Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.283
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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1.283 ! jmc 36: .\" $OpenBSD: ssh_config.5,v 1.282 2018/09/20 03:30:44 djm Exp $
! 37: .Dd $Mdocdate: September 20 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
293: .Cm ProxyCommand ,
294: .Xr ssh 1
1.173 djm 295: will attempt to canonicalize the hostname specified on the command line
1.171 djm 296: using the
297: .Cm CanonicalDomains
298: suffixes and
1.173 djm 299: .Cm CanonicalizePermittedCNAMEs
1.171 djm 300: rules.
301: If
1.173 djm 302: .Cm CanonicalizeHostname
1.171 djm 303: is set to
1.240 jmc 304: .Cm always ,
1.174 djm 305: then canonicalization is applied to proxied connections too.
1.185 djm 306: .Pp
1.193 djm 307: If this option is enabled, then the configuration files are processed
308: again using the new target name to pick up any new configuration in matching
1.185 djm 309: .Cm Host
1.193 djm 310: and
311: .Cm Match
1.185 djm 312: stanzas.
1.173 djm 313: .It Cm CanonicalizeMaxDots
1.172 jmc 314: Specifies the maximum number of dot characters in a hostname before
1.174 djm 315: canonicalization is disabled.
1.240 jmc 316: The default, 1,
1.172 jmc 317: allows a single dot (i.e. hostname.subdomain).
1.173 djm 318: .It Cm CanonicalizePermittedCNAMEs
1.172 jmc 319: Specifies rules to determine whether CNAMEs should be followed when
1.173 djm 320: canonicalizing hostnames.
1.171 djm 321: The rules consist of one or more arguments of
1.172 jmc 322: .Ar source_domain_list : Ns Ar target_domain_list ,
1.171 djm 323: where
324: .Ar source_domain_list
1.174 djm 325: is a pattern-list of domains that may follow CNAMEs in canonicalization,
1.171 djm 326: and
327: .Ar target_domain_list
1.172 jmc 328: is a pattern-list of domains that they may resolve to.
1.171 djm 329: .Pp
330: For example,
1.240 jmc 331: .Qq *.a.example.com:*.b.example.com,*.c.example.com
1.171 djm 332: will allow hostnames matching
1.240 jmc 333: .Qq *.a.example.com
1.173 djm 334: to be canonicalized to names in the
1.240 jmc 335: .Qq *.b.example.com
1.171 djm 336: or
1.240 jmc 337: .Qq *.c.example.com
1.171 djm 338: domains.
1.283 ! jmc 339: .It Cm CASignatureAlgorithms
! 340: Specifies which algorithms are allowed for signing of certificates
! 341: by certificate authorities (CAs).
! 342: The default is:
! 343: .Bd -literal -offset indent
! 344: ecdsa-sha2-nistp256.ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
! 345: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
! 346: .Ed
! 347: .Pp
! 348: .Xr ssh 1
! 349: will not accept host certificates signed using algorithms other than those
! 350: specified.
1.221 djm 351: .It Cm CertificateFile
352: Specifies a file from which the user's certificate is read.
353: A corresponding private key must be provided separately in order
354: to use this certificate either
355: from an
356: .Cm IdentityFile
357: directive or
358: .Fl i
359: flag to
360: .Xr ssh 1 ,
361: via
362: .Xr ssh-agent 1 ,
363: or via a
364: .Cm PKCS11Provider .
365: .Pp
1.239 jmc 366: Arguments to
367: .Cm CertificateFile
368: may use the tilde syntax to refer to a user's home directory
369: or the tokens described in the
370: .Sx TOKENS
371: section.
1.221 djm 372: .Pp
373: It is possible to have multiple certificate files specified in
374: configuration files; these certificates will be tried in sequence.
375: Multiple
376: .Cm CertificateFile
377: directives will add to the list of certificates used for
378: authentication.
1.1 stevesk 379: .It Cm ChallengeResponseAuthentication
1.82 jmc 380: Specifies whether to use challenge-response authentication.
1.1 stevesk 381: The argument to this keyword must be
1.240 jmc 382: .Cm yes
383: (the default)
1.1 stevesk 384: or
1.240 jmc 385: .Cm no .
1.1 stevesk 386: .It Cm CheckHostIP
1.240 jmc 387: If set to
388: .Cm yes
389: (the default),
1.84 jmc 390: .Xr ssh 1
391: will additionally check the host IP address in the
1.1 stevesk 392: .Pa known_hosts
393: file.
1.240 jmc 394: This allows it to detect if a host key changed due to DNS spoofing
1.211 djm 395: and will add addresses of destination hosts to
396: .Pa ~/.ssh/known_hosts
397: in the process, regardless of the setting of
398: .Cm StrictHostKeyChecking .
1.107 grunk 399: If the option is set to
1.240 jmc 400: .Cm no ,
1.1 stevesk 401: the check will not be executed.
402: .It Cm Ciphers
1.245 djm 403: Specifies the ciphers allowed and their order of preference.
1.1 stevesk 404: Multiple ciphers must be comma-separated.
1.214 djm 405: If the specified value begins with a
406: .Sq +
407: character, then the specified ciphers will be appended to the default set
408: instead of replacing them.
1.241 djm 409: If the specified value begins with a
410: .Sq -
411: character, then the specified ciphers (including wildcards) will be removed
412: from the default set instead of replacing them.
1.214 djm 413: .Pp
1.180 djm 414: The supported ciphers are:
1.240 jmc 415: .Bd -literal -offset indent
1.186 naddy 416: 3des-cbc
417: aes128-cbc
418: aes192-cbc
419: aes256-cbc
420: aes128-ctr
421: aes192-ctr
422: aes256-ctr
423: aes128-gcm@openssh.com
424: aes256-gcm@openssh.com
425: chacha20-poly1305@openssh.com
1.240 jmc 426: .Ed
1.180 djm 427: .Pp
1.84 jmc 428: The default is:
1.186 naddy 429: .Bd -literal -offset indent
1.215 jmc 430: chacha20-poly1305@openssh.com,
1.186 naddy 431: aes128-ctr,aes192-ctr,aes256-ctr,
1.270 djm 432: aes128-gcm@openssh.com,aes256-gcm@openssh.com
1.1 stevesk 433: .Ed
1.180 djm 434: .Pp
1.240 jmc 435: The list of available ciphers may also be obtained using
436: .Qq ssh -Q cipher .
1.1 stevesk 437: .It Cm ClearAllForwardings
1.84 jmc 438: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 439: specified in the configuration files or on the command line be
1.7 jmc 440: cleared.
441: This option is primarily useful when used from the
1.84 jmc 442: .Xr ssh 1
1.1 stevesk 443: command line to clear port forwardings set in
444: configuration files, and is automatically set by
445: .Xr scp 1
446: and
447: .Xr sftp 1 .
448: The argument must be
1.240 jmc 449: .Cm yes
1.1 stevesk 450: or
1.240 jmc 451: .Cm no
452: (the default).
1.1 stevesk 453: .It Cm Compression
454: Specifies whether to use compression.
455: The argument must be
1.240 jmc 456: .Cm yes
1.1 stevesk 457: or
1.240 jmc 458: .Cm no
459: (the default).
1.247 naddy 460: .It Cm ConnectionAttempts
461: Specifies the number of tries (one per second) to make before exiting.
462: The argument must be an integer.
463: This may be useful in scripts if the connection sometimes fails.
464: The default is 1.
1.9 djm 465: .It Cm ConnectTimeout
1.84 jmc 466: Specifies the timeout (in seconds) used when connecting to the
467: SSH server, instead of using the default system TCP timeout.
1.11 jmc 468: This value is used only when the target is down or really unreachable,
469: not when it refuses the connection.
1.36 djm 470: .It Cm ControlMaster
471: Enables the sharing of multiple sessions over a single network connection.
472: When set to
1.240 jmc 473: .Cm yes ,
1.84 jmc 474: .Xr ssh 1
1.36 djm 475: will listen for connections on a control socket specified using the
476: .Cm ControlPath
477: argument.
478: Additional sessions can connect to this socket using the same
479: .Cm ControlPath
480: with
481: .Cm ControlMaster
482: set to
1.240 jmc 483: .Cm no
1.38 jmc 484: (the default).
1.64 jmc 485: These sessions will try to reuse the master instance's network connection
1.63 djm 486: rather than initiating new ones, but will fall back to connecting normally
487: if the control socket does not exist, or is not listening.
488: .Pp
1.37 djm 489: Setting this to
1.240 jmc 490: .Cm ask
491: will cause
492: .Xr ssh 1
1.206 jmc 493: to listen for control connections, but require confirmation using
494: .Xr ssh-askpass 1 .
1.51 jakob 495: If the
496: .Cm ControlPath
1.84 jmc 497: cannot be opened,
1.240 jmc 498: .Xr ssh 1
499: will continue without connecting to a master instance.
1.58 djm 500: .Pp
501: X11 and
1.59 jmc 502: .Xr ssh-agent 1
1.58 djm 503: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 504: display and agent forwarded will be the one belonging to the master
1.59 jmc 505: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 506: .Pp
507: Two additional options allow for opportunistic multiplexing: try to use a
508: master connection but fall back to creating a new one if one does not already
509: exist.
510: These options are:
1.240 jmc 511: .Cm auto
1.56 djm 512: and
1.240 jmc 513: .Cm autoask .
1.56 djm 514: The latter requires confirmation like the
1.240 jmc 515: .Cm ask
1.56 djm 516: option.
1.36 djm 517: .It Cm ControlPath
1.55 djm 518: Specify the path to the control socket used for connection sharing as described
519: in the
1.36 djm 520: .Cm ControlMaster
1.57 djm 521: section above or the string
1.240 jmc 522: .Cm none
1.57 djm 523: to disable connection sharing.
1.239 jmc 524: Arguments to
525: .Cm ControlPath
526: may use the tilde syntax to refer to a user's home directory
527: or the tokens described in the
528: .Sx TOKENS
529: section.
1.56 djm 530: It is recommended that any
531: .Cm ControlPath
532: used for opportunistic connection sharing include
1.195 djm 533: at least %h, %p, and %r (or alternatively %C) and be placed in a directory
534: that is not writable by other users.
1.56 djm 535: This ensures that shared connections are uniquely identified.
1.137 djm 536: .It Cm ControlPersist
537: When used in conjunction with
538: .Cm ControlMaster ,
539: specifies that the master connection should remain open
540: in the background (waiting for future client connections)
541: after the initial client connection has been closed.
542: If set to
1.240 jmc 543: .Cm no ,
1.137 djm 544: then the master connection will not be placed into the background,
545: and will close as soon as the initial client connection is closed.
546: If set to
1.240 jmc 547: .Cm yes
548: or 0,
1.137 djm 549: then the master connection will remain in the background indefinitely
550: (until killed or closed via a mechanism such as the
1.240 jmc 551: .Qq ssh -O exit ) .
1.137 djm 552: If set to a time in seconds, or a time in any of the formats documented in
553: .Xr sshd_config 5 ,
554: then the backgrounded master connection will automatically terminate
555: after it has remained idle (with no client connections) for the
556: specified time.
1.38 jmc 557: .It Cm DynamicForward
1.74 jmc 558: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 559: over the secure channel, and the application
560: protocol is then used to determine where to connect to from the
561: remote machine.
1.62 djm 562: .Pp
563: The argument must be
564: .Sm off
565: .Oo Ar bind_address : Oc Ar port .
566: .Sm on
1.138 djm 567: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 568: By default, the local port is bound in accordance with the
569: .Cm GatewayPorts
570: setting.
571: However, an explicit
572: .Ar bind_address
573: may be used to bind the connection to a specific address.
574: The
575: .Ar bind_address
576: of
1.240 jmc 577: .Cm localhost
1.62 djm 578: indicates that the listening port be bound for local use only, while an
579: empty address or
580: .Sq *
581: indicates that the port should be available from all interfaces.
582: .Pp
1.38 jmc 583: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 584: .Xr ssh 1
1.38 jmc 585: will act as a SOCKS server.
586: Multiple forwardings may be specified, and
587: additional forwardings can be given on the command line.
588: Only the superuser can forward privileged ports.
1.14 markus 589: .It Cm EnableSSHKeysign
590: Setting this option to
1.240 jmc 591: .Cm yes
1.14 markus 592: in the global client configuration file
593: .Pa /etc/ssh/ssh_config
594: enables the use of the helper program
595: .Xr ssh-keysign 8
596: during
597: .Cm HostbasedAuthentication .
598: The argument must be
1.240 jmc 599: .Cm yes
1.14 markus 600: or
1.240 jmc 601: .Cm no
602: (the default).
1.23 jmc 603: This option should be placed in the non-hostspecific section.
1.14 markus 604: See
605: .Xr ssh-keysign 8
606: for more information.
1.1 stevesk 607: .It Cm EscapeChar
608: Sets the escape character (default:
609: .Ql ~ ) .
610: The escape character can also
611: be set on the command line.
612: The argument should be a single character,
613: .Ql ^
614: followed by a letter, or
1.240 jmc 615: .Cm none
1.1 stevesk 616: to disable the escape
617: character entirely (making the connection transparent for binary
618: data).
1.96 markus 619: .It Cm ExitOnForwardFailure
620: Specifies whether
621: .Xr ssh 1
622: should terminate the connection if it cannot set up all requested
1.216 djm 623: dynamic, tunnel, local, and remote port forwardings, (e.g.\&
1.217 jmc 624: if either end is unable to bind and listen on a specified port).
1.216 djm 625: Note that
626: .Cm ExitOnForwardFailure
627: does not apply to connections made over port forwardings and will not,
628: for example, cause
629: .Xr ssh 1
630: to exit if TCP connections to the ultimate forwarding destination fail.
1.96 markus 631: The argument must be
1.240 jmc 632: .Cm yes
1.96 markus 633: or
1.240 jmc 634: .Cm no
635: (the default).
1.197 djm 636: .It Cm FingerprintHash
637: Specifies the hash algorithm used when displaying key fingerprints.
638: Valid options are:
1.240 jmc 639: .Cm md5
1.197 djm 640: and
1.240 jmc 641: .Cm sha256
642: (the default).
1.1 stevesk 643: .It Cm ForwardAgent
644: Specifies whether the connection to the authentication agent (if any)
645: will be forwarded to the remote machine.
646: The argument must be
1.240 jmc 647: .Cm yes
1.1 stevesk 648: or
1.240 jmc 649: .Cm no
650: (the default).
1.3 stevesk 651: .Pp
1.7 jmc 652: Agent forwarding should be enabled with caution.
653: Users with the ability to bypass file permissions on the remote host
654: (for the agent's Unix-domain socket)
655: can access the local agent through the forwarded connection.
656: An attacker cannot obtain key material from the agent,
1.3 stevesk 657: however they can perform operations on the keys that enable them to
658: authenticate using the identities loaded into the agent.
1.1 stevesk 659: .It Cm ForwardX11
660: Specifies whether X11 connections will be automatically redirected
661: over the secure channel and
662: .Ev DISPLAY
663: set.
664: The argument must be
1.240 jmc 665: .Cm yes
1.1 stevesk 666: or
1.240 jmc 667: .Cm no
668: (the default).
1.3 stevesk 669: .Pp
1.7 jmc 670: X11 forwarding should be enabled with caution.
671: Users with the ability to bypass file permissions on the remote host
1.22 markus 672: (for the user's X11 authorization database)
1.7 jmc 673: can access the local X11 display through the forwarded connection.
1.22 markus 674: An attacker may then be able to perform activities such as keystroke monitoring
675: if the
676: .Cm ForwardX11Trusted
677: option is also enabled.
1.134 djm 678: .It Cm ForwardX11Timeout
1.135 jmc 679: Specify a timeout for untrusted X11 forwarding
680: using the format described in the
1.240 jmc 681: .Sx TIME FORMATS
682: section of
1.134 djm 683: .Xr sshd_config 5 .
684: X11 connections received by
685: .Xr ssh 1
686: after this time will be refused.
687: The default is to disable untrusted X11 forwarding after twenty minutes has
688: elapsed.
1.22 markus 689: .It Cm ForwardX11Trusted
1.34 jmc 690: If this option is set to
1.240 jmc 691: .Cm yes ,
1.84 jmc 692: remote X11 clients will have full access to the original X11 display.
1.42 djm 693: .Pp
1.22 markus 694: If this option is set to
1.240 jmc 695: .Cm no
696: (the default),
1.84 jmc 697: remote X11 clients will be considered untrusted and prevented
1.22 markus 698: from stealing or tampering with data belonging to trusted X11
699: clients.
1.42 djm 700: Furthermore, the
701: .Xr xauth 1
702: token used for the session will be set to expire after 20 minutes.
703: Remote clients will be refused access after this time.
1.22 markus 704: .Pp
705: See the X11 SECURITY extension specification for full details on
706: the restrictions imposed on untrusted clients.
1.1 stevesk 707: .It Cm GatewayPorts
708: Specifies whether remote hosts are allowed to connect to local
709: forwarded ports.
710: By default,
1.84 jmc 711: .Xr ssh 1
1.7 jmc 712: binds local port forwardings to the loopback address.
713: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 714: .Cm GatewayPorts
1.84 jmc 715: can be used to specify that ssh
1.1 stevesk 716: should bind local port forwardings to the wildcard address,
717: thus allowing remote hosts to connect to forwarded ports.
718: The argument must be
1.240 jmc 719: .Cm yes
1.1 stevesk 720: or
1.240 jmc 721: .Cm no
722: (the default).
1.1 stevesk 723: .It Cm GlobalKnownHostsFile
1.151 djm 724: Specifies one or more files to use for the global
725: host key database, separated by whitespace.
726: The default is
727: .Pa /etc/ssh/ssh_known_hosts ,
728: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 729: .It Cm GSSAPIAuthentication
1.27 markus 730: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 731: The default is
1.240 jmc 732: .Cm no .
1.18 markus 733: .It Cm GSSAPIDelegateCredentials
734: Forward (delegate) credentials to the server.
735: The default is
1.240 jmc 736: .Cm no .
1.44 djm 737: .It Cm HashKnownHosts
738: Indicates that
1.84 jmc 739: .Xr ssh 1
1.44 djm 740: should hash host names and addresses when they are added to
1.50 djm 741: .Pa ~/.ssh/known_hosts .
1.44 djm 742: These hashed names may be used normally by
1.84 jmc 743: .Xr ssh 1
1.44 djm 744: and
1.84 jmc 745: .Xr sshd 8 ,
1.44 djm 746: but they do not reveal identifying information should the file's contents
747: be disclosed.
748: The default is
1.240 jmc 749: .Cm no .
1.97 jmc 750: Note that existing names and addresses in known hosts files
751: will not be converted automatically,
752: but may be manually hashed using
1.45 djm 753: .Xr ssh-keygen 1 .
1.1 stevesk 754: .It Cm HostbasedAuthentication
755: Specifies whether to try rhosts based authentication with public key
756: authentication.
757: The argument must be
1.240 jmc 758: .Cm yes
1.1 stevesk 759: or
1.240 jmc 760: .Cm no
761: (the default).
1.202 djm 762: .It Cm HostbasedKeyTypes
763: Specifies the key types that will be used for hostbased authentication
1.279 djm 764: as a comma-separated list of patterns.
1.214 djm 765: Alternately if the specified value begins with a
766: .Sq +
767: character, then the specified key types will be appended to the default set
768: instead of replacing them.
1.241 djm 769: If the specified value begins with a
770: .Sq -
771: character, then the specified key types (including wildcards) will be removed
772: from the default set instead of replacing them.
1.213 markus 773: The default for this option is:
774: .Bd -literal -offset 3n
775: ecdsa-sha2-nistp256-cert-v01@openssh.com,
776: ecdsa-sha2-nistp384-cert-v01@openssh.com,
777: ecdsa-sha2-nistp521-cert-v01@openssh.com,
778: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 779: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 780: ssh-rsa-cert-v01@openssh.com,
781: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 782: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 783: .Ed
784: .Pp
1.202 djm 785: The
786: .Fl Q
787: option of
788: .Xr ssh 1
789: may be used to list supported key types.
1.1 stevesk 790: .It Cm HostKeyAlgorithms
1.226 jmc 791: Specifies the host key algorithms
1.1 stevesk 792: that the client wants to use in order of preference.
1.214 djm 793: Alternately if the specified value begins with a
794: .Sq +
795: character, then the specified key types will be appended to the default set
796: instead of replacing them.
1.241 djm 797: If the specified value begins with a
798: .Sq -
799: character, then the specified key types (including wildcards) will be removed
800: from the default set instead of replacing them.
1.1 stevesk 801: The default for this option is:
1.139 djm 802: .Bd -literal -offset 3n
803: ecdsa-sha2-nistp256-cert-v01@openssh.com,
804: ecdsa-sha2-nistp384-cert-v01@openssh.com,
805: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1.183 naddy 806: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 807: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 808: ssh-rsa-cert-v01@openssh.com,
1.139 djm 809: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 810: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.139 djm 811: .Ed
1.145 djm 812: .Pp
813: If hostkeys are known for the destination host then this default is modified
814: to prefer their algorithms.
1.198 djm 815: .Pp
1.240 jmc 816: The list of available key types may also be obtained using
817: .Qq ssh -Q key .
1.1 stevesk 818: .It Cm HostKeyAlias
819: Specifies an alias that should be used instead of the
820: real host name when looking up or saving the host key
1.251 djm 821: in the host key database files and when validating host certificates.
1.84 jmc 822: This option is useful for tunneling SSH connections
1.1 stevesk 823: or for multiple servers running on a single host.
824: .It Cm HostName
825: Specifies the real host name to log into.
826: This can be used to specify nicknames or abbreviations for hosts.
1.239 jmc 827: Arguments to
828: .Cm HostName
829: accept the tokens described in the
830: .Sx TOKENS
831: section.
1.1 stevesk 832: Numeric IP addresses are also permitted (both on the command line and in
833: .Cm HostName
834: specifications).
1.239 jmc 835: The default is the name given on the command line.
1.29 markus 836: .It Cm IdentitiesOnly
837: Specifies that
1.84 jmc 838: .Xr ssh 1
1.221 djm 839: should only use the authentication identity and certificate files explicitly
840: configured in the
1.31 jmc 841: .Nm
1.221 djm 842: files
843: or passed on the
844: .Xr ssh 1
845: command-line,
1.84 jmc 846: even if
847: .Xr ssh-agent 1
1.159 djm 848: or a
849: .Cm PKCS11Provider
1.29 markus 850: offers more identities.
851: The argument to this keyword must be
1.240 jmc 852: .Cm yes
1.29 markus 853: or
1.240 jmc 854: .Cm no
855: (the default).
1.84 jmc 856: This option is intended for situations where ssh-agent
1.29 markus 857: offers many different identities.
1.231 markus 858: .It Cm IdentityAgent
859: Specifies the
860: .Ux Ns -domain
861: socket used to communicate with the authentication agent.
862: .Pp
863: This option overrides the
1.240 jmc 864: .Ev SSH_AUTH_SOCK
1.231 markus 865: environment variable and can be used to select a specific agent.
866: Setting the socket name to
1.240 jmc 867: .Cm none
1.231 markus 868: disables the use of an authentication agent.
1.232 markus 869: If the string
1.240 jmc 870: .Qq SSH_AUTH_SOCK
1.232 markus 871: is specified, the location of the socket will be read from the
872: .Ev SSH_AUTH_SOCK
873: environment variable.
1.231 markus 874: .Pp
1.239 jmc 875: Arguments to
876: .Cm IdentityAgent
877: may use the tilde syntax to refer to a user's home directory
878: or the tokens described in the
879: .Sx TOKENS
880: section.
1.67 jmc 881: .It Cm IdentityFile
1.192 sobrado 882: Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA authentication
1.139 djm 883: identity is read.
1.67 jmc 884: The default is
1.139 djm 885: .Pa ~/.ssh/id_dsa ,
1.183 naddy 886: .Pa ~/.ssh/id_ecdsa ,
887: .Pa ~/.ssh/id_ed25519
1.139 djm 888: and
1.245 djm 889: .Pa ~/.ssh/id_rsa .
1.67 jmc 890: Additionally, any identities represented by the authentication agent
1.165 djm 891: will be used for authentication unless
892: .Cm IdentitiesOnly
893: is set.
1.221 djm 894: If no certificates have been explicitly specified by
895: .Cm CertificateFile ,
1.129 djm 896: .Xr ssh 1
897: will try to load certificate information from the filename obtained by
898: appending
899: .Pa -cert.pub
900: to the path of a specified
901: .Cm IdentityFile .
1.90 djm 902: .Pp
1.239 jmc 903: Arguments to
904: .Cm IdentityFile
905: may use the tilde syntax to refer to a user's home directory
906: or the tokens described in the
907: .Sx TOKENS
908: section.
1.90 djm 909: .Pp
1.67 jmc 910: It is possible to have
911: multiple identity files specified in configuration files; all these
912: identities will be tried in sequence.
1.152 djm 913: Multiple
914: .Cm IdentityFile
915: directives will add to the list of identities tried (this behaviour
916: differs from that of other configuration directives).
1.165 djm 917: .Pp
918: .Cm IdentityFile
919: may be used in conjunction with
920: .Cm IdentitiesOnly
921: to select which identities in an agent are offered during authentication.
1.221 djm 922: .Cm IdentityFile
923: may also be used in conjunction with
924: .Cm CertificateFile
925: in order to provide any certificate also needed for authentication with
926: the identity.
1.164 jmc 927: .It Cm IgnoreUnknown
928: Specifies a pattern-list of unknown options to be ignored if they are
929: encountered in configuration parsing.
930: This may be used to suppress errors if
931: .Nm
932: contains options that are unrecognised by
933: .Xr ssh 1 .
934: It is recommended that
935: .Cm IgnoreUnknown
936: be listed early in the configuration file as it will not be applied
937: to unknown options that appear before it.
1.229 djm 938: .It Cm Include
939: Include the specified configuration file(s).
1.230 jmc 940: Multiple pathnames may be specified and each pathname may contain
1.281 kn 941: .Xr glob 7
1.229 djm 942: wildcards and, for user configurations, shell-like
1.240 jmc 943: .Sq ~
1.229 djm 944: references to user home directories.
945: Files without absolute paths are assumed to be in
946: .Pa ~/.ssh
1.230 jmc 947: if included in a user configuration file or
1.229 djm 948: .Pa /etc/ssh
949: if included from the system configuration file.
950: .Cm Include
951: directive may appear inside a
952: .Cm Match
953: or
954: .Cm Host
955: block
956: to perform conditional inclusion.
1.143 djm 957: .It Cm IPQoS
958: Specifies the IPv4 type-of-service or DSCP class for connections.
959: Accepted values are
1.240 jmc 960: .Cm af11 ,
961: .Cm af12 ,
962: .Cm af13 ,
963: .Cm af21 ,
964: .Cm af22 ,
965: .Cm af23 ,
966: .Cm af31 ,
967: .Cm af32 ,
968: .Cm af33 ,
969: .Cm af41 ,
970: .Cm af42 ,
971: .Cm af43 ,
972: .Cm cs0 ,
973: .Cm cs1 ,
974: .Cm cs2 ,
975: .Cm cs3 ,
976: .Cm cs4 ,
977: .Cm cs5 ,
978: .Cm cs6 ,
979: .Cm cs7 ,
980: .Cm ef ,
981: .Cm lowdelay ,
982: .Cm throughput ,
983: .Cm reliability ,
1.253 djm 984: a numeric value, or
985: .Cm none
986: to use the operating system default.
1.146 djm 987: This option may take one or two arguments, separated by whitespace.
1.143 djm 988: If one argument is specified, it is used as the packet class unconditionally.
989: If two values are specified, the first is automatically selected for
990: interactive sessions and the second for non-interactive sessions.
991: The default is
1.269 job 992: .Cm af21
1.272 jmc 993: (Low-Latency Data)
1.143 djm 994: for interactive sessions and
1.269 job 995: .Cm cs1
1.272 jmc 996: (Lower Effort)
1.143 djm 997: for non-interactive sessions.
1.103 djm 998: .It Cm KbdInteractiveAuthentication
999: Specifies whether to use keyboard-interactive authentication.
1000: The argument to this keyword must be
1.240 jmc 1001: .Cm yes
1002: (the default)
1.103 djm 1003: or
1.240 jmc 1004: .Cm no .
1.39 djm 1005: .It Cm KbdInteractiveDevices
1006: Specifies the list of methods to use in keyboard-interactive authentication.
1007: Multiple method names must be comma-separated.
1008: The default is to use the server specified list.
1.85 jmc 1009: The methods available vary depending on what the server supports.
1010: For an OpenSSH server,
1011: it may be zero or more of:
1.240 jmc 1012: .Cm bsdauth ,
1013: .Cm pam ,
1.85 jmc 1014: and
1.240 jmc 1015: .Cm skey .
1.140 djm 1016: .It Cm KexAlgorithms
1017: Specifies the available KEX (Key Exchange) algorithms.
1018: Multiple algorithms must be comma-separated.
1.214 djm 1019: Alternately if the specified value begins with a
1020: .Sq +
1021: character, then the specified methods will be appended to the default set
1022: instead of replacing them.
1.241 djm 1023: If the specified value begins with a
1024: .Sq -
1025: character, then the specified methods (including wildcards) will be removed
1026: from the default set instead of replacing them.
1.141 jmc 1027: The default is:
1028: .Bd -literal -offset indent
1.238 djm 1029: curve25519-sha256,curve25519-sha256@libssh.org,
1.141 jmc 1030: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1031: diffie-hellman-group-exchange-sha256,
1.266 djm 1032: diffie-hellman-group16-sha512,
1033: diffie-hellman-group18-sha512,
1.209 dtucker 1034: diffie-hellman-group-exchange-sha1,
1.266 djm 1035: diffie-hellman-group14-sha256,
1.212 djm 1036: diffie-hellman-group14-sha1
1.141 jmc 1037: .Ed
1.198 djm 1038: .Pp
1.240 jmc 1039: The list of available key exchange algorithms may also be obtained using
1040: .Qq ssh -Q kex .
1.65 reyk 1041: .It Cm LocalCommand
1042: Specifies a command to execute on the local machine after successfully
1043: connecting to the server.
1044: The command string extends to the end of the line, and is executed with
1.105 jmc 1045: the user's shell.
1.239 jmc 1046: Arguments to
1047: .Cm LocalCommand
1048: accept the tokens described in the
1049: .Sx TOKENS
1050: section.
1.123 djm 1051: .Pp
1052: The command is run synchronously and does not have access to the
1053: session of the
1054: .Xr ssh 1
1055: that spawned it.
1056: It should not be used for interactive commands.
1057: .Pp
1.65 reyk 1058: This directive is ignored unless
1059: .Cm PermitLocalCommand
1060: has been enabled.
1.1 stevesk 1061: .It Cm LocalForward
1.74 jmc 1062: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 1063: the secure channel to the specified host and port from the remote machine.
1.49 jmc 1064: The first argument must be
1.43 djm 1065: .Sm off
1.49 jmc 1066: .Oo Ar bind_address : Oc Ar port
1.43 djm 1067: .Sm on
1.49 jmc 1068: and the second argument must be
1069: .Ar host : Ns Ar hostport .
1.138 djm 1070: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 1071: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 1072: given on the command line.
1.1 stevesk 1073: Only the superuser can forward privileged ports.
1.43 djm 1074: By default, the local port is bound in accordance with the
1075: .Cm GatewayPorts
1076: setting.
1077: However, an explicit
1078: .Ar bind_address
1079: may be used to bind the connection to a specific address.
1080: The
1081: .Ar bind_address
1082: of
1.240 jmc 1083: .Cm localhost
1.46 jmc 1084: indicates that the listening port be bound for local use only, while an
1085: empty address or
1086: .Sq *
1.43 djm 1087: indicates that the port should be available from all interfaces.
1.1 stevesk 1088: .It Cm LogLevel
1089: Gives the verbosity level that is used when logging messages from
1.84 jmc 1090: .Xr ssh 1 .
1.1 stevesk 1091: The possible values are:
1.84 jmc 1092: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 1093: The default is INFO.
1094: DEBUG and DEBUG1 are equivalent.
1095: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 1096: .It Cm MACs
1097: Specifies the MAC (message authentication code) algorithms
1098: in order of preference.
1.226 jmc 1099: The MAC algorithm is used for data integrity protection.
1.1 stevesk 1100: Multiple algorithms must be comma-separated.
1.214 djm 1101: If the specified value begins with a
1102: .Sq +
1103: character, then the specified algorithms will be appended to the default set
1104: instead of replacing them.
1.241 djm 1105: If the specified value begins with a
1106: .Sq -
1107: character, then the specified algorithms (including wildcards) will be removed
1108: from the default set instead of replacing them.
1.214 djm 1109: .Pp
1.160 markus 1110: The algorithms that contain
1.240 jmc 1111: .Qq -etm
1.160 markus 1112: calculate the MAC after encryption (encrypt-then-mac).
1113: These are considered safer and their use recommended.
1.214 djm 1114: .Pp
1.84 jmc 1115: The default is:
1.101 jmc 1116: .Bd -literal -offset indent
1.160 markus 1117: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1118: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.224 djm 1119: hmac-sha1-etm@openssh.com,
1.186 naddy 1120: umac-64@openssh.com,umac-128@openssh.com,
1.224 djm 1121: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.101 jmc 1122: .Ed
1.198 djm 1123: .Pp
1.240 jmc 1124: The list of available MAC algorithms may also be obtained using
1125: .Qq ssh -Q mac .
1.1 stevesk 1126: .It Cm NoHostAuthenticationForLocalhost
1.264 djm 1127: Disable host authentication for localhost (loopback addresses).
1.1 stevesk 1128: The argument to this keyword must be
1.240 jmc 1129: .Cm yes
1.1 stevesk 1130: or
1.242 jmc 1131: .Cm no
1.240 jmc 1132: (the default).
1.1 stevesk 1133: .It Cm NumberOfPasswordPrompts
1134: Specifies the number of password prompts before giving up.
1135: The argument to this keyword must be an integer.
1.84 jmc 1136: The default is 3.
1.1 stevesk 1137: .It Cm PasswordAuthentication
1138: Specifies whether to use password authentication.
1139: The argument to this keyword must be
1.240 jmc 1140: .Cm yes
1141: (the default)
1.1 stevesk 1142: or
1.240 jmc 1143: .Cm no .
1.65 reyk 1144: .It Cm PermitLocalCommand
1145: Allow local command execution via the
1146: .Ic LocalCommand
1147: option or using the
1.66 jmc 1148: .Ic !\& Ns Ar command
1.65 reyk 1149: escape sequence in
1150: .Xr ssh 1 .
1151: The argument must be
1.240 jmc 1152: .Cm yes
1.65 reyk 1153: or
1.240 jmc 1154: .Cm no
1155: (the default).
1.127 markus 1156: .It Cm PKCS11Provider
1157: Specifies which PKCS#11 provider to use.
1.144 jmc 1158: The argument to this keyword is the PKCS#11 shared library
1.127 markus 1159: .Xr ssh 1
1.128 markus 1160: should use to communicate with a PKCS#11 token providing the user's
1.127 markus 1161: private RSA key.
1.67 jmc 1162: .It Cm Port
1163: Specifies the port number to connect on the remote host.
1.84 jmc 1164: The default is 22.
1.1 stevesk 1165: .It Cm PreferredAuthentications
1.226 jmc 1166: Specifies the order in which the client should try authentication methods.
1.48 jmc 1167: This allows a client to prefer one method (e.g.\&
1.1 stevesk 1168: .Cm keyboard-interactive )
1.48 jmc 1169: over another method (e.g.\&
1.131 jmc 1170: .Cm password ) .
1171: The default is:
1172: .Bd -literal -offset indent
1173: gssapi-with-mic,hostbased,publickey,
1174: keyboard-interactive,password
1175: .Ed
1.1 stevesk 1176: .It Cm ProxyCommand
1177: Specifies the command to use to connect to the server.
1178: The command
1.190 djm 1179: string extends to the end of the line, and is executed
1180: using the user's shell
1181: .Ql exec
1182: directive to avoid a lingering shell process.
1183: .Pp
1.239 jmc 1184: Arguments to
1185: .Cm ProxyCommand
1186: accept the tokens described in the
1187: .Sx TOKENS
1188: section.
1.1 stevesk 1189: The command can be basically anything,
1190: and should read from its standard input and write to its standard output.
1191: It should eventually connect an
1192: .Xr sshd 8
1193: server running on some machine, or execute
1194: .Ic sshd -i
1195: somewhere.
1196: Host key management will be done using the
1197: HostName of the host being connected (defaulting to the name typed by
1198: the user).
1.7 jmc 1199: Setting the command to
1.240 jmc 1200: .Cm none
1.6 markus 1201: disables this option entirely.
1.1 stevesk 1202: Note that
1203: .Cm CheckHostIP
1204: is not available for connects with a proxy command.
1.52 djm 1205: .Pp
1206: This directive is useful in conjunction with
1207: .Xr nc 1
1208: and its proxy support.
1.53 jmc 1209: For example, the following directive would connect via an HTTP proxy at
1.52 djm 1210: 192.0.2.0:
1211: .Bd -literal -offset 3n
1212: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1213: .Ed
1.233 djm 1214: .It Cm ProxyJump
1.260 millert 1215: Specifies one or more jump proxies as either
1.233 djm 1216: .Xo
1217: .Sm off
1.234 jmc 1218: .Op Ar user No @
1.233 djm 1219: .Ar host
1.234 jmc 1220: .Op : Ns Ar port
1.233 djm 1221: .Sm on
1.260 millert 1222: or an ssh URI
1.233 djm 1223: .Xc .
1.235 djm 1224: Multiple proxies may be separated by comma characters and will be visited
1.236 djm 1225: sequentially.
1.233 djm 1226: Setting this option will cause
1227: .Xr ssh 1
1228: to connect to the target host by first making a
1229: .Xr ssh 1
1230: connection to the specified
1231: .Cm ProxyJump
1232: host and then establishing a
1.234 jmc 1233: TCP forwarding to the ultimate target from there.
1.233 djm 1234: .Pp
1235: Note that this option will compete with the
1236: .Cm ProxyCommand
1237: option - whichever is specified first will prevent later instances of the
1238: other from taking effect.
1.167 djm 1239: .It Cm ProxyUseFdpass
1.168 jmc 1240: Specifies that
1.167 djm 1241: .Cm ProxyCommand
1242: will pass a connected file descriptor back to
1.168 jmc 1243: .Xr ssh 1
1.167 djm 1244: instead of continuing to execute and pass data.
1245: The default is
1.240 jmc 1246: .Cm no .
1.213 markus 1247: .It Cm PubkeyAcceptedKeyTypes
1248: Specifies the key types that will be used for public key authentication
1.279 djm 1249: as a comma-separated list of patterns.
1.214 djm 1250: Alternately if the specified value begins with a
1251: .Sq +
1252: character, then the key types after it will be appended to the default
1253: instead of replacing it.
1.241 djm 1254: If the specified value begins with a
1255: .Sq -
1256: character, then the specified key types (including wildcards) will be removed
1257: from the default set instead of replacing them.
1.213 markus 1258: The default for this option is:
1259: .Bd -literal -offset 3n
1260: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1261: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1262: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1263: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 1264: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 1265: ssh-rsa-cert-v01@openssh.com,
1266: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 1267: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 1268: .Ed
1269: .Pp
1.240 jmc 1270: The list of available key types may also be obtained using
1271: .Qq ssh -Q key .
1.1 stevesk 1272: .It Cm PubkeyAuthentication
1273: Specifies whether to try public key authentication.
1274: The argument to this keyword must be
1.240 jmc 1275: .Cm yes
1276: (the default)
1.1 stevesk 1277: or
1.240 jmc 1278: .Cm no .
1.75 dtucker 1279: .It Cm RekeyLimit
1280: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1281: session key is renegotiated, optionally followed a maximum amount of
1282: time that may pass before the session key is renegotiated.
1283: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1284: .Sq K ,
1285: .Sq M ,
1.75 dtucker 1286: or
1.76 jmc 1287: .Sq G
1.75 dtucker 1288: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1289: The default is between
1.84 jmc 1290: .Sq 1G
1.75 dtucker 1291: and
1.84 jmc 1292: .Sq 4G ,
1.75 dtucker 1293: depending on the cipher.
1.162 dtucker 1294: The optional second value is specified in seconds and may use any of the
1295: units documented in the
1.240 jmc 1296: .Sx TIME FORMATS
1297: section of
1.162 dtucker 1298: .Xr sshd_config 5 .
1299: The default value for
1300: .Cm RekeyLimit
1301: is
1.240 jmc 1302: .Cm default none ,
1.162 dtucker 1303: which means that rekeying is performed after the cipher's default amount
1304: of data has been sent or received and no time based rekeying is done.
1.249 bluhm 1305: .It Cm RemoteCommand
1306: Specifies a command to execute on the remote machine after successfully
1307: connecting to the server.
1308: The command string extends to the end of the line, and is executed with
1309: the user's shell.
1.250 jmc 1310: Arguments to
1311: .Cm RemoteCommand
1312: accept the tokens described in the
1313: .Sx TOKENS
1314: section.
1.1 stevesk 1315: .It Cm RemoteForward
1.74 jmc 1316: Specifies that a TCP port on the remote machine be forwarded over
1.256 markus 1317: the secure channel.
1.273 djm 1318: The remote port may either be forwarded to a specified host and port
1.256 markus 1319: from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
1320: client to connect to arbitrary destinations from the local machine.
1.49 jmc 1321: The first argument must be
1.43 djm 1322: .Sm off
1.49 jmc 1323: .Oo Ar bind_address : Oc Ar port
1.43 djm 1324: .Sm on
1.256 markus 1325: If forwarding to a specific destination then the second argument must be
1326: .Ar host : Ns Ar hostport ,
1327: otherwise if no destination argument is specified then the remote forwarding
1328: will be established as a SOCKS proxy.
1329: .Pp
1.138 djm 1330: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.1 stevesk 1331: Multiple forwardings may be specified, and additional
1332: forwardings can be given on the command line.
1.113 stevesk 1333: Privileged ports can be forwarded only when
1334: logging in as root on the remote machine.
1.118 jmc 1335: .Pp
1.117 djm 1336: If the
1337: .Ar port
1.240 jmc 1338: argument is 0,
1.117 djm 1339: the listen port will be dynamically allocated on the server and reported
1340: to the client at run time.
1.43 djm 1341: .Pp
1342: If the
1343: .Ar bind_address
1344: is not specified, the default is to only bind to loopback addresses.
1345: If the
1346: .Ar bind_address
1347: is
1348: .Ql *
1349: or an empty string, then the forwarding is requested to listen on all
1350: interfaces.
1351: Specifying a remote
1352: .Ar bind_address
1.46 jmc 1353: will only succeed if the server's
1354: .Cm GatewayPorts
1.43 djm 1355: option is enabled (see
1.46 jmc 1356: .Xr sshd_config 5 ) .
1.149 djm 1357: .It Cm RequestTTY
1358: Specifies whether to request a pseudo-tty for the session.
1359: The argument may be one of:
1.240 jmc 1360: .Cm no
1.149 djm 1361: (never request a TTY),
1.240 jmc 1362: .Cm yes
1.149 djm 1363: (always request a TTY when standard input is a TTY),
1.240 jmc 1364: .Cm force
1.149 djm 1365: (always request a TTY) or
1.240 jmc 1366: .Cm auto
1.149 djm 1367: (request a TTY when opening a login session).
1368: This option mirrors the
1369: .Fl t
1370: and
1371: .Fl T
1372: flags for
1373: .Xr ssh 1 .
1.196 djm 1374: .It Cm RevokedHostKeys
1375: Specifies revoked host public keys.
1376: Keys listed in this file will be refused for host authentication.
1377: Note that if this file does not exist or is not readable,
1378: then host authentication will be refused for all hosts.
1379: Keys may be specified as a text file, listing one public key per line, or as
1380: an OpenSSH Key Revocation List (KRL) as generated by
1381: .Xr ssh-keygen 1 .
1382: For more information on KRLs, see the KEY REVOCATION LISTS section in
1383: .Xr ssh-keygen 1 .
1.32 djm 1384: .It Cm SendEnv
1385: Specifies what variables from the local
1386: .Xr environ 7
1387: should be sent to the server.
1.84 jmc 1388: The server must also support it, and the server must be configured to
1.33 djm 1389: accept these environment variables.
1.207 dtucker 1390: Note that the
1391: .Ev TERM
1.208 jmc 1392: environment variable is always sent whenever a
1.207 dtucker 1393: pseudo-terminal is requested as it is required by the protocol.
1.32 djm 1394: Refer to
1395: .Cm AcceptEnv
1396: in
1397: .Xr sshd_config 5
1398: for how to configure the server.
1.80 jmc 1399: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1400: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1401: across multiple
1402: .Cm SendEnv
1403: directives.
1.81 jmc 1404: .Pp
1405: See
1406: .Sx PATTERNS
1407: for more information on patterns.
1.271 djm 1408: .Pp
1.272 jmc 1409: It is possible to clear previously set
1.271 djm 1410: .Cm SendEnv
1411: variable names by prefixing patterns with
1412: .Pa - .
1413: The default is not to send any environment variables.
1.28 markus 1414: .It Cm ServerAliveCountMax
1.73 jmc 1415: Sets the number of server alive messages (see below) which may be
1.28 markus 1416: sent without
1.84 jmc 1417: .Xr ssh 1
1.28 markus 1418: receiving any messages back from the server.
1419: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1420: ssh will disconnect from the server, terminating the session.
1.28 markus 1421: It is important to note that the use of server alive messages is very
1422: different from
1423: .Cm TCPKeepAlive
1424: (below).
1425: The server alive messages are sent through the encrypted channel
1426: and therefore will not be spoofable.
1427: The TCP keepalive option enabled by
1428: .Cm TCPKeepAlive
1429: is spoofable.
1430: The server alive mechanism is valuable when the client or
1431: server depend on knowing when a connection has become inactive.
1432: .Pp
1433: The default value is 3.
1434: If, for example,
1435: .Cm ServerAliveInterval
1.84 jmc 1436: (see below) is set to 15 and
1.28 markus 1437: .Cm ServerAliveCountMax
1.84 jmc 1438: is left at the default, if the server becomes unresponsive,
1439: ssh will disconnect after approximately 45 seconds.
1.67 jmc 1440: .It Cm ServerAliveInterval
1441: Sets a timeout interval in seconds after which if no data has been received
1442: from the server,
1.84 jmc 1443: .Xr ssh 1
1.67 jmc 1444: will send a message through the encrypted
1445: channel to request a response from the server.
1446: The default
1447: is 0, indicating that these messages will not be sent to the server.
1.277 jmc 1448: .It Cm SetEnv
1449: Directly specify one or more environment variables and their contents to
1450: be sent to the server.
1451: Similarly to
1452: .Cm SendEnv ,
1453: the server must be prepared to accept the environment variable.
1.191 millert 1454: .It Cm StreamLocalBindMask
1455: Sets the octal file creation mode mask
1456: .Pq umask
1457: used when creating a Unix-domain socket file for local or remote
1458: port forwarding.
1459: This option is only used for port forwarding to a Unix-domain socket file.
1460: .Pp
1461: The default value is 0177, which creates a Unix-domain socket file that is
1462: readable and writable only by the owner.
1463: Note that not all operating systems honor the file mode on Unix-domain
1464: socket files.
1465: .It Cm StreamLocalBindUnlink
1466: Specifies whether to remove an existing Unix-domain socket file for local
1467: or remote port forwarding before creating a new one.
1468: If the socket file already exists and
1469: .Cm StreamLocalBindUnlink
1470: is not enabled,
1471: .Nm ssh
1472: will be unable to forward the port to the Unix-domain socket file.
1473: This option is only used for port forwarding to a Unix-domain socket file.
1474: .Pp
1475: The argument must be
1.240 jmc 1476: .Cm yes
1.191 millert 1477: or
1.240 jmc 1478: .Cm no
1479: (the default).
1.1 stevesk 1480: .It Cm StrictHostKeyChecking
1481: If this flag is set to
1.240 jmc 1482: .Cm yes ,
1.84 jmc 1483: .Xr ssh 1
1.1 stevesk 1484: will never automatically add host keys to the
1.50 djm 1485: .Pa ~/.ssh/known_hosts
1.1 stevesk 1486: file, and refuses to connect to hosts whose host key has changed.
1.263 dtucker 1487: This provides maximum protection against man-in-the-middle (MITM) attacks,
1.84 jmc 1488: though it can be annoying when the
1.1 stevesk 1489: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1490: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1491: frequently made.
1492: This option forces the user to manually
1493: add all new hosts.
1.255 jmc 1494: .Pp
1.1 stevesk 1495: If this flag is set to
1.254 djm 1496: .Dq accept-new
1.255 jmc 1497: then ssh will automatically add new host keys to the user
1.254 djm 1498: known hosts files, but will not permit connections to hosts with
1499: changed host keys.
1500: If this flag is set to
1501: .Dq no
1502: or
1503: .Dq off ,
1.255 jmc 1504: ssh will automatically add new host keys to the user known hosts files
1505: and allow connections to hosts with changed hostkeys to proceed,
1506: subject to some restrictions.
1.1 stevesk 1507: If this flag is set to
1.240 jmc 1508: .Cm ask
1509: (the default),
1.1 stevesk 1510: new host keys
1511: will be added to the user known host files only after the user
1512: has confirmed that is what they really want to do, and
1.84 jmc 1513: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1514: The host keys of
1515: known hosts will be verified automatically in all cases.
1.244 jmc 1516: .It Cm SyslogFacility
1517: Gives the facility code that is used when logging messages from
1518: .Xr ssh 1 .
1519: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1520: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1521: The default is USER.
1.26 markus 1522: .It Cm TCPKeepAlive
1523: Specifies whether the system should send TCP keepalive messages to the
1524: other side.
1525: If they are sent, death of the connection or crash of one
1526: of the machines will be properly noticed.
1527: However, this means that
1528: connections will die if the route is down temporarily, and some people
1529: find it annoying.
1530: .Pp
1531: The default is
1.240 jmc 1532: .Cm yes
1.26 markus 1533: (to send TCP keepalive messages), and the client will notice
1534: if the network goes down or the remote host dies.
1535: This is important in scripts, and many users want it too.
1536: .Pp
1537: To disable TCP keepalive messages, the value should be set to
1.240 jmc 1538: .Cm no .
1.265 djm 1539: See also
1540: .Cm ServerAliveInterval
1541: for protocol-level keepalives.
1.65 reyk 1542: .It Cm Tunnel
1.95 stevesk 1543: Request
1.65 reyk 1544: .Xr tun 4
1.69 jmc 1545: device forwarding between the client and the server.
1.65 reyk 1546: The argument must be
1.240 jmc 1547: .Cm yes ,
1548: .Cm point-to-point
1.95 stevesk 1549: (layer 3),
1.240 jmc 1550: .Cm ethernet
1.95 stevesk 1551: (layer 2),
1.65 reyk 1552: or
1.240 jmc 1553: .Cm no
1554: (the default).
1.95 stevesk 1555: Specifying
1.240 jmc 1556: .Cm yes
1.95 stevesk 1557: requests the default tunnel mode, which is
1.240 jmc 1558: .Cm point-to-point .
1.65 reyk 1559: .It Cm TunnelDevice
1.95 stevesk 1560: Specifies the
1.65 reyk 1561: .Xr tun 4
1.95 stevesk 1562: devices to open on the client
1563: .Pq Ar local_tun
1564: and the server
1565: .Pq Ar remote_tun .
1566: .Pp
1567: The argument must be
1568: .Sm off
1569: .Ar local_tun Op : Ar remote_tun .
1570: .Sm on
1571: The devices may be specified by numerical ID or the keyword
1.240 jmc 1572: .Cm any ,
1.95 stevesk 1573: which uses the next available tunnel device.
1574: If
1575: .Ar remote_tun
1576: is not specified, it defaults to
1.240 jmc 1577: .Cm any .
1.95 stevesk 1578: The default is
1.240 jmc 1579: .Cm any:any .
1.201 djm 1580: .It Cm UpdateHostKeys
1.200 djm 1581: Specifies whether
1582: .Xr ssh 1
1583: should accept notifications of additional hostkeys from the server sent
1584: after authentication has completed and add them to
1585: .Cm UserKnownHostsFile .
1586: The argument must be
1.240 jmc 1587: .Cm yes ,
1588: .Cm no
1.204 djm 1589: (the default) or
1.240 jmc 1590: .Cm ask .
1.200 djm 1591: Enabling this option allows learning alternate hostkeys for a server
1.201 djm 1592: and supports graceful key rotation by allowing a server to send replacement
1593: public keys before old ones are removed.
1.200 djm 1594: Additional hostkeys are only accepted if the key used to authenticate the
1.220 sobrado 1595: host was already trusted or explicitly accepted by the user.
1.204 djm 1596: If
1597: .Cm UpdateHostKeys
1598: is set to
1.240 jmc 1599: .Cm ask ,
1.204 djm 1600: then the user is asked to confirm the modifications to the known_hosts file.
1.205 djm 1601: Confirmation is currently incompatible with
1602: .Cm ControlPersist ,
1603: and will be disabled if it is enabled.
1.200 djm 1604: .Pp
1605: Presently, only
1606: .Xr sshd 8
1607: from OpenSSH 6.8 and greater support the
1.240 jmc 1608: .Qq hostkeys@openssh.com
1.200 djm 1609: protocol extension used to inform the client of all the server's hostkeys.
1.1 stevesk 1610: .It Cm User
1611: Specifies the user to log in as.
1612: This can be useful when a different user name is used on different machines.
1613: This saves the trouble of
1614: having to remember to give the user name on the command line.
1615: .It Cm UserKnownHostsFile
1.151 djm 1616: Specifies one or more files to use for the user
1617: host key database, separated by whitespace.
1618: The default is
1619: .Pa ~/.ssh/known_hosts ,
1620: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1621: .It Cm VerifyHostKeyDNS
1622: Specifies whether to verify the remote key using DNS and SSHFP resource
1623: records.
1.24 jakob 1624: If this option is set to
1.240 jmc 1625: .Cm yes ,
1.25 jmc 1626: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1627: from DNS.
1628: Insecure fingerprints will be handled as if this option was set to
1.240 jmc 1629: .Cm ask .
1.24 jakob 1630: If this option is set to
1.240 jmc 1631: .Cm ask ,
1.24 jakob 1632: information on fingerprint match will be displayed, but the user will still
1633: need to confirm new host keys according to the
1634: .Cm StrictHostKeyChecking
1635: option.
1.8 jakob 1636: The default is
1.240 jmc 1637: .Cm no .
1.84 jmc 1638: .Pp
1.240 jmc 1639: See also
1640: .Sx VERIFYING HOST KEYS
1641: in
1.84 jmc 1642: .Xr ssh 1 .
1.111 grunk 1643: .It Cm VisualHostKey
1644: If this flag is set to
1.240 jmc 1645: .Cm yes ,
1.111 grunk 1646: an ASCII art representation of the remote host key fingerprint is
1.197 djm 1647: printed in addition to the fingerprint string at login and
1.114 stevesk 1648: for unknown host keys.
1.111 grunk 1649: If this flag is set to
1.240 jmc 1650: .Cm no
1651: (the default),
1.114 stevesk 1652: no fingerprint strings are printed at login and
1.197 djm 1653: only the fingerprint string will be printed for unknown host keys.
1.1 stevesk 1654: .It Cm XAuthLocation
1.5 stevesk 1655: Specifies the full pathname of the
1.1 stevesk 1656: .Xr xauth 1
1657: program.
1658: The default is
1659: .Pa /usr/X11R6/bin/xauth .
1660: .El
1.86 jmc 1661: .Sh PATTERNS
1662: A
1663: .Em pattern
1664: consists of zero or more non-whitespace characters,
1665: .Sq *
1666: (a wildcard that matches zero or more characters),
1667: or
1668: .Sq ?\&
1669: (a wildcard that matches exactly one character).
1670: For example, to specify a set of declarations for any host in the
1.240 jmc 1671: .Qq .co.uk
1.86 jmc 1672: set of domains,
1673: the following pattern could be used:
1674: .Pp
1675: .Dl Host *.co.uk
1676: .Pp
1677: The following pattern
1678: would match any host in the 192.168.0.[0-9] network range:
1679: .Pp
1680: .Dl Host 192.168.0.?
1681: .Pp
1682: A
1683: .Em pattern-list
1684: is a comma-separated list of patterns.
1685: Patterns within pattern-lists may be negated
1686: by preceding them with an exclamation mark
1687: .Pq Sq !\& .
1688: For example,
1.174 djm 1689: to allow a key to be used from anywhere within an organization
1.86 jmc 1690: except from the
1.240 jmc 1691: .Qq dialup
1.86 jmc 1692: pool,
1693: the following entry (in authorized_keys) could be used:
1694: .Pp
1695: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.258 djm 1696: .Pp
1697: Note that a negated match will never produce a positive result by itself.
1698: For example, attempting to match
1699: .Qq host3
1700: against the following pattern-list will fail:
1701: .Pp
1702: .Dl from=\&"!host1,!host2\&"
1703: .Pp
1704: The solution here is to include a term that will yield a positive match,
1705: such as a wildcard:
1706: .Pp
1707: .Dl from=\&"!host1,!host2,*\&"
1.239 jmc 1708: .Sh TOKENS
1709: Arguments to some keywords can make use of tokens,
1710: which are expanded at runtime:
1711: .Pp
1712: .Bl -tag -width XXXX -offset indent -compact
1713: .It %%
1714: A literal
1715: .Sq % .
1716: .It \&%C
1.257 jmc 1717: Hash of %l%h%p%r.
1.239 jmc 1718: .It %d
1719: Local user's home directory.
1720: .It %h
1721: The remote hostname.
1722: .It %i
1723: The local user ID.
1724: .It %L
1725: The local hostname.
1726: .It %l
1727: The local hostname, including the domain name.
1728: .It %n
1729: The original remote hostname, as given on the command line.
1730: .It %p
1731: The remote port.
1732: .It %r
1733: The remote username.
1.261 djm 1734: .It \&%T
1735: The local
1736: .Xr tun 4
1737: or
1738: .Xr tap 4
1739: network interface assigned if
1.262 jmc 1740: tunnel forwarding was requested, or
1741: .Qq NONE
1.261 djm 1742: otherwise.
1.239 jmc 1743: .It %u
1744: The local username.
1745: .El
1746: .Pp
1747: .Cm Match exec
1.274 djm 1748: accepts the tokens %%, %h, %i, %L, %l, %n, %p, %r, and %u.
1.239 jmc 1749: .Pp
1750: .Cm CertificateFile
1.275 jmc 1751: accepts the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1752: .Pp
1753: .Cm ControlPath
1754: accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
1755: .Pp
1756: .Cm HostName
1757: accepts the tokens %% and %h.
1758: .Pp
1759: .Cm IdentityAgent
1760: and
1761: .Cm IdentityFile
1.275 jmc 1762: accept the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1763: .Pp
1764: .Cm LocalCommand
1.275 jmc 1765: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, %T, and %u.
1.239 jmc 1766: .Pp
1767: .Cm ProxyCommand
1768: accepts the tokens %%, %h, %p, and %r.
1.250 jmc 1769: .Pp
1770: .Cm RemoteCommand
1.274 djm 1771: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, and %u.
1.1 stevesk 1772: .Sh FILES
1773: .Bl -tag -width Ds
1.50 djm 1774: .It Pa ~/.ssh/config
1.1 stevesk 1775: This is the per-user configuration file.
1776: The format of this file is described above.
1.84 jmc 1777: This file is used by the SSH client.
1.30 djm 1778: Because of the potential for abuse, this file must have strict permissions:
1779: read/write for the user, and not accessible by others.
1.1 stevesk 1780: .It Pa /etc/ssh/ssh_config
1781: Systemwide configuration file.
1782: This file provides defaults for those
1783: values that are not specified in the user's configuration file, and
1784: for those users who do not have a configuration file.
1785: This file must be world-readable.
1786: .El
1.13 jmc 1787: .Sh SEE ALSO
1788: .Xr ssh 1
1.1 stevesk 1789: .Sh AUTHORS
1.240 jmc 1790: .An -nosplit
1.1 stevesk 1791: OpenSSH is a derivative of the original and free
1.240 jmc 1792: ssh 1.2.12 release by
1793: .An Tatu Ylonen .
1794: .An Aaron Campbell , Bob Beck , Markus Friedl ,
1795: .An Niels Provos , Theo de Raadt
1796: and
1797: .An Dug Song
1.1 stevesk 1798: removed many bugs, re-added newer features and
1799: created OpenSSH.
1.240 jmc 1800: .An Markus Friedl
1801: contributed the support for SSH protocol versions 1.5 and 2.0.
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