
==== NAME ====

    vpe - Overview of the virtual private ethernet suite.


==== DESCRIPTION ====

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

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

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

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

    "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.


==   DESIGN GOALS   ==

:   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.

:   EASY TO SETUP
        A few lines of config (the config file is shared unmodified between
        all hosts) and a single run of ``vpectrl'' to generate the keys
        suffices to make it work.

:   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 packest by
        MAC address, e.g. to ensure that packets from a specific IP address
        come, in fact, from a specific host.


==== PROGRAMS ====

    Vpe comes with two programs: one daemon (``vped'') and one control
    program (``vpectrl'').

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

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


==== COMPILETIME CONFIGURATION ====

    Here are a few recipes for compiling your vpe:


==   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).


==   MINIMIZE CPU TIME REQUIRED   ==

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

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


==   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 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).


==== 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.


==   STEP 1: configuration   ==

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

    Put the following lines into ``/etc/vpe/vped.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 ``if-up'' script that initializes
    the local ethernet interface. Put the following lines into
    ``/etc/vpe/if-up'' and make it execute (``chmod 755 /etc/vpe/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
    ``10.0/16'' network. The internal network (e.g. the ``eth0'' interface)
    should then be set to a subset of that network, e.g. ``10.0.1.0/24'' on
    node ``first'', ``10.0.2.0/24'' on node ``second'', and so on.

    By enabling routing on the gateway host that runs ``vped'' 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.


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

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

       vpectrl -c /etc/vpe -g

    This command will put the public keys into
    ``/etc/vpe/pubkeys/*nodename*'' and the private keys into
    ``/etc/vpe/hostkeys/*nodename*''.


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

    Then the hostkeys should be copied:

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

    You should now check the configration by issuing the command ``vpectrl
    -c /etc/vpe -s'' on each node and verify it's output.


==   STEP 4: starting vped   ==

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

       vped -D -linfo first # first is the nodename

    This will make the vped 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 vped run more permanently you can either run it as a daemon (by
    starting it without the ``-D'' switch), or, much better, from your
    inittab. I use a line like this on my systems:

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


==   STEP 5: enjoy   ==

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


==== SEE ALSO ====

    vpe(5), vped.conf(5), vpectrl(8).


==== AUTHOR ====

    Marc Lehmann <vpe@plan9.de>

