1 \input texinfo @c -*-texinfo-*-
2 @c $Id: tinc.texi,v 1.8.4.9 2000/11/30 23:39:55 zarq Exp $
11 * tinc: (tinc). The tinc Manual.
14 This is the info manual for tinc, a Virtual Private Network daemon.
16 Copyright @copyright{} 1998,199,2000 Ivo Timmermans
17 <itimmermans@@bigfoot.com>, Guus Sliepen <guus@@sliepen.warande.net> and
18 Wessel Dankers <wsl@@nl.linux.org>.
20 $Id: tinc.texi,v 1.8.4.9 2000/11/30 23:39:55 zarq Exp $
22 Permission is granted to make and distribute verbatim copies of this
23 manual provided the copyright notice and this permission notice are
24 preserved on all copies.
26 Permission is granted to copy and distribute modified versions of this
27 manual under the conditions for verbatim copying, provided that the
28 entire resulting derived work is distributed under the terms of a
29 permission notice identical to this one.
35 @subtitle Setting up a Virtual Private Network with tinc
36 @author Ivo Timmermans and Guus Sliepen
39 @vskip 0pt plus 1filll
41 Copyright @copyright{} 1998,1999,2000 Ivo Timmermans
42 <itimmermans@@bigfoot.com>, Guus Sliepen <guus@@sliepen.warande.net> and
43 Wessel Dankers <wsl@@nl.linux.org>.
45 $Id: tinc.texi,v 1.8.4.9 2000/11/30 23:39:55 zarq Exp $
47 Permission is granted to make and distribute verbatim copies of this
48 manual provided the copyright notice and this permission notice are
49 preserved on all copies.
51 Permission is granted to copy and distribute modified versions of this
52 manual under the conditions for verbatim copying, provided that the
53 entire resulting derived work is distributed under the terms of a
54 permission notice identical to this one.
58 @c ==================================================================
59 @node Top, Introduction, (dir), (dir)
62 * Introduction:: Introduction
63 * Installing tinc - preparations::
64 * Installing tinc - installation::
67 * Technical information::
69 * Concept Index:: All used terms explained
75 @c ==================================================================
76 @node Introduction, Installing tinc - preparations, Top, Top
80 tinc is a Virtual Private Network (VPN) daemon that uses tunneling and
81 encryption to create a secure private network between hosts on the
84 Because the tunnel appears to the IP level network code as a normal
85 network device, there is no need to adapt any existing software.
87 This tunneling 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 do not interfere with
122 each other. Mostly, virtual networks appear like a singe LAN, even though
123 they can span the entire world. But virtual networks can't be secured
124 by using firewalls, because the traffic that flows through it has to go
125 through the internet, where other people can look at it.
127 When one introduces encryption, we can form a true VPN. Other people may
128 see encrypted traffic, but if they don't know how to decipher it (they
129 need to know the key for that), they cannot read the information that flows
130 through the VPN. This is what tinc was made for.
133 tinc uses normal IP datagrams to encapsulate data that goes over the VPN
134 network link. In this case it's also clear that the network is
135 @emph{virtual}, because no direct network link has to exist between to
138 As is the case with either type of VPN, anybody could eavesdrop. Or
139 worse, alter data. Hence it's probably advisable to encrypt the data
140 that flows over the network.
143 @c ==================================================================
144 @node tinc, Supported platforms, VPNs, Introduction
149 I really don't quite remember what got us started, but it must have been
150 Guus' idea. He wrote a simple implementation (about 50 lines of C) that
151 used the @emph{ethertap} device that Linux knows of since somewhere
152 about kernel 2.1.60. It didn't work immediately and he improved it a
153 bit. At this stage, the project was still simply called @samp{vpnd}.
155 Since then, a lot has changed---to say the least.
158 tinc now supports encryption, it consists of a single daemon (tincd) for
159 both the receiving and sending end, it has become largely
160 runtime-configurable---in short, it has become a full-fledged
161 professional package.
163 A lot can---and will be---changed. I have a few things that I'd like to
164 see in the future releases of tinc. Not everything will be available in
165 the near future. Our first objective is to make tinc work perfectly as
166 it stands, and then add more advanced features.
168 Meanwhile, we're always open-minded towards new ideas. And we're
172 @c ==================================================================
173 @node Supported platforms, , tinc, Introduction
174 @section Supported platforms
176 tinc works on Linux, FreeBSD and Solaris. These are the three platforms
177 that are supported by the universial TUN/TAP device driver, so if
178 support for other operating systems is added to this driver, perhaps
179 tinc will run on them as well. Without this driver, tinc will most
180 likely compile and run, but it will not be able to send or receive data
183 For a more up to date list, please check the list on our website:
184 @uref{http://tinc.nl.linux.org/platforms.html}.
187 @c ==================================================================
190 tinc was first written for Linux running on an intel x86 processor, so
191 this is the best supported platform. The protocol however, and actually
192 anything about tinc, has been rewritten to support random byte ordering
193 and arbitrary word length. So in theory it should run on other
194 processors that Linux runs on. Take care however, we haven't been able
195 to really test it yet. If you want to run tinc on another platform than
196 x86, and want to tell us how it went, please do so.
198 tinc uses the ethertap device that is provided in the standard kernel
199 since version 2.1.60, so anything above that (2.2.x, 2.3.x, and the
200 2.4.0-testx (which is current at the time of this writing) kernel
201 versions) is able to support tinc.
204 @c ==================================================================
207 tinc on FreeBSD 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: FreeBSD 3.x, 4.x, 5.x.
212 @c ==================================================================
215 tinc on Solaris relies on the universial TUN/TAP driver for its data
216 acquisition from the kernel. Therefore, tinc suports the same platforms
217 as this driver. These are: Solaris, 2.1.x.
226 @c Preparing your system
233 @c ==================================================================
234 @node Installing tinc - preparations, Installing tinc - installation, Introduction, Top
235 @chapter Installing tinc: preparations
237 This chapter contains information on how to prepare your system to
241 * Configuring the kernel::
246 @c ==================================================================
247 @node Configuring the kernel, Libraries, Installing tinc - preparations, Installing tinc - preparations
248 @section Configuring the kernel
250 If you are running Linux, chances are good that your kernel already
251 supports all the devices that tinc needs for proper operation. For
252 example, the standard kernel from Redhat Linux already has support for
253 ethertap and netlink compiled in. Debian users can use the modconf
254 utility to select the modules. If your Linux distribution supports this
255 method of selecting devices, look out for something called `ethertap',
256 and `netlink_dev'. You need both these devices.
258 If you can install these devices in a similar manner, you may skip this
262 * Configuration of the Linux kernel::
263 * Configuration of the FreeBSD kernel::
264 * Configuration of the Solaris kernel::
268 @c ==================================================================
269 @node Configuration of the Linux kernel, Configuration of the FreeBSD kernel, Configuring the kernel, Configuring the kernel
270 @subsection Configuring the Linux kernel
272 Since this particular implementation only runs on 2.1 or higher Linux
273 kernels, you should grab one (2.2 is current at this time). A 2.0 port
274 is not really possible, unless someone tells me someone ported the
275 ethertap and netlink devices back to 2.0.
277 If you are unfamiliar with the process of configuring and compiling a
278 new kernel, you should read the
279 @uref{http://howto.linuxberg.com/LDP/HOWTO/Kernel-HOWTO.html, Kernel
280 HOWTO} first. Do that now!
282 Here are the options you have to turn on when configuring a new
288 Code maturity level options
289 [*] Prompt for development and/or incomplete code/drivers
291 [*] Kernel/User netlink socket
292 <*> Netlink device emulation
293 Network device support
294 <*> Ethertap network tap
297 For kernel 2.3.x and 2.4.x:
300 Code maturity level options
301 [*] Prompt for development and/or incomplete code/drivers
303 [*] Kernel/User netlink socket
304 <*> Netlink device emulation
305 Network device support
306 <*> Universal TUN/TAP device driver support
310 Any other options not mentioned here are not relevant to tinc. If you
311 decide to build any of these as dynamic kernel modules, it's a good idea
312 to add these lines to @file{/etc/modules.conf}.
316 alias char-major-36 netlink_dev
319 If you have a 2.4 kernel, you can also choose to use the `Ethertap
320 network tap' device. This is marked obsolete, because the universal
321 TUN/TAP driver is a newer implementation that is supposed to be used in
322 favor of ethertap. For tinc, it doesn't really matter which one you
323 choose; based on the device file name, tinc will make the right choice
324 about what protocol to use.
326 Finally, after having set up other options, build the kernel and boot
327 it. Unfortunately it's not possible to insert these modules in a
331 @c ==================================================================
332 @node Configuration of the FreeBSD kernel, Configuration of the Solaris kernel, Configuration of the Linux kernel, Configuring the kernel
333 @subsection Configuring the FreeBSD kernel
335 This section will contain information on how to configure your FreeBSD
336 kernel to support the universal TUN/TAP device. For 5.0 and 4.1
337 systems, this is included in the kernel configuration, for earlier
338 systems (4.0 and 3.x), you need to install the universal TUN/TAP driver
341 Unfortunately somebody still has to write the text.
344 @c ==================================================================
345 @node Configuration of the Solaris kernel, , Configuration of the FreeBSD kernel, Configuring the kernel
346 @subsection Configuring the Solaris kernel
348 This section will contain information on how to configure your Solaris
349 kernel to support the universal TUN/TAP device. You need to install
350 this driver yourself.
352 Unfortunately somebody still has to write the text.
355 @c ==================================================================
356 @node Libraries, , Configuring the kernel, Installing tinc - preparations
360 Before you can configure or build tinc, you need to have the OpenSSL
361 library installed on your system. If you try to configure tinc without
362 having installed it, configure will give you an error message, and stop.
369 @c ==================================================================
370 @node OpenSSL, , Libraries, Libraries
374 For all cryptography-related functions, tinc uses the functions provided
375 by the OpenSSL library. We recommend using version 0.9.5 or 0.9.6 of
376 this library. Other versions may also work, but we can guarantee
379 If this library is not installed, you wil get an error when configuring
380 tinc for build. Support for running tinc without having OpenSSL
381 installed @emph{may} be added in the future.
383 You can use your operating system's package manager to install this if
384 available. Make sure you install the development AND runtime versions
387 If you have to install OpenSSL manually, you can get the source code
388 from @url{http://www.openssl.org/}. Instructions on how to configure,
389 build and install this package are included within the package. Please
390 make sure you build development and runtime libraries (which is the
393 If you installed the OpenSSL libraries from source, it may be necessary
394 to let configure know where they are, by passing configure one of the
395 --with-openssl-* parameters.
398 --with-openssl=DIR OpenSSL library and headers prefix
399 --with-openssl-include=DIR OpenSSL headers directory
400 (Default is OPENSSL_DIR/include)
401 --with-openssl-lib=DIR OpenSSL library directory
402 (Default is OPENSSL_DIR/lib)
415 @c ==================================================================
416 @node Installing tinc - installation, Configuring tinc, Installing tinc - preparations, Top
417 @chapter Installing tinc: installation
419 If you use Redhat or Debian, you may want to install one of the
420 precompiled packages for your system. These packages are equipped with
421 system startup scripts and sample configurations.
423 If you don't run either of these systems, or you want to compile tinc
424 for yourself, you can use the source. The source is distributed under
425 the GNU General Public License (GPL). Download the source from the
426 @uref{http://tinc.nl.linux.org/download.html, download page}, which has
427 the checksums of these files listed; you may wish to check these with
428 md5sum before continuing.
430 tinc comes in a handy autoconf/automake package, which you can just
431 treat the same as any other package. Which is just untar it, type
432 `configure' and then `make'.
434 More detailed instructions are in the file @file{INSTALL}, which is
435 included in the source distribution.
444 @c ==================================================================
445 @node Building tinc, System files, Installing tinc - installation, Installing tinc - installation
446 @section Building tinc
448 Detailed instructions on configuring the source and building tinc can be
449 found in the file called @file{INSTALL}.
452 @c ==================================================================
453 @node System files, Interfaces, Building tinc, Installing tinc - installation
454 @section System files
456 Before you can run tinc, you
464 @c ==================================================================
465 @node Device files, Other files, System files, System files
466 @subsection Device files
468 First, you'll need the special device file(s) that form the interface
469 between the kernel and the daemon.
471 The permissions for these files have to be such that only the super user
472 may read/write to this file. You'd want this, because otherwise
473 eavesdropping would become a bit too easy. This does, however, imply
474 that you'd have to run tincd as root.
476 If you use the universal TUN/TAP driver, you have to create the
477 following device files (unless they already exist):
480 mknod -m 600 /dev/... c .. ..
484 If you want to have more devices, the device numbers will be .. .. ...
486 If you use Linux, and you run the new 2.4 kernel using the devfs
487 filesystem, then the tap device will be automatically generated as
488 @file{/dev/netlink/tap0}.
490 If you use Linux and have kernel 2.2.x, you have to make the ethertap
494 mknod -m 600 /dev/tap0 c 36 16
498 Any further ethertap devices have minor device number 16 through 31.
501 @c ==================================================================
502 @node Other files, , Device files, System files
503 @subsection Other files
505 @subsubheading @file{/etc/networks}
507 You may add a line to @file{/etc/networks} so that your VPN will get a
508 symbolic name. For example:
514 This has nothing to do with the MyVPNIP configuration variable that will be
515 discussed later, it is only to make the output of the route command more
518 @subsubheading @file{/etc/services}
520 You may add this line to @file{/etc/services}. The effect is that you
521 may supply a @samp{tinc} as a valid port number to some programs. The
522 number 655 is registered with the IANA.
527 # Ivo Timmermans <itimmermans@@bigfoot.com>
531 @c ==================================================================
532 @node Interfaces, , System files, Installing tinc - installation
535 Before you can start transmitting data over the tinc tunnel, you must
536 set up the ethertap network devices.
538 First, decide which IP addresses you want to have associated with these
539 devices, and what network mask they must have. You also need these
540 numbers when you are going to configure tinc itself. @xref{Configuring
543 It doesn't matter much which part you do first, setting up the network
544 devices or configure tinc. But they both have to be done before you try
547 The actual setup of the ethertap device is quite simple, just repeat
551 ifconfig tap@emph{n} hw ether fe:fd:00:00:00:00
555 @cindex hardware address
556 @strong{Note:} Since version 1.0pre3, all interface addresses are set to
557 this address, whereas previous versions required the MAC to match the
561 To activate the device, you have to assign an IP address to it. To set
562 an IP address @emph{IP} with network mask @emph{mask}, do the following:
565 ifconfig tap@emph{n} @emph{xx}.@emph{xx}.@emph{xx}.@emph{xx} netmask @emph{mask}
569 The netmask is the mask of the @emph{entire} VPN network, not just your
570 own subnet. It is the same netmask you will have to specify with the
571 VpnMask configuration variable.
585 @c ==================================================================
586 @node Configuring tinc, Running tinc, Installing tinc - installation, Top
587 @chapter Configuring tinc
590 * Multiple networks::
591 * How connections work::
592 * Configuration file::
596 @c ==================================================================
597 @node Multiple networks, How connections work, Configuring tinc, Configuring tinc
598 @section Multiple networks
602 It is perfectly OK for you to run more than one tinc daemon.
603 However, in its default form, you will soon notice that you can't use
604 two different configuration files without the -c option.
606 We have thought of another way of dealing with this: network names. This
607 means that you call tincd with the -n argument, which will assign a name
610 The effect of this is that the daemon will set its configuration
611 ``root'' to /etc/tinc/nn/, where nn is your argument to the -n
612 option. You'll notice that it appears in syslog as ``tinc.nn''.
614 However, it is not strictly necessary that you call tinc with the -n
615 option. In this case, the network name would just be empty, and it will
616 be used as such. tinc now looks for files in /etc/tinc/, instead of
617 /etc/tinc/nn/; the configuration file should be /etc/tinc/tinc.conf,
618 and the passphrases are now expected to be in /etc/tinc/passphrases/.
620 But it is highly recommended that you use this feature of tinc, because
621 it will be so much clearer whom your daemon talks to. Hence, we will
622 assume that you use it.
625 @c ==================================================================
626 @node How connections work, Configuration file, Multiple networks, Configuring tinc
627 @section How connections work
629 Before going on, first a bit on how tinc sees connections.
631 When tinc starts up, it reads in the configuration file and parses the
632 command-line options. If it sees a `ConnectTo' value in the file, it
633 will try to connect to it, on the given port. If this fails, tinc exits.
636 @c ==================================================================
637 @node Configuration file, Example, How connections work, Configuring tinc
638 @section Configuration file
640 The actual configuration of the daemon is done in the file
641 @file{/etc/tinc/nn/tinc.conf}.
643 This file consists of comments (lines started with a #) or assignments
650 The variable names are case insensitive, and any spaces, tabs, newlines
651 and carriage returns are ignored. Note: it is not required that you put
652 in the `=' sign, but doing so improves readability. If you leave it
653 out, remember to replace it with at least one space character.
659 @c ==================================================================
660 @node Variables, , Configuration file, Configuration file
661 @subsection Variables
663 Here are all valid variables, listed in alphabetical order. The default
664 value, required or optional is given between parentheses.
666 @c straight from the manpage
668 @item ConnectPort = <port> (655)
669 Connect to the upstream host (given with the ConnectTo directive) on
670 port port. port may be given in decimal (default), octal (when preceded
671 by a single zero) or hexadecimal (prefixed with 0x). port is the port
672 number for both the UDP and the TCP (meta) connections.
674 @item ConnectTo = <IP address|hostname> (optional)
675 Specifies which host to connect to on startup. Multiple ConnectTo variables
676 may be specified, if connecting to the first one fails then tinc will try
677 the next one, and so on. It is possible to specify hostnames for dynamic IP
678 addresses (like those given on dyndns.org), tinc will not cache the resolved
681 If you don't specify a host with ConnectTo, regardless of whether a
682 value for ConnectPort is given, tinc won't connect at all, and will
683 instead just listen for incoming connections.
685 @item Hostnames = <yes|no> (no)
686 This option selects whether IP addresses (both real and on the VPN) should
687 be resolved. Since DNS lookups are blocking, it might affect tinc's
688 efficiency, even stopping the daemon for a few seconds everytime it does
689 a lookup if your DNS server is not responding.
691 This does not affect resolving hostnames to IP addresses from the configuration
694 @item IndirectData = <yes|no> (no)
695 This option specifies whether other tinc daemons besides the one you
696 specified with ConnectTo can make a direct connection to you. This is
697 especially useful if you are behind a firewall and it is impossible
698 to make a connection from the outside to your tinc daemon. Otherwise,
699 it is best to leave this option out or set it to no.
701 @item Interface = <device> (optional)
702 If you have more than one network interface in your computer, tinc will by
703 default listen on all of them for incoming connections. It is possible to
704 bind tinc to a single interface like eth0 or ppp0 with this variable.
706 @item InterfaceIP = <local address> (optional)
707 If your computer has more than one IP address on a single interface (for example
708 if you are running virtual hosts), tinc will by default listen on all of them for
709 incoming connections. It is possible to bind tinc to a single IP address with
710 this variable. It is still possible to listen on several interfaces at the same
711 time though, if they share the same IP address.
713 @item KeyExpire = <seconds> (3600)
714 This option controls the time the encryption keys used to encrypt the data
715 are valid. It is common practice to change keys at regular intervals to
716 make it even harder for crackers, even though it is thought to be nearly
717 impossible to crack a single key.
719 @item ListenPort = <port> (655)
720 Listen on local port port. The computer connecting to this daemon should
721 use this number as the argument for his ConnectPort.
723 @item MyOwnVPNIP = <local address[/maskbits]> (required)
724 The local address is the number that the daemon will propagate to
725 other daemons on the network when it is identifying itself. Hence this
726 will be the file name of the passphrase file that the other end expects
727 to find the passphrase in.
729 The local address is the IP address of the tap device, not the real IP
730 address of the host running tincd. Due to changes in recent kernels, it
731 is also necessary that you make the ethernet (also known as MAC) address
732 equal to the IP address (see the example).
734 maskbits is the number of bits set to 1 in the netmask part.
736 @item MyVirtualIP = <local address[/maskbits]>
737 This is an alias for MyOwnVPNIP.
739 @item PingTimeout = <seconds> (5)
740 The number of seconds of inactivity that tinc will wait before sending a
741 probe to the other end. If that other end doesn't answer within that
742 same amount of seconds, the connection is terminated, and the others
743 will be notified of this.
745 @item PrivateKey = <key>
746 This is a sequence of hexadecimal numbers, as generated by ``tincd
747 --generate-keys''. Please be careful with line breaking, the entire key
748 should be on one line.
750 @item PublicKey = <key>
751 This is a sequence of hexadecimal numbers, as generated by ``tincd
752 --generate-keys''. Please be careful with line breaking, the entire key
753 should be on one line.
755 @item TapDevice = <device> (/dev/tap0)
756 The ethertap device to use. Note that you can only use one device per
757 daemon. The info pages of the tinc package contain more information
758 about configuring an ethertap device for Linux.
760 @item TCPonly = <yes|no> (no, experimental)
761 If this variable is set to yes, then the packets are tunnelled over a TCP
762 connection instead of a UDP connection. This is especially useful for those
763 who want to run a tinc daemon from behind a masquerading firewall, or if
764 UDP packet routing is disabled somehow. This is experimental code,
765 try this at your own risk.
767 @item VpnMask = <mask> (optional)
768 The mask that defines the scope of the entire VPN. This option is not used
769 by the tinc daemon itself, but can be used by startup scripts to configure
770 the ethertap devices correctly.
775 @c ==================================================================
776 @node Example, , Configuration file, Configuring tinc
780 Imagine the following situation. An A-based company wants to connect
781 three branch offices in B, C and D using the internet. All four offices
782 have a 24/7 connection to the internet.
784 A is going to serve as the center of the network. B and C will connect
785 to A, and D will connect to C. Each office will be assigned their own IP
789 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
790 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
791 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
792 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
795 ``gateway'' is the VPN IP address of the machine that is running the
796 tincd. ``internet IP'' is the IP address of the firewall, which does not
797 need to run tincd, but it must do a port forwarding of TCP&UDP on port
798 655 (unless otherwise configured).
800 In this example, it is assumed that eth0 is the interface that points to
801 the inner LAN of the office, although this could also be the same as the
802 interface that leads to the internet. The configuration of the real
803 interface is also shown as a comment, to give you an idea of how these
804 example host is set up.
808 @emph{A} would be configured like this:
811 #ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
812 ifconfig tap0 hw ether fe:fd:0a:01:36:01
813 ifconfig tap0 10.1.54.1 netmask 255.0.0.0
816 and in /etc/tinc/tinc.conf:
819 TapDevice = /dev/tap0
820 MyVirtualIP = 10.1.54.1/16
827 #ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
828 ifconfig tap0 hw ether fe:fd:0a:02:01:0c
829 ifconfig tap0 10.2.1.12 netmask 255.0.0.0
832 and in /etc/tinc/tinc.conf:
835 TapDevice = /dev/tap0
836 MyVirtualIP = 10.2.1.12/16
841 Note here that the internal address (on eth0) doesn't have to be the
842 same as on the tap0 device. Also, ConnectTo is given so that no-one can
843 connect to this node.
848 #ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
849 ifconfig tap0 hw ether fe:fd:0a:03:45:fe
850 ifconfig tap0 10.3.69.254 netmask 255.0.0.0
853 and in /etc/tinc/A/tinc.conf:
856 MyVirtualIP = 10.3.69.254/16
857 TapDevice = /dev/tap1
863 C already has another daemon that runs on port 655, so they have to
864 reserve another port for tinc. It can connect to other tinc daemons on
865 the regular port though, so no ConnectPort variable is needed.
866 They also use the netname to distinguish
867 between the two. tinc is started with `tincd -n A'.
872 #ifconfig tap0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
873 ifconfig tap0 hw ether fe:fd:0a:04:03:20
874 ifconfig tap0 10.4.3.32 netmask 255.0.0.0
877 and in /etc/tinc/tinc.conf:
880 MyVirtualIP = 10.4.3.32/16
886 D will be connecting to C, which has a tincd running for this network on
887 port 2000. Hence they need to put in a ConnectPort, but it doesn't need
888 to have a different ListenPort.
890 @subsubheading Authentication
892 A, B, C and D all generate a passphrase with genauth 2048, the output is
893 stored in /etc/tinc/passphrases/local, except for C, where it should be
894 /etc/tinc/A/passphrases/local.
896 A stores a copy of B's passphrase in /etc/tinc/passphrases/10.2.1.12
898 A stores a copy of C's passphrase in /etc/tinc/passphrases/10.3.69.254
900 B stores a copy of A's passphrase in /etc/tinc/passphrases/10.1.54.1
902 C stores a copy of A's passphrase in /etc/tinc/A/passphrases/10.1.54.1
904 C stores a copy of D's passphrase in /etc/tinc/A/passphrases/10.4.3.32
906 D stores a copy of C's passphrase in /etc/tinc/passphrases/10.3.69.254
908 @subsubheading Starting
910 A has to start their tincd first. Then come B and C, where C has to
911 provide the option `-n A', because they have more than one tinc
912 network. Finally, D's tincd is started.
916 @c ==================================================================
917 @node Running tinc, Technical information, Configuring tinc, Top
918 @chapter Running tinc
920 Running tinc isn't just as easy as typing `tincd' and hoping everything
921 will just work out the way you wanted. Instead, the use of tinc is a
922 project that involves trust relations and more than one computer.
930 @c ==================================================================
931 @node Managing keys, Runtime options, Running tinc, Running tinc
932 @section Managing keys
934 Before attempting to start tinc, you have to create passphrases. When
935 tinc tries to make a connection, it exchanges some sensitive
936 data. Before doing so, it likes to know if the other end is
939 To do this, both ends must have some knowledge about the other. In the
940 case of tinc this is the authentication passphrase.
942 This passphrase is a number, which is chosen at random. This number is
943 then sent to the other computers which want to talk to us directly. To
944 avoid breaking security, this should be done over a known secure channel
945 (such as ssh or similar).
947 All passphrases are stored in the passphrases directory, which is
948 normally /etc/tinc/nn/passphrases/, but it may be changed using the
949 `Passphrases' option in the config file.
951 To generate a passphrase, run `genauth'. genauth takes one argument,
952 which is the length of the passphrase in bits. The length of the
953 passphrase should be in the range 1024--2048 for a key length of 128
954 bits. genauth creates a random number of the specified length, and puts
957 Every computer that wants to participate in the VPN should do this, and
958 store the output in the passphrases directory, in the file @file{local}.
960 When every computer has his own local key, it should copy it to the
961 computer that it wants to talk to directly. (i.e. the one it connects to
962 during startup.) This should be done via a secure channel, because it is
963 sensitive information. If this is not done securely, someone might break
966 Those non-local passphrase files must have the name of the VPN IP
967 address that they will advertise to you. For instance, if a computer
968 tells us it likes to be 10.1.1.3 with netmask 255.255.0.0, the file
969 should still be called 10.1.1.3, and not 10.1.0.0.
972 @c ==================================================================
973 @node Runtime options, , Managing keys, Running tinc
974 @section Runtime options
976 Besides the settings in the configuration file, tinc also accepts some
977 command line options.
979 This list is a longer version of that in the manpage. The latter is
980 generated automatically, so may be more up-to-date.
984 @item -c, --config=FILE
985 Read configuration options from FILE. The default is
986 @file{/etc/tinc/nn/tinc.conf}.
989 Increase debug level. The higher it gets, the more gets
990 logged. Everything goes via syslog.
992 0 is the default, only some basic information connection attempts get
993 logged. Setting it to 1 will log a bit more, still not very
994 disturbing. With two -d's tincd will log protocol information, which can
995 get pretty noisy. Three or more -d's will output every single packet
996 that goes out or comes in, which probably generates more data than the
1000 Attempt to kill a running tincd and exit. A TERM signal (15) gets sent
1001 to the daemon that his its PID in /var/run/tinc.nn.pid.
1003 Because it kills only one tincd, you should use -n here if you use it
1006 @item -n, --net=NETNAME
1007 Connect to net NETNAME. @xref{Multiple networks}.
1009 @item -t, --timeout=TIMEOUT
1010 Seconds to wait before giving a timeout. Should not be set too low,
1011 because every time tincd senses a timeout, it disconnects and reconnects
1012 again, which will cause unnecessary network traffic and log messages.
1015 Display a short reminder of these runtime options and terminate.
1018 Output version information and exit.
1023 @c ==================================================================
1024 @node Technical information, About us, Running tinc, Top
1025 @chapter Technical information
1028 @c ==================================================================
1034 @node The Connection, Security, Technical information, Technical information
1035 @section The basic philosophy of the way tinc works
1038 tinc is a daemon that takes VPN data and transmit that to another host
1039 computer over the existing Internet infrastructure.
1042 * Protocol Preview::
1043 * The Meta-connection::
1047 @c ==================================================================
1048 @node Protocol Preview, The Meta-connection, The Connection, The Connection
1049 @subsection A preview of the way the tinc works
1053 The data itself is read from a character device file, the so-called
1054 @emph{ethertap} device. This device is associated with a network
1055 interface. Any data sent to this interface can be read from the device,
1056 and any data written to the device gets sent from the interface. Data to
1057 and from the device is formatted as if it were a normal ethernet card,
1058 so a frame is preceded by two MAC addresses and a @emph{frame type}
1061 So when tinc reads an ethernet frame from the device, it determines its
1062 type. Right now, tinc can only handle Internet Protocol version 4 (IPv4)
1063 frames. Plans to support other protocols are being made. When tinc knows
1064 which type of frame it has read, it can also read the source and
1065 destination address from it.
1067 Now it is time that the frame gets encrypted. Currently the only
1068 encryption algorithm available is blowfish.
1070 @cindex encapsulating
1071 When the encryption is ready, time has come to actually transport the
1072 packet to the destination computer. We do this by sending the packet
1073 over an UDP connection to the destination host. This is called
1074 @emph{encapsulating}, the VPN packet (though now encrypted) is
1075 encapsulated in another IP datagram.
1077 When the destination receives this packet, the same thing happens, only
1078 in reverse. So it does a decrypt on the contents of the UDP datagram,
1079 and it writes the decrypted information to its own ethertap device.
1082 @c ==================================================================
1083 @node The Meta-connection, , Protocol Preview, The Connection
1084 @subsection The meta-connection
1086 Having only an UDP connection available is not enough. Though suitable
1087 for transmitting data, we want to be able to reliably send other
1088 information, such as routing and encryption information to somebody.
1090 TCP is a better alternative, because it already contains protection
1091 against information being lost, unlike UDP.
1093 So we establish two connections. One for the encrypted VPN data, and one
1094 for other information, the meta-data. Hence, we call the second
1095 connection the meta-connection. We can now be sure that the
1096 meta-information doesn't get lost on the way to another computer.
1098 @cindex data-protocol
1099 @cindex meta-protocol
1100 Like with any communication, we must have a protocol, so that everybody
1101 knows what everything stands for, an how he should react. Because we
1102 have two connections, we also have two protocols. The protocol used for
1103 the UDP data is the ``data-protocol,'' the other one is the
1106 The reason we don't use TCP for both protocols is that UDP is much
1107 better for encapsulation, even while it is less reliable. The real
1108 problem is that when TCP would be used to encapsulate a TCP stream
1109 that's on the private network, for every packet sent there would be
1110 three ACK's sent instead of just one. Furthermore, if there would be
1111 a timeout, both TCP streams would sense the timeout, and both would
1112 start resending packets.
1114 @c ==================================================================
1115 @node Security, , The Connection, Technical information
1116 @section About tinc's encryption and other security-related issues.
1120 tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
1121 alleged Cabal was/is an organization that was said to keep an eye on the
1122 entire Internet. As this is exactly what you @emph{don't} want, we named
1123 the tinc project after TINC.
1126 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
1127 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
1128 exactly that: encrypt.
1130 This chapter is a mixture of ideas, reasoning and explanation, please
1131 don't take it too serious.
1140 @c ==================================================================
1141 @node Key Types, Key Management, Security, Security
1142 @subsection Key Types
1143 @c FIXME: check if I'm not talking nonsense
1145 There are several types of encryption keys. Tinc uses two of them,
1146 symmetric private keypairs and public/private keypairs.
1148 Public/private keypairs are used in public key cryptography. It enables
1149 someone to send out a public key with which other people can encrypt their
1150 data. The encrypted data now can only be decrypted by the person who has
1151 the private key that matches the public key. So, a public key only allows
1152 @emph{other} people to send encrypted messages to you. This is very useful
1153 in setting up private communications channels. Just send out your public key
1154 and other people can talk to you in a secure way. But how can you know
1155 the other person is who he says he is?
1157 For authentication itself tinc uses symmetric private keypairs, referred
1158 to as a passphrase. The identity of each tinc daemon is defined by it's
1159 passphrase (like you can be identified by your social security number).
1160 Every tinc daemon that is allowed to connect to you has a copy of your
1161 passphrase (hence symmetrical).
1163 It would also be possible to use public/private keypairs for authentication,
1164 so that you could shout out your public key and don't need to keep it
1165 secret (like the passphrase you would have to send to someone else). Also,
1166 no one else has to know a private key from you.
1167 Both forms have their pros and cons, and at the moment tinc just uses passphrases
1168 (which are computationaly more efficient and perhaps in some way more
1171 @c ==================================================================
1172 @node Key Management, Authentication, Key Types, Security
1173 @subsection Key Management
1174 @c FIXME change for the current protocol
1176 @cindex Diffie-Hellman
1177 You can't just send a private encryption key to your peer, because
1178 somebody else might already be listening to you. So you'll have to
1179 negotiate over a shared but secret key. One way to do this is by using
1180 the ``Diffie-Hellman key exchange'' protocol
1181 (@uref{http://www.rsa.com/rsalabs/faq/html/3-6-1.html}). The idea is as
1184 You have two participants A and B that want to agree over a shared
1185 secret encryption key. Both parties have some large prime number p and a
1186 generator g. These numbers may be known to the outside world, and hence
1187 may be included in the source distribution.
1190 Both parties then generate a secret key. A generates a, and computes g^a
1191 mod p. This is then sent to B; while B computes g^b mod p, and transmits
1192 this to A, b being generated by B. Both a and b must be smaller than
1195 Both parties then calculate g^ab mod p = k. k is the new, shared, but
1198 To obtain a key k of a sufficient length (128 bits in our vpnd), p
1199 should be 2^129-1 or more.
1202 @c ==================================================================
1203 @node Authentication, Protection, Key Management, Security
1204 @subsection Authentication
1207 @cindex man-in-the-middle attack
1208 Because the Diffie-Hellman protocol is in itself vulnerable to the
1209 ``man-in-the-middle attack,'' we should introduce an authentication
1212 We will let A transmit a passphrase that is also known to B encrypted
1213 with g^a, before A sends this to B. This way, B can check whether A is
1214 really A or just someone else.
1215 B will never receive the real passphrase though, because it was
1216 encrypted using public/private keypairs. This way there is no way an
1217 imposter could steal A's passphrase.
1220 @c ehrmz... but we only use 1024 bits passphrases ourselves? [guus]
1221 This passphrase should be 2304 bits for a symmetric encryption
1222 system. But since an asymmetric system is more secure, we could do with
1223 2048 bits. This only holds if the passphrase is very random.
1225 These passphrases could be stored in a file that is non-readable by
1226 anyone else but root; e.g. @file{/etc/tinc/passphrases} with UID 0
1227 and permissions mode 700.
1229 The only thing that needs to be taken care of is how A can securely send
1230 a copy of it's passphrase to B if B doesn't have it yet. This could be
1231 done via mail with PGP, but you should be really convinced of the
1232 identity of the person who owns the email address you are sending this to.
1233 Swapping floppy disks in real life might be the best way to do this!
1236 @c ==================================================================
1237 @node Protection, , Authentication, Security
1238 @subsection Protecting your data
1240 Now we have securely hidden our data. But a malicious cracker may still
1241 bother you by randomly altering the encrypted data he intercepts.
1243 @c FIXME what the hell is this all about? remove? IT
1245 @c ==================================================================
1246 @node About us, Concept Index, Technical information, Top
1251 * Contact Information::
1256 @c ==================================================================
1257 @node Contact Information, Authors, About us, About us
1258 @section Contact information
1260 tinc's main page is at @url{http://tinc.nl.linux.org/},
1261 this server is located in the Netherlands.
1263 We have an IRC channel on the Open Projects IRC network. Connect to
1264 @uref{http://openprojects.nu/services/irc.html, irc.openprojects.net},
1265 and join channel #tinc.
1268 @c ==================================================================
1269 @node Authors, , Contact Information, About us
1273 @item Ivo Timmermans (zarq) (@email{itimmermans@@bigfoot.com})
1274 Main coder/hacker and maintainer of the package.
1276 @item Guus Sliepen (guus)
1277 Originator of it all, co-author.
1279 @item Wessel Dankers (Ubiq)
1280 General obfuscater of the code.
1284 Thank you's to: Dekan, Emphyrio, vDong
1286 Greetings to: braque, Fluor, giggles, macro, smoke, tribbel
1289 @c ==================================================================
1290 @node Concept Index, , About us, Top
1291 @c node-name, next, previous, up
1292 @unnumbered Concept Index
1294 @c ==================================================================
1298 @c ==================================================================