Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.306
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
18: .\" are met:
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
23: .\" documentation and/or other materials provided with the distribution.
24: .\"
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
27: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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1.306 ! djm 36: .\" $OpenBSD: ssh_config.5,v 1.305 2019/11/07 08:38:38 naddy Exp $
! 37: .Dd $Mdocdate: November 7 2019 $
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 ,
1.287 djm 142: .Cm final ,
1.176 djm 143: .Cm exec ,
1.169 djm 144: .Cm host ,
145: .Cm originalhost ,
146: .Cm user ,
147: and
148: .Cm localuser .
1.193 djm 149: The
150: .Cm all
151: criteria must appear alone or immediately after
1.287 djm 152: .Cm canonical
153: or
154: .Cm final .
1.193 djm 155: Other criteria may be combined arbitrarily.
156: All criteria but
1.288 jmc 157: .Cm all ,
158: .Cm canonical ,
1.193 djm 159: and
1.287 djm 160: .Cm final
1.193 djm 161: require an argument.
162: Criteria may be negated by prepending an exclamation mark
163: .Pq Sq !\& .
1.169 djm 164: .Pp
1.177 jmc 165: The
1.193 djm 166: .Cm canonical
1.210 dtucker 167: keyword matches only when the configuration file is being re-parsed
1.193 djm 168: after hostname canonicalization (see the
169: .Cm CanonicalizeHostname
1.288 jmc 170: option).
1.193 djm 171: This may be useful to specify conditions that work with canonical host
172: names only.
1.287 djm 173: .Pp
174: The
175: .Cm final
176: keyword requests that the configuration be re-parsed (regardless of whether
177: .Cm CanonicalizeHostname
178: is enabled), and matches only during this final pass.
179: If
180: .Cm CanonicalizeHostname
181: is enabled, then
182: .Cm canonical
183: and
184: .Cm final
185: match during the same pass.
186: .Pp
1.193 djm 187: The
1.176 djm 188: .Cm exec
1.177 jmc 189: keyword executes the specified command under the user's shell.
1.169 djm 190: If the command returns a zero exit status then the condition is considered true.
191: Commands containing whitespace characters must be quoted.
1.239 jmc 192: Arguments to
193: .Cm exec
194: accept the tokens described in the
195: .Sx TOKENS
196: section.
1.169 djm 197: .Pp
198: The other keywords' criteria must be single entries or comma-separated
199: lists and may use the wildcard and negation operators described in the
200: .Sx PATTERNS
201: section.
202: The criteria for the
203: .Cm host
204: keyword are matched against the target hostname, after any substitution
205: by the
1.295 jmc 206: .Cm Hostname
1.193 djm 207: or
208: .Cm CanonicalizeHostname
209: options.
1.169 djm 210: The
211: .Cm originalhost
212: keyword matches against the hostname as it was specified on the command-line.
213: The
214: .Cm user
215: keyword matches against the target username on the remote host.
216: The
217: .Cm localuser
218: keyword matches against the name of the local user running
219: .Xr ssh 1
220: (this keyword may be useful in system-wide
221: .Nm
222: files).
1.222 jcs 223: .It Cm AddKeysToAgent
224: Specifies whether keys should be automatically added to a running
1.223 jmc 225: .Xr ssh-agent 1 .
1.222 jcs 226: If this option is set to
1.240 jmc 227: .Cm yes
1.222 jcs 228: and a key is loaded from a file, the key and its passphrase are added to
229: the agent with the default lifetime, as if by
230: .Xr ssh-add 1 .
231: If this option is set to
1.240 jmc 232: .Cm ask ,
233: .Xr ssh 1
1.222 jcs 234: will require confirmation using the
235: .Ev SSH_ASKPASS
236: program before adding a key (see
237: .Xr ssh-add 1
238: for details).
239: If this option is set to
1.240 jmc 240: .Cm confirm ,
1.222 jcs 241: each use of the key must be confirmed, as if the
242: .Fl c
243: option was specified to
244: .Xr ssh-add 1 .
245: If this option is set to
1.240 jmc 246: .Cm no ,
1.222 jcs 247: no keys are added to the agent.
248: The argument must be
1.240 jmc 249: .Cm yes ,
250: .Cm confirm ,
251: .Cm ask ,
1.222 jcs 252: or
1.240 jmc 253: .Cm no
254: (the default).
1.10 djm 255: .It Cm AddressFamily
1.11 jmc 256: Specifies which address family to use when connecting.
257: Valid arguments are
1.240 jmc 258: .Cm any
259: (the default),
260: .Cm inet
1.84 jmc 261: (use IPv4 only), or
1.240 jmc 262: .Cm inet6
1.40 jmc 263: (use IPv6 only).
1.1 stevesk 264: .It Cm BatchMode
265: If set to
1.240 jmc 266: .Cm yes ,
1.1 stevesk 267: passphrase/password querying will be disabled.
268: This option is useful in scripts and other batch jobs where no user
269: is present to supply the password.
270: The argument must be
1.240 jmc 271: .Cm yes
1.1 stevesk 272: or
1.240 jmc 273: .Cm no
274: (the default).
1.268 jmc 275: .It Cm BindAddress
276: Use the specified address on the local machine as the source address of
277: the connection.
278: Only useful on systems with more than one address.
279: .It Cm BindInterface
280: Use the address of the specified interface on the local machine as the
281: source address of the connection.
1.171 djm 282: .It Cm CanonicalDomains
1.172 jmc 283: When
1.173 djm 284: .Cm CanonicalizeHostname
1.171 djm 285: is enabled, this option specifies the list of domain suffixes in which to
286: search for the specified destination host.
1.173 djm 287: .It Cm CanonicalizeFallbackLocal
1.174 djm 288: Specifies whether to fail with an error when hostname canonicalization fails.
1.172 jmc 289: The default,
1.240 jmc 290: .Cm yes ,
1.172 jmc 291: will attempt to look up the unqualified hostname using the system resolver's
1.171 djm 292: search rules.
293: A value of
1.240 jmc 294: .Cm no
1.171 djm 295: will cause
296: .Xr ssh 1
297: to fail instantly if
1.173 djm 298: .Cm CanonicalizeHostname
1.171 djm 299: is enabled and the target hostname cannot be found in any of the domains
300: specified by
301: .Cm CanonicalDomains .
1.173 djm 302: .It Cm CanonicalizeHostname
1.174 djm 303: Controls whether explicit hostname canonicalization is performed.
1.172 jmc 304: The default,
1.240 jmc 305: .Cm no ,
1.171 djm 306: is not to perform any name rewriting and let the system resolver handle all
307: hostname lookups.
308: If set to
1.240 jmc 309: .Cm yes
1.171 djm 310: then, for connections that do not use a
1.284 djm 311: .Cm ProxyCommand
312: or
313: .Cm ProxyJump ,
1.171 djm 314: .Xr ssh 1
1.173 djm 315: will attempt to canonicalize the hostname specified on the command line
1.171 djm 316: using the
317: .Cm CanonicalDomains
318: suffixes and
1.173 djm 319: .Cm CanonicalizePermittedCNAMEs
1.171 djm 320: rules.
321: If
1.173 djm 322: .Cm CanonicalizeHostname
1.171 djm 323: is set to
1.240 jmc 324: .Cm always ,
1.174 djm 325: then canonicalization is applied to proxied connections too.
1.185 djm 326: .Pp
1.193 djm 327: If this option is enabled, then the configuration files are processed
328: again using the new target name to pick up any new configuration in matching
1.185 djm 329: .Cm Host
1.193 djm 330: and
331: .Cm Match
1.185 djm 332: stanzas.
1.173 djm 333: .It Cm CanonicalizeMaxDots
1.172 jmc 334: Specifies the maximum number of dot characters in a hostname before
1.174 djm 335: canonicalization is disabled.
1.240 jmc 336: The default, 1,
1.172 jmc 337: allows a single dot (i.e. hostname.subdomain).
1.173 djm 338: .It Cm CanonicalizePermittedCNAMEs
1.172 jmc 339: Specifies rules to determine whether CNAMEs should be followed when
1.173 djm 340: canonicalizing hostnames.
1.171 djm 341: The rules consist of one or more arguments of
1.172 jmc 342: .Ar source_domain_list : Ns Ar target_domain_list ,
1.171 djm 343: where
344: .Ar source_domain_list
1.174 djm 345: is a pattern-list of domains that may follow CNAMEs in canonicalization,
1.171 djm 346: and
347: .Ar target_domain_list
1.172 jmc 348: is a pattern-list of domains that they may resolve to.
1.171 djm 349: .Pp
350: For example,
1.240 jmc 351: .Qq *.a.example.com:*.b.example.com,*.c.example.com
1.171 djm 352: will allow hostnames matching
1.240 jmc 353: .Qq *.a.example.com
1.173 djm 354: to be canonicalized to names in the
1.240 jmc 355: .Qq *.b.example.com
1.171 djm 356: or
1.240 jmc 357: .Qq *.c.example.com
1.171 djm 358: domains.
1.283 jmc 359: .It Cm CASignatureAlgorithms
360: Specifies which algorithms are allowed for signing of certificates
361: by certificate authorities (CAs).
362: The default is:
363: .Bd -literal -offset indent
1.297 djm 364: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.283 jmc 365: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
366: .Ed
367: .Pp
368: .Xr ssh 1
369: will not accept host certificates signed using algorithms other than those
370: specified.
1.221 djm 371: .It Cm CertificateFile
372: Specifies a file from which the user's certificate is read.
373: A corresponding private key must be provided separately in order
374: to use this certificate either
375: from an
376: .Cm IdentityFile
377: directive or
378: .Fl i
379: flag to
380: .Xr ssh 1 ,
381: via
382: .Xr ssh-agent 1 ,
383: or via a
1.305 naddy 384: .Cm PKCS11Provider
385: or
386: .Cm SecurityKeyProvider .
1.221 djm 387: .Pp
1.239 jmc 388: Arguments to
389: .Cm CertificateFile
390: may use the tilde syntax to refer to a user's home directory
391: or the tokens described in the
392: .Sx TOKENS
393: section.
1.221 djm 394: .Pp
395: It is possible to have multiple certificate files specified in
396: configuration files; these certificates will be tried in sequence.
397: Multiple
398: .Cm CertificateFile
399: directives will add to the list of certificates used for
400: authentication.
1.1 stevesk 401: .It Cm ChallengeResponseAuthentication
1.82 jmc 402: Specifies whether to use challenge-response authentication.
1.1 stevesk 403: The argument to this keyword must be
1.240 jmc 404: .Cm yes
405: (the default)
1.1 stevesk 406: or
1.240 jmc 407: .Cm no .
1.1 stevesk 408: .It Cm CheckHostIP
1.240 jmc 409: If set to
410: .Cm yes
411: (the default),
1.84 jmc 412: .Xr ssh 1
413: will additionally check the host IP address in the
1.1 stevesk 414: .Pa known_hosts
415: file.
1.240 jmc 416: This allows it to detect if a host key changed due to DNS spoofing
1.211 djm 417: and will add addresses of destination hosts to
418: .Pa ~/.ssh/known_hosts
419: in the process, regardless of the setting of
420: .Cm StrictHostKeyChecking .
1.107 grunk 421: If the option is set to
1.240 jmc 422: .Cm no ,
1.1 stevesk 423: the check will not be executed.
424: .It Cm Ciphers
1.245 djm 425: Specifies the ciphers allowed and their order of preference.
1.1 stevesk 426: Multiple ciphers must be comma-separated.
1.299 kn 427: If the specified list begins with a
1.214 djm 428: .Sq +
429: character, then the specified ciphers will be appended to the default set
430: instead of replacing them.
1.299 kn 431: If the specified list begins with a
1.241 djm 432: .Sq -
433: character, then the specified ciphers (including wildcards) will be removed
434: from the default set instead of replacing them.
1.301 naddy 435: If the specified list begins with a
436: .Sq ^
437: character, then the specified ciphers will be placed at the head of the
438: default set.
1.214 djm 439: .Pp
1.180 djm 440: The supported ciphers are:
1.240 jmc 441: .Bd -literal -offset indent
1.186 naddy 442: 3des-cbc
443: aes128-cbc
444: aes192-cbc
445: aes256-cbc
446: aes128-ctr
447: aes192-ctr
448: aes256-ctr
449: aes128-gcm@openssh.com
450: aes256-gcm@openssh.com
451: chacha20-poly1305@openssh.com
1.240 jmc 452: .Ed
1.180 djm 453: .Pp
1.84 jmc 454: The default is:
1.186 naddy 455: .Bd -literal -offset indent
1.215 jmc 456: chacha20-poly1305@openssh.com,
1.186 naddy 457: aes128-ctr,aes192-ctr,aes256-ctr,
1.270 djm 458: aes128-gcm@openssh.com,aes256-gcm@openssh.com
1.1 stevesk 459: .Ed
1.180 djm 460: .Pp
1.240 jmc 461: The list of available ciphers may also be obtained using
462: .Qq ssh -Q cipher .
1.1 stevesk 463: .It Cm ClearAllForwardings
1.84 jmc 464: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 465: specified in the configuration files or on the command line be
1.7 jmc 466: cleared.
467: This option is primarily useful when used from the
1.84 jmc 468: .Xr ssh 1
1.1 stevesk 469: command line to clear port forwardings set in
470: configuration files, and is automatically set by
471: .Xr scp 1
472: and
473: .Xr sftp 1 .
474: The argument must be
1.240 jmc 475: .Cm yes
1.1 stevesk 476: or
1.240 jmc 477: .Cm no
478: (the default).
1.1 stevesk 479: .It Cm Compression
480: Specifies whether to use compression.
481: The argument must be
1.240 jmc 482: .Cm yes
1.1 stevesk 483: or
1.240 jmc 484: .Cm no
485: (the default).
1.247 naddy 486: .It Cm ConnectionAttempts
487: Specifies the number of tries (one per second) to make before exiting.
488: The argument must be an integer.
489: This may be useful in scripts if the connection sometimes fails.
490: The default is 1.
1.9 djm 491: .It Cm ConnectTimeout
1.84 jmc 492: Specifies the timeout (in seconds) used when connecting to the
493: SSH server, instead of using the default system TCP timeout.
1.302 djm 494: This timeout is applied both to establishing the connection and to performing
495: the initial SSH protocol handshake and key exchange.
1.36 djm 496: .It Cm ControlMaster
497: Enables the sharing of multiple sessions over a single network connection.
498: When set to
1.240 jmc 499: .Cm yes ,
1.84 jmc 500: .Xr ssh 1
1.36 djm 501: will listen for connections on a control socket specified using the
502: .Cm ControlPath
503: argument.
504: Additional sessions can connect to this socket using the same
505: .Cm ControlPath
506: with
507: .Cm ControlMaster
508: set to
1.240 jmc 509: .Cm no
1.38 jmc 510: (the default).
1.64 jmc 511: These sessions will try to reuse the master instance's network connection
1.63 djm 512: rather than initiating new ones, but will fall back to connecting normally
513: if the control socket does not exist, or is not listening.
514: .Pp
1.37 djm 515: Setting this to
1.240 jmc 516: .Cm ask
517: will cause
518: .Xr ssh 1
1.206 jmc 519: to listen for control connections, but require confirmation using
520: .Xr ssh-askpass 1 .
1.51 jakob 521: If the
522: .Cm ControlPath
1.84 jmc 523: cannot be opened,
1.240 jmc 524: .Xr ssh 1
525: will continue without connecting to a master instance.
1.58 djm 526: .Pp
527: X11 and
1.59 jmc 528: .Xr ssh-agent 1
1.58 djm 529: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 530: display and agent forwarded will be the one belonging to the master
1.59 jmc 531: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 532: .Pp
533: Two additional options allow for opportunistic multiplexing: try to use a
534: master connection but fall back to creating a new one if one does not already
535: exist.
536: These options are:
1.240 jmc 537: .Cm auto
1.56 djm 538: and
1.240 jmc 539: .Cm autoask .
1.56 djm 540: The latter requires confirmation like the
1.240 jmc 541: .Cm ask
1.56 djm 542: option.
1.36 djm 543: .It Cm ControlPath
1.55 djm 544: Specify the path to the control socket used for connection sharing as described
545: in the
1.36 djm 546: .Cm ControlMaster
1.57 djm 547: section above or the string
1.240 jmc 548: .Cm none
1.57 djm 549: to disable connection sharing.
1.239 jmc 550: Arguments to
551: .Cm ControlPath
552: may use the tilde syntax to refer to a user's home directory
553: or the tokens described in the
554: .Sx TOKENS
555: section.
1.56 djm 556: It is recommended that any
557: .Cm ControlPath
558: used for opportunistic connection sharing include
1.195 djm 559: at least %h, %p, and %r (or alternatively %C) and be placed in a directory
560: that is not writable by other users.
1.56 djm 561: This ensures that shared connections are uniquely identified.
1.137 djm 562: .It Cm ControlPersist
563: When used in conjunction with
564: .Cm ControlMaster ,
565: specifies that the master connection should remain open
566: in the background (waiting for future client connections)
567: after the initial client connection has been closed.
568: If set to
1.240 jmc 569: .Cm no ,
1.137 djm 570: then the master connection will not be placed into the background,
571: and will close as soon as the initial client connection is closed.
572: If set to
1.240 jmc 573: .Cm yes
574: or 0,
1.137 djm 575: then the master connection will remain in the background indefinitely
576: (until killed or closed via a mechanism such as the
1.240 jmc 577: .Qq ssh -O exit ) .
1.137 djm 578: If set to a time in seconds, or a time in any of the formats documented in
579: .Xr sshd_config 5 ,
580: then the backgrounded master connection will automatically terminate
581: after it has remained idle (with no client connections) for the
582: specified time.
1.38 jmc 583: .It Cm DynamicForward
1.74 jmc 584: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 585: over the secure channel, and the application
586: protocol is then used to determine where to connect to from the
587: remote machine.
1.62 djm 588: .Pp
589: The argument must be
590: .Sm off
591: .Oo Ar bind_address : Oc Ar port .
592: .Sm on
1.138 djm 593: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 594: By default, the local port is bound in accordance with the
595: .Cm GatewayPorts
596: setting.
597: However, an explicit
598: .Ar bind_address
599: may be used to bind the connection to a specific address.
600: The
601: .Ar bind_address
602: of
1.240 jmc 603: .Cm localhost
1.62 djm 604: indicates that the listening port be bound for local use only, while an
605: empty address or
606: .Sq *
607: indicates that the port should be available from all interfaces.
608: .Pp
1.38 jmc 609: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 610: .Xr ssh 1
1.38 jmc 611: will act as a SOCKS server.
612: Multiple forwardings may be specified, and
613: additional forwardings can be given on the command line.
614: Only the superuser can forward privileged ports.
1.14 markus 615: .It Cm EnableSSHKeysign
616: Setting this option to
1.240 jmc 617: .Cm yes
1.14 markus 618: in the global client configuration file
619: .Pa /etc/ssh/ssh_config
620: enables the use of the helper program
621: .Xr ssh-keysign 8
622: during
623: .Cm HostbasedAuthentication .
624: The argument must be
1.240 jmc 625: .Cm yes
1.14 markus 626: or
1.240 jmc 627: .Cm no
628: (the default).
1.23 jmc 629: This option should be placed in the non-hostspecific section.
1.14 markus 630: See
631: .Xr ssh-keysign 8
632: for more information.
1.1 stevesk 633: .It Cm EscapeChar
634: Sets the escape character (default:
635: .Ql ~ ) .
636: The escape character can also
637: be set on the command line.
638: The argument should be a single character,
639: .Ql ^
640: followed by a letter, or
1.240 jmc 641: .Cm none
1.1 stevesk 642: to disable the escape
643: character entirely (making the connection transparent for binary
644: data).
1.96 markus 645: .It Cm ExitOnForwardFailure
646: Specifies whether
647: .Xr ssh 1
648: should terminate the connection if it cannot set up all requested
1.216 djm 649: dynamic, tunnel, local, and remote port forwardings, (e.g.\&
1.217 jmc 650: if either end is unable to bind and listen on a specified port).
1.216 djm 651: Note that
652: .Cm ExitOnForwardFailure
653: does not apply to connections made over port forwardings and will not,
654: for example, cause
655: .Xr ssh 1
656: to exit if TCP connections to the ultimate forwarding destination fail.
1.96 markus 657: The argument must be
1.240 jmc 658: .Cm yes
1.96 markus 659: or
1.240 jmc 660: .Cm no
661: (the default).
1.197 djm 662: .It Cm FingerprintHash
663: Specifies the hash algorithm used when displaying key fingerprints.
664: Valid options are:
1.240 jmc 665: .Cm md5
1.197 djm 666: and
1.240 jmc 667: .Cm sha256
668: (the default).
1.1 stevesk 669: .It Cm ForwardAgent
670: Specifies whether the connection to the authentication agent (if any)
671: will be forwarded to the remote machine.
672: The argument must be
1.240 jmc 673: .Cm yes
1.1 stevesk 674: or
1.240 jmc 675: .Cm no
676: (the default).
1.3 stevesk 677: .Pp
1.7 jmc 678: Agent forwarding should be enabled with caution.
679: Users with the ability to bypass file permissions on the remote host
680: (for the agent's Unix-domain socket)
681: can access the local agent through the forwarded connection.
682: An attacker cannot obtain key material from the agent,
1.3 stevesk 683: however they can perform operations on the keys that enable them to
684: authenticate using the identities loaded into the agent.
1.1 stevesk 685: .It Cm ForwardX11
686: Specifies whether X11 connections will be automatically redirected
687: over the secure channel and
688: .Ev DISPLAY
689: set.
690: The argument must be
1.240 jmc 691: .Cm yes
1.1 stevesk 692: or
1.240 jmc 693: .Cm no
694: (the default).
1.3 stevesk 695: .Pp
1.7 jmc 696: X11 forwarding should be enabled with caution.
697: Users with the ability to bypass file permissions on the remote host
1.22 markus 698: (for the user's X11 authorization database)
1.7 jmc 699: can access the local X11 display through the forwarded connection.
1.22 markus 700: An attacker may then be able to perform activities such as keystroke monitoring
701: if the
702: .Cm ForwardX11Trusted
703: option is also enabled.
1.134 djm 704: .It Cm ForwardX11Timeout
1.135 jmc 705: Specify a timeout for untrusted X11 forwarding
706: using the format described in the
1.240 jmc 707: .Sx TIME FORMATS
708: section of
1.134 djm 709: .Xr sshd_config 5 .
710: X11 connections received by
711: .Xr ssh 1
712: after this time will be refused.
1.285 djm 713: Setting
714: .Cm ForwardX11Timeout
715: to zero will disable the timeout and permit X11 forwarding for the life
716: of the connection.
1.134 djm 717: The default is to disable untrusted X11 forwarding after twenty minutes has
718: elapsed.
1.22 markus 719: .It Cm ForwardX11Trusted
1.34 jmc 720: If this option is set to
1.240 jmc 721: .Cm yes ,
1.84 jmc 722: remote X11 clients will have full access to the original X11 display.
1.42 djm 723: .Pp
1.22 markus 724: If this option is set to
1.240 jmc 725: .Cm no
726: (the default),
1.84 jmc 727: remote X11 clients will be considered untrusted and prevented
1.22 markus 728: from stealing or tampering with data belonging to trusted X11
729: clients.
1.42 djm 730: Furthermore, the
731: .Xr xauth 1
732: token used for the session will be set to expire after 20 minutes.
733: Remote clients will be refused access after this time.
1.22 markus 734: .Pp
735: See the X11 SECURITY extension specification for full details on
736: the restrictions imposed on untrusted clients.
1.1 stevesk 737: .It Cm GatewayPorts
738: Specifies whether remote hosts are allowed to connect to local
739: forwarded ports.
740: By default,
1.84 jmc 741: .Xr ssh 1
1.7 jmc 742: binds local port forwardings to the loopback address.
743: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 744: .Cm GatewayPorts
1.84 jmc 745: can be used to specify that ssh
1.1 stevesk 746: should bind local port forwardings to the wildcard address,
747: thus allowing remote hosts to connect to forwarded ports.
748: The argument must be
1.240 jmc 749: .Cm yes
1.1 stevesk 750: or
1.240 jmc 751: .Cm no
752: (the default).
1.1 stevesk 753: .It Cm GlobalKnownHostsFile
1.151 djm 754: Specifies one or more files to use for the global
755: host key database, separated by whitespace.
756: The default is
757: .Pa /etc/ssh/ssh_known_hosts ,
758: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 759: .It Cm GSSAPIAuthentication
1.27 markus 760: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 761: The default is
1.240 jmc 762: .Cm no .
1.18 markus 763: .It Cm GSSAPIDelegateCredentials
764: Forward (delegate) credentials to the server.
765: The default is
1.240 jmc 766: .Cm no .
1.44 djm 767: .It Cm HashKnownHosts
768: Indicates that
1.84 jmc 769: .Xr ssh 1
1.44 djm 770: should hash host names and addresses when they are added to
1.50 djm 771: .Pa ~/.ssh/known_hosts .
1.44 djm 772: These hashed names may be used normally by
1.84 jmc 773: .Xr ssh 1
1.44 djm 774: and
1.84 jmc 775: .Xr sshd 8 ,
1.44 djm 776: but they do not reveal identifying information should the file's contents
777: be disclosed.
778: The default is
1.240 jmc 779: .Cm no .
1.97 jmc 780: Note that existing names and addresses in known hosts files
781: will not be converted automatically,
782: but may be manually hashed using
1.45 djm 783: .Xr ssh-keygen 1 .
1.1 stevesk 784: .It Cm HostbasedAuthentication
785: Specifies whether to try rhosts based authentication with public key
786: authentication.
787: The argument must be
1.240 jmc 788: .Cm yes
1.1 stevesk 789: or
1.240 jmc 790: .Cm no
791: (the default).
1.202 djm 792: .It Cm HostbasedKeyTypes
793: Specifies the key types that will be used for hostbased authentication
1.279 djm 794: as a comma-separated list of patterns.
1.300 naddy 795: Alternately if the specified list begins with a
1.214 djm 796: .Sq +
797: character, then the specified key types will be appended to the default set
798: instead of replacing them.
1.300 naddy 799: If the specified list begins with a
1.241 djm 800: .Sq -
801: character, then the specified key types (including wildcards) will be removed
802: from the default set instead of replacing them.
1.301 naddy 803: If the specified list begins with a
804: .Sq ^
805: character, then the specified key types will be placed at the head of the
806: default set.
1.213 markus 807: The default for this option is:
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,
812: ssh-ed25519-cert-v01@openssh.com,
1.305 naddy 813: rsa-sha2-512-cert-v01@openssh.com,
814: rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 815: ssh-rsa-cert-v01@openssh.com,
816: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 817: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 818: .Ed
819: .Pp
1.202 djm 820: The
821: .Fl Q
822: option of
823: .Xr ssh 1
824: may be used to list supported key types.
1.1 stevesk 825: .It Cm HostKeyAlgorithms
1.226 jmc 826: Specifies the host key algorithms
1.1 stevesk 827: that the client wants to use in order of preference.
1.300 naddy 828: Alternately if the specified list begins with a
1.214 djm 829: .Sq +
830: character, then the specified key types will be appended to the default set
831: instead of replacing them.
1.300 naddy 832: If the specified list begins with a
1.241 djm 833: .Sq -
834: character, then the specified key types (including wildcards) will be removed
835: from the default set instead of replacing them.
1.301 naddy 836: If the specified list begins with a
837: .Sq ^
838: character, then the specified key types will be placed at the head of the
839: default set.
1.1 stevesk 840: The default for this option is:
1.139 djm 841: .Bd -literal -offset 3n
842: ecdsa-sha2-nistp256-cert-v01@openssh.com,
843: ecdsa-sha2-nistp384-cert-v01@openssh.com,
844: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1.183 naddy 845: ssh-ed25519-cert-v01@openssh.com,
1.305 naddy 846: rsa-sha2-512-cert-v01@openssh.com,
847: rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 848: ssh-rsa-cert-v01@openssh.com,
1.139 djm 849: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 850: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.139 djm 851: .Ed
1.145 djm 852: .Pp
853: If hostkeys are known for the destination host then this default is modified
854: to prefer their algorithms.
1.198 djm 855: .Pp
1.240 jmc 856: The list of available key types may also be obtained using
857: .Qq ssh -Q key .
1.1 stevesk 858: .It Cm HostKeyAlias
859: Specifies an alias that should be used instead of the
860: real host name when looking up or saving the host key
1.251 djm 861: in the host key database files and when validating host certificates.
1.84 jmc 862: This option is useful for tunneling SSH connections
1.1 stevesk 863: or for multiple servers running on a single host.
1.295 jmc 864: .It Cm Hostname
1.1 stevesk 865: Specifies the real host name to log into.
866: This can be used to specify nicknames or abbreviations for hosts.
1.239 jmc 867: Arguments to
1.295 jmc 868: .Cm Hostname
1.239 jmc 869: accept the tokens described in the
870: .Sx TOKENS
871: section.
1.1 stevesk 872: Numeric IP addresses are also permitted (both on the command line and in
1.295 jmc 873: .Cm Hostname
1.1 stevesk 874: specifications).
1.239 jmc 875: The default is the name given on the command line.
1.29 markus 876: .It Cm IdentitiesOnly
877: Specifies that
1.84 jmc 878: .Xr ssh 1
1.304 djm 879: should only use the configured authentication identity and certificate files
880: (either the default files, or those explicitly configured in the
1.31 jmc 881: .Nm
1.221 djm 882: files
883: or passed on the
884: .Xr ssh 1
1.304 djm 885: command-line),
1.84 jmc 886: even if
887: .Xr ssh-agent 1
1.159 djm 888: or a
889: .Cm PKCS11Provider
1.305 naddy 890: or
891: .Cm SecurityKeyProvider
1.29 markus 892: offers more identities.
893: The argument to this keyword must be
1.240 jmc 894: .Cm yes
1.29 markus 895: or
1.240 jmc 896: .Cm no
897: (the default).
1.84 jmc 898: This option is intended for situations where ssh-agent
1.29 markus 899: offers many different identities.
1.231 markus 900: .It Cm IdentityAgent
901: Specifies the
902: .Ux Ns -domain
903: socket used to communicate with the authentication agent.
904: .Pp
905: This option overrides the
1.240 jmc 906: .Ev SSH_AUTH_SOCK
1.231 markus 907: environment variable and can be used to select a specific agent.
908: Setting the socket name to
1.240 jmc 909: .Cm none
1.231 markus 910: disables the use of an authentication agent.
1.232 markus 911: If the string
1.240 jmc 912: .Qq SSH_AUTH_SOCK
1.232 markus 913: is specified, the location of the socket will be read from the
914: .Ev SSH_AUTH_SOCK
915: environment variable.
1.286 djm 916: Otherwise if the specified value begins with a
917: .Sq $
918: character, then it will be treated as an environment variable containing
919: the location of the socket.
1.231 markus 920: .Pp
1.239 jmc 921: Arguments to
922: .Cm IdentityAgent
923: may use the tilde syntax to refer to a user's home directory
924: or the tokens described in the
925: .Sx TOKENS
926: section.
1.67 jmc 927: .It Cm IdentityFile
1.305 naddy 928: Specifies a file from which the user's DSA, ECDSA, security key-hosted ECDSA,
929: Ed25519 or RSA authentication identity is read.
1.67 jmc 930: The default is
1.139 djm 931: .Pa ~/.ssh/id_dsa ,
1.183 naddy 932: .Pa ~/.ssh/id_ecdsa ,
1.305 naddy 933: .Pa ~/.ssh/id_ecdsa_sk ,
1.183 naddy 934: .Pa ~/.ssh/id_ed25519
1.139 djm 935: and
1.245 djm 936: .Pa ~/.ssh/id_rsa .
1.67 jmc 937: Additionally, any identities represented by the authentication agent
1.165 djm 938: will be used for authentication unless
939: .Cm IdentitiesOnly
940: is set.
1.221 djm 941: If no certificates have been explicitly specified by
942: .Cm CertificateFile ,
1.129 djm 943: .Xr ssh 1
944: will try to load certificate information from the filename obtained by
945: appending
946: .Pa -cert.pub
947: to the path of a specified
948: .Cm IdentityFile .
1.90 djm 949: .Pp
1.239 jmc 950: Arguments to
951: .Cm IdentityFile
952: may use the tilde syntax to refer to a user's home directory
953: or the tokens described in the
954: .Sx TOKENS
955: section.
1.90 djm 956: .Pp
1.67 jmc 957: It is possible to have
958: multiple identity files specified in configuration files; all these
959: identities will be tried in sequence.
1.152 djm 960: Multiple
961: .Cm IdentityFile
962: directives will add to the list of identities tried (this behaviour
963: differs from that of other configuration directives).
1.165 djm 964: .Pp
965: .Cm IdentityFile
966: may be used in conjunction with
967: .Cm IdentitiesOnly
968: to select which identities in an agent are offered during authentication.
1.221 djm 969: .Cm IdentityFile
970: may also be used in conjunction with
971: .Cm CertificateFile
972: in order to provide any certificate also needed for authentication with
973: the identity.
1.164 jmc 974: .It Cm IgnoreUnknown
975: Specifies a pattern-list of unknown options to be ignored if they are
976: encountered in configuration parsing.
977: This may be used to suppress errors if
978: .Nm
979: contains options that are unrecognised by
980: .Xr ssh 1 .
981: It is recommended that
982: .Cm IgnoreUnknown
983: be listed early in the configuration file as it will not be applied
984: to unknown options that appear before it.
1.229 djm 985: .It Cm Include
986: Include the specified configuration file(s).
1.230 jmc 987: Multiple pathnames may be specified and each pathname may contain
1.281 kn 988: .Xr glob 7
1.229 djm 989: wildcards and, for user configurations, shell-like
1.240 jmc 990: .Sq ~
1.229 djm 991: references to user home directories.
992: Files without absolute paths are assumed to be in
993: .Pa ~/.ssh
1.230 jmc 994: if included in a user configuration file or
1.229 djm 995: .Pa /etc/ssh
996: if included from the system configuration file.
997: .Cm Include
998: directive may appear inside a
999: .Cm Match
1000: or
1001: .Cm Host
1002: block
1003: to perform conditional inclusion.
1.143 djm 1004: .It Cm IPQoS
1005: Specifies the IPv4 type-of-service or DSCP class for connections.
1006: Accepted values are
1.240 jmc 1007: .Cm af11 ,
1008: .Cm af12 ,
1009: .Cm af13 ,
1010: .Cm af21 ,
1011: .Cm af22 ,
1012: .Cm af23 ,
1013: .Cm af31 ,
1014: .Cm af32 ,
1015: .Cm af33 ,
1016: .Cm af41 ,
1017: .Cm af42 ,
1018: .Cm af43 ,
1019: .Cm cs0 ,
1020: .Cm cs1 ,
1021: .Cm cs2 ,
1022: .Cm cs3 ,
1023: .Cm cs4 ,
1024: .Cm cs5 ,
1025: .Cm cs6 ,
1026: .Cm cs7 ,
1027: .Cm ef ,
1028: .Cm lowdelay ,
1029: .Cm throughput ,
1030: .Cm reliability ,
1.253 djm 1031: a numeric value, or
1032: .Cm none
1033: to use the operating system default.
1.146 djm 1034: This option may take one or two arguments, separated by whitespace.
1.143 djm 1035: If one argument is specified, it is used as the packet class unconditionally.
1036: If two values are specified, the first is automatically selected for
1037: interactive sessions and the second for non-interactive sessions.
1038: The default is
1.269 job 1039: .Cm af21
1.272 jmc 1040: (Low-Latency Data)
1.143 djm 1041: for interactive sessions and
1.269 job 1042: .Cm cs1
1.272 jmc 1043: (Lower Effort)
1.143 djm 1044: for non-interactive sessions.
1.103 djm 1045: .It Cm KbdInteractiveAuthentication
1046: Specifies whether to use keyboard-interactive authentication.
1047: The argument to this keyword must be
1.240 jmc 1048: .Cm yes
1049: (the default)
1.103 djm 1050: or
1.240 jmc 1051: .Cm no .
1.39 djm 1052: .It Cm KbdInteractiveDevices
1053: Specifies the list of methods to use in keyboard-interactive authentication.
1054: Multiple method names must be comma-separated.
1055: The default is to use the server specified list.
1.85 jmc 1056: The methods available vary depending on what the server supports.
1057: For an OpenSSH server,
1058: it may be zero or more of:
1.240 jmc 1059: .Cm bsdauth ,
1060: .Cm pam ,
1.85 jmc 1061: and
1.240 jmc 1062: .Cm skey .
1.140 djm 1063: .It Cm KexAlgorithms
1064: Specifies the available KEX (Key Exchange) algorithms.
1065: Multiple algorithms must be comma-separated.
1.299 kn 1066: If the specified list begins with a
1.214 djm 1067: .Sq +
1068: character, then the specified methods will be appended to the default set
1069: instead of replacing them.
1.299 kn 1070: If the specified list begins with a
1.241 djm 1071: .Sq -
1072: character, then the specified methods (including wildcards) will be removed
1073: from the default set instead of replacing them.
1.301 naddy 1074: If the specified list begins with a
1075: .Sq ^
1076: character, then the specified methods will be placed at the head of the
1077: default set.
1.141 jmc 1078: The default is:
1079: .Bd -literal -offset indent
1.238 djm 1080: curve25519-sha256,curve25519-sha256@libssh.org,
1.141 jmc 1081: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1082: diffie-hellman-group-exchange-sha256,
1.266 djm 1083: diffie-hellman-group16-sha512,
1084: diffie-hellman-group18-sha512,
1085: diffie-hellman-group14-sha256,
1.212 djm 1086: diffie-hellman-group14-sha1
1.141 jmc 1087: .Ed
1.198 djm 1088: .Pp
1.240 jmc 1089: The list of available key exchange algorithms may also be obtained using
1090: .Qq ssh -Q kex .
1.65 reyk 1091: .It Cm LocalCommand
1092: Specifies a command to execute on the local machine after successfully
1093: connecting to the server.
1094: The command string extends to the end of the line, and is executed with
1.105 jmc 1095: the user's shell.
1.239 jmc 1096: Arguments to
1097: .Cm LocalCommand
1098: accept the tokens described in the
1099: .Sx TOKENS
1100: section.
1.123 djm 1101: .Pp
1102: The command is run synchronously and does not have access to the
1103: session of the
1104: .Xr ssh 1
1105: that spawned it.
1106: It should not be used for interactive commands.
1107: .Pp
1.65 reyk 1108: This directive is ignored unless
1109: .Cm PermitLocalCommand
1110: has been enabled.
1.1 stevesk 1111: .It Cm LocalForward
1.74 jmc 1112: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 1113: the secure channel to the specified host and port from the remote machine.
1.49 jmc 1114: The first argument must be
1.43 djm 1115: .Sm off
1.49 jmc 1116: .Oo Ar bind_address : Oc Ar port
1.43 djm 1117: .Sm on
1.49 jmc 1118: and the second argument must be
1119: .Ar host : Ns Ar hostport .
1.138 djm 1120: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 1121: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 1122: given on the command line.
1.1 stevesk 1123: Only the superuser can forward privileged ports.
1.43 djm 1124: By default, the local port is bound in accordance with the
1125: .Cm GatewayPorts
1126: setting.
1127: However, an explicit
1128: .Ar bind_address
1129: may be used to bind the connection to a specific address.
1130: The
1131: .Ar bind_address
1132: of
1.240 jmc 1133: .Cm localhost
1.46 jmc 1134: indicates that the listening port be bound for local use only, while an
1135: empty address or
1136: .Sq *
1.43 djm 1137: indicates that the port should be available from all interfaces.
1.1 stevesk 1138: .It Cm LogLevel
1139: Gives the verbosity level that is used when logging messages from
1.84 jmc 1140: .Xr ssh 1 .
1.1 stevesk 1141: The possible values are:
1.84 jmc 1142: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 1143: The default is INFO.
1144: DEBUG and DEBUG1 are equivalent.
1145: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 1146: .It Cm MACs
1147: Specifies the MAC (message authentication code) algorithms
1148: in order of preference.
1.226 jmc 1149: The MAC algorithm is used for data integrity protection.
1.1 stevesk 1150: Multiple algorithms must be comma-separated.
1.299 kn 1151: If the specified list begins with a
1.214 djm 1152: .Sq +
1153: character, then the specified algorithms will be appended to the default set
1154: instead of replacing them.
1.299 kn 1155: If the specified list begins with a
1.241 djm 1156: .Sq -
1157: character, then the specified algorithms (including wildcards) will be removed
1158: from the default set instead of replacing them.
1.301 naddy 1159: If the specified list begins with a
1160: .Sq ^
1161: character, then the specified algorithms will be placed at the head of the
1162: default set.
1.214 djm 1163: .Pp
1.160 markus 1164: The algorithms that contain
1.240 jmc 1165: .Qq -etm
1.160 markus 1166: calculate the MAC after encryption (encrypt-then-mac).
1167: These are considered safer and their use recommended.
1.214 djm 1168: .Pp
1.84 jmc 1169: The default is:
1.101 jmc 1170: .Bd -literal -offset indent
1.160 markus 1171: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1172: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.224 djm 1173: hmac-sha1-etm@openssh.com,
1.186 naddy 1174: umac-64@openssh.com,umac-128@openssh.com,
1.224 djm 1175: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.101 jmc 1176: .Ed
1.198 djm 1177: .Pp
1.240 jmc 1178: The list of available MAC algorithms may also be obtained using
1179: .Qq ssh -Q mac .
1.1 stevesk 1180: .It Cm NoHostAuthenticationForLocalhost
1.264 djm 1181: Disable host authentication for localhost (loopback addresses).
1.1 stevesk 1182: The argument to this keyword must be
1.240 jmc 1183: .Cm yes
1.1 stevesk 1184: or
1.242 jmc 1185: .Cm no
1.240 jmc 1186: (the default).
1.1 stevesk 1187: .It Cm NumberOfPasswordPrompts
1188: Specifies the number of password prompts before giving up.
1189: The argument to this keyword must be an integer.
1.84 jmc 1190: The default is 3.
1.1 stevesk 1191: .It Cm PasswordAuthentication
1192: Specifies whether to use password authentication.
1193: The argument to this keyword must be
1.240 jmc 1194: .Cm yes
1195: (the default)
1.1 stevesk 1196: or
1.240 jmc 1197: .Cm no .
1.65 reyk 1198: .It Cm PermitLocalCommand
1199: Allow local command execution via the
1200: .Ic LocalCommand
1201: option or using the
1.66 jmc 1202: .Ic !\& Ns Ar command
1.65 reyk 1203: escape sequence in
1204: .Xr ssh 1 .
1205: The argument must be
1.240 jmc 1206: .Cm yes
1.65 reyk 1207: or
1.240 jmc 1208: .Cm no
1209: (the default).
1.127 markus 1210: .It Cm PKCS11Provider
1.292 djm 1211: Specifies which PKCS#11 provider to use or
1212: .Cm none
1213: to indicate that no provider should be used (the default).
1214: The argument to this keyword is a path to the PKCS#11 shared library
1.127 markus 1215: .Xr ssh 1
1.292 djm 1216: should use to communicate with a PKCS#11 token providing keys for user
1217: authentication.
1.67 jmc 1218: .It Cm Port
1219: Specifies the port number to connect on the remote host.
1.84 jmc 1220: The default is 22.
1.1 stevesk 1221: .It Cm PreferredAuthentications
1.226 jmc 1222: Specifies the order in which the client should try authentication methods.
1.48 jmc 1223: This allows a client to prefer one method (e.g.\&
1.1 stevesk 1224: .Cm keyboard-interactive )
1.48 jmc 1225: over another method (e.g.\&
1.131 jmc 1226: .Cm password ) .
1227: The default is:
1228: .Bd -literal -offset indent
1229: gssapi-with-mic,hostbased,publickey,
1230: keyboard-interactive,password
1231: .Ed
1.1 stevesk 1232: .It Cm ProxyCommand
1233: Specifies the command to use to connect to the server.
1234: The command
1.190 djm 1235: string extends to the end of the line, and is executed
1236: using the user's shell
1237: .Ql exec
1238: directive to avoid a lingering shell process.
1239: .Pp
1.239 jmc 1240: Arguments to
1241: .Cm ProxyCommand
1242: accept the tokens described in the
1243: .Sx TOKENS
1244: section.
1.1 stevesk 1245: The command can be basically anything,
1246: and should read from its standard input and write to its standard output.
1247: It should eventually connect an
1248: .Xr sshd 8
1249: server running on some machine, or execute
1250: .Ic sshd -i
1251: somewhere.
1252: Host key management will be done using the
1.296 jmc 1253: .Cm Hostname
1254: of the host being connected (defaulting to the name typed by the user).
1.7 jmc 1255: Setting the command to
1.240 jmc 1256: .Cm none
1.6 markus 1257: disables this option entirely.
1.1 stevesk 1258: Note that
1259: .Cm CheckHostIP
1260: is not available for connects with a proxy command.
1.52 djm 1261: .Pp
1262: This directive is useful in conjunction with
1263: .Xr nc 1
1264: and its proxy support.
1.53 jmc 1265: For example, the following directive would connect via an HTTP proxy at
1.52 djm 1266: 192.0.2.0:
1267: .Bd -literal -offset 3n
1268: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1269: .Ed
1.233 djm 1270: .It Cm ProxyJump
1.260 millert 1271: Specifies one or more jump proxies as either
1.233 djm 1272: .Xo
1273: .Sm off
1.234 jmc 1274: .Op Ar user No @
1.233 djm 1275: .Ar host
1.234 jmc 1276: .Op : Ns Ar port
1.233 djm 1277: .Sm on
1.260 millert 1278: or an ssh URI
1.233 djm 1279: .Xc .
1.235 djm 1280: Multiple proxies may be separated by comma characters and will be visited
1.236 djm 1281: sequentially.
1.233 djm 1282: Setting this option will cause
1283: .Xr ssh 1
1284: to connect to the target host by first making a
1285: .Xr ssh 1
1286: connection to the specified
1287: .Cm ProxyJump
1288: host and then establishing a
1.234 jmc 1289: TCP forwarding to the ultimate target from there.
1.233 djm 1290: .Pp
1291: Note that this option will compete with the
1292: .Cm ProxyCommand
1293: option - whichever is specified first will prevent later instances of the
1294: other from taking effect.
1.289 djm 1295: .Pp
1296: Note also that the configuration for the destination host (either supplied
1297: via the command-line or the configuration file) is not generally applied
1298: to jump hosts.
1299: .Pa ~/.ssh/config
1300: should be used if specific configuration is required for jump hosts.
1.167 djm 1301: .It Cm ProxyUseFdpass
1.168 jmc 1302: Specifies that
1.167 djm 1303: .Cm ProxyCommand
1304: will pass a connected file descriptor back to
1.168 jmc 1305: .Xr ssh 1
1.167 djm 1306: instead of continuing to execute and pass data.
1307: The default is
1.240 jmc 1308: .Cm no .
1.213 markus 1309: .It Cm PubkeyAcceptedKeyTypes
1310: Specifies the key types that will be used for public key authentication
1.279 djm 1311: as a comma-separated list of patterns.
1.299 kn 1312: If the specified list begins with a
1.214 djm 1313: .Sq +
1314: character, then the key types after it will be appended to the default
1315: instead of replacing it.
1.299 kn 1316: If the specified list begins with a
1.241 djm 1317: .Sq -
1318: character, then the specified key types (including wildcards) will be removed
1319: from the default set instead of replacing them.
1.301 naddy 1320: If the specified list begins with a
1321: .Sq ^
1322: character, then the specified key types will be placed at the head of the
1323: default set.
1.213 markus 1324: The default for this option is:
1325: .Bd -literal -offset 3n
1.305 naddy 1326: sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
1.213 markus 1327: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1328: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1329: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1330: ssh-ed25519-cert-v01@openssh.com,
1.305 naddy 1331: rsa-sha2-512-cert-v01@openssh.com,
1332: rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 1333: ssh-rsa-cert-v01@openssh.com,
1.305 naddy 1334: sk-ecdsa-sha2-nistp256@openssh.com,
1.213 markus 1335: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 1336: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 1337: .Ed
1338: .Pp
1.240 jmc 1339: The list of available key types may also be obtained using
1340: .Qq ssh -Q key .
1.1 stevesk 1341: .It Cm PubkeyAuthentication
1342: Specifies whether to try public key authentication.
1343: The argument to this keyword must be
1.240 jmc 1344: .Cm yes
1345: (the default)
1.1 stevesk 1346: or
1.240 jmc 1347: .Cm no .
1.75 dtucker 1348: .It Cm RekeyLimit
1349: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1350: session key is renegotiated, optionally followed a maximum amount of
1351: time that may pass before the session key is renegotiated.
1352: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1353: .Sq K ,
1354: .Sq M ,
1.75 dtucker 1355: or
1.76 jmc 1356: .Sq G
1.75 dtucker 1357: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1358: The default is between
1.84 jmc 1359: .Sq 1G
1.75 dtucker 1360: and
1.84 jmc 1361: .Sq 4G ,
1.75 dtucker 1362: depending on the cipher.
1.162 dtucker 1363: The optional second value is specified in seconds and may use any of the
1.293 schwarze 1364: units documented in the TIME FORMATS section of
1.162 dtucker 1365: .Xr sshd_config 5 .
1366: The default value for
1367: .Cm RekeyLimit
1368: is
1.240 jmc 1369: .Cm default none ,
1.162 dtucker 1370: which means that rekeying is performed after the cipher's default amount
1371: of data has been sent or received and no time based rekeying is done.
1.249 bluhm 1372: .It Cm RemoteCommand
1373: Specifies a command to execute on the remote machine after successfully
1374: connecting to the server.
1375: The command string extends to the end of the line, and is executed with
1376: the user's shell.
1.250 jmc 1377: Arguments to
1378: .Cm RemoteCommand
1379: accept the tokens described in the
1380: .Sx TOKENS
1381: section.
1.1 stevesk 1382: .It Cm RemoteForward
1.74 jmc 1383: Specifies that a TCP port on the remote machine be forwarded over
1.256 markus 1384: the secure channel.
1.273 djm 1385: The remote port may either be forwarded to a specified host and port
1.256 markus 1386: from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
1387: client to connect to arbitrary destinations from the local machine.
1.49 jmc 1388: The first argument must be
1.43 djm 1389: .Sm off
1.49 jmc 1390: .Oo Ar bind_address : Oc Ar port
1.43 djm 1391: .Sm on
1.256 markus 1392: If forwarding to a specific destination then the second argument must be
1393: .Ar host : Ns Ar hostport ,
1394: otherwise if no destination argument is specified then the remote forwarding
1395: will be established as a SOCKS proxy.
1396: .Pp
1.138 djm 1397: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.1 stevesk 1398: Multiple forwardings may be specified, and additional
1399: forwardings can be given on the command line.
1.113 stevesk 1400: Privileged ports can be forwarded only when
1401: logging in as root on the remote machine.
1.118 jmc 1402: .Pp
1.117 djm 1403: If the
1404: .Ar port
1.240 jmc 1405: argument is 0,
1.117 djm 1406: the listen port will be dynamically allocated on the server and reported
1407: to the client at run time.
1.43 djm 1408: .Pp
1409: If the
1410: .Ar bind_address
1411: is not specified, the default is to only bind to loopback addresses.
1412: If the
1413: .Ar bind_address
1414: is
1415: .Ql *
1416: or an empty string, then the forwarding is requested to listen on all
1417: interfaces.
1418: Specifying a remote
1419: .Ar bind_address
1.46 jmc 1420: will only succeed if the server's
1421: .Cm GatewayPorts
1.43 djm 1422: option is enabled (see
1.46 jmc 1423: .Xr sshd_config 5 ) .
1.149 djm 1424: .It Cm RequestTTY
1425: Specifies whether to request a pseudo-tty for the session.
1426: The argument may be one of:
1.240 jmc 1427: .Cm no
1.149 djm 1428: (never request a TTY),
1.240 jmc 1429: .Cm yes
1.149 djm 1430: (always request a TTY when standard input is a TTY),
1.240 jmc 1431: .Cm force
1.149 djm 1432: (always request a TTY) or
1.240 jmc 1433: .Cm auto
1.149 djm 1434: (request a TTY when opening a login session).
1435: This option mirrors the
1436: .Fl t
1437: and
1438: .Fl T
1439: flags for
1440: .Xr ssh 1 .
1.196 djm 1441: .It Cm RevokedHostKeys
1442: Specifies revoked host public keys.
1443: Keys listed in this file will be refused for host authentication.
1444: Note that if this file does not exist or is not readable,
1445: then host authentication will be refused for all hosts.
1446: Keys may be specified as a text file, listing one public key per line, or as
1447: an OpenSSH Key Revocation List (KRL) as generated by
1448: .Xr ssh-keygen 1 .
1449: For more information on KRLs, see the KEY REVOCATION LISTS section in
1450: .Xr ssh-keygen 1 .
1.305 naddy 1451: .It Cm SecurityKeyProvider
1452: Specifies a path to a security key provider library that will be used when
1.306 ! djm 1453: loading any security key-hosted keys, overriding the default of using
! 1454: the build-in support for USB HID keys.
1.32 djm 1455: .It Cm SendEnv
1456: Specifies what variables from the local
1457: .Xr environ 7
1458: should be sent to the server.
1.84 jmc 1459: The server must also support it, and the server must be configured to
1.33 djm 1460: accept these environment variables.
1.207 dtucker 1461: Note that the
1462: .Ev TERM
1.208 jmc 1463: environment variable is always sent whenever a
1.207 dtucker 1464: pseudo-terminal is requested as it is required by the protocol.
1.32 djm 1465: Refer to
1466: .Cm AcceptEnv
1467: in
1468: .Xr sshd_config 5
1469: for how to configure the server.
1.80 jmc 1470: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1471: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1472: across multiple
1473: .Cm SendEnv
1474: directives.
1.81 jmc 1475: .Pp
1476: See
1477: .Sx PATTERNS
1478: for more information on patterns.
1.271 djm 1479: .Pp
1.272 jmc 1480: It is possible to clear previously set
1.271 djm 1481: .Cm SendEnv
1482: variable names by prefixing patterns with
1483: .Pa - .
1484: The default is not to send any environment variables.
1.28 markus 1485: .It Cm ServerAliveCountMax
1.73 jmc 1486: Sets the number of server alive messages (see below) which may be
1.28 markus 1487: sent without
1.84 jmc 1488: .Xr ssh 1
1.28 markus 1489: receiving any messages back from the server.
1490: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1491: ssh will disconnect from the server, terminating the session.
1.28 markus 1492: It is important to note that the use of server alive messages is very
1493: different from
1494: .Cm TCPKeepAlive
1495: (below).
1496: The server alive messages are sent through the encrypted channel
1497: and therefore will not be spoofable.
1498: The TCP keepalive option enabled by
1499: .Cm TCPKeepAlive
1500: is spoofable.
1501: The server alive mechanism is valuable when the client or
1.298 dtucker 1502: server depend on knowing when a connection has become unresponsive.
1.28 markus 1503: .Pp
1504: The default value is 3.
1505: If, for example,
1506: .Cm ServerAliveInterval
1.84 jmc 1507: (see below) is set to 15 and
1.28 markus 1508: .Cm ServerAliveCountMax
1.84 jmc 1509: is left at the default, if the server becomes unresponsive,
1510: ssh will disconnect after approximately 45 seconds.
1.67 jmc 1511: .It Cm ServerAliveInterval
1512: Sets a timeout interval in seconds after which if no data has been received
1513: from the server,
1.84 jmc 1514: .Xr ssh 1
1.67 jmc 1515: will send a message through the encrypted
1516: channel to request a response from the server.
1517: The default
1518: is 0, indicating that these messages will not be sent to the server.
1.277 jmc 1519: .It Cm SetEnv
1520: Directly specify one or more environment variables and their contents to
1521: be sent to the server.
1522: Similarly to
1523: .Cm SendEnv ,
1524: the server must be prepared to accept the environment variable.
1.191 millert 1525: .It Cm StreamLocalBindMask
1526: Sets the octal file creation mode mask
1527: .Pq umask
1528: used when creating a Unix-domain socket file for local or remote
1529: port forwarding.
1530: This option is only used for port forwarding to a Unix-domain socket file.
1531: .Pp
1532: The default value is 0177, which creates a Unix-domain socket file that is
1533: readable and writable only by the owner.
1534: Note that not all operating systems honor the file mode on Unix-domain
1535: socket files.
1536: .It Cm StreamLocalBindUnlink
1537: Specifies whether to remove an existing Unix-domain socket file for local
1538: or remote port forwarding before creating a new one.
1539: If the socket file already exists and
1540: .Cm StreamLocalBindUnlink
1541: is not enabled,
1542: .Nm ssh
1543: will be unable to forward the port to the Unix-domain socket file.
1544: This option is only used for port forwarding to a Unix-domain socket file.
1545: .Pp
1546: The argument must be
1.240 jmc 1547: .Cm yes
1.191 millert 1548: or
1.240 jmc 1549: .Cm no
1550: (the default).
1.1 stevesk 1551: .It Cm StrictHostKeyChecking
1552: If this flag is set to
1.240 jmc 1553: .Cm yes ,
1.84 jmc 1554: .Xr ssh 1
1.1 stevesk 1555: will never automatically add host keys to the
1.50 djm 1556: .Pa ~/.ssh/known_hosts
1.1 stevesk 1557: file, and refuses to connect to hosts whose host key has changed.
1.263 dtucker 1558: This provides maximum protection against man-in-the-middle (MITM) attacks,
1.84 jmc 1559: though it can be annoying when the
1.1 stevesk 1560: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1561: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1562: frequently made.
1563: This option forces the user to manually
1564: add all new hosts.
1.255 jmc 1565: .Pp
1.1 stevesk 1566: If this flag is set to
1.254 djm 1567: .Dq accept-new
1.255 jmc 1568: then ssh will automatically add new host keys to the user
1.254 djm 1569: known hosts files, but will not permit connections to hosts with
1570: changed host keys.
1571: If this flag is set to
1572: .Dq no
1573: or
1574: .Dq off ,
1.255 jmc 1575: ssh will automatically add new host keys to the user known hosts files
1576: and allow connections to hosts with changed hostkeys to proceed,
1577: subject to some restrictions.
1.1 stevesk 1578: If this flag is set to
1.240 jmc 1579: .Cm ask
1580: (the default),
1.1 stevesk 1581: new host keys
1582: will be added to the user known host files only after the user
1583: has confirmed that is what they really want to do, and
1.84 jmc 1584: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1585: The host keys of
1586: known hosts will be verified automatically in all cases.
1.244 jmc 1587: .It Cm SyslogFacility
1588: Gives the facility code that is used when logging messages from
1589: .Xr ssh 1 .
1590: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1591: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1592: The default is USER.
1.26 markus 1593: .It Cm TCPKeepAlive
1594: Specifies whether the system should send TCP keepalive messages to the
1595: other side.
1596: If they are sent, death of the connection or crash of one
1597: of the machines will be properly noticed.
1598: However, this means that
1599: connections will die if the route is down temporarily, and some people
1600: find it annoying.
1601: .Pp
1602: The default is
1.240 jmc 1603: .Cm yes
1.26 markus 1604: (to send TCP keepalive messages), and the client will notice
1605: if the network goes down or the remote host dies.
1606: This is important in scripts, and many users want it too.
1607: .Pp
1608: To disable TCP keepalive messages, the value should be set to
1.240 jmc 1609: .Cm no .
1.265 djm 1610: See also
1611: .Cm ServerAliveInterval
1612: for protocol-level keepalives.
1.65 reyk 1613: .It Cm Tunnel
1.95 stevesk 1614: Request
1.65 reyk 1615: .Xr tun 4
1.69 jmc 1616: device forwarding between the client and the server.
1.65 reyk 1617: The argument must be
1.240 jmc 1618: .Cm yes ,
1619: .Cm point-to-point
1.95 stevesk 1620: (layer 3),
1.240 jmc 1621: .Cm ethernet
1.95 stevesk 1622: (layer 2),
1.65 reyk 1623: or
1.240 jmc 1624: .Cm no
1625: (the default).
1.95 stevesk 1626: Specifying
1.240 jmc 1627: .Cm yes
1.95 stevesk 1628: requests the default tunnel mode, which is
1.240 jmc 1629: .Cm point-to-point .
1.65 reyk 1630: .It Cm TunnelDevice
1.95 stevesk 1631: Specifies the
1.65 reyk 1632: .Xr tun 4
1.95 stevesk 1633: devices to open on the client
1634: .Pq Ar local_tun
1635: and the server
1636: .Pq Ar remote_tun .
1637: .Pp
1638: The argument must be
1639: .Sm off
1640: .Ar local_tun Op : Ar remote_tun .
1641: .Sm on
1642: The devices may be specified by numerical ID or the keyword
1.240 jmc 1643: .Cm any ,
1.95 stevesk 1644: which uses the next available tunnel device.
1645: If
1646: .Ar remote_tun
1647: is not specified, it defaults to
1.240 jmc 1648: .Cm any .
1.95 stevesk 1649: The default is
1.240 jmc 1650: .Cm any:any .
1.201 djm 1651: .It Cm UpdateHostKeys
1.200 djm 1652: Specifies whether
1653: .Xr ssh 1
1654: should accept notifications of additional hostkeys from the server sent
1655: after authentication has completed and add them to
1656: .Cm UserKnownHostsFile .
1657: The argument must be
1.240 jmc 1658: .Cm yes ,
1659: .Cm no
1.204 djm 1660: (the default) or
1.240 jmc 1661: .Cm ask .
1.200 djm 1662: Enabling this option allows learning alternate hostkeys for a server
1.201 djm 1663: and supports graceful key rotation by allowing a server to send replacement
1664: public keys before old ones are removed.
1.200 djm 1665: Additional hostkeys are only accepted if the key used to authenticate the
1.220 sobrado 1666: host was already trusted or explicitly accepted by the user.
1.204 djm 1667: If
1668: .Cm UpdateHostKeys
1669: is set to
1.240 jmc 1670: .Cm ask ,
1.204 djm 1671: then the user is asked to confirm the modifications to the known_hosts file.
1.205 djm 1672: Confirmation is currently incompatible with
1673: .Cm ControlPersist ,
1674: and will be disabled if it is enabled.
1.200 djm 1675: .Pp
1676: Presently, only
1677: .Xr sshd 8
1678: from OpenSSH 6.8 and greater support the
1.240 jmc 1679: .Qq hostkeys@openssh.com
1.200 djm 1680: protocol extension used to inform the client of all the server's hostkeys.
1.1 stevesk 1681: .It Cm User
1682: Specifies the user to log in as.
1683: This can be useful when a different user name is used on different machines.
1684: This saves the trouble of
1685: having to remember to give the user name on the command line.
1686: .It Cm UserKnownHostsFile
1.151 djm 1687: Specifies one or more files to use for the user
1688: host key database, separated by whitespace.
1689: The default is
1690: .Pa ~/.ssh/known_hosts ,
1691: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1692: .It Cm VerifyHostKeyDNS
1693: Specifies whether to verify the remote key using DNS and SSHFP resource
1694: records.
1.24 jakob 1695: If this option is set to
1.240 jmc 1696: .Cm yes ,
1.25 jmc 1697: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1698: from DNS.
1699: Insecure fingerprints will be handled as if this option was set to
1.240 jmc 1700: .Cm ask .
1.24 jakob 1701: If this option is set to
1.240 jmc 1702: .Cm ask ,
1.24 jakob 1703: information on fingerprint match will be displayed, but the user will still
1704: need to confirm new host keys according to the
1705: .Cm StrictHostKeyChecking
1706: option.
1.8 jakob 1707: The default is
1.240 jmc 1708: .Cm no .
1.84 jmc 1709: .Pp
1.240 jmc 1710: See also
1711: .Sx VERIFYING HOST KEYS
1712: in
1.84 jmc 1713: .Xr ssh 1 .
1.111 grunk 1714: .It Cm VisualHostKey
1715: If this flag is set to
1.240 jmc 1716: .Cm yes ,
1.111 grunk 1717: an ASCII art representation of the remote host key fingerprint is
1.197 djm 1718: printed in addition to the fingerprint string at login and
1.114 stevesk 1719: for unknown host keys.
1.111 grunk 1720: If this flag is set to
1.240 jmc 1721: .Cm no
1722: (the default),
1.114 stevesk 1723: no fingerprint strings are printed at login and
1.197 djm 1724: only the fingerprint string will be printed for unknown host keys.
1.1 stevesk 1725: .It Cm XAuthLocation
1.5 stevesk 1726: Specifies the full pathname of the
1.1 stevesk 1727: .Xr xauth 1
1728: program.
1729: The default is
1730: .Pa /usr/X11R6/bin/xauth .
1731: .El
1.86 jmc 1732: .Sh PATTERNS
1733: A
1734: .Em pattern
1735: consists of zero or more non-whitespace characters,
1736: .Sq *
1737: (a wildcard that matches zero or more characters),
1738: or
1739: .Sq ?\&
1740: (a wildcard that matches exactly one character).
1741: For example, to specify a set of declarations for any host in the
1.240 jmc 1742: .Qq .co.uk
1.86 jmc 1743: set of domains,
1744: the following pattern could be used:
1745: .Pp
1746: .Dl Host *.co.uk
1747: .Pp
1748: The following pattern
1749: would match any host in the 192.168.0.[0-9] network range:
1750: .Pp
1751: .Dl Host 192.168.0.?
1752: .Pp
1753: A
1754: .Em pattern-list
1755: is a comma-separated list of patterns.
1756: Patterns within pattern-lists may be negated
1757: by preceding them with an exclamation mark
1758: .Pq Sq !\& .
1759: For example,
1.174 djm 1760: to allow a key to be used from anywhere within an organization
1.86 jmc 1761: except from the
1.240 jmc 1762: .Qq dialup
1.86 jmc 1763: pool,
1764: the following entry (in authorized_keys) could be used:
1765: .Pp
1766: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.258 djm 1767: .Pp
1768: Note that a negated match will never produce a positive result by itself.
1769: For example, attempting to match
1770: .Qq host3
1771: against the following pattern-list will fail:
1772: .Pp
1773: .Dl from=\&"!host1,!host2\&"
1774: .Pp
1775: The solution here is to include a term that will yield a positive match,
1776: such as a wildcard:
1777: .Pp
1778: .Dl from=\&"!host1,!host2,*\&"
1.239 jmc 1779: .Sh TOKENS
1780: Arguments to some keywords can make use of tokens,
1781: which are expanded at runtime:
1782: .Pp
1783: .Bl -tag -width XXXX -offset indent -compact
1784: .It %%
1785: A literal
1786: .Sq % .
1787: .It \&%C
1.257 jmc 1788: Hash of %l%h%p%r.
1.239 jmc 1789: .It %d
1790: Local user's home directory.
1791: .It %h
1792: The remote hostname.
1793: .It %i
1794: The local user ID.
1795: .It %L
1796: The local hostname.
1797: .It %l
1798: The local hostname, including the domain name.
1799: .It %n
1800: The original remote hostname, as given on the command line.
1801: .It %p
1802: The remote port.
1803: .It %r
1804: The remote username.
1.261 djm 1805: .It \&%T
1806: The local
1807: .Xr tun 4
1808: or
1809: .Xr tap 4
1810: network interface assigned if
1.262 jmc 1811: tunnel forwarding was requested, or
1812: .Qq NONE
1.261 djm 1813: otherwise.
1.239 jmc 1814: .It %u
1815: The local username.
1816: .El
1817: .Pp
1818: .Cm Match exec
1.274 djm 1819: accepts the tokens %%, %h, %i, %L, %l, %n, %p, %r, and %u.
1.239 jmc 1820: .Pp
1821: .Cm CertificateFile
1.275 jmc 1822: accepts the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1823: .Pp
1824: .Cm ControlPath
1825: accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
1826: .Pp
1.295 jmc 1827: .Cm Hostname
1.239 jmc 1828: accepts the tokens %% and %h.
1829: .Pp
1830: .Cm IdentityAgent
1831: and
1832: .Cm IdentityFile
1.275 jmc 1833: accept the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1834: .Pp
1835: .Cm LocalCommand
1.275 jmc 1836: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, %T, and %u.
1.239 jmc 1837: .Pp
1838: .Cm ProxyCommand
1.303 djm 1839: accepts the tokens %%, %h, %n, %p, and %r.
1.250 jmc 1840: .Pp
1841: .Cm RemoteCommand
1.274 djm 1842: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, and %u.
1.1 stevesk 1843: .Sh FILES
1844: .Bl -tag -width Ds
1.50 djm 1845: .It Pa ~/.ssh/config
1.1 stevesk 1846: This is the per-user configuration file.
1847: The format of this file is described above.
1.84 jmc 1848: This file is used by the SSH client.
1.30 djm 1849: Because of the potential for abuse, this file must have strict permissions:
1.290 jmc 1850: read/write for the user, and not writable by others.
1.1 stevesk 1851: .It Pa /etc/ssh/ssh_config
1852: Systemwide configuration file.
1853: This file provides defaults for those
1854: values that are not specified in the user's configuration file, and
1855: for those users who do not have a configuration file.
1856: This file must be world-readable.
1857: .El
1.13 jmc 1858: .Sh SEE ALSO
1859: .Xr ssh 1
1.1 stevesk 1860: .Sh AUTHORS
1.240 jmc 1861: .An -nosplit
1.1 stevesk 1862: OpenSSH is a derivative of the original and free
1.240 jmc 1863: ssh 1.2.12 release by
1864: .An Tatu Ylonen .
1865: .An Aaron Campbell , Bob Beck , Markus Friedl ,
1866: .An Niels Provos , Theo de Raadt
1867: and
1868: .An Dug Song
1.1 stevesk 1869: removed many bugs, re-added newer features and
1870: created OpenSSH.
1.240 jmc 1871: .An Markus Friedl
1872: contributed the support for SSH protocol versions 1.5 and 2.0.
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