1 \input texinfo @c -*-texinfo-*-
2 @c $Id: tinc.texi,v 1.8.4.22 2002/03/01 13:38:02 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 1.8.4.22 2002/03/01 13:38:02 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 1.8.4.22 2002/03/01 13:38:02 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) [experimental]
741 This option affects the address family of listening and outgoing sockets.
742 If "any" is selected, then depending on the operating system
743 both IPv4 and IPv6 or just IPv6 listening sockets will be created.
745 Mixing IPv4 and IPv6 may not work as desired.
746 It's best to choose one address family
747 and use that for all tinc daemons on the VPN.
749 @cindex BindToInterface
750 @item BindToInterface = <interface> [experimental]
751 If you have more than one network interface in your computer, tinc will
752 by default listen on all of them for incoming connections. It is
753 possible to bind tinc to a single interface like eth0 or ppp0 with this
756 This option may not work on all platforms.
759 @item BindToIP = <address> [experimental]
760 If your computer has more than one IP address on a single interface (for
761 example if you are running virtual hosts), tinc will by default listen
762 on all of them for incoming connections. It is possible to bind tinc to
763 a single IP address with this variable. It is still possible to listen
764 on several interfaces at the same time though, if they share the same IP
767 This option may not work on all platforms.
770 @item @strong{ConnectTo = <name>}
771 Specifies which host to connect to on startup. Multiple ConnectTo
772 variables may be specified, if connecting to the first one fails then
773 tinc will try the next one, and so on. It is possible to specify
774 hostnames for dynamic IP addresses (like those given on dyndns.org),
775 tinc will not cache the resolved IP address.
777 If you don't specify a host with ConnectTo, regardless of whether a
778 value for ConnectPort is given, tinc won't connect at all, and will
779 instead just listen for incoming connections.
782 @item @strong{Device = <device>} (/dev/tap0 or /dev/misc/net/tun)
783 The virtual network device to use. Note that you can only use one device per
784 daemon. See also @ref{Device files}.
787 @item Hostnames = <yes|no> (no)
788 This option selects whether IP addresses (both real and on the VPN)
789 should be resolved. Since DNS lookups are blocking, it might affect
790 tinc's efficiency, even stopping the daemon for a few seconds everytime
791 it does a lookup if your DNS server is not responding.
793 This does not affect resolving hostnames to IP addresses from the
797 @item Interface = <interface>
798 Defines the name of the interface corresponding to the virtual network device.
799 Depending on the operating system and the type of device this may or may not actually set the name.
800 Currently this option only affects the Linux tun/tap device.
803 @item Mode = <router|switch|hub> (router)
804 This option selects the way packets are routed to other daemons.
810 variables in the host configuration files will be used to form a routing table.
811 Only unicast packets of routable protocols (IPv4 and IPv6) are supported in this mode.
815 In this mode the MAC addresses of the packets on the VPN will be used to
816 dynamically create a routing table just like a network switch does.
817 Unicast, multicast and broadcast packets of every ethernet protocol are supported in this mode
818 at the cost of frequent broadcast ARP requests and routing table updates.
822 In this mode every packet will be broadcast to the other daemons.
826 @item KeyExpire = <seconds> (3600)
827 This option controls the time the encryption keys used to encrypt the data
828 are valid. It is common practice to change keys at regular intervals to
829 make it even harder for crackers, even though it is thought to be nearly
830 impossible to crack a single key.
833 @item @strong{Name = <name>}
834 This is a symbolic name for this connection. It can be anything
837 @item PingTimeout = <seconds> (60)
838 The number of seconds of inactivity that tinc will wait before sending a
839 probe to the other end. If that other end doesn't answer within that
840 same amount of seconds, the connection is terminated, and the others
841 will be notified of this.
843 @cindex PriorityInheritance
844 @item PriorityInheritance = <yes|no> (no) [experimental]
845 When this option is enabled the value of the TOS field of tunneled IPv4 packets
846 will be inherited by the UDP packets that are sent out.
849 @item PrivateKey = <key> [obsolete]
850 This is the RSA private key for tinc. However, for safety reasons it is
851 advised to store private keys of any kind in separate files. This prevents
852 accidental eavesdropping if you are editting the configuration file.
854 @cindex PrivateKeyFile
855 @item @strong{PrivateKeyFile = <path>} [recommended]
856 This is the full path name of the RSA private key file that was
857 generated by ``tincd --generate-keys''. It must be a full path, not a
860 Note that there must be exactly one of PrivateKey
862 specified in the configuration file.
867 @c ==================================================================
868 @node Host configuration variables, How to configure, Main configuration variables, Configuration files
869 @subsection Host configuration variables
873 @item @strong{Address = <IP address|hostname>} [recommended]
874 This variable is only required if you want to connect to this host. It
875 must resolve to the external IP address where the host can be reached,
876 not the one that is internal to the VPN.
879 @item Cipher = <cipher> (blowfish)
880 The symmetric cipher algorithm used to encrypt UDP packets.
881 Any cipher supported by OpenSSL is recognized.
884 @item Compression = <level> (0)
885 This option sets the level of compression used for UDP packets.
886 Possible values are 0 (off), 1 (fast) and any integer up to 9 (best).
889 @item Digest = <digest> (sha1)
890 The digest algorithm used to authenticate UDP packets.
891 Any digest supported by OpenSSL is recognized.
892 Furthermore, specifying "none" will turn off packet authentication.
895 @item IndirectData = <yes|no> (no) [experimental]
896 This option specifies whether other tinc daemons besides the one you
897 specified with ConnectTo can make a direct connection to you. This is
898 especially useful if you are behind a firewall and it is impossible to
899 make a connection from the outside to your tinc daemon. Otherwise, it
900 is best to leave this option out or set it to no.
903 @item MACLength = <length> (4)
904 The length of the message authentication code used to authenticate UDP packets.
905 Can be anything from 0
906 up to the length of the digest produced by the digest algorithm.
909 @item Port = <port> (655)
910 Connect to the upstream host (given with the ConnectTo directive) on
911 port port. port may be given in decimal (default), octal (when preceded
912 by a single zero) o hexadecimal (prefixed with 0x). port is the port
913 number for both the UDP and the TCP (meta) connections.
916 @item PublicKey = <key> [obsolete]
917 This is the RSA public key for this host.
919 @cindex PublicKeyFile
920 @item PublicKeyFile = <path> [obsolete]
921 This is the full path name of the RSA public key file that was generated
922 by ``tincd --generate-keys''. It must be a full path, not a relative
926 From version 1.0pre4 on tinc will store the public key directly into the
927 host configuration file in PEM format, the above two options then are not
928 necessary. Either the PEM format is used, or exactly
929 @strong{one of the above two options} must be specified
930 in each host configuration file, if you want to be able to establish a
931 connection with that host.
934 @item Subnet = <address[/masklength]>
935 The subnet which this tinc daemon will serve.
936 tinc tries to look up which other daemon it should send a packet to by searching the appropiate subnet.
937 If the packet matches a subnet,
938 it will be sent to the daemon who has this subnet in his host configuration file.
939 Multiple subnet lines can be specified for each daemon.
941 Subnets can either be single MAC, IPv4 or IPv6 addresses,
942 in which case a subnet consisting of only that single address is assumed,
943 or they can be a IPv4 or IPv6 network address with a masklength.
944 For example, IPv4 subnets must be in a form like 192.168.1.0/24,
945 where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
946 Note that subnets like 192.168.1.1/24 are invalid!
948 @cindex CIDR notation
949 masklength is the number of bits set to 1 in the netmask part; for
950 example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
951 /22. This conforms to standard CIDR notation as described in
952 @uref{ftp://ftp.isi.edu/in-notes/rfc1519.txt, RFC1519}
955 @item TCPonly = <yes|no> (no) [experimental]
956 If this variable is set to yes, then the packets are tunnelled over a
957 TCP connection instead of a UDP connection. This is especially useful
958 for those who want to run a tinc daemon from behind a masquerading
959 firewall, or if UDP packet routing is disabled somehow. This is
960 experimental code, try this at your own risk. It may not work at all.
961 Setting this options also implicitly sets IndirectData.
965 @c ==================================================================
966 @node How to configure, , Host configuration variables, Configuration files
967 @subsection How to configure
969 @subsubheading Step 1. Creating the main configuration file
971 The main configuration file will be called @file{/etc/tinc/netname/tinc.conf}.
972 Adapt the following example to create a basic configuration file:
975 Name = @emph{yourname}
976 Device = @emph{/dev/tap0}
977 PrivateKeyFile = /etc/tinc/@emph{netname}/rsa_key.priv
980 Then, if you know to which other tinc daemon(s) yours is going to connect,
981 add `ConnectTo' values.
983 @subsubheading Step 2. Creating your host configuration file
985 If you added a line containing `Name = yourname' in the main configuarion file,
986 you will need to create a host configuration file @file{/etc/tinc/netname/hosts/yourname}.
987 Adapt the following example to create a host configuration file:
990 Address = @emph{your.real.hostname.org}
991 Subnet = @emph{192.168.1.0/24}
994 You can also use an IP address instead of a hostname.
995 The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
996 If you have multiple address ranges you can specify more than one `Subnet'.
997 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).
1000 @c ==================================================================
1001 @node Generating keypairs, Network interfaces, Configuration files, Configuration
1002 @section Generating keypairs
1004 @cindex key generation
1005 Now that you have already created the main configuration file and your host configuration file,
1006 you can easily create a public/private keypair by entering the following command:
1009 tincd -n @emph{netname} -K
1012 tinc will generate a public and a private key and ask you where to put them.
1013 Just press enter to accept the defaults.
1016 @c ==================================================================
1017 @node Network interfaces, Example configuration, Generating keypairs, Configuration
1018 @section Network interfaces
1020 Before tinc can start transmitting data over the tunnel, it must
1021 set up the virtual network interface.
1023 First, decide which IP addresses you want to have associated with these
1024 devices, and what network mask they must have.
1026 tinc will open a virtual network device (@file{/dev/tun}, @file{/dev/tap0} or similar),
1027 which will also create a network interface called something like `tun0', `tap0', or,
1028 if you are using the Linux tun/tap driver, the network interface will by default have the same name as the netname.
1031 You can configure the network interface by putting ordinary ifconfig, route, and other commands
1032 to a script named @file{/etc/tinc/netname/tinc-up}. When tinc starts, this script
1033 will be executed. When tinc exits, it will execute the script named
1034 @file{/etc/tinc/netname/tinc-down}, but normally you don't need to create that script.
1036 An example @file{tinc-up} script:
1040 ifconfig $INTERFACE hw ether fe:fd:0:0:0:0
1041 ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0
1042 ifconfig $INTERFACE -arp
1046 @cindex hardware address
1047 The first line sets up the MAC address of the network interface.
1048 Due to the nature of how Ethernet and tinc work, it has to be set to fe:fd:0:0:0:0
1049 for tinc to work in it's normal mode.
1050 If you configured tinc to work in `switch' or `hub' mode, the hardware address should instead
1051 be set to a unique address instead of fe:fd:0:0:0:0.
1053 You can use the environment variable $INTERFACE to get the name of the interface.
1054 If you are using the ethertap driver however, you need to replace it with tap@emph{N},
1055 corresponding to the device file name.
1058 The next line gives the interface an IP address and a netmask.
1059 The kernel will also automatically add a route to this interface, so normally you don't need
1060 to add route commands to the @file{tinc-up} script.
1061 The kernel will also bring the interface up after this command.
1063 The netmask is the mask of the @emph{entire} VPN network, not just your
1067 The last line tells the kernel not to use ARP on that interface.
1068 Again this has to do with how Ethernet and tinc work.
1069 Use this option only if you are running tinc under Linux and are using tinc's normal routing mode.
1072 @c ==================================================================
1073 @node Example configuration, , Network interfaces, Configuration
1074 @section Example configuration
1078 Imagine the following situation. Branch A of our example `company' wants to connect
1079 three branch offices in B, C and D using the Internet. All four offices
1080 have a 24/7 connection to the Internet.
1082 A is going to serve as the center of the network. B and C will connect
1083 to A, and D will connect to C. Each office will be assigned their own IP
1087 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
1088 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
1089 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
1090 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
1093 ``gateway'' is the VPN IP address of the machine that is running the
1094 tincd. ``internet IP'' is the IP address of the firewall, which does not
1095 need to run tincd, but it must do a port forwarding of TCP&UDP on port
1096 655 (unless otherwise configured).
1098 In this example, it is assumed that eth0 is the interface that points to
1099 the inner (physical) LAN of the office, although this could also be the
1100 same as the interface that leads to the Internet. The configuration of
1101 the real interface is also shown as a comment, to give you an idea of
1102 how these example host is set up. All branches use the netname `company'
1103 for this particular VPN.
1105 @subsubheading For Branch A
1107 @emph{BranchA} would be configured like this:
1109 In @file{/etc/tinc/company/tinc-up}:
1112 # Real interface of internal network:
1113 # ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
1115 ifconfig tap0 hw ether fe:fd:0:0:0:0
1116 ifconfig tap0 10.1.54.1 netmask 255.0.0.0
1120 and in @file{/etc/tinc/company/tinc.conf}:
1124 PrivateKey = /etc/tinc/company/rsa_key.priv
1128 On all hosts, /etc/tinc/company/hosts/BranchA contains:
1131 Subnet = 10.1.0.0/16
1134 Note that the IP addresses of eth0 and tap0 are the same.
1135 This is quite possible, if you make sure that the netmasks of the interfaces are different.
1136 It is in fact recommended to give give both real internal network interfaces and tap interfaces the same IP address,
1137 since that will make things a lot easier to remember and set up.
1139 -----BEGIN RSA PUBLIC KEY-----
1141 -----END RSA PUBLIC KEY-----
1145 @subsubheading For Branch B
1147 In @file{/etc/tinc/company/tinc-up}:
1150 # Real interface of internal network:
1151 # ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
1153 ifconfig tap0 hw ether fe:fd:0:0:0:0
1154 ifconfig tap0 10.2.1.12 netmask 255.0.0.0
1158 and in @file{/etc/tinc/company/tinc.conf}:
1163 PrivateKey = /etc/tinc/company/rsa_key.priv
1166 Note here that the internal address (on eth0) doesn't have to be the
1167 same as on the tap0 device. Also, ConnectTo is given so that no-one can
1168 connect to this node.
1170 On all hosts, in @file{/etc/tinc/company/hosts/BranchB}:
1173 Subnet = 10.2.0.0/16
1176 -----BEGIN RSA PUBLIC KEY-----
1178 -----END RSA PUBLIC KEY-----
1182 @subsubheading For Branch C
1184 In @file{/etc/tinc/company/tinc-up}:
1187 # Real interface of internal network:
1188 # ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
1190 ifconfig tap1 hw ether fe:fd:0:0:0:0
1191 ifconfig tap1 10.3.69.254 netmask 255.0.0.0
1195 and in @file{/etc/tinc/company/tinc.conf}:
1203 C already has another daemon that runs on port 655, so they have to
1204 reserve another port for tinc. It knows the portnumber it has to listen on
1205 from it's own host configuration file.
1207 On all hosts, in @file{/etc/tinc/company/hosts/BranchC}:
1211 Subnet = 10.3.0.0/16
1214 -----BEGIN RSA PUBLIC KEY-----
1216 -----END RSA PUBLIC KEY-----
1220 @subsubheading For Branch D
1222 In @file{/etc/tinc/company/tinc-up}:
1225 # Real interface of internal network:
1226 # ifconfig eth0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
1228 ifconfig company hw ether fe:fd:0a:04:03:20
1229 ifconfig company 10.4.3.32 netmask 255.0.0.0
1230 ifconfig company -arp
1233 and in @file{/etc/tinc/company/tinc.conf}:
1238 Device = /dev/misc/net/tun
1239 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1242 D will be connecting to C, which has a tincd running for this network on
1243 port 2000. It knows the port number from the host configuration file.
1244 Also note that since D uses the tun/tap driver, the network interface
1245 will not be called `tun' or `tap0' or something like that, but will
1246 have the same name as netname.
1248 On all hosts, in @file{/etc/tinc/company/hosts/BranchD}:
1251 Subnet = 10.4.0.0/16
1254 -----BEGIN RSA PUBLIC KEY-----
1256 -----END RSA PUBLIC KEY-----
1259 @subsubheading Key files
1261 A, B, C and D all have generated a public/private keypair with the following command:
1267 The private key is stored in @file{/etc/tinc/company/rsa_key.priv},
1268 the public key is put into the host configuration file in the @file{/etc/tinc/company/hosts/} directory.
1269 During key generation, tinc automatically guesses the right filenames based on the -n option and
1270 the Name directive in the @file{tinc.conf} file (if it is available).
1272 @subsubheading Starting
1274 After each branch has finished configuration and they have distributed
1275 the host configuration files amongst them, they can start their tinc daemons.
1276 They don't necessarily have to wait for the other branches to have started
1277 their daemons, tinc will try connecting until they are available.
1280 @c ==================================================================
1281 @node Running tinc, Technical information, Configuration, Top
1282 @chapter Running tinc
1284 If everything else is done, you can start tinc by typing the following command:
1287 tincd -n @emph{netname}
1291 tinc will detach from the terminal and continue to run in the background like a good daemon.
1292 If there are any problems however you can try to increase the debug level
1293 and look in the syslog to find out what the problems are.
1301 @c ==================================================================
1302 @node Runtime options, Error messages, , Running tinc
1303 @section Runtime options
1305 Besides the settings in the configuration file, tinc also accepts some
1306 command line options.
1308 This list is a longer version of that in the manpage. The latter is
1309 generated automatically, so may be more up-to-date.
1311 @cindex command line
1312 @cindex runtime options
1316 @item --bypass-security
1317 Disables encryption and authentication.
1318 Only useful for debugging.
1320 @item -c, --config=PATH
1321 Read configuration options from the directory PATH. The default is
1322 @file{/etc/tinc/netname/}.
1325 @item -d, --debug=LEVEL
1326 Set debug level to LEVEL. The higher the debug level, the more gets
1327 logged. Everything goes via syslog.
1329 @item -K, --generate-keys[=BITS]
1330 Generate public/private keypair of BITS length. If BITS is not specified,
1331 1024 is the default. tinc will ask where you want to store the files,
1332 but will default to the configuration directory (you can use the -c or -n option
1333 in combination with -K). After that, tinc will quit.
1336 Display a short reminder of these runtime options and terminate.
1339 Attempt to kill a running tincd and exit. A TERM signal (15) gets sent
1340 to the daemon that his its PID in @file{/var/run/tinc.NETNAME.pid}.
1341 Use it in conjunction with the -n option to make sure you kill the right tinc daemon.
1343 @item -n, --net=NETNAME
1344 Connect to net NETNAME. @xref{Multiple networks}.
1346 @item -D, --no-detach
1347 Don't fork and detach.
1348 This will also disable the automatic restart mechanism for fatal errors.
1351 Output version information and exit.
1356 @c ==================================================================
1357 @node Error messages, , Runtime options, Running tinc
1358 @section Error messages
1360 What follows is a list of the most common error messages you can see
1361 when configuring tinc. Most of these messages are visible in the syslog
1362 only, so keep an eye on it!
1365 @item Could not open /dev/tap0: No such device
1368 @item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
1369 @item You forgot to compile `Netlink device emulation' in the kernel.
1372 @item Can't write to /dev/misc/net/tun: No such device
1375 @item You forgot to `modprobe tun'.
1376 @item You forgot to compile `Universal TUN/TAP driver' in the kernel.
1379 @item Packet with destination 1.2.3.4 is looping back to us!
1382 @item Something is not configured right. Packets are being sent out to the
1383 virtual network device, but according to the Subnet directives in your host configuration
1384 file, those packets should go to your own host. Most common mistake is that
1385 you have a Subnet line in your host configuration file with a netmask which is
1386 just as large as the netmask of the virtual network interface. The latter should in almost all
1387 cases be larger. Rethink your configuration.
1388 Note that you will only see this message if you specified a debug
1389 level of 5 or higher!
1390 @item Chances are that a `Subnet = ...' line in the host configuration file of this tinc daemon is wrong.
1391 Change it to a subnet that is accepted locally by another interface,
1392 or if that is not the case, try changing the prefix length into /32.
1395 @item Network doesn't work, syslog shows only packets of length 46
1399 Jan 1 12:00:00 host tinc.net[1234]: Read packet of length 46 from tap device
1400 Jan 1 12:00:00 host tinc.net[1234]: Trying to look up 0.0.192.168 in connection list failed!
1403 @item Add the `ifconfig $INTERFACE -arp' to tinc-up.
1406 @item Network address and subnet mask do not match!
1409 @item The Subnet field must contain a @emph{network} address.
1410 @item If you only want to use one IP address, set the netmask to /32.
1413 @item This is a bug: net.c:253: 24: Some error
1416 @item This is something that should not have happened.
1417 Please report this, and tell us exactly what went wrong before you got
1418 this message. In normal operation, these errors should not occur.
1421 @item Error reading RSA key file `rsa_key.priv': No such file or directory
1424 @item You must specify the complete pathname.
1425 Specifying a relative path does not make sense here. tinc changes its
1426 directory to / when starting (to avoid keeping a mount point busy); and
1427 even if we built in a default directory to look for these files, the key
1428 files are bound to be in a different directory.
1433 @c ==================================================================
1434 @node Technical information, About us, Running tinc, Top
1435 @chapter Technical information
1440 * The meta-protocol::
1445 @c ==================================================================
1446 @node The connection, The meta-protocol, Technical information, Technical information
1447 @section The connection
1450 tinc is a daemon that takes VPN data and transmit that to another host
1451 computer over the existing Internet infrastructure.
1455 * The meta-connection::
1459 @c ==================================================================
1460 @node The UDP tunnel, The meta-connection, The connection, The connection
1461 @subsection The UDP tunnel
1463 @cindex virtual network device
1465 The data itself is read from a character device file, the so-called
1466 @emph{virtual network device}. This device is associated with a network
1467 interface. Any data sent to this interface can be read from the device,
1468 and any data written to the device gets sent from the interface. Data to
1469 and from the device is formatted as if it were a normal Ethernet card,
1470 so a frame is preceded by two MAC addresses and a @emph{frame type}
1473 So when tinc reads an Ethernet frame from the device, it determines its
1474 type. When tinc is in it's default routing mode, it can handle IPv4 and IPv6
1475 packets. Depending on the Subnet lines, it will send the packets off to their destination.
1476 In the `switch' and `hub' mode, tinc will use broadcasts and MAC address discovery
1477 to deduce the destination of the packets.
1478 Since the latter modes only depend on the link layer information,
1479 any protocol that runs over Ethernet is supported (for instance IPX and Appletalk).
1481 After the destination has been determined, a sequence number will be added to the packet.
1482 The packet will then be encrypted and a message authentication
1483 code will be appended.
1485 @cindex encapsulating
1487 When that is done, time has come to actually transport the
1488 packet to the destination computer. We do this by sending the packet
1489 over an UDP connection to the destination host. This is called
1490 @emph{encapsulating}, the VPN packet (though now encrypted) is
1491 encapsulated in another IP datagram.
1493 When the destination receives this packet, the same thing happens, only
1494 in reverse. So it checks the message authentication code, decrypts the contents of the UDP datagram,
1495 checks the sequence number
1496 and writes the decrypted information to its own virtual network device.
1498 To let the kernel on the receiving end accept the packet, the destination MAC
1499 address must match that of the virtual network interface.
1500 If tinc is in it's default routing mode, ARP does not work, so the correct destination MAC cannot be set
1501 by the sending daemons.
1502 tinc solves this by always overwriting the
1503 destination MAC address with fe:fd:0:0:0:0. That is also the reason why you must
1504 set the MAC address of your tap interface to that address.
1507 @c ==================================================================
1508 @node The meta-connection, , The UDP tunnel, The connection
1509 @subsection The meta-connection
1511 Having only an UDP connection available is not enough. Though suitable
1512 for transmitting data, we want to be able to reliably send other
1513 information, such as routing and session key information to somebody.
1516 TCP is a better alternative, because it already contains protection
1517 against information being lost, unlike UDP.
1519 So we establish two connections. One for the encrypted VPN data, and one
1520 for other information, the meta-data. Hence, we call the second
1521 connection the meta-connection. We can now be sure that the
1522 meta-information doesn't get lost on the way to another computer.
1524 @cindex data-protocol
1525 @cindex meta-protocol
1526 Like with any communication, we must have a protocol, so that everybody
1527 knows what everything stands for, and how she should react. Because we
1528 have two connections, we also have two protocols. The protocol used for
1529 the UDP data is the ``data-protocol,'' the other one is the
1532 The reason we don't use TCP for both protocols is that UDP is much
1533 better for encapsulation, even while it is less reliable. The real
1534 problem is that when TCP would be used to encapsulate a TCP stream
1535 that's on the private network, for every packet sent there would be
1536 three ACKs sent instead of just one. Furthermore, if there would be
1537 a timeout, both TCP streams would sense the timeout, and both would
1538 start re-sending packets.
1541 @c ==================================================================
1542 @node The meta-protocol, Security, The connection, Technical information
1543 @section The meta-protocol
1545 The meta protocol is used to tie all tinc daemons together, and
1546 exchange information about which tinc daemon serves which virtual
1549 The meta protocol consists of requests that can be sent to the other
1550 side. Each request has a unique number and several parameters. All
1551 requests are represented in the standard ASCII character set. It is
1552 possible to use tools such as telnet or netcat to connect to a tinc
1553 daemon and to read and write requests by hand, provided that one
1554 understands the numeric codes sent.
1556 The authentication scheme is described in @ref{Authentication protocol}. After a
1557 successful authentication, the server and the client will exchange all the
1558 information about other tinc daemons and subnets they know of, so that both
1559 sides (and all the other tinc daemons behind them) have their information
1566 --------------------------------------------------------------------------
1567 origin ADD_EDGE node1 12.23.34.45 655 node2 21.32.43.54 655 222 0
1568 | | | \___________________/ | +-> options
1569 | | | | +----> weight
1570 | | | +----------------> see below
1572 | +----------> real address
1573 +------------------> name of node on one side of the edge
1575 origin ADD_SUBNET node 192.168.1.0/24
1577 | +--------> IPv4 network address
1578 +------------------> owner of this subnet
1579 --------------------------------------------------------------------------
1583 In case a connection between two daemons is closed or broken, DEL_EDGE messages
1584 are sent to inform the other daemons of that fact. Each daemon will calculate a
1585 new route to the the daemons, or mark them unreachable if there isn't any.
1587 The keys used to encrypt VPN packets are not sent out directly. This is
1588 because it would generate a lot of traffic on VPNs with many daemons, and
1589 chances are that not every tinc daemon will ever send a packet to every
1590 other daemon. Instead, if a daemon needs a key it sends a request for it
1591 via the meta connection of the nearest hop in the direction of the
1592 destination. If any hop on the way has already learned the key, it will
1593 act as a proxy and forward its copy back to the requester.
1600 --------------------------------------------------------------------------
1601 daemon REQ_KEY origin destination
1602 | +--> name of the tinc daemon it wants the key from
1603 +----------> name of the daemon that wants the key
1605 daemon ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
1606 | | \______________/ | | +--> MAC length
1607 | | | | +-----> digest algorithm
1608 | | | +--------> cipher algorithm
1609 | | +--> 128 bits key
1610 | +--> name of the daemon that wants the key
1611 +----------> name of the daemon that uses this key
1613 daemon KEY_CHANGED origin
1614 +--> daemon that has changed it's packet key
1615 --------------------------------------------------------------------------
1618 There is also a mechanism to check if hosts are still alive. Since network
1619 failures or a crash can cause a daemon to be killed without properly
1620 shutting down the TCP connection, this is necessary to keep an up to date
1621 connection list. PINGs are sent at regular intervals, except when there
1622 is also some other traffic. A little bit of salt (random data) is added
1623 with each PING and PONG message, to make sure that long sequences of PING/PONG
1624 messages without any other traffic won't result in known plaintext.
1630 --------------------------------------------------------------------------
1633 --------------------------------------------------------------------------
1636 This basically covers what is sent over the meta connection by
1640 @c ==================================================================
1641 @node Security, , The meta-protocol, Technical information
1642 @section About tinc's encryption and other security-related issues.
1646 tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
1647 alleged Cabal was/is an organisation that was said to keep an eye on the
1648 entire Internet. As this is exactly what you @emph{don't} want, we named
1649 the tinc project after TINC.
1652 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
1653 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
1654 exactly that: encrypt.
1655 tinc uses blowfish encryption in CBC mode, sequence numbers and message authentication codes
1656 to make sure eavesdroppers cannot get and cannot change any information at all from the packets they can intercept.
1659 * Authentication protocol::
1660 * Encryption of network packets::
1664 @c ==================================================================
1665 @node Authentication protocol, Encryption of network packets, Security, Security
1666 @subsection Authentication protocol
1668 @cindex authentication
1669 A new scheme for authentication in tinc has been devised, which offers some
1670 improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
1680 --------------------------------------------------------------------------
1681 client <attempts connection>
1683 server <accepts connection>
1687 +-------> name of tinc daemon
1691 +-------> name of tinc daemon
1693 client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
1694 \_________________________________/
1695 +-> RSAKEYLEN bits totally random string S1,
1696 encrypted with server's public RSA key
1698 server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
1699 \_________________________________/
1700 +-> RSAKEYLEN bits totally random string S2,
1701 encrypted with client's public RSA key
1704 - the client will symmetrically encrypt outgoing traffic using S1
1705 - the server will symmetrically encrypt outgoing traffic using S2
1707 client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
1708 \_________________________________/
1709 +-> CHALLEN bits totally random string H1
1711 server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
1712 \_________________________________/
1713 +-> CHALLEN bits totally random string H2
1715 client CHAL_REPLY 816a86
1716 +-> 160 bits SHA1 of H2
1718 server CHAL_REPLY 928ffe
1719 +-> 160 bits SHA1 of H1
1721 After the correct challenge replies are received, both ends have proved
1722 their identity. Further information is exchanged.
1724 client ACK 655 12.23.34.45 123 0
1726 | | +----> estimated weight
1727 | +------------> IP address of server as seen by client
1728 +--------------------> UDP port of client
1730 server ACK 655 21.32.43.54 321 0
1732 | | +----> estimated weight
1733 | +------------> IP address of client as seen by server
1734 +--------------------> UDP port of server
1735 --------------------------------------------------------------------------
1738 This new scheme has several improvements, both in efficiency and security.
1740 First of all, the server sends exactly the same kind of messages over the wire
1741 as the client. The previous versions of tinc first authenticated the client,
1742 and then the server. This scheme even allows both sides to send their messages
1743 simultaneously, there is no need to wait for the other to send something first.
1744 This means that any calculations that need to be done upon sending or receiving
1745 a message can also be done in parallel. This is especially important when doing
1746 RSA encryption/decryption. Given that these calculations are the main part of
1747 the CPU time spent for the authentication, speed is improved by a factor 2.
1749 Second, only one RSA encrypted message is sent instead of two. This reduces the
1750 amount of information attackers can see (and thus use for a cryptographic
1751 attack). It also improves speed by a factor two, making the total speedup a
1754 Third, and most important:
1755 The symmetric cipher keys are exchanged first, the challenge is done
1756 afterwards. In the previous authentication scheme, because a man-in-the-middle
1757 could pass the challenge/chal_reply phase (by just copying the messages between
1758 the two real tinc daemons), but no information was exchanged that was really
1759 needed to read the rest of the messages, the challenge/chal_reply phase was of
1760 no real use. The man-in-the-middle was only stopped by the fact that only after
1761 the ACK messages were encrypted with the symmetric cipher. Potentially, it
1762 could even send it's own symmetric key to the server (if it knew the server's
1763 public key) and read some of the metadata the server would send it (it was
1764 impossible for the mitm to read actual network packets though). The new scheme
1765 however prevents this.
1767 This new scheme makes sure that first of all, symmetric keys are exchanged. The
1768 rest of the messages are then encrypted with the symmetric cipher. Then, each
1769 side can only read received messages if they have their private key. The
1770 challenge is there to let the other side know that the private key is really
1771 known, because a challenge reply can only be sent back if the challenge is
1772 decrypted correctly, and that can only be done with knowledge of the private
1775 Fourth: the first thing that is send via the symmetric cipher encrypted
1776 connection is a totally random string, so that there is no known plaintext (for
1777 an attacker) in the beginning of the encrypted stream.
1780 @c ==================================================================
1781 @node Encryption of network packets, , Authentication protocol, Security
1782 @subsection Encryption of network packet
1785 A data packet can only be sent if the encryption key is known to both
1786 parties, and the connection is activated. If the encryption key is not
1787 known, a request is sent to the destination using the meta connection
1788 to retrieve it. The packet is stored in a queue while waiting for the
1792 The UDP packet containing the network packet from the VPN has the following layout:
1795 ... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
1796 \___________________/\_____/
1798 V +---> digest algorithm
1799 Encrypted with symmetric cipher
1802 So, the entire VPN packet is encrypted using a symmetric cipher. A 32 bits
1803 sequence number is added in front of the actual VPN packet, to act as a unique
1804 IV for each packet and to prevent replay attacks. A message authentication code
1805 is added to the UDP packet to prevent alteration of packets. By default the
1806 first 4 bytes of the digest are used for this, but this can be changed using
1807 the MACLength configuration variable.
1809 @c ==================================================================
1810 @node About us, Concept Index, Technical information, Top
1815 * Contact Information::
1820 @c ==================================================================
1821 @node Contact Information, Authors, About us, About us
1822 @section Contact information
1825 tinc's website is at @url{http://tinc.nl.linux.org/},
1826 this server is located in the Netherlands.
1829 We have an IRC channel on the Open Projects IRC network. Connect to
1830 @uref{http://openprojects.nu/services/irc.html, irc.openprojects.net},
1831 and join channel #tinc.
1834 @c ==================================================================
1835 @node Authors, , Contact Information, About us
1839 @item Ivo Timmermans (zarq) (@email{itimmermans@@bigfoot.com})
1840 Main coder/hacker and maintainer of the package.
1842 @item Guus Sliepen (guus) (@email{guus@@sliepen.warande.net})
1843 Originator of it all, co-author.
1845 @item Wessel Dankers (Ubiq) (@email{wsl@@nl.linux.org})
1846 For the name `tinc' and various suggestions.
1850 We have received a lot of valuable input from users. With their help,
1851 tinc has become the flexible and robust tool that it is today. We have
1852 composed a list of contributions, in the file called @file{THANKS} in
1853 the source distribution.
1856 @c ==================================================================
1857 @node Concept Index, , About us, Top
1858 @c node-name, next, previous, up
1859 @unnumbered Concept Index
1861 @c ==================================================================
1865 @c ==================================================================