Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.281
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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1.281 ! kn 36: .\" $OpenBSD: ssh_config.5,v 1.280 2018/07/19 10:28:47 dtucker Exp $
! 37: .Dd $Mdocdate: July 19 2018 $
1.1 stevesk 38: .Dt SSH_CONFIG 5
39: .Os
40: .Sh NAME
41: .Nm ssh_config
42: .Nd OpenSSH SSH client configuration files
43: .Sh DESCRIPTION
1.84 jmc 44: .Xr ssh 1
1.1 stevesk 45: obtains configuration data from the following sources in
46: the following order:
1.79 jmc 47: .Pp
1.2 stevesk 48: .Bl -enum -offset indent -compact
49: .It
50: command-line options
51: .It
52: user's configuration file
1.50 djm 53: .Pq Pa ~/.ssh/config
1.2 stevesk 54: .It
55: system-wide configuration file
56: .Pq Pa /etc/ssh/ssh_config
57: .El
1.1 stevesk 58: .Pp
59: For each parameter, the first obtained value
60: will be used.
1.41 jmc 61: The configuration files contain sections separated by
1.240 jmc 62: .Cm Host
1.1 stevesk 63: specifications, and that section is only applied for hosts that
64: match one of the patterns given in the specification.
1.193 djm 65: The matched host name is usually the one given on the command line
66: (see the
67: .Cm CanonicalizeHostname
1.240 jmc 68: option for exceptions).
1.1 stevesk 69: .Pp
70: Since the first obtained value for each parameter is used, more
71: host-specific declarations should be given near the beginning of the
72: file, and general defaults at the end.
1.80 jmc 73: .Pp
1.240 jmc 74: The file contains keyword-argument pairs, one per line.
75: Lines starting with
1.1 stevesk 76: .Ql #
1.240 jmc 77: and empty lines are interpreted as comments.
78: Arguments may optionally be enclosed in double quotes
79: .Pq \&"
80: in order to represent arguments containing spaces.
1.1 stevesk 81: Configuration options may be separated by whitespace or
82: optional whitespace and exactly one
83: .Ql = ;
84: the latter format is useful to avoid the need to quote whitespace
85: when specifying configuration options using the
86: .Nm ssh ,
1.87 jmc 87: .Nm scp ,
1.1 stevesk 88: and
89: .Nm sftp
90: .Fl o
91: option.
92: .Pp
93: The possible
94: keywords and their meanings are as follows (note that
95: keywords are case-insensitive and arguments are case-sensitive):
96: .Bl -tag -width Ds
97: .It Cm Host
98: Restricts the following declarations (up to the next
99: .Cm Host
1.169 djm 100: or
101: .Cm Match
1.1 stevesk 102: keyword) to be only for those hosts that match one of the patterns
103: given after the keyword.
1.112 krw 104: If more than one pattern is provided, they should be separated by whitespace.
1.1 stevesk 105: A single
1.83 jmc 106: .Ql *
1.1 stevesk 107: as a pattern can be used to provide global
108: defaults for all hosts.
1.193 djm 109: The host is usually the
1.1 stevesk 110: .Ar hostname
1.193 djm 111: argument given on the command line
112: (see the
113: .Cm CanonicalizeHostname
1.240 jmc 114: keyword for exceptions).
1.148 djm 115: .Pp
116: A pattern entry may be negated by prefixing it with an exclamation mark
117: .Pq Sq !\& .
118: If a negated entry is matched, then the
119: .Cm Host
120: entry is ignored, regardless of whether any other patterns on the line
121: match.
122: Negated matches are therefore useful to provide exceptions for wildcard
123: matches.
1.81 jmc 124: .Pp
125: See
126: .Sx PATTERNS
127: for more information on patterns.
1.170 jmc 128: .It Cm Match
1.169 djm 129: Restricts the following declarations (up to the next
130: .Cm Host
131: or
132: .Cm Match
133: keyword) to be used only when the conditions following the
134: .Cm Match
135: keyword are satisfied.
1.220 sobrado 136: Match conditions are specified using one or more criteria
1.178 dtucker 137: or the single token
138: .Cm all
1.193 djm 139: which always matches.
140: The available criteria keywords are:
141: .Cm canonical ,
1.176 djm 142: .Cm exec ,
1.169 djm 143: .Cm host ,
144: .Cm originalhost ,
145: .Cm user ,
146: and
147: .Cm localuser .
1.193 djm 148: The
149: .Cm all
150: criteria must appear alone or immediately after
1.194 jmc 151: .Cm canonical .
1.193 djm 152: Other criteria may be combined arbitrarily.
153: All criteria but
154: .Cm all
155: and
156: .Cm canonical
157: require an argument.
158: Criteria may be negated by prepending an exclamation mark
159: .Pq Sq !\& .
1.169 djm 160: .Pp
1.177 jmc 161: The
1.193 djm 162: .Cm canonical
1.210 dtucker 163: keyword matches only when the configuration file is being re-parsed
1.193 djm 164: after hostname canonicalization (see the
165: .Cm CanonicalizeHostname
166: option.)
167: This may be useful to specify conditions that work with canonical host
168: names only.
169: The
1.176 djm 170: .Cm exec
1.177 jmc 171: keyword executes the specified command under the user's shell.
1.169 djm 172: If the command returns a zero exit status then the condition is considered true.
173: Commands containing whitespace characters must be quoted.
1.239 jmc 174: Arguments to
175: .Cm exec
176: accept the tokens described in the
177: .Sx TOKENS
178: section.
1.169 djm 179: .Pp
180: The other keywords' criteria must be single entries or comma-separated
181: lists and may use the wildcard and negation operators described in the
182: .Sx PATTERNS
183: section.
184: The criteria for the
185: .Cm host
186: keyword are matched against the target hostname, after any substitution
187: by the
188: .Cm Hostname
1.193 djm 189: or
190: .Cm CanonicalizeHostname
191: options.
1.169 djm 192: The
193: .Cm originalhost
194: keyword matches against the hostname as it was specified on the command-line.
195: The
196: .Cm user
197: keyword matches against the target username on the remote host.
198: The
199: .Cm localuser
200: keyword matches against the name of the local user running
201: .Xr ssh 1
202: (this keyword may be useful in system-wide
203: .Nm
204: files).
1.222 jcs 205: .It Cm AddKeysToAgent
206: Specifies whether keys should be automatically added to a running
1.223 jmc 207: .Xr ssh-agent 1 .
1.222 jcs 208: If this option is set to
1.240 jmc 209: .Cm yes
1.222 jcs 210: and a key is loaded from a file, the key and its passphrase are added to
211: the agent with the default lifetime, as if by
212: .Xr ssh-add 1 .
213: If this option is set to
1.240 jmc 214: .Cm ask ,
215: .Xr ssh 1
1.222 jcs 216: will require confirmation using the
217: .Ev SSH_ASKPASS
218: program before adding a key (see
219: .Xr ssh-add 1
220: for details).
221: If this option is set to
1.240 jmc 222: .Cm confirm ,
1.222 jcs 223: each use of the key must be confirmed, as if the
224: .Fl c
225: option was specified to
226: .Xr ssh-add 1 .
227: If this option is set to
1.240 jmc 228: .Cm no ,
1.222 jcs 229: no keys are added to the agent.
230: The argument must be
1.240 jmc 231: .Cm yes ,
232: .Cm confirm ,
233: .Cm ask ,
1.222 jcs 234: or
1.240 jmc 235: .Cm no
236: (the default).
1.10 djm 237: .It Cm AddressFamily
1.11 jmc 238: Specifies which address family to use when connecting.
239: Valid arguments are
1.240 jmc 240: .Cm any
241: (the default),
242: .Cm inet
1.84 jmc 243: (use IPv4 only), or
1.240 jmc 244: .Cm inet6
1.40 jmc 245: (use IPv6 only).
1.1 stevesk 246: .It Cm BatchMode
247: If set to
1.240 jmc 248: .Cm yes ,
1.1 stevesk 249: passphrase/password querying will be disabled.
250: This option is useful in scripts and other batch jobs where no user
251: is present to supply the password.
252: The argument must be
1.240 jmc 253: .Cm yes
1.1 stevesk 254: or
1.240 jmc 255: .Cm no
256: (the default).
1.268 jmc 257: .It Cm BindAddress
258: Use the specified address on the local machine as the source address of
259: the connection.
260: Only useful on systems with more than one address.
261: .It Cm BindInterface
262: Use the address of the specified interface on the local machine as the
263: source address of the connection.
1.171 djm 264: .It Cm CanonicalDomains
1.172 jmc 265: When
1.173 djm 266: .Cm CanonicalizeHostname
1.171 djm 267: is enabled, this option specifies the list of domain suffixes in which to
268: search for the specified destination host.
1.173 djm 269: .It Cm CanonicalizeFallbackLocal
1.174 djm 270: Specifies whether to fail with an error when hostname canonicalization fails.
1.172 jmc 271: The default,
1.240 jmc 272: .Cm yes ,
1.172 jmc 273: will attempt to look up the unqualified hostname using the system resolver's
1.171 djm 274: search rules.
275: A value of
1.240 jmc 276: .Cm no
1.171 djm 277: will cause
278: .Xr ssh 1
279: to fail instantly if
1.173 djm 280: .Cm CanonicalizeHostname
1.171 djm 281: is enabled and the target hostname cannot be found in any of the domains
282: specified by
283: .Cm CanonicalDomains .
1.173 djm 284: .It Cm CanonicalizeHostname
1.174 djm 285: Controls whether explicit hostname canonicalization is performed.
1.172 jmc 286: The default,
1.240 jmc 287: .Cm no ,
1.171 djm 288: is not to perform any name rewriting and let the system resolver handle all
289: hostname lookups.
290: If set to
1.240 jmc 291: .Cm yes
1.171 djm 292: then, for connections that do not use a
293: .Cm ProxyCommand ,
294: .Xr ssh 1
1.173 djm 295: will attempt to canonicalize the hostname specified on the command line
1.171 djm 296: using the
297: .Cm CanonicalDomains
298: suffixes and
1.173 djm 299: .Cm CanonicalizePermittedCNAMEs
1.171 djm 300: rules.
301: If
1.173 djm 302: .Cm CanonicalizeHostname
1.171 djm 303: is set to
1.240 jmc 304: .Cm always ,
1.174 djm 305: then canonicalization is applied to proxied connections too.
1.185 djm 306: .Pp
1.193 djm 307: If this option is enabled, then the configuration files are processed
308: again using the new target name to pick up any new configuration in matching
1.185 djm 309: .Cm Host
1.193 djm 310: and
311: .Cm Match
1.185 djm 312: stanzas.
1.173 djm 313: .It Cm CanonicalizeMaxDots
1.172 jmc 314: Specifies the maximum number of dot characters in a hostname before
1.174 djm 315: canonicalization is disabled.
1.240 jmc 316: The default, 1,
1.172 jmc 317: allows a single dot (i.e. hostname.subdomain).
1.173 djm 318: .It Cm CanonicalizePermittedCNAMEs
1.172 jmc 319: Specifies rules to determine whether CNAMEs should be followed when
1.173 djm 320: canonicalizing hostnames.
1.171 djm 321: The rules consist of one or more arguments of
1.172 jmc 322: .Ar source_domain_list : Ns Ar target_domain_list ,
1.171 djm 323: where
324: .Ar source_domain_list
1.174 djm 325: is a pattern-list of domains that may follow CNAMEs in canonicalization,
1.171 djm 326: and
327: .Ar target_domain_list
1.172 jmc 328: is a pattern-list of domains that they may resolve to.
1.171 djm 329: .Pp
330: For example,
1.240 jmc 331: .Qq *.a.example.com:*.b.example.com,*.c.example.com
1.171 djm 332: will allow hostnames matching
1.240 jmc 333: .Qq *.a.example.com
1.173 djm 334: to be canonicalized to names in the
1.240 jmc 335: .Qq *.b.example.com
1.171 djm 336: or
1.240 jmc 337: .Qq *.c.example.com
1.171 djm 338: domains.
1.221 djm 339: .It Cm CertificateFile
340: Specifies a file from which the user's certificate is read.
341: A corresponding private key must be provided separately in order
342: to use this certificate either
343: from an
344: .Cm IdentityFile
345: directive or
346: .Fl i
347: flag to
348: .Xr ssh 1 ,
349: via
350: .Xr ssh-agent 1 ,
351: or via a
352: .Cm PKCS11Provider .
353: .Pp
1.239 jmc 354: Arguments to
355: .Cm CertificateFile
356: may use the tilde syntax to refer to a user's home directory
357: or the tokens described in the
358: .Sx TOKENS
359: section.
1.221 djm 360: .Pp
361: It is possible to have multiple certificate files specified in
362: configuration files; these certificates will be tried in sequence.
363: Multiple
364: .Cm CertificateFile
365: directives will add to the list of certificates used for
366: authentication.
1.1 stevesk 367: .It Cm ChallengeResponseAuthentication
1.82 jmc 368: Specifies whether to use challenge-response authentication.
1.1 stevesk 369: The argument to this keyword must be
1.240 jmc 370: .Cm yes
371: (the default)
1.1 stevesk 372: or
1.240 jmc 373: .Cm no .
1.1 stevesk 374: .It Cm CheckHostIP
1.240 jmc 375: If set to
376: .Cm yes
377: (the default),
1.84 jmc 378: .Xr ssh 1
379: will additionally check the host IP address in the
1.1 stevesk 380: .Pa known_hosts
381: file.
1.240 jmc 382: This allows it to detect if a host key changed due to DNS spoofing
1.211 djm 383: and will add addresses of destination hosts to
384: .Pa ~/.ssh/known_hosts
385: in the process, regardless of the setting of
386: .Cm StrictHostKeyChecking .
1.107 grunk 387: If the option is set to
1.240 jmc 388: .Cm no ,
1.1 stevesk 389: the check will not be executed.
390: .It Cm Ciphers
1.245 djm 391: Specifies the ciphers allowed and their order of preference.
1.1 stevesk 392: Multiple ciphers must be comma-separated.
1.214 djm 393: If the specified value begins with a
394: .Sq +
395: character, then the specified ciphers will be appended to the default set
396: instead of replacing them.
1.241 djm 397: If the specified value begins with a
398: .Sq -
399: character, then the specified ciphers (including wildcards) will be removed
400: from the default set instead of replacing them.
1.214 djm 401: .Pp
1.180 djm 402: The supported ciphers are:
1.240 jmc 403: .Bd -literal -offset indent
1.186 naddy 404: 3des-cbc
405: aes128-cbc
406: aes192-cbc
407: aes256-cbc
408: aes128-ctr
409: aes192-ctr
410: aes256-ctr
411: aes128-gcm@openssh.com
412: aes256-gcm@openssh.com
413: chacha20-poly1305@openssh.com
1.240 jmc 414: .Ed
1.180 djm 415: .Pp
1.84 jmc 416: The default is:
1.186 naddy 417: .Bd -literal -offset indent
1.215 jmc 418: chacha20-poly1305@openssh.com,
1.186 naddy 419: aes128-ctr,aes192-ctr,aes256-ctr,
1.270 djm 420: aes128-gcm@openssh.com,aes256-gcm@openssh.com
1.1 stevesk 421: .Ed
1.180 djm 422: .Pp
1.240 jmc 423: The list of available ciphers may also be obtained using
424: .Qq ssh -Q cipher .
1.1 stevesk 425: .It Cm ClearAllForwardings
1.84 jmc 426: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 427: specified in the configuration files or on the command line be
1.7 jmc 428: cleared.
429: This option is primarily useful when used from the
1.84 jmc 430: .Xr ssh 1
1.1 stevesk 431: command line to clear port forwardings set in
432: configuration files, and is automatically set by
433: .Xr scp 1
434: and
435: .Xr sftp 1 .
436: The argument must be
1.240 jmc 437: .Cm yes
1.1 stevesk 438: or
1.240 jmc 439: .Cm no
440: (the default).
1.1 stevesk 441: .It Cm Compression
442: Specifies whether to use compression.
443: The argument must be
1.240 jmc 444: .Cm yes
1.1 stevesk 445: or
1.240 jmc 446: .Cm no
447: (the default).
1.247 naddy 448: .It Cm ConnectionAttempts
449: Specifies the number of tries (one per second) to make before exiting.
450: The argument must be an integer.
451: This may be useful in scripts if the connection sometimes fails.
452: The default is 1.
1.9 djm 453: .It Cm ConnectTimeout
1.84 jmc 454: Specifies the timeout (in seconds) used when connecting to the
455: SSH server, instead of using the default system TCP timeout.
1.11 jmc 456: This value is used only when the target is down or really unreachable,
457: not when it refuses the connection.
1.36 djm 458: .It Cm ControlMaster
459: Enables the sharing of multiple sessions over a single network connection.
460: When set to
1.240 jmc 461: .Cm yes ,
1.84 jmc 462: .Xr ssh 1
1.36 djm 463: will listen for connections on a control socket specified using the
464: .Cm ControlPath
465: argument.
466: Additional sessions can connect to this socket using the same
467: .Cm ControlPath
468: with
469: .Cm ControlMaster
470: set to
1.240 jmc 471: .Cm no
1.38 jmc 472: (the default).
1.64 jmc 473: These sessions will try to reuse the master instance's network connection
1.63 djm 474: rather than initiating new ones, but will fall back to connecting normally
475: if the control socket does not exist, or is not listening.
476: .Pp
1.37 djm 477: Setting this to
1.240 jmc 478: .Cm ask
479: will cause
480: .Xr ssh 1
1.206 jmc 481: to listen for control connections, but require confirmation using
482: .Xr ssh-askpass 1 .
1.51 jakob 483: If the
484: .Cm ControlPath
1.84 jmc 485: cannot be opened,
1.240 jmc 486: .Xr ssh 1
487: will continue without connecting to a master instance.
1.58 djm 488: .Pp
489: X11 and
1.59 jmc 490: .Xr ssh-agent 1
1.58 djm 491: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 492: display and agent forwarded will be the one belonging to the master
1.59 jmc 493: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 494: .Pp
495: Two additional options allow for opportunistic multiplexing: try to use a
496: master connection but fall back to creating a new one if one does not already
497: exist.
498: These options are:
1.240 jmc 499: .Cm auto
1.56 djm 500: and
1.240 jmc 501: .Cm autoask .
1.56 djm 502: The latter requires confirmation like the
1.240 jmc 503: .Cm ask
1.56 djm 504: option.
1.36 djm 505: .It Cm ControlPath
1.55 djm 506: Specify the path to the control socket used for connection sharing as described
507: in the
1.36 djm 508: .Cm ControlMaster
1.57 djm 509: section above or the string
1.240 jmc 510: .Cm none
1.57 djm 511: to disable connection sharing.
1.239 jmc 512: Arguments to
513: .Cm ControlPath
514: may use the tilde syntax to refer to a user's home directory
515: or the tokens described in the
516: .Sx TOKENS
517: section.
1.56 djm 518: It is recommended that any
519: .Cm ControlPath
520: used for opportunistic connection sharing include
1.195 djm 521: at least %h, %p, and %r (or alternatively %C) and be placed in a directory
522: that is not writable by other users.
1.56 djm 523: This ensures that shared connections are uniquely identified.
1.137 djm 524: .It Cm ControlPersist
525: When used in conjunction with
526: .Cm ControlMaster ,
527: specifies that the master connection should remain open
528: in the background (waiting for future client connections)
529: after the initial client connection has been closed.
530: If set to
1.240 jmc 531: .Cm no ,
1.137 djm 532: then the master connection will not be placed into the background,
533: and will close as soon as the initial client connection is closed.
534: If set to
1.240 jmc 535: .Cm yes
536: or 0,
1.137 djm 537: then the master connection will remain in the background indefinitely
538: (until killed or closed via a mechanism such as the
1.240 jmc 539: .Qq ssh -O exit ) .
1.137 djm 540: If set to a time in seconds, or a time in any of the formats documented in
541: .Xr sshd_config 5 ,
542: then the backgrounded master connection will automatically terminate
543: after it has remained idle (with no client connections) for the
544: specified time.
1.38 jmc 545: .It Cm DynamicForward
1.74 jmc 546: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 547: over the secure channel, and the application
548: protocol is then used to determine where to connect to from the
549: remote machine.
1.62 djm 550: .Pp
551: The argument must be
552: .Sm off
553: .Oo Ar bind_address : Oc Ar port .
554: .Sm on
1.138 djm 555: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 556: By default, the local port is bound in accordance with the
557: .Cm GatewayPorts
558: setting.
559: However, an explicit
560: .Ar bind_address
561: may be used to bind the connection to a specific address.
562: The
563: .Ar bind_address
564: of
1.240 jmc 565: .Cm localhost
1.62 djm 566: indicates that the listening port be bound for local use only, while an
567: empty address or
568: .Sq *
569: indicates that the port should be available from all interfaces.
570: .Pp
1.38 jmc 571: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 572: .Xr ssh 1
1.38 jmc 573: will act as a SOCKS server.
574: Multiple forwardings may be specified, and
575: additional forwardings can be given on the command line.
576: Only the superuser can forward privileged ports.
1.14 markus 577: .It Cm EnableSSHKeysign
578: Setting this option to
1.240 jmc 579: .Cm yes
1.14 markus 580: in the global client configuration file
581: .Pa /etc/ssh/ssh_config
582: enables the use of the helper program
583: .Xr ssh-keysign 8
584: during
585: .Cm HostbasedAuthentication .
586: The argument must be
1.240 jmc 587: .Cm yes
1.14 markus 588: or
1.240 jmc 589: .Cm no
590: (the default).
1.23 jmc 591: This option should be placed in the non-hostspecific section.
1.14 markus 592: See
593: .Xr ssh-keysign 8
594: for more information.
1.1 stevesk 595: .It Cm EscapeChar
596: Sets the escape character (default:
597: .Ql ~ ) .
598: The escape character can also
599: be set on the command line.
600: The argument should be a single character,
601: .Ql ^
602: followed by a letter, or
1.240 jmc 603: .Cm none
1.1 stevesk 604: to disable the escape
605: character entirely (making the connection transparent for binary
606: data).
1.96 markus 607: .It Cm ExitOnForwardFailure
608: Specifies whether
609: .Xr ssh 1
610: should terminate the connection if it cannot set up all requested
1.216 djm 611: dynamic, tunnel, local, and remote port forwardings, (e.g.\&
1.217 jmc 612: if either end is unable to bind and listen on a specified port).
1.216 djm 613: Note that
614: .Cm ExitOnForwardFailure
615: does not apply to connections made over port forwardings and will not,
616: for example, cause
617: .Xr ssh 1
618: to exit if TCP connections to the ultimate forwarding destination fail.
1.96 markus 619: The argument must be
1.240 jmc 620: .Cm yes
1.96 markus 621: or
1.240 jmc 622: .Cm no
623: (the default).
1.197 djm 624: .It Cm FingerprintHash
625: Specifies the hash algorithm used when displaying key fingerprints.
626: Valid options are:
1.240 jmc 627: .Cm md5
1.197 djm 628: and
1.240 jmc 629: .Cm sha256
630: (the default).
1.1 stevesk 631: .It Cm ForwardAgent
632: Specifies whether the connection to the authentication agent (if any)
633: will be forwarded to the remote machine.
634: The argument must be
1.240 jmc 635: .Cm yes
1.1 stevesk 636: or
1.240 jmc 637: .Cm no
638: (the default).
1.3 stevesk 639: .Pp
1.7 jmc 640: Agent forwarding should be enabled with caution.
641: Users with the ability to bypass file permissions on the remote host
642: (for the agent's Unix-domain socket)
643: can access the local agent through the forwarded connection.
644: An attacker cannot obtain key material from the agent,
1.3 stevesk 645: however they can perform operations on the keys that enable them to
646: authenticate using the identities loaded into the agent.
1.1 stevesk 647: .It Cm ForwardX11
648: Specifies whether X11 connections will be automatically redirected
649: over the secure channel and
650: .Ev DISPLAY
651: set.
652: The argument must be
1.240 jmc 653: .Cm yes
1.1 stevesk 654: or
1.240 jmc 655: .Cm no
656: (the default).
1.3 stevesk 657: .Pp
1.7 jmc 658: X11 forwarding should be enabled with caution.
659: Users with the ability to bypass file permissions on the remote host
1.22 markus 660: (for the user's X11 authorization database)
1.7 jmc 661: can access the local X11 display through the forwarded connection.
1.22 markus 662: An attacker may then be able to perform activities such as keystroke monitoring
663: if the
664: .Cm ForwardX11Trusted
665: option is also enabled.
1.134 djm 666: .It Cm ForwardX11Timeout
1.135 jmc 667: Specify a timeout for untrusted X11 forwarding
668: using the format described in the
1.240 jmc 669: .Sx TIME FORMATS
670: section of
1.134 djm 671: .Xr sshd_config 5 .
672: X11 connections received by
673: .Xr ssh 1
674: after this time will be refused.
675: The default is to disable untrusted X11 forwarding after twenty minutes has
676: elapsed.
1.22 markus 677: .It Cm ForwardX11Trusted
1.34 jmc 678: If this option is set to
1.240 jmc 679: .Cm yes ,
1.84 jmc 680: remote X11 clients will have full access to the original X11 display.
1.42 djm 681: .Pp
1.22 markus 682: If this option is set to
1.240 jmc 683: .Cm no
684: (the default),
1.84 jmc 685: remote X11 clients will be considered untrusted and prevented
1.22 markus 686: from stealing or tampering with data belonging to trusted X11
687: clients.
1.42 djm 688: Furthermore, the
689: .Xr xauth 1
690: token used for the session will be set to expire after 20 minutes.
691: Remote clients will be refused access after this time.
1.22 markus 692: .Pp
693: See the X11 SECURITY extension specification for full details on
694: the restrictions imposed on untrusted clients.
1.1 stevesk 695: .It Cm GatewayPorts
696: Specifies whether remote hosts are allowed to connect to local
697: forwarded ports.
698: By default,
1.84 jmc 699: .Xr ssh 1
1.7 jmc 700: binds local port forwardings to the loopback address.
701: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 702: .Cm GatewayPorts
1.84 jmc 703: can be used to specify that ssh
1.1 stevesk 704: should bind local port forwardings to the wildcard address,
705: thus allowing remote hosts to connect to forwarded ports.
706: The argument must be
1.240 jmc 707: .Cm yes
1.1 stevesk 708: or
1.240 jmc 709: .Cm no
710: (the default).
1.1 stevesk 711: .It Cm GlobalKnownHostsFile
1.151 djm 712: Specifies one or more files to use for the global
713: host key database, separated by whitespace.
714: The default is
715: .Pa /etc/ssh/ssh_known_hosts ,
716: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 717: .It Cm GSSAPIAuthentication
1.27 markus 718: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 719: The default is
1.240 jmc 720: .Cm no .
1.18 markus 721: .It Cm GSSAPIDelegateCredentials
722: Forward (delegate) credentials to the server.
723: The default is
1.240 jmc 724: .Cm no .
1.44 djm 725: .It Cm HashKnownHosts
726: Indicates that
1.84 jmc 727: .Xr ssh 1
1.44 djm 728: should hash host names and addresses when they are added to
1.50 djm 729: .Pa ~/.ssh/known_hosts .
1.44 djm 730: These hashed names may be used normally by
1.84 jmc 731: .Xr ssh 1
1.44 djm 732: and
1.84 jmc 733: .Xr sshd 8 ,
1.44 djm 734: but they do not reveal identifying information should the file's contents
735: be disclosed.
736: The default is
1.240 jmc 737: .Cm no .
1.97 jmc 738: Note that existing names and addresses in known hosts files
739: will not be converted automatically,
740: but may be manually hashed using
1.45 djm 741: .Xr ssh-keygen 1 .
1.1 stevesk 742: .It Cm HostbasedAuthentication
743: Specifies whether to try rhosts based authentication with public key
744: authentication.
745: The argument must be
1.240 jmc 746: .Cm yes
1.1 stevesk 747: or
1.240 jmc 748: .Cm no
749: (the default).
1.202 djm 750: .It Cm HostbasedKeyTypes
751: Specifies the key types that will be used for hostbased authentication
1.279 djm 752: as a comma-separated list of patterns.
1.214 djm 753: Alternately if the specified value begins with a
754: .Sq +
755: character, then the specified key types will be appended to the default set
756: instead of replacing them.
1.241 djm 757: If the specified value begins with a
758: .Sq -
759: character, then the specified key types (including wildcards) will be removed
760: from the default set instead of replacing them.
1.213 markus 761: The default for this option is:
762: .Bd -literal -offset 3n
763: ecdsa-sha2-nistp256-cert-v01@openssh.com,
764: ecdsa-sha2-nistp384-cert-v01@openssh.com,
765: ecdsa-sha2-nistp521-cert-v01@openssh.com,
766: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 767: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 768: ssh-rsa-cert-v01@openssh.com,
769: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 770: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 771: .Ed
772: .Pp
1.202 djm 773: The
774: .Fl Q
775: option of
776: .Xr ssh 1
777: may be used to list supported key types.
1.1 stevesk 778: .It Cm HostKeyAlgorithms
1.226 jmc 779: Specifies the host key algorithms
1.1 stevesk 780: that the client wants to use in order of preference.
1.214 djm 781: Alternately if the specified value begins with a
782: .Sq +
783: character, then the specified key types will be appended to the default set
784: instead of replacing them.
1.241 djm 785: If the specified value begins with a
786: .Sq -
787: character, then the specified key types (including wildcards) will be removed
788: from the default set instead of replacing them.
1.1 stevesk 789: The default for this option is:
1.139 djm 790: .Bd -literal -offset 3n
791: ecdsa-sha2-nistp256-cert-v01@openssh.com,
792: ecdsa-sha2-nistp384-cert-v01@openssh.com,
793: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1.183 naddy 794: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 795: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 796: ssh-rsa-cert-v01@openssh.com,
1.139 djm 797: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 798: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.139 djm 799: .Ed
1.145 djm 800: .Pp
801: If hostkeys are known for the destination host then this default is modified
802: to prefer their algorithms.
1.198 djm 803: .Pp
1.240 jmc 804: The list of available key types may also be obtained using
805: .Qq ssh -Q key .
1.1 stevesk 806: .It Cm HostKeyAlias
807: Specifies an alias that should be used instead of the
808: real host name when looking up or saving the host key
1.251 djm 809: in the host key database files and when validating host certificates.
1.84 jmc 810: This option is useful for tunneling SSH connections
1.1 stevesk 811: or for multiple servers running on a single host.
812: .It Cm HostName
813: Specifies the real host name to log into.
814: This can be used to specify nicknames or abbreviations for hosts.
1.239 jmc 815: Arguments to
816: .Cm HostName
817: accept the tokens described in the
818: .Sx TOKENS
819: section.
1.1 stevesk 820: Numeric IP addresses are also permitted (both on the command line and in
821: .Cm HostName
822: specifications).
1.239 jmc 823: The default is the name given on the command line.
1.29 markus 824: .It Cm IdentitiesOnly
825: Specifies that
1.84 jmc 826: .Xr ssh 1
1.221 djm 827: should only use the authentication identity and certificate files explicitly
828: configured in the
1.31 jmc 829: .Nm
1.221 djm 830: files
831: or passed on the
832: .Xr ssh 1
833: command-line,
1.84 jmc 834: even if
835: .Xr ssh-agent 1
1.159 djm 836: or a
837: .Cm PKCS11Provider
1.29 markus 838: offers more identities.
839: The argument to this keyword must be
1.240 jmc 840: .Cm yes
1.29 markus 841: or
1.240 jmc 842: .Cm no
843: (the default).
1.84 jmc 844: This option is intended for situations where ssh-agent
1.29 markus 845: offers many different identities.
1.231 markus 846: .It Cm IdentityAgent
847: Specifies the
848: .Ux Ns -domain
849: socket used to communicate with the authentication agent.
850: .Pp
851: This option overrides the
1.240 jmc 852: .Ev SSH_AUTH_SOCK
1.231 markus 853: environment variable and can be used to select a specific agent.
854: Setting the socket name to
1.240 jmc 855: .Cm none
1.231 markus 856: disables the use of an authentication agent.
1.232 markus 857: If the string
1.240 jmc 858: .Qq SSH_AUTH_SOCK
1.232 markus 859: is specified, the location of the socket will be read from the
860: .Ev SSH_AUTH_SOCK
861: environment variable.
1.231 markus 862: .Pp
1.239 jmc 863: Arguments to
864: .Cm IdentityAgent
865: may use the tilde syntax to refer to a user's home directory
866: or the tokens described in the
867: .Sx TOKENS
868: section.
1.67 jmc 869: .It Cm IdentityFile
1.192 sobrado 870: Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA authentication
1.139 djm 871: identity is read.
1.67 jmc 872: The default is
1.139 djm 873: .Pa ~/.ssh/id_dsa ,
1.183 naddy 874: .Pa ~/.ssh/id_ecdsa ,
875: .Pa ~/.ssh/id_ed25519
1.139 djm 876: and
1.245 djm 877: .Pa ~/.ssh/id_rsa .
1.67 jmc 878: Additionally, any identities represented by the authentication agent
1.165 djm 879: will be used for authentication unless
880: .Cm IdentitiesOnly
881: is set.
1.221 djm 882: If no certificates have been explicitly specified by
883: .Cm CertificateFile ,
1.129 djm 884: .Xr ssh 1
885: will try to load certificate information from the filename obtained by
886: appending
887: .Pa -cert.pub
888: to the path of a specified
889: .Cm IdentityFile .
1.90 djm 890: .Pp
1.239 jmc 891: Arguments to
892: .Cm IdentityFile
893: may use the tilde syntax to refer to a user's home directory
894: or the tokens described in the
895: .Sx TOKENS
896: section.
1.90 djm 897: .Pp
1.67 jmc 898: It is possible to have
899: multiple identity files specified in configuration files; all these
900: identities will be tried in sequence.
1.152 djm 901: Multiple
902: .Cm IdentityFile
903: directives will add to the list of identities tried (this behaviour
904: differs from that of other configuration directives).
1.165 djm 905: .Pp
906: .Cm IdentityFile
907: may be used in conjunction with
908: .Cm IdentitiesOnly
909: to select which identities in an agent are offered during authentication.
1.221 djm 910: .Cm IdentityFile
911: may also be used in conjunction with
912: .Cm CertificateFile
913: in order to provide any certificate also needed for authentication with
914: the identity.
1.164 jmc 915: .It Cm IgnoreUnknown
916: Specifies a pattern-list of unknown options to be ignored if they are
917: encountered in configuration parsing.
918: This may be used to suppress errors if
919: .Nm
920: contains options that are unrecognised by
921: .Xr ssh 1 .
922: It is recommended that
923: .Cm IgnoreUnknown
924: be listed early in the configuration file as it will not be applied
925: to unknown options that appear before it.
1.229 djm 926: .It Cm Include
927: Include the specified configuration file(s).
1.230 jmc 928: Multiple pathnames may be specified and each pathname may contain
1.281 ! kn 929: .Xr glob 7
1.229 djm 930: wildcards and, for user configurations, shell-like
1.240 jmc 931: .Sq ~
1.229 djm 932: references to user home directories.
933: Files without absolute paths are assumed to be in
934: .Pa ~/.ssh
1.230 jmc 935: if included in a user configuration file or
1.229 djm 936: .Pa /etc/ssh
937: if included from the system configuration file.
938: .Cm Include
939: directive may appear inside a
940: .Cm Match
941: or
942: .Cm Host
943: block
944: to perform conditional inclusion.
1.143 djm 945: .It Cm IPQoS
946: Specifies the IPv4 type-of-service or DSCP class for connections.
947: Accepted values are
1.240 jmc 948: .Cm af11 ,
949: .Cm af12 ,
950: .Cm af13 ,
951: .Cm af21 ,
952: .Cm af22 ,
953: .Cm af23 ,
954: .Cm af31 ,
955: .Cm af32 ,
956: .Cm af33 ,
957: .Cm af41 ,
958: .Cm af42 ,
959: .Cm af43 ,
960: .Cm cs0 ,
961: .Cm cs1 ,
962: .Cm cs2 ,
963: .Cm cs3 ,
964: .Cm cs4 ,
965: .Cm cs5 ,
966: .Cm cs6 ,
967: .Cm cs7 ,
968: .Cm ef ,
969: .Cm lowdelay ,
970: .Cm throughput ,
971: .Cm reliability ,
1.253 djm 972: a numeric value, or
973: .Cm none
974: to use the operating system default.
1.146 djm 975: This option may take one or two arguments, separated by whitespace.
1.143 djm 976: If one argument is specified, it is used as the packet class unconditionally.
977: If two values are specified, the first is automatically selected for
978: interactive sessions and the second for non-interactive sessions.
979: The default is
1.269 job 980: .Cm af21
1.272 jmc 981: (Low-Latency Data)
1.143 djm 982: for interactive sessions and
1.269 job 983: .Cm cs1
1.272 jmc 984: (Lower Effort)
1.143 djm 985: for non-interactive sessions.
1.103 djm 986: .It Cm KbdInteractiveAuthentication
987: Specifies whether to use keyboard-interactive authentication.
988: The argument to this keyword must be
1.240 jmc 989: .Cm yes
990: (the default)
1.103 djm 991: or
1.240 jmc 992: .Cm no .
1.39 djm 993: .It Cm KbdInteractiveDevices
994: Specifies the list of methods to use in keyboard-interactive authentication.
995: Multiple method names must be comma-separated.
996: The default is to use the server specified list.
1.85 jmc 997: The methods available vary depending on what the server supports.
998: For an OpenSSH server,
999: it may be zero or more of:
1.240 jmc 1000: .Cm bsdauth ,
1001: .Cm pam ,
1.85 jmc 1002: and
1.240 jmc 1003: .Cm skey .
1.140 djm 1004: .It Cm KexAlgorithms
1005: Specifies the available KEX (Key Exchange) algorithms.
1006: Multiple algorithms must be comma-separated.
1.214 djm 1007: Alternately if the specified value begins with a
1008: .Sq +
1009: character, then the specified methods will be appended to the default set
1010: instead of replacing them.
1.241 djm 1011: If the specified value begins with a
1012: .Sq -
1013: character, then the specified methods (including wildcards) will be removed
1014: from the default set instead of replacing them.
1.141 jmc 1015: The default is:
1016: .Bd -literal -offset indent
1.238 djm 1017: curve25519-sha256,curve25519-sha256@libssh.org,
1.141 jmc 1018: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1019: diffie-hellman-group-exchange-sha256,
1.266 djm 1020: diffie-hellman-group16-sha512,
1021: diffie-hellman-group18-sha512,
1.209 dtucker 1022: diffie-hellman-group-exchange-sha1,
1.266 djm 1023: diffie-hellman-group14-sha256,
1.212 djm 1024: diffie-hellman-group14-sha1
1.141 jmc 1025: .Ed
1.198 djm 1026: .Pp
1.240 jmc 1027: The list of available key exchange algorithms may also be obtained using
1028: .Qq ssh -Q kex .
1.65 reyk 1029: .It Cm LocalCommand
1030: Specifies a command to execute on the local machine after successfully
1031: connecting to the server.
1032: The command string extends to the end of the line, and is executed with
1.105 jmc 1033: the user's shell.
1.239 jmc 1034: Arguments to
1035: .Cm LocalCommand
1036: accept the tokens described in the
1037: .Sx TOKENS
1038: section.
1.123 djm 1039: .Pp
1040: The command is run synchronously and does not have access to the
1041: session of the
1042: .Xr ssh 1
1043: that spawned it.
1044: It should not be used for interactive commands.
1045: .Pp
1.65 reyk 1046: This directive is ignored unless
1047: .Cm PermitLocalCommand
1048: has been enabled.
1.1 stevesk 1049: .It Cm LocalForward
1.74 jmc 1050: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 1051: the secure channel to the specified host and port from the remote machine.
1.49 jmc 1052: The first argument must be
1.43 djm 1053: .Sm off
1.49 jmc 1054: .Oo Ar bind_address : Oc Ar port
1.43 djm 1055: .Sm on
1.49 jmc 1056: and the second argument must be
1057: .Ar host : Ns Ar hostport .
1.138 djm 1058: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 1059: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 1060: given on the command line.
1.1 stevesk 1061: Only the superuser can forward privileged ports.
1.43 djm 1062: By default, the local port is bound in accordance with the
1063: .Cm GatewayPorts
1064: setting.
1065: However, an explicit
1066: .Ar bind_address
1067: may be used to bind the connection to a specific address.
1068: The
1069: .Ar bind_address
1070: of
1.240 jmc 1071: .Cm localhost
1.46 jmc 1072: indicates that the listening port be bound for local use only, while an
1073: empty address or
1074: .Sq *
1.43 djm 1075: indicates that the port should be available from all interfaces.
1.1 stevesk 1076: .It Cm LogLevel
1077: Gives the verbosity level that is used when logging messages from
1.84 jmc 1078: .Xr ssh 1 .
1.1 stevesk 1079: The possible values are:
1.84 jmc 1080: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 1081: The default is INFO.
1082: DEBUG and DEBUG1 are equivalent.
1083: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 1084: .It Cm MACs
1085: Specifies the MAC (message authentication code) algorithms
1086: in order of preference.
1.226 jmc 1087: The MAC algorithm is used for data integrity protection.
1.1 stevesk 1088: Multiple algorithms must be comma-separated.
1.214 djm 1089: If the specified value begins with a
1090: .Sq +
1091: character, then the specified algorithms will be appended to the default set
1092: instead of replacing them.
1.241 djm 1093: If the specified value begins with a
1094: .Sq -
1095: character, then the specified algorithms (including wildcards) will be removed
1096: from the default set instead of replacing them.
1.214 djm 1097: .Pp
1.160 markus 1098: The algorithms that contain
1.240 jmc 1099: .Qq -etm
1.160 markus 1100: calculate the MAC after encryption (encrypt-then-mac).
1101: These are considered safer and their use recommended.
1.214 djm 1102: .Pp
1.84 jmc 1103: The default is:
1.101 jmc 1104: .Bd -literal -offset indent
1.160 markus 1105: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1106: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.224 djm 1107: hmac-sha1-etm@openssh.com,
1.186 naddy 1108: umac-64@openssh.com,umac-128@openssh.com,
1.224 djm 1109: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.101 jmc 1110: .Ed
1.198 djm 1111: .Pp
1.240 jmc 1112: The list of available MAC algorithms may also be obtained using
1113: .Qq ssh -Q mac .
1.1 stevesk 1114: .It Cm NoHostAuthenticationForLocalhost
1.264 djm 1115: Disable host authentication for localhost (loopback addresses).
1.1 stevesk 1116: The argument to this keyword must be
1.240 jmc 1117: .Cm yes
1.1 stevesk 1118: or
1.242 jmc 1119: .Cm no
1.240 jmc 1120: (the default).
1.1 stevesk 1121: .It Cm NumberOfPasswordPrompts
1122: Specifies the number of password prompts before giving up.
1123: The argument to this keyword must be an integer.
1.84 jmc 1124: The default is 3.
1.1 stevesk 1125: .It Cm PasswordAuthentication
1126: Specifies whether to use password authentication.
1127: The argument to this keyword must be
1.240 jmc 1128: .Cm yes
1129: (the default)
1.1 stevesk 1130: or
1.240 jmc 1131: .Cm no .
1.65 reyk 1132: .It Cm PermitLocalCommand
1133: Allow local command execution via the
1134: .Ic LocalCommand
1135: option or using the
1.66 jmc 1136: .Ic !\& Ns Ar command
1.65 reyk 1137: escape sequence in
1138: .Xr ssh 1 .
1139: The argument must be
1.240 jmc 1140: .Cm yes
1.65 reyk 1141: or
1.240 jmc 1142: .Cm no
1143: (the default).
1.127 markus 1144: .It Cm PKCS11Provider
1145: Specifies which PKCS#11 provider to use.
1.144 jmc 1146: The argument to this keyword is the PKCS#11 shared library
1.127 markus 1147: .Xr ssh 1
1.128 markus 1148: should use to communicate with a PKCS#11 token providing the user's
1.127 markus 1149: private RSA key.
1.67 jmc 1150: .It Cm Port
1151: Specifies the port number to connect on the remote host.
1.84 jmc 1152: The default is 22.
1.1 stevesk 1153: .It Cm PreferredAuthentications
1.226 jmc 1154: Specifies the order in which the client should try authentication methods.
1.48 jmc 1155: This allows a client to prefer one method (e.g.\&
1.1 stevesk 1156: .Cm keyboard-interactive )
1.48 jmc 1157: over another method (e.g.\&
1.131 jmc 1158: .Cm password ) .
1159: The default is:
1160: .Bd -literal -offset indent
1161: gssapi-with-mic,hostbased,publickey,
1162: keyboard-interactive,password
1163: .Ed
1.1 stevesk 1164: .It Cm ProxyCommand
1165: Specifies the command to use to connect to the server.
1166: The command
1.190 djm 1167: string extends to the end of the line, and is executed
1168: using the user's shell
1169: .Ql exec
1170: directive to avoid a lingering shell process.
1171: .Pp
1.239 jmc 1172: Arguments to
1173: .Cm ProxyCommand
1174: accept the tokens described in the
1175: .Sx TOKENS
1176: section.
1.1 stevesk 1177: The command can be basically anything,
1178: and should read from its standard input and write to its standard output.
1179: It should eventually connect an
1180: .Xr sshd 8
1181: server running on some machine, or execute
1182: .Ic sshd -i
1183: somewhere.
1184: Host key management will be done using the
1185: HostName of the host being connected (defaulting to the name typed by
1186: the user).
1.7 jmc 1187: Setting the command to
1.240 jmc 1188: .Cm none
1.6 markus 1189: disables this option entirely.
1.1 stevesk 1190: Note that
1191: .Cm CheckHostIP
1192: is not available for connects with a proxy command.
1.52 djm 1193: .Pp
1194: This directive is useful in conjunction with
1195: .Xr nc 1
1196: and its proxy support.
1.53 jmc 1197: For example, the following directive would connect via an HTTP proxy at
1.52 djm 1198: 192.0.2.0:
1199: .Bd -literal -offset 3n
1200: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1201: .Ed
1.233 djm 1202: .It Cm ProxyJump
1.260 millert 1203: Specifies one or more jump proxies as either
1.233 djm 1204: .Xo
1205: .Sm off
1.234 jmc 1206: .Op Ar user No @
1.233 djm 1207: .Ar host
1.234 jmc 1208: .Op : Ns Ar port
1.233 djm 1209: .Sm on
1.260 millert 1210: or an ssh URI
1.233 djm 1211: .Xc .
1.235 djm 1212: Multiple proxies may be separated by comma characters and will be visited
1.236 djm 1213: sequentially.
1.233 djm 1214: Setting this option will cause
1215: .Xr ssh 1
1216: to connect to the target host by first making a
1217: .Xr ssh 1
1218: connection to the specified
1219: .Cm ProxyJump
1220: host and then establishing a
1.234 jmc 1221: TCP forwarding to the ultimate target from there.
1.233 djm 1222: .Pp
1223: Note that this option will compete with the
1224: .Cm ProxyCommand
1225: option - whichever is specified first will prevent later instances of the
1226: other from taking effect.
1.167 djm 1227: .It Cm ProxyUseFdpass
1.168 jmc 1228: Specifies that
1.167 djm 1229: .Cm ProxyCommand
1230: will pass a connected file descriptor back to
1.168 jmc 1231: .Xr ssh 1
1.167 djm 1232: instead of continuing to execute and pass data.
1233: The default is
1.240 jmc 1234: .Cm no .
1.213 markus 1235: .It Cm PubkeyAcceptedKeyTypes
1236: Specifies the key types that will be used for public key authentication
1.279 djm 1237: as a comma-separated list of patterns.
1.214 djm 1238: Alternately if the specified value begins with a
1239: .Sq +
1240: character, then the key types after it will be appended to the default
1241: instead of replacing it.
1.241 djm 1242: If the specified value begins with a
1243: .Sq -
1244: character, then the specified key types (including wildcards) will be removed
1245: from the default set instead of replacing them.
1.213 markus 1246: The default for this option is:
1247: .Bd -literal -offset 3n
1248: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1249: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1250: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1251: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 1252: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 1253: ssh-rsa-cert-v01@openssh.com,
1254: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 1255: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 1256: .Ed
1257: .Pp
1.240 jmc 1258: The list of available key types may also be obtained using
1259: .Qq ssh -Q key .
1.1 stevesk 1260: .It Cm PubkeyAuthentication
1261: Specifies whether to try public key authentication.
1262: The argument to this keyword must be
1.240 jmc 1263: .Cm yes
1264: (the default)
1.1 stevesk 1265: or
1.240 jmc 1266: .Cm no .
1.75 dtucker 1267: .It Cm RekeyLimit
1268: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1269: session key is renegotiated, optionally followed a maximum amount of
1270: time that may pass before the session key is renegotiated.
1271: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1272: .Sq K ,
1273: .Sq M ,
1.75 dtucker 1274: or
1.76 jmc 1275: .Sq G
1.75 dtucker 1276: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1277: The default is between
1.84 jmc 1278: .Sq 1G
1.75 dtucker 1279: and
1.84 jmc 1280: .Sq 4G ,
1.75 dtucker 1281: depending on the cipher.
1.162 dtucker 1282: The optional second value is specified in seconds and may use any of the
1283: units documented in the
1.240 jmc 1284: .Sx TIME FORMATS
1285: section of
1.162 dtucker 1286: .Xr sshd_config 5 .
1287: The default value for
1288: .Cm RekeyLimit
1289: is
1.240 jmc 1290: .Cm default none ,
1.162 dtucker 1291: which means that rekeying is performed after the cipher's default amount
1292: of data has been sent or received and no time based rekeying is done.
1.249 bluhm 1293: .It Cm RemoteCommand
1294: Specifies a command to execute on the remote machine after successfully
1295: connecting to the server.
1296: The command string extends to the end of the line, and is executed with
1297: the user's shell.
1.250 jmc 1298: Arguments to
1299: .Cm RemoteCommand
1300: accept the tokens described in the
1301: .Sx TOKENS
1302: section.
1.1 stevesk 1303: .It Cm RemoteForward
1.74 jmc 1304: Specifies that a TCP port on the remote machine be forwarded over
1.256 markus 1305: the secure channel.
1.273 djm 1306: The remote port may either be forwarded to a specified host and port
1.256 markus 1307: from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
1308: client to connect to arbitrary destinations from the local machine.
1.49 jmc 1309: The first argument must be
1.43 djm 1310: .Sm off
1.49 jmc 1311: .Oo Ar bind_address : Oc Ar port
1.43 djm 1312: .Sm on
1.256 markus 1313: If forwarding to a specific destination then the second argument must be
1314: .Ar host : Ns Ar hostport ,
1315: otherwise if no destination argument is specified then the remote forwarding
1316: will be established as a SOCKS proxy.
1317: .Pp
1.138 djm 1318: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.1 stevesk 1319: Multiple forwardings may be specified, and additional
1320: forwardings can be given on the command line.
1.113 stevesk 1321: Privileged ports can be forwarded only when
1322: logging in as root on the remote machine.
1.118 jmc 1323: .Pp
1.117 djm 1324: If the
1325: .Ar port
1.240 jmc 1326: argument is 0,
1.117 djm 1327: the listen port will be dynamically allocated on the server and reported
1328: to the client at run time.
1.43 djm 1329: .Pp
1330: If the
1331: .Ar bind_address
1332: is not specified, the default is to only bind to loopback addresses.
1333: If the
1334: .Ar bind_address
1335: is
1336: .Ql *
1337: or an empty string, then the forwarding is requested to listen on all
1338: interfaces.
1339: Specifying a remote
1340: .Ar bind_address
1.46 jmc 1341: will only succeed if the server's
1342: .Cm GatewayPorts
1.43 djm 1343: option is enabled (see
1.46 jmc 1344: .Xr sshd_config 5 ) .
1.149 djm 1345: .It Cm RequestTTY
1346: Specifies whether to request a pseudo-tty for the session.
1347: The argument may be one of:
1.240 jmc 1348: .Cm no
1.149 djm 1349: (never request a TTY),
1.240 jmc 1350: .Cm yes
1.149 djm 1351: (always request a TTY when standard input is a TTY),
1.240 jmc 1352: .Cm force
1.149 djm 1353: (always request a TTY) or
1.240 jmc 1354: .Cm auto
1.149 djm 1355: (request a TTY when opening a login session).
1356: This option mirrors the
1357: .Fl t
1358: and
1359: .Fl T
1360: flags for
1361: .Xr ssh 1 .
1.196 djm 1362: .It Cm RevokedHostKeys
1363: Specifies revoked host public keys.
1364: Keys listed in this file will be refused for host authentication.
1365: Note that if this file does not exist or is not readable,
1366: then host authentication will be refused for all hosts.
1367: Keys may be specified as a text file, listing one public key per line, or as
1368: an OpenSSH Key Revocation List (KRL) as generated by
1369: .Xr ssh-keygen 1 .
1370: For more information on KRLs, see the KEY REVOCATION LISTS section in
1371: .Xr ssh-keygen 1 .
1.32 djm 1372: .It Cm SendEnv
1373: Specifies what variables from the local
1374: .Xr environ 7
1375: should be sent to the server.
1.84 jmc 1376: The server must also support it, and the server must be configured to
1.33 djm 1377: accept these environment variables.
1.207 dtucker 1378: Note that the
1379: .Ev TERM
1.208 jmc 1380: environment variable is always sent whenever a
1.207 dtucker 1381: pseudo-terminal is requested as it is required by the protocol.
1.32 djm 1382: Refer to
1383: .Cm AcceptEnv
1384: in
1385: .Xr sshd_config 5
1386: for how to configure the server.
1.80 jmc 1387: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1388: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1389: across multiple
1390: .Cm SendEnv
1391: directives.
1.81 jmc 1392: .Pp
1393: See
1394: .Sx PATTERNS
1395: for more information on patterns.
1.271 djm 1396: .Pp
1.272 jmc 1397: It is possible to clear previously set
1.271 djm 1398: .Cm SendEnv
1399: variable names by prefixing patterns with
1400: .Pa - .
1401: The default is not to send any environment variables.
1.28 markus 1402: .It Cm ServerAliveCountMax
1.73 jmc 1403: Sets the number of server alive messages (see below) which may be
1.28 markus 1404: sent without
1.84 jmc 1405: .Xr ssh 1
1.28 markus 1406: receiving any messages back from the server.
1407: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1408: ssh will disconnect from the server, terminating the session.
1.28 markus 1409: It is important to note that the use of server alive messages is very
1410: different from
1411: .Cm TCPKeepAlive
1412: (below).
1413: The server alive messages are sent through the encrypted channel
1414: and therefore will not be spoofable.
1415: The TCP keepalive option enabled by
1416: .Cm TCPKeepAlive
1417: is spoofable.
1418: The server alive mechanism is valuable when the client or
1419: server depend on knowing when a connection has become inactive.
1420: .Pp
1421: The default value is 3.
1422: If, for example,
1423: .Cm ServerAliveInterval
1.84 jmc 1424: (see below) is set to 15 and
1.28 markus 1425: .Cm ServerAliveCountMax
1.84 jmc 1426: is left at the default, if the server becomes unresponsive,
1427: ssh will disconnect after approximately 45 seconds.
1.67 jmc 1428: .It Cm ServerAliveInterval
1429: Sets a timeout interval in seconds after which if no data has been received
1430: from the server,
1.84 jmc 1431: .Xr ssh 1
1.67 jmc 1432: will send a message through the encrypted
1433: channel to request a response from the server.
1434: The default
1435: is 0, indicating that these messages will not be sent to the server.
1.277 jmc 1436: .It Cm SetEnv
1437: Directly specify one or more environment variables and their contents to
1438: be sent to the server.
1439: Similarly to
1440: .Cm SendEnv ,
1441: the server must be prepared to accept the environment variable.
1.191 millert 1442: .It Cm StreamLocalBindMask
1443: Sets the octal file creation mode mask
1444: .Pq umask
1445: used when creating a Unix-domain socket file for local or remote
1446: port forwarding.
1447: This option is only used for port forwarding to a Unix-domain socket file.
1448: .Pp
1449: The default value is 0177, which creates a Unix-domain socket file that is
1450: readable and writable only by the owner.
1451: Note that not all operating systems honor the file mode on Unix-domain
1452: socket files.
1453: .It Cm StreamLocalBindUnlink
1454: Specifies whether to remove an existing Unix-domain socket file for local
1455: or remote port forwarding before creating a new one.
1456: If the socket file already exists and
1457: .Cm StreamLocalBindUnlink
1458: is not enabled,
1459: .Nm ssh
1460: will be unable to forward the port to the Unix-domain socket file.
1461: This option is only used for port forwarding to a Unix-domain socket file.
1462: .Pp
1463: The argument must be
1.240 jmc 1464: .Cm yes
1.191 millert 1465: or
1.240 jmc 1466: .Cm no
1467: (the default).
1.1 stevesk 1468: .It Cm StrictHostKeyChecking
1469: If this flag is set to
1.240 jmc 1470: .Cm yes ,
1.84 jmc 1471: .Xr ssh 1
1.1 stevesk 1472: will never automatically add host keys to the
1.50 djm 1473: .Pa ~/.ssh/known_hosts
1.1 stevesk 1474: file, and refuses to connect to hosts whose host key has changed.
1.263 dtucker 1475: This provides maximum protection against man-in-the-middle (MITM) attacks,
1.84 jmc 1476: though it can be annoying when the
1.1 stevesk 1477: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1478: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1479: frequently made.
1480: This option forces the user to manually
1481: add all new hosts.
1.255 jmc 1482: .Pp
1.1 stevesk 1483: If this flag is set to
1.254 djm 1484: .Dq accept-new
1.255 jmc 1485: then ssh will automatically add new host keys to the user
1.254 djm 1486: known hosts files, but will not permit connections to hosts with
1487: changed host keys.
1488: If this flag is set to
1489: .Dq no
1490: or
1491: .Dq off ,
1.255 jmc 1492: ssh will automatically add new host keys to the user known hosts files
1493: and allow connections to hosts with changed hostkeys to proceed,
1494: subject to some restrictions.
1.1 stevesk 1495: If this flag is set to
1.240 jmc 1496: .Cm ask
1497: (the default),
1.1 stevesk 1498: new host keys
1499: will be added to the user known host files only after the user
1500: has confirmed that is what they really want to do, and
1.84 jmc 1501: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1502: The host keys of
1503: known hosts will be verified automatically in all cases.
1.244 jmc 1504: .It Cm SyslogFacility
1505: Gives the facility code that is used when logging messages from
1506: .Xr ssh 1 .
1507: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1508: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1509: The default is USER.
1.26 markus 1510: .It Cm TCPKeepAlive
1511: Specifies whether the system should send TCP keepalive messages to the
1512: other side.
1513: If they are sent, death of the connection or crash of one
1514: of the machines will be properly noticed.
1515: However, this means that
1516: connections will die if the route is down temporarily, and some people
1517: find it annoying.
1518: .Pp
1519: The default is
1.240 jmc 1520: .Cm yes
1.26 markus 1521: (to send TCP keepalive messages), and the client will notice
1522: if the network goes down or the remote host dies.
1523: This is important in scripts, and many users want it too.
1524: .Pp
1525: To disable TCP keepalive messages, the value should be set to
1.240 jmc 1526: .Cm no .
1.265 djm 1527: See also
1528: .Cm ServerAliveInterval
1529: for protocol-level keepalives.
1.65 reyk 1530: .It Cm Tunnel
1.95 stevesk 1531: Request
1.65 reyk 1532: .Xr tun 4
1.69 jmc 1533: device forwarding between the client and the server.
1.65 reyk 1534: The argument must be
1.240 jmc 1535: .Cm yes ,
1536: .Cm point-to-point
1.95 stevesk 1537: (layer 3),
1.240 jmc 1538: .Cm ethernet
1.95 stevesk 1539: (layer 2),
1.65 reyk 1540: or
1.240 jmc 1541: .Cm no
1542: (the default).
1.95 stevesk 1543: Specifying
1.240 jmc 1544: .Cm yes
1.95 stevesk 1545: requests the default tunnel mode, which is
1.240 jmc 1546: .Cm point-to-point .
1.65 reyk 1547: .It Cm TunnelDevice
1.95 stevesk 1548: Specifies the
1.65 reyk 1549: .Xr tun 4
1.95 stevesk 1550: devices to open on the client
1551: .Pq Ar local_tun
1552: and the server
1553: .Pq Ar remote_tun .
1554: .Pp
1555: The argument must be
1556: .Sm off
1557: .Ar local_tun Op : Ar remote_tun .
1558: .Sm on
1559: The devices may be specified by numerical ID or the keyword
1.240 jmc 1560: .Cm any ,
1.95 stevesk 1561: which uses the next available tunnel device.
1562: If
1563: .Ar remote_tun
1564: is not specified, it defaults to
1.240 jmc 1565: .Cm any .
1.95 stevesk 1566: The default is
1.240 jmc 1567: .Cm any:any .
1.201 djm 1568: .It Cm UpdateHostKeys
1.200 djm 1569: Specifies whether
1570: .Xr ssh 1
1571: should accept notifications of additional hostkeys from the server sent
1572: after authentication has completed and add them to
1573: .Cm UserKnownHostsFile .
1574: The argument must be
1.240 jmc 1575: .Cm yes ,
1576: .Cm no
1.204 djm 1577: (the default) or
1.240 jmc 1578: .Cm ask .
1.200 djm 1579: Enabling this option allows learning alternate hostkeys for a server
1.201 djm 1580: and supports graceful key rotation by allowing a server to send replacement
1581: public keys before old ones are removed.
1.200 djm 1582: Additional hostkeys are only accepted if the key used to authenticate the
1.220 sobrado 1583: host was already trusted or explicitly accepted by the user.
1.204 djm 1584: If
1585: .Cm UpdateHostKeys
1586: is set to
1.240 jmc 1587: .Cm ask ,
1.204 djm 1588: then the user is asked to confirm the modifications to the known_hosts file.
1.205 djm 1589: Confirmation is currently incompatible with
1590: .Cm ControlPersist ,
1591: and will be disabled if it is enabled.
1.200 djm 1592: .Pp
1593: Presently, only
1594: .Xr sshd 8
1595: from OpenSSH 6.8 and greater support the
1.240 jmc 1596: .Qq hostkeys@openssh.com
1.200 djm 1597: protocol extension used to inform the client of all the server's hostkeys.
1.1 stevesk 1598: .It Cm User
1599: Specifies the user to log in as.
1600: This can be useful when a different user name is used on different machines.
1601: This saves the trouble of
1602: having to remember to give the user name on the command line.
1603: .It Cm UserKnownHostsFile
1.151 djm 1604: Specifies one or more files to use for the user
1605: host key database, separated by whitespace.
1606: The default is
1607: .Pa ~/.ssh/known_hosts ,
1608: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1609: .It Cm VerifyHostKeyDNS
1610: Specifies whether to verify the remote key using DNS and SSHFP resource
1611: records.
1.24 jakob 1612: If this option is set to
1.240 jmc 1613: .Cm yes ,
1.25 jmc 1614: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1615: from DNS.
1616: Insecure fingerprints will be handled as if this option was set to
1.240 jmc 1617: .Cm ask .
1.24 jakob 1618: If this option is set to
1.240 jmc 1619: .Cm ask ,
1.24 jakob 1620: information on fingerprint match will be displayed, but the user will still
1621: need to confirm new host keys according to the
1622: .Cm StrictHostKeyChecking
1623: option.
1.8 jakob 1624: The default is
1.240 jmc 1625: .Cm no .
1.84 jmc 1626: .Pp
1.240 jmc 1627: See also
1628: .Sx VERIFYING HOST KEYS
1629: in
1.84 jmc 1630: .Xr ssh 1 .
1.111 grunk 1631: .It Cm VisualHostKey
1632: If this flag is set to
1.240 jmc 1633: .Cm yes ,
1.111 grunk 1634: an ASCII art representation of the remote host key fingerprint is
1.197 djm 1635: printed in addition to the fingerprint string at login and
1.114 stevesk 1636: for unknown host keys.
1.111 grunk 1637: If this flag is set to
1.240 jmc 1638: .Cm no
1639: (the default),
1.114 stevesk 1640: no fingerprint strings are printed at login and
1.197 djm 1641: only the fingerprint string will be printed for unknown host keys.
1.1 stevesk 1642: .It Cm XAuthLocation
1.5 stevesk 1643: Specifies the full pathname of the
1.1 stevesk 1644: .Xr xauth 1
1645: program.
1646: The default is
1647: .Pa /usr/X11R6/bin/xauth .
1648: .El
1.86 jmc 1649: .Sh PATTERNS
1650: A
1651: .Em pattern
1652: consists of zero or more non-whitespace characters,
1653: .Sq *
1654: (a wildcard that matches zero or more characters),
1655: or
1656: .Sq ?\&
1657: (a wildcard that matches exactly one character).
1658: For example, to specify a set of declarations for any host in the
1.240 jmc 1659: .Qq .co.uk
1.86 jmc 1660: set of domains,
1661: the following pattern could be used:
1662: .Pp
1663: .Dl Host *.co.uk
1664: .Pp
1665: The following pattern
1666: would match any host in the 192.168.0.[0-9] network range:
1667: .Pp
1668: .Dl Host 192.168.0.?
1669: .Pp
1670: A
1671: .Em pattern-list
1672: is a comma-separated list of patterns.
1673: Patterns within pattern-lists may be negated
1674: by preceding them with an exclamation mark
1675: .Pq Sq !\& .
1676: For example,
1.174 djm 1677: to allow a key to be used from anywhere within an organization
1.86 jmc 1678: except from the
1.240 jmc 1679: .Qq dialup
1.86 jmc 1680: pool,
1681: the following entry (in authorized_keys) could be used:
1682: .Pp
1683: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.258 djm 1684: .Pp
1685: Note that a negated match will never produce a positive result by itself.
1686: For example, attempting to match
1687: .Qq host3
1688: against the following pattern-list will fail:
1689: .Pp
1690: .Dl from=\&"!host1,!host2\&"
1691: .Pp
1692: The solution here is to include a term that will yield a positive match,
1693: such as a wildcard:
1694: .Pp
1695: .Dl from=\&"!host1,!host2,*\&"
1.239 jmc 1696: .Sh TOKENS
1697: Arguments to some keywords can make use of tokens,
1698: which are expanded at runtime:
1699: .Pp
1700: .Bl -tag -width XXXX -offset indent -compact
1701: .It %%
1702: A literal
1703: .Sq % .
1704: .It \&%C
1.257 jmc 1705: Hash of %l%h%p%r.
1.239 jmc 1706: .It %d
1707: Local user's home directory.
1708: .It %h
1709: The remote hostname.
1710: .It %i
1711: The local user ID.
1712: .It %L
1713: The local hostname.
1714: .It %l
1715: The local hostname, including the domain name.
1716: .It %n
1717: The original remote hostname, as given on the command line.
1718: .It %p
1719: The remote port.
1720: .It %r
1721: The remote username.
1.261 djm 1722: .It \&%T
1723: The local
1724: .Xr tun 4
1725: or
1726: .Xr tap 4
1727: network interface assigned if
1.262 jmc 1728: tunnel forwarding was requested, or
1729: .Qq NONE
1.261 djm 1730: otherwise.
1.239 jmc 1731: .It %u
1732: The local username.
1733: .El
1734: .Pp
1735: .Cm Match exec
1.274 djm 1736: accepts the tokens %%, %h, %i, %L, %l, %n, %p, %r, and %u.
1.239 jmc 1737: .Pp
1738: .Cm CertificateFile
1.275 jmc 1739: accepts the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1740: .Pp
1741: .Cm ControlPath
1742: accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
1743: .Pp
1744: .Cm HostName
1745: accepts the tokens %% and %h.
1746: .Pp
1747: .Cm IdentityAgent
1748: and
1749: .Cm IdentityFile
1.275 jmc 1750: accept the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1751: .Pp
1752: .Cm LocalCommand
1.275 jmc 1753: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, %T, and %u.
1.239 jmc 1754: .Pp
1755: .Cm ProxyCommand
1756: accepts the tokens %%, %h, %p, and %r.
1.250 jmc 1757: .Pp
1758: .Cm RemoteCommand
1.274 djm 1759: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, and %u.
1.1 stevesk 1760: .Sh FILES
1761: .Bl -tag -width Ds
1.50 djm 1762: .It Pa ~/.ssh/config
1.1 stevesk 1763: This is the per-user configuration file.
1764: The format of this file is described above.
1.84 jmc 1765: This file is used by the SSH client.
1.30 djm 1766: Because of the potential for abuse, this file must have strict permissions:
1767: read/write for the user, and not accessible by others.
1.1 stevesk 1768: .It Pa /etc/ssh/ssh_config
1769: Systemwide configuration file.
1770: This file provides defaults for those
1771: values that are not specified in the user's configuration file, and
1772: for those users who do not have a configuration file.
1773: This file must be world-readable.
1774: .El
1.13 jmc 1775: .Sh SEE ALSO
1776: .Xr ssh 1
1.1 stevesk 1777: .Sh AUTHORS
1.240 jmc 1778: .An -nosplit
1.1 stevesk 1779: OpenSSH is a derivative of the original and free
1.240 jmc 1780: ssh 1.2.12 release by
1781: .An Tatu Ylonen .
1782: .An Aaron Campbell , Bob Beck , Markus Friedl ,
1783: .An Niels Provos , Theo de Raadt
1784: and
1785: .An Dug Song
1.1 stevesk 1786: removed many bugs, re-added newer features and
1787: created OpenSSH.
1.240 jmc 1788: .An Markus Friedl
1789: contributed the support for SSH protocol versions 1.5 and 2.0.
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