Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.278
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
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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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1.278 ! djm 36: .\" $OpenBSD: ssh_config.5,v 1.277 2018/06/09 06:36:31 jmc Exp $
1.277 jmc 37: .Dd $Mdocdate: June 9 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.
1.267 djm 261: Note that this option does not work if
262: .Cm UsePrivilegedPort
263: is set to
264: .Cm yes .
1.268 jmc 265: .It Cm BindInterface
266: Use the address of the specified interface on the local machine as the
267: source address of the connection.
1.1 stevesk 268: Note that this option does not work if
269: .Cm UsePrivilegedPort
270: is set to
1.240 jmc 271: .Cm yes .
1.171 djm 272: .It Cm CanonicalDomains
1.172 jmc 273: When
1.173 djm 274: .Cm CanonicalizeHostname
1.171 djm 275: is enabled, this option specifies the list of domain suffixes in which to
276: search for the specified destination host.
1.173 djm 277: .It Cm CanonicalizeFallbackLocal
1.174 djm 278: Specifies whether to fail with an error when hostname canonicalization fails.
1.172 jmc 279: The default,
1.240 jmc 280: .Cm yes ,
1.172 jmc 281: will attempt to look up the unqualified hostname using the system resolver's
1.171 djm 282: search rules.
283: A value of
1.240 jmc 284: .Cm no
1.171 djm 285: will cause
286: .Xr ssh 1
287: to fail instantly if
1.173 djm 288: .Cm CanonicalizeHostname
1.171 djm 289: is enabled and the target hostname cannot be found in any of the domains
290: specified by
291: .Cm CanonicalDomains .
1.173 djm 292: .It Cm CanonicalizeHostname
1.174 djm 293: Controls whether explicit hostname canonicalization is performed.
1.172 jmc 294: The default,
1.240 jmc 295: .Cm no ,
1.171 djm 296: is not to perform any name rewriting and let the system resolver handle all
297: hostname lookups.
298: If set to
1.240 jmc 299: .Cm yes
1.171 djm 300: then, for connections that do not use a
301: .Cm ProxyCommand ,
302: .Xr ssh 1
1.173 djm 303: will attempt to canonicalize the hostname specified on the command line
1.171 djm 304: using the
305: .Cm CanonicalDomains
306: suffixes and
1.173 djm 307: .Cm CanonicalizePermittedCNAMEs
1.171 djm 308: rules.
309: If
1.173 djm 310: .Cm CanonicalizeHostname
1.171 djm 311: is set to
1.240 jmc 312: .Cm always ,
1.174 djm 313: then canonicalization is applied to proxied connections too.
1.185 djm 314: .Pp
1.193 djm 315: If this option is enabled, then the configuration files are processed
316: again using the new target name to pick up any new configuration in matching
1.185 djm 317: .Cm Host
1.193 djm 318: and
319: .Cm Match
1.185 djm 320: stanzas.
1.173 djm 321: .It Cm CanonicalizeMaxDots
1.172 jmc 322: Specifies the maximum number of dot characters in a hostname before
1.174 djm 323: canonicalization is disabled.
1.240 jmc 324: The default, 1,
1.172 jmc 325: allows a single dot (i.e. hostname.subdomain).
1.173 djm 326: .It Cm CanonicalizePermittedCNAMEs
1.172 jmc 327: Specifies rules to determine whether CNAMEs should be followed when
1.173 djm 328: canonicalizing hostnames.
1.171 djm 329: The rules consist of one or more arguments of
1.172 jmc 330: .Ar source_domain_list : Ns Ar target_domain_list ,
1.171 djm 331: where
332: .Ar source_domain_list
1.174 djm 333: is a pattern-list of domains that may follow CNAMEs in canonicalization,
1.171 djm 334: and
335: .Ar target_domain_list
1.172 jmc 336: is a pattern-list of domains that they may resolve to.
1.171 djm 337: .Pp
338: For example,
1.240 jmc 339: .Qq *.a.example.com:*.b.example.com,*.c.example.com
1.171 djm 340: will allow hostnames matching
1.240 jmc 341: .Qq *.a.example.com
1.173 djm 342: to be canonicalized to names in the
1.240 jmc 343: .Qq *.b.example.com
1.171 djm 344: or
1.240 jmc 345: .Qq *.c.example.com
1.171 djm 346: domains.
1.221 djm 347: .It Cm CertificateFile
348: Specifies a file from which the user's certificate is read.
349: A corresponding private key must be provided separately in order
350: to use this certificate either
351: from an
352: .Cm IdentityFile
353: directive or
354: .Fl i
355: flag to
356: .Xr ssh 1 ,
357: via
358: .Xr ssh-agent 1 ,
359: or via a
360: .Cm PKCS11Provider .
361: .Pp
1.239 jmc 362: Arguments to
363: .Cm CertificateFile
364: may use the tilde syntax to refer to a user's home directory
365: or the tokens described in the
366: .Sx TOKENS
367: section.
1.221 djm 368: .Pp
369: It is possible to have multiple certificate files specified in
370: configuration files; these certificates will be tried in sequence.
371: Multiple
372: .Cm CertificateFile
373: directives will add to the list of certificates used for
374: authentication.
1.1 stevesk 375: .It Cm ChallengeResponseAuthentication
1.82 jmc 376: Specifies whether to use challenge-response authentication.
1.1 stevesk 377: The argument to this keyword must be
1.240 jmc 378: .Cm yes
379: (the default)
1.1 stevesk 380: or
1.240 jmc 381: .Cm no .
1.1 stevesk 382: .It Cm CheckHostIP
1.240 jmc 383: If set to
384: .Cm yes
385: (the default),
1.84 jmc 386: .Xr ssh 1
387: will additionally check the host IP address in the
1.1 stevesk 388: .Pa known_hosts
389: file.
1.240 jmc 390: This allows it to detect if a host key changed due to DNS spoofing
1.211 djm 391: and will add addresses of destination hosts to
392: .Pa ~/.ssh/known_hosts
393: in the process, regardless of the setting of
394: .Cm StrictHostKeyChecking .
1.107 grunk 395: If the option is set to
1.240 jmc 396: .Cm no ,
1.1 stevesk 397: the check will not be executed.
398: .It Cm Ciphers
1.245 djm 399: Specifies the ciphers allowed and their order of preference.
1.1 stevesk 400: Multiple ciphers must be comma-separated.
1.214 djm 401: If the specified value begins with a
402: .Sq +
403: character, then the specified ciphers will be appended to the default set
404: instead of replacing them.
1.241 djm 405: If the specified value begins with a
406: .Sq -
407: character, then the specified ciphers (including wildcards) will be removed
408: from the default set instead of replacing them.
1.214 djm 409: .Pp
1.180 djm 410: The supported ciphers are:
1.240 jmc 411: .Bd -literal -offset indent
1.186 naddy 412: 3des-cbc
413: aes128-cbc
414: aes192-cbc
415: aes256-cbc
416: aes128-ctr
417: aes192-ctr
418: aes256-ctr
419: aes128-gcm@openssh.com
420: aes256-gcm@openssh.com
421: chacha20-poly1305@openssh.com
1.240 jmc 422: .Ed
1.180 djm 423: .Pp
1.84 jmc 424: The default is:
1.186 naddy 425: .Bd -literal -offset indent
1.215 jmc 426: chacha20-poly1305@openssh.com,
1.186 naddy 427: aes128-ctr,aes192-ctr,aes256-ctr,
1.270 djm 428: aes128-gcm@openssh.com,aes256-gcm@openssh.com
1.1 stevesk 429: .Ed
1.180 djm 430: .Pp
1.240 jmc 431: The list of available ciphers may also be obtained using
432: .Qq ssh -Q cipher .
1.1 stevesk 433: .It Cm ClearAllForwardings
1.84 jmc 434: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 435: specified in the configuration files or on the command line be
1.7 jmc 436: cleared.
437: This option is primarily useful when used from the
1.84 jmc 438: .Xr ssh 1
1.1 stevesk 439: command line to clear port forwardings set in
440: configuration files, and is automatically set by
441: .Xr scp 1
442: and
443: .Xr sftp 1 .
444: The argument must be
1.240 jmc 445: .Cm yes
1.1 stevesk 446: or
1.240 jmc 447: .Cm no
448: (the default).
1.1 stevesk 449: .It Cm Compression
450: Specifies whether to use compression.
451: The argument must be
1.240 jmc 452: .Cm yes
1.1 stevesk 453: or
1.240 jmc 454: .Cm no
455: (the default).
1.247 naddy 456: .It Cm ConnectionAttempts
457: Specifies the number of tries (one per second) to make before exiting.
458: The argument must be an integer.
459: This may be useful in scripts if the connection sometimes fails.
460: The default is 1.
1.9 djm 461: .It Cm ConnectTimeout
1.84 jmc 462: Specifies the timeout (in seconds) used when connecting to the
463: SSH server, instead of using the default system TCP timeout.
1.11 jmc 464: This value is used only when the target is down or really unreachable,
465: not when it refuses the connection.
1.36 djm 466: .It Cm ControlMaster
467: Enables the sharing of multiple sessions over a single network connection.
468: When set to
1.240 jmc 469: .Cm yes ,
1.84 jmc 470: .Xr ssh 1
1.36 djm 471: will listen for connections on a control socket specified using the
472: .Cm ControlPath
473: argument.
474: Additional sessions can connect to this socket using the same
475: .Cm ControlPath
476: with
477: .Cm ControlMaster
478: set to
1.240 jmc 479: .Cm no
1.38 jmc 480: (the default).
1.64 jmc 481: These sessions will try to reuse the master instance's network connection
1.63 djm 482: rather than initiating new ones, but will fall back to connecting normally
483: if the control socket does not exist, or is not listening.
484: .Pp
1.37 djm 485: Setting this to
1.240 jmc 486: .Cm ask
487: will cause
488: .Xr ssh 1
1.206 jmc 489: to listen for control connections, but require confirmation using
490: .Xr ssh-askpass 1 .
1.51 jakob 491: If the
492: .Cm ControlPath
1.84 jmc 493: cannot be opened,
1.240 jmc 494: .Xr ssh 1
495: will continue without connecting to a master instance.
1.58 djm 496: .Pp
497: X11 and
1.59 jmc 498: .Xr ssh-agent 1
1.58 djm 499: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 500: display and agent forwarded will be the one belonging to the master
1.59 jmc 501: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 502: .Pp
503: Two additional options allow for opportunistic multiplexing: try to use a
504: master connection but fall back to creating a new one if one does not already
505: exist.
506: These options are:
1.240 jmc 507: .Cm auto
1.56 djm 508: and
1.240 jmc 509: .Cm autoask .
1.56 djm 510: The latter requires confirmation like the
1.240 jmc 511: .Cm ask
1.56 djm 512: option.
1.36 djm 513: .It Cm ControlPath
1.55 djm 514: Specify the path to the control socket used for connection sharing as described
515: in the
1.36 djm 516: .Cm ControlMaster
1.57 djm 517: section above or the string
1.240 jmc 518: .Cm none
1.57 djm 519: to disable connection sharing.
1.239 jmc 520: Arguments to
521: .Cm ControlPath
522: may use the tilde syntax to refer to a user's home directory
523: or the tokens described in the
524: .Sx TOKENS
525: section.
1.56 djm 526: It is recommended that any
527: .Cm ControlPath
528: used for opportunistic connection sharing include
1.195 djm 529: at least %h, %p, and %r (or alternatively %C) and be placed in a directory
530: that is not writable by other users.
1.56 djm 531: This ensures that shared connections are uniquely identified.
1.137 djm 532: .It Cm ControlPersist
533: When used in conjunction with
534: .Cm ControlMaster ,
535: specifies that the master connection should remain open
536: in the background (waiting for future client connections)
537: after the initial client connection has been closed.
538: If set to
1.240 jmc 539: .Cm no ,
1.137 djm 540: then the master connection will not be placed into the background,
541: and will close as soon as the initial client connection is closed.
542: If set to
1.240 jmc 543: .Cm yes
544: or 0,
1.137 djm 545: then the master connection will remain in the background indefinitely
546: (until killed or closed via a mechanism such as the
1.240 jmc 547: .Qq ssh -O exit ) .
1.137 djm 548: If set to a time in seconds, or a time in any of the formats documented in
549: .Xr sshd_config 5 ,
550: then the backgrounded master connection will automatically terminate
551: after it has remained idle (with no client connections) for the
552: specified time.
1.38 jmc 553: .It Cm DynamicForward
1.74 jmc 554: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 555: over the secure channel, and the application
556: protocol is then used to determine where to connect to from the
557: remote machine.
1.62 djm 558: .Pp
559: The argument must be
560: .Sm off
561: .Oo Ar bind_address : Oc Ar port .
562: .Sm on
1.138 djm 563: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 564: By default, the local port is bound in accordance with the
565: .Cm GatewayPorts
566: setting.
567: However, an explicit
568: .Ar bind_address
569: may be used to bind the connection to a specific address.
570: The
571: .Ar bind_address
572: of
1.240 jmc 573: .Cm localhost
1.62 djm 574: indicates that the listening port be bound for local use only, while an
575: empty address or
576: .Sq *
577: indicates that the port should be available from all interfaces.
578: .Pp
1.38 jmc 579: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 580: .Xr ssh 1
1.38 jmc 581: will act as a SOCKS server.
582: Multiple forwardings may be specified, and
583: additional forwardings can be given on the command line.
584: Only the superuser can forward privileged ports.
1.14 markus 585: .It Cm EnableSSHKeysign
586: Setting this option to
1.240 jmc 587: .Cm yes
1.14 markus 588: in the global client configuration file
589: .Pa /etc/ssh/ssh_config
590: enables the use of the helper program
591: .Xr ssh-keysign 8
592: during
593: .Cm HostbasedAuthentication .
594: The argument must be
1.240 jmc 595: .Cm yes
1.14 markus 596: or
1.240 jmc 597: .Cm no
598: (the default).
1.23 jmc 599: This option should be placed in the non-hostspecific section.
1.14 markus 600: See
601: .Xr ssh-keysign 8
602: for more information.
1.1 stevesk 603: .It Cm EscapeChar
604: Sets the escape character (default:
605: .Ql ~ ) .
606: The escape character can also
607: be set on the command line.
608: The argument should be a single character,
609: .Ql ^
610: followed by a letter, or
1.240 jmc 611: .Cm none
1.1 stevesk 612: to disable the escape
613: character entirely (making the connection transparent for binary
614: data).
1.96 markus 615: .It Cm ExitOnForwardFailure
616: Specifies whether
617: .Xr ssh 1
618: should terminate the connection if it cannot set up all requested
1.216 djm 619: dynamic, tunnel, local, and remote port forwardings, (e.g.\&
1.217 jmc 620: if either end is unable to bind and listen on a specified port).
1.216 djm 621: Note that
622: .Cm ExitOnForwardFailure
623: does not apply to connections made over port forwardings and will not,
624: for example, cause
625: .Xr ssh 1
626: to exit if TCP connections to the ultimate forwarding destination fail.
1.96 markus 627: The argument must be
1.240 jmc 628: .Cm yes
1.96 markus 629: or
1.240 jmc 630: .Cm no
631: (the default).
1.197 djm 632: .It Cm FingerprintHash
633: Specifies the hash algorithm used when displaying key fingerprints.
634: Valid options are:
1.240 jmc 635: .Cm md5
1.197 djm 636: and
1.240 jmc 637: .Cm sha256
638: (the default).
1.1 stevesk 639: .It Cm ForwardAgent
640: Specifies whether the connection to the authentication agent (if any)
641: will be forwarded to the remote machine.
642: The argument must be
1.240 jmc 643: .Cm yes
1.1 stevesk 644: or
1.240 jmc 645: .Cm no
646: (the default).
1.3 stevesk 647: .Pp
1.7 jmc 648: Agent forwarding should be enabled with caution.
649: Users with the ability to bypass file permissions on the remote host
650: (for the agent's Unix-domain socket)
651: can access the local agent through the forwarded connection.
652: An attacker cannot obtain key material from the agent,
1.3 stevesk 653: however they can perform operations on the keys that enable them to
654: authenticate using the identities loaded into the agent.
1.1 stevesk 655: .It Cm ForwardX11
656: Specifies whether X11 connections will be automatically redirected
657: over the secure channel and
658: .Ev DISPLAY
659: set.
660: The argument must be
1.240 jmc 661: .Cm yes
1.1 stevesk 662: or
1.240 jmc 663: .Cm no
664: (the default).
1.3 stevesk 665: .Pp
1.7 jmc 666: X11 forwarding should be enabled with caution.
667: Users with the ability to bypass file permissions on the remote host
1.22 markus 668: (for the user's X11 authorization database)
1.7 jmc 669: can access the local X11 display through the forwarded connection.
1.22 markus 670: An attacker may then be able to perform activities such as keystroke monitoring
671: if the
672: .Cm ForwardX11Trusted
673: option is also enabled.
1.134 djm 674: .It Cm ForwardX11Timeout
1.135 jmc 675: Specify a timeout for untrusted X11 forwarding
676: using the format described in the
1.240 jmc 677: .Sx TIME FORMATS
678: section of
1.134 djm 679: .Xr sshd_config 5 .
680: X11 connections received by
681: .Xr ssh 1
682: after this time will be refused.
683: The default is to disable untrusted X11 forwarding after twenty minutes has
684: elapsed.
1.22 markus 685: .It Cm ForwardX11Trusted
1.34 jmc 686: If this option is set to
1.240 jmc 687: .Cm yes ,
1.84 jmc 688: remote X11 clients will have full access to the original X11 display.
1.42 djm 689: .Pp
1.22 markus 690: If this option is set to
1.240 jmc 691: .Cm no
692: (the default),
1.84 jmc 693: remote X11 clients will be considered untrusted and prevented
1.22 markus 694: from stealing or tampering with data belonging to trusted X11
695: clients.
1.42 djm 696: Furthermore, the
697: .Xr xauth 1
698: token used for the session will be set to expire after 20 minutes.
699: Remote clients will be refused access after this time.
1.22 markus 700: .Pp
701: See the X11 SECURITY extension specification for full details on
702: the restrictions imposed on untrusted clients.
1.1 stevesk 703: .It Cm GatewayPorts
704: Specifies whether remote hosts are allowed to connect to local
705: forwarded ports.
706: By default,
1.84 jmc 707: .Xr ssh 1
1.7 jmc 708: binds local port forwardings to the loopback address.
709: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 710: .Cm GatewayPorts
1.84 jmc 711: can be used to specify that ssh
1.1 stevesk 712: should bind local port forwardings to the wildcard address,
713: thus allowing remote hosts to connect to forwarded ports.
714: The argument must be
1.240 jmc 715: .Cm yes
1.1 stevesk 716: or
1.240 jmc 717: .Cm no
718: (the default).
1.1 stevesk 719: .It Cm GlobalKnownHostsFile
1.151 djm 720: Specifies one or more files to use for the global
721: host key database, separated by whitespace.
722: The default is
723: .Pa /etc/ssh/ssh_known_hosts ,
724: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 725: .It Cm GSSAPIAuthentication
1.27 markus 726: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 727: The default is
1.240 jmc 728: .Cm no .
1.18 markus 729: .It Cm GSSAPIDelegateCredentials
730: Forward (delegate) credentials to the server.
731: The default is
1.240 jmc 732: .Cm no .
1.44 djm 733: .It Cm HashKnownHosts
734: Indicates that
1.84 jmc 735: .Xr ssh 1
1.44 djm 736: should hash host names and addresses when they are added to
1.50 djm 737: .Pa ~/.ssh/known_hosts .
1.44 djm 738: These hashed names may be used normally by
1.84 jmc 739: .Xr ssh 1
1.44 djm 740: and
1.84 jmc 741: .Xr sshd 8 ,
1.44 djm 742: but they do not reveal identifying information should the file's contents
743: be disclosed.
744: The default is
1.240 jmc 745: .Cm no .
1.97 jmc 746: Note that existing names and addresses in known hosts files
747: will not be converted automatically,
748: but may be manually hashed using
1.45 djm 749: .Xr ssh-keygen 1 .
1.1 stevesk 750: .It Cm HostbasedAuthentication
751: Specifies whether to try rhosts based authentication with public key
752: authentication.
753: The argument must be
1.240 jmc 754: .Cm yes
1.1 stevesk 755: or
1.240 jmc 756: .Cm no
757: (the default).
1.202 djm 758: .It Cm HostbasedKeyTypes
759: Specifies the key types that will be used for hostbased authentication
760: as a comma-separated pattern list.
1.214 djm 761: Alternately if the specified value begins with a
762: .Sq +
763: character, then the specified key types will be appended to the default set
764: instead of replacing them.
1.241 djm 765: If the specified value begins with a
766: .Sq -
767: character, then the specified key types (including wildcards) will be removed
768: from the default set instead of replacing them.
1.213 markus 769: The default for this option is:
770: .Bd -literal -offset 3n
771: ecdsa-sha2-nistp256-cert-v01@openssh.com,
772: ecdsa-sha2-nistp384-cert-v01@openssh.com,
773: ecdsa-sha2-nistp521-cert-v01@openssh.com,
774: ssh-ed25519-cert-v01@openssh.com,
1.278 ! djm 775: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 776: ssh-rsa-cert-v01@openssh.com,
777: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 ! djm 778: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 779: .Ed
780: .Pp
1.202 djm 781: The
782: .Fl Q
783: option of
784: .Xr ssh 1
785: may be used to list supported key types.
1.1 stevesk 786: .It Cm HostKeyAlgorithms
1.226 jmc 787: Specifies the host key algorithms
1.1 stevesk 788: that the client wants to use in order of preference.
1.214 djm 789: Alternately if the specified value begins with a
790: .Sq +
791: character, then the specified key types will be appended to the default set
792: instead of replacing them.
1.241 djm 793: If the specified value begins with a
794: .Sq -
795: character, then the specified key types (including wildcards) will be removed
796: from the default set instead of replacing them.
1.1 stevesk 797: The default for this option is:
1.139 djm 798: .Bd -literal -offset 3n
799: ecdsa-sha2-nistp256-cert-v01@openssh.com,
800: ecdsa-sha2-nistp384-cert-v01@openssh.com,
801: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1.183 naddy 802: ssh-ed25519-cert-v01@openssh.com,
1.278 ! djm 803: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 804: ssh-rsa-cert-v01@openssh.com,
1.139 djm 805: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 ! djm 806: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.139 djm 807: .Ed
1.145 djm 808: .Pp
809: If hostkeys are known for the destination host then this default is modified
810: to prefer their algorithms.
1.198 djm 811: .Pp
1.240 jmc 812: The list of available key types may also be obtained using
813: .Qq ssh -Q key .
1.1 stevesk 814: .It Cm HostKeyAlias
815: Specifies an alias that should be used instead of the
816: real host name when looking up or saving the host key
1.251 djm 817: in the host key database files and when validating host certificates.
1.84 jmc 818: This option is useful for tunneling SSH connections
1.1 stevesk 819: or for multiple servers running on a single host.
820: .It Cm HostName
821: Specifies the real host name to log into.
822: This can be used to specify nicknames or abbreviations for hosts.
1.239 jmc 823: Arguments to
824: .Cm HostName
825: accept the tokens described in the
826: .Sx TOKENS
827: section.
1.1 stevesk 828: Numeric IP addresses are also permitted (both on the command line and in
829: .Cm HostName
830: specifications).
1.239 jmc 831: The default is the name given on the command line.
1.29 markus 832: .It Cm IdentitiesOnly
833: Specifies that
1.84 jmc 834: .Xr ssh 1
1.221 djm 835: should only use the authentication identity and certificate files explicitly
836: configured in the
1.31 jmc 837: .Nm
1.221 djm 838: files
839: or passed on the
840: .Xr ssh 1
841: command-line,
1.84 jmc 842: even if
843: .Xr ssh-agent 1
1.159 djm 844: or a
845: .Cm PKCS11Provider
1.29 markus 846: offers more identities.
847: The argument to this keyword must be
1.240 jmc 848: .Cm yes
1.29 markus 849: or
1.240 jmc 850: .Cm no
851: (the default).
1.84 jmc 852: This option is intended for situations where ssh-agent
1.29 markus 853: offers many different identities.
1.231 markus 854: .It Cm IdentityAgent
855: Specifies the
856: .Ux Ns -domain
857: socket used to communicate with the authentication agent.
858: .Pp
859: This option overrides the
1.240 jmc 860: .Ev SSH_AUTH_SOCK
1.231 markus 861: environment variable and can be used to select a specific agent.
862: Setting the socket name to
1.240 jmc 863: .Cm none
1.231 markus 864: disables the use of an authentication agent.
1.232 markus 865: If the string
1.240 jmc 866: .Qq SSH_AUTH_SOCK
1.232 markus 867: is specified, the location of the socket will be read from the
868: .Ev SSH_AUTH_SOCK
869: environment variable.
1.231 markus 870: .Pp
1.239 jmc 871: Arguments to
872: .Cm IdentityAgent
873: may use the tilde syntax to refer to a user's home directory
874: or the tokens described in the
875: .Sx TOKENS
876: section.
1.67 jmc 877: .It Cm IdentityFile
1.192 sobrado 878: Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA authentication
1.139 djm 879: identity is read.
1.67 jmc 880: The default is
1.139 djm 881: .Pa ~/.ssh/id_dsa ,
1.183 naddy 882: .Pa ~/.ssh/id_ecdsa ,
883: .Pa ~/.ssh/id_ed25519
1.139 djm 884: and
1.245 djm 885: .Pa ~/.ssh/id_rsa .
1.67 jmc 886: Additionally, any identities represented by the authentication agent
1.165 djm 887: will be used for authentication unless
888: .Cm IdentitiesOnly
889: is set.
1.221 djm 890: If no certificates have been explicitly specified by
891: .Cm CertificateFile ,
1.129 djm 892: .Xr ssh 1
893: will try to load certificate information from the filename obtained by
894: appending
895: .Pa -cert.pub
896: to the path of a specified
897: .Cm IdentityFile .
1.90 djm 898: .Pp
1.239 jmc 899: Arguments to
900: .Cm IdentityFile
901: may use the tilde syntax to refer to a user's home directory
902: or the tokens described in the
903: .Sx TOKENS
904: section.
1.90 djm 905: .Pp
1.67 jmc 906: It is possible to have
907: multiple identity files specified in configuration files; all these
908: identities will be tried in sequence.
1.152 djm 909: Multiple
910: .Cm IdentityFile
911: directives will add to the list of identities tried (this behaviour
912: differs from that of other configuration directives).
1.165 djm 913: .Pp
914: .Cm IdentityFile
915: may be used in conjunction with
916: .Cm IdentitiesOnly
917: to select which identities in an agent are offered during authentication.
1.221 djm 918: .Cm IdentityFile
919: may also be used in conjunction with
920: .Cm CertificateFile
921: in order to provide any certificate also needed for authentication with
922: the identity.
1.164 jmc 923: .It Cm IgnoreUnknown
924: Specifies a pattern-list of unknown options to be ignored if they are
925: encountered in configuration parsing.
926: This may be used to suppress errors if
927: .Nm
928: contains options that are unrecognised by
929: .Xr ssh 1 .
930: It is recommended that
931: .Cm IgnoreUnknown
932: be listed early in the configuration file as it will not be applied
933: to unknown options that appear before it.
1.229 djm 934: .It Cm Include
935: Include the specified configuration file(s).
1.230 jmc 936: Multiple pathnames may be specified and each pathname may contain
1.229 djm 937: .Xr glob 3
938: wildcards and, for user configurations, shell-like
1.240 jmc 939: .Sq ~
1.229 djm 940: references to user home directories.
941: Files without absolute paths are assumed to be in
942: .Pa ~/.ssh
1.230 jmc 943: if included in a user configuration file or
1.229 djm 944: .Pa /etc/ssh
945: if included from the system configuration file.
946: .Cm Include
947: directive may appear inside a
948: .Cm Match
949: or
950: .Cm Host
951: block
952: to perform conditional inclusion.
1.143 djm 953: .It Cm IPQoS
954: Specifies the IPv4 type-of-service or DSCP class for connections.
955: Accepted values are
1.240 jmc 956: .Cm af11 ,
957: .Cm af12 ,
958: .Cm af13 ,
959: .Cm af21 ,
960: .Cm af22 ,
961: .Cm af23 ,
962: .Cm af31 ,
963: .Cm af32 ,
964: .Cm af33 ,
965: .Cm af41 ,
966: .Cm af42 ,
967: .Cm af43 ,
968: .Cm cs0 ,
969: .Cm cs1 ,
970: .Cm cs2 ,
971: .Cm cs3 ,
972: .Cm cs4 ,
973: .Cm cs5 ,
974: .Cm cs6 ,
975: .Cm cs7 ,
976: .Cm ef ,
977: .Cm lowdelay ,
978: .Cm throughput ,
979: .Cm reliability ,
1.253 djm 980: a numeric value, or
981: .Cm none
982: to use the operating system default.
1.146 djm 983: This option may take one or two arguments, separated by whitespace.
1.143 djm 984: If one argument is specified, it is used as the packet class unconditionally.
985: If two values are specified, the first is automatically selected for
986: interactive sessions and the second for non-interactive sessions.
987: The default is
1.269 job 988: .Cm af21
1.272 jmc 989: (Low-Latency Data)
1.143 djm 990: for interactive sessions and
1.269 job 991: .Cm cs1
1.272 jmc 992: (Lower Effort)
1.143 djm 993: for non-interactive sessions.
1.103 djm 994: .It Cm KbdInteractiveAuthentication
995: Specifies whether to use keyboard-interactive authentication.
996: The argument to this keyword must be
1.240 jmc 997: .Cm yes
998: (the default)
1.103 djm 999: or
1.240 jmc 1000: .Cm no .
1.39 djm 1001: .It Cm KbdInteractiveDevices
1002: Specifies the list of methods to use in keyboard-interactive authentication.
1003: Multiple method names must be comma-separated.
1004: The default is to use the server specified list.
1.85 jmc 1005: The methods available vary depending on what the server supports.
1006: For an OpenSSH server,
1007: it may be zero or more of:
1.240 jmc 1008: .Cm bsdauth ,
1009: .Cm pam ,
1.85 jmc 1010: and
1.240 jmc 1011: .Cm skey .
1.140 djm 1012: .It Cm KexAlgorithms
1013: Specifies the available KEX (Key Exchange) algorithms.
1014: Multiple algorithms must be comma-separated.
1.214 djm 1015: Alternately if the specified value begins with a
1016: .Sq +
1017: character, then the specified methods will be appended to the default set
1018: instead of replacing them.
1.241 djm 1019: If the specified value begins with a
1020: .Sq -
1021: character, then the specified methods (including wildcards) will be removed
1022: from the default set instead of replacing them.
1.141 jmc 1023: The default is:
1024: .Bd -literal -offset indent
1.238 djm 1025: curve25519-sha256,curve25519-sha256@libssh.org,
1.141 jmc 1026: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1027: diffie-hellman-group-exchange-sha256,
1.266 djm 1028: diffie-hellman-group16-sha512,
1029: diffie-hellman-group18-sha512,
1.209 dtucker 1030: diffie-hellman-group-exchange-sha1,
1.266 djm 1031: diffie-hellman-group14-sha256,
1.212 djm 1032: diffie-hellman-group14-sha1
1.141 jmc 1033: .Ed
1.198 djm 1034: .Pp
1.240 jmc 1035: The list of available key exchange algorithms may also be obtained using
1036: .Qq ssh -Q kex .
1.65 reyk 1037: .It Cm LocalCommand
1038: Specifies a command to execute on the local machine after successfully
1039: connecting to the server.
1040: The command string extends to the end of the line, and is executed with
1.105 jmc 1041: the user's shell.
1.239 jmc 1042: Arguments to
1043: .Cm LocalCommand
1044: accept the tokens described in the
1045: .Sx TOKENS
1046: section.
1.123 djm 1047: .Pp
1048: The command is run synchronously and does not have access to the
1049: session of the
1050: .Xr ssh 1
1051: that spawned it.
1052: It should not be used for interactive commands.
1053: .Pp
1.65 reyk 1054: This directive is ignored unless
1055: .Cm PermitLocalCommand
1056: has been enabled.
1.1 stevesk 1057: .It Cm LocalForward
1.74 jmc 1058: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 1059: the secure channel to the specified host and port from the remote machine.
1.49 jmc 1060: The first argument must be
1.43 djm 1061: .Sm off
1.49 jmc 1062: .Oo Ar bind_address : Oc Ar port
1.43 djm 1063: .Sm on
1.49 jmc 1064: and the second argument must be
1065: .Ar host : Ns Ar hostport .
1.138 djm 1066: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 1067: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 1068: given on the command line.
1.1 stevesk 1069: Only the superuser can forward privileged ports.
1.43 djm 1070: By default, the local port is bound in accordance with the
1071: .Cm GatewayPorts
1072: setting.
1073: However, an explicit
1074: .Ar bind_address
1075: may be used to bind the connection to a specific address.
1076: The
1077: .Ar bind_address
1078: of
1.240 jmc 1079: .Cm localhost
1.46 jmc 1080: indicates that the listening port be bound for local use only, while an
1081: empty address or
1082: .Sq *
1.43 djm 1083: indicates that the port should be available from all interfaces.
1.1 stevesk 1084: .It Cm LogLevel
1085: Gives the verbosity level that is used when logging messages from
1.84 jmc 1086: .Xr ssh 1 .
1.1 stevesk 1087: The possible values are:
1.84 jmc 1088: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 1089: The default is INFO.
1090: DEBUG and DEBUG1 are equivalent.
1091: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 1092: .It Cm MACs
1093: Specifies the MAC (message authentication code) algorithms
1094: in order of preference.
1.226 jmc 1095: The MAC algorithm is used for data integrity protection.
1.1 stevesk 1096: Multiple algorithms must be comma-separated.
1.214 djm 1097: If the specified value begins with a
1098: .Sq +
1099: character, then the specified algorithms will be appended to the default set
1100: instead of replacing them.
1.241 djm 1101: If the specified value begins with a
1102: .Sq -
1103: character, then the specified algorithms (including wildcards) will be removed
1104: from the default set instead of replacing them.
1.214 djm 1105: .Pp
1.160 markus 1106: The algorithms that contain
1.240 jmc 1107: .Qq -etm
1.160 markus 1108: calculate the MAC after encryption (encrypt-then-mac).
1109: These are considered safer and their use recommended.
1.214 djm 1110: .Pp
1.84 jmc 1111: The default is:
1.101 jmc 1112: .Bd -literal -offset indent
1.160 markus 1113: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1114: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.224 djm 1115: hmac-sha1-etm@openssh.com,
1.186 naddy 1116: umac-64@openssh.com,umac-128@openssh.com,
1.224 djm 1117: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.101 jmc 1118: .Ed
1.198 djm 1119: .Pp
1.240 jmc 1120: The list of available MAC algorithms may also be obtained using
1121: .Qq ssh -Q mac .
1.1 stevesk 1122: .It Cm NoHostAuthenticationForLocalhost
1.264 djm 1123: Disable host authentication for localhost (loopback addresses).
1.1 stevesk 1124: The argument to this keyword must be
1.240 jmc 1125: .Cm yes
1.1 stevesk 1126: or
1.242 jmc 1127: .Cm no
1.240 jmc 1128: (the default).
1.1 stevesk 1129: .It Cm NumberOfPasswordPrompts
1130: Specifies the number of password prompts before giving up.
1131: The argument to this keyword must be an integer.
1.84 jmc 1132: The default is 3.
1.1 stevesk 1133: .It Cm PasswordAuthentication
1134: Specifies whether to use password authentication.
1135: The argument to this keyword must be
1.240 jmc 1136: .Cm yes
1137: (the default)
1.1 stevesk 1138: or
1.240 jmc 1139: .Cm no .
1.65 reyk 1140: .It Cm PermitLocalCommand
1141: Allow local command execution via the
1142: .Ic LocalCommand
1143: option or using the
1.66 jmc 1144: .Ic !\& Ns Ar command
1.65 reyk 1145: escape sequence in
1146: .Xr ssh 1 .
1147: The argument must be
1.240 jmc 1148: .Cm yes
1.65 reyk 1149: or
1.240 jmc 1150: .Cm no
1151: (the default).
1.127 markus 1152: .It Cm PKCS11Provider
1153: Specifies which PKCS#11 provider to use.
1.144 jmc 1154: The argument to this keyword is the PKCS#11 shared library
1.127 markus 1155: .Xr ssh 1
1.128 markus 1156: should use to communicate with a PKCS#11 token providing the user's
1.127 markus 1157: private RSA key.
1.67 jmc 1158: .It Cm Port
1159: Specifies the port number to connect on the remote host.
1.84 jmc 1160: The default is 22.
1.1 stevesk 1161: .It Cm PreferredAuthentications
1.226 jmc 1162: Specifies the order in which the client should try authentication methods.
1.48 jmc 1163: This allows a client to prefer one method (e.g.\&
1.1 stevesk 1164: .Cm keyboard-interactive )
1.48 jmc 1165: over another method (e.g.\&
1.131 jmc 1166: .Cm password ) .
1167: The default is:
1168: .Bd -literal -offset indent
1169: gssapi-with-mic,hostbased,publickey,
1170: keyboard-interactive,password
1171: .Ed
1.1 stevesk 1172: .It Cm ProxyCommand
1173: Specifies the command to use to connect to the server.
1174: The command
1.190 djm 1175: string extends to the end of the line, and is executed
1176: using the user's shell
1177: .Ql exec
1178: directive to avoid a lingering shell process.
1179: .Pp
1.239 jmc 1180: Arguments to
1181: .Cm ProxyCommand
1182: accept the tokens described in the
1183: .Sx TOKENS
1184: section.
1.1 stevesk 1185: The command can be basically anything,
1186: and should read from its standard input and write to its standard output.
1187: It should eventually connect an
1188: .Xr sshd 8
1189: server running on some machine, or execute
1190: .Ic sshd -i
1191: somewhere.
1192: Host key management will be done using the
1193: HostName of the host being connected (defaulting to the name typed by
1194: the user).
1.7 jmc 1195: Setting the command to
1.240 jmc 1196: .Cm none
1.6 markus 1197: disables this option entirely.
1.1 stevesk 1198: Note that
1199: .Cm CheckHostIP
1200: is not available for connects with a proxy command.
1.52 djm 1201: .Pp
1202: This directive is useful in conjunction with
1203: .Xr nc 1
1204: and its proxy support.
1.53 jmc 1205: For example, the following directive would connect via an HTTP proxy at
1.52 djm 1206: 192.0.2.0:
1207: .Bd -literal -offset 3n
1208: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1209: .Ed
1.233 djm 1210: .It Cm ProxyJump
1.260 millert 1211: Specifies one or more jump proxies as either
1.233 djm 1212: .Xo
1213: .Sm off
1.234 jmc 1214: .Op Ar user No @
1.233 djm 1215: .Ar host
1.234 jmc 1216: .Op : Ns Ar port
1.233 djm 1217: .Sm on
1.260 millert 1218: or an ssh URI
1.233 djm 1219: .Xc .
1.235 djm 1220: Multiple proxies may be separated by comma characters and will be visited
1.236 djm 1221: sequentially.
1.233 djm 1222: Setting this option will cause
1223: .Xr ssh 1
1224: to connect to the target host by first making a
1225: .Xr ssh 1
1226: connection to the specified
1227: .Cm ProxyJump
1228: host and then establishing a
1.234 jmc 1229: TCP forwarding to the ultimate target from there.
1.233 djm 1230: .Pp
1231: Note that this option will compete with the
1232: .Cm ProxyCommand
1233: option - whichever is specified first will prevent later instances of the
1234: other from taking effect.
1.167 djm 1235: .It Cm ProxyUseFdpass
1.168 jmc 1236: Specifies that
1.167 djm 1237: .Cm ProxyCommand
1238: will pass a connected file descriptor back to
1.168 jmc 1239: .Xr ssh 1
1.167 djm 1240: instead of continuing to execute and pass data.
1241: The default is
1.240 jmc 1242: .Cm no .
1.213 markus 1243: .It Cm PubkeyAcceptedKeyTypes
1244: Specifies the key types that will be used for public key authentication
1245: as a comma-separated pattern list.
1.214 djm 1246: Alternately if the specified value begins with a
1247: .Sq +
1248: character, then the key types after it will be appended to the default
1249: instead of replacing it.
1.241 djm 1250: If the specified value begins with a
1251: .Sq -
1252: character, then the specified key types (including wildcards) will be removed
1253: from the default set instead of replacing them.
1.213 markus 1254: The default for this option is:
1255: .Bd -literal -offset 3n
1256: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1257: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1258: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1259: ssh-ed25519-cert-v01@openssh.com,
1.278 ! djm 1260: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 1261: ssh-rsa-cert-v01@openssh.com,
1262: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 ! djm 1263: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 1264: .Ed
1265: .Pp
1.240 jmc 1266: The list of available key types may also be obtained using
1267: .Qq ssh -Q key .
1.1 stevesk 1268: .It Cm PubkeyAuthentication
1269: Specifies whether to try public key authentication.
1270: The argument to this keyword must be
1.240 jmc 1271: .Cm yes
1272: (the default)
1.1 stevesk 1273: or
1.240 jmc 1274: .Cm no .
1.75 dtucker 1275: .It Cm RekeyLimit
1276: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1277: session key is renegotiated, optionally followed a maximum amount of
1278: time that may pass before the session key is renegotiated.
1279: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1280: .Sq K ,
1281: .Sq M ,
1.75 dtucker 1282: or
1.76 jmc 1283: .Sq G
1.75 dtucker 1284: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1285: The default is between
1.84 jmc 1286: .Sq 1G
1.75 dtucker 1287: and
1.84 jmc 1288: .Sq 4G ,
1.75 dtucker 1289: depending on the cipher.
1.162 dtucker 1290: The optional second value is specified in seconds and may use any of the
1291: units documented in the
1.240 jmc 1292: .Sx TIME FORMATS
1293: section of
1.162 dtucker 1294: .Xr sshd_config 5 .
1295: The default value for
1296: .Cm RekeyLimit
1297: is
1.240 jmc 1298: .Cm default none ,
1.162 dtucker 1299: which means that rekeying is performed after the cipher's default amount
1300: of data has been sent or received and no time based rekeying is done.
1.249 bluhm 1301: .It Cm RemoteCommand
1302: Specifies a command to execute on the remote machine after successfully
1303: connecting to the server.
1304: The command string extends to the end of the line, and is executed with
1305: the user's shell.
1.250 jmc 1306: Arguments to
1307: .Cm RemoteCommand
1308: accept the tokens described in the
1309: .Sx TOKENS
1310: section.
1.1 stevesk 1311: .It Cm RemoteForward
1.74 jmc 1312: Specifies that a TCP port on the remote machine be forwarded over
1.256 markus 1313: the secure channel.
1.273 djm 1314: The remote port may either be forwarded to a specified host and port
1.256 markus 1315: from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
1316: client to connect to arbitrary destinations from the local machine.
1.49 jmc 1317: The first argument must be
1.43 djm 1318: .Sm off
1.49 jmc 1319: .Oo Ar bind_address : Oc Ar port
1.43 djm 1320: .Sm on
1.256 markus 1321: If forwarding to a specific destination then the second argument must be
1322: .Ar host : Ns Ar hostport ,
1323: otherwise if no destination argument is specified then the remote forwarding
1324: will be established as a SOCKS proxy.
1325: .Pp
1.138 djm 1326: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.1 stevesk 1327: Multiple forwardings may be specified, and additional
1328: forwardings can be given on the command line.
1.113 stevesk 1329: Privileged ports can be forwarded only when
1330: logging in as root on the remote machine.
1.118 jmc 1331: .Pp
1.117 djm 1332: If the
1333: .Ar port
1.240 jmc 1334: argument is 0,
1.117 djm 1335: the listen port will be dynamically allocated on the server and reported
1336: to the client at run time.
1.43 djm 1337: .Pp
1338: If the
1339: .Ar bind_address
1340: is not specified, the default is to only bind to loopback addresses.
1341: If the
1342: .Ar bind_address
1343: is
1344: .Ql *
1345: or an empty string, then the forwarding is requested to listen on all
1346: interfaces.
1347: Specifying a remote
1348: .Ar bind_address
1.46 jmc 1349: will only succeed if the server's
1350: .Cm GatewayPorts
1.43 djm 1351: option is enabled (see
1.46 jmc 1352: .Xr sshd_config 5 ) .
1.149 djm 1353: .It Cm RequestTTY
1354: Specifies whether to request a pseudo-tty for the session.
1355: The argument may be one of:
1.240 jmc 1356: .Cm no
1.149 djm 1357: (never request a TTY),
1.240 jmc 1358: .Cm yes
1.149 djm 1359: (always request a TTY when standard input is a TTY),
1.240 jmc 1360: .Cm force
1.149 djm 1361: (always request a TTY) or
1.240 jmc 1362: .Cm auto
1.149 djm 1363: (request a TTY when opening a login session).
1364: This option mirrors the
1365: .Fl t
1366: and
1367: .Fl T
1368: flags for
1369: .Xr ssh 1 .
1.196 djm 1370: .It Cm RevokedHostKeys
1371: Specifies revoked host public keys.
1372: Keys listed in this file will be refused for host authentication.
1373: Note that if this file does not exist or is not readable,
1374: then host authentication will be refused for all hosts.
1375: Keys may be specified as a text file, listing one public key per line, or as
1376: an OpenSSH Key Revocation List (KRL) as generated by
1377: .Xr ssh-keygen 1 .
1378: For more information on KRLs, see the KEY REVOCATION LISTS section in
1379: .Xr ssh-keygen 1 .
1.32 djm 1380: .It Cm SendEnv
1381: Specifies what variables from the local
1382: .Xr environ 7
1383: should be sent to the server.
1.84 jmc 1384: The server must also support it, and the server must be configured to
1.33 djm 1385: accept these environment variables.
1.207 dtucker 1386: Note that the
1387: .Ev TERM
1.208 jmc 1388: environment variable is always sent whenever a
1.207 dtucker 1389: pseudo-terminal is requested as it is required by the protocol.
1.32 djm 1390: Refer to
1391: .Cm AcceptEnv
1392: in
1393: .Xr sshd_config 5
1394: for how to configure the server.
1.80 jmc 1395: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1396: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1397: across multiple
1398: .Cm SendEnv
1399: directives.
1.81 jmc 1400: .Pp
1401: See
1402: .Sx PATTERNS
1403: for more information on patterns.
1.271 djm 1404: .Pp
1.272 jmc 1405: It is possible to clear previously set
1.271 djm 1406: .Cm SendEnv
1407: variable names by prefixing patterns with
1408: .Pa - .
1409: The default is not to send any environment variables.
1.28 markus 1410: .It Cm ServerAliveCountMax
1.73 jmc 1411: Sets the number of server alive messages (see below) which may be
1.28 markus 1412: sent without
1.84 jmc 1413: .Xr ssh 1
1.28 markus 1414: receiving any messages back from the server.
1415: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1416: ssh will disconnect from the server, terminating the session.
1.28 markus 1417: It is important to note that the use of server alive messages is very
1418: different from
1419: .Cm TCPKeepAlive
1420: (below).
1421: The server alive messages are sent through the encrypted channel
1422: and therefore will not be spoofable.
1423: The TCP keepalive option enabled by
1424: .Cm TCPKeepAlive
1425: is spoofable.
1426: The server alive mechanism is valuable when the client or
1427: server depend on knowing when a connection has become inactive.
1428: .Pp
1429: The default value is 3.
1430: If, for example,
1431: .Cm ServerAliveInterval
1.84 jmc 1432: (see below) is set to 15 and
1.28 markus 1433: .Cm ServerAliveCountMax
1.84 jmc 1434: is left at the default, if the server becomes unresponsive,
1435: ssh will disconnect after approximately 45 seconds.
1.67 jmc 1436: .It Cm ServerAliveInterval
1437: Sets a timeout interval in seconds after which if no data has been received
1438: from the server,
1.84 jmc 1439: .Xr ssh 1
1.67 jmc 1440: will send a message through the encrypted
1441: channel to request a response from the server.
1442: The default
1443: is 0, indicating that these messages will not be sent to the server.
1.277 jmc 1444: .It Cm SetEnv
1445: Directly specify one or more environment variables and their contents to
1446: be sent to the server.
1447: Similarly to
1448: .Cm SendEnv ,
1449: the server must be prepared to accept the environment variable.
1.191 millert 1450: .It Cm StreamLocalBindMask
1451: Sets the octal file creation mode mask
1452: .Pq umask
1453: used when creating a Unix-domain socket file for local or remote
1454: port forwarding.
1455: This option is only used for port forwarding to a Unix-domain socket file.
1456: .Pp
1457: The default value is 0177, which creates a Unix-domain socket file that is
1458: readable and writable only by the owner.
1459: Note that not all operating systems honor the file mode on Unix-domain
1460: socket files.
1461: .It Cm StreamLocalBindUnlink
1462: Specifies whether to remove an existing Unix-domain socket file for local
1463: or remote port forwarding before creating a new one.
1464: If the socket file already exists and
1465: .Cm StreamLocalBindUnlink
1466: is not enabled,
1467: .Nm ssh
1468: will be unable to forward the port to the Unix-domain socket file.
1469: This option is only used for port forwarding to a Unix-domain socket file.
1470: .Pp
1471: The argument must be
1.240 jmc 1472: .Cm yes
1.191 millert 1473: or
1.240 jmc 1474: .Cm no
1475: (the default).
1.1 stevesk 1476: .It Cm StrictHostKeyChecking
1477: If this flag is set to
1.240 jmc 1478: .Cm yes ,
1.84 jmc 1479: .Xr ssh 1
1.1 stevesk 1480: will never automatically add host keys to the
1.50 djm 1481: .Pa ~/.ssh/known_hosts
1.1 stevesk 1482: file, and refuses to connect to hosts whose host key has changed.
1.263 dtucker 1483: This provides maximum protection against man-in-the-middle (MITM) attacks,
1.84 jmc 1484: though it can be annoying when the
1.1 stevesk 1485: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1486: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1487: frequently made.
1488: This option forces the user to manually
1489: add all new hosts.
1.255 jmc 1490: .Pp
1.1 stevesk 1491: If this flag is set to
1.254 djm 1492: .Dq accept-new
1.255 jmc 1493: then ssh will automatically add new host keys to the user
1.254 djm 1494: known hosts files, but will not permit connections to hosts with
1495: changed host keys.
1496: If this flag is set to
1497: .Dq no
1498: or
1499: .Dq off ,
1.255 jmc 1500: ssh will automatically add new host keys to the user known hosts files
1501: and allow connections to hosts with changed hostkeys to proceed,
1502: subject to some restrictions.
1.1 stevesk 1503: If this flag is set to
1.240 jmc 1504: .Cm ask
1505: (the default),
1.1 stevesk 1506: new host keys
1507: will be added to the user known host files only after the user
1508: has confirmed that is what they really want to do, and
1.84 jmc 1509: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1510: The host keys of
1511: known hosts will be verified automatically in all cases.
1.244 jmc 1512: .It Cm SyslogFacility
1513: Gives the facility code that is used when logging messages from
1514: .Xr ssh 1 .
1515: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1516: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1517: The default is USER.
1.26 markus 1518: .It Cm TCPKeepAlive
1519: Specifies whether the system should send TCP keepalive messages to the
1520: other side.
1521: If they are sent, death of the connection or crash of one
1522: of the machines will be properly noticed.
1523: However, this means that
1524: connections will die if the route is down temporarily, and some people
1525: find it annoying.
1526: .Pp
1527: The default is
1.240 jmc 1528: .Cm yes
1.26 markus 1529: (to send TCP keepalive messages), and the client will notice
1530: if the network goes down or the remote host dies.
1531: This is important in scripts, and many users want it too.
1532: .Pp
1533: To disable TCP keepalive messages, the value should be set to
1.240 jmc 1534: .Cm no .
1.265 djm 1535: See also
1536: .Cm ServerAliveInterval
1537: for protocol-level keepalives.
1.65 reyk 1538: .It Cm Tunnel
1.95 stevesk 1539: Request
1.65 reyk 1540: .Xr tun 4
1.69 jmc 1541: device forwarding between the client and the server.
1.65 reyk 1542: The argument must be
1.240 jmc 1543: .Cm yes ,
1544: .Cm point-to-point
1.95 stevesk 1545: (layer 3),
1.240 jmc 1546: .Cm ethernet
1.95 stevesk 1547: (layer 2),
1.65 reyk 1548: or
1.240 jmc 1549: .Cm no
1550: (the default).
1.95 stevesk 1551: Specifying
1.240 jmc 1552: .Cm yes
1.95 stevesk 1553: requests the default tunnel mode, which is
1.240 jmc 1554: .Cm point-to-point .
1.65 reyk 1555: .It Cm TunnelDevice
1.95 stevesk 1556: Specifies the
1.65 reyk 1557: .Xr tun 4
1.95 stevesk 1558: devices to open on the client
1559: .Pq Ar local_tun
1560: and the server
1561: .Pq Ar remote_tun .
1562: .Pp
1563: The argument must be
1564: .Sm off
1565: .Ar local_tun Op : Ar remote_tun .
1566: .Sm on
1567: The devices may be specified by numerical ID or the keyword
1.240 jmc 1568: .Cm any ,
1.95 stevesk 1569: which uses the next available tunnel device.
1570: If
1571: .Ar remote_tun
1572: is not specified, it defaults to
1.240 jmc 1573: .Cm any .
1.95 stevesk 1574: The default is
1.240 jmc 1575: .Cm any:any .
1.201 djm 1576: .It Cm UpdateHostKeys
1.200 djm 1577: Specifies whether
1578: .Xr ssh 1
1579: should accept notifications of additional hostkeys from the server sent
1580: after authentication has completed and add them to
1581: .Cm UserKnownHostsFile .
1582: The argument must be
1.240 jmc 1583: .Cm yes ,
1584: .Cm no
1.204 djm 1585: (the default) or
1.240 jmc 1586: .Cm ask .
1.200 djm 1587: Enabling this option allows learning alternate hostkeys for a server
1.201 djm 1588: and supports graceful key rotation by allowing a server to send replacement
1589: public keys before old ones are removed.
1.200 djm 1590: Additional hostkeys are only accepted if the key used to authenticate the
1.220 sobrado 1591: host was already trusted or explicitly accepted by the user.
1.204 djm 1592: If
1593: .Cm UpdateHostKeys
1594: is set to
1.240 jmc 1595: .Cm ask ,
1.204 djm 1596: then the user is asked to confirm the modifications to the known_hosts file.
1.205 djm 1597: Confirmation is currently incompatible with
1598: .Cm ControlPersist ,
1599: and will be disabled if it is enabled.
1.200 djm 1600: .Pp
1601: Presently, only
1602: .Xr sshd 8
1603: from OpenSSH 6.8 and greater support the
1.240 jmc 1604: .Qq hostkeys@openssh.com
1.200 djm 1605: protocol extension used to inform the client of all the server's hostkeys.
1.72 jmc 1606: .It Cm UsePrivilegedPort
1607: Specifies whether to use a privileged port for outgoing connections.
1608: The argument must be
1.240 jmc 1609: .Cm yes
1.72 jmc 1610: or
1.240 jmc 1611: .Cm no
1612: (the default).
1.72 jmc 1613: If set to
1.240 jmc 1614: .Cm yes ,
1.84 jmc 1615: .Xr ssh 1
1.72 jmc 1616: must be setuid root.
1.1 stevesk 1617: .It Cm User
1618: Specifies the user to log in as.
1619: This can be useful when a different user name is used on different machines.
1620: This saves the trouble of
1621: having to remember to give the user name on the command line.
1622: .It Cm UserKnownHostsFile
1.151 djm 1623: Specifies one or more files to use for the user
1624: host key database, separated by whitespace.
1625: The default is
1626: .Pa ~/.ssh/known_hosts ,
1627: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1628: .It Cm VerifyHostKeyDNS
1629: Specifies whether to verify the remote key using DNS and SSHFP resource
1630: records.
1.24 jakob 1631: If this option is set to
1.240 jmc 1632: .Cm yes ,
1.25 jmc 1633: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1634: from DNS.
1635: Insecure fingerprints will be handled as if this option was set to
1.240 jmc 1636: .Cm ask .
1.24 jakob 1637: If this option is set to
1.240 jmc 1638: .Cm ask ,
1.24 jakob 1639: information on fingerprint match will be displayed, but the user will still
1640: need to confirm new host keys according to the
1641: .Cm StrictHostKeyChecking
1642: option.
1.8 jakob 1643: The default is
1.240 jmc 1644: .Cm no .
1.84 jmc 1645: .Pp
1.240 jmc 1646: See also
1647: .Sx VERIFYING HOST KEYS
1648: in
1.84 jmc 1649: .Xr ssh 1 .
1.111 grunk 1650: .It Cm VisualHostKey
1651: If this flag is set to
1.240 jmc 1652: .Cm yes ,
1.111 grunk 1653: an ASCII art representation of the remote host key fingerprint is
1.197 djm 1654: printed in addition to the fingerprint string at login and
1.114 stevesk 1655: for unknown host keys.
1.111 grunk 1656: If this flag is set to
1.240 jmc 1657: .Cm no
1658: (the default),
1.114 stevesk 1659: no fingerprint strings are printed at login and
1.197 djm 1660: only the fingerprint string will be printed for unknown host keys.
1.1 stevesk 1661: .It Cm XAuthLocation
1.5 stevesk 1662: Specifies the full pathname of the
1.1 stevesk 1663: .Xr xauth 1
1664: program.
1665: The default is
1666: .Pa /usr/X11R6/bin/xauth .
1667: .El
1.86 jmc 1668: .Sh PATTERNS
1669: A
1670: .Em pattern
1671: consists of zero or more non-whitespace characters,
1672: .Sq *
1673: (a wildcard that matches zero or more characters),
1674: or
1675: .Sq ?\&
1676: (a wildcard that matches exactly one character).
1677: For example, to specify a set of declarations for any host in the
1.240 jmc 1678: .Qq .co.uk
1.86 jmc 1679: set of domains,
1680: the following pattern could be used:
1681: .Pp
1682: .Dl Host *.co.uk
1683: .Pp
1684: The following pattern
1685: would match any host in the 192.168.0.[0-9] network range:
1686: .Pp
1687: .Dl Host 192.168.0.?
1688: .Pp
1689: A
1690: .Em pattern-list
1691: is a comma-separated list of patterns.
1692: Patterns within pattern-lists may be negated
1693: by preceding them with an exclamation mark
1694: .Pq Sq !\& .
1695: For example,
1.174 djm 1696: to allow a key to be used from anywhere within an organization
1.86 jmc 1697: except from the
1.240 jmc 1698: .Qq dialup
1.86 jmc 1699: pool,
1700: the following entry (in authorized_keys) could be used:
1701: .Pp
1702: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.258 djm 1703: .Pp
1704: Note that a negated match will never produce a positive result by itself.
1705: For example, attempting to match
1706: .Qq host3
1707: against the following pattern-list will fail:
1708: .Pp
1709: .Dl from=\&"!host1,!host2\&"
1710: .Pp
1711: The solution here is to include a term that will yield a positive match,
1712: such as a wildcard:
1713: .Pp
1714: .Dl from=\&"!host1,!host2,*\&"
1.239 jmc 1715: .Sh TOKENS
1716: Arguments to some keywords can make use of tokens,
1717: which are expanded at runtime:
1718: .Pp
1719: .Bl -tag -width XXXX -offset indent -compact
1720: .It %%
1721: A literal
1722: .Sq % .
1723: .It \&%C
1.257 jmc 1724: Hash of %l%h%p%r.
1.239 jmc 1725: .It %d
1726: Local user's home directory.
1727: .It %h
1728: The remote hostname.
1729: .It %i
1730: The local user ID.
1731: .It %L
1732: The local hostname.
1733: .It %l
1734: The local hostname, including the domain name.
1735: .It %n
1736: The original remote hostname, as given on the command line.
1737: .It %p
1738: The remote port.
1739: .It %r
1740: The remote username.
1.261 djm 1741: .It \&%T
1742: The local
1743: .Xr tun 4
1744: or
1745: .Xr tap 4
1746: network interface assigned if
1.262 jmc 1747: tunnel forwarding was requested, or
1748: .Qq NONE
1.261 djm 1749: otherwise.
1.239 jmc 1750: .It %u
1751: The local username.
1752: .El
1753: .Pp
1754: .Cm Match exec
1.274 djm 1755: accepts the tokens %%, %h, %i, %L, %l, %n, %p, %r, and %u.
1.239 jmc 1756: .Pp
1757: .Cm CertificateFile
1.275 jmc 1758: accepts the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1759: .Pp
1760: .Cm ControlPath
1761: accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
1762: .Pp
1763: .Cm HostName
1764: accepts the tokens %% and %h.
1765: .Pp
1766: .Cm IdentityAgent
1767: and
1768: .Cm IdentityFile
1.275 jmc 1769: accept the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1770: .Pp
1771: .Cm LocalCommand
1.275 jmc 1772: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, %T, and %u.
1.239 jmc 1773: .Pp
1774: .Cm ProxyCommand
1775: accepts the tokens %%, %h, %p, and %r.
1.250 jmc 1776: .Pp
1777: .Cm RemoteCommand
1.274 djm 1778: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, and %u.
1.1 stevesk 1779: .Sh FILES
1780: .Bl -tag -width Ds
1.50 djm 1781: .It Pa ~/.ssh/config
1.1 stevesk 1782: This is the per-user configuration file.
1783: The format of this file is described above.
1.84 jmc 1784: This file is used by the SSH client.
1.30 djm 1785: Because of the potential for abuse, this file must have strict permissions:
1786: read/write for the user, and not accessible by others.
1.1 stevesk 1787: .It Pa /etc/ssh/ssh_config
1788: Systemwide configuration file.
1789: This file provides defaults for those
1790: values that are not specified in the user's configuration file, and
1791: for those users who do not have a configuration file.
1792: This file must be world-readable.
1793: .El
1.13 jmc 1794: .Sh SEE ALSO
1795: .Xr ssh 1
1.1 stevesk 1796: .Sh AUTHORS
1.240 jmc 1797: .An -nosplit
1.1 stevesk 1798: OpenSSH is a derivative of the original and free
1.240 jmc 1799: ssh 1.2.12 release by
1800: .An Tatu Ylonen .
1801: .An Aaron Campbell , Bob Beck , Markus Friedl ,
1802: .An Niels Provos , Theo de Raadt
1803: and
1804: .An Dug Song
1.1 stevesk 1805: removed many bugs, re-added newer features and
1806: created OpenSSH.
1.240 jmc 1807: .An Markus Friedl
1808: contributed the support for SSH protocol versions 1.5 and 2.0.