gvpe/doc/gvpe.5.pod

=head1 NAME

GNU-VPE - Overview of the GNU Virtual Private Ethernet suite.

=head1 DESCRIPTION

GVPE is a suite designed to provide a virtual private network for multiple
nodes over an untrusted network.

=over 4

=item X<Virtual>

Virtual means that no physical network is created (of course), but an
ethernet is emulated by creating multiple tunnels between the member
nodes.

=item X<Private>

Private means that non-participating nodes cannot decode ("sniff)" nor
inject ("spoof") packets.

In the case of gvpe, even participating nodes cannot sniff packets send to
other nodes or spoof packets as if sent from other nodes.

=item X<Network>

Network means that more than two parties can participate in the network,
so for instance it's possible to connect multiple branches of a company
into a single network. Many so-called "vpn" solutions only create
point-to-point tunnels.

=back

=head2 DESIGN GOALS

=over 4 

=item SIMPLE DESIGN

Cipher, HMAC algorithms and other key parameters must be selected
at compile time - this makes it possible to only link in algorithms
you actually need. It also makes the crypto part of the source very
transparent and easy to inspect.

=item EASY TO SETUP

A few lines of config (the config file is shared unmodified between all
hosts) and a single run of C<gvpectrl> to generate the keys suffices to
make it work.

=item MAC-BASED SECURITY

Since every host has it's own private key, other hosts cannot spoof
traffic from this host. That makes it possible to filter packet by MAC
address, e.g. to ensure that packets from a specific IP address come, in
fact, from a specific host that is associated with that IP and not from
another host.

=back

=head1 PROGRAMS

Vpe comes with two programs: one daemon (C<gvpe>) and one control program
(C<gvpectrl>).

=over 4

=item gvpectrl

Is used to generate the keys, check and give an overview of of the
configuration and contorl the daemon (restarting etc.).

=item gvpe

Is the daemon used to establish and maintain connections to the other
network members. It should be run on the gateway machine.

=back

=head1 COMPILETIME CONFIGURATION

Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific
information.

Here are a few recipes for compiling your gvpe:

=head2 AS LOW PACKET OVERHEAD AS POSSIBLE

   ./configure --enable-hmac-length=4 --enable-rand-length=0

Minimize the header overhead of VPN packets (the above will result in only
4 bytes of overhead over the raw ethernet frame).

=head2 MINIMIZE CPU TIME REQUIRED

   ./configure --enable-cipher=bf --enable-digest=md4

Use the fastest cipher and digest algorithms currently available in gvpe.

=head2 MAXIMIZE SECURITY

   ./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1

This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12
would also be pretty secure ;) and will additionally prefix each packet
with 8 bytes of random data. In the long run, people should move to
SHA-224 and beyond, but support in openssl is missing as of writing this
document.

In general, remember that AES-128 seems to be more secure and faster than
AES-192 or AES-256, more randomness helps against sniffing and a longer
HMAC helps against spoofing. MD4 is a fast digest, SHA1 or RIPEMD160 are
better, and Blowfish is a fast cipher (and also quite secure).

=head1 HOW TO SET UP A SIMPLE VPN

In this section I will describe how to get a simple VPN consisting of
three hosts up and running.

=head2 STEP 1: configuration

First you have to create a daemon configuation file and put it into the
configuration directory. This is usually C</etc/gvpe>, depending on how you
configured gvpe, and can be overwritten using the C<-c> commandline switch.

Put the following lines into C</etc/gvpe/gvpe.conf>:

   udp-port = 50000 # the external port to listen on (configure your firewall)
   mtu = 1400       # minimum MTU of all outgoing interfaces on all hosts
   ifname = vpn0    # the local network device name

   node = first     # just a nickname
   hostname = first.example.net # the DNS name or IP address of the host

   node = second
   hostname = 133.55.82.9

   node = third
   hostname = third.example.net

The only other file neccessary if the C<if-up> script that initializes the
local ethernet interface. Put the following lines into C</etc/gvpe/if-up>
and make it execute (C<chmod 755 /etc/gvpe/if-up>):

   #!/bin/sh
   ip link set $IFNAME address $MAC mtu $MTU up
   [ $NODENAME = first  ] && ip addr add 10.0.1.1 dev $IFNAME
   [ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
   [ $NODENAME = third  ] && ip addr add 10.0.3.1 dev $IFNAME
   ip route add 10.0.0.0/16 dev $IFNAME

This script will give each node a different IP address in the C<10.0/16>
network.  The internal network (e.g. the C<eth0> interface) should then be
set to a subset of that network, e.g.  C<10.0.1.0/24> on node C<first>,
C<10.0.2.0/24> on node C<second>, and so on.

By enabling routing on the gateway host that runs C<gvpe> all nodes will
be able to reach the other nodes. You can, of course, also use proxy arp
or other means of pseudo-bridging (or even real briding), or (best) full
routing - the choice is yours.

=head2 STEP 2: create the RSA key pairs for all hosts

Run the following command to generate all key pairs (that might take a
while):

   gvpectrl -c /etc/gvpe -g

This command will put the public keys into C<<
/etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<<
/etc/gvpe/hostkeys/I<nodename> >>.

=head2 STEP 3: distribute the config files to all nodes

Now distribute the config files to the other nodes. This should be done in two steps, since the
private keys should not be distributed. The example uses rsync-over-ssh

First all the config files without the hostkeys should be distributed:

   rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys
   rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys
   rsync -avzessh /etc/gvpe third.example.net:/etc/. --exclude hostkeys

Then the hostkeys should be copied:

   rsync -avzessh /etc/gvpe/hostkeys/first  first.example.net:/etc/hostkey
   rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey
   rsync -avzessh /etc/gvpe/hostkeys/third  third.example.net:/etc/hostkey

You should now check the configration by issuing the command C<gvpectrl -c
/etc/gvpe -s> on each node and verify it's output.

=head2 STEP 4: starting gvpe

You should then start gvpe on each node by issuing a command like:

   gvpe -D -linfo first # first is the nodename

This will make the gvpe stay in foreground. You should then see
"connection established" messages. If you don't see them check your
firewall and routing (use tcpdump ;).

If this works you should check your networking setup by pinging various
endpoints.

To make gvpe run more permanently you can either run it as a daemon
(by starting it without the C<-D> switch), or, much better, from your
inittab. I use a line like this on my systems:

   t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1

=head2 STEP 5: enjoy

... and play around. Sending a -HUP (C<gvpectrl -kHUP>) to the daemon
will make it try to connect to all other nodes again. If you run it from
inittab, as is recommended, C<gvpectrl -k> (or simply C<killall gvpe>) will
kill the daemon, start it again, making it read it's configuration files
again.

=head1 SEE ALSO

gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), and
for a description of the protocol and routing algorithms, gvpe.protocol(7).

=head1 AUTHOR

Marc Lehmann <gvpe@plan9.de>

=head1 COPYRIGHTS AND LICENSES

GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file
COPYING that should be part of your distribution).

In some configurations it uses modified versions of the tinc vpn suite,
which is also available under the GENERAL PUBLIC LICENSE.

Revision:	1.3
Committed:	Thu Jan 27 06:58:48 2005 UTC (19 years, 5 months ago) by pcg
Branch:	MAIN
Changes since 1.2:	+15 -5 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	pcg	1.1	=head1 NAME
2
3			GNU-VPE - Overview of the GNU Virtual Private Ethernet suite.
4
5			=head1 DESCRIPTION
6
7			GVPE is a suite designed to provide a virtual private network for multiple
8			nodes over an untrusted network.
9
10	pcg	1.3	=over 4
11
12			=item X<Virtual>
13
14			Virtual means that no physical network is created (of course), but an
15	pcg	1.1	ethernet is emulated by creating multiple tunnels between the member
16			nodes.
17
18	pcg	1.3	=item X<Private>
19
20			Private means that non-participating nodes cannot decode ("sniff)" nor
21	pcg	1.1	inject ("spoof") packets.
22
23			In the case of gvpe, even participating nodes cannot sniff packets send to
24			other nodes or spoof packets as if sent from other nodes.
25
26	pcg	1.3	=item X<Network>
27
28			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
30			into a single network. Many so-called "vpn" solutions only create
31	pcg	1.1	point-to-point tunnels.
32
33	pcg	1.3	=back
34
35	pcg	1.1	=head2 DESIGN GOALS
36
37			=over 4
38
39			=item SIMPLE DESIGN
40
41			Cipher, HMAC algorithms and other key parameters must be selected
42			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
44			transparent and easy to inspect.
45
46			=item EASY TO SETUP
47
48			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
50			make it work.
51
52			=item MAC-BASED SECURITY
53
54			Since every host has it's own private key, other hosts cannot spoof
55			traffic from this host. That makes it possible to filter packet by MAC
56			address, e.g. to ensure that packets from a specific IP address come, in
57			fact, from a specific host that is associated with that IP and not from
58			another host.
59
60			=back
61
62			=head1 PROGRAMS
63
64			Vpe comes with two programs: one daemon (C<gvpe>) and one control program
65			(C<gvpectrl>).
66
67			=over 4
68
69			=item gvpectrl
70
71			Is used to generate the keys, check and give an overview of of the
72			configuration and contorl the daemon (restarting etc.).
73
74			=item gvpe
75
76			Is the daemon used to establish and maintain connections to the other
77			network members. It should be run on the gateway machine.
78
79			=back
80
81			=head1 COMPILETIME CONFIGURATION
82
83			Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific
84			information.
85
86			Here are a few recipes for compiling your gvpe:
87
88			=head2 AS LOW PACKET OVERHEAD AS POSSIBLE
89
90			./configure --enable-hmac-length=4 --enable-rand-length=0
91
92			Minimize the header overhead of VPN packets (the above will result in only
93			4 bytes of overhead over the raw ethernet frame).
94
95			=head2 MINIMIZE CPU TIME REQUIRED
96
97			./configure --enable-cipher=bf --enable-digest=md4
98
99			Use the fastest cipher and digest algorithms currently available in gvpe.
100
101			=head2 MAXIMIZE SECURITY
102
103			./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1
104
105			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
107	pcg	1.2	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
109			document.
110	pcg	1.1
111			In general, remember that AES-128 seems to be more secure and faster than
112			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
114			better, and Blowfish is a fast cipher (and also quite secure).
115
116			=head1 HOW TO SET UP A SIMPLE VPN
117
118			In this section I will describe how to get a simple VPN consisting of
119			three hosts up and running.
120
121			=head2 STEP 1: configuration
122
123			First you have to create a daemon configuation file and put it into the
124			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.
126
127			Put the following lines into C</etc/gvpe/gvpe.conf>:
128
129			udp-port = 50000 # the external port to listen on (configure your firewall)
130			mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts
131			ifname = vpn0 # the local network device name
132
133			node = first # just a nickname
134			hostname = first.example.net # the DNS name or IP address of the host
135
136			node = second
137			hostname = 133.55.82.9
138
139			node = third
140			hostname = third.example.net
141
142			The only other file neccessary if the C<if-up> script that initializes the
143			local ethernet interface. Put the following lines into C</etc/gvpe/if-up>
144			and make it execute (C<chmod 755 /etc/gvpe/if-up>):
145
146			#!/bin/sh
147			ip link set $IFNAME address $MAC mtu $MTU up
148			[ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME
149			[ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
150			[ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME
151			ip route add 10.0.0.0/16 dev $IFNAME
152
153			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
155			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.
157
158			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
160			or other means of pseudo-bridging (or even real briding), or (best) full
161			routing - the choice is yours.
162
163			=head2 STEP 2: create the RSA key pairs for all hosts
164
165			Run the following command to generate all key pairs (that might take a
166			while):
167
168			gvpectrl -c /etc/gvpe -g
169
170			This command will put the public keys into C<<
171			/etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<<
172			/etc/gvpe/hostkeys/I<nodename> >>.
173
174			=head2 STEP 3: distribute the config files to all nodes
175
176			Now distribute the config files to the other nodes. This should be done in two steps, since the
177			private keys should not be distributed. The example uses rsync-over-ssh
178
179			First all the config files without the hostkeys should be distributed:
180
181			rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys
182			rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys
183			rsync -avzessh /etc/gvpe third.example.net:/etc/. --exclude hostkeys
184
185			Then the hostkeys should be copied:
186
187			rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey
188			rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey
189			rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey
190
191			You should now check the configration by issuing the command C<gvpectrl -c
192			/etc/gvpe -s> on each node and verify it's output.
193
194			=head2 STEP 4: starting gvpe
195
196			You should then start gvpe on each node by issuing a command like:
197
198			gvpe -D -linfo first # first is the nodename
199
200			This will make the gvpe stay in foreground. You should then see
201			"connection established" messages. If you don't see them check your
202			firewall and routing (use tcpdump ;).
203
204			If this works you should check your networking setup by pinging various
205			endpoints.
206
207			To make gvpe run more permanently you can either run it as a daemon
208			(by starting it without the C<-D> switch), or, much better, from your
209			inittab. I use a line like this on my systems:
210
211			t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1
212
213			=head2 STEP 5: enjoy
214
215			... and play around. Sending a -HUP (C<gvpectrl -kHUP>) to the daemon
216			will make it try to connect to all other nodes again. If you run it from
217			inittab, as is recommended, C<gvpectrl -k> (or simply C<killall gvpe>) will
218			kill the daemon, start it again, making it read it's configuration files
219			again.
220
221			=head1 SEE ALSO
222
223			gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), and
224			for a description of the protocol and routing algorithms, gvpe.protocol(7).
225
226			=head1 AUTHOR
227
228			Marc Lehmann <gvpe@plan9.de>
229
230			=head1 COPYRIGHTS AND LICENSES
231
232			GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file
233			COPYING that should be part of your distribution).
234
235			In some configurations it uses modified versions of the tinc vpn suite,
236			which is also available under the GENERAL PUBLIC LICENSE.
237