Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.240
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
18: .\" are met:
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
23: .\" documentation and/or other materials provided with the distribution.
24: .\"
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
27: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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1.240 ! jmc 36: .\" $OpenBSD: ssh_config.5,v 1.239 2016/09/28 17:59:22 jmc Exp $
! 37: .Dd $Mdocdate: September 28 2016 $
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 SYNOPSIS
1.98 jmc 44: .Nm ~/.ssh/config
45: .Nm /etc/ssh/ssh_config
1.1 stevesk 46: .Sh DESCRIPTION
1.84 jmc 47: .Xr ssh 1
1.1 stevesk 48: obtains configuration data from the following sources in
49: the following order:
1.79 jmc 50: .Pp
1.2 stevesk 51: .Bl -enum -offset indent -compact
52: .It
53: command-line options
54: .It
55: user's configuration file
1.50 djm 56: .Pq Pa ~/.ssh/config
1.2 stevesk 57: .It
58: system-wide configuration file
59: .Pq Pa /etc/ssh/ssh_config
60: .El
1.1 stevesk 61: .Pp
62: For each parameter, the first obtained value
63: will be used.
1.41 jmc 64: The configuration files contain sections separated by
1.240 ! jmc 65: .Cm Host
1.1 stevesk 66: specifications, and that section is only applied for hosts that
67: match one of the patterns given in the specification.
1.193 djm 68: The matched host name is usually the one given on the command line
69: (see the
70: .Cm CanonicalizeHostname
1.240 ! jmc 71: option for exceptions).
1.1 stevesk 72: .Pp
73: Since the first obtained value for each parameter is used, more
74: host-specific declarations should be given near the beginning of the
75: file, and general defaults at the end.
1.80 jmc 76: .Pp
1.240 ! jmc 77: The file contains keyword-argument pairs, one per line.
! 78: Lines starting with
1.1 stevesk 79: .Ql #
1.240 ! jmc 80: and empty lines are interpreted as comments.
! 81: Arguments may optionally be enclosed in double quotes
! 82: .Pq \&"
! 83: in order to represent arguments containing spaces.
1.1 stevesk 84: Configuration options may be separated by whitespace or
85: optional whitespace and exactly one
86: .Ql = ;
87: the latter format is useful to avoid the need to quote whitespace
88: when specifying configuration options using the
89: .Nm ssh ,
1.87 jmc 90: .Nm scp ,
1.1 stevesk 91: and
92: .Nm sftp
93: .Fl o
94: option.
95: .Pp
96: The possible
97: keywords and their meanings are as follows (note that
98: keywords are case-insensitive and arguments are case-sensitive):
99: .Bl -tag -width Ds
100: .It Cm Host
101: Restricts the following declarations (up to the next
102: .Cm Host
1.169 djm 103: or
104: .Cm Match
1.1 stevesk 105: keyword) to be only for those hosts that match one of the patterns
106: given after the keyword.
1.112 krw 107: If more than one pattern is provided, they should be separated by whitespace.
1.1 stevesk 108: A single
1.83 jmc 109: .Ql *
1.1 stevesk 110: as a pattern can be used to provide global
111: defaults for all hosts.
1.193 djm 112: The host is usually the
1.1 stevesk 113: .Ar hostname
1.193 djm 114: argument given on the command line
115: (see the
116: .Cm CanonicalizeHostname
1.240 ! jmc 117: keyword for exceptions).
1.148 djm 118: .Pp
119: A pattern entry may be negated by prefixing it with an exclamation mark
120: .Pq Sq !\& .
121: If a negated entry is matched, then the
122: .Cm Host
123: entry is ignored, regardless of whether any other patterns on the line
124: match.
125: Negated matches are therefore useful to provide exceptions for wildcard
126: matches.
1.81 jmc 127: .Pp
128: See
129: .Sx PATTERNS
130: for more information on patterns.
1.170 jmc 131: .It Cm Match
1.169 djm 132: Restricts the following declarations (up to the next
133: .Cm Host
134: or
135: .Cm Match
136: keyword) to be used only when the conditions following the
137: .Cm Match
138: keyword are satisfied.
1.220 sobrado 139: Match conditions are specified using one or more criteria
1.178 dtucker 140: or the single token
141: .Cm all
1.193 djm 142: which always matches.
143: The available criteria keywords are:
144: .Cm canonical ,
1.176 djm 145: .Cm exec ,
1.169 djm 146: .Cm host ,
147: .Cm originalhost ,
148: .Cm user ,
149: and
150: .Cm localuser .
1.193 djm 151: The
152: .Cm all
153: criteria must appear alone or immediately after
1.194 jmc 154: .Cm canonical .
1.193 djm 155: Other criteria may be combined arbitrarily.
156: All criteria but
157: .Cm all
158: and
159: .Cm canonical
160: require an argument.
161: Criteria may be negated by prepending an exclamation mark
162: .Pq Sq !\& .
1.169 djm 163: .Pp
1.177 jmc 164: The
1.193 djm 165: .Cm canonical
1.210 dtucker 166: keyword matches only when the configuration file is being re-parsed
1.193 djm 167: after hostname canonicalization (see the
168: .Cm CanonicalizeHostname
169: option.)
170: This may be useful to specify conditions that work with canonical host
171: names only.
172: The
1.176 djm 173: .Cm exec
1.177 jmc 174: keyword executes the specified command under the user's shell.
1.169 djm 175: If the command returns a zero exit status then the condition is considered true.
176: Commands containing whitespace characters must be quoted.
1.239 jmc 177: Arguments to
178: .Cm exec
179: accept the tokens described in the
180: .Sx TOKENS
181: section.
1.169 djm 182: .Pp
183: The other keywords' criteria must be single entries or comma-separated
184: lists and may use the wildcard and negation operators described in the
185: .Sx PATTERNS
186: section.
187: The criteria for the
188: .Cm host
189: keyword are matched against the target hostname, after any substitution
190: by the
191: .Cm Hostname
1.193 djm 192: or
193: .Cm CanonicalizeHostname
194: options.
1.169 djm 195: The
196: .Cm originalhost
197: keyword matches against the hostname as it was specified on the command-line.
198: The
199: .Cm user
200: keyword matches against the target username on the remote host.
201: The
202: .Cm localuser
203: keyword matches against the name of the local user running
204: .Xr ssh 1
205: (this keyword may be useful in system-wide
206: .Nm
207: files).
1.222 jcs 208: .It Cm AddKeysToAgent
209: Specifies whether keys should be automatically added to a running
1.223 jmc 210: .Xr ssh-agent 1 .
1.222 jcs 211: If this option is set to
1.240 ! jmc 212: .Cm yes
1.222 jcs 213: and a key is loaded from a file, the key and its passphrase are added to
214: the agent with the default lifetime, as if by
215: .Xr ssh-add 1 .
216: If this option is set to
1.240 ! jmc 217: .Cm ask ,
! 218: .Xr ssh 1
1.222 jcs 219: will require confirmation using the
220: .Ev SSH_ASKPASS
221: program before adding a key (see
222: .Xr ssh-add 1
223: for details).
224: If this option is set to
1.240 ! jmc 225: .Cm confirm ,
1.222 jcs 226: each use of the key must be confirmed, as if the
227: .Fl c
228: option was specified to
229: .Xr ssh-add 1 .
230: If this option is set to
1.240 ! jmc 231: .Cm no ,
1.222 jcs 232: no keys are added to the agent.
233: The argument must be
1.240 ! jmc 234: .Cm yes ,
! 235: .Cm confirm ,
! 236: .Cm ask ,
1.222 jcs 237: or
1.240 ! jmc 238: .Cm no
! 239: (the default).
1.10 djm 240: .It Cm AddressFamily
1.11 jmc 241: Specifies which address family to use when connecting.
242: Valid arguments are
1.240 ! jmc 243: .Cm any
! 244: (the default),
! 245: .Cm inet
1.84 jmc 246: (use IPv4 only), or
1.240 ! jmc 247: .Cm inet6
1.40 jmc 248: (use IPv6 only).
1.1 stevesk 249: .It Cm BatchMode
250: If set to
1.240 ! jmc 251: .Cm yes ,
1.1 stevesk 252: passphrase/password querying will be disabled.
253: This option is useful in scripts and other batch jobs where no user
254: is present to supply the password.
255: The argument must be
1.240 ! jmc 256: .Cm yes
1.1 stevesk 257: or
1.240 ! jmc 258: .Cm no
! 259: (the default).
1.1 stevesk 260: .It Cm BindAddress
1.60 dtucker 261: Use the specified address on the local machine as the source address of
1.61 jmc 262: the connection.
263: Only useful on systems with more than one address.
1.1 stevesk 264: Note that this option does not work if
265: .Cm UsePrivilegedPort
266: is set to
1.240 ! jmc 267: .Cm yes .
1.171 djm 268: .It Cm CanonicalDomains
1.172 jmc 269: When
1.173 djm 270: .Cm CanonicalizeHostname
1.171 djm 271: is enabled, this option specifies the list of domain suffixes in which to
272: search for the specified destination host.
1.173 djm 273: .It Cm CanonicalizeFallbackLocal
1.174 djm 274: Specifies whether to fail with an error when hostname canonicalization fails.
1.172 jmc 275: The default,
1.240 ! jmc 276: .Cm yes ,
1.172 jmc 277: will attempt to look up the unqualified hostname using the system resolver's
1.171 djm 278: search rules.
279: A value of
1.240 ! jmc 280: .Cm no
1.171 djm 281: will cause
282: .Xr ssh 1
283: to fail instantly if
1.173 djm 284: .Cm CanonicalizeHostname
1.171 djm 285: is enabled and the target hostname cannot be found in any of the domains
286: specified by
287: .Cm CanonicalDomains .
1.173 djm 288: .It Cm CanonicalizeHostname
1.174 djm 289: Controls whether explicit hostname canonicalization is performed.
1.172 jmc 290: The default,
1.240 ! jmc 291: .Cm no ,
1.171 djm 292: is not to perform any name rewriting and let the system resolver handle all
293: hostname lookups.
294: If set to
1.240 ! jmc 295: .Cm yes
1.171 djm 296: then, for connections that do not use a
297: .Cm ProxyCommand ,
298: .Xr ssh 1
1.173 djm 299: will attempt to canonicalize the hostname specified on the command line
1.171 djm 300: using the
301: .Cm CanonicalDomains
302: suffixes and
1.173 djm 303: .Cm CanonicalizePermittedCNAMEs
1.171 djm 304: rules.
305: If
1.173 djm 306: .Cm CanonicalizeHostname
1.171 djm 307: is set to
1.240 ! jmc 308: .Cm always ,
1.174 djm 309: then canonicalization is applied to proxied connections too.
1.185 djm 310: .Pp
1.193 djm 311: If this option is enabled, then the configuration files are processed
312: again using the new target name to pick up any new configuration in matching
1.185 djm 313: .Cm Host
1.193 djm 314: and
315: .Cm Match
1.185 djm 316: stanzas.
1.173 djm 317: .It Cm CanonicalizeMaxDots
1.172 jmc 318: Specifies the maximum number of dot characters in a hostname before
1.174 djm 319: canonicalization is disabled.
1.240 ! jmc 320: The default, 1,
1.172 jmc 321: allows a single dot (i.e. hostname.subdomain).
1.173 djm 322: .It Cm CanonicalizePermittedCNAMEs
1.172 jmc 323: Specifies rules to determine whether CNAMEs should be followed when
1.173 djm 324: canonicalizing hostnames.
1.171 djm 325: The rules consist of one or more arguments of
1.172 jmc 326: .Ar source_domain_list : Ns Ar target_domain_list ,
1.171 djm 327: where
328: .Ar source_domain_list
1.174 djm 329: is a pattern-list of domains that may follow CNAMEs in canonicalization,
1.171 djm 330: and
331: .Ar target_domain_list
1.172 jmc 332: is a pattern-list of domains that they may resolve to.
1.171 djm 333: .Pp
334: For example,
1.240 ! jmc 335: .Qq *.a.example.com:*.b.example.com,*.c.example.com
1.171 djm 336: will allow hostnames matching
1.240 ! jmc 337: .Qq *.a.example.com
1.173 djm 338: to be canonicalized to names in the
1.240 ! jmc 339: .Qq *.b.example.com
1.171 djm 340: or
1.240 ! jmc 341: .Qq *.c.example.com
1.171 djm 342: domains.
1.221 djm 343: .It Cm CertificateFile
344: Specifies a file from which the user's certificate is read.
345: A corresponding private key must be provided separately in order
346: to use this certificate either
347: from an
348: .Cm IdentityFile
349: directive or
350: .Fl i
351: flag to
352: .Xr ssh 1 ,
353: via
354: .Xr ssh-agent 1 ,
355: or via a
356: .Cm PKCS11Provider .
357: .Pp
1.239 jmc 358: Arguments to
359: .Cm CertificateFile
360: may use the tilde syntax to refer to a user's home directory
361: or the tokens described in the
362: .Sx TOKENS
363: section.
1.221 djm 364: .Pp
365: It is possible to have multiple certificate files specified in
366: configuration files; these certificates will be tried in sequence.
367: Multiple
368: .Cm CertificateFile
369: directives will add to the list of certificates used for
370: authentication.
1.1 stevesk 371: .It Cm ChallengeResponseAuthentication
1.82 jmc 372: Specifies whether to use challenge-response authentication.
1.1 stevesk 373: The argument to this keyword must be
1.240 ! jmc 374: .Cm yes
! 375: (the default)
1.1 stevesk 376: or
1.240 ! jmc 377: .Cm no .
1.1 stevesk 378: .It Cm CheckHostIP
1.240 ! jmc 379: If set to
! 380: .Cm yes
! 381: (the default),
1.84 jmc 382: .Xr ssh 1
383: will additionally check the host IP address in the
1.1 stevesk 384: .Pa known_hosts
385: file.
1.240 ! jmc 386: This allows it to detect if a host key changed due to DNS spoofing
1.211 djm 387: and will add addresses of destination hosts to
388: .Pa ~/.ssh/known_hosts
389: in the process, regardless of the setting of
390: .Cm StrictHostKeyChecking .
1.107 grunk 391: If the option is set to
1.240 ! jmc 392: .Cm no ,
1.1 stevesk 393: the check will not be executed.
394: .It Cm Cipher
395: Specifies the cipher to use for encrypting the session
396: in protocol version 1.
397: Currently,
1.240 ! jmc 398: .Cm blowfish ,
! 399: .Cm 3des
! 400: (the default),
1.1 stevesk 401: and
1.240 ! jmc 402: .Cm des
! 403: are supported,
! 404: though
! 405: .Cm des
1.1 stevesk 406: is only supported in the
1.84 jmc 407: .Xr ssh 1
1.240 ! jmc 408: client for interoperability with legacy protocol 1 implementations;
! 409: its use is strongly discouraged due to cryptographic weaknesses.
1.1 stevesk 410: .It Cm Ciphers
411: Specifies the ciphers allowed for protocol version 2
412: in order of preference.
413: Multiple ciphers must be comma-separated.
1.214 djm 414: If the specified value begins with a
415: .Sq +
416: character, then the specified ciphers will be appended to the default set
417: instead of replacing them.
418: .Pp
1.180 djm 419: The supported ciphers are:
1.240 ! jmc 420: .Bd -literal -offset indent
1.186 naddy 421: 3des-cbc
422: aes128-cbc
423: aes192-cbc
424: aes256-cbc
425: aes128-ctr
426: aes192-ctr
427: aes256-ctr
428: aes128-gcm@openssh.com
429: aes256-gcm@openssh.com
430: arcfour
431: arcfour128
432: arcfour256
433: blowfish-cbc
434: cast128-cbc
435: chacha20-poly1305@openssh.com
1.240 ! jmc 436: .Ed
1.180 djm 437: .Pp
1.84 jmc 438: The default is:
1.186 naddy 439: .Bd -literal -offset indent
1.215 jmc 440: chacha20-poly1305@openssh.com,
1.186 naddy 441: aes128-ctr,aes192-ctr,aes256-ctr,
1.161 markus 442: aes128-gcm@openssh.com,aes256-gcm@openssh.com,
1.237 djm 443: aes128-cbc,aes192-cbc,aes256-cbc
1.1 stevesk 444: .Ed
1.180 djm 445: .Pp
1.240 ! jmc 446: The list of available ciphers may also be obtained using
! 447: .Qq ssh -Q cipher .
1.1 stevesk 448: .It Cm ClearAllForwardings
1.84 jmc 449: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 450: specified in the configuration files or on the command line be
1.7 jmc 451: cleared.
452: This option is primarily useful when used from the
1.84 jmc 453: .Xr ssh 1
1.1 stevesk 454: command line to clear port forwardings set in
455: configuration files, and is automatically set by
456: .Xr scp 1
457: and
458: .Xr sftp 1 .
459: The argument must be
1.240 ! jmc 460: .Cm yes
1.1 stevesk 461: or
1.240 ! jmc 462: .Cm no
! 463: (the default).
1.1 stevesk 464: .It Cm Compression
465: Specifies whether to use compression.
466: The argument must be
1.240 ! jmc 467: .Cm yes
1.1 stevesk 468: or
1.240 ! jmc 469: .Cm no
! 470: (the default).
1.1 stevesk 471: .It Cm CompressionLevel
472: Specifies the compression level to use if compression is enabled.
473: The argument must be an integer from 1 (fast) to 9 (slow, best).
474: The default level is 6, which is good for most applications.
475: The meaning of the values is the same as in
476: .Xr gzip 1 .
477: Note that this option applies to protocol version 1 only.
478: .It Cm ConnectionAttempts
479: Specifies the number of tries (one per second) to make before exiting.
480: The argument must be an integer.
481: This may be useful in scripts if the connection sometimes fails.
482: The default is 1.
1.9 djm 483: .It Cm ConnectTimeout
1.84 jmc 484: Specifies the timeout (in seconds) used when connecting to the
485: SSH server, instead of using the default system TCP timeout.
1.11 jmc 486: This value is used only when the target is down or really unreachable,
487: not when it refuses the connection.
1.36 djm 488: .It Cm ControlMaster
489: Enables the sharing of multiple sessions over a single network connection.
490: When set to
1.240 ! jmc 491: .Cm yes ,
1.84 jmc 492: .Xr ssh 1
1.36 djm 493: will listen for connections on a control socket specified using the
494: .Cm ControlPath
495: argument.
496: Additional sessions can connect to this socket using the same
497: .Cm ControlPath
498: with
499: .Cm ControlMaster
500: set to
1.240 ! jmc 501: .Cm no
1.38 jmc 502: (the default).
1.64 jmc 503: These sessions will try to reuse the master instance's network connection
1.63 djm 504: rather than initiating new ones, but will fall back to connecting normally
505: if the control socket does not exist, or is not listening.
506: .Pp
1.37 djm 507: Setting this to
1.240 ! jmc 508: .Cm ask
! 509: will cause
! 510: .Xr ssh 1
1.206 jmc 511: to listen for control connections, but require confirmation using
512: .Xr ssh-askpass 1 .
1.51 jakob 513: If the
514: .Cm ControlPath
1.84 jmc 515: cannot be opened,
1.240 ! jmc 516: .Xr ssh 1
! 517: will continue without connecting to a master instance.
1.58 djm 518: .Pp
519: X11 and
1.59 jmc 520: .Xr ssh-agent 1
1.58 djm 521: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 522: display and agent forwarded will be the one belonging to the master
1.59 jmc 523: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 524: .Pp
525: Two additional options allow for opportunistic multiplexing: try to use a
526: master connection but fall back to creating a new one if one does not already
527: exist.
528: These options are:
1.240 ! jmc 529: .Cm auto
1.56 djm 530: and
1.240 ! jmc 531: .Cm autoask .
1.56 djm 532: The latter requires confirmation like the
1.240 ! jmc 533: .Cm ask
1.56 djm 534: option.
1.36 djm 535: .It Cm ControlPath
1.55 djm 536: Specify the path to the control socket used for connection sharing as described
537: in the
1.36 djm 538: .Cm ControlMaster
1.57 djm 539: section above or the string
1.240 ! jmc 540: .Cm none
1.57 djm 541: to disable connection sharing.
1.239 jmc 542: Arguments to
543: .Cm ControlPath
544: may use the tilde syntax to refer to a user's home directory
545: or the tokens described in the
546: .Sx TOKENS
547: section.
1.56 djm 548: It is recommended that any
549: .Cm ControlPath
550: used for opportunistic connection sharing include
1.195 djm 551: at least %h, %p, and %r (or alternatively %C) and be placed in a directory
552: that is not writable by other users.
1.56 djm 553: This ensures that shared connections are uniquely identified.
1.137 djm 554: .It Cm ControlPersist
555: When used in conjunction with
556: .Cm ControlMaster ,
557: specifies that the master connection should remain open
558: in the background (waiting for future client connections)
559: after the initial client connection has been closed.
560: If set to
1.240 ! jmc 561: .Cm no ,
1.137 djm 562: then the master connection will not be placed into the background,
563: and will close as soon as the initial client connection is closed.
564: If set to
1.240 ! jmc 565: .Cm yes
! 566: or 0,
1.137 djm 567: then the master connection will remain in the background indefinitely
568: (until killed or closed via a mechanism such as the
1.240 ! jmc 569: .Qq ssh -O exit ) .
1.137 djm 570: If set to a time in seconds, or a time in any of the formats documented in
571: .Xr sshd_config 5 ,
572: then the backgrounded master connection will automatically terminate
573: after it has remained idle (with no client connections) for the
574: specified time.
1.38 jmc 575: .It Cm DynamicForward
1.74 jmc 576: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 577: over the secure channel, and the application
578: protocol is then used to determine where to connect to from the
579: remote machine.
1.62 djm 580: .Pp
581: The argument must be
582: .Sm off
583: .Oo Ar bind_address : Oc Ar port .
584: .Sm on
1.138 djm 585: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 586: By default, the local port is bound in accordance with the
587: .Cm GatewayPorts
588: setting.
589: However, an explicit
590: .Ar bind_address
591: may be used to bind the connection to a specific address.
592: The
593: .Ar bind_address
594: of
1.240 ! jmc 595: .Cm localhost
1.62 djm 596: indicates that the listening port be bound for local use only, while an
597: empty address or
598: .Sq *
599: indicates that the port should be available from all interfaces.
600: .Pp
1.38 jmc 601: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 602: .Xr ssh 1
1.38 jmc 603: will act as a SOCKS server.
604: Multiple forwardings may be specified, and
605: additional forwardings can be given on the command line.
606: Only the superuser can forward privileged ports.
1.14 markus 607: .It Cm EnableSSHKeysign
608: Setting this option to
1.240 ! jmc 609: .Cm yes
1.14 markus 610: in the global client configuration file
611: .Pa /etc/ssh/ssh_config
612: enables the use of the helper program
613: .Xr ssh-keysign 8
614: during
615: .Cm HostbasedAuthentication .
616: The argument must be
1.240 ! jmc 617: .Cm yes
1.14 markus 618: or
1.240 ! jmc 619: .Cm no
! 620: (the default).
1.23 jmc 621: This option should be placed in the non-hostspecific section.
1.14 markus 622: See
623: .Xr ssh-keysign 8
624: for more information.
1.1 stevesk 625: .It Cm EscapeChar
626: Sets the escape character (default:
627: .Ql ~ ) .
628: The escape character can also
629: be set on the command line.
630: The argument should be a single character,
631: .Ql ^
632: followed by a letter, or
1.240 ! jmc 633: .Cm none
1.1 stevesk 634: to disable the escape
635: character entirely (making the connection transparent for binary
636: data).
1.96 markus 637: .It Cm ExitOnForwardFailure
638: Specifies whether
639: .Xr ssh 1
640: should terminate the connection if it cannot set up all requested
1.216 djm 641: dynamic, tunnel, local, and remote port forwardings, (e.g.\&
1.217 jmc 642: if either end is unable to bind and listen on a specified port).
1.216 djm 643: Note that
644: .Cm ExitOnForwardFailure
645: does not apply to connections made over port forwardings and will not,
646: for example, cause
647: .Xr ssh 1
648: to exit if TCP connections to the ultimate forwarding destination fail.
1.96 markus 649: The argument must be
1.240 ! jmc 650: .Cm yes
1.96 markus 651: or
1.240 ! jmc 652: .Cm no
! 653: (the default).
1.197 djm 654: .It Cm FingerprintHash
655: Specifies the hash algorithm used when displaying key fingerprints.
656: Valid options are:
1.240 ! jmc 657: .Cm md5
1.197 djm 658: and
1.240 ! jmc 659: .Cm sha256
! 660: (the default).
1.1 stevesk 661: .It Cm ForwardAgent
662: Specifies whether the connection to the authentication agent (if any)
663: will be forwarded to the remote machine.
664: The argument must be
1.240 ! jmc 665: .Cm yes
1.1 stevesk 666: or
1.240 ! jmc 667: .Cm no
! 668: (the default).
1.3 stevesk 669: .Pp
1.7 jmc 670: Agent forwarding should be enabled with caution.
671: Users with the ability to bypass file permissions on the remote host
672: (for the agent's Unix-domain socket)
673: can access the local agent through the forwarded connection.
674: An attacker cannot obtain key material from the agent,
1.3 stevesk 675: however they can perform operations on the keys that enable them to
676: authenticate using the identities loaded into the agent.
1.1 stevesk 677: .It Cm ForwardX11
678: Specifies whether X11 connections will be automatically redirected
679: over the secure channel and
680: .Ev DISPLAY
681: set.
682: The argument must be
1.240 ! jmc 683: .Cm yes
1.1 stevesk 684: or
1.240 ! jmc 685: .Cm no
! 686: (the default).
1.3 stevesk 687: .Pp
1.7 jmc 688: X11 forwarding should be enabled with caution.
689: Users with the ability to bypass file permissions on the remote host
1.22 markus 690: (for the user's X11 authorization database)
1.7 jmc 691: can access the local X11 display through the forwarded connection.
1.22 markus 692: An attacker may then be able to perform activities such as keystroke monitoring
693: if the
694: .Cm ForwardX11Trusted
695: option is also enabled.
1.134 djm 696: .It Cm ForwardX11Timeout
1.135 jmc 697: Specify a timeout for untrusted X11 forwarding
698: using the format described in the
1.240 ! jmc 699: .Sx TIME FORMATS
! 700: section of
1.134 djm 701: .Xr sshd_config 5 .
702: X11 connections received by
703: .Xr ssh 1
704: after this time will be refused.
705: The default is to disable untrusted X11 forwarding after twenty minutes has
706: elapsed.
1.22 markus 707: .It Cm ForwardX11Trusted
1.34 jmc 708: If this option is set to
1.240 ! jmc 709: .Cm yes ,
1.84 jmc 710: remote X11 clients will have full access to the original X11 display.
1.42 djm 711: .Pp
1.22 markus 712: If this option is set to
1.240 ! jmc 713: .Cm no
! 714: (the default),
1.84 jmc 715: remote X11 clients will be considered untrusted and prevented
1.22 markus 716: from stealing or tampering with data belonging to trusted X11
717: clients.
1.42 djm 718: Furthermore, the
719: .Xr xauth 1
720: token used for the session will be set to expire after 20 minutes.
721: Remote clients will be refused access after this time.
1.22 markus 722: .Pp
723: See the X11 SECURITY extension specification for full details on
724: the restrictions imposed on untrusted clients.
1.1 stevesk 725: .It Cm GatewayPorts
726: Specifies whether remote hosts are allowed to connect to local
727: forwarded ports.
728: By default,
1.84 jmc 729: .Xr ssh 1
1.7 jmc 730: binds local port forwardings to the loopback address.
731: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 732: .Cm GatewayPorts
1.84 jmc 733: can be used to specify that ssh
1.1 stevesk 734: should bind local port forwardings to the wildcard address,
735: thus allowing remote hosts to connect to forwarded ports.
736: The argument must be
1.240 ! jmc 737: .Cm yes
1.1 stevesk 738: or
1.240 ! jmc 739: .Cm no
! 740: (the default).
1.1 stevesk 741: .It Cm GlobalKnownHostsFile
1.151 djm 742: Specifies one or more files to use for the global
743: host key database, separated by whitespace.
744: The default is
745: .Pa /etc/ssh/ssh_known_hosts ,
746: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 747: .It Cm GSSAPIAuthentication
1.27 markus 748: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 749: The default is
1.240 ! jmc 750: .Cm no .
1.18 markus 751: .It Cm GSSAPIDelegateCredentials
752: Forward (delegate) credentials to the server.
753: The default is
1.240 ! jmc 754: .Cm no .
1.44 djm 755: .It Cm HashKnownHosts
756: Indicates that
1.84 jmc 757: .Xr ssh 1
1.44 djm 758: should hash host names and addresses when they are added to
1.50 djm 759: .Pa ~/.ssh/known_hosts .
1.44 djm 760: These hashed names may be used normally by
1.84 jmc 761: .Xr ssh 1
1.44 djm 762: and
1.84 jmc 763: .Xr sshd 8 ,
1.44 djm 764: but they do not reveal identifying information should the file's contents
765: be disclosed.
766: The default is
1.240 ! jmc 767: .Cm no .
1.97 jmc 768: Note that existing names and addresses in known hosts files
769: will not be converted automatically,
770: but may be manually hashed using
1.45 djm 771: .Xr ssh-keygen 1 .
1.1 stevesk 772: .It Cm HostbasedAuthentication
773: Specifies whether to try rhosts based authentication with public key
774: authentication.
775: The argument must be
1.240 ! jmc 776: .Cm yes
1.1 stevesk 777: or
1.240 ! jmc 778: .Cm no
! 779: (the default).
1.202 djm 780: .It Cm HostbasedKeyTypes
781: Specifies the key types that will be used for hostbased authentication
782: as a comma-separated pattern list.
1.214 djm 783: Alternately if the specified value begins with a
784: .Sq +
785: character, then the specified key types will be appended to the default set
786: instead of replacing them.
1.213 markus 787: The default for this option is:
788: .Bd -literal -offset 3n
789: ecdsa-sha2-nistp256-cert-v01@openssh.com,
790: ecdsa-sha2-nistp384-cert-v01@openssh.com,
791: ecdsa-sha2-nistp521-cert-v01@openssh.com,
792: ssh-ed25519-cert-v01@openssh.com,
793: ssh-rsa-cert-v01@openssh.com,
794: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.227 djm 795: ssh-ed25519,ssh-rsa
1.213 markus 796: .Ed
797: .Pp
1.202 djm 798: The
799: .Fl Q
800: option of
801: .Xr ssh 1
802: may be used to list supported key types.
1.1 stevesk 803: .It Cm HostKeyAlgorithms
1.226 jmc 804: Specifies the host key algorithms
1.1 stevesk 805: that the client wants to use in order of preference.
1.214 djm 806: Alternately if the specified value begins with a
807: .Sq +
808: character, then the specified key types will be appended to the default set
809: instead of replacing them.
1.1 stevesk 810: The default for this option is:
1.139 djm 811: .Bd -literal -offset 3n
812: ecdsa-sha2-nistp256-cert-v01@openssh.com,
813: ecdsa-sha2-nistp384-cert-v01@openssh.com,
814: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1.183 naddy 815: ssh-ed25519-cert-v01@openssh.com,
1.213 markus 816: ssh-rsa-cert-v01@openssh.com,
1.139 djm 817: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.227 djm 818: ssh-ed25519,ssh-rsa
1.139 djm 819: .Ed
1.145 djm 820: .Pp
821: If hostkeys are known for the destination host then this default is modified
822: to prefer their algorithms.
1.198 djm 823: .Pp
1.240 ! jmc 824: The list of available key types may also be obtained using
! 825: .Qq ssh -Q key .
1.1 stevesk 826: .It Cm HostKeyAlias
827: Specifies an alias that should be used instead of the
828: real host name when looking up or saving the host key
829: in the host key database files.
1.84 jmc 830: This option is useful for tunneling SSH connections
1.1 stevesk 831: or for multiple servers running on a single host.
832: .It Cm HostName
833: Specifies the real host name to log into.
834: This can be used to specify nicknames or abbreviations for hosts.
1.239 jmc 835: Arguments to
836: .Cm HostName
837: accept the tokens described in the
838: .Sx TOKENS
839: section.
1.1 stevesk 840: Numeric IP addresses are also permitted (both on the command line and in
841: .Cm HostName
842: specifications).
1.239 jmc 843: The default is the name given on the command line.
1.29 markus 844: .It Cm IdentitiesOnly
845: Specifies that
1.84 jmc 846: .Xr ssh 1
1.221 djm 847: should only use the authentication identity and certificate files explicitly
848: configured in the
1.31 jmc 849: .Nm
1.221 djm 850: files
851: or passed on the
852: .Xr ssh 1
853: command-line,
1.84 jmc 854: even if
855: .Xr ssh-agent 1
1.159 djm 856: or a
857: .Cm PKCS11Provider
1.29 markus 858: offers more identities.
859: The argument to this keyword must be
1.240 ! jmc 860: .Cm yes
1.29 markus 861: or
1.240 ! jmc 862: .Cm no
! 863: (the default).
1.84 jmc 864: This option is intended for situations where ssh-agent
1.29 markus 865: offers many different identities.
1.231 markus 866: .It Cm IdentityAgent
867: Specifies the
868: .Ux Ns -domain
869: socket used to communicate with the authentication agent.
870: .Pp
871: This option overrides the
1.240 ! jmc 872: .Ev SSH_AUTH_SOCK
1.231 markus 873: environment variable and can be used to select a specific agent.
874: Setting the socket name to
1.240 ! jmc 875: .Cm none
1.231 markus 876: disables the use of an authentication agent.
1.232 markus 877: If the string
1.240 ! jmc 878: .Qq SSH_AUTH_SOCK
1.232 markus 879: is specified, the location of the socket will be read from the
880: .Ev SSH_AUTH_SOCK
881: environment variable.
1.231 markus 882: .Pp
1.239 jmc 883: Arguments to
884: .Cm IdentityAgent
885: may use the tilde syntax to refer to a user's home directory
886: or the tokens described in the
887: .Sx TOKENS
888: section.
1.67 jmc 889: .It Cm IdentityFile
1.192 sobrado 890: Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA authentication
1.139 djm 891: identity is read.
1.67 jmc 892: The default is
893: .Pa ~/.ssh/identity
894: for protocol version 1, and
1.139 djm 895: .Pa ~/.ssh/id_dsa ,
1.183 naddy 896: .Pa ~/.ssh/id_ecdsa ,
897: .Pa ~/.ssh/id_ed25519
1.139 djm 898: and
1.67 jmc 899: .Pa ~/.ssh/id_rsa
900: for protocol version 2.
901: Additionally, any identities represented by the authentication agent
1.165 djm 902: will be used for authentication unless
903: .Cm IdentitiesOnly
904: is set.
1.221 djm 905: If no certificates have been explicitly specified by
906: .Cm CertificateFile ,
1.129 djm 907: .Xr ssh 1
908: will try to load certificate information from the filename obtained by
909: appending
910: .Pa -cert.pub
911: to the path of a specified
912: .Cm IdentityFile .
1.90 djm 913: .Pp
1.239 jmc 914: Arguments to
915: .Cm IdentityFile
916: may use the tilde syntax to refer to a user's home directory
917: or the tokens described in the
918: .Sx TOKENS
919: section.
1.90 djm 920: .Pp
1.67 jmc 921: It is possible to have
922: multiple identity files specified in configuration files; all these
923: identities will be tried in sequence.
1.152 djm 924: Multiple
925: .Cm IdentityFile
926: directives will add to the list of identities tried (this behaviour
927: differs from that of other configuration directives).
1.165 djm 928: .Pp
929: .Cm IdentityFile
930: may be used in conjunction with
931: .Cm IdentitiesOnly
932: to select which identities in an agent are offered during authentication.
1.221 djm 933: .Cm IdentityFile
934: may also be used in conjunction with
935: .Cm CertificateFile
936: in order to provide any certificate also needed for authentication with
937: the identity.
1.164 jmc 938: .It Cm IgnoreUnknown
939: Specifies a pattern-list of unknown options to be ignored if they are
940: encountered in configuration parsing.
941: This may be used to suppress errors if
942: .Nm
943: contains options that are unrecognised by
944: .Xr ssh 1 .
945: It is recommended that
946: .Cm IgnoreUnknown
947: be listed early in the configuration file as it will not be applied
948: to unknown options that appear before it.
1.229 djm 949: .It Cm Include
950: Include the specified configuration file(s).
1.230 jmc 951: Multiple pathnames may be specified and each pathname may contain
1.229 djm 952: .Xr glob 3
953: wildcards and, for user configurations, shell-like
1.240 ! jmc 954: .Sq ~
1.229 djm 955: references to user home directories.
956: Files without absolute paths are assumed to be in
957: .Pa ~/.ssh
1.230 jmc 958: if included in a user configuration file or
1.229 djm 959: .Pa /etc/ssh
960: if included from the system configuration file.
961: .Cm Include
962: directive may appear inside a
963: .Cm Match
964: or
965: .Cm Host
966: block
967: to perform conditional inclusion.
1.143 djm 968: .It Cm IPQoS
969: Specifies the IPv4 type-of-service or DSCP class for connections.
970: Accepted values are
1.240 ! jmc 971: .Cm af11 ,
! 972: .Cm af12 ,
! 973: .Cm af13 ,
! 974: .Cm af21 ,
! 975: .Cm af22 ,
! 976: .Cm af23 ,
! 977: .Cm af31 ,
! 978: .Cm af32 ,
! 979: .Cm af33 ,
! 980: .Cm af41 ,
! 981: .Cm af42 ,
! 982: .Cm af43 ,
! 983: .Cm cs0 ,
! 984: .Cm cs1 ,
! 985: .Cm cs2 ,
! 986: .Cm cs3 ,
! 987: .Cm cs4 ,
! 988: .Cm cs5 ,
! 989: .Cm cs6 ,
! 990: .Cm cs7 ,
! 991: .Cm ef ,
! 992: .Cm lowdelay ,
! 993: .Cm throughput ,
! 994: .Cm reliability ,
1.143 djm 995: or a numeric value.
1.146 djm 996: This option may take one or two arguments, separated by whitespace.
1.143 djm 997: If one argument is specified, it is used as the packet class unconditionally.
998: If two values are specified, the first is automatically selected for
999: interactive sessions and the second for non-interactive sessions.
1000: The default is
1.240 ! jmc 1001: .Cm lowdelay
1.143 djm 1002: for interactive sessions and
1.240 ! jmc 1003: .Cm throughput
1.143 djm 1004: for non-interactive sessions.
1.103 djm 1005: .It Cm KbdInteractiveAuthentication
1006: Specifies whether to use keyboard-interactive authentication.
1007: The argument to this keyword must be
1.240 ! jmc 1008: .Cm yes
! 1009: (the default)
1.103 djm 1010: or
1.240 ! jmc 1011: .Cm no .
1.39 djm 1012: .It Cm KbdInteractiveDevices
1013: Specifies the list of methods to use in keyboard-interactive authentication.
1014: Multiple method names must be comma-separated.
1015: The default is to use the server specified list.
1.85 jmc 1016: The methods available vary depending on what the server supports.
1017: For an OpenSSH server,
1018: it may be zero or more of:
1.240 ! jmc 1019: .Cm bsdauth ,
! 1020: .Cm pam ,
1.85 jmc 1021: and
1.240 ! jmc 1022: .Cm skey .
1.140 djm 1023: .It Cm KexAlgorithms
1024: Specifies the available KEX (Key Exchange) algorithms.
1025: Multiple algorithms must be comma-separated.
1.214 djm 1026: Alternately if the specified value begins with a
1027: .Sq +
1028: character, then the specified methods will be appended to the default set
1029: instead of replacing them.
1.141 jmc 1030: The default is:
1031: .Bd -literal -offset indent
1.238 djm 1032: curve25519-sha256,curve25519-sha256@libssh.org,
1.141 jmc 1033: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1034: diffie-hellman-group-exchange-sha256,
1.209 dtucker 1035: diffie-hellman-group-exchange-sha1,
1.212 djm 1036: diffie-hellman-group14-sha1
1.141 jmc 1037: .Ed
1.198 djm 1038: .Pp
1.240 ! jmc 1039: The list of available key exchange algorithms may also be obtained using
! 1040: .Qq ssh -Q kex .
1.65 reyk 1041: .It Cm LocalCommand
1042: Specifies a command to execute on the local machine after successfully
1043: connecting to the server.
1044: The command string extends to the end of the line, and is executed with
1.105 jmc 1045: the user's shell.
1.239 jmc 1046: Arguments to
1047: .Cm LocalCommand
1048: accept the tokens described in the
1049: .Sx TOKENS
1050: section.
1.123 djm 1051: .Pp
1052: The command is run synchronously and does not have access to the
1053: session of the
1054: .Xr ssh 1
1055: that spawned it.
1056: It should not be used for interactive commands.
1057: .Pp
1.65 reyk 1058: This directive is ignored unless
1059: .Cm PermitLocalCommand
1060: has been enabled.
1.1 stevesk 1061: .It Cm LocalForward
1.74 jmc 1062: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 1063: the secure channel to the specified host and port from the remote machine.
1.49 jmc 1064: The first argument must be
1.43 djm 1065: .Sm off
1.49 jmc 1066: .Oo Ar bind_address : Oc Ar port
1.43 djm 1067: .Sm on
1.49 jmc 1068: and the second argument must be
1069: .Ar host : Ns Ar hostport .
1.138 djm 1070: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 1071: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 1072: given on the command line.
1.1 stevesk 1073: Only the superuser can forward privileged ports.
1.43 djm 1074: By default, the local port is bound in accordance with the
1075: .Cm GatewayPorts
1076: setting.
1077: However, an explicit
1078: .Ar bind_address
1079: may be used to bind the connection to a specific address.
1080: The
1081: .Ar bind_address
1082: of
1.240 ! jmc 1083: .Cm localhost
1.46 jmc 1084: indicates that the listening port be bound for local use only, while an
1085: empty address or
1086: .Sq *
1.43 djm 1087: indicates that the port should be available from all interfaces.
1.1 stevesk 1088: .It Cm LogLevel
1089: Gives the verbosity level that is used when logging messages from
1.84 jmc 1090: .Xr ssh 1 .
1.1 stevesk 1091: The possible values are:
1.84 jmc 1092: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 1093: The default is INFO.
1094: DEBUG and DEBUG1 are equivalent.
1095: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 1096: .It Cm MACs
1097: Specifies the MAC (message authentication code) algorithms
1098: in order of preference.
1.226 jmc 1099: The MAC algorithm is used for data integrity protection.
1.1 stevesk 1100: Multiple algorithms must be comma-separated.
1.214 djm 1101: If the specified value begins with a
1102: .Sq +
1103: character, then the specified algorithms will be appended to the default set
1104: instead of replacing them.
1105: .Pp
1.160 markus 1106: The algorithms that contain
1.240 ! jmc 1107: .Qq -etm
1.160 markus 1108: calculate the MAC after encryption (encrypt-then-mac).
1109: These are considered safer and their use recommended.
1.214 djm 1110: .Pp
1.84 jmc 1111: The default is:
1.101 jmc 1112: .Bd -literal -offset indent
1.160 markus 1113: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1114: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.224 djm 1115: hmac-sha1-etm@openssh.com,
1.186 naddy 1116: umac-64@openssh.com,umac-128@openssh.com,
1.224 djm 1117: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.101 jmc 1118: .Ed
1.198 djm 1119: .Pp
1.240 ! jmc 1120: The list of available MAC algorithms may also be obtained using
! 1121: .Qq ssh -Q mac .
1.1 stevesk 1122: .It Cm NoHostAuthenticationForLocalhost
1123: This option can be used if the home directory is shared across machines.
1124: In this case localhost will refer to a different machine on each of
1125: the machines and the user will get many warnings about changed host keys.
1126: However, this option disables host authentication for localhost.
1127: The argument to this keyword must be
1.240 ! jmc 1128: .Cm yes
1.1 stevesk 1129: or
1.240 ! jmc 1130: .Cm no .
! 1131: (the default).
1.1 stevesk 1132: .It Cm NumberOfPasswordPrompts
1133: Specifies the number of password prompts before giving up.
1134: The argument to this keyword must be an integer.
1.84 jmc 1135: The default is 3.
1.1 stevesk 1136: .It Cm PasswordAuthentication
1137: Specifies whether to use password authentication.
1138: The argument to this keyword must be
1.240 ! jmc 1139: .Cm yes
! 1140: (the default)
1.1 stevesk 1141: or
1.240 ! jmc 1142: .Cm no .
1.65 reyk 1143: .It Cm PermitLocalCommand
1144: Allow local command execution via the
1145: .Ic LocalCommand
1146: option or using the
1.66 jmc 1147: .Ic !\& Ns Ar command
1.65 reyk 1148: escape sequence in
1149: .Xr ssh 1 .
1150: The argument must be
1.240 ! jmc 1151: .Cm yes
1.65 reyk 1152: or
1.240 ! jmc 1153: .Cm no
! 1154: (the default).
1.127 markus 1155: .It Cm PKCS11Provider
1156: Specifies which PKCS#11 provider to use.
1.144 jmc 1157: The argument to this keyword is the PKCS#11 shared library
1.127 markus 1158: .Xr ssh 1
1.128 markus 1159: should use to communicate with a PKCS#11 token providing the user's
1.127 markus 1160: private RSA key.
1.67 jmc 1161: .It Cm Port
1162: Specifies the port number to connect on the remote host.
1.84 jmc 1163: The default is 22.
1.1 stevesk 1164: .It Cm PreferredAuthentications
1.226 jmc 1165: Specifies the order in which the client should try authentication methods.
1.48 jmc 1166: This allows a client to prefer one method (e.g.\&
1.1 stevesk 1167: .Cm keyboard-interactive )
1.48 jmc 1168: over another method (e.g.\&
1.131 jmc 1169: .Cm password ) .
1170: The default is:
1171: .Bd -literal -offset indent
1172: gssapi-with-mic,hostbased,publickey,
1173: keyboard-interactive,password
1174: .Ed
1.1 stevesk 1175: .It Cm Protocol
1176: Specifies the protocol versions
1.84 jmc 1177: .Xr ssh 1
1.1 stevesk 1178: should support in order of preference.
1.240 ! jmc 1179: The possible values are 1 and 2.
1.1 stevesk 1180: Multiple versions must be comma-separated.
1.120 markus 1181: When this option is set to
1.240 ! jmc 1182: .Cm 2,1
1.120 markus 1183: .Nm ssh
1184: will try version 2 and fall back to version 1
1185: if version 2 is not available.
1.240 ! jmc 1186: The default is version 2.
1.225 djm 1187: Protocol 1 suffers from a number of cryptographic weaknesses and should
1188: not be used.
1189: It is only offered to support legacy devices.
1.1 stevesk 1190: .It Cm ProxyCommand
1191: Specifies the command to use to connect to the server.
1192: The command
1.190 djm 1193: string extends to the end of the line, and is executed
1194: using the user's shell
1195: .Ql exec
1196: directive to avoid a lingering shell process.
1197: .Pp
1.239 jmc 1198: Arguments to
1199: .Cm ProxyCommand
1200: accept the tokens described in the
1201: .Sx TOKENS
1202: section.
1.1 stevesk 1203: The command can be basically anything,
1204: and should read from its standard input and write to its standard output.
1205: It should eventually connect an
1206: .Xr sshd 8
1207: server running on some machine, or execute
1208: .Ic sshd -i
1209: somewhere.
1210: Host key management will be done using the
1211: HostName of the host being connected (defaulting to the name typed by
1212: the user).
1.7 jmc 1213: Setting the command to
1.240 ! jmc 1214: .Cm none
1.6 markus 1215: disables this option entirely.
1.1 stevesk 1216: Note that
1217: .Cm CheckHostIP
1218: is not available for connects with a proxy command.
1.52 djm 1219: .Pp
1220: This directive is useful in conjunction with
1221: .Xr nc 1
1222: and its proxy support.
1.53 jmc 1223: For example, the following directive would connect via an HTTP proxy at
1.52 djm 1224: 192.0.2.0:
1225: .Bd -literal -offset 3n
1226: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1227: .Ed
1.233 djm 1228: .It Cm ProxyJump
1229: Specifies one or more jump proxies as
1230: .Xo
1231: .Sm off
1.234 jmc 1232: .Op Ar user No @
1.233 djm 1233: .Ar host
1.234 jmc 1234: .Op : Ns Ar port
1.233 djm 1235: .Sm on
1236: .Xc .
1.235 djm 1237: Multiple proxies may be separated by comma characters and will be visited
1.236 djm 1238: sequentially.
1.233 djm 1239: Setting this option will cause
1240: .Xr ssh 1
1241: to connect to the target host by first making a
1242: .Xr ssh 1
1243: connection to the specified
1244: .Cm ProxyJump
1245: host and then establishing a
1.234 jmc 1246: TCP forwarding to the ultimate target from there.
1.233 djm 1247: .Pp
1248: Note that this option will compete with the
1249: .Cm ProxyCommand
1250: option - whichever is specified first will prevent later instances of the
1251: other from taking effect.
1.167 djm 1252: .It Cm ProxyUseFdpass
1.168 jmc 1253: Specifies that
1.167 djm 1254: .Cm ProxyCommand
1255: will pass a connected file descriptor back to
1.168 jmc 1256: .Xr ssh 1
1.167 djm 1257: instead of continuing to execute and pass data.
1258: The default is
1.240 ! jmc 1259: .Cm no .
1.213 markus 1260: .It Cm PubkeyAcceptedKeyTypes
1261: Specifies the key types that will be used for public key authentication
1262: as a comma-separated pattern list.
1.214 djm 1263: Alternately if the specified value begins with a
1264: .Sq +
1265: character, then the key types after it will be appended to the default
1266: instead of replacing it.
1.213 markus 1267: The default for this option is:
1268: .Bd -literal -offset 3n
1269: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1270: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1271: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1272: ssh-ed25519-cert-v01@openssh.com,
1273: ssh-rsa-cert-v01@openssh.com,
1274: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.227 djm 1275: ssh-ed25519,ssh-rsa
1.213 markus 1276: .Ed
1277: .Pp
1.240 ! jmc 1278: The list of available key types may also be obtained using
! 1279: .Qq ssh -Q key .
1.1 stevesk 1280: .It Cm PubkeyAuthentication
1281: Specifies whether to try public key authentication.
1282: The argument to this keyword must be
1.240 ! jmc 1283: .Cm yes
! 1284: (the default)
1.1 stevesk 1285: or
1.240 ! jmc 1286: .Cm no .
1.75 dtucker 1287: .It Cm RekeyLimit
1288: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1289: session key is renegotiated, optionally followed a maximum amount of
1290: time that may pass before the session key is renegotiated.
1291: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1292: .Sq K ,
1293: .Sq M ,
1.75 dtucker 1294: or
1.76 jmc 1295: .Sq G
1.75 dtucker 1296: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1297: The default is between
1.84 jmc 1298: .Sq 1G
1.75 dtucker 1299: and
1.84 jmc 1300: .Sq 4G ,
1.75 dtucker 1301: depending on the cipher.
1.162 dtucker 1302: The optional second value is specified in seconds and may use any of the
1303: units documented in the
1.240 ! jmc 1304: .Sx TIME FORMATS
! 1305: section of
1.162 dtucker 1306: .Xr sshd_config 5 .
1307: The default value for
1308: .Cm RekeyLimit
1309: is
1.240 ! jmc 1310: .Cm default none ,
1.162 dtucker 1311: which means that rekeying is performed after the cipher's default amount
1312: of data has been sent or received and no time based rekeying is done.
1.1 stevesk 1313: .It Cm RemoteForward
1.74 jmc 1314: Specifies that a TCP port on the remote machine be forwarded over
1.1 stevesk 1315: the secure channel to the specified host and port from the local machine.
1.49 jmc 1316: The first argument must be
1.43 djm 1317: .Sm off
1.49 jmc 1318: .Oo Ar bind_address : Oc Ar port
1.43 djm 1319: .Sm on
1.49 jmc 1320: and the second argument must be
1321: .Ar host : Ns Ar hostport .
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 .
1.1 stevesk 1376: .It Cm RhostsRSAAuthentication
1377: Specifies whether to try rhosts based authentication with RSA host
1378: authentication.
1379: The argument must be
1.240 ! jmc 1380: .Cm yes
1.1 stevesk 1381: or
1.240 ! jmc 1382: .Cm no
! 1383: (the default).
1.1 stevesk 1384: This option applies to protocol version 1 only and requires
1.84 jmc 1385: .Xr ssh 1
1.1 stevesk 1386: to be setuid root.
1387: .It Cm RSAAuthentication
1388: Specifies whether to try RSA authentication.
1389: The argument to this keyword must be
1.240 ! jmc 1390: .Cm yes
! 1391: (the default)
1.1 stevesk 1392: or
1.240 ! jmc 1393: .Cm no .
1.1 stevesk 1394: RSA authentication will only be
1395: attempted if the identity file exists, or an authentication agent is
1396: running.
1397: Note that this option applies to protocol version 1 only.
1.32 djm 1398: .It Cm SendEnv
1399: Specifies what variables from the local
1400: .Xr environ 7
1401: should be sent to the server.
1.84 jmc 1402: The server must also support it, and the server must be configured to
1.33 djm 1403: accept these environment variables.
1.207 dtucker 1404: Note that the
1405: .Ev TERM
1.208 jmc 1406: environment variable is always sent whenever a
1.207 dtucker 1407: pseudo-terminal is requested as it is required by the protocol.
1.32 djm 1408: Refer to
1409: .Cm AcceptEnv
1410: in
1411: .Xr sshd_config 5
1412: for how to configure the server.
1.80 jmc 1413: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1414: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1415: across multiple
1416: .Cm SendEnv
1417: directives.
1418: The default is not to send any environment variables.
1.81 jmc 1419: .Pp
1420: See
1421: .Sx PATTERNS
1422: for more information on patterns.
1.28 markus 1423: .It Cm ServerAliveCountMax
1.73 jmc 1424: Sets the number of server alive messages (see below) which may be
1.28 markus 1425: sent without
1.84 jmc 1426: .Xr ssh 1
1.28 markus 1427: receiving any messages back from the server.
1428: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1429: ssh will disconnect from the server, terminating the session.
1.28 markus 1430: It is important to note that the use of server alive messages is very
1431: different from
1432: .Cm TCPKeepAlive
1433: (below).
1434: The server alive messages are sent through the encrypted channel
1435: and therefore will not be spoofable.
1436: The TCP keepalive option enabled by
1437: .Cm TCPKeepAlive
1438: is spoofable.
1439: The server alive mechanism is valuable when the client or
1440: server depend on knowing when a connection has become inactive.
1441: .Pp
1442: The default value is 3.
1443: If, for example,
1444: .Cm ServerAliveInterval
1.84 jmc 1445: (see below) is set to 15 and
1.28 markus 1446: .Cm ServerAliveCountMax
1.84 jmc 1447: is left at the default, if the server becomes unresponsive,
1448: ssh will disconnect after approximately 45 seconds.
1.67 jmc 1449: .It Cm ServerAliveInterval
1450: Sets a timeout interval in seconds after which if no data has been received
1451: from the server,
1.84 jmc 1452: .Xr ssh 1
1.67 jmc 1453: will send a message through the encrypted
1454: channel to request a response from the server.
1455: The default
1456: is 0, indicating that these messages will not be sent to the server.
1.191 millert 1457: .It Cm StreamLocalBindMask
1458: Sets the octal file creation mode mask
1459: .Pq umask
1460: used when creating a Unix-domain socket file for local or remote
1461: port forwarding.
1462: This option is only used for port forwarding to a Unix-domain socket file.
1463: .Pp
1464: The default value is 0177, which creates a Unix-domain socket file that is
1465: readable and writable only by the owner.
1466: Note that not all operating systems honor the file mode on Unix-domain
1467: socket files.
1468: .It Cm StreamLocalBindUnlink
1469: Specifies whether to remove an existing Unix-domain socket file for local
1470: or remote port forwarding before creating a new one.
1471: If the socket file already exists and
1472: .Cm StreamLocalBindUnlink
1473: is not enabled,
1474: .Nm ssh
1475: will be unable to forward the port to the Unix-domain socket file.
1476: This option is only used for port forwarding to a Unix-domain socket file.
1477: .Pp
1478: The argument must be
1.240 ! jmc 1479: .Cm yes
1.191 millert 1480: or
1.240 ! jmc 1481: .Cm no
! 1482: (the default).
1.1 stevesk 1483: .It Cm StrictHostKeyChecking
1484: If this flag is set to
1.240 ! jmc 1485: .Cm yes ,
1.84 jmc 1486: .Xr ssh 1
1.1 stevesk 1487: will never automatically add host keys to the
1.50 djm 1488: .Pa ~/.ssh/known_hosts
1.1 stevesk 1489: file, and refuses to connect to hosts whose host key has changed.
1490: This provides maximum protection against trojan horse attacks,
1.84 jmc 1491: though it can be annoying when the
1.1 stevesk 1492: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1493: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1494: frequently made.
1495: This option forces the user to manually
1496: add all new hosts.
1497: If this flag is set to
1.240 ! jmc 1498: .Cm no ,
1.84 jmc 1499: ssh will automatically add new host keys to the
1.1 stevesk 1500: user known hosts files.
1501: If this flag is set to
1.240 ! jmc 1502: .Cm ask
! 1503: (the default),
1.1 stevesk 1504: new host keys
1505: will be added to the user known host files only after the user
1506: has confirmed that is what they really want to do, and
1.84 jmc 1507: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1508: The host keys of
1509: known hosts will be verified automatically in all cases.
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 .
1.65 reyk 1527: .It Cm Tunnel
1.95 stevesk 1528: Request
1.65 reyk 1529: .Xr tun 4
1.69 jmc 1530: device forwarding between the client and the server.
1.65 reyk 1531: The argument must be
1.240 ! jmc 1532: .Cm yes ,
! 1533: .Cm point-to-point
1.95 stevesk 1534: (layer 3),
1.240 ! jmc 1535: .Cm ethernet
1.95 stevesk 1536: (layer 2),
1.65 reyk 1537: or
1.240 ! jmc 1538: .Cm no
! 1539: (the default).
1.95 stevesk 1540: Specifying
1.240 ! jmc 1541: .Cm yes
1.95 stevesk 1542: requests the default tunnel mode, which is
1.240 ! jmc 1543: .Cm point-to-point .
1.65 reyk 1544: .It Cm TunnelDevice
1.95 stevesk 1545: Specifies the
1.65 reyk 1546: .Xr tun 4
1.95 stevesk 1547: devices to open on the client
1548: .Pq Ar local_tun
1549: and the server
1550: .Pq Ar remote_tun .
1551: .Pp
1552: The argument must be
1553: .Sm off
1554: .Ar local_tun Op : Ar remote_tun .
1555: .Sm on
1556: The devices may be specified by numerical ID or the keyword
1.240 ! jmc 1557: .Cm any ,
1.95 stevesk 1558: which uses the next available tunnel device.
1559: If
1560: .Ar remote_tun
1561: is not specified, it defaults to
1.240 ! jmc 1562: .Cm any .
1.95 stevesk 1563: The default is
1.240 ! jmc 1564: .Cm any:any .
1.201 djm 1565: .It Cm UpdateHostKeys
1.200 djm 1566: Specifies whether
1567: .Xr ssh 1
1568: should accept notifications of additional hostkeys from the server sent
1569: after authentication has completed and add them to
1570: .Cm UserKnownHostsFile .
1571: The argument must be
1.240 ! jmc 1572: .Cm yes ,
! 1573: .Cm no
1.204 djm 1574: (the default) or
1.240 ! jmc 1575: .Cm ask .
1.200 djm 1576: Enabling this option allows learning alternate hostkeys for a server
1.201 djm 1577: and supports graceful key rotation by allowing a server to send replacement
1578: public keys before old ones are removed.
1.200 djm 1579: Additional hostkeys are only accepted if the key used to authenticate the
1.220 sobrado 1580: host was already trusted or explicitly accepted by the user.
1.204 djm 1581: If
1582: .Cm UpdateHostKeys
1583: is set to
1.240 ! jmc 1584: .Cm ask ,
1.204 djm 1585: then the user is asked to confirm the modifications to the known_hosts file.
1.205 djm 1586: Confirmation is currently incompatible with
1587: .Cm ControlPersist ,
1588: and will be disabled if it is enabled.
1.200 djm 1589: .Pp
1590: Presently, only
1591: .Xr sshd 8
1592: from OpenSSH 6.8 and greater support the
1.240 ! jmc 1593: .Qq hostkeys@openssh.com
1.200 djm 1594: protocol extension used to inform the client of all the server's hostkeys.
1.72 jmc 1595: .It Cm UsePrivilegedPort
1596: Specifies whether to use a privileged port for outgoing connections.
1597: The argument must be
1.240 ! jmc 1598: .Cm yes
1.72 jmc 1599: or
1.240 ! jmc 1600: .Cm no
! 1601: (the default).
1.72 jmc 1602: If set to
1.240 ! jmc 1603: .Cm yes ,
1.84 jmc 1604: .Xr ssh 1
1.72 jmc 1605: must be setuid root.
1606: Note that this option must be set to
1.240 ! jmc 1607: .Cm yes
1.72 jmc 1608: for
1609: .Cm RhostsRSAAuthentication
1610: with older servers.
1.1 stevesk 1611: .It Cm User
1612: Specifies the user to log in as.
1613: This can be useful when a different user name is used on different machines.
1614: This saves the trouble of
1615: having to remember to give the user name on the command line.
1616: .It Cm UserKnownHostsFile
1.151 djm 1617: Specifies one or more files to use for the user
1618: host key database, separated by whitespace.
1619: The default is
1620: .Pa ~/.ssh/known_hosts ,
1621: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1622: .It Cm VerifyHostKeyDNS
1623: Specifies whether to verify the remote key using DNS and SSHFP resource
1624: records.
1.24 jakob 1625: If this option is set to
1.240 ! jmc 1626: .Cm yes ,
1.25 jmc 1627: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1628: from DNS.
1629: Insecure fingerprints will be handled as if this option was set to
1.240 ! jmc 1630: .Cm ask .
1.24 jakob 1631: If this option is set to
1.240 ! jmc 1632: .Cm ask ,
1.24 jakob 1633: information on fingerprint match will be displayed, but the user will still
1634: need to confirm new host keys according to the
1635: .Cm StrictHostKeyChecking
1636: option.
1.8 jakob 1637: The default is
1.240 ! jmc 1638: .Cm no .
1.84 jmc 1639: .Pp
1.240 ! jmc 1640: See also
! 1641: .Sx VERIFYING HOST KEYS
! 1642: in
1.84 jmc 1643: .Xr ssh 1 .
1.111 grunk 1644: .It Cm VisualHostKey
1645: If this flag is set to
1.240 ! jmc 1646: .Cm yes ,
1.111 grunk 1647: an ASCII art representation of the remote host key fingerprint is
1.197 djm 1648: printed in addition to the fingerprint string at login and
1.114 stevesk 1649: for unknown host keys.
1.111 grunk 1650: If this flag is set to
1.240 ! jmc 1651: .Cm no
! 1652: (the default),
1.114 stevesk 1653: no fingerprint strings are printed at login and
1.197 djm 1654: only the fingerprint string will be printed for unknown host keys.
1.1 stevesk 1655: .It Cm XAuthLocation
1.5 stevesk 1656: Specifies the full pathname of the
1.1 stevesk 1657: .Xr xauth 1
1658: program.
1659: The default is
1660: .Pa /usr/X11R6/bin/xauth .
1661: .El
1.86 jmc 1662: .Sh PATTERNS
1663: A
1664: .Em pattern
1665: consists of zero or more non-whitespace characters,
1666: .Sq *
1667: (a wildcard that matches zero or more characters),
1668: or
1669: .Sq ?\&
1670: (a wildcard that matches exactly one character).
1671: For example, to specify a set of declarations for any host in the
1.240 ! jmc 1672: .Qq .co.uk
1.86 jmc 1673: set of domains,
1674: the following pattern could be used:
1675: .Pp
1676: .Dl Host *.co.uk
1677: .Pp
1678: The following pattern
1679: would match any host in the 192.168.0.[0-9] network range:
1680: .Pp
1681: .Dl Host 192.168.0.?
1682: .Pp
1683: A
1684: .Em pattern-list
1685: is a comma-separated list of patterns.
1686: Patterns within pattern-lists may be negated
1687: by preceding them with an exclamation mark
1688: .Pq Sq !\& .
1689: For example,
1.174 djm 1690: to allow a key to be used from anywhere within an organization
1.86 jmc 1691: except from the
1.240 ! jmc 1692: .Qq dialup
1.86 jmc 1693: pool,
1694: the following entry (in authorized_keys) could be used:
1695: .Pp
1696: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.239 jmc 1697: .Sh TOKENS
1698: Arguments to some keywords can make use of tokens,
1699: which are expanded at runtime:
1700: .Pp
1701: .Bl -tag -width XXXX -offset indent -compact
1702: .It %%
1703: A literal
1704: .Sq % .
1705: .It \&%C
1706: Shorthand for %l%h%p%r.
1707: .It %d
1708: Local user's home directory.
1709: .It %h
1710: The remote hostname.
1711: .It %i
1712: The local user ID.
1713: .It %L
1714: The local hostname.
1715: .It %l
1716: The local hostname, including the domain name.
1717: .It %n
1718: The original remote hostname, as given on the command line.
1719: .It %p
1720: The remote port.
1721: .It %r
1722: The remote username.
1723: .It %u
1724: The local username.
1725: .El
1726: .Pp
1727: .Cm Match exec
1728: accepts the tokens %%, %h, %L, %l, %n, %p, %r, and %u.
1729: .Pp
1730: .Cm CertificateFile
1731: accepts the tokens %%, %d, %h, %l, %r, and %u.
1732: .Pp
1733: .Cm ControlPath
1734: accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
1735: .Pp
1736: .Cm HostName
1737: accepts the tokens %% and %h.
1738: .Pp
1739: .Cm IdentityAgent
1740: and
1741: .Cm IdentityFile
1742: accept the tokens %%, %d, %h, %l, %r, and %u.
1743: .Pp
1744: .Cm LocalCommand
1745: accepts the tokens %%, %C, %d, %h, %l, %n, %p, %r, and %u.
1746: .Pp
1747: .Cm ProxyCommand
1748: accepts the tokens %%, %h, %p, and %r.
1.1 stevesk 1749: .Sh FILES
1750: .Bl -tag -width Ds
1.50 djm 1751: .It Pa ~/.ssh/config
1.1 stevesk 1752: This is the per-user configuration file.
1753: The format of this file is described above.
1.84 jmc 1754: This file is used by the SSH client.
1.30 djm 1755: Because of the potential for abuse, this file must have strict permissions:
1756: read/write for the user, and not accessible by others.
1.1 stevesk 1757: .It Pa /etc/ssh/ssh_config
1758: Systemwide configuration file.
1759: This file provides defaults for those
1760: values that are not specified in the user's configuration file, and
1761: for those users who do not have a configuration file.
1762: This file must be world-readable.
1763: .El
1.13 jmc 1764: .Sh SEE ALSO
1765: .Xr ssh 1
1.1 stevesk 1766: .Sh AUTHORS
1.240 ! jmc 1767: .An -nosplit
1.1 stevesk 1768: OpenSSH is a derivative of the original and free
1.240 ! jmc 1769: ssh 1.2.12 release by
! 1770: .An Tatu Ylonen .
! 1771: .An Aaron Campbell , Bob Beck , Markus Friedl ,
! 1772: .An Niels Provos , Theo de Raadt
! 1773: and
! 1774: .An Dug Song
1.1 stevesk 1775: removed many bugs, re-added newer features and
1776: created OpenSSH.
1.240 ! jmc 1777: .An Markus Friedl
! 1778: contributed the support for SSH protocol versions 1.5 and 2.0.
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