1 \input texinfo @c -*-texinfo-*-
2 @c $Id: tinc.texi,v 1.8.4.32 2002/09/15 22:19:37 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 <ivo@@o2w.nl>, Guus Sliepen <guus@@sliepen.eu.org> and
19 Wessel Dankers <wsl@@nl.linux.org>.
21 $Id: tinc.texi,v 1.8.4.32 2002/09/15 22:19:37 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 <ivo@@o2w.nl>, Guus Sliepen <guus@@sliepen.eu.org> and
44 Wessel Dankers <wsl@@nl.linux.org>.
46 $Id: tinc.texi,v 1.8.4.32 2002/09/15 22:19:37 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.
224 Tunneling IPv6 packets may not work on OpenBSD.
227 @c ==================================================================
230 @c ==================================================================
234 tinc on NetBSD relies on the tun driver for its data
235 acquisition from the kernel. It has been verified to work under at least NetBSD 1.5.2.
237 Tunneling IPv6 does not work on OpenBSD.
240 @c ==================================================================
244 tinc on Solaris relies on the universal tun/tap driver for its data
245 acquisition from the kernel. Therefore, tinc will work on the same platforms
246 as this driver. These are: Solaris 8 (SunOS 5.8).
248 IPv6 packets cannot be tunneled on Solaris.
250 @c ==================================================================
251 @subsection Darwin (MacOS/X)
255 tinc on Darwin relies on the tunnel driver for its data
256 acquisition from the kernel. This driver is not part of Darwin but can be
257 downloaded from @uref{http://chrisp.de/en/projects/tunnel.html}.
259 IPv6 packets cannot be tunneled on Darwin.
268 @c Preparing your system
275 @c ==================================================================
276 @node Preparations, Installation, Introduction, Top
277 @chapter Preparations
279 This chapter contains information on how to prepare your system to
283 * Configuring the kernel::
288 @c ==================================================================
289 @node Configuring the kernel, Libraries, Preparations, Preparations
290 @section Configuring the kernel
297 If you are running Linux, chances are good that your kernel already supports
298 all the devices that tinc needs for proper operation. For example, the
299 standard kernel from Redhat Linux already has support for ethertap and netlink
300 compiled in. Debian users can use the modconf utility to select the modules.
301 If your Linux distribution supports this method of selecting devices, look out
302 for something called `ethertap', and `netlink_dev' if it is using a kernel
303 version prior to 2.4.0. In that case you will need both these devices. If you
304 are using kernel 2.4.0 or later, you need to select `tun'.
307 If you can install these devices in a similar manner, you may skip this section.
308 Otherwise, you will have to recompile the kernel in order to turn on the required features.
309 If you are unfamiliar with the process of configuring and compiling a new kernel,
310 you should read the @uref{http://howto.linuxberg.com/LDP/HOWTO/Kernel-HOWTO.html, Kernel HOWTO} first.
313 * Configuration of Linux kernels 2.1.60 up to 2.4.0::
314 * Configuration of Linux kernels 2.4.0 and higher::
315 * Configuration of FreeBSD kernels::
316 * Configuration of OpenBSD kernels::
317 * Configuration of NetBSD kernels::
318 * Configuration of Solaris kernels::
319 * Configuration of Darwin (MacOS/X) kernels::
323 @c ==================================================================
324 @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
325 @subsection Configuration of Linux kernels 2.1.60 up to 2.4.0
327 Here are the options you have to turn on when configuring a new kernel:
330 Code maturity level options
331 [*] Prompt for development and/or incomplete code/drivers
333 [*] Kernel/User netlink socket
334 <M> Netlink device emulation
335 Network device support
336 <M> Ethertap network tap
339 If you want to run more than one instance of tinc or other programs that use
340 the ethertap, you have to compile the ethertap driver as a module, otherwise
341 you can also choose to compile it directly into the kernel.
343 If you decide to build any of these as dynamic kernel modules, it's a good idea
344 to add these lines to @file{/etc/modules.conf}:
347 alias char-major-36 netlink_dev
349 options tap0 -o tap0 unit=0
351 options tap1 -o tap1 unit=1
353 alias tap@emph{N} ethertap
354 options tap@emph{N} -o tap@emph{N} unit=@emph{N}
357 Add as much alias/options lines as necessary.
360 @c ==================================================================
361 @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
362 @subsection Configuration of Linux kernels 2.4.0 and higher
364 Here are the options you have to turn on when configuring a new kernel:
367 Code maturity level options
368 [*] Prompt for development and/or incomplete code/drivers
369 Network device support
370 <M> Universal tun/tap device driver support
373 It's not necessary to compile this driver as a module, even if you are going to
374 run more than one instance of tinc.
376 If you have an early 2.4 kernel, you can choose both the tun/tap driver and the
377 `Ethertap network tap' device. This latter is marked obsolete, and chances are
378 that it won't even function correctly anymore. Make sure you select the
379 universal tun/tap driver.
381 If you decide to build the tun/tap driver as a kernel module, add these lines
382 to @file{/etc/modules.conf}:
385 alias char-major-10-200 tun
389 @c ==================================================================
390 @node Configuration of FreeBSD kernels, Configuration of OpenBSD kernels, Configuration of Linux kernels 2.4.0 and higher, Configuring the kernel
391 @subsection Configuration of FreeBSD kernels
393 This section will contain information on how to configure your FreeBSD
394 kernel to support the universal tun/tap device. For 4.1 and higher
395 versions, this is included in the default kernel configuration, for earlier
396 systems (4.0 and earlier), you need to install the universal tun/tap driver
399 Unfortunately somebody still has to write the text.
402 @c ==================================================================
403 @node Configuration of OpenBSD kernels, Configuration of NetBSD kernels, Configuration of FreeBSD kernels, Configuring the kernel
404 @subsection Configuration of OpenBSD kernels
406 This section will contain information on how to configure your OpenBSD
407 kernel to support the tun device. For 2.9 and 3.0 systems,
408 this is included in the default kernel configuration.
410 Unfortunately somebody still has to write the text.
413 @c ==================================================================
414 @node Configuration of NetBSD kernels, Configuration of Solaris kernels, Configuration of OpenBSD kernels, Configuring the kernel
415 @subsection Configuration of NetBSD kernels
417 This section will contain information on how to configure your NetBSD
418 kernel to support the tun device. For 1.5.2 systems,
419 this is included in the default kernel configuration.
421 Unfortunately somebody still has to write the text.
424 @c ==================================================================
425 @node Configuration of Solaris kernels, Configuration of Darwin (MacOS/X) kernels, Configuration of NetBSD kernels, Configuring the kernel
426 @subsection Configuration of Solaris kernels
428 This section will contain information on how to configure your Solaris
429 kernel to support the universal tun/tap device. For Solaris 8 (SunOS 5.8),
430 this is included in the default kernel configuration.
432 Unfortunately somebody still has to write the text.
435 @c ==================================================================
436 @node Configuration of Darwin (MacOS/X) kernels, , Configuration of Solaris kernels, Configuring the kernel
437 @subsection Configuration of Darwin (MacOS/X) kernels
439 Darwin does not come with a tunnel driver. You must download it at
440 @uref{http://chrisp.de/en/projects/tunnel.html}. If compiling the source fails,
441 try the binary module. The tunnel driver must be loaded before starting tinc
442 with the following command:
448 Once loaded, the tunnel driver will automatically create @file{/dev/tun0}..@file{/dev/tun3}
449 and the corresponding network interfaces.
452 @c ==================================================================
453 @node Libraries, , Configuring the kernel, Preparations
458 Before you can configure or build tinc, you need to have the OpenSSL
459 and zlib libraries installed on your system. If you try to configure tinc without
460 having them installed, configure will give you an error message, and stop.
468 @c ==================================================================
469 @node OpenSSL, zlib, Libraries, Libraries
473 For all cryptography-related functions, tinc uses the functions provided
474 by the OpenSSL library.
476 If this library is not installed, you wil get an error when configuring
477 tinc for build. Support for running tinc without having OpenSSL
478 installed @emph{may} be added in the future.
480 You can use your operating system's package manager to install this if
481 available. Make sure you install the development AND runtime versions
484 If you have to install OpenSSL manually, you can get the source code
485 from @url{http://www.openssl.org/}. Instructions on how to configure,
486 build and install this package are included within the package. Please
487 make sure you build development and runtime libraries (which is the
490 If you installed the OpenSSL libraries from source, it may be necessary
491 to let configure know where they are, by passing configure one of the
492 --with-openssl-* parameters.
495 --with-openssl=DIR OpenSSL library and headers prefix
496 --with-openssl-include=DIR OpenSSL headers directory
497 (Default is OPENSSL_DIR/include)
498 --with-openssl-lib=DIR OpenSSL library directory
499 (Default is OPENSSL_DIR/lib)
503 @subsubheading License
506 Since the license under which OpenSSL is distributed is not directly
507 compatible with the terms of the GNU GPL
508 @uref{http://www.openssl.org/support/faq.html#LEGAL2}, therefore we
509 include an addition to the GPL (see also the file COPYING.README):
512 This program is released under the GPL with the additional exemption
513 that compiling, linking, and/or using OpenSSL is allowed. You may
514 provide binary packages linked to the OpenSSL libraries, provided that
515 all other requirements of the GPL are met.
519 @c ==================================================================
520 @node zlib, , OpenSSL, Libraries
524 For the optional compression of UDP packets, tinc uses the functions provided
527 If this library is not installed, you wil get an error when configuring
528 tinc for build. Support for running tinc without having zlib
529 installed @emph{may} be added in the future.
531 You can use your operating system's package manager to install this if
532 available. Make sure you install the development AND runtime versions
535 If you have to install zlib manually, you can get the source code
536 from @url{http://www.gzip.org/zlib/}. Instructions on how to configure,
537 build and install this package are included within the package. Please
538 make sure you build development and runtime libraries (which is the
551 @c ==================================================================
552 @node Installation, Configuration, Preparations, Top
553 @chapter Installation
555 If you use Debian, you may want to install one of the
556 precompiled packages for your system. These packages are equipped with
557 system startup scripts and sample configurations.
559 If you cannot use one of the precompiled packages, or you want to compile tinc
560 for yourself, you can use the source. The source is distributed under
561 the GNU General Public License (GPL). Download the source from the
562 @uref{http://tinc.nl.linux.org/download.html, download page}, which has
563 the checksums of these files listed; you may wish to check these with
564 md5sum before continuing.
566 tinc comes in a convenient autoconf/automake package, which you can just
567 treat the same as any other package. Which is just untar it, type
568 `./configure' and then `make'.
569 More detailed instructions are in the file @file{INSTALL}, which is
570 included in the source distribution.
573 * Building and installing tinc::
578 @c ==================================================================
579 @node Building and installing tinc, System files, Installation, Installation
580 @section Building and installing tinc
582 Detailed instructions on configuring the source, building tinc and installing tinc
583 can be found in the file called @file{INSTALL}.
585 @cindex binary package
586 If you happen to have a binary package for tinc for your distribution,
587 you can use the package management tools of that distribution to install tinc.
588 The documentation that comes along with your distribution will tell you how to do that.
591 * Darwin (MacOS/X) build environment::
595 @c ==================================================================
596 @node Darwin (MacOS/X) build environment, , , Building and installing tinc
597 @subsection Darwin (MacOS/X) build environment
599 In order to build tinc on Darwin, you need to install the MacOS/X Developer Tools
600 from @uref{http://developer.apple.com/tools/macosxtools.html} and
601 a recent version of Fink from @uref{http://fink.sourceforge.net/}.
603 After installation use fink to download and install the following packages:
604 autoconf25, automake, dlcompat, m4, openssl and zlib.
607 @c ==================================================================
608 @node System files, , Building and installing tinc, Installation
609 @section System files
611 Before you can run tinc, you must make sure you have all the needed
612 files on your system.
620 @c ==================================================================
621 @node Device files, Other files, System files, System files
622 @subsection Device files
625 First, you'll need the special device file(s) that form the interface
626 between the kernel and the daemon.
628 The permissions for these files have to be such that only the super user
629 may read/write to this file. You'd want this, because otherwise
630 eavesdropping would become a bit too easy. This does, however, imply
631 that you'd have to run tincd as root.
633 If you use Linux and have a kernel version prior to 2.4.0, you have to make the
637 mknod -m 600 /dev/tap0 c 36 16
638 mknod -m 600 /dev/tap1 c 36 17
640 mknod -m 600 /dev/tap@emph{N} c 36 @emph{N+16}
643 There is a maximum of 16 ethertap devices.
645 If you use the universal tun/tap driver, you have to create the
646 following device file (unless it already exist):
649 mknod -m 600 /dev/tun c 10 200
652 If you use Linux, and you run the new 2.4 kernel using the devfs filesystem,
653 then the tun/tap device will probably be automatically generated as
656 Unlike the ethertap device, you do not need multiple device files if
657 you are planning to run multiple tinc daemons.
660 @c ==================================================================
661 @node Other files, , Device files, System files
662 @subsection Other files
664 @subsubheading @file{/etc/networks}
666 You may add a line to @file{/etc/networks} so that your VPN will get a
667 symbolic name. For example:
673 @subsubheading @file{/etc/services}
676 You may add this line to @file{/etc/services}. The effect is that you
677 may supply a @samp{tinc} as a valid port number to some programs. The
678 number 655 is registered with the IANA.
683 # Ivo Timmermans <ivo@@o2w.nl>
698 @c ==================================================================
699 @node Configuration, Running tinc, Installation, Top
700 @chapter Configuration
703 * Configuration introduction::
704 * Multiple networks::
705 * How connections work::
706 * Configuration files::
707 * Generating keypairs::
708 * Network interfaces::
709 * Example configuration::
712 @c ==================================================================
713 @node Configuration introduction, Multiple networks, Configuration, Configuration
714 @section Configuration introduction
716 @cindex Network Administrators Guide
717 Before actually starting to configure tinc and editing files,
718 make sure you have read this entire section so you know what to expect.
719 Then, make it clear to yourself how you want to organize your VPN:
720 What are the nodes (computers running tinc)?
721 What IP addresses/subnets do they have?
722 What is the network mask of the entire VPN?
723 Do you need special firewall rules?
724 Do you have to set up masquerading or forwarding rules?
725 These questions can only be answered by yourself,
726 you will not find the answers in this documentation.
727 Make sure you have an adequate understanding of networks in general.
728 A good resource on networking is the
729 @uref{http://www.linuxdoc.org/LDP/nag2/, Linux Network Administrators Guide}.
731 If you have everything clearly pictured in your mind,
732 proceed in the following order:
733 First, generate the configuration files (@file{tinc.conf}, your host configuration file, @file{tinc-up} and perhaps @file{tinc-down}).
734 Then generate the keypairs.
735 Finally, distribute the host configuration files.
736 These steps are described in the subsections below.
739 @c ==================================================================
740 @node Multiple networks, How connections work, Configuration introduction, Configuration
741 @section Multiple networks
743 @cindex multiple networks
745 In order to allow you to run more than one tinc daemon on one computer,
746 for instance if your computer is part of more than one VPN,
747 you can assign a ``netname'' to your VPN.
748 It is not required if you only run one tinc daemon,
749 it doesn't even have to be the same on all the sites of your VPN,
750 but it is recommended that you choose one anyway.
752 We will asume you use a netname throughout this document.
753 This means that you call tincd with the -n argument,
754 which will assign a netname to this daemon.
756 The effect of this is that the daemon will set its configuration
757 ``root'' to /etc/tinc/netname/, where netname is your argument to the -n
758 option. You'll notice that it appears in syslog as ``tinc.netname''.
760 However, it is not strictly necessary that you call tinc with the -n
761 option. In this case, the network name would just be empty, and it will
762 be used as such. tinc now looks for files in /etc/tinc/, instead of
763 /etc/tinc/netname/; the configuration file should be /etc/tinc/tinc.conf,
764 and the host configuration files are now expected to be in /etc/tinc/hosts/.
766 But it is highly recommended that you use this feature of tinc, because
767 it will be so much clearer whom your daemon talks to. Hence, we will
768 assume that you use it.
771 @c ==================================================================
772 @node How connections work, Configuration files, Multiple networks, Configuration
773 @section How connections work
775 When tinc starts up, it parses the command-line options and then
776 reads in the configuration file tinc.conf.
777 If it sees one or more `ConnectTo' values pointing to other tinc daemons in that file,
778 it will try to connect to those other daemons.
779 Whether this succeeds or not and whether `ConnectTo' is specified or not,
780 tinc will listen for incoming connection from other deamons.
781 If you did specify a `ConnectTo' value and the other side is not responding,
782 tinc will keep retrying.
783 This means that once started, tinc will stay running until you tell it to stop,
784 and failures to connect to other tinc daemons will not stop your tinc daemon
785 for trying again later.
786 This means you don't have to intervene if there are temporary network problems.
790 There is no real distinction between a server and a client in tinc.
791 If you wish, you can view a tinc daemon without a `ConnectTo' value as a server,
792 and one which does specify such a value as a client.
793 It does not matter if two tinc daemons have a `ConnectTo' value pointing to each other however.
796 @c ==================================================================
797 @node Configuration files, Generating keypairs, How connections work, Configuration
798 @section Configuration files
800 The actual configuration of the daemon is done in the file
801 @file{/etc/tinc/netname/tinc.conf} and at least one other file in the directory
802 @file{/etc/tinc/netname/hosts/}.
804 These file consists of comments (lines started with a #) or assignments
811 The variable names are case insensitive, and any spaces, tabs, newlines
812 and carriage returns are ignored. Note: it is not required that you put
813 in the `=' sign, but doing so improves readability. If you leave it
814 out, remember to replace it with at least one space character.
816 In this section all valid variables are listed in alphabetical order.
817 The default value is given between parentheses,
818 other comments are between square brackets and
819 required directives are given in @strong{bold}.
822 * Main configuration variables::
823 * Host configuration variables::
828 @c ==================================================================
829 @node Main configuration variables, Host configuration variables, Configuration files, Configuration files
830 @subsection Main configuration variables
833 @cindex AddressFamily
834 @item AddressFamily = <ipv4|ipv6|any> (ipv4) [experimental]
835 This option affects the address family of listening and outgoing sockets.
836 If "any" is selected, then depending on the operating system
837 both IPv4 and IPv6 or just IPv6 listening sockets will be created.
839 @cindex BindToInterface
840 @item BindToInterface = <interface> [experimental]
841 If you have more than one network interface in your computer, tinc will
842 by default listen on all of them for incoming connections. It is
843 possible to bind tinc to a single interface like eth0 or ppp0 with this
846 This option may not work on all platforms.
849 @item @strong{ConnectTo = <name>}
850 Specifies which other tinc daemon to connect to on startup.
851 Multiple ConnectTo variables may be specified,
852 in which case outgoing connections to each specified tinc daemon are made.
853 The names should be known to this tinc daemon
854 (i.e., there should be a host configuration file for the name on the ConnectTo line).
856 If you don't specify a host with ConnectTo,
857 tinc won't try to connect to other daemons at all,
858 and will instead just listen for incoming connections.
861 @item @strong{Device = <device>} (/dev/tap0 or /dev/net/tun)
862 The virtual network device to use. Note that you can only use one device per
863 daemon. See also @ref{Device files}.
866 @item Hostnames = <yes|no> (no)
867 This option selects whether IP addresses (both real and on the VPN)
868 should be resolved. Since DNS lookups are blocking, it might affect
869 tinc's efficiency, even stopping the daemon for a few seconds everytime
870 it does a lookup if your DNS server is not responding.
872 This does not affect resolving hostnames to IP addresses from the
876 @item Interface = <interface>
877 Defines the name of the interface corresponding to the virtual network device.
878 Depending on the operating system and the type of device this may or may not actually set the name.
879 Currently this option only affects the Linux tun/tap device.
882 @item Mode = <router|switch|hub> (router)
883 This option selects the way packets are routed to other daemons.
889 variables in the host configuration files will be used to form a routing table.
890 Only unicast packets of routable protocols (IPv4 and IPv6) are supported in this mode.
894 In this mode the MAC addresses of the packets on the VPN will be used to
895 dynamically create a routing table just like an Ethernet switch does.
896 Unicast, multicast and broadcast packets of every protocol that runs over Ethernet are supported in this mode
897 at the cost of frequent broadcast ARP requests and routing table updates.
901 This mode is almost the same as the switch mode, but instead
902 every packet will be broadcast to the other daemons
903 while no routing table is managed.
907 @item KeyExpire = <seconds> (3600)
908 This option controls the time the encryption keys used to encrypt the data
909 are valid. It is common practice to change keys at regular intervals to
910 make it even harder for crackers, even though it is thought to be nearly
911 impossible to crack a single key.
914 @item MACExpire = <seconds> (600)
915 This option controls the amount of time MAC addresses are kept before they are removed.
916 This only has effect when Mode is set to "switch".
919 @item @strong{Name = <name>}
920 This is a symbolic name for this connection. It can be anything
923 @item PingTimeout = <seconds> (60)
924 The number of seconds of inactivity that tinc will wait before sending a
925 probe to the other end. If that other end doesn't answer within that
926 same amount of seconds, the connection is terminated, and the others
927 will be notified of this.
929 @cindex PriorityInheritance
930 @item PriorityInheritance = <yes|no> (no) [experimental]
931 When this option is enabled the value of the TOS field of tunneled IPv4 packets
932 will be inherited by the UDP packets that are sent out.
935 @item PrivateKey = <key> [obsolete]
936 This is the RSA private key for tinc. However, for safety reasons it is
937 advised to store private keys of any kind in separate files. This prevents
938 accidental eavesdropping if you are editting the configuration file.
940 @cindex PrivateKeyFile
941 @item @strong{PrivateKeyFile = <path>} [recommended]
942 This is the full path name of the RSA private key file that was
943 generated by ``tincd --generate-keys''. It must be a full path, not a
946 Note that there must be exactly one of PrivateKey
948 specified in the configuration file.
953 @c ==================================================================
954 @node Host configuration variables, How to configure, Main configuration variables, Configuration files
955 @subsection Host configuration variables
959 @item @strong{Address = <IP address|hostname>} [recommended]
960 This variable is only required if you want to connect to this host. It
961 must resolve to the external IP address where the host can be reached,
962 not the one that is internal to the VPN.
965 @item Cipher = <cipher> (blowfish)
966 The symmetric cipher algorithm used to encrypt UDP packets.
967 Any cipher supported by OpenSSL is recognized.
970 @item Compression = <level> (0)
971 This option sets the level of compression used for UDP packets.
972 Possible values are 0 (off), 1 (fast) and any integer up to 9 (best).
975 @item Digest = <digest> (sha1)
976 The digest algorithm used to authenticate UDP packets.
977 Any digest supported by OpenSSL is recognized.
978 Furthermore, specifying "none" will turn off packet authentication.
981 @item IndirectData = <yes|no> (no)
982 This option specifies whether other tinc daemons besides the one you
983 specified with ConnectTo can make a direct connection to you. This is
984 especially useful if you are behind a firewall and it is impossible to
985 make a connection from the outside to your tinc daemon. Otherwise, it
986 is best to leave this option out or set it to no.
989 @item MACLength = <length> (4)
990 The length of the message authentication code used to authenticate UDP packets.
991 Can be anything from 0
992 up to the length of the digest produced by the digest algorithm.
995 @item Port = <port> (655)
996 This is the port this tinc daemon listens on.
997 You can use decimal portnumbers or symbolic names (as listed in /etc/services).
1000 @item PublicKey = <key> [obsolete]
1001 This is the RSA public key for this host.
1003 @cindex PublicKeyFile
1004 @item PublicKeyFile = <path> [obsolete]
1005 This is the full path name of the RSA public key file that was generated
1006 by ``tincd --generate-keys''. It must be a full path, not a relative
1010 From version 1.0pre4 on tinc will store the public key directly into the
1011 host configuration file in PEM format, the above two options then are not
1012 necessary. Either the PEM format is used, or exactly
1013 @strong{one of the above two options} must be specified
1014 in each host configuration file, if you want to be able to establish a
1015 connection with that host.
1018 @item Subnet = <address[/prefixlength]>
1019 The subnet which this tinc daemon will serve.
1020 tinc tries to look up which other daemon it should send a packet to by searching the appropiate subnet.
1021 If the packet matches a subnet,
1022 it will be sent to the daemon who has this subnet in his host configuration file.
1023 Multiple subnet lines can be specified for each daemon.
1025 Subnets can either be single MAC, IPv4 or IPv6 addresses,
1026 in which case a subnet consisting of only that single address is assumed,
1027 or they can be a IPv4 or IPv6 network address with a prefixlength.
1028 Shorthand notations are not supported.
1029 For example, IPv4 subnets must be in a form like 192.168.1.0/24,
1030 where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
1031 Note that subnets like 192.168.1.1/24 are invalid!
1032 Read a networking HOWTO/FAQ/guide if you don't understand this.
1033 IPv6 subnets are notated like fec0:0:0:1:0:0:0:0/64.
1034 MAC addresses are notated like 0:1a:2b:3c:4d:5e.
1036 @cindex CIDR notation
1037 prefixlength is the number of bits set to 1 in the netmask part; for
1038 example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
1039 /22. This conforms to standard CIDR notation as described in
1040 @uref{ftp://ftp.isi.edu/in-notes/rfc1519.txt, RFC1519}
1043 @item TCPonly = <yes|no> (no) [experimental]
1044 If this variable is set to yes, then the packets are tunnelled over a
1045 TCP connection instead of a UDP connection. This is especially useful
1046 for those who want to run a tinc daemon from behind a masquerading
1047 firewall, or if UDP packet routing is disabled somehow.
1048 Setting this options also implicitly sets IndirectData.
1052 @c ==================================================================
1053 @node How to configure, , Host configuration variables, Configuration files
1054 @subsection How to configure
1056 @subsubheading Step 1. Creating the main configuration file
1058 The main configuration file will be called @file{/etc/tinc/netname/tinc.conf}.
1059 Adapt the following example to create a basic configuration file:
1062 Name = @emph{yourname}
1063 Device = @emph{/dev/tap0}
1064 PrivateKeyFile = /etc/tinc/@emph{netname}/rsa_key.priv
1067 Then, if you know to which other tinc daemon(s) yours is going to connect,
1068 add `ConnectTo' values.
1070 @subsubheading Step 2. Creating your host configuration file
1072 If you added a line containing `Name = yourname' in the main configuarion file,
1073 you will need to create a host configuration file @file{/etc/tinc/netname/hosts/yourname}.
1074 Adapt the following example to create a host configuration file:
1077 Address = @emph{your.real.hostname.org}
1078 Subnet = @emph{192.168.1.0/24}
1081 You can also use an IP address instead of a hostname.
1082 The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
1083 If you have multiple address ranges you can specify more than one `Subnet'.
1084 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).
1087 @c ==================================================================
1088 @node Generating keypairs, Network interfaces, Configuration files, Configuration
1089 @section Generating keypairs
1091 @cindex key generation
1092 Now that you have already created the main configuration file and your host configuration file,
1093 you can easily create a public/private keypair by entering the following command:
1096 tincd -n @emph{netname} -K
1099 tinc will generate a public and a private key and ask you where to put them.
1100 Just press enter to accept the defaults.
1103 @c ==================================================================
1104 @node Network interfaces, Example configuration, Generating keypairs, Configuration
1105 @section Network interfaces
1107 Before tinc can start transmitting data over the tunnel, it must
1108 set up the virtual network interface.
1110 First, decide which IP addresses you want to have associated with these
1111 devices, and what network mask they must have.
1113 tinc will open a virtual network device (@file{/dev/tun}, @file{/dev/tap0} or similar),
1114 which will also create a network interface called something like `tun0', `tap0', or,
1115 if you are using the Linux tun/tap driver, the network interface will by default have the same name as the netname.
1118 You can configure the network interface by putting ordinary ifconfig, route, and other commands
1119 to a script named @file{/etc/tinc/netname/tinc-up}. When tinc starts, this script
1120 will be executed. When tinc exits, it will execute the script named
1121 @file{/etc/tinc/netname/tinc-down}, but normally you don't need to create that script.
1123 An example @file{tinc-up} script:
1127 ifconfig $INTERFACE hw ether fe:fd:0:0:0:0
1128 ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0
1129 ifconfig $INTERFACE -arp
1133 @cindex hardware address
1134 The first line sets up the MAC address of the network interface.
1135 Due to the nature of how Ethernet and tinc work, it has to be set to fe:fd:0:0:0:0
1136 for tinc to work in it's normal mode.
1137 If you configured tinc to work in `switch' or `hub' mode, the hardware address should instead
1138 be set to a unique address instead of fe:fd:0:0:0:0.
1140 You can use the environment variable $INTERFACE to get the name of the interface.
1141 However, this might not be reliable. If in doubt, use the name of the interface explicitly.
1144 The next line gives the interface an IP address and a netmask.
1145 The kernel will also automatically add a route to this interface, so normally you don't need
1146 to add route commands to the @file{tinc-up} script.
1147 The kernel will also bring the interface up after this command.
1149 The netmask is the mask of the @emph{entire} VPN network, not just your
1153 The last line tells the kernel not to use ARP on that interface.
1154 Again this has to do with how Ethernet and tinc work.
1155 Use this option only if you are running tinc under Linux and are using tinc's normal routing mode.
1158 @c ==================================================================
1159 @node Example configuration, , Network interfaces, Configuration
1160 @section Example configuration
1164 Imagine the following situation. Branch A of our example `company' wants to connect
1165 three branch offices in B, C and D using the Internet. All four offices
1166 have a 24/7 connection to the Internet.
1168 A is going to serve as the center of the network. B and C will connect
1169 to A, and D will connect to C. Each office will be assigned their own IP
1173 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
1174 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
1175 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
1176 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
1179 ``gateway'' is the VPN IP address of the machine that is running the
1180 tincd. ``internet IP'' is the IP address of the firewall, which does not
1181 need to run tincd, but it must do a port forwarding of TCP&UDP on port
1182 655 (unless otherwise configured).
1184 In this example, it is assumed that eth0 is the interface that points to
1185 the inner (physical) LAN of the office, although this could also be the
1186 same as the interface that leads to the Internet. The configuration of
1187 the real interface is also shown as a comment, to give you an idea of
1188 how these example host is set up. All branches use the netname `company'
1189 for this particular VPN.
1191 @subsubheading For Branch A
1193 @emph{BranchA} would be configured like this:
1195 In @file{/etc/tinc/company/tinc-up}:
1198 # Real interface of internal network:
1199 # ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
1201 ifconfig tap0 hw ether fe:fd:0:0:0:0
1202 ifconfig tap0 10.1.54.1 netmask 255.0.0.0
1206 and in @file{/etc/tinc/company/tinc.conf}:
1210 PrivateKey = /etc/tinc/company/rsa_key.priv
1214 On all hosts, /etc/tinc/company/hosts/BranchA contains:
1217 Subnet = 10.1.0.0/16
1220 Note that the IP addresses of eth0 and tap0 are the same.
1221 This is quite possible, if you make sure that the netmasks of the interfaces are different.
1222 It is in fact recommended to give give both real internal network interfaces and tap interfaces the same IP address,
1223 since that will make things a lot easier to remember and set up.
1225 -----BEGIN RSA PUBLIC KEY-----
1227 -----END RSA PUBLIC KEY-----
1231 @subsubheading For Branch B
1233 In @file{/etc/tinc/company/tinc-up}:
1236 # Real interface of internal network:
1237 # ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
1239 ifconfig tap0 hw ether fe:fd:0:0:0:0
1240 ifconfig tap0 10.2.1.12 netmask 255.0.0.0
1244 and in @file{/etc/tinc/company/tinc.conf}:
1249 PrivateKey = /etc/tinc/company/rsa_key.priv
1252 Note here that the internal address (on eth0) doesn't have to be the
1253 same as on the tap0 device. Also, ConnectTo is given so that no-one can
1254 connect to this node.
1256 On all hosts, in @file{/etc/tinc/company/hosts/BranchB}:
1259 Subnet = 10.2.0.0/16
1262 -----BEGIN RSA PUBLIC KEY-----
1264 -----END RSA PUBLIC KEY-----
1268 @subsubheading For Branch C
1270 In @file{/etc/tinc/company/tinc-up}:
1273 # Real interface of internal network:
1274 # ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
1276 ifconfig tap1 hw ether fe:fd:0:0:0:0
1277 ifconfig tap1 10.3.69.254 netmask 255.0.0.0
1281 and in @file{/etc/tinc/company/tinc.conf}:
1289 C already has another daemon that runs on port 655, so they have to
1290 reserve another port for tinc. It knows the portnumber it has to listen on
1291 from it's own host configuration file.
1293 On all hosts, in @file{/etc/tinc/company/hosts/BranchC}:
1297 Subnet = 10.3.0.0/16
1300 -----BEGIN RSA PUBLIC KEY-----
1302 -----END RSA PUBLIC KEY-----
1306 @subsubheading For Branch D
1308 In @file{/etc/tinc/company/tinc-up}:
1311 # Real interface of internal network:
1312 # ifconfig eth0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
1314 ifconfig company hw ether fe:fd:0:0:0:0
1315 ifconfig company 10.4.3.32 netmask 255.0.0.0
1316 ifconfig company -arp
1319 and in @file{/etc/tinc/company/tinc.conf}:
1324 Device = /dev/net/tun
1325 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1328 D will be connecting to C, which has a tincd running for this network on
1329 port 2000. It knows the port number from the host configuration file.
1330 Also note that since D uses the tun/tap driver, the network interface
1331 will not be called `tun' or `tap0' or something like that, but will
1332 have the same name as netname.
1334 On all hosts, in @file{/etc/tinc/company/hosts/BranchD}:
1337 Subnet = 10.4.0.0/16
1340 -----BEGIN RSA PUBLIC KEY-----
1342 -----END RSA PUBLIC KEY-----
1345 @subsubheading Key files
1347 A, B, C and D all have generated a public/private keypair with the following command:
1353 The private key is stored in @file{/etc/tinc/company/rsa_key.priv},
1354 the public key is put into the host configuration file in the @file{/etc/tinc/company/hosts/} directory.
1355 During key generation, tinc automatically guesses the right filenames based on the -n option and
1356 the Name directive in the @file{tinc.conf} file (if it is available).
1358 @subsubheading Starting
1360 After each branch has finished configuration and they have distributed
1361 the host configuration files amongst them, they can start their tinc daemons.
1362 They don't necessarily have to wait for the other branches to have started
1363 their daemons, tinc will try connecting until they are available.
1366 @c ==================================================================
1367 @node Running tinc, Technical information, Configuration, Top
1368 @chapter Running tinc
1370 If everything else is done, you can start tinc by typing the following command:
1373 tincd -n @emph{netname}
1377 tinc will detach from the terminal and continue to run in the background like a good daemon.
1378 If there are any problems however you can try to increase the debug level
1379 and look in the syslog to find out what the problems are.
1387 @c ==================================================================
1388 @node Runtime options, Error messages, , Running tinc
1389 @section Runtime options
1391 Besides the settings in the configuration file, tinc also accepts some
1392 command line options.
1394 @cindex command line
1395 @cindex runtime options
1399 @item --bypass-security
1400 Disables encryption and authentication.
1401 Only useful for debugging.
1403 @item -c, --config=PATH
1404 Read configuration options from the directory PATH. The default is
1405 @file{/etc/tinc/netname/}.
1408 @item -d, --debug=LEVEL
1409 Set debug level to LEVEL. The higher the debug level, the more gets
1410 logged. Everything goes via syslog.
1412 @item -K, --generate-keys[=BITS]
1413 Generate public/private keypair of BITS length. If BITS is not specified,
1414 1024 is the default. tinc will ask where you want to store the files,
1415 but will default to the configuration directory (you can use the -c or -n option
1416 in combination with -K). After that, tinc will quit.
1419 Display a short reminder of these runtime options and terminate.
1421 @item -k, --kill[=SIGNAL]
1422 Attempt to kill a running tincd (optionally with the specified SIGNAL instead of SIGTERM) and exit.
1423 Use it in conjunction with the -n option to make sure you kill the right tinc daemon.
1425 @item -n, --net=NETNAME
1426 Connect to net NETNAME. @xref{Multiple networks}.
1428 @item -D, --no-detach
1429 Don't fork and detach.
1430 This will also disable the automatic restart mechanism for fatal errors.
1433 Lock tinc into main memory.
1434 This will prevent sensitive data like shared private keys to be written to the system swap files/partitions.
1437 Output version information and exit.
1442 @c ==================================================================
1443 @node Error messages, , Runtime options, Running tinc
1444 @section Error messages
1446 What follows is a list of the most common error messages you can see
1447 when configuring tinc. Most of these messages are visible in the syslog
1448 only, so keep an eye on it!
1451 @item Could not open /dev/tap0: No such device
1454 @item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
1455 @item You forgot to compile `Netlink device emulation' in the kernel.
1458 @item Can't write to /dev/net/tun: No such device
1461 @item You forgot to `modprobe tun'.
1462 @item You forgot to compile `Universal TUN/TAP driver' in the kernel.
1465 @item Packet with destination 1.2.3.4 is looping back to us!
1468 @item Something is not configured right. Packets are being sent out to the
1469 virtual network device, but according to the Subnet directives in your host configuration
1470 file, those packets should go to your own host. Most common mistake is that
1471 you have a Subnet line in your host configuration file with a prefix length which is
1472 just as large as the prefix of the virtual network interface. The latter should in almost all
1473 cases be larger. Rethink your configuration.
1474 Note that you will only see this message if you specified a debug
1475 level of 5 or higher!
1476 @item Chances are that a `Subnet = ...' line in the host configuration file of this tinc daemon is wrong.
1477 Change it to a subnet that is accepted locally by another interface,
1478 or if that is not the case, try changing the prefix length into /32.
1481 @item Network doesn't work, syslog shows only packets of length 46
1483 @item Network address and prefix length do not match!
1486 @item The Subnet field must contain a @emph{network} address.
1487 @item If you only want to use one IP address, set the netmask to /32.
1490 @item This is a bug: net.c:253: 24: Some error
1493 @item This is something that should not have happened.
1494 Please report this, and tell us exactly what went wrong before you got
1495 this message. In normal operation, these errors should not occur.
1498 @item Error reading RSA key file `rsa_key.priv': No such file or directory
1501 @item You must specify the complete pathname.
1502 Specifying a relative path does not make sense here. tinc changes its
1503 directory to / when starting (to avoid keeping a mount point busy).
1508 @c ==================================================================
1509 @node Technical information, About us, Running tinc, Top
1510 @chapter Technical information
1515 * The meta-protocol::
1520 @c ==================================================================
1521 @node The connection, The meta-protocol, Technical information, Technical information
1522 @section The connection
1525 tinc is a daemon that takes VPN data and transmit that to another host
1526 computer over the existing Internet infrastructure.
1530 * The meta-connection::
1534 @c ==================================================================
1535 @node The UDP tunnel, The meta-connection, The connection, The connection
1536 @subsection The UDP tunnel
1538 @cindex virtual network device
1540 The data itself is read from a character device file, the so-called
1541 @emph{virtual network device}. This device is associated with a network
1542 interface. Any data sent to this interface can be read from the device,
1543 and any data written to the device gets sent from the interface. Data to
1544 and from the device is formatted as if it were a normal Ethernet card,
1545 so a frame is preceded by two MAC addresses and a @emph{frame type}
1548 So when tinc reads an Ethernet frame from the device, it determines its
1549 type. When tinc is in it's default routing mode, it can handle IPv4 and IPv6
1550 packets. Depending on the Subnet lines, it will send the packets off to their destination.
1551 In the `switch' and `hub' mode, tinc will use broadcasts and MAC address discovery
1552 to deduce the destination of the packets.
1553 Since the latter modes only depend on the link layer information,
1554 any protocol that runs over Ethernet is supported (for instance IPX and Appletalk).
1556 After the destination has been determined,
1557 the packet will be compressed (optionally),
1558 a sequence number will be added to the packet,
1559 the packet will then be encrypted
1560 and a message authentication code will be appended.
1562 @cindex encapsulating
1564 When that is done, time has come to actually transport the
1565 packet to the destination computer. We do this by sending the packet
1566 over an UDP connection to the destination host. This is called
1567 @emph{encapsulating}, the VPN packet (though now encrypted) is
1568 encapsulated in another IP datagram.
1570 When the destination receives this packet, the same thing happens, only
1571 in reverse. So it checks the message authentication code, decrypts the contents of the UDP datagram,
1572 checks the sequence number
1573 and writes the decrypted information to its own virtual network device.
1575 To let the kernel on the receiving end accept the packet, the destination MAC
1576 address must match that of the virtual network interface.
1577 If tinc is in it's default routing mode, ARP does not work, so the correct destination MAC cannot be set
1578 by the sending daemons.
1579 tinc solves this by letting the receiving end detect the MAC address
1580 and overwriting the destination MAC address of the received packet.
1581 However, the MAC address of the network interface at the receiver might not always be known to tinc.
1582 That is the reason why you should set the MAC address of your tap interface to that address
1583 when in routing mode.
1585 In switch or hub modes ARP does work so the sender already knows the correct destination MAC address.
1586 In those modes every interface should have a unique MAC address, so make sure they are not the same.
1589 @c ==================================================================
1590 @node The meta-connection, , The UDP tunnel, The connection
1591 @subsection The meta-connection
1593 Having only a UDP connection available is not enough. Though suitable
1594 for transmitting data, we want to be able to reliably send other
1595 information, such as routing and session key information to somebody.
1598 TCP is a better alternative, because it already contains protection
1599 against information being lost, unlike UDP.
1601 So we establish two connections. One for the encrypted VPN data, and one
1602 for other information, the meta-data. Hence, we call the second
1603 connection the meta-connection. We can now be sure that the
1604 meta-information doesn't get lost on the way to another computer.
1606 @cindex data-protocol
1607 @cindex meta-protocol
1608 Like with any communication, we must have a protocol, so that everybody
1609 knows what everything stands for, and how she should react. Because we
1610 have two connections, we also have two protocols. The protocol used for
1611 the UDP data is the ``data-protocol,'' the other one is the
1614 The reason we don't use TCP for both protocols is that UDP is much
1615 better for encapsulation, even while it is less reliable. The real
1616 problem is that when TCP would be used to encapsulate a TCP stream
1617 that's on the private network, for every packet sent there would be
1618 three ACKs sent instead of just one. Furthermore, if there would be
1619 a timeout, both TCP streams would sense the timeout, and both would
1620 start re-sending packets.
1623 @c ==================================================================
1624 @node The meta-protocol, Security, The connection, Technical information
1625 @section The meta-protocol
1627 The meta protocol is used to tie all tinc daemons together, and
1628 exchange information about which tinc daemon serves which virtual
1631 The meta protocol consists of requests that can be sent to the other
1632 side. Each request has a unique number and several parameters. All
1633 requests are represented in the standard ASCII character set. It is
1634 possible to use tools such as telnet or netcat to connect to a tinc
1635 daemon started with the --bypass-security option
1636 and to read and write requests by hand, provided that one
1637 understands the numeric codes sent.
1639 The authentication scheme is described in @ref{Authentication protocol}. After a
1640 successful authentication, the server and the client will exchange all the
1641 information about other tinc daemons and subnets they know of, so that both
1642 sides (and all the other tinc daemons behind them) have their information
1649 --------------------------------------------------------------------------
1650 origin ADD_EDGE node1 node2 21.32.43.54 655 222 0
1651 | | | | | +-> options
1652 | | | | +----> weight
1653 | | | +--------> UDP port of node2
1654 | | +----------------> real address of node2
1655 | +-------------------------> name of destination node
1656 +-------------------------------> name of source node
1658 origin ADD_SUBNET node 192.168.1.0/24
1659 | | +--> prefixlength
1660 | +--------> network address
1661 +------------------> owner of this subnet
1662 --------------------------------------------------------------------------
1665 The ADD_EDGE messages are to inform other tinc daemons that a connection between
1666 two nodes exist. The address of the destination node is available so that
1667 VPN packets can be sent directly to that node.
1669 The ADD_SUBNET messages inform other tinc daemons that certain subnets belong
1670 to certain nodes. tinc will use it to determine to which node a VPN packet has
1677 ------------------------------------------------------------------
1678 DEL_EDGE node1 node2
1679 | +----> name of destination node
1680 +----------> name of source node
1682 DEL_SUBNET node 192.168.1.0/24
1683 | | +--> prefixlength
1684 | +--------> network address
1685 +------------------> owner of this subnet
1686 ------------------------------------------------------------------
1689 In case a connection between two daemons is closed or broken, DEL_EDGE messages
1690 are sent to inform the other daemons of that fact. Each daemon will calculate a
1691 new route to the the daemons, or mark them unreachable if there isn't any.
1698 ------------------------------------------------------------------
1699 REQ_KEY origin destination
1700 | +--> name of the tinc daemon it wants the key from
1701 +----------> name of the daemon that wants the key
1703 ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
1704 | | \______________/ | | +--> MAC length
1705 | | | | +-----> digest algorithm
1706 | | | +--------> cipher algorithm
1707 | | +--> 128 bits key
1708 | +--> name of the daemon that wants the key
1709 +----------> name of the daemon that uses this key
1712 +--> daemon that has changed it's packet key
1713 --------------------------------------------------------------------------
1716 The keys used to encrypt VPN packets are not sent out directly. This is
1717 because it would generate a lot of traffic on VPNs with many daemons, and
1718 chances are that not every tinc daemon will ever send a packet to every
1719 other daemon. Instead, if a daemon needs a key it sends a request for it
1720 via the meta connection of the nearest hop in the direction of the
1727 --------------------------------------------------------------------------
1730 --------------------------------------------------------------------------
1733 There is also a mechanism to check if hosts are still alive. Since network
1734 failures or a crash can cause a daemon to be killed without properly
1735 shutting down the TCP connection, this is necessary to keep an up to date
1736 connection list. PINGs are sent at regular intervals, except when there
1737 is also some other traffic. A little bit of salt (random data) is added
1738 with each PING and PONG message, to make sure that long sequences of PING/PONG
1739 messages without any other traffic won't result in known plaintext.
1741 This basically covers what is sent over the meta connection by
1745 @c ==================================================================
1746 @node Security, , The meta-protocol, Technical information
1747 @section About tinc's encryption and other security-related issues.
1751 tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
1752 alleged Cabal was/is an organisation that was said to keep an eye on the
1753 entire Internet. As this is exactly what you @emph{don't} want, we named
1754 the tinc project after TINC.
1757 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
1758 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
1759 exactly that: encrypt.
1760 tinc by default uses blowfish encryption with 128 bit keys in CBC mode, 32 bit
1761 sequence numbers and 4 byte long message authentication codes to make sure
1762 eavesdroppers cannot get and cannot change any information at all from the
1763 packets they can intercept. The encryption algorithm and message authentication
1764 algorithm can be changed in the configuration. The length of the message
1765 authentication codes is also adjustable. The length of the key for the
1766 encryption algorithm is always the default length used by OpenSSL.
1769 * Authentication protocol::
1770 * Encryption of network packets::
1774 @c ==================================================================
1775 @node Authentication protocol, Encryption of network packets, Security, Security
1776 @subsection Authentication protocol
1778 @cindex authentication
1779 A new scheme for authentication in tinc has been devised, which offers some
1780 improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
1790 --------------------------------------------------------------------------
1791 client <attempts connection>
1793 server <accepts connection>
1797 +-------> name of tinc daemon
1801 +-------> name of tinc daemon
1803 client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
1804 \_________________________________/
1805 +-> RSAKEYLEN bits totally random string S1,
1806 encrypted with server's public RSA key
1808 server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
1809 \_________________________________/
1810 +-> RSAKEYLEN bits totally random string S2,
1811 encrypted with client's public RSA key
1814 - the client will symmetrically encrypt outgoing traffic using S1
1815 - the server will symmetrically encrypt outgoing traffic using S2
1817 client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
1818 \_________________________________/
1819 +-> CHALLEN bits totally random string H1
1821 server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
1822 \_________________________________/
1823 +-> CHALLEN bits totally random string H2
1825 client CHAL_REPLY 816a86
1826 +-> 160 bits SHA1 of H2
1828 server CHAL_REPLY 928ffe
1829 +-> 160 bits SHA1 of H1
1831 After the correct challenge replies are received, both ends have proved
1832 their identity. Further information is exchanged.
1834 client ACK 655 123 0
1836 | +----> estimated weight
1837 +--------> listening port of client
1839 server ACK 655 321 0
1841 | +----> estimated weight
1842 +--------> listening port of server
1843 --------------------------------------------------------------------------
1846 This new scheme has several improvements, both in efficiency and security.
1848 First of all, the server sends exactly the same kind of messages over the wire
1849 as the client. The previous versions of tinc first authenticated the client,
1850 and then the server. This scheme even allows both sides to send their messages
1851 simultaneously, there is no need to wait for the other to send something first.
1852 This means that any calculations that need to be done upon sending or receiving
1853 a message can also be done in parallel. This is especially important when doing
1854 RSA encryption/decryption. Given that these calculations are the main part of
1855 the CPU time spent for the authentication, speed is improved by a factor 2.
1857 Second, only one RSA encrypted message is sent instead of two. This reduces the
1858 amount of information attackers can see (and thus use for a cryptographic
1859 attack). It also improves speed by a factor two, making the total speedup a
1862 Third, and most important:
1863 The symmetric cipher keys are exchanged first, the challenge is done
1864 afterwards. In the previous authentication scheme, because a man-in-the-middle
1865 could pass the challenge/chal_reply phase (by just copying the messages between
1866 the two real tinc daemons), but no information was exchanged that was really
1867 needed to read the rest of the messages, the challenge/chal_reply phase was of
1868 no real use. The man-in-the-middle was only stopped by the fact that only after
1869 the ACK messages were encrypted with the symmetric cipher. Potentially, it
1870 could even send it's own symmetric key to the server (if it knew the server's
1871 public key) and read some of the metadata the server would send it (it was
1872 impossible for the mitm to read actual network packets though). The new scheme
1873 however prevents this.
1875 This new scheme makes sure that first of all, symmetric keys are exchanged. The
1876 rest of the messages are then encrypted with the symmetric cipher. Then, each
1877 side can only read received messages if they have their private key. The
1878 challenge is there to let the other side know that the private key is really
1879 known, because a challenge reply can only be sent back if the challenge is
1880 decrypted correctly, and that can only be done with knowledge of the private
1883 Fourth: the first thing that is send via the symmetric cipher encrypted
1884 connection is a totally random string, so that there is no known plaintext (for
1885 an attacker) in the beginning of the encrypted stream.
1888 @c ==================================================================
1889 @node Encryption of network packets, , Authentication protocol, Security
1890 @subsection Encryption of network packet
1893 A data packet can only be sent if the encryption key is known to both
1894 parties, and the connection is activated. If the encryption key is not
1895 known, a request is sent to the destination using the meta connection
1896 to retrieve it. The packet is stored in a queue while waiting for the
1900 The UDP packet containing the network packet from the VPN has the following layout:
1903 ... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
1904 \___________________/\_____/
1906 V +---> digest algorithm
1907 Encrypted with symmetric cipher
1910 So, the entire VPN packet is encrypted using a symmetric cipher, including a 32 bits
1911 sequence number that is added in front of the actual VPN packet, to act as a unique
1912 IV for each packet and to prevent replay attacks. A message authentication code
1913 is added to the UDP packet to prevent alteration of packets. By default the
1914 first 4 bytes of the digest are used for this, but this can be changed using
1915 the MACLength configuration variable.
1917 @c ==================================================================
1918 @node About us, Concept Index, Technical information, Top
1923 * Contact Information::
1928 @c ==================================================================
1929 @node Contact Information, Authors, About us, About us
1930 @section Contact information
1933 tinc's website is at @url{http://tinc.nl.linux.org/},
1934 this server is located in the Netherlands.
1937 We have an IRC channel on the FreeNode IRC network. Connect to
1938 @uref{http://www.freenode.net/, irc.freenode.net}
1939 and join channel #tinc.
1942 @c ==================================================================
1943 @node Authors, , Contact Information, About us
1947 @item Ivo Timmermans (zarq) (@email{ivo@@o2w.nl})
1948 @item Guus Sliepen (guus) (@email{guus@@sliepen.eu.org})
1951 We have received a lot of valuable input from users. With their help,
1952 tinc has become the flexible and robust tool that it is today. We have
1953 composed a list of contributions, in the file called @file{THANKS} in
1954 the source distribution.
1957 @c ==================================================================
1958 @node Concept Index, , About us, Top
1959 @c node-name, next, previous, up
1960 @unnumbered Concept Index
1962 @c ==================================================================
1966 @c ==================================================================