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1 | .\" -*- nroff -*- | |
2 | .\" | |
3 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> | |
4 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
5 | .\" All rights reserved | |
6 | .\" | |
7 | .\" As far as I am concerned, the code I have written for this software | |
8 | .\" can be used freely for any purpose. Any derived versions of this | |
9 | .\" software must be clearly marked as such, and if the derived work is | |
10 | .\" incompatible with the protocol description in the RFC file, it must be | |
11 | .\" called by a name other than "ssh" or "Secure Shell". | |
12 | .\" | |
13 | .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. | |
14 | .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. | |
15 | .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. | |
16 | .\" | |
17 | .\" Redistribution and use in source and binary forms, with or without | |
18 | .\" modification, are permitted provided that the following conditions | |
19 | .\" are met: | |
20 | .\" 1. Redistributions of source code must retain the above copyright | |
21 | .\" notice, this list of conditions and the following disclaimer. | |
22 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
23 | .\" notice, this list of conditions and the following disclaimer in the | |
24 | .\" documentation and/or other materials provided with the distribution. | |
25 | .\" | |
26 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
27 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
28 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
29 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
30 | .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
31 | .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
32 | .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
33 | .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
34 | .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
35 | .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
36 | .\" | |
37 | .\" $OpenBSD: ssh.1,v 1.227 2005/12/21 12:53:31 jmc Exp $ | |
38 | .Dd September 25, 1999 | |
39 | .Dt SSH 1 | |
40 | .Os | |
41 | .Sh NAME | |
42 | .Nm ssh | |
43 | .Nd OpenSSH SSH client (remote login program) | |
44 | .Sh SYNOPSIS | |
45 | .Nm ssh | |
46 | .Op Fl 1246AaCfgkMNnqsTtVvXxY | |
47 | .Op Fl b Ar bind_address | |
48 | .Op Fl c Ar cipher_spec | |
49 | .Oo Fl D\ \& | |
50 | .Sm off | |
51 | .Oo Ar bind_address : Oc | |
52 | .Ar port | |
53 | .Sm on | |
54 | .Oc | |
55 | .Op Fl e Ar escape_char | |
56 | .Op Fl F Ar configfile | |
57 | .Bk -words | |
58 | .Op Fl i Ar identity_file | |
59 | .Ek | |
60 | .Oo Fl L\ \& | |
61 | .Sm off | |
62 | .Oo Ar bind_address : Oc | |
63 | .Ar port : host : hostport | |
64 | .Sm on | |
65 | .Oc | |
66 | .Bk -words | |
67 | .Op Fl l Ar login_name | |
68 | .Ek | |
69 | .Op Fl m Ar mac_spec | |
70 | .Op Fl O Ar ctl_cmd | |
71 | .Op Fl o Ar option | |
72 | .Op Fl p Ar port | |
73 | .Oo Fl R\ \& | |
74 | .Sm off | |
75 | .Oo Ar bind_address : Oc | |
76 | .Ar port : host : hostport | |
77 | .Sm on | |
78 | .Oc | |
79 | .Op Fl S Ar ctl_path | |
80 | .Bk -words | |
81 | .Op Fl w Ar tunnel : Ns Ar tunnel | |
82 | .Oo Ar user Ns @ Oc Ns Ar hostname | |
83 | .Op Ar command | |
84 | .Ek | |
85 | .Sh DESCRIPTION | |
86 | .Nm | |
87 | (SSH client) is a program for logging into a remote machine and for | |
88 | executing commands on a remote machine. | |
89 | It is intended to replace rlogin and rsh, | |
90 | and provide secure encrypted communications between | |
91 | two untrusted hosts over an insecure network. | |
92 | X11 connections and arbitrary TCP/IP ports | |
93 | can also be forwarded over the secure channel. | |
94 | .Pp | |
95 | .Nm | |
96 | connects and logs into the specified | |
97 | .Ar hostname | |
98 | (with optional | |
99 | .Ar user | |
100 | name). | |
101 | The user must prove | |
102 | his/her identity to the remote machine using one of several methods | |
103 | depending on the protocol version used (see below). | |
104 | .Pp | |
105 | If | |
106 | .Ar command | |
107 | is specified, | |
108 | it is executed on the remote host instead of a login shell. | |
109 | .Pp | |
110 | The options are as follows: | |
111 | .Bl -tag -width Ds | |
112 | .It Fl 1 | |
113 | Forces | |
114 | .Nm | |
115 | to try protocol version 1 only. | |
116 | .It Fl 2 | |
117 | Forces | |
118 | .Nm | |
119 | to try protocol version 2 only. | |
120 | .It Fl 4 | |
121 | Forces | |
122 | .Nm | |
123 | to use IPv4 addresses only. | |
124 | .It Fl 6 | |
125 | Forces | |
126 | .Nm | |
127 | to use IPv6 addresses only. | |
128 | .It Fl A | |
129 | Enables forwarding of the authentication agent connection. | |
130 | This can also be specified on a per-host basis in a configuration file. | |
131 | .Pp | |
132 | Agent forwarding should be enabled with caution. | |
133 | Users with the ability to bypass file permissions on the remote host | |
134 | (for the agent's Unix-domain socket) | |
135 | can access the local agent through the forwarded connection. | |
136 | An attacker cannot obtain key material from the agent, | |
137 | however they can perform operations on the keys that enable them to | |
138 | authenticate using the identities loaded into the agent. | |
139 | .It Fl a | |
140 | Disables forwarding of the authentication agent connection. | |
141 | .It Fl b Ar bind_address | |
142 | Use | |
143 | .Ar bind_address | |
144 | on the local machine as the source address | |
145 | of the connection. | |
146 | Only useful on systems with more than one address. | |
147 | .It Fl C | |
148 | Requests compression of all data (including stdin, stdout, stderr, and | |
149 | data for forwarded X11 and TCP/IP connections). | |
150 | The compression algorithm is the same used by | |
151 | .Xr gzip 1 , | |
152 | and the | |
153 | .Dq level | |
154 | can be controlled by the | |
155 | .Cm CompressionLevel | |
156 | option for protocol version 1. | |
157 | Compression is desirable on modem lines and other | |
158 | slow connections, but will only slow down things on fast networks. | |
159 | The default value can be set on a host-by-host basis in the | |
160 | configuration files; see the | |
161 | .Cm Compression | |
162 | option. | |
163 | .It Fl c Ar cipher_spec | |
164 | Selects the cipher specification for encrypting the session. | |
165 | .Pp | |
166 | Protocol version 1 allows specification of a single cipher. | |
167 | The supported values are | |
168 | .Dq 3des , | |
169 | .Dq blowfish , | |
170 | and | |
171 | .Dq des . | |
172 | .Ar 3des | |
173 | (triple-des) is an encrypt-decrypt-encrypt triple with three different keys. | |
174 | It is believed to be secure. | |
175 | .Ar blowfish | |
176 | is a fast block cipher; it appears very secure and is much faster than | |
177 | .Ar 3des . | |
178 | .Ar des | |
179 | is only supported in the | |
180 | .Nm | |
181 | client for interoperability with legacy protocol 1 implementations | |
182 | that do not support the | |
183 | .Ar 3des | |
184 | cipher. | |
185 | Its use is strongly discouraged due to cryptographic weaknesses. | |
186 | The default is | |
187 | .Dq 3des . | |
188 | .Pp | |
189 | For protocol version 2 | |
190 | .Ar cipher_spec | |
191 | is a comma-separated list of ciphers | |
192 | listed in order of preference. | |
193 | The supported ciphers are | |
194 | .Dq 3des-cbc , | |
195 | .Dq aes128-cbc , | |
196 | .Dq aes192-cbc , | |
197 | .Dq aes256-cbc , | |
198 | .Dq aes128-ctr , | |
199 | .Dq aes192-ctr , | |
200 | .Dq aes256-ctr , | |
201 | .Dq arcfour128 , | |
202 | .Dq arcfour256 , | |
203 | .Dq arcfour , | |
204 | .Dq blowfish-cbc , | |
205 | and | |
206 | .Dq cast128-cbc . | |
207 | The default is: | |
208 | .Bd -literal -offset indent | |
209 | aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128, | |
210 | arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr, | |
211 | aes192-ctr,aes256-ctr | |
212 | .Ed | |
213 | .It Fl D Xo | |
214 | .Sm off | |
215 | .Oo Ar bind_address : Oc | |
216 | .Ar port | |
217 | .Sm on | |
218 | .Xc | |
219 | Specifies a local | |
220 | .Dq dynamic | |
221 | application-level port forwarding. | |
222 | This works by allocating a socket to listen to | |
223 | .Ar port | |
224 | on the local side, optionally bound to the specified | |
225 | .Ar bind_address . | |
226 | Whenever a connection is made to this port, the | |
227 | connection is forwarded over the secure channel, and the application | |
228 | protocol is then used to determine where to connect to from the | |
229 | remote machine. | |
230 | Currently the SOCKS4 and SOCKS5 protocols are supported, and | |
231 | .Nm | |
232 | will act as a SOCKS server. | |
233 | Only root can forward privileged ports. | |
234 | Dynamic port forwardings can also be specified in the configuration file. | |
235 | .Pp | |
236 | IPv6 addresses can be specified with an alternative syntax: | |
237 | .Sm off | |
238 | .Xo | |
239 | .Op Ar bind_address No / | |
240 | .Ar port | |
241 | .Xc | |
242 | .Sm on | |
243 | or by enclosing the address in square brackets. | |
244 | Only the superuser can forward privileged ports. | |
245 | By default, the local port is bound in accordance with the | |
246 | .Cm GatewayPorts | |
247 | setting. | |
248 | However, an explicit | |
249 | .Ar bind_address | |
250 | may be used to bind the connection to a specific address. | |
251 | The | |
252 | .Ar bind_address | |
253 | of | |
254 | .Dq localhost | |
255 | indicates that the listening port be bound for local use only, while an | |
256 | empty address or | |
257 | .Sq * | |
258 | indicates that the port should be available from all interfaces. | |
259 | .It Fl e Ar ch | ^ch | none | |
260 | Sets the escape character for sessions with a pty (default: | |
261 | .Ql ~ ) . | |
262 | The escape character is only recognized at the beginning of a line. | |
263 | The escape character followed by a dot | |
264 | .Pq Ql \&. | |
265 | closes the connection; | |
266 | followed by control-Z suspends the connection; | |
267 | and followed by itself sends the escape character once. | |
268 | Setting the character to | |
269 | .Dq none | |
270 | disables any escapes and makes the session fully transparent. | |
271 | .It Fl F Ar configfile | |
272 | Specifies an alternative per-user configuration file. | |
273 | If a configuration file is given on the command line, | |
274 | the system-wide configuration file | |
275 | .Pq Pa /etc/ssh/ssh_config | |
276 | will be ignored. | |
277 | The default for the per-user configuration file is | |
278 | .Pa ~/.ssh/config . | |
279 | .It Fl f | |
280 | Requests | |
281 | .Nm | |
282 | to go to background just before command execution. | |
283 | This is useful if | |
284 | .Nm | |
285 | is going to ask for passwords or passphrases, but the user | |
286 | wants it in the background. | |
287 | This implies | |
288 | .Fl n . | |
289 | The recommended way to start X11 programs at a remote site is with | |
290 | something like | |
291 | .Ic ssh -f host xterm . | |
292 | .It Fl g | |
293 | Allows remote hosts to connect to local forwarded ports. | |
294 | .It Fl I Ar smartcard_device | |
295 | Specifies which smartcard device to use. | |
296 | The argument is the device | |
297 | .Nm | |
298 | should use to communicate with a smartcard used for storing the user's | |
299 | private RSA key. | |
300 | .It Fl i Ar identity_file | |
301 | Selects a file from which the identity (private key) for | |
302 | RSA or DSA authentication is read. | |
303 | The default is | |
304 | .Pa ~/.ssh/identity | |
305 | for protocol version 1, and | |
306 | .Pa ~/.ssh/id_rsa | |
307 | and | |
308 | .Pa ~/.ssh/id_dsa | |
309 | for protocol version 2. | |
310 | Identity files may also be specified on | |
311 | a per-host basis in the configuration file. | |
312 | It is possible to have multiple | |
313 | .Fl i | |
314 | options (and multiple identities specified in | |
315 | configuration files). | |
316 | .It Fl k | |
317 | Disables forwarding (delegation) of GSSAPI credentials to the server. | |
318 | .It Fl L Xo | |
319 | .Sm off | |
320 | .Oo Ar bind_address : Oc | |
321 | .Ar port : host : hostport | |
322 | .Sm on | |
323 | .Xc | |
324 | Specifies that the given port on the local (client) host is to be | |
325 | forwarded to the given host and port on the remote side. | |
326 | This works by allocating a socket to listen to | |
327 | .Ar port | |
328 | on the local side, optionally bound to the specified | |
329 | .Ar bind_address . | |
330 | Whenever a connection is made to this port, the | |
331 | connection is forwarded over the secure channel, and a connection is | |
332 | made to | |
333 | .Ar host | |
334 | port | |
335 | .Ar hostport | |
336 | from the remote machine. | |
337 | Port forwardings can also be specified in the configuration file. | |
338 | IPv6 addresses can be specified with an alternative syntax: | |
339 | .Sm off | |
340 | .Xo | |
341 | .Op Ar bind_address No / | |
342 | .Ar port No / Ar host No / | |
343 | .Ar hostport | |
344 | .Xc | |
345 | .Sm on | |
346 | or by enclosing the address in square brackets. | |
347 | Only the superuser can forward privileged ports. | |
348 | By default, the local port is bound in accordance with the | |
349 | .Cm GatewayPorts | |
350 | setting. | |
351 | However, an explicit | |
352 | .Ar bind_address | |
353 | may be used to bind the connection to a specific address. | |
354 | The | |
355 | .Ar bind_address | |
356 | of | |
357 | .Dq localhost | |
358 | indicates that the listening port be bound for local use only, while an | |
359 | empty address or | |
360 | .Sq * | |
361 | indicates that the port should be available from all interfaces. | |
362 | .It Fl l Ar login_name | |
363 | Specifies the user to log in as on the remote machine. | |
364 | This also may be specified on a per-host basis in the configuration file. | |
365 | .It Fl M | |
366 | Places the | |
367 | .Nm | |
368 | client into | |
369 | .Dq master | |
370 | mode for connection sharing. | |
371 | Refer to the description of | |
372 | .Cm ControlMaster | |
373 | in | |
374 | .Xr ssh_config 5 | |
375 | for details. | |
376 | .It Fl m Ar mac_spec | |
377 | Additionally, for protocol version 2 a comma-separated list of MAC | |
378 | (message authentication code) algorithms can | |
379 | be specified in order of preference. | |
380 | See the | |
381 | .Cm MACs | |
382 | keyword for more information. | |
383 | .It Fl N | |
384 | Do not execute a remote command. | |
385 | This is useful for just forwarding ports | |
386 | (protocol version 2 only). | |
387 | .It Fl n | |
388 | Redirects stdin from | |
389 | .Pa /dev/null | |
390 | (actually, prevents reading from stdin). | |
391 | This must be used when | |
392 | .Nm | |
393 | is run in the background. | |
394 | A common trick is to use this to run X11 programs on a remote machine. | |
395 | For example, | |
396 | .Ic ssh -n shadows.cs.hut.fi emacs & | |
397 | will start an emacs on shadows.cs.hut.fi, and the X11 | |
398 | connection will be automatically forwarded over an encrypted channel. | |
399 | The | |
400 | .Nm | |
401 | program will be put in the background. | |
402 | (This does not work if | |
403 | .Nm | |
404 | needs to ask for a password or passphrase; see also the | |
405 | .Fl f | |
406 | option.) | |
407 | .It Fl O Ar ctl_cmd | |
408 | Control an active connection multiplexing master process. | |
409 | When the | |
410 | .Fl O | |
411 | option is specified, the | |
412 | .Ar ctl_cmd | |
413 | argument is interpreted and passed to the master process. | |
414 | Valid commands are: | |
415 | .Dq check | |
416 | (check that the master process is running) and | |
417 | .Dq exit | |
418 | (request the master to exit). | |
419 | .It Fl o Ar option | |
420 | Can be used to give options in the format used in the configuration file. | |
421 | This is useful for specifying options for which there is no separate | |
422 | command-line flag. | |
423 | For full details of the options listed below, and their possible values, see | |
424 | .Xr ssh_config 5 . | |
425 | .Pp | |
426 | .Bl -tag -width Ds -offset indent -compact | |
427 | .It AddressFamily | |
428 | .It BatchMode | |
429 | .It BindAddress | |
430 | .It ChallengeResponseAuthentication | |
431 | .It CheckHostIP | |
432 | .It Cipher | |
433 | .It Ciphers | |
434 | .It ClearAllForwardings | |
435 | .It Compression | |
436 | .It CompressionLevel | |
437 | .It ConnectionAttempts | |
438 | .It ConnectTimeout | |
439 | .It ControlMaster | |
440 | .It ControlPath | |
441 | .It DynamicForward | |
442 | .It EscapeChar | |
443 | .It ForwardAgent | |
444 | .It ForwardX11 | |
445 | .It ForwardX11Trusted | |
446 | .It GatewayPorts | |
447 | .It GlobalKnownHostsFile | |
448 | .It GSSAPIAuthentication | |
449 | .It GSSAPIDelegateCredentials | |
450 | .It HashKnownHosts | |
451 | .It Host | |
452 | .It HostbasedAuthentication | |
453 | .It HostKeyAlgorithms | |
454 | .It HostKeyAlias | |
455 | .It HostName | |
456 | .It IdentityFile | |
457 | .It IdentitiesOnly | |
458 | .It KbdInteractiveDevices | |
459 | .It LocalCommand | |
460 | .It LocalForward | |
461 | .It LogLevel | |
462 | .It MACs | |
463 | .It NoHostAuthenticationForLocalhost | |
464 | .It NumberOfPasswordPrompts | |
465 | .It PasswordAuthentication | |
466 | .It PermitLocalCommand | |
467 | .It Port | |
468 | .It PreferredAuthentications | |
469 | .It Protocol | |
470 | .It ProxyCommand | |
471 | .It PubkeyAuthentication | |
472 | .It RemoteForward | |
473 | .It RhostsRSAAuthentication | |
474 | .It RSAAuthentication | |
475 | .It SendEnv | |
476 | .It ServerAliveInterval | |
477 | .It ServerAliveCountMax | |
478 | .It SmartcardDevice | |
479 | .It StrictHostKeyChecking | |
480 | .It TCPKeepAlive | |
481 | .It Tunnel | |
482 | .It TunnelDevice | |
483 | .It UsePrivilegedPort | |
484 | .It User | |
485 | .It UserKnownHostsFile | |
486 | .It VerifyHostKeyDNS | |
487 | .It XAuthLocation | |
488 | .El | |
489 | .It Fl p Ar port | |
490 | Port to connect to on the remote host. | |
491 | This can be specified on a | |
492 | per-host basis in the configuration file. | |
493 | .It Fl q | |
494 | Quiet mode. | |
495 | Causes all warning and diagnostic messages to be suppressed. | |
496 | .It Fl R Xo | |
497 | .Sm off | |
498 | .Oo Ar bind_address : Oc | |
499 | .Ar port : host : hostport | |
500 | .Sm on | |
501 | .Xc | |
502 | Specifies that the given port on the remote (server) host is to be | |
503 | forwarded to the given host and port on the local side. | |
504 | This works by allocating a socket to listen to | |
505 | .Ar port | |
506 | on the remote side, and whenever a connection is made to this port, the | |
507 | connection is forwarded over the secure channel, and a connection is | |
508 | made to | |
509 | .Ar host | |
510 | port | |
511 | .Ar hostport | |
512 | from the local machine. | |
513 | .Pp | |
514 | Port forwardings can also be specified in the configuration file. | |
515 | Privileged ports can be forwarded only when | |
516 | logging in as root on the remote machine. | |
517 | IPv6 addresses can be specified by enclosing the address in square braces or | |
518 | using an alternative syntax: | |
519 | .Sm off | |
520 | .Xo | |
521 | .Op Ar bind_address No / | |
522 | .Ar host No / Ar port No / | |
523 | .Ar hostport | |
524 | .Xc . | |
525 | .Sm on | |
526 | .Pp | |
527 | By default, the listening socket on the server will be bound to the loopback | |
528 | interface only. | |
529 | This may be overriden by specifying a | |
530 | .Ar bind_address . | |
531 | An empty | |
532 | .Ar bind_address , | |
533 | or the address | |
534 | .Ql * , | |
535 | indicates that the remote socket should listen on all interfaces. | |
536 | Specifying a remote | |
537 | .Ar bind_address | |
538 | will only succeed if the server's | |
539 | .Cm GatewayPorts | |
540 | option is enabled (see | |
541 | .Xr sshd_config 5 ) . | |
542 | .It Fl S Ar ctl_path | |
543 | Specifies the location of a control socket for connection sharing. | |
544 | Refer to the description of | |
545 | .Cm ControlPath | |
546 | and | |
547 | .Cm ControlMaster | |
548 | in | |
549 | .Xr ssh_config 5 | |
550 | for details. | |
551 | .It Fl s | |
552 | May be used to request invocation of a subsystem on the remote system. | |
553 | Subsystems are a feature of the SSH2 protocol which facilitate the use | |
554 | of SSH as a secure transport for other applications (eg.\& | |
555 | .Xr sftp 1 ) . | |
556 | The subsystem is specified as the remote command. | |
557 | .It Fl T | |
558 | Disable pseudo-tty allocation. | |
559 | .It Fl t | |
560 | Force pseudo-tty allocation. | |
561 | This can be used to execute arbitrary | |
562 | screen-based programs on a remote machine, which can be very useful, | |
563 | e.g., when implementing menu services. | |
564 | Multiple | |
565 | .Fl t | |
566 | options force tty allocation, even if | |
567 | .Nm | |
568 | has no local tty. | |
569 | .It Fl V | |
570 | Display the version number and exit. | |
571 | .It Fl v | |
572 | Verbose mode. | |
573 | Causes | |
574 | .Nm | |
575 | to print debugging messages about its progress. | |
576 | This is helpful in | |
577 | debugging connection, authentication, and configuration problems. | |
578 | Multiple | |
579 | .Fl v | |
580 | options increase the verbosity. | |
581 | The maximum is 3. | |
582 | .It Fl w Ar tunnel : Ns Ar tunnel | |
583 | Requests a | |
584 | .Xr tun 4 | |
585 | device on the client and server like the | |
586 | .Cm Tunnel | |
587 | directive in | |
588 | .Xr ssh_config 5 . | |
589 | .It Fl X | |
590 | Enables X11 forwarding. | |
591 | This can also be specified on a per-host basis in a configuration file. | |
592 | .Pp | |
593 | X11 forwarding should be enabled with caution. | |
594 | Users with the ability to bypass file permissions on the remote host | |
595 | (for the user's X authorization database) | |
596 | can access the local X11 display through the forwarded connection. | |
597 | An attacker may then be able to perform activities such as keystroke monitoring. | |
598 | .Pp | |
599 | For this reason, X11 forwarding is subjected to X11 SECURITY extension | |
600 | restrictions by default. | |
601 | Please refer to the | |
602 | .Nm | |
603 | .Fl Y | |
604 | option and the | |
605 | .Cm ForwardX11Trusted | |
606 | directive in | |
607 | .Xr ssh_config 5 | |
608 | for more information. | |
609 | .It Fl x | |
610 | Disables X11 forwarding. | |
611 | .It Fl Y | |
612 | Enables trusted X11 forwarding. | |
613 | Trusted X11 forwardings are not subjected to the X11 SECURITY extension | |
614 | controls. | |
615 | .El | |
616 | .Pp | |
617 | .Nm | |
618 | may additionally obtain configuration data from | |
619 | a per-user configuration file and a system-wide configuration file. | |
620 | The file format and configuration options are described in | |
621 | .Xr ssh_config 5 . | |
622 | .Pp | |
623 | .Nm | |
624 | exits with the exit status of the remote command or with 255 | |
625 | if an error occurred. | |
626 | .Sh AUTHENTICATION | |
627 | The OpenSSH SSH client supports OpenSSH protocols 1 and 2. | |
628 | Protocol 2 is the default, with | |
629 | .Nm | |
630 | falling back to protocol 1 if it detects protocol 2 is unsupported. | |
631 | These settings may be altered using the | |
632 | .Cm Protocol | |
633 | option in | |
634 | .Xr ssh_config 5 , | |
635 | or enforced using the | |
636 | .Fl 1 | |
637 | and | |
638 | .Fl 2 | |
639 | options (see above). | |
640 | Both protocols support similar authentication methods, | |
641 | but protocol 2 is preferred since | |
642 | it provides additional mechanisms for confidentiality | |
643 | (the traffic is encrypted using AES, 3DES, Blowfish, CAST128, or Arcfour) | |
644 | and integrity (hmac-md5, hmac-sha1, hmac-ripemd160). | |
645 | Protocol 1 lacks a strong mechanism for ensuring the | |
646 | integrity of the connection. | |
647 | .Pp | |
648 | The methods available for authentication are: | |
649 | host-based authentication, | |
650 | public key authentication, | |
651 | challenge-response authentication, | |
652 | and password authentication. | |
653 | Authentication methods are tried in the order specified above, | |
654 | though protocol 2 has a configuration option to change the default order: | |
655 | .Cm PreferredAuthentications . | |
656 | .Pp | |
657 | Host-based authentication works as follows: | |
658 | If the machine the user logs in from is listed in | |
659 | .Pa /etc/hosts.equiv | |
660 | or | |
661 | .Pa /etc/shosts.equiv | |
662 | on the remote machine, and the user names are | |
663 | the same on both sides, or if the files | |
664 | .Pa ~/.rhosts | |
665 | or | |
666 | .Pa ~/.shosts | |
667 | exist in the user's home directory on the | |
668 | remote machine and contain a line containing the name of the client | |
669 | machine and the name of the user on that machine, the user is | |
670 | considered for login. | |
671 | Additionally, the server | |
672 | .Em must | |
673 | be able to verify the client's | |
674 | host key (see the description of | |
675 | .Pa /etc/ssh/ssh_known_hosts | |
676 | and | |
677 | .Pa ~/.ssh/known_hosts , | |
678 | below) | |
679 | for login to be permitted. | |
680 | This authentication method closes security holes due to IP | |
681 | spoofing, DNS spoofing, and routing spoofing. | |
682 | [Note to the administrator: | |
683 | .Pa /etc/hosts.equiv , | |
684 | .Pa ~/.rhosts , | |
685 | and the rlogin/rsh protocol in general, are inherently insecure and should be | |
686 | disabled if security is desired.] | |
687 | .Pp | |
688 | Public key authentication works as follows: | |
689 | The scheme is based on public-key cryptography, | |
690 | using cryptosystems | |
691 | where encryption and decryption are done using separate keys, | |
692 | and it is unfeasible to derive the decryption key from the encryption key. | |
693 | The idea is that each user creates a public/private | |
694 | key pair for authentication purposes. | |
695 | The server knows the public key, and only the user knows the private key. | |
696 | .Nm | |
697 | implements public key authentication protocol automatically, | |
698 | using either the RSA or DSA algorithms. | |
699 | Protocol 1 is restricted to using only RSA keys, | |
700 | but protocol 2 may use either. | |
701 | The | |
702 | .Sx HISTORY | |
703 | section of | |
704 | .Xr ssl 8 | |
705 | contains a brief discussion of the two algorithms. | |
706 | .Pp | |
707 | The file | |
708 | .Pa ~/.ssh/authorized_keys | |
709 | lists the public keys that are permitted for logging in. | |
710 | When the user logs in, the | |
711 | .Nm | |
712 | program tells the server which key pair it would like to use for | |
713 | authentication. | |
714 | The client proves that it has access to the private key | |
715 | and the server checks that the corresponding public key | |
716 | is authorized to accept the account. | |
717 | .Pp | |
718 | The user creates his/her key pair by running | |
719 | .Xr ssh-keygen 1 . | |
720 | This stores the private key in | |
721 | .Pa ~/.ssh/identity | |
722 | (protocol 1), | |
723 | .Pa ~/.ssh/id_dsa | |
724 | (protocol 2 DSA), | |
725 | or | |
726 | .Pa ~/.ssh/id_rsa | |
727 | (protocol 2 RSA) | |
728 | and stores the public key in | |
729 | .Pa ~/.ssh/identity.pub | |
730 | (protocol 1), | |
731 | .Pa ~/.ssh/id_dsa.pub | |
732 | (protocol 2 DSA), | |
733 | or | |
734 | .Pa ~/.ssh/id_rsa.pub | |
735 | (protocol 2 RSA) | |
736 | in the user's home directory. | |
737 | The user should then copy the public key | |
738 | to | |
739 | .Pa ~/.ssh/authorized_keys | |
740 | in his/her home directory on the remote machine. | |
741 | The | |
742 | .Pa authorized_keys | |
743 | file corresponds to the conventional | |
744 | .Pa ~/.rhosts | |
745 | file, and has one key | |
746 | per line, though the lines can be very long. | |
747 | After this, the user can log in without giving the password. | |
748 | .Pp | |
749 | The most convenient way to use public key authentication may be with an | |
750 | authentication agent. | |
751 | See | |
752 | .Xr ssh-agent 1 | |
753 | for more information. | |
754 | .Pp | |
755 | Challenge-response authentication works as follows: | |
756 | The server sends an arbitrary | |
757 | .Qq challenge | |
758 | text, and prompts for a response. | |
759 | Protocol 2 allows multiple challenges and responses; | |
760 | protocol 1 is restricted to just one challenge/response. | |
761 | Examples of challenge-response authentication include | |
762 | BSD Authentication (see | |
763 | .Xr login.conf 5 ) | |
764 | and PAM (some non-OpenBSD systems). | |
765 | .Pp | |
766 | Finally, if other authentication methods fail, | |
767 | .Nm | |
768 | prompts the user for a password. | |
769 | The password is sent to the remote | |
770 | host for checking; however, since all communications are encrypted, | |
771 | the password cannot be seen by someone listening on the network. | |
772 | .Sh LOGIN SESSION AND REMOTE EXECUTION | |
773 | When the user's identity has been accepted by the server, the server | |
774 | either executes the given command, or logs into the machine and gives | |
775 | the user a normal shell on the remote machine. | |
776 | All communication with | |
777 | the remote command or shell will be automatically encrypted. | |
778 | .Pp | |
779 | If a pseudo-terminal has been allocated (normal login session), the | |
780 | user may use the escape characters noted below. | |
781 | .Pp | |
782 | If no pseudo-tty has been allocated, | |
783 | the session is transparent and can be used to reliably transfer binary data. | |
784 | On most systems, setting the escape character to | |
785 | .Dq none | |
786 | will also make the session transparent even if a tty is used. | |
787 | .Pp | |
788 | The session terminates when the command or shell on the remote | |
789 | machine exits and all X11 and TCP/IP connections have been closed. | |
790 | .Sh ESCAPE CHARACTERS | |
791 | When a pseudo-terminal has been requested, | |
792 | .Nm | |
793 | supports a number of functions through the use of an escape character. | |
794 | .Pp | |
795 | A single tilde character can be sent as | |
796 | .Ic ~~ | |
797 | or by following the tilde by a character other than those described below. | |
798 | The escape character must always follow a newline to be interpreted as | |
799 | special. | |
800 | The escape character can be changed in configuration files using the | |
801 | .Cm EscapeChar | |
802 | configuration directive or on the command line by the | |
803 | .Fl e | |
804 | option. | |
805 | .Pp | |
806 | The supported escapes (assuming the default | |
807 | .Ql ~ ) | |
808 | are: | |
809 | .Bl -tag -width Ds | |
810 | .It Cm ~. | |
811 | Disconnect. | |
812 | .It Cm ~^Z | |
813 | Background | |
814 | .Nm ssh . | |
815 | .It Cm ~# | |
816 | List forwarded connections. | |
817 | .It Cm ~& | |
818 | Background | |
819 | .Nm | |
820 | at logout when waiting for forwarded connection / X11 sessions to terminate. | |
821 | .It Cm ~? | |
822 | Display a list of escape characters. | |
823 | .It Cm ~B | |
824 | Send a BREAK to the remote system | |
825 | (only useful for SSH protocol version 2 and if the peer supports it). | |
826 | .It Cm ~C | |
827 | Open command line. | |
828 | Currently this allows the addition of port forwardings using the | |
829 | .Fl L | |
830 | and | |
831 | .Fl R | |
832 | options (see above). | |
833 | It also allows the cancellation of existing remote port-forwardings | |
834 | using | |
835 | .Fl KR Ar hostport . | |
836 | .Ic !\& Ns Ar command | |
837 | allows the user to execute a local command if the | |
838 | .Ic PermitLocalCommand | |
839 | option is enabled in | |
840 | .Xr ssh_config 5 . | |
841 | Basic help is available, using the | |
842 | .Fl h | |
843 | option. | |
844 | .It Cm ~R | |
845 | Request rekeying of the connection | |
846 | (only useful for SSH protocol version 2 and if the peer supports it). | |
847 | .El | |
848 | .Sh X11 AND TCP FORWARDING | |
849 | If the | |
850 | .Cm ForwardX11 | |
851 | variable is set to | |
852 | .Dq yes | |
853 | (or see the description of the | |
854 | .Fl X , | |
855 | .Fl x , | |
856 | and | |
857 | .Fl Y | |
858 | options above) | |
859 | and the user is using X11 (the | |
860 | .Ev DISPLAY | |
861 | environment variable is set), the connection to the X11 display is | |
862 | automatically forwarded to the remote side in such a way that any X11 | |
863 | programs started from the shell (or command) will go through the | |
864 | encrypted channel, and the connection to the real X server will be made | |
865 | from the local machine. | |
866 | The user should not manually set | |
867 | .Ev DISPLAY . | |
868 | Forwarding of X11 connections can be | |
869 | configured on the command line or in configuration files. | |
870 | .Pp | |
871 | The | |
872 | .Ev DISPLAY | |
873 | value set by | |
874 | .Nm | |
875 | will point to the server machine, but with a display number greater than zero. | |
876 | This is normal, and happens because | |
877 | .Nm | |
878 | creates a | |
879 | .Dq proxy | |
880 | X server on the server machine for forwarding the | |
881 | connections over the encrypted channel. | |
882 | .Pp | |
883 | .Nm | |
884 | will also automatically set up Xauthority data on the server machine. | |
885 | For this purpose, it will generate a random authorization cookie, | |
886 | store it in Xauthority on the server, and verify that any forwarded | |
887 | connections carry this cookie and replace it by the real cookie when | |
888 | the connection is opened. | |
889 | The real authentication cookie is never | |
890 | sent to the server machine (and no cookies are sent in the plain). | |
891 | .Pp | |
892 | If the | |
893 | .Cm ForwardAgent | |
894 | variable is set to | |
895 | .Dq yes | |
896 | (or see the description of the | |
897 | .Fl A | |
898 | and | |
899 | .Fl a | |
900 | options above) and | |
901 | the user is using an authentication agent, the connection to the agent | |
902 | is automatically forwarded to the remote side. | |
903 | .Pp | |
904 | Forwarding of arbitrary TCP/IP connections over the secure channel can | |
905 | be specified either on the command line or in a configuration file. | |
906 | One possible application of TCP/IP forwarding is a secure connection to an | |
907 | electronic purse; another is going through firewalls. | |
908 | .Sh SERVER AUTHENTICATION | |
909 | .Nm | |
910 | automatically maintains and checks a database containing | |
911 | identifications for all hosts it has ever been used with. | |
912 | Host keys are stored in | |
913 | .Pa ~/.ssh/known_hosts | |
914 | in the user's home directory. | |
915 | Additionally, the file | |
916 | .Pa /etc/ssh/ssh_known_hosts | |
917 | is automatically checked for known hosts. | |
918 | Any new hosts are automatically added to the user's file. | |
919 | If a host's identification ever changes, | |
920 | .Nm | |
921 | warns about this and disables password authentication to prevent a | |
922 | trojan horse from getting the user's password. | |
923 | Another purpose of this mechanism is to prevent man-in-the-middle attacks | |
924 | which could otherwise be used to circumvent the encryption. | |
925 | The | |
926 | .Cm StrictHostKeyChecking | |
927 | option can be used to prevent logins to machines whose | |
928 | host key is not known or has changed. | |
929 | .Pp | |
930 | .Nm | |
931 | can be configured to verify host identification using fingerprint resource | |
932 | records (SSHFP) published in DNS. | |
933 | The | |
934 | .Cm VerifyHostKeyDNS | |
935 | option can be used to control how DNS lookups are performed. | |
936 | SSHFP resource records can be generated using | |
937 | .Xr ssh-keygen 1 . | |
938 | .Sh ENVIRONMENT | |
939 | .Nm | |
940 | will normally set the following environment variables: | |
941 | .Bl -tag -width LOGNAME | |
942 | .It Ev DISPLAY | |
943 | The | |
944 | .Ev DISPLAY | |
945 | variable indicates the location of the X11 server. | |
946 | It is automatically set by | |
947 | .Nm | |
948 | to point to a value of the form | |
949 | .Dq hostname:n | |
950 | where hostname indicates | |
951 | the host where the shell runs, and n is an integer \*(Ge 1. | |
952 | .Nm | |
953 | uses this special value to forward X11 connections over the secure | |
954 | channel. | |
955 | The user should normally not set | |
956 | .Ev DISPLAY | |
957 | explicitly, as that | |
958 | will render the X11 connection insecure (and will require the user to | |
959 | manually copy any required authorization cookies). | |
960 | .It Ev HOME | |
961 | Set to the path of the user's home directory. | |
962 | .It Ev LOGNAME | |
963 | Synonym for | |
964 | .Ev USER ; | |
965 | set for compatibility with systems that use this variable. | |
966 | .It Ev MAIL | |
967 | Set to the path of the user's mailbox. | |
968 | .It Ev PATH | |
969 | Set to the default | |
970 | .Ev PATH , | |
971 | as specified when compiling | |
972 | .Nm ssh . | |
973 | .It Ev SSH_ASKPASS | |
974 | If | |
975 | .Nm | |
976 | needs a passphrase, it will read the passphrase from the current | |
977 | terminal if it was run from a terminal. | |
978 | If | |
979 | .Nm | |
980 | does not have a terminal associated with it but | |
981 | .Ev DISPLAY | |
982 | and | |
983 | .Ev SSH_ASKPASS | |
984 | are set, it will execute the program specified by | |
985 | .Ev SSH_ASKPASS | |
986 | and open an X11 window to read the passphrase. | |
987 | This is particularly useful when calling | |
988 | .Nm | |
989 | from a | |
990 | .Pa .xsession | |
991 | or related script. | |
992 | (Note that on some machines it | |
993 | may be necessary to redirect the input from | |
994 | .Pa /dev/null | |
995 | to make this work.) | |
996 | .It Ev SSH_AUTH_SOCK | |
997 | Identifies the path of a unix-domain socket used to communicate with the | |
998 | agent. | |
999 | .It Ev SSH_CONNECTION | |
1000 | Identifies the client and server ends of the connection. | |
1001 | The variable contains | |
1002 | four space-separated values: client ip-address, client port number, | |
1003 | server ip-address and server port number. | |
1004 | .It Ev SSH_ORIGINAL_COMMAND | |
1005 | The variable contains the original command line if a forced command | |
1006 | is executed. | |
1007 | It can be used to extract the original arguments. | |
1008 | .It Ev SSH_TTY | |
1009 | This is set to the name of the tty (path to the device) associated | |
1010 | with the current shell or command. | |
1011 | If the current session has no tty, | |
1012 | this variable is not set. | |
1013 | .It Ev TZ | |
1014 | This variable is set to indicate the present time zone if it | |
1015 | was set when the daemon was started (i.e., the daemon passes the value | |
1016 | on to new connections). | |
1017 | .It Ev USER | |
1018 | Set to the name of the user logging in. | |
1019 | .El | |
1020 | .Pp | |
1021 | Additionally, | |
1022 | .Nm | |
1023 | reads | |
1024 | .Pa ~/.ssh/environment , | |
1025 | and adds lines of the format | |
1026 | .Dq VARNAME=value | |
1027 | to the environment if the file exists and if users are allowed to | |
1028 | change their environment. | |
1029 | For more information, see the | |
1030 | .Cm PermitUserEnvironment | |
1031 | option in | |
1032 | .Xr sshd_config 5 . | |
1033 | .Sh FILES | |
1034 | .Bl -tag -width Ds | |
1035 | .It Pa ~/.ssh/known_hosts | |
1036 | Records host keys for all hosts the user has logged into that are not | |
1037 | in | |
1038 | .Pa /etc/ssh/ssh_known_hosts . | |
1039 | See | |
1040 | .Xr sshd 8 . | |
1041 | .It Pa ~/.ssh/identity, ~/.ssh/id_dsa, ~/.ssh/id_rsa | |
1042 | Contains the authentication identity of the user. | |
1043 | They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively. | |
1044 | These files | |
1045 | contain sensitive data and should be readable by the user but not | |
1046 | accessible by others (read/write/execute). | |
1047 | Note that | |
1048 | .Nm | |
1049 | ignores a private key file if it is accessible by others. | |
1050 | It is possible to specify a passphrase when | |
1051 | generating the key; the passphrase will be used to encrypt the | |
1052 | sensitive part of this file using 3DES. | |
1053 | .It Pa ~/.ssh/identity.pub, ~/.ssh/id_dsa.pub, ~/.ssh/id_rsa.pub | |
1054 | Contains the public key for authentication (public part of the | |
1055 | identity file in human-readable form). | |
1056 | The contents of the | |
1057 | .Pa ~/.ssh/identity.pub | |
1058 | file should be added to the file | |
1059 | .Pa ~/.ssh/authorized_keys | |
1060 | on all machines | |
1061 | where the user wishes to log in using protocol version 1 RSA authentication. | |
1062 | The contents of the | |
1063 | .Pa ~/.ssh/id_dsa.pub | |
1064 | and | |
1065 | .Pa ~/.ssh/id_rsa.pub | |
1066 | file should be added to | |
1067 | .Pa ~/.ssh/authorized_keys | |
1068 | on all machines | |
1069 | where the user wishes to log in using protocol version 2 DSA/RSA authentication. | |
1070 | These files are not | |
1071 | sensitive and can (but need not) be readable by anyone. | |
1072 | These files are | |
1073 | never used automatically and are not necessary; they are only provided for | |
1074 | the convenience of the user. | |
1075 | .It Pa ~/.ssh/config | |
1076 | This is the per-user configuration file. | |
1077 | The file format and configuration options are described in | |
1078 | .Xr ssh_config 5 . | |
1079 | Because of the potential for abuse, this file must have strict permissions: | |
1080 | read/write for the user, and not accessible by others. | |
1081 | .It Pa ~/.ssh/authorized_keys | |
1082 | Lists the public keys (RSA/DSA) that can be used for logging in as this user. | |
1083 | The format of this file is described in the | |
1084 | .Xr sshd 8 | |
1085 | manual page. | |
1086 | In the simplest form the format is the same as the | |
1087 | .Pa .pub | |
1088 | identity files. | |
1089 | This file is not highly sensitive, but the recommended | |
1090 | permissions are read/write for the user, and not accessible by others. | |
1091 | .It Pa /etc/ssh/ssh_known_hosts | |
1092 | Systemwide list of known host keys. | |
1093 | This file should be prepared by the | |
1094 | system administrator to contain the public host keys of all machines in the | |
1095 | organization. | |
1096 | This file should be world-readable. | |
1097 | This file contains | |
1098 | public keys, one per line, in the following format (fields separated | |
1099 | by spaces): system name, public key and optional comment field. | |
1100 | When different names are used | |
1101 | for the same machine, all such names should be listed, separated by | |
1102 | commas. | |
1103 | The format is described in the | |
1104 | .Xr sshd 8 | |
1105 | manual page. | |
1106 | .Pp | |
1107 | The canonical system name (as returned by name servers) is used by | |
1108 | .Xr sshd 8 | |
1109 | to verify the client host when logging in; other names are needed because | |
1110 | .Nm | |
1111 | does not convert the user-supplied name to a canonical name before | |
1112 | checking the key, because someone with access to the name servers | |
1113 | would then be able to fool host authentication. | |
1114 | .It Pa /etc/ssh/ssh_config | |
1115 | Systemwide configuration file. | |
1116 | The file format and configuration options are described in | |
1117 | .Xr ssh_config 5 . | |
1118 | .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key | |
1119 | These three files contain the private parts of the host keys | |
1120 | and are used for | |
1121 | .Cm RhostsRSAAuthentication | |
1122 | and | |
1123 | .Cm HostbasedAuthentication . | |
1124 | If the protocol version 1 | |
1125 | .Cm RhostsRSAAuthentication | |
1126 | method is used, | |
1127 | .Nm | |
1128 | must be setuid root, since the host key is readable only by root. | |
1129 | For protocol version 2, | |
1130 | .Nm | |
1131 | uses | |
1132 | .Xr ssh-keysign 8 | |
1133 | to access the host keys for | |
1134 | .Cm HostbasedAuthentication . | |
1135 | This eliminates the requirement that | |
1136 | .Nm | |
1137 | be setuid root when that authentication method is used. | |
1138 | By default | |
1139 | .Nm | |
1140 | is not setuid root. | |
1141 | .It Pa ~/.rhosts | |
1142 | This file is used in | |
1143 | .Cm RhostsRSAAuthentication | |
1144 | and | |
1145 | .Cm HostbasedAuthentication | |
1146 | authentication to list the | |
1147 | host/user pairs that are permitted to log in. | |
1148 | (Note that this file is | |
1149 | also used by rlogin and rsh, which makes using this file insecure.) | |
1150 | Each line of the file contains a host name (in the canonical form | |
1151 | returned by name servers), and then a user name on that host, | |
1152 | separated by a space. | |
1153 | On some machines this file may need to be | |
1154 | world-readable if the user's home directory is on a NFS partition, | |
1155 | because | |
1156 | .Xr sshd 8 | |
1157 | reads it as root. | |
1158 | Additionally, this file must be owned by the user, | |
1159 | and must not have write permissions for anyone else. | |
1160 | The recommended | |
1161 | permission for most machines is read/write for the user, and not | |
1162 | accessible by others. | |
1163 | .Pp | |
1164 | Note that | |
1165 | .Xr sshd 8 | |
1166 | allows authentication only in combination with client host key | |
1167 | authentication before permitting log in. | |
1168 | If the server machine does not have the client's host key in | |
1169 | .Pa /etc/ssh/ssh_known_hosts , | |
1170 | it can be stored in | |
1171 | .Pa ~/.ssh/known_hosts . | |
1172 | The easiest way to do this is to | |
1173 | connect back to the client from the server machine using ssh; this | |
1174 | will automatically add the host key to | |
1175 | .Pa ~/.ssh/known_hosts . | |
1176 | .It Pa ~/.shosts | |
1177 | This file is used exactly the same way as | |
1178 | .Pa .rhosts . | |
1179 | The purpose for | |
1180 | having this file is to be able to use | |
1181 | .Cm RhostsRSAAuthentication | |
1182 | and | |
1183 | .Cm HostbasedAuthentication | |
1184 | authentication without permitting login with | |
1185 | .Xr rlogin | |
1186 | or | |
1187 | .Xr rsh 1 . | |
1188 | .It Pa /etc/hosts.equiv | |
1189 | This file is used during | |
1190 | .Cm RhostsRSAAuthentication | |
1191 | and | |
1192 | .Cm HostbasedAuthentication | |
1193 | authentication. | |
1194 | It contains | |
1195 | canonical hosts names, one per line (the full format is described in the | |
1196 | .Xr sshd 8 | |
1197 | manual page). | |
1198 | If the client host is found in this file, login is | |
1199 | automatically permitted provided client and server user names are the | |
1200 | same. | |
1201 | Additionally, successful client host key authentication is required. | |
1202 | This file should only be writable by root. | |
1203 | .It Pa /etc/shosts.equiv | |
1204 | This file is processed exactly as | |
1205 | .Pa /etc/hosts.equiv . | |
1206 | This file may be useful to permit logins using | |
1207 | .Nm | |
1208 | but not using rsh/rlogin. | |
1209 | .It Pa /etc/ssh/sshrc | |
1210 | Commands in this file are executed by | |
1211 | .Nm | |
1212 | when the user logs in just before the user's shell (or command) is started. | |
1213 | See the | |
1214 | .Xr sshd 8 | |
1215 | manual page for more information. | |
1216 | .It Pa ~/.ssh/rc | |
1217 | Commands in this file are executed by | |
1218 | .Nm | |
1219 | when the user logs in just before the user's shell (or command) is | |
1220 | started. | |
1221 | See the | |
1222 | .Xr sshd 8 | |
1223 | manual page for more information. | |
1224 | .It Pa ~/.ssh/environment | |
1225 | Contains additional definitions for environment variables, see section | |
1226 | .Sx ENVIRONMENT | |
1227 | above. | |
1228 | .El | |
1229 | .Sh SEE ALSO | |
1230 | .Xr gzip 1 , | |
1231 | .Xr rsh 1 , | |
1232 | .Xr scp 1 , | |
1233 | .Xr sftp 1 , | |
1234 | .Xr ssh-add 1 , | |
1235 | .Xr ssh-agent 1 , | |
1236 | .Xr ssh-keygen 1 , | |
1237 | .Xr telnet 1 , | |
1238 | .Xr hosts.equiv 5 , | |
1239 | .Xr ssh_config 5 , | |
1240 | .Xr ssh-keysign 8 , | |
1241 | .Xr sshd 8 | |
1242 | .Rs | |
1243 | .%A T. Ylonen | |
1244 | .%A T. Kivinen | |
1245 | .%A M. Saarinen | |
1246 | .%A T. Rinne | |
1247 | .%A S. Lehtinen | |
1248 | .%T "SSH Protocol Architecture" | |
1249 | .%N draft-ietf-secsh-architecture-12.txt | |
1250 | .%D January 2002 | |
1251 | .%O work in progress material | |
1252 | .Re | |
1253 | .Sh AUTHORS | |
1254 | OpenSSH is a derivative of the original and free | |
1255 | ssh 1.2.12 release by Tatu Ylonen. | |
1256 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, | |
1257 | Theo de Raadt and Dug Song | |
1258 | removed many bugs, re-added newer features and | |
1259 | created OpenSSH. | |
1260 | Markus Friedl contributed the support for SSH | |
1261 | protocol versions 1.5 and 2.0. |