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3 | GNU-VPE - Overview of the GNU Virtual Private Ethernet suite. |
3 | GNU-VPE - Overview of the GNU Virtual Private Ethernet suite. |
4 | |
4 | |
5 | =head1 DESCRIPTION |
5 | =head1 DESCRIPTION |
6 | |
6 | |
7 | GVPE is a suite designed to provide a virtual private network for multiple |
7 | GVPE is a suite designed to provide a virtual private network for multiple |
8 | nodes over an untrusted network. |
8 | nodes over an untrusted network. This document first gives an introduction |
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9 | to VPNs in general and then describes the specific implementation of GVPE. |
9 | |
10 | |
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11 | =head2 WHAT IS A VPN? |
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12 | |
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13 | VPN is an acronym, it stands for: |
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14 | |
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15 | =over 4 |
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16 | |
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17 | =item X<Virtual> |
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18 | |
10 | "Virtual"X<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 |
11 | ethernet is emulated by creating multiple tunnels between the member |
20 | network is I<emulated> by creating multiple tunnels between the member |
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21 | nodes by encapsulating and sending data over another transport network. |
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22 | |
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23 | Usually the emulated network is a normal IP or Ethernet, and the transport |
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24 | network is the Internet. However, using a VPN system like GVPE to connect |
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25 | nodes over other untrusted networks such as Wireless LAN is not uncommon. |
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26 | |
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27 | =item X<Private> |
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28 | |
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29 | Private means that non-participating nodes cannot decode ("sniff)" nor |
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30 | inject ("spoof") packets. This means that nodes can be connected over |
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31 | untrusted networks such as the public Internet without fear of being |
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32 | eavesdropped while at the same time being able to trust data sent by other |
12 | nodes. |
33 | nodes. |
13 | |
34 | |
14 | "Private"X<Private> means that non-participating nodes cannot decode ("sniff)" nor |
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15 | inject ("spoof") packets. |
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16 | |
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17 | In the case of gvpe, even participating nodes cannot sniff packets send to |
35 | In the case of GVPE, even participating nodes cannot sniff packets |
18 | 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 |
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37 | communications between any two nodes is private to those two nodes. |
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38 | |
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39 | =item X<Network> |
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40 | |
20 | "Network"X<Network> means that more than two parties can participate in the |
41 | Network means that more than two parties can participate in the network, |
21 | network, so for instance it's possible to connect multiple branches of a |
42 | so for instance it's possible to connect multiple branches of a company |
22 | company into a single network. Many so-called "vpn" solutions only create |
43 | into a single network. Many so-called "vpn" solutions only create |
23 | point-to-point tunnels. |
44 | point-to-point tunnels, which in turn can be used to build larger |
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45 | networks. |
24 | |
46 | |
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47 | GVPE provides a true multi-point network in wich any number of nodes (at |
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48 | least a few dozen in practise, the theoretical limit is 4095 nodes) can |
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49 | participate. |
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50 | |
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51 | =back |
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52 | |
25 | =head2 DESIGN GOALS |
53 | =head2 GVPE DESIGN GOALS |
26 | |
54 | |
27 | =over 4 |
55 | =over 4 |
28 | |
56 | |
29 | =item SIMPLE DESIGN |
57 | =item SIMPLE DESIGN |
30 | |
58 | |
31 | Cipher, HMAC algorithms and other key parameters must be selected |
59 | Cipher, HMAC algorithms and other key parameters must be selected |
32 | at compile time - this makes it possible to only link in algorithms |
60 | at compile time - this makes it possible to only link in algorithms |
33 | you actually need. It also makes the crypto part of the source very |
61 | you actually need. It also makes the crypto part of the source very |
34 | transparent and easy to inspect. |
62 | transparent and easy to inspect, and last not least this makes it possible |
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63 | to hardcode the layout of all packets into the binary. GVPE goes a step |
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64 | further and internally reserves blocks of the same length for all packets, |
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65 | which virtually removes all possibilities of buffer overflows, as there is |
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66 | only a single type of buffer and it's always of fixed length. |
35 | |
67 | |
36 | =item EASY TO SETUP |
68 | =item EASY TO SETUP |
37 | |
69 | |
38 | A few lines of config (the config file is shared unmodified between all |
70 | A few lines of config (the config file is shared unmodified between all |
39 | hosts) and a single run of C<gvpectrl> to generate the keys suffices to |
71 | hosts) and a single run of C<gvpectrl> to generate the keys suffices to |
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71 | =head1 COMPILETIME CONFIGURATION |
103 | =head1 COMPILETIME CONFIGURATION |
72 | |
104 | |
73 | Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific |
105 | Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific |
74 | information. |
106 | information. |
75 | |
107 | |
76 | Here are a few recipes for compiling your gvpe: |
108 | Here are a few recipes for compiling your gvpe, showing the extremes |
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109 | (fast, small, insecure OR slow, large, more secure), between you should |
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110 | choose: |
77 | |
111 | |
78 | =head2 AS LOW PACKET OVERHEAD AS POSSIBLE |
112 | =head2 AS LOW PACKET OVERHEAD AS POSSIBLE |
79 | |
113 | |
80 | ./configure --enable-hmac-length=4 --enable-rand-length=0 |
114 | ./configure --enable-hmac-length=4 --enable-rand-length=0 |
81 | |
115 | |
82 | Minimize the header overhead of VPN packets (the above will result in only |
116 | Minimize the header overhead of VPN packets (the above will result in |
83 | 4 bytes of overhead over the raw ethernet frame). |
117 | only 4 bytes of overhead over the raw ethernet frame). This is a insecure |
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118 | configuration because a HMAC length of 4 makes collision attacks based on |
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119 | the birthday paradox easy, though. |
84 | |
120 | |
85 | =head2 MINIMIZE CPU TIME REQUIRED |
121 | =head2 MINIMIZE CPU TIME REQUIRED |
86 | |
122 | |
87 | ./configure --enable-cipher=bf --enable-digest=md4 |
123 | ./configure --enable-cipher=bf --enable-digest=md4 |
88 | |
124 | |
89 | Use the fastest cipher and digest algorithms currently available in gvpe. |
125 | Use the fastest cipher and digest algorithms currently available in |
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126 | gvpe. MD4 has been broken and is quite insecure, though. |
90 | |
127 | |
91 | =head2 MAXIMIZE SECURITY |
128 | =head2 MAXIMIZE SECURITY |
92 | |
129 | |
93 | ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1 |
130 | ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1 |
94 | |
131 | |
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208 | kill the daemon, start it again, making it read it's configuration files |
245 | kill the daemon, start it again, making it read it's configuration files |
209 | again. |
246 | again. |
210 | |
247 | |
211 | =head1 SEE ALSO |
248 | =head1 SEE ALSO |
212 | |
249 | |
213 | gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), and |
250 | gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), |
214 | for a description of the protocol and routing algorithms, gvpe.protocol(7). |
251 | and for a description of the transports, protocol, and routing algorithm, |
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252 | gvpe.protocol(7). |
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253 | |
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254 | The GVPE mailinglist, at L<http://lists.schmorp.de/>, or |
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255 | C<gvpe@lists.schmorp.de>. |
215 | |
256 | |
216 | =head1 AUTHOR |
257 | =head1 AUTHOR |
217 | |
258 | |
218 | Marc Lehmann <gvpe@plan9.de> |
259 | Marc Lehmann <gvpe@schmorp.de> |
219 | |
260 | |
220 | =head1 COPYRIGHTS AND LICENSES |
261 | =head1 COPYRIGHTS AND LICENSES |
221 | |
262 | |
222 | GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file |
263 | GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file |
223 | COPYING that should be part of your distribution). |
264 | COPYING that should be part of your distribution). |