summaryrefslogtreecommitdiff
path: root/ssh_config.0
diff options
context:
space:
mode:
Diffstat (limited to 'ssh_config.0')
-rw-r--r--ssh_config.0465
1 files changed, 465 insertions, 0 deletions
diff --git a/ssh_config.0 b/ssh_config.0
new file mode 100644
index 000000000..4be1d7f3f
--- /dev/null
+++ b/ssh_config.0
@@ -0,0 +1,465 @@
1SSH_CONFIG(5) OpenBSD Programmer's Manual SSH_CONFIG(5)
2
3NAME
4 ssh_config - OpenSSH SSH client configuration files
5
6SYNOPSIS
7 $HOME/.ssh/config
8 /etc/ssh/ssh_config
9
10DESCRIPTION
11 ssh obtains configuration data from the following sources in the follow-
12 ing order:
13 1. command-line options
14 2. user's configuration file ($HOME/.ssh/config)
15 3. system-wide configuration file (/etc/ssh/ssh_config)
16
17 For each parameter, the first obtained value will be used. The configu-
18 ration files contain sections bracketed by ``Host'' specifications, and
19 that section is only applied for hosts that match one of the patterns
20 given in the specification. The matched host name is the one given on
21 the command line.
22
23 Since the first obtained value for each parameter is used, more host-spe-
24 cific declarations should be given near the beginning of the file, and
25 general defaults at the end.
26
27 The configuration file has the following format:
28
29 Empty lines and lines starting with `#' are comments.
30
31 Otherwise a line is of the format ``keyword arguments''. Configuration
32 options may be separated by whitespace or optional whitespace and exactly
33 one `='; the latter format is useful to avoid the need to quote whites-
34 pace when specifying configuration options using the ssh, scp and sftp -o
35 option.
36
37 The possible keywords and their meanings are as follows (note that key-
38 words are case-insensitive and arguments are case-sensitive):
39
40 Host Restricts the following declarations (up to the next Host key-
41 word) to be only for those hosts that match one of the patterns
42 given after the keyword. `*' and `?' can be used as wildcards in
43 the patterns. A single `*' as a pattern can be used to provide
44 global defaults for all hosts. The host is the hostname argument
45 given on the command line (i.e., the name is not converted to a
46 canonicalized host name before matching).
47
48 AddressFamily
49 Specifies which address family to use when connecting. Valid ar-
50 guments are ``any'', ``inet'' (Use IPv4 only) or ``inet6'' (Use
51 IPv6 only.)
52
53 BatchMode
54 If set to ``yes'', passphrase/password querying will be disabled.
55 This option is useful in scripts and other batch jobs where no
56 user is present to supply the password. The argument must be
57 ``yes'' or ``no''. The default is ``no''.
58
59 BindAddress
60 Specify the interface to transmit from on machines with multiple
61 interfaces or aliased addresses. Note that this option does not
62 work if UsePrivilegedPort is set to ``yes''.
63
64 ChallengeResponseAuthentication
65 Specifies whether to use challenge response authentication. The
66 argument to this keyword must be ``yes'' or ``no''. The default
67 is ``yes''.
68
69 CheckHostIP
70 If this flag is set to ``yes'', ssh will additionally check the
71 host IP address in the known_hosts file. This allows ssh to de-
72 tect if a host key changed due to DNS spoofing. If the option is
73 set to ``no'', the check will not be executed. The default is
74 ``yes''.
75
76 Cipher Specifies the cipher to use for encrypting the session in proto-
77 col version 1. Currently, ``blowfish'', ``3des'', and ``des''
78 are supported. des is only supported in the ssh client for in-
79 teroperability with legacy protocol 1 implementations that do not
80 support the 3des cipher. Its use is strongly discouraged due to
81 cryptographic weaknesses. The default is ``3des''.
82
83 Ciphers
84 Specifies the ciphers allowed for protocol version 2 in order of
85 preference. Multiple ciphers must be comma-separated. The de-
86 fault is
87
88 ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
89 aes192-cbc,aes256-cbc''
90
91 ClearAllForwardings
92 Specifies that all local, remote and dynamic port forwardings
93 specified in the configuration files or on the command line be
94 cleared. This option is primarily useful when used from the ssh
95 command line to clear port forwardings set in configuration
96 files, and is automatically set by scp(1) and sftp(1). The argu-
97 ment must be ``yes'' or ``no''. The default is ``no''.
98
99 Compression
100 Specifies whether to use compression. The argument must be
101 ``yes'' or ``no''. The default is ``no''.
102
103 CompressionLevel
104 Specifies the compression level to use if compression is enabled.
105 The argument must be an integer from 1 (fast) to 9 (slow, best).
106 The default level is 6, which is good for most applications. The
107 meaning of the values is the same as in gzip(1). Note that this
108 option applies to protocol version 1 only.
109
110 ConnectionAttempts
111 Specifies the number of tries (one per second) to make before ex-
112 iting. The argument must be an integer. This may be useful in
113 scripts if the connection sometimes fails. The default is 1.
114
115 ConnectTimeout
116 Specifies the timeout (in seconds) used when connecting to the
117 ssh server, instead of using the default system TCP timeout.
118 This value is used only when the target is down or really un-
119 reachable, not when it refuses the connection.
120
121 DynamicForward
122 Specifies that a TCP/IP port on the local machine be forwarded
123 over the secure channel, and the application protocol is then
124 used to determine where to connect to from the remote machine.
125 The argument must be a port number. Currently the SOCKS4 and
126 SOCKS5 protocols are supported, and ssh will act as a SOCKS serv-
127 er. Multiple forwardings may be specified, and additional for-
128 wardings can be given on the command line. Only the superuser
129 can forward privileged ports.
130
131 EnableSSHKeysign
132 Setting this option to ``yes'' in the global client configuration
133 file /etc/ssh/ssh_config enables the use of the helper program
134 ssh-keysign(8) during HostbasedAuthentication. The argument must
135 be ``yes'' or ``no''. The default is ``no''. This option should
136 be placed in the non-hostspecific section. See ssh-keysign(8)
137 for more information.
138
139 EscapeChar
140 Sets the escape character (default: `~'). The escape character
141 can also be set on the command line. The argument should be a
142 single character, `^' followed by a letter, or ``none'' to dis-
143 able the escape character entirely (making the connection trans-
144 parent for binary data).
145
146 ForwardAgent
147 Specifies whether the connection to the authentication agent (if
148 any) will be forwarded to the remote machine. The argument must
149 be ``yes'' or ``no''. The default is ``no''.
150
151 Agent forwarding should be enabled with caution. Users with the
152 ability to bypass file permissions on the remote host (for the
153 agent's Unix-domain socket) can access the local agent through
154 the forwarded connection. An attacker cannot obtain key material
155 from the agent, however they can perform operations on the keys
156 that enable them to authenticate using the identities loaded into
157 the agent.
158
159 ForwardX11
160 Specifies whether X11 connections will be automatically redirect-
161 ed over the secure channel and DISPLAY set. The argument must be
162 ``yes'' or ``no''. The default is ``no''.
163
164 X11 forwarding should be enabled with caution. Users with the
165 ability to bypass file permissions on the remote host (for the
166 user's X11 authorization database) can access the local X11 dis-
167 play through the forwarded connection. An attacker may then be
168 able to perform activities such as keystroke monitoring if the
169 ForwardX11Trusted option is also enabled.
170
171 ForwardX11Trusted
172 If the this option is set to ``yes'' then remote X11 clients will
173 have full access to the original X11 display. If this option is
174 set to ``no'' then remote X11 clients will be considered untrust-
175 ed and prevented from stealing or tampering with data belonging
176 to trusted X11 clients.
177
178 The default is ``no''.
179
180 See the X11 SECURITY extension specification for full details on
181 the restrictions imposed on untrusted clients.
182
183 GatewayPorts
184 Specifies whether remote hosts are allowed to connect to local
185 forwarded ports. By default, ssh binds local port forwardings to
186 the loopback address. This prevents other remote hosts from con-
187 necting to forwarded ports. GatewayPorts can be used to specify
188 that ssh should bind local port forwardings to the wildcard ad-
189 dress, thus allowing remote hosts to connect to forwarded ports.
190 The argument must be ``yes'' or ``no''. The default is ``no''.
191
192 GlobalKnownHostsFile
193 Specifies a file to use for the global host key database instead
194 of /etc/ssh/ssh_known_hosts.
195
196 GSSAPIAuthentication
197 Specifies whether user authentication based on GSSAPI is allowed.
198 The default is ``no''. Note that this option applies to protocol
199 version 2 only.
200
201 GSSAPIDelegateCredentials
202 Forward (delegate) credentials to the server. The default is
203 ``no''. Note that this option applies to protocol version 2 on-
204 ly.
205
206 HostbasedAuthentication
207 Specifies whether to try rhosts based authentication with public
208 key authentication. The argument must be ``yes'' or ``no''. The
209 default is ``no''. This option applies to protocol version 2 on-
210 ly and is similar to RhostsRSAAuthentication.
211
212 HostKeyAlgorithms
213 Specifies the protocol version 2 host key algorithms that the
214 client wants to use in order of preference. The default for this
215 option is: ``ssh-rsa,ssh-dss''.
216
217 HostKeyAlias
218 Specifies an alias that should be used instead of the real host
219 name when looking up or saving the host key in the host key
220 database files. This option is useful for tunneling ssh connec-
221 tions or for multiple servers running on a single host.
222
223 HostName
224 Specifies the real host name to log into. This can be used to
225 specify nicknames or abbreviations for hosts. Default is the
226 name given on the command line. Numeric IP addresses are also
227 permitted (both on the command line and in HostName specifica-
228 tions).
229
230 IdentityFile
231 Specifies a file from which the user's RSA or DSA authentication
232 identity is read. The default is $HOME/.ssh/identity for proto-
233 col version 1, and $HOME/.ssh/id_rsa and $HOME/.ssh/id_dsa for
234 protocol version 2. Additionally, any identities represented by
235 the authentication agent will be used for authentication. The
236 file name may use the tilde syntax to refer to a user's home di-
237 rectory. It is possible to have multiple identity files speci-
238 fied in configuration files; all these identities will be tried
239 in sequence.
240
241 IdentitiesOnly
242 Specifies that ssh should only use the authentication identity
243 files configured in the ssh_config files, even if the ssh-agent
244 offers more identities. The argument to this keyword must be
245 ``yes'' or ``no''. This option is intented for situations where
246 ssh-agent offers many different identities. The default is
247 ``no''.
248
249 LocalForward
250 Specifies that a TCP/IP port on the local machine be forwarded
251 over the secure channel to the specified host and port from the
252 remote machine. The first argument must be a port number, and
253 the second must be host:port. IPv6 addresses can be specified
254 with an alternative syntax: host/port. Multiple forwardings may
255 be specified, and additional forwardings can be given on the com-
256 mand line. Only the superuser can forward privileged ports.
257
258 LogLevel
259 Gives the verbosity level that is used when logging messages from
260 ssh. The possible values are: QUIET, FATAL, ERROR, INFO, VER-
261 BOSE, DEBUG, DEBUG1, DEBUG2 and DEBUG3. The default is INFO.
262 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify
263 higher levels of verbose output.
264
265 MACs Specifies the MAC (message authentication code) algorithms in or-
266 der of preference. The MAC algorithm is used in protocol version
267 2 for data integrity protection. Multiple algorithms must be
268 comma-separated. The default is ``hmac-md5,hmac-sha1,hmac-
269 ripemd160,hmac-sha1-96,hmac-md5-96''.
270
271 NoHostAuthenticationForLocalhost
272 This option can be used if the home directory is shared across
273 machines. In this case localhost will refer to a different ma-
274 chine on each of the machines and the user will get many warnings
275 about changed host keys. However, this option disables host au-
276 thentication for localhost. The argument to this keyword must be
277 ``yes'' or ``no''. The default is to check the host key for lo-
278 calhost.
279
280 NumberOfPasswordPrompts
281 Specifies the number of password prompts before giving up. The
282 argument to this keyword must be an integer. Default is 3.
283
284 PasswordAuthentication
285 Specifies whether to use password authentication. The argument
286 to this keyword must be ``yes'' or ``no''. The default is
287 ``yes''.
288
289 Port Specifies the port number to connect on the remote host. Default
290 is 22.
291
292 PreferredAuthentications
293 Specifies the order in which the client should try protocol 2 au-
294 thentication methods. This allows a client to prefer one method
295 (e.g. keyboard-interactive) over another method (e.g. password)
296 The default for this option is: ``hostbased,publickey,keyboard-
297 interactive,password''.
298
299 Protocol
300 Specifies the protocol versions ssh should support in order of
301 preference. The possible values are ``1'' and ``2''. Multiple
302 versions must be comma-separated. The default is ``2,1''. This
303 means that ssh tries version 2 and falls back to version 1 if
304 version 2 is not available.
305
306 ProxyCommand
307 Specifies the command to use to connect to the server. The com-
308 mand string extends to the end of the line, and is executed with
309 /bin/sh. In the command string, `%h' will be substituted by the
310 host name to connect and `%p' by the port. The command can be
311 basically anything, and should read from its standard input and
312 write to its standard output. It should eventually connect an
313 sshd(8) server running on some machine, or execute sshd -i some-
314 where. Host key management will be done using the HostName of
315 the host being connected (defaulting to the name typed by the us-
316 er). Setting the command to ``none'' disables this option en-
317 tirely. Note that CheckHostIP is not available for connects with
318 a proxy command.
319
320 PubkeyAuthentication
321 Specifies whether to try public key authentication. The argument
322 to this keyword must be ``yes'' or ``no''. The default is
323 ``yes''. This option applies to protocol version 2 only.
324
325 RemoteForward
326 Specifies that a TCP/IP port on the remote machine be forwarded
327 over the secure channel to the specified host and port from the
328 local machine. The first argument must be a port number, and the
329 second must be host:port. IPv6 addresses can be specified with
330 an alternative syntax: host/port. Multiple forwardings may be
331 specified, and additional forwardings can be given on the command
332 line. Only the superuser can forward privileged ports.
333
334 RhostsRSAAuthentication
335 Specifies whether to try rhosts based authentication with RSA
336 host authentication. The argument must be ``yes'' or ``no''.
337 The default is ``no''. This option applies to protocol version 1
338 only and requires ssh to be setuid root.
339
340 RSAAuthentication
341 Specifies whether to try RSA authentication. The argument to
342 this keyword must be ``yes'' or ``no''. RSA authentication will
343 only be attempted if the identity file exists, or an authentica-
344 tion agent is running. The default is ``yes''. Note that this
345 option applies to protocol version 1 only.
346
347 ServerAliveInterval
348 Sets a timeout interval in seconds after which if no data has
349 been received from the server, ssh will send a message through
350 the encrypted channel to request a response from the server. The
351 default is 0, indicating that these messages will not be sent to
352 the server. This option applies to protocol version 2 only.
353
354 ServerAliveCountMax
355 Sets the number of server alive messages (see above) which may be
356 sent without ssh receiving any messages back from the server. If
357 this threshold is reached while server alive messages are being
358 sent, ssh will disconnect from the server, terminating the ses-
359 sion. It is important to note that the use of server alive mes-
360 sages is very different from TCPKeepAlive (below). The server
361 alive messages are sent through the encrypted channel and there-
362 fore will not be spoofable. The TCP keepalive option enabled by
363 TCPKeepAlive is spoofable. The server alive mechanism is valu-
364 able when the client or server depend on knowing when a connec-
365 tion has become inactive.
366
367 The default value is 3. If, for example, ServerAliveInterval
368 (above) is set to 15, and ServerAliveCountMax is left at the de-
369 fault, if the server becomes unresponsive ssh will disconnect af-
370 ter approximately 45 seconds.
371
372 SmartcardDevice
373 Specifies which smartcard device to use. The argument to this
374 keyword is the device ssh should use to communicate with a smart-
375 card used for storing the user's private RSA key. By default, no
376 device is specified and smartcard support is not activated.
377
378 StrictHostKeyChecking
379 If this flag is set to ``yes'', ssh will never automatically add
380 host keys to the $HOME/.ssh/known_hosts file, and refuses to con-
381 nect to hosts whose host key has changed. This provides maximum
382 protection against trojan horse attacks, however, can be annoying
383 when the /etc/ssh/ssh_known_hosts file is poorly maintained, or
384 connections to new hosts are frequently made. This option forces
385 the user to manually add all new hosts. If this flag is set to
386 ``no'', ssh will automatically add new host keys to the user
387 known hosts files. If this flag is set to ``ask'', new host keys
388 will be added to the user known host files only after the user
389 has confirmed that is what they really want to do, and ssh will
390 refuse to connect to hosts whose host key has changed. The host
391 keys of known hosts will be verified automatically in all cases.
392 The argument must be ``yes'', ``no'' or ``ask''. The default is
393 ``ask''.
394
395 TCPKeepAlive
396 Specifies whether the system should send TCP keepalive messages
397 to the other side. If they are sent, death of the connection or
398 crash of one of the machines will be properly noticed. However,
399 this means that connections will die if the route is down tem-
400 porarily, and some people find it annoying.
401
402 The default is ``yes'' (to send TCP keepalive messages), and the
403 client will notice if the network goes down or the remote host
404 dies. This is important in scripts, and many users want it too.
405
406 To disable TCP keepalive messages, the value should be set to
407 ``no''.
408
409 UsePrivilegedPort
410 Specifies whether to use a privileged port for outgoing connec-
411 tions. The argument must be ``yes'' or ``no''. The default is
412 ``no''. If set to ``yes'' ssh must be setuid root. Note that
413 this option must be set to ``yes'' for RhostsRSAAuthentication
414 with older servers.
415
416 User Specifies the user to log in as. This can be useful when a dif-
417 ferent user name is used on different machines. This saves the
418 trouble of having to remember to give the user name on the com-
419 mand line.
420
421 UserKnownHostsFile
422 Specifies a file to use for the user host key database instead of
423 $HOME/.ssh/known_hosts.
424
425 VerifyHostKeyDNS
426 Specifies whether to verify the remote key using DNS and SSHFP
427 resource records. If this option is set to ``yes'', the client
428 will implicitly trust keys that match a secure fingerprint from
429 DNS. Insecure fingerprints will be handled as if this option was
430 set to ``ask''. If this option is set to ``ask'', information on
431 fingerprint match will be displayed, but the user will still need
432 to confirm new host keys according to the StrictHostKeyChecking
433 option. The argument must be ``yes'', ``no'' or ``ask''. The
434 default is ``no''. Note that this option applies to protocol
435 version 2 only.
436
437 XAuthLocation
438 Specifies the full pathname of the xauth(1) program. The default
439 is /usr/X11R6/bin/xauth.
440
441FILES
442 $HOME/.ssh/config
443 This is the per-user configuration file. The format of this file
444 is described above. This file is used by the ssh client. This
445 file does not usually contain any sensitive information, but the
446 recommended permissions are read/write for the user, and not ac-
447 cessible by others.
448
449 /etc/ssh/ssh_config
450 Systemwide configuration file. This file provides defaults for
451 those values that are not specified in the user's configuration
452 file, and for those users who do not have a configuration file.
453 This file must be world-readable.
454
455SEE ALSO
456 ssh(1)
457
458AUTHORS
459 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
460 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
461 de Raadt and Dug Song removed many bugs, re-added newer features and cre-
462 ated OpenSSH. Markus Friedl contributed the support for SSH protocol
463 versions 1.5 and 2.0.
464
465OpenBSD 3.5 September 25, 1999 8
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-10 20:49:15 +0000