1 \input texinfo @c -*-texinfo-*-
10 * tinc: (tinc). The tinc Manual.
13 This is the info manual for tinc, a Virtual Private Network daemon.
15 Copyright @copyright{} 1998,199,2000 Ivo Timmermans
16 <itimmermans@@bigfoot.com>, Guus Sliepen <guus@@sliepen.warande.net> and
17 Wessel Dankers <wsl@@nl.linux.org>.
20 Permission is granted to make and distribute verbatim copies of this
21 manual provided the copyright notice and this permission notice are
22 preserved on all copies.
24 Permission is granted to copy and distribute modified versions of this
25 manual under the conditions for verbatim copying, provided that the
26 entire resulting derived work is distributed under the terms of a
27 permission notice identical to this one.
33 @subtitle Setting up a Virtual Private Network with tinc
34 @author Ivo Timmermans and Guus Sliepen
37 @vskip 0pt plus 1filll
39 Copyright @copyright{} 1998,1999,2000 Ivo Timmermans
40 <itimmermans@@bigfoot.com>, Guus Sliepen <guus@@sliepen.warande.net> and
41 Wessel Dankers <wsl@@nl.linux.org>.
43 Permission is granted to make and distribute verbatim copies of this
44 manual provided the copyright notice and this permission notice are
45 preserved on all copies.
47 Permission is granted to copy and distribute modified versions of this
48 manual under the conditions for verbatim copying, provided that the
49 entire resulting derived work is distributed under the terms of a
50 permission notice identical to this one.
54 @c ==================================================================
55 @node Top, Introduction, (dir), (dir)
58 * Introduction:: Introduction
59 * Installing tinc - preparations::
60 * Installing tinc - installation::
63 * Technical information::
65 * Concept Index:: All used terms explained
71 @c ==================================================================
72 @node Introduction, Installing tinc - preparations, Top, Top
76 tinc is a Virtual Private Network (VPN) daemon that uses tunneling and
77 encryption to create a secure private network between hosts on the
80 Because the tunnel appears to the IP level network code as a normal
81 network device, there is no need to adapt any existing software.
83 This tunneling allows VPN sites to share information with each other
84 over the Internet without exposing any information to others.
86 This document is the manual for tinc. Included are chapters on how to
87 configure your computer to use tinc, as well as the configuration
88 process of tinc itself.
91 * VPNs:: Virtual Private Networks in general
93 * Supported platforms::
96 @c ==================================================================
97 @node VPNs, tinc, Introduction, Introduction
98 @section Virtual Private Networks
101 A Virtual Private Network or VPN is a network that can only be accessed
102 by a few elected computers that participate. This goal is achievable in
103 more than just one way.
106 Private networks can consist of a single stand-alone ethernet LAN. Or
107 even two computers hooked up using a null-modem cable. In these cases,
109 obvious that the network is @emph{private}, no one can access it from the
110 outside. But if your computers are linked to the internet, the network
111 is not private anymore, unless one uses firewalls to block all private
112 traffic. But then, there is no way to send private data to trusted
113 computers on the other end of the internet.
116 This problem can be solved by using @emph{virtual} networks. Virtual
117 networks can live on top of other networks, but do not interfere with
118 each other. Mostly, virtual networks appear like a singe LAN, even though
119 they can span the entire world. But virtual networks can't be secured
120 by using firewalls, because the traffic that flows through it has to go
121 through the internet, where other people can look at it.
123 When one introduces encryption, we can form a true VPN. Other people may
124 see encrypted traffic, but if they don't know how to decipher it (they
125 need to know the key for that), they cannot read the information that flows
126 through the VPN. This is what tinc was made for.
129 tinc uses normal IP datagrams to encapsulate data that goes over the VPN
130 network link. In this case it's also clear that the network is
131 @emph{virtual}, because no direct network link has to exist between to
134 As is the case with either type of VPN, anybody could eavesdrop. Or
135 worse, alter data. Hence it's probably advisable to encrypt the data
136 that flows over the network.
139 @c ==================================================================
140 @node tinc, Supported platforms, VPNs, Introduction
145 I really don't quite remember what got us started, but it must have been
146 Guus' idea. He wrote a simple implementation (about 50 lines of C) that
147 used the @emph{ethertap} device that Linux knows of since somewhere
148 about kernel 2.1.60. It didn't work immediately and he improved it a
149 bit. At this stage, the project was still simply called @samp{vpnd}.
151 Since then, a lot has changed---to say the least.
154 tinc now supports encryption, it consists of a single daemon (tincd) for
155 both the receiving and sending end, it has become largely
156 runtime-configurable---in short, it has become a full-fledged
157 professional package.
159 A lot can---and will be---changed. I have a few things that I'd like to
160 see in the future releases of tinc. Not everything will be available in
161 the near future. Our first objective is to make tinc work perfectly as
162 it stands, and then add more advanced features.
164 Meanwhile, we're always open-minded towards new ideas. And we're
168 @c ==================================================================
169 @node Supported platforms, , tinc, Introduction
170 @section Supported platforms
172 tinc works on Linux, FreeBSD and Solaris. These are the three platforms
173 that are supported by the universial TUN/TAP device driver, so if
174 support for other operating systems is added to this driver, perhaps
175 tinc will run on them as well. Without this driver, tinc will most
176 likely compile and run, but it will not be able to send or receive data
179 @c ==================================================================
182 tinc was first written for Linux running on an intel x86 processor, so
183 this is the best supported platform. The protocol however, and actually
184 anything about tinc, has been rewritten to support random byte ordering
185 and arbitrary word length. So in theory it should run on other
186 processors that Linux runs on. Take care however, we haven't been able
187 to really test it yet. If you want to run tinc on another platform than
188 x86, and want to tell us how it went, please do so.
190 tinc uses the ethertap device that is provided in the standard kernel
191 since version 2.1.60, so anything above that (2.2.x, 2.3.x, and the
192 2.4.0-testx (which is current at the time of this writing) kernel
193 versions) is able to support tinc.
196 @c ==================================================================
199 tinc on FreeBSD relies on the universial TUN/TAP driver for its data
200 acquisition from the kernel. Therefore, tinc suports the same platforms
201 as this driver. These are: FreeBSD 3.x, 4.x, 5.x.
204 @c ==================================================================
207 tinc on Solaris relies on the universial TUN/TAP driver for its data
208 acquisition from the kernel. Therefore, tinc suports the same platforms
209 as this driver. These are: Solaris, 2.1.x.
218 @c Preparing your system
225 @c ==================================================================
226 @node Installing tinc - preparations, Installing tinc - installation, Introduction, Top
227 @chapter Installing tinc: preparations
229 This chapter contains information on how to prepare your system to
233 * Configuring the kernel::
238 @c ==================================================================
239 @node Configuring the kernel, Libraries, Installing tinc - preparations, Installing tinc - preparations
240 @section Configuring the kernel
242 If you are running Linux, chances are good that your kernel already
243 supports all the devices that tinc needs for proper operation. For
244 example, the standard kernel from Redhat Linux already has support for
245 ethertap and netlink compiled in. Debian users can use the modconf
246 utility to select the modules. If your Linux distribution supports this
247 method of selecting devices, look out for something called `ethertap',
248 and `netlink_dev'. You need both these devices.
250 If you can install these devices in a similar manner, you may skip this
254 * Configuration of the Linux kernel::
255 * Configuration of the FreeBSD kernel::
256 * Configuration of the Solaris kernel::
260 @c ==================================================================
261 @node Configuration of the Linux kernel, Configuration of the FreeBSD kernel, Configuring the kernel, Configuring the kernel
262 @subsection Configuring the Linux kernel
264 Since this particular implementation only runs on 2.1 or higher Linux
265 kernels, you should grab one (2.2 is current at this time). A 2.0 port
266 is not really possible, unless someone tells me someone ported the
267 ethertap and netlink devices back to 2.0.
269 If you are unfamiliar with the process of configuring and compiling a
270 new kernel, you should read the
271 @uref{http://howto.linuxberg.com/LDP/HOWTO/Kernel-HOWTO.html, Kernel
272 HOWTO} first. Do that now!
274 Here are the options you have to turn on when configuring a new
280 Code maturity level options
281 [*] Prompt for development and/or incomplete code/drivers
283 [*] Kernel/User netlink socket
284 <*> Netlink device emulation
285 Network device support
286 <*> Ethertap network tap
289 For kernel 2.3.x and 2.4.x:
292 Code maturity level options
293 [*] Prompt for development and/or incomplete code/drivers
295 [*] Kernel/User netlink socket
296 <*> Netlink device emulation
297 Network device support
298 <*> Universal TUN/TAP device driver support
302 Any other options not mentioned here are not relevant to tinc. If you
303 decide to build any of these as dynamic kernel modules, it's a good idea
304 to add these lines to @file{/etc/modules.conf}.
308 alias char-major-36 netlink_dev
311 If you have a 2.4 kernel, you can also choose to use the `Ethertap
312 network tap' device. This is marked obsolete, because the universal
313 TUN/TAP driver is a newer implementation that is supposed to be used in
314 favor of ethertap. For tinc, it doesn't really matter which one you
315 choose; based on the device file name, tinc will make the right choice
316 about what protocol to use.
318 Finally, after having set up other options, build the kernel and boot
319 it. Unfortunately it's not possible to insert these modules in a
323 @c ==================================================================
324 @node Configuration of the FreeBSD kernel, Configuration of the Solaris kernel, Configuration of the Linux kernel, Configuring the kernel
325 @subsection Configuring the FreeBSD kernel
327 This section will contain information on how to configure your FreeBSD
328 kernel to support the universal TUN/TAP device. For 5.0 and 4.1
329 systems, this is included in the kernel configuration, for earlier
330 systems (4.0 and 3.x), you need to install the universal TUN/TAP driver
333 Unfortunately somebody still has to write the text.
336 @c ==================================================================
337 @node Configuration of the Solaris kernel, , Configuration of the FreeBSD kernel, Configuring the kernel
338 @subsection Configuring the Solaris kernel
340 This section will contain information on how to configure your Solaris
341 kernel to support the universal TUN/TAP device. You need to install
342 this driver yourself.
344 Unfortunately somebody still has to write the text.
347 @c ==================================================================
348 @node Libraries, , Configuring the kernel, Installing tinc - preparations
352 Before you can configure or build tinc, you need to have two libraries
353 installed on your system, GMP and OpenSSL. If you try to configure tinc
354 without having installed both, configure will give you an error message,
363 @c ==================================================================
364 @node GMP, OpenSSL, Libraries, Libraries
368 tinc uses the GNU Multiple Precision (GMP) library to do some
369 authentication-related calculations. tinc cannot run without this
370 library. If you try to configure the tinc source code without this
371 library installed, you will get an error message.
373 Currently, versions 1.x, 2.x, 3.0 and 3.0.1 of this library are
374 supported. You may try to configure if you have another version
375 installed, chances are big it works without a problem.
377 You can use your operating system's package manager to install this if
378 available. Make sure you install the development AND runtime versions
381 If you can't install GMP this way, you can get the source of this latest
382 version of this library from
383 @url{http://www.gnu.org/software/gmp/gmp.html}. Instructions on how to
384 configure, build and install this package are included within the
385 package. Please make sure you build development and runtime libraries
386 (which is the default).
389 @c ==================================================================
390 @node OpenSSL, , GMP, Libraries
394 For all cryptography-related functions, tinc uses the functions provided
395 by the OpenSSL library. We recommend using version 0.9.5 or 0.9.6 of
396 this library. Other versions may also work, but we can guarantee
399 Disclaimers from the subsection on GMP also apply here; if this library
400 is not installed, you wil get an error when running configure. Support
401 for running tinc without having OpenSSL installed @emph{may} be added in
404 If you have to install OpenSSL manually, you can get the source code
405 from @url{http://www.openssl.org/}. Instructions on how to configure,
406 build and install this package are included within the package. Please
407 make sure you build development and runtime libraries (which is the
420 @c ==================================================================
421 @node Installing tinc - installation, Configuring tinc, Installing tinc - preparations, Top
422 @chapter Installing tinc: installation
424 If you use Redhat or Debian, you may want to install one of the
425 precompiled packages for your system. These packages are equipped with
426 system startup scripts and sample configurations.
428 If you don't run either of these systems, or you want to compile tinc
429 for yourself, you can use the source. The source is distributed under
430 the GNU General Public License (GPL). Download the source from the
431 @uref{http://tinc.nl.linux.org/download.html, download page}, which has
432 the checksums of these files listed; you may wish to check these with
433 md5sum before continuing.
435 tinc comes in a handy autoconf/automake package, which you can just
436 treat the same as any other package. Which is just untar it, type
437 `configure' and then `make'.
439 More detailed instructions are in the file @file{INSTALL}, which is
440 included in the source distribution.
449 @c ==================================================================
450 @node Building tinc, System files, Installing tinc - installation, Installing tinc - installation
451 @section Building tinc
453 Detailed instructions on configuring the source and building tinc can be
454 found in the file called @file{INSTALL}.
457 @c ==================================================================
458 @node System files, Interfaces, Building tinc, Installing tinc - installation
459 @section System files
461 Before you can run tinc, you
469 @c ==================================================================
470 @node Device files, Other files, System files, System files
471 @subsection Device files
473 First, you'll need the special device file(s) that form the interface
474 between the kernel and the daemon.
476 The permissions for these files have to be such that only the super user
477 may read/write to this file. You'd want this, because otherwise
478 eavesdropping would become a bit too easy. This does, however, imply
479 that you'd have to run tincd as root.
481 If you use the universal TUN/TAP driver, you have to create the
482 following device files (unless they already exist):
485 mknod -m 600 /dev/... c .. ..
489 If you want to have more devices, the device numbers will be .. .. ...
491 If you use Linux, and you run the new 2.4 kernel using the devfs
492 filesystem, then the tap device will be automatically generated as
493 @file{/dev/netlink/tap0}.
495 If you use Linux and have kernel 2.2.x, you have to make the ethertap
499 mknod -m 600 /dev/tap0 c 36 16
503 Any further ethertap devices have minor device number 16 through 31.
506 @c ==================================================================
507 @node Other files, , Device files, System files
508 @subsection Other files
510 @subsubheading @file{/etc/networks}
512 You may add a line to @file{/etc/networks} so that your VPN will get a
513 symbolic name. For example:
519 This has nothing to do with the MyVPNIP configuration variable that will be
520 discussed later, it is only to make the output of the route command more
523 @subsubheading @file{/etc/services}
525 You may add this line to @file{/etc/services}. The effect is that you
526 may supply a @samp{tinc} as a valid port number to some programs. The
527 number 655 is registered with the IANA.
532 # Ivo Timmermans <itimmermans@@bigfoot.com>
536 @c ==================================================================
537 @node Interfaces, , System files, Installing tinc - installation
540 Before you can start transmitting data over the tinc tunnel, you must
541 set up the ethertap network devices.
543 First, decide which IP addresses you want to have associated with these
544 devices, and what network mask they must have. You also need these
545 numbers when you are going to configure tinc itself. @xref{Configuring
548 It doesn't matter much which part you do first, setting up the network
549 devices or configure tinc. But they both have to be done before you try
552 The actual setup of the ethertap device is quite simple, just repeat
556 ifconfig tap@emph{n} hw ether fe:fd:@emph{xx}:@emph{xx}:@emph{xx}:@emph{xx}
559 The @emph{n} here is the number of the ethertap device you want to use.
560 It should be the same @emph{n} as the one you use for
561 @file{/dev/tap@emph{n}}. The @emph{xx}s are four hexadecimal numbers
562 (0--ff). With previous versions of tincd, it didn't matter what they
563 were. But newer kernels require properly set up ethernet addresses. In
564 fact, the old behavior was wrong. It is required that the @emph{xx}s
565 match the numbers of the IP address you will give to the tap device and
566 to the MyOwnVPNIP configuration (which will be discussed later).
569 @cindex hardware address
570 @strong{Tip}: for finding out what the MAC address of the tap interface
571 should be, you can use the following command:
574 $ printf 'fe:fd:%02x:%02x:%02x:%02x' 10 1 54 1
579 To activate the device, you have to assign an IP address to it. To set
580 an IP address @emph{IP} with network mask @emph{mask}, do the following:
583 ifconfig tap@emph{n} @emph{xx}.@emph{xx}.@emph{xx}.@emph{xx} netmask @emph{mask}
587 The netmask is the mask of the @emph{entire} VPN network, not just your
588 own subnet. It is the same netmask you will have to specify with the
589 VpnMask configuration variable.
603 @c ==================================================================
604 @node Configuring tinc, Running tinc, Installing tinc - installation, Top
605 @chapter Configuring tinc
608 * Multiple networks::
609 * How connections work::
610 * Configuration file::
614 @c ==================================================================
615 @node Multiple networks, How connections work, Configuring tinc, Configuring tinc
616 @section Multiple networks
620 It is perfectly OK for you to run more than one tinc daemon.
621 However, in its default form, you will soon notice that you can't use
622 two different configuration files without the -c option.
624 We have thought of another way of dealing with this: network names. This
625 means that you call tincd with the -n argument, which will assign a name
628 The effect of this is that the daemon will set its configuration
629 ``root'' to /etc/tinc/nn/, where nn is your argument to the -n
630 option. You'll notice that it appears in syslog as ``tinc.nn''.
632 However, it is not strictly necessary that you call tinc with the -n
633 option. In this case, the network name would just be empty, and it will
634 be used as such. tinc now looks for files in /etc/tinc/, instead of
635 /etc/tinc/nn/; the configuration file should be /etc/tinc/tinc.conf,
636 and the passphrases are now expected to be in /etc/tinc/passphrases/.
638 But it is highly recommended that you use this feature of tinc, because
639 it will be so much clearer whom your daemon talks to. Hence, we will
640 assume that you use it.
643 @c ==================================================================
644 @node How connections work, Configuration file, Multiple networks, Configuring tinc
645 @section How connections work
647 Before going on, first a bit on how tinc sees connections.
649 When tinc starts up, it reads in the configuration file and parses the
650 command-line options. If it sees a `ConnectTo' value in the file, it
651 will try to connect to it, on the given port. If this fails, tinc exits.
654 @c ==================================================================
655 @node Configuration file, Example, How connections work, Configuring tinc
656 @section Configuration file
658 The actual configuration of the daemon is done in the file
659 @file{/etc/tinc/nn/tinc.conf}.
661 This file consists of comments (lines started with a #) or assignments
668 The variable names are case insensitive, and any spaces, tabs, newlines
669 and carriage returns are ignored. Note: it is not required that you put
670 in the `=' sign, but doing so improves readability. If you leave it
671 out, remember to replace it with at least one space character.
677 @c ==================================================================
678 @node Variables, , Configuration file, Configuration file
679 @subsection Variables
681 Here are all valid variables, listed in alphabetical order. The default
682 value, required or optional is given between parentheses.
684 @c straight from the manpage
686 @item ConnectPort = <port> (655)
687 Connect to the upstream host (given with the ConnectTo directive) on
688 port port. port may be given in decimal (default), octal (when preceded
689 by a single zero) or hexadecimal (prefixed with 0x). port is the port
690 number for both the UDP and the TCP (meta) connections.
692 @item ConnectTo = <IP address|hostname> (optional)
693 Specifies which host to connect to on startup. Multiple ConnectTo variables
694 may be specified, if connecting to the first one fails then tinc will try
695 the next one, and so on. It is possible to specify hostnames for dynamic IP
696 addresses (like those given on dyndns.org), tinc will not cache the resolved
699 If you don't specify a host with ConnectTo, regardless of whether a
700 value for ConnectPort is given, tinc won't connect at all, and will
701 instead just listen for incoming connections.
703 @item Hostnames = <yes|no> (no)
704 This option selects whether IP addresses (both real and on the VPN) should
705 be resolved. Since DNS lookups are blocking, it might affect tinc's
706 efficiency, even stopping the daemon for a few seconds everytime it does
707 a lookup if your DNS server is not responding.
709 This does not affect resolving hostnames to IP addresses from the configuration
712 @item IndirectData = <yes|no> (no)
713 This option specifies whether other tinc daemons besides the one you
714 specified with ConnectTo can make a direct connection to you. This is
715 especially useful if you are behind a firewall and it is impossible
716 to make a connection from the outside to your tinc daemon. Otherwise,
717 it is best to leave this option out or set it to no.
719 @item Interface = <device> (optional)
720 If you have more than one network interface in your computer, tinc will by
721 default listen on all of them for incoming connections. It is possible to
722 bind tinc to a single interface like eth0 or ppp0 with this variable.
724 @item InterfaceIP = <local address> (optional)
725 If your computer has more than one IP address on a single interface (for example
726 if you are running virtual hosts), tinc will by default listen on all of them for
727 incoming connections. It is possible to bind tinc to a single IP address with
728 this variable. It is still possible to listen on several interfaces at the same
729 time though, if they share the same IP address.
731 @item KeyExpire = <seconds> (3600)
732 This option controls the time the encryption keys used to encrypt the data
733 are valid. It is common practice to change keys at regular intervals to
734 make it even harder for crackers, even though it is thought to be nearly
735 impossible to crack a single key.
737 @item ListenPort = <port> (655)
738 Listen on local port port. The computer connecting to this daemon should
739 use this number as the argument for his ConnectPort.
741 @item MyOwnVPNIP = <local address[/maskbits]> (required)
742 The local address is the number that the daemon will propagate to
743 other daemons on the network when it is identifying itself. Hence this
744 will be the file name of the passphrase file that the other end expects
745 to find the passphrase in.
747 The local address is the IP address of the tap device, not the real IP
748 address of the host running tincd. Due to changes in recent kernels, it
749 is also necessary that you make the ethernet (also known as MAC) address
750 equal to the IP address (see the example).
752 maskbits is the number of bits set to 1 in the netmask part.
754 @item MyVirtualIP = <local address[/maskbits]>
755 This is an alias for MyOwnVPNIP.
757 @item Passphrases = <directory> (/etc/tinc/NETNAME/passphrases)
758 The directory where tinc will look for passphrases when someone tries to
759 connect. Please see the manpage for genauth(8) for more information
760 about passphrases as used by tinc.
762 @item PingTimeout = <seconds> (5)
763 The number of seconds of inactivity that tinc will wait before sending a
764 probe to the other end. If that other end doesn't answer within that
765 same amount of seconds, the connection is terminated, and the others
766 will be notified of this.
768 @item TapDevice = <device> (/dev/tap0)
769 The ethertap device to use. Note that you can only use one device per
770 daemon. The info pages of the tinc package contain more information
771 about configuring an ethertap device for Linux.
773 @item TCPonly = <yes|no> (no, experimental)
774 If this variable is set to yes, then the packets are tunnelled over a TCP
775 connection instead of a UDP connection. This is especially useful for those
776 who want to run a tinc daemon from behind a masquerading firewall, or if
777 UDP packet routing is disabled somehow. This is experimental code,
778 try this at your own risk.
780 @item VpnMask = <mask> (optional)
781 The mask that defines the scope of the entire VPN. This option is not used
782 by the tinc daemon itself, but can be used by startup scripts to configure
783 the ethertap devices correctly.
788 @c ==================================================================
789 @node Example, , Configuration file, Configuring tinc
793 Imagine the following situation. An A-based company wants to connect
794 three branch offices in B, C and D using the internet. All four offices
795 have a 24/7 connection to the internet.
797 A is going to serve as the center of the network. B and C will connect
798 to A, and D will connect to C. Each office will be assigned their own IP
802 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
803 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
804 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
805 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
808 ``gateway'' is the VPN IP address of the machine that is running the
809 tincd. ``internet IP'' is the IP address of the firewall, which does not
810 need to run tincd, but it must do a port forwarding of TCP&UDP on port
811 655 (unless otherwise configured).
813 In this example, it is assumed that eth0 is the interface that points to
814 the inner LAN of the office, although this could also be the same as the
815 interface that leads to the internet. The configuration of the real
816 interface is also shown as a comment, to give you an idea of how these
817 example host is set up.
821 @emph{A} would be configured like this:
824 #ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
825 ifconfig tap0 hw ether fe:fd:0a:01:36:01
826 ifconfig tap0 10.1.54.1 netmask 255.0.0.0
829 and in /etc/tinc/tinc.conf:
832 TapDevice = /dev/tap0
833 MyVirtualIP = 10.1.54.1/16
840 #ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
841 ifconfig tap0 hw ether fe:fd:0a:02:01:0c
842 ifconfig tap0 10.2.1.12 netmask 255.0.0.0
845 and in /etc/tinc/tinc.conf:
848 TapDevice = /dev/tap0
849 MyVirtualIP = 10.2.1.12/16
854 Note here that the internal address (on eth0) doesn't have to be the
855 same as on the tap0 device. Also, ConnectTo is given so that no-one can
856 connect to this node.
861 #ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
862 ifconfig tap0 hw ether fe:fd:0a:03:45:fe
863 ifconfig tap0 10.3.69.254 netmask 255.0.0.0
866 and in /etc/tinc/A/tinc.conf:
869 MyVirtualIP = 10.3.69.254/16
870 TapDevice = /dev/tap1
876 C already has another daemon that runs on port 655, so they have to
877 reserve another port for tinc. It can connect to other tinc daemons on
878 the regular port though, so no ConnectPort variable is needed.
879 They also use the netname to distinguish
880 between the two. tinc is started with `tincd -n A'.
885 #ifconfig tap0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
886 ifconfig tap0 hw ether fe:fd:0a:04:03:20
887 ifconfig tap0 10.4.3.32 netmask 255.0.0.0
890 and in /etc/tinc/tinc.conf:
893 MyVirtualIP = 10.4.3.32/16
899 D will be connecting to C, which has a tincd running for this network on
900 port 2000. Hence they need to put in a ConnectPort, but it doesn't need
901 to have a different ListenPort.
903 @subsubheading Authentication
905 A, B, C and D all generate a passphrase with genauth 2048, the output is
906 stored in /etc/tinc/passphrases/local, except for C, where it should be
907 /etc/tinc/A/passphrases/local.
909 A stores a copy of B's passphrase in /etc/tinc/passphrases/10.2.1.12
911 A stores a copy of C's passphrase in /etc/tinc/passphrases/10.3.69.254
913 B stores a copy of A's passphrase in /etc/tinc/passphrases/10.1.54.1
915 C stores a copy of A's passphrase in /etc/tinc/A/passphrases/10.1.54.1
917 C stores a copy of D's passphrase in /etc/tinc/A/passphrases/10.4.3.32
919 D stores a copy of C's passphrase in /etc/tinc/passphrases/10.3.69.254
921 @subsubheading Starting
923 A has to start their tincd first. Then come B and C, where C has to
924 provide the option `-n A', because they have more than one tinc
925 network. Finally, D's tincd is started.
929 @c ==================================================================
930 @node Running tinc, Technical information, Configuring tinc, Top
931 @chapter Running tinc
933 Running tinc isn't just as easy as typing `tincd' and hoping everything
934 will just work out the way you wanted. Instead, the use of tinc is a
935 project that involves trust relations and more than one computer.
943 @c ==================================================================
944 @node Managing keys, Runtime options, Running tinc, Running tinc
945 @section Managing keys
947 Before attempting to start tinc, you have to create passphrases. When
948 tinc tries to make a connection, it exchanges some sensitive
949 data. Before doing so, it likes to know if the other end is
952 To do this, both ends must have some knowledge about the other. In the
953 case of tinc this is the authentication passphrase.
955 This passphrase is a number, which is chosen at random. This number is
956 then sent to the other computers which want to talk to us directly. To
957 avoid breaking security, this should be done over a known secure channel
958 (such as ssh or similar).
960 All passphrases are stored in the passphrases directory, which is
961 normally /etc/tinc/nn/passphrases/, but it may be changed using the
962 `Passphrases' option in the config file.
964 To generate a passphrase, run `genauth'. genauth takes one argument,
965 which is the length of the passphrase in bits. The length of the
966 passphrase should be in the range 1024--2048 for a key length of 128
967 bits. genauth creates a random number of the specified length, and puts
970 Every computer that wants to participate in the VPN should do this, and
971 store the output in the passphrases directory, in the file @file{local}.
973 When every computer has his own local key, it should copy it to the
974 computer that it wants to talk to directly. (i.e. the one it connects to
975 during startup.) This should be done via a secure channel, because it is
976 sensitive information. If this is not done securely, someone might break
979 Those non-local passphrase files must have the name of the VPN IP
980 address that they will advertise to you. For instance, if a computer
981 tells us it likes to be 10.1.1.3 with netmask 255.255.0.0, the file
982 should still be called 10.1.1.3, and not 10.1.0.0.
985 @c ==================================================================
986 @node Runtime options, , Managing keys, Running tinc
987 @section Runtime options
989 Besides the settings in the configuration file, tinc also accepts some
990 command line options.
992 This list is a longer version of that in the manpage. The latter is
993 generated automatically, so may be more up-to-date.
997 @item -c, --config=FILE
998 Read configuration options from FILE. The default is
999 @file{/etc/tinc/nn/tinc.conf}.
1002 Increase debug level. The higher it gets, the more gets
1003 logged. Everything goes via syslog.
1005 0 is the default, only some basic information connection attempts get
1006 logged. Setting it to 1 will log a bit more, still not very
1007 disturbing. With two -d's tincd will log protocol information, which can
1008 get pretty noisy. Three or more -d's will output every single packet
1009 that goes out or comes in, which probably generates more data than the
1013 Attempt to kill a running tincd and exit. A TERM signal (15) gets sent
1014 to the daemon that his its PID in /var/run/tinc.nn.pid.
1016 Because it kills only one tincd, you should use -n here if you use it
1019 @item -n, --net=NETNAME
1020 Connect to net NETNAME. @xref{Multiple networks}.
1022 @item -t, --timeout=TIMEOUT
1023 Seconds to wait before giving a timeout. Should not be set too low,
1024 because every time tincd senses a timeout, it disconnects and reconnects
1025 again, which will cause unnecessary network traffic and log messages.
1028 Display a short reminder of these runtime options and terminate.
1031 Output version information and exit.
1036 @c ==================================================================
1037 @node Technical information, About us, Running tinc, Top
1038 @chapter Technical information
1041 @c ==================================================================
1047 @node The Connection, Security, Technical information, Technical information
1048 @section The basic philosophy of the way tinc works
1051 tinc is a daemon that takes VPN data and transmit that to another host
1052 computer over the existing Internet infrastructure.
1055 * Protocol Preview::
1056 * The Meta-connection::
1060 @c ==================================================================
1061 @node Protocol Preview, The Meta-connection, The Connection, The Connection
1062 @subsection A preview of the way the tinc works
1066 The data itself is read from a character device file, the so-called
1067 @emph{ethertap} device. This device is associated with a network
1068 interface. Any data sent to this interface can be read from the device,
1069 and any data written to the device gets sent from the interface. Data to
1070 and from the device is formatted as if it were a normal ethernet card,
1071 so a frame is preceded by two MAC addresses and a @emph{frame type}
1074 So when tinc reads an ethernet frame from the device, it determines its
1075 type. Right now, tinc can only handle Internet Protocol version 4 (IPv4)
1076 frames. Plans to support other protocols are being made. When tinc knows
1077 which type of frame it has read, it can also read the source and
1078 destination address from it.
1080 Now it is time that the frame gets encrypted. Currently the only
1081 encryption algorithm available is blowfish.
1083 @cindex encapsulating
1084 When the encryption is ready, time has come to actually transport the
1085 packet to the destination computer. We do this by sending the packet
1086 over an UDP connection to the destination host. This is called
1087 @emph{encapsulating}, the VPN packet (though now encrypted) is
1088 encapsulated in another IP datagram.
1090 When the destination receives this packet, the same thing happens, only
1091 in reverse. So it does a decrypt on the contents of the UDP datagram,
1092 and it writes the decrypted information to its own ethertap device.
1095 @c ==================================================================
1096 @node The Meta-connection, , Protocol Preview, The Connection
1097 @subsection The meta-connection
1099 Having only an UDP connection available is not enough. Though suitable
1100 for transmitting data, we want to be able to reliably send other
1101 information, such as routing and encryption information to somebody.
1103 TCP is a better alternative, because it already contains protection
1104 against information being lost, unlike UDP.
1106 So we establish two connections. One for the encrypted VPN data, and one
1107 for other information, the meta-data. Hence, we call the second
1108 connection the meta-connection. We can now be sure that the
1109 meta-information doesn't get lost on the way to another computer.
1111 @cindex data-protocol
1112 @cindex meta-protocol
1113 Like with any communication, we must have a protocol, so that everybody
1114 knows what everything stands for, an how he should react. Because we
1115 have two connections, we also have two protocols. The protocol used for
1116 the UDP data is the ``data-protocol,'' the other one is the
1119 The reason we don't use TCP for both protocols is that UDP is much
1120 better for encapsulation, even while it is less reliable. The real
1121 problem is that when TCP would be used to encapsulate a TCP stream
1122 that's on the private network, for every packet sent there would be
1123 three ACK's sent instead of just one. Furthermore, if there would be
1124 a timeout, both TCP streams would sense the timeout, and both would
1125 start resending packets.
1127 @c ==================================================================
1128 @node Security, , The Connection, Technical information
1129 @section About tinc's encryption and other security-related issues.
1133 tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
1134 alleged Cabal was/is an organization that was said to keep an eye on the
1135 entire Internet. As this is exactly what you @emph{don't} want, we named
1136 the tinc project after TINC.
1139 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
1140 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
1141 exactly that: encrypt.
1143 This chapter is a mixture of ideas, reasoning and explanation, please
1144 don't take it too serious.
1153 @c ==================================================================
1154 @node Key Types, Key Management, Security, Security
1155 @subsection Key Types
1156 @c FIXME: check if I'm not talking nonsense
1158 There are several types of encryption keys. Tinc uses two of them,
1159 symmetric private keypairs and public/private keypairs.
1161 Public/private keypairs are used in public key cryptography. It enables
1162 someone to send out a public key with which other people can encrypt their
1163 data. The encrypted data now can only be decrypted by the person who has
1164 the private key that matches the public key. So, a public key only allows
1165 @emph{other} people to send encrypted messages to you. This is very useful
1166 in setting up private communications channels. Just send out your public key
1167 and other people can talk to you in a secure way. But how can you know
1168 the other person is who he says he is?
1170 For authentication itself tinc uses symmetric private keypairs, referred
1171 to as a passphrase. The identity of each tinc daemon is defined by it's
1172 passphrase (like you can be identified by your social security number).
1173 Every tinc daemon that is allowed to connect to you has a copy of your
1174 passphrase (hence symmetrical).
1176 It would also be possible to use public/private keypairs for authentication,
1177 so that you could shout out your public key and don't need to keep it
1178 secret (like the passphrase you would have to send to someone else). Also,
1179 no one else has to know a private key from you.
1180 Both forms have their pros and cons, and at the moment tinc just uses passphrases
1181 (which are computationaly more efficient and perhaps in some way more
1184 @c ==================================================================
1185 @node Key Management, Authentication, Key Types, Security
1186 @subsection Key Management
1187 @c FIXME change for the current protocol
1189 @cindex Diffie-Hellman
1190 You can't just send a private encryption key to your peer, because
1191 somebody else might already be listening to you. So you'll have to
1192 negotiate over a shared but secret key. One way to do this is by using
1193 the ``Diffie-Hellman key exchange'' protocol
1194 (@uref{http://www.rsa.com/rsalabs/faq/html/3-6-1.html}). The idea is as
1197 You have two participants A and B that want to agree over a shared
1198 secret encryption key. Both parties have some large prime number p and a
1199 generator g. These numbers may be known to the outside world, and hence
1200 may be included in the source distribution.
1203 Both parties then generate a secret key. A generates a, and computes g^a
1204 mod p. This is then sent to B; while B computes g^b mod p, and transmits
1205 this to A, b being generated by B. Both a and b must be smaller than
1208 Both parties then calculate g^ab mod p = k. k is the new, shared, but
1211 To obtain a key k of a sufficient length (128 bits in our vpnd), p
1212 should be 2^129-1 or more.
1215 @c ==================================================================
1216 @node Authentication, Protection, Key Management, Security
1217 @subsection Authentication
1220 @cindex man-in-the-middle attack
1221 Because the Diffie-Hellman protocol is in itself vulnerable to the
1222 ``man-in-the-middle attack,'' we should introduce an authentication
1225 We will let A transmit a passphrase that is also known to B encrypted
1226 with g^a, before A sends this to B. This way, B can check whether A is
1227 really A or just someone else.
1228 B will never receive the real passphrase though, because it was
1229 encrypted using public/private keypairs. This way there is no way an
1230 imposter could steal A's passphrase.
1233 @c ehrmz... but we only use 1024 bits passphrases ourselves? [guus]
1234 This passphrase should be 2304 bits for a symmetric encryption
1235 system. But since an asymmetric system is more secure, we could do with
1236 2048 bits. This only holds if the passphrase is very random.
1238 These passphrases could be stored in a file that is non-readable by
1239 anyone else but root; e.g. @file{/etc/tinc/passphrases} with UID 0
1240 and permissions mode 700.
1242 The only thing that needs to be taken care of is how A can securely send
1243 a copy of it's passphrase to B if B doesn't have it yet. This could be
1244 done via mail with PGP, but you should be really convinced of the
1245 identity of the person who owns the email address you are sending this to.
1246 Swapping floppy disks in real life might be the best way to do this!
1249 @c ==================================================================
1250 @node Protection, , Authentication, Security
1251 @subsection Protecting your data
1253 Now we have securely hidden our data. But a malicious cracker may still
1254 bother you by randomly altering the encrypted data he intercepts.
1256 @c FIXME what the hell is this all about? remove? IT
1258 @c ==================================================================
1259 @node About us, Concept Index, Technical information, Top
1264 * Contact Information::
1269 @c ==================================================================
1270 @node Contact Information, Authors, About us, About us
1271 @section Contact information
1273 tinc's main page is at @url{http://tinc.nl.linux.org/},
1274 this server is located in the Netherlands.
1276 We have an IRC channel on the Open Projects IRC network. Connect to
1277 @uref{http://openprojects.nu/services/irc.html, irc.openprojects.net},
1278 and join channel #tinc.
1281 @c ==================================================================
1282 @node Authors, , Contact Information, About us
1286 @item Ivo Timmermans (zarq) (@email{itimmermans@@bigfoot.com})
1287 Main coder/hacker and maintainer of the package.
1289 @item Guus Sliepen (guus)
1290 Originator of it all, co-author.
1292 @item Wessel Dankers (Ubiq)
1293 General obfuscater of the code.
1297 Thank you's to: Dekan, Emphyrio, vDong
1299 Greetings to: braque, Fluor, giggles, macro, smoke, tribbel
1302 @c ==================================================================
1303 @node Concept Index, , About us, Top
1304 @c node-name, next, previous, up
1305 @unnumbered Concept Index
1307 @c ==================================================================
1311 @c ==================================================================