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.\" ======================================================================== |
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.\" |
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.IX Title "GVPE 5" |
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.TH GVPE 5 "2013-07-10" "2.24" "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. |
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.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 |
| 137 |
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. |
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.SS "\s-1WHAT\s0 \s-1IS\s0 A \s-1VPN\s0?" |
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.IX Subsection "WHAT IS A VPN?" |
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\&\s-1VPN\s0 is an acronym, it stands for: |
| 142 |
.IP "Virtual" 4 |
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.IX Item "Virtual" |
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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 |
| 146 |
nodes by encapsulating and sending data over another transport network. |
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.Sp |
| 148 |
Usually the emulated network is a normal \s-1IP\s0 or Ethernet, and the transport |
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network is the Internet. However, using a \s-1VPN\s0 system like \s-1GVPE\s0 to connect |
| 150 |
nodes over other untrusted networks such as Wireless \s-1LAN\s0 is not uncommon. |
| 151 |
.IP "Private" 4 |
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.IX Item "Private" |
| 153 |
Private means that non-participating nodes cannot decode (\*(L"sniff)\*(R" nor |
| 154 |
inject (\*(L"spoof\*(R") packets. This means that nodes can be connected over |
| 155 |
untrusted networks such as the public Internet without fear of being |
| 156 |
eavesdropped while at the same time being able to trust data sent by other |
| 157 |
nodes. |
| 158 |
.Sp |
| 159 |
In the case of \s-1GVPE\s0, even participating nodes cannot sniff packets |
| 160 |
send to other nodes or spoof packets as if sent from other nodes, so |
| 161 |
communications between any two nodes is private to those two nodes. |
| 162 |
.IP "Network" 4 |
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.IX Item "Network" |
| 164 |
Network means that more than two parties can participate in the network, |
| 165 |
so for instance it's possible to connect multiple branches of a company |
| 166 |
into a single network. Many so-called \*(L"\s-1VPN\s0\*(R" solutions only create |
| 167 |
point-to-point tunnels, which in turn can be used to build larger |
| 168 |
networks. |
| 169 |
.Sp |
| 170 |
\&\s-1GVPE\s0 provides a true multi-point network in which any number of nodes (at |
| 171 |
least a few dozen in practise, the theoretical limit is 4095 nodes) can |
| 172 |
participate. |
| 173 |
.SS "\s-1GVPE\s0 \s-1DESIGN\s0 \s-1GOALS\s0" |
| 174 |
.IX Subsection "GVPE DESIGN GOALS" |
| 175 |
.IP "\s-1SIMPLE\s0 \s-1DESIGN\s0" 4 |
| 176 |
.IX Item "SIMPLE DESIGN" |
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Cipher, \s-1HMAC\s0 algorithms and other key parameters must be selected |
| 178 |
at compile time \- this makes it possible to only link in algorithms |
| 179 |
you actually need. It also makes the crypto part of the source very |
| 180 |
transparent and easy to inspect, and last not least this makes it possible |
| 181 |
to hardcode the layout of all packets into the binary. \s-1GVPE\s0 goes a step |
| 182 |
further and internally reserves blocks of the same length for all packets, |
| 183 |
which virtually removes all possibilities of buffer overflows, as there is |
| 184 |
only a single type of buffer and it's always of fixed length. |
| 185 |
.IP "\s-1EASY\s0 \s-1TO\s0 \s-1SETUP\s0" 4 |
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.IX Item "EASY TO SETUP" |
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A few lines of config (the config file is shared unmodified between all |
| 188 |
hosts) and a single run of \f(CW\*(C`gvpectrl\*(C'\fR to generate the keys suffices to |
| 189 |
make it work. |
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.IP "MAC-BASED \s-1SECURITY\s0" 4 |
| 191 |
.IX Item "MAC-BASED SECURITY" |
| 192 |
Since every host has it's own private key, other hosts cannot spoof |
| 193 |
traffic from this host. That makes it possible to filter packet by \s-1MAC\s0 |
| 194 |
address, e.g. to ensure that packets from a specific \s-1IP\s0 address come, in |
| 195 |
fact, from a specific host that is associated with that \s-1IP\s0 and not from |
| 196 |
another host. |
| 197 |
.SH "PROGRAMS" |
| 198 |
.IX Header "PROGRAMS" |
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Gvpe comes with two programs: one daemon (\f(CW\*(C`gvpe\*(C'\fR) and one control program |
| 200 |
(\f(CW\*(C`gvpectrl\*(C'\fR). |
| 201 |
.IP "gvpectrl" 4 |
| 202 |
.IX Item "gvpectrl" |
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This program is used to generate the keys, check and give an overview of of the |
| 204 |
configuration and to control the daemon (restarting etc.). |
| 205 |
.IP "gvpe" 4 |
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.IX Item "gvpe" |
| 207 |
This is the daemon used to establish and maintain connections to the other |
| 208 |
network nodes. It should be run on the gateway of each \s-1VPN\s0 subnet. |
| 209 |
.SH "COMPILETIME CONFIGURATION" |
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.IX Header "COMPILETIME CONFIGURATION" |
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Please have a look at the \f(CW\*(C`gvpe.osdep(5)\*(C'\fR manpage for platform-specific |
| 212 |
information. |
| 213 |
.PP |
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Gvpe hardcodes most encryption parameters. While this reduces flexibility, |
| 215 |
it makes the program much simpler and helps making buffer overflows |
| 216 |
impossible under most circumstances. |
| 217 |
.PP |
| 218 |
Here are a few recipes for compiling your gvpe, showing the extremes |
| 219 |
(fast, small, insecure \s-1OR\s0 slow, large, more secure), between which you |
| 220 |
should choose: |
| 221 |
.SS "\s-1AS\s0 \s-1LOW\s0 \s-1PACKET\s0 \s-1OVERHEAD\s0 \s-1AS\s0 \s-1POSSIBLE\s0" |
| 222 |
.IX Subsection "AS LOW PACKET OVERHEAD AS POSSIBLE" |
| 223 |
.Vb 1 |
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\& ./configure \-\-enable\-hmac\-length=4 \-\-enable\-rand\-length=0 |
| 225 |
.Ve |
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.PP |
| 227 |
Minimize the header overhead of \s-1VPN\s0 packets (the above will result in |
| 228 |
only 4 bytes of overhead over the raw ethernet frame). This is a insecure |
| 229 |
configuration because a \s-1HMAC\s0 length of 4 makes collision attacks almost |
| 230 |
trivial. |
| 231 |
.SS "\s-1MINIMIZE\s0 \s-1CPU\s0 \s-1TIME\s0 \s-1REQUIRED\s0" |
| 232 |
.IX Subsection "MINIMIZE CPU TIME REQUIRED" |
| 233 |
.Vb 1 |
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\& ./configure \-\-enable\-cipher=bf \-\-enable\-digest=md4 |
| 235 |
.Ve |
| 236 |
.PP |
| 237 |
Use the fastest cipher and digest algorithms currently available in |
| 238 |
gvpe. \s-1MD4\s0 has been broken and is quite insecure, though, so using another |
| 239 |
digest algorithm is recommended. |
| 240 |
.SS "\s-1MAXIMIZE\s0 \s-1SECURITY\s0" |
| 241 |
.IX Subsection "MAXIMIZE SECURITY" |
| 242 |
.Vb 1 |
| 243 |
\& ./configure \-\-enable\-hmac\-length=16 \-\-enable\-rand\-length=12 \-\-enable\-digest=ripemd610 |
| 244 |
.Ve |
| 245 |
.PP |
| 246 |
This uses a 16 byte \s-1HMAC\s0 checksum to authenticate packets (I guess 8\-12 |
| 247 |
would also be pretty secure ;) and will additionally prefix each packet |
| 248 |
with 12 bytes of random data. |
| 249 |
.PP |
| 250 |
In general, remember that \s-1AES\-128\s0 seems to be as secure but faster than |
| 251 |
\&\s-1AES\-192\s0 or \s-1AES\-256\s0, more randomness helps against sniffing and a longer |
| 252 |
\&\s-1HMAC\s0 helps against spoofing. \s-1MD4\s0 is a fast digest, \s-1SHA1\s0, \s-1RIPEMD160\s0, \s-1SHA256\s0 |
| 253 |
are consecutively better, and Blowfish is a fast cipher (and also quite |
| 254 |
secure). |
| 255 |
.SH "HOW TO SET UP A SIMPLE VPN" |
| 256 |
.IX Header "HOW TO SET UP A SIMPLE VPN" |
| 257 |
In this section I will describe how to get a simple \s-1VPN\s0 consisting of |
| 258 |
three hosts up and running. |
| 259 |
.SS "\s-1STEP\s0 1: configuration" |
| 260 |
.IX Subsection "STEP 1: configuration" |
| 261 |
First you have to create a daemon configuration file and put it into the |
| 262 |
configuration directory. This is usually \f(CW\*(C`/etc/gvpe\*(C'\fR, depending on how you |
| 263 |
configured gvpe, and can be overwritten using the \f(CW\*(C`\-c\*(C'\fR command line switch. |
| 264 |
.PP |
| 265 |
Put the following lines into \f(CW\*(C`/etc/gvpe/gvpe.conf\*(C'\fR: |
| 266 |
.PP |
| 267 |
.Vb 3 |
| 268 |
\& udp\-port = 50000 # the external port to listen on (configure your firewall) |
| 269 |
\& mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts |
| 270 |
\& ifname = vpn0 # the local network device name |
| 271 |
\& |
| 272 |
\& node = first # just a nickname |
| 273 |
\& hostname = first.example.net # the DNS name or IP address of the host |
| 274 |
\& |
| 275 |
\& node = second |
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\& hostname = 133.55.82.9 |
| 277 |
\& |
| 278 |
\& node = third |
| 279 |
\& hostname = third.example.net |
| 280 |
.Ve |
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.PP |
| 282 |
The only other file necessary is the \f(CW\*(C`if\-up\*(C'\fR script that initializes the |
| 283 |
virtual ethernet interface on the local host. Put the following lines into |
| 284 |
\&\f(CW\*(C`/etc/gvpe/if\-up\*(C'\fR and make it executable (\f(CW\*(C`chmod 755 /etc/gvpe/if\-up\*(C'\fR): |
| 285 |
.PP |
| 286 |
.Vb 6 |
| 287 |
\& #!/bin/sh |
| 288 |
\& ip link set $IFNAME address $MAC mtu $MTU up |
| 289 |
\& [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME |
| 290 |
\& [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME |
| 291 |
\& [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME |
| 292 |
\& ip route add 10.0.0.0/16 dev $IFNAME |
| 293 |
.Ve |
| 294 |
.PP |
| 295 |
This script will give each node a different \s-1IP\s0 address in the \f(CW\*(C`10.0/16\*(C'\fR |
| 296 |
network. The internal network (if gvpe runs on a router) should then be |
| 297 |
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, |
| 298 |
\&\f(CW\*(C`10.0.2.0/24\*(C'\fR on node \f(CW\*(C`second\*(C'\fR, and so on. |
| 299 |
.PP |
| 300 |
By enabling routing on the gateway host that runs \f(CW\*(C`gvpe\*(C'\fR all nodes will |
| 301 |
be able to reach the other nodes. You can, of course, also use proxy \s-1ARP\s0 |
| 302 |
or other means of pseudo-bridging, or (best) full routing \- the choice is |
| 303 |
yours. |
| 304 |
.SS "\s-1STEP\s0 2: create the \s-1RSA\s0 key pairs for all hosts" |
| 305 |
.IX Subsection "STEP 2: create the RSA key pairs for all hosts" |
| 306 |
Run the following command to generate all key pairs for all nodes (that |
| 307 |
might take a while): |
| 308 |
.PP |
| 309 |
.Vb 1 |
| 310 |
\& gvpectrl \-c /etc/gvpe \-g |
| 311 |
.Ve |
| 312 |
.PP |
| 313 |
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. |
| 314 |
.SS "\s-1STEP\s0 3: distribute the config files to all nodes" |
| 315 |
.IX Subsection "STEP 3: distribute the config files to all nodes" |
| 316 |
Now distribute the config files and private keys to the other nodes. This |
| 317 |
should be done in two steps, since only the private keys meant for a node |
| 318 |
should be distributed (so each node has only it's own private key). |
| 319 |
.PP |
| 320 |
The example uses rsync-over-ssh |
| 321 |
.PP |
| 322 |
First all the config files without the hostkeys should be distributed: |
| 323 |
.PP |
| 324 |
.Vb 3 |
| 325 |
\& rsync \-avzessh /etc/gvpe first.example.net:/etc/. \-\-exclude hostkeys |
| 326 |
\& rsync \-avzessh /etc/gvpe 133.55.82.9:/etc/. \-\-exclude hostkeys |
| 327 |
\& rsync \-avzessh /etc/gvpe third.example.net:/etc/. \-\-exclude hostkeys |
| 328 |
.Ve |
| 329 |
.PP |
| 330 |
Then the hostkeys should be copied: |
| 331 |
.PP |
| 332 |
.Vb 3 |
| 333 |
\& rsync \-avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey |
| 334 |
\& rsync \-avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey |
| 335 |
\& rsync \-avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey |
| 336 |
.Ve |
| 337 |
.PP |
| 338 |
You should now check the configuration by issuing the command \f(CW\*(C`gvpectrl \-c |
| 339 |
/etc/gvpe \-s\*(C'\fR on each node and verify it's output. |
| 340 |
.SS "\s-1STEP\s0 4: starting gvpe" |
| 341 |
.IX Subsection "STEP 4: starting gvpe" |
| 342 |
You should then start gvpe on each node by issuing a command like: |
| 343 |
.PP |
| 344 |
.Vb 1 |
| 345 |
\& gvpe \-D \-l info first # first is the nodename |
| 346 |
.Ve |
| 347 |
.PP |
| 348 |
This will make the gvpe daemon stay in foreground. You should then see |
| 349 |
\&\*(L"connection established\*(R" messages. If you don't see them check your |
| 350 |
firewall and routing (use tcpdump ;). |
| 351 |
.PP |
| 352 |
If this works you should check your networking setup by pinging various |
| 353 |
endpoints. |
| 354 |
.PP |
| 355 |
To make gvpe run more permanently you can either run it as a daemon (by |
| 356 |
starting it without the \f(CW\*(C`\-D\*(C'\fR switch), or, much better, from your inittab |
| 357 |
or equivalent. I use a line like this on all my systems: |
| 358 |
.PP |
| 359 |
.Vb 1 |
| 360 |
\& t1:2345:respawn:/opt/gvpe/sbin/gvpe \-D \-L first >/dev/null 2>&1 |
| 361 |
.Ve |
| 362 |
.SS "\s-1STEP\s0 5: enjoy" |
| 363 |
.IX Subsection "STEP 5: enjoy" |
| 364 |
\&... and play around. Sending a \-HUP (\f(CW\*(C`gvpectrl \-kHUP\*(C'\fR) to the daemon |
| 365 |
will make it try to connect to all other nodes again. If you run it from |
| 366 |
inittab, as is recommended, \f(CW\*(C`gvpectrl \-k\*(C'\fR (or simply \f(CW\*(C`killall gvpe\*(C'\fR) will |
| 367 |
kill the daemon, start it again, making it read it's configuration files |
| 368 |
again. |
| 369 |
.SH "SEE ALSO" |
| 370 |
.IX Header "SEE ALSO" |
| 371 |
\&\fIgvpe.osdep\fR\|(5) for OS-dependent information, \fIgvpe.conf\fR\|(5), \fIgvpectrl\fR\|(8), |
| 372 |
and for a description of the transports, protocol, and routing algorithm, |
| 373 |
\&\fIgvpe.protocol\fR\|(7). |
| 374 |
.PP |
| 375 |
The \s-1GVPE\s0 mailing list, at <http://lists.schmorp.de/>, or |
| 376 |
\&\f(CW\*(C`gvpe@lists.schmorp.de\*(C'\fR. |
| 377 |
.SH "AUTHOR" |
| 378 |
.IX Header "AUTHOR" |
| 379 |
Marc Lehmann <gvpe@schmorp.de> |
| 380 |
.SH "COPYRIGHTS AND LICENSES" |
| 381 |
.IX Header "COPYRIGHTS AND LICENSES" |
| 382 |
\&\s-1GVPE\s0 itself is distributed under the \s-1GENERAL\s0 \s-1PUBLIC\s0 \s-1LICENSE\s0 (see the file |
| 383 |
\&\s-1COPYING\s0 that should be part of your distribution). |
| 384 |
.PP |
| 385 |
In some configurations it uses modified versions of the tinc vpn suite, |
| 386 |
which is also available under the \s-1GENERAL\s0 \s-1PUBLIC\s0 \s-1LICENSE\s0. |
