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1 | .\" -*-nroff-*- |
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2 | .\" |
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3 | .\" $Id: fw.1,v 1.5 1999/09/26 18:18:05 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 $ |
cdc917d3 |
31 | .\" Revision 1.5 1999/09/26 18:18:05 mdw |
32 | .\" Remove a fixed bug from the list. Fix some nasty formatting |
33 | .\" misfeatures. |
34 | .\" |
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35 | .\" Revision 1.4 1999/08/19 18:32:48 mdw |
36 | .\" Improve lexical analysis. In particular, `chmod' patterns don't have to |
37 | .\" be quoted any more. |
38 | .\" |
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39 | .\" Revision 1.3 1999/07/30 06:49:00 mdw |
40 | .\" Minor tidying and typo correction. |
41 | .\" |
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42 | .\" Revision 1.2 1999/07/26 23:31:04 mdw |
43 | .\" Document lots of new features and syntax. |
44 | .\" |
45 | . |
46 | .\"----- Various bits of fancy styling -------------------------------------- |
47 | . |
48 | .\" --- Indented paragraphs with right-aligned tags --- |
49 | . |
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50 | .de hP |
51 | .IP |
52 | \h'-\w'\fB\\$1\ \fP'u'\fB\\$1\ \fP\c |
53 | .. |
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54 | . |
55 | .\" --- Verbatim-oid typesetting --- |
56 | .de VS |
57 | .sp 1 |
58 | .RS |
59 | .nf |
60 | .ft B |
61 | .. |
62 | .de VE |
63 | .ft R |
64 | .fi |
65 | .RE |
66 | .sp 1 |
67 | .. |
68 | . |
69 | .\" --- Other bits of styling --- |
70 | . |
71 | .ie t \{\ |
72 | . ds o \(bu |
73 | . ds ss \s8\u |
74 | . ds se \d\s0 |
75 | . if \n(.g \{\ |
76 | . fam P |
77 | . \} |
78 | .\} |
79 | .el \{\ |
80 | . ds o o |
81 | . ds ss ^ |
82 | . ds se |
83 | .\} |
84 | . |
85 | .\"-------------------------------------------------------------------------- |
86 | . |
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87 | .TH fw 1 "1 July 1999" fw |
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88 | . |
89 | .\"-------------------------------------------------------------------------- |
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90 | .SH NAME |
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91 | . |
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92 | fw \- port forwarder |
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93 | . |
94 | .\"-------------------------------------------------------------------------- |
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95 | .SH SYNOPSIS |
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96 | . |
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97 | .B fw |
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98 | .RB [ \-dq ] |
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99 | .RB [ \-f |
100 | .IR file ] |
101 | .IR config-stmt ... |
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102 | . |
103 | .\"-------------------------------------------------------------------------- |
104 | .SH "DESCRIPTION" |
105 | . |
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106 | The |
107 | .B fw |
108 | program is a simple port forwarder. It supports a number of features |
109 | the author hasn't found in similar programs: |
110 | .TP |
111 | .I "Connection logging" |
112 | Each connection attempt to the forwarder is logged, giving the time of |
113 | the connection, the DNS-resolved hostname (if available), and the user |
114 | name resulting from an RFC931 lookup. These lookups are done |
115 | asynchronously to the main forwarder's operation. |
116 | .TP |
117 | .I "Access control" |
118 | Each forwarded port may have an access control list attached to it. |
119 | Only authorized hosts are allowed to connect. Access control checks are |
120 | performed by quick checks on the client's IP address. |
121 | .TP |
122 | .I "Nonblocking single-process design" |
123 | The internal structure of the server is completely nonblocking. The |
124 | connections don't block; the reading and writing don't block; the name |
125 | lookups don't block. This is all done in a single process, with the |
126 | single exception of the DNS resolver. |
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127 | .TP |
128 | .I "Support for Unix-domain sockets" |
129 | Connections from and to Unix-domain sockets can be handled just as |
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130 | easily as more normal Internet sockets. Access control doesn't work on |
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131 | Unix domain sockets, though. (Yet.) |
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132 | .SS "Command line options" |
133 | The |
134 | .B fw |
135 | program understands a few simple command line options: |
136 | .TP |
137 | .B "\-h, \-\-help" |
138 | Displays a screen of help text on standard output and exits |
139 | successfully. |
140 | .TP |
141 | .B "\-v, \-\-version" |
142 | Writes the version number to standard output and exits successfully. |
143 | .TP |
144 | .B "\-u, \-\-usage" |
145 | Writes a terse usage summary to standard output and exits successfully. |
146 | .TP |
147 | .BI "\-f, \-\-file=" file |
148 | Read configuration information from |
149 | .IR file . |
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150 | Equivalent to an |
151 | .RB ` include |
152 | .IR file ' |
153 | configuration file statement. |
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154 | .TP |
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155 | .B "\-d, \-\-daemon, \-\-fork" |
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156 | Forks into the background after reading the configuration and |
157 | initializing properly. |
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158 | .TP |
159 | .B "-q, \-\-quiet" |
160 | Don't output any logging information. This option is not recommended |
161 | for normal use, although it can make system call traces clearer so I use |
162 | it when debugging. |
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163 | .PP |
164 | Any further command line arguments are interpreted as configuration |
165 | lines to be read. Configuration supplied in command line arguments has |
166 | precisely the same syntax as configuration in files. If there are no |
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167 | configuration statements on the command line, and no |
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168 | .B \-f |
169 | options were supplied, configuration is read from standard input, if |
170 | stdin is not a terminal. |
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171 | . |
172 | .\"-------------------------------------------------------------------------- |
173 | .SH "CONFIGURATION LANGUAGE" |
174 | . |
175 | The |
176 | .B fw |
177 | program has a fairly sophisticated configuration language to let you |
178 | describe which things should be forwarded where and what special |
179 | features there should be. |
180 | .SS "Lexical structure" |
181 | There are four types of characters. |
182 | .TP |
183 | .I "word constituent characters" |
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184 | Word constituent characters are gathered together into words. |
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185 | Depending on its surrounding context, a word might act as a keyword or a |
186 | string. All alphanumerics are word constituents, as is the hyphen |
187 | .RB ` \- '. |
188 | Other characters may change their status in future versions. |
189 | .TP |
190 | .I "self-delimiting characters" |
191 | Self-delimiting characters always stand alone. They act as punctuation, |
192 | shaping the sequence of words into more complex grammatical forms. The |
193 | characters |
194 | .RB ` { ', |
195 | .RB ` } ', |
196 | .RB ` [ ', |
197 | .RB ` ] ', |
198 | .RB ` / ', |
199 | .RB ` , ', |
200 | .RB ` = ', |
201 | .RB ` : ', |
202 | .RB ` ; ' |
203 | and |
204 | .RB ` . ' |
205 | are self-delimiting. Note that while some characters, e.g., |
206 | .RB ` [ ' |
207 | and |
208 | .RB ` ; ', |
209 | require escaping by the shell, they are strictly optional in the grammar |
210 | and can be omitted in quick hacks at the shell prompt. |
211 | .TP |
212 | .I "whitespace characters" |
213 | Whitespace characters separate words but are otherwise ignored. All |
214 | `normal' whitespace characters (e.g., space, tab and newline) are |
215 | considered to be whitespace for these purposes. |
216 | .TP |
217 | .I "special characters" |
218 | There are three special characters. The |
219 | .RB ` # ' |
220 | character, if it appears at the start of a word, introduces a |
221 | .I comment |
222 | which extends to the end of the current line or command-line argument. |
223 | Within a word, it behaves like a normal word-constituent character. The |
224 | backslash |
225 | .RB ` \e ' |
226 | escapes the following character causing it to be interpreted as a word |
227 | constituent regardless of its normal type. The double-quote |
228 | .RB ` """" ' |
229 | escapes all characters other than backslashes up to the next |
230 | double-quote and causes them to be regarded as word constituents. Note |
231 | that you don't have to quote a whole word. The backslash can escape a |
232 | quote character allowing you to insert it into a word if really |
233 | necessary. |
234 | . |
235 | .SS "Basic syntax" |
236 | The overall syntax looks a bit like this: |
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237 | .PP |
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238 | .I file |
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239 | ::= |
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240 | .I empty |
241 | | |
242 | .I file |
243 | .I stmt |
244 | .RB [ ; ] |
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245 | .br |
246 | .I stmt |
247 | ::= |
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248 | .I option-stmt |
249 | | |
250 | .I fw-stmt |
251 | .br |
252 | .I fw-stmt |
253 | ::= |
254 | .B fw |
255 | .I source |
256 | .I options |
257 | .RB [ to | \-> ] |
258 | .I target |
259 | .I options |
260 | .br |
261 | .I options |
262 | ::= |
263 | .B { |
264 | .I option-seq |
265 | .B } |
266 | .br |
267 | .I option-seq |
268 | ::= |
269 | .I empty |
270 | | |
271 | .I option-stmt |
272 | .RB [ ; ] |
273 | .I option-seq |
274 | .PP |
275 | If you prefer, the keyword |
276 | .RB ` fw ' |
277 | may be spelt |
278 | .RB ` forward ' |
279 | or |
280 | .RB ` from '. |
281 | All are equivalent. |
282 | . |
283 | .SS "Sources and targets" |
284 | Forwarding is set up by attaching |
285 | .I targets |
286 | to |
287 | .IR sources . |
288 | Sources are things which are capable of |
289 | .I initiating |
290 | one end of a data flow on their own, while targets are things which are |
291 | capable of setting up the other end on demand. In the case of a TCP |
292 | port forwarder, the part which listens for incoming client connections |
293 | is the source, while the part which sets up outgoing connections to the |
294 | destination server is the target. |
295 | .PP |
296 | Essentially, all |
297 | .B fw |
298 | does is set up a collection of sources and targets based on your |
299 | configuration file so that when a source decides to initiate a data |
300 | flow, it tells its target to set its end up, and then squirts data back |
301 | and forth between the two until there's no more. |
302 | .PP |
303 | Some sources are |
304 | .IR persistent : |
305 | they stay around indefinitely setting up multiple attachments to |
306 | targets. Others are |
307 | .IR transient : |
308 | they set up one connection and then disappear. If all the sources |
309 | defined are transient, then |
310 | .B fw |
311 | will quit when no more active sources remain and all connections have |
312 | terminated. |
313 | .PP |
314 | The |
315 | .B fw |
316 | program is fairly versatile. It allows you to attach any supported type |
317 | of source to any supported type of target. This will, I hope, be the |
318 | case in all future versions. |
319 | .PP |
320 | The syntax of a |
321 | .I source |
322 | or |
323 | .I target |
324 | depend on the source or target type, and are therefore described in the |
325 | sections specific to the various types. |
326 | . |
327 | .SS "Options structure" |
328 | Most of the objects that |
329 | .B fw |
330 | knows about (including sources and targets, but also other more specific |
331 | things such as socket address types) can have their behaviour modified |
332 | by |
333 | .IR options . |
334 | The options available at a particular point in the configuration depend |
335 | on the |
336 | .IR context . |
337 | A global option, outside of a |
338 | .I fw-stmt |
339 | has no context unless it is explicitly qualified, and affects global |
340 | behaviour. Local options, applied to a source or target in a |
341 | .I fw-stmt |
342 | has the context of the type of source or target to which it is applied, |
343 | and affects only that source or target. |
344 | .PP |
345 | Note that it's important to distinguish between an option's context |
346 | (which is affected by its qualification) and its local or global |
347 | status. No matter how qualified, a global option will always control |
348 | default options for objects, and a local option will only affect a |
349 | specific source or target. |
350 | .PP |
351 | The syntax for qualifying options is like this: |
352 | .PP |
353 | .I option-stmt |
354 | ::= |
355 | .I q-option |
356 | .br |
357 | .I q-option |
358 | ::= |
359 | .I option |
360 | .br |
361 | | |
362 | .I prefix |
363 | .B . |
364 | .I q-option |
365 | .br |
366 | | |
367 | .I prefix |
368 | .B { |
369 | .I option-seq |
370 | .B } |
371 | .br |
372 | .I prefix |
373 | ::= |
374 | .I word |
375 | .PP |
376 | Thus, you may qualify either an individual option or a sequence of |
377 | options. The two are equivalent; for example, |
378 | .VS |
379 | exec.rlimit { |
380 | core = 0; |
381 | cpu = 60; |
382 | } |
383 | .VE |
384 | is equivalent to |
385 | .VS |
386 | exec.rlimit.core = 0; |
387 | exec.rlimit.cpu = 0; |
388 | .VE |
389 | For each option, there is a sequence of prefixes which maximally qualify |
390 | that option. An option prefixed with this sequence is |
391 | .IR "fully qualified" . |
392 | In actual use, some or all of those prefixes may be omitted. However, |
393 | it's possible for the option to become |
394 | .I ambiguous |
395 | if you do this. For example, the option |
396 | .B fattr.owner |
397 | may refer either to |
398 | .B file.fattr.owner |
399 | or to |
400 | .BR socket.unix.fattr.owner . |
401 | In this case, the ambiguity is benign: a local option will have as its |
402 | context an appropriate source or target, and both global options |
403 | actually control the same default. However, the option |
404 | .B logging |
405 | may mean either |
406 | .B socket.logging |
407 | or |
408 | .BR exec.logging , |
409 | which have separate defaults, and which one you actually get depends on |
410 | the exact implementation of |
411 | .BR fw 's |
412 | option parser. (Currently this would resolve to |
413 | .BR exec.logging , |
414 | although this may change in a later version.) |
415 | .PP |
416 | In this manual, options are usually shown in their fully-qualified form. |
417 | . |
418 | .SS "The `file' source and target types" |
419 | The |
420 | .B file |
421 | source and target allow data to move to and from objects other |
422 | than sockets within the Unix filesystem. (Unix-domain sockets are |
423 | handled using the |
424 | .B socket |
425 | source and target.) |
426 | .PP |
427 | If a |
428 | .B file |
429 | is used as a source, it is set up immediately. |
430 | .PP |
431 | The syntax of |
432 | .B file |
433 | sources and targets is like this: |
434 | .PP |
435 | .I source |
436 | ::= |
437 | .I file |
438 | .br |
439 | .I target |
440 | ::= |
441 | .I file |
442 | .br |
443 | .I file |
444 | ::= |
445 | .B file |
446 | .RB [ . ] |
447 | .I fspec |
448 | .RB [ , |
449 | .IR fspec ] |
450 | .br |
451 | .I fspec |
452 | ::= |
453 | .I fd-spec |
454 | | |
455 | .I name-spec |
456 | | |
457 | .I null-spec |
458 | .br |
459 | .I fd-spec |
460 | ::= |
461 | .RB [[ : ] fd [ : ]] |
462 | .IR number \c |
463 | .RB | stdin | stdout |
464 | .br |
465 | .I name-spec |
466 | ::= |
467 | .RB [[ : ] file [ : ]] |
468 | .I file-name |
469 | .br |
470 | .I file-name |
471 | ::= |
472 | .I path-seq |
473 | | |
474 | .B [ |
475 | .I path-seq |
476 | .B ] |
477 | .br |
478 | .I path-seq |
479 | ::= |
480 | .I path-elt |
481 | | |
482 | .I path-seq |
483 | .I path-elt |
484 | .br |
485 | .I path-elt |
486 | ::= |
487 | .B / |
488 | | |
489 | .I word |
490 | .br |
491 | .I null-spec |
492 | ::= |
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493 | .RB [ : ] null [ : ] |
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494 | .PP |
495 | The |
496 | .I file |
497 | specification describes two files, the first to be used as input, the |
498 | second to be used as output, each described by an |
499 | .IR fspec . |
500 | .PP |
501 | If none of the keywords |
502 | .RB ` fd ', |
503 | .RB ` name ' |
504 | or |
505 | .RB ` null ' |
506 | are given, the type of an |
507 | .I fspec |
508 | is deduced from its nature: if it matches one of the strings |
509 | .RB ` stdin ' |
510 | or |
511 | .RB ` stdout ', |
512 | or begins with a digit, it's considered to be a file descriptor; |
513 | otherwise it's interpreted as a filename. |
514 | .PP |
515 | A |
516 | .RB ` name ' |
517 | spec describes a file by its name within the filesystem. It is opened |
518 | when needed and closed again after use. For output files, the precise |
519 | behaviour is controlled by options described below. |
520 | .PP |
521 | A |
522 | .RB ` null ' |
523 | spec attaches the input or output of the source or target to |
524 | .BR /dev/null . |
525 | .PP |
526 | An |
527 | .RB ` fd ' |
528 | spec uses an existing open file descriptor, given either by number or a |
529 | symbolic name. The name |
530 | .RB ` stdin ' |
531 | refers to standard input (file descriptor 0 on normal systems) and |
532 | .RB ` stdout ' |
533 | refers to standard output (file descriptor 1). The names work in |
534 | exactly the same way as the equivalent file descriptor numbers. |
535 | .PP |
536 | If the output |
537 | .I fspec |
538 | is omitted, the input |
539 | .I fspec |
540 | is used for both input and output. Exception: if the input refers to |
541 | standard input then the output will refer to standard output instead. |
542 | .PP |
543 | All |
544 | .B file |
545 | options apply equally to sources and targets. The options are as |
546 | follows: |
547 | .PP |
548 | .B file.create |
549 | .RB [ = ] |
550 | .BR yes | no |
551 | .RS |
552 | Whether to create the output file if it doesn't exist. If |
553 | .B no |
554 | (the default), an error is reported if the file doesn't exist. If |
555 | .BR yes , |
556 | the file is created if it doesn't exist. |
557 | .RE |
558 | .PP |
559 | .B file.open |
560 | .RB [ = ] |
561 | .BR no | truncate | append |
562 | .RS |
563 | Controls the behaviour if the output file already exists. If |
564 | .BR no , |
565 | an error is reported. If |
566 | .B truncate |
567 | (the default), the existing file is replaced by the new data. If |
568 | .BR append , |
569 | the new data is appended to the file. |
570 | .RE |
571 | .PP |
572 | Under no circumstances will |
573 | .B fw |
574 | create a file through a `dangling' symbolic link. |
575 | .PP |
576 | The |
577 | .B file |
578 | source and target also accept |
579 | .B fattr |
580 | options for controlling the attributes of the created file. The prefix |
581 | for setting file attributes is |
582 | .BR file.fattr . |
583 | . |
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584 | .SS "File attributes for created files: `fattr'" |
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585 | Both the |
586 | .B file |
587 | and |
588 | .B socket |
589 | sources and targets can create new filesystem objects. The |
590 | .B fattr |
591 | options allow control over the attributes of the newly-created objects. |
592 | Both |
593 | .B file |
594 | and |
595 | .B socket |
596 | use the same set of defaults, so a prefix of |
597 | .B fattr |
598 | is good enough for setting global options, and the implicit context |
599 | disambiguates local options. |
600 | .PP |
601 | The following file attribute options are supported: |
602 | .PP |
603 | .IB prefix .fattr.mode |
604 | .RB [ = ] |
605 | .I mode |
606 | .RS |
607 | Sets the permissions mode for a new file. The |
608 | .I mode |
609 | argument may be either an octal number or a |
610 | .BR chmod (1)-style |
611 | string which acts on the default permissions established by the |
612 | prevailing |
613 | .BR umask (2) |
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614 | setting. The characters |
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615 | .RB ` = ' |
616 | and |
617 | .RB ` , ' |
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618 | do not have to be quoted within the mode string. |
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619 | .RE |
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620 | .PP |
621 | .IB prefix .fattr.owner |
622 | .RB [ = ] |
623 | .I user |
624 | .RS |
625 | Sets the owner for newly created files. On non-broken systems you will |
626 | need to be the superuser to set the owner on a file. The |
627 | .I user |
628 | may either be a numeric uid or a username. The default is not to change |
629 | the owner of the file once it's created. The synonyms |
630 | .B uid |
631 | and |
632 | .B user |
633 | are accepted in place of |
634 | .BR owner . |
635 | .RE |
636 | .PP |
637 | .IB prefix .fattr.group |
638 | .RB [ = ] |
639 | .I group |
640 | .RS |
641 | Sets the group for newly created files. You will usually need to be a |
642 | member of the group in question order to set the group of a file. The |
643 | .I group |
644 | may either be a numeric gid or a group name. The default is not to |
645 | change the group of the file once it's created. The synonym |
646 | .B gid |
647 | is accepted in place of |
648 | .BR group . |
649 | .RE |
650 | . |
651 | .SS "The `exec' source and target types" |
652 | The |
653 | .B exec |
654 | source and target execute programs and allow access to their standard |
655 | input and output streams. Both source and target have the same syntax, |
656 | which is as follows: |
657 | .PP |
658 | .I source |
659 | ::= |
660 | .I exec |
661 | .br |
662 | .I target |
663 | ::= |
664 | exec |
665 | .br |
666 | .I exec |
667 | ::= |
668 | .BR exec |
669 | .RB [ . ] |
670 | .I cmd-spec |
671 | .br |
672 | .I cmd-spec |
673 | ::= |
674 | .I shell-cmd |
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675 | | |
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676 | .RI [ prog-name ] |
677 | .B [ |
678 | .I argv0 |
679 | .I arg-seq |
680 | .B ] |
681 | .br |
682 | .I arg-seq |
683 | ::= |
684 | .I word |
685 | | |
686 | .I arg-seq |
687 | .I word |
688 | .br |
689 | .I shell-cmd |
690 | ::= |
691 | .I word |
692 | .br |
693 | .I argv0 |
694 | ::= |
695 | .I word |
696 | .PP |
697 | If a single word is given, it is a |
698 | .I shell-cmd |
699 | and will be passed to the Bourne shell for execution. If a |
700 | bracket-enclosed sequence of words is given, it is considered to be a |
701 | list of arguments to pass to the program: if a |
702 | .I prog-name |
703 | is also supplied, it names the file containing the program to execute; |
704 | otherwise the file named by the first argument |
705 | .RI ( argv0 ) |
706 | is used. |
707 | .PP |
708 | The standard input and output of the program are forwarded to the other |
709 | end of the connection. The standard error stream is caught by |
710 | .B fw |
711 | and logged. |
712 | .PP |
713 | The |
714 | .B exec |
715 | source and target both understand the same set of options. The list of |
716 | options supported is as follows: |
717 | .PP |
718 | .B exec.logging |
719 | .RB [ = ] |
720 | .BR yes | no |
721 | .RS |
722 | Whether to log the start and end of executed programs. If |
723 | .B yes |
724 | (the default), a log message is emitted when the program is started |
725 | listing its process id, and another is emitted when the program finishes |
726 | giving its process id and exit status. If |
727 | .BR no , |
728 | these messages are not emitted. However the standard error stream is |
729 | still logged. The |
730 | .B log |
731 | abbreviation is accepted as a synonym for |
732 | .BR logging . |
733 | .RE |
734 | .PP |
735 | .B exec.dir |
736 | .RB [ = ] |
737 | .I file-name |
738 | .RS |
739 | Sets the current directory from which the the program should be run. |
740 | The default is not to change directory. The synonyms |
741 | .BR cd , |
742 | .B chdir |
743 | and |
744 | .B cwd |
745 | are accepted in place of |
746 | .BR dir . |
747 | .RE |
748 | .PP |
749 | .B exec.root |
750 | .RB [ = ] |
751 | .I file-name |
752 | .RS |
753 | Sets the root directory for the program, using the |
754 | .BR chroot (2) |
755 | system call. You must be the superuser for this option to work. The |
756 | default is not to set a root directory. The synonyms |
757 | .BR cd , |
758 | .B chdir |
759 | and |
760 | .B cwd |
761 | are accepted in place of |
762 | .B dir . |
763 | .RE |
764 | .PP |
765 | .B exec.user |
766 | .RB [ = ] |
767 | .I user |
768 | .RS |
769 | Sets the user (real and effective uid) to run the program as. This will |
770 | usually require superuser privileges to work. The default is not to |
771 | change uid. The synonym |
772 | .B uid |
773 | is accepted in place of |
774 | .BR user . |
775 | .RE |
776 | .PP |
777 | .B exec.group |
778 | .RB [ = ] |
779 | .I group |
780 | .RS |
781 | Sets the group (real and effective gid) to run the program as. If |
782 | running with superuser privileges, the supplementary groups list is |
783 | cleared at the same time. The default is not to change gid (or clear |
784 | the supplementary groups list). The synonym |
785 | .B gid |
786 | is accepted in place of |
787 | .BR group . |
788 | .RE |
789 | .PP |
790 | .BI exec.rlimit. limit \c |
791 | .RB [ .hard | .soft ] |
792 | .RB [ = ] |
793 | .I value |
794 | .RS |
795 | Set resource limits for the program. The |
796 | .I limit |
797 | may be one of the resource limit names described in |
798 | .BR setrlimit (2), |
799 | in lower-case and without the |
800 | .B RLIMIT_ |
801 | prefix; for example, |
802 | .B RLIMIT_CORE |
803 | becomes simply |
804 | .BR core . |
805 | The |
806 | .I value |
807 | is a number, followed optionally by |
808 | .B k |
809 | to multiply by 1024 (2\*(ss10\*(se), |
810 | .B m |
811 | to multiply by 1048576 (2\*(ss20\*(se), or |
812 | .B g |
813 | to multiply by 1073741824 (2\*(ss30\*(se); purists can use upper-case |
814 | versions of these if they want. If |
815 | .B .hard |
816 | or |
817 | .B .soft |
818 | was specified, only the hard or soft limit is set; otherwise both are |
819 | set to the same value. Only the superuser can raise the hard limit. |
820 | The soft limit cannot be set above the hard limit. |
821 | .RE |
822 | .PP |
823 | .B exec.env.clear |
824 | .RS |
825 | Clears the program's environment. |
826 | .RE |
827 | .PP |
828 | .B exec.env.unset |
829 | .I var |
830 | .RS |
831 | Removes |
832 | .I var |
833 | from the program's environment. It is not an error if no variable named |
834 | .I var |
835 | exists. |
836 | .RE |
837 | .PP |
838 | .BR exec.env. [ set ] |
839 | .I var |
840 | .RB [ = ] |
841 | .I value |
842 | .RS |
96bc31ba |
843 | Assigns the variable |
667fb920 |
844 | .I var |
845 | the value |
846 | .I value |
847 | in the program's environment, possibly replacing the existing value. |
848 | The |
849 | .B set |
850 | may be omitted if the |
851 | .B env |
852 | qualifier is present. |
853 | .RE |
854 | .PP |
855 | Note that environment variable modifications are performed in order, |
856 | global modifications before local ones. |
857 | . |
858 | .SS "The `socket' source and target types" |
859 | The |
860 | .B socket |
861 | source and target provide access to network services. Support is |
862 | currently provided for TCP/IP and Unix-domain sockets, although other |
863 | address types can be added with reasonable ease. |
864 | .PP |
865 | The syntax for socket sources and targets is: |
866 | .PP |
867 | .ll +8i |
868 | .I source |
869 | ::= |
870 | .I socket-source |
10a454ad |
871 | .br |
667fb920 |
872 | .I target |
873 | ::= |
874 | .I socket-target |
875 | .br |
876 | .I socket-source |
877 | ::= |
878 | .RB [ socket [ . ]] |
879 | .RB [[ : ] \c |
880 | .IR addr-type \c |
881 | .RB [ : ]] |
882 | .I source-addr |
883 | .br |
884 | .I socket-target |
885 | ::= |
886 | .RB [ socket [ . ]] |
887 | .RB [[ : ] \c |
888 | .IR addr-type \c |
889 | .RB [ : ]] |
890 | .I target-addr |
891 | .ll -8i |
892 | .PP |
893 | The syntax of the source and target addresses depend on the address |
894 | types, which are described below. The default address type, if no |
895 | .I addr-type |
896 | is given, is |
897 | .BR inet . |
898 | .PP |
899 | Socket sources support options; socket targets do not. The source |
900 | options provided are: |
901 | .PP |
902 | .B socket.conn |
903 | .RB [ = ] |
904 | .I number |
905 | .RS |
906 | Limits the number of simultaneous connections to this socket to the |
907 | .I number |
908 | given. The default is 256. |
909 | .RE |
910 | .PP |
911 | .B socket.logging |
912 | .RB [ = ] |
913 | .BR yes | no |
914 | .RS |
915 | Whether to log incoming connections. If |
916 | .B yes |
917 | (the default) incoming connections are logged, together with information |
918 | about the client (where available) and whether the connection was |
919 | accepted or refused. If |
920 | .BR no , |
921 | log messages are not generated. |
922 | .RE |
923 | .PP |
924 | Address types also provide their own options. |
925 | . |
926 | .SS "The `inet' socket address type" |
927 | The |
928 | .B inet |
929 | address type provides access to TCP ports. The |
930 | .B inet |
931 | source and target addresses have the following syntax: |
932 | .PP |
933 | .I inet-source-addr |
10a454ad |
934 | ::= |
10a454ad |
935 | .RB [ port ] |
936 | .I port |
667fb920 |
937 | .br |
938 | .I inet-target-addr |
939 | ::= |
940 | .I address |
10a454ad |
941 | .RB [ : ] |
942 | .I port |
10a454ad |
943 | .br |
667fb920 |
944 | .I address |
10a454ad |
945 | ::= |
667fb920 |
946 | .I addr-elt |
947 | | |
948 | .I address |
949 | .I addr-elt |
10a454ad |
950 | .br |
667fb920 |
951 | .I addr-elt |
10a454ad |
952 | ::= |
667fb920 |
953 | .B . |
10a454ad |
954 | | |
667fb920 |
955 | .I word |
956 | .PP |
957 | A |
958 | .I port |
959 | may be given as a port number or a service name from the |
960 | .B /etc/services |
961 | file (or YP map if you do that sort of thing). A |
962 | .B hostname |
963 | may be a textual hostname or a numerical IP address. |
964 | .PP |
965 | The |
966 | .B inet |
967 | source address accepts the following options: |
968 | .PP |
969 | .BR socket.inet. [ allow | deny ] |
10a454ad |
970 | .RB [ from ] |
667fb920 |
971 | .I address |
10a454ad |
972 | .RB [ / |
667fb920 |
973 | .IR address ] |
974 | .RS |
975 | Adds an entry to the source's access control list. If only one |
976 | .I address |
977 | is given, the entry applies only to that address; if two are given, the |
978 | first is a network address and the second is a netmask either in |
979 | dotted-quad format or a simple number of bits (e.g., |
980 | .B /255.255.255.192 |
981 | and |
982 | .B /26 |
983 | mean the same), and the entry applies to any address which, when masked |
984 | by the netmask, is equal to the masked network address. |
10a454ad |
985 | .PP |
667fb920 |
986 | The access |
987 | control rules are examined in the order: local entries first, then |
988 | global ones, each in the order given in the configuration file. The |
989 | first matching entry is used. If no entries match, the behaviour is the |
990 | .I opposite |
991 | of the last entry tried. If there are no entries defined, the default |
992 | is to allow all clients. |
993 | .RE |
994 | . |
995 | .SS "The `unix' socket address type" |
10a454ad |
996 | The |
667fb920 |
997 | .B unix |
998 | address type allows access to Unix-domain sockets. The syntax for |
999 | .B unix |
1000 | source and target addresses is like this: |
1001 | .PP |
1002 | .I source-addr |
1003 | ::= |
1004 | .I unix-addr |
1005 | .br |
1006 | .I target-addr |
1007 | ::= |
1008 | .I unix-addr |
1009 | .br |
1010 | .I unix-addr |
1011 | ::= |
1012 | .I file-name |
1013 | .PP |
1014 | The |
1015 | .B unix |
1016 | source address accepts |
1017 | .B fattr |
1018 | options to control the attributes of the socket file created. Sockets |
1019 | are removed if |
10a454ad |
1020 | .B fw |
667fb920 |
1021 | exits normally (which it will do if it runs out of sources or |
1022 | connections, or if killed by SIGINT or SIGTERM). |
1023 | .SH "EXAMPLES" |
1024 | To forward the local port 25 to a main mail server: |
1025 | .VS |
1026 | from 25 to mailserv:25 |
1027 | .VE |
1028 | To attach a fortune server to a Unix-domain socket: |
1029 | .VS |
1030 | from unix:/tmp/fortunes |
1031 | to exec [/usr/games/fortune] { user nobody } |
1032 | .VE |
1033 | To fetch a fortune from the server: |
1034 | .VS |
1035 | from file stdin, stdout to unix:/tmp/fortunes |
1036 | .VE |
1037 | To emulate |
1038 | .BR cat (1): |
1039 | .VS |
1040 | from stdin, null to null, stdout |
1041 | .VE |
1042 | . |
1043 | .\"-------------------------------------------------------------------------- |
10a454ad |
1044 | .SH "BUGS" |
667fb920 |
1045 | . |
cdc917d3 |
1046 | The syntax for IP addresses and filenames is nasty. |
10a454ad |
1047 | .PP |
667fb920 |
1048 | IPv6 is not supported yet. It's probably not a major piece of work to |
1049 | add. |
10a454ad |
1050 | .PP |
667fb920 |
1051 | Please inform me of any security problems you think you've identified in |
1052 | this program. I take security very seriously, and I will fix security |
1053 | holes as a matter of priority when I find out about them. I will be |
1054 | annoyed if I have to read about problems on Bugtraq because they weren't |
1055 | mailed to me first. |
1056 | . |
1057 | .\"-------------------------------------------------------------------------- |
10a454ad |
1058 | .SH "AUTHOR" |
667fb920 |
1059 | . |
10a454ad |
1060 | Mark Wooding, <mdw@nsict.org> |
667fb920 |
1061 | . |
1062 | .\"----- That's all, folks -------------------------------------------------- |