==== 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(8), vpectrl(8), vped.conf(5). ==== AUTHOR ==== Marc Lehmann