\input texinfo @c -*-texinfo-*- @c $Id: tinc.texi,v 1.8.4.11 2001/01/06 20:02:21 guus Exp $ @c %**start of header @setfilename tinc.info @settitle tinc Manual @setchapternewpage odd @c %**end of header @ifinfo @direntry * tinc: (tinc). The tinc Manual. @end direntry This is the info manual for tinc, a Virtual Private Network daemon. Copyright @copyright{} 1998,199,2000 Ivo Timmermans , Guus Sliepen and Wessel Dankers . $Id: tinc.texi,v 1.8.4.11 2001/01/06 20:02:21 guus Exp $ Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual 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. @end ifinfo @titlepage @title tinc Manual @subtitle Setting up a Virtual Private Network with tinc @author Ivo Timmermans and Guus Sliepen @page @vskip 0pt plus 1filll @cindex copyright Copyright @copyright{} 1998,1999,2000 Ivo Timmermans , Guus Sliepen and Wessel Dankers . $Id: tinc.texi,v 1.8.4.11 2001/01/06 20:02:21 guus Exp $ Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual 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. @end titlepage @c ================================================================== @node Top, Introduction, (dir), (dir) @menu * Introduction:: Introduction * Installing tinc - preparations:: * Installing tinc - installation:: * Configuring tinc:: * Running tinc:: * Technical information:: * About us:: * Concept Index:: All used terms explained @end menu @contents @c ================================================================== @node Introduction, Installing tinc - preparations, Top, Top @chapter Introduction @cindex tinc tinc is a Virtual Private Network (VPN) daemon that uses tunneling and encryption to create a secure private network between hosts on the Internet. Because the tunnel appears to the IP level network code as a normal network device, there is no need to adapt any existing software. This tunneling allows VPN sites to share information with each other over the Internet without exposing any information to others. This document is the manual for tinc. Included are chapters on how to configure your computer to use tinc, as well as the configuration process of tinc itself. @menu * VPNs:: Virtual Private Networks in general * tinc:: about tinc * Supported platforms:: @end menu @c ================================================================== @node VPNs, tinc, Introduction, Introduction @section Virtual Private Networks @cindex VPN A Virtual Private Network or VPN is a network that can only be accessed by a few elected computers that participate. This goal is achievable in more than just one way. @cindex private Private networks can consist of a single stand-alone ethernet LAN. Or even two computers hooked up using a null-modem cable. In these cases, it is obvious that the network is @emph{private}, no one can access it from the outside. But if your computers are linked to the internet, the network is not private anymore, unless one uses firewalls to block all private traffic. But then, there is no way to send private data to trusted computers on the other end of the internet. @cindex virtual This problem can be solved by using @emph{virtual} networks. Virtual networks can live on top of other networks, but they use encapsulation to keep using their private address space so they do not interfere with each other. Mostly, virtual networks appear like a singe LAN, even though they can span the entire world. But virtual networks can't be secured by using firewalls, because the traffic that flows through it has to go through the internet, where other people can look at it. When one introduces encryption, we can form a true VPN. Other people may see encrypted traffic, but if they don't know how to decipher it (they need to know the key for that), they cannot read the information that flows through the VPN. This is what tinc was made for. @cindex virtual tinc uses normal IP datagrams to encapsulate data that goes over the VPN network link. In this case it's also clear that the network is @emph{virtual}, because no direct network link has to exist between to participants. As is the case with either type of VPN, anybody could eavesdrop. Or worse, alter data. Hence it's probably advisable to encrypt the data that flows over the network. @c ================================================================== @node tinc, Supported platforms, VPNs, Introduction @section tinc @cindex vpnd @cindex ethertap I really don't quite remember what got us started, but it must have been Guus' idea. He wrote a simple implementation (about 50 lines of C) that used the @emph{ethertap} device that Linux knows of since somewhere about kernel 2.1.60. It didn't work immediately and he improved it a bit. At this stage, the project was still simply called @samp{vpnd}. Since then, a lot has changed---to say the least. @cindex tincd tinc now supports encryption, it consists of a single daemon (tincd) for both the receiving and sending end, it has become largely runtime-configurable---in short, it has become a full-fledged professional package. A lot can---and will be---changed. We have a number of things that we would like to see in the future releases of tinc. Not everything will be available in the near future. Our first objective is to make tinc work perfectly as it stands, and then add more advanced features. Meanwhile, we're always open-minded towards new ideas. And we're available too. @c ================================================================== @node Supported platforms, , tinc, Introduction @section Supported platforms tinc has been verified to work under Linux, FreeBSD and Solaris, with various hardware architectures. These are the three platforms that are supported by the universial TUN/TAP device driver, so if support for other operating systems is added to this driver, perhaps tinc will run on them as well. Without this driver, tinc will most likely compile and run, but it will not be able to send or receive data packets. For an up to date list of supported platforms, please check the list on our website: @uref{http://tinc.nl.linux.org/platforms.html}. @c ================================================================== @subsection Linux tinc was first written for Linux running on an intel x86 processor, so this is the best supported platform. The protocol however, and actually anything about tinc, has been rewritten to support random byte ordering and arbitrary word length. So in theory it should run on other processors that Linux runs on. It has already been verified to run on alpha and sparc processors as well. tinc uses the ethertap device that is provided in the standard kernel since version 2.1.60, so anything above that (2.2.x, 2.3.x, and 2.4.0) kernel version is able to support tinc. @c ================================================================== @subsection FreeBSD tinc on FreeBSD relies on the universial TUN/TAP driver for its data acquisition from the kernel. Therefore, tinc suports the same platforms as this driver. These are: FreeBSD 3.x, 4.x, 5.x. @c ================================================================== @subsection Solaris tinc on Solaris relies on the universial TUN/TAP driver for its data acquisition from the kernel. Therefore, tinc suports the same platforms as this driver. These are: Solaris, 2.1.x. @c @c @c @c @c @c @c Preparing your system @c @c @c @c @c @c ================================================================== @node Installing tinc - preparations, Installing tinc - installation, Introduction, Top @chapter Installing tinc: preparations This chapter contains information on how to prepare your system to support tinc. @menu * Configuring the kernel:: * Libraries:: @end menu @c ================================================================== @node Configuring the kernel, Libraries, Installing tinc - preparations, Installing tinc - preparations @section Configuring the kernel If you are running Linux, chances are good that your kernel already supports all the devices that tinc needs for proper operation. For example, the standard kernel from Redhat Linux already has support for ethertap and netlink compiled in. Debian users can use the modconf utility to select the modules. If your Linux distribution supports this method of selecting devices, look out for something called `ethertap', and `netlink_dev'. You need both these devices. If you can install these devices in a similar manner, you may skip this section. @menu * Configuration of the Linux kernel:: * Configuration of the FreeBSD kernel:: * Configuration of the Solaris kernel:: @end menu @c ================================================================== @node Configuration of the Linux kernel, Configuration of the FreeBSD kernel, Configuring the kernel, Configuring the kernel @subsection Configuring the Linux kernel Since this particular implementation only runs on 2.1 or higher Linux kernels, you should grab one (2.2 is current at this time). A 2.0 port is not really possible, unless someone tells me someone ported the ethertap and netlink devices back to 2.0. If you are unfamiliar with the process of configuring and compiling a new kernel, you should read the @uref{http://howto.linuxberg.com/LDP/HOWTO/Kernel-HOWTO.html, Kernel HOWTO} first. Do that now! Here are the options you have to turn on when configuring a new kernel. For kernel 2.2.x: @example Code maturity level options [*] Prompt for development and/or incomplete code/drivers Networking options [*] Kernel/User netlink socket <*> Netlink device emulation Network device support <*> Ethertap network tap @end example Note that if you want to run more than one instance of tinc or other programs that use the ethertap, you have to compile the ethertap driver as a module. For kernel 2.3.x and 2.4.x: @example Code maturity level options [*] Prompt for development and/or incomplete code/drivers Networking options [*] Kernel/User netlink socket <*> Netlink device emulation Network device support <*> Universal TUN/TAP device driver support @end example Any other options not mentioned here are not relevant to tinc. If you decide to build any of these as dynamic kernel modules, it's a good idea to add these lines to @file{/etc/modules.conf}. @example alias tap0 ethertap alias char-major-36 netlink_dev @end example If you have a 2.4-pre kernel, you can choose both the TUN/TAP driver and the `Ethertap network tap' device. This latter is marked obsolete, because the universal TUN/TAP driver is a newer implementation that is supposed to be used in favour of ethertap. For tinc, it doesn't really matter which one you choose; based on the device file name, tinc will make the right choice about what protocol to use. However, chances are that although you can choose the obsolote ethertap driver, it will not function at all. The TUN/TAP driver is the safe choice. Finally, after having set up other options, build the kernel and boot it. Unfortunately it's not possible to insert these modules in a running kernel. @c ================================================================== @node Configuration of the FreeBSD kernel, Configuration of the Solaris kernel, Configuration of the Linux kernel, Configuring the kernel @subsection Configuring the FreeBSD kernel This section will contain information on how to configure your FreeBSD kernel to support the universal TUN/TAP device. For 5.0 and 4.1 systems, this is included in the kernel configuration, for earlier systems (4.0 and 3.x), you need to install the universal TUN/TAP driver yourself. Unfortunately somebody still has to write the text. @c ================================================================== @node Configuration of the Solaris kernel, , Configuration of the FreeBSD kernel, Configuring the kernel @subsection Configuring the Solaris kernel This section will contain information on how to configure your Solaris kernel to support the universal TUN/TAP device. You need to install this driver yourself. Unfortunately somebody still has to write the text. @c ================================================================== @node Libraries, , Configuring the kernel, Installing tinc - preparations @section Libraries @cindex requirements Before you can configure or build tinc, you need to have the OpenSSL library installed on your system. If you try to configure tinc without having installed it, configure will give you an error message, and stop. @menu * OpenSSL:: @end menu @c ================================================================== @node OpenSSL, , Libraries, Libraries @subsection OpenSSL @cindex OpenSSL For all cryptography-related functions, tinc uses the functions provided by the OpenSSL library. We recommend using version 0.9.5 or 0.9.6 of this library. Other versions may also work, but we can guarantee nothing. If this library is not installed, you wil get an error when configuring tinc for build. Support for running tinc without having OpenSSL installed @emph{may} be added in the future. You can use your operating system's package manager to install this if available. Make sure you install the development AND runtime versions of this package. If you have to install OpenSSL manually, you can get the source code from @url{http://www.openssl.org/}. Instructions on how to configure, build and install this package are included within the package. Please make sure you build development and runtime libraries (which is the default). If you installed the OpenSSL libraries from source, it may be necessary to let configure know where they are, by passing configure one of the --with-openssl-* parameters. @example --with-openssl=DIR OpenSSL library and headers prefix --with-openssl-include=DIR OpenSSL headers directory (Default is OPENSSL_DIR/include) --with-openssl-lib=DIR OpenSSL library directory (Default is OPENSSL_DIR/lib) @end example @subsubheading License Since the license under which OpenSSL is distributed is not directly compatible with the terms of the GNU GPL @uref{http://www.openssl.org/support/faq.html#LEGAL2}, therefore we include an addition to the GPL (see also the file COPYING.README): @quotation This program is released under the GPL with the additional exemption that compiling, linking, and/or using OpenSSL is allowed. You may provide binary packages linked to the OpenSSL libraries, provided that all other requirements of the GPL are met. @end quotation @c @c @c @c Installing tinc @c @c @c @c @c ================================================================== @node Installing tinc - installation, Configuring tinc, Installing tinc - preparations, Top @chapter Installing tinc: installation If you use Redhat or Debian, you may want to install one of the precompiled packages for your system. These packages are equipped with system startup scripts and sample configurations. If you don't run either of these systems, or you want to compile tinc for yourself, you can use the source. The source is distributed under the GNU General Public License (GPL). Download the source from the @uref{http://tinc.nl.linux.org/download.html, download page}, which has the checksums of these files listed; you may wish to check these with md5sum before continuing. tinc comes in a convenient autoconf/automake package, which you can just treat the same as any other package. Which is just untar it, type `configure' and then `make'. More detailed instructions are in the file @file{INSTALL}, which is included in the source distribution. @menu * Building tinc:: * System files:: * Interfaces:: @end menu @c ================================================================== @node Building tinc, System files, Installing tinc - installation, Installing tinc - installation @section Building tinc Detailed instructions on configuring the source and building tinc can be found in the file called @file{INSTALL}. @c ================================================================== @node System files, Interfaces, Building tinc, Installing tinc - installation @section System files Before you can run tinc, you must make sure you have all the needed files on your system. @menu * Device files:: * Other files:: @end menu @c ================================================================== @node Device files, Other files, System files, System files @subsection Device files First, you'll need the special device file(s) that form the interface between the kernel and the daemon. The permissions for these files have to be such that only the super user may read/write to this file. You'd want this, because otherwise eavesdropping would become a bit too easy. This does, however, imply that you'd have to run tincd as root. If you use the universal TUN/TAP driver, you have to create the following device files (unless they already exist): @example mknod -m 600 /dev/... c .. .. chown 0.0 /dev/... @end example If you want to have more devices, the device numbers will be .. .. ... If you use Linux, and you run the new 2.4 kernel using the devfs filesystem, then the tap device will be automatically generated as @file{/dev/netlink/tap0}. If you use Linux and have kernel 2.2.x, you have to make the ethertap devices: @example mknod -m 600 /dev/tap0 c 36 16 chown 0.0 /dev/tap0 @end example Any further ethertap devices have minor device number 16 through 31. @c ================================================================== @node Other files, , Device files, System files @subsection Other files @subsubheading @file{/etc/networks} You may add a line to @file{/etc/networks} so that your VPN will get a symbolic name. For example: @example myvpn 10.0.0.0 @end example This has nothing to do with the MyVPNIP configuration variable that will be discussed later, it is only to make the output of the route command more legible. @subsubheading @file{/etc/services} You may add this line to @file{/etc/services}. The effect is that you may supply a @samp{tinc} as a valid port number to some programs. The number 655 is registered with the IANA. @example tinc 655/tcp TINC tinc 655/udp TINC # Ivo Timmermans @end example @c ================================================================== @node Interfaces, , System files, Installing tinc - installation @section Interfaces Before you can start transmitting data over the tinc tunnel, you must set up the ethertap network devices. First, decide which IP addresses you want to have associated with these devices, and what network mask they must have. You also need these numbers when you are going to configure tinc itself. @xref{Configuring tinc}. It doesn't matter much which part you do first, setting up the network devices or configure tinc. But they both have to be done before you try to start a tincd. The actual setup of the ethertap device is quite simple, just repeat after me: @example ifconfig tap@emph{n} hw ether fe:fd:00:00:00:00 @end example @cindex MAC address @cindex hardware address @strong{Note:} Since version 1.0pre3, all interface addresses are set to this address, whereas previous versions required the MAC to match the actual IP address. @cindex ifconfig To activate the device, you have to assign an IP address to it. To set an IP address @emph{IP} with network mask @emph{mask}, do the following: @example ifconfig tap@emph{n} @emph{xx}.@emph{xx}.@emph{xx}.@emph{xx} netmask @emph{mask} @end example @cindex netmask The netmask is the mask of the @emph{entire} VPN network, not just your own subnet. It is the same netmask you will have to specify with the VpnMask configuration variable. @c @c @c @c @c Configuring tinc @c @c @c @c @c ================================================================== @node Configuring tinc, Running tinc, Installing tinc - installation, Top @chapter Configuring tinc @menu * Multiple networks:: * How connections work:: * Configuration file:: * Example:: @end menu @c ================================================================== @node Multiple networks, How connections work, Configuring tinc, Configuring tinc @section Multiple networks @c from the manpage It is perfectly OK for you to run more than one tinc daemon. However, in its default form, you will soon notice that you can't use two different configuration files without the -c option. We have thought of another way of dealing with this: network names. This means that you call tincd with the -n argument, which will assign a name to this daemon. The effect of this is that the daemon will set its configuration ``root'' to /etc/tinc/nn/, where nn is your argument to the -n option. You'll notice that it appears in syslog as ``tinc.nn''. However, it is not strictly necessary that you call tinc with the -n option. In this case, the network name would just be empty, and it will be used as such. tinc now looks for files in /etc/tinc/, instead of /etc/tinc/nn/; the configuration file should be /etc/tinc/tinc.conf, and the passphrases are now expected to be in /etc/tinc/passphrases/. But it is highly recommended that you use this feature of tinc, because it will be so much clearer whom your daemon talks to. Hence, we will assume that you use it. @c ================================================================== @node How connections work, Configuration file, Multiple networks, Configuring tinc @section How connections work Before going on, first a bit on how tinc sees connections. When tinc starts up, it reads in the configuration file and parses the command-line options. If it sees a `ConnectTo' value in the file, it will try to connect to it, on the given port. If this fails, tinc exits. @c ================================================================== @node Configuration file, Example, How connections work, Configuring tinc @section Configuration file The actual configuration of the daemon is done in the file @file{/etc/tinc/nn/tinc.conf}. This file consists of comments (lines started with a #) or assignments in the form of @example Variable = Value. @end example The variable names are case insensitive, and any spaces, tabs, newlines and carriage returns are ignored. Note: it is not required that you put in the `=' sign, but doing so improves readability. If you leave it out, remember to replace it with at least one space character. In this section all valid variables are listed in alphabetical order. The default value is given between parentheses; required directives are given in @strong{bold}. @menu * Main configuration variables:: * Host configuration variables:: * How to configure:: @end menu @c ================================================================== @node Main configuration variables, Host configuration variables, Configuration file, Configuration file @subsection Main configuration variables @table @asis @item @strong{ConnectTo = } Specifies which host to connect to on startup. Multiple ConnectTo variables may be specified, if connecting to the first one fails then tinc will try the next one, and so on. It is possible to specify hostnames for dynamic IP addresses (like those given on dyndns.org), tinc will not cache the resolved IP address. If you don't specify a host with ConnectTo, regardless of whether a value for ConnectPort is given, tinc won't connect at all, and will instead just listen for incoming connections. @item Hostnames = (no) This option selects whether IP addresses (both real and on the VPN) should be resolved. Since DNS lookups are blocking, it might affect tinc's efficiency, even stopping the daemon for a few seconds everytime it does a lookup if your DNS server is not responding. This does not affect resolving hostnames to IP addresses from the configuration file. @item Interface = If you have more than one network interface in your computer, tinc will by default listen on all of them for incoming connections. It is possible to bind tinc to a single interface like eth0 or ppp0 with this variable. @item InterfaceIP = If your computer has more than one IP address on a single interface (for example if you are running virtual hosts), tinc will by default listen on all of them for incoming connections. It is possible to bind tinc to a single IP address with this variable. It is still possible to listen on several interfaces at the same time though, if they share the same IP address. @item KeyExpire = (3600) This option controls the time the encryption keys used to encrypt the data are valid. It is common practice to change keys at regular intervals to make it even harder for crackers, even though it is thought to be nearly impossible to crack a single key. @item @strong{Name = } This is a symbolic name for this connection. It can be anything @item PingTimeout = (5) The number of seconds of inactivity that tinc will wait before sending a probe to the other end. If that other end doesn't answer within that same amount of seconds, the connection is terminated, and the others will be notified of this. @item PrivateKey = This is the RSA private key for tinc. However, for safety reasons it is advised to store private keys of any kind in separate files. This prevents accidental eavesdropping if you are editting the configuration file. @item PrivateKeyFile = This is the full path name of the RSA private key file that was generated by ``tincd --generate-keys''. It must be a full path, not a relative directory. Note that exactly @strong{one of the above two options} must be specified. @item TapDevice = (/dev/tap0) The ethertap device to use. Note that you can only use one device per daemon. The info pages of the tinc package contain more information about configuring an ethertap device for Linux. @item VpnMask = The mask that defines the scope of the entire VPN. This option is not used by the tinc daemon itself, but can be used by startup scripts to configure the ethertap devices correctly. @end table @c ================================================================== @node Host configuration variables, How to configure, Main configuration variables, Configuration file @subsection Host configuration variables @table @asis @item @strong{Address = } This variable is only required if you want to connect to this host. It must resolve to the external IP address where the host can be reached, not the one that is internal to the VPN. @item IndirectData = (no) This option specifies whether other tinc daemons besides the one you specified with ConnectTo can make a direct connection to you. This is especially useful if you are behind a firewall and it is impossible to make a connection from the outside to your tinc daemon. Otherwise, it is best to leave this option out or set it to no. @item Port = (655) Connect to the upstream host (given with the ConnectTo directive) on port port. port may be given in decimal (default), octal (when preceded by a single zero) o hexadecimal (prefixed with 0x). port is the port number for both the UDP and the TCP (meta) connections. @item PublicKey = This is the RSA public key for this host. @item PublicKeyFile = This is the full path name of the RSA public key file that was generated by ``tincd --generate-keys''. It must be a full path, not a relative directory. Note that exactly @strong{one of the above two options} must be specified in each host configuration file, if you want to be able to establish a connection with that host. @item Subnet = This is the subnet range of all IP addresses that will be accepted by the host that defines it. The range must be contained in the IP address range of the tap device, not the real IP address of the host running tincd. maskbits is the number of bits set to 1 in the netmask part; for example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes /22. This conforms to standard CIDR notation as described in @uref{ftp://ftp.isi.edu/in-notes/rfc1519.txt, RFC1519} @item TCPonly = (no) If this variable is set to yes, then the packets are tunnelled over a TCP connection instead of a UDP connection. This is especially useful for those who want to run a tinc daemon from behind a masquerading firewall, or if UDP packet routing is disabled somehow. @emph{This is experimental code, try this at your own risk. It may not work at all.} @end table @c ================================================================== @node How to configure, , Host configuration variables, Configuration file @subsection How to configure @subsubheading Step 1. Creating the key files For each host, you have to create a pair of RSA keys. One key is your private key, which is only known to you. The other one is the public key, which you should copy to all hosts wanting to authenticate to you. @subsubheading Step 2. Configuring each host For every host in the VPN, you have to create two files. First there is the main configuration file, @file{/etc/tinc/vpn-name/tinc.conf}. In this file there should at least be three directives: @table @samp @item Name You should fill in the name of this host (or rather, the name of this leaf of the VPN). It can be called after the hostname, the physical location, the department, or the name of one of your boss' pets. It can be anything, as long as all these names are unique across the entire VPN. @item PrivateKey Fill in the full pathname to the file that contains the private RSA key. @item ConnectTo This is the name of the host that you want to connect to (not a DNS name, rather the name that is given with the Name parameter in that hosts tinc.conf). This is the upstream connection. If your computer is a central node, you might want to leave this out to make it stay idle until someone connects to it. @end table @cindex host configuration file Then you should create a file with the name you gave yourself in tinc.conf (the `Name' parameter), located in @file{/etc/tinc/vpn-name/hosts/}. In this file, which we call the `@emph{host configuration file}', only one variable is required: @table @samp @item Subnet The IP range that this host accepts as being `local'. All packets with a destination address that is within this subnet will be sent to us. @end table @subsubheading Step 3. Bringing it all together Now for all hosts that you want to create a direct connection to, -- you connect to them or they connect to you -- you get a copy of their host configuration file and their public RSA key. For each host configuration file, you add two variables: @table @samp @item Address Enter the IP address or DNS hostname for this host. This is only needed if you connect to this host. @item PublicKey Put the full pathname to this hosts public RSA key here. @end table When you did this, you should be ready to create your first connection. Pay attention to the system log, most errors will only be visible there. If you get an error, you can check @ref{Error messages}. @c ================================================================== @node Example, , Configuration file, Configuring tinc @section Example @cindex example Imagine the following situation. An A-based company wants to connect three branch offices in B, C and D using the internet. All four offices have a 24/7 connection to the internet. A is going to serve as the center of the network. B and C will connect to A, and D will connect to C. Each office will be assigned their own IP network, 10.x.0.0. @example A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7 @end example ``gateway'' is the VPN IP address of the machine that is running the tincd. ``internet IP'' is the IP address of the firewall, which does not need to run tincd, but it must do a port forwarding of TCP&UDP on port 655 (unless otherwise configured). In this example, it is assumed that eth0 is the interface that points to the inner (physical) LAN of the office, although this could also be the same as the interface that leads to the internet. The configuration of the real interface is also shown as a comment, to give you an idea of how these example host is set up. @subsubheading For A @emph{A} would be configured like this: @example #ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255 ifconfig tap0 hw ether fe:fd:00:00:00:00 ifconfig tap0 10.1.54.1 netmask 255.0.0.0 @end example and in /etc/tinc/tinc.conf: @example Name = A PrivateKey = /etc/tinc/A.priv VpnMask = 255.0.0.0 @end example On all hosts, /etc/tinc/hosts/A contains: @example Subnet = 10.1.0.0/16 Address = 1.2.3.4 PublicKey = /etc/tinc/hosts/A.pub @end example @subsubheading For B @example #ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255 ifconfig tap0 hw ether fe:fd:00:00:00:00 ifconfig tap0 10.2.1.12 netmask 255.0.0.0 @end example and in /etc/tinc/tinc.conf: @example Name = B ConnectTo = A PrivateKey = /etc/tinc/B.priv VpnMask = 255.0.0.0 @end example Note here that the internal address (on eth0) doesn't have to be the same as on the tap0 device. Also, ConnectTo is given so that no-one can connect to this node. On all hosts, /etc/tinc/hosts/B: @example Subnet = 10.2.0.0/16 Address = 2.3.4.5 PublicKey = /etc/tinc/hosts/B.pub @end example @subsubheading For C @example #ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255 ifconfig tap0 hw ether fe:fd:00:00:00:00 ifconfig tap0 10.3.69.254 netmask 255.0.0.0 @end example and in /etc/tinc/A/tinc.conf: @example Name = C ConnectTo = A TapDevice = /dev/tap1 VpnMask = 255.0.0.0 @end example C already has another daemon that runs on port 655, so they have to reserve another port for tinc. It can connect to other tinc daemons on the regular port though, so no ConnectPort variable is needed. They also use the netname to distinguish between the two. tinc is started with `tincd -n A'. On all hosts, /etc/tinc/hosts/C: @example Subnet = 10.3.0.0/16 Port = 2000 PublicKey = /etc/tinc/hosts/C.pub @end example @subsubheading For D @example #ifconfig tap0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255 ifconfig tap0 hw ether fe:fd:0a:04:03:20 ifconfig tap0 10.4.3.32 netmask 255.0.0.0 @end example and in /etc/tinc/tinc.conf: @example MyVirtualIP = 10.4.3.32/16 ConnectTo = 3.4.5.6 ConnectPort = 2000 VpnMask=255.0.0.0 @end example D will be connecting to C, which has a tincd running for this network on port 2000. Hence they need to put in a ConnectPort, but it doesn't need to have a different ListenPort. @subsubheading Key files A, B, C and D all have generate a public key with tincd -K, the output is stored in /etc/tinc/hosts/X.pub (where X is A, B or D), except for C, who stored it in /etc/tinc/A/hosts/C.pub. A stores a copy of B's public key in /etc/tinc/hosts/B.pub A stores a copy of C's public key in /etc/tinc/hosts/C.pub B stores a copy of A's public key in /etc/tinc/hosts/A.pub C stores a copy of A's public key in /etc/tinc/A/hosts/A.pub C stores a copy of D's public key in /etc/tinc/A/hosts/D.pub D stores a copy of C's public key in /etc/tinc/hosts/C.pub @subsubheading Starting A has to start their tincd first. Then come B and C, where C has to provide the option `-n A', because they have more than one tinc network. Finally, D's tincd is started. @c ================================================================== @node Running tinc, Technical information, Configuring tinc, Top @chapter Running tinc Running tinc isn't just as easy as typing `tincd' and hoping everything will just work out the way you wanted. Instead, the use of tinc is a project that involves trust relations and more than one computer. @menu * Managing keys:: * Runtime options:: * Error messages:: @end menu @c ================================================================== @node Managing keys, Runtime options, Running tinc, Running tinc @section Managing keys Before attempting to start tinc, you have to create public/private keypairs. When tinc tries to make a connection, it exchanges some sensitive data. Before doing so, it likes to know if the other end is trustworthy. To do this, both ends must have some knowledge about the other. In the case of tinc this is the public keys. To generate a public/private keypair, run `tincd -n vpn-name -K'. is optional, you can use it to specify the length of the keys. The length of the public/private keypairs should be at least 1024 for reasonable security (reasonable being good enough to keep the NSA busy for a few weeks). Every computer that wants to participate in the VPN should do this. The public keyfile should get the name of each tinc daemon and an extension .pub, and it should be stored in the hosts directory. When every computer has his own keys and configuration files, the files in the hosts directory should be exchanged with each other computer that it wants to talk to directly. Since only public keys are involved, you can safely do this via email, telnet or ftp, or even putting the contents on a public billboard. @c ================================================================== @node Runtime options, Error messages, Managing keys, Running tinc @section Runtime options Besides the settings in the configuration file, tinc also accepts some command line options. This list is a longer version of that in the manpage. The latter is generated automatically, so may be more up-to-date. @cindex command line @cindex runtime options @cindex options @c from the manpage @table @samp @item -c, --config=PATH Read configuration options from the directory PATH. The default is @file{/etc/tinc/nn/}. @item -d Increase debug level. The higher it gets, the more gets logged. Everything goes via syslog. 0 is the default, only some basic information connection attempts get logged. Setting it to 1 will log a bit more, still not very disturbing. With two -d's tincd will log protocol information, which can get pretty noisy. Three or more -d's will output every single packet that goes out or comes in, which probably generates more data than the packets themselves. @item -k, --kill Attempt to kill a running tincd and exit. A TERM signal (15) gets sent to the daemon that his its PID in /var/run/tinc.pid. Because it kills only one tinc daemon, you should use -n here if you started it that way. It will then read the PID from @file{/var/run/tinc.NETNAME.pid}. @item -n, --net=NETNAME Connect to net NETNAME. @xref{Multiple networks}. @item -K, --generate-keys[=BITS] Generate public/private keypair of BITS length. If BITS is not specified, 1024 is the default. tinc will ask where you want to store the files, but will default to the configuration directory (you can use the -c or -n option in combination with -K). After that, tinc will quit. @item --help Display a short reminder of these runtime options and terminate. @item --version Output version information and exit. @end table @c ================================================================== @node Error messages, , Runtime options, Running tinc @section Error messages What follows is a list of the most common error messages you can see when configuring tinc. Most of these messages are visible in the syslog only, so keep an eye on it! @table @strong @item Could not open /dev/tap0: No such device @table @bullet @item You forgot to insmod netlink_dev.o @item You forgot to compile `Netlink device emulation' in the kernel @end table @item Can't write to tun/tap device: No such device @table @bullet @item You forgot to insmod tun.o @item You forgot to compile `Universal TUN/TAP driver' in the kernel @end table @item Packet with destination 1.2.3.4 is looping back to us! @table @bullet @item Something is not configured right. Packets are being sent out to the tap device, but according to the Subnet directives in your host configuration file, those packets should go to your own host. Most common mistake is that you have a Subnet line in your host configuration file with a netmask which is just as large as the netmask of the tap device. The latter should in almost all cases be larger. Rethink your configuration. Note that you will only see this message if you specified a debug level of 5 or higher! @end table @item Network address and subnet mask do not match! @table @bullet @item The Subnet field must contain a network address. That means that the lower order bits of the address must be zero. For example, 192.168.1.1/24 is wrong, you should use 192.168.1.0/24. @item If you only want to use one IP address, set the netmask to /32. @end table @item This is a bug: net.c:253: 24: Some error @table @bullet @item This is something that should not have happened Please report this, and tell us exactly what went wrong before you got this message. In normal operation, these errors should not occur. @end table @item Error reading RSA key file `rsa_key.priv': No such file or directory @table @bullet @item You must specify the complete pathname Specifying a relative path does not make sense here. tinc changes its directory to / when starting (to avoid keeping a mount point busy); and even if we built in a default directory to look for these files, the key files are bound to be in a different directory. @end table @end table @c ================================================================== @node Technical information, About us, Running tinc, Top @chapter Technical information @menu * The Connection:: * Security:: @end menu @c ================================================================== @node The Connection, Security, Technical information, Technical information @section The basic philosophy of the way tinc works @cindex connection tinc is a daemon that takes VPN data and transmit that to another host computer over the existing Internet infrastructure. @menu * Protocol Preview:: * The Meta-connection:: @end menu @c ================================================================== @node Protocol Preview, The Meta-connection, The Connection, The Connection @subsection A preview of the way the tinc works @cindex ethertap @cindex frame type The data itself is read from a character device file, the so-called @emph{ethertap} device. This device is associated with a network interface. Any data sent to this interface can be read from the device, and any data written to the device gets sent from the interface. Data to and from the device is formatted as if it were a normal ethernet card, so a frame is preceded by two MAC addresses and a @emph{frame type} field. So when tinc reads an ethernet frame from the device, it determines its type. Right now, tinc can only handle Internet Protocol version 4 (IPv4) frames, because it needs IP headers for routing. Plans to support other protocols and switching instead of routing are being made. When tinc knows which type of frame it has read, it can also read the source and destination address from it. Now it is time that the frame gets encrypted. Currently the only encryption algorithm available is blowfish. @cindex encapsulating When the encryption is ready, time has come to actually transport the packet to the destination computer. We do this by sending the packet over an UDP connection to the destination host. This is called @emph{encapsulating}, the VPN packet (though now encrypted) is encapsulated in another IP datagram. When the destination receives this packet, the same thing happens, only in reverse. So it does a decrypt on the contents of the UDP datagram, and it writes the decrypted information to its own ethertap device. To let the kernel on the receiving end accept the packet, the destination MAC address must match that of the tap interface. Because of the routing nature of tinc, ARP is not possible. tinc solves this by always overwriting the destination MAC address with fe:fd:0:0:0:0. That is also the reason why you must set the MAC address of your tap interface to that address. @c ================================================================== @node The Meta-connection, , Protocol Preview, The Connection @subsection The meta-connection Having only an UDP connection available is not enough. Though suitable for transmitting data, we want to be able to reliably send other information, such as routing and encryption information to somebody. TCP is a better alternative, because it already contains protection against information being lost, unlike UDP. So we establish two connections. One for the encrypted VPN data, and one for other information, the meta-data. Hence, we call the second connection the meta-connection. We can now be sure that the meta-information doesn't get lost on the way to another computer. @cindex data-protocol @cindex meta-protocol Like with any communication, we must have a protocol, so that everybody knows what everything stands for, and how she should react. Because we have two connections, we also have two protocols. The protocol used for the UDP data is the ``data-protocol,'' the other one is the ``meta-protocol.'' The reason we don't use TCP for both protocols is that UDP is much better for encapsulation, even while it is less reliable. The real problem is that when TCP would be used to encapsulate a TCP stream that's on the private network, for every packet sent there would be three ACK's sent instead of just one. Furthermore, if there would be a timeout, both TCP streams would sense the timeout, and both would start resending packets. @c ================================================================== @node Security, , The Connection, Technical information @section About tinc's encryption and other security-related issues. @cindex tinc @cindex Cabal tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the alleged Cabal was/is an organization that was said to keep an eye on the entire Internet. As this is exactly what you @emph{don't} want, we named the tinc project after TINC. @cindex SVPN But in order to be ``immune'' to eavesdropping, you'll have to encrypt your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does exactly that: encrypt. This chapter is a mixture of ideas, reasoning and explanation, please don't take it too serious. @menu * Key Types:: @end menu @c ================================================================== @node Key Types, , Security, Security @subsection Key Types @c FIXME: check if I'm not talking nonsense There are several types of encryption keys. Tinc uses two of them, symmetric private keypairs and public/private keypairs. Public/private keypairs are used in public key cryptography. It enables someone to send out a public key with which other people can encrypt their data. The encrypted data now can only be decrypted by the person who has the private key that matches the public key. So, a public key only allows @emph{other} people to send encrypted messages to you. This is very useful in setting up private communications channels. Just send out your public key and other people can talk to you in a secure way. But how can you know the other person is who she says she is? This is done by sending out an encrypted challenge that only the person with the right private key can decode an respond to. However, encryption with public/private keys is very slow. Symmetric key cryptography is orders of magnitudes faster, but it is very hard to safely exchange the symmetric keys, since they should be kept private. The idea is to use public/private cryptography for authentication, and for exchanging symmetric keys in a safe way. After that, all communications are encrypted with the symmetric cipher. @c ================================================================== @node About us, Concept Index, Technical information, Top @chapter About us @menu * Contact Information:: * Authors:: @end menu @c ================================================================== @node Contact Information, Authors, About us, About us @section Contact information tinc's main page is at @url{http://tinc.nl.linux.org/}, this server is located in the Netherlands. We have an IRC channel on the Open Projects IRC network. Connect to @uref{http://openprojects.nu/services/irc.html, irc.openprojects.net}, and join channel #tinc. @c ================================================================== @node Authors, , Contact Information, About us @section Authors @table @asis @item Ivo Timmermans (zarq) (@email{itimmermans@@bigfoot.com}) Main coder/hacker and maintainer of the package. @item Guus Sliepen (guus) (@email{guus@@sliepen.warande.net}) Originator of it all, co-author. @item Wessel Dankers (Ubiq) (@email{wsl@@nl.linux.org}) For the name `tinc' and various suggestions. @end table We have received a lot of valuable input from users. With their help, tinc has become the flexible and robust tool that it is today. We have composed a list of contributions, in the file called @file{THANKS} in the source distribution. @c ================================================================== @node Concept Index, , About us, Top @c node-name, next, previous, up @unnumbered Concept Index @c ================================================================== @printindex cp @c ================================================================== @contents @bye