ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/gvpe/doc/gvpe.5.pod
(Generate patch)

Comparing gvpe/doc/gvpe.5.pod (file contents):
Revision 1.4 by pcg, Thu Jan 27 07:02:18 2005 UTC vs.
Revision 1.8 by pcg, Mon Sep 1 05:31:28 2008 UTC

… …
3GNU-VPE - Overview of the GNU Virtual Private Ethernet suite. 3GNU-VPE - Overview of the GNU Virtual Private Ethernet suite.
4 4
5=head1 DESCRIPTION 5=head1 DESCRIPTION
6 6
7GVPE is a suite designed to provide a virtual private network for multiple 7GVPE is a suite designed to provide a virtual private network for multiple
8nodes over an untrusted network. 8nodes over an untrusted network. This document first gives an introduction
9to VPNs in general and then describes the specific implementation of GVPE.
10
11=head2 WHAT IS A VPN?
12
13VPN 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
14Virtual means that no physical network is created (of course), but an 19Virtual means that no physical network is created (of course), but a
15ethernet is emulated by creating multiple tunnels between the member 20network is I<emulated> by creating multiple tunnels between the member
21nodes by encapsulating and sending data over another transport network.
22
23Usually the emulated network is a normal IP or Ethernet, and the transport
24network is the Internet. However, using a VPN system like GVPE to connect
25nodes over other untrusted networks such as Wireless LAN is not uncommon.
26
27=item X<Private>
28
29Private means that non-participating nodes cannot decode ("sniff)" nor
30inject ("spoof") packets. This means that nodes can be connected over
31untrusted networks such as the public Internet without fear of being
32eavesdropped while at the same time being able to trust data sent by other
16nodes. 33nodes.
17 34
18=item X<Private>
19
20Private means that non-participating nodes cannot decode ("sniff)" nor
21inject ("spoof") packets.
22
23In the case of gvpe, even participating nodes cannot sniff packets send to 35In the case of GVPE, even participating nodes cannot sniff packets
24other nodes or spoof packets as if sent from other nodes. 36send to other nodes or spoof packets as if sent from other nodes, so
37communications between any two nodes is private to those two nodes.
25 38
26=item X<Network> 39=item X<Network>
27 40
28Network means that more than two parties can participate in the network, 41Network means that more than two parties can participate in the network,
29so for instance it's possible to connect multiple branches of a company 42so for instance it's possible to connect multiple branches of a company
30into a single network. Many so-called "vpn" solutions only create 43into a single network. Many so-called "VPN" solutions only create
31point-to-point tunnels. 44point-to-point tunnels, which in turn can be used to build larger
45networks.
46
47GVPE provides a true multi-point network in which any number of nodes (at
48least a few dozen in practise, the theoretical limit is 4095 nodes) can
49participate.
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
41Cipher, HMAC algorithms and other key parameters must be selected 59Cipher, HMAC algorithms and other key parameters must be selected
42at compile time - this makes it possible to only link in algorithms 60at compile time - this makes it possible to only link in algorithms
43you actually need. It also makes the crypto part of the source very 61you actually need. It also makes the crypto part of the source very
44transparent and easy to inspect. 62transparent and easy to inspect, and last not least this makes it possible
63to hardcode the layout of all packets into the binary. GVPE goes a step
64further and internally reserves blocks of the same length for all packets,
65which virtually removes all possibilities of buffer overflows, as there is
66only 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
48A few lines of config (the config file is shared unmodified between all 70A few lines of config (the config file is shared unmodified between all
49hosts) and a single run of C<gvpectrl> to generate the keys suffices to 71hosts) and a single run of C<gvpectrl> to generate the keys suffices to
… …
59 81
60=back 82=back
61 83
62=head1 PROGRAMS 84=head1 PROGRAMS
63 85
64Vpe comes with two programs: one daemon (C<gvpe>) and one control program 86Gvpe 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
71Is used to generate the keys, check and give an overview of of the 93This program is used to generate the keys, check and give an overview of of the
72configuration and contorl the daemon (restarting etc.). 94configuration and to control the daemon (restarting etc.).
73 95
74=item gvpe 96=item gvpe
75 97
76Is the daemon used to establish and maintain connections to the other 98This is the daemon used to establish and maintain connections to the other
77network members. It should be run on the gateway machine. 99network 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
83Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific 105Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific
84information. 106information.
85 107
108Gvpe hardcodes most encryption parameters. While this reduces flexibility,
109it makes the program much simpler and helps making buffer overflows
110impossible under most circumstances.
111
86Here are a few recipes for compiling your gvpe, showing the extremes 112Here are a few recipes for compiling your gvpe, showing the extremes
87(fast, small, insecure OR slow, large, more secure), between you should 113(fast, small, insecure OR slow, large, more secure), between which you
88choose: 114should choose:
89 115
90=head2 AS LOW PACKET OVERHEAD AS POSSIBLE 116=head2 AS LOW PACKET OVERHEAD AS POSSIBLE
91 117
92 ./configure --enable-hmac-length=4 --enable-rand-length=0 118 ./configure --enable-hmac-length=4 --enable-rand-length=0
93 119
94Minimize the header overhead of VPN packets (the above will result in 120Minimize the header overhead of VPN packets (the above will result in
95only 4 bytes of overhead over the raw ethernet frame). This is a insecure 121only 4 bytes of overhead over the raw ethernet frame). This is a insecure
96configuration because a HMAC length of 4 makes collision attacks based on 122configuration because a HMAC length of 4 makes collision attacks based on
97the birthday paradox easy, though. 123the birthday paradox pretty easy.
98 124
99=head2 MINIMIZE CPU TIME REQUIRED 125=head2 MINIMIZE CPU TIME REQUIRED
100 126
101 ./configure --enable-cipher=bf --enable-digest=md4 127 ./configure --enable-cipher=bf --enable-digest=md4
102 128
103Use the fastest cipher and digest algorithms currently available in 129Use the fastest cipher and digest algorithms currently available in
104gvpe. MD4 has been broken and is quite insecure, though. 130gvpe. MD4 has been broken and is quite insecure, though, so using another
131digest algorithm is recommended.
105 132
106=head2 MAXIMIZE SECURITY 133=head2 MAXIMIZE SECURITY
107 134
108 ./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
109 136
110This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12 137This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12
111would also be pretty secure ;) and will additionally prefix each packet 138would also be pretty secure ;) and will additionally prefix each packet
112with 8 bytes of random data. In the long run, people should move to 139with 8 bytes of random data. In the long run, people should move to
113SHA-224 and beyond, but support in openssl is missing as of writing this 140SHA-256 and beyond).
114document.
115 141
116In general, remember that AES-128 seems to be more secure and faster than 142In general, remember that AES-128 seems to be as secure but faster than
117AES-192 or AES-256, more randomness helps against sniffing and a longer 143AES-192 or AES-256, more randomness helps against sniffing and a longer
118HMAC helps against spoofing. MD4 is a fast digest, SHA1 or RIPEMD160 are 144HMAC helps against spoofing. MD4 is a fast digest, SHA1, RIPEMD160, SHA256
119better, and Blowfish is a fast cipher (and also quite secure). 145are consecutively better, and Blowfish is a fast cipher (and also quite
146secure).
120 147
121=head1 HOW TO SET UP A SIMPLE VPN 148=head1 HOW TO SET UP A SIMPLE VPN
122 149
123In this section I will describe how to get a simple VPN consisting of 150In this section I will describe how to get a simple VPN consisting of
124three hosts up and running. 151three hosts up and running.
125 152
126=head2 STEP 1: configuration 153=head2 STEP 1: configuration
127 154
128First you have to create a daemon configuation file and put it into the 155First you have to create a daemon configuration file and put it into the
129configuration directory. This is usually C</etc/gvpe>, depending on how you 156configuration directory. This is usually C</etc/gvpe>, depending on how you
130configured gvpe, and can be overwritten using the C<-c> commandline switch. 157configured gvpe, and can be overwritten using the C<-c> command line switch.
131 158
132Put the following lines into C</etc/gvpe/gvpe.conf>: 159Put the following lines into C</etc/gvpe/gvpe.conf>:
133 160
134 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)
135 mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts 162 mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts
… …
142 hostname = 133.55.82.9 169 hostname = 133.55.82.9
143 170
144 node = third 171 node = third
145 hostname = third.example.net 172 hostname = third.example.net
146 173
147The only other file neccessary if the C<if-up> script that initializes the 174The only other file necessary is the C<if-up> script that initializes the
148local ethernet interface. Put the following lines into C</etc/gvpe/if-up> 175virtual ethernet interface on the local host. Put the following lines into
149and make it execute (C<chmod 755 /etc/gvpe/if-up>): 176C</etc/gvpe/if-up> and make it executable (C<chmod 755 /etc/gvpe/if-up>):
150 177
151 #!/bin/sh 178 #!/bin/sh
152 ip link set $IFNAME address $MAC mtu $MTU up 179 ip link set $IFNAME address $MAC mtu $MTU up
153 [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME 180 [ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME
154 [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME 181 [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
155 [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME 182 [ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME
156 ip route add 10.0.0.0/16 dev $IFNAME 183 ip route add 10.0.0.0/16 dev $IFNAME
157 184
158This script will give each node a different IP address in the C<10.0/16> 185This script will give each node a different IP address in the C<10.0/16>
159network. The internal network (e.g. the C<eth0> interface) should then be 186network. The internal network (if gvpe runs on a router) should then be
160set to a subset of that network, e.g. C<10.0.1.0/24> on node C<first>, 187set to a subset of that network, e.g. C<10.0.1.0/24> on node C<first>,
161C<10.0.2.0/24> on node C<second>, and so on. 188C<10.0.2.0/24> on node C<second>, and so on.
162 189
163By enabling routing on the gateway host that runs C<gvpe> all nodes will 190By enabling routing on the gateway host that runs C<gvpe> all nodes will
164be able to reach the other nodes. You can, of course, also use proxy arp 191be able to reach the other nodes. You can, of course, also use proxy ARP
165or other means of pseudo-bridging (or even real briding), or (best) full 192or other means of pseudo-bridging, or (best) full routing - the choice is
166routing - the choice is yours. 193yours.
167 194
168=head2 STEP 2: create the RSA key pairs for all hosts 195=head2 STEP 2: create the RSA key pairs for all hosts
169 196
170Run the following command to generate all key pairs (that might take a 197Run the following command to generate all key pairs for all nodes (that
171while): 198might take a while):
172 199
173 gvpectrl -c /etc/gvpe -g 200 gvpectrl -c /etc/gvpe -g
174 201
175This command will put the public keys into C<< 202This command will put the public keys into C<<
176/etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<< 203/etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<<
177/etc/gvpe/hostkeys/I<nodename> >>. 204/etc/gvpe/hostkeys/I<nodename> >>.
178 205
179=head2 STEP 3: distribute the config files to all nodes 206=head2 STEP 3: distribute the config files to all nodes
180 207
181Now distribute the config files to the other nodes. This should be done in two steps, since the 208Now distribute the config files and private keys to the other nodes. This
182private keys should not be distributed. The example uses rsync-over-ssh 209should be done in two steps, since only the private keys meant for a node
210should be distributed (so each node has only it's own private key).
211
212The example uses rsync-over-ssh
183 213
184First all the config files without the hostkeys should be distributed: 214First all the config files without the hostkeys should be distributed:
185 215
186 rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys 216 rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys
187 rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys 217 rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys
… …
191 221
192 rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey 222 rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey
193 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
194 rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey 224 rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey
195 225
196You should now check the configration by issuing the command C<gvpectrl -c 226You should now check the configuration by issuing the command C<gvpectrl -c
197/etc/gvpe -s> on each node and verify it's output. 227/etc/gvpe -s> on each node and verify it's output.
198 228
199=head2 STEP 4: starting gvpe 229=head2 STEP 4: starting gvpe
200 230
201You should then start gvpe on each node by issuing a command like: 231You should then start gvpe on each node by issuing a command like:
202 232
203 gvpe -D -linfo first # first is the nodename 233 gvpe -D -l info first # first is the nodename
204 234
205This will make the gvpe stay in foreground. You should then see 235This will make the gvpe daemon stay in foreground. You should then see
206"connection established" messages. If you don't see them check your 236"connection established" messages. If you don't see them check your
207firewall and routing (use tcpdump ;). 237firewall and routing (use tcpdump ;).
208 238
209If this works you should check your networking setup by pinging various 239If this works you should check your networking setup by pinging various
210endpoints. 240endpoints.
211 241
212To make gvpe run more permanently you can either run it as a daemon 242To make gvpe run more permanently you can either run it as a daemon (by
213(by starting it without the C<-D> switch), or, much better, from your 243starting it without the C<-D> switch), or, much better, from your inittab
214inittab. I use a line like this on my systems: 244or equivalent. I use a line like this on all my systems:
215 245
216 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
217 247
218=head2 STEP 5: enjoy 248=head2 STEP 5: enjoy
219 249
… …
223kill the daemon, start it again, making it read it's configuration files 253kill the daemon, start it again, making it read it's configuration files
224again. 254again.
225 255
226=head1 SEE ALSO 256=head1 SEE ALSO
227 257
228gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), and 258gvpe.osdep(5) for OS-dependent information, gvpe.conf(5), gvpectrl(8),
229for a description of the protocol and routing algorithms, gvpe.protocol(7). 259and for a description of the transports, protocol, and routing algorithm,
260gvpe.protocol(7).
261
262The GVPE mailing list, at L<http://lists.schmorp.de/>, or
263C<gvpe@lists.schmorp.de>.
230 264
231=head1 AUTHOR 265=head1 AUTHOR
232 266
233Marc Lehmann <gvpe@plan9.de> 267Marc Lehmann <gvpe@schmorp.de>
234 268
235=head1 COPYRIGHTS AND LICENSES 269=head1 COPYRIGHTS AND LICENSES
236 270
237GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file 271GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file
238COPYING that should be part of your distribution). 272COPYING that should be part of your distribution).

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines