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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. |
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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: |
9 | |
14 | |
10 | =over 4 |
15 | =over 4 |
11 | |
16 | |
12 | =item X<Virtual> |
17 | =item X<Virtual> |
13 | |
18 | |
14 | 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 |
15 | 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 |
16 | nodes. |
33 | nodes. |
17 | |
34 | |
18 | =item X<Private> |
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19 | |
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20 | Private means that non-participating nodes cannot decode ("sniff)" nor |
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21 | inject ("spoof") packets. |
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22 | |
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23 | 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 |
24 | 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. |
25 | |
38 | |
26 | =item X<Network> |
39 | =item X<Network> |
27 | |
40 | |
28 | Network means that more than two parties can participate in the network, |
41 | Network means that more than two parties can participate in the network, |
29 | so for instance it's possible to connect multiple branches of a company |
42 | so for instance it's possible to connect multiple branches of a company |
30 | into a single network. Many so-called "vpn" solutions only create |
43 | into a single network. Many so-called "VPN" solutions only create |
31 | point-to-point tunnels. |
44 | point-to-point tunnels, which in turn can be used to build larger |
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45 | networks. |
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46 | |
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47 | GVPE provides a true multi-point network in which 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. |
32 | |
50 | |
33 | =back |
51 | =back |
34 | |
52 | |
35 | =head2 DESIGN GOALS |
53 | =head2 GVPE DESIGN GOALS |
36 | |
54 | |
37 | =over 4 |
55 | =over 4 |
38 | |
56 | |
39 | =item SIMPLE DESIGN |
57 | =item SIMPLE DESIGN |
40 | |
58 | |
41 | Cipher, HMAC algorithms and other key parameters must be selected |
59 | Cipher, HMAC algorithms and other key parameters must be selected |
42 | 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 |
43 | 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 |
44 | 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. |
45 | |
67 | |
46 | =item EASY TO SETUP |
68 | =item EASY TO SETUP |
47 | |
69 | |
48 | 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 |
49 | 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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59 | |
81 | |
60 | =back |
82 | =back |
61 | |
83 | |
62 | =head1 PROGRAMS |
84 | =head1 PROGRAMS |
63 | |
85 | |
64 | Vpe comes with two programs: one daemon (C<gvpe>) and one control program |
86 | Gvpe comes with two programs: one daemon (C<gvpe>) and one control program |
65 | (C<gvpectrl>). |
87 | (C<gvpectrl>). |
66 | |
88 | |
67 | =over 4 |
89 | =over 4 |
68 | |
90 | |
69 | =item gvpectrl |
91 | =item gvpectrl |
70 | |
92 | |
71 | Is used to generate the keys, check and give an overview of of the |
93 | This program is used to generate the keys, check and give an overview of of the |
72 | configuration and contorl the daemon (restarting etc.). |
94 | configuration and to control the daemon (restarting etc.). |
73 | |
95 | |
74 | =item gvpe |
96 | =item gvpe |
75 | |
97 | |
76 | Is the daemon used to establish and maintain connections to the other |
98 | This is the daemon used to establish and maintain connections to the other |
77 | network members. It should be run on the gateway machine. |
99 | network nodes. It should be run on the gateway of each VPN subnet. |
78 | |
100 | |
79 | =back |
101 | =back |
80 | |
102 | |
81 | =head1 COMPILETIME CONFIGURATION |
103 | =head1 COMPILETIME CONFIGURATION |
82 | |
104 | |
83 | 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 |
84 | information. |
106 | information. |
85 | |
107 | |
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108 | Gvpe hardcodes most encryption parameters. While this reduces flexibility, |
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109 | it makes the program much simpler and helps making buffer overflows |
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110 | impossible under most circumstances. |
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111 | |
86 | Here are a few recipes for compiling your gvpe: |
112 | Here are a few recipes for compiling your gvpe, showing the extremes |
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113 | (fast, small, insecure OR slow, large, more secure), between which you |
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114 | should choose: |
87 | |
115 | |
88 | =head2 AS LOW PACKET OVERHEAD AS POSSIBLE |
116 | =head2 AS LOW PACKET OVERHEAD AS POSSIBLE |
89 | |
117 | |
90 | ./configure --enable-hmac-length=4 --enable-rand-length=0 |
118 | ./configure --enable-hmac-length=4 --enable-rand-length=0 |
91 | |
119 | |
92 | Minimize the header overhead of VPN packets (the above will result in only |
120 | Minimize the header overhead of VPN packets (the above will result in |
93 | 4 bytes of overhead over the raw ethernet frame). |
121 | only 4 bytes of overhead over the raw ethernet frame). This is a insecure |
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122 | configuration because a HMAC length of 4 makes collision attacks based on |
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123 | the birthday paradox pretty easy. |
94 | |
124 | |
95 | =head2 MINIMIZE CPU TIME REQUIRED |
125 | =head2 MINIMIZE CPU TIME REQUIRED |
96 | |
126 | |
97 | ./configure --enable-cipher=bf --enable-digest=md4 |
127 | ./configure --enable-cipher=bf --enable-digest=md4 |
98 | |
128 | |
99 | Use the fastest cipher and digest algorithms currently available in gvpe. |
129 | Use the fastest cipher and digest algorithms currently available in |
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130 | gvpe. MD4 has been broken and is quite insecure, though, so using another |
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131 | digest algorithm is recommended. |
100 | |
132 | |
101 | =head2 MAXIMIZE SECURITY |
133 | =head2 MAXIMIZE SECURITY |
102 | |
134 | |
103 | ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1 |
135 | ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1 |
104 | |
136 | |
105 | This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12 |
137 | This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12 |
106 | would also be pretty secure ;) and will additionally prefix each packet |
138 | would also be pretty secure ;) and will additionally prefix each packet |
107 | with 8 bytes of random data. In the long run, people should move to |
139 | with 8 bytes of random data. In the long run, people should move to |
108 | SHA-224 and beyond, but support in openssl is missing as of writing this |
140 | SHA-256 and beyond). |
109 | document. |
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110 | |
141 | |
111 | In general, remember that AES-128 seems to be more secure and faster than |
142 | In general, remember that AES-128 seems to be as secure but faster than |
112 | AES-192 or AES-256, more randomness helps against sniffing and a longer |
143 | AES-192 or AES-256, more randomness helps against sniffing and a longer |
113 | HMAC helps against spoofing. MD4 is a fast digest, SHA1 or RIPEMD160 are |
144 | HMAC helps against spoofing. MD4 is a fast digest, SHA1, RIPEMD160, SHA256 |
114 | better, and Blowfish is a fast cipher (and also quite secure). |
145 | are consecutively better, and Blowfish is a fast cipher (and also quite |
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146 | secure). |
115 | |
147 | |
116 | =head1 HOW TO SET UP A SIMPLE VPN |
148 | =head1 HOW TO SET UP A SIMPLE VPN |
117 | |
149 | |
118 | In this section I will describe how to get a simple VPN consisting of |
150 | In this section I will describe how to get a simple VPN consisting of |
119 | three hosts up and running. |
151 | three hosts up and running. |
120 | |
152 | |
121 | =head2 STEP 1: configuration |
153 | =head2 STEP 1: configuration |
122 | |
154 | |
123 | First you have to create a daemon configuation file and put it into the |
155 | First you have to create a daemon configuration file and put it into the |
124 | configuration directory. This is usually C</etc/gvpe>, depending on how you |
156 | configuration directory. This is usually C</etc/gvpe>, depending on how you |
125 | configured gvpe, and can be overwritten using the C<-c> commandline switch. |
157 | configured gvpe, and can be overwritten using the C<-c> command line switch. |
126 | |
158 | |
127 | Put the following lines into C</etc/gvpe/gvpe.conf>: |
159 | Put the following lines into C</etc/gvpe/gvpe.conf>: |
128 | |
160 | |
129 | udp-port = 50000 # the external port to listen on (configure your firewall) |
161 | udp-port = 50000 # the external port to listen on (configure your firewall) |
130 | mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts |
162 | mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts |
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137 | hostname = 133.55.82.9 |
169 | hostname = 133.55.82.9 |
138 | |
170 | |
139 | node = third |
171 | node = third |
140 | hostname = third.example.net |
172 | hostname = third.example.net |
141 | |
173 | |
142 | The only other file neccessary if the C<if-up> script that initializes the |
174 | The only other file necessary is the C<if-up> script that initializes the |
143 | local ethernet interface. Put the following lines into C</etc/gvpe/if-up> |
175 | virtual ethernet interface on the local host. Put the following lines into |
144 | and make it execute (C<chmod 755 /etc/gvpe/if-up>): |
176 | C</etc/gvpe/if-up> and make it executable (C<chmod 755 /etc/gvpe/if-up>): |
145 | |
177 | |
146 | #!/bin/sh |
178 | #!/bin/sh |
147 | ip link set $IFNAME address $MAC mtu $MTU up |
179 | ip link set $IFNAME address $MAC mtu $MTU up |
148 | [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME |
180 | [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME |
149 | [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME |
181 | [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME |
150 | [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME |
182 | [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME |
151 | ip route add 10.0.0.0/16 dev $IFNAME |
183 | ip route add 10.0.0.0/16 dev $IFNAME |
152 | |
184 | |
153 | This script will give each node a different IP address in the C<10.0/16> |
185 | This script will give each node a different IP address in the C<10.0/16> |
154 | network. The internal network (e.g. the C<eth0> interface) should then be |
186 | network. The internal network (if gvpe runs on a router) should then be |
155 | set to a subset of that network, e.g. C<10.0.1.0/24> on node C<first>, |
187 | set to a subset of that network, e.g. C<10.0.1.0/24> on node C<first>, |
156 | C<10.0.2.0/24> on node C<second>, and so on. |
188 | C<10.0.2.0/24> on node C<second>, and so on. |
157 | |
189 | |
158 | By enabling routing on the gateway host that runs C<gvpe> all nodes will |
190 | By enabling routing on the gateway host that runs C<gvpe> all nodes will |
159 | be able to reach the other nodes. You can, of course, also use proxy arp |
191 | be able to reach the other nodes. You can, of course, also use proxy ARP |
160 | or other means of pseudo-bridging (or even real briding), or (best) full |
192 | or other means of pseudo-bridging, or (best) full routing - the choice is |
161 | routing - the choice is yours. |
193 | yours. |
162 | |
194 | |
163 | =head2 STEP 2: create the RSA key pairs for all hosts |
195 | =head2 STEP 2: create the RSA key pairs for all hosts |
164 | |
196 | |
165 | Run the following command to generate all key pairs (that might take a |
197 | Run the following command to generate all key pairs for all nodes (that |
166 | while): |
198 | might take a while): |
167 | |
199 | |
168 | gvpectrl -c /etc/gvpe -g |
200 | gvpectrl -c /etc/gvpe -g |
169 | |
201 | |
170 | This command will put the public keys into C<< |
202 | This command will put the public keys into C<< |
171 | /etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<< |
203 | /etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<< |
172 | /etc/gvpe/hostkeys/I<nodename> >>. |
204 | /etc/gvpe/hostkeys/I<nodename> >>. |
173 | |
205 | |
174 | =head2 STEP 3: distribute the config files to all nodes |
206 | =head2 STEP 3: distribute the config files to all nodes |
175 | |
207 | |
176 | Now distribute the config files to the other nodes. This should be done in two steps, since the |
208 | Now distribute the config files and private keys to the other nodes. This |
177 | private keys should not be distributed. The example uses rsync-over-ssh |
209 | should be done in two steps, since only the private keys meant for a node |
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210 | should be distributed (so each node has only it's own private key). |
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211 | |
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212 | The example uses rsync-over-ssh |
178 | |
213 | |
179 | First all the config files without the hostkeys should be distributed: |
214 | First all the config files without the hostkeys should be distributed: |
180 | |
215 | |
181 | rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys |
216 | rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys |
182 | rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys |
217 | rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys |
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186 | |
221 | |
187 | rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey |
222 | rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey |
188 | rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey |
223 | rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey |
189 | rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey |
224 | rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey |
190 | |
225 | |
191 | You should now check the configration by issuing the command C<gvpectrl -c |
226 | You should now check the configuration by issuing the command C<gvpectrl -c |
192 | /etc/gvpe -s> on each node and verify it's output. |
227 | /etc/gvpe -s> on each node and verify it's output. |
193 | |
228 | |
194 | =head2 STEP 4: starting gvpe |
229 | =head2 STEP 4: starting gvpe |
195 | |
230 | |
196 | You should then start gvpe on each node by issuing a command like: |
231 | You should then start gvpe on each node by issuing a command like: |
197 | |
232 | |
198 | gvpe -D -linfo first # first is the nodename |
233 | gvpe -D -l info first # first is the nodename |
199 | |
234 | |
200 | This will make the gvpe stay in foreground. You should then see |
235 | This will make the gvpe daemon stay in foreground. You should then see |
201 | "connection established" messages. If you don't see them check your |
236 | "connection established" messages. If you don't see them check your |
202 | firewall and routing (use tcpdump ;). |
237 | firewall and routing (use tcpdump ;). |
203 | |
238 | |
204 | If this works you should check your networking setup by pinging various |
239 | If this works you should check your networking setup by pinging various |
205 | endpoints. |
240 | endpoints. |
206 | |
241 | |
207 | To make gvpe run more permanently you can either run it as a daemon |
242 | To make gvpe run more permanently you can either run it as a daemon (by |
208 | (by starting it without the C<-D> switch), or, much better, from your |
243 | starting it without the C<-D> switch), or, much better, from your inittab |
209 | inittab. I use a line like this on my systems: |
244 | or equivalent. I use a line like this on all my systems: |
210 | |
245 | |
211 | t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1 |
246 | t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1 |
212 | |
247 | |
213 | =head2 STEP 5: enjoy |
248 | =head2 STEP 5: enjoy |
214 | |
249 | |
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218 | kill the daemon, start it again, making it read it's configuration files |
253 | kill the daemon, start it again, making it read it's configuration files |
219 | again. |
254 | again. |
220 | |
255 | |
221 | =head1 SEE ALSO |
256 | =head1 SEE ALSO |
222 | |
257 | |
223 | gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), and |
258 | gvpe.osdep(5) for OS-dependent information, gvpe.conf(5), gvpectrl(8), |
224 | for a description of the protocol and routing algorithms, gvpe.protocol(7). |
259 | and for a description of the transports, protocol, and routing algorithm, |
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260 | gvpe.protocol(7). |
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261 | |
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262 | The GVPE mailing list, at L<http://lists.schmorp.de/>, or |
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263 | C<gvpe@lists.schmorp.de>. |
225 | |
264 | |
226 | =head1 AUTHOR |
265 | =head1 AUTHOR |
227 | |
266 | |
228 | Marc Lehmann <gvpe@plan9.de> |
267 | Marc Lehmann <gvpe@schmorp.de> |
229 | |
268 | |
230 | =head1 COPYRIGHTS AND LICENSES |
269 | =head1 COPYRIGHTS AND LICENSES |
231 | |
270 | |
232 | GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file |
271 | GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file |
233 | COPYING that should be part of your distribution). |
272 | COPYING that should be part of your distribution). |