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74eb47db | 1 | .\" -*-nroff-*- |
2 | .\". | |
fc916a09 MW |
3 | .\" Manual for the server |
4 | .\" | |
5 | .\" (c) 2008 Straylight/Edgeware | |
6 | .\" | |
7 | . | |
8 | .\"----- Licensing notice --------------------------------------------------- | |
9 | .\" | |
10 | .\" This file is part of Trivial IP Encryption (TrIPE). | |
11 | .\" | |
11ad66c2 MW |
12 | .\" TrIPE is free software: you can redistribute it and/or modify it under |
13 | .\" the terms of the GNU General Public License as published by the Free | |
14 | .\" Software Foundation; either version 3 of the License, or (at your | |
15 | .\" option) any later version. | |
fc916a09 | 16 | .\" |
11ad66c2 MW |
17 | .\" TrIPE is distributed in the hope that it will be useful, but WITHOUT |
18 | .\" ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
19 | .\" FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
20 | .\" for more details. | |
fc916a09 MW |
21 | .\" |
22 | .\" You should have received a copy of the GNU General Public License | |
11ad66c2 | 23 | .\" along with TrIPE. If not, see <https://www.gnu.org/licenses/>. |
fc916a09 MW |
24 | . |
25 | .\"-------------------------------------------------------------------------- | |
e99aedcf | 26 | .so ../common/defs.man \" @@@PRE@@@ |
fc916a09 MW |
27 | . |
28 | .\"-------------------------------------------------------------------------- | |
0647ba7c | 29 | .TH tripe 8tripe "10 February 2001" "Straylight/Edgeware" "TrIPE: Trivial IP Encryption" |
fc916a09 MW |
30 | . |
31 | .\"-------------------------------------------------------------------------- | |
74eb47db | 32 | .SH "NAME" |
fc916a09 | 33 | . |
74eb47db | 34 | tripe \- a simple VPN daemon |
fc916a09 MW |
35 | . |
36 | .\"-------------------------------------------------------------------------- | |
74eb47db | 37 | .SH "SYNOPSIS" |
fc916a09 | 38 | . |
74eb47db | 39 | .B tripe |
47828bd9 | 40 | .RB [ \-46DF ] |
74eb47db | 41 | .RB [ \-d |
42 | .IR dir ] | |
d13e5724 | 43 | .RB [ \-b |
44 | .IR addr ] | |
33ced0d3 | 45 | .RB [ \-p |
46 | .IR port ] | |
42da2a58 | 47 | .RB [ \-n |
48 | .IR tunnel ] | |
d13e5724 | 49 | .br |
85b1ebd6 | 50 | \c |
33ced0d3 | 51 | .RB [ \-U |
52 | .IR user ] | |
53 | .RB [ \-G | |
54 | .IR group ] | |
d13e5724 | 55 | .RB [ \-a |
56 | .IR socket ] | |
a9279e37 MW |
57 | .RB [ \-m |
58 | .IR mode ] | |
d13e5724 | 59 | .RB [ \-T |
60 | .IR trace-opts ] | |
74eb47db | 61 | .br |
85b1ebd6 | 62 | \c |
74eb47db | 63 | .RB [ \-k |
64 | .IR priv-keyring ] | |
65 | .RB [ \-K | |
66 | .IR pub-keyring ] | |
67 | .RB [ \-t | |
68 | .IR key-tag ] | |
fc916a09 MW |
69 | . |
70 | .\"-------------------------------------------------------------------------- | |
74eb47db | 71 | .SH "DESCRIPTION" |
fc916a09 | 72 | . |
74eb47db | 73 | The |
74 | .B tripe | |
75 | program is a server which can provide strong IP-level encryption and | |
1a19f865 | 76 | authentication between co-operating hosts. The program and its protocol |
77 | are deliberately very simple, to make analysing them easy and to help | |
78 | build trust rapidly in the system. | |
74eb47db | 79 | .SS "Overview" |
80 | The | |
81 | .B tripe | |
82 | server manages a number of secure connections to other `peer' hosts. | |
83 | Each daemon is given a private key of its own, and a file of public keys | |
84 | for the peers with which it is meant to communicate. It is responsible | |
85 | for negotiating sets of symmetric keys with its peers, and for | |
86 | encrypting, encapsulating and sending IP packets to its peers, and | |
87 | decrypting, checking and de-encapsulating packets it receives from | |
88 | them. | |
89 | .PP | |
90 | When the server starts, it creates a Unix-domain socket on which it | |
91 | listens for administration commands. It also logs warnings and | |
92 | diagnostic information to the programs connected to its admin socket. | |
93 | Clients connected to the socket can add new peers, and remove or find | |
94 | out about existing peers. The textual protocol used to give the | |
95 | .B tripe | |
96 | server admin commands is described in | |
97 | .BR tripe\-admin (5). | |
98 | A client program | |
99 | .BR tripectl (1) | |
100 | is provided to allow commands to be sent to the server either | |
101 | interactively or by simple scripts. | |
102 | .SS "Command-line arguments" | |
103 | If not given any command-line arguments, | |
104 | .B tripe | |
105 | will initialize by following these steps: | |
1a19f865 | 106 | .hP 1. |
107 | It sets the directory named by the | |
108 | .B TRIPEDIR | |
109 | environment variable (or | |
f7b5d108 | 110 | .B "\*(/c" |
1a19f865 | 111 | if the variable is unset) as the current directory. |
112 | .hP 2. | |
f492fa0b | 113 | It acquires a UDP socket. The default port is 4070 |
74eb47db | 114 | It will use this socket to send and receive all communications with its |
115 | peer servers. The port chosen may be discovered by means of the | |
116 | .B PORT | |
117 | admin command (see | |
118 | .BR tripe\-admin (5)). | |
1a19f865 | 119 | .hP 3. |
74eb47db | 120 | It loads the private key with the tag or type name |
fc5f4823 MW |
121 | .B tripe |
122 | (or, failing that, | |
74eb47db | 123 | .B tripe\-dh |
fc5f4823 | 124 | for backwards compatibility reasons) from the Catacomb-format file |
74eb47db | 125 | .BR keyring , |
126 | and loads the file | |
127 | .B keyring.pub | |
128 | ready for extracting the public keys of peers as they're introduced. | |
129 | (The format of these files is described in | |
130 | .BR keyring (5). | |
131 | They are maintained using the program | |
132 | .BR key (1) | |
133 | provided with the Catacomb distribution.) | |
1a19f865 | 134 | .hP 4. |
74eb47db | 135 | It creates and listens to the Unix-domain socket |
136 | .BR tripesock . | |
137 | .PP | |
138 | Following this, the server enters its main loop, accepting admin | |
139 | connections and obeying any administrative commands, and communicating | |
140 | with peers. It also treats its standard input and standard output | |
141 | streams as an admin connection, reading commands from standard input and | |
33ced0d3 | 142 | writing responses and diagnostics messages to standard output. Finally, |
143 | it will reload keys from its keyring files if it notices that they've | |
144 | changed (it checks inode number and modification time) \- there's no | |
145 | need to send a signal. | |
74eb47db | 146 | .PP |
147 | Much of this behaviour may be altered by giving | |
148 | .B tripe | |
149 | suitable command-line options: | |
150 | .TP | |
151 | .B "\-h, \-\-help" | |
152 | Writes a brief description of the command-line options available to | |
153 | standard output and exits with status 0. | |
154 | .TP | |
155 | .B "\-v, \-\-version" | |
156 | Writes | |
157 | .BR tripe 's | |
158 | version number to standard output and exits with status 0. | |
159 | .TP | |
160 | .B "\-u, \-\-usage" | |
161 | Writes a brief usage summary to standard output and exits with status 0. | |
162 | .TP | |
42da2a58 | 163 | .B "\-\-tunnels" |
164 | Writes to standard output a list of the configured tunnel drivers, one | |
165 | per line, and exits with status 0. This is intended for the use of the | |
3cdc3f3a | 166 | start-up script, so that it can check that it will actually work. |
167 | .TP | |
47828bd9 MW |
168 | .B "\-4, \-\-ipv4" |
169 | Use only IPv4 addresses. The server will resolve names only to IPv4 | |
170 | addresses, and not attempt to create IPv6 sockets. | |
171 | .TP | |
172 | .B "\-6, \-\-ipv6" | |
173 | Use only IPv6 addresses. The server will resolve names only to IPv6 | |
174 | addresses, and not attempt to create IPv4 sockets. Note that v6-mapped | |
175 | IPv4 addresses won't work either. | |
176 | .TP | |
74eb47db | 177 | .B "\-D, \-\-daemon" |
178 | Dissociates from its terminal and starts running in the background after | |
179 | completing the initialization procedure described above. If running as | |
180 | a daemon, | |
181 | .B tripe | |
182 | will not read commands from standard input or write diagnostics to | |
183 | standard output. A better way to start | |
184 | .B tripe | |
185 | in the background is with | |
186 | .BR tripectl (1). | |
187 | .TP | |
46dde080 MW |
188 | .B "\-F, \-\-foreground" |
189 | Runs the server in the `foreground'; i.e., | |
190 | .B tripe | |
191 | will quit if it sees end-of-file on its standard input. This is | |
192 | incompatible with | |
193 | .BR \-D . | |
194 | .TP | |
74eb47db | 195 | .BI "\-d, \-\-directory=" dir |
196 | Makes | |
197 | .I dir | |
797cf76b MW |
198 | the current directory. The default directory to change to is given by |
199 | the environment variable | |
200 | .BR TRIPEDIR ; | |
201 | if that's not specified, a default default of | |
f7b5d108 | 202 | .B "\*(/c" |
797cf76b | 203 | is used. Give a current directory of |
74eb47db | 204 | .B . |
205 | if you don't want it to change directory at all. | |
206 | .TP | |
d13e5724 | 207 | .BI "\-b, \-\-bind-address="addr |
208 | Bind the UDP socket to IP address | |
209 | .I addr | |
210 | rather than the default of | |
211 | .BR INADDR_ANY . | |
212 | This is useful if your main globally-routable IP address is one you want | |
213 | to tunnel through the VPN. | |
214 | .TP | |
74eb47db | 215 | .BI "\-p, \-\-port=" port |
216 | Use the specified UDP port for all communications with peers, rather | |
f492fa0b MW |
217 | than the default port 4070. If this is zero, the kernel will assign a |
218 | free port, which can be determined using the | |
219 | .B PORT | |
220 | administration command (see | |
221 | .BR tripe-admin (5)). | |
74eb47db | 222 | .TP |
42da2a58 | 223 | .BI "\-n, \-\-tunnel=" tunnel |
224 | Use the specified tunnel driver for new peers by default. | |
225 | .TP | |
33ced0d3 | 226 | .BI "\-U, \-\-setuid=" user |
227 | Set uid to that of | |
228 | .I user | |
229 | (either a user name or integer uid) after initialization. Also set gid | |
230 | to | |
231 | .IR user 's | |
232 | primary group, unless overridden by a | |
233 | .B \-G | |
aa2405e8 MW |
234 | option. The selected user (and group) will also be the owner of the |
235 | administration socket. | |
33ced0d3 | 236 | .TP |
237 | .BI "\-G, \-\-setgid=" group | |
ec9b8aed MW |
238 | If the current effective uid is zero (i.e., the daemon was invoked as |
239 | .BR root ) | |
240 | then set gid to that of | |
33ced0d3 | 241 | .I group |
ec9b8aed MW |
242 | (either a group name or integer gid) after initialization. In any |
243 | event, arrange hat the administration socket be owned by the given | |
244 | .IR group . | |
33ced0d3 | 245 | .TP |
74eb47db | 246 | .BI "\-k, \-\-priv\-keyring=" file |
247 | Reads the private key from | |
248 | .I file | |
249 | rather than the default | |
250 | .BR keyring . | |
251 | .TP | |
252 | .BI "\-K, \-\-pub\-keyring=" file | |
253 | Reads public keys from | |
254 | .I file | |
255 | rather than the default | |
256 | .BR keyring.pub . | |
257 | This can be the same as the private keyring, but that's not recommended. | |
258 | .TP | |
259 | .BI "\-t, \-\-tag=" tag | |
260 | Uses the private key whose tag or type is | |
261 | .I tag | |
262 | rather than the default | |
fc5f4823 MW |
263 | .B tripe |
264 | or | |
74eb47db | 265 | .BR tripe\-dh . |
266 | .TP | |
267 | .BI "\-a, \-\-admin\-socket=" socket | |
268 | Accept admin connections to a Unix-domain socket named | |
797cf76b MW |
269 | .IR socket . |
270 | The default socket, if this option isn't specified, is given by the | |
271 | environment variable | |
272 | .BR TRIPESOCK ; | |
273 | if that's not set either, then a default default of | |
f7b5d108 | 274 | .B "\*(/s/tripesock" |
797cf76b | 275 | is used instead. |
74eb47db | 276 | .TP |
a9279e37 MW |
277 | .BI "\-m, \-\-admin\-perms=" mode |
278 | Permissions (as an octal number) to set on the administration socket. The | |
279 | default is 600, which allows only the socket owner. Setting 660 allows | |
280 | members of the | |
281 | .I group | |
282 | configured through the | |
283 | .B \-G | |
284 | option to connect to the socket, which may be useful. Allowing world access | |
285 | is a terrible idea. | |
286 | .TP | |
74eb47db | 287 | .BI "\-T, \-\-trace=" trace-opts |
288 | Allows the enabling or disabling of various internal diagnostics. See | |
289 | below for the list of options. | |
fc5f4823 | 290 | .SS "Key exchange group types" |
d6623498 | 291 | The |
292 | .B tripe | |
fc5f4823 | 293 | server uses Diffie\(en\&Hellman key exchange to agree the symmetric keys |
b86e6f3f | 294 | used for bulk data transfer. |
fc5f4823 MW |
295 | .PP |
296 | The server works out which it should be doing based on the key's | |
297 | .B kx-group | |
b86e6f3f | 298 | attribute. |
fc5f4823 MW |
299 | If this attribute isn't present, then the key's type is examined: if |
300 | it's of the form | |
1a0b1e9f | 301 | .BI tripe\- group |
fc5f4823 MW |
302 | then the |
303 | .I group | |
304 | is used. If no group is specified, | |
305 | .B dh | |
306 | is used as a fallback. | |
b86e6f3f MW |
307 | The following groups are defined. |
308 | .TP | |
309 | .B dh | |
310 | .RS | |
311 | Use traditional Diffie\(enHellman in a | |
312 | .IR "Schnorr group" : | |
313 | a prime-order subgroup of the multiplicative group of | |
314 | a finite field; this is the usual | |
315 | .I g\*(ssx\*(se | |
316 | mod | |
317 | .I p | |
318 | kind of Diffie\(en\&Hellman. | |
fc5f4823 MW |
319 | .PP |
320 | To create usual Schnorr-group keys, say something like | |
74eb47db | 321 | .VS |
fc5f4823 MW |
322 | key add \-adh-param \-LS \-b3072 \-B256 \e |
323 | \-eforever \-tparam tripe\-param kx-group=dh | |
74eb47db | 324 | .VE |
fc5f4823 | 325 | to construct a parameters key; and create the private keys by |
d6623498 | 326 | .VS |
327 | key add \-adh \-pparam \-talice \e | |
fc5f4823 | 328 | \-e"now + 1 year" tripe |
d6623498 | 329 | .VE |
b86e6f3f MW |
330 | .RE |
331 | .sv -1 | |
332 | .TP | |
333 | .B ec | |
334 | .RS | |
335 | Use elliptic curve Diffie\(enHellman. | |
336 | An elliptic curve group is a prime-order | |
337 | subgroup of the abelian group of | |
338 | .BR K -rational | |
339 | points on an elliptic curve defined over a finite field | |
340 | .BR K . | |
341 | .PP | |
342 | Given current public knowledge, elliptic curves can provide similar or | |
343 | better security to systems based on integer discrete log problems, | |
344 | faster, and with less transmitted data. It's a matter of controversy | |
345 | whether this will continue to be the case. The author uses elliptic | |
346 | curves. | |
347 | .PP | |
fc5f4823 | 348 | To create elliptic curve keys, say something like |
d6623498 | 349 | .VS |
fc5f4823 MW |
350 | key add \-aec\-param \-Cnist-p256 \-eforever \e |
351 | \-tparam tripe\-param kx-group=ec | |
52c03a2a | 352 | .VE |
353 | to construct a parameters key, using your preferred elliptic curve in | |
354 | the | |
355 | .B \-C | |
356 | option (see | |
357 | .BR key (1) | |
358 | for details); and create the private keys by | |
359 | .VS | |
360 | key add \-aec \-pparam \-talice \e | |
fc5f4823 | 361 | \-e"now + 1 year" tripe |
52c03a2a | 362 | .VE |
b86e6f3f | 363 | .RE |
26936c83 MW |
364 | .sv -1 |
365 | .TP | |
366 | .B x25519 | |
367 | .RS | |
368 | Use Bernstein's X25519 Diffie\(enHellman function. | |
369 | This is technically a variant on | |
370 | the general elliptic curve Diffie\(enHellman | |
371 | available through the | |
372 | .B ec | |
373 | setting, | |
374 | but carefully designed and heavily optimized. | |
375 | .PP | |
376 | To create | |
377 | .B x25519 | |
378 | keys, | |
379 | say something like | |
380 | .VS | |
381 | key add \-aempty \-eforever \e | |
382 | \-tparam tripe\-param kx-group=x25519 | |
383 | .VE | |
384 | to construct a parameters key | |
385 | (see | |
386 | .BR key (1) | |
387 | for details); | |
388 | and create the private keys by | |
389 | .VS | |
390 | key add \-ax25519 \-pparam \-talice \e | |
391 | \-e"now + 1 year" tripe | |
392 | .VE | |
393 | .RE | |
394 | .sv -1 | |
395 | .TP | |
396 | .B x448 | |
397 | .RS | |
398 | Use Hamburg's X448 Diffie\(enHellman function. | |
399 | Like | |
400 | .B x25519 | |
401 | above, | |
402 | this is technically a variant on | |
403 | the general elliptic curve Diffie\(enHellman | |
404 | available through the | |
405 | .B ec | |
406 | setting, | |
407 | but carefully designed and heavily optimized. | |
408 | .PP | |
409 | To create | |
410 | .B x448 | |
411 | keys, | |
412 | say something like | |
413 | .VS | |
414 | key add \-aempty \-eforever \e | |
415 | \-tparam tripe\-param kx-group=x448 | |
416 | .VE | |
417 | to construct a parameters key | |
418 | (see | |
419 | .BR key (1) | |
420 | for details); | |
421 | and create the private keys by | |
422 | .VS | |
423 | key add \-ax448 \-pparam \-talice \e | |
424 | \-e"now + 1 year" tripe | |
425 | .VE | |
426 | .RE | |
fc5f4823 MW |
427 | Note that the |
428 | .BR tripe-keys (8) | |
429 | program provides a rather more convenient means for generating and | |
430 | managing keys for | |
431 | .BR tripe . | |
b5c45da1 | 432 | .SS "Using other symmetric algorithms" |
433 | The default symmetric algorithms | |
434 | .B tripe | |
435 | uses are Blowfish (by Schneier) for symmetric encryption, and RIPEMD-160 | |
436 | (by Dobbertin, Bosselaers and Preneel) for hashing and as a MAC (in HMAC | |
437 | mode, designed by Bellare, Canetti and Krawczyk). These can all be | |
438 | overridden by setting attributes on your private key, as follows. | |
439 | .TP | |
a93aacce | 440 | .B bulk |
b87bffcb MW |
441 | Names the bulk-crypto transform to use. See below. |
442 | .TP | |
443 | .B blkc | |
b2177d04 | 444 | Names a blockcipher, used by some bulk-crypto transforms (e.g., |
a305982d | 445 | .BR iiv ). |
b2177d04 | 446 | The default is to use the blockcipher underlying the chosen |
b87bffcb MW |
447 | .BR cipher , |
448 | if any. | |
a93aacce | 449 | .TP |
b5c45da1 | 450 | .B cipher |
451 | Names the symmetric encryption scheme to use. The default is | |
452 | .BR blowfish\-cbc . | |
453 | .TP | |
454 | .B hash | |
455 | Names the hash function to use. The default is | |
456 | .BR rmd160 . | |
457 | .TP | |
458 | .B mac | |
459 | Names the message authentication code to use. The name of the MAC may | |
460 | be followed by a | |
461 | .RB ` / ' | |
462 | and the desired tag length in bits. The default is | |
463 | .IB hash \-hmac | |
464 | at half the underlying hash function's output length. | |
73d383c0 MW |
465 | If the MAC's name contains a |
466 | .RB ` / ' | |
467 | character, | |
468 | e.g., | |
469 | .RB ` sha512/256 ', | |
470 | then an | |
471 | .I additional | |
472 | .RB ` / ' | |
473 | and the tag size is required to disambiguate, | |
474 | so, e.g., | |
475 | one might write | |
476 | .RB ` sha512/256/256 '. | |
b5c45da1 | 477 | .TP |
478 | .B mgf | |
479 | A `mask-generation function', used in the key-exchange. The default is | |
480 | .IB hash \-mgf | |
481 | and there's no good reason to change it. | |
b87bffcb MW |
482 | .PP |
483 | The available bulk-crypto transforms are as follows. | |
484 | .TP | |
485 | .B v0 | |
486 | Originally this was the only transform available. It's a standard | |
487 | generic composition of a CPA-secure symmetric encryption scheme with a | |
488 | MAC; initialization vectors for symmetric encryption are chosen at | |
489 | random and included explicitly in the cryptogram. | |
490 | .TP | |
491 | .B iiv | |
492 | A newer `implicit-IV' transform. Rather than having an explicit random | |
b2177d04 | 493 | IV, the IV is computed from the sequence number using a blockcipher. |
b87bffcb MW |
494 | This has two advantages over the |
495 | .B v0 | |
496 | transform. Firstly, it adds less overhead to encrypted messages | |
497 | (because the IV no longer needs to be sent explicitly). Secondly, and | |
498 | more significantly, the transform is entirely deterministic, so (a) it | |
499 | doesn't need the (possibly slow) random number generator, and (b) it | |
500 | closes a kleptographic channel, over which a compromised implementation | |
501 | could leak secret information to a third party. | |
de8edc7f | 502 | .TP |
e53273ef MW |
503 | .B aead |
504 | A transform based on an all-in-one `authenticated encryption with | |
505 | additional data' scheme. The scheme is named in the | |
506 | .B cipher | |
507 | attribute; the default is | |
508 | .BR rijndael-ocb3 . | |
509 | If the | |
510 | .B mac | |
511 | attribute is given, it must be either | |
512 | .B aead | |
513 | or | |
514 | .BR aead/ \c | |
515 | .IR tagsz , | |
516 | where | |
517 | .I tagsz | |
518 | is the desired tag length in bits; alternatively, the tag length can be | |
519 | set in the | |
520 | .B tagsz | |
521 | attribute. The chosen AEAD scheme must accept at least a 64-bit nonce | |
522 | (this rules out OCB3 and CCM with 64-bit blockciphers); it mustn't | |
523 | require an absurdly large nonce size (none of the schemes implemented in | |
524 | Catacomb present a problem here, but it bears mentioning); it must | |
525 | actually support additional header data (which rules out the | |
526 | .B naclbox | |
527 | schemes, but see the | |
528 | .B naclbox | |
529 | transform below); and it must produce an empty ciphertext when | |
530 | encrypting an empty message (again, all of Catacomb's schemes meet this | |
531 | requirement). | |
532 | .TP | |
de8edc7f MW |
533 | .B naclbox |
534 | A transform based on the NaCl | |
535 | .B crypto_secretbox | |
536 | transformation. | |
537 | The main difference is that NaCl uses XSalsa20, | |
538 | while TrIPE uses plain Salsa20 or ChaCha, | |
539 | because it doesn't need the larger nonce space. | |
540 | You can set the | |
541 | .B cipher | |
542 | key attribute to one of | |
543 | .BR salsa20 , | |
544 | .BR salsa20/12 , | |
545 | .BR salsa20/8 , | |
546 | .BR chacha20 , | |
547 | .BR chacha12 , | |
548 | or | |
549 | .B chacha8 | |
550 | to select the main cipher. | |
551 | You can set the | |
552 | .B mac | |
553 | key attribute to | |
554 | .B poly1305 | |
555 | or | |
556 | .B poly1305/128 | |
557 | but these are the default and no other choice is permitted. | |
558 | (This is for forward compatibility, | |
559 | in case other MACs and/or tag sizes are allowed later.) | |
07bdda1f MW |
560 | .SS "Other key attributes" |
561 | The following attributes can also be set on keys. | |
562 | .TP | |
563 | .B serialization | |
564 | Selects group-element serialization formats. | |
565 | The recommended setting is | |
566 | .BR constlen , | |
567 | which selects a constant-length encoding when hashing group elements. | |
568 | The default, | |
569 | for backwards compatibility, is | |
570 | .BR v0 ; | |
571 | but this is deprecated. | |
572 | (The old format uses a variable length format for hashing, | |
573 | which can leak information through timing.) | |
b9066fbb | 574 | .SS "Using SLIP interfaces" |
575 | Though not for the faint of heart, it is possible to get | |
576 | .B tripe | |
577 | to read and write network packets to a pair of file descriptors using | |
578 | SLIP encapsulation. No fancy header compression of any kind is | |
98fdb08d | 579 | supported. |
580 | .PP | |
581 | Two usage modes are supported: a preallocation system, whereby SLIP | |
582 | interfaces are created and passed to the | |
583 | .B tripe | |
584 | server at startup; and a dynamic system, where the server runs a script | |
585 | to allocate a new SLIP interface when it needs one. It is possible to | |
586 | use a mixture of these two modes, starting | |
b9066fbb | 587 | .B tripe |
98fdb08d | 588 | with a few preallocated interfaces and having it allocate more |
589 | dynamically as it needs them. | |
590 | .PP | |
591 | The behaviour of | |
592 | .BR tripe 's | |
593 | SLIP driver is controlled by the | |
594 | .B TRIPE_SLIPIF | |
1f68dfc5 | 595 | environment variable. The server will not create SLIP tunnels if this |
596 | variable is not defined. The variable's value is a colon-delimited list | |
597 | of preallocated interfaces, followed optionally by the filename of a | |
598 | script to run to dynamically allocate more interfaces. | |
b9066fbb | 599 | .PP |
98fdb08d | 600 | A static allocation entry has the form |
b9066fbb | 601 | .IR infd [ \c |
602 | .BI , outfd \c | |
603 | .RB ] \c | |
604 | .BI = \c | |
98fdb08d | 605 | .IR ifname , |
b9066fbb | 606 | If the |
607 | .I outfd | |
608 | is omitted, the same file descriptor is used for input and output. | |
609 | .PP | |
98fdb08d | 610 | The dynamic allocation script must be named by an absolute or relative |
e04c2d50 | 611 | pathname, beginning with |
98fdb08d | 612 | .RB ` / ' |
613 | or | |
614 | .RB ` . '. | |
615 | The server will pass the script an argument, which is the name of the | |
616 | peer for which the interface is being created. The script should | |
617 | allocate a new SLIP interface (presumably by creating a pty pair), | |
618 | configure it appropriately, and write the interface's name to its | |
619 | standard output, followed by a newline. It should then read and write | |
620 | SLIP packets on its stdin and stdout. The script's stdin will be closed | |
621 | when the interface is no longer needed, and the server will attempt to | |
622 | send it a | |
623 | .B SIGTERM | |
624 | signal (though this may fail if the script runs with higher privileges | |
625 | than the server). | |
626 | .PP | |
b9066fbb | 627 | The output file descriptor should not block unless it really needs to: |
628 | the | |
629 | .B tripe | |
1f68dfc5 | 630 | daemon assumes that it won't, and will get wedged waiting for it to |
631 | accept output. | |
74eb47db | 632 | .SS "About the name" |
633 | The program's name is | |
634 | .BR tripe , | |
635 | all in lower-case. The name of the protocol it uses is `TrIPE', with | |
636 | four capital letters and one lower-case. The name stands for `Trivial | |
637 | IP Encryption'. | |
fc916a09 MW |
638 | . |
639 | .\"-------------------------------------------------------------------------- | |
74eb47db | 640 | .SH "BUGS" |
fc916a09 | 641 | . |
74eb47db | 642 | The code hasn't been audited. It may contain security bugs. If you |
643 | find one, please inform the author | |
644 | .IR immediately . | |
fc916a09 MW |
645 | . |
646 | .\"-------------------------------------------------------------------------- | |
74eb47db | 647 | .SH "SEE ALSO" |
fc916a09 | 648 | . |
74eb47db | 649 | .BR key (1), |
650 | .BR tripectl (1), | |
fc5f4823 MW |
651 | .BR tripe\-admin (5), |
652 | .BR tripe\-keys (8). | |
74eb47db | 653 | .PP |
654 | .IR "The Trivial IP Encryption Protocol" , | |
655 | .IR "The Wrestlers Protocol" . | |
fc916a09 MW |
656 | . |
657 | .\"-------------------------------------------------------------------------- | |
74eb47db | 658 | .SH "AUTHOR" |
fc916a09 | 659 | . |
d36eda2a | 660 | Mark Wooding, <mdw@distorted.org.uk> |
fc916a09 MW |
661 | . |
662 | .\"----- That's all, folks -------------------------------------------------- |