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, showing the extremes
(fast, small, insecure OR slow, large, more secure), between you should
choose:

=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). This is a insecure
configuration because a HMAC length of 4 makes collision attacks based on
the birthday paradox easy, though.

=head2 MINIMIZE CPU TIME REQUIRED

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

Use the fastest cipher and digest algorithms currently available in
gvpe. MD4 has been broken and is quite insecure, though.

=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:	1.4
Committed:	Thu Jan 27 07:02:18 2005 UTC (19 years, 3 months ago) by pcg
Branch:	MAIN
Changes since 1.3:	+9 -4 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	pcg	1.4	Here are a few recipes for compiling your gvpe, showing the extremes
87			(fast, small, insecure OR slow, large, more secure), between you should
88			choose:
89	pcg	1.1
90			=head2 AS LOW PACKET OVERHEAD AS POSSIBLE
91
92			./configure --enable-hmac-length=4 --enable-rand-length=0
93
94	pcg	1.4	Minimize the header overhead of VPN packets (the above will result in
95			only 4 bytes of overhead over the raw ethernet frame). This is a insecure
96			configuration because a HMAC length of 4 makes collision attacks based on
97			the birthday paradox easy, though.
98	pcg	1.1
99			=head2 MINIMIZE CPU TIME REQUIRED
100
101			./configure --enable-cipher=bf --enable-digest=md4
102
103	pcg	1.4	Use the fastest cipher and digest algorithms currently available in
104			gvpe. MD4 has been broken and is quite insecure, though.
105	pcg	1.1
106			=head2 MAXIMIZE SECURITY
107
108			./configure --enable-hmac-length=16 --enable-rand-length=8 --enable-digest=sha1
109
110			This uses a 16 byte HMAC checksum to authenticate packets (I guess 8-12
111			would also be pretty secure ;) and will additionally prefix each packet
112	pcg	1.2	with 8 bytes of random data. In the long run, people should move to
113			SHA-224 and beyond, but support in openssl is missing as of writing this
114			document.
115	pcg	1.1
116			In general, remember that AES-128 seems to be more secure and faster than
117			AES-192 or AES-256, more randomness helps against sniffing and a longer
118			HMAC helps against spoofing. MD4 is a fast digest, SHA1 or RIPEMD160 are
119			better, and Blowfish is a fast cipher (and also quite secure).
120
121			=head1 HOW TO SET UP A SIMPLE VPN
122
123			In this section I will describe how to get a simple VPN consisting of
124			three hosts up and running.
125
126			=head2 STEP 1: configuration
127
128			First you have to create a daemon configuation file and put it into the
129			configuration directory. This is usually C</etc/gvpe>, depending on how you
130			configured gvpe, and can be overwritten using the C<-c> commandline switch.
131
132			Put the following lines into C</etc/gvpe/gvpe.conf>:
133
134			udp-port = 50000 # the external port to listen on (configure your firewall)
135			mtu = 1400 # minimum MTU of all outgoing interfaces on all hosts
136			ifname = vpn0 # the local network device name
137
138			node = first # just a nickname
139			hostname = first.example.net # the DNS name or IP address of the host
140
141			node = second
142			hostname = 133.55.82.9
143
144			node = third
145			hostname = third.example.net
146
147			The only other file neccessary if the C<if-up> script that initializes the
148			local ethernet interface. Put the following lines into C</etc/gvpe/if-up>
149			and make it execute (C<chmod 755 /etc/gvpe/if-up>):
150
151			#!/bin/sh
152			ip link set $IFNAME address $MAC mtu $MTU up
153			[ $NODENAME = first ] && ip addr add 10.0.1.1 dev $IFNAME
154			[ $NODENAME = second ] && ip addr add 10.0.2.1 dev $IFNAME
155			[ $NODENAME = third ] && ip addr add 10.0.3.1 dev $IFNAME
156			ip route add 10.0.0.0/16 dev $IFNAME
157
158			This script will give each node a different IP address in the C<10.0/16>
159			network. The internal network (e.g. the C<eth0> interface) should then be
160			set to a subset of that network, e.g. C<10.0.1.0/24> on node C<first>,
161			C<10.0.2.0/24> on node C<second>, and so on.
162
163			By enabling routing on the gateway host that runs C<gvpe> all nodes will
164			be able to reach the other nodes. You can, of course, also use proxy arp
165			or other means of pseudo-bridging (or even real briding), or (best) full
166			routing - the choice is yours.
167
168			=head2 STEP 2: create the RSA key pairs for all hosts
169
170			Run the following command to generate all key pairs (that might take a
171			while):
172
173			gvpectrl -c /etc/gvpe -g
174
175			This command will put the public keys into C<<
176			/etc/gvpe/pubkeys/I<nodename> >> and the private keys into C<<
177			/etc/gvpe/hostkeys/I<nodename> >>.
178
179			=head2 STEP 3: distribute the config files to all nodes
180
181			Now distribute the config files to the other nodes. This should be done in two steps, since the
182			private keys should not be distributed. The example uses rsync-over-ssh
183
184			First all the config files without the hostkeys should be distributed:
185
186			rsync -avzessh /etc/gvpe first.example.net:/etc/. --exclude hostkeys
187			rsync -avzessh /etc/gvpe 133.55.82.9:/etc/. --exclude hostkeys
188			rsync -avzessh /etc/gvpe third.example.net:/etc/. --exclude hostkeys
189
190			Then the hostkeys should be copied:
191
192			rsync -avzessh /etc/gvpe/hostkeys/first first.example.net:/etc/hostkey
193			rsync -avzessh /etc/gvpe/hostkeys/second 133.55.82.9:/etc/hostkey
194			rsync -avzessh /etc/gvpe/hostkeys/third third.example.net:/etc/hostkey
195
196			You should now check the configration by issuing the command C<gvpectrl -c
197			/etc/gvpe -s> on each node and verify it's output.
198
199			=head2 STEP 4: starting gvpe
200
201			You should then start gvpe on each node by issuing a command like:
202
203			gvpe -D -linfo first # first is the nodename
204
205			This will make the gvpe stay in foreground. You should then see
206			"connection established" messages. If you don't see them check your
207			firewall and routing (use tcpdump ;).
208
209			If this works you should check your networking setup by pinging various
210			endpoints.
211
212			To make gvpe run more permanently you can either run it as a daemon
213			(by starting it without the C<-D> switch), or, much better, from your
214			inittab. I use a line like this on my systems:
215
216			t1:2345:respawn:/opt/gvpe/sbin/gvpe -D -L first >/dev/null 2>&1
217
218			=head2 STEP 5: enjoy
219
220			... and play around. Sending a -HUP (C<gvpectrl -kHUP>) to the daemon
221			will make it try to connect to all other nodes again. If you run it from
222			inittab, as is recommended, C<gvpectrl -k> (or simply C<killall gvpe>) will
223			kill the daemon, start it again, making it read it's configuration files
224			again.
225
226			=head1 SEE ALSO
227
228			gvpe.osdep(5) for OS-depedendent information, gvpe.conf(5), gvpectrl(8), and
229			for a description of the protocol and routing algorithms, gvpe.protocol(7).
230
231			=head1 AUTHOR
232
233			Marc Lehmann <gvpe@plan9.de>
234
235			=head1 COPYRIGHTS AND LICENSES
236
237			GVPE itself is distributed under the GENERAL PUBLIC LICENSE (see the file
238			COPYING that should be part of your distribution).
239
240			In some configurations it uses modified versions of the tinc vpn suite,
241			which is also available under the GENERAL PUBLIC LICENSE.
242