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1 | .\" -*-nroff-*- |
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2 | .\" |
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3 | .\" $Id: fw.1,v 1.4 1999/08/19 18:32:48 mdw Exp $ |
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4 | .\" |
5 | .\" Manual page for fw |
6 | .\" |
7 | .\" (c) 1999 Straylight/Edgeware |
8 | .\" |
9 | . |
10 | .\"----- Licensing notice --------------------------------------------------- |
11 | .\" |
12 | .\" This file is part of the `fw' port forwarder. |
13 | .\" |
14 | .\" `fw' is free software; you can redistribute it and/or modify |
15 | .\" it under the terms of the GNU General Public License as published by |
16 | .\" the Free Software Foundation; either version 2 of the License, or |
17 | .\" (at your option) any later version. |
18 | .\" |
19 | .\" `fw' is distributed in the hope that it will be useful, |
20 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | .\" GNU General Public License for more details. |
23 | .\" |
24 | .\" You should have received a copy of the GNU General Public License |
25 | .\" along with `fw'; if not, write to the Free Software Foundation, |
26 | .\" Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
27 | . |
28 | .\" ---- Revision history --------------------------------------------------- |
29 | .\" |
30 | .\" $Log: fw.1,v $ |
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31 | .\" Revision 1.4 1999/08/19 18:32:48 mdw |
32 | .\" Improve lexical analysis. In particular, `chmod' patterns don't have to |
33 | .\" be quoted any more. |
34 | .\" |
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35 | .\" Revision 1.3 1999/07/30 06:49:00 mdw |
36 | .\" Minor tidying and typo correction. |
37 | .\" |
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38 | .\" Revision 1.2 1999/07/26 23:31:04 mdw |
39 | .\" Document lots of new features and syntax. |
40 | .\" |
41 | . |
42 | .\"----- Various bits of fancy styling -------------------------------------- |
43 | . |
44 | .\" --- Indented paragraphs with right-aligned tags --- |
45 | . |
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46 | .de hP |
47 | .IP |
48 | \h'-\w'\fB\\$1\ \fP'u'\fB\\$1\ \fP\c |
49 | .. |
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50 | . |
51 | .\" --- Verbatim-oid typesetting --- |
52 | .de VS |
53 | .sp 1 |
54 | .RS |
55 | .nf |
56 | .ft B |
57 | .. |
58 | .de VE |
59 | .ft R |
60 | .fi |
61 | .RE |
62 | .sp 1 |
63 | .. |
64 | . |
65 | .\" --- Other bits of styling --- |
66 | . |
67 | .ie t \{\ |
68 | . ds o \(bu |
69 | . ds ss \s8\u |
70 | . ds se \d\s0 |
71 | . if \n(.g \{\ |
72 | . fam P |
73 | . \} |
74 | .\} |
75 | .el \{\ |
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78 | . ds se |
79 | .\} |
80 | . |
81 | .\"-------------------------------------------------------------------------- |
82 | . |
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83 | .TH fw 1 "1 July 1999" fw |
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84 | . |
85 | .\"-------------------------------------------------------------------------- |
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86 | .SH NAME |
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87 | . |
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88 | fw \- port forwarder |
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89 | . |
90 | .\"-------------------------------------------------------------------------- |
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91 | .SH SYNOPSIS |
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92 | . |
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93 | .B fw |
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94 | .RB [ \-dq ] |
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95 | .RB [ \-f |
96 | .IR file ] |
97 | .IR config-stmt ... |
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98 | . |
99 | .\"-------------------------------------------------------------------------- |
100 | .SH "DESCRIPTION" |
101 | . |
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102 | The |
103 | .B fw |
104 | program is a simple port forwarder. It supports a number of features |
105 | the author hasn't found in similar programs: |
106 | .TP |
107 | .I "Connection logging" |
108 | Each connection attempt to the forwarder is logged, giving the time of |
109 | the connection, the DNS-resolved hostname (if available), and the user |
110 | name resulting from an RFC931 lookup. These lookups are done |
111 | asynchronously to the main forwarder's operation. |
112 | .TP |
113 | .I "Access control" |
114 | Each forwarded port may have an access control list attached to it. |
115 | Only authorized hosts are allowed to connect. Access control checks are |
116 | performed by quick checks on the client's IP address. |
117 | .TP |
118 | .I "Nonblocking single-process design" |
119 | The internal structure of the server is completely nonblocking. The |
120 | connections don't block; the reading and writing don't block; the name |
121 | lookups don't block. This is all done in a single process, with the |
122 | single exception of the DNS resolver. |
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123 | .TP |
124 | .I "Support for Unix-domain sockets" |
125 | Connections from and to Unix-domain sockets can be handled just as |
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126 | easily as more normal Internet sockets. Access control doesn't work on |
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127 | Unix domain sockets, though. (Yet.) |
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128 | .SS "Command line options" |
129 | The |
130 | .B fw |
131 | program understands a few simple command line options: |
132 | .TP |
133 | .B "\-h, \-\-help" |
134 | Displays a screen of help text on standard output and exits |
135 | successfully. |
136 | .TP |
137 | .B "\-v, \-\-version" |
138 | Writes the version number to standard output and exits successfully. |
139 | .TP |
140 | .B "\-u, \-\-usage" |
141 | Writes a terse usage summary to standard output and exits successfully. |
142 | .TP |
143 | .BI "\-f, \-\-file=" file |
144 | Read configuration information from |
145 | .IR file . |
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146 | Equivalent to an |
147 | .RB ` include |
148 | .IR file ' |
149 | configuration file statement. |
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150 | .TP |
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151 | .B "\-d, \-\-daemon, \-\-fork" |
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152 | Forks into the background after reading the configuration and |
153 | initializing properly. |
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154 | .TP |
155 | .B "-q, \-\-quiet" |
156 | Don't output any logging information. This option is not recommended |
157 | for normal use, although it can make system call traces clearer so I use |
158 | it when debugging. |
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159 | .PP |
160 | Any further command line arguments are interpreted as configuration |
161 | lines to be read. Configuration supplied in command line arguments has |
162 | precisely the same syntax as configuration in files. If there are no |
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163 | configuration statements on the command line, and no |
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164 | .B \-f |
165 | options were supplied, configuration is read from standard input, if |
166 | stdin is not a terminal. |
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167 | . |
168 | .\"-------------------------------------------------------------------------- |
169 | .SH "CONFIGURATION LANGUAGE" |
170 | . |
171 | The |
172 | .B fw |
173 | program has a fairly sophisticated configuration language to let you |
174 | describe which things should be forwarded where and what special |
175 | features there should be. |
176 | .SS "Lexical structure" |
177 | There are four types of characters. |
178 | .TP |
179 | .I "word constituent characters" |
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180 | Word constituent characters are gathered together into words. |
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181 | Depending on its surrounding context, a word might act as a keyword or a |
182 | string. All alphanumerics are word constituents, as is the hyphen |
183 | .RB ` \- '. |
184 | Other characters may change their status in future versions. |
185 | .TP |
186 | .I "self-delimiting characters" |
187 | Self-delimiting characters always stand alone. They act as punctuation, |
188 | shaping the sequence of words into more complex grammatical forms. The |
189 | characters |
190 | .RB ` { ', |
191 | .RB ` } ', |
192 | .RB ` [ ', |
193 | .RB ` ] ', |
194 | .RB ` / ', |
195 | .RB ` , ', |
196 | .RB ` = ', |
197 | .RB ` : ', |
198 | .RB ` ; ' |
199 | and |
200 | .RB ` . ' |
201 | are self-delimiting. Note that while some characters, e.g., |
202 | .RB ` [ ' |
203 | and |
204 | .RB ` ; ', |
205 | require escaping by the shell, they are strictly optional in the grammar |
206 | and can be omitted in quick hacks at the shell prompt. |
207 | .TP |
208 | .I "whitespace characters" |
209 | Whitespace characters separate words but are otherwise ignored. All |
210 | `normal' whitespace characters (e.g., space, tab and newline) are |
211 | considered to be whitespace for these purposes. |
212 | .TP |
213 | .I "special characters" |
214 | There are three special characters. The |
215 | .RB ` # ' |
216 | character, if it appears at the start of a word, introduces a |
217 | .I comment |
218 | which extends to the end of the current line or command-line argument. |
219 | Within a word, it behaves like a normal word-constituent character. The |
220 | backslash |
221 | .RB ` \e ' |
222 | escapes the following character causing it to be interpreted as a word |
223 | constituent regardless of its normal type. The double-quote |
224 | .RB ` """" ' |
225 | escapes all characters other than backslashes up to the next |
226 | double-quote and causes them to be regarded as word constituents. Note |
227 | that you don't have to quote a whole word. The backslash can escape a |
228 | quote character allowing you to insert it into a word if really |
229 | necessary. |
230 | . |
231 | .SS "Basic syntax" |
232 | The overall syntax looks a bit like this: |
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233 | .PP |
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234 | .I file |
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235 | ::= |
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236 | .I empty |
237 | | |
238 | .I file |
239 | .I stmt |
240 | .RB [ ; ] |
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241 | .br |
242 | .I stmt |
243 | ::= |
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244 | .I option-stmt |
245 | | |
246 | .I fw-stmt |
247 | .br |
248 | .I fw-stmt |
249 | ::= |
250 | .B fw |
251 | .I source |
252 | .I options |
253 | .RB [ to | \-> ] |
254 | .I target |
255 | .I options |
256 | .br |
257 | .I options |
258 | ::= |
259 | .B { |
260 | .I option-seq |
261 | .B } |
262 | .br |
263 | .I option-seq |
264 | ::= |
265 | .I empty |
266 | | |
267 | .I option-stmt |
268 | .RB [ ; ] |
269 | .I option-seq |
270 | .PP |
271 | If you prefer, the keyword |
272 | .RB ` fw ' |
273 | may be spelt |
274 | .RB ` forward ' |
275 | or |
276 | .RB ` from '. |
277 | All are equivalent. |
278 | . |
279 | .SS "Sources and targets" |
280 | Forwarding is set up by attaching |
281 | .I targets |
282 | to |
283 | .IR sources . |
284 | Sources are things which are capable of |
285 | .I initiating |
286 | one end of a data flow on their own, while targets are things which are |
287 | capable of setting up the other end on demand. In the case of a TCP |
288 | port forwarder, the part which listens for incoming client connections |
289 | is the source, while the part which sets up outgoing connections to the |
290 | destination server is the target. |
291 | .PP |
292 | Essentially, all |
293 | .B fw |
294 | does is set up a collection of sources and targets based on your |
295 | configuration file so that when a source decides to initiate a data |
296 | flow, it tells its target to set its end up, and then squirts data back |
297 | and forth between the two until there's no more. |
298 | .PP |
299 | Some sources are |
300 | .IR persistent : |
301 | they stay around indefinitely setting up multiple attachments to |
302 | targets. Others are |
303 | .IR transient : |
304 | they set up one connection and then disappear. If all the sources |
305 | defined are transient, then |
306 | .B fw |
307 | will quit when no more active sources remain and all connections have |
308 | terminated. |
309 | .PP |
310 | The |
311 | .B fw |
312 | program is fairly versatile. It allows you to attach any supported type |
313 | of source to any supported type of target. This will, I hope, be the |
314 | case in all future versions. |
315 | .PP |
316 | The syntax of a |
317 | .I source |
318 | or |
319 | .I target |
320 | depend on the source or target type, and are therefore described in the |
321 | sections specific to the various types. |
322 | . |
323 | .SS "Options structure" |
324 | Most of the objects that |
325 | .B fw |
326 | knows about (including sources and targets, but also other more specific |
327 | things such as socket address types) can have their behaviour modified |
328 | by |
329 | .IR options . |
330 | The options available at a particular point in the configuration depend |
331 | on the |
332 | .IR context . |
333 | A global option, outside of a |
334 | .I fw-stmt |
335 | has no context unless it is explicitly qualified, and affects global |
336 | behaviour. Local options, applied to a source or target in a |
337 | .I fw-stmt |
338 | has the context of the type of source or target to which it is applied, |
339 | and affects only that source or target. |
340 | .PP |
341 | Note that it's important to distinguish between an option's context |
342 | (which is affected by its qualification) and its local or global |
343 | status. No matter how qualified, a global option will always control |
344 | default options for objects, and a local option will only affect a |
345 | specific source or target. |
346 | .PP |
347 | The syntax for qualifying options is like this: |
348 | .PP |
349 | .I option-stmt |
350 | ::= |
351 | .I q-option |
352 | .br |
353 | .I q-option |
354 | ::= |
355 | .I option |
356 | .br |
357 | | |
358 | .I prefix |
359 | .B . |
360 | .I q-option |
361 | .br |
362 | | |
363 | .I prefix |
364 | .B { |
365 | .I option-seq |
366 | .B } |
367 | .br |
368 | .I prefix |
369 | ::= |
370 | .I word |
371 | .PP |
372 | Thus, you may qualify either an individual option or a sequence of |
373 | options. The two are equivalent; for example, |
374 | .VS |
375 | exec.rlimit { |
376 | core = 0; |
377 | cpu = 60; |
378 | } |
379 | .VE |
380 | is equivalent to |
381 | .VS |
382 | exec.rlimit.core = 0; |
383 | exec.rlimit.cpu = 0; |
384 | .VE |
385 | For each option, there is a sequence of prefixes which maximally qualify |
386 | that option. An option prefixed with this sequence is |
387 | .IR "fully qualified" . |
388 | In actual use, some or all of those prefixes may be omitted. However, |
389 | it's possible for the option to become |
390 | .I ambiguous |
391 | if you do this. For example, the option |
392 | .B fattr.owner |
393 | may refer either to |
394 | .B file.fattr.owner |
395 | or to |
396 | .BR socket.unix.fattr.owner . |
397 | In this case, the ambiguity is benign: a local option will have as its |
398 | context an appropriate source or target, and both global options |
399 | actually control the same default. However, the option |
400 | .B logging |
401 | may mean either |
402 | .B socket.logging |
403 | or |
404 | .BR exec.logging , |
405 | which have separate defaults, and which one you actually get depends on |
406 | the exact implementation of |
407 | .BR fw 's |
408 | option parser. (Currently this would resolve to |
409 | .BR exec.logging , |
410 | although this may change in a later version.) |
411 | .PP |
412 | In this manual, options are usually shown in their fully-qualified form. |
413 | . |
414 | .SS "The `file' source and target types" |
415 | The |
416 | .B file |
417 | source and target allow data to move to and from objects other |
418 | than sockets within the Unix filesystem. (Unix-domain sockets are |
419 | handled using the |
420 | .B socket |
421 | source and target.) |
422 | .PP |
423 | If a |
424 | .B file |
425 | is used as a source, it is set up immediately. |
426 | .PP |
427 | The syntax of |
428 | .B file |
429 | sources and targets is like this: |
430 | .PP |
431 | .I source |
432 | ::= |
433 | .I file |
434 | .br |
435 | .I target |
436 | ::= |
437 | .I file |
438 | .br |
439 | .I file |
440 | ::= |
441 | .B file |
442 | .RB [ . ] |
443 | .I fspec |
444 | .RB [ , |
445 | .IR fspec ] |
446 | .br |
447 | .I fspec |
448 | ::= |
449 | .I fd-spec |
450 | | |
451 | .I name-spec |
452 | | |
453 | .I null-spec |
454 | .br |
455 | .I fd-spec |
456 | ::= |
457 | .RB [[ : ] fd [ : ]] |
458 | .IR number \c |
459 | .RB | stdin | stdout |
460 | .br |
461 | .I name-spec |
462 | ::= |
463 | .RB [[ : ] file [ : ]] |
464 | .I file-name |
465 | .br |
466 | .I file-name |
467 | ::= |
468 | .I path-seq |
469 | | |
470 | .B [ |
471 | .I path-seq |
472 | .B ] |
473 | .br |
474 | .I path-seq |
475 | ::= |
476 | .I path-elt |
477 | | |
478 | .I path-seq |
479 | .I path-elt |
480 | .br |
481 | .I path-elt |
482 | ::= |
483 | .B / |
484 | | |
485 | .I word |
486 | .br |
487 | .I null-spec |
488 | ::= |
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489 | .RB [ : ] null [ : ] |
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490 | .PP |
491 | The |
492 | .I file |
493 | specification describes two files, the first to be used as input, the |
494 | second to be used as output, each described by an |
495 | .IR fspec . |
496 | .PP |
497 | If none of the keywords |
498 | .RB ` fd ', |
499 | .RB ` name ' |
500 | or |
501 | .RB ` null ' |
502 | are given, the type of an |
503 | .I fspec |
504 | is deduced from its nature: if it matches one of the strings |
505 | .RB ` stdin ' |
506 | or |
507 | .RB ` stdout ', |
508 | or begins with a digit, it's considered to be a file descriptor; |
509 | otherwise it's interpreted as a filename. |
510 | .PP |
511 | A |
512 | .RB ` name ' |
513 | spec describes a file by its name within the filesystem. It is opened |
514 | when needed and closed again after use. For output files, the precise |
515 | behaviour is controlled by options described below. |
516 | .PP |
517 | A |
518 | .RB ` null ' |
519 | spec attaches the input or output of the source or target to |
520 | .BR /dev/null . |
521 | .PP |
522 | An |
523 | .RB ` fd ' |
524 | spec uses an existing open file descriptor, given either by number or a |
525 | symbolic name. The name |
526 | .RB ` stdin ' |
527 | refers to standard input (file descriptor 0 on normal systems) and |
528 | .RB ` stdout ' |
529 | refers to standard output (file descriptor 1). The names work in |
530 | exactly the same way as the equivalent file descriptor numbers. |
531 | .PP |
532 | If the output |
533 | .I fspec |
534 | is omitted, the input |
535 | .I fspec |
536 | is used for both input and output. Exception: if the input refers to |
537 | standard input then the output will refer to standard output instead. |
538 | .PP |
539 | All |
540 | .B file |
541 | options apply equally to sources and targets. The options are as |
542 | follows: |
543 | .PP |
544 | .B file.create |
545 | .RB [ = ] |
546 | .BR yes | no |
547 | .RS |
548 | Whether to create the output file if it doesn't exist. If |
549 | .B no |
550 | (the default), an error is reported if the file doesn't exist. If |
551 | .BR yes , |
552 | the file is created if it doesn't exist. |
553 | .RE |
554 | .PP |
555 | .B file.open |
556 | .RB [ = ] |
557 | .BR no | truncate | append |
558 | .RS |
559 | Controls the behaviour if the output file already exists. If |
560 | .BR no , |
561 | an error is reported. If |
562 | .B truncate |
563 | (the default), the existing file is replaced by the new data. If |
564 | .BR append , |
565 | the new data is appended to the file. |
566 | .RE |
567 | .PP |
568 | Under no circumstances will |
569 | .B fw |
570 | create a file through a `dangling' symbolic link. |
571 | .PP |
572 | The |
573 | .B file |
574 | source and target also accept |
575 | .B fattr |
576 | options for controlling the attributes of the created file. The prefix |
577 | for setting file attributes is |
578 | .BR file.fattr . |
579 | . |
580 | .SS "File attributes for created files `fattr'" |
581 | Both the |
582 | .B file |
583 | and |
584 | .B socket |
585 | sources and targets can create new filesystem objects. The |
586 | .B fattr |
587 | options allow control over the attributes of the newly-created objects. |
588 | Both |
589 | .B file |
590 | and |
591 | .B socket |
592 | use the same set of defaults, so a prefix of |
593 | .B fattr |
594 | is good enough for setting global options, and the implicit context |
595 | disambiguates local options. |
596 | .PP |
597 | The following file attribute options are supported: |
598 | .PP |
599 | .IB prefix .fattr.mode |
600 | .RB [ = ] |
601 | .I mode |
602 | .RS |
603 | Sets the permissions mode for a new file. The |
604 | .I mode |
605 | argument may be either an octal number or a |
606 | .BR chmod (1)-style |
607 | string which acts on the default permissions established by the |
608 | prevailing |
609 | .BR umask (2) |
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610 | setting. The characters |
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611 | .RB ` = ' |
612 | and |
613 | .RB ` , ' |
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614 | do not have to be quoted within the mode string. |
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615 | .PP |
616 | .IB prefix .fattr.owner |
617 | .RB [ = ] |
618 | .I user |
619 | .RS |
620 | Sets the owner for newly created files. On non-broken systems you will |
621 | need to be the superuser to set the owner on a file. The |
622 | .I user |
623 | may either be a numeric uid or a username. The default is not to change |
624 | the owner of the file once it's created. The synonyms |
625 | .B uid |
626 | and |
627 | .B user |
628 | are accepted in place of |
629 | .BR owner . |
630 | .RE |
631 | .PP |
632 | .IB prefix .fattr.group |
633 | .RB [ = ] |
634 | .I group |
635 | .RS |
636 | Sets the group for newly created files. You will usually need to be a |
637 | member of the group in question order to set the group of a file. The |
638 | .I group |
639 | may either be a numeric gid or a group name. The default is not to |
640 | change the group of the file once it's created. The synonym |
641 | .B gid |
642 | is accepted in place of |
643 | .BR group . |
644 | .RE |
645 | . |
646 | .SS "The `exec' source and target types" |
647 | The |
648 | .B exec |
649 | source and target execute programs and allow access to their standard |
650 | input and output streams. Both source and target have the same syntax, |
651 | which is as follows: |
652 | .PP |
653 | .I source |
654 | ::= |
655 | .I exec |
656 | .br |
657 | .I target |
658 | ::= |
659 | exec |
660 | .br |
661 | .I exec |
662 | ::= |
663 | .BR exec |
664 | .RB [ . ] |
665 | .I cmd-spec |
666 | .br |
667 | .I cmd-spec |
668 | ::= |
669 | .I shell-cmd |
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670 | | |
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671 | .RI [ prog-name ] |
672 | .B [ |
673 | .I argv0 |
674 | .I arg-seq |
675 | .B ] |
676 | .br |
677 | .I arg-seq |
678 | ::= |
679 | .I word |
680 | | |
681 | .I arg-seq |
682 | .I word |
683 | .br |
684 | .I shell-cmd |
685 | ::= |
686 | .I word |
687 | .br |
688 | .I argv0 |
689 | ::= |
690 | .I word |
691 | .PP |
692 | If a single word is given, it is a |
693 | .I shell-cmd |
694 | and will be passed to the Bourne shell for execution. If a |
695 | bracket-enclosed sequence of words is given, it is considered to be a |
696 | list of arguments to pass to the program: if a |
697 | .I prog-name |
698 | is also supplied, it names the file containing the program to execute; |
699 | otherwise the file named by the first argument |
700 | .RI ( argv0 ) |
701 | is used. |
702 | .PP |
703 | The standard input and output of the program are forwarded to the other |
704 | end of the connection. The standard error stream is caught by |
705 | .B fw |
706 | and logged. |
707 | .PP |
708 | The |
709 | .B exec |
710 | source and target both understand the same set of options. The list of |
711 | options supported is as follows: |
712 | .PP |
713 | .B exec.logging |
714 | .RB [ = ] |
715 | .BR yes | no |
716 | .RS |
717 | Whether to log the start and end of executed programs. If |
718 | .B yes |
719 | (the default), a log message is emitted when the program is started |
720 | listing its process id, and another is emitted when the program finishes |
721 | giving its process id and exit status. If |
722 | .BR no , |
723 | these messages are not emitted. However the standard error stream is |
724 | still logged. The |
725 | .B log |
726 | abbreviation is accepted as a synonym for |
727 | .BR logging . |
728 | .RE |
729 | .PP |
730 | .B exec.dir |
731 | .RB [ = ] |
732 | .I file-name |
733 | .RS |
734 | Sets the current directory from which the the program should be run. |
735 | The default is not to change directory. The synonyms |
736 | .BR cd , |
737 | .B chdir |
738 | and |
739 | .B cwd |
740 | are accepted in place of |
741 | .BR dir . |
742 | .RE |
743 | .PP |
744 | .B exec.root |
745 | .RB [ = ] |
746 | .I file-name |
747 | .RS |
748 | Sets the root directory for the program, using the |
749 | .BR chroot (2) |
750 | system call. You must be the superuser for this option to work. The |
751 | default is not to set a root directory. The synonyms |
752 | .BR cd , |
753 | .B chdir |
754 | and |
755 | .B cwd |
756 | are accepted in place of |
757 | .B dir . |
758 | .RE |
759 | .PP |
760 | .B exec.user |
761 | .RB [ = ] |
762 | .I user |
763 | .RS |
764 | Sets the user (real and effective uid) to run the program as. This will |
765 | usually require superuser privileges to work. The default is not to |
766 | change uid. The synonym |
767 | .B uid |
768 | is accepted in place of |
769 | .BR user . |
770 | .RE |
771 | .PP |
772 | .B exec.group |
773 | .RB [ = ] |
774 | .I group |
775 | .RS |
776 | Sets the group (real and effective gid) to run the program as. If |
777 | running with superuser privileges, the supplementary groups list is |
778 | cleared at the same time. The default is not to change gid (or clear |
779 | the supplementary groups list). The synonym |
780 | .B gid |
781 | is accepted in place of |
782 | .BR group . |
783 | .RE |
784 | .PP |
785 | .BI exec.rlimit. limit \c |
786 | .RB [ .hard | .soft ] |
787 | .RB [ = ] |
788 | .I value |
789 | .RS |
790 | Set resource limits for the program. The |
791 | .I limit |
792 | may be one of the resource limit names described in |
793 | .BR setrlimit (2), |
794 | in lower-case and without the |
795 | .B RLIMIT_ |
796 | prefix; for example, |
797 | .B RLIMIT_CORE |
798 | becomes simply |
799 | .BR core . |
800 | The |
801 | .I value |
802 | is a number, followed optionally by |
803 | .B k |
804 | to multiply by 1024 (2\*(ss10\*(se), |
805 | .B m |
806 | to multiply by 1048576 (2\*(ss20\*(se), or |
807 | .B g |
808 | to multiply by 1073741824 (2\*(ss30\*(se); purists can use upper-case |
809 | versions of these if they want. If |
810 | .B .hard |
811 | or |
812 | .B .soft |
813 | was specified, only the hard or soft limit is set; otherwise both are |
814 | set to the same value. Only the superuser can raise the hard limit. |
815 | The soft limit cannot be set above the hard limit. |
816 | .RE |
817 | .PP |
818 | .B exec.env.clear |
819 | .RS |
820 | Clears the program's environment. |
821 | .RE |
822 | .PP |
823 | .B exec.env.unset |
824 | .I var |
825 | .RS |
826 | Removes |
827 | .I var |
828 | from the program's environment. It is not an error if no variable named |
829 | .I var |
830 | exists. |
831 | .RE |
832 | .PP |
833 | .BR exec.env. [ set ] |
834 | .I var |
835 | .RB [ = ] |
836 | .I value |
837 | .RS |
96bc31ba |
838 | Assigns the variable |
667fb920 |
839 | .I var |
840 | the value |
841 | .I value |
842 | in the program's environment, possibly replacing the existing value. |
843 | The |
844 | .B set |
845 | may be omitted if the |
846 | .B env |
847 | qualifier is present. |
848 | .RE |
849 | .PP |
850 | Note that environment variable modifications are performed in order, |
851 | global modifications before local ones. |
852 | . |
853 | .SS "The `socket' source and target types" |
854 | The |
855 | .B socket |
856 | source and target provide access to network services. Support is |
857 | currently provided for TCP/IP and Unix-domain sockets, although other |
858 | address types can be added with reasonable ease. |
859 | .PP |
860 | The syntax for socket sources and targets is: |
861 | .PP |
862 | .ll +8i |
863 | .I source |
864 | ::= |
865 | .I socket-source |
10a454ad |
866 | .br |
667fb920 |
867 | .I target |
868 | ::= |
869 | .I socket-target |
870 | .br |
871 | .I socket-source |
872 | ::= |
873 | .RB [ socket [ . ]] |
874 | .RB [[ : ] \c |
875 | .IR addr-type \c |
876 | .RB [ : ]] |
877 | .I source-addr |
878 | .br |
879 | .I socket-target |
880 | ::= |
881 | .RB [ socket [ . ]] |
882 | .RB [[ : ] \c |
883 | .IR addr-type \c |
884 | .RB [ : ]] |
885 | .I target-addr |
886 | .ll -8i |
887 | .PP |
888 | The syntax of the source and target addresses depend on the address |
889 | types, which are described below. The default address type, if no |
890 | .I addr-type |
891 | is given, is |
892 | .BR inet . |
893 | .PP |
894 | Socket sources support options; socket targets do not. The source |
895 | options provided are: |
896 | .PP |
897 | .B socket.conn |
898 | .RB [ = ] |
899 | .I number |
900 | .RS |
901 | Limits the number of simultaneous connections to this socket to the |
902 | .I number |
903 | given. The default is 256. |
904 | .RE |
905 | .PP |
906 | .B socket.logging |
907 | .RB [ = ] |
908 | .BR yes | no |
909 | .RS |
910 | Whether to log incoming connections. If |
911 | .B yes |
912 | (the default) incoming connections are logged, together with information |
913 | about the client (where available) and whether the connection was |
914 | accepted or refused. If |
915 | .BR no , |
916 | log messages are not generated. |
917 | .RE |
918 | .PP |
919 | Address types also provide their own options. |
920 | . |
921 | .SS "The `inet' socket address type" |
922 | The |
923 | .B inet |
924 | address type provides access to TCP ports. The |
925 | .B inet |
926 | source and target addresses have the following syntax: |
927 | .PP |
928 | .I inet-source-addr |
10a454ad |
929 | ::= |
10a454ad |
930 | .RB [ port ] |
931 | .I port |
667fb920 |
932 | .br |
933 | .I inet-target-addr |
934 | ::= |
935 | .I address |
10a454ad |
936 | .RB [ : ] |
937 | .I port |
10a454ad |
938 | .br |
667fb920 |
939 | .I address |
10a454ad |
940 | ::= |
667fb920 |
941 | .I addr-elt |
942 | | |
943 | .I address |
944 | .I addr-elt |
10a454ad |
945 | .br |
667fb920 |
946 | .I addr-elt |
10a454ad |
947 | ::= |
667fb920 |
948 | .B . |
10a454ad |
949 | | |
667fb920 |
950 | .I word |
951 | .PP |
952 | A |
953 | .I port |
954 | may be given as a port number or a service name from the |
955 | .B /etc/services |
956 | file (or YP map if you do that sort of thing). A |
957 | .B hostname |
958 | may be a textual hostname or a numerical IP address. |
959 | .PP |
960 | The |
961 | .B inet |
962 | source address accepts the following options: |
963 | .PP |
964 | .BR socket.inet. [ allow | deny ] |
10a454ad |
965 | .RB [ from ] |
667fb920 |
966 | .I address |
10a454ad |
967 | .RB [ / |
667fb920 |
968 | .IR address ] |
969 | .RS |
970 | Adds an entry to the source's access control list. If only one |
971 | .I address |
972 | is given, the entry applies only to that address; if two are given, the |
973 | first is a network address and the second is a netmask either in |
974 | dotted-quad format or a simple number of bits (e.g., |
975 | .B /255.255.255.192 |
976 | and |
977 | .B /26 |
978 | mean the same), and the entry applies to any address which, when masked |
979 | by the netmask, is equal to the masked network address. |
10a454ad |
980 | .PP |
667fb920 |
981 | The access |
982 | control rules are examined in the order: local entries first, then |
983 | global ones, each in the order given in the configuration file. The |
984 | first matching entry is used. If no entries match, the behaviour is the |
985 | .I opposite |
986 | of the last entry tried. If there are no entries defined, the default |
987 | is to allow all clients. |
988 | .RE |
989 | . |
990 | .SS "The `unix' socket address type" |
10a454ad |
991 | The |
667fb920 |
992 | .B unix |
993 | address type allows access to Unix-domain sockets. The syntax for |
994 | .B unix |
995 | source and target addresses is like this: |
996 | .PP |
997 | .I source-addr |
998 | ::= |
999 | .I unix-addr |
1000 | .br |
1001 | .I target-addr |
1002 | ::= |
1003 | .I unix-addr |
1004 | .br |
1005 | .I unix-addr |
1006 | ::= |
1007 | .I file-name |
1008 | .PP |
1009 | The |
1010 | .B unix |
1011 | source address accepts |
1012 | .B fattr |
1013 | options to control the attributes of the socket file created. Sockets |
1014 | are removed if |
10a454ad |
1015 | .B fw |
667fb920 |
1016 | exits normally (which it will do if it runs out of sources or |
1017 | connections, or if killed by SIGINT or SIGTERM). |
1018 | .SH "EXAMPLES" |
1019 | To forward the local port 25 to a main mail server: |
1020 | .VS |
1021 | from 25 to mailserv:25 |
1022 | .VE |
1023 | To attach a fortune server to a Unix-domain socket: |
1024 | .VS |
1025 | from unix:/tmp/fortunes |
1026 | to exec [/usr/games/fortune] { user nobody } |
1027 | .VE |
1028 | To fetch a fortune from the server: |
1029 | .VS |
1030 | from file stdin, stdout to unix:/tmp/fortunes |
1031 | .VE |
1032 | To emulate |
1033 | .BR cat (1): |
1034 | .VS |
1035 | from stdin, null to null, stdout |
1036 | .VE |
1037 | . |
1038 | .\"-------------------------------------------------------------------------- |
10a454ad |
1039 | .SH "BUGS" |
667fb920 |
1040 | . |
1041 | The syntax for IP addresses and filenames is nasty. The requirement |
1042 | that textual permissions strings be quoted is probably nastier. |
10a454ad |
1043 | .PP |
667fb920 |
1044 | IPv6 is not supported yet. It's probably not a major piece of work to |
1045 | add. |
10a454ad |
1046 | .PP |
667fb920 |
1047 | Please inform me of any security problems you think you've identified in |
1048 | this program. I take security very seriously, and I will fix security |
1049 | holes as a matter of priority when I find out about them. I will be |
1050 | annoyed if I have to read about problems on Bugtraq because they weren't |
1051 | mailed to me first. |
1052 | . |
1053 | .\"-------------------------------------------------------------------------- |
10a454ad |
1054 | .SH "AUTHOR" |
667fb920 |
1055 | . |
10a454ad |
1056 | Mark Wooding, <mdw@nsict.org> |
667fb920 |
1057 | . |
1058 | .\"----- That's all, folks -------------------------------------------------- |