Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.301
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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1.301 ! naddy 36: .\" $OpenBSD: ssh_config.5,v 1.300 2019/09/04 20:31:15 naddy Exp $
! 37: .Dd $Mdocdate: September 4 2019 $
1.1 stevesk 38: .Dt SSH_CONFIG 5
39: .Os
40: .Sh NAME
41: .Nm ssh_config
42: .Nd OpenSSH SSH client configuration files
43: .Sh DESCRIPTION
1.84 jmc 44: .Xr ssh 1
1.1 stevesk 45: obtains configuration data from the following sources in
46: the following order:
1.79 jmc 47: .Pp
1.2 stevesk 48: .Bl -enum -offset indent -compact
49: .It
50: command-line options
51: .It
52: user's configuration file
1.50 djm 53: .Pq Pa ~/.ssh/config
1.2 stevesk 54: .It
55: system-wide configuration file
56: .Pq Pa /etc/ssh/ssh_config
57: .El
1.1 stevesk 58: .Pp
59: For each parameter, the first obtained value
60: will be used.
1.41 jmc 61: The configuration files contain sections separated by
1.240 jmc 62: .Cm Host
1.1 stevesk 63: specifications, and that section is only applied for hosts that
64: match one of the patterns given in the specification.
1.193 djm 65: The matched host name is usually the one given on the command line
66: (see the
67: .Cm CanonicalizeHostname
1.240 jmc 68: option for exceptions).
1.1 stevesk 69: .Pp
70: Since the first obtained value for each parameter is used, more
71: host-specific declarations should be given near the beginning of the
72: file, and general defaults at the end.
1.80 jmc 73: .Pp
1.240 jmc 74: The file contains keyword-argument pairs, one per line.
75: Lines starting with
1.1 stevesk 76: .Ql #
1.240 jmc 77: and empty lines are interpreted as comments.
78: Arguments may optionally be enclosed in double quotes
79: .Pq \&"
80: in order to represent arguments containing spaces.
1.1 stevesk 81: Configuration options may be separated by whitespace or
82: optional whitespace and exactly one
83: .Ql = ;
84: the latter format is useful to avoid the need to quote whitespace
85: when specifying configuration options using the
86: .Nm ssh ,
1.87 jmc 87: .Nm scp ,
1.1 stevesk 88: and
89: .Nm sftp
90: .Fl o
91: option.
92: .Pp
93: The possible
94: keywords and their meanings are as follows (note that
95: keywords are case-insensitive and arguments are case-sensitive):
96: .Bl -tag -width Ds
97: .It Cm Host
98: Restricts the following declarations (up to the next
99: .Cm Host
1.169 djm 100: or
101: .Cm Match
1.1 stevesk 102: keyword) to be only for those hosts that match one of the patterns
103: given after the keyword.
1.112 krw 104: If more than one pattern is provided, they should be separated by whitespace.
1.1 stevesk 105: A single
1.83 jmc 106: .Ql *
1.1 stevesk 107: as a pattern can be used to provide global
108: defaults for all hosts.
1.193 djm 109: The host is usually the
1.1 stevesk 110: .Ar hostname
1.193 djm 111: argument given on the command line
112: (see the
113: .Cm CanonicalizeHostname
1.240 jmc 114: keyword for exceptions).
1.148 djm 115: .Pp
116: A pattern entry may be negated by prefixing it with an exclamation mark
117: .Pq Sq !\& .
118: If a negated entry is matched, then the
119: .Cm Host
120: entry is ignored, regardless of whether any other patterns on the line
121: match.
122: Negated matches are therefore useful to provide exceptions for wildcard
123: matches.
1.81 jmc 124: .Pp
125: See
126: .Sx PATTERNS
127: for more information on patterns.
1.170 jmc 128: .It Cm Match
1.169 djm 129: Restricts the following declarations (up to the next
130: .Cm Host
131: or
132: .Cm Match
133: keyword) to be used only when the conditions following the
134: .Cm Match
135: keyword are satisfied.
1.220 sobrado 136: Match conditions are specified using one or more criteria
1.178 dtucker 137: or the single token
138: .Cm all
1.193 djm 139: which always matches.
140: The available criteria keywords are:
141: .Cm canonical ,
1.287 djm 142: .Cm final ,
1.176 djm 143: .Cm exec ,
1.169 djm 144: .Cm host ,
145: .Cm originalhost ,
146: .Cm user ,
147: and
148: .Cm localuser .
1.193 djm 149: The
150: .Cm all
151: criteria must appear alone or immediately after
1.287 djm 152: .Cm canonical
153: or
154: .Cm final .
1.193 djm 155: Other criteria may be combined arbitrarily.
156: All criteria but
1.288 jmc 157: .Cm all ,
158: .Cm canonical ,
1.193 djm 159: and
1.287 djm 160: .Cm final
1.193 djm 161: require an argument.
162: Criteria may be negated by prepending an exclamation mark
163: .Pq Sq !\& .
1.169 djm 164: .Pp
1.177 jmc 165: The
1.193 djm 166: .Cm canonical
1.210 dtucker 167: keyword matches only when the configuration file is being re-parsed
1.193 djm 168: after hostname canonicalization (see the
169: .Cm CanonicalizeHostname
1.288 jmc 170: option).
1.193 djm 171: This may be useful to specify conditions that work with canonical host
172: names only.
1.287 djm 173: .Pp
174: The
175: .Cm final
176: keyword requests that the configuration be re-parsed (regardless of whether
177: .Cm CanonicalizeHostname
178: is enabled), and matches only during this final pass.
179: If
180: .Cm CanonicalizeHostname
181: is enabled, then
182: .Cm canonical
183: and
184: .Cm final
185: match during the same pass.
186: .Pp
1.193 djm 187: The
1.176 djm 188: .Cm exec
1.177 jmc 189: keyword executes the specified command under the user's shell.
1.169 djm 190: If the command returns a zero exit status then the condition is considered true.
191: Commands containing whitespace characters must be quoted.
1.239 jmc 192: Arguments to
193: .Cm exec
194: accept the tokens described in the
195: .Sx TOKENS
196: section.
1.169 djm 197: .Pp
198: The other keywords' criteria must be single entries or comma-separated
199: lists and may use the wildcard and negation operators described in the
200: .Sx PATTERNS
201: section.
202: The criteria for the
203: .Cm host
204: keyword are matched against the target hostname, after any substitution
205: by the
1.295 jmc 206: .Cm Hostname
1.193 djm 207: or
208: .Cm CanonicalizeHostname
209: options.
1.169 djm 210: The
211: .Cm originalhost
212: keyword matches against the hostname as it was specified on the command-line.
213: The
214: .Cm user
215: keyword matches against the target username on the remote host.
216: The
217: .Cm localuser
218: keyword matches against the name of the local user running
219: .Xr ssh 1
220: (this keyword may be useful in system-wide
221: .Nm
222: files).
1.222 jcs 223: .It Cm AddKeysToAgent
224: Specifies whether keys should be automatically added to a running
1.223 jmc 225: .Xr ssh-agent 1 .
1.222 jcs 226: If this option is set to
1.240 jmc 227: .Cm yes
1.222 jcs 228: and a key is loaded from a file, the key and its passphrase are added to
229: the agent with the default lifetime, as if by
230: .Xr ssh-add 1 .
231: If this option is set to
1.240 jmc 232: .Cm ask ,
233: .Xr ssh 1
1.222 jcs 234: will require confirmation using the
235: .Ev SSH_ASKPASS
236: program before adding a key (see
237: .Xr ssh-add 1
238: for details).
239: If this option is set to
1.240 jmc 240: .Cm confirm ,
1.222 jcs 241: each use of the key must be confirmed, as if the
242: .Fl c
243: option was specified to
244: .Xr ssh-add 1 .
245: If this option is set to
1.240 jmc 246: .Cm no ,
1.222 jcs 247: no keys are added to the agent.
248: The argument must be
1.240 jmc 249: .Cm yes ,
250: .Cm confirm ,
251: .Cm ask ,
1.222 jcs 252: or
1.240 jmc 253: .Cm no
254: (the default).
1.10 djm 255: .It Cm AddressFamily
1.11 jmc 256: Specifies which address family to use when connecting.
257: Valid arguments are
1.240 jmc 258: .Cm any
259: (the default),
260: .Cm inet
1.84 jmc 261: (use IPv4 only), or
1.240 jmc 262: .Cm inet6
1.40 jmc 263: (use IPv6 only).
1.1 stevesk 264: .It Cm BatchMode
265: If set to
1.240 jmc 266: .Cm yes ,
1.1 stevesk 267: passphrase/password querying will be disabled.
268: This option is useful in scripts and other batch jobs where no user
269: is present to supply the password.
270: The argument must be
1.240 jmc 271: .Cm yes
1.1 stevesk 272: or
1.240 jmc 273: .Cm no
274: (the default).
1.268 jmc 275: .It Cm BindAddress
276: Use the specified address on the local machine as the source address of
277: the connection.
278: Only useful on systems with more than one address.
279: .It Cm BindInterface
280: Use the address of the specified interface on the local machine as the
281: source address of the connection.
1.171 djm 282: .It Cm CanonicalDomains
1.172 jmc 283: When
1.173 djm 284: .Cm CanonicalizeHostname
1.171 djm 285: is enabled, this option specifies the list of domain suffixes in which to
286: search for the specified destination host.
1.173 djm 287: .It Cm CanonicalizeFallbackLocal
1.174 djm 288: Specifies whether to fail with an error when hostname canonicalization fails.
1.172 jmc 289: The default,
1.240 jmc 290: .Cm yes ,
1.172 jmc 291: will attempt to look up the unqualified hostname using the system resolver's
1.171 djm 292: search rules.
293: A value of
1.240 jmc 294: .Cm no
1.171 djm 295: will cause
296: .Xr ssh 1
297: to fail instantly if
1.173 djm 298: .Cm CanonicalizeHostname
1.171 djm 299: is enabled and the target hostname cannot be found in any of the domains
300: specified by
301: .Cm CanonicalDomains .
1.173 djm 302: .It Cm CanonicalizeHostname
1.174 djm 303: Controls whether explicit hostname canonicalization is performed.
1.172 jmc 304: The default,
1.240 jmc 305: .Cm no ,
1.171 djm 306: is not to perform any name rewriting and let the system resolver handle all
307: hostname lookups.
308: If set to
1.240 jmc 309: .Cm yes
1.171 djm 310: then, for connections that do not use a
1.284 djm 311: .Cm ProxyCommand
312: or
313: .Cm ProxyJump ,
1.171 djm 314: .Xr ssh 1
1.173 djm 315: will attempt to canonicalize the hostname specified on the command line
1.171 djm 316: using the
317: .Cm CanonicalDomains
318: suffixes and
1.173 djm 319: .Cm CanonicalizePermittedCNAMEs
1.171 djm 320: rules.
321: If
1.173 djm 322: .Cm CanonicalizeHostname
1.171 djm 323: is set to
1.240 jmc 324: .Cm always ,
1.174 djm 325: then canonicalization is applied to proxied connections too.
1.185 djm 326: .Pp
1.193 djm 327: If this option is enabled, then the configuration files are processed
328: again using the new target name to pick up any new configuration in matching
1.185 djm 329: .Cm Host
1.193 djm 330: and
331: .Cm Match
1.185 djm 332: stanzas.
1.173 djm 333: .It Cm CanonicalizeMaxDots
1.172 jmc 334: Specifies the maximum number of dot characters in a hostname before
1.174 djm 335: canonicalization is disabled.
1.240 jmc 336: The default, 1,
1.172 jmc 337: allows a single dot (i.e. hostname.subdomain).
1.173 djm 338: .It Cm CanonicalizePermittedCNAMEs
1.172 jmc 339: Specifies rules to determine whether CNAMEs should be followed when
1.173 djm 340: canonicalizing hostnames.
1.171 djm 341: The rules consist of one or more arguments of
1.172 jmc 342: .Ar source_domain_list : Ns Ar target_domain_list ,
1.171 djm 343: where
344: .Ar source_domain_list
1.174 djm 345: is a pattern-list of domains that may follow CNAMEs in canonicalization,
1.171 djm 346: and
347: .Ar target_domain_list
1.172 jmc 348: is a pattern-list of domains that they may resolve to.
1.171 djm 349: .Pp
350: For example,
1.240 jmc 351: .Qq *.a.example.com:*.b.example.com,*.c.example.com
1.171 djm 352: will allow hostnames matching
1.240 jmc 353: .Qq *.a.example.com
1.173 djm 354: to be canonicalized to names in the
1.240 jmc 355: .Qq *.b.example.com
1.171 djm 356: or
1.240 jmc 357: .Qq *.c.example.com
1.171 djm 358: domains.
1.283 jmc 359: .It Cm CASignatureAlgorithms
360: Specifies which algorithms are allowed for signing of certificates
361: by certificate authorities (CAs).
362: The default is:
363: .Bd -literal -offset indent
1.297 djm 364: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.283 jmc 365: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
366: .Ed
367: .Pp
368: .Xr ssh 1
369: will not accept host certificates signed using algorithms other than those
370: specified.
1.221 djm 371: .It Cm CertificateFile
372: Specifies a file from which the user's certificate is read.
373: A corresponding private key must be provided separately in order
374: to use this certificate either
375: from an
376: .Cm IdentityFile
377: directive or
378: .Fl i
379: flag to
380: .Xr ssh 1 ,
381: via
382: .Xr ssh-agent 1 ,
383: or via a
384: .Cm PKCS11Provider .
385: .Pp
1.239 jmc 386: Arguments to
387: .Cm CertificateFile
388: may use the tilde syntax to refer to a user's home directory
389: or the tokens described in the
390: .Sx TOKENS
391: section.
1.221 djm 392: .Pp
393: It is possible to have multiple certificate files specified in
394: configuration files; these certificates will be tried in sequence.
395: Multiple
396: .Cm CertificateFile
397: directives will add to the list of certificates used for
398: authentication.
1.1 stevesk 399: .It Cm ChallengeResponseAuthentication
1.82 jmc 400: Specifies whether to use challenge-response authentication.
1.1 stevesk 401: The argument to this keyword must be
1.240 jmc 402: .Cm yes
403: (the default)
1.1 stevesk 404: or
1.240 jmc 405: .Cm no .
1.1 stevesk 406: .It Cm CheckHostIP
1.240 jmc 407: If set to
408: .Cm yes
409: (the default),
1.84 jmc 410: .Xr ssh 1
411: will additionally check the host IP address in the
1.1 stevesk 412: .Pa known_hosts
413: file.
1.240 jmc 414: This allows it to detect if a host key changed due to DNS spoofing
1.211 djm 415: and will add addresses of destination hosts to
416: .Pa ~/.ssh/known_hosts
417: in the process, regardless of the setting of
418: .Cm StrictHostKeyChecking .
1.107 grunk 419: If the option is set to
1.240 jmc 420: .Cm no ,
1.1 stevesk 421: the check will not be executed.
422: .It Cm Ciphers
1.245 djm 423: Specifies the ciphers allowed and their order of preference.
1.1 stevesk 424: Multiple ciphers must be comma-separated.
1.299 kn 425: If the specified list begins with a
1.214 djm 426: .Sq +
427: character, then the specified ciphers will be appended to the default set
428: instead of replacing them.
1.299 kn 429: If the specified list begins with a
1.241 djm 430: .Sq -
431: character, then the specified ciphers (including wildcards) will be removed
432: from the default set instead of replacing them.
1.301 ! naddy 433: If the specified list begins with a
! 434: .Sq ^
! 435: character, then the specified ciphers will be placed at the head of the
! 436: default set.
1.214 djm 437: .Pp
1.180 djm 438: The supported ciphers are:
1.240 jmc 439: .Bd -literal -offset indent
1.186 naddy 440: 3des-cbc
441: aes128-cbc
442: aes192-cbc
443: aes256-cbc
444: aes128-ctr
445: aes192-ctr
446: aes256-ctr
447: aes128-gcm@openssh.com
448: aes256-gcm@openssh.com
449: chacha20-poly1305@openssh.com
1.240 jmc 450: .Ed
1.180 djm 451: .Pp
1.84 jmc 452: The default is:
1.186 naddy 453: .Bd -literal -offset indent
1.215 jmc 454: chacha20-poly1305@openssh.com,
1.186 naddy 455: aes128-ctr,aes192-ctr,aes256-ctr,
1.270 djm 456: aes128-gcm@openssh.com,aes256-gcm@openssh.com
1.1 stevesk 457: .Ed
1.180 djm 458: .Pp
1.240 jmc 459: The list of available ciphers may also be obtained using
460: .Qq ssh -Q cipher .
1.1 stevesk 461: .It Cm ClearAllForwardings
1.84 jmc 462: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 463: specified in the configuration files or on the command line be
1.7 jmc 464: cleared.
465: This option is primarily useful when used from the
1.84 jmc 466: .Xr ssh 1
1.1 stevesk 467: command line to clear port forwardings set in
468: configuration files, and is automatically set by
469: .Xr scp 1
470: and
471: .Xr sftp 1 .
472: The argument must be
1.240 jmc 473: .Cm yes
1.1 stevesk 474: or
1.240 jmc 475: .Cm no
476: (the default).
1.1 stevesk 477: .It Cm Compression
478: Specifies whether to use compression.
479: The argument must be
1.240 jmc 480: .Cm yes
1.1 stevesk 481: or
1.240 jmc 482: .Cm no
483: (the default).
1.247 naddy 484: .It Cm ConnectionAttempts
485: Specifies the number of tries (one per second) to make before exiting.
486: The argument must be an integer.
487: This may be useful in scripts if the connection sometimes fails.
488: The default is 1.
1.9 djm 489: .It Cm ConnectTimeout
1.84 jmc 490: Specifies the timeout (in seconds) used when connecting to the
491: SSH server, instead of using the default system TCP timeout.
1.11 jmc 492: This value is used only when the target is down or really unreachable,
493: not when it refuses the connection.
1.36 djm 494: .It Cm ControlMaster
495: Enables the sharing of multiple sessions over a single network connection.
496: When set to
1.240 jmc 497: .Cm yes ,
1.84 jmc 498: .Xr ssh 1
1.36 djm 499: will listen for connections on a control socket specified using the
500: .Cm ControlPath
501: argument.
502: Additional sessions can connect to this socket using the same
503: .Cm ControlPath
504: with
505: .Cm ControlMaster
506: set to
1.240 jmc 507: .Cm no
1.38 jmc 508: (the default).
1.64 jmc 509: These sessions will try to reuse the master instance's network connection
1.63 djm 510: rather than initiating new ones, but will fall back to connecting normally
511: if the control socket does not exist, or is not listening.
512: .Pp
1.37 djm 513: Setting this to
1.240 jmc 514: .Cm ask
515: will cause
516: .Xr ssh 1
1.206 jmc 517: to listen for control connections, but require confirmation using
518: .Xr ssh-askpass 1 .
1.51 jakob 519: If the
520: .Cm ControlPath
1.84 jmc 521: cannot be opened,
1.240 jmc 522: .Xr ssh 1
523: will continue without connecting to a master instance.
1.58 djm 524: .Pp
525: X11 and
1.59 jmc 526: .Xr ssh-agent 1
1.58 djm 527: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 528: display and agent forwarded will be the one belonging to the master
1.59 jmc 529: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 530: .Pp
531: Two additional options allow for opportunistic multiplexing: try to use a
532: master connection but fall back to creating a new one if one does not already
533: exist.
534: These options are:
1.240 jmc 535: .Cm auto
1.56 djm 536: and
1.240 jmc 537: .Cm autoask .
1.56 djm 538: The latter requires confirmation like the
1.240 jmc 539: .Cm ask
1.56 djm 540: option.
1.36 djm 541: .It Cm ControlPath
1.55 djm 542: Specify the path to the control socket used for connection sharing as described
543: in the
1.36 djm 544: .Cm ControlMaster
1.57 djm 545: section above or the string
1.240 jmc 546: .Cm none
1.57 djm 547: to disable connection sharing.
1.239 jmc 548: Arguments to
549: .Cm ControlPath
550: may use the tilde syntax to refer to a user's home directory
551: or the tokens described in the
552: .Sx TOKENS
553: section.
1.56 djm 554: It is recommended that any
555: .Cm ControlPath
556: used for opportunistic connection sharing include
1.195 djm 557: at least %h, %p, and %r (or alternatively %C) and be placed in a directory
558: that is not writable by other users.
1.56 djm 559: This ensures that shared connections are uniquely identified.
1.137 djm 560: .It Cm ControlPersist
561: When used in conjunction with
562: .Cm ControlMaster ,
563: specifies that the master connection should remain open
564: in the background (waiting for future client connections)
565: after the initial client connection has been closed.
566: If set to
1.240 jmc 567: .Cm no ,
1.137 djm 568: then the master connection will not be placed into the background,
569: and will close as soon as the initial client connection is closed.
570: If set to
1.240 jmc 571: .Cm yes
572: or 0,
1.137 djm 573: then the master connection will remain in the background indefinitely
574: (until killed or closed via a mechanism such as the
1.240 jmc 575: .Qq ssh -O exit ) .
1.137 djm 576: If set to a time in seconds, or a time in any of the formats documented in
577: .Xr sshd_config 5 ,
578: then the backgrounded master connection will automatically terminate
579: after it has remained idle (with no client connections) for the
580: specified time.
1.38 jmc 581: .It Cm DynamicForward
1.74 jmc 582: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 583: over the secure channel, and the application
584: protocol is then used to determine where to connect to from the
585: remote machine.
1.62 djm 586: .Pp
587: The argument must be
588: .Sm off
589: .Oo Ar bind_address : Oc Ar port .
590: .Sm on
1.138 djm 591: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 592: By default, the local port is bound in accordance with the
593: .Cm GatewayPorts
594: setting.
595: However, an explicit
596: .Ar bind_address
597: may be used to bind the connection to a specific address.
598: The
599: .Ar bind_address
600: of
1.240 jmc 601: .Cm localhost
1.62 djm 602: indicates that the listening port be bound for local use only, while an
603: empty address or
604: .Sq *
605: indicates that the port should be available from all interfaces.
606: .Pp
1.38 jmc 607: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 608: .Xr ssh 1
1.38 jmc 609: will act as a SOCKS server.
610: Multiple forwardings may be specified, and
611: additional forwardings can be given on the command line.
612: Only the superuser can forward privileged ports.
1.14 markus 613: .It Cm EnableSSHKeysign
614: Setting this option to
1.240 jmc 615: .Cm yes
1.14 markus 616: in the global client configuration file
617: .Pa /etc/ssh/ssh_config
618: enables the use of the helper program
619: .Xr ssh-keysign 8
620: during
621: .Cm HostbasedAuthentication .
622: The argument must be
1.240 jmc 623: .Cm yes
1.14 markus 624: or
1.240 jmc 625: .Cm no
626: (the default).
1.23 jmc 627: This option should be placed in the non-hostspecific section.
1.14 markus 628: See
629: .Xr ssh-keysign 8
630: for more information.
1.1 stevesk 631: .It Cm EscapeChar
632: Sets the escape character (default:
633: .Ql ~ ) .
634: The escape character can also
635: be set on the command line.
636: The argument should be a single character,
637: .Ql ^
638: followed by a letter, or
1.240 jmc 639: .Cm none
1.1 stevesk 640: to disable the escape
641: character entirely (making the connection transparent for binary
642: data).
1.96 markus 643: .It Cm ExitOnForwardFailure
644: Specifies whether
645: .Xr ssh 1
646: should terminate the connection if it cannot set up all requested
1.216 djm 647: dynamic, tunnel, local, and remote port forwardings, (e.g.\&
1.217 jmc 648: if either end is unable to bind and listen on a specified port).
1.216 djm 649: Note that
650: .Cm ExitOnForwardFailure
651: does not apply to connections made over port forwardings and will not,
652: for example, cause
653: .Xr ssh 1
654: to exit if TCP connections to the ultimate forwarding destination fail.
1.96 markus 655: The argument must be
1.240 jmc 656: .Cm yes
1.96 markus 657: or
1.240 jmc 658: .Cm no
659: (the default).
1.197 djm 660: .It Cm FingerprintHash
661: Specifies the hash algorithm used when displaying key fingerprints.
662: Valid options are:
1.240 jmc 663: .Cm md5
1.197 djm 664: and
1.240 jmc 665: .Cm sha256
666: (the default).
1.1 stevesk 667: .It Cm ForwardAgent
668: Specifies whether the connection to the authentication agent (if any)
669: will be forwarded to the remote machine.
670: The argument must be
1.240 jmc 671: .Cm yes
1.1 stevesk 672: or
1.240 jmc 673: .Cm no
674: (the default).
1.3 stevesk 675: .Pp
1.7 jmc 676: Agent forwarding should be enabled with caution.
677: Users with the ability to bypass file permissions on the remote host
678: (for the agent's Unix-domain socket)
679: can access the local agent through the forwarded connection.
680: An attacker cannot obtain key material from the agent,
1.3 stevesk 681: however they can perform operations on the keys that enable them to
682: authenticate using the identities loaded into the agent.
1.1 stevesk 683: .It Cm ForwardX11
684: Specifies whether X11 connections will be automatically redirected
685: over the secure channel and
686: .Ev DISPLAY
687: set.
688: The argument must be
1.240 jmc 689: .Cm yes
1.1 stevesk 690: or
1.240 jmc 691: .Cm no
692: (the default).
1.3 stevesk 693: .Pp
1.7 jmc 694: X11 forwarding should be enabled with caution.
695: Users with the ability to bypass file permissions on the remote host
1.22 markus 696: (for the user's X11 authorization database)
1.7 jmc 697: can access the local X11 display through the forwarded connection.
1.22 markus 698: An attacker may then be able to perform activities such as keystroke monitoring
699: if the
700: .Cm ForwardX11Trusted
701: option is also enabled.
1.134 djm 702: .It Cm ForwardX11Timeout
1.135 jmc 703: Specify a timeout for untrusted X11 forwarding
704: using the format described in the
1.240 jmc 705: .Sx TIME FORMATS
706: section of
1.134 djm 707: .Xr sshd_config 5 .
708: X11 connections received by
709: .Xr ssh 1
710: after this time will be refused.
1.285 djm 711: Setting
712: .Cm ForwardX11Timeout
713: to zero will disable the timeout and permit X11 forwarding for the life
714: of the connection.
1.134 djm 715: The default is to disable untrusted X11 forwarding after twenty minutes has
716: elapsed.
1.22 markus 717: .It Cm ForwardX11Trusted
1.34 jmc 718: If this option is set to
1.240 jmc 719: .Cm yes ,
1.84 jmc 720: remote X11 clients will have full access to the original X11 display.
1.42 djm 721: .Pp
1.22 markus 722: If this option is set to
1.240 jmc 723: .Cm no
724: (the default),
1.84 jmc 725: remote X11 clients will be considered untrusted and prevented
1.22 markus 726: from stealing or tampering with data belonging to trusted X11
727: clients.
1.42 djm 728: Furthermore, the
729: .Xr xauth 1
730: token used for the session will be set to expire after 20 minutes.
731: Remote clients will be refused access after this time.
1.22 markus 732: .Pp
733: See the X11 SECURITY extension specification for full details on
734: the restrictions imposed on untrusted clients.
1.1 stevesk 735: .It Cm GatewayPorts
736: Specifies whether remote hosts are allowed to connect to local
737: forwarded ports.
738: By default,
1.84 jmc 739: .Xr ssh 1
1.7 jmc 740: binds local port forwardings to the loopback address.
741: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 742: .Cm GatewayPorts
1.84 jmc 743: can be used to specify that ssh
1.1 stevesk 744: should bind local port forwardings to the wildcard address,
745: thus allowing remote hosts to connect to forwarded ports.
746: The argument must be
1.240 jmc 747: .Cm yes
1.1 stevesk 748: or
1.240 jmc 749: .Cm no
750: (the default).
1.1 stevesk 751: .It Cm GlobalKnownHostsFile
1.151 djm 752: Specifies one or more files to use for the global
753: host key database, separated by whitespace.
754: The default is
755: .Pa /etc/ssh/ssh_known_hosts ,
756: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 757: .It Cm GSSAPIAuthentication
1.27 markus 758: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 759: The default is
1.240 jmc 760: .Cm no .
1.18 markus 761: .It Cm GSSAPIDelegateCredentials
762: Forward (delegate) credentials to the server.
763: The default is
1.240 jmc 764: .Cm no .
1.44 djm 765: .It Cm HashKnownHosts
766: Indicates that
1.84 jmc 767: .Xr ssh 1
1.44 djm 768: should hash host names and addresses when they are added to
1.50 djm 769: .Pa ~/.ssh/known_hosts .
1.44 djm 770: These hashed names may be used normally by
1.84 jmc 771: .Xr ssh 1
1.44 djm 772: and
1.84 jmc 773: .Xr sshd 8 ,
1.44 djm 774: but they do not reveal identifying information should the file's contents
775: be disclosed.
776: The default is
1.240 jmc 777: .Cm no .
1.97 jmc 778: Note that existing names and addresses in known hosts files
779: will not be converted automatically,
780: but may be manually hashed using
1.45 djm 781: .Xr ssh-keygen 1 .
1.1 stevesk 782: .It Cm HostbasedAuthentication
783: Specifies whether to try rhosts based authentication with public key
784: authentication.
785: The argument must be
1.240 jmc 786: .Cm yes
1.1 stevesk 787: or
1.240 jmc 788: .Cm no
789: (the default).
1.202 djm 790: .It Cm HostbasedKeyTypes
791: Specifies the key types that will be used for hostbased authentication
1.279 djm 792: as a comma-separated list of patterns.
1.300 naddy 793: Alternately if the specified list begins with a
1.214 djm 794: .Sq +
795: character, then the specified key types will be appended to the default set
796: instead of replacing them.
1.300 naddy 797: If the specified list begins with a
1.241 djm 798: .Sq -
799: character, then the specified key types (including wildcards) will be removed
800: from the default set instead of replacing them.
1.301 ! naddy 801: If the specified list begins with a
! 802: .Sq ^
! 803: character, then the specified key types will be placed at the head of the
! 804: default set.
1.213 markus 805: The default for this option is:
806: .Bd -literal -offset 3n
807: ecdsa-sha2-nistp256-cert-v01@openssh.com,
808: ecdsa-sha2-nistp384-cert-v01@openssh.com,
809: ecdsa-sha2-nistp521-cert-v01@openssh.com,
810: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 811: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 812: ssh-rsa-cert-v01@openssh.com,
813: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 814: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 815: .Ed
816: .Pp
1.202 djm 817: The
818: .Fl Q
819: option of
820: .Xr ssh 1
821: may be used to list supported key types.
1.1 stevesk 822: .It Cm HostKeyAlgorithms
1.226 jmc 823: Specifies the host key algorithms
1.1 stevesk 824: that the client wants to use in order of preference.
1.300 naddy 825: Alternately if the specified list begins with a
1.214 djm 826: .Sq +
827: character, then the specified key types will be appended to the default set
828: instead of replacing them.
1.300 naddy 829: If the specified list begins with a
1.241 djm 830: .Sq -
831: character, then the specified key types (including wildcards) will be removed
832: from the default set instead of replacing them.
1.301 ! naddy 833: If the specified list begins with a
! 834: .Sq ^
! 835: character, then the specified key types will be placed at the head of the
! 836: default set.
1.1 stevesk 837: The default for this option is:
1.139 djm 838: .Bd -literal -offset 3n
839: ecdsa-sha2-nistp256-cert-v01@openssh.com,
840: ecdsa-sha2-nistp384-cert-v01@openssh.com,
841: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1.183 naddy 842: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 843: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 844: ssh-rsa-cert-v01@openssh.com,
1.139 djm 845: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 846: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.139 djm 847: .Ed
1.145 djm 848: .Pp
849: If hostkeys are known for the destination host then this default is modified
850: to prefer their algorithms.
1.198 djm 851: .Pp
1.240 jmc 852: The list of available key types may also be obtained using
853: .Qq ssh -Q key .
1.1 stevesk 854: .It Cm HostKeyAlias
855: Specifies an alias that should be used instead of the
856: real host name when looking up or saving the host key
1.251 djm 857: in the host key database files and when validating host certificates.
1.84 jmc 858: This option is useful for tunneling SSH connections
1.1 stevesk 859: or for multiple servers running on a single host.
1.295 jmc 860: .It Cm Hostname
1.1 stevesk 861: Specifies the real host name to log into.
862: This can be used to specify nicknames or abbreviations for hosts.
1.239 jmc 863: Arguments to
1.295 jmc 864: .Cm Hostname
1.239 jmc 865: accept the tokens described in the
866: .Sx TOKENS
867: section.
1.1 stevesk 868: Numeric IP addresses are also permitted (both on the command line and in
1.295 jmc 869: .Cm Hostname
1.1 stevesk 870: specifications).
1.239 jmc 871: The default is the name given on the command line.
1.29 markus 872: .It Cm IdentitiesOnly
873: Specifies that
1.84 jmc 874: .Xr ssh 1
1.221 djm 875: should only use the authentication identity and certificate files explicitly
876: configured in the
1.31 jmc 877: .Nm
1.221 djm 878: files
879: or passed on the
880: .Xr ssh 1
881: command-line,
1.84 jmc 882: even if
883: .Xr ssh-agent 1
1.159 djm 884: or a
885: .Cm PKCS11Provider
1.29 markus 886: offers more identities.
887: The argument to this keyword must be
1.240 jmc 888: .Cm yes
1.29 markus 889: or
1.240 jmc 890: .Cm no
891: (the default).
1.84 jmc 892: This option is intended for situations where ssh-agent
1.29 markus 893: offers many different identities.
1.231 markus 894: .It Cm IdentityAgent
895: Specifies the
896: .Ux Ns -domain
897: socket used to communicate with the authentication agent.
898: .Pp
899: This option overrides the
1.240 jmc 900: .Ev SSH_AUTH_SOCK
1.231 markus 901: environment variable and can be used to select a specific agent.
902: Setting the socket name to
1.240 jmc 903: .Cm none
1.231 markus 904: disables the use of an authentication agent.
1.232 markus 905: If the string
1.240 jmc 906: .Qq SSH_AUTH_SOCK
1.232 markus 907: is specified, the location of the socket will be read from the
908: .Ev SSH_AUTH_SOCK
909: environment variable.
1.286 djm 910: Otherwise if the specified value begins with a
911: .Sq $
912: character, then it will be treated as an environment variable containing
913: the location of the socket.
1.231 markus 914: .Pp
1.239 jmc 915: Arguments to
916: .Cm IdentityAgent
917: may use the tilde syntax to refer to a user's home directory
918: or the tokens described in the
919: .Sx TOKENS
920: section.
1.67 jmc 921: .It Cm IdentityFile
1.192 sobrado 922: Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA authentication
1.139 djm 923: identity is read.
1.67 jmc 924: The default is
1.139 djm 925: .Pa ~/.ssh/id_dsa ,
1.183 naddy 926: .Pa ~/.ssh/id_ecdsa ,
927: .Pa ~/.ssh/id_ed25519
1.139 djm 928: and
1.245 djm 929: .Pa ~/.ssh/id_rsa .
1.67 jmc 930: Additionally, any identities represented by the authentication agent
1.165 djm 931: will be used for authentication unless
932: .Cm IdentitiesOnly
933: is set.
1.221 djm 934: If no certificates have been explicitly specified by
935: .Cm CertificateFile ,
1.129 djm 936: .Xr ssh 1
937: will try to load certificate information from the filename obtained by
938: appending
939: .Pa -cert.pub
940: to the path of a specified
941: .Cm IdentityFile .
1.90 djm 942: .Pp
1.239 jmc 943: Arguments to
944: .Cm IdentityFile
945: may use the tilde syntax to refer to a user's home directory
946: or the tokens described in the
947: .Sx TOKENS
948: section.
1.90 djm 949: .Pp
1.67 jmc 950: It is possible to have
951: multiple identity files specified in configuration files; all these
952: identities will be tried in sequence.
1.152 djm 953: Multiple
954: .Cm IdentityFile
955: directives will add to the list of identities tried (this behaviour
956: differs from that of other configuration directives).
1.165 djm 957: .Pp
958: .Cm IdentityFile
959: may be used in conjunction with
960: .Cm IdentitiesOnly
961: to select which identities in an agent are offered during authentication.
1.221 djm 962: .Cm IdentityFile
963: may also be used in conjunction with
964: .Cm CertificateFile
965: in order to provide any certificate also needed for authentication with
966: the identity.
1.164 jmc 967: .It Cm IgnoreUnknown
968: Specifies a pattern-list of unknown options to be ignored if they are
969: encountered in configuration parsing.
970: This may be used to suppress errors if
971: .Nm
972: contains options that are unrecognised by
973: .Xr ssh 1 .
974: It is recommended that
975: .Cm IgnoreUnknown
976: be listed early in the configuration file as it will not be applied
977: to unknown options that appear before it.
1.229 djm 978: .It Cm Include
979: Include the specified configuration file(s).
1.230 jmc 980: Multiple pathnames may be specified and each pathname may contain
1.281 kn 981: .Xr glob 7
1.229 djm 982: wildcards and, for user configurations, shell-like
1.240 jmc 983: .Sq ~
1.229 djm 984: references to user home directories.
985: Files without absolute paths are assumed to be in
986: .Pa ~/.ssh
1.230 jmc 987: if included in a user configuration file or
1.229 djm 988: .Pa /etc/ssh
989: if included from the system configuration file.
990: .Cm Include
991: directive may appear inside a
992: .Cm Match
993: or
994: .Cm Host
995: block
996: to perform conditional inclusion.
1.143 djm 997: .It Cm IPQoS
998: Specifies the IPv4 type-of-service or DSCP class for connections.
999: Accepted values are
1.240 jmc 1000: .Cm af11 ,
1001: .Cm af12 ,
1002: .Cm af13 ,
1003: .Cm af21 ,
1004: .Cm af22 ,
1005: .Cm af23 ,
1006: .Cm af31 ,
1007: .Cm af32 ,
1008: .Cm af33 ,
1009: .Cm af41 ,
1010: .Cm af42 ,
1011: .Cm af43 ,
1012: .Cm cs0 ,
1013: .Cm cs1 ,
1014: .Cm cs2 ,
1015: .Cm cs3 ,
1016: .Cm cs4 ,
1017: .Cm cs5 ,
1018: .Cm cs6 ,
1019: .Cm cs7 ,
1020: .Cm ef ,
1021: .Cm lowdelay ,
1022: .Cm throughput ,
1023: .Cm reliability ,
1.253 djm 1024: a numeric value, or
1025: .Cm none
1026: to use the operating system default.
1.146 djm 1027: This option may take one or two arguments, separated by whitespace.
1.143 djm 1028: If one argument is specified, it is used as the packet class unconditionally.
1029: If two values are specified, the first is automatically selected for
1030: interactive sessions and the second for non-interactive sessions.
1031: The default is
1.269 job 1032: .Cm af21
1.272 jmc 1033: (Low-Latency Data)
1.143 djm 1034: for interactive sessions and
1.269 job 1035: .Cm cs1
1.272 jmc 1036: (Lower Effort)
1.143 djm 1037: for non-interactive sessions.
1.103 djm 1038: .It Cm KbdInteractiveAuthentication
1039: Specifies whether to use keyboard-interactive authentication.
1040: The argument to this keyword must be
1.240 jmc 1041: .Cm yes
1042: (the default)
1.103 djm 1043: or
1.240 jmc 1044: .Cm no .
1.39 djm 1045: .It Cm KbdInteractiveDevices
1046: Specifies the list of methods to use in keyboard-interactive authentication.
1047: Multiple method names must be comma-separated.
1048: The default is to use the server specified list.
1.85 jmc 1049: The methods available vary depending on what the server supports.
1050: For an OpenSSH server,
1051: it may be zero or more of:
1.240 jmc 1052: .Cm bsdauth ,
1053: .Cm pam ,
1.85 jmc 1054: and
1.240 jmc 1055: .Cm skey .
1.140 djm 1056: .It Cm KexAlgorithms
1057: Specifies the available KEX (Key Exchange) algorithms.
1058: Multiple algorithms must be comma-separated.
1.299 kn 1059: If the specified list begins with a
1.214 djm 1060: .Sq +
1061: character, then the specified methods will be appended to the default set
1062: instead of replacing them.
1.299 kn 1063: If the specified list begins with a
1.241 djm 1064: .Sq -
1065: character, then the specified methods (including wildcards) will be removed
1066: from the default set instead of replacing them.
1.301 ! naddy 1067: If the specified list begins with a
! 1068: .Sq ^
! 1069: character, then the specified methods will be placed at the head of the
! 1070: default set.
1.141 jmc 1071: The default is:
1072: .Bd -literal -offset indent
1.238 djm 1073: curve25519-sha256,curve25519-sha256@libssh.org,
1.141 jmc 1074: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1075: diffie-hellman-group-exchange-sha256,
1.266 djm 1076: diffie-hellman-group16-sha512,
1077: diffie-hellman-group18-sha512,
1078: diffie-hellman-group14-sha256,
1.212 djm 1079: diffie-hellman-group14-sha1
1.141 jmc 1080: .Ed
1.198 djm 1081: .Pp
1.240 jmc 1082: The list of available key exchange algorithms may also be obtained using
1083: .Qq ssh -Q kex .
1.65 reyk 1084: .It Cm LocalCommand
1085: Specifies a command to execute on the local machine after successfully
1086: connecting to the server.
1087: The command string extends to the end of the line, and is executed with
1.105 jmc 1088: the user's shell.
1.239 jmc 1089: Arguments to
1090: .Cm LocalCommand
1091: accept the tokens described in the
1092: .Sx TOKENS
1093: section.
1.123 djm 1094: .Pp
1095: The command is run synchronously and does not have access to the
1096: session of the
1097: .Xr ssh 1
1098: that spawned it.
1099: It should not be used for interactive commands.
1100: .Pp
1.65 reyk 1101: This directive is ignored unless
1102: .Cm PermitLocalCommand
1103: has been enabled.
1.1 stevesk 1104: .It Cm LocalForward
1.74 jmc 1105: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 1106: the secure channel to the specified host and port from the remote machine.
1.49 jmc 1107: The first argument must be
1.43 djm 1108: .Sm off
1.49 jmc 1109: .Oo Ar bind_address : Oc Ar port
1.43 djm 1110: .Sm on
1.49 jmc 1111: and the second argument must be
1112: .Ar host : Ns Ar hostport .
1.138 djm 1113: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 1114: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 1115: given on the command line.
1.1 stevesk 1116: Only the superuser can forward privileged ports.
1.43 djm 1117: By default, the local port is bound in accordance with the
1118: .Cm GatewayPorts
1119: setting.
1120: However, an explicit
1121: .Ar bind_address
1122: may be used to bind the connection to a specific address.
1123: The
1124: .Ar bind_address
1125: of
1.240 jmc 1126: .Cm localhost
1.46 jmc 1127: indicates that the listening port be bound for local use only, while an
1128: empty address or
1129: .Sq *
1.43 djm 1130: indicates that the port should be available from all interfaces.
1.1 stevesk 1131: .It Cm LogLevel
1132: Gives the verbosity level that is used when logging messages from
1.84 jmc 1133: .Xr ssh 1 .
1.1 stevesk 1134: The possible values are:
1.84 jmc 1135: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 1136: The default is INFO.
1137: DEBUG and DEBUG1 are equivalent.
1138: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 1139: .It Cm MACs
1140: Specifies the MAC (message authentication code) algorithms
1141: in order of preference.
1.226 jmc 1142: The MAC algorithm is used for data integrity protection.
1.1 stevesk 1143: Multiple algorithms must be comma-separated.
1.299 kn 1144: If the specified list begins with a
1.214 djm 1145: .Sq +
1146: character, then the specified algorithms will be appended to the default set
1147: instead of replacing them.
1.299 kn 1148: If the specified list begins with a
1.241 djm 1149: .Sq -
1150: character, then the specified algorithms (including wildcards) will be removed
1151: from the default set instead of replacing them.
1.301 ! naddy 1152: If the specified list begins with a
! 1153: .Sq ^
! 1154: character, then the specified algorithms will be placed at the head of the
! 1155: default set.
1.214 djm 1156: .Pp
1.160 markus 1157: The algorithms that contain
1.240 jmc 1158: .Qq -etm
1.160 markus 1159: calculate the MAC after encryption (encrypt-then-mac).
1160: These are considered safer and their use recommended.
1.214 djm 1161: .Pp
1.84 jmc 1162: The default is:
1.101 jmc 1163: .Bd -literal -offset indent
1.160 markus 1164: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1165: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.224 djm 1166: hmac-sha1-etm@openssh.com,
1.186 naddy 1167: umac-64@openssh.com,umac-128@openssh.com,
1.224 djm 1168: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.101 jmc 1169: .Ed
1.198 djm 1170: .Pp
1.240 jmc 1171: The list of available MAC algorithms may also be obtained using
1172: .Qq ssh -Q mac .
1.1 stevesk 1173: .It Cm NoHostAuthenticationForLocalhost
1.264 djm 1174: Disable host authentication for localhost (loopback addresses).
1.1 stevesk 1175: The argument to this keyword must be
1.240 jmc 1176: .Cm yes
1.1 stevesk 1177: or
1.242 jmc 1178: .Cm no
1.240 jmc 1179: (the default).
1.1 stevesk 1180: .It Cm NumberOfPasswordPrompts
1181: Specifies the number of password prompts before giving up.
1182: The argument to this keyword must be an integer.
1.84 jmc 1183: The default is 3.
1.1 stevesk 1184: .It Cm PasswordAuthentication
1185: Specifies whether to use password authentication.
1186: The argument to this keyword must be
1.240 jmc 1187: .Cm yes
1188: (the default)
1.1 stevesk 1189: or
1.240 jmc 1190: .Cm no .
1.65 reyk 1191: .It Cm PermitLocalCommand
1192: Allow local command execution via the
1193: .Ic LocalCommand
1194: option or using the
1.66 jmc 1195: .Ic !\& Ns Ar command
1.65 reyk 1196: escape sequence in
1197: .Xr ssh 1 .
1198: The argument must be
1.240 jmc 1199: .Cm yes
1.65 reyk 1200: or
1.240 jmc 1201: .Cm no
1202: (the default).
1.127 markus 1203: .It Cm PKCS11Provider
1.292 djm 1204: Specifies which PKCS#11 provider to use or
1205: .Cm none
1206: to indicate that no provider should be used (the default).
1207: The argument to this keyword is a path to the PKCS#11 shared library
1.127 markus 1208: .Xr ssh 1
1.292 djm 1209: should use to communicate with a PKCS#11 token providing keys for user
1210: authentication.
1.67 jmc 1211: .It Cm Port
1212: Specifies the port number to connect on the remote host.
1.84 jmc 1213: The default is 22.
1.1 stevesk 1214: .It Cm PreferredAuthentications
1.226 jmc 1215: Specifies the order in which the client should try authentication methods.
1.48 jmc 1216: This allows a client to prefer one method (e.g.\&
1.1 stevesk 1217: .Cm keyboard-interactive )
1.48 jmc 1218: over another method (e.g.\&
1.131 jmc 1219: .Cm password ) .
1220: The default is:
1221: .Bd -literal -offset indent
1222: gssapi-with-mic,hostbased,publickey,
1223: keyboard-interactive,password
1224: .Ed
1.1 stevesk 1225: .It Cm ProxyCommand
1226: Specifies the command to use to connect to the server.
1227: The command
1.190 djm 1228: string extends to the end of the line, and is executed
1229: using the user's shell
1230: .Ql exec
1231: directive to avoid a lingering shell process.
1232: .Pp
1.239 jmc 1233: Arguments to
1234: .Cm ProxyCommand
1235: accept the tokens described in the
1236: .Sx TOKENS
1237: section.
1.1 stevesk 1238: The command can be basically anything,
1239: and should read from its standard input and write to its standard output.
1240: It should eventually connect an
1241: .Xr sshd 8
1242: server running on some machine, or execute
1243: .Ic sshd -i
1244: somewhere.
1245: Host key management will be done using the
1.296 jmc 1246: .Cm Hostname
1247: of the host being connected (defaulting to the name typed by the user).
1.7 jmc 1248: Setting the command to
1.240 jmc 1249: .Cm none
1.6 markus 1250: disables this option entirely.
1.1 stevesk 1251: Note that
1252: .Cm CheckHostIP
1253: is not available for connects with a proxy command.
1.52 djm 1254: .Pp
1255: This directive is useful in conjunction with
1256: .Xr nc 1
1257: and its proxy support.
1.53 jmc 1258: For example, the following directive would connect via an HTTP proxy at
1.52 djm 1259: 192.0.2.0:
1260: .Bd -literal -offset 3n
1261: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1262: .Ed
1.233 djm 1263: .It Cm ProxyJump
1.260 millert 1264: Specifies one or more jump proxies as either
1.233 djm 1265: .Xo
1266: .Sm off
1.234 jmc 1267: .Op Ar user No @
1.233 djm 1268: .Ar host
1.234 jmc 1269: .Op : Ns Ar port
1.233 djm 1270: .Sm on
1.260 millert 1271: or an ssh URI
1.233 djm 1272: .Xc .
1.235 djm 1273: Multiple proxies may be separated by comma characters and will be visited
1.236 djm 1274: sequentially.
1.233 djm 1275: Setting this option will cause
1276: .Xr ssh 1
1277: to connect to the target host by first making a
1278: .Xr ssh 1
1279: connection to the specified
1280: .Cm ProxyJump
1281: host and then establishing a
1.234 jmc 1282: TCP forwarding to the ultimate target from there.
1.233 djm 1283: .Pp
1284: Note that this option will compete with the
1285: .Cm ProxyCommand
1286: option - whichever is specified first will prevent later instances of the
1287: other from taking effect.
1.289 djm 1288: .Pp
1289: Note also that the configuration for the destination host (either supplied
1290: via the command-line or the configuration file) is not generally applied
1291: to jump hosts.
1292: .Pa ~/.ssh/config
1293: should be used if specific configuration is required for jump hosts.
1.167 djm 1294: .It Cm ProxyUseFdpass
1.168 jmc 1295: Specifies that
1.167 djm 1296: .Cm ProxyCommand
1297: will pass a connected file descriptor back to
1.168 jmc 1298: .Xr ssh 1
1.167 djm 1299: instead of continuing to execute and pass data.
1300: The default is
1.240 jmc 1301: .Cm no .
1.213 markus 1302: .It Cm PubkeyAcceptedKeyTypes
1303: Specifies the key types that will be used for public key authentication
1.279 djm 1304: as a comma-separated list of patterns.
1.299 kn 1305: If the specified list begins with a
1.214 djm 1306: .Sq +
1307: character, then the key types after it will be appended to the default
1308: instead of replacing it.
1.299 kn 1309: If the specified list begins with a
1.241 djm 1310: .Sq -
1311: character, then the specified key types (including wildcards) will be removed
1312: from the default set instead of replacing them.
1.301 ! naddy 1313: If the specified list begins with a
! 1314: .Sq ^
! 1315: character, then the specified key types will be placed at the head of the
! 1316: default set.
1.213 markus 1317: The default for this option is:
1318: .Bd -literal -offset 3n
1319: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1320: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1321: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1322: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 1323: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 1324: ssh-rsa-cert-v01@openssh.com,
1325: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 1326: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 1327: .Ed
1328: .Pp
1.240 jmc 1329: The list of available key types may also be obtained using
1330: .Qq ssh -Q key .
1.1 stevesk 1331: .It Cm PubkeyAuthentication
1332: Specifies whether to try public key authentication.
1333: The argument to this keyword must be
1.240 jmc 1334: .Cm yes
1335: (the default)
1.1 stevesk 1336: or
1.240 jmc 1337: .Cm no .
1.75 dtucker 1338: .It Cm RekeyLimit
1339: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1340: session key is renegotiated, optionally followed a maximum amount of
1341: time that may pass before the session key is renegotiated.
1342: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1343: .Sq K ,
1344: .Sq M ,
1.75 dtucker 1345: or
1.76 jmc 1346: .Sq G
1.75 dtucker 1347: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1348: The default is between
1.84 jmc 1349: .Sq 1G
1.75 dtucker 1350: and
1.84 jmc 1351: .Sq 4G ,
1.75 dtucker 1352: depending on the cipher.
1.162 dtucker 1353: The optional second value is specified in seconds and may use any of the
1.293 schwarze 1354: units documented in the TIME FORMATS section of
1.162 dtucker 1355: .Xr sshd_config 5 .
1356: The default value for
1357: .Cm RekeyLimit
1358: is
1.240 jmc 1359: .Cm default none ,
1.162 dtucker 1360: which means that rekeying is performed after the cipher's default amount
1361: of data has been sent or received and no time based rekeying is done.
1.249 bluhm 1362: .It Cm RemoteCommand
1363: Specifies a command to execute on the remote machine after successfully
1364: connecting to the server.
1365: The command string extends to the end of the line, and is executed with
1366: the user's shell.
1.250 jmc 1367: Arguments to
1368: .Cm RemoteCommand
1369: accept the tokens described in the
1370: .Sx TOKENS
1371: section.
1.1 stevesk 1372: .It Cm RemoteForward
1.74 jmc 1373: Specifies that a TCP port on the remote machine be forwarded over
1.256 markus 1374: the secure channel.
1.273 djm 1375: The remote port may either be forwarded to a specified host and port
1.256 markus 1376: from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
1377: client to connect to arbitrary destinations from the local machine.
1.49 jmc 1378: The first argument must be
1.43 djm 1379: .Sm off
1.49 jmc 1380: .Oo Ar bind_address : Oc Ar port
1.43 djm 1381: .Sm on
1.256 markus 1382: If forwarding to a specific destination then the second argument must be
1383: .Ar host : Ns Ar hostport ,
1384: otherwise if no destination argument is specified then the remote forwarding
1385: will be established as a SOCKS proxy.
1386: .Pp
1.138 djm 1387: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.1 stevesk 1388: Multiple forwardings may be specified, and additional
1389: forwardings can be given on the command line.
1.113 stevesk 1390: Privileged ports can be forwarded only when
1391: logging in as root on the remote machine.
1.118 jmc 1392: .Pp
1.117 djm 1393: If the
1394: .Ar port
1.240 jmc 1395: argument is 0,
1.117 djm 1396: the listen port will be dynamically allocated on the server and reported
1397: to the client at run time.
1.43 djm 1398: .Pp
1399: If the
1400: .Ar bind_address
1401: is not specified, the default is to only bind to loopback addresses.
1402: If the
1403: .Ar bind_address
1404: is
1405: .Ql *
1406: or an empty string, then the forwarding is requested to listen on all
1407: interfaces.
1408: Specifying a remote
1409: .Ar bind_address
1.46 jmc 1410: will only succeed if the server's
1411: .Cm GatewayPorts
1.43 djm 1412: option is enabled (see
1.46 jmc 1413: .Xr sshd_config 5 ) .
1.149 djm 1414: .It Cm RequestTTY
1415: Specifies whether to request a pseudo-tty for the session.
1416: The argument may be one of:
1.240 jmc 1417: .Cm no
1.149 djm 1418: (never request a TTY),
1.240 jmc 1419: .Cm yes
1.149 djm 1420: (always request a TTY when standard input is a TTY),
1.240 jmc 1421: .Cm force
1.149 djm 1422: (always request a TTY) or
1.240 jmc 1423: .Cm auto
1.149 djm 1424: (request a TTY when opening a login session).
1425: This option mirrors the
1426: .Fl t
1427: and
1428: .Fl T
1429: flags for
1430: .Xr ssh 1 .
1.196 djm 1431: .It Cm RevokedHostKeys
1432: Specifies revoked host public keys.
1433: Keys listed in this file will be refused for host authentication.
1434: Note that if this file does not exist or is not readable,
1435: then host authentication will be refused for all hosts.
1436: Keys may be specified as a text file, listing one public key per line, or as
1437: an OpenSSH Key Revocation List (KRL) as generated by
1438: .Xr ssh-keygen 1 .
1439: For more information on KRLs, see the KEY REVOCATION LISTS section in
1440: .Xr ssh-keygen 1 .
1.32 djm 1441: .It Cm SendEnv
1442: Specifies what variables from the local
1443: .Xr environ 7
1444: should be sent to the server.
1.84 jmc 1445: The server must also support it, and the server must be configured to
1.33 djm 1446: accept these environment variables.
1.207 dtucker 1447: Note that the
1448: .Ev TERM
1.208 jmc 1449: environment variable is always sent whenever a
1.207 dtucker 1450: pseudo-terminal is requested as it is required by the protocol.
1.32 djm 1451: Refer to
1452: .Cm AcceptEnv
1453: in
1454: .Xr sshd_config 5
1455: for how to configure the server.
1.80 jmc 1456: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1457: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1458: across multiple
1459: .Cm SendEnv
1460: directives.
1.81 jmc 1461: .Pp
1462: See
1463: .Sx PATTERNS
1464: for more information on patterns.
1.271 djm 1465: .Pp
1.272 jmc 1466: It is possible to clear previously set
1.271 djm 1467: .Cm SendEnv
1468: variable names by prefixing patterns with
1469: .Pa - .
1470: The default is not to send any environment variables.
1.28 markus 1471: .It Cm ServerAliveCountMax
1.73 jmc 1472: Sets the number of server alive messages (see below) which may be
1.28 markus 1473: sent without
1.84 jmc 1474: .Xr ssh 1
1.28 markus 1475: receiving any messages back from the server.
1476: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1477: ssh will disconnect from the server, terminating the session.
1.28 markus 1478: It is important to note that the use of server alive messages is very
1479: different from
1480: .Cm TCPKeepAlive
1481: (below).
1482: The server alive messages are sent through the encrypted channel
1483: and therefore will not be spoofable.
1484: The TCP keepalive option enabled by
1485: .Cm TCPKeepAlive
1486: is spoofable.
1487: The server alive mechanism is valuable when the client or
1.298 dtucker 1488: server depend on knowing when a connection has become unresponsive.
1.28 markus 1489: .Pp
1490: The default value is 3.
1491: If, for example,
1492: .Cm ServerAliveInterval
1.84 jmc 1493: (see below) is set to 15 and
1.28 markus 1494: .Cm ServerAliveCountMax
1.84 jmc 1495: is left at the default, if the server becomes unresponsive,
1496: ssh will disconnect after approximately 45 seconds.
1.67 jmc 1497: .It Cm ServerAliveInterval
1498: Sets a timeout interval in seconds after which if no data has been received
1499: from the server,
1.84 jmc 1500: .Xr ssh 1
1.67 jmc 1501: will send a message through the encrypted
1502: channel to request a response from the server.
1503: The default
1504: is 0, indicating that these messages will not be sent to the server.
1.277 jmc 1505: .It Cm SetEnv
1506: Directly specify one or more environment variables and their contents to
1507: be sent to the server.
1508: Similarly to
1509: .Cm SendEnv ,
1510: the server must be prepared to accept the environment variable.
1.191 millert 1511: .It Cm StreamLocalBindMask
1512: Sets the octal file creation mode mask
1513: .Pq umask
1514: used when creating a Unix-domain socket file for local or remote
1515: port forwarding.
1516: This option is only used for port forwarding to a Unix-domain socket file.
1517: .Pp
1518: The default value is 0177, which creates a Unix-domain socket file that is
1519: readable and writable only by the owner.
1520: Note that not all operating systems honor the file mode on Unix-domain
1521: socket files.
1522: .It Cm StreamLocalBindUnlink
1523: Specifies whether to remove an existing Unix-domain socket file for local
1524: or remote port forwarding before creating a new one.
1525: If the socket file already exists and
1526: .Cm StreamLocalBindUnlink
1527: is not enabled,
1528: .Nm ssh
1529: will be unable to forward the port to the Unix-domain socket file.
1530: This option is only used for port forwarding to a Unix-domain socket file.
1531: .Pp
1532: The argument must be
1.240 jmc 1533: .Cm yes
1.191 millert 1534: or
1.240 jmc 1535: .Cm no
1536: (the default).
1.1 stevesk 1537: .It Cm StrictHostKeyChecking
1538: If this flag is set to
1.240 jmc 1539: .Cm yes ,
1.84 jmc 1540: .Xr ssh 1
1.1 stevesk 1541: will never automatically add host keys to the
1.50 djm 1542: .Pa ~/.ssh/known_hosts
1.1 stevesk 1543: file, and refuses to connect to hosts whose host key has changed.
1.263 dtucker 1544: This provides maximum protection against man-in-the-middle (MITM) attacks,
1.84 jmc 1545: though it can be annoying when the
1.1 stevesk 1546: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1547: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1548: frequently made.
1549: This option forces the user to manually
1550: add all new hosts.
1.255 jmc 1551: .Pp
1.1 stevesk 1552: If this flag is set to
1.254 djm 1553: .Dq accept-new
1.255 jmc 1554: then ssh will automatically add new host keys to the user
1.254 djm 1555: known hosts files, but will not permit connections to hosts with
1556: changed host keys.
1557: If this flag is set to
1558: .Dq no
1559: or
1560: .Dq off ,
1.255 jmc 1561: ssh will automatically add new host keys to the user known hosts files
1562: and allow connections to hosts with changed hostkeys to proceed,
1563: subject to some restrictions.
1.1 stevesk 1564: If this flag is set to
1.240 jmc 1565: .Cm ask
1566: (the default),
1.1 stevesk 1567: new host keys
1568: will be added to the user known host files only after the user
1569: has confirmed that is what they really want to do, and
1.84 jmc 1570: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1571: The host keys of
1572: known hosts will be verified automatically in all cases.
1.244 jmc 1573: .It Cm SyslogFacility
1574: Gives the facility code that is used when logging messages from
1575: .Xr ssh 1 .
1576: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1577: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1578: The default is USER.
1.26 markus 1579: .It Cm TCPKeepAlive
1580: Specifies whether the system should send TCP keepalive messages to the
1581: other side.
1582: If they are sent, death of the connection or crash of one
1583: of the machines will be properly noticed.
1584: However, this means that
1585: connections will die if the route is down temporarily, and some people
1586: find it annoying.
1587: .Pp
1588: The default is
1.240 jmc 1589: .Cm yes
1.26 markus 1590: (to send TCP keepalive messages), and the client will notice
1591: if the network goes down or the remote host dies.
1592: This is important in scripts, and many users want it too.
1593: .Pp
1594: To disable TCP keepalive messages, the value should be set to
1.240 jmc 1595: .Cm no .
1.265 djm 1596: See also
1597: .Cm ServerAliveInterval
1598: for protocol-level keepalives.
1.65 reyk 1599: .It Cm Tunnel
1.95 stevesk 1600: Request
1.65 reyk 1601: .Xr tun 4
1.69 jmc 1602: device forwarding between the client and the server.
1.65 reyk 1603: The argument must be
1.240 jmc 1604: .Cm yes ,
1605: .Cm point-to-point
1.95 stevesk 1606: (layer 3),
1.240 jmc 1607: .Cm ethernet
1.95 stevesk 1608: (layer 2),
1.65 reyk 1609: or
1.240 jmc 1610: .Cm no
1611: (the default).
1.95 stevesk 1612: Specifying
1.240 jmc 1613: .Cm yes
1.95 stevesk 1614: requests the default tunnel mode, which is
1.240 jmc 1615: .Cm point-to-point .
1.65 reyk 1616: .It Cm TunnelDevice
1.95 stevesk 1617: Specifies the
1.65 reyk 1618: .Xr tun 4
1.95 stevesk 1619: devices to open on the client
1620: .Pq Ar local_tun
1621: and the server
1622: .Pq Ar remote_tun .
1623: .Pp
1624: The argument must be
1625: .Sm off
1626: .Ar local_tun Op : Ar remote_tun .
1627: .Sm on
1628: The devices may be specified by numerical ID or the keyword
1.240 jmc 1629: .Cm any ,
1.95 stevesk 1630: which uses the next available tunnel device.
1631: If
1632: .Ar remote_tun
1633: is not specified, it defaults to
1.240 jmc 1634: .Cm any .
1.95 stevesk 1635: The default is
1.240 jmc 1636: .Cm any:any .
1.201 djm 1637: .It Cm UpdateHostKeys
1.200 djm 1638: Specifies whether
1639: .Xr ssh 1
1640: should accept notifications of additional hostkeys from the server sent
1641: after authentication has completed and add them to
1642: .Cm UserKnownHostsFile .
1643: The argument must be
1.240 jmc 1644: .Cm yes ,
1645: .Cm no
1.204 djm 1646: (the default) or
1.240 jmc 1647: .Cm ask .
1.200 djm 1648: Enabling this option allows learning alternate hostkeys for a server
1.201 djm 1649: and supports graceful key rotation by allowing a server to send replacement
1650: public keys before old ones are removed.
1.200 djm 1651: Additional hostkeys are only accepted if the key used to authenticate the
1.220 sobrado 1652: host was already trusted or explicitly accepted by the user.
1.204 djm 1653: If
1654: .Cm UpdateHostKeys
1655: is set to
1.240 jmc 1656: .Cm ask ,
1.204 djm 1657: then the user is asked to confirm the modifications to the known_hosts file.
1.205 djm 1658: Confirmation is currently incompatible with
1659: .Cm ControlPersist ,
1660: and will be disabled if it is enabled.
1.200 djm 1661: .Pp
1662: Presently, only
1663: .Xr sshd 8
1664: from OpenSSH 6.8 and greater support the
1.240 jmc 1665: .Qq hostkeys@openssh.com
1.200 djm 1666: protocol extension used to inform the client of all the server's hostkeys.
1.1 stevesk 1667: .It Cm User
1668: Specifies the user to log in as.
1669: This can be useful when a different user name is used on different machines.
1670: This saves the trouble of
1671: having to remember to give the user name on the command line.
1672: .It Cm UserKnownHostsFile
1.151 djm 1673: Specifies one or more files to use for the user
1674: host key database, separated by whitespace.
1675: The default is
1676: .Pa ~/.ssh/known_hosts ,
1677: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1678: .It Cm VerifyHostKeyDNS
1679: Specifies whether to verify the remote key using DNS and SSHFP resource
1680: records.
1.24 jakob 1681: If this option is set to
1.240 jmc 1682: .Cm yes ,
1.25 jmc 1683: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1684: from DNS.
1685: Insecure fingerprints will be handled as if this option was set to
1.240 jmc 1686: .Cm ask .
1.24 jakob 1687: If this option is set to
1.240 jmc 1688: .Cm ask ,
1.24 jakob 1689: information on fingerprint match will be displayed, but the user will still
1690: need to confirm new host keys according to the
1691: .Cm StrictHostKeyChecking
1692: option.
1.8 jakob 1693: The default is
1.240 jmc 1694: .Cm no .
1.84 jmc 1695: .Pp
1.240 jmc 1696: See also
1697: .Sx VERIFYING HOST KEYS
1698: in
1.84 jmc 1699: .Xr ssh 1 .
1.111 grunk 1700: .It Cm VisualHostKey
1701: If this flag is set to
1.240 jmc 1702: .Cm yes ,
1.111 grunk 1703: an ASCII art representation of the remote host key fingerprint is
1.197 djm 1704: printed in addition to the fingerprint string at login and
1.114 stevesk 1705: for unknown host keys.
1.111 grunk 1706: If this flag is set to
1.240 jmc 1707: .Cm no
1708: (the default),
1.114 stevesk 1709: no fingerprint strings are printed at login and
1.197 djm 1710: only the fingerprint string will be printed for unknown host keys.
1.1 stevesk 1711: .It Cm XAuthLocation
1.5 stevesk 1712: Specifies the full pathname of the
1.1 stevesk 1713: .Xr xauth 1
1714: program.
1715: The default is
1716: .Pa /usr/X11R6/bin/xauth .
1717: .El
1.86 jmc 1718: .Sh PATTERNS
1719: A
1720: .Em pattern
1721: consists of zero or more non-whitespace characters,
1722: .Sq *
1723: (a wildcard that matches zero or more characters),
1724: or
1725: .Sq ?\&
1726: (a wildcard that matches exactly one character).
1727: For example, to specify a set of declarations for any host in the
1.240 jmc 1728: .Qq .co.uk
1.86 jmc 1729: set of domains,
1730: the following pattern could be used:
1731: .Pp
1732: .Dl Host *.co.uk
1733: .Pp
1734: The following pattern
1735: would match any host in the 192.168.0.[0-9] network range:
1736: .Pp
1737: .Dl Host 192.168.0.?
1738: .Pp
1739: A
1740: .Em pattern-list
1741: is a comma-separated list of patterns.
1742: Patterns within pattern-lists may be negated
1743: by preceding them with an exclamation mark
1744: .Pq Sq !\& .
1745: For example,
1.174 djm 1746: to allow a key to be used from anywhere within an organization
1.86 jmc 1747: except from the
1.240 jmc 1748: .Qq dialup
1.86 jmc 1749: pool,
1750: the following entry (in authorized_keys) could be used:
1751: .Pp
1752: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.258 djm 1753: .Pp
1754: Note that a negated match will never produce a positive result by itself.
1755: For example, attempting to match
1756: .Qq host3
1757: against the following pattern-list will fail:
1758: .Pp
1759: .Dl from=\&"!host1,!host2\&"
1760: .Pp
1761: The solution here is to include a term that will yield a positive match,
1762: such as a wildcard:
1763: .Pp
1764: .Dl from=\&"!host1,!host2,*\&"
1.239 jmc 1765: .Sh TOKENS
1766: Arguments to some keywords can make use of tokens,
1767: which are expanded at runtime:
1768: .Pp
1769: .Bl -tag -width XXXX -offset indent -compact
1770: .It %%
1771: A literal
1772: .Sq % .
1773: .It \&%C
1.257 jmc 1774: Hash of %l%h%p%r.
1.239 jmc 1775: .It %d
1776: Local user's home directory.
1777: .It %h
1778: The remote hostname.
1779: .It %i
1780: The local user ID.
1781: .It %L
1782: The local hostname.
1783: .It %l
1784: The local hostname, including the domain name.
1785: .It %n
1786: The original remote hostname, as given on the command line.
1787: .It %p
1788: The remote port.
1789: .It %r
1790: The remote username.
1.261 djm 1791: .It \&%T
1792: The local
1793: .Xr tun 4
1794: or
1795: .Xr tap 4
1796: network interface assigned if
1.262 jmc 1797: tunnel forwarding was requested, or
1798: .Qq NONE
1.261 djm 1799: otherwise.
1.239 jmc 1800: .It %u
1801: The local username.
1802: .El
1803: .Pp
1804: .Cm Match exec
1.274 djm 1805: accepts the tokens %%, %h, %i, %L, %l, %n, %p, %r, and %u.
1.239 jmc 1806: .Pp
1807: .Cm CertificateFile
1.275 jmc 1808: accepts the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1809: .Pp
1810: .Cm ControlPath
1811: accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
1812: .Pp
1.295 jmc 1813: .Cm Hostname
1.239 jmc 1814: accepts the tokens %% and %h.
1815: .Pp
1816: .Cm IdentityAgent
1817: and
1818: .Cm IdentityFile
1.275 jmc 1819: accept the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1820: .Pp
1821: .Cm LocalCommand
1.275 jmc 1822: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, %T, and %u.
1.239 jmc 1823: .Pp
1824: .Cm ProxyCommand
1825: accepts the tokens %%, %h, %p, and %r.
1.250 jmc 1826: .Pp
1827: .Cm RemoteCommand
1.274 djm 1828: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, and %u.
1.1 stevesk 1829: .Sh FILES
1830: .Bl -tag -width Ds
1.50 djm 1831: .It Pa ~/.ssh/config
1.1 stevesk 1832: This is the per-user configuration file.
1833: The format of this file is described above.
1.84 jmc 1834: This file is used by the SSH client.
1.30 djm 1835: Because of the potential for abuse, this file must have strict permissions:
1.290 jmc 1836: read/write for the user, and not writable by others.
1.1 stevesk 1837: .It Pa /etc/ssh/ssh_config
1838: Systemwide configuration file.
1839: This file provides defaults for those
1840: values that are not specified in the user's configuration file, and
1841: for those users who do not have a configuration file.
1842: This file must be world-readable.
1843: .El
1.13 jmc 1844: .Sh SEE ALSO
1845: .Xr ssh 1
1.1 stevesk 1846: .Sh AUTHORS
1.240 jmc 1847: .An -nosplit
1.1 stevesk 1848: OpenSSH is a derivative of the original and free
1.240 jmc 1849: ssh 1.2.12 release by
1850: .An Tatu Ylonen .
1851: .An Aaron Campbell , Bob Beck , Markus Friedl ,
1852: .An Niels Provos , Theo de Raadt
1853: and
1854: .An Dug Song
1.1 stevesk 1855: removed many bugs, re-added newer features and
1856: created OpenSSH.
1.240 jmc 1857: .An Markus Friedl
1858: contributed the support for SSH protocol versions 1.5 and 2.0.
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