s0" 4 |
185 |
.IX Item "SIMPLE DESIGN" |
186 |
Cipher, \s-1HMAC\s0 algorithms and other key parameters must be selected |
187 |
at compile time \- this makes it possible to only link in algorithms |
188 |
you actually need. It also makes the crypto part of the source very |
189 |
transparent and easy to inspect, and last not least this makes it possible |
190 |
to hardcode the layout of all packets into the binary. \s-1GVPE\s0 goes a step |
191 |
further and internally reserves blocks of the same length for all packets, |
192 |
which virtually removes all possibilities of buffer overflows, as there is |
193 |
only a single type of buffer and it's always of fixed length. |
194 |
.IP "\s-1EASY TO SETUP\s0" 4 |
195 |
.IX Item "EASY TO SETUP" |
196 |
A few lines of config (the config file is shared unmodified between all |
197 |
hosts) and generating an \s-1RSA\s0 key-pair on each node suffices to make it |
198 |
work. |
199 |
.IP "MAC-BASED \s-1SECURITY\s0" 4 |
200 |
.IX Item "MAC-BASED SECURITY" |
201 |
Since every host has it's own private key, other hosts cannot spoof |
202 |
traffic from this host. That makes it possible to filter packet by \s-1MAC\s0 |
203 |
address, e.g. to ensure that packets from a specific \s-1IP\s0 address come, in |
204 |
fact, from a specific host that is associated with that \s-1IP\s0 and not from |
205 |
another host. |
206 |
.SH "PROGRAMS" |
207 |
.IX Header "PROGRAMS" |
208 |
Gvpe comes with two programs: one daemon (\f(CW\*(C`gvpe\*(C'\fR) and one control program |
209 |
(\f(CW\*(C`gvpectrl\*(C'\fR). |
210 |
.IP "gvpectrl" 4 |
211 |
.IX Item "gvpectrl" |
212 |
This program is used to generate the keys, check and give an overview of of the |
213 |
configuration and to control the daemon (restarting etc.). |
214 |
.IP "gvpe" 4 |
215 |
.IX Item "gvpe" |
216 |
This is the daemon used to establish and maintain connections to the other |
217 |
network nodes. It should be run on the gateway of each \s-1VPN\s0 subnet. |
218 |
.SH "COMPILETIME CONFIGURATION" |
219 |
.IX Header "COMPILETIME CONFIGURATION" |
220 |
Please have a look at the \f(CW\*(C`gvpe.osdep(5)\*(C'\fR manpage for platform-specific |
221 |
information. |
222 |
.PP |
223 |
Gvpe hardcodes most encryption parameters. While this reduces flexibility, |
224 |
it makes the program much simpler and helps making buffer overflows |
225 |
impossible under most circumstances. |
226 |
.PP |
227 |
Here are a few recipes for compiling your gvpe, showing the extremes |
228 |
(fast, small, insecure \s-1OR\s0 slow, large, more secure), between which you |
229 |
should choose: |
230 |
.SS "\s-1AS LOW PACKET OVERHEAD AS POSSIBLE\s0" |
231 |
.IX Subsection "AS LOW PACKET OVERHEAD AS POSSIBLE" |
232 |
.Vb 1 |
233 |
\& ./configure \-\-enable\-hmac\-length=4 \-\-enable\-rand\-length=0 |
234 |
.Ve |
235 |
.PP |
236 |
Minimize the header overhead of \s-1VPN\s0 packets (the above will result in |
237 |
only 4 bytes of overhead over the raw ethernet frame). This is a insecure |
238 |
configuration because a \s-1HMAC\s0 length of 4 makes collision attacks almost |
239 |
trivial. |
240 |
.SS "\s-1MINIMIZE CPU TIME REQUIRED\s0" |
241 |
.IX Subsection "MINIMIZE CPU TIME REQUIRED" |
242 |
.Vb 1 |
243 |
\& ./configure \-\-enable\-cipher=bf \-\-enable\-digest=md4 |
244 |
.Ve |
245 |
.PP |
246 |
Use the fastest cipher and digest algorithms currently available in |
247 |
gvpe. \s-1MD4\s0 has been broken and is quite insecure, though, so using another |
248 |
digest algorithm is recommended. |
249 |
.SS "\s-1MAXIMIZE SECURITY\s0" |
250 |
.IX Subsection "MAXIMIZE SECURITY" |
251 |
.Vb 1 |
252 |
\& ./configure \-\-enable\-hmac\-length=16 \-\-enable\-rand\-length=12 \-\-enable\-digest=ripemd610 |
253 |
.Ve |
254 |
.PP |
255 |
This uses a 16 byte \s-1HMAC\s0 checksum to authenticate packets (I guess 8\-12 |
256 |
would also be pretty secure ;) and will additionally prefix each packet |
257 |
with 12 bytes of random data. |
258 |
.PP |
259 |
In general, remember that \s-1AES\-128\s0 seems to be as secure but faster than |
260 |
\&\s-1AES\-192\s0 or \s-1AES\-256,\s0 more randomness helps against sniffing and a longer |
261 |
\&\s-1HMAC\s0 helps against spoofing. \s-1MD4\s0 is a fast digest, \s-1SHA1, RIPEMD160, SHA256\s0 |
262 |
are consecutively better, and Blowfish is a fast cipher (and also quite |
263 |
secure). |
264 |
.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 |
.SS "\s-1STEP 1:\s0 configuration" |
269 |
.IX Subsection "STEP 1: configuration" |
270 |
First you have to create a daemon configuration file and put it into the |
271 |
configuration directory. This is usually \f(CW\*(C`/etc/gvpe\*(C'\fR, depending on how you |
272 |
configured gvpe, and can be overwritten using the \f(CW\*(C`\-c\*(C'\fR command line switch. |
273 |
.PP |
274 |
Put the following lines into \f(CW\*(C`/etc/gvpe/gvpe.conf\*(C'\fR: |
275 |
.PP |
276 |
.Vb 3 |
277 |
\& udp\-port = 50000 # the external port to listen on (configure your firewall) |
278 |
\& mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts |
279 |
\& ifname = vpn0 # the local network device name |
280 |
\& |
281 |
\& node = first # just a nickname |
282 |
\& hostname = first.example.net # the DNS name or IP address of the host |
283 |
\& |
284 |
\& node = second |
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\& hostname = 133.55.82.9 |
286 |
\& |
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\& node = third |
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\& hostname = third.example.net |
289 |
.Ve |
290 |
.PP |
291 |
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 |
.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 |
network. The internal network (if gvpe runs on a router) should then be |
306 |
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 |
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 |
.SS "\s-1STEP 2:\s0 create the \s-1RSA\s0 key pair for each node" |
314 |
.IX Subsection "STEP 2: create the RSA key pair for each node" |
315 |
Next you have to generate the \s-1RSA\s0 keys for the nodes. While you can set |
316 |
up \s-1GVPE\s0 so you can generate all keys on a single host and centrally |
317 |
distribute all keys, it is safer to generate the key for each node on the |
318 |
node, so that the secret/private key does not have to be copied over the |
319 |
network. |
320 |
.PP |
321 |
To do so, run the following command to generate a key pair: |
322 |
.PP |
323 |
.Vb 1 |
324 |
\& gvpectrl \-c /etc/gvpe \-g nodekey |
325 |
.Ve |
326 |
.PP |
327 |
This will create two files, \fInodekey\fR and \fInodekey.privkey\fR. The former |
328 |
should be copied to \fI/etc/gvpe/pubkey/\fInodename\fI\fR on the host where |
329 |
your config file is (you will have to create the \fIpubkey\fR directory |
330 |
first): |
331 |
.PP |
332 |
.Vb 1 |
333 |
\& scp nodekey confighost:/etc/gvpe/pubkey/nodename |
334 |
.Ve |
335 |
.PP |
336 |
The private key \fInodekey.privkey\fR should be moved to \fI/etc/gvpe/hostkey\fR: |
337 |
.PP |
338 |
.Vb 2 |
339 |
\& mkdir \-p /etc/gvpe |
340 |
\& mv nodekey.privkey /etc/gvpe/hostkey |
341 |
.Ve |
342 |
.SS "\s-1STEP 3:\s0 distribute the config files to all nodes" |
343 |
.IX Subsection "STEP 3: distribute the config files to all nodes" |
344 |
Now distribute the config files and public keys to the other nodes. |
345 |
.PP |
346 |
The example uses rsync-over-ssh to copy the config file and all the public |
347 |
keys: |
348 |
.PP |
349 |
.Vb 3 |
350 |
\& rsync \-avzessh /etc/gvpe first.example.net:/etc/. \-\-exclude hostkey |
351 |
\& rsync \-avzessh /etc/gvpe 133.55.82.9:/etc/. \-\-exclude hostkey |
352 |
\& rsync \-avzessh /etc/gvpe third.example.net:/etc/. \-\-exclude hostkey |
353 |
.Ve |
354 |
.PP |
355 |
You should now check the configuration by issuing the command \f(CW\*(C`gvpectrl |
356 |
\&\-c /etc/gvpe \-s\*(C'\fR on each node and verify it's output. |
357 |
.SS "\s-1STEP 4:\s0 starting gvpe" |
358 |
.IX Subsection "STEP 4: starting gvpe" |
359 |
You should then start gvpe on each node by issuing a command like: |
360 |
.PP |
361 |
.Vb 1 |
362 |
\& gvpe \-D \-l info first # first is the nodename |
363 |
.Ve |
364 |
.PP |
365 |
This will make the gvpe daemon stay in foreground. You should then see |
366 |
\&\*(L"connection established\*(R" messages. If you don't see them check your |
367 |
firewall and routing (use tcpdump ;). |
368 |
.PP |
369 |
If this works you should check your networking setup by pinging various |
370 |
endpoints. |
371 |
.PP |
372 |
To make gvpe run more permanently you can either run it as a daemon (by |
373 |
starting it without the \f(CW\*(C`\-D\*(C'\fR switch), or, much better, from your inittab |
374 |
or equivalent. I use a line like this on all my systems: |
375 |
.PP |
376 |
.Vb 1 |
377 |
\& t1:2345:respawn:/opt/gvpe/sbin/gvpe \-D \-L first >/dev/null 2>&1 |
378 |
.Ve |
379 |
.SS "\s-1STEP 5:\s0 enjoy" |
380 |
.IX Subsection "STEP 5: enjoy" |
381 |
\&... and play around. Sending a \-HUP (\f(CW\*(C`gvpectrl \-kHUP\*(C'\fR) to the daemon |
382 |
will make it try to connect to all other nodes again. If you run it from |
383 |
inittab \f(CW\*(C`gvpectrl \-k\*(C'\fR (or simply \f(CW\*(C`killall gvpe\*(C'\fR) will kill the daemon, |
384 |
start it again, making it read it's configuration files again. |
385 |
.PP |
386 |
To run the \s-1GVPE\s0 daemon permanently from your SysV init, you can add it to |
387 |
your \fIinittab\fR, e.g.: |
388 |
.PP |
389 |
.Vb 1 |
390 |
\& t1:2345:respawn:/bin/sh \-c "exec nice \-n\-20 /path/to/gvpe \-D node >/var/log/gvpe.log 2>&1" |
391 |
.Ve |
392 |
.PP |
393 |
For systems using systemd, you can use a unit file similar to this one: |
394 |
.PP |
395 |
.Vb 4 |
396 |
\& [Unit] |
397 |
\& Description=gvpe |
398 |
\& After=network.target |
399 |
\& Before=remote\-fs.target |
400 |
\& |
401 |
\& [Service] |
402 |
\& ExecStart=/path/to/gvpe \-D node |
403 |
\& KillMode=process |
404 |
\& Restart=always |
405 |
\& |
406 |
\& [Install] |
407 |
\& WantedBy=multi\-user.target |
408 |
.Ve |
409 |
.SH "SEE ALSO" |
410 |
.IX Header "SEE ALSO" |
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\&\fIgvpe.osdep\fR\|(5) for OS-dependent information, \fIgvpe.conf\fR\|(5), \fIgvpectrl\fR\|(8), |
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and for a description of the transports, protocol, and routing algorithm, |
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\&\fIgvpe.protocol\fR\|(7). |
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.PP |
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The \s-1GVPE\s0 mailing list, at <http://lists.schmorp.de/>, or |
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\&\f(CW\*(C`gvpe@lists.schmorp.de\*(C'\fR. |
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.SH "AUTHOR" |
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.IX Header "AUTHOR" |
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Marc Lehmann <gvpe@schmorp.de> |
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.SH "COPYRIGHTS AND LICENSES" |
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.IX Header "COPYRIGHTS AND LICENSES" |
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\&\s-1GVPE\s0 itself is distributed under the \s-1GENERAL PUBLIC LICENSE \s0(see the file |
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\&\s-1COPYING\s0 that should be part of your distribution). |
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.PP |
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In some configurations it uses modified versions of the tinc vpn suite, |
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which is also available under the \s-1GENERAL PUBLIC LICENSE.\s0 |