1 \input texinfo @c -*-texinfo-*-
2 @c $Id: tinc.texi,v 1.8.4.21 2002/02/18 16:25:15 guus Exp $
10 @dircategory Networking tools
12 * tinc: (tinc). The tinc Manual.
15 This is the info manual for tinc, a Virtual Private Network daemon.
17 Copyright @copyright{} 1998-2002 Ivo Timmermans
18 <itimmermans@@bigfoot.com>, Guus Sliepen <guus@@sliepen.warande.net> and
19 Wessel Dankers <wsl@@nl.linux.org>.
21 $Id: tinc.texi,v 1.8.4.21 2002/02/18 16:25:15 guus Exp $
23 Permission is granted to make and distribute verbatim copies of this
24 manual provided the copyright notice and this permission notice are
25 preserved on all copies.
27 Permission is granted to copy and distribute modified versions of this
28 manual under the conditions for verbatim copying, provided that the
29 entire resulting derived work is distributed under the terms of a
30 permission notice identical to this one.
36 @subtitle Setting up a Virtual Private Network with tinc
37 @author Ivo Timmermans and Guus Sliepen
40 @vskip 0pt plus 1filll
42 Copyright @copyright{} 1998-2002 Ivo Timmermans
43 <itimmermans@@bigfoot.com>, Guus Sliepen <guus@@sliepen.warande.net> and
44 Wessel Dankers <wsl@@nl.linux.org>.
46 $Id: tinc.texi,v 1.8.4.21 2002/02/18 16:25:15 guus Exp $
48 Permission is granted to make and distribute verbatim copies of this
49 manual provided the copyright notice and this permission notice are
50 preserved on all copies.
52 Permission is granted to copy and distribute modified versions of this
53 manual under the conditions for verbatim copying, provided that the
54 entire resulting derived work is distributed under the terms of a
55 permission notice identical to this one.
59 @c ==================================================================
60 @node Top, Introduction, (dir), (dir)
63 * Introduction:: Introduction
68 * Technical information::
70 * Concept Index:: All used terms explained
76 @c ==================================================================
77 @node Introduction, Preparations, Top, Top
81 tinc is a Virtual Private Network (VPN) daemon that uses tunneling and
82 encryption to create a secure private network between hosts on the
85 Because the tunnel appears to the IP level network code as a normal
86 network device, there is no need to adapt any existing software.
87 The encrypted tunnels allows VPN sites to share information with each other
88 over the Internet without exposing any information to others.
90 This document is the manual for tinc. Included are chapters on how to
91 configure your computer to use tinc, as well as the configuration
92 process of tinc itself.
95 * VPNs:: Virtual Private Networks in general
97 * Supported platforms::
100 @c ==================================================================
101 @node VPNs, tinc, Introduction, Introduction
102 @section Virtual Private Networks
105 A Virtual Private Network or VPN is a network that can only be accessed
106 by a few elected computers that participate. This goal is achievable in
107 more than just one way.
110 Private networks can consist of a single stand-alone Ethernet LAN. Or
111 even two computers hooked up using a null-modem cable. In these cases,
113 obvious that the network is @emph{private}, no one can access it from the
114 outside. But if your computers are linked to the Internet, the network
115 is not private anymore, unless one uses firewalls to block all private
116 traffic. But then, there is no way to send private data to trusted
117 computers on the other end of the Internet.
120 This problem can be solved by using @emph{virtual} networks. Virtual
121 networks can live on top of other networks, but they use encapsulation to
122 keep using their private address space so they do not interfere with
123 the Internet. Mostly, virtual networks appear like a singe LAN, even though
124 they can span the entire world. But virtual networks can't be secured
125 by using firewalls, because the traffic that flows through it has to go
126 through the Internet, where other people can look at it.
128 As is the case with either type of VPN, anybody could eavesdrop. Or
129 worse, alter data. Hence it's probably advisable to encrypt the data
130 that flows over the network.
132 When one introduces encryption, we can form a true VPN. Other people may
133 see encrypted traffic, but if they don't know how to decipher it (they
134 need to know the key for that), they cannot read the information that flows
135 through the VPN. This is what tinc was made for.
138 @c ==================================================================
139 @node tinc, Supported platforms, VPNs, Introduction
143 I really don't quite remember what got us started, but it must have been
144 Guus' idea. He wrote a simple implementation (about 50 lines of C) that
145 used the ethertap device that Linux knows of since somewhere
146 about kernel 2.1.60. It didn't work immediately and he improved it a
147 bit. At this stage, the project was still simply called @samp{vpnd}.
149 Since then, a lot has changed---to say the least.
152 tinc now supports encryption, it consists of a single daemon (tincd) for
153 both the receiving and sending end, it has become largely
154 runtime-configurable---in short, it has become a full-fledged
155 professional package.
157 @cindex Traditional VPNs
159 tinc also allows more than two sites to connect to eachother and form a single VPN.
160 Traditionally VPNs are created by making tunnels, which only have two endpoints.
161 Larger VPNs with more sites are created by adding more tunnels.
162 tinc takes another approach: only endpoints are specified,
163 the software itself will take care of creating the tunnels.
164 This allows for easier configuration and improved scalability.
166 A lot can---and will be---changed. We have a number of things that we would like to
167 see in the future releases of tinc. Not everything will be available in
168 the near future. Our first objective is to make tinc work perfectly as
169 it stands, and then add more advanced features.
171 Meanwhile, we're always open-minded towards new ideas. And we're
175 @c ==================================================================
176 @node Supported platforms, , tinc, Introduction
177 @section Supported platforms
180 tinc has been verified to work under Linux, FreeBSD, OpenBSD and Solaris, with
181 various hardware architectures. These are some of the platforms
182 that are supported by the universal tun/tap device driver or other virtual network device drivers.
183 Without such a driver, tinc will most
184 likely compile and run, but it will not be able to send or receive data
188 For an up to date list of supported platforms, please check the list on
190 @uref{http://tinc.nl.linux.org/platforms.html}.
193 @c ==================================================================
197 tinc was first written for Linux running on an intel x86 processor, so
198 this is the best supported platform. The protocol however, and actually
199 anything about tinc, has been rewritten to support random byte ordering
200 and arbitrary word length. So in theory it should run on other
201 processors that Linux runs on. It has already been verified to run on
202 alpha and sparc processors as well.
204 tinc uses the ethertap device or the universal tun/tap driver. The former is provided in the standard kernel
205 from version 2.1.60 up to 2.3.x, but has been replaced in favour of the tun/tap driver in kernel versions 2.4.0 and later.
208 @c ==================================================================
212 tinc on FreeBSD relies on the universal tun/tap driver for its data
213 acquisition from the kernel. Therefore, tinc will work on the same platforms
214 as this driver. These are: FreeBSD 3.x, 4.x, 5.x.
217 @c ==================================================================
221 tinc on OpenBSD relies on the tun driver for its data
222 acquisition from the kernel. It has been verified to work under at least OpenBSD 2.9.
225 @c ==================================================================
229 tinc on Solaris relies on the universal tun/tap driver for its data
230 acquisition from the kernel. Therefore, tinc will work on the same platforms
231 as this driver. These are: Solaris, 2.1.x.
240 @c Preparing your system
247 @c ==================================================================
248 @node Preparations, Installation, Introduction, Top
249 @chapter Preparations
251 This chapter contains information on how to prepare your system to
255 * Configuring the kernel::
260 @c ==================================================================
261 @node Configuring the kernel, Libraries, Preparations, Preparations
262 @section Configuring the kernel
269 If you are running Linux, chances are good that your kernel already supports
270 all the devices that tinc needs for proper operation. For example, the
271 standard kernel from Redhat Linux already has support for ethertap and netlink
272 compiled in. Debian users can use the modconf utility to select the modules.
273 If your Linux distribution supports this method of selecting devices, look out
274 for something called `ethertap', and `netlink_dev' if it is using a kernel
275 version prior to 2.4.0. In that case you will need both these devices. If you
276 are using kernel 2.4.0 or later, you need to select `tun'.
279 If you can install these devices in a similar manner, you may skip this section.
280 Otherwise, you will have to recompile the kernel in order to turn on the required features.
281 If you are unfamiliar with the process of configuring and compiling a new kernel,
282 you should read the @uref{http://howto.linuxberg.com/LDP/HOWTO/Kernel-HOWTO.html, Kernel HOWTO} first.
285 * Configuration of Linux kernels 2.1.60 up to 2.4.0::
286 * Configuration of Linux kernels 2.4.0 and higher::
287 * Configuration of FreeBSD kernels::
288 * Configuration of OpenBSD kernels::
289 * Configuration of Solaris kernels::
293 @c ==================================================================
294 @node Configuration of Linux kernels 2.1.60 up to 2.4.0, Configuration of Linux kernels 2.4.0 and higher, Configuring the kernel, Configuring the kernel
295 @subsection Configuration of Linux kernels 2.1.60 up to 2.4.0
297 Here are the options you have to turn on when configuring a new kernel:
300 Code maturity level options
301 [*] Prompt for development and/or incomplete code/drivers
303 [*] Kernel/User netlink socket
304 <M> Netlink device emulation
305 Network device support
306 <M> Ethertap network tap
309 If you want to run more than one instance of tinc or other programs that use
310 the ethertap, you have to compile the ethertap driver as a module, otherwise
311 you can also choose to compile it directly into the kernel.
313 If you decide to build any of these as dynamic kernel modules, it's a good idea
314 to add these lines to @file{/etc/modules.conf}:
317 alias char-major-36 netlink_dev
319 options tap0 -o tap0 unit=0
321 options tap1 -o tap1 unit=1
323 alias tap@emph{N} ethertap
324 options tap@emph{N} -o tap@emph{N} unit=@emph{N}
327 Add as much alias/options lines as necessary.
330 @c ==================================================================
331 @node Configuration of Linux kernels 2.4.0 and higher, Configuration of FreeBSD kernels, Configuration of Linux kernels 2.1.60 up to 2.4.0, Configuring the kernel
332 @subsection Configuration of Linux kernels 2.4.0 and higher
334 Here are the options you have to turn on when configuring a new kernel:
337 Code maturity level options
338 [*] Prompt for development and/or incomplete code/drivers
339 Network device support
340 <M> Universal tun/tap device driver support
343 It's not necessary to compile this driver as a module, even if you are going to
344 run more than one instance of tinc.
346 If you have an early 2.4 kernel, you can choose both the tun/tap driver and the
347 `Ethertap network tap' device. This latter is marked obsolete, and chances are
348 that it won't even function correctly anymore. Make sure you select the
349 universal tun/tap driver.
351 If you decide to build the tun/tap driver as a kernel module, add these lines
352 to @file{/etc/modules.conf}:
355 alias char-major-10-200 tun
359 @c ==================================================================
360 @node Configuration of FreeBSD kernels, Configuration of OpenBSD kernels, Configuration of Linux kernels 2.4.0 and higher, Configuring the kernel
361 @subsection Configuration of FreeBSD kernels
363 This section will contain information on how to configure your FreeBSD
364 kernel to support the universal tun/tap device. For 4.1 and higher
365 versions, this is included in the default kernel configuration, for earlier
366 systems (4.0 and earlier), you need to install the universal tun/tap driver
369 Unfortunately somebody still has to write the text.
372 @c ==================================================================
373 @node Configuration of OpenBSD kernels, Configuration of Solaris kernels, Configuration of FreeBSD kernels, Configuring the kernel
374 @subsection Configuration of OpenBSD kernels
376 This section will contain information on how to configure your OpenBSD
377 kernel to support the tun device. For 2.9 and 3.0 systems,
378 this is included in the default kernel configuration.
380 Unfortunately somebody still has to write the text.
383 @c ==================================================================
384 @node Configuration of Solaris kernels, , Configuration of OpenBSD kernels, Configuring the kernel
385 @subsection Configuration of Solaris kernels
387 This section will contain information on how to configure your Solaris
388 kernel to support the universal tun/tap device. You need to install
389 this driver yourself.
391 Unfortunately somebody still has to write the text.
394 @c ==================================================================
395 @node Libraries, , Configuring the kernel, Preparations
400 Before you can configure or build tinc, you need to have the OpenSSL
401 library installed on your system. If you try to configure tinc without
402 having installed it, configure will give you an error message, and stop.
409 @c ==================================================================
410 @node OpenSSL, , Libraries, Libraries
414 For all cryptography-related functions, tinc uses the functions provided
415 by the OpenSSL library.
417 If this library is not installed, you wil get an error when configuring
418 tinc for build. Support for running tinc without having OpenSSL
419 installed @emph{may} be added in the future.
421 You can use your operating system's package manager to install this if
422 available. Make sure you install the development AND runtime versions
425 If you have to install OpenSSL manually, you can get the source code
426 from @url{http://www.openssl.org/}. Instructions on how to configure,
427 build and install this package are included within the package. Please
428 make sure you build development and runtime libraries (which is the
431 If you installed the OpenSSL libraries from source, it may be necessary
432 to let configure know where they are, by passing configure one of the
433 --with-openssl-* parameters.
436 --with-openssl=DIR OpenSSL library and headers prefix
437 --with-openssl-include=DIR OpenSSL headers directory
438 (Default is OPENSSL_DIR/include)
439 --with-openssl-lib=DIR OpenSSL library directory
440 (Default is OPENSSL_DIR/lib)
444 @subsubheading License
447 Since the license under which OpenSSL is distributed is not directly
448 compatible with the terms of the GNU GPL
449 @uref{http://www.openssl.org/support/faq.html#LEGAL2}, therefore we
450 include an addition to the GPL (see also the file COPYING.README):
453 This program is released under the GPL with the additional exemption
454 that compiling, linking, and/or using OpenSSL is allowed. You may
455 provide binary packages linked to the OpenSSL libraries, provided that
456 all other requirements of the GPL are met.
469 @c ==================================================================
470 @node Installation, Configuration, Preparations, Top
471 @chapter Installation
473 If you use Debian, you may want to install one of the
474 precompiled packages for your system. These packages are equipped with
475 system startup scripts and sample configurations.
477 If you cannot use one of the precompiled packages, or you want to compile tinc
478 for yourself, you can use the source. The source is distributed under
479 the GNU General Public License (GPL). Download the source from the
480 @uref{http://tinc.nl.linux.org/download.html, download page}, which has
481 the checksums of these files listed; you may wish to check these with
482 md5sum before continuing.
484 tinc comes in a convenient autoconf/automake package, which you can just
485 treat the same as any other package. Which is just untar it, type
486 `configure' and then `make'.
487 More detailed instructions are in the file @file{INSTALL}, which is
488 included in the source distribution.
491 * Building and installing tinc::
496 @c ==================================================================
497 @node Building and installing tinc, System files, Installation, Installation
498 @section Building and installing tinc
500 Detailed instructions on configuring the source, building tinc and installing tinc
501 can be found in the file called @file{INSTALL}.
503 @cindex binary package
504 If you happen to have a binary package for tinc for your distribution,
505 you can use the package management tools of that distribution to install tinc.
506 The documentation that comes along with your distribution will tell you how to do that.
509 @c ==================================================================
510 @node System files, , Building and installing tinc, Installation
511 @section System files
513 Before you can run tinc, you must make sure you have all the needed
514 files on your system.
522 @c ==================================================================
523 @node Device files, Other files, System files, System files
524 @subsection Device files
527 First, you'll need the special device file(s) that form the interface
528 between the kernel and the daemon.
530 The permissions for these files have to be such that only the super user
531 may read/write to this file. You'd want this, because otherwise
532 eavesdropping would become a bit too easy. This does, however, imply
533 that you'd have to run tincd as root.
535 If you use Linux and have a kernel version prior to 2.4.0, you have to make the
539 mknod -m 600 /dev/tap0 c 36 16
541 mknod -m 600 /dev/tap1 c 36 17
544 mknod -m 600 /dev/tap@emph{N} c 36 @emph{N+16}
545 chown 0.0 /dev/tap@emph{N}
548 There is a maximum of 16 ethertap devices.
550 If you use the universal tun/tap driver, you have to create the
551 following device file (unless it already exist):
554 mknod -m 600 /dev/tun c 10 200
558 If you use Linux, and you run the new 2.4 kernel using the devfs filesystem,
559 then the tun/tap device will probably be automatically generated as
560 @file{/dev/misc/net/tun}.
562 Unlike the ethertap device, you do not need multiple device files if
563 you are planning to run multiple tinc daemons.
566 @c ==================================================================
567 @node Other files, , Device files, System files
568 @subsection Other files
570 @subsubheading @file{/etc/networks}
572 You may add a line to @file{/etc/networks} so that your VPN will get a
573 symbolic name. For example:
579 @subsubheading @file{/etc/services}
582 You may add this line to @file{/etc/services}. The effect is that you
583 may supply a @samp{tinc} as a valid port number to some programs. The
584 number 655 is registered with the IANA.
589 # Ivo Timmermans <itimmermans@@bigfoot.com>
604 @c ==================================================================
605 @node Configuration, Running tinc, Installation, Top
606 @chapter Configuration
609 * Configuration introduction::
610 * Multiple networks::
611 * How connections work::
612 * Configuration files::
613 * Generating keypairs::
614 * Network interfaces::
615 * Example configuration::
618 @c ==================================================================
619 @node Configuration introduction, Multiple networks, Configuration, Configuration
620 @section Configuration introduction
622 @cindex Network Administrators Guide
623 Before actually starting to configure tinc and editing files,
624 make sure you have read this entire section so you know what to expect.
625 Then, make it clear to yourself how you want to organize your VPN:
626 What are the nodes (computers running tinc)?
627 What IP addresses/subnets do they have?
628 What is the network mask of the entire VPN?
629 Do you need special firewall rules?
630 Do you have to set up masquerading or forwarding rules?
631 These questions can only be answered by yourself,
632 you will not find the answers in this documentation.
633 Make sure you have an adequate understanding of networks in general.
634 A good resource on networking is the
635 @uref{http://www.linuxdoc.org/LDP/nag2/, Linux Network Administrators Guide}.
637 If you have everything clearly pictured in your mind,
638 proceed in the following order:
639 First, generate the configuration files (@file{tinc.conf}, your host configuration file, @file{tinc-up} and perhaps @file{tinc-down}).
640 Then generate the keypairs.
641 Finally, distribute the host configuration files.
642 These steps are described in the subsections below.
645 @c ==================================================================
646 @node Multiple networks, How connections work, Configuration introduction, Configuration
647 @section Multiple networks
649 @cindex multiple networks
651 In order to allow you to run more than one tinc daemon on one computer,
652 for instance if your computer is part of more than one VPN,
653 you can assign a ``netname'' to your VPN.
654 It is not required if you only run one tinc daemon,
655 it doesn't even have to be the same on all the sites of your VPN,
656 but it is recommended that you choose one anyway.
658 We will asume you use a netname throughout this document.
659 This means that you call tincd with the -n argument,
660 which will assign a netname to this daemon.
662 The effect of this is that the daemon will set its configuration
663 ``root'' to /etc/tinc/netname/, where netname is your argument to the -n
664 option. You'll notice that it appears in syslog as ``tinc.netname''.
666 However, it is not strictly necessary that you call tinc with the -n
667 option. In this case, the network name would just be empty, and it will
668 be used as such. tinc now looks for files in /etc/tinc/, instead of
669 /etc/tinc/netname/; the configuration file should be /etc/tinc/tinc.conf,
670 and the host configuration files are now expected to be in /etc/tinc/hosts/.
672 But it is highly recommended that you use this feature of tinc, because
673 it will be so much clearer whom your daemon talks to. Hence, we will
674 assume that you use it.
677 @c ==================================================================
678 @node How connections work, Configuration files, Multiple networks, Configuration
679 @section How connections work
681 When tinc starts up, it parses the command-line options and then
682 reads in the configuration file.
683 If it sees a `ConnectTo' value pointing to another tinc daemon in the file,
684 it will try to connect to that other one.
685 Whether this succeeds or not and whether `ConnectTo' is specified or not,
686 tinc will listen for incoming connection from other deamons.
687 If you did specify a `ConnectTo' value and the other side is not responding,
688 tinc will keep retrying.
689 This means that once started, tinc will stay running until you tell it to stop,
690 and failures to connect to other tinc daemons will not stop your tinc daemon
691 for trying again later.
692 This means you don't have to intervene if there are any network problems.
696 There is no real distinction between a server and a client in tinc.
697 If you wish, you can view a tinc daemon without a `ConnectTo' value as a server,
698 and one which does specify such a value as a client.
699 It does not matter if two tinc daemons have a `ConnectTo' value pointing to eachother however.
702 @c ==================================================================
703 @node Configuration files, Generating keypairs, How connections work, Configuration
704 @section Configuration files
706 The actual configuration of the daemon is done in the file
707 @file{/etc/tinc/netname/tinc.conf} and at least one other file in the directory
708 @file{/etc/tinc/netname/hosts/}.
710 These file consists of comments (lines started with a #) or assignments
717 The variable names are case insensitive, and any spaces, tabs, newlines
718 and carriage returns are ignored. Note: it is not required that you put
719 in the `=' sign, but doing so improves readability. If you leave it
720 out, remember to replace it with at least one space character.
722 In this section all valid variables are listed in alphabetical order.
723 The default value is given between parentheses,
724 other comments are between square brackets and
725 required directives are given in @strong{bold}.
728 * Main configuration variables::
729 * Host configuration variables::
734 @c ==================================================================
735 @node Main configuration variables, Host configuration variables, Configuration files, Configuration files
736 @subsection Main configuration variables
739 @cindex AddressFamily
740 @item AddressFamily = <ipv4|ipv6|any> (ipv4)
741 This option affects the address family of listening and outgoing sockets.
742 If "any" is selected, then the listening sockets will be IPv6 sockets,
743 but on most platforms those will also accept IPv4 connections.
745 @cindex BindToInterface
746 @item BindToInterface = <interface>
747 If you have more than one network interface in your computer, tinc will
748 by default listen on all of them for incoming connections. It is
749 possible to bind tinc to a single interface like eth0 or ppp0 with this
752 This option may not work on all platforms.
755 @item BindToIP = <address>
756 If your computer has more than one IP address on a single interface (for
757 example if you are running virtual hosts), tinc will by default listen
758 on all of them for incoming connections. It is possible to bind tinc to
759 a single IP address with this variable. It is still possible to listen
760 on several interfaces at the same time though, if they share the same IP
763 This option may not work on all platforms.
766 @item @strong{ConnectTo = <name>}
767 Specifies which host to connect to on startup. Multiple ConnectTo
768 variables may be specified, if connecting to the first one fails then
769 tinc will try the next one, and so on. It is possible to specify
770 hostnames for dynamic IP addresses (like those given on dyndns.org),
771 tinc will not cache the resolved IP address.
773 If you don't specify a host with ConnectTo, regardless of whether a
774 value for ConnectPort is given, tinc won't connect at all, and will
775 instead just listen for incoming connections.
778 @item @strong{Device = <device>} (/dev/tap0 or /dev/misc/net/tun)
779 The virtual network device to use. Note that you can only use one device per
780 daemon. See also @ref{Device files}.
783 @item Hostnames = <yes|no> (no)
784 This option selects whether IP addresses (both real and on the VPN)
785 should be resolved. Since DNS lookups are blocking, it might affect
786 tinc's efficiency, even stopping the daemon for a few seconds everytime
787 it does a lookup if your DNS server is not responding.
789 This does not affect resolving hostnames to IP addresses from the
793 @item Interface = <interface>
794 Defines the name of the interface corresponding to the virtual network device.
795 Depending on the operating system and the type of device this may or may not actually set the name.
796 Currently this option only affects the Linux tun/tap device.
799 @item Mode = <router|switch|hub> (router)
800 This option selects the way packets are routed to other daemons.
806 variables in the host configuration files will be used to form a routing table.
807 Only unicast packets of routable protocols (IPv4 and IPv6) are supported in this mode.
811 In this mode the MAC addresses of the packets on the VPN will be used to
812 dynamically create a routing table just like a network switch does.
813 Unicast, multicast and broadcast packets of every ethernet protocol are supported in this mode
814 at the cost of frequent broadcast ARP requests and routing table updates.
818 In this mode every packet will be broadcast to the other daemons.
822 @item KeyExpire = <seconds> (3600)
823 This option controls the time the encryption keys used to encrypt the data
824 are valid. It is common practice to change keys at regular intervals to
825 make it even harder for crackers, even though it is thought to be nearly
826 impossible to crack a single key.
829 @item @strong{Name = <name>}
830 This is a symbolic name for this connection. It can be anything
833 @item PingTimeout = <seconds> (60)
834 The number of seconds of inactivity that tinc will wait before sending a
835 probe to the other end. If that other end doesn't answer within that
836 same amount of seconds, the connection is terminated, and the others
837 will be notified of this.
840 @item PrivateKey = <key> [obsolete]
841 This is the RSA private key for tinc. However, for safety reasons it is
842 advised to store private keys of any kind in separate files. This prevents
843 accidental eavesdropping if you are editting the configuration file.
845 @cindex PrivateKeyFile
846 @item @strong{PrivateKeyFile = <path>} [recommended]
847 This is the full path name of the RSA private key file that was
848 generated by ``tincd --generate-keys''. It must be a full path, not a
851 Note that there must be exactly one of PrivateKey
853 specified in the configuration file.
858 @c ==================================================================
859 @node Host configuration variables, How to configure, Main configuration variables, Configuration files
860 @subsection Host configuration variables
864 @item @strong{Address = <IP address|hostname>} [recommended]
865 This variable is only required if you want to connect to this host. It
866 must resolve to the external IP address where the host can be reached,
867 not the one that is internal to the VPN.
870 @item Cipher = <cipher> (blowfish)
871 The symmetric cipher algorithm used to encrypt UDP packets.
872 Any cipher supported by OpenSSL is recognized.
875 @item Compression = <level> (0)
876 This option sets the level of compression used for UDP packets.
877 Possible values are 0 (off), 1 (fast) and any integer up to 9 (best).
880 @item Digest = <digest> (sha1)
881 The digest algorithm used to authenticate UDP packets.
882 Any digest supported by OpenSSL is recognized.
883 Furthermore, specifying "none" will turn off packet authentication.
886 @item IndirectData = <yes|no> (no) [experimental]
887 This option specifies whether other tinc daemons besides the one you
888 specified with ConnectTo can make a direct connection to you. This is
889 especially useful if you are behind a firewall and it is impossible to
890 make a connection from the outside to your tinc daemon. Otherwise, it
891 is best to leave this option out or set it to no.
894 @item MACLength = <length> (4)
895 The length of the message authentication code used to authenticate UDP packets.
896 Can be anything from 0
897 up to the length of the digest produced by the digest algorithm.
900 @item Port = <port> (655)
901 Connect to the upstream host (given with the ConnectTo directive) on
902 port port. port may be given in decimal (default), octal (when preceded
903 by a single zero) o hexadecimal (prefixed with 0x). port is the port
904 number for both the UDP and the TCP (meta) connections.
907 @item PublicKey = <key> [obsolete]
908 This is the RSA public key for this host.
910 @cindex PublicKeyFile
911 @item PublicKeyFile = <path> [obsolete]
912 This is the full path name of the RSA public key file that was generated
913 by ``tincd --generate-keys''. It must be a full path, not a relative
917 From version 1.0pre4 on tinc will store the public key directly into the
918 host configuration file in PEM format, the above two options then are not
919 necessary. Either the PEM format is used, or exactly
920 @strong{one of the above two options} must be specified
921 in each host configuration file, if you want to be able to establish a
922 connection with that host.
925 @item Subnet = <address[/masklength]>
926 The subnet which this tinc daemon will serve.
927 tinc tries to look up which other daemon it should send a packet to by searching the appropiate subnet.
928 If the packet matches a subnet,
929 it will be sent to the daemon who has this subnet in his host configuration file.
930 Multiple subnet lines can be specified for each daemon.
932 Subnets can either be single MAC, IPv4 or IPv6 addresses,
933 in which case a subnet consisting of only that single address is assumed,
934 or they can be a IPv4 or IPv6 network address with a masklength.
935 For example, IPv4 subnets must be in a form like 192.168.1.0/24,
936 where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
937 Note that subnets like 192.168.1.1/24 are invalid!
939 @cindex CIDR notation
940 masklength is the number of bits set to 1 in the netmask part; for
941 example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
942 /22. This conforms to standard CIDR notation as described in
943 @uref{ftp://ftp.isi.edu/in-notes/rfc1519.txt, RFC1519}
946 @item TCPonly = <yes|no> (no) [experimental]
947 If this variable is set to yes, then the packets are tunnelled over a
948 TCP connection instead of a UDP connection. This is especially useful
949 for those who want to run a tinc daemon from behind a masquerading
950 firewall, or if UDP packet routing is disabled somehow. This is
951 experimental code, try this at your own risk. It may not work at all.
952 Setting this options also implicitly sets IndirectData.
956 @c ==================================================================
957 @node How to configure, , Host configuration variables, Configuration files
958 @subsection How to configure
960 @subsubheading Step 1. Creating the main configuration file
962 The main configuration file will be called @file{/etc/tinc/netname/tinc.conf}.
963 Adapt the following example to create a basic configuration file:
966 Name = @emph{yourname}
967 Device = @emph{/dev/tap0}
968 PrivateKeyFile = /etc/tinc/@emph{netname}/rsa_key.priv
971 Then, if you know to which other tinc daemon(s) yours is going to connect,
972 add `ConnectTo' values.
974 @subsubheading Step 2. Creating your host configuration file
976 If you added a line containing `Name = yourname' in the main configuarion file,
977 you will need to create a host configuration file @file{/etc/tinc/netname/hosts/yourname}.
978 Adapt the following example to create a host configuration file:
981 Address = @emph{your.real.hostname.org}
982 Subnet = @emph{192.168.1.0/24}
985 You can also use an IP address instead of a hostname.
986 The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
987 If you have multiple address ranges you can specify more than one `Subnet'.
988 You might also need to add a `Port' if you want your tinc daemon to run on a different port number than the default (655).
991 @c ==================================================================
992 @node Generating keypairs, Network interfaces, Configuration files, Configuration
993 @section Generating keypairs
995 @cindex key generation
996 Now that you have already created the main configuration file and your host configuration file,
997 you can easily create a public/private keypair by entering the following command:
1000 tincd -n @emph{netname} -K
1003 tinc will generate a public and a private key and ask you where to put them.
1004 Just press enter to accept the defaults.
1007 @c ==================================================================
1008 @node Network interfaces, Example configuration, Generating keypairs, Configuration
1009 @section Network interfaces
1011 Before tinc can start transmitting data over the tunnel, it must
1012 set up the virtual network interface.
1014 First, decide which IP addresses you want to have associated with these
1015 devices, and what network mask they must have.
1017 tinc will open a virtual network device (@file{/dev/tun}, @file{/dev/tap0} or similar),
1018 which will also create a network interface called something like `tun0', `tap0', or,
1019 if you are using the Linux tun/tap driver, the network interface will by default have the same name as the netname.
1022 You can configure the network interface by putting ordinary ifconfig, route, and other commands
1023 to a script named @file{/etc/tinc/netname/tinc-up}. When tinc starts, this script
1024 will be executed. When tinc exits, it will execute the script named
1025 @file{/etc/tinc/netname/tinc-down}, but normally you don't need to create that script.
1027 An example @file{tinc-up} script:
1031 ifconfig $INTERFACE hw ether fe:fd:0:0:0:0
1032 ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0
1033 ifconfig $INTERFACE -arp
1037 @cindex hardware address
1038 The first line sets up the MAC address of the network interface.
1039 Due to the nature of how Ethernet and tinc work, it has to be set to fe:fd:0:0:0:0
1040 for tinc to work in it's normal mode.
1041 If you configured tinc to work in `switch' or `hub' mode, the hardware address should instead
1042 be set to a unique address instead of fe:fd:0:0:0:0.
1044 You can use the environment variable $INTERFACE to get the name of the interface.
1045 If you are using the ethertap driver however, you need to replace it with tap@emph{N},
1046 corresponding to the device file name.
1049 The next line gives the interface an IP address and a netmask.
1050 The kernel will also automatically add a route to this interface, so normally you don't need
1051 to add route commands to the @file{tinc-up} script.
1052 The kernel will also bring the interface up after this command.
1054 The netmask is the mask of the @emph{entire} VPN network, not just your
1058 The last line tells the kernel not to use ARP on that interface.
1059 Again this has to do with how Ethernet and tinc work.
1060 Use this option only if you are running tinc under Linux and are using tinc's normal routing mode.
1063 @c ==================================================================
1064 @node Example configuration, , Network interfaces, Configuration
1065 @section Example configuration
1069 Imagine the following situation. Branch A of our example `company' wants to connect
1070 three branch offices in B, C and D using the Internet. All four offices
1071 have a 24/7 connection to the Internet.
1073 A is going to serve as the center of the network. B and C will connect
1074 to A, and D will connect to C. Each office will be assigned their own IP
1078 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
1079 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
1080 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
1081 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
1084 ``gateway'' is the VPN IP address of the machine that is running the
1085 tincd. ``internet IP'' is the IP address of the firewall, which does not
1086 need to run tincd, but it must do a port forwarding of TCP&UDP on port
1087 655 (unless otherwise configured).
1089 In this example, it is assumed that eth0 is the interface that points to
1090 the inner (physical) LAN of the office, although this could also be the
1091 same as the interface that leads to the Internet. The configuration of
1092 the real interface is also shown as a comment, to give you an idea of
1093 how these example host is set up. All branches use the netname `company'
1094 for this particular VPN.
1096 @subsubheading For Branch A
1098 @emph{BranchA} would be configured like this:
1100 In @file{/etc/tinc/company/tinc-up}:
1103 # Real interface of internal network:
1104 # ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
1106 ifconfig tap0 hw ether fe:fd:0:0:0:0
1107 ifconfig tap0 10.1.54.1 netmask 255.0.0.0
1111 and in @file{/etc/tinc/company/tinc.conf}:
1115 PrivateKey = /etc/tinc/company/rsa_key.priv
1119 On all hosts, /etc/tinc/company/hosts/BranchA contains:
1122 Subnet = 10.1.0.0/16
1125 Note that the IP addresses of eth0 and tap0 are the same.
1126 This is quite possible, if you make sure that the netmasks of the interfaces are different.
1127 It is in fact recommended to give give both real internal network interfaces and tap interfaces the same IP address,
1128 since that will make things a lot easier to remember and set up.
1130 -----BEGIN RSA PUBLIC KEY-----
1132 -----END RSA PUBLIC KEY-----
1136 @subsubheading For Branch B
1138 In @file{/etc/tinc/company/tinc-up}:
1141 # Real interface of internal network:
1142 # ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
1144 ifconfig tap0 hw ether fe:fd:0:0:0:0
1145 ifconfig tap0 10.2.1.12 netmask 255.0.0.0
1149 and in @file{/etc/tinc/company/tinc.conf}:
1154 PrivateKey = /etc/tinc/company/rsa_key.priv
1157 Note here that the internal address (on eth0) doesn't have to be the
1158 same as on the tap0 device. Also, ConnectTo is given so that no-one can
1159 connect to this node.
1161 On all hosts, in @file{/etc/tinc/company/hosts/BranchB}:
1164 Subnet = 10.2.0.0/16
1167 -----BEGIN RSA PUBLIC KEY-----
1169 -----END RSA PUBLIC KEY-----
1173 @subsubheading For Branch C
1175 In @file{/etc/tinc/company/tinc-up}:
1178 # Real interface of internal network:
1179 # ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
1181 ifconfig tap1 hw ether fe:fd:0:0:0:0
1182 ifconfig tap1 10.3.69.254 netmask 255.0.0.0
1186 and in @file{/etc/tinc/company/tinc.conf}:
1194 C already has another daemon that runs on port 655, so they have to
1195 reserve another port for tinc. It knows the portnumber it has to listen on
1196 from it's own host configuration file.
1198 On all hosts, in @file{/etc/tinc/company/hosts/BranchC}:
1202 Subnet = 10.3.0.0/16
1205 -----BEGIN RSA PUBLIC KEY-----
1207 -----END RSA PUBLIC KEY-----
1211 @subsubheading For Branch D
1213 In @file{/etc/tinc/company/tinc-up}:
1216 # Real interface of internal network:
1217 # ifconfig eth0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
1219 ifconfig company hw ether fe:fd:0a:04:03:20
1220 ifconfig company 10.4.3.32 netmask 255.0.0.0
1221 ifconfig company -arp
1224 and in @file{/etc/tinc/company/tinc.conf}:
1229 Device = /dev/misc/net/tun
1230 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1233 D will be connecting to C, which has a tincd running for this network on
1234 port 2000. It knows the port number from the host configuration file.
1235 Also note that since D uses the tun/tap driver, the network interface
1236 will not be called `tun' or `tap0' or something like that, but will
1237 have the same name as netname.
1239 On all hosts, in @file{/etc/tinc/company/hosts/BranchD}:
1242 Subnet = 10.4.0.0/16
1245 -----BEGIN RSA PUBLIC KEY-----
1247 -----END RSA PUBLIC KEY-----
1250 @subsubheading Key files
1252 A, B, C and D all have generated a public/private keypair with the following command:
1258 The private key is stored in @file{/etc/tinc/company/rsa_key.priv},
1259 the public key is put into the host configuration file in the @file{/etc/tinc/company/hosts/} directory.
1260 During key generation, tinc automatically guesses the right filenames based on the -n option and
1261 the Name directive in the @file{tinc.conf} file (if it is available).
1263 @subsubheading Starting
1265 After each branch has finished configuration and they have distributed
1266 the host configuration files amongst them, they can start their tinc daemons.
1267 They don't necessarily have to wait for the other branches to have started
1268 their daemons, tinc will try connecting until they are available.
1271 @c ==================================================================
1272 @node Running tinc, Technical information, Configuration, Top
1273 @chapter Running tinc
1275 If everything else is done, you can start tinc by typing the following command:
1278 tincd -n @emph{netname}
1282 tinc will detach from the terminal and continue to run in the background like a good daemon.
1283 If there are any problems however you can try to increase the debug level
1284 and look in the syslog to find out what the problems are.
1292 @c ==================================================================
1293 @node Runtime options, Error messages, , Running tinc
1294 @section Runtime options
1296 Besides the settings in the configuration file, tinc also accepts some
1297 command line options.
1299 This list is a longer version of that in the manpage. The latter is
1300 generated automatically, so may be more up-to-date.
1302 @cindex command line
1303 @cindex runtime options
1307 @item --bypass-security
1308 Disables encryption and authentication.
1309 Only useful for debugging.
1311 @item -c, --config=PATH
1312 Read configuration options from the directory PATH. The default is
1313 @file{/etc/tinc/netname/}.
1316 @item -d, --debug=LEVEL
1317 Set debug level to LEVEL. The higher the debug level, the more gets
1318 logged. Everything goes via syslog.
1320 @item -K, --generate-keys[=BITS]
1321 Generate public/private keypair of BITS length. If BITS is not specified,
1322 1024 is the default. tinc will ask where you want to store the files,
1323 but will default to the configuration directory (you can use the -c or -n option
1324 in combination with -K). After that, tinc will quit.
1327 Display a short reminder of these runtime options and terminate.
1330 Attempt to kill a running tincd and exit. A TERM signal (15) gets sent
1331 to the daemon that his its PID in @file{/var/run/tinc.NETNAME.pid}.
1332 Use it in conjunction with the -n option to make sure you kill the right tinc daemon.
1334 @item -n, --net=NETNAME
1335 Connect to net NETNAME. @xref{Multiple networks}.
1337 @item -D, --no-detach
1338 Don't fork and detach.
1339 This will also disable the automatic restart mechanism for fatal errors.
1342 Output version information and exit.
1347 @c ==================================================================
1348 @node Error messages, , Runtime options, Running tinc
1349 @section Error messages
1351 What follows is a list of the most common error messages you can see
1352 when configuring tinc. Most of these messages are visible in the syslog
1353 only, so keep an eye on it!
1356 @item Could not open /dev/tap0: No such device
1359 @item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
1360 @item You forgot to compile `Netlink device emulation' in the kernel.
1363 @item Can't write to /dev/misc/net/tun: No such device
1366 @item You forgot to `modprobe tun'.
1367 @item You forgot to compile `Universal TUN/TAP driver' in the kernel.
1370 @item Packet with destination 1.2.3.4 is looping back to us!
1373 @item Something is not configured right. Packets are being sent out to the
1374 virtual network device, but according to the Subnet directives in your host configuration
1375 file, those packets should go to your own host. Most common mistake is that
1376 you have a Subnet line in your host configuration file with a netmask which is
1377 just as large as the netmask of the virtual network interface. The latter should in almost all
1378 cases be larger. Rethink your configuration.
1379 Note that you will only see this message if you specified a debug
1380 level of 5 or higher!
1381 @item Chances are that a `Subnet = ...' line in the host configuration file of this tinc daemon is wrong.
1382 Change it to a subnet that is accepted locally by another interface,
1383 or if that is not the case, try changing the prefix length into /32.
1386 @item Network doesn't work, syslog shows only packets of length 46
1390 Jan 1 12:00:00 host tinc.net[1234]: Read packet of length 46 from tap device
1391 Jan 1 12:00:00 host tinc.net[1234]: Trying to look up 0.0.192.168 in connection list failed!
1394 @item Add the `ifconfig $INTERFACE -arp' to tinc-up.
1397 @item Network address and subnet mask do not match!
1400 @item The Subnet field must contain a @emph{network} address.
1401 @item If you only want to use one IP address, set the netmask to /32.
1404 @item This is a bug: net.c:253: 24: Some error
1407 @item This is something that should not have happened.
1408 Please report this, and tell us exactly what went wrong before you got
1409 this message. In normal operation, these errors should not occur.
1412 @item Error reading RSA key file `rsa_key.priv': No such file or directory
1415 @item You must specify the complete pathname.
1416 Specifying a relative path does not make sense here. tinc changes its
1417 directory to / when starting (to avoid keeping a mount point busy); and
1418 even if we built in a default directory to look for these files, the key
1419 files are bound to be in a different directory.
1424 @c ==================================================================
1425 @node Technical information, About us, Running tinc, Top
1426 @chapter Technical information
1431 * The meta-protocol::
1436 @c ==================================================================
1437 @node The connection, The meta-protocol, Technical information, Technical information
1438 @section The connection
1441 tinc is a daemon that takes VPN data and transmit that to another host
1442 computer over the existing Internet infrastructure.
1446 * The meta-connection::
1450 @c ==================================================================
1451 @node The UDP tunnel, The meta-connection, The connection, The connection
1452 @subsection The UDP tunnel
1454 @cindex virtual network device
1456 The data itself is read from a character device file, the so-called
1457 @emph{virtual network device}. This device is associated with a network
1458 interface. Any data sent to this interface can be read from the device,
1459 and any data written to the device gets sent from the interface. Data to
1460 and from the device is formatted as if it were a normal Ethernet card,
1461 so a frame is preceded by two MAC addresses and a @emph{frame type}
1464 So when tinc reads an Ethernet frame from the device, it determines its
1465 type. When tinc is in it's default routing mode, it can handle IPv4 and IPv6
1466 packets. Depending on the Subnet lines, it will send the packets off to their destination.
1467 In the `switch' and `hub' mode, tinc will use broadcasts and MAC address discovery
1468 to deduce the destination of the packets.
1469 Since the latter modes only depend on the link layer information,
1470 any protocol that runs over Ethernet is supported (for instance IPX and Appletalk).
1472 After the destination has been determined, a sequence number will be added to the packet.
1473 The packet will then be encrypted and a message authentication
1474 code will be appended.
1476 @cindex encapsulating
1478 When that is done, time has come to actually transport the
1479 packet to the destination computer. We do this by sending the packet
1480 over an UDP connection to the destination host. This is called
1481 @emph{encapsulating}, the VPN packet (though now encrypted) is
1482 encapsulated in another IP datagram.
1484 When the destination receives this packet, the same thing happens, only
1485 in reverse. So it checks the message authentication code, decrypts the contents of the UDP datagram,
1486 checks the sequence number
1487 and writes the decrypted information to its own virtual network device.
1489 To let the kernel on the receiving end accept the packet, the destination MAC
1490 address must match that of the virtual network interface.
1491 If tinc is in it's default routing mode, ARP does not work, so the correct destination MAC cannot be set
1492 by the sending daemons.
1493 tinc solves this by always overwriting the
1494 destination MAC address with fe:fd:0:0:0:0. That is also the reason why you must
1495 set the MAC address of your tap interface to that address.
1498 @c ==================================================================
1499 @node The meta-connection, , The UDP tunnel, The connection
1500 @subsection The meta-connection
1502 Having only an UDP connection available is not enough. Though suitable
1503 for transmitting data, we want to be able to reliably send other
1504 information, such as routing and session key information to somebody.
1507 TCP is a better alternative, because it already contains protection
1508 against information being lost, unlike UDP.
1510 So we establish two connections. One for the encrypted VPN data, and one
1511 for other information, the meta-data. Hence, we call the second
1512 connection the meta-connection. We can now be sure that the
1513 meta-information doesn't get lost on the way to another computer.
1515 @cindex data-protocol
1516 @cindex meta-protocol
1517 Like with any communication, we must have a protocol, so that everybody
1518 knows what everything stands for, and how she should react. Because we
1519 have two connections, we also have two protocols. The protocol used for
1520 the UDP data is the ``data-protocol,'' the other one is the
1523 The reason we don't use TCP for both protocols is that UDP is much
1524 better for encapsulation, even while it is less reliable. The real
1525 problem is that when TCP would be used to encapsulate a TCP stream
1526 that's on the private network, for every packet sent there would be
1527 three ACKs sent instead of just one. Furthermore, if there would be
1528 a timeout, both TCP streams would sense the timeout, and both would
1529 start re-sending packets.
1532 @c ==================================================================
1533 @node The meta-protocol, Security, The connection, Technical information
1534 @section The meta-protocol
1536 The meta protocol is used to tie all tinc daemons together, and
1537 exchange information about which tinc daemon serves which virtual
1540 The meta protocol consists of requests that can be sent to the other
1541 side. Each request has a unique number and several parameters. All
1542 requests are represented in the standard ASCII character set. It is
1543 possible to use tools such as telnet or netcat to connect to a tinc
1544 daemon and to read and write requests by hand, provided that one
1545 understands the numeric codes sent.
1547 The authentication scheme is described in @ref{Authentication protocol}. After a
1548 successful authentication, the server and the client will exchange all the
1549 information about other tinc daemons and subnets they know of, so that both
1550 sides (and all the other tinc daemons behind them) have their information
1557 --------------------------------------------------------------------------
1558 origin ADD_EDGE node1 12.23.34.45 655 node2 21.32.43.54 655 222 0
1559 | | | \___________________/ | +-> options
1560 | | | | +----> weight
1561 | | | +----------------> see below
1563 | +----------> real address
1564 +------------------> name of node on one side of the edge
1566 origin ADD_SUBNET node 192.168.1.0/24
1568 | +--------> IPv4 network address
1569 +------------------> owner of this subnet
1570 --------------------------------------------------------------------------
1574 In case a connection between two daemons is closed or broken, DEL_EDGE messages
1575 are sent to inform the other daemons of that fact. Each daemon will calculate a
1576 new route to the the daemons, or mark them unreachable if there isn't any.
1578 The keys used to encrypt VPN packets are not sent out directly. This is
1579 because it would generate a lot of traffic on VPNs with many daemons, and
1580 chances are that not every tinc daemon will ever send a packet to every
1581 other daemon. Instead, if a daemon needs a key it sends a request for it
1582 via the meta connection of the nearest hop in the direction of the
1583 destination. If any hop on the way has already learned the key, it will
1584 act as a proxy and forward its copy back to the requester.
1591 --------------------------------------------------------------------------
1592 daemon REQ_KEY origin destination
1593 | +--> name of the tinc daemon it wants the key from
1594 +----------> name of the daemon that wants the key
1596 daemon ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
1597 | | \______________/ | | +--> MAC length
1598 | | | | +-----> digest algorithm
1599 | | | +--------> cipher algorithm
1600 | | +--> 128 bits key
1601 | +--> name of the daemon that wants the key
1602 +----------> name of the daemon that uses this key
1604 daemon KEY_CHANGED origin
1605 +--> daemon that has changed it's packet key
1606 --------------------------------------------------------------------------
1609 There is also a mechanism to check if hosts are still alive. Since network
1610 failures or a crash can cause a daemon to be killed without properly
1611 shutting down the TCP connection, this is necessary to keep an up to date
1612 connection list. PINGs are sent at regular intervals, except when there
1613 is also some other traffic. A little bit of salt (random data) is added
1614 with each PING and PONG message, to make sure that long sequences of PING/PONG
1615 messages without any other traffic won't result in known plaintext.
1621 --------------------------------------------------------------------------
1624 --------------------------------------------------------------------------
1627 This basically covers what is sent over the meta connection by
1631 @c ==================================================================
1632 @node Security, , The meta-protocol, Technical information
1633 @section About tinc's encryption and other security-related issues.
1637 tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
1638 alleged Cabal was/is an organisation that was said to keep an eye on the
1639 entire Internet. As this is exactly what you @emph{don't} want, we named
1640 the tinc project after TINC.
1643 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
1644 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
1645 exactly that: encrypt.
1646 tinc uses blowfish encryption in CBC mode, sequence numbers and message authentication codes
1647 to make sure eavesdroppers cannot get and cannot change any information at all from the packets they can intercept.
1650 * Authentication protocol::
1651 * Encryption of network packets::
1655 @c ==================================================================
1656 @node Authentication protocol, Encryption of network packets, Security, Security
1657 @subsection Authentication protocol
1659 @cindex authentication
1660 A new scheme for authentication in tinc has been devised, which offers some
1661 improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
1671 --------------------------------------------------------------------------
1672 client <attempts connection>
1674 server <accepts connection>
1678 +-------> name of tinc daemon
1682 +-------> name of tinc daemon
1684 client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
1685 \_________________________________/
1686 +-> RSAKEYLEN bits totally random string S1,
1687 encrypted with server's public RSA key
1689 server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
1690 \_________________________________/
1691 +-> RSAKEYLEN bits totally random string S2,
1692 encrypted with client's public RSA key
1695 - the client will symmetrically encrypt outgoing traffic using S1
1696 - the server will symmetrically encrypt outgoing traffic using S2
1698 client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
1699 \_________________________________/
1700 +-> CHALLEN bits totally random string H1
1702 server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
1703 \_________________________________/
1704 +-> CHALLEN bits totally random string H2
1706 client CHAL_REPLY 816a86
1707 +-> 160 bits SHA1 of H2
1709 server CHAL_REPLY 928ffe
1710 +-> 160 bits SHA1 of H1
1712 After the correct challenge replies are received, both ends have proved
1713 their identity. Further information is exchanged.
1715 client ACK 655 12.23.34.45 123 0
1717 | | +----> estimated weight
1718 | +------------> IP address of server as seen by client
1719 +--------------------> UDP port of client
1721 server ACK 655 21.32.43.54 321 0
1723 | | +----> estimated weight
1724 | +------------> IP address of client as seen by server
1725 +--------------------> UDP port of server
1726 --------------------------------------------------------------------------
1729 This new scheme has several improvements, both in efficiency and security.
1731 First of all, the server sends exactly the same kind of messages over the wire
1732 as the client. The previous versions of tinc first authenticated the client,
1733 and then the server. This scheme even allows both sides to send their messages
1734 simultaneously, there is no need to wait for the other to send something first.
1735 This means that any calculations that need to be done upon sending or receiving
1736 a message can also be done in parallel. This is especially important when doing
1737 RSA encryption/decryption. Given that these calculations are the main part of
1738 the CPU time spent for the authentication, speed is improved by a factor 2.
1740 Second, only one RSA encrypted message is sent instead of two. This reduces the
1741 amount of information attackers can see (and thus use for a cryptographic
1742 attack). It also improves speed by a factor two, making the total speedup a
1745 Third, and most important:
1746 The symmetric cipher keys are exchanged first, the challenge is done
1747 afterwards. In the previous authentication scheme, because a man-in-the-middle
1748 could pass the challenge/chal_reply phase (by just copying the messages between
1749 the two real tinc daemons), but no information was exchanged that was really
1750 needed to read the rest of the messages, the challenge/chal_reply phase was of
1751 no real use. The man-in-the-middle was only stopped by the fact that only after
1752 the ACK messages were encrypted with the symmetric cipher. Potentially, it
1753 could even send it's own symmetric key to the server (if it knew the server's
1754 public key) and read some of the metadata the server would send it (it was
1755 impossible for the mitm to read actual network packets though). The new scheme
1756 however prevents this.
1758 This new scheme makes sure that first of all, symmetric keys are exchanged. The
1759 rest of the messages are then encrypted with the symmetric cipher. Then, each
1760 side can only read received messages if they have their private key. The
1761 challenge is there to let the other side know that the private key is really
1762 known, because a challenge reply can only be sent back if the challenge is
1763 decrypted correctly, and that can only be done with knowledge of the private
1766 Fourth: the first thing that is send via the symmetric cipher encrypted
1767 connection is a totally random string, so that there is no known plaintext (for
1768 an attacker) in the beginning of the encrypted stream.
1771 @c ==================================================================
1772 @node Encryption of network packets, , Authentication protocol, Security
1773 @subsection Encryption of network packet
1776 A data packet can only be sent if the encryption key is known to both
1777 parties, and the connection is activated. If the encryption key is not
1778 known, a request is sent to the destination using the meta connection
1779 to retrieve it. The packet is stored in a queue while waiting for the
1783 The UDP packet containing the network packet from the VPN has the following layout:
1786 ... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
1787 \___________________/\_____/
1789 V +---> digest algorithm
1790 Encrypted with symmetric cipher
1793 So, the entire VPN packet is encrypted using a symmetric cipher. A 32 bits
1794 sequence number is added in front of the actual VPN packet, to act as a unique
1795 IV for each packet and to prevent replay attacks. A message authentication code
1796 is added to the UDP packet to prevent alteration of packets. By default the
1797 first 4 bytes of the digest are used for this, but this can be changed using
1798 the MACLength configuration variable.
1800 @c ==================================================================
1801 @node About us, Concept Index, Technical information, Top
1806 * Contact Information::
1811 @c ==================================================================
1812 @node Contact Information, Authors, About us, About us
1813 @section Contact information
1816 tinc's website is at @url{http://tinc.nl.linux.org/},
1817 this server is located in the Netherlands.
1820 We have an IRC channel on the Open Projects IRC network. Connect to
1821 @uref{http://openprojects.nu/services/irc.html, irc.openprojects.net},
1822 and join channel #tinc.
1825 @c ==================================================================
1826 @node Authors, , Contact Information, About us
1830 @item Ivo Timmermans (zarq) (@email{itimmermans@@bigfoot.com})
1831 Main coder/hacker and maintainer of the package.
1833 @item Guus Sliepen (guus) (@email{guus@@sliepen.warande.net})
1834 Originator of it all, co-author.
1836 @item Wessel Dankers (Ubiq) (@email{wsl@@nl.linux.org})
1837 For the name `tinc' and various suggestions.
1841 We have received a lot of valuable input from users. With their help,
1842 tinc has become the flexible and robust tool that it is today. We have
1843 composed a list of contributions, in the file called @file{THANKS} in
1844 the source distribution.
1847 @c ==================================================================
1848 @node Concept Index, , About us, Top
1849 @c node-name, next, previous, up
1850 @unnumbered Concept Index
1852 @c ==================================================================
1856 @c ==================================================================