1 secnet - flexible VPN software
5 secnet is Copyright (C) 1995--2003 Stephen Early <steve@greenend.org.uk>
6 It is distributed under the terms of the GNU General Public License,
7 version 2 or later. See the file COPYING for more information.
9 The portable snprintf implementation in snprintf.c is Copyright (C)
10 1999 Mark Martinec <mark.martinec@ijs.si> and is distributed under the
11 terms of the Frontier Artistic License. You can find the standard
12 version of snprintf.c at http://www.ijs.si/software/snprintf/
14 The IP address handling library in ipaddr.py is Copyright (C)
15 1996--2000 Cendio Systems AB, and is distributed under the terms of
20 secnet allows large virtual private networks to be constructed
21 spanning multiple separate sites. It is designed for the case where a
22 private network connecting many hosts is 'hidden' behind a single
23 globally-routable IP address, but can also be applied in other
24 circumstances. It communicates entirely using UDP, and works well
25 with gateways that implement network address translation.
27 If you are installing secnet to join an existing VPN, you should read
28 the 'INSTALL' file and your particular VPN's documentation now. You
29 may need to refer back to this file for information on the netlink and
30 comm sections of the configuration file.
32 If you are thinking about setting up a new VPN of any size (from one
33 providing complete links between multiple sites to a simple
34 laptop-to-host link), read the section in this file on 'Creating a
37 * Mailing lists and bug reporting
39 There are two mailing lists associated with secnet: an 'announce' list
40 and a 'discuss' list. Their addresses are:
41 http://www.chiark.greenend.org.uk/mailman/listinfo/secnet-announce
42 http://www.chiark.greenend.org.uk/mailman/listinfo/secnet-discuss
44 The -announce list receives one message per secnet release. The
45 -discuss list is for general discussion, including help with
46 configuration, bug reports, feature requests, etc.
48 Bug reports should be sent to <steve@greenend.org.uk>; they will be
49 forwarded to the -discuss list by me.
55 * secnet configuration file format
57 By default secnet on linux reads /etc/secnet/secnet.conf. The default
58 may be different on other platforms.
60 This file defines a dictionary (a mapping from keys to values) full of
61 configuration information for secnet. Two keys must be defined in
62 this file for secnet to start. One is "system", a dictionary
63 containing systemwide control parameters. The other is "sites", a
64 list of all the sites that you intend to communicate with.
66 The configuration file has a very simple syntax; keys are defined as
75 Keys must match the following regular expression:
76 [[:alpha:]_][[:alnum:]\-_]*
78 i.e. the first character must be an alpha or an underscore, and the
79 remaining characters may be alphanumeric, '-' or '_'.
81 Keys can be defined to be a comma-separated list of any of the
87 a dictionary of definitions, enclosed in { }
88 a "closure", followed by arguments
89 a path to a key that already exists, to reference that definition
91 Note that dictionaries can be nested: a key in one dictionary can
92 refer to another dictionary. When secnet looks for a key in a
93 particular directory and can't find it, it looks in the dictionary's
94 lexical 'parents' in turn until it finds it (or fails to find it at
95 all and stops with an error).
97 Definitions can refer to previous definitions by naming them with a
98 path. Paths are key1/key2/key3... (starting from wherever we find
99 key1, i.e. in the current dictionary or any of its parents), or
100 alternatively /key1/key2/key3... (to start from the root).
101 Definitions cannot refer to future definitions.
110 The following paths are valid:
122 Note that f/g/e is NOT 4.
124 Elements that are lists are inserted into lists in definitions, not
125 referenced by them (i.e. you can't have lists of lists).
127 Some closures may be followed by an argument list in ( ), and may
128 return any number of whatever type they like (including other
129 closures). Some types of closure (typically those returned from
130 invokations of other closures) cannot be invoked.
132 closure { definitions } is short for closure({definitions}).
134 The main body of secnet, and all the additional modules, predefine
135 some keys in the root dictionary. The main ones are:
137 yes, true, True, TRUE, on: the boolean value True
138 no, false, False, FALSE, off: the boolean value False
139 makelist: turns a dictionary (arg1) into a list of definitions
141 readfile: reads a file (arg1) and returns it as a string
142 map: applies the closure specified as arg1 to each of the
143 remaining elements in the list in turn. Returns a list
144 made up of the outputs of the closure.
146 Keys defined by modules are described below, in the module
149 Other configuration files can be included inline by writing "include
150 filename" at the start of a line.
152 After the configuration file is read, secnet looks for particular keys
153 in configuration space to tell it what to do:
155 system: a dictionary which can contain the following keys:
156 log (log closure): a destination for system messages
157 userid (string): the userid for secnet to run as once it drops privileges
158 pidfile (string): where to store its PID
160 sites: a list of closures of type 'site', which define other tunnel
161 endpoints that secnet will attempt to communicate with
163 * secnet command line options
165 Usage: secnet [OPTION]...
167 -f, --silent, --quiet suppress error messages
168 -w, --nowarnings suppress warnings
169 -v, --verbose output extra diagnostics
170 -c, --config=filename specify a configuration file
171 -j, --just-check-config stop after reading configfile
172 -n, --nodetach do not run in background
173 -d, --debug=item,... set debug options
174 --help display this help and exit
175 --version output version information and exit
177 * secnet builtin modules
182 adns (closure => resolver closure)
185 config (string): optional, a resolv.conf for ADNS to use
190 randomsrc (closure => randomsrc closure)
192 randomsrc: string[,bool]
193 arg1: filename of random source
194 arg2: if True then source is blocking
199 udp (closure => comm closure)
202 address (string): IP address to listen and send on
203 port (integer): UDP port to listen and send on
204 buffer (buffer closure): buffer for incoming packets
205 authbind (string): optional, path to authbind-helper program
210 logfile (closure => log closure)
211 syslog (closure => log closure)
213 logfile: dict argument
214 filename (string): where to log to
215 class (string list): what type of messages to log
216 { "debug-config", M_DEBUG_CONFIG },
217 { "debug-phase", M_DEBUG_PHASE },
218 { "debug", M_DEBUG },
219 { "all-debug", M_DEBUG|M_DEBUG_PHASE|M_DEBUG_CONFIG },
221 { "notice", M_NOTICE },
222 { "warning", M_WARNING },
223 { "error", M_ERROR },
224 { "security", M_SECURITY },
225 { "fatal", M_FATAL },
226 { "default", M_WARNING|M_ERROR|M_SECURITY|M_FATAL },
227 { "verbose", M_INFO|M_NOTICE|M_WARNING|M_ERROR|M_SECURITY|M_FATAL },
230 logfile will close and reopen its file upon receipt of SIGHUP.
232 syslog: dict argument
233 ident (string): include this string in every log message
234 facility (string): facility to log as
235 { "authpriv", LOG_AUTHPRIV },
236 { "cron", LOG_CRON },
237 { "daemon", LOG_DAEMON },
238 { "kern", LOG_KERN },
239 { "local0", LOG_LOCAL0 },
240 { "local1", LOG_LOCAL1 },
241 { "local2", LOG_LOCAL2 },
242 { "local3", LOG_LOCAL3 },
243 { "local4", LOG_LOCAL4 },
244 { "local5", LOG_LOCAL5 },
245 { "local6", LOG_LOCAL6 },
246 { "local7", LOG_LOCAL7 },
248 { "mail", LOG_MAIL },
249 { "news", LOG_NEWS },
250 { "syslog", LOG_SYSLOG },
251 { "user", LOG_USER },
257 sysbuffer (closure => buffer closure)
259 sysbuffer: integer[,dict]
262 lockdown (boolean): if True, mlock() the buffer
267 site (closure => site closure)
270 local-name (string): this site's name for itself
271 name (string): the name of the site's peer
272 link (netlink closure)
274 resolver (resolver closure)
275 random (randomsrc closure)
276 local-key (rsaprivkey closure)
277 address (string): optional, DNS name used to find our peer
278 port (integer): mandatory if 'address' is specified: the port used
280 key (rsapubkey closure): our peer's public key
281 transform (transform closure): how to mangle packets sent between sites
284 key-lifetime (integer): max lifetime of a session key, in ms [one hour]
285 setup-retries (integer): max number of times to transmit a key negotiation
287 setup-timeout (integer): time between retransmissions of key negotiation
288 packets, in ms [2000]
289 wait-time (integer): after failed key setup, wait this long (in ms) before
290 allowing another attempt [20000]
291 renegotiate-time (integer): if we see traffic on the link after this time
292 then renegotiate another session key immediately (in ms)
293 [half key-lifetime, or key-lifetime minus 5 mins, whichever is longer].
294 keepalive (bool): if True then attempt always to keep a valid session key.
295 Not actually currently implemented. [false]
296 log-events (string list): types of events to log for this site
297 unexpected: unexpected key setup packets (may be late retransmissions)
298 setup-init: start of attempt to setup a session key
299 setup-timeout: failure of attempt to setup a session key, through timeout
300 activate-key: activation of a new session key
301 timeout-key: deletion of current session key through age
302 security: anything potentially suspicious
303 state-change: steps in the key setup protocol
304 packet-drop: whenever we throw away an outgoing packet
305 dump-packets: every key setup packet we see
306 errors: failure of name resolution, internal errors
307 peer-addrs: changes to sets of peer addresses (interesting for mobile peers)
308 all: everything (too much!)
309 mobile (bool): if True then peer is "mobile" ie we assume it may
310 change its apparent IP address and port number without either it
311 or us being aware of the change; so, we remember the last several
312 port/addr pairs we've seen and send packets to all of them
313 (subject to a timeout). We maintain one set of addresses for key
314 setup exchanges, and another for data traffic. Two communicating
315 peers must not each regard the other as mobile, or all the traffic
316 in each direction will be triplicated (strictly, transmitted
317 mobile-peers-max times) and anyway two peers whose public contact
318 address may suddenly change couldn't communicate reliably because
319 their contact addresses might both change at once. [false]
320 mobile-peers-max (integer): Maximum number of peer port/addr pairs we
321 remember and send to. Must be at least 1 and no more than 5. [3]
322 mobile-peer-expiry (integer): For "mobile" peers only, the length
323 of time (in seconds) for which we will keep sending to multiple
324 address/ports from which we have not seen incoming traffic. [120]
325 local-mobile (bool): if True then other peers have been told we are
326 "mobile". This should be True iff the peers' site configurations
327 for us have "mobile True" (and if we find a site configuration for
328 ourselves in the config, we insist on this). The effect is to
329 check that there are no links both ends of which are allegedly
330 mobile (which is not supported, so those links are ignored). [false]
335 serpent256-cbc (closure => transform closure)
340 null-netlink (closure => closure or netlink closure)
342 null-netlink: dict argument
343 name (string): name for netlink device, used in log messages
344 networks (string list): networks on the host side of the netlink device
345 remote-networks (string list): networks that may be claimed
346 by the remote site using this netlink device
347 local-address (string): IP address of host's tunnel interface
348 secnet-address (string): IP address of this netlink device
349 ptp-address (string): IP address of the other end of a point-to-point link
350 mtu (integer): MTU of host's tunnel interface
352 Only one of secnet-address or ptp-address may be specified. If
353 point-to-point mode is in use then the "routes" option must also be
354 specified, and netlink returns a netlink closure that should be used
355 directly with the "link" option to the site closure. If
356 point-to-point mode is not in use then netlink returns a closure that
357 may be invoked using a dict argument with the following keys to yield
359 routes (string list): networks reachable down the tunnel attached to
360 this instance of netlink
361 options (string list):
362 allow-route: allow packets coming from this tunnel to be routed to
363 other tunnels as well as the host (used for mobile devices like laptops)
364 soft: remove these routes from the host's routing table when
365 the tunnel link quality is zero
366 mtu (integer): default MTU over this link; may be updated by tunnel code
368 Netlink will dump its current routing table to the system/log on
374 userv-ipif (closure => netlink closure)
376 userv-ipif: dict argument
377 userv-path (string): optional, where to find userv ["userv"]
378 service-user (string): optional, username for userv-ipif service ["root"]
379 service-name (string): optional, name of userv-ipif service ["ipif"]
380 buffer (buffer closure): buffer for assembly of host->secnet packets
381 plus generic netlink options, as for 'null-netlink'
386 tun (closure => netlink closure) [only on linux-2.4]
387 tun-old (closure => netlink closure)
390 flavour (string): optional, type of TUN interface to use
391 ("guess","linux","bsd","streams")
392 device (string): optional, path of TUN/TAP device file ["/dev/net/tun"]
393 interface (string): optional, name of tunnel network interface
394 ifconfig-path (string): optional, path to ifconfig command
395 route-path (string): optional, path to route command
396 ifconfig-type (string): optional, how to perform ifconfig
397 route-type (string): optional, how to add and remove routes
398 types are: "guess", "ioctl", "bsd", "linux", "solaris-2.5"
399 buffer (buffer closure): buffer for host->secnet packets
400 plus generic netlink options, as for 'null-netlink'
402 I recommend you don't specify the 'interface' option unless you're
403 doing something that requires the interface name to be constant.
408 rsa-private (closure => rsaprivkey closure)
409 rsa-public (closure => rsapubkey closure)
411 rsa-private: string[,bool]
412 arg1: filename of SSH private key file (version 1, no password)
413 arg2: whether to check that the key is usable [default True]
415 rsa-public: string,string
416 arg1: encryption key (decimal)
417 arg2: modulus (decimal)
422 diffie-hellman (closure => dh closure)
424 diffie-hellman: string,string[,bool]
426 arg2: generator (hex)
427 arg3: whether to check that the modulus is prime [default True]
442 makelist (dictionary => list of definitions)
443 readfile (string => string)
444 map (closure,list => list)
447 returns a list consisting of the definitions in the dictionary. The keys
451 reads the named file and returns its contents as a string
454 applies the closure specified as arg1 to each of the elements in the list.
455 Returns a list made up of the outputs of the closure.