--- /dev/null
+zarq:Ivo Timmermans <itimmermans@bigfoot.com>
+guus:Guus Sliepen <guus@sliepen.warande.net>
+wsl:Wessel Dankers <wsl@nl.linux.org>
--- /dev/null
+This document describes how nodes in a VPN find and connect to eachother and
+maintain a stable network.
+
+ Copyright 2001-2002 Guus Sliepen <guus@sliepen.warande.net>
+
+ Permission is granted to make and distribute verbatim copies of
+ this documentation provided the copyright notice and this
+ permission notice are preserved on all copies.
+
+ Permission is granted to copy and distribute modified versions of
+ this documentation under the conditions for verbatim copying,
+ provided that the entire resulting derived work is distributed
+ under the terms of a permission notice identical to this one.
+
+ $Id: CONNECTIVITY,v 1.2 2002/04/12 08:25:01 guus Exp $
+
+1. Problem
+==========
+
+We have a set of nodes (A, B, C, ...) that are part of the same VPN. They need
+to connect to eachother and form a single graph that satisfies the tree
+property.
+
+There is the possibility that loops are formed, the offending connections must
+be eliminated.
+
+Suppose we start with two smaller graphs that want to form a single larger
+graph. Both graphs consist of three nodes:
+
+ A-----B-----C
+
+
+
+ D-----E-----F
+
+It is very well possible that A wants to connect to D, and F wants to connect
+to C, both at the same time. The following loop will occur:
+
+ A-----B-----C
+ | ^
+ | |
+ v |
+ D-----E-----F
+
+The situation described here is totally symmetric, there is no preference to
+one connection over the other. The problem of resolving the loop, maintaining
+consistency and stability is therefore not a trivial one.
+
+What happens when A---D and C---F are connected to eachother? They exchange
+lists of known hosts. A knows of B and C, and D knows of E and F. The protocol
+defines ADD_HOST messages, from now on we will say that "node X sends and
+ADD_HOST(Y) to Z".
+
+There are two possible scenarios: either both A---D and C---F finish
+authentication at the same time, or A---D finishes first, so that ADD_HOST
+messages will reach C and F before they finish authentication.
+
+1.1 A---D finishes first
+------------------------
+
+After A---D authentication finishes the following actions are taken:
+
+ 1 A sends ADD_HOST(B) to D
+ A sends ADD_HOST(C) to D
+ D sends ADD_HOST(E) to A
+ D sends ADD_HOST(F) to A
+
+ 2 A sends ADD_HOST(D) to B
+ A receives ADD_HOST(E) from D:
+ A sends ADD_HOST(E) to B
+ A receives ADD_HOST(F) from D:
+ A sends ADD_HOST(F) to B
+ D sends ADD_HOST(A) to E
+ D receives ADD_HOST(B) from A:
+ D sends ADD_HOST(B) to E
+ D receives ADD_HOST(C) from A:
+ D sends ADD_HOST(C) to E
+
+ 3 B receives ADD_HOST(D) from A,
+ B sends ADD_HOST(D) to C
+ B receives ADD_HOST(E) from A:
+ B sends ADD_HOST(E) to C
+ B receives ADD_HOST(F) from A:
+ B sends ADD_HOST(F) to C
+ E receives ADD_HOST(A) from D:
+ E sends ADD_HOST(A) to F
+ E receives ADD_HOST(B) from D:
+ E sends ADD_HOST(B) to F
+ E receives ADD_HOST(C) from D:
+ E sends ADD_HOST(C) to F
+
+ 4 C receives ADD_HOST(D) from B.
+ C receives ADD_HOST(E) from B.
+ C receives ADD_HOST(F) from B.
+ F receives ADD_HOST(A) from E.
+ F receives ADD_HOST(B) from E.
+ F receives ADD_HOST(C) from E.
+
+Then C---F authentication finishes, the following actions are taken:
+
+ 1 C notes that F is already known:
+ Connection is closed.
+ F notes that C is already known:
+ Connection is closed.
+
+1.2 Both A---D and C---F finish at the same time.
+-------------------------------------------------
+
+ 1 A sends ADD_HOST(B) to D
+ A sends ADD_HOST(C) to D
+ D sends ADD_HOST(E) to A
+ D sends ADD_HOST(F) to A
+
+ C sends ADD_HOST(A) to F
+ C sends ADD_HOST(B) to F
+ F sends ADD_HOST(D) to C
+ F sends ADD_HOST(E) to C
+
+ 2 A sends ADD_HOST(D) to B
+ A receives ADD_HOST(E) from D:
+ A sends ADD_HOST(E) to B
+ A receives ADD_HOST(F) from D:
+ A sends ADD_HOST(F) to B
+ D sends ADD_HOST(A) to E
+ D receives ADD_HOST(B) from A:
+ D sends ADD_HOST(B) to E
+ D receives ADD_HOST(C) from A:
+ D sends ADD_HOST(C) to E
+
+ C sends ADD_HOST(F) to B
+ C receives ADD_HOST(D) from F:
+ A sends ADD_HOST(D) to B
+ C receives ADD_HOST(E) from F:
+ A sends ADD_HOST(E) to B
+ F sends ADD_HOSTS(C) to E
+ F receives ADD_HOST(A) from C:
+ D sends ADD_HOST(A) to E
+ F receives ADD_HOST(B) from C:
+ D sends ADD_HOST(B) to E
+
+ 3 B receives ADD_HOST(D) from A,
+ B sends ADD_HOST(D) to C
+ B receives ADD_HOST(E) from A:
+ B sends ADD_HOST(E) to C
+ B receives ADD_HOST(F) from A:
+ B sends ADD_HOST(F) to C
+ E receives ADD_HOST(A) from D:
+ E sends ADD_HOST(A) to F
+ E receives ADD_HOST(B) from D:
+ E sends ADD_HOST(B) to F
+ E receives ADD_HOST(C) from D:
+ E sends ADD_HOST(C) to F
+
+ B receives ADD_HOST(F) from C, and notes that is is already known:
+ <insert solution here>
+ B receives ADD_HOST(D) from C, and notes that is is already known:
+ <insert solution here>
+ B receives ADD_HOST(E) from C, and notes that is is already known:
+ <insert solution here>
+ E receives ADD_HOST(C) from F, and notes that is is already known:
+ <insert solution here>
+ E receives ADD_HOST(A) from F, and notes that is is already known:
+ <insert solution here>
+ E receives ADD_HOST(B) from F, and notes that is is already known:
+ <insert solution here>
+
+ 4 A receives ADD_HOST(D) from B, and notes that it is already known:
+ <insert solution here>
+ A receives ADD_HOST(E) from B, and notes that it is already known:
+ <insert solution here>
+ A receives ADD_HOST(F) from B, and notes that it is already known:
+ <insert solution here>
+ F receives ADD_HOST(A) from E, and notes that it is already known:
+ <insert solution here>
+ F receives ADD_HOST(B) from E, and notes that it is already known:
+ <insert solution here>
+ F receives ADD_HOST(B) from E, and notes that it is already known:
+ <insert solution here>
+
+ ...
+
+1.2.1 Augmenting ADD_HOST
+-------------------------
+
+A solution would be to augment ADD_HOST with an extra parameter, the nexthop of
+the added host:
+
+ 3 B receives ADD_HOST(D,A) from A,
+ B sends ADD_HOST(D,A) to C
+ B receives ADD_HOST(E,D) from A:
+ B sends ADD_HOST(E,D) to C
+ B receives ADD_HOST(F,E) from A:
+ B sends ADD_HOST(F,E) to C
+ E receives ADD_HOST(A,D) from D:
+ E sends ADD_HOST(A,D) to F
+ E receives ADD_HOST(B,A) from D:
+ E sends ADD_HOST(B,A) to F
+ E receives ADD_HOST(C,B) from D:
+ E sends ADD_HOST(C,B) to F
+
+ B receives ADD_HOST(F,C) from C, and notes that F is already known:
+ <insert solution here>
+ B receives ADD_HOST(D,E) from C, and notes that D is already known:
+ <insert solution here>
+ B receives ADD_HOST(E,F) from C, and notes that E is already known:
+ <insert solution here>
+ E receives ADD_HOST(C,F) from F, and notes that C is already known:
+ <insert solution here>
+ E receives ADD_HOST(A,B) from F, and notes that A is already known:
+ <insert solution here>
+ E receives ADD_HOST(B,C) from F, and notes that B is already known:
+ <insert solution here>
+
+So, B and E have to make a choice. Which ADD_HOST is going to win? Fortunately,
+since the ADD_HOST messages are augmented, they have an extra piece of
+information they can use to decide in a deterministic way which one is going to
+win. For example, B got ADD_HOST(F,E) and ADD_HOST(F,C). Since "E" > "C", it
+could let ADD_HOST(F,E) win.
+
+ B receives ADD_HOST(F,C) from C, and notes that F is already known:
+ since "C" < "E", B ignores ADD_HOST(F,E)
+ B sends ADD_HOST(F,C) to A
+ ...
+ E receives ADD_HOST(C,F) from F, and notes that C is already known:
+ since "F" > "B", E removes the ADD_HOST(C,B) in favour of the new one
+ E sends ADD_HOST(C,F) to D
+
+ 4 A receives ADD_HOST(F,E) from B, and notes that F is already known:
+ since "E" < "D", A ignores ADD_HOST(F,D).
+ ...
+ D receives ADD_HOST(C,F) from E, and notes that C is already known:
+ since "F" > "B", D removes the ADD_HOST(C,B),
+ closes the connection with C, in favour of the new one.
+
+Ok, time to forget this crap.
+
+1.2.2
+-----
+
+The problem with the current ADD/DEL_HOST technique is that each host only
+knows the general direction in which to send packets for the other hosts. It
+really doesn't know much about the true topology of the network, only about
+it's direct neighbours. With so little information each host cannot make a
+certain decision which it knows for sure all the others will decide too.
+
+Let's do something totally different. Instead of notifying every host of the
+addition of a new host, which is represented by a vertex in a graph, lets send
+out notifications of new connections, which are the edges in a graph. This is
+rather cheap, since our graphs are (almost) spanning trees, there is
+approximately one edge for each vertex in the graph, so we don't need to send
+more messages. Furthermore, an edge is characterized by two vertices, so we
+only send a fixed amount of extra information. The size/complexity of the
+problem therefore does not increase much.
+
+What is the advantage of notifying each vertex of new edges instead of new
+vertices? Well, all the vertices now know exactly which connections are made
+between each host. This was not known with the former schemes.
+
+Ok back to our problem:
+
+ A-----B-----C
+
+
+
+ D-----E-----F
+
+Edges are undirected, and are characterised by the vertices it connects, sorted
+alphabetically, so the edges in the two graphs are:
+
+(A,B), (B,C), (D,E) and (E,F).
+
+So again we have that A wants to connect to D, and F wants to connect to C,
+both at the same time. The following loop will occur:
+
+ A-----B-----C
+ | ^
+ | |
+ v |
+ D-----E-----F
+
+Instead of sending ADD_HOSTs, lets assume the hosts send ADD_EDGEs. So, after
+making the connections:
+
+ 1 A sends ADD_EDGE(A,D) to B
+ A sends ADD_EDGE(A,B) to D
+ A sends ADD_EDGE(B,C) to D
+ D sends ADD_EDGE(A,D) to E
+ D sends ADD_EDGE(D,E) to A
+ D sends ADD_EDGE(E,F) to A
+
+ C sends ADD_EDGE(C,F) to B
+ C sends ADD_EDGE(A,B) to F
+ C sends ADD_EDGE(B,C) to F
+ F sends ADD_EDGE(C,F) to E
+ F sends ADD_EDGE(D,E) to C
+ F sends ADD_EDGE(E,F) to C
+
+ 2 B receives ADD_EDGE(A,D) from A:
+ B sends ADD_EDGE(A,D) to C
+ B receives ADD_EDGE(D,E) from A:
+ B sends ADD_EDGE(D,E) to C
+ B receives ADD_EDGE(E,F) from A:
+ B sends ADD_EDGE(E,F) to C
+ ...
+
+ B receives ADD_EDGE(C,F) from C, notes that both C and F are already known,
+ but that the edge (C,F) was not known, so a loop has been created:
+ <resolve loop here>
+
+Ok, how to resolve the loop? Remeber, we want to do that in such a way that it
+is consistent with the way all the other hosts resolve the loop. Here is the
+things B does when it notices that a loop is going to be formed:
+
+ B performs a Breadth First Search from the first element of the list of all
+ known hosts sorted alfabetically, in this case A, and thereby finds a
+ spanning tree. (This might later be changed into a minimum spanning tree
+ alhorithm, but the key point here is that all hosts do this with exactly the
+ same starting parameters.) All known edges that are not in the spanning tree
+ are marked inactive.
+
+An edge marked inactive does not mean anything, unless this edge is connected
+to B itself. In that case, B will stop sending messages over that edge. B might
+consider closing this edge, but this is not really needed. Keeping it means no
+DEL_EDGE has to be sent for it, and if another edge is removed (which will
+quite certainly split the graph if it's a spanning tree), this edge might be
+reactivated, without the need of sending a new ADD_EDGE for it. On the other
+hand, we mustn't keep to many inactive edges, because we want to keep the
+number of known edges linear to the number of hosts (otherwise the size of the
+problem will grow quadratically).
+
+So, since B didn't deactivate one of it's own edges, it forwards the
+ADD_EDGE(C,F) to A, which also does a BFS, and so on, until it reaches F. F of
+course also does a BFS, notes that is is one of it's own edges. It deactivates
+the edge (C,F), and consequently will not forward the ADD_EDGE(C,F) to C
+anymore. In the mean time, C got messages from B which will make C do the same.
+
+Ok, suppose a DEL_EDGE was sent, and it means an inactive edge has to be
+reactivated. The vertices connected by that edge must exchange their entire
+knowledge of edges again, because in the mean time other messages could have
+been sent, which were not properly forwarded. Take this example:
+
+ X C-----D
+ | | |
+ | | |
+ v | |
+ A-----B- - -E
+
+The edge (B,E) is inactive. X is trying to make a new connection with A. A
+sends an ADD_EDGE(A,X) to B, which forwards it to C. At that time, the
+connection between C and D goes down, so C sends a DEL_EDGE(C,D) to B, and D
+sends a DEL_EDGE(C,D) to E. If we just allow (B,E) to be reactivated again
+without anything else, then E and D will never have received the ADD_EDGE(A,X).
+So, B and E have to exchange edges again, and propagate them to the hosts they
+already know.
--- /dev/null
+ ==============
+ The TINC HOWTO
+ ==============
+
+ Wessel Dankers
+ wsl@nl.linux.org
+\f
+Introduction
+------------
+Tinc is a system to create a virtual ethernet network on top of an existing
+infrastructure. This infrastructure can be anything from modem lines to
+gigabit ethernet networks, as long as they talk IP. Once you install and
+configure tinc, your host will get an extra IP address, just like it would
+when you stick an extra ethernet card into it. Using this IP address, it can
+communicate with all hosts in its virtual network using strong encryption.
+
+If you install Tinc on a router (and pick your numbers correctly) you can
+have the router forward all packets. This way you can---instead of
+connecting hosts---connect entire sites together! Now you need only one
+outgoing network connection for both internet and intranet.
+\f
+Architecture
+------------
+When a few Tinc daemons are running they will try to seek contact with
+eachother. A daemon is all the time connected to a few other daemons,
+but if traffic is required with a daemon it doesn't know yet, it will
+instantly contact it and exchange keys. These so-called meta-connections
+are made over TCP, using encryption of course.
+
+When actual traffic has to be sent, a daemon checks his connection list to
+see if the addressee is known (and makes contact with it if neccessary).
+All packets are then sent using UDP to the other host, just like in a real
+network. If a packet gets lost, the connection layer of Linux will resend
+the packet, just like it would over a normal network.
+
+Once in a while the daemons will renegotiate keys so that even if a cracker
+breaks one, it'll be of limited use.
+\f
+Getting Tinc
+------------
+Before you fetch the latest tarball, you might want to check if there's a
+package for your Linux distribution. One of the main authors is a Debian
+Developer, so you can expect the Debian packages to be very up to date.
+
+The official website for Tinc can be found at http://tinc.nl.linux.org/.
+There you can find Debian packages, RPM's and of course... the tarball!
+Since we run Doohickey Linux Pro 1.0, for which no package exists (or
+indeed the distribution itself) we shall compile the package ourselves.
+\f
+Building
+--------
+The Tinc source adheres to so many standards it makes you head spin.
+Even the debug messages have been localized! Amazing. Tinc also comes
+with a configuration script. If you like to see what is there to
+configure run ./configure --help | more. If you don't have time for such
+nonsense:
+
+ ./configure --sysconfdir=/etc
+
+This will see if your system is nice enough to run tinc on, and will
+create some Makefiles and other stuff which will together build tinc.
+
+ make
+ make install
+
+The first will do the actual build, the second copies all files into place.
+\f
+The kernel
+----------
+Next you will have to configure the kernel to support the tap device.
+It is important that you run a recent kernel, but anything after 2.2.16
+will do. You have to enable both the netlink device AND the ethertap
+device (in that order). Enable them as modules!
+Compile, install =) You don't even have to reboot.
+\f
+Picking your numbers
+--------------------
+The first thing we should do is pick network numbers. Tinc has a very
+peculiar taste for network numbers, which is caused by the way it routes
+traffic. However, it turns out to be really handy if you want to use
+your tinc host as a router for a site.
+
+The numbers have to be in a range that is not yet in use in your existing,
+real network! In this example we will use numbers from the 192.168.0/16
+range. This is standard CIDR notation for all IP addresses from 192.168.0.0
+to 192.168.255.255. The /16 means that the first 16 bits form the network
+part.
+
+It is common practice for Tinc networks to use private (RFC 1918) addresses.
+This is not necessary, but it would be a waste to use official addresses
+for a private network!
+
+In the example we will connect three machines: f00f, fdiv and hlt. We will
+give each an address, but not just that, also a slice of our address space
+to play with.
+
+ Host Real address Tinc network
+ ---------------------------------------------------
+ f00f 126.202.37.20 192.168.1.1/24
+ fdiv 126.202.37.81 192.168.2.1/24
+ hlt 103.22.1.218 192.168.3.1/24
+
+It is very important that none of the Tinc netmasks overlap! Note how the
+192.168.0/16 network covers the entire address space of the three hosts.
+We will refer to the 192.168.0/16 network as the `umbrella' from now on.
+As you can see we can fit 256 hosts into this umbrella this way, which is
+also the practical maximum for tinc. Let's name our VPN 'fubar'.
+\f
+The configuration file
+----------------------
+Let's create a configuration file for f00f. We have to put it in
+/etc/tinc/fubar because that's how we named our VPN.
+
+ MyOwnVPNIP = 192.168.1.1/24
+ VpnMask = 255.255.0.0
+ ConnectTo = 126.202.37.81
+ ConnectTo = 103.22.1.218
+ TapDevice = /dev/tap0
+
+The first two lines tell Tinc about the numbers we have chosen above.
+Using the ConnectTo lines, the daemon will seek contact with the rest of
+the umbrella. It's possible to configure any number of ConnectTo lines,
+you can even omit them so that it just sits and waits until someone else
+contacts it. Until someone does, the poor daemon won't be able to send
+any data because it doesn't know where everybody is.
+The TapDevice is where the tinc daemon will interface with the kernel.
+\f
+The passphrases
+---------------
+We will have to generate keys for ourselves, and get a key from everybody
+we want to ConnectTo. All of these go into a directory named
+/etc/tinc/fubar/passphrases. PROTECT THIS DIRECTORY!
+
+ mkdir -m 700 /etc/tinc/fubar/passphrases
+
+To generate our own key:
+
+ genauth 1024 >/etc/tinc/fubar/passphrases/local
+
+You should then proceed to give this key to anyone who wants to ConnectTo
+you. DO THIS IN A SECURE MANNER! Anyone who has this number can do icky
+things to the umbrella network! Encrypt it using PGP, GPG or another
+program using asymmetric keys. Read it over the phone (without anyone
+listening of course). Send it by snailmail. Write the key down and bring
+it to your partners personally!
+
+If you get any keys from your partners, store them under their network
+number. For example, the key we get from fdiv's network administrator
+will be stored in /etc/tinc/fubar/passphrases/192.168.2.0 (note the 0).
+\f
+Running the daemon
+------------------
+If you use a package manager to install Tinc, the startup scripts use a file
+called /etc/tinc/nets.boot to see which umbrella's exist. It has a line
+per VPN, and lines starting with a # are ignored. Ours will contain:
+
+ # Example VPN from the HOWTO
+ fubar
+
+In Debian, /etc/init.d/tinc start will start the daemons.
+
+If you use Doohickey Linux just like we do, you'll have to edit the systems
+startup scripts by hand. It should contain something along the lines of:
+
+ insmod ethertap -s --name=tap0 unit=0
+ ifconfig tap0 hw ether fe:fd:c0:a8:01:01
+ ifconfig tap0 192.168.1.1 netmask 255.255.0.0 broadcast 192.168.255.255 -arp
+
+There are two things to note here! First, the MAC address of the ethertap
+device is very important. It must start with fe:fd, and end in the
+hexadecimal representation of the VPN IP number.
+Second, the netmask of the tap device is set to that of the umbrella!
+
+--
+$Id: HOWTO,v 1.6 2002/04/12 08:25:01 guus Exp $
--- /dev/null
+This is the network infrastructure documentation for tinc, a Virtual Private
+Network daemon.
+
+ Copyright 2001-2002 Guus Sliepen <guus@sliepen.warande.net>
+
+ Permission is granted to make and distribute verbatim copies of
+ this documentation provided the copyright notice and this
+ permission notice are preserved on all copies.
+
+ Permission is granted to copy and distribute modified versions of
+ this documentation under the conditions for verbatim copying,
+ provided that the entire resulting derived work is distributed
+ under the terms of a permission notice identical to this one.
+
+ $Id: NETWORKING,v 1.2 2002/04/12 08:25:01 guus Exp $
+
+1. Packet flow
+==============
+
+There are two directions for packets. There are packets received from the tap
+device that have to be sent out to other tinc daemon, and there are packets
+that are received from other tinc daemons which have to be send to the tap
+device. The first direction will be called the outgoing direction, while the
+latter will be called the incoming direction.
+
+1.1 Outgoing flow
+-----------------
+
+ handle_tap_input()
+ |
+ |
+ V
+ route_outgoing()
+ |
+ |
+ V
+ send_packet() ----
+ / \ / \
+ / \ | queue
+ V V V /
+send_tcppacket() send_udppacket()--
+
+Packets are read from the tap device by handle_tap_input(). The packets will be
+marked as coming from ourself, and are then handled by route_outgoing(). This
+function will determine the destination tinc daemon this packet has to be sent
+to, and in the future it may also determine if this packet has to be broadcast
+or multicast. route_outgoing() will call send_packet() (in case of
+broad/multicast several times). send_packet() will check the destination
+connection_t entry to see if it is a valid destination, and whether it has to
+be sent via TCP or UDP. It will then either call send_tcppacket() or
+send_udppacket(). Since a different key is used for UDP packets, which might
+not be available at that time, send_udppacket() might put the packet in a queue
+and send a REQ_KEY to the destination tinc daemon. If the key has been retrieved,
+the packet will be fed to send_udppacket() again.
+
+1.2 Incoming flow
+-----------------
+
+ handle_vpn_input()
+ |
+ |
+ V
+tcppacket_h() receive_udppacket()
+ \ /
+ \ /
+ V V
+ receive_packet()
+ |
+ |
+ V
+ route_incoming()
+ |
+ |
+ V
+ accept_packet()
+
+Packets from other tinc daemons can be received by tcppacket_h(), for TCP
+packets, and receive_udppacket() via handle_vpn_input() for UDP packets.
+receive_packet() actually does not have to do much, except logging and calling
+route_incoming(), but it's there for symmetry with the scheme for the outgoing
+flow. route_incoming() will change the MAC header of the packet if necessary to
+let the kernel accept the packet after it has been sent to the tap device by
+accept_packet().
--- /dev/null
+This is the protocol documentation for tinc, a Virtual Private Network daemon.
+
+ Copyright 2000-2002 Guus Sliepen <guus@sliepen.warande.net>,
+ 2000-2002 Ivo Timmmermans <itimmermans@bigfoot.com>
+
+ Permission is granted to make and distribute verbatim copies of
+ this documentation provided the copyright notice and this
+ permission notice are preserved on all copies.
+
+ Permission is granted to copy and distribute modified versions of
+ this documentation under the conditions for verbatim copying,
+ provided that the entire resulting derived work is distributed
+ under the terms of a permission notice identical to this one.
+
+ $Id: PROTOCOL,v 1.2 2002/04/12 08:25:01 guus Exp $
+
+
+1. Protocols used in tinc
+-------------------------
+
+tinc uses several protocols to function correctly. To enter the
+network of tinc daemons that make up the virtual private network, tinc
+makes TCP connections to other tinc daemons. It uses the "meta
+protocol" for these connections. To exchange packets on the virtual
+network, UDP connections are made and the "packet protocol" is used.
+Tinc also needs to exchange network packets with the kernel. This is
+done using the ethertap device or the universal TUN/TAP device that
+can be found in various UNIX flavours.
+
+2. Packet protocol
+------------------
+
+Normal packets are sent without any state information, so the layout
+is pretty basic.
+
+A data packet can only be sent if the encryption key, cipher and digest are
+known to both parties, and the connection is activated. If the encryption key
+is not known, a request is sent to the destination using the meta connection to
+retreive it.
+
+0 1 2 3 4 5 6 7 ... 97 98 99 100
+| seqno | data | MAC |
+\____________________________________/\_______________/
+ | |
+ encrypted using symmetric cipher digest
+
+The sequence number prevents replay attacks, the message authentication code
+prevents altered packets from being accepted.
+
+3. Meta protocol
+----------------
+
+The meta protocol is used to tie all tinc daemons together, and
+exchange information about which tinc daemon serves which virtual
+subnet.
+
+The meta protocol consists of requests that can be sent to the other
+side. Each request has a unique number and several parameters. All
+requests are represented in the standard ASCII character set. It is
+possible to use tools such as telnet or netcat to connect to a tinc
+daemon and to read and write requests by hand, provided that one
+understands the numeric codes sent.
+
+The authentication scheme is described in the SECURITY2 file. After a
+succesful authentication, the server and the client will exchange all the
+information about other tinc daemons and subnets they know of, so that both
+sides (and all the other tinc daemons behind them) have their information
+synchronised.
+
+daemon message
+--------------------------------------------------------------------------
+origin ADD_EDGE node1 12.23.34.45 655 node2 21.32.43.54 655 222 0
+ | | | \___________________/ | +-> options
+ | | | | +----> weight
+ | | | +----------------> see below
+ | | +--> UDP port
+ | +----------> real address
+ +------------------> name of node on one side of the edge
+
+origin ADD_SUBNET node 192.168.1.0/24
+ | | +--> prefixlength
+ | +--------> IPv4 network address
+ +------------------> owner of this subnet
+--------------------------------------------------------------------------
+
+In case a connection between two daemons is closed or broken, DEL_EDGE messages
+are sent to inform the other daemons of that fact. Each daemon will calculate a
+new route to the the daemons, or mark them unreachable if there isn't any.
+
+The keys used to encrypt VPN packets are not sent out directly. This is
+because it would generate a lot of traffic on VPNs with many daemons, and
+chances are that not every tinc daemon will ever send a packet to every
+other daemon. Instead, if a daemon needs a key it sends a request for it
+via the meta connection of the nearest hop in the direction of the
+destination. If any hop on the way has already learned the key, it will
+act as a proxy and forward its copy back to the requestor.
+
+daemon message
+--------------------------------------------------------------------------
+daemon REQ_KEY origin destination
+ | +--> name of the tinc daemon it wants the key from
+ +----------> name of the daemon that wants the key
+
+daemon ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
+ | | \______________/ | | +--> MAC length
+ | | | | +-----> digest algorithm
+ | | | +--------> cipher algorithm
+ | | +--> 128 bits key
+ | +--> name of the daemon that wants the key
+ +----------> name of the daemon that uses this key
+
+daemon KEY_CHANGED origin
+ +--> daemon that has changed it's packet key
+--------------------------------------------------------------------------
+
+There is also a mechanism to check if hosts are still alive. Since network
+failures or a crash can cause a daemon to be killed without properly
+shutting down the TCP connection, this is necessary to keep an up to date
+connection list. Pings are sent at regular intervals, except when there
+is also some other traffic.
+
+daemon message
+--------------------------------------------------------------------------
+origin PING
+dest. PONG
+--------------------------------------------------------------------------
+
+This basically covers everything that is sent over the meta connection by
+tinc.
--- /dev/null
+This is the security documentation for tinc, a Virtual Private Network daemon.
+
+ Copyright 2001-2002 Guus Sliepen <guus@sliepen.warande.net>,
+ 2001-2002 Wessel Dankers <wsl@nl.linux.org>
+
+ Permission is granted to make and distribute verbatim copies of
+ this documentation provided the copyright notice and this
+ permission notice are preserved on all copies.
+
+ Permission is granted to copy and distribute modified versions of
+ this documentation under the conditions for verbatim copying,
+ provided that the entire resulting derived work is distributed
+ under the terms of a permission notice identical to this one.
+
+ $Id: SECURITY2,v 1.2 2002/04/12 08:25:01 guus Exp $
+
+Proposed new authentication scheme
+----------------------------------
+
+A new scheme for authentication in tinc has been devised, which offers some
+improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
+below.
+
+daemon message
+--------------------------------------------------------------------------
+client <attempts connection>
+
+server <accepts connection>
+
+client ID client 12
+ | +---> version
+ +-------> name of tinc daemon
+
+server ID server 12
+ | +---> version
+ +-------> name of tinc daemon
+
+client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
+ \_________________________________/
+ +-> RSAKEYLEN bits totally random string S1,
+ encrypted with server's public RSA key
+
+server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
+ \_________________________________/
+ +-> RSAKEYLEN bits totally random string S2,
+ encrypted with client's public RSA key
+
+From now on:
+ - the client will symmetrically encrypt outgoing traffic using S1
+ - the server will symmetrically encrypt outgoing traffic using S2
+
+client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
+ \_________________________________/
+ +-> CHALLEN bits totally random string H1
+
+server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
+ \_________________________________/
+ +-> CHALLEN bits totally random string H2
+
+client CHAL_REPLY 816a86
+ +-> 160 bits SHA1 of H2
+
+server CHAL_REPLY 928ffe
+ +-> 160 bits SHA1 of H1
+
+After the correct challenge replies are recieved, both ends have proved
+their identity. Further information is exchanged.
+
+client ACK 655 12.23.34.45 123 0
+ | | | +-> options
+ | | +----> estimated weight
+ | +------------> IP address of server as seen by client
+ +--------------------> UDP port of client
+
+server ACK 655 21.32.43.54 321 0
+ | | | +-> options
+ | | +----> estimated weight
+ | +------------> IP address of client as seen by server
+ +--------------------> UDP port of server
+--------------------------------------------------------------------------
+
+This new scheme has several improvements, both in efficiency and security.
+
+First of all, the server sends exactly the same kind of messages over the wire
+as the client. The previous versions of tinc first authenticated the client,
+and then the server. This scheme even allows both sides to send their messages
+simultaneously, there is no need to wait for the other to send something first.
+This means that any calculations that need to be done upon sending or receiving
+a message can also be done in parallel. This is especially important when doing
+RSA encryption/decryption. Given that these calculations are the main part of
+the CPU time spent for the authentication, speed is improved by a factor 2.
+
+Second, only one RSA encrypted message is sent instead of two. This reduces the
+amount of information attackers can see (and thus use for a crypto attack). It
+also improves speed by a factor two, making the total speedup a factor 4.
+
+Third, and most important:
+
+The symmetric cipher keys are exchanged first, the challenge is done
+afterwards. In the previous authentication scheme, because a man-in-the-middle
+could pass the challenge/chal_reply phase (by just copying the messages between
+the two real tinc daemons), but no information was exchanged that was really
+needed to read the rest of the messages, the challenge/chal_reply phase was of
+no real use. The man-in-the-middle was only stopped by the fact that only after
+the ACK messages were encrypted with the symmetric cipher. Potentially, it
+could even send it's own symmetric key to the server (if it knew the server's
+public key) and read some of the metadata the server would send it (it was
+impossible for the mitm to read actual network packets though). The new scheme
+however prevents this.
+
+This new scheme makes sure that first of all, symmetric keys are exchanged. The
+rest of the messages are then encrypted with the symmetric cipher. Then, each
+side can only read received messages if they have their private key. The
+challenge is there to let the other side know that the private key is really
+known, because a challenge reply can only be sent back if the challenge is
+decrypted correctly, and that can only be done with knowledge of the private
+key.
+
+Fourth: the first thing that is send via the symmetric cipher encrypted
+connection is a totally random string, so that there is no known plaintext (for
+an attacker) in the beginning of the encrypted stream.
+
+Some things to be discussed:
+
+ - What should CHALLEN be? Same as RSAKEYLEN? 256 bits? More/less?
projects / meshlink / commitdiff