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authorColin Watson <cjwatson@debian.org>2007-12-23 15:20:40 +0000
committerColin Watson <cjwatson@debian.org>2007-12-23 15:20:40 +0000
commit70847d299887abb96f8703ca99db6d817b78960e (patch)
treef8e6473c82fb339cbbb1d6598a9dc1c7f122c7cc /ssh_config.0
parent09bfb50d0dc78390593749e6f37e403da404dc94 (diff)
parent086ea76990b1e6287c24b6db74adffd4605eb3b0 (diff)
Import OpenSSH 4.7p1.
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1SSH_CONFIG(5) OpenBSD Programmer's Manual SSH_CONFIG(5)
2
3NAME
4 ssh_config - OpenSSH SSH client configuration files
5
6SYNOPSIS
7 ~/.ssh/config
8 /etc/ssh/ssh_config
9
10DESCRIPTION
11 ssh(1) obtains configuration data from the following sources in the fol-
12 lowing order:
13
14 1. command-line options
15 2. user's configuration file (~/.ssh/config)
16 3. system-wide configuration file (/etc/ssh/ssh_config)
17
18 For each parameter, the first obtained value will be used. The configu-
19 ration files contain sections separated by ``Host'' specifications, and
20 that section is only applied for hosts that match one of the patterns
21 given in the specification. The matched host name is the one given on
22 the command line.
23
24 Since the first obtained value for each parameter is used, more host-spe-
25 cific declarations should be given near the beginning of the file, and
26 general defaults at the end.
27
28 The configuration file has the following format:
29
30 Empty lines and lines starting with `#' are comments. Otherwise a line
31 is of the format ``keyword arguments''. Configuration options may be
32 separated by whitespace or optional whitespace and exactly one `='; the
33 latter format is useful to avoid the need to quote whitespace when speci-
34 fying configuration options using the ssh, scp, and sftp -o option. Ar-
35 guments may optionally be enclosed in double quotes (") in order to rep-
36 resent arguments containing spaces.
37
38 The possible keywords and their meanings are as follows (note that key-
39 words are case-insensitive and arguments are case-sensitive):
40
41 Host Restricts the following declarations (up to the next Host key-
42 word) to be only for those hosts that match one of the patterns
43 given after the keyword. A single `*' as a pattern can be used
44 to provide global defaults for all hosts. The host is the
45 hostname argument given on the command line (i.e. the name is not
46 converted to a canonicalized host name before matching).
47
48 See PATTERNS for more information on patterns.
49
50 AddressFamily
51 Specifies which address family to use when connecting. Valid ar-
52 guments are ``any'', ``inet'' (use IPv4 only), or ``inet6'' (use
53 IPv6 only).
54
55 BatchMode
56 If set to ``yes'', passphrase/password querying will be disabled.
57 This option is useful in scripts and other batch jobs where no
58 user is present to supply the password. The argument must be
59 ``yes'' or ``no''. The default is ``no''.
60
61 BindAddress
62 Use the specified address on the local machine as the source ad-
63 dress of the connection. Only useful on systems with more than
64 one address. Note that this option does not work if
65 UsePrivilegedPort is set to ``yes''.
66
67 ChallengeResponseAuthentication
68 Specifies whether to use challenge-response authentication. The
69 argument to this keyword must be ``yes'' or ``no''. The default
70 is ``yes''.
71
72 CheckHostIP
73 If this flag is set to ``yes'', ssh(1) will additionally check
74 the host IP address in the known_hosts file. This allows ssh to
75 detect if a host key changed due to DNS spoofing. If the option
76 is set to ``no'', the check will not be executed. The default is
77 ``yes''.
78
79 Cipher Specifies the cipher to use for encrypting the session in proto-
80 col version 1. Currently, ``blowfish'', ``3des'', and ``des''
81 are supported. des is only supported in the ssh(1) client for
82 interoperability with legacy protocol 1 implementations that do
83 not support the 3des cipher. Its use is strongly discouraged due
84 to cryptographic weaknesses. The default is ``3des''.
85
86 Ciphers
87 Specifies the ciphers allowed for protocol version 2 in order of
88 preference. Multiple ciphers must be comma-separated. The sup-
89 ported ciphers are ``3des-cbc'', ``aes128-cbc'', ``aes192-cbc'',
90 ``aes256-cbc'', ``aes128-ctr'', ``aes192-ctr'', ``aes256-ctr'',
91 ``arcfour128'', ``arcfour256'', ``arcfour'', ``blowfish-cbc'',
92 and ``cast128-cbc''. The default is:
93
94 aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,
95 arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,
96 aes192-ctr,aes256-ctr
97
98 ClearAllForwardings
99 Specifies that all local, remote, and dynamic port forwardings
100 specified in the configuration files or on the command line be
101 cleared. This option is primarily useful when used from the
102 ssh(1) command line to clear port forwardings set in configura-
103 tion files, and is automatically set by scp(1) and sftp(1). The
104 argument must be ``yes'' or ``no''. The default is ``no''.
105
106 Compression
107 Specifies whether to use compression. The argument must be
108 ``yes'' or ``no''. The default is ``no''.
109
110 CompressionLevel
111 Specifies the compression level to use if compression is enabled.
112 The argument must be an integer from 1 (fast) to 9 (slow, best).
113 The default level is 6, which is good for most applications. The
114 meaning of the values is the same as in gzip(1). Note that this
115 option applies to protocol version 1 only.
116
117 ConnectionAttempts
118 Specifies the number of tries (one per second) to make before ex-
119 iting. The argument must be an integer. This may be useful in
120 scripts if the connection sometimes fails. The default is 1.
121
122 ConnectTimeout
123 Specifies the timeout (in seconds) used when connecting to the
124 SSH server, instead of using the default system TCP timeout.
125 This value is used only when the target is down or really un-
126 reachable, not when it refuses the connection.
127
128 ControlMaster
129 Enables the sharing of multiple sessions over a single network
130 connection. When set to ``yes'', ssh(1) will listen for connec-
131 tions on a control socket specified using the ControlPath argu-
132 ment. Additional sessions can connect to this socket using the
133 same ControlPath with ControlMaster set to ``no'' (the default).
134 These sessions will try to reuse the master instance's network
135 connection rather than initiating new ones, but will fall back to
136 connecting normally if the control socket does not exist, or is
137 not listening.
138
139 Setting this to ``ask'' will cause ssh to listen for control con-
140 nections, but require confirmation using the SSH_ASKPASS program
141 before they are accepted (see ssh-add(1) for details). If the
142 ControlPath cannot be opened, ssh will continue without connect-
143 ing to a master instance.
144
145 X11 and ssh-agent(1) forwarding is supported over these multi-
146 plexed connections, however the display and agent forwarded will
147 be the one belonging to the master connection i.e. it is not pos-
148 sible to forward multiple displays or agents.
149
150 Two additional options allow for opportunistic multiplexing: try
151 to use a master connection but fall back to creating a new one if
152 one does not already exist. These options are: ``auto'' and
153 ``autoask''. The latter requires confirmation like the ``ask''
154 option.
155
156 ControlPath
157 Specify the path to the control socket used for connection shar-
158 ing as described in the ControlMaster section above or the string
159 ``none'' to disable connection sharing. In the path, `%l' will
160 be substituted by the local host name, `%h' will be substituted
161 by the target host name, `%p' the port, and `%r' by the remote
162 login username. It is recommended that any ControlPath used for
163 opportunistic connection sharing include at least %h, %p, and %r.
164 This ensures that shared connections are uniquely identified.
165
166 DynamicForward
167 Specifies that a TCP port on the local machine be forwarded over
168 the secure channel, and the application protocol is then used to
169 determine where to connect to from the remote machine.
170
171 The argument must be [bind_address:]port. IPv6 addresses can be
172 specified by enclosing addresses in square brackets or by using
173 an alternative syntax: [bind_address/]port. By default, the lo-
174 cal port is bound in accordance with the GatewayPorts setting.
175 However, an explicit bind_address may be used to bind the connec-
176 tion to a specific address. The bind_address of ``localhost''
177 indicates that the listening port be bound for local use only,
178 while an empty address or `*' indicates that the port should be
179 available from all interfaces.
180
181 Currently the SOCKS4 and SOCKS5 protocols are supported, and
182 ssh(1) will act as a SOCKS server. Multiple forwardings may be
183 specified, and additional forwardings can be given on the command
184 line. Only the superuser can forward privileged ports.
185
186 EnableSSHKeysign
187 Setting this option to ``yes'' in the global client configuration
188 file /etc/ssh/ssh_config enables the use of the helper program
189 ssh-keysign(8) during HostbasedAuthentication. The argument must
190 be ``yes'' or ``no''. The default is ``no''. This option should
191 be placed in the non-hostspecific section. See ssh-keysign(8)
192 for more information.
193
194 EscapeChar
195 Sets the escape character (default: `~'). The escape character
196 can also be set on the command line. The argument should be a
197 single character, `^' followed by a letter, or ``none'' to dis-
198 able the escape character entirely (making the connection trans-
199 parent for binary data).
200
201 ExitOnForwardFailure
202 Specifies whether ssh(1) should terminate the connection if it
203 cannot set up all requested dynamic, tunnel, local, and remote
204 port forwardings. The argument must be ``yes'' or ``no''. The
205 default is ``no''.
206
207 ForwardAgent
208 Specifies whether the connection to the authentication agent (if
209 any) will be forwarded to the remote machine. The argument must
210 be ``yes'' or ``no''. The default is ``no''.
211
212 Agent forwarding should be enabled with caution. Users with the
213 ability to bypass file permissions on the remote host (for the
214 agent's Unix-domain socket) can access the local agent through
215 the forwarded connection. An attacker cannot obtain key material
216 from the agent, however they can perform operations on the keys
217 that enable them to authenticate using the identities loaded into
218 the agent.
219
220 ForwardX11
221 Specifies whether X11 connections will be automatically redirect-
222 ed over the secure channel and DISPLAY set. The argument must be
223 ``yes'' or ``no''. The default is ``no''.
224
225 X11 forwarding should be enabled with caution. Users with the
226 ability to bypass file permissions on the remote host (for the
227 user's X11 authorization database) can access the local X11 dis-
228 play through the forwarded connection. An attacker may then be
229 able to perform activities such as keystroke monitoring if the
230 ForwardX11Trusted option is also enabled.
231
232 ForwardX11Trusted
233 If this option is set to ``yes'', remote X11 clients will have
234 full access to the original X11 display.
235
236 If this option is set to ``no'', remote X11 clients will be con-
237 sidered untrusted and prevented from stealing or tampering with
238 data belonging to trusted X11 clients. Furthermore, the xauth(1)
239 token used for the session will be set to expire after 20 min-
240 utes. Remote clients will be refused access after this time.
241
242 The default is ``no''.
243
244 See the X11 SECURITY extension specification for full details on
245 the restrictions imposed on untrusted clients.
246
247 GatewayPorts
248 Specifies whether remote hosts are allowed to connect to local
249 forwarded ports. By default, ssh(1) binds local port forwardings
250 to the loopback address. This prevents other remote hosts from
251 connecting to forwarded ports. GatewayPorts can be used to spec-
252 ify that ssh should bind local port forwardings to the wildcard
253 address, thus allowing remote hosts to connect to forwarded
254 ports. The argument must be ``yes'' or ``no''. The default is
255 ``no''.
256
257 GlobalKnownHostsFile
258 Specifies a file to use for the global host key database instead
259 of /etc/ssh/ssh_known_hosts.
260
261 GSSAPIAuthentication
262 Specifies whether user authentication based on GSSAPI is allowed.
263 The default is ``no''. Note that this option applies to protocol
264 version 2 only.
265
266 GSSAPIDelegateCredentials
267 Forward (delegate) credentials to the server. The default is
268 ``no''. Note that this option applies to protocol version 2 on-
269 ly.
270
271 HashKnownHosts
272 Indicates that ssh(1) should hash host names and addresses when
273 they are added to ~/.ssh/known_hosts. These hashed names may be
274 used normally by ssh(1) and sshd(8), but they do not reveal iden-
275 tifying information should the file's contents be disclosed. The
276 default is ``no''. Note that existing names and addresses in
277 known hosts files will not be converted automatically, but may be
278 manually hashed using ssh-keygen(1).
279
280 HostbasedAuthentication
281 Specifies whether to try rhosts based authentication with public
282 key authentication. The argument must be ``yes'' or ``no''. The
283 default is ``no''. This option applies to protocol version 2 on-
284 ly and is similar to RhostsRSAAuthentication.
285
286 HostKeyAlgorithms
287 Specifies the protocol version 2 host key algorithms that the
288 client wants to use in order of preference. The default for this
289 option is: ``ssh-rsa,ssh-dss''.
290
291 HostKeyAlias
292 Specifies an alias that should be used instead of the real host
293 name when looking up or saving the host key in the host key
294 database files. This option is useful for tunneling SSH connec-
295 tions or for multiple servers running on a single host.
296
297 HostName
298 Specifies the real host name to log into. This can be used to
299 specify nicknames or abbreviations for hosts. The default is the
300 name given on the command line. Numeric IP addresses are also
301 permitted (both on the command line and in HostName specifica-
302 tions).
303
304 IdentitiesOnly
305 Specifies that ssh(1) should only use the authentication identity
306 files configured in the ssh_config files, even if ssh-agent(1)
307 offers more identities. The argument to this keyword must be
308 ``yes'' or ``no''. This option is intended for situations where
309 ssh-agent offers many different identities. The default is
310 ``no''.
311
312 IdentityFile
313 Specifies a file from which the user's RSA or DSA authentication
314 identity is read. The default is ~/.ssh/identity for protocol
315 version 1, and ~/.ssh/id_rsa and ~/.ssh/id_dsa for protocol ver-
316 sion 2. Additionally, any identities represented by the authen-
317 tication agent will be used for authentication.
318
319 The file name may use the tilde syntax to refer to a user's home
320 directory or one of the following escape characters: `%d' (local
321 user's home directory), `%u' (local user name), `%l' (local host
322 name), `%h' (remote host name) or `%r' (remote user name).
323
324 It is possible to have multiple identity files specified in con-
325 figuration files; all these identities will be tried in sequence.
326
327 KbdInteractiveDevices
328 Specifies the list of methods to use in keyboard-interactive au-
329 thentication. Multiple method names must be comma-separated.
330 The default is to use the server specified list. The methods
331 available vary depending on what the server supports. For an
332 OpenSSH server, it may be zero or more of: ``bsdauth'', ``pam'',
333 and ``skey''.
334
335 LocalCommand
336 Specifies a command to execute on the local machine after suc-
337 cessfully connecting to the server. The command string extends
338 to the end of the line, and is executed with /bin/sh. This di-
339 rective is ignored unless PermitLocalCommand has been enabled.
340
341 LocalForward
342 Specifies that a TCP port on the local machine be forwarded over
343 the secure channel to the specified host and port from the remote
344 machine. The first argument must be [bind_address:]port and the
345 second argument must be host:hostport. IPv6 addresses can be
346 specified by enclosing addresses in square brackets or by using
347 an alternative syntax: [bind_address/]port and host/hostport.
348 Multiple forwardings may be specified, and additional forwardings
349 can be given on the command line. Only the superuser can forward
350 privileged ports. By default, the local port is bound in accor-
351 dance with the GatewayPorts setting. However, an explicit
352 bind_address may be used to bind the connection to a specific ad-
353 dress. The bind_address of ``localhost'' indicates that the lis-
354 tening port be bound for local use only, while an empty address
355 or `*' indicates that the port should be available from all in-
356 terfaces.
357
358 LogLevel
359 Gives the verbosity level that is used when logging messages from
360 ssh(1). The possible values are: QUIET, FATAL, ERROR, INFO, VER-
361 BOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO.
362 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify
363 higher levels of verbose output.
364
365 MACs Specifies the MAC (message authentication code) algorithms in or-
366 der of preference. The MAC algorithm is used in protocol version
367 2 for data integrity protection. Multiple algorithms must be
368 comma-separated. The default is:
369
370 hmac-md5,hmac-sha1,umac-64@openssh.com,
371 hmac-ripemd160,hmac-sha1-96,hmac-md5-96
372
373 NoHostAuthenticationForLocalhost
374 This option can be used if the home directory is shared across
375 machines. In this case localhost will refer to a different ma-
376 chine on each of the machines and the user will get many warnings
377 about changed host keys. However, this option disables host au-
378 thentication for localhost. The argument to this keyword must be
379 ``yes'' or ``no''. The default is to check the host key for lo-
380 calhost.
381
382 NumberOfPasswordPrompts
383 Specifies the number of password prompts before giving up. The
384 argument to this keyword must be an integer. The default is 3.
385
386 PasswordAuthentication
387 Specifies whether to use password authentication. The argument
388 to this keyword must be ``yes'' or ``no''. The default is
389 ``yes''.
390
391 PermitLocalCommand
392 Allow local command execution via the LocalCommand option or us-
393 ing the !command escape sequence in ssh(1). The argument must be
394 ``yes'' or ``no''. The default is ``no''.
395
396 Port Specifies the port number to connect on the remote host. The de-
397 fault is 22.
398
399 PreferredAuthentications
400 Specifies the order in which the client should try protocol 2 au-
401 thentication methods. This allows a client to prefer one method
402 (e.g. keyboard-interactive) over another method (e.g. password)
403 The default for this option is: ``gssapi-with-mic,hostbased,
404 publickey, keyboard-interactive, password''.
405
406 Protocol
407 Specifies the protocol versions ssh(1) should support in order of
408 preference. The possible values are `1' and `2'. Multiple ver-
409 sions must be comma-separated. The default is ``2,1''. This
410 means that ssh tries version 2 and falls back to version 1 if
411 version 2 is not available.
412
413 ProxyCommand
414 Specifies the command to use to connect to the server. The com-
415 mand string extends to the end of the line, and is executed with
416 /bin/sh. In the command string, `%h' will be substituted by the
417 host name to connect and `%p' by the port. The command can be
418 basically anything, and should read from its standard input and
419 write to its standard output. It should eventually connect an
420 sshd(8) server running on some machine, or execute sshd -i some-
421 where. Host key management will be done using the HostName of
422 the host being connected (defaulting to the name typed by the us-
423 er). Setting the command to ``none'' disables this option en-
424 tirely. Note that CheckHostIP is not available for connects with
425 a proxy command.
426
427 This directive is useful in conjunction with nc(1) and its proxy
428 support. For example, the following directive would connect via
429 an HTTP proxy at 192.0.2.0:
430
431 ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
432
433 PubkeyAuthentication
434 Specifies whether to try public key authentication. The argument
435 to this keyword must be ``yes'' or ``no''. The default is
436 ``yes''. This option applies to protocol version 2 only.
437
438 RekeyLimit
439 Specifies the maximum amount of data that may be transmitted be-
440 fore the session key is renegotiated. The argument is the number
441 of bytes, with an optional suffix of `K', `M', or `G' to indicate
442 Kilobytes, Megabytes, or Gigabytes, respectively. The default is
443 between `1G' and `4G', depending on the cipher. This option ap-
444 plies to protocol version 2 only.
445
446 RemoteForward
447 Specifies that a TCP port on the remote machine be forwarded over
448 the secure channel to the specified host and port from the local
449 machine. The first argument must be [bind_address:]port and the
450 second argument must be host:hostport. IPv6 addresses can be
451 specified by enclosing addresses in square brackets or by using
452 an alternative syntax: [bind_address/]port and host/hostport.
453 Multiple forwardings may be specified, and additional forwardings
454 can be given on the command line. Only the superuser can forward
455 privileged ports.
456
457 If the bind_address is not specified, the default is to only bind
458 to loopback addresses. If the bind_address is `*' or an empty
459 string, then the forwarding is requested to listen on all inter-
460 faces. Specifying a remote bind_address will only succeed if the
461 server's GatewayPorts option is enabled (see sshd_config(5)).
462
463 RhostsRSAAuthentication
464 Specifies whether to try rhosts based authentication with RSA
465 host authentication. The argument must be ``yes'' or ``no''.
466 The default is ``no''. This option applies to protocol version 1
467 only and requires ssh(1) to be setuid root.
468
469 RSAAuthentication
470 Specifies whether to try RSA authentication. The argument to
471 this keyword must be ``yes'' or ``no''. RSA authentication will
472 only be attempted if the identity file exists, or an authentica-
473 tion agent is running. The default is ``yes''. Note that this
474 option applies to protocol version 1 only.
475
476 SendEnv
477 Specifies what variables from the local environ(7) should be sent
478 to the server. Note that environment passing is only supported
479 for protocol 2. The server must also support it, and the server
480 must be configured to accept these environment variables. Refer
481 to AcceptEnv in sshd_config(5) for how to configure the server.
482 Variables are specified by name, which may contain wildcard char-
483 acters. Multiple environment variables may be separated by
484 whitespace or spread across multiple SendEnv directives. The de-
485 fault is not to send any environment variables.
486
487 See PATTERNS for more information on patterns.
488
489 ServerAliveCountMax
490 Sets the number of server alive messages (see below) which may be
491 sent without ssh(1) receiving any messages back from the server.
492 If this threshold is reached while server alive messages are be-
493 ing sent, ssh will disconnect from the server, terminating the
494 session. It is important to note that the use of server alive
495 messages is very different from TCPKeepAlive (below). The server
496 alive messages are sent through the encrypted channel and there-
497 fore will not be spoofable. The TCP keepalive option enabled by
498 TCPKeepAlive is spoofable. The server alive mechanism is valu-
499 able when the client or server depend on knowing when a connec-
500 tion has become inactive.
501
502 The default value is 3. If, for example, ServerAliveInterval
503 (see below) is set to 15 and ServerAliveCountMax is left at the
504 default, if the server becomes unresponsive, ssh will disconnect
505 after approximately 45 seconds. This option applies to protocol
506 version 2 only.
507
508 ServerAliveInterval
509 Sets a timeout interval in seconds after which if no data has
510 been received from the server, ssh(1) will send a message through
511 the encrypted channel to request a response from the server. The
512 default is 0, indicating that these messages will not be sent to
513 the server. This option applies to protocol version 2 only.
514
515 SmartcardDevice
516 Specifies which smartcard device to use. The argument to this
517 keyword is the device ssh(1) should use to communicate with a
518 smartcard used for storing the user's private RSA key. By de-
519 fault, no device is specified and smartcard support is not acti-
520 vated.
521
522 StrictHostKeyChecking
523 If this flag is set to ``yes'', ssh(1) will never automatically
524 add host keys to the ~/.ssh/known_hosts file, and refuses to con-
525 nect to hosts whose host key has changed. This provides maximum
526 protection against trojan horse attacks, though it can be annoy-
527 ing when the /etc/ssh/ssh_known_hosts file is poorly maintained
528 or when connections to new hosts are frequently made. This op-
529 tion forces the user to manually add all new hosts. If this flag
530 is set to ``no'', ssh will automatically add new host keys to the
531 user known hosts files. If this flag is set to ``ask'', new host
532 keys will be added to the user known host files only after the
533 user has confirmed that is what they really want to do, and ssh
534 will refuse to connect to hosts whose host key has changed. The
535 host keys of known hosts will be verified automatically in all
536 cases. The argument must be ``yes'', ``no'', or ``ask''. The
537 default is ``ask''.
538
539 TCPKeepAlive
540 Specifies whether the system should send TCP keepalive messages
541 to the other side. If they are sent, death of the connection or
542 crash of one of the machines will be properly noticed. However,
543 this means that connections will die if the route is down tem-
544 porarily, and some people find it annoying.
545
546 The default is ``yes'' (to send TCP keepalive messages), and the
547 client will notice if the network goes down or the remote host
548 dies. This is important in scripts, and many users want it too.
549
550 To disable TCP keepalive messages, the value should be set to
551 ``no''.
552
553 Tunnel Request tun(4) device forwarding between the client and the serv-
554 er. The argument must be ``yes'', ``point-to-point'' (layer 3),
555 ``ethernet'' (layer 2), or ``no''. Specifying ``yes'' requests
556 the default tunnel mode, which is ``point-to-point''. The de-
557 fault is ``no''.
558
559 TunnelDevice
560 Specifies the tun(4) devices to open on the client (local_tun)
561 and the server (remote_tun).
562
563 The argument must be local_tun[:remote_tun]. The devices may be
564 specified by numerical ID or the keyword ``any'', which uses the
565 next available tunnel device. If remote_tun is not specified, it
566 defaults to ``any''. The default is ``any:any''.
567
568 UsePrivilegedPort
569 Specifies whether to use a privileged port for outgoing connec-
570 tions. The argument must be ``yes'' or ``no''. The default is
571 ``no''. If set to ``yes'', ssh(1) must be setuid root. Note
572 that this option must be set to ``yes'' for
573 RhostsRSAAuthentication with older servers.
574
575 User Specifies the user to log in as. This can be useful when a dif-
576 ferent user name is used on different machines. This saves the
577 trouble of having to remember to give the user name on the com-
578 mand line.
579
580 UserKnownHostsFile
581 Specifies a file to use for the user host key database instead of
582 ~/.ssh/known_hosts.
583
584 VerifyHostKeyDNS
585 Specifies whether to verify the remote key using DNS and SSHFP
586 resource records. If this option is set to ``yes'', the client
587 will implicitly trust keys that match a secure fingerprint from
588 DNS. Insecure fingerprints will be handled as if this option was
589 set to ``ask''. If this option is set to ``ask'', information on
590 fingerprint match will be displayed, but the user will still need
591 to confirm new host keys according to the StrictHostKeyChecking
592 option. The argument must be ``yes'', ``no'', or ``ask''. The
593 default is ``no''. Note that this option applies to protocol
594 version 2 only.
595
596 See also VERIFYING HOST KEYS in ssh(1).
597
598 XAuthLocation
599 Specifies the full pathname of the xauth(1) program. The default
600 is /usr/X11R6/bin/xauth.
601
602PATTERNS
603 A pattern consists of zero or more non-whitespace characters, `*' (a
604 wildcard that matches zero or more characters), or `?' (a wildcard that
605 matches exactly one character). For example, to specify a set of decla-
606 rations for any host in the ``.co.uk'' set of domains, the following pat-
607 tern could be used:
608
609 Host *.co.uk
610
611 The following pattern would match any host in the 192.168.0.[0-9] network
612 range:
613
614 Host 192.168.0.?
615
616 A pattern-list is a comma-separated list of patterns. Patterns within
617 pattern-lists may be negated by preceding them with an exclamation mark
618 (`!'). For example, to allow a key to be used from anywhere within an
619 organisation except from the ``dialup'' pool, the following entry (in au-
620 thorized_keys) could be used:
621
622 from="!*.dialup.example.com,*.example.com"
623
624FILES
625 ~/.ssh/config
626 This is the per-user configuration file. The format of this file
627 is described above. This file is used by the SSH client. Be-
628 cause of the potential for abuse, this file must have strict per-
629 missions: read/write for the user, and not accessible by others.
630
631 /etc/ssh/ssh_config
632 Systemwide configuration file. This file provides defaults for
633 those values that are not specified in the user's configuration
634 file, and for those users who do not have a configuration file.
635 This file must be world-readable.
636
637SEE ALSO
638 ssh(1)
639
640AUTHORS
641 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
642 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
643 de Raadt and Dug Song removed many bugs, re-added newer features and cre-
644 ated OpenSSH. Markus Friedl contributed the support for SSH protocol
645 versions 1.5 and 2.0.
646
647OpenBSD 4.2 August 15, 2007 10