Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.268
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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1.268 ! jmc 36: .\" $OpenBSD: ssh_config.5,v 1.267 2018/02/23 02:34:33 djm Exp $
! 37: .Dd $Mdocdate: February 23 2018 $
1.1 stevesk 38: .Dt SSH_CONFIG 5
39: .Os
40: .Sh NAME
41: .Nm ssh_config
42: .Nd OpenSSH SSH client configuration files
43: .Sh DESCRIPTION
1.84 jmc 44: .Xr ssh 1
1.1 stevesk 45: obtains configuration data from the following sources in
46: the following order:
1.79 jmc 47: .Pp
1.2 stevesk 48: .Bl -enum -offset indent -compact
49: .It
50: command-line options
51: .It
52: user's configuration file
1.50 djm 53: .Pq Pa ~/.ssh/config
1.2 stevesk 54: .It
55: system-wide configuration file
56: .Pq Pa /etc/ssh/ssh_config
57: .El
1.1 stevesk 58: .Pp
59: For each parameter, the first obtained value
60: will be used.
1.41 jmc 61: The configuration files contain sections separated by
1.240 jmc 62: .Cm Host
1.1 stevesk 63: specifications, and that section is only applied for hosts that
64: match one of the patterns given in the specification.
1.193 djm 65: The matched host name is usually the one given on the command line
66: (see the
67: .Cm CanonicalizeHostname
1.240 jmc 68: option for exceptions).
1.1 stevesk 69: .Pp
70: Since the first obtained value for each parameter is used, more
71: host-specific declarations should be given near the beginning of the
72: file, and general defaults at the end.
1.80 jmc 73: .Pp
1.240 jmc 74: The file contains keyword-argument pairs, one per line.
75: Lines starting with
1.1 stevesk 76: .Ql #
1.240 jmc 77: and empty lines are interpreted as comments.
78: Arguments may optionally be enclosed in double quotes
79: .Pq \&"
80: in order to represent arguments containing spaces.
1.1 stevesk 81: Configuration options may be separated by whitespace or
82: optional whitespace and exactly one
83: .Ql = ;
84: the latter format is useful to avoid the need to quote whitespace
85: when specifying configuration options using the
86: .Nm ssh ,
1.87 jmc 87: .Nm scp ,
1.1 stevesk 88: and
89: .Nm sftp
90: .Fl o
91: option.
92: .Pp
93: The possible
94: keywords and their meanings are as follows (note that
95: keywords are case-insensitive and arguments are case-sensitive):
96: .Bl -tag -width Ds
97: .It Cm Host
98: Restricts the following declarations (up to the next
99: .Cm Host
1.169 djm 100: or
101: .Cm Match
1.1 stevesk 102: keyword) to be only for those hosts that match one of the patterns
103: given after the keyword.
1.112 krw 104: If more than one pattern is provided, they should be separated by whitespace.
1.1 stevesk 105: A single
1.83 jmc 106: .Ql *
1.1 stevesk 107: as a pattern can be used to provide global
108: defaults for all hosts.
1.193 djm 109: The host is usually the
1.1 stevesk 110: .Ar hostname
1.193 djm 111: argument given on the command line
112: (see the
113: .Cm CanonicalizeHostname
1.240 jmc 114: keyword for exceptions).
1.148 djm 115: .Pp
116: A pattern entry may be negated by prefixing it with an exclamation mark
117: .Pq Sq !\& .
118: If a negated entry is matched, then the
119: .Cm Host
120: entry is ignored, regardless of whether any other patterns on the line
121: match.
122: Negated matches are therefore useful to provide exceptions for wildcard
123: matches.
1.81 jmc 124: .Pp
125: See
126: .Sx PATTERNS
127: for more information on patterns.
1.170 jmc 128: .It Cm Match
1.169 djm 129: Restricts the following declarations (up to the next
130: .Cm Host
131: or
132: .Cm Match
133: keyword) to be used only when the conditions following the
134: .Cm Match
135: keyword are satisfied.
1.220 sobrado 136: Match conditions are specified using one or more criteria
1.178 dtucker 137: or the single token
138: .Cm all
1.193 djm 139: which always matches.
140: The available criteria keywords are:
141: .Cm canonical ,
1.176 djm 142: .Cm exec ,
1.169 djm 143: .Cm host ,
144: .Cm originalhost ,
145: .Cm user ,
146: and
147: .Cm localuser .
1.193 djm 148: The
149: .Cm all
150: criteria must appear alone or immediately after
1.194 jmc 151: .Cm canonical .
1.193 djm 152: Other criteria may be combined arbitrarily.
153: All criteria but
154: .Cm all
155: and
156: .Cm canonical
157: require an argument.
158: Criteria may be negated by prepending an exclamation mark
159: .Pq Sq !\& .
1.169 djm 160: .Pp
1.177 jmc 161: The
1.193 djm 162: .Cm canonical
1.210 dtucker 163: keyword matches only when the configuration file is being re-parsed
1.193 djm 164: after hostname canonicalization (see the
165: .Cm CanonicalizeHostname
166: option.)
167: This may be useful to specify conditions that work with canonical host
168: names only.
169: The
1.176 djm 170: .Cm exec
1.177 jmc 171: keyword executes the specified command under the user's shell.
1.169 djm 172: If the command returns a zero exit status then the condition is considered true.
173: Commands containing whitespace characters must be quoted.
1.239 jmc 174: Arguments to
175: .Cm exec
176: accept the tokens described in the
177: .Sx TOKENS
178: section.
1.169 djm 179: .Pp
180: The other keywords' criteria must be single entries or comma-separated
181: lists and may use the wildcard and negation operators described in the
182: .Sx PATTERNS
183: section.
184: The criteria for the
185: .Cm host
186: keyword are matched against the target hostname, after any substitution
187: by the
188: .Cm Hostname
1.193 djm 189: or
190: .Cm CanonicalizeHostname
191: options.
1.169 djm 192: The
193: .Cm originalhost
194: keyword matches against the hostname as it was specified on the command-line.
195: The
196: .Cm user
197: keyword matches against the target username on the remote host.
198: The
199: .Cm localuser
200: keyword matches against the name of the local user running
201: .Xr ssh 1
202: (this keyword may be useful in system-wide
203: .Nm
204: files).
1.222 jcs 205: .It Cm AddKeysToAgent
206: Specifies whether keys should be automatically added to a running
1.223 jmc 207: .Xr ssh-agent 1 .
1.222 jcs 208: If this option is set to
1.240 jmc 209: .Cm yes
1.222 jcs 210: and a key is loaded from a file, the key and its passphrase are added to
211: the agent with the default lifetime, as if by
212: .Xr ssh-add 1 .
213: If this option is set to
1.240 jmc 214: .Cm ask ,
215: .Xr ssh 1
1.222 jcs 216: will require confirmation using the
217: .Ev SSH_ASKPASS
218: program before adding a key (see
219: .Xr ssh-add 1
220: for details).
221: If this option is set to
1.240 jmc 222: .Cm confirm ,
1.222 jcs 223: each use of the key must be confirmed, as if the
224: .Fl c
225: option was specified to
226: .Xr ssh-add 1 .
227: If this option is set to
1.240 jmc 228: .Cm no ,
1.222 jcs 229: no keys are added to the agent.
230: The argument must be
1.240 jmc 231: .Cm yes ,
232: .Cm confirm ,
233: .Cm ask ,
1.222 jcs 234: or
1.240 jmc 235: .Cm no
236: (the default).
1.10 djm 237: .It Cm AddressFamily
1.11 jmc 238: Specifies which address family to use when connecting.
239: Valid arguments are
1.240 jmc 240: .Cm any
241: (the default),
242: .Cm inet
1.84 jmc 243: (use IPv4 only), or
1.240 jmc 244: .Cm inet6
1.40 jmc 245: (use IPv6 only).
1.1 stevesk 246: .It Cm BatchMode
247: If set to
1.240 jmc 248: .Cm yes ,
1.1 stevesk 249: passphrase/password querying will be disabled.
250: This option is useful in scripts and other batch jobs where no user
251: is present to supply the password.
252: The argument must be
1.240 jmc 253: .Cm yes
1.1 stevesk 254: or
1.240 jmc 255: .Cm no
256: (the default).
1.268 ! jmc 257: .It Cm BindAddress
! 258: Use the specified address on the local machine as the source address of
! 259: the connection.
! 260: Only useful on systems with more than one address.
1.267 djm 261: Note that this option does not work if
262: .Cm UsePrivilegedPort
263: is set to
264: .Cm yes .
1.268 ! jmc 265: .It Cm BindInterface
! 266: Use the address of the specified interface on the local machine as the
! 267: source address of the connection.
1.1 stevesk 268: Note that this option does not work if
269: .Cm UsePrivilegedPort
270: is set to
1.240 jmc 271: .Cm yes .
1.171 djm 272: .It Cm CanonicalDomains
1.172 jmc 273: When
1.173 djm 274: .Cm CanonicalizeHostname
1.171 djm 275: is enabled, this option specifies the list of domain suffixes in which to
276: search for the specified destination host.
1.173 djm 277: .It Cm CanonicalizeFallbackLocal
1.174 djm 278: Specifies whether to fail with an error when hostname canonicalization fails.
1.172 jmc 279: The default,
1.240 jmc 280: .Cm yes ,
1.172 jmc 281: will attempt to look up the unqualified hostname using the system resolver's
1.171 djm 282: search rules.
283: A value of
1.240 jmc 284: .Cm no
1.171 djm 285: will cause
286: .Xr ssh 1
287: to fail instantly if
1.173 djm 288: .Cm CanonicalizeHostname
1.171 djm 289: is enabled and the target hostname cannot be found in any of the domains
290: specified by
291: .Cm CanonicalDomains .
1.173 djm 292: .It Cm CanonicalizeHostname
1.174 djm 293: Controls whether explicit hostname canonicalization is performed.
1.172 jmc 294: The default,
1.240 jmc 295: .Cm no ,
1.171 djm 296: is not to perform any name rewriting and let the system resolver handle all
297: hostname lookups.
298: If set to
1.240 jmc 299: .Cm yes
1.171 djm 300: then, for connections that do not use a
301: .Cm ProxyCommand ,
302: .Xr ssh 1
1.173 djm 303: will attempt to canonicalize the hostname specified on the command line
1.171 djm 304: using the
305: .Cm CanonicalDomains
306: suffixes and
1.173 djm 307: .Cm CanonicalizePermittedCNAMEs
1.171 djm 308: rules.
309: If
1.173 djm 310: .Cm CanonicalizeHostname
1.171 djm 311: is set to
1.240 jmc 312: .Cm always ,
1.174 djm 313: then canonicalization is applied to proxied connections too.
1.185 djm 314: .Pp
1.193 djm 315: If this option is enabled, then the configuration files are processed
316: again using the new target name to pick up any new configuration in matching
1.185 djm 317: .Cm Host
1.193 djm 318: and
319: .Cm Match
1.185 djm 320: stanzas.
1.173 djm 321: .It Cm CanonicalizeMaxDots
1.172 jmc 322: Specifies the maximum number of dot characters in a hostname before
1.174 djm 323: canonicalization is disabled.
1.240 jmc 324: The default, 1,
1.172 jmc 325: allows a single dot (i.e. hostname.subdomain).
1.173 djm 326: .It Cm CanonicalizePermittedCNAMEs
1.172 jmc 327: Specifies rules to determine whether CNAMEs should be followed when
1.173 djm 328: canonicalizing hostnames.
1.171 djm 329: The rules consist of one or more arguments of
1.172 jmc 330: .Ar source_domain_list : Ns Ar target_domain_list ,
1.171 djm 331: where
332: .Ar source_domain_list
1.174 djm 333: is a pattern-list of domains that may follow CNAMEs in canonicalization,
1.171 djm 334: and
335: .Ar target_domain_list
1.172 jmc 336: is a pattern-list of domains that they may resolve to.
1.171 djm 337: .Pp
338: For example,
1.240 jmc 339: .Qq *.a.example.com:*.b.example.com,*.c.example.com
1.171 djm 340: will allow hostnames matching
1.240 jmc 341: .Qq *.a.example.com
1.173 djm 342: to be canonicalized to names in the
1.240 jmc 343: .Qq *.b.example.com
1.171 djm 344: or
1.240 jmc 345: .Qq *.c.example.com
1.171 djm 346: domains.
1.221 djm 347: .It Cm CertificateFile
348: Specifies a file from which the user's certificate is read.
349: A corresponding private key must be provided separately in order
350: to use this certificate either
351: from an
352: .Cm IdentityFile
353: directive or
354: .Fl i
355: flag to
356: .Xr ssh 1 ,
357: via
358: .Xr ssh-agent 1 ,
359: or via a
360: .Cm PKCS11Provider .
361: .Pp
1.239 jmc 362: Arguments to
363: .Cm CertificateFile
364: may use the tilde syntax to refer to a user's home directory
365: or the tokens described in the
366: .Sx TOKENS
367: section.
1.221 djm 368: .Pp
369: It is possible to have multiple certificate files specified in
370: configuration files; these certificates will be tried in sequence.
371: Multiple
372: .Cm CertificateFile
373: directives will add to the list of certificates used for
374: authentication.
1.1 stevesk 375: .It Cm ChallengeResponseAuthentication
1.82 jmc 376: Specifies whether to use challenge-response authentication.
1.1 stevesk 377: The argument to this keyword must be
1.240 jmc 378: .Cm yes
379: (the default)
1.1 stevesk 380: or
1.240 jmc 381: .Cm no .
1.1 stevesk 382: .It Cm CheckHostIP
1.240 jmc 383: If set to
384: .Cm yes
385: (the default),
1.84 jmc 386: .Xr ssh 1
387: will additionally check the host IP address in the
1.1 stevesk 388: .Pa known_hosts
389: file.
1.240 jmc 390: This allows it to detect if a host key changed due to DNS spoofing
1.211 djm 391: and will add addresses of destination hosts to
392: .Pa ~/.ssh/known_hosts
393: in the process, regardless of the setting of
394: .Cm StrictHostKeyChecking .
1.107 grunk 395: If the option is set to
1.240 jmc 396: .Cm no ,
1.1 stevesk 397: the check will not be executed.
398: .It Cm Ciphers
1.245 djm 399: Specifies the ciphers allowed and their order of preference.
1.1 stevesk 400: Multiple ciphers must be comma-separated.
1.214 djm 401: If the specified value begins with a
402: .Sq +
403: character, then the specified ciphers will be appended to the default set
404: instead of replacing them.
1.241 djm 405: If the specified value begins with a
406: .Sq -
407: character, then the specified ciphers (including wildcards) will be removed
408: from the default set instead of replacing them.
1.214 djm 409: .Pp
1.180 djm 410: The supported ciphers are:
1.240 jmc 411: .Bd -literal -offset indent
1.186 naddy 412: 3des-cbc
413: aes128-cbc
414: aes192-cbc
415: aes256-cbc
416: aes128-ctr
417: aes192-ctr
418: aes256-ctr
419: aes128-gcm@openssh.com
420: aes256-gcm@openssh.com
421: chacha20-poly1305@openssh.com
1.240 jmc 422: .Ed
1.180 djm 423: .Pp
1.84 jmc 424: The default is:
1.186 naddy 425: .Bd -literal -offset indent
1.215 jmc 426: chacha20-poly1305@openssh.com,
1.186 naddy 427: aes128-ctr,aes192-ctr,aes256-ctr,
1.161 markus 428: aes128-gcm@openssh.com,aes256-gcm@openssh.com,
1.237 djm 429: aes128-cbc,aes192-cbc,aes256-cbc
1.1 stevesk 430: .Ed
1.180 djm 431: .Pp
1.240 jmc 432: The list of available ciphers may also be obtained using
433: .Qq ssh -Q cipher .
1.1 stevesk 434: .It Cm ClearAllForwardings
1.84 jmc 435: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 436: specified in the configuration files or on the command line be
1.7 jmc 437: cleared.
438: This option is primarily useful when used from the
1.84 jmc 439: .Xr ssh 1
1.1 stevesk 440: command line to clear port forwardings set in
441: configuration files, and is automatically set by
442: .Xr scp 1
443: and
444: .Xr sftp 1 .
445: The argument must be
1.240 jmc 446: .Cm yes
1.1 stevesk 447: or
1.240 jmc 448: .Cm no
449: (the default).
1.1 stevesk 450: .It Cm Compression
451: Specifies whether to use compression.
452: The argument must be
1.240 jmc 453: .Cm yes
1.1 stevesk 454: or
1.240 jmc 455: .Cm no
456: (the default).
1.247 naddy 457: .It Cm ConnectionAttempts
458: Specifies the number of tries (one per second) to make before exiting.
459: The argument must be an integer.
460: This may be useful in scripts if the connection sometimes fails.
461: The default is 1.
1.9 djm 462: .It Cm ConnectTimeout
1.84 jmc 463: Specifies the timeout (in seconds) used when connecting to the
464: SSH server, instead of using the default system TCP timeout.
1.11 jmc 465: This value is used only when the target is down or really unreachable,
466: not when it refuses the connection.
1.36 djm 467: .It Cm ControlMaster
468: Enables the sharing of multiple sessions over a single network connection.
469: When set to
1.240 jmc 470: .Cm yes ,
1.84 jmc 471: .Xr ssh 1
1.36 djm 472: will listen for connections on a control socket specified using the
473: .Cm ControlPath
474: argument.
475: Additional sessions can connect to this socket using the same
476: .Cm ControlPath
477: with
478: .Cm ControlMaster
479: set to
1.240 jmc 480: .Cm no
1.38 jmc 481: (the default).
1.64 jmc 482: These sessions will try to reuse the master instance's network connection
1.63 djm 483: rather than initiating new ones, but will fall back to connecting normally
484: if the control socket does not exist, or is not listening.
485: .Pp
1.37 djm 486: Setting this to
1.240 jmc 487: .Cm ask
488: will cause
489: .Xr ssh 1
1.206 jmc 490: to listen for control connections, but require confirmation using
491: .Xr ssh-askpass 1 .
1.51 jakob 492: If the
493: .Cm ControlPath
1.84 jmc 494: cannot be opened,
1.240 jmc 495: .Xr ssh 1
496: will continue without connecting to a master instance.
1.58 djm 497: .Pp
498: X11 and
1.59 jmc 499: .Xr ssh-agent 1
1.58 djm 500: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 501: display and agent forwarded will be the one belonging to the master
1.59 jmc 502: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 503: .Pp
504: Two additional options allow for opportunistic multiplexing: try to use a
505: master connection but fall back to creating a new one if one does not already
506: exist.
507: These options are:
1.240 jmc 508: .Cm auto
1.56 djm 509: and
1.240 jmc 510: .Cm autoask .
1.56 djm 511: The latter requires confirmation like the
1.240 jmc 512: .Cm ask
1.56 djm 513: option.
1.36 djm 514: .It Cm ControlPath
1.55 djm 515: Specify the path to the control socket used for connection sharing as described
516: in the
1.36 djm 517: .Cm ControlMaster
1.57 djm 518: section above or the string
1.240 jmc 519: .Cm none
1.57 djm 520: to disable connection sharing.
1.239 jmc 521: Arguments to
522: .Cm ControlPath
523: may use the tilde syntax to refer to a user's home directory
524: or the tokens described in the
525: .Sx TOKENS
526: section.
1.56 djm 527: It is recommended that any
528: .Cm ControlPath
529: used for opportunistic connection sharing include
1.195 djm 530: at least %h, %p, and %r (or alternatively %C) and be placed in a directory
531: that is not writable by other users.
1.56 djm 532: This ensures that shared connections are uniquely identified.
1.137 djm 533: .It Cm ControlPersist
534: When used in conjunction with
535: .Cm ControlMaster ,
536: specifies that the master connection should remain open
537: in the background (waiting for future client connections)
538: after the initial client connection has been closed.
539: If set to
1.240 jmc 540: .Cm no ,
1.137 djm 541: then the master connection will not be placed into the background,
542: and will close as soon as the initial client connection is closed.
543: If set to
1.240 jmc 544: .Cm yes
545: or 0,
1.137 djm 546: then the master connection will remain in the background indefinitely
547: (until killed or closed via a mechanism such as the
1.240 jmc 548: .Qq ssh -O exit ) .
1.137 djm 549: If set to a time in seconds, or a time in any of the formats documented in
550: .Xr sshd_config 5 ,
551: then the backgrounded master connection will automatically terminate
552: after it has remained idle (with no client connections) for the
553: specified time.
1.38 jmc 554: .It Cm DynamicForward
1.74 jmc 555: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 556: over the secure channel, and the application
557: protocol is then used to determine where to connect to from the
558: remote machine.
1.62 djm 559: .Pp
560: The argument must be
561: .Sm off
562: .Oo Ar bind_address : Oc Ar port .
563: .Sm on
1.138 djm 564: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 565: By default, the local port is bound in accordance with the
566: .Cm GatewayPorts
567: setting.
568: However, an explicit
569: .Ar bind_address
570: may be used to bind the connection to a specific address.
571: The
572: .Ar bind_address
573: of
1.240 jmc 574: .Cm localhost
1.62 djm 575: indicates that the listening port be bound for local use only, while an
576: empty address or
577: .Sq *
578: indicates that the port should be available from all interfaces.
579: .Pp
1.38 jmc 580: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 581: .Xr ssh 1
1.38 jmc 582: will act as a SOCKS server.
583: Multiple forwardings may be specified, and
584: additional forwardings can be given on the command line.
585: Only the superuser can forward privileged ports.
1.14 markus 586: .It Cm EnableSSHKeysign
587: Setting this option to
1.240 jmc 588: .Cm yes
1.14 markus 589: in the global client configuration file
590: .Pa /etc/ssh/ssh_config
591: enables the use of the helper program
592: .Xr ssh-keysign 8
593: during
594: .Cm HostbasedAuthentication .
595: The argument must be
1.240 jmc 596: .Cm yes
1.14 markus 597: or
1.240 jmc 598: .Cm no
599: (the default).
1.23 jmc 600: This option should be placed in the non-hostspecific section.
1.14 markus 601: See
602: .Xr ssh-keysign 8
603: for more information.
1.1 stevesk 604: .It Cm EscapeChar
605: Sets the escape character (default:
606: .Ql ~ ) .
607: The escape character can also
608: be set on the command line.
609: The argument should be a single character,
610: .Ql ^
611: followed by a letter, or
1.240 jmc 612: .Cm none
1.1 stevesk 613: to disable the escape
614: character entirely (making the connection transparent for binary
615: data).
1.96 markus 616: .It Cm ExitOnForwardFailure
617: Specifies whether
618: .Xr ssh 1
619: should terminate the connection if it cannot set up all requested
1.216 djm 620: dynamic, tunnel, local, and remote port forwardings, (e.g.\&
1.217 jmc 621: if either end is unable to bind and listen on a specified port).
1.216 djm 622: Note that
623: .Cm ExitOnForwardFailure
624: does not apply to connections made over port forwardings and will not,
625: for example, cause
626: .Xr ssh 1
627: to exit if TCP connections to the ultimate forwarding destination fail.
1.96 markus 628: The argument must be
1.240 jmc 629: .Cm yes
1.96 markus 630: or
1.240 jmc 631: .Cm no
632: (the default).
1.197 djm 633: .It Cm FingerprintHash
634: Specifies the hash algorithm used when displaying key fingerprints.
635: Valid options are:
1.240 jmc 636: .Cm md5
1.197 djm 637: and
1.240 jmc 638: .Cm sha256
639: (the default).
1.1 stevesk 640: .It Cm ForwardAgent
641: Specifies whether the connection to the authentication agent (if any)
642: will be forwarded to the remote machine.
643: The argument must be
1.240 jmc 644: .Cm yes
1.1 stevesk 645: or
1.240 jmc 646: .Cm no
647: (the default).
1.3 stevesk 648: .Pp
1.7 jmc 649: Agent forwarding should be enabled with caution.
650: Users with the ability to bypass file permissions on the remote host
651: (for the agent's Unix-domain socket)
652: can access the local agent through the forwarded connection.
653: An attacker cannot obtain key material from the agent,
1.3 stevesk 654: however they can perform operations on the keys that enable them to
655: authenticate using the identities loaded into the agent.
1.1 stevesk 656: .It Cm ForwardX11
657: Specifies whether X11 connections will be automatically redirected
658: over the secure channel and
659: .Ev DISPLAY
660: set.
661: The argument must be
1.240 jmc 662: .Cm yes
1.1 stevesk 663: or
1.240 jmc 664: .Cm no
665: (the default).
1.3 stevesk 666: .Pp
1.7 jmc 667: X11 forwarding should be enabled with caution.
668: Users with the ability to bypass file permissions on the remote host
1.22 markus 669: (for the user's X11 authorization database)
1.7 jmc 670: can access the local X11 display through the forwarded connection.
1.22 markus 671: An attacker may then be able to perform activities such as keystroke monitoring
672: if the
673: .Cm ForwardX11Trusted
674: option is also enabled.
1.134 djm 675: .It Cm ForwardX11Timeout
1.135 jmc 676: Specify a timeout for untrusted X11 forwarding
677: using the format described in the
1.240 jmc 678: .Sx TIME FORMATS
679: section of
1.134 djm 680: .Xr sshd_config 5 .
681: X11 connections received by
682: .Xr ssh 1
683: after this time will be refused.
684: The default is to disable untrusted X11 forwarding after twenty minutes has
685: elapsed.
1.22 markus 686: .It Cm ForwardX11Trusted
1.34 jmc 687: If this option is set to
1.240 jmc 688: .Cm yes ,
1.84 jmc 689: remote X11 clients will have full access to the original X11 display.
1.42 djm 690: .Pp
1.22 markus 691: If this option is set to
1.240 jmc 692: .Cm no
693: (the default),
1.84 jmc 694: remote X11 clients will be considered untrusted and prevented
1.22 markus 695: from stealing or tampering with data belonging to trusted X11
696: clients.
1.42 djm 697: Furthermore, the
698: .Xr xauth 1
699: token used for the session will be set to expire after 20 minutes.
700: Remote clients will be refused access after this time.
1.22 markus 701: .Pp
702: See the X11 SECURITY extension specification for full details on
703: the restrictions imposed on untrusted clients.
1.1 stevesk 704: .It Cm GatewayPorts
705: Specifies whether remote hosts are allowed to connect to local
706: forwarded ports.
707: By default,
1.84 jmc 708: .Xr ssh 1
1.7 jmc 709: binds local port forwardings to the loopback address.
710: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 711: .Cm GatewayPorts
1.84 jmc 712: can be used to specify that ssh
1.1 stevesk 713: should bind local port forwardings to the wildcard address,
714: thus allowing remote hosts to connect to forwarded ports.
715: The argument must be
1.240 jmc 716: .Cm yes
1.1 stevesk 717: or
1.240 jmc 718: .Cm no
719: (the default).
1.1 stevesk 720: .It Cm GlobalKnownHostsFile
1.151 djm 721: Specifies one or more files to use for the global
722: host key database, separated by whitespace.
723: The default is
724: .Pa /etc/ssh/ssh_known_hosts ,
725: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 726: .It Cm GSSAPIAuthentication
1.27 markus 727: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 728: The default is
1.240 jmc 729: .Cm no .
1.18 markus 730: .It Cm GSSAPIDelegateCredentials
731: Forward (delegate) credentials to the server.
732: The default is
1.240 jmc 733: .Cm no .
1.44 djm 734: .It Cm HashKnownHosts
735: Indicates that
1.84 jmc 736: .Xr ssh 1
1.44 djm 737: should hash host names and addresses when they are added to
1.50 djm 738: .Pa ~/.ssh/known_hosts .
1.44 djm 739: These hashed names may be used normally by
1.84 jmc 740: .Xr ssh 1
1.44 djm 741: and
1.84 jmc 742: .Xr sshd 8 ,
1.44 djm 743: but they do not reveal identifying information should the file's contents
744: be disclosed.
745: The default is
1.240 jmc 746: .Cm no .
1.97 jmc 747: Note that existing names and addresses in known hosts files
748: will not be converted automatically,
749: but may be manually hashed using
1.45 djm 750: .Xr ssh-keygen 1 .
1.1 stevesk 751: .It Cm HostbasedAuthentication
752: Specifies whether to try rhosts based authentication with public key
753: authentication.
754: The argument must be
1.240 jmc 755: .Cm yes
1.1 stevesk 756: or
1.240 jmc 757: .Cm no
758: (the default).
1.202 djm 759: .It Cm HostbasedKeyTypes
760: Specifies the key types that will be used for hostbased authentication
761: as a comma-separated pattern list.
1.214 djm 762: Alternately if the specified value begins with a
763: .Sq +
764: character, then the specified key types will be appended to the default set
765: instead of replacing them.
1.241 djm 766: If the specified value begins with a
767: .Sq -
768: character, then the specified key types (including wildcards) will be removed
769: from the default set instead of replacing them.
1.213 markus 770: The default for this option is:
771: .Bd -literal -offset 3n
772: ecdsa-sha2-nistp256-cert-v01@openssh.com,
773: ecdsa-sha2-nistp384-cert-v01@openssh.com,
774: ecdsa-sha2-nistp521-cert-v01@openssh.com,
775: ssh-ed25519-cert-v01@openssh.com,
776: ssh-rsa-cert-v01@openssh.com,
777: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.227 djm 778: ssh-ed25519,ssh-rsa
1.213 markus 779: .Ed
780: .Pp
1.202 djm 781: The
782: .Fl Q
783: option of
784: .Xr ssh 1
785: may be used to list supported key types.
1.1 stevesk 786: .It Cm HostKeyAlgorithms
1.226 jmc 787: Specifies the host key algorithms
1.1 stevesk 788: that the client wants to use in order of preference.
1.214 djm 789: Alternately if the specified value begins with a
790: .Sq +
791: character, then the specified key types will be appended to the default set
792: instead of replacing them.
1.241 djm 793: If the specified value begins with a
794: .Sq -
795: character, then the specified key types (including wildcards) will be removed
796: from the default set instead of replacing them.
1.1 stevesk 797: The default for this option is:
1.139 djm 798: .Bd -literal -offset 3n
799: ecdsa-sha2-nistp256-cert-v01@openssh.com,
800: ecdsa-sha2-nistp384-cert-v01@openssh.com,
801: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1.183 naddy 802: ssh-ed25519-cert-v01@openssh.com,
1.213 markus 803: ssh-rsa-cert-v01@openssh.com,
1.139 djm 804: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.227 djm 805: ssh-ed25519,ssh-rsa
1.139 djm 806: .Ed
1.145 djm 807: .Pp
808: If hostkeys are known for the destination host then this default is modified
809: to prefer their algorithms.
1.198 djm 810: .Pp
1.240 jmc 811: The list of available key types may also be obtained using
812: .Qq ssh -Q key .
1.1 stevesk 813: .It Cm HostKeyAlias
814: Specifies an alias that should be used instead of the
815: real host name when looking up or saving the host key
1.251 djm 816: in the host key database files and when validating host certificates.
1.84 jmc 817: This option is useful for tunneling SSH connections
1.1 stevesk 818: or for multiple servers running on a single host.
819: .It Cm HostName
820: Specifies the real host name to log into.
821: This can be used to specify nicknames or abbreviations for hosts.
1.239 jmc 822: Arguments to
823: .Cm HostName
824: accept the tokens described in the
825: .Sx TOKENS
826: section.
1.1 stevesk 827: Numeric IP addresses are also permitted (both on the command line and in
828: .Cm HostName
829: specifications).
1.239 jmc 830: The default is the name given on the command line.
1.29 markus 831: .It Cm IdentitiesOnly
832: Specifies that
1.84 jmc 833: .Xr ssh 1
1.221 djm 834: should only use the authentication identity and certificate files explicitly
835: configured in the
1.31 jmc 836: .Nm
1.221 djm 837: files
838: or passed on the
839: .Xr ssh 1
840: command-line,
1.84 jmc 841: even if
842: .Xr ssh-agent 1
1.159 djm 843: or a
844: .Cm PKCS11Provider
1.29 markus 845: offers more identities.
846: The argument to this keyword must be
1.240 jmc 847: .Cm yes
1.29 markus 848: or
1.240 jmc 849: .Cm no
850: (the default).
1.84 jmc 851: This option is intended for situations where ssh-agent
1.29 markus 852: offers many different identities.
1.231 markus 853: .It Cm IdentityAgent
854: Specifies the
855: .Ux Ns -domain
856: socket used to communicate with the authentication agent.
857: .Pp
858: This option overrides the
1.240 jmc 859: .Ev SSH_AUTH_SOCK
1.231 markus 860: environment variable and can be used to select a specific agent.
861: Setting the socket name to
1.240 jmc 862: .Cm none
1.231 markus 863: disables the use of an authentication agent.
1.232 markus 864: If the string
1.240 jmc 865: .Qq SSH_AUTH_SOCK
1.232 markus 866: is specified, the location of the socket will be read from the
867: .Ev SSH_AUTH_SOCK
868: environment variable.
1.231 markus 869: .Pp
1.239 jmc 870: Arguments to
871: .Cm IdentityAgent
872: may use the tilde syntax to refer to a user's home directory
873: or the tokens described in the
874: .Sx TOKENS
875: section.
1.67 jmc 876: .It Cm IdentityFile
1.192 sobrado 877: Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA authentication
1.139 djm 878: identity is read.
1.67 jmc 879: The default is
1.139 djm 880: .Pa ~/.ssh/id_dsa ,
1.183 naddy 881: .Pa ~/.ssh/id_ecdsa ,
882: .Pa ~/.ssh/id_ed25519
1.139 djm 883: and
1.245 djm 884: .Pa ~/.ssh/id_rsa .
1.67 jmc 885: Additionally, any identities represented by the authentication agent
1.165 djm 886: will be used for authentication unless
887: .Cm IdentitiesOnly
888: is set.
1.221 djm 889: If no certificates have been explicitly specified by
890: .Cm CertificateFile ,
1.129 djm 891: .Xr ssh 1
892: will try to load certificate information from the filename obtained by
893: appending
894: .Pa -cert.pub
895: to the path of a specified
896: .Cm IdentityFile .
1.90 djm 897: .Pp
1.239 jmc 898: Arguments to
899: .Cm IdentityFile
900: may use the tilde syntax to refer to a user's home directory
901: or the tokens described in the
902: .Sx TOKENS
903: section.
1.90 djm 904: .Pp
1.67 jmc 905: It is possible to have
906: multiple identity files specified in configuration files; all these
907: identities will be tried in sequence.
1.152 djm 908: Multiple
909: .Cm IdentityFile
910: directives will add to the list of identities tried (this behaviour
911: differs from that of other configuration directives).
1.165 djm 912: .Pp
913: .Cm IdentityFile
914: may be used in conjunction with
915: .Cm IdentitiesOnly
916: to select which identities in an agent are offered during authentication.
1.221 djm 917: .Cm IdentityFile
918: may also be used in conjunction with
919: .Cm CertificateFile
920: in order to provide any certificate also needed for authentication with
921: the identity.
1.164 jmc 922: .It Cm IgnoreUnknown
923: Specifies a pattern-list of unknown options to be ignored if they are
924: encountered in configuration parsing.
925: This may be used to suppress errors if
926: .Nm
927: contains options that are unrecognised by
928: .Xr ssh 1 .
929: It is recommended that
930: .Cm IgnoreUnknown
931: be listed early in the configuration file as it will not be applied
932: to unknown options that appear before it.
1.229 djm 933: .It Cm Include
934: Include the specified configuration file(s).
1.230 jmc 935: Multiple pathnames may be specified and each pathname may contain
1.229 djm 936: .Xr glob 3
937: wildcards and, for user configurations, shell-like
1.240 jmc 938: .Sq ~
1.229 djm 939: references to user home directories.
940: Files without absolute paths are assumed to be in
941: .Pa ~/.ssh
1.230 jmc 942: if included in a user configuration file or
1.229 djm 943: .Pa /etc/ssh
944: if included from the system configuration file.
945: .Cm Include
946: directive may appear inside a
947: .Cm Match
948: or
949: .Cm Host
950: block
951: to perform conditional inclusion.
1.143 djm 952: .It Cm IPQoS
953: Specifies the IPv4 type-of-service or DSCP class for connections.
954: Accepted values are
1.240 jmc 955: .Cm af11 ,
956: .Cm af12 ,
957: .Cm af13 ,
958: .Cm af21 ,
959: .Cm af22 ,
960: .Cm af23 ,
961: .Cm af31 ,
962: .Cm af32 ,
963: .Cm af33 ,
964: .Cm af41 ,
965: .Cm af42 ,
966: .Cm af43 ,
967: .Cm cs0 ,
968: .Cm cs1 ,
969: .Cm cs2 ,
970: .Cm cs3 ,
971: .Cm cs4 ,
972: .Cm cs5 ,
973: .Cm cs6 ,
974: .Cm cs7 ,
975: .Cm ef ,
976: .Cm lowdelay ,
977: .Cm throughput ,
978: .Cm reliability ,
1.253 djm 979: a numeric value, or
980: .Cm none
981: to use the operating system default.
1.146 djm 982: This option may take one or two arguments, separated by whitespace.
1.143 djm 983: If one argument is specified, it is used as the packet class unconditionally.
984: If two values are specified, the first is automatically selected for
985: interactive sessions and the second for non-interactive sessions.
986: The default is
1.240 jmc 987: .Cm lowdelay
1.143 djm 988: for interactive sessions and
1.240 jmc 989: .Cm throughput
1.143 djm 990: for non-interactive sessions.
1.103 djm 991: .It Cm KbdInteractiveAuthentication
992: Specifies whether to use keyboard-interactive authentication.
993: The argument to this keyword must be
1.240 jmc 994: .Cm yes
995: (the default)
1.103 djm 996: or
1.240 jmc 997: .Cm no .
1.39 djm 998: .It Cm KbdInteractiveDevices
999: Specifies the list of methods to use in keyboard-interactive authentication.
1000: Multiple method names must be comma-separated.
1001: The default is to use the server specified list.
1.85 jmc 1002: The methods available vary depending on what the server supports.
1003: For an OpenSSH server,
1004: it may be zero or more of:
1.240 jmc 1005: .Cm bsdauth ,
1006: .Cm pam ,
1.85 jmc 1007: and
1.240 jmc 1008: .Cm skey .
1.140 djm 1009: .It Cm KexAlgorithms
1010: Specifies the available KEX (Key Exchange) algorithms.
1011: Multiple algorithms must be comma-separated.
1.214 djm 1012: Alternately if the specified value begins with a
1013: .Sq +
1014: character, then the specified methods will be appended to the default set
1015: instead of replacing them.
1.241 djm 1016: If the specified value begins with a
1017: .Sq -
1018: character, then the specified methods (including wildcards) will be removed
1019: from the default set instead of replacing them.
1.141 jmc 1020: The default is:
1021: .Bd -literal -offset indent
1.238 djm 1022: curve25519-sha256,curve25519-sha256@libssh.org,
1.141 jmc 1023: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1024: diffie-hellman-group-exchange-sha256,
1.266 djm 1025: diffie-hellman-group16-sha512,
1026: diffie-hellman-group18-sha512,
1.209 dtucker 1027: diffie-hellman-group-exchange-sha1,
1.266 djm 1028: diffie-hellman-group14-sha256,
1.212 djm 1029: diffie-hellman-group14-sha1
1.141 jmc 1030: .Ed
1.198 djm 1031: .Pp
1.240 jmc 1032: The list of available key exchange algorithms may also be obtained using
1033: .Qq ssh -Q kex .
1.65 reyk 1034: .It Cm LocalCommand
1035: Specifies a command to execute on the local machine after successfully
1036: connecting to the server.
1037: The command string extends to the end of the line, and is executed with
1.105 jmc 1038: the user's shell.
1.239 jmc 1039: Arguments to
1040: .Cm LocalCommand
1041: accept the tokens described in the
1042: .Sx TOKENS
1043: section.
1.123 djm 1044: .Pp
1045: The command is run synchronously and does not have access to the
1046: session of the
1047: .Xr ssh 1
1048: that spawned it.
1049: It should not be used for interactive commands.
1050: .Pp
1.65 reyk 1051: This directive is ignored unless
1052: .Cm PermitLocalCommand
1053: has been enabled.
1.1 stevesk 1054: .It Cm LocalForward
1.74 jmc 1055: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 1056: the secure channel to the specified host and port from the remote machine.
1.49 jmc 1057: The first argument must be
1.43 djm 1058: .Sm off
1.49 jmc 1059: .Oo Ar bind_address : Oc Ar port
1.43 djm 1060: .Sm on
1.49 jmc 1061: and the second argument must be
1062: .Ar host : Ns Ar hostport .
1.138 djm 1063: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 1064: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 1065: given on the command line.
1.1 stevesk 1066: Only the superuser can forward privileged ports.
1.43 djm 1067: By default, the local port is bound in accordance with the
1068: .Cm GatewayPorts
1069: setting.
1070: However, an explicit
1071: .Ar bind_address
1072: may be used to bind the connection to a specific address.
1073: The
1074: .Ar bind_address
1075: of
1.240 jmc 1076: .Cm localhost
1.46 jmc 1077: indicates that the listening port be bound for local use only, while an
1078: empty address or
1079: .Sq *
1.43 djm 1080: indicates that the port should be available from all interfaces.
1.1 stevesk 1081: .It Cm LogLevel
1082: Gives the verbosity level that is used when logging messages from
1.84 jmc 1083: .Xr ssh 1 .
1.1 stevesk 1084: The possible values are:
1.84 jmc 1085: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 1086: The default is INFO.
1087: DEBUG and DEBUG1 are equivalent.
1088: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 1089: .It Cm MACs
1090: Specifies the MAC (message authentication code) algorithms
1091: in order of preference.
1.226 jmc 1092: The MAC algorithm is used for data integrity protection.
1.1 stevesk 1093: Multiple algorithms must be comma-separated.
1.214 djm 1094: If the specified value begins with a
1095: .Sq +
1096: character, then the specified algorithms will be appended to the default set
1097: instead of replacing them.
1.241 djm 1098: If the specified value begins with a
1099: .Sq -
1100: character, then the specified algorithms (including wildcards) will be removed
1101: from the default set instead of replacing them.
1.214 djm 1102: .Pp
1.160 markus 1103: The algorithms that contain
1.240 jmc 1104: .Qq -etm
1.160 markus 1105: calculate the MAC after encryption (encrypt-then-mac).
1106: These are considered safer and their use recommended.
1.214 djm 1107: .Pp
1.84 jmc 1108: The default is:
1.101 jmc 1109: .Bd -literal -offset indent
1.160 markus 1110: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1111: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.224 djm 1112: hmac-sha1-etm@openssh.com,
1.186 naddy 1113: umac-64@openssh.com,umac-128@openssh.com,
1.224 djm 1114: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.101 jmc 1115: .Ed
1.198 djm 1116: .Pp
1.240 jmc 1117: The list of available MAC algorithms may also be obtained using
1118: .Qq ssh -Q mac .
1.1 stevesk 1119: .It Cm NoHostAuthenticationForLocalhost
1.264 djm 1120: Disable host authentication for localhost (loopback addresses).
1.1 stevesk 1121: The argument to this keyword must be
1.240 jmc 1122: .Cm yes
1.1 stevesk 1123: or
1.242 jmc 1124: .Cm no
1.240 jmc 1125: (the default).
1.1 stevesk 1126: .It Cm NumberOfPasswordPrompts
1127: Specifies the number of password prompts before giving up.
1128: The argument to this keyword must be an integer.
1.84 jmc 1129: The default is 3.
1.1 stevesk 1130: .It Cm PasswordAuthentication
1131: Specifies whether to use password authentication.
1132: The argument to this keyword must be
1.240 jmc 1133: .Cm yes
1134: (the default)
1.1 stevesk 1135: or
1.240 jmc 1136: .Cm no .
1.65 reyk 1137: .It Cm PermitLocalCommand
1138: Allow local command execution via the
1139: .Ic LocalCommand
1140: option or using the
1.66 jmc 1141: .Ic !\& Ns Ar command
1.65 reyk 1142: escape sequence in
1143: .Xr ssh 1 .
1144: The argument must be
1.240 jmc 1145: .Cm yes
1.65 reyk 1146: or
1.240 jmc 1147: .Cm no
1148: (the default).
1.127 markus 1149: .It Cm PKCS11Provider
1150: Specifies which PKCS#11 provider to use.
1.144 jmc 1151: The argument to this keyword is the PKCS#11 shared library
1.127 markus 1152: .Xr ssh 1
1.128 markus 1153: should use to communicate with a PKCS#11 token providing the user's
1.127 markus 1154: private RSA key.
1.67 jmc 1155: .It Cm Port
1156: Specifies the port number to connect on the remote host.
1.84 jmc 1157: The default is 22.
1.1 stevesk 1158: .It Cm PreferredAuthentications
1.226 jmc 1159: Specifies the order in which the client should try authentication methods.
1.48 jmc 1160: This allows a client to prefer one method (e.g.\&
1.1 stevesk 1161: .Cm keyboard-interactive )
1.48 jmc 1162: over another method (e.g.\&
1.131 jmc 1163: .Cm password ) .
1164: The default is:
1165: .Bd -literal -offset indent
1166: gssapi-with-mic,hostbased,publickey,
1167: keyboard-interactive,password
1168: .Ed
1.1 stevesk 1169: .It Cm ProxyCommand
1170: Specifies the command to use to connect to the server.
1171: The command
1.190 djm 1172: string extends to the end of the line, and is executed
1173: using the user's shell
1174: .Ql exec
1175: directive to avoid a lingering shell process.
1176: .Pp
1.239 jmc 1177: Arguments to
1178: .Cm ProxyCommand
1179: accept the tokens described in the
1180: .Sx TOKENS
1181: section.
1.1 stevesk 1182: The command can be basically anything,
1183: and should read from its standard input and write to its standard output.
1184: It should eventually connect an
1185: .Xr sshd 8
1186: server running on some machine, or execute
1187: .Ic sshd -i
1188: somewhere.
1189: Host key management will be done using the
1190: HostName of the host being connected (defaulting to the name typed by
1191: the user).
1.7 jmc 1192: Setting the command to
1.240 jmc 1193: .Cm none
1.6 markus 1194: disables this option entirely.
1.1 stevesk 1195: Note that
1196: .Cm CheckHostIP
1197: is not available for connects with a proxy command.
1.52 djm 1198: .Pp
1199: This directive is useful in conjunction with
1200: .Xr nc 1
1201: and its proxy support.
1.53 jmc 1202: For example, the following directive would connect via an HTTP proxy at
1.52 djm 1203: 192.0.2.0:
1204: .Bd -literal -offset 3n
1205: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1206: .Ed
1.233 djm 1207: .It Cm ProxyJump
1.260 millert 1208: Specifies one or more jump proxies as either
1.233 djm 1209: .Xo
1210: .Sm off
1.234 jmc 1211: .Op Ar user No @
1.233 djm 1212: .Ar host
1.234 jmc 1213: .Op : Ns Ar port
1.233 djm 1214: .Sm on
1.260 millert 1215: or an ssh URI
1.233 djm 1216: .Xc .
1.235 djm 1217: Multiple proxies may be separated by comma characters and will be visited
1.236 djm 1218: sequentially.
1.233 djm 1219: Setting this option will cause
1220: .Xr ssh 1
1221: to connect to the target host by first making a
1222: .Xr ssh 1
1223: connection to the specified
1224: .Cm ProxyJump
1225: host and then establishing a
1.234 jmc 1226: TCP forwarding to the ultimate target from there.
1.233 djm 1227: .Pp
1228: Note that this option will compete with the
1229: .Cm ProxyCommand
1230: option - whichever is specified first will prevent later instances of the
1231: other from taking effect.
1.167 djm 1232: .It Cm ProxyUseFdpass
1.168 jmc 1233: Specifies that
1.167 djm 1234: .Cm ProxyCommand
1235: will pass a connected file descriptor back to
1.168 jmc 1236: .Xr ssh 1
1.167 djm 1237: instead of continuing to execute and pass data.
1238: The default is
1.240 jmc 1239: .Cm no .
1.213 markus 1240: .It Cm PubkeyAcceptedKeyTypes
1241: Specifies the key types that will be used for public key authentication
1242: as a comma-separated pattern list.
1.214 djm 1243: Alternately if the specified value begins with a
1244: .Sq +
1245: character, then the key types after it will be appended to the default
1246: instead of replacing it.
1.241 djm 1247: If the specified value begins with a
1248: .Sq -
1249: character, then the specified key types (including wildcards) will be removed
1250: from the default set instead of replacing them.
1.213 markus 1251: The default for this option is:
1252: .Bd -literal -offset 3n
1253: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1254: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1255: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1256: ssh-ed25519-cert-v01@openssh.com,
1257: ssh-rsa-cert-v01@openssh.com,
1258: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.227 djm 1259: ssh-ed25519,ssh-rsa
1.213 markus 1260: .Ed
1261: .Pp
1.240 jmc 1262: The list of available key types may also be obtained using
1263: .Qq ssh -Q key .
1.1 stevesk 1264: .It Cm PubkeyAuthentication
1265: Specifies whether to try public key authentication.
1266: The argument to this keyword must be
1.240 jmc 1267: .Cm yes
1268: (the default)
1.1 stevesk 1269: or
1.240 jmc 1270: .Cm no .
1.75 dtucker 1271: .It Cm RekeyLimit
1272: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1273: session key is renegotiated, optionally followed a maximum amount of
1274: time that may pass before the session key is renegotiated.
1275: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1276: .Sq K ,
1277: .Sq M ,
1.75 dtucker 1278: or
1.76 jmc 1279: .Sq G
1.75 dtucker 1280: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1281: The default is between
1.84 jmc 1282: .Sq 1G
1.75 dtucker 1283: and
1.84 jmc 1284: .Sq 4G ,
1.75 dtucker 1285: depending on the cipher.
1.162 dtucker 1286: The optional second value is specified in seconds and may use any of the
1287: units documented in the
1.240 jmc 1288: .Sx TIME FORMATS
1289: section of
1.162 dtucker 1290: .Xr sshd_config 5 .
1291: The default value for
1292: .Cm RekeyLimit
1293: is
1.240 jmc 1294: .Cm default none ,
1.162 dtucker 1295: which means that rekeying is performed after the cipher's default amount
1296: of data has been sent or received and no time based rekeying is done.
1.249 bluhm 1297: .It Cm RemoteCommand
1298: Specifies a command to execute on the remote machine after successfully
1299: connecting to the server.
1300: The command string extends to the end of the line, and is executed with
1301: the user's shell.
1.250 jmc 1302: Arguments to
1303: .Cm RemoteCommand
1304: accept the tokens described in the
1305: .Sx TOKENS
1306: section.
1.1 stevesk 1307: .It Cm RemoteForward
1.74 jmc 1308: Specifies that a TCP port on the remote machine be forwarded over
1.256 markus 1309: the secure channel.
1310: The remote port may either be fowarded to a specified host and port
1311: from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
1312: client to connect to arbitrary destinations from the local machine.
1.49 jmc 1313: The first argument must be
1.43 djm 1314: .Sm off
1.49 jmc 1315: .Oo Ar bind_address : Oc Ar port
1.43 djm 1316: .Sm on
1.256 markus 1317: If forwarding to a specific destination then the second argument must be
1318: .Ar host : Ns Ar hostport ,
1319: otherwise if no destination argument is specified then the remote forwarding
1320: will be established as a SOCKS proxy.
1321: .Pp
1.138 djm 1322: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.1 stevesk 1323: Multiple forwardings may be specified, and additional
1324: forwardings can be given on the command line.
1.113 stevesk 1325: Privileged ports can be forwarded only when
1326: logging in as root on the remote machine.
1.118 jmc 1327: .Pp
1.117 djm 1328: If the
1329: .Ar port
1.240 jmc 1330: argument is 0,
1.117 djm 1331: the listen port will be dynamically allocated on the server and reported
1332: to the client at run time.
1.43 djm 1333: .Pp
1334: If the
1335: .Ar bind_address
1336: is not specified, the default is to only bind to loopback addresses.
1337: If the
1338: .Ar bind_address
1339: is
1340: .Ql *
1341: or an empty string, then the forwarding is requested to listen on all
1342: interfaces.
1343: Specifying a remote
1344: .Ar bind_address
1.46 jmc 1345: will only succeed if the server's
1346: .Cm GatewayPorts
1.43 djm 1347: option is enabled (see
1.46 jmc 1348: .Xr sshd_config 5 ) .
1.149 djm 1349: .It Cm RequestTTY
1350: Specifies whether to request a pseudo-tty for the session.
1351: The argument may be one of:
1.240 jmc 1352: .Cm no
1.149 djm 1353: (never request a TTY),
1.240 jmc 1354: .Cm yes
1.149 djm 1355: (always request a TTY when standard input is a TTY),
1.240 jmc 1356: .Cm force
1.149 djm 1357: (always request a TTY) or
1.240 jmc 1358: .Cm auto
1.149 djm 1359: (request a TTY when opening a login session).
1360: This option mirrors the
1361: .Fl t
1362: and
1363: .Fl T
1364: flags for
1365: .Xr ssh 1 .
1.196 djm 1366: .It Cm RevokedHostKeys
1367: Specifies revoked host public keys.
1368: Keys listed in this file will be refused for host authentication.
1369: Note that if this file does not exist or is not readable,
1370: then host authentication will be refused for all hosts.
1371: Keys may be specified as a text file, listing one public key per line, or as
1372: an OpenSSH Key Revocation List (KRL) as generated by
1373: .Xr ssh-keygen 1 .
1374: For more information on KRLs, see the KEY REVOCATION LISTS section in
1375: .Xr ssh-keygen 1 .
1.32 djm 1376: .It Cm SendEnv
1377: Specifies what variables from the local
1378: .Xr environ 7
1379: should be sent to the server.
1.84 jmc 1380: The server must also support it, and the server must be configured to
1.33 djm 1381: accept these environment variables.
1.207 dtucker 1382: Note that the
1383: .Ev TERM
1.208 jmc 1384: environment variable is always sent whenever a
1.207 dtucker 1385: pseudo-terminal is requested as it is required by the protocol.
1.32 djm 1386: Refer to
1387: .Cm AcceptEnv
1388: in
1389: .Xr sshd_config 5
1390: for how to configure the server.
1.80 jmc 1391: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1392: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1393: across multiple
1394: .Cm SendEnv
1395: directives.
1396: The default is not to send any environment variables.
1.81 jmc 1397: .Pp
1398: See
1399: .Sx PATTERNS
1400: for more information on patterns.
1.28 markus 1401: .It Cm ServerAliveCountMax
1.73 jmc 1402: Sets the number of server alive messages (see below) which may be
1.28 markus 1403: sent without
1.84 jmc 1404: .Xr ssh 1
1.28 markus 1405: receiving any messages back from the server.
1406: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1407: ssh will disconnect from the server, terminating the session.
1.28 markus 1408: It is important to note that the use of server alive messages is very
1409: different from
1410: .Cm TCPKeepAlive
1411: (below).
1412: The server alive messages are sent through the encrypted channel
1413: and therefore will not be spoofable.
1414: The TCP keepalive option enabled by
1415: .Cm TCPKeepAlive
1416: is spoofable.
1417: The server alive mechanism is valuable when the client or
1418: server depend on knowing when a connection has become inactive.
1419: .Pp
1420: The default value is 3.
1421: If, for example,
1422: .Cm ServerAliveInterval
1.84 jmc 1423: (see below) is set to 15 and
1.28 markus 1424: .Cm ServerAliveCountMax
1.84 jmc 1425: is left at the default, if the server becomes unresponsive,
1426: ssh will disconnect after approximately 45 seconds.
1.67 jmc 1427: .It Cm ServerAliveInterval
1428: Sets a timeout interval in seconds after which if no data has been received
1429: from the server,
1.84 jmc 1430: .Xr ssh 1
1.67 jmc 1431: will send a message through the encrypted
1432: channel to request a response from the server.
1433: The default
1434: is 0, indicating that these messages will not be sent to the server.
1.191 millert 1435: .It Cm StreamLocalBindMask
1436: Sets the octal file creation mode mask
1437: .Pq umask
1438: used when creating a Unix-domain socket file for local or remote
1439: port forwarding.
1440: This option is only used for port forwarding to a Unix-domain socket file.
1441: .Pp
1442: The default value is 0177, which creates a Unix-domain socket file that is
1443: readable and writable only by the owner.
1444: Note that not all operating systems honor the file mode on Unix-domain
1445: socket files.
1446: .It Cm StreamLocalBindUnlink
1447: Specifies whether to remove an existing Unix-domain socket file for local
1448: or remote port forwarding before creating a new one.
1449: If the socket file already exists and
1450: .Cm StreamLocalBindUnlink
1451: is not enabled,
1452: .Nm ssh
1453: will be unable to forward the port to the Unix-domain socket file.
1454: This option is only used for port forwarding to a Unix-domain socket file.
1455: .Pp
1456: The argument must be
1.240 jmc 1457: .Cm yes
1.191 millert 1458: or
1.240 jmc 1459: .Cm no
1460: (the default).
1.1 stevesk 1461: .It Cm StrictHostKeyChecking
1462: If this flag is set to
1.240 jmc 1463: .Cm yes ,
1.84 jmc 1464: .Xr ssh 1
1.1 stevesk 1465: will never automatically add host keys to the
1.50 djm 1466: .Pa ~/.ssh/known_hosts
1.1 stevesk 1467: file, and refuses to connect to hosts whose host key has changed.
1.263 dtucker 1468: This provides maximum protection against man-in-the-middle (MITM) attacks,
1.84 jmc 1469: though it can be annoying when the
1.1 stevesk 1470: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1471: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1472: frequently made.
1473: This option forces the user to manually
1474: add all new hosts.
1.255 jmc 1475: .Pp
1.1 stevesk 1476: If this flag is set to
1.254 djm 1477: .Dq accept-new
1.255 jmc 1478: then ssh will automatically add new host keys to the user
1.254 djm 1479: known hosts files, but will not permit connections to hosts with
1480: changed host keys.
1481: If this flag is set to
1482: .Dq no
1483: or
1484: .Dq off ,
1.255 jmc 1485: ssh will automatically add new host keys to the user known hosts files
1486: and allow connections to hosts with changed hostkeys to proceed,
1487: subject to some restrictions.
1.1 stevesk 1488: If this flag is set to
1.240 jmc 1489: .Cm ask
1490: (the default),
1.1 stevesk 1491: new host keys
1492: will be added to the user known host files only after the user
1493: has confirmed that is what they really want to do, and
1.84 jmc 1494: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1495: The host keys of
1496: known hosts will be verified automatically in all cases.
1.244 jmc 1497: .It Cm SyslogFacility
1498: Gives the facility code that is used when logging messages from
1499: .Xr ssh 1 .
1500: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1501: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1502: The default is USER.
1.26 markus 1503: .It Cm TCPKeepAlive
1504: Specifies whether the system should send TCP keepalive messages to the
1505: other side.
1506: If they are sent, death of the connection or crash of one
1507: of the machines will be properly noticed.
1508: However, this means that
1509: connections will die if the route is down temporarily, and some people
1510: find it annoying.
1511: .Pp
1512: The default is
1.240 jmc 1513: .Cm yes
1.26 markus 1514: (to send TCP keepalive messages), and the client will notice
1515: if the network goes down or the remote host dies.
1516: This is important in scripts, and many users want it too.
1517: .Pp
1518: To disable TCP keepalive messages, the value should be set to
1.240 jmc 1519: .Cm no .
1.265 djm 1520: See also
1521: .Cm ServerAliveInterval
1522: for protocol-level keepalives.
1.65 reyk 1523: .It Cm Tunnel
1.95 stevesk 1524: Request
1.65 reyk 1525: .Xr tun 4
1.69 jmc 1526: device forwarding between the client and the server.
1.65 reyk 1527: The argument must be
1.240 jmc 1528: .Cm yes ,
1529: .Cm point-to-point
1.95 stevesk 1530: (layer 3),
1.240 jmc 1531: .Cm ethernet
1.95 stevesk 1532: (layer 2),
1.65 reyk 1533: or
1.240 jmc 1534: .Cm no
1535: (the default).
1.95 stevesk 1536: Specifying
1.240 jmc 1537: .Cm yes
1.95 stevesk 1538: requests the default tunnel mode, which is
1.240 jmc 1539: .Cm point-to-point .
1.65 reyk 1540: .It Cm TunnelDevice
1.95 stevesk 1541: Specifies the
1.65 reyk 1542: .Xr tun 4
1.95 stevesk 1543: devices to open on the client
1544: .Pq Ar local_tun
1545: and the server
1546: .Pq Ar remote_tun .
1547: .Pp
1548: The argument must be
1549: .Sm off
1550: .Ar local_tun Op : Ar remote_tun .
1551: .Sm on
1552: The devices may be specified by numerical ID or the keyword
1.240 jmc 1553: .Cm any ,
1.95 stevesk 1554: which uses the next available tunnel device.
1555: If
1556: .Ar remote_tun
1557: is not specified, it defaults to
1.240 jmc 1558: .Cm any .
1.95 stevesk 1559: The default is
1.240 jmc 1560: .Cm any:any .
1.201 djm 1561: .It Cm UpdateHostKeys
1.200 djm 1562: Specifies whether
1563: .Xr ssh 1
1564: should accept notifications of additional hostkeys from the server sent
1565: after authentication has completed and add them to
1566: .Cm UserKnownHostsFile .
1567: The argument must be
1.240 jmc 1568: .Cm yes ,
1569: .Cm no
1.204 djm 1570: (the default) or
1.240 jmc 1571: .Cm ask .
1.200 djm 1572: Enabling this option allows learning alternate hostkeys for a server
1.201 djm 1573: and supports graceful key rotation by allowing a server to send replacement
1574: public keys before old ones are removed.
1.200 djm 1575: Additional hostkeys are only accepted if the key used to authenticate the
1.220 sobrado 1576: host was already trusted or explicitly accepted by the user.
1.204 djm 1577: If
1578: .Cm UpdateHostKeys
1579: is set to
1.240 jmc 1580: .Cm ask ,
1.204 djm 1581: then the user is asked to confirm the modifications to the known_hosts file.
1.205 djm 1582: Confirmation is currently incompatible with
1583: .Cm ControlPersist ,
1584: and will be disabled if it is enabled.
1.200 djm 1585: .Pp
1586: Presently, only
1587: .Xr sshd 8
1588: from OpenSSH 6.8 and greater support the
1.240 jmc 1589: .Qq hostkeys@openssh.com
1.200 djm 1590: protocol extension used to inform the client of all the server's hostkeys.
1.72 jmc 1591: .It Cm UsePrivilegedPort
1592: Specifies whether to use a privileged port for outgoing connections.
1593: The argument must be
1.240 jmc 1594: .Cm yes
1.72 jmc 1595: or
1.240 jmc 1596: .Cm no
1597: (the default).
1.72 jmc 1598: If set to
1.240 jmc 1599: .Cm yes ,
1.84 jmc 1600: .Xr ssh 1
1.72 jmc 1601: must be setuid root.
1.1 stevesk 1602: .It Cm User
1603: Specifies the user to log in as.
1604: This can be useful when a different user name is used on different machines.
1605: This saves the trouble of
1606: having to remember to give the user name on the command line.
1607: .It Cm UserKnownHostsFile
1.151 djm 1608: Specifies one or more files to use for the user
1609: host key database, separated by whitespace.
1610: The default is
1611: .Pa ~/.ssh/known_hosts ,
1612: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1613: .It Cm VerifyHostKeyDNS
1614: Specifies whether to verify the remote key using DNS and SSHFP resource
1615: records.
1.24 jakob 1616: If this option is set to
1.240 jmc 1617: .Cm yes ,
1.25 jmc 1618: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1619: from DNS.
1620: Insecure fingerprints will be handled as if this option was set to
1.240 jmc 1621: .Cm ask .
1.24 jakob 1622: If this option is set to
1.240 jmc 1623: .Cm ask ,
1.24 jakob 1624: information on fingerprint match will be displayed, but the user will still
1625: need to confirm new host keys according to the
1626: .Cm StrictHostKeyChecking
1627: option.
1.8 jakob 1628: The default is
1.240 jmc 1629: .Cm no .
1.84 jmc 1630: .Pp
1.240 jmc 1631: See also
1632: .Sx VERIFYING HOST KEYS
1633: in
1.84 jmc 1634: .Xr ssh 1 .
1.111 grunk 1635: .It Cm VisualHostKey
1636: If this flag is set to
1.240 jmc 1637: .Cm yes ,
1.111 grunk 1638: an ASCII art representation of the remote host key fingerprint is
1.197 djm 1639: printed in addition to the fingerprint string at login and
1.114 stevesk 1640: for unknown host keys.
1.111 grunk 1641: If this flag is set to
1.240 jmc 1642: .Cm no
1643: (the default),
1.114 stevesk 1644: no fingerprint strings are printed at login and
1.197 djm 1645: only the fingerprint string will be printed for unknown host keys.
1.1 stevesk 1646: .It Cm XAuthLocation
1.5 stevesk 1647: Specifies the full pathname of the
1.1 stevesk 1648: .Xr xauth 1
1649: program.
1650: The default is
1651: .Pa /usr/X11R6/bin/xauth .
1652: .El
1.86 jmc 1653: .Sh PATTERNS
1654: A
1655: .Em pattern
1656: consists of zero or more non-whitespace characters,
1657: .Sq *
1658: (a wildcard that matches zero or more characters),
1659: or
1660: .Sq ?\&
1661: (a wildcard that matches exactly one character).
1662: For example, to specify a set of declarations for any host in the
1.240 jmc 1663: .Qq .co.uk
1.86 jmc 1664: set of domains,
1665: the following pattern could be used:
1666: .Pp
1667: .Dl Host *.co.uk
1668: .Pp
1669: The following pattern
1670: would match any host in the 192.168.0.[0-9] network range:
1671: .Pp
1672: .Dl Host 192.168.0.?
1673: .Pp
1674: A
1675: .Em pattern-list
1676: is a comma-separated list of patterns.
1677: Patterns within pattern-lists may be negated
1678: by preceding them with an exclamation mark
1679: .Pq Sq !\& .
1680: For example,
1.174 djm 1681: to allow a key to be used from anywhere within an organization
1.86 jmc 1682: except from the
1.240 jmc 1683: .Qq dialup
1.86 jmc 1684: pool,
1685: the following entry (in authorized_keys) could be used:
1686: .Pp
1687: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.258 djm 1688: .Pp
1689: Note that a negated match will never produce a positive result by itself.
1690: For example, attempting to match
1691: .Qq host3
1692: against the following pattern-list will fail:
1693: .Pp
1694: .Dl from=\&"!host1,!host2\&"
1695: .Pp
1696: The solution here is to include a term that will yield a positive match,
1697: such as a wildcard:
1698: .Pp
1699: .Dl from=\&"!host1,!host2,*\&"
1.239 jmc 1700: .Sh TOKENS
1701: Arguments to some keywords can make use of tokens,
1702: which are expanded at runtime:
1703: .Pp
1704: .Bl -tag -width XXXX -offset indent -compact
1705: .It %%
1706: A literal
1707: .Sq % .
1708: .It \&%C
1.257 jmc 1709: Hash of %l%h%p%r.
1.239 jmc 1710: .It %d
1711: Local user's home directory.
1712: .It %h
1713: The remote hostname.
1714: .It %i
1715: The local user ID.
1716: .It %L
1717: The local hostname.
1718: .It %l
1719: The local hostname, including the domain name.
1720: .It %n
1721: The original remote hostname, as given on the command line.
1722: .It %p
1723: The remote port.
1724: .It %r
1725: The remote username.
1.261 djm 1726: .It \&%T
1727: The local
1728: .Xr tun 4
1729: or
1730: .Xr tap 4
1731: network interface assigned if
1.262 jmc 1732: tunnel forwarding was requested, or
1733: .Qq NONE
1.261 djm 1734: otherwise.
1.239 jmc 1735: .It %u
1736: The local username.
1737: .El
1738: .Pp
1739: .Cm Match exec
1740: accepts the tokens %%, %h, %L, %l, %n, %p, %r, and %u.
1741: .Pp
1742: .Cm CertificateFile
1743: accepts the tokens %%, %d, %h, %l, %r, and %u.
1744: .Pp
1745: .Cm ControlPath
1746: accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
1747: .Pp
1748: .Cm HostName
1749: accepts the tokens %% and %h.
1750: .Pp
1751: .Cm IdentityAgent
1752: and
1753: .Cm IdentityFile
1754: accept the tokens %%, %d, %h, %l, %r, and %u.
1755: .Pp
1756: .Cm LocalCommand
1.261 djm 1757: accepts the tokens %%, %C, %d, %h, %l, %n, %p, %r, %T, and %u.
1.239 jmc 1758: .Pp
1759: .Cm ProxyCommand
1760: accepts the tokens %%, %h, %p, and %r.
1.250 jmc 1761: .Pp
1762: .Cm RemoteCommand
1763: accepts the tokens %%, %C, %d, %h, %l, %n, %p, %r, and %u.
1.1 stevesk 1764: .Sh FILES
1765: .Bl -tag -width Ds
1.50 djm 1766: .It Pa ~/.ssh/config
1.1 stevesk 1767: This is the per-user configuration file.
1768: The format of this file is described above.
1.84 jmc 1769: This file is used by the SSH client.
1.30 djm 1770: Because of the potential for abuse, this file must have strict permissions:
1771: read/write for the user, and not accessible by others.
1.1 stevesk 1772: .It Pa /etc/ssh/ssh_config
1773: Systemwide configuration file.
1774: This file provides defaults for those
1775: values that are not specified in the user's configuration file, and
1776: for those users who do not have a configuration file.
1777: This file must be world-readable.
1778: .El
1.13 jmc 1779: .Sh SEE ALSO
1780: .Xr ssh 1
1.1 stevesk 1781: .Sh AUTHORS
1.240 jmc 1782: .An -nosplit
1.1 stevesk 1783: OpenSSH is a derivative of the original and free
1.240 jmc 1784: ssh 1.2.12 release by
1785: .An Tatu Ylonen .
1786: .An Aaron Campbell , Bob Beck , Markus Friedl ,
1787: .An Niels Provos , Theo de Raadt
1788: and
1789: .An Dug Song
1.1 stevesk 1790: removed many bugs, re-added newer features and
1791: created OpenSSH.
1.240 jmc 1792: .An Markus Friedl
1793: contributed the support for SSH protocol versions 1.5 and 2.0.
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