| 1 | .\" -*-nroff-*- |
| 2 | .\" |
| 3 | .\" Manual page for fw |
| 4 | .\" |
| 5 | .\" (c) 1999 Straylight/Edgeware |
| 6 | .\" |
| 7 | . |
| 8 | .\"----- Licensing notice --------------------------------------------------- |
| 9 | .\" |
| 10 | .\" This file is part of the `fw' port forwarder. |
| 11 | .\" |
| 12 | .\" `fw' is free software; you can redistribute it and/or modify |
| 13 | .\" it under the terms of the GNU General Public License as published by |
| 14 | .\" the Free Software Foundation; either version 2 of the License, or |
| 15 | .\" (at your option) any later version. |
| 16 | .\" |
| 17 | .\" `fw' is distributed in the hope that it will be useful, |
| 18 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | .\" GNU General Public License for more details. |
| 21 | .\" |
| 22 | .\" You should have received a copy of the GNU General Public License |
| 23 | .\" along with `fw'; if not, write to the Free Software Foundation, |
| 24 | .\" Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 25 | . |
| 26 | .\"----- Various bits of fancy styling -------------------------------------- |
| 27 | . |
| 28 | .\" --- Indented paragraphs with right-aligned tags --- |
| 29 | . |
| 30 | .de hP |
| 31 | .IP |
| 32 | \h'-\w'\fB\\$1\ \fP'u'\fB\\$1\ \fP\c |
| 33 | .. |
| 34 | . |
| 35 | .\" --- Verbatim-oid typesetting --- |
| 36 | .de VS |
| 37 | .sp 1 |
| 38 | .RS |
| 39 | .nf |
| 40 | .ft B |
| 41 | .. |
| 42 | .de VE |
| 43 | .ft R |
| 44 | .fi |
| 45 | .RE |
| 46 | .sp 1 |
| 47 | .. |
| 48 | . |
| 49 | .\" --- Grammar markup --- |
| 50 | .\" |
| 51 | .\" This is mainly for the benefit of the automatic scripts which |
| 52 | .\" generate the grammar summary. |
| 53 | . |
| 54 | .de GS |
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| 56 | .. |
| 57 | .de GE |
| 58 | .PP |
| 59 | .. |
| 60 | .de GL |
| 61 | .. |
| 62 | . |
| 63 | .de OS |
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| 65 | .. |
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| 67 | .RS |
| 68 | .. |
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| 73 | .. |
| 74 | . |
| 75 | .\" --- Other bits of styling --- |
| 76 | . |
| 77 | .ie t \{\ |
| 78 | . ds o \(bu |
| 79 | . ds ss \s8\u |
| 80 | . ds se \d\s0 |
| 81 | . if \n(.g \{\ |
| 82 | . fam P |
| 83 | . \} |
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| 85 | .el \{\ |
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| 89 | .\} |
| 90 | . |
| 91 | .\"-------------------------------------------------------------------------- |
| 92 | . |
| 93 | .TH fw 1 "1 July 1999" "Straylight/Edgeware" "fw port forwarder" |
| 94 | . |
| 95 | .\"-------------------------------------------------------------------------- |
| 96 | .SH NAME |
| 97 | . |
| 98 | fw \- port forwarder |
| 99 | . |
| 100 | .\"-------------------------------------------------------------------------- |
| 101 | .SH SYNOPSIS |
| 102 | . |
| 103 | .B fw |
| 104 | .RB [ \-dlq ] |
| 105 | .RB [ \-p |
| 106 | .IR file ] |
| 107 | .RB [ \-f |
| 108 | .IR file ] |
| 109 | .RB [ \-s |
| 110 | .IR user ] |
| 111 | .RB [ \-g |
| 112 | .IR group ] |
| 113 | .IR config-stmt ... |
| 114 | . |
| 115 | .\"-------------------------------------------------------------------------- |
| 116 | .SH "DESCRIPTION" |
| 117 | . |
| 118 | The |
| 119 | .B fw |
| 120 | program is a simple port forwarder. It supports a number of features |
| 121 | the author hasn't found in similar programs: |
| 122 | .TP |
| 123 | .I "Connection logging" |
| 124 | Each connection attempt to the forwarder is logged, giving the time of |
| 125 | the connection, the DNS-resolved hostname (if available), and the user |
| 126 | name resulting from an RFC931 lookup. These lookups are done |
| 127 | asynchronously to the main forwarder's operation. |
| 128 | .TP |
| 129 | .I "Access control" |
| 130 | Each forwarded port may have an access control list attached to it. |
| 131 | Only authorized hosts are allowed to connect. Access control checks are |
| 132 | performed by quick checks on the client's IP address. |
| 133 | .TP |
| 134 | .I "Nonblocking single-process design" |
| 135 | The internal structure of the server is completely nonblocking. The |
| 136 | connections don't block; the reading and writing don't block; the name |
| 137 | lookups don't block. This is all done in a single process, with the |
| 138 | single exception of the DNS resolver. |
| 139 | .TP |
| 140 | .I "Support for Unix-domain sockets" |
| 141 | Connections from and to Unix-domain sockets can be handled just as |
| 142 | easily as more normal Internet sockets. Access control doesn't work on |
| 143 | Unix domain sockets, though. (Yet.) |
| 144 | .SS "Command line options" |
| 145 | The |
| 146 | .B fw |
| 147 | program understands a few simple command line options: |
| 148 | .TP |
| 149 | .B "\-h, \-\-help" |
| 150 | Displays a screen of help text on standard output and exits |
| 151 | successfully. |
| 152 | .TP |
| 153 | .B "\-v, \-\-version" |
| 154 | Writes the version number to standard output and exits successfully. |
| 155 | .TP |
| 156 | .B "\-u, \-\-usage" |
| 157 | Writes a terse usage summary to standard output and exits successfully. |
| 158 | .TP |
| 159 | .B "\-G, \-\-grammar" |
| 160 | Writes a summary of the configuration file grammar to standard output |
| 161 | and exits successfully. |
| 162 | .TP |
| 163 | .B "\-O, \-\-options" |
| 164 | Writes a summary of the source and target options to standard output and |
| 165 | exits successfully. |
| 166 | .TP |
| 167 | .BI "\-f, \-\-file=" file |
| 168 | Read configuration information from |
| 169 | .IR file . |
| 170 | Equivalent to an |
| 171 | .RB ` include |
| 172 | .IR file ' |
| 173 | configuration file statement. |
| 174 | .TP |
| 175 | .B "\-d, \-\-daemon, \-\-fork" |
| 176 | Forks into the background after reading the configuration and |
| 177 | initializing properly. |
| 178 | .TP |
| 179 | .B "\-l, \-\-syslog, \-\-log" |
| 180 | Emit logging information to the system log, rather than standard error. |
| 181 | .TP |
| 182 | .BI "\-p, \-\-pidfile=" file |
| 183 | Write |
| 184 | .BR fw 's |
| 185 | process-id to |
| 186 | .I file |
| 187 | during start-up. If |
| 188 | .B \-d |
| 189 | is given too, then the process-id is written after forking (obviously). |
| 190 | .TP |
| 191 | .B "\-q, \-\-quiet" |
| 192 | Don't output any logging information. This option is not recommended |
| 193 | for normal use, although it can make system call traces clearer so I use |
| 194 | it when debugging. |
| 195 | .TP |
| 196 | .BI "\-s, \-\-setuid=" user |
| 197 | Change uid to that of |
| 198 | .IR user , |
| 199 | which may be either a user name or uid number, after initializing all |
| 200 | the sources. This will usually require elevated privileges. |
| 201 | .TP |
| 202 | .BI "\-g, \-\-setgid=" group |
| 203 | Change gid to that of |
| 204 | .IR group , |
| 205 | which may be either a group name or gid number, after initializing all |
| 206 | the sources. If the operating system understands supplementary groups |
| 207 | then the supplementary groups list is altered to include only |
| 208 | .IR group . |
| 209 | .PP |
| 210 | Any further command line arguments are interpreted as configuration |
| 211 | lines to be read. Configuration supplied in command line arguments has |
| 212 | precisely the same syntax as configuration in files. If there are no |
| 213 | configuration statements on the command line, and no |
| 214 | .B \-f |
| 215 | options were supplied, configuration is read from standard input, if |
| 216 | stdin is not a terminal. |
| 217 | . |
| 218 | .\"-------------------------------------------------------------------------- |
| 219 | .SH "CONFIGURATION LANGUAGE" |
| 220 | . |
| 221 | The |
| 222 | .B fw |
| 223 | program has a fairly sophisticated configuration language to let you |
| 224 | describe which things should be forwarded where and what special |
| 225 | features there should be. |
| 226 | .SS "Lexical structure" |
| 227 | There are four types of characters. |
| 228 | .TP |
| 229 | .I "word constituent characters" |
| 230 | Word constituent characters are gathered together into words. |
| 231 | Depending on its surrounding context, a word might act as a keyword or a |
| 232 | string. All alphanumerics are word constituents, as is the hyphen |
| 233 | .RB ` \- '. |
| 234 | Other characters may change their status in future versions. |
| 235 | .TP |
| 236 | .I "self-delimiting characters" |
| 237 | Self-delimiting characters always stand alone. They act as punctuation, |
| 238 | shaping the sequence of words into more complex grammatical forms. The |
| 239 | characters |
| 240 | .RB ` { ', |
| 241 | .RB ` } ', |
| 242 | .RB ` [ ', |
| 243 | .RB ` ] ', |
| 244 | .RB ` / ', |
| 245 | .RB ` , ', |
| 246 | .RB ` = ', |
| 247 | .RB ` : ', |
| 248 | .RB ` ; ' |
| 249 | and |
| 250 | .RB ` . ' |
| 251 | are self-delimiting. Note that while some characters, e.g., |
| 252 | .RB ` [ ' |
| 253 | and |
| 254 | .RB ` ; ', |
| 255 | require escaping by the shell, they are mostly optional in the grammar |
| 256 | and can tend to be omitted in quick hacks at the shell prompt. |
| 257 | .TP |
| 258 | .I "whitespace characters" |
| 259 | Whitespace characters separate words but are otherwise ignored. All |
| 260 | `normal' whitespace characters (e.g., space, tab and newline) are |
| 261 | considered to be whitespace for these purposes. |
| 262 | .TP |
| 263 | .I "special characters" |
| 264 | There are three special characters. The |
| 265 | .RB ` # ' |
| 266 | character, if it appears at the start of a word, introduces a |
| 267 | .I comment |
| 268 | which extends to the end of the current line or command-line argument. |
| 269 | Within a word, it behaves like a normal word-constituent character. The |
| 270 | backslash |
| 271 | .RB ` \e ' |
| 272 | escapes the following character causing it to be interpreted as a word |
| 273 | constituent regardless of its normal type. The double-quote |
| 274 | .RB ` """" ' |
| 275 | escapes all characters other than backslashes up to the next |
| 276 | double-quote and causes them to be regarded as word constituents. Note |
| 277 | that you don't have to quote a whole word. The backslash can escape a |
| 278 | quote character allowing you to insert it into a word if really |
| 279 | necessary. |
| 280 | . |
| 281 | .SS "Basic syntax" |
| 282 | The overall syntax looks a bit like this: |
| 283 | .GS "Basic syntax" |
| 284 | .I file |
| 285 | ::= |
| 286 | .I empty |
| 287 | | |
| 288 | .I file |
| 289 | .I stmt |
| 290 | .RB [ ; ] |
| 291 | .br |
| 292 | .I stmt |
| 293 | ::= |
| 294 | .I option-stmt |
| 295 | | |
| 296 | .I fw-stmt |
| 297 | .br |
| 298 | .I fw-stmt |
| 299 | ::= |
| 300 | .B fw |
| 301 | .I source |
| 302 | .I options |
| 303 | .RB [ to | \-> ] |
| 304 | .I target |
| 305 | .I options |
| 306 | .br |
| 307 | .I options |
| 308 | ::= |
| 309 | .B { |
| 310 | .I option-seq |
| 311 | .B } |
| 312 | .br |
| 313 | .I option-seq |
| 314 | ::= |
| 315 | .I empty |
| 316 | | |
| 317 | .I option-stmt |
| 318 | .RB [ ; ] |
| 319 | .I option-seq |
| 320 | .GE |
| 321 | If you prefer, the keyword |
| 322 | .RB ` fw ' |
| 323 | may be spelt |
| 324 | .RB ` forward ' |
| 325 | or |
| 326 | .RB ` from '. |
| 327 | All are equivalent. |
| 328 | . |
| 329 | .SS "Sources and targets" |
| 330 | Forwarding is set up by attaching |
| 331 | .I targets |
| 332 | to |
| 333 | .IR sources . |
| 334 | Sources are things which are capable of |
| 335 | .I initiating |
| 336 | one end of a data flow on their own, while targets are things which are |
| 337 | capable of setting up the other end on demand. In the case of a TCP |
| 338 | port forwarder, the part which listens for incoming client connections |
| 339 | is the source, while the part which sets up outgoing connections to the |
| 340 | destination server is the target. |
| 341 | .PP |
| 342 | Essentially, all |
| 343 | .B fw |
| 344 | does is set up a collection of sources and targets based on your |
| 345 | configuration file so that when a source decides to initiate a data |
| 346 | flow, it tells its target to set its end up, and then squirts data back |
| 347 | and forth between the two until there's no more. |
| 348 | .PP |
| 349 | Some sources are |
| 350 | .IR persistent : |
| 351 | they stay around indefinitely setting up multiple attachments to |
| 352 | targets. Others are |
| 353 | .IR transient : |
| 354 | they set up one connection and then disappear. If all the sources |
| 355 | defined are transient, then |
| 356 | .B fw |
| 357 | will quit when no more active sources remain and all connections have |
| 358 | terminated. |
| 359 | .PP |
| 360 | The |
| 361 | .B fw |
| 362 | program is fairly versatile. It allows you to attach any supported type |
| 363 | of source to any supported type of target. This will, I hope, be the |
| 364 | case in all future versions. |
| 365 | .PP |
| 366 | The syntax of a |
| 367 | .I source |
| 368 | or |
| 369 | .I target |
| 370 | depend on the source or target type, and are therefore described in the |
| 371 | sections specific to the various types. |
| 372 | . |
| 373 | .SS "Options structure" |
| 374 | Most of the objects that |
| 375 | .B fw |
| 376 | knows about (including sources and targets, but also other more specific |
| 377 | things such as socket address types) can have their behaviour modified |
| 378 | by |
| 379 | .IR options . |
| 380 | The options available at a particular point in the configuration depend |
| 381 | on the |
| 382 | .IR context . |
| 383 | A global option, outside of a |
| 384 | .I fw-stmt |
| 385 | has no context unless it is explicitly qualified, and affects global |
| 386 | behaviour. A local option, applied to a source or target in a |
| 387 | .IR fw-stmt , |
| 388 | has the context of the type of source or target to which it is applied, |
| 389 | and affects only that source or target. |
| 390 | .PP |
| 391 | Note that it's important to distinguish between an option's context |
| 392 | (which is affected by its qualification) and its local or global |
| 393 | status. No matter how qualified, a global option will always control |
| 394 | default options for objects, and a local option will only affect a |
| 395 | specific source or target. |
| 396 | .PP |
| 397 | The syntax for qualifying options is like this: |
| 398 | .GS "Option syntax" |
| 399 | .I option-stmt |
| 400 | ::= |
| 401 | .I q-option |
| 402 | .br |
| 403 | .I q-option |
| 404 | ::= |
| 405 | .I option |
| 406 | .br |
| 407 | | |
| 408 | .I prefix |
| 409 | .B .\& |
| 410 | .I q-option |
| 411 | .br |
| 412 | | |
| 413 | .I prefix |
| 414 | .B { |
| 415 | .I option-seq |
| 416 | .B } |
| 417 | .br |
| 418 | .I prefix |
| 419 | ::= |
| 420 | .I word |
| 421 | .GE |
| 422 | Thus, you may qualify either an individual option or a sequence of |
| 423 | options. The two are equivalent; for example, |
| 424 | .VS |
| 425 | exec.rlimit { |
| 426 | core = 0; |
| 427 | cpu = 60; |
| 428 | } |
| 429 | .VE |
| 430 | means the same as |
| 431 | .VS |
| 432 | exec.rlimit.core = 0; |
| 433 | exec.rlimit.cpu = 0; |
| 434 | .VE |
| 435 | For each option, there is a sequence of prefixes which maximally qualify |
| 436 | that option. An option prefixed with this sequence is |
| 437 | .IR "fully qualified" . |
| 438 | In actual use, some or all of those prefixes may be omitted. However, |
| 439 | it's possible for the option to become |
| 440 | .I ambiguous |
| 441 | if you do this. For example, the option |
| 442 | .B fattr.owner |
| 443 | may refer either to |
| 444 | .B file.fattr.owner |
| 445 | or to |
| 446 | .BR socket.unix.fattr.owner . |
| 447 | In this case, the ambiguity is benign: a local option will have as its |
| 448 | context an appropriate source or target, and both global options |
| 449 | actually control the same default. However, the option |
| 450 | .B logging |
| 451 | may mean either |
| 452 | .B socket.logging |
| 453 | or |
| 454 | .BR exec.logging , |
| 455 | which have separate defaults, and which one you actually get depends on |
| 456 | the exact implementation of |
| 457 | .BR fw 's |
| 458 | option parser. (Currently this would resolve to |
| 459 | .BR exec.logging , |
| 460 | although this may change in a later version.) |
| 461 | .PP |
| 462 | In this manual, options are usually shown in their fully-qualified form. |
| 463 | . |
| 464 | .SS "File attributes for created files: `fattr'" |
| 465 | Both the |
| 466 | .B file |
| 467 | and |
| 468 | .B socket |
| 469 | sources and targets can create new filesystem objects. The |
| 470 | .B fattr |
| 471 | options allow control over the attributes of the newly-created objects. |
| 472 | Both |
| 473 | .B file |
| 474 | and |
| 475 | .B socket |
| 476 | use the same set of defaults, so a prefix of |
| 477 | .B fattr |
| 478 | is good enough for setting global options, and the implicit context |
| 479 | disambiguates local options. |
| 480 | .PP |
| 481 | The following file attribute options are supported: |
| 482 | .OS "File attributes (`fattr')" |
| 483 | .IB prefix .fattr.mode |
| 484 | .RB [ = ] |
| 485 | .I mode |
| 486 | .OD |
| 487 | Sets the permissions mode for a new file. The |
| 488 | .I mode |
| 489 | argument may be either an octal number or a |
| 490 | .BR chmod (1)-style |
| 491 | string which acts on the default permissions established by the |
| 492 | prevailing |
| 493 | .BR umask (2) |
| 494 | setting. The characters |
| 495 | .RB ` = ' |
| 496 | and |
| 497 | .RB ` , ' |
| 498 | do not have to be quoted within the mode string. |
| 499 | .OE |
| 500 | .OS "File attributes (`fattr')" |
| 501 | .IB prefix .fattr.owner |
| 502 | .RB [ = ] |
| 503 | .I user |
| 504 | .OD |
| 505 | Sets the owner for newly created files. On non-broken systems you will |
| 506 | need to be the superuser to set the owner on a file. The |
| 507 | .I user |
| 508 | may either be a numeric uid or a username. The default is not to change |
| 509 | the owner of the file once it's created. The synonyms |
| 510 | .B uid |
| 511 | and |
| 512 | .B user |
| 513 | are accepted in place of |
| 514 | .BR owner . |
| 515 | .OE |
| 516 | .OS "File attributes (`fattr')" |
| 517 | .IB prefix .fattr.group |
| 518 | .RB [ = ] |
| 519 | .I group |
| 520 | .OD |
| 521 | Sets the group for newly created files. You will usually need to be a |
| 522 | member of the group in question order to set the group of a file. The |
| 523 | .I group |
| 524 | may either be a numeric gid or a group name. The default is not to |
| 525 | change the group of the file once it's created. The synonym |
| 526 | .B gid |
| 527 | is accepted in place of |
| 528 | .BR group . |
| 529 | .OE |
| 530 | . |
| 531 | .SS "The `file' source and target types" |
| 532 | The |
| 533 | .B file |
| 534 | source and target allow data to move to and from objects other |
| 535 | than sockets within the Unix filesystem. (Unix-domain sockets are |
| 536 | handled using the |
| 537 | .B socket |
| 538 | source and target.) |
| 539 | .PP |
| 540 | If a |
| 541 | .B file |
| 542 | is used as a source, it is set up immediately. |
| 543 | .PP |
| 544 | The syntax of |
| 545 | .B file |
| 546 | sources and targets is like this: |
| 547 | .GS "File source and target" |
| 548 | .I source |
| 549 | ::= |
| 550 | .I file |
| 551 | .br |
| 552 | .I target |
| 553 | ::= |
| 554 | .I file |
| 555 | .br |
| 556 | .I file |
| 557 | ::= |
| 558 | .B file |
| 559 | .RB [ .\& ] |
| 560 | .I fspec |
| 561 | .RB [ , |
| 562 | .IR fspec ] |
| 563 | .br |
| 564 | .I fspec |
| 565 | ::= |
| 566 | .I fd-spec |
| 567 | | |
| 568 | .I name-spec |
| 569 | | |
| 570 | .I null-spec |
| 571 | .br |
| 572 | .I fd-spec |
| 573 | ::= |
| 574 | .RB [[ : ] fd [ : ]] |
| 575 | .IR number \c |
| 576 | .RB | stdin | stdout |
| 577 | .br |
| 578 | .I name-spec |
| 579 | ::= |
| 580 | .RB [[ : ] name [ : ]] |
| 581 | .I file-name |
| 582 | .br |
| 583 | .I file-name |
| 584 | ::= |
| 585 | .I path-seq |
| 586 | | |
| 587 | .B [ |
| 588 | .I path-seq |
| 589 | .B ] |
| 590 | .br |
| 591 | .I path-seq |
| 592 | ::= |
| 593 | .I path-elt |
| 594 | | |
| 595 | .I path-seq |
| 596 | .I path-elt |
| 597 | .br |
| 598 | .I path-elt |
| 599 | ::= |
| 600 | .B / |
| 601 | | |
| 602 | .I word |
| 603 | .br |
| 604 | .I null-spec |
| 605 | ::= |
| 606 | .RB [ : ] null [ : ] |
| 607 | .GE |
| 608 | The |
| 609 | .I file |
| 610 | specification describes two files, the first to be used as input, the |
| 611 | second to be used as output, each described by an |
| 612 | .IR fspec . |
| 613 | .PP |
| 614 | If none of the keywords |
| 615 | .RB ` fd ', |
| 616 | .RB ` name ' |
| 617 | or |
| 618 | .RB ` null ' |
| 619 | are given, the type of an |
| 620 | .I fspec |
| 621 | is deduced from its nature: if it matches one of the strings |
| 622 | .RB ` stdin ' |
| 623 | or |
| 624 | .RB ` stdout ', |
| 625 | or begins with a digit, it's considered to be a file descriptor; |
| 626 | otherwise it's interpreted as a filename. |
| 627 | .PP |
| 628 | A |
| 629 | .RB ` name ' |
| 630 | spec describes a file by its name within the filesystem. It is opened |
| 631 | when needed and closed again after use. For output files, the precise |
| 632 | behaviour is controlled by options described below. |
| 633 | .PP |
| 634 | A |
| 635 | .RB ` null ' |
| 636 | spec attaches the input or output of the source or target to |
| 637 | .BR /dev/null . |
| 638 | .PP |
| 639 | An |
| 640 | .RB ` fd ' |
| 641 | spec uses an existing open file descriptor, given either by number or a |
| 642 | symbolic name. The name |
| 643 | .RB ` stdin ' |
| 644 | refers to standard input (file descriptor 0 on normal systems) and |
| 645 | .RB ` stdout ' |
| 646 | refers to standard output (file descriptor 1). The names work in |
| 647 | exactly the same way as the equivalent file descriptor numbers. |
| 648 | .PP |
| 649 | If the output |
| 650 | .I fspec |
| 651 | is omitted, the input |
| 652 | .I fspec |
| 653 | is used for both input and output. Exception: if the input refers to |
| 654 | standard input then the output will refer to standard output instead. |
| 655 | .PP |
| 656 | All |
| 657 | .B file |
| 658 | options apply equally to sources and targets. The options are as |
| 659 | follows: |
| 660 | .OS "File options" |
| 661 | .B file.create |
| 662 | .RB [ = ] |
| 663 | .BR yes | no |
| 664 | .OD |
| 665 | Whether to create the output file if it doesn't exist. If |
| 666 | .B no |
| 667 | (the default), an error is reported if the file doesn't exist. If |
| 668 | .BR yes , |
| 669 | the file is created if it doesn't exist. |
| 670 | .OE |
| 671 | .OS "File options" |
| 672 | .B file.open |
| 673 | .RB [ = ] |
| 674 | .BR no | truncate | append |
| 675 | .OD |
| 676 | Controls the behaviour if the output file already exists. If |
| 677 | .BR no , |
| 678 | an error is reported. If |
| 679 | .B truncate |
| 680 | (the default), the existing file is replaced by the new data. If |
| 681 | .BR append , |
| 682 | the new data is appended to the file. |
| 683 | .OE |
| 684 | .OS "File options" |
| 685 | .BR file.fattr. * |
| 686 | .OD |
| 687 | The |
| 688 | .B file |
| 689 | source and target also accept |
| 690 | .B fattr |
| 691 | options for controlling the attributes of the created file. |
| 692 | .OE |
| 693 | .PP |
| 694 | Under no circumstances will |
| 695 | .B fw |
| 696 | create a file through a `dangling' symbolic link. |
| 697 | . |
| 698 | .SS "The `exec' source and target types" |
| 699 | The |
| 700 | .B exec |
| 701 | source and target execute programs and allow access to their standard |
| 702 | input and output streams. Both source and target have the same syntax, |
| 703 | which is as follows: |
| 704 | .GS "Exec source and target" |
| 705 | .I source |
| 706 | ::= |
| 707 | .I exec |
| 708 | .br |
| 709 | .I target |
| 710 | ::= |
| 711 | .I exec |
| 712 | .br |
| 713 | .I exec |
| 714 | ::= |
| 715 | .BR exec |
| 716 | .RB [ .\& ] |
| 717 | .I cmd-spec |
| 718 | .br |
| 719 | .I cmd-spec |
| 720 | ::= |
| 721 | .I shell-cmd |
| 722 | | |
| 723 | .RI [ prog-name ] |
| 724 | .B [ |
| 725 | .I argv0 |
| 726 | .I arg-seq |
| 727 | .B ] |
| 728 | .br |
| 729 | .I arg-seq |
| 730 | ::= |
| 731 | .I word |
| 732 | | |
| 733 | .I arg-seq |
| 734 | .I word |
| 735 | .br |
| 736 | .I shell-cmd |
| 737 | ::= |
| 738 | .I word |
| 739 | .br |
| 740 | .I argv0 |
| 741 | ::= |
| 742 | .I word |
| 743 | .GE |
| 744 | If a single word is given, it is a |
| 745 | .I shell-cmd |
| 746 | and will be passed to the Bourne shell for execution. If a |
| 747 | bracket-enclosed sequence of words is given, it is considered to be a |
| 748 | list of arguments to pass to the program: if a |
| 749 | .I prog-name |
| 750 | is also supplied, it names the file containing the program to execute; |
| 751 | otherwise the file named by the first argument |
| 752 | .RI ( argv0 ) |
| 753 | is used. |
| 754 | .PP |
| 755 | Note that the shell command or program name string must, if present, |
| 756 | have any delimiter characters (including |
| 757 | .RB ` / ' |
| 758 | and |
| 759 | .RB ` . ') |
| 760 | quoted; this is not required in the |
| 761 | .RB ` [ '-enclosed |
| 762 | argument list. |
| 763 | .PP |
| 764 | The standard input and output of the program are forwarded to the other |
| 765 | end of the connection. The standard error stream is caught by |
| 766 | .B fw |
| 767 | and logged. |
| 768 | .PP |
| 769 | The |
| 770 | .B exec |
| 771 | source and target both understand the same set of options. The list of |
| 772 | options supported is as follows: |
| 773 | .OS "Exec options" |
| 774 | .B exec.logging |
| 775 | .RB [ = ] |
| 776 | .BR yes | no |
| 777 | .OD |
| 778 | Whether to log the start and end of executed programs. If |
| 779 | .B yes |
| 780 | (the default), a log message is emitted when the program is started |
| 781 | listing its process id, and another is emitted when the program finishes |
| 782 | giving its process id and exit status. If |
| 783 | .BR no , |
| 784 | these messages are not emitted. However the standard error stream is |
| 785 | still logged. The |
| 786 | .B log |
| 787 | abbreviation is accepted as a synonym for |
| 788 | .BR logging . |
| 789 | .OE |
| 790 | .OS "Exec options" |
| 791 | .B exec.dir |
| 792 | .RB [ = ] |
| 793 | .I file-name |
| 794 | .OD |
| 795 | Sets the current directory from which the the program should be run. |
| 796 | The default is not to change directory. The synonyms |
| 797 | .BR cd , |
| 798 | .B chdir |
| 799 | and |
| 800 | .B cwd |
| 801 | are accepted in place of |
| 802 | .BR dir . |
| 803 | .OE |
| 804 | .OS "Exec options" |
| 805 | .B exec.root |
| 806 | .RB [ = ] |
| 807 | .I file-name |
| 808 | .OD |
| 809 | Sets the root directory for the program, using the |
| 810 | .BR chroot (2) |
| 811 | system call. You must be the superuser for this option to work. The |
| 812 | default is not to set a root directory. The synonym |
| 813 | .B chroot |
| 814 | is accepted in place of |
| 815 | .BR root . |
| 816 | .OE |
| 817 | .OS "Exec options" |
| 818 | .B exec.user |
| 819 | .RB [ = ] |
| 820 | .I user |
| 821 | .OD |
| 822 | Sets the user (real and effective uid) to run the program as. This will |
| 823 | usually require superuser privileges to work. The default is not to |
| 824 | change uid. The synonym |
| 825 | .B uid |
| 826 | is accepted in place of |
| 827 | .BR user . |
| 828 | .OE |
| 829 | .OS "Exec options" |
| 830 | .B exec.group |
| 831 | .RB [ = ] |
| 832 | .I group |
| 833 | .OD |
| 834 | Sets the group (real and effective gid) to run the program as. If |
| 835 | running with superuser privileges, the supplementary groups list is |
| 836 | cleared at the same time. The default is not to change gid (or clear |
| 837 | the supplementary groups list). The synonym |
| 838 | .B gid |
| 839 | is accepted in place of |
| 840 | .BR group . |
| 841 | .OE |
| 842 | .OS "Exec options" |
| 843 | .BI exec.rlimit. limit \c |
| 844 | .RB [ .hard | .soft ] |
| 845 | .RB [ = ] |
| 846 | .I value |
| 847 | .OD |
| 848 | Set resource limits for the program. The |
| 849 | .I limit |
| 850 | may be one of the resource limit names described in |
| 851 | .BR setrlimit (2), |
| 852 | in lower-case and without the |
| 853 | .B RLIMIT_ |
| 854 | prefix; for example, |
| 855 | .B RLIMIT_CORE |
| 856 | becomes simply |
| 857 | .BR core . |
| 858 | The |
| 859 | .I value |
| 860 | is a number, followed optionally by |
| 861 | .B k |
| 862 | to multiply by 1024 (2\*(ss10\*(se), |
| 863 | .B m |
| 864 | to multiply by 1048576 (2\*(ss20\*(se), or |
| 865 | .B g |
| 866 | to multiply by 1073741824 (2\*(ss30\*(se); purists can use upper-case |
| 867 | versions of these if they want. If |
| 868 | .B .hard |
| 869 | or |
| 870 | .B .soft |
| 871 | was specified, only the hard or soft limit is set; otherwise both are |
| 872 | set to the same value. Only the superuser can raise the hard limit. |
| 873 | The soft limit cannot be set above the hard limit. |
| 874 | .OE |
| 875 | .OS "Exec options" |
| 876 | .B exec.env.clear |
| 877 | .OD |
| 878 | Clears the program's environment. |
| 879 | .OE |
| 880 | .OS "Exec options" |
| 881 | .B exec.env.unset |
| 882 | .I var |
| 883 | .OD |
| 884 | Removes |
| 885 | .I var |
| 886 | from the program's environment. It is not an error if no variable named |
| 887 | .I var |
| 888 | exists. |
| 889 | .OE |
| 890 | .OS "Exec options" |
| 891 | .BR exec.env. [ set ] |
| 892 | .I var |
| 893 | .RB [ = ] |
| 894 | .I value |
| 895 | .OD |
| 896 | Assigns the variable |
| 897 | .I var |
| 898 | the value |
| 899 | .I value |
| 900 | in the program's environment, possibly replacing the existing value. |
| 901 | The |
| 902 | .B set |
| 903 | may be omitted if the |
| 904 | .B env |
| 905 | qualifier is present. |
| 906 | .OE |
| 907 | .PP |
| 908 | Note that environment variable modifications are performed in order, |
| 909 | global modifications before local ones. |
| 910 | . |
| 911 | .SS "The `socket' source and target types" |
| 912 | The |
| 913 | .B socket |
| 914 | source and target provide access to network services. Support is |
| 915 | currently provided for TCP/IP and Unix-domain sockets, although other |
| 916 | address types can be added with reasonable ease. |
| 917 | .PP |
| 918 | The syntax for socket sources and targets is: |
| 919 | .GS "Socket source and target" |
| 920 | .ll +8i |
| 921 | .I source |
| 922 | ::= |
| 923 | .I socket-source |
| 924 | .br |
| 925 | .I target |
| 926 | ::= |
| 927 | .I socket-target |
| 928 | .br |
| 929 | .I socket-source |
| 930 | ::= |
| 931 | .RB [ socket [ .\& ]] |
| 932 | .RB [[ : ] \c |
| 933 | .IR addr-type \c |
| 934 | .RB [ : ]] |
| 935 | .I source-addr |
| 936 | .br |
| 937 | .I socket-target |
| 938 | ::= |
| 939 | .RB [ socket [ .\& ]] |
| 940 | .RB [[ : ] \c |
| 941 | .IR addr-type \c |
| 942 | .RB [ : ]] |
| 943 | .I target-addr |
| 944 | .ll -8i |
| 945 | .GE |
| 946 | The syntax of the source and target addresses depend on the address |
| 947 | types, which are described below. The default address type, if no |
| 948 | .I addr-type |
| 949 | is given, is |
| 950 | .BR inet . |
| 951 | .PP |
| 952 | Socket sources support options; socket targets do not. The source |
| 953 | options provided are: |
| 954 | .OS "Socket options" |
| 955 | .B socket.conn |
| 956 | .RB [ = ] |
| 957 | .IR number | \c |
| 958 | .BR unlimited | one-shot |
| 959 | .OD |
| 960 | Controls the behaviour of the source when it receives connections. A |
| 961 | .I number |
| 962 | limits the number of simultaneous connections. The value |
| 963 | .B unlimited |
| 964 | (or |
| 965 | .BR infinite ) |
| 966 | removes any limit on the number of connections possible. The value |
| 967 | .B one-shot |
| 968 | will remove the socket source after a single successful connection. |
| 969 | (Connections refused by access control systems don't count here.) |
| 970 | The default is to apply a limit of 256 concurrent connections. Use of |
| 971 | the |
| 972 | .B unlimited |
| 973 | option is not recommended. |
| 974 | .OE |
| 975 | .OS "Socket options" |
| 976 | .B socket.listen |
| 977 | .RB [ = ] |
| 978 | .I number |
| 979 | .OD |
| 980 | Sets the maximum of the kernel incoming connection queue for this socket |
| 981 | source. This is the number given to the |
| 982 | .BR listen (2) |
| 983 | system call. The default is 5. |
| 984 | .OE |
| 985 | .OS "Socket options" |
| 986 | .B socket.logging |
| 987 | .RB [ = ] |
| 988 | .BR yes | no |
| 989 | .OD |
| 990 | Whether to log incoming connections. If |
| 991 | .B yes |
| 992 | (the default) incoming connections are logged, together with information |
| 993 | about the client (where available) and whether the connection was |
| 994 | accepted or refused. If |
| 995 | .BR no , |
| 996 | log messages are not generated. |
| 997 | .OE |
| 998 | .PP |
| 999 | Address types also provide their own options. |
| 1000 | . |
| 1001 | .SS "The `inet' socket address type" |
| 1002 | .GL "Socket source and target" |
| 1003 | .OL "Socket options" |
| 1004 | The |
| 1005 | .B inet |
| 1006 | address type provides access to TCP ports. The |
| 1007 | .B inet |
| 1008 | source and target addresses have the following syntax: |
| 1009 | .GS "Socket source and target" |
| 1010 | .I inet-source-addr |
| 1011 | ::= |
| 1012 | .RB [ port ] |
| 1013 | .I port |
| 1014 | .br |
| 1015 | .I inet-target-addr |
| 1016 | ::= |
| 1017 | .I address |
| 1018 | .RB [ : ] |
| 1019 | .I port |
| 1020 | .br |
| 1021 | .I address |
| 1022 | ::= |
| 1023 | .I addr-elt |
| 1024 | | |
| 1025 | .I address |
| 1026 | .I addr-elt |
| 1027 | .br |
| 1028 | .I addr-elt |
| 1029 | ::= |
| 1030 | .B .\& |
| 1031 | | |
| 1032 | .I word |
| 1033 | .GE |
| 1034 | A |
| 1035 | .I port |
| 1036 | may be given as a port number or a service name from the |
| 1037 | .B /etc/services |
| 1038 | file (or YP map if you do that sort of thing). A |
| 1039 | .B hostname |
| 1040 | may be a textual hostname or a numerical IP address. |
| 1041 | .PP |
| 1042 | The |
| 1043 | .B inet |
| 1044 | source address accepts the following options: |
| 1045 | .OS "Socket options" |
| 1046 | .B socket.inet.source.addr |
| 1047 | .RB [ = ] |
| 1048 | .BR any | \c |
| 1049 | .I addr |
| 1050 | .OD |
| 1051 | Specify the IP address on which to listen for incoming connections. The |
| 1052 | default is |
| 1053 | .BR any , |
| 1054 | which means to listen on all addresses, though it may be useful to |
| 1055 | specify this explicitly, if the global setting is different. |
| 1056 | .OE |
| 1057 | .OS "Socket options" |
| 1058 | .BR socket.inet.source. [ allow | deny ] |
| 1059 | .RB [ host ] |
| 1060 | .I addr |
| 1061 | .RB [ / |
| 1062 | .IR addr ] |
| 1063 | .OD |
| 1064 | Adds an entry to the source's access control list. If only one |
| 1065 | .I address |
| 1066 | is given, the entry applies only to that address; if two are given, the |
| 1067 | first is a network address and the second is a netmask either in |
| 1068 | dotted-quad format or a simple number of bits (e.g., |
| 1069 | .B /255.255.255.192 |
| 1070 | and |
| 1071 | .B /26 |
| 1072 | mean the same), and the entry applies to any address which, when masked |
| 1073 | by the netmask, is equal to the masked network address. |
| 1074 | .OE |
| 1075 | .OS "Socket options" |
| 1076 | .BR socket.inet.source. [ allow | deny ] |
| 1077 | .B priv-port |
| 1078 | .OD |
| 1079 | Accept or reject connections from low-numbered `privileged' ports, in |
| 1080 | the range 0--1023. |
| 1081 | .OE |
| 1082 | .OS "Socket options" |
| 1083 | .B socket.inet.dest.addr |
| 1084 | .RB [ = ] |
| 1085 | .BR any | \c |
| 1086 | .I addr |
| 1087 | .OD |
| 1088 | Specify the IP address to bind the local socket to when making an |
| 1089 | outbound connection. The default is |
| 1090 | .BR any , |
| 1091 | which means to use whichever address the kernel thinks is most |
| 1092 | convenient. This option is useful if the destination is doing |
| 1093 | host-based access control and your server is multi-homed. |
| 1094 | .OE |
| 1095 | .OS "Socket options" |
| 1096 | .B socket.inet.dest.priv-port |
| 1097 | .RB [=] |
| 1098 | .BR yes | no |
| 1099 | .OD |
| 1100 | Make a privileged connection (i.e., from a low-numbered port) to the |
| 1101 | target. This only works if |
| 1102 | .B fw |
| 1103 | was started with root privileges. However, it still works if |
| 1104 | .B fw |
| 1105 | has |
| 1106 | .I dropped |
| 1107 | privileges after initialization (the |
| 1108 | .B \-s |
| 1109 | option). Before dropping privileges, |
| 1110 | .B fw |
| 1111 | forks off a separate process which continues to run with root |
| 1112 | privileges, and on demand passes sockets bound to privileged ports and |
| 1113 | connected to the appropriate peer back to the main program. The |
| 1114 | privileged child only passes back sockets connected to peer addresses |
| 1115 | named in the configuration; even if the |
| 1116 | .B fw |
| 1117 | process is compromised, it can't make privileged connections to other |
| 1118 | addresses. Note that because of this privilege separation, it's also |
| 1119 | not possible to reconfigure |
| 1120 | .B fw |
| 1121 | to make privileged connections to different peer addresses later by |
| 1122 | changing configuration files and sending the daemon a |
| 1123 | .BR SIGHUP . |
| 1124 | .OE |
| 1125 | .PP |
| 1126 | The access control rules are examined in the order: local entries first, |
| 1127 | then global ones, each in the order given in the configuration file. |
| 1128 | The first matching entry is used. If no entries match, the behaviour is |
| 1129 | the |
| 1130 | .I opposite |
| 1131 | of the last entry tried. If there are no entries defined, the default |
| 1132 | is to allow all clients. |
| 1133 | . |
| 1134 | .SS "The `unix' socket address type" |
| 1135 | .GL "Socket source and target" |
| 1136 | .OL "Socket options" |
| 1137 | The |
| 1138 | .B unix |
| 1139 | address type allows access to Unix-domain sockets. The syntax for |
| 1140 | .B unix |
| 1141 | source and target addresses is like this: |
| 1142 | .GS "Socket source and target" |
| 1143 | .I unix-source-addr |
| 1144 | ::= |
| 1145 | .I file-name |
| 1146 | .br |
| 1147 | .I unix-target-addr |
| 1148 | ::= |
| 1149 | .I file-name |
| 1150 | .GE |
| 1151 | The following options are supported by the |
| 1152 | .B unix |
| 1153 | source address type: |
| 1154 | .OS "Socket options" |
| 1155 | .BR socket.unix.fattr. * |
| 1156 | .OD |
| 1157 | The |
| 1158 | .B unix |
| 1159 | source address accepts |
| 1160 | .B fattr |
| 1161 | options to control the attributes of the socket file created. |
| 1162 | .OE |
| 1163 | .PP |
| 1164 | Sockets are removed if |
| 1165 | .B fw |
| 1166 | exits normally (which it will do if it runs out of sources or |
| 1167 | connections, or if |
| 1168 | .B fw |
| 1169 | shuts down in a clean way). |
| 1170 | .SH "EXAMPLES" |
| 1171 | To forward the local port 25 to a main mail server: |
| 1172 | .VS |
| 1173 | from 25 to mailserv:25 |
| 1174 | .VE |
| 1175 | To attach a fortune server to a Unix-domain socket: |
| 1176 | .VS |
| 1177 | from unix:/tmp/fortunes |
| 1178 | to exec [/usr/games/fortune] { user nobody } |
| 1179 | .VE |
| 1180 | To fetch a fortune from the server: |
| 1181 | .VS |
| 1182 | from file stdin, stdout to unix:/tmp/fortunes |
| 1183 | .VE |
| 1184 | To emulate |
| 1185 | .BR cat (1): |
| 1186 | .VS |
| 1187 | from file stdin, null to file null, stdout |
| 1188 | .VE |
| 1189 | .sp -1 \" undo final space |
| 1190 | . |
| 1191 | .\"-------------------------------------------------------------------------- |
| 1192 | .SH "SIGNAL HANDLING" |
| 1193 | . |
| 1194 | The |
| 1195 | .B fw |
| 1196 | program responds to various signals when it's running. If it receives |
| 1197 | .B SIGTERM |
| 1198 | or |
| 1199 | .BR SIGINT , |
| 1200 | .B fw |
| 1201 | performs a |
| 1202 | .I graceful |
| 1203 | shutdown: it removes all of its sources, and will exit when no more |
| 1204 | connections are running. (Note that if the disposition |
| 1205 | .B SIGINT |
| 1206 | was to ignore it, |
| 1207 | .B fw |
| 1208 | does not re-enable the signal. You'll have to send |
| 1209 | .B SIGTERM |
| 1210 | in that case.) If |
| 1211 | .B fw |
| 1212 | receives |
| 1213 | .BR SIGQUIT , |
| 1214 | it performs an |
| 1215 | .I abrupt |
| 1216 | shutdown: it removes all sources and extant connections and closes down |
| 1217 | more-or-less immediately. |
| 1218 | .PP |
| 1219 | Finally, if any configuration files (other than standard input) were |
| 1220 | provided to |
| 1221 | .B fw |
| 1222 | on its command line using the |
| 1223 | .B \-f |
| 1224 | option, a |
| 1225 | .B SIGHUP |
| 1226 | signal may be sent to instruct |
| 1227 | .B fw |
| 1228 | to reload its configuration. Any existing connections are allowed to |
| 1229 | run their course. If no such configuration files are available, |
| 1230 | .B fw |
| 1231 | just logs a message about the signal and continues. |
| 1232 | . |
| 1233 | .\"-------------------------------------------------------------------------- |
| 1234 | .SH "GRAMMAR SUMMARY" |
| 1235 | . |
| 1236 | @@@ grammar |
| 1237 | .\"-------------------------------------------------------------------------- |
| 1238 | .SH "OPTION SUMMARY" |
| 1239 | . |
| 1240 | @@@ option |
| 1241 | .\"-------------------------------------------------------------------------- |
| 1242 | .SH "BUGS" |
| 1243 | . |
| 1244 | The syntax for IP addresses and filenames is nasty. |
| 1245 | .PP |
| 1246 | IPv6 is not supported yet. Because of |
| 1247 | .BR fw 's |
| 1248 | socket address architecture, it's probably not a major piece of work to |
| 1249 | add. |
| 1250 | .PP |
| 1251 | Please inform me of any security problems you think you've identified in |
| 1252 | this program. I take security very seriously, and I will fix security |
| 1253 | holes as a matter of priority when I find out about them. I will be |
| 1254 | annoyed if I have to read about problems on Bugtraq because they weren't |
| 1255 | mailed to me first. |
| 1256 | .PP |
| 1257 | The program is too complicated, and this manual page is too long. |
| 1258 | . |
| 1259 | .\"-------------------------------------------------------------------------- |
| 1260 | .SH "AUTHOR" |
| 1261 | . |
| 1262 | Mark Wooding, <mdw@distorted.org.uk> |
| 1263 | . |
| 1264 | .\"----- That's all, folks -------------------------------------------------- |