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884dc78b | 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 | .\" | |
b5afdff5 | 37 | .\" $OpenBSD: sshd_config.5,v 1.106 2009/04/21 15:13:17 stevesk Exp $ |
38 | .Dd $Mdocdate: April 21 2009 $ | |
884dc78b | 39 | .Dt SSHD_CONFIG 5 |
40 | .Os | |
41 | .Sh NAME | |
42 | .Nm sshd_config | |
43 | .Nd OpenSSH SSH daemon configuration file | |
44 | .Sh SYNOPSIS | |
0b90ac93 | 45 | .Nm /etc/ssh/sshd_config |
884dc78b | 46 | .Sh DESCRIPTION |
30460aeb | 47 | .Xr sshd 8 |
884dc78b | 48 | reads configuration data from |
49 | .Pa /etc/ssh/sshd_config | |
50 | (or the file specified with | |
51 | .Fl f | |
52 | on the command line). | |
53 | The file contains keyword-argument pairs, one per line. | |
54 | Lines starting with | |
55 | .Ql # | |
56 | and empty lines are interpreted as comments. | |
30460aeb | 57 | Arguments may optionally be enclosed in double quotes |
58 | .Pq \&" | |
59 | in order to represent arguments containing spaces. | |
884dc78b | 60 | .Pp |
61 | The possible | |
62 | keywords and their meanings are as follows (note that | |
63 | keywords are case-insensitive and arguments are case-sensitive): | |
64 | .Bl -tag -width Ds | |
7e82606e | 65 | .It Cm AcceptEnv |
66 | Specifies what environment variables sent by the client will be copied into | |
67 | the session's | |
68 | .Xr environ 7 . | |
69 | See | |
70 | .Cm SendEnv | |
71 | in | |
72 | .Xr ssh_config 5 | |
73 | for how to configure the client. | |
74 | Note that environment passing is only supported for protocol 2. | |
75 | Variables are specified by name, which may contain the wildcard characters | |
30460aeb | 76 | .Ql * |
7e82606e | 77 | and |
78 | .Ql \&? . | |
79 | Multiple environment variables may be separated by whitespace or spread | |
80 | across multiple | |
81 | .Cm AcceptEnv | |
82 | directives. | |
83 | Be warned that some environment variables could be used to bypass restricted | |
84 | user environments. | |
85 | For this reason, care should be taken in the use of this directive. | |
86 | The default is not to accept any environment variables. | |
dfddba3d | 87 | .It Cm AddressFamily |
88 | Specifies which address family should be used by | |
30460aeb | 89 | .Xr sshd 8 . |
dfddba3d | 90 | Valid arguments are |
91 | .Dq any , | |
92 | .Dq inet | |
30460aeb | 93 | (use IPv4 only), or |
dfddba3d | 94 | .Dq inet6 |
95 | (use IPv6 only). | |
96 | The default is | |
97 | .Dq any . | |
5156b1a1 | 98 | .It Cm AllowAgentForwarding |
99 | Specifies whether | |
100 | .Xr ssh-agent 1 | |
101 | forwarding is permitted. | |
102 | The default is | |
103 | .Dq yes . | |
104 | Note that disabling agent forwarding does not improve security | |
105 | unless users are also denied shell access, as they can always install | |
106 | their own forwarders. | |
884dc78b | 107 | .It Cm AllowGroups |
108 | This keyword can be followed by a list of group name patterns, separated | |
109 | by spaces. | |
110 | If specified, login is allowed only for users whose primary | |
111 | group or supplementary group list matches one of the patterns. | |
884dc78b | 112 | Only group names are valid; a numerical group ID is not recognized. |
113 | By default, login is allowed for all groups. | |
30460aeb | 114 | The allow/deny directives are processed in the following order: |
115 | .Cm DenyUsers , | |
116 | .Cm AllowUsers , | |
117 | .Cm DenyGroups , | |
118 | and finally | |
119 | .Cm AllowGroups . | |
120 | .Pp | |
121 | See | |
122 | .Sx PATTERNS | |
123 | in | |
124 | .Xr ssh_config 5 | |
125 | for more information on patterns. | |
884dc78b | 126 | .It Cm AllowTcpForwarding |
127 | Specifies whether TCP forwarding is permitted. | |
128 | The default is | |
129 | .Dq yes . | |
130 | Note that disabling TCP forwarding does not improve security unless | |
131 | users are also denied shell access, as they can always install their | |
132 | own forwarders. | |
884dc78b | 133 | .It Cm AllowUsers |
134 | This keyword can be followed by a list of user name patterns, separated | |
135 | by spaces. | |
bfe49944 | 136 | If specified, login is allowed only for user names that |
884dc78b | 137 | match one of the patterns. |
884dc78b | 138 | Only user names are valid; a numerical user ID is not recognized. |
139 | By default, login is allowed for all users. | |
140 | If the pattern takes the form USER@HOST then USER and HOST | |
141 | are separately checked, restricting logins to particular | |
142 | users from particular hosts. | |
30460aeb | 143 | The allow/deny directives are processed in the following order: |
144 | .Cm DenyUsers , | |
145 | .Cm AllowUsers , | |
146 | .Cm DenyGroups , | |
147 | and finally | |
148 | .Cm AllowGroups . | |
149 | .Pp | |
150 | See | |
151 | .Sx PATTERNS | |
152 | in | |
153 | .Xr ssh_config 5 | |
154 | for more information on patterns. | |
884dc78b | 155 | .It Cm AuthorizedKeysFile |
156 | Specifies the file that contains the public keys that can be used | |
157 | for user authentication. | |
158 | .Cm AuthorizedKeysFile | |
159 | may contain tokens of the form %T which are substituted during connection | |
30460aeb | 160 | setup. |
7cac2b65 | 161 | The following tokens are defined: %% is replaced by a literal '%', |
30460aeb | 162 | %h is replaced by the home directory of the user being authenticated, and |
884dc78b | 163 | %u is replaced by the username of that user. |
164 | After expansion, | |
165 | .Cm AuthorizedKeysFile | |
166 | is taken to be an absolute path or one relative to the user's home | |
167 | directory. | |
168 | The default is | |
169 | .Dq .ssh/authorized_keys . | |
170 | .It Cm Banner | |
884dc78b | 171 | The contents of the specified file are sent to the remote user before |
172 | authentication is allowed. | |
e74dc197 | 173 | If the argument is |
174 | .Dq none | |
175 | then no banner is displayed. | |
884dc78b | 176 | This option is only available for protocol version 2. |
177 | By default, no banner is displayed. | |
884dc78b | 178 | .It Cm ChallengeResponseAuthentication |
b5afdff5 | 179 | Specifies whether challenge-response authentication is allowed (e.g. via |
180 | PAM or though authentication styles supported in | |
181 | .Xr login.conf 5 ) | |
884dc78b | 182 | The default is |
183 | .Dq yes . | |
e74dc197 | 184 | .It Cm ChrootDirectory |
185 | Specifies a path to | |
186 | .Xr chroot 2 | |
187 | to after authentication. | |
188 | This path, and all its components, must be root-owned directories that are | |
189 | not writable by any other user or group. | |
b5afdff5 | 190 | After the chroot, |
191 | .Xr sshd 8 | |
192 | changes the working directory to the user's home directory. | |
e74dc197 | 193 | .Pp |
194 | The path may contain the following tokens that are expanded at runtime once | |
195 | the connecting user has been authenticated: %% is replaced by a literal '%', | |
196 | %h is replaced by the home directory of the user being authenticated, and | |
197 | %u is replaced by the username of that user. | |
198 | .Pp | |
199 | The | |
200 | .Cm ChrootDirectory | |
201 | must contain the necessary files and directories to support the | |
b5afdff5 | 202 | user's session. |
e74dc197 | 203 | For an interactive session this requires at least a shell, typically |
204 | .Xr sh 1 , | |
205 | and basic | |
206 | .Pa /dev | |
207 | nodes such as | |
208 | .Xr null 4 , | |
209 | .Xr zero 4 , | |
210 | .Xr stdin 4 , | |
211 | .Xr stdout 4 , | |
212 | .Xr stderr 4 , | |
213 | .Xr arandom 4 | |
214 | and | |
215 | .Xr tty 4 | |
216 | devices. | |
217 | For file transfer sessions using | |
218 | .Dq sftp , | |
219 | no additional configuration of the environment is necessary if the | |
b5afdff5 | 220 | in-process sftp server is used, |
221 | though sessions which use logging do require | |
222 | .Pa /dev/log | |
223 | inside the chroot directory (see | |
224 | .Xr sftp-server 8 | |
e74dc197 | 225 | for details). |
226 | .Pp | |
227 | The default is not to | |
228 | .Xr chroot 2 . | |
884dc78b | 229 | .It Cm Ciphers |
230 | Specifies the ciphers allowed for protocol version 2. | |
231 | Multiple ciphers must be comma-separated. | |
7e82606e | 232 | The supported ciphers are |
233 | .Dq 3des-cbc , | |
234 | .Dq aes128-cbc , | |
235 | .Dq aes192-cbc , | |
236 | .Dq aes256-cbc , | |
237 | .Dq aes128-ctr , | |
238 | .Dq aes192-ctr , | |
239 | .Dq aes256-ctr , | |
2ce0bfe4 | 240 | .Dq arcfour128 , |
241 | .Dq arcfour256 , | |
7e82606e | 242 | .Dq arcfour , |
243 | .Dq blowfish-cbc , | |
244 | and | |
245 | .Dq cast128-cbc . | |
30460aeb | 246 | The default is: |
247 | .Bd -literal -offset 3n | |
5262cbfb | 248 | aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128, |
249 | aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc, | |
250 | aes256-cbc,arcfour | |
884dc78b | 251 | .Ed |
884dc78b | 252 | .It Cm ClientAliveCountMax |
08822d99 | 253 | Sets the number of client alive messages (see below) which may be |
884dc78b | 254 | sent without |
30460aeb | 255 | .Xr sshd 8 |
7cac2b65 | 256 | receiving any messages back from the client. |
257 | If this threshold is reached while client alive messages are being sent, | |
30460aeb | 258 | sshd will disconnect the client, terminating the session. |
7cac2b65 | 259 | It is important to note that the use of client alive messages is very |
260 | different from | |
540d72c3 | 261 | .Cm TCPKeepAlive |
7cac2b65 | 262 | (below). |
263 | The client alive messages are sent through the encrypted channel | |
264 | and therefore will not be spoofable. | |
265 | The TCP keepalive option enabled by | |
540d72c3 | 266 | .Cm TCPKeepAlive |
7cac2b65 | 267 | is spoofable. |
268 | The client alive mechanism is valuable when the client or | |
884dc78b | 269 | server depend on knowing when a connection has become inactive. |
270 | .Pp | |
7cac2b65 | 271 | The default value is 3. |
272 | If | |
884dc78b | 273 | .Cm ClientAliveInterval |
08822d99 | 274 | (see below) is set to 15, and |
884dc78b | 275 | .Cm ClientAliveCountMax |
30460aeb | 276 | is left at the default, unresponsive SSH clients |
884dc78b | 277 | will be disconnected after approximately 45 seconds. |
30460aeb | 278 | This option applies to protocol version 2 only. |
2ce0bfe4 | 279 | .It Cm ClientAliveInterval |
280 | Sets a timeout interval in seconds after which if no data has been received | |
281 | from the client, | |
30460aeb | 282 | .Xr sshd 8 |
2ce0bfe4 | 283 | will send a message through the encrypted |
284 | channel to request a response from the client. | |
285 | The default | |
286 | is 0, indicating that these messages will not be sent to the client. | |
287 | This option applies to protocol version 2 only. | |
884dc78b | 288 | .It Cm Compression |
2ce0bfe4 | 289 | Specifies whether compression is allowed, or delayed until |
290 | the user has authenticated successfully. | |
884dc78b | 291 | The argument must be |
2ce0bfe4 | 292 | .Dq yes , |
293 | .Dq delayed , | |
884dc78b | 294 | or |
295 | .Dq no . | |
296 | The default is | |
2ce0bfe4 | 297 | .Dq delayed . |
884dc78b | 298 | .It Cm DenyGroups |
299 | This keyword can be followed by a list of group name patterns, separated | |
300 | by spaces. | |
301 | Login is disallowed for users whose primary group or supplementary | |
302 | group list matches one of the patterns. | |
884dc78b | 303 | Only group names are valid; a numerical group ID is not recognized. |
304 | By default, login is allowed for all groups. | |
30460aeb | 305 | The allow/deny directives are processed in the following order: |
306 | .Cm DenyUsers , | |
307 | .Cm AllowUsers , | |
308 | .Cm DenyGroups , | |
309 | and finally | |
310 | .Cm AllowGroups . | |
311 | .Pp | |
312 | See | |
313 | .Sx PATTERNS | |
314 | in | |
315 | .Xr ssh_config 5 | |
316 | for more information on patterns. | |
884dc78b | 317 | .It Cm DenyUsers |
318 | This keyword can be followed by a list of user name patterns, separated | |
319 | by spaces. | |
320 | Login is disallowed for user names that match one of the patterns. | |
884dc78b | 321 | Only user names are valid; a numerical user ID is not recognized. |
322 | By default, login is allowed for all users. | |
323 | If the pattern takes the form USER@HOST then USER and HOST | |
324 | are separately checked, restricting logins to particular | |
325 | users from particular hosts. | |
30460aeb | 326 | The allow/deny directives are processed in the following order: |
327 | .Cm DenyUsers , | |
328 | .Cm AllowUsers , | |
329 | .Cm DenyGroups , | |
330 | and finally | |
331 | .Cm AllowGroups . | |
332 | .Pp | |
333 | See | |
334 | .Sx PATTERNS | |
335 | in | |
336 | .Xr ssh_config 5 | |
337 | for more information on patterns. | |
338 | .It Cm ForceCommand | |
339 | Forces the execution of the command specified by | |
340 | .Cm ForceCommand , | |
e74dc197 | 341 | ignoring any command supplied by the client and |
342 | .Pa ~/.ssh/rc | |
343 | if present. | |
30460aeb | 344 | The command is invoked by using the user's login shell with the -c option. |
345 | This applies to shell, command, or subsystem execution. | |
346 | It is most useful inside a | |
347 | .Cm Match | |
348 | block. | |
349 | The command originally supplied by the client is available in the | |
350 | .Ev SSH_ORIGINAL_COMMAND | |
351 | environment variable. | |
e74dc197 | 352 | Specifying a command of |
353 | .Dq internal-sftp | |
354 | will force the use of an in-process sftp server that requires no support | |
355 | files when used with | |
356 | .Cm ChrootDirectory . | |
884dc78b | 357 | .It Cm GatewayPorts |
358 | Specifies whether remote hosts are allowed to connect to ports | |
359 | forwarded for the client. | |
360 | By default, | |
30460aeb | 361 | .Xr sshd 8 |
bfe49944 | 362 | binds remote port forwardings to the loopback address. |
363 | This prevents other remote hosts from connecting to forwarded ports. | |
884dc78b | 364 | .Cm GatewayPorts |
30460aeb | 365 | can be used to specify that sshd |
dfddba3d | 366 | should allow remote port forwardings to bind to non-loopback addresses, thus |
367 | allowing other hosts to connect. | |
368 | The argument may be | |
369 | .Dq no | |
370 | to force remote port forwardings to be available to the local host only, | |
884dc78b | 371 | .Dq yes |
dfddba3d | 372 | to force remote port forwardings to bind to the wildcard address, or |
373 | .Dq clientspecified | |
374 | to allow the client to select the address to which the forwarding is bound. | |
884dc78b | 375 | The default is |
376 | .Dq no . | |
7cac2b65 | 377 | .It Cm GSSAPIAuthentication |
378 | Specifies whether user authentication based on GSSAPI is allowed. | |
540d72c3 | 379 | The default is |
c5448518 | 380 | .Dq yes . |
7cac2b65 | 381 | Note that this option applies to protocol version 2 only. |
05ed7e1e | 382 | .It Cm GSSAPIDelegateCredentials |
383 | Specifies whether delegated credentials are stored in the user's environment. | |
384 | The default is | |
385 | .Dq yes . | |
c5448518 | 386 | .It Cm GSSAPIKeyExchange |
fe4ad273 | 387 | Specifies whether key exchange based on GSSAPI is allowed. GSSAPI key exchange |
388 | doesn't rely on ssh keys to verify host identity. | |
44a053a3 | 389 | The default is |
390 | .Dq yes . | |
c5448518 | 391 | Note that this option applies to protocol version 2 only. |
fe4ad273 | 392 | .It Cm GSSAPICleanupCredentials |
393 | Specifies whether to automatically destroy the user's credentials cache | |
394 | on logout. | |
44a053a3 | 395 | The default is |
396 | .Dq yes . | |
c5448518 | 397 | Note that this option applies to protocol version 2 only. |
c7931c9a | 398 | .It Cm GSSAPICredentialsPath |
399 | If specified, the delegated GSSAPI credential is stored in the | |
400 | given path, overwriting any existing credentials. | |
401 | Paths can be specified with syntax similar to the AuthorizedKeysFile | |
402 | option (i.e., accepting %h and %u tokens). | |
403 | When using this option, | |
404 | setting 'GssapiCleanupCredentials no' is recommended, | |
405 | so logging out of one session | |
406 | doesn't remove the credentials in use by another session of | |
407 | the same user. | |
408 | Currently only implemented for the GSI mechanism. | |
409 | .It Cm GSIAllowLimitedProxy | |
410 | Specifies whether to accept limited proxy credentials for | |
411 | authentication. | |
412 | The default is | |
413 | .Dq no . | |
f713db99 | 414 | .It Cm GSSAPIStrictAcceptorCheck |
415 | Determines whether to be strict about the identity of the GSSAPI acceptor | |
416 | a client authenticates against. If | |
417 | .Dq yes | |
418 | then the client must authenticate against the | |
419 | .Pa host | |
420 | service on the current hostname. If | |
421 | .Dq no | |
422 | then the client may authenticate against any service key stored in the | |
423 | machine's default store. This facility is provided to assist with operation | |
424 | on multi homed machines. | |
425 | The default is | |
426 | .Dq yes . | |
427 | Note that this option applies only to protocol version 2 GSSAPI connections, | |
428 | and setting it to | |
429 | .Dq no | |
430 | may only work with recent Kerberos GSSAPI libraries. | |
f97edba6 | 431 | .It Cm GSSAPIStoreCredentialsOnRekey |
432 | Controls whether the user's GSSAPI credentials should be updated following a | |
433 | successful connection rekeying. This option can be used to accepted renewed | |
434 | or updated credentials from a compatible client. The default is | |
826a9049 | 435 | .Dq no . |
c5448518 | 436 | .It Cm HostbasedAuthentication |
437 | Specifies whether rhosts or /etc/hosts.equiv authentication together | |
438 | with successful public key client host authentication is allowed | |
30460aeb | 439 | (host-based authentication). |
c5448518 | 440 | This option is similar to |
441 | .Cm RhostsRSAAuthentication | |
442 | and applies to protocol version 2 only. | |
52b36949 | 443 | The default is |
c5448518 | 444 | .Dq no . |
30460aeb | 445 | .It Cm HostbasedUsesNameFromPacketOnly |
446 | Specifies whether or not the server will attempt to perform a reverse | |
447 | name lookup when matching the name in the | |
448 | .Pa ~/.shosts , | |
449 | .Pa ~/.rhosts , | |
450 | and | |
451 | .Pa /etc/hosts.equiv | |
452 | files during | |
453 | .Cm HostbasedAuthentication . | |
454 | A setting of | |
455 | .Dq yes | |
456 | means that | |
457 | .Xr sshd 8 | |
458 | uses the name supplied by the client rather than | |
459 | attempting to resolve the name from the TCP connection itself. | |
460 | The default is | |
461 | .Dq no . | |
884dc78b | 462 | .It Cm HostKey |
463 | Specifies a file containing a private host key | |
464 | used by SSH. | |
465 | The default is | |
466 | .Pa /etc/ssh/ssh_host_key | |
467 | for protocol version 1, and | |
468 | .Pa /etc/ssh/ssh_host_rsa_key | |
469 | and | |
470 | .Pa /etc/ssh/ssh_host_dsa_key | |
471 | for protocol version 2. | |
472 | Note that | |
30460aeb | 473 | .Xr sshd 8 |
884dc78b | 474 | will refuse to use a file if it is group/world-accessible. |
475 | It is possible to have multiple host key files. | |
476 | .Dq rsa1 | |
477 | keys are used for version 1 and | |
478 | .Dq dsa | |
479 | or | |
480 | .Dq rsa | |
481 | are used for version 2 of the SSH protocol. | |
482 | .It Cm IgnoreRhosts | |
483 | Specifies that | |
484 | .Pa .rhosts | |
485 | and | |
486 | .Pa .shosts | |
487 | files will not be used in | |
884dc78b | 488 | .Cm RhostsRSAAuthentication |
489 | or | |
490 | .Cm HostbasedAuthentication . | |
491 | .Pp | |
492 | .Pa /etc/hosts.equiv | |
493 | and | |
494 | .Pa /etc/shosts.equiv | |
495 | are still used. | |
496 | The default is | |
497 | .Dq yes . | |
498 | .It Cm IgnoreUserKnownHosts | |
499 | Specifies whether | |
30460aeb | 500 | .Xr sshd 8 |
884dc78b | 501 | should ignore the user's |
2ce0bfe4 | 502 | .Pa ~/.ssh/known_hosts |
884dc78b | 503 | during |
504 | .Cm RhostsRSAAuthentication | |
505 | or | |
506 | .Cm HostbasedAuthentication . | |
507 | The default is | |
508 | .Dq no . | |
884dc78b | 509 | .It Cm KerberosAuthentication |
7cac2b65 | 510 | Specifies whether the password provided by the user for |
884dc78b | 511 | .Cm PasswordAuthentication |
7cac2b65 | 512 | will be validated through the Kerberos KDC. |
884dc78b | 513 | To use this option, the server needs a |
514 | Kerberos servtab which allows the verification of the KDC's identity. | |
30460aeb | 515 | The default is |
884dc78b | 516 | .Dq no . |
12a403af | 517 | .It Cm KerberosGetAFSToken |
08822d99 | 518 | If AFS is active and the user has a Kerberos 5 TGT, attempt to acquire |
12a403af | 519 | an AFS token before accessing the user's home directory. |
30460aeb | 520 | The default is |
12a403af | 521 | .Dq no . |
884dc78b | 522 | .It Cm KerberosOrLocalPasswd |
30460aeb | 523 | If password authentication through Kerberos fails then |
884dc78b | 524 | the password will be validated via any additional local mechanism |
525 | such as | |
526 | .Pa /etc/passwd . | |
30460aeb | 527 | The default is |
884dc78b | 528 | .Dq yes . |
884dc78b | 529 | .It Cm KerberosTicketCleanup |
530 | Specifies whether to automatically destroy the user's ticket cache | |
531 | file on logout. | |
30460aeb | 532 | The default is |
884dc78b | 533 | .Dq yes . |
534 | .It Cm KeyRegenerationInterval | |
535 | In protocol version 1, the ephemeral server key is automatically regenerated | |
536 | after this many seconds (if it has been used). | |
537 | The purpose of regeneration is to prevent | |
538 | decrypting captured sessions by later breaking into the machine and | |
539 | stealing the keys. | |
540 | The key is never stored anywhere. | |
541 | If the value is 0, the key is never regenerated. | |
542 | The default is 3600 (seconds). | |
543 | .It Cm ListenAddress | |
544 | Specifies the local addresses | |
30460aeb | 545 | .Xr sshd 8 |
884dc78b | 546 | should listen on. |
547 | The following forms may be used: | |
548 | .Pp | |
549 | .Bl -item -offset indent -compact | |
550 | .It | |
551 | .Cm ListenAddress | |
552 | .Sm off | |
553 | .Ar host No | Ar IPv4_addr No | Ar IPv6_addr | |
554 | .Sm on | |
555 | .It | |
556 | .Cm ListenAddress | |
557 | .Sm off | |
558 | .Ar host No | Ar IPv4_addr No : Ar port | |
559 | .Sm on | |
560 | .It | |
561 | .Cm ListenAddress | |
562 | .Sm off | |
563 | .Oo | |
564 | .Ar host No | Ar IPv6_addr Oc : Ar port | |
565 | .Sm on | |
566 | .El | |
567 | .Pp | |
568 | If | |
569 | .Ar port | |
570 | is not specified, | |
30460aeb | 571 | sshd will listen on the address and all prior |
884dc78b | 572 | .Cm Port |
7cac2b65 | 573 | options specified. |
574 | The default is to listen on all local addresses. | |
bfe49944 | 575 | Multiple |
884dc78b | 576 | .Cm ListenAddress |
7cac2b65 | 577 | options are permitted. |
578 | Additionally, any | |
884dc78b | 579 | .Cm Port |
30460aeb | 580 | options must precede this option for non-port qualified addresses. |
884dc78b | 581 | .It Cm LoginGraceTime |
582 | The server disconnects after this time if the user has not | |
583 | successfully logged in. | |
584 | If the value is 0, there is no time limit. | |
d03f4262 | 585 | The default is 120 seconds. |
884dc78b | 586 | .It Cm LogLevel |
587 | Gives the verbosity level that is used when logging messages from | |
30460aeb | 588 | .Xr sshd 8 . |
884dc78b | 589 | The possible values are: |
30460aeb | 590 | QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. |
bfe49944 | 591 | The default is INFO. |
592 | DEBUG and DEBUG1 are equivalent. | |
593 | DEBUG2 and DEBUG3 each specify higher levels of debugging output. | |
594 | Logging with a DEBUG level violates the privacy of users and is not recommended. | |
884dc78b | 595 | .It Cm MACs |
596 | Specifies the available MAC (message authentication code) algorithms. | |
597 | The MAC algorithm is used in protocol version 2 | |
598 | for data integrity protection. | |
599 | Multiple algorithms must be comma-separated. | |
30460aeb | 600 | The default is: |
fa0f0f45 | 601 | .Bd -literal -offset indent |
602 | hmac-md5,hmac-sha1,umac-64@openssh.com, | |
603 | hmac-ripemd160,hmac-sha1-96,hmac-md5-96 | |
604 | .Ed | |
30460aeb | 605 | .It Cm Match |
606 | Introduces a conditional block. | |
607 | If all of the criteria on the | |
608 | .Cm Match | |
609 | line are satisfied, the keywords on the following lines override those | |
610 | set in the global section of the config file, until either another | |
611 | .Cm Match | |
612 | line or the end of the file. | |
5156b1a1 | 613 | .Pp |
30460aeb | 614 | The arguments to |
615 | .Cm Match | |
616 | are one or more criteria-pattern pairs. | |
617 | The available criteria are | |
618 | .Cm User , | |
619 | .Cm Group , | |
620 | .Cm Host , | |
621 | and | |
622 | .Cm Address . | |
5156b1a1 | 623 | The match patterns may consist of single entries or comma-separated |
624 | lists and may use the wildcard and negation operators described in the | |
625 | .Sx PATTERNS | |
626 | section of | |
627 | .Xr ssh_config 5 . | |
628 | .Pp | |
629 | The patterns in an | |
630 | .Cm Address | |
631 | criteria may additionally contain addresses to match in CIDR | |
632 | address/masklen format, e.g.\& | |
633 | .Dq 192.0.2.0/24 | |
634 | or | |
635 | .Dq 3ffe:ffff::/32 . | |
636 | Note that the mask length provided must be consistent with the address - | |
637 | it is an error to specify a mask length that is too long for the address | |
638 | or one with bits set in this host portion of the address. | |
639 | For example, | |
640 | .Dq 192.0.2.0/33 | |
641 | and | |
642 | .Dq 192.0.2.0/8 | |
643 | respectively. | |
644 | .Pp | |
30460aeb | 645 | Only a subset of keywords may be used on the lines following a |
646 | .Cm Match | |
647 | keyword. | |
648 | Available keywords are | |
5262cbfb | 649 | .Cm AllowAgentForwarding , |
30460aeb | 650 | .Cm AllowTcpForwarding , |
0b90ac93 | 651 | .Cm Banner , |
5156b1a1 | 652 | .Cm ChrootDirectory , |
30460aeb | 653 | .Cm ForceCommand , |
654 | .Cm GatewayPorts , | |
5156b1a1 | 655 | .Cm GSSAPIAuthentication , |
656 | .Cm HostbasedAuthentication , | |
0b90ac93 | 657 | .Cm KbdInteractiveAuthentication , |
658 | .Cm KerberosAuthentication , | |
5156b1a1 | 659 | .Cm MaxAuthTries , |
660 | .Cm MaxSessions , | |
0b90ac93 | 661 | .Cm PasswordAuthentication , |
5262cbfb | 662 | .Cm PermitEmptyPasswords , |
30460aeb | 663 | .Cm PermitOpen , |
e74dc197 | 664 | .Cm PermitRootLogin , |
0b90ac93 | 665 | .Cm RhostsRSAAuthentication , |
666 | .Cm RSAAuthentication , | |
30460aeb | 667 | .Cm X11DisplayOffset , |
5262cbfb | 668 | .Cm X11Forwarding |
30460aeb | 669 | and |
670 | .Cm X11UseLocalHost . | |
7e82606e | 671 | .It Cm MaxAuthTries |
672 | Specifies the maximum number of authentication attempts permitted per | |
673 | connection. | |
674 | Once the number of failures reaches half this value, | |
675 | additional failures are logged. | |
676 | The default is 6. | |
5156b1a1 | 677 | .It Cm MaxSessions |
678 | Specifies the maximum number of open sessions permitted per network connection. | |
679 | The default is 10. | |
884dc78b | 680 | .It Cm MaxStartups |
681 | Specifies the maximum number of concurrent unauthenticated connections to the | |
30460aeb | 682 | SSH daemon. |
884dc78b | 683 | Additional connections will be dropped until authentication succeeds or the |
684 | .Cm LoginGraceTime | |
685 | expires for a connection. | |
686 | The default is 10. | |
687 | .Pp | |
688 | Alternatively, random early drop can be enabled by specifying | |
689 | the three colon separated values | |
690 | .Dq start:rate:full | |
30460aeb | 691 | (e.g. "10:30:60"). |
692 | .Xr sshd 8 | |
884dc78b | 693 | will refuse connection attempts with a probability of |
694 | .Dq rate/100 | |
695 | (30%) | |
696 | if there are currently | |
697 | .Dq start | |
698 | (10) | |
699 | unauthenticated connections. | |
700 | The probability increases linearly and all connection attempts | |
701 | are refused if the number of unauthenticated connections reaches | |
702 | .Dq full | |
703 | (60). | |
704 | .It Cm PasswordAuthentication | |
705 | Specifies whether password authentication is allowed. | |
706 | The default is | |
707 | .Dq yes . | |
708 | .It Cm PermitEmptyPasswords | |
709 | When password authentication is allowed, it specifies whether the | |
710 | server allows login to accounts with empty password strings. | |
711 | The default is | |
712 | .Dq no . | |
30460aeb | 713 | .It Cm PermitOpen |
714 | Specifies the destinations to which TCP port forwarding is permitted. | |
715 | The forwarding specification must be one of the following forms: | |
716 | .Pp | |
717 | .Bl -item -offset indent -compact | |
718 | .It | |
719 | .Cm PermitOpen | |
720 | .Sm off | |
721 | .Ar host : port | |
722 | .Sm on | |
723 | .It | |
724 | .Cm PermitOpen | |
725 | .Sm off | |
726 | .Ar IPv4_addr : port | |
727 | .Sm on | |
728 | .It | |
729 | .Cm PermitOpen | |
730 | .Sm off | |
731 | .Ar \&[ IPv6_addr \&] : port | |
732 | .Sm on | |
733 | .El | |
734 | .Pp | |
735 | Multiple forwards may be specified by separating them with whitespace. | |
736 | An argument of | |
737 | .Dq any | |
738 | can be used to remove all restrictions and permit any forwarding requests. | |
739 | By default all port forwarding requests are permitted. | |
884dc78b | 740 | .It Cm PermitRootLogin |
dfddba3d | 741 | Specifies whether root can log in using |
884dc78b | 742 | .Xr ssh 1 . |
743 | The argument must be | |
744 | .Dq yes , | |
745 | .Dq without-password , | |
30460aeb | 746 | .Dq forced-commands-only , |
884dc78b | 747 | or |
748 | .Dq no . | |
749 | The default is | |
750 | .Dq yes . | |
751 | .Pp | |
752 | If this option is set to | |
30460aeb | 753 | .Dq without-password , |
dfddba3d | 754 | password authentication is disabled for root. |
884dc78b | 755 | .Pp |
756 | If this option is set to | |
30460aeb | 757 | .Dq forced-commands-only , |
884dc78b | 758 | root login with public key authentication will be allowed, |
759 | but only if the | |
760 | .Ar command | |
761 | option has been specified | |
762 | (which may be useful for taking remote backups even if root login is | |
7cac2b65 | 763 | normally not allowed). |
764 | All other authentication methods are disabled for root. | |
884dc78b | 765 | .Pp |
766 | If this option is set to | |
30460aeb | 767 | .Dq no , |
dfddba3d | 768 | root is not allowed to log in. |
08822d99 | 769 | .It Cm PermitTunnel |
770 | Specifies whether | |
771 | .Xr tun 4 | |
772 | device forwarding is allowed. | |
773 | The argument must be | |
774 | .Dq yes , | |
30460aeb | 775 | .Dq point-to-point |
776 | (layer 3), | |
08822d99 | 777 | .Dq ethernet |
30460aeb | 778 | (layer 2), or |
08822d99 | 779 | .Dq no . |
30460aeb | 780 | Specifying |
781 | .Dq yes | |
782 | permits both | |
783 | .Dq point-to-point | |
784 | and | |
785 | .Dq ethernet . | |
08822d99 | 786 | The default is |
787 | .Dq no . | |
d03f4262 | 788 | .It Cm PermitUserEnvironment |
789 | Specifies whether | |
790 | .Pa ~/.ssh/environment | |
791 | and | |
792 | .Cm environment= | |
793 | options in | |
794 | .Pa ~/.ssh/authorized_keys | |
795 | are processed by | |
30460aeb | 796 | .Xr sshd 8 . |
d03f4262 | 797 | The default is |
798 | .Dq no . | |
799 | Enabling environment processing may enable users to bypass access | |
800 | restrictions in some configurations using mechanisms such as | |
801 | .Ev LD_PRELOAD . | |
884dc78b | 802 | .It Cm PidFile |
276b07a3 | 803 | Specifies the file that contains the process ID of the |
30460aeb | 804 | SSH daemon. |
884dc78b | 805 | The default is |
806 | .Pa /var/run/sshd.pid . | |
807 | .It Cm Port | |
808 | Specifies the port number that | |
30460aeb | 809 | .Xr sshd 8 |
884dc78b | 810 | listens on. |
811 | The default is 22. | |
812 | Multiple options of this type are permitted. | |
813 | See also | |
814 | .Cm ListenAddress . | |
815 | .It Cm PrintLastLog | |
816 | Specifies whether | |
30460aeb | 817 | .Xr sshd 8 |
dfddba3d | 818 | should print the date and time of the last user login when a user logs |
819 | in interactively. | |
884dc78b | 820 | The default is |
821 | .Dq yes . | |
822 | .It Cm PrintMotd | |
823 | Specifies whether | |
30460aeb | 824 | .Xr sshd 8 |
884dc78b | 825 | should print |
826 | .Pa /etc/motd | |
827 | when a user logs in interactively. | |
828 | (On some systems it is also printed by the shell, | |
829 | .Pa /etc/profile , | |
830 | or equivalent.) | |
831 | The default is | |
832 | .Dq yes . | |
833 | .It Cm Protocol | |
834 | Specifies the protocol versions | |
30460aeb | 835 | .Xr sshd 8 |
d03f4262 | 836 | supports. |
884dc78b | 837 | The possible values are |
30460aeb | 838 | .Sq 1 |
884dc78b | 839 | and |
30460aeb | 840 | .Sq 2 . |
884dc78b | 841 | Multiple versions must be comma-separated. |
842 | The default is | |
843 | .Dq 2,1 . | |
d03f4262 | 844 | Note that the order of the protocol list does not indicate preference, |
845 | because the client selects among multiple protocol versions offered | |
846 | by the server. | |
847 | Specifying | |
848 | .Dq 2,1 | |
849 | is identical to | |
850 | .Dq 1,2 . | |
884dc78b | 851 | .It Cm PubkeyAuthentication |
852 | Specifies whether public key authentication is allowed. | |
853 | The default is | |
854 | .Dq yes . | |
855 | Note that this option applies to protocol version 2 only. | |
884dc78b | 856 | .It Cm RhostsRSAAuthentication |
857 | Specifies whether rhosts or /etc/hosts.equiv authentication together | |
858 | with successful RSA host authentication is allowed. | |
859 | The default is | |
860 | .Dq no . | |
861 | This option applies to protocol version 1 only. | |
862 | .It Cm RSAAuthentication | |
863 | Specifies whether pure RSA authentication is allowed. | |
864 | The default is | |
865 | .Dq yes . | |
866 | This option applies to protocol version 1 only. | |
867 | .It Cm ServerKeyBits | |
868 | Defines the number of bits in the ephemeral protocol version 1 server key. | |
5156b1a1 | 869 | The minimum value is 512, and the default is 1024. |
884dc78b | 870 | .It Cm StrictModes |
871 | Specifies whether | |
30460aeb | 872 | .Xr sshd 8 |
884dc78b | 873 | should check file modes and ownership of the |
874 | user's files and home directory before accepting login. | |
875 | This is normally desirable because novices sometimes accidentally leave their | |
876 | directory or files world-writable. | |
877 | The default is | |
878 | .Dq yes . | |
879 | .It Cm Subsystem | |
30460aeb | 880 | Configures an external subsystem (e.g. file transfer daemon). |
881 | Arguments should be a subsystem name and a command (with optional arguments) | |
882 | to execute upon subsystem request. | |
e74dc197 | 883 | .Pp |
884dc78b | 884 | The command |
885 | .Xr sftp-server 8 | |
886 | implements the | |
887 | .Dq sftp | |
888 | file transfer subsystem. | |
e74dc197 | 889 | .Pp |
890 | Alternately the name | |
891 | .Dq internal-sftp | |
892 | implements an in-process | |
893 | .Dq sftp | |
894 | server. | |
895 | This may simplify configurations using | |
896 | .Cm ChrootDirectory | |
897 | to force a different filesystem root on clients. | |
898 | .Pp | |
884dc78b | 899 | By default no subsystems are defined. |
900 | Note that this option applies to protocol version 2 only. | |
901 | .It Cm SyslogFacility | |
902 | Gives the facility code that is used when logging messages from | |
30460aeb | 903 | .Xr sshd 8 . |
884dc78b | 904 | The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, |
905 | LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. | |
906 | The default is AUTH. | |
540d72c3 | 907 | .It Cm TCPKeepAlive |
908 | Specifies whether the system should send TCP keepalive messages to the | |
909 | other side. | |
910 | If they are sent, death of the connection or crash of one | |
911 | of the machines will be properly noticed. | |
912 | However, this means that | |
913 | connections will die if the route is down temporarily, and some people | |
914 | find it annoying. | |
915 | On the other hand, if TCP keepalives are not sent, | |
916 | sessions may hang indefinitely on the server, leaving | |
917 | .Dq ghost | |
918 | users and consuming server resources. | |
919 | .Pp | |
920 | The default is | |
921 | .Dq yes | |
922 | (to send TCP keepalive messages), and the server will notice | |
923 | if the network goes down or the client host crashes. | |
924 | This avoids infinitely hanging sessions. | |
925 | .Pp | |
926 | To disable TCP keepalive messages, the value should be set to | |
927 | .Dq no . | |
7cac2b65 | 928 | .It Cm UseDNS |
929 | Specifies whether | |
30460aeb | 930 | .Xr sshd 8 |
8b32eddc | 931 | should look up the remote host name and check that |
7cac2b65 | 932 | the resolved host name for the remote IP address maps back to the |
933 | very same IP address. | |
934 | The default is | |
935 | .Dq yes . | |
884dc78b | 936 | .It Cm UseLogin |
937 | Specifies whether | |
938 | .Xr login 1 | |
939 | is used for interactive login sessions. | |
940 | The default is | |
941 | .Dq no . | |
942 | Note that | |
943 | .Xr login 1 | |
944 | is never used for remote command execution. | |
945 | Note also, that if this is enabled, | |
946 | .Cm X11Forwarding | |
947 | will be disabled because | |
948 | .Xr login 1 | |
949 | does not know how to handle | |
950 | .Xr xauth 1 | |
bfe49944 | 951 | cookies. |
952 | If | |
884dc78b | 953 | .Cm UsePrivilegeSeparation |
954 | is specified, it will be disabled after authentication. | |
7cac2b65 | 955 | .It Cm UsePAM |
7e82606e | 956 | Enables the Pluggable Authentication Module interface. |
957 | If set to | |
958 | .Dq yes | |
959 | this will enable PAM authentication using | |
960 | .Cm ChallengeResponseAuthentication | |
30460aeb | 961 | and |
962 | .Cm PasswordAuthentication | |
963 | in addition to PAM account and session module processing for all | |
964 | authentication types. | |
7e82606e | 965 | .Pp |
966 | Because PAM challenge-response authentication usually serves an equivalent | |
967 | role to password authentication, you should disable either | |
968 | .Cm PasswordAuthentication | |
969 | or | |
970 | .Cm ChallengeResponseAuthentication. | |
971 | .Pp | |
972 | If | |
973 | .Cm UsePAM | |
974 | is enabled, you will not be able to run | |
975 | .Xr sshd 8 | |
976 | as a non-root user. | |
977 | The default is | |
540d72c3 | 978 | .Dq no . |
d037a8b0 | 979 | .It Cm PermitPAMUserChange |
980 | If set to | |
981 | .Dq yes | |
982 | this will enable PAM authentication to change the name of the user being | |
983 | authenticated. The default is | |
984 | .Dq no . | |
884dc78b | 985 | .It Cm UsePrivilegeSeparation |
986 | Specifies whether | |
30460aeb | 987 | .Xr sshd 8 |
884dc78b | 988 | separates privileges by creating an unprivileged child process |
bfe49944 | 989 | to deal with incoming network traffic. |
990 | After successful authentication, another process will be created that has | |
991 | the privilege of the authenticated user. | |
992 | The goal of privilege separation is to prevent privilege | |
884dc78b | 993 | escalation by containing any corruption within the unprivileged processes. |
994 | The default is | |
995 | .Dq yes . | |
884dc78b | 996 | .It Cm X11DisplayOffset |
997 | Specifies the first display number available for | |
30460aeb | 998 | .Xr sshd 8 Ns 's |
884dc78b | 999 | X11 forwarding. |
30460aeb | 1000 | This prevents sshd from interfering with real X11 servers. |
884dc78b | 1001 | The default is 10. |
1002 | .It Cm X11Forwarding | |
1003 | Specifies whether X11 forwarding is permitted. | |
d03f4262 | 1004 | The argument must be |
1005 | .Dq yes | |
1006 | or | |
1007 | .Dq no . | |
884dc78b | 1008 | The default is |
1009 | .Dq no . | |
d03f4262 | 1010 | .Pp |
1011 | When X11 forwarding is enabled, there may be additional exposure to | |
1012 | the server and to client displays if the | |
30460aeb | 1013 | .Xr sshd 8 |
d03f4262 | 1014 | proxy display is configured to listen on the wildcard address (see |
1015 | .Cm X11UseLocalhost | |
30460aeb | 1016 | below), though this is not the default. |
d03f4262 | 1017 | Additionally, the authentication spoofing and authentication data |
1018 | verification and substitution occur on the client side. | |
1019 | The security risk of using X11 forwarding is that the client's X11 | |
30460aeb | 1020 | display server may be exposed to attack when the SSH client requests |
d03f4262 | 1021 | forwarding (see the warnings for |
1022 | .Cm ForwardX11 | |
1023 | in | |
7cac2b65 | 1024 | .Xr ssh_config 5 ) . |
d03f4262 | 1025 | A system administrator may have a stance in which they want to |
1026 | protect clients that may expose themselves to attack by unwittingly | |
1027 | requesting X11 forwarding, which can warrant a | |
1028 | .Dq no | |
1029 | setting. | |
1030 | .Pp | |
1031 | Note that disabling X11 forwarding does not prevent users from | |
1032 | forwarding X11 traffic, as users can always install their own forwarders. | |
884dc78b | 1033 | X11 forwarding is automatically disabled if |
1034 | .Cm UseLogin | |
1035 | is enabled. | |
1036 | .It Cm X11UseLocalhost | |
1037 | Specifies whether | |
30460aeb | 1038 | .Xr sshd 8 |
884dc78b | 1039 | should bind the X11 forwarding server to the loopback address or to |
bfe49944 | 1040 | the wildcard address. |
1041 | By default, | |
30460aeb | 1042 | sshd binds the forwarding server to the loopback address and sets the |
884dc78b | 1043 | hostname part of the |
1044 | .Ev DISPLAY | |
1045 | environment variable to | |
1046 | .Dq localhost . | |
d03f4262 | 1047 | This prevents remote hosts from connecting to the proxy display. |
884dc78b | 1048 | However, some older X11 clients may not function with this |
1049 | configuration. | |
1050 | .Cm X11UseLocalhost | |
1051 | may be set to | |
1052 | .Dq no | |
1053 | to specify that the forwarding server should be bound to the wildcard | |
1054 | address. | |
1055 | The argument must be | |
1056 | .Dq yes | |
1057 | or | |
1058 | .Dq no . | |
1059 | The default is | |
1060 | .Dq yes . | |
1061 | .It Cm XAuthLocation | |
d03f4262 | 1062 | Specifies the full pathname of the |
884dc78b | 1063 | .Xr xauth 1 |
1064 | program. | |
1065 | The default is | |
1066 | .Pa /usr/X11R6/bin/xauth . | |
1067 | .El | |
30460aeb | 1068 | .Sh TIME FORMATS |
1069 | .Xr sshd 8 | |
884dc78b | 1070 | command-line arguments and configuration file options that specify time |
1071 | may be expressed using a sequence of the form: | |
1072 | .Sm off | |
d03f4262 | 1073 | .Ar time Op Ar qualifier , |
884dc78b | 1074 | .Sm on |
1075 | where | |
1076 | .Ar time | |
1077 | is a positive integer value and | |
1078 | .Ar qualifier | |
1079 | is one of the following: | |
1080 | .Pp | |
1081 | .Bl -tag -width Ds -compact -offset indent | |
30460aeb | 1082 | .It Aq Cm none |
884dc78b | 1083 | seconds |
1084 | .It Cm s | Cm S | |
1085 | seconds | |
1086 | .It Cm m | Cm M | |
1087 | minutes | |
1088 | .It Cm h | Cm H | |
1089 | hours | |
1090 | .It Cm d | Cm D | |
1091 | days | |
1092 | .It Cm w | Cm W | |
1093 | weeks | |
1094 | .El | |
1095 | .Pp | |
1096 | Each member of the sequence is added together to calculate | |
1097 | the total time value. | |
1098 | .Pp | |
1099 | Time format examples: | |
1100 | .Pp | |
1101 | .Bl -tag -width Ds -compact -offset indent | |
1102 | .It 600 | |
1103 | 600 seconds (10 minutes) | |
1104 | .It 10m | |
1105 | 10 minutes | |
1106 | .It 1h30m | |
1107 | 1 hour 30 minutes (90 minutes) | |
1108 | .El | |
1109 | .Sh FILES | |
1110 | .Bl -tag -width Ds | |
1111 | .It Pa /etc/ssh/sshd_config | |
1112 | Contains configuration data for | |
30460aeb | 1113 | .Xr sshd 8 . |
884dc78b | 1114 | This file should be writable by root only, but it is recommended |
1115 | (though not necessary) that it be world-readable. | |
1116 | .El | |
7cac2b65 | 1117 | .Sh SEE ALSO |
1118 | .Xr sshd 8 | |
884dc78b | 1119 | .Sh AUTHORS |
1120 | OpenSSH is a derivative of the original and free | |
1121 | ssh 1.2.12 release by Tatu Ylonen. | |
1122 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, | |
1123 | Theo de Raadt and Dug Song | |
1124 | removed many bugs, re-added newer features and | |
1125 | created OpenSSH. | |
1126 | Markus Friedl contributed the support for SSH | |
1127 | protocol versions 1.5 and 2.0. | |
1128 | Niels Provos and Markus Friedl contributed support | |
1129 | for privilege separation. |