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.

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

"Private"X<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.

"Network"X<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.

=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:	1.2
Committed:	Tue Oct 12 11:54:33 2004 UTC (19 years, 7 months ago) by pcg
Branch:	MAIN
Changes since 1.1:	+3 -1 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			"Virtual"X<Virtual> means that no physical network is created (of course), but an
11			ethernet is emulated by creating multiple tunnels between the member
12			nodes.
13
14			"Private"X<Private> means that non-participating nodes cannot decode ("sniff)" nor
15			inject ("spoof") packets.
16
17			In the case of gvpe, even participating nodes cannot sniff packets send to
18			other nodes or spoof packets as if sent from other nodes.
19
20			"Network"X<Network> means that more than two parties can participate in the
21			network, so for instance it's possible to connect multiple branches of a
22			company into a single network. Many so-called "vpn" solutions only create
23			point-to-point tunnels.
24
25			=head2 DESIGN GOALS
26
27			=over 4
28
29			=item SIMPLE DESIGN
30
31			Cipher, HMAC algorithms and other key parameters must be selected
32			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
34			transparent and easy to inspect.
35
36			=item EASY TO SETUP
37
38			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
40			make it work.
41
42			=item MAC-BASED SECURITY
43
44			Since every host has it's own private key, other hosts cannot spoof
45			traffic from this host. That makes it possible to filter packet by MAC
46			address, e.g. to ensure that packets from a specific IP address come, in
47			fact, from a specific host that is associated with that IP and not from
48			another host.
49
50			=back
51
52			=head1 PROGRAMS
53
54			Vpe comes with two programs: one daemon (C<gvpe>) and one control program
55			(C<gvpectrl>).
56
57			=over 4
58
59			=item gvpectrl
60
61			Is used to generate the keys, check and give an overview of of the
62			configuration and contorl the daemon (restarting etc.).
63
64			=item gvpe
65
66			Is the daemon used to establish and maintain connections to the other
67			network members. It should be run on the gateway machine.
68
69			=back
70
71			=head1 COMPILETIME CONFIGURATION
72
73			Please have a look at the C<gvpe.osdep(5)> manpage for platform-specific
74			information.
75
76			Here are a few recipes for compiling your gvpe:
77
78			=head2 AS LOW PACKET OVERHEAD AS POSSIBLE
79
80			./configure --enable-hmac-length=4 --enable-rand-length=0
81
82			Minimize the header overhead of VPN packets (the above will result in only
83			4 bytes of overhead over the raw ethernet frame).
84
85			=head2 MINIMIZE CPU TIME REQUIRED
86
87			./configure --enable-cipher=bf --enable-digest=md4
88
89			Use the fastest cipher and digest algorithms currently available in gvpe.
90
91			=head2 MAXIMIZE SECURITY
92
93			./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1
94
95			This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12
96			would also be pretty secure ;) and will additionally prefix each packet
97	pcg	1.2	with 8 bytes of random data. In the long run, people should move to
98			SHA-224 and beyond, but support in openssl is missing as of writing this
99			document.
100	pcg	1.1
101			In general, remember that AES-128 seems to be more secure and faster than
102			AES-192 or AES-256, more randomness helps against sniffing and a longer
103			HMAC helps against spoofing. MD4 is a fast digest, SHA1 or RIPEMD160 are
104			better, and Blowfish is a fast cipher (and also quite secure).
105
106			=head1 HOW TO SET UP A SIMPLE VPN
107
108			In this section I will describe how to get a simple VPN consisting of
109			three hosts up and running.
110
111			=head2 STEP 1: configuration
112
113			First you have to create a daemon configuation file and put it into the
114			configuration directory. This is usually C</etc/gvpe>, depending on how you
115			configured gvpe, and can be overwritten using the C<-c> commandline switch.
116
117			Put the following lines into C</etc/gvpe/gvpe.conf>:
118
119			udp-port = 50000 # the external port to listen on (configure your firewall)
120			mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts
121			ifname = vpn0 # the local network device name
122
123			node = first # just a nickname
124			hostname = first.example.net # the DNS name or IP address of the host
125
126			node = second
127			hostname = 133.55.82.9
128
129			node = third
130			hostname = third.example.net
131
132			The only other file neccessary if the C<if-up> script that initializes the
133			local ethernet interface. Put the following lines into C</etc/gvpe/if-up>
134			and make it execute (C<chmod 755 /etc/gvpe/if-up>):
135
136			#!/bin/sh
137			ip link set $IFNAME address $MAC mtu $MTU up
138			[ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME
139			[ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
140			[ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME
141			ip route add 10.0.0.0/16 dev $IFNAME
142
143			This script will give each node a different IP address in the C<10.0/16>
144			network. The internal network (e.g. the C<eth0> interface) should then be
145			set to a subset of that network, e.g. C<10.0.1.0/24> on node C<first>,
146			C<10.0.2.0/24> on node C<second>, and so on.
147
148			By enabling routing on the gateway host that runs C<gvpe> all nodes will
149			be able to reach the other nodes. You can, of course, also use proxy arp
150			or other means of pseudo-bridging (or even real briding), or (best) full
151			routing - the choice is yours.
152
153			=head2 STEP 2: create the RSA key pairs for all hosts
154
155			Run the following command to generate all key pairs (that might take a
156			while):
157
158			gvpectrl -c /etc/gvpe -g
159
160			This command will put the public keys into C<<
161			/etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<<
162			/etc/gvpe/hostkeys/I<nodename> >>.
163
164			=head2 STEP 3: distribute the config files to all nodes
165
166			Now distribute the config files to the other nodes. This should be done in two steps, since the
167			private keys should not be distributed. The example uses rsync-over-ssh
168
169			First all the config files without the hostkeys should be distributed:
170
171			rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys
172			rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys
173			rsync -avzessh /etc/gvpe third.example.net:/etc/. --exclude hostkeys
174
175			Then the hostkeys should be copied:
176
177			rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey
178			rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey
179			rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey
180
181			You should now check the configration by issuing the command C<gvpectrl -c
182			/etc/gvpe -s> on each node and verify it's output.
183
184			=head2 STEP 4: starting gvpe
185
186			You should then start gvpe on each node by issuing a command like:
187
188			gvpe -D -linfo first # first is the nodename
189
190			This will make the gvpe stay in foreground. You should then see
191			"connection established" messages. If you don't see them check your
192			firewall and routing (use tcpdump ;).
193
194			If this works you should check your networking setup by pinging various
195			endpoints.
196
197			To make gvpe run more permanently you can either run it as a daemon
198			(by starting it without the C<-D> switch), or, much better, from your
199			inittab. I use a line like this on my systems:
200
201			t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1
202
203			=head2 STEP 5: enjoy
204
205			... and play around. Sending a -HUP (C<gvpectrl -kHUP>) to the daemon
206			will make it try to connect to all other nodes again. If you run it from
207			inittab, as is recommended, C<gvpectrl -k> (or simply C<killall gvpe>) will
208			kill the daemon, start it again, making it read it's configuration files
209			again.
210
211			=head1 SEE ALSO
212
213			gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), and
214			for a description of the protocol and routing algorithms, gvpe.protocol(7).
215
216			=head1 AUTHOR
217
218			Marc Lehmann <gvpe@plan9.de>
219
220			=head1 COPYRIGHTS AND LICENSES
221
222			GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file
223			COPYING that should be part of your distribution).
224
225			In some configurations it uses modified versions of the tinc vpn suite,
226			which is also available under the GENERAL PUBLIC LICENSE.
227