Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.285
1.1 stevesk 1: .\"
2: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
3: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: .\" All rights reserved
5: .\"
6: .\" As far as I am concerned, the code I have written for this software
7: .\" can be used freely for any purpose. Any derived versions of this
8: .\" software must be clearly marked as such, and if the derived work is
9: .\" incompatible with the protocol description in the RFC file, it must be
10: .\" called by a name other than "ssh" or "Secure Shell".
11: .\"
12: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
13: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
14: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
15: .\"
16: .\" Redistribution and use in source and binary forms, with or without
17: .\" modification, are permitted provided that the following conditions
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19: .\" 1. Redistributions of source code must retain the above copyright
20: .\" notice, this list of conditions and the following disclaimer.
21: .\" 2. Redistributions in binary form must reproduce the above copyright
22: .\" notice, this list of conditions and the following disclaimer in the
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25: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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1.285 ! djm 36: .\" $OpenBSD: ssh_config.5,v 1.284 2018/09/21 03:11:36 djm Exp $
! 37: .Dd $Mdocdate: September 21 2018 $
1.1 stevesk 38: .Dt SSH_CONFIG 5
39: .Os
40: .Sh NAME
41: .Nm ssh_config
42: .Nd OpenSSH SSH client configuration files
43: .Sh DESCRIPTION
1.84 jmc 44: .Xr ssh 1
1.1 stevesk 45: obtains configuration data from the following sources in
46: the following order:
1.79 jmc 47: .Pp
1.2 stevesk 48: .Bl -enum -offset indent -compact
49: .It
50: command-line options
51: .It
52: user's configuration file
1.50 djm 53: .Pq Pa ~/.ssh/config
1.2 stevesk 54: .It
55: system-wide configuration file
56: .Pq Pa /etc/ssh/ssh_config
57: .El
1.1 stevesk 58: .Pp
59: For each parameter, the first obtained value
60: will be used.
1.41 jmc 61: The configuration files contain sections separated by
1.240 jmc 62: .Cm Host
1.1 stevesk 63: specifications, and that section is only applied for hosts that
64: match one of the patterns given in the specification.
1.193 djm 65: The matched host name is usually the one given on the command line
66: (see the
67: .Cm CanonicalizeHostname
1.240 jmc 68: option for exceptions).
1.1 stevesk 69: .Pp
70: Since the first obtained value for each parameter is used, more
71: host-specific declarations should be given near the beginning of the
72: file, and general defaults at the end.
1.80 jmc 73: .Pp
1.240 jmc 74: The file contains keyword-argument pairs, one per line.
75: Lines starting with
1.1 stevesk 76: .Ql #
1.240 jmc 77: and empty lines are interpreted as comments.
78: Arguments may optionally be enclosed in double quotes
79: .Pq \&"
80: in order to represent arguments containing spaces.
1.1 stevesk 81: Configuration options may be separated by whitespace or
82: optional whitespace and exactly one
83: .Ql = ;
84: the latter format is useful to avoid the need to quote whitespace
85: when specifying configuration options using the
86: .Nm ssh ,
1.87 jmc 87: .Nm scp ,
1.1 stevesk 88: and
89: .Nm sftp
90: .Fl o
91: option.
92: .Pp
93: The possible
94: keywords and their meanings are as follows (note that
95: keywords are case-insensitive and arguments are case-sensitive):
96: .Bl -tag -width Ds
97: .It Cm Host
98: Restricts the following declarations (up to the next
99: .Cm Host
1.169 djm 100: or
101: .Cm Match
1.1 stevesk 102: keyword) to be only for those hosts that match one of the patterns
103: given after the keyword.
1.112 krw 104: If more than one pattern is provided, they should be separated by whitespace.
1.1 stevesk 105: A single
1.83 jmc 106: .Ql *
1.1 stevesk 107: as a pattern can be used to provide global
108: defaults for all hosts.
1.193 djm 109: The host is usually the
1.1 stevesk 110: .Ar hostname
1.193 djm 111: argument given on the command line
112: (see the
113: .Cm CanonicalizeHostname
1.240 jmc 114: keyword for exceptions).
1.148 djm 115: .Pp
116: A pattern entry may be negated by prefixing it with an exclamation mark
117: .Pq Sq !\& .
118: If a negated entry is matched, then the
119: .Cm Host
120: entry is ignored, regardless of whether any other patterns on the line
121: match.
122: Negated matches are therefore useful to provide exceptions for wildcard
123: matches.
1.81 jmc 124: .Pp
125: See
126: .Sx PATTERNS
127: for more information on patterns.
1.170 jmc 128: .It Cm Match
1.169 djm 129: Restricts the following declarations (up to the next
130: .Cm Host
131: or
132: .Cm Match
133: keyword) to be used only when the conditions following the
134: .Cm Match
135: keyword are satisfied.
1.220 sobrado 136: Match conditions are specified using one or more criteria
1.178 dtucker 137: or the single token
138: .Cm all
1.193 djm 139: which always matches.
140: The available criteria keywords are:
141: .Cm canonical ,
1.176 djm 142: .Cm exec ,
1.169 djm 143: .Cm host ,
144: .Cm originalhost ,
145: .Cm user ,
146: and
147: .Cm localuser .
1.193 djm 148: The
149: .Cm all
150: criteria must appear alone or immediately after
1.194 jmc 151: .Cm canonical .
1.193 djm 152: Other criteria may be combined arbitrarily.
153: All criteria but
154: .Cm all
155: and
156: .Cm canonical
157: require an argument.
158: Criteria may be negated by prepending an exclamation mark
159: .Pq Sq !\& .
1.169 djm 160: .Pp
1.177 jmc 161: The
1.193 djm 162: .Cm canonical
1.210 dtucker 163: keyword matches only when the configuration file is being re-parsed
1.193 djm 164: after hostname canonicalization (see the
165: .Cm CanonicalizeHostname
166: option.)
167: This may be useful to specify conditions that work with canonical host
168: names only.
169: The
1.176 djm 170: .Cm exec
1.177 jmc 171: keyword executes the specified command under the user's shell.
1.169 djm 172: If the command returns a zero exit status then the condition is considered true.
173: Commands containing whitespace characters must be quoted.
1.239 jmc 174: Arguments to
175: .Cm exec
176: accept the tokens described in the
177: .Sx TOKENS
178: section.
1.169 djm 179: .Pp
180: The other keywords' criteria must be single entries or comma-separated
181: lists and may use the wildcard and negation operators described in the
182: .Sx PATTERNS
183: section.
184: The criteria for the
185: .Cm host
186: keyword are matched against the target hostname, after any substitution
187: by the
188: .Cm Hostname
1.193 djm 189: or
190: .Cm CanonicalizeHostname
191: options.
1.169 djm 192: The
193: .Cm originalhost
194: keyword matches against the hostname as it was specified on the command-line.
195: The
196: .Cm user
197: keyword matches against the target username on the remote host.
198: The
199: .Cm localuser
200: keyword matches against the name of the local user running
201: .Xr ssh 1
202: (this keyword may be useful in system-wide
203: .Nm
204: files).
1.222 jcs 205: .It Cm AddKeysToAgent
206: Specifies whether keys should be automatically added to a running
1.223 jmc 207: .Xr ssh-agent 1 .
1.222 jcs 208: If this option is set to
1.240 jmc 209: .Cm yes
1.222 jcs 210: and a key is loaded from a file, the key and its passphrase are added to
211: the agent with the default lifetime, as if by
212: .Xr ssh-add 1 .
213: If this option is set to
1.240 jmc 214: .Cm ask ,
215: .Xr ssh 1
1.222 jcs 216: will require confirmation using the
217: .Ev SSH_ASKPASS
218: program before adding a key (see
219: .Xr ssh-add 1
220: for details).
221: If this option is set to
1.240 jmc 222: .Cm confirm ,
1.222 jcs 223: each use of the key must be confirmed, as if the
224: .Fl c
225: option was specified to
226: .Xr ssh-add 1 .
227: If this option is set to
1.240 jmc 228: .Cm no ,
1.222 jcs 229: no keys are added to the agent.
230: The argument must be
1.240 jmc 231: .Cm yes ,
232: .Cm confirm ,
233: .Cm ask ,
1.222 jcs 234: or
1.240 jmc 235: .Cm no
236: (the default).
1.10 djm 237: .It Cm AddressFamily
1.11 jmc 238: Specifies which address family to use when connecting.
239: Valid arguments are
1.240 jmc 240: .Cm any
241: (the default),
242: .Cm inet
1.84 jmc 243: (use IPv4 only), or
1.240 jmc 244: .Cm inet6
1.40 jmc 245: (use IPv6 only).
1.1 stevesk 246: .It Cm BatchMode
247: If set to
1.240 jmc 248: .Cm yes ,
1.1 stevesk 249: passphrase/password querying will be disabled.
250: This option is useful in scripts and other batch jobs where no user
251: is present to supply the password.
252: The argument must be
1.240 jmc 253: .Cm yes
1.1 stevesk 254: or
1.240 jmc 255: .Cm no
256: (the default).
1.268 jmc 257: .It Cm BindAddress
258: Use the specified address on the local machine as the source address of
259: the connection.
260: Only useful on systems with more than one address.
261: .It Cm BindInterface
262: Use the address of the specified interface on the local machine as the
263: source address of the connection.
1.171 djm 264: .It Cm CanonicalDomains
1.172 jmc 265: When
1.173 djm 266: .Cm CanonicalizeHostname
1.171 djm 267: is enabled, this option specifies the list of domain suffixes in which to
268: search for the specified destination host.
1.173 djm 269: .It Cm CanonicalizeFallbackLocal
1.174 djm 270: Specifies whether to fail with an error when hostname canonicalization fails.
1.172 jmc 271: The default,
1.240 jmc 272: .Cm yes ,
1.172 jmc 273: will attempt to look up the unqualified hostname using the system resolver's
1.171 djm 274: search rules.
275: A value of
1.240 jmc 276: .Cm no
1.171 djm 277: will cause
278: .Xr ssh 1
279: to fail instantly if
1.173 djm 280: .Cm CanonicalizeHostname
1.171 djm 281: is enabled and the target hostname cannot be found in any of the domains
282: specified by
283: .Cm CanonicalDomains .
1.173 djm 284: .It Cm CanonicalizeHostname
1.174 djm 285: Controls whether explicit hostname canonicalization is performed.
1.172 jmc 286: The default,
1.240 jmc 287: .Cm no ,
1.171 djm 288: is not to perform any name rewriting and let the system resolver handle all
289: hostname lookups.
290: If set to
1.240 jmc 291: .Cm yes
1.171 djm 292: then, for connections that do not use a
1.284 djm 293: .Cm ProxyCommand
294: or
295: .Cm ProxyJump ,
1.171 djm 296: .Xr ssh 1
1.173 djm 297: will attempt to canonicalize the hostname specified on the command line
1.171 djm 298: using the
299: .Cm CanonicalDomains
300: suffixes and
1.173 djm 301: .Cm CanonicalizePermittedCNAMEs
1.171 djm 302: rules.
303: If
1.173 djm 304: .Cm CanonicalizeHostname
1.171 djm 305: is set to
1.240 jmc 306: .Cm always ,
1.174 djm 307: then canonicalization is applied to proxied connections too.
1.185 djm 308: .Pp
1.193 djm 309: If this option is enabled, then the configuration files are processed
310: again using the new target name to pick up any new configuration in matching
1.185 djm 311: .Cm Host
1.193 djm 312: and
313: .Cm Match
1.185 djm 314: stanzas.
1.173 djm 315: .It Cm CanonicalizeMaxDots
1.172 jmc 316: Specifies the maximum number of dot characters in a hostname before
1.174 djm 317: canonicalization is disabled.
1.240 jmc 318: The default, 1,
1.172 jmc 319: allows a single dot (i.e. hostname.subdomain).
1.173 djm 320: .It Cm CanonicalizePermittedCNAMEs
1.172 jmc 321: Specifies rules to determine whether CNAMEs should be followed when
1.173 djm 322: canonicalizing hostnames.
1.171 djm 323: The rules consist of one or more arguments of
1.172 jmc 324: .Ar source_domain_list : Ns Ar target_domain_list ,
1.171 djm 325: where
326: .Ar source_domain_list
1.174 djm 327: is a pattern-list of domains that may follow CNAMEs in canonicalization,
1.171 djm 328: and
329: .Ar target_domain_list
1.172 jmc 330: is a pattern-list of domains that they may resolve to.
1.171 djm 331: .Pp
332: For example,
1.240 jmc 333: .Qq *.a.example.com:*.b.example.com,*.c.example.com
1.171 djm 334: will allow hostnames matching
1.240 jmc 335: .Qq *.a.example.com
1.173 djm 336: to be canonicalized to names in the
1.240 jmc 337: .Qq *.b.example.com
1.171 djm 338: or
1.240 jmc 339: .Qq *.c.example.com
1.171 djm 340: domains.
1.283 jmc 341: .It Cm CASignatureAlgorithms
342: Specifies which algorithms are allowed for signing of certificates
343: by certificate authorities (CAs).
344: The default is:
345: .Bd -literal -offset indent
346: ecdsa-sha2-nistp256.ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
347: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
348: .Ed
349: .Pp
350: .Xr ssh 1
351: will not accept host certificates signed using algorithms other than those
352: specified.
1.221 djm 353: .It Cm CertificateFile
354: Specifies a file from which the user's certificate is read.
355: A corresponding private key must be provided separately in order
356: to use this certificate either
357: from an
358: .Cm IdentityFile
359: directive or
360: .Fl i
361: flag to
362: .Xr ssh 1 ,
363: via
364: .Xr ssh-agent 1 ,
365: or via a
366: .Cm PKCS11Provider .
367: .Pp
1.239 jmc 368: Arguments to
369: .Cm CertificateFile
370: may use the tilde syntax to refer to a user's home directory
371: or the tokens described in the
372: .Sx TOKENS
373: section.
1.221 djm 374: .Pp
375: It is possible to have multiple certificate files specified in
376: configuration files; these certificates will be tried in sequence.
377: Multiple
378: .Cm CertificateFile
379: directives will add to the list of certificates used for
380: authentication.
1.1 stevesk 381: .It Cm ChallengeResponseAuthentication
1.82 jmc 382: Specifies whether to use challenge-response authentication.
1.1 stevesk 383: The argument to this keyword must be
1.240 jmc 384: .Cm yes
385: (the default)
1.1 stevesk 386: or
1.240 jmc 387: .Cm no .
1.1 stevesk 388: .It Cm CheckHostIP
1.240 jmc 389: If set to
390: .Cm yes
391: (the default),
1.84 jmc 392: .Xr ssh 1
393: will additionally check the host IP address in the
1.1 stevesk 394: .Pa known_hosts
395: file.
1.240 jmc 396: This allows it to detect if a host key changed due to DNS spoofing
1.211 djm 397: and will add addresses of destination hosts to
398: .Pa ~/.ssh/known_hosts
399: in the process, regardless of the setting of
400: .Cm StrictHostKeyChecking .
1.107 grunk 401: If the option is set to
1.240 jmc 402: .Cm no ,
1.1 stevesk 403: the check will not be executed.
404: .It Cm Ciphers
1.245 djm 405: Specifies the ciphers allowed and their order of preference.
1.1 stevesk 406: Multiple ciphers must be comma-separated.
1.214 djm 407: If the specified value begins with a
408: .Sq +
409: character, then the specified ciphers will be appended to the default set
410: instead of replacing them.
1.241 djm 411: If the specified value begins with a
412: .Sq -
413: character, then the specified ciphers (including wildcards) will be removed
414: from the default set instead of replacing them.
1.214 djm 415: .Pp
1.180 djm 416: The supported ciphers are:
1.240 jmc 417: .Bd -literal -offset indent
1.186 naddy 418: 3des-cbc
419: aes128-cbc
420: aes192-cbc
421: aes256-cbc
422: aes128-ctr
423: aes192-ctr
424: aes256-ctr
425: aes128-gcm@openssh.com
426: aes256-gcm@openssh.com
427: chacha20-poly1305@openssh.com
1.240 jmc 428: .Ed
1.180 djm 429: .Pp
1.84 jmc 430: The default is:
1.186 naddy 431: .Bd -literal -offset indent
1.215 jmc 432: chacha20-poly1305@openssh.com,
1.186 naddy 433: aes128-ctr,aes192-ctr,aes256-ctr,
1.270 djm 434: aes128-gcm@openssh.com,aes256-gcm@openssh.com
1.1 stevesk 435: .Ed
1.180 djm 436: .Pp
1.240 jmc 437: The list of available ciphers may also be obtained using
438: .Qq ssh -Q cipher .
1.1 stevesk 439: .It Cm ClearAllForwardings
1.84 jmc 440: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 441: specified in the configuration files or on the command line be
1.7 jmc 442: cleared.
443: This option is primarily useful when used from the
1.84 jmc 444: .Xr ssh 1
1.1 stevesk 445: command line to clear port forwardings set in
446: configuration files, and is automatically set by
447: .Xr scp 1
448: and
449: .Xr sftp 1 .
450: The argument must be
1.240 jmc 451: .Cm yes
1.1 stevesk 452: or
1.240 jmc 453: .Cm no
454: (the default).
1.1 stevesk 455: .It Cm Compression
456: Specifies whether to use compression.
457: The argument must be
1.240 jmc 458: .Cm yes
1.1 stevesk 459: or
1.240 jmc 460: .Cm no
461: (the default).
1.247 naddy 462: .It Cm ConnectionAttempts
463: Specifies the number of tries (one per second) to make before exiting.
464: The argument must be an integer.
465: This may be useful in scripts if the connection sometimes fails.
466: The default is 1.
1.9 djm 467: .It Cm ConnectTimeout
1.84 jmc 468: Specifies the timeout (in seconds) used when connecting to the
469: SSH server, instead of using the default system TCP timeout.
1.11 jmc 470: This value is used only when the target is down or really unreachable,
471: not when it refuses the connection.
1.36 djm 472: .It Cm ControlMaster
473: Enables the sharing of multiple sessions over a single network connection.
474: When set to
1.240 jmc 475: .Cm yes ,
1.84 jmc 476: .Xr ssh 1
1.36 djm 477: will listen for connections on a control socket specified using the
478: .Cm ControlPath
479: argument.
480: Additional sessions can connect to this socket using the same
481: .Cm ControlPath
482: with
483: .Cm ControlMaster
484: set to
1.240 jmc 485: .Cm no
1.38 jmc 486: (the default).
1.64 jmc 487: These sessions will try to reuse the master instance's network connection
1.63 djm 488: rather than initiating new ones, but will fall back to connecting normally
489: if the control socket does not exist, or is not listening.
490: .Pp
1.37 djm 491: Setting this to
1.240 jmc 492: .Cm ask
493: will cause
494: .Xr ssh 1
1.206 jmc 495: to listen for control connections, but require confirmation using
496: .Xr ssh-askpass 1 .
1.51 jakob 497: If the
498: .Cm ControlPath
1.84 jmc 499: cannot be opened,
1.240 jmc 500: .Xr ssh 1
501: will continue without connecting to a master instance.
1.58 djm 502: .Pp
503: X11 and
1.59 jmc 504: .Xr ssh-agent 1
1.58 djm 505: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 506: display and agent forwarded will be the one belonging to the master
1.59 jmc 507: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 508: .Pp
509: Two additional options allow for opportunistic multiplexing: try to use a
510: master connection but fall back to creating a new one if one does not already
511: exist.
512: These options are:
1.240 jmc 513: .Cm auto
1.56 djm 514: and
1.240 jmc 515: .Cm autoask .
1.56 djm 516: The latter requires confirmation like the
1.240 jmc 517: .Cm ask
1.56 djm 518: option.
1.36 djm 519: .It Cm ControlPath
1.55 djm 520: Specify the path to the control socket used for connection sharing as described
521: in the
1.36 djm 522: .Cm ControlMaster
1.57 djm 523: section above or the string
1.240 jmc 524: .Cm none
1.57 djm 525: to disable connection sharing.
1.239 jmc 526: Arguments to
527: .Cm ControlPath
528: may use the tilde syntax to refer to a user's home directory
529: or the tokens described in the
530: .Sx TOKENS
531: section.
1.56 djm 532: It is recommended that any
533: .Cm ControlPath
534: used for opportunistic connection sharing include
1.195 djm 535: at least %h, %p, and %r (or alternatively %C) and be placed in a directory
536: that is not writable by other users.
1.56 djm 537: This ensures that shared connections are uniquely identified.
1.137 djm 538: .It Cm ControlPersist
539: When used in conjunction with
540: .Cm ControlMaster ,
541: specifies that the master connection should remain open
542: in the background (waiting for future client connections)
543: after the initial client connection has been closed.
544: If set to
1.240 jmc 545: .Cm no ,
1.137 djm 546: then the master connection will not be placed into the background,
547: and will close as soon as the initial client connection is closed.
548: If set to
1.240 jmc 549: .Cm yes
550: or 0,
1.137 djm 551: then the master connection will remain in the background indefinitely
552: (until killed or closed via a mechanism such as the
1.240 jmc 553: .Qq ssh -O exit ) .
1.137 djm 554: If set to a time in seconds, or a time in any of the formats documented in
555: .Xr sshd_config 5 ,
556: then the backgrounded master connection will automatically terminate
557: after it has remained idle (with no client connections) for the
558: specified time.
1.38 jmc 559: .It Cm DynamicForward
1.74 jmc 560: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 561: over the secure channel, and the application
562: protocol is then used to determine where to connect to from the
563: remote machine.
1.62 djm 564: .Pp
565: The argument must be
566: .Sm off
567: .Oo Ar bind_address : Oc Ar port .
568: .Sm on
1.138 djm 569: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 570: By default, the local port is bound in accordance with the
571: .Cm GatewayPorts
572: setting.
573: However, an explicit
574: .Ar bind_address
575: may be used to bind the connection to a specific address.
576: The
577: .Ar bind_address
578: of
1.240 jmc 579: .Cm localhost
1.62 djm 580: indicates that the listening port be bound for local use only, while an
581: empty address or
582: .Sq *
583: indicates that the port should be available from all interfaces.
584: .Pp
1.38 jmc 585: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 586: .Xr ssh 1
1.38 jmc 587: will act as a SOCKS server.
588: Multiple forwardings may be specified, and
589: additional forwardings can be given on the command line.
590: Only the superuser can forward privileged ports.
1.14 markus 591: .It Cm EnableSSHKeysign
592: Setting this option to
1.240 jmc 593: .Cm yes
1.14 markus 594: in the global client configuration file
595: .Pa /etc/ssh/ssh_config
596: enables the use of the helper program
597: .Xr ssh-keysign 8
598: during
599: .Cm HostbasedAuthentication .
600: The argument must be
1.240 jmc 601: .Cm yes
1.14 markus 602: or
1.240 jmc 603: .Cm no
604: (the default).
1.23 jmc 605: This option should be placed in the non-hostspecific section.
1.14 markus 606: See
607: .Xr ssh-keysign 8
608: for more information.
1.1 stevesk 609: .It Cm EscapeChar
610: Sets the escape character (default:
611: .Ql ~ ) .
612: The escape character can also
613: be set on the command line.
614: The argument should be a single character,
615: .Ql ^
616: followed by a letter, or
1.240 jmc 617: .Cm none
1.1 stevesk 618: to disable the escape
619: character entirely (making the connection transparent for binary
620: data).
1.96 markus 621: .It Cm ExitOnForwardFailure
622: Specifies whether
623: .Xr ssh 1
624: should terminate the connection if it cannot set up all requested
1.216 djm 625: dynamic, tunnel, local, and remote port forwardings, (e.g.\&
1.217 jmc 626: if either end is unable to bind and listen on a specified port).
1.216 djm 627: Note that
628: .Cm ExitOnForwardFailure
629: does not apply to connections made over port forwardings and will not,
630: for example, cause
631: .Xr ssh 1
632: to exit if TCP connections to the ultimate forwarding destination fail.
1.96 markus 633: The argument must be
1.240 jmc 634: .Cm yes
1.96 markus 635: or
1.240 jmc 636: .Cm no
637: (the default).
1.197 djm 638: .It Cm FingerprintHash
639: Specifies the hash algorithm used when displaying key fingerprints.
640: Valid options are:
1.240 jmc 641: .Cm md5
1.197 djm 642: and
1.240 jmc 643: .Cm sha256
644: (the default).
1.1 stevesk 645: .It Cm ForwardAgent
646: Specifies whether the connection to the authentication agent (if any)
647: will be forwarded to the remote machine.
648: The argument must be
1.240 jmc 649: .Cm yes
1.1 stevesk 650: or
1.240 jmc 651: .Cm no
652: (the default).
1.3 stevesk 653: .Pp
1.7 jmc 654: Agent forwarding should be enabled with caution.
655: Users with the ability to bypass file permissions on the remote host
656: (for the agent's Unix-domain socket)
657: can access the local agent through the forwarded connection.
658: An attacker cannot obtain key material from the agent,
1.3 stevesk 659: however they can perform operations on the keys that enable them to
660: authenticate using the identities loaded into the agent.
1.1 stevesk 661: .It Cm ForwardX11
662: Specifies whether X11 connections will be automatically redirected
663: over the secure channel and
664: .Ev DISPLAY
665: set.
666: The argument must be
1.240 jmc 667: .Cm yes
1.1 stevesk 668: or
1.240 jmc 669: .Cm no
670: (the default).
1.3 stevesk 671: .Pp
1.7 jmc 672: X11 forwarding should be enabled with caution.
673: Users with the ability to bypass file permissions on the remote host
1.22 markus 674: (for the user's X11 authorization database)
1.7 jmc 675: can access the local X11 display through the forwarded connection.
1.22 markus 676: An attacker may then be able to perform activities such as keystroke monitoring
677: if the
678: .Cm ForwardX11Trusted
679: option is also enabled.
1.134 djm 680: .It Cm ForwardX11Timeout
1.135 jmc 681: Specify a timeout for untrusted X11 forwarding
682: using the format described in the
1.240 jmc 683: .Sx TIME FORMATS
684: section of
1.134 djm 685: .Xr sshd_config 5 .
686: X11 connections received by
687: .Xr ssh 1
688: after this time will be refused.
1.285 ! djm 689: Setting
! 690: .Cm ForwardX11Timeout
! 691: to zero will disable the timeout and permit X11 forwarding for the life
! 692: of the connection.
1.134 djm 693: The default is to disable untrusted X11 forwarding after twenty minutes has
694: elapsed.
1.22 markus 695: .It Cm ForwardX11Trusted
1.34 jmc 696: If this option is set to
1.240 jmc 697: .Cm yes ,
1.84 jmc 698: remote X11 clients will have full access to the original X11 display.
1.42 djm 699: .Pp
1.22 markus 700: If this option is set to
1.240 jmc 701: .Cm no
702: (the default),
1.84 jmc 703: remote X11 clients will be considered untrusted and prevented
1.22 markus 704: from stealing or tampering with data belonging to trusted X11
705: clients.
1.42 djm 706: Furthermore, the
707: .Xr xauth 1
708: token used for the session will be set to expire after 20 minutes.
709: Remote clients will be refused access after this time.
1.22 markus 710: .Pp
711: See the X11 SECURITY extension specification for full details on
712: the restrictions imposed on untrusted clients.
1.1 stevesk 713: .It Cm GatewayPorts
714: Specifies whether remote hosts are allowed to connect to local
715: forwarded ports.
716: By default,
1.84 jmc 717: .Xr ssh 1
1.7 jmc 718: binds local port forwardings to the loopback address.
719: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 720: .Cm GatewayPorts
1.84 jmc 721: can be used to specify that ssh
1.1 stevesk 722: should bind local port forwardings to the wildcard address,
723: thus allowing remote hosts to connect to forwarded ports.
724: The argument must be
1.240 jmc 725: .Cm yes
1.1 stevesk 726: or
1.240 jmc 727: .Cm no
728: (the default).
1.1 stevesk 729: .It Cm GlobalKnownHostsFile
1.151 djm 730: Specifies one or more files to use for the global
731: host key database, separated by whitespace.
732: The default is
733: .Pa /etc/ssh/ssh_known_hosts ,
734: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 735: .It Cm GSSAPIAuthentication
1.27 markus 736: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 737: The default is
1.240 jmc 738: .Cm no .
1.18 markus 739: .It Cm GSSAPIDelegateCredentials
740: Forward (delegate) credentials to the server.
741: The default is
1.240 jmc 742: .Cm no .
1.44 djm 743: .It Cm HashKnownHosts
744: Indicates that
1.84 jmc 745: .Xr ssh 1
1.44 djm 746: should hash host names and addresses when they are added to
1.50 djm 747: .Pa ~/.ssh/known_hosts .
1.44 djm 748: These hashed names may be used normally by
1.84 jmc 749: .Xr ssh 1
1.44 djm 750: and
1.84 jmc 751: .Xr sshd 8 ,
1.44 djm 752: but they do not reveal identifying information should the file's contents
753: be disclosed.
754: The default is
1.240 jmc 755: .Cm no .
1.97 jmc 756: Note that existing names and addresses in known hosts files
757: will not be converted automatically,
758: but may be manually hashed using
1.45 djm 759: .Xr ssh-keygen 1 .
1.1 stevesk 760: .It Cm HostbasedAuthentication
761: Specifies whether to try rhosts based authentication with public key
762: authentication.
763: The argument must be
1.240 jmc 764: .Cm yes
1.1 stevesk 765: or
1.240 jmc 766: .Cm no
767: (the default).
1.202 djm 768: .It Cm HostbasedKeyTypes
769: Specifies the key types that will be used for hostbased authentication
1.279 djm 770: as a comma-separated list of patterns.
1.214 djm 771: Alternately if the specified value begins with a
772: .Sq +
773: character, then the specified key types will be appended to the default set
774: instead of replacing them.
1.241 djm 775: If the specified value begins with a
776: .Sq -
777: character, then the specified key types (including wildcards) will be removed
778: from the default set instead of replacing them.
1.213 markus 779: The default for this option is:
780: .Bd -literal -offset 3n
781: ecdsa-sha2-nistp256-cert-v01@openssh.com,
782: ecdsa-sha2-nistp384-cert-v01@openssh.com,
783: ecdsa-sha2-nistp521-cert-v01@openssh.com,
784: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 785: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 786: ssh-rsa-cert-v01@openssh.com,
787: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 788: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 789: .Ed
790: .Pp
1.202 djm 791: The
792: .Fl Q
793: option of
794: .Xr ssh 1
795: may be used to list supported key types.
1.1 stevesk 796: .It Cm HostKeyAlgorithms
1.226 jmc 797: Specifies the host key algorithms
1.1 stevesk 798: that the client wants to use in order of preference.
1.214 djm 799: Alternately if the specified value begins with a
800: .Sq +
801: character, then the specified key types will be appended to the default set
802: instead of replacing them.
1.241 djm 803: If the specified value begins with a
804: .Sq -
805: character, then the specified key types (including wildcards) will be removed
806: from the default set instead of replacing them.
1.1 stevesk 807: The default for this option is:
1.139 djm 808: .Bd -literal -offset 3n
809: ecdsa-sha2-nistp256-cert-v01@openssh.com,
810: ecdsa-sha2-nistp384-cert-v01@openssh.com,
811: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1.183 naddy 812: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 813: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 814: ssh-rsa-cert-v01@openssh.com,
1.139 djm 815: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 816: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.139 djm 817: .Ed
1.145 djm 818: .Pp
819: If hostkeys are known for the destination host then this default is modified
820: to prefer their algorithms.
1.198 djm 821: .Pp
1.240 jmc 822: The list of available key types may also be obtained using
823: .Qq ssh -Q key .
1.1 stevesk 824: .It Cm HostKeyAlias
825: Specifies an alias that should be used instead of the
826: real host name when looking up or saving the host key
1.251 djm 827: in the host key database files and when validating host certificates.
1.84 jmc 828: This option is useful for tunneling SSH connections
1.1 stevesk 829: or for multiple servers running on a single host.
830: .It Cm HostName
831: Specifies the real host name to log into.
832: This can be used to specify nicknames or abbreviations for hosts.
1.239 jmc 833: Arguments to
834: .Cm HostName
835: accept the tokens described in the
836: .Sx TOKENS
837: section.
1.1 stevesk 838: Numeric IP addresses are also permitted (both on the command line and in
839: .Cm HostName
840: specifications).
1.239 jmc 841: The default is the name given on the command line.
1.29 markus 842: .It Cm IdentitiesOnly
843: Specifies that
1.84 jmc 844: .Xr ssh 1
1.221 djm 845: should only use the authentication identity and certificate files explicitly
846: configured in the
1.31 jmc 847: .Nm
1.221 djm 848: files
849: or passed on the
850: .Xr ssh 1
851: command-line,
1.84 jmc 852: even if
853: .Xr ssh-agent 1
1.159 djm 854: or a
855: .Cm PKCS11Provider
1.29 markus 856: offers more identities.
857: The argument to this keyword must be
1.240 jmc 858: .Cm yes
1.29 markus 859: or
1.240 jmc 860: .Cm no
861: (the default).
1.84 jmc 862: This option is intended for situations where ssh-agent
1.29 markus 863: offers many different identities.
1.231 markus 864: .It Cm IdentityAgent
865: Specifies the
866: .Ux Ns -domain
867: socket used to communicate with the authentication agent.
868: .Pp
869: This option overrides the
1.240 jmc 870: .Ev SSH_AUTH_SOCK
1.231 markus 871: environment variable and can be used to select a specific agent.
872: Setting the socket name to
1.240 jmc 873: .Cm none
1.231 markus 874: disables the use of an authentication agent.
1.232 markus 875: If the string
1.240 jmc 876: .Qq SSH_AUTH_SOCK
1.232 markus 877: is specified, the location of the socket will be read from the
878: .Ev SSH_AUTH_SOCK
879: environment variable.
1.231 markus 880: .Pp
1.239 jmc 881: Arguments to
882: .Cm IdentityAgent
883: may use the tilde syntax to refer to a user's home directory
884: or the tokens described in the
885: .Sx TOKENS
886: section.
1.67 jmc 887: .It Cm IdentityFile
1.192 sobrado 888: Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA authentication
1.139 djm 889: identity is read.
1.67 jmc 890: The default is
1.139 djm 891: .Pa ~/.ssh/id_dsa ,
1.183 naddy 892: .Pa ~/.ssh/id_ecdsa ,
893: .Pa ~/.ssh/id_ed25519
1.139 djm 894: and
1.245 djm 895: .Pa ~/.ssh/id_rsa .
1.67 jmc 896: Additionally, any identities represented by the authentication agent
1.165 djm 897: will be used for authentication unless
898: .Cm IdentitiesOnly
899: is set.
1.221 djm 900: If no certificates have been explicitly specified by
901: .Cm CertificateFile ,
1.129 djm 902: .Xr ssh 1
903: will try to load certificate information from the filename obtained by
904: appending
905: .Pa -cert.pub
906: to the path of a specified
907: .Cm IdentityFile .
1.90 djm 908: .Pp
1.239 jmc 909: Arguments to
910: .Cm IdentityFile
911: may use the tilde syntax to refer to a user's home directory
912: or the tokens described in the
913: .Sx TOKENS
914: section.
1.90 djm 915: .Pp
1.67 jmc 916: It is possible to have
917: multiple identity files specified in configuration files; all these
918: identities will be tried in sequence.
1.152 djm 919: Multiple
920: .Cm IdentityFile
921: directives will add to the list of identities tried (this behaviour
922: differs from that of other configuration directives).
1.165 djm 923: .Pp
924: .Cm IdentityFile
925: may be used in conjunction with
926: .Cm IdentitiesOnly
927: to select which identities in an agent are offered during authentication.
1.221 djm 928: .Cm IdentityFile
929: may also be used in conjunction with
930: .Cm CertificateFile
931: in order to provide any certificate also needed for authentication with
932: the identity.
1.164 jmc 933: .It Cm IgnoreUnknown
934: Specifies a pattern-list of unknown options to be ignored if they are
935: encountered in configuration parsing.
936: This may be used to suppress errors if
937: .Nm
938: contains options that are unrecognised by
939: .Xr ssh 1 .
940: It is recommended that
941: .Cm IgnoreUnknown
942: be listed early in the configuration file as it will not be applied
943: to unknown options that appear before it.
1.229 djm 944: .It Cm Include
945: Include the specified configuration file(s).
1.230 jmc 946: Multiple pathnames may be specified and each pathname may contain
1.281 kn 947: .Xr glob 7
1.229 djm 948: wildcards and, for user configurations, shell-like
1.240 jmc 949: .Sq ~
1.229 djm 950: references to user home directories.
951: Files without absolute paths are assumed to be in
952: .Pa ~/.ssh
1.230 jmc 953: if included in a user configuration file or
1.229 djm 954: .Pa /etc/ssh
955: if included from the system configuration file.
956: .Cm Include
957: directive may appear inside a
958: .Cm Match
959: or
960: .Cm Host
961: block
962: to perform conditional inclusion.
1.143 djm 963: .It Cm IPQoS
964: Specifies the IPv4 type-of-service or DSCP class for connections.
965: Accepted values are
1.240 jmc 966: .Cm af11 ,
967: .Cm af12 ,
968: .Cm af13 ,
969: .Cm af21 ,
970: .Cm af22 ,
971: .Cm af23 ,
972: .Cm af31 ,
973: .Cm af32 ,
974: .Cm af33 ,
975: .Cm af41 ,
976: .Cm af42 ,
977: .Cm af43 ,
978: .Cm cs0 ,
979: .Cm cs1 ,
980: .Cm cs2 ,
981: .Cm cs3 ,
982: .Cm cs4 ,
983: .Cm cs5 ,
984: .Cm cs6 ,
985: .Cm cs7 ,
986: .Cm ef ,
987: .Cm lowdelay ,
988: .Cm throughput ,
989: .Cm reliability ,
1.253 djm 990: a numeric value, or
991: .Cm none
992: to use the operating system default.
1.146 djm 993: This option may take one or two arguments, separated by whitespace.
1.143 djm 994: If one argument is specified, it is used as the packet class unconditionally.
995: If two values are specified, the first is automatically selected for
996: interactive sessions and the second for non-interactive sessions.
997: The default is
1.269 job 998: .Cm af21
1.272 jmc 999: (Low-Latency Data)
1.143 djm 1000: for interactive sessions and
1.269 job 1001: .Cm cs1
1.272 jmc 1002: (Lower Effort)
1.143 djm 1003: for non-interactive sessions.
1.103 djm 1004: .It Cm KbdInteractiveAuthentication
1005: Specifies whether to use keyboard-interactive authentication.
1006: The argument to this keyword must be
1.240 jmc 1007: .Cm yes
1008: (the default)
1.103 djm 1009: or
1.240 jmc 1010: .Cm no .
1.39 djm 1011: .It Cm KbdInteractiveDevices
1012: Specifies the list of methods to use in keyboard-interactive authentication.
1013: Multiple method names must be comma-separated.
1014: The default is to use the server specified list.
1.85 jmc 1015: The methods available vary depending on what the server supports.
1016: For an OpenSSH server,
1017: it may be zero or more of:
1.240 jmc 1018: .Cm bsdauth ,
1019: .Cm pam ,
1.85 jmc 1020: and
1.240 jmc 1021: .Cm skey .
1.140 djm 1022: .It Cm KexAlgorithms
1023: Specifies the available KEX (Key Exchange) algorithms.
1024: Multiple algorithms must be comma-separated.
1.214 djm 1025: Alternately if the specified value begins with a
1026: .Sq +
1027: character, then the specified methods will be appended to the default set
1028: instead of replacing them.
1.241 djm 1029: If the specified value begins with a
1030: .Sq -
1031: character, then the specified methods (including wildcards) will be removed
1032: from the default set instead of replacing them.
1.141 jmc 1033: The default is:
1034: .Bd -literal -offset indent
1.238 djm 1035: curve25519-sha256,curve25519-sha256@libssh.org,
1.141 jmc 1036: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1037: diffie-hellman-group-exchange-sha256,
1.266 djm 1038: diffie-hellman-group16-sha512,
1039: diffie-hellman-group18-sha512,
1.209 dtucker 1040: diffie-hellman-group-exchange-sha1,
1.266 djm 1041: diffie-hellman-group14-sha256,
1.212 djm 1042: diffie-hellman-group14-sha1
1.141 jmc 1043: .Ed
1.198 djm 1044: .Pp
1.240 jmc 1045: The list of available key exchange algorithms may also be obtained using
1046: .Qq ssh -Q kex .
1.65 reyk 1047: .It Cm LocalCommand
1048: Specifies a command to execute on the local machine after successfully
1049: connecting to the server.
1050: The command string extends to the end of the line, and is executed with
1.105 jmc 1051: the user's shell.
1.239 jmc 1052: Arguments to
1053: .Cm LocalCommand
1054: accept the tokens described in the
1055: .Sx TOKENS
1056: section.
1.123 djm 1057: .Pp
1058: The command is run synchronously and does not have access to the
1059: session of the
1060: .Xr ssh 1
1061: that spawned it.
1062: It should not be used for interactive commands.
1063: .Pp
1.65 reyk 1064: This directive is ignored unless
1065: .Cm PermitLocalCommand
1066: has been enabled.
1.1 stevesk 1067: .It Cm LocalForward
1.74 jmc 1068: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 1069: the secure channel to the specified host and port from the remote machine.
1.49 jmc 1070: The first argument must be
1.43 djm 1071: .Sm off
1.49 jmc 1072: .Oo Ar bind_address : Oc Ar port
1.43 djm 1073: .Sm on
1.49 jmc 1074: and the second argument must be
1075: .Ar host : Ns Ar hostport .
1.138 djm 1076: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 1077: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 1078: given on the command line.
1.1 stevesk 1079: Only the superuser can forward privileged ports.
1.43 djm 1080: By default, the local port is bound in accordance with the
1081: .Cm GatewayPorts
1082: setting.
1083: However, an explicit
1084: .Ar bind_address
1085: may be used to bind the connection to a specific address.
1086: The
1087: .Ar bind_address
1088: of
1.240 jmc 1089: .Cm localhost
1.46 jmc 1090: indicates that the listening port be bound for local use only, while an
1091: empty address or
1092: .Sq *
1.43 djm 1093: indicates that the port should be available from all interfaces.
1.1 stevesk 1094: .It Cm LogLevel
1095: Gives the verbosity level that is used when logging messages from
1.84 jmc 1096: .Xr ssh 1 .
1.1 stevesk 1097: The possible values are:
1.84 jmc 1098: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 1099: The default is INFO.
1100: DEBUG and DEBUG1 are equivalent.
1101: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 1102: .It Cm MACs
1103: Specifies the MAC (message authentication code) algorithms
1104: in order of preference.
1.226 jmc 1105: The MAC algorithm is used for data integrity protection.
1.1 stevesk 1106: Multiple algorithms must be comma-separated.
1.214 djm 1107: If the specified value begins with a
1108: .Sq +
1109: character, then the specified algorithms will be appended to the default set
1110: instead of replacing them.
1.241 djm 1111: If the specified value begins with a
1112: .Sq -
1113: character, then the specified algorithms (including wildcards) will be removed
1114: from the default set instead of replacing them.
1.214 djm 1115: .Pp
1.160 markus 1116: The algorithms that contain
1.240 jmc 1117: .Qq -etm
1.160 markus 1118: calculate the MAC after encryption (encrypt-then-mac).
1119: These are considered safer and their use recommended.
1.214 djm 1120: .Pp
1.84 jmc 1121: The default is:
1.101 jmc 1122: .Bd -literal -offset indent
1.160 markus 1123: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1124: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.224 djm 1125: hmac-sha1-etm@openssh.com,
1.186 naddy 1126: umac-64@openssh.com,umac-128@openssh.com,
1.224 djm 1127: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.101 jmc 1128: .Ed
1.198 djm 1129: .Pp
1.240 jmc 1130: The list of available MAC algorithms may also be obtained using
1131: .Qq ssh -Q mac .
1.1 stevesk 1132: .It Cm NoHostAuthenticationForLocalhost
1.264 djm 1133: Disable host authentication for localhost (loopback addresses).
1.1 stevesk 1134: The argument to this keyword must be
1.240 jmc 1135: .Cm yes
1.1 stevesk 1136: or
1.242 jmc 1137: .Cm no
1.240 jmc 1138: (the default).
1.1 stevesk 1139: .It Cm NumberOfPasswordPrompts
1140: Specifies the number of password prompts before giving up.
1141: The argument to this keyword must be an integer.
1.84 jmc 1142: The default is 3.
1.1 stevesk 1143: .It Cm PasswordAuthentication
1144: Specifies whether to use password authentication.
1145: The argument to this keyword must be
1.240 jmc 1146: .Cm yes
1147: (the default)
1.1 stevesk 1148: or
1.240 jmc 1149: .Cm no .
1.65 reyk 1150: .It Cm PermitLocalCommand
1151: Allow local command execution via the
1152: .Ic LocalCommand
1153: option or using the
1.66 jmc 1154: .Ic !\& Ns Ar command
1.65 reyk 1155: escape sequence in
1156: .Xr ssh 1 .
1157: The argument must be
1.240 jmc 1158: .Cm yes
1.65 reyk 1159: or
1.240 jmc 1160: .Cm no
1161: (the default).
1.127 markus 1162: .It Cm PKCS11Provider
1163: Specifies which PKCS#11 provider to use.
1.144 jmc 1164: The argument to this keyword is the PKCS#11 shared library
1.127 markus 1165: .Xr ssh 1
1.128 markus 1166: should use to communicate with a PKCS#11 token providing the user's
1.127 markus 1167: private RSA key.
1.67 jmc 1168: .It Cm Port
1169: Specifies the port number to connect on the remote host.
1.84 jmc 1170: The default is 22.
1.1 stevesk 1171: .It Cm PreferredAuthentications
1.226 jmc 1172: Specifies the order in which the client should try authentication methods.
1.48 jmc 1173: This allows a client to prefer one method (e.g.\&
1.1 stevesk 1174: .Cm keyboard-interactive )
1.48 jmc 1175: over another method (e.g.\&
1.131 jmc 1176: .Cm password ) .
1177: The default is:
1178: .Bd -literal -offset indent
1179: gssapi-with-mic,hostbased,publickey,
1180: keyboard-interactive,password
1181: .Ed
1.1 stevesk 1182: .It Cm ProxyCommand
1183: Specifies the command to use to connect to the server.
1184: The command
1.190 djm 1185: string extends to the end of the line, and is executed
1186: using the user's shell
1187: .Ql exec
1188: directive to avoid a lingering shell process.
1189: .Pp
1.239 jmc 1190: Arguments to
1191: .Cm ProxyCommand
1192: accept the tokens described in the
1193: .Sx TOKENS
1194: section.
1.1 stevesk 1195: The command can be basically anything,
1196: and should read from its standard input and write to its standard output.
1197: It should eventually connect an
1198: .Xr sshd 8
1199: server running on some machine, or execute
1200: .Ic sshd -i
1201: somewhere.
1202: Host key management will be done using the
1203: HostName of the host being connected (defaulting to the name typed by
1204: the user).
1.7 jmc 1205: Setting the command to
1.240 jmc 1206: .Cm none
1.6 markus 1207: disables this option entirely.
1.1 stevesk 1208: Note that
1209: .Cm CheckHostIP
1210: is not available for connects with a proxy command.
1.52 djm 1211: .Pp
1212: This directive is useful in conjunction with
1213: .Xr nc 1
1214: and its proxy support.
1.53 jmc 1215: For example, the following directive would connect via an HTTP proxy at
1.52 djm 1216: 192.0.2.0:
1217: .Bd -literal -offset 3n
1218: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1219: .Ed
1.233 djm 1220: .It Cm ProxyJump
1.260 millert 1221: Specifies one or more jump proxies as either
1.233 djm 1222: .Xo
1223: .Sm off
1.234 jmc 1224: .Op Ar user No @
1.233 djm 1225: .Ar host
1.234 jmc 1226: .Op : Ns Ar port
1.233 djm 1227: .Sm on
1.260 millert 1228: or an ssh URI
1.233 djm 1229: .Xc .
1.235 djm 1230: Multiple proxies may be separated by comma characters and will be visited
1.236 djm 1231: sequentially.
1.233 djm 1232: Setting this option will cause
1233: .Xr ssh 1
1234: to connect to the target host by first making a
1235: .Xr ssh 1
1236: connection to the specified
1237: .Cm ProxyJump
1238: host and then establishing a
1.234 jmc 1239: TCP forwarding to the ultimate target from there.
1.233 djm 1240: .Pp
1241: Note that this option will compete with the
1242: .Cm ProxyCommand
1243: option - whichever is specified first will prevent later instances of the
1244: other from taking effect.
1.167 djm 1245: .It Cm ProxyUseFdpass
1.168 jmc 1246: Specifies that
1.167 djm 1247: .Cm ProxyCommand
1248: will pass a connected file descriptor back to
1.168 jmc 1249: .Xr ssh 1
1.167 djm 1250: instead of continuing to execute and pass data.
1251: The default is
1.240 jmc 1252: .Cm no .
1.213 markus 1253: .It Cm PubkeyAcceptedKeyTypes
1254: Specifies the key types that will be used for public key authentication
1.279 djm 1255: as a comma-separated list of patterns.
1.214 djm 1256: Alternately if the specified value begins with a
1257: .Sq +
1258: character, then the key types after it will be appended to the default
1259: instead of replacing it.
1.241 djm 1260: If the specified value begins with a
1261: .Sq -
1262: character, then the specified key types (including wildcards) will be removed
1263: from the default set instead of replacing them.
1.213 markus 1264: The default for this option is:
1265: .Bd -literal -offset 3n
1266: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1267: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1268: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1269: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 1270: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 1271: ssh-rsa-cert-v01@openssh.com,
1272: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 1273: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 1274: .Ed
1275: .Pp
1.240 jmc 1276: The list of available key types may also be obtained using
1277: .Qq ssh -Q key .
1.1 stevesk 1278: .It Cm PubkeyAuthentication
1279: Specifies whether to try public key authentication.
1280: The argument to this keyword must be
1.240 jmc 1281: .Cm yes
1282: (the default)
1.1 stevesk 1283: or
1.240 jmc 1284: .Cm no .
1.75 dtucker 1285: .It Cm RekeyLimit
1286: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1287: session key is renegotiated, optionally followed a maximum amount of
1288: time that may pass before the session key is renegotiated.
1289: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1290: .Sq K ,
1291: .Sq M ,
1.75 dtucker 1292: or
1.76 jmc 1293: .Sq G
1.75 dtucker 1294: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1295: The default is between
1.84 jmc 1296: .Sq 1G
1.75 dtucker 1297: and
1.84 jmc 1298: .Sq 4G ,
1.75 dtucker 1299: depending on the cipher.
1.162 dtucker 1300: The optional second value is specified in seconds and may use any of the
1301: units documented in the
1.240 jmc 1302: .Sx TIME FORMATS
1303: section of
1.162 dtucker 1304: .Xr sshd_config 5 .
1305: The default value for
1306: .Cm RekeyLimit
1307: is
1.240 jmc 1308: .Cm default none ,
1.162 dtucker 1309: which means that rekeying is performed after the cipher's default amount
1310: of data has been sent or received and no time based rekeying is done.
1.249 bluhm 1311: .It Cm RemoteCommand
1312: Specifies a command to execute on the remote machine after successfully
1313: connecting to the server.
1314: The command string extends to the end of the line, and is executed with
1315: the user's shell.
1.250 jmc 1316: Arguments to
1317: .Cm RemoteCommand
1318: accept the tokens described in the
1319: .Sx TOKENS
1320: section.
1.1 stevesk 1321: .It Cm RemoteForward
1.74 jmc 1322: Specifies that a TCP port on the remote machine be forwarded over
1.256 markus 1323: the secure channel.
1.273 djm 1324: The remote port may either be forwarded to a specified host and port
1.256 markus 1325: from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
1326: client to connect to arbitrary destinations from the local machine.
1.49 jmc 1327: The first argument must be
1.43 djm 1328: .Sm off
1.49 jmc 1329: .Oo Ar bind_address : Oc Ar port
1.43 djm 1330: .Sm on
1.256 markus 1331: If forwarding to a specific destination then the second argument must be
1332: .Ar host : Ns Ar hostport ,
1333: otherwise if no destination argument is specified then the remote forwarding
1334: will be established as a SOCKS proxy.
1335: .Pp
1.138 djm 1336: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.1 stevesk 1337: Multiple forwardings may be specified, and additional
1338: forwardings can be given on the command line.
1.113 stevesk 1339: Privileged ports can be forwarded only when
1340: logging in as root on the remote machine.
1.118 jmc 1341: .Pp
1.117 djm 1342: If the
1343: .Ar port
1.240 jmc 1344: argument is 0,
1.117 djm 1345: the listen port will be dynamically allocated on the server and reported
1346: to the client at run time.
1.43 djm 1347: .Pp
1348: If the
1349: .Ar bind_address
1350: is not specified, the default is to only bind to loopback addresses.
1351: If the
1352: .Ar bind_address
1353: is
1354: .Ql *
1355: or an empty string, then the forwarding is requested to listen on all
1356: interfaces.
1357: Specifying a remote
1358: .Ar bind_address
1.46 jmc 1359: will only succeed if the server's
1360: .Cm GatewayPorts
1.43 djm 1361: option is enabled (see
1.46 jmc 1362: .Xr sshd_config 5 ) .
1.149 djm 1363: .It Cm RequestTTY
1364: Specifies whether to request a pseudo-tty for the session.
1365: The argument may be one of:
1.240 jmc 1366: .Cm no
1.149 djm 1367: (never request a TTY),
1.240 jmc 1368: .Cm yes
1.149 djm 1369: (always request a TTY when standard input is a TTY),
1.240 jmc 1370: .Cm force
1.149 djm 1371: (always request a TTY) or
1.240 jmc 1372: .Cm auto
1.149 djm 1373: (request a TTY when opening a login session).
1374: This option mirrors the
1375: .Fl t
1376: and
1377: .Fl T
1378: flags for
1379: .Xr ssh 1 .
1.196 djm 1380: .It Cm RevokedHostKeys
1381: Specifies revoked host public keys.
1382: Keys listed in this file will be refused for host authentication.
1383: Note that if this file does not exist or is not readable,
1384: then host authentication will be refused for all hosts.
1385: Keys may be specified as a text file, listing one public key per line, or as
1386: an OpenSSH Key Revocation List (KRL) as generated by
1387: .Xr ssh-keygen 1 .
1388: For more information on KRLs, see the KEY REVOCATION LISTS section in
1389: .Xr ssh-keygen 1 .
1.32 djm 1390: .It Cm SendEnv
1391: Specifies what variables from the local
1392: .Xr environ 7
1393: should be sent to the server.
1.84 jmc 1394: The server must also support it, and the server must be configured to
1.33 djm 1395: accept these environment variables.
1.207 dtucker 1396: Note that the
1397: .Ev TERM
1.208 jmc 1398: environment variable is always sent whenever a
1.207 dtucker 1399: pseudo-terminal is requested as it is required by the protocol.
1.32 djm 1400: Refer to
1401: .Cm AcceptEnv
1402: in
1403: .Xr sshd_config 5
1404: for how to configure the server.
1.80 jmc 1405: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1406: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1407: across multiple
1408: .Cm SendEnv
1409: directives.
1.81 jmc 1410: .Pp
1411: See
1412: .Sx PATTERNS
1413: for more information on patterns.
1.271 djm 1414: .Pp
1.272 jmc 1415: It is possible to clear previously set
1.271 djm 1416: .Cm SendEnv
1417: variable names by prefixing patterns with
1418: .Pa - .
1419: The default is not to send any environment variables.
1.28 markus 1420: .It Cm ServerAliveCountMax
1.73 jmc 1421: Sets the number of server alive messages (see below) which may be
1.28 markus 1422: sent without
1.84 jmc 1423: .Xr ssh 1
1.28 markus 1424: receiving any messages back from the server.
1425: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1426: ssh will disconnect from the server, terminating the session.
1.28 markus 1427: It is important to note that the use of server alive messages is very
1428: different from
1429: .Cm TCPKeepAlive
1430: (below).
1431: The server alive messages are sent through the encrypted channel
1432: and therefore will not be spoofable.
1433: The TCP keepalive option enabled by
1434: .Cm TCPKeepAlive
1435: is spoofable.
1436: The server alive mechanism is valuable when the client or
1437: server depend on knowing when a connection has become inactive.
1438: .Pp
1439: The default value is 3.
1440: If, for example,
1441: .Cm ServerAliveInterval
1.84 jmc 1442: (see below) is set to 15 and
1.28 markus 1443: .Cm ServerAliveCountMax
1.84 jmc 1444: is left at the default, if the server becomes unresponsive,
1445: ssh will disconnect after approximately 45 seconds.
1.67 jmc 1446: .It Cm ServerAliveInterval
1447: Sets a timeout interval in seconds after which if no data has been received
1448: from the server,
1.84 jmc 1449: .Xr ssh 1
1.67 jmc 1450: will send a message through the encrypted
1451: channel to request a response from the server.
1452: The default
1453: is 0, indicating that these messages will not be sent to the server.
1.277 jmc 1454: .It Cm SetEnv
1455: Directly specify one or more environment variables and their contents to
1456: be sent to the server.
1457: Similarly to
1458: .Cm SendEnv ,
1459: the server must be prepared to accept the environment variable.
1.191 millert 1460: .It Cm StreamLocalBindMask
1461: Sets the octal file creation mode mask
1462: .Pq umask
1463: used when creating a Unix-domain socket file for local or remote
1464: port forwarding.
1465: This option is only used for port forwarding to a Unix-domain socket file.
1466: .Pp
1467: The default value is 0177, which creates a Unix-domain socket file that is
1468: readable and writable only by the owner.
1469: Note that not all operating systems honor the file mode on Unix-domain
1470: socket files.
1471: .It Cm StreamLocalBindUnlink
1472: Specifies whether to remove an existing Unix-domain socket file for local
1473: or remote port forwarding before creating a new one.
1474: If the socket file already exists and
1475: .Cm StreamLocalBindUnlink
1476: is not enabled,
1477: .Nm ssh
1478: will be unable to forward the port to the Unix-domain socket file.
1479: This option is only used for port forwarding to a Unix-domain socket file.
1480: .Pp
1481: The argument must be
1.240 jmc 1482: .Cm yes
1.191 millert 1483: or
1.240 jmc 1484: .Cm no
1485: (the default).
1.1 stevesk 1486: .It Cm StrictHostKeyChecking
1487: If this flag is set to
1.240 jmc 1488: .Cm yes ,
1.84 jmc 1489: .Xr ssh 1
1.1 stevesk 1490: will never automatically add host keys to the
1.50 djm 1491: .Pa ~/.ssh/known_hosts
1.1 stevesk 1492: file, and refuses to connect to hosts whose host key has changed.
1.263 dtucker 1493: This provides maximum protection against man-in-the-middle (MITM) attacks,
1.84 jmc 1494: though it can be annoying when the
1.1 stevesk 1495: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1496: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1497: frequently made.
1498: This option forces the user to manually
1499: add all new hosts.
1.255 jmc 1500: .Pp
1.1 stevesk 1501: If this flag is set to
1.254 djm 1502: .Dq accept-new
1.255 jmc 1503: then ssh will automatically add new host keys to the user
1.254 djm 1504: known hosts files, but will not permit connections to hosts with
1505: changed host keys.
1506: If this flag is set to
1507: .Dq no
1508: or
1509: .Dq off ,
1.255 jmc 1510: ssh will automatically add new host keys to the user known hosts files
1511: and allow connections to hosts with changed hostkeys to proceed,
1512: subject to some restrictions.
1.1 stevesk 1513: If this flag is set to
1.240 jmc 1514: .Cm ask
1515: (the default),
1.1 stevesk 1516: new host keys
1517: will be added to the user known host files only after the user
1518: has confirmed that is what they really want to do, and
1.84 jmc 1519: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1520: The host keys of
1521: known hosts will be verified automatically in all cases.
1.244 jmc 1522: .It Cm SyslogFacility
1523: Gives the facility code that is used when logging messages from
1524: .Xr ssh 1 .
1525: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1526: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1527: The default is USER.
1.26 markus 1528: .It Cm TCPKeepAlive
1529: Specifies whether the system should send TCP keepalive messages to the
1530: other side.
1531: If they are sent, death of the connection or crash of one
1532: of the machines will be properly noticed.
1533: However, this means that
1534: connections will die if the route is down temporarily, and some people
1535: find it annoying.
1536: .Pp
1537: The default is
1.240 jmc 1538: .Cm yes
1.26 markus 1539: (to send TCP keepalive messages), and the client will notice
1540: if the network goes down or the remote host dies.
1541: This is important in scripts, and many users want it too.
1542: .Pp
1543: To disable TCP keepalive messages, the value should be set to
1.240 jmc 1544: .Cm no .
1.265 djm 1545: See also
1546: .Cm ServerAliveInterval
1547: for protocol-level keepalives.
1.65 reyk 1548: .It Cm Tunnel
1.95 stevesk 1549: Request
1.65 reyk 1550: .Xr tun 4
1.69 jmc 1551: device forwarding between the client and the server.
1.65 reyk 1552: The argument must be
1.240 jmc 1553: .Cm yes ,
1554: .Cm point-to-point
1.95 stevesk 1555: (layer 3),
1.240 jmc 1556: .Cm ethernet
1.95 stevesk 1557: (layer 2),
1.65 reyk 1558: or
1.240 jmc 1559: .Cm no
1560: (the default).
1.95 stevesk 1561: Specifying
1.240 jmc 1562: .Cm yes
1.95 stevesk 1563: requests the default tunnel mode, which is
1.240 jmc 1564: .Cm point-to-point .
1.65 reyk 1565: .It Cm TunnelDevice
1.95 stevesk 1566: Specifies the
1.65 reyk 1567: .Xr tun 4
1.95 stevesk 1568: devices to open on the client
1569: .Pq Ar local_tun
1570: and the server
1571: .Pq Ar remote_tun .
1572: .Pp
1573: The argument must be
1574: .Sm off
1575: .Ar local_tun Op : Ar remote_tun .
1576: .Sm on
1577: The devices may be specified by numerical ID or the keyword
1.240 jmc 1578: .Cm any ,
1.95 stevesk 1579: which uses the next available tunnel device.
1580: If
1581: .Ar remote_tun
1582: is not specified, it defaults to
1.240 jmc 1583: .Cm any .
1.95 stevesk 1584: The default is
1.240 jmc 1585: .Cm any:any .
1.201 djm 1586: .It Cm UpdateHostKeys
1.200 djm 1587: Specifies whether
1588: .Xr ssh 1
1589: should accept notifications of additional hostkeys from the server sent
1590: after authentication has completed and add them to
1591: .Cm UserKnownHostsFile .
1592: The argument must be
1.240 jmc 1593: .Cm yes ,
1594: .Cm no
1.204 djm 1595: (the default) or
1.240 jmc 1596: .Cm ask .
1.200 djm 1597: Enabling this option allows learning alternate hostkeys for a server
1.201 djm 1598: and supports graceful key rotation by allowing a server to send replacement
1599: public keys before old ones are removed.
1.200 djm 1600: Additional hostkeys are only accepted if the key used to authenticate the
1.220 sobrado 1601: host was already trusted or explicitly accepted by the user.
1.204 djm 1602: If
1603: .Cm UpdateHostKeys
1604: is set to
1.240 jmc 1605: .Cm ask ,
1.204 djm 1606: then the user is asked to confirm the modifications to the known_hosts file.
1.205 djm 1607: Confirmation is currently incompatible with
1608: .Cm ControlPersist ,
1609: and will be disabled if it is enabled.
1.200 djm 1610: .Pp
1611: Presently, only
1612: .Xr sshd 8
1613: from OpenSSH 6.8 and greater support the
1.240 jmc 1614: .Qq hostkeys@openssh.com
1.200 djm 1615: protocol extension used to inform the client of all the server's hostkeys.
1.1 stevesk 1616: .It Cm User
1617: Specifies the user to log in as.
1618: This can be useful when a different user name is used on different machines.
1619: This saves the trouble of
1620: having to remember to give the user name on the command line.
1621: .It Cm UserKnownHostsFile
1.151 djm 1622: Specifies one or more files to use for the user
1623: host key database, separated by whitespace.
1624: The default is
1625: .Pa ~/.ssh/known_hosts ,
1626: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1627: .It Cm VerifyHostKeyDNS
1628: Specifies whether to verify the remote key using DNS and SSHFP resource
1629: records.
1.24 jakob 1630: If this option is set to
1.240 jmc 1631: .Cm yes ,
1.25 jmc 1632: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1633: from DNS.
1634: Insecure fingerprints will be handled as if this option was set to
1.240 jmc 1635: .Cm ask .
1.24 jakob 1636: If this option is set to
1.240 jmc 1637: .Cm ask ,
1.24 jakob 1638: information on fingerprint match will be displayed, but the user will still
1639: need to confirm new host keys according to the
1640: .Cm StrictHostKeyChecking
1641: option.
1.8 jakob 1642: The default is
1.240 jmc 1643: .Cm no .
1.84 jmc 1644: .Pp
1.240 jmc 1645: See also
1646: .Sx VERIFYING HOST KEYS
1647: in
1.84 jmc 1648: .Xr ssh 1 .
1.111 grunk 1649: .It Cm VisualHostKey
1650: If this flag is set to
1.240 jmc 1651: .Cm yes ,
1.111 grunk 1652: an ASCII art representation of the remote host key fingerprint is
1.197 djm 1653: printed in addition to the fingerprint string at login and
1.114 stevesk 1654: for unknown host keys.
1.111 grunk 1655: If this flag is set to
1.240 jmc 1656: .Cm no
1657: (the default),
1.114 stevesk 1658: no fingerprint strings are printed at login and
1.197 djm 1659: only the fingerprint string will be printed for unknown host keys.
1.1 stevesk 1660: .It Cm XAuthLocation
1.5 stevesk 1661: Specifies the full pathname of the
1.1 stevesk 1662: .Xr xauth 1
1663: program.
1664: The default is
1665: .Pa /usr/X11R6/bin/xauth .
1666: .El
1.86 jmc 1667: .Sh PATTERNS
1668: A
1669: .Em pattern
1670: consists of zero or more non-whitespace characters,
1671: .Sq *
1672: (a wildcard that matches zero or more characters),
1673: or
1674: .Sq ?\&
1675: (a wildcard that matches exactly one character).
1676: For example, to specify a set of declarations for any host in the
1.240 jmc 1677: .Qq .co.uk
1.86 jmc 1678: set of domains,
1679: the following pattern could be used:
1680: .Pp
1681: .Dl Host *.co.uk
1682: .Pp
1683: The following pattern
1684: would match any host in the 192.168.0.[0-9] network range:
1685: .Pp
1686: .Dl Host 192.168.0.?
1687: .Pp
1688: A
1689: .Em pattern-list
1690: is a comma-separated list of patterns.
1691: Patterns within pattern-lists may be negated
1692: by preceding them with an exclamation mark
1693: .Pq Sq !\& .
1694: For example,
1.174 djm 1695: to allow a key to be used from anywhere within an organization
1.86 jmc 1696: except from the
1.240 jmc 1697: .Qq dialup
1.86 jmc 1698: pool,
1699: the following entry (in authorized_keys) could be used:
1700: .Pp
1701: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.258 djm 1702: .Pp
1703: Note that a negated match will never produce a positive result by itself.
1704: For example, attempting to match
1705: .Qq host3
1706: against the following pattern-list will fail:
1707: .Pp
1708: .Dl from=\&"!host1,!host2\&"
1709: .Pp
1710: The solution here is to include a term that will yield a positive match,
1711: such as a wildcard:
1712: .Pp
1713: .Dl from=\&"!host1,!host2,*\&"
1.239 jmc 1714: .Sh TOKENS
1715: Arguments to some keywords can make use of tokens,
1716: which are expanded at runtime:
1717: .Pp
1718: .Bl -tag -width XXXX -offset indent -compact
1719: .It %%
1720: A literal
1721: .Sq % .
1722: .It \&%C
1.257 jmc 1723: Hash of %l%h%p%r.
1.239 jmc 1724: .It %d
1725: Local user's home directory.
1726: .It %h
1727: The remote hostname.
1728: .It %i
1729: The local user ID.
1730: .It %L
1731: The local hostname.
1732: .It %l
1733: The local hostname, including the domain name.
1734: .It %n
1735: The original remote hostname, as given on the command line.
1736: .It %p
1737: The remote port.
1738: .It %r
1739: The remote username.
1.261 djm 1740: .It \&%T
1741: The local
1742: .Xr tun 4
1743: or
1744: .Xr tap 4
1745: network interface assigned if
1.262 jmc 1746: tunnel forwarding was requested, or
1747: .Qq NONE
1.261 djm 1748: otherwise.
1.239 jmc 1749: .It %u
1750: The local username.
1751: .El
1752: .Pp
1753: .Cm Match exec
1.274 djm 1754: accepts the tokens %%, %h, %i, %L, %l, %n, %p, %r, and %u.
1.239 jmc 1755: .Pp
1756: .Cm CertificateFile
1.275 jmc 1757: accepts the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1758: .Pp
1759: .Cm ControlPath
1760: accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
1761: .Pp
1762: .Cm HostName
1763: accepts the tokens %% and %h.
1764: .Pp
1765: .Cm IdentityAgent
1766: and
1767: .Cm IdentityFile
1.275 jmc 1768: accept the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1769: .Pp
1770: .Cm LocalCommand
1.275 jmc 1771: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, %T, and %u.
1.239 jmc 1772: .Pp
1773: .Cm ProxyCommand
1774: accepts the tokens %%, %h, %p, and %r.
1.250 jmc 1775: .Pp
1776: .Cm RemoteCommand
1.274 djm 1777: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, and %u.
1.1 stevesk 1778: .Sh FILES
1779: .Bl -tag -width Ds
1.50 djm 1780: .It Pa ~/.ssh/config
1.1 stevesk 1781: This is the per-user configuration file.
1782: The format of this file is described above.
1.84 jmc 1783: This file is used by the SSH client.
1.30 djm 1784: Because of the potential for abuse, this file must have strict permissions:
1785: read/write for the user, and not accessible by others.
1.1 stevesk 1786: .It Pa /etc/ssh/ssh_config
1787: Systemwide configuration file.
1788: This file provides defaults for those
1789: values that are not specified in the user's configuration file, and
1790: for those users who do not have a configuration file.
1791: This file must be world-readable.
1792: .El
1.13 jmc 1793: .Sh SEE ALSO
1794: .Xr ssh 1
1.1 stevesk 1795: .Sh AUTHORS
1.240 jmc 1796: .An -nosplit
1.1 stevesk 1797: OpenSSH is a derivative of the original and free
1.240 jmc 1798: ssh 1.2.12 release by
1799: .An Tatu Ylonen .
1800: .An Aaron Campbell , Bob Beck , Markus Friedl ,
1801: .An Niels Provos , Theo de Raadt
1802: and
1803: .An Dug Song
1.1 stevesk 1804: removed many bugs, re-added newer features and
1805: created OpenSSH.
1.240 jmc 1806: .An Markus Friedl
1807: contributed the support for SSH protocol versions 1.5 and 2.0.
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