Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.299
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.
28: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35: .\"
1.299 ! kn 36: .\" $OpenBSD: ssh_config.5,v 1.298 2019/08/09 04:24:03 dtucker Exp $
! 37: .Dd $Mdocdate: August 9 2019 $
1.1 stevesk 38: .Dt SSH_CONFIG 5
39: .Os
40: .Sh NAME
41: .Nm ssh_config
42: .Nd OpenSSH SSH client configuration files
43: .Sh DESCRIPTION
1.84 jmc 44: .Xr ssh 1
1.1 stevesk 45: obtains configuration data from the following sources in
46: the following order:
1.79 jmc 47: .Pp
1.2 stevesk 48: .Bl -enum -offset indent -compact
49: .It
50: command-line options
51: .It
52: user's configuration file
1.50 djm 53: .Pq Pa ~/.ssh/config
1.2 stevesk 54: .It
55: system-wide configuration file
56: .Pq Pa /etc/ssh/ssh_config
57: .El
1.1 stevesk 58: .Pp
59: For each parameter, the first obtained value
60: will be used.
1.41 jmc 61: The configuration files contain sections separated by
1.240 jmc 62: .Cm Host
1.1 stevesk 63: specifications, and that section is only applied for hosts that
64: match one of the patterns given in the specification.
1.193 djm 65: The matched host name is usually the one given on the command line
66: (see the
67: .Cm CanonicalizeHostname
1.240 jmc 68: option for exceptions).
1.1 stevesk 69: .Pp
70: Since the first obtained value for each parameter is used, more
71: host-specific declarations should be given near the beginning of the
72: file, and general defaults at the end.
1.80 jmc 73: .Pp
1.240 jmc 74: The file contains keyword-argument pairs, one per line.
75: Lines starting with
1.1 stevesk 76: .Ql #
1.240 jmc 77: and empty lines are interpreted as comments.
78: Arguments may optionally be enclosed in double quotes
79: .Pq \&"
80: in order to represent arguments containing spaces.
1.1 stevesk 81: Configuration options may be separated by whitespace or
82: optional whitespace and exactly one
83: .Ql = ;
84: the latter format is useful to avoid the need to quote whitespace
85: when specifying configuration options using the
86: .Nm ssh ,
1.87 jmc 87: .Nm scp ,
1.1 stevesk 88: and
89: .Nm sftp
90: .Fl o
91: option.
92: .Pp
93: The possible
94: keywords and their meanings are as follows (note that
95: keywords are case-insensitive and arguments are case-sensitive):
96: .Bl -tag -width Ds
97: .It Cm Host
98: Restricts the following declarations (up to the next
99: .Cm Host
1.169 djm 100: or
101: .Cm Match
1.1 stevesk 102: keyword) to be only for those hosts that match one of the patterns
103: given after the keyword.
1.112 krw 104: If more than one pattern is provided, they should be separated by whitespace.
1.1 stevesk 105: A single
1.83 jmc 106: .Ql *
1.1 stevesk 107: as a pattern can be used to provide global
108: defaults for all hosts.
1.193 djm 109: The host is usually the
1.1 stevesk 110: .Ar hostname
1.193 djm 111: argument given on the command line
112: (see the
113: .Cm CanonicalizeHostname
1.240 jmc 114: keyword for exceptions).
1.148 djm 115: .Pp
116: A pattern entry may be negated by prefixing it with an exclamation mark
117: .Pq Sq !\& .
118: If a negated entry is matched, then the
119: .Cm Host
120: entry is ignored, regardless of whether any other patterns on the line
121: match.
122: Negated matches are therefore useful to provide exceptions for wildcard
123: matches.
1.81 jmc 124: .Pp
125: See
126: .Sx PATTERNS
127: for more information on patterns.
1.170 jmc 128: .It Cm Match
1.169 djm 129: Restricts the following declarations (up to the next
130: .Cm Host
131: or
132: .Cm Match
133: keyword) to be used only when the conditions following the
134: .Cm Match
135: keyword are satisfied.
1.220 sobrado 136: Match conditions are specified using one or more criteria
1.178 dtucker 137: or the single token
138: .Cm all
1.193 djm 139: which always matches.
140: The available criteria keywords are:
141: .Cm canonical ,
1.287 djm 142: .Cm final ,
1.176 djm 143: .Cm exec ,
1.169 djm 144: .Cm host ,
145: .Cm originalhost ,
146: .Cm user ,
147: and
148: .Cm localuser .
1.193 djm 149: The
150: .Cm all
151: criteria must appear alone or immediately after
1.287 djm 152: .Cm canonical
153: or
154: .Cm final .
1.193 djm 155: Other criteria may be combined arbitrarily.
156: All criteria but
1.288 jmc 157: .Cm all ,
158: .Cm canonical ,
1.193 djm 159: and
1.287 djm 160: .Cm final
1.193 djm 161: require an argument.
162: Criteria may be negated by prepending an exclamation mark
163: .Pq Sq !\& .
1.169 djm 164: .Pp
1.177 jmc 165: The
1.193 djm 166: .Cm canonical
1.210 dtucker 167: keyword matches only when the configuration file is being re-parsed
1.193 djm 168: after hostname canonicalization (see the
169: .Cm CanonicalizeHostname
1.288 jmc 170: option).
1.193 djm 171: This may be useful to specify conditions that work with canonical host
172: names only.
1.287 djm 173: .Pp
174: The
175: .Cm final
176: keyword requests that the configuration be re-parsed (regardless of whether
177: .Cm CanonicalizeHostname
178: is enabled), and matches only during this final pass.
179: If
180: .Cm CanonicalizeHostname
181: is enabled, then
182: .Cm canonical
183: and
184: .Cm final
185: match during the same pass.
186: .Pp
1.193 djm 187: The
1.176 djm 188: .Cm exec
1.177 jmc 189: keyword executes the specified command under the user's shell.
1.169 djm 190: If the command returns a zero exit status then the condition is considered true.
191: Commands containing whitespace characters must be quoted.
1.239 jmc 192: Arguments to
193: .Cm exec
194: accept the tokens described in the
195: .Sx TOKENS
196: section.
1.169 djm 197: .Pp
198: The other keywords' criteria must be single entries or comma-separated
199: lists and may use the wildcard and negation operators described in the
200: .Sx PATTERNS
201: section.
202: The criteria for the
203: .Cm host
204: keyword are matched against the target hostname, after any substitution
205: by the
1.295 jmc 206: .Cm Hostname
1.193 djm 207: or
208: .Cm CanonicalizeHostname
209: options.
1.169 djm 210: The
211: .Cm originalhost
212: keyword matches against the hostname as it was specified on the command-line.
213: The
214: .Cm user
215: keyword matches against the target username on the remote host.
216: The
217: .Cm localuser
218: keyword matches against the name of the local user running
219: .Xr ssh 1
220: (this keyword may be useful in system-wide
221: .Nm
222: files).
1.222 jcs 223: .It Cm AddKeysToAgent
224: Specifies whether keys should be automatically added to a running
1.223 jmc 225: .Xr ssh-agent 1 .
1.222 jcs 226: If this option is set to
1.240 jmc 227: .Cm yes
1.222 jcs 228: and a key is loaded from a file, the key and its passphrase are added to
229: the agent with the default lifetime, as if by
230: .Xr ssh-add 1 .
231: If this option is set to
1.240 jmc 232: .Cm ask ,
233: .Xr ssh 1
1.222 jcs 234: will require confirmation using the
235: .Ev SSH_ASKPASS
236: program before adding a key (see
237: .Xr ssh-add 1
238: for details).
239: If this option is set to
1.240 jmc 240: .Cm confirm ,
1.222 jcs 241: each use of the key must be confirmed, as if the
242: .Fl c
243: option was specified to
244: .Xr ssh-add 1 .
245: If this option is set to
1.240 jmc 246: .Cm no ,
1.222 jcs 247: no keys are added to the agent.
248: The argument must be
1.240 jmc 249: .Cm yes ,
250: .Cm confirm ,
251: .Cm ask ,
1.222 jcs 252: or
1.240 jmc 253: .Cm no
254: (the default).
1.10 djm 255: .It Cm AddressFamily
1.11 jmc 256: Specifies which address family to use when connecting.
257: Valid arguments are
1.240 jmc 258: .Cm any
259: (the default),
260: .Cm inet
1.84 jmc 261: (use IPv4 only), or
1.240 jmc 262: .Cm inet6
1.40 jmc 263: (use IPv6 only).
1.1 stevesk 264: .It Cm BatchMode
265: If set to
1.240 jmc 266: .Cm yes ,
1.1 stevesk 267: passphrase/password querying will be disabled.
268: This option is useful in scripts and other batch jobs where no user
269: is present to supply the password.
270: The argument must be
1.240 jmc 271: .Cm yes
1.1 stevesk 272: or
1.240 jmc 273: .Cm no
274: (the default).
1.268 jmc 275: .It Cm BindAddress
276: Use the specified address on the local machine as the source address of
277: the connection.
278: Only useful on systems with more than one address.
279: .It Cm BindInterface
280: Use the address of the specified interface on the local machine as the
281: source address of the connection.
1.171 djm 282: .It Cm CanonicalDomains
1.172 jmc 283: When
1.173 djm 284: .Cm CanonicalizeHostname
1.171 djm 285: is enabled, this option specifies the list of domain suffixes in which to
286: search for the specified destination host.
1.173 djm 287: .It Cm CanonicalizeFallbackLocal
1.174 djm 288: Specifies whether to fail with an error when hostname canonicalization fails.
1.172 jmc 289: The default,
1.240 jmc 290: .Cm yes ,
1.172 jmc 291: will attempt to look up the unqualified hostname using the system resolver's
1.171 djm 292: search rules.
293: A value of
1.240 jmc 294: .Cm no
1.171 djm 295: will cause
296: .Xr ssh 1
297: to fail instantly if
1.173 djm 298: .Cm CanonicalizeHostname
1.171 djm 299: is enabled and the target hostname cannot be found in any of the domains
300: specified by
301: .Cm CanonicalDomains .
1.173 djm 302: .It Cm CanonicalizeHostname
1.174 djm 303: Controls whether explicit hostname canonicalization is performed.
1.172 jmc 304: The default,
1.240 jmc 305: .Cm no ,
1.171 djm 306: is not to perform any name rewriting and let the system resolver handle all
307: hostname lookups.
308: If set to
1.240 jmc 309: .Cm yes
1.171 djm 310: then, for connections that do not use a
1.284 djm 311: .Cm ProxyCommand
312: or
313: .Cm ProxyJump ,
1.171 djm 314: .Xr ssh 1
1.173 djm 315: will attempt to canonicalize the hostname specified on the command line
1.171 djm 316: using the
317: .Cm CanonicalDomains
318: suffixes and
1.173 djm 319: .Cm CanonicalizePermittedCNAMEs
1.171 djm 320: rules.
321: If
1.173 djm 322: .Cm CanonicalizeHostname
1.171 djm 323: is set to
1.240 jmc 324: .Cm always ,
1.174 djm 325: then canonicalization is applied to proxied connections too.
1.185 djm 326: .Pp
1.193 djm 327: If this option is enabled, then the configuration files are processed
328: again using the new target name to pick up any new configuration in matching
1.185 djm 329: .Cm Host
1.193 djm 330: and
331: .Cm Match
1.185 djm 332: stanzas.
1.173 djm 333: .It Cm CanonicalizeMaxDots
1.172 jmc 334: Specifies the maximum number of dot characters in a hostname before
1.174 djm 335: canonicalization is disabled.
1.240 jmc 336: The default, 1,
1.172 jmc 337: allows a single dot (i.e. hostname.subdomain).
1.173 djm 338: .It Cm CanonicalizePermittedCNAMEs
1.172 jmc 339: Specifies rules to determine whether CNAMEs should be followed when
1.173 djm 340: canonicalizing hostnames.
1.171 djm 341: The rules consist of one or more arguments of
1.172 jmc 342: .Ar source_domain_list : Ns Ar target_domain_list ,
1.171 djm 343: where
344: .Ar source_domain_list
1.174 djm 345: is a pattern-list of domains that may follow CNAMEs in canonicalization,
1.171 djm 346: and
347: .Ar target_domain_list
1.172 jmc 348: is a pattern-list of domains that they may resolve to.
1.171 djm 349: .Pp
350: For example,
1.240 jmc 351: .Qq *.a.example.com:*.b.example.com,*.c.example.com
1.171 djm 352: will allow hostnames matching
1.240 jmc 353: .Qq *.a.example.com
1.173 djm 354: to be canonicalized to names in the
1.240 jmc 355: .Qq *.b.example.com
1.171 djm 356: or
1.240 jmc 357: .Qq *.c.example.com
1.171 djm 358: domains.
1.283 jmc 359: .It Cm CASignatureAlgorithms
360: Specifies which algorithms are allowed for signing of certificates
361: by certificate authorities (CAs).
362: The default is:
363: .Bd -literal -offset indent
1.297 djm 364: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.283 jmc 365: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
366: .Ed
367: .Pp
368: .Xr ssh 1
369: will not accept host certificates signed using algorithms other than those
370: specified.
1.221 djm 371: .It Cm CertificateFile
372: Specifies a file from which the user's certificate is read.
373: A corresponding private key must be provided separately in order
374: to use this certificate either
375: from an
376: .Cm IdentityFile
377: directive or
378: .Fl i
379: flag to
380: .Xr ssh 1 ,
381: via
382: .Xr ssh-agent 1 ,
383: or via a
384: .Cm PKCS11Provider .
385: .Pp
1.239 jmc 386: Arguments to
387: .Cm CertificateFile
388: may use the tilde syntax to refer to a user's home directory
389: or the tokens described in the
390: .Sx TOKENS
391: section.
1.221 djm 392: .Pp
393: It is possible to have multiple certificate files specified in
394: configuration files; these certificates will be tried in sequence.
395: Multiple
396: .Cm CertificateFile
397: directives will add to the list of certificates used for
398: authentication.
1.1 stevesk 399: .It Cm ChallengeResponseAuthentication
1.82 jmc 400: Specifies whether to use challenge-response authentication.
1.1 stevesk 401: The argument to this keyword must be
1.240 jmc 402: .Cm yes
403: (the default)
1.1 stevesk 404: or
1.240 jmc 405: .Cm no .
1.1 stevesk 406: .It Cm CheckHostIP
1.240 jmc 407: If set to
408: .Cm yes
409: (the default),
1.84 jmc 410: .Xr ssh 1
411: will additionally check the host IP address in the
1.1 stevesk 412: .Pa known_hosts
413: file.
1.240 jmc 414: This allows it to detect if a host key changed due to DNS spoofing
1.211 djm 415: and will add addresses of destination hosts to
416: .Pa ~/.ssh/known_hosts
417: in the process, regardless of the setting of
418: .Cm StrictHostKeyChecking .
1.107 grunk 419: If the option is set to
1.240 jmc 420: .Cm no ,
1.1 stevesk 421: the check will not be executed.
422: .It Cm Ciphers
1.245 djm 423: Specifies the ciphers allowed and their order of preference.
1.1 stevesk 424: Multiple ciphers must be comma-separated.
1.299 ! kn 425: If the specified list begins with a
1.214 djm 426: .Sq +
427: character, then the specified ciphers will be appended to the default set
428: instead of replacing them.
1.299 ! kn 429: If the specified list begins with a
1.241 djm 430: .Sq -
431: character, then the specified ciphers (including wildcards) will be removed
432: from the default set instead of replacing them.
1.214 djm 433: .Pp
1.180 djm 434: The supported ciphers are:
1.240 jmc 435: .Bd -literal -offset indent
1.186 naddy 436: 3des-cbc
437: aes128-cbc
438: aes192-cbc
439: aes256-cbc
440: aes128-ctr
441: aes192-ctr
442: aes256-ctr
443: aes128-gcm@openssh.com
444: aes256-gcm@openssh.com
445: chacha20-poly1305@openssh.com
1.240 jmc 446: .Ed
1.180 djm 447: .Pp
1.84 jmc 448: The default is:
1.186 naddy 449: .Bd -literal -offset indent
1.215 jmc 450: chacha20-poly1305@openssh.com,
1.186 naddy 451: aes128-ctr,aes192-ctr,aes256-ctr,
1.270 djm 452: aes128-gcm@openssh.com,aes256-gcm@openssh.com
1.1 stevesk 453: .Ed
1.180 djm 454: .Pp
1.240 jmc 455: The list of available ciphers may also be obtained using
456: .Qq ssh -Q cipher .
1.1 stevesk 457: .It Cm ClearAllForwardings
1.84 jmc 458: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 459: specified in the configuration files or on the command line be
1.7 jmc 460: cleared.
461: This option is primarily useful when used from the
1.84 jmc 462: .Xr ssh 1
1.1 stevesk 463: command line to clear port forwardings set in
464: configuration files, and is automatically set by
465: .Xr scp 1
466: and
467: .Xr sftp 1 .
468: The argument must be
1.240 jmc 469: .Cm yes
1.1 stevesk 470: or
1.240 jmc 471: .Cm no
472: (the default).
1.1 stevesk 473: .It Cm Compression
474: Specifies whether to use compression.
475: The argument must be
1.240 jmc 476: .Cm yes
1.1 stevesk 477: or
1.240 jmc 478: .Cm no
479: (the default).
1.247 naddy 480: .It Cm ConnectionAttempts
481: Specifies the number of tries (one per second) to make before exiting.
482: The argument must be an integer.
483: This may be useful in scripts if the connection sometimes fails.
484: The default is 1.
1.9 djm 485: .It Cm ConnectTimeout
1.84 jmc 486: Specifies the timeout (in seconds) used when connecting to the
487: SSH server, instead of using the default system TCP timeout.
1.11 jmc 488: This value is used only when the target is down or really unreachable,
489: not when it refuses the connection.
1.36 djm 490: .It Cm ControlMaster
491: Enables the sharing of multiple sessions over a single network connection.
492: When set to
1.240 jmc 493: .Cm yes ,
1.84 jmc 494: .Xr ssh 1
1.36 djm 495: will listen for connections on a control socket specified using the
496: .Cm ControlPath
497: argument.
498: Additional sessions can connect to this socket using the same
499: .Cm ControlPath
500: with
501: .Cm ControlMaster
502: set to
1.240 jmc 503: .Cm no
1.38 jmc 504: (the default).
1.64 jmc 505: These sessions will try to reuse the master instance's network connection
1.63 djm 506: rather than initiating new ones, but will fall back to connecting normally
507: if the control socket does not exist, or is not listening.
508: .Pp
1.37 djm 509: Setting this to
1.240 jmc 510: .Cm ask
511: will cause
512: .Xr ssh 1
1.206 jmc 513: to listen for control connections, but require confirmation using
514: .Xr ssh-askpass 1 .
1.51 jakob 515: If the
516: .Cm ControlPath
1.84 jmc 517: cannot be opened,
1.240 jmc 518: .Xr ssh 1
519: will continue without connecting to a master instance.
1.58 djm 520: .Pp
521: X11 and
1.59 jmc 522: .Xr ssh-agent 1
1.58 djm 523: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 524: display and agent forwarded will be the one belonging to the master
1.59 jmc 525: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 526: .Pp
527: Two additional options allow for opportunistic multiplexing: try to use a
528: master connection but fall back to creating a new one if one does not already
529: exist.
530: These options are:
1.240 jmc 531: .Cm auto
1.56 djm 532: and
1.240 jmc 533: .Cm autoask .
1.56 djm 534: The latter requires confirmation like the
1.240 jmc 535: .Cm ask
1.56 djm 536: option.
1.36 djm 537: .It Cm ControlPath
1.55 djm 538: Specify the path to the control socket used for connection sharing as described
539: in the
1.36 djm 540: .Cm ControlMaster
1.57 djm 541: section above or the string
1.240 jmc 542: .Cm none
1.57 djm 543: to disable connection sharing.
1.239 jmc 544: Arguments to
545: .Cm ControlPath
546: may use the tilde syntax to refer to a user's home directory
547: or the tokens described in the
548: .Sx TOKENS
549: section.
1.56 djm 550: It is recommended that any
551: .Cm ControlPath
552: used for opportunistic connection sharing include
1.195 djm 553: at least %h, %p, and %r (or alternatively %C) and be placed in a directory
554: that is not writable by other users.
1.56 djm 555: This ensures that shared connections are uniquely identified.
1.137 djm 556: .It Cm ControlPersist
557: When used in conjunction with
558: .Cm ControlMaster ,
559: specifies that the master connection should remain open
560: in the background (waiting for future client connections)
561: after the initial client connection has been closed.
562: If set to
1.240 jmc 563: .Cm no ,
1.137 djm 564: then the master connection will not be placed into the background,
565: and will close as soon as the initial client connection is closed.
566: If set to
1.240 jmc 567: .Cm yes
568: or 0,
1.137 djm 569: then the master connection will remain in the background indefinitely
570: (until killed or closed via a mechanism such as the
1.240 jmc 571: .Qq ssh -O exit ) .
1.137 djm 572: If set to a time in seconds, or a time in any of the formats documented in
573: .Xr sshd_config 5 ,
574: then the backgrounded master connection will automatically terminate
575: after it has remained idle (with no client connections) for the
576: specified time.
1.38 jmc 577: .It Cm DynamicForward
1.74 jmc 578: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 579: over the secure channel, and the application
580: protocol is then used to determine where to connect to from the
581: remote machine.
1.62 djm 582: .Pp
583: The argument must be
584: .Sm off
585: .Oo Ar bind_address : Oc Ar port .
586: .Sm on
1.138 djm 587: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 588: By default, the local port is bound in accordance with the
589: .Cm GatewayPorts
590: setting.
591: However, an explicit
592: .Ar bind_address
593: may be used to bind the connection to a specific address.
594: The
595: .Ar bind_address
596: of
1.240 jmc 597: .Cm localhost
1.62 djm 598: indicates that the listening port be bound for local use only, while an
599: empty address or
600: .Sq *
601: indicates that the port should be available from all interfaces.
602: .Pp
1.38 jmc 603: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 604: .Xr ssh 1
1.38 jmc 605: will act as a SOCKS server.
606: Multiple forwardings may be specified, and
607: additional forwardings can be given on the command line.
608: Only the superuser can forward privileged ports.
1.14 markus 609: .It Cm EnableSSHKeysign
610: Setting this option to
1.240 jmc 611: .Cm yes
1.14 markus 612: in the global client configuration file
613: .Pa /etc/ssh/ssh_config
614: enables the use of the helper program
615: .Xr ssh-keysign 8
616: during
617: .Cm HostbasedAuthentication .
618: The argument must be
1.240 jmc 619: .Cm yes
1.14 markus 620: or
1.240 jmc 621: .Cm no
622: (the default).
1.23 jmc 623: This option should be placed in the non-hostspecific section.
1.14 markus 624: See
625: .Xr ssh-keysign 8
626: for more information.
1.1 stevesk 627: .It Cm EscapeChar
628: Sets the escape character (default:
629: .Ql ~ ) .
630: The escape character can also
631: be set on the command line.
632: The argument should be a single character,
633: .Ql ^
634: followed by a letter, or
1.240 jmc 635: .Cm none
1.1 stevesk 636: to disable the escape
637: character entirely (making the connection transparent for binary
638: data).
1.96 markus 639: .It Cm ExitOnForwardFailure
640: Specifies whether
641: .Xr ssh 1
642: should terminate the connection if it cannot set up all requested
1.216 djm 643: dynamic, tunnel, local, and remote port forwardings, (e.g.\&
1.217 jmc 644: if either end is unable to bind and listen on a specified port).
1.216 djm 645: Note that
646: .Cm ExitOnForwardFailure
647: does not apply to connections made over port forwardings and will not,
648: for example, cause
649: .Xr ssh 1
650: to exit if TCP connections to the ultimate forwarding destination fail.
1.96 markus 651: The argument must be
1.240 jmc 652: .Cm yes
1.96 markus 653: or
1.240 jmc 654: .Cm no
655: (the default).
1.197 djm 656: .It Cm FingerprintHash
657: Specifies the hash algorithm used when displaying key fingerprints.
658: Valid options are:
1.240 jmc 659: .Cm md5
1.197 djm 660: and
1.240 jmc 661: .Cm sha256
662: (the default).
1.1 stevesk 663: .It Cm ForwardAgent
664: Specifies whether the connection to the authentication agent (if any)
665: will be forwarded to the remote machine.
666: The argument must be
1.240 jmc 667: .Cm yes
1.1 stevesk 668: or
1.240 jmc 669: .Cm no
670: (the default).
1.3 stevesk 671: .Pp
1.7 jmc 672: Agent forwarding should be enabled with caution.
673: Users with the ability to bypass file permissions on the remote host
674: (for the agent's Unix-domain socket)
675: can access the local agent through the forwarded connection.
676: An attacker cannot obtain key material from the agent,
1.3 stevesk 677: however they can perform operations on the keys that enable them to
678: authenticate using the identities loaded into the agent.
1.1 stevesk 679: .It Cm ForwardX11
680: Specifies whether X11 connections will be automatically redirected
681: over the secure channel and
682: .Ev DISPLAY
683: set.
684: The argument must be
1.240 jmc 685: .Cm yes
1.1 stevesk 686: or
1.240 jmc 687: .Cm no
688: (the default).
1.3 stevesk 689: .Pp
1.7 jmc 690: X11 forwarding should be enabled with caution.
691: Users with the ability to bypass file permissions on the remote host
1.22 markus 692: (for the user's X11 authorization database)
1.7 jmc 693: can access the local X11 display through the forwarded connection.
1.22 markus 694: An attacker may then be able to perform activities such as keystroke monitoring
695: if the
696: .Cm ForwardX11Trusted
697: option is also enabled.
1.134 djm 698: .It Cm ForwardX11Timeout
1.135 jmc 699: Specify a timeout for untrusted X11 forwarding
700: using the format described in the
1.240 jmc 701: .Sx TIME FORMATS
702: section of
1.134 djm 703: .Xr sshd_config 5 .
704: X11 connections received by
705: .Xr ssh 1
706: after this time will be refused.
1.285 djm 707: Setting
708: .Cm ForwardX11Timeout
709: to zero will disable the timeout and permit X11 forwarding for the life
710: of the connection.
1.134 djm 711: The default is to disable untrusted X11 forwarding after twenty minutes has
712: elapsed.
1.22 markus 713: .It Cm ForwardX11Trusted
1.34 jmc 714: If this option is set to
1.240 jmc 715: .Cm yes ,
1.84 jmc 716: remote X11 clients will have full access to the original X11 display.
1.42 djm 717: .Pp
1.22 markus 718: If this option is set to
1.240 jmc 719: .Cm no
720: (the default),
1.84 jmc 721: remote X11 clients will be considered untrusted and prevented
1.22 markus 722: from stealing or tampering with data belonging to trusted X11
723: clients.
1.42 djm 724: Furthermore, the
725: .Xr xauth 1
726: token used for the session will be set to expire after 20 minutes.
727: Remote clients will be refused access after this time.
1.22 markus 728: .Pp
729: See the X11 SECURITY extension specification for full details on
730: the restrictions imposed on untrusted clients.
1.1 stevesk 731: .It Cm GatewayPorts
732: Specifies whether remote hosts are allowed to connect to local
733: forwarded ports.
734: By default,
1.84 jmc 735: .Xr ssh 1
1.7 jmc 736: binds local port forwardings to the loopback address.
737: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 738: .Cm GatewayPorts
1.84 jmc 739: can be used to specify that ssh
1.1 stevesk 740: should bind local port forwardings to the wildcard address,
741: thus allowing remote hosts to connect to forwarded ports.
742: The argument must be
1.240 jmc 743: .Cm yes
1.1 stevesk 744: or
1.240 jmc 745: .Cm no
746: (the default).
1.1 stevesk 747: .It Cm GlobalKnownHostsFile
1.151 djm 748: Specifies one or more files to use for the global
749: host key database, separated by whitespace.
750: The default is
751: .Pa /etc/ssh/ssh_known_hosts ,
752: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 753: .It Cm GSSAPIAuthentication
1.27 markus 754: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 755: The default is
1.240 jmc 756: .Cm no .
1.18 markus 757: .It Cm GSSAPIDelegateCredentials
758: Forward (delegate) credentials to the server.
759: The default is
1.240 jmc 760: .Cm no .
1.44 djm 761: .It Cm HashKnownHosts
762: Indicates that
1.84 jmc 763: .Xr ssh 1
1.44 djm 764: should hash host names and addresses when they are added to
1.50 djm 765: .Pa ~/.ssh/known_hosts .
1.44 djm 766: These hashed names may be used normally by
1.84 jmc 767: .Xr ssh 1
1.44 djm 768: and
1.84 jmc 769: .Xr sshd 8 ,
1.44 djm 770: but they do not reveal identifying information should the file's contents
771: be disclosed.
772: The default is
1.240 jmc 773: .Cm no .
1.97 jmc 774: Note that existing names and addresses in known hosts files
775: will not be converted automatically,
776: but may be manually hashed using
1.45 djm 777: .Xr ssh-keygen 1 .
1.1 stevesk 778: .It Cm HostbasedAuthentication
779: Specifies whether to try rhosts based authentication with public key
780: authentication.
781: The argument must be
1.240 jmc 782: .Cm yes
1.1 stevesk 783: or
1.240 jmc 784: .Cm no
785: (the default).
1.202 djm 786: .It Cm HostbasedKeyTypes
787: Specifies the key types that will be used for hostbased authentication
1.279 djm 788: as a comma-separated list of patterns.
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.
1.213 markus 797: The default for this option is:
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,
802: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 803: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 804: ssh-rsa-cert-v01@openssh.com,
805: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 806: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 807: .Ed
808: .Pp
1.202 djm 809: The
810: .Fl Q
811: option of
812: .Xr ssh 1
813: may be used to list supported key types.
1.1 stevesk 814: .It Cm HostKeyAlgorithms
1.226 jmc 815: Specifies the host key algorithms
1.1 stevesk 816: that the client wants to use in order of preference.
1.214 djm 817: Alternately if the specified value begins with a
818: .Sq +
819: character, then the specified key types will be appended to the default set
820: instead of replacing them.
1.241 djm 821: If the specified value begins with a
822: .Sq -
823: character, then the specified key types (including wildcards) will be removed
824: from the default set instead of replacing them.
1.1 stevesk 825: The default for this option is:
1.139 djm 826: .Bd -literal -offset 3n
827: ecdsa-sha2-nistp256-cert-v01@openssh.com,
828: ecdsa-sha2-nistp384-cert-v01@openssh.com,
829: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1.183 naddy 830: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 831: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 832: ssh-rsa-cert-v01@openssh.com,
1.139 djm 833: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 834: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.139 djm 835: .Ed
1.145 djm 836: .Pp
837: If hostkeys are known for the destination host then this default is modified
838: to prefer their algorithms.
1.198 djm 839: .Pp
1.240 jmc 840: The list of available key types may also be obtained using
841: .Qq ssh -Q key .
1.1 stevesk 842: .It Cm HostKeyAlias
843: Specifies an alias that should be used instead of the
844: real host name when looking up or saving the host key
1.251 djm 845: in the host key database files and when validating host certificates.
1.84 jmc 846: This option is useful for tunneling SSH connections
1.1 stevesk 847: or for multiple servers running on a single host.
1.295 jmc 848: .It Cm Hostname
1.1 stevesk 849: Specifies the real host name to log into.
850: This can be used to specify nicknames or abbreviations for hosts.
1.239 jmc 851: Arguments to
1.295 jmc 852: .Cm Hostname
1.239 jmc 853: accept the tokens described in the
854: .Sx TOKENS
855: section.
1.1 stevesk 856: Numeric IP addresses are also permitted (both on the command line and in
1.295 jmc 857: .Cm Hostname
1.1 stevesk 858: specifications).
1.239 jmc 859: The default is the name given on the command line.
1.29 markus 860: .It Cm IdentitiesOnly
861: Specifies that
1.84 jmc 862: .Xr ssh 1
1.221 djm 863: should only use the authentication identity and certificate files explicitly
864: configured in the
1.31 jmc 865: .Nm
1.221 djm 866: files
867: or passed on the
868: .Xr ssh 1
869: command-line,
1.84 jmc 870: even if
871: .Xr ssh-agent 1
1.159 djm 872: or a
873: .Cm PKCS11Provider
1.29 markus 874: offers more identities.
875: The argument to this keyword must be
1.240 jmc 876: .Cm yes
1.29 markus 877: or
1.240 jmc 878: .Cm no
879: (the default).
1.84 jmc 880: This option is intended for situations where ssh-agent
1.29 markus 881: offers many different identities.
1.231 markus 882: .It Cm IdentityAgent
883: Specifies the
884: .Ux Ns -domain
885: socket used to communicate with the authentication agent.
886: .Pp
887: This option overrides the
1.240 jmc 888: .Ev SSH_AUTH_SOCK
1.231 markus 889: environment variable and can be used to select a specific agent.
890: Setting the socket name to
1.240 jmc 891: .Cm none
1.231 markus 892: disables the use of an authentication agent.
1.232 markus 893: If the string
1.240 jmc 894: .Qq SSH_AUTH_SOCK
1.232 markus 895: is specified, the location of the socket will be read from the
896: .Ev SSH_AUTH_SOCK
897: environment variable.
1.286 djm 898: Otherwise if the specified value begins with a
899: .Sq $
900: character, then it will be treated as an environment variable containing
901: the location of the socket.
1.231 markus 902: .Pp
1.239 jmc 903: Arguments to
904: .Cm IdentityAgent
905: may use the tilde syntax to refer to a user's home directory
906: or the tokens described in the
907: .Sx TOKENS
908: section.
1.67 jmc 909: .It Cm IdentityFile
1.192 sobrado 910: Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA authentication
1.139 djm 911: identity is read.
1.67 jmc 912: The default is
1.139 djm 913: .Pa ~/.ssh/id_dsa ,
1.183 naddy 914: .Pa ~/.ssh/id_ecdsa ,
915: .Pa ~/.ssh/id_ed25519
1.139 djm 916: and
1.245 djm 917: .Pa ~/.ssh/id_rsa .
1.67 jmc 918: Additionally, any identities represented by the authentication agent
1.165 djm 919: will be used for authentication unless
920: .Cm IdentitiesOnly
921: is set.
1.221 djm 922: If no certificates have been explicitly specified by
923: .Cm CertificateFile ,
1.129 djm 924: .Xr ssh 1
925: will try to load certificate information from the filename obtained by
926: appending
927: .Pa -cert.pub
928: to the path of a specified
929: .Cm IdentityFile .
1.90 djm 930: .Pp
1.239 jmc 931: Arguments to
932: .Cm IdentityFile
933: may use the tilde syntax to refer to a user's home directory
934: or the tokens described in the
935: .Sx TOKENS
936: section.
1.90 djm 937: .Pp
1.67 jmc 938: It is possible to have
939: multiple identity files specified in configuration files; all these
940: identities will be tried in sequence.
1.152 djm 941: Multiple
942: .Cm IdentityFile
943: directives will add to the list of identities tried (this behaviour
944: differs from that of other configuration directives).
1.165 djm 945: .Pp
946: .Cm IdentityFile
947: may be used in conjunction with
948: .Cm IdentitiesOnly
949: to select which identities in an agent are offered during authentication.
1.221 djm 950: .Cm IdentityFile
951: may also be used in conjunction with
952: .Cm CertificateFile
953: in order to provide any certificate also needed for authentication with
954: the identity.
1.164 jmc 955: .It Cm IgnoreUnknown
956: Specifies a pattern-list of unknown options to be ignored if they are
957: encountered in configuration parsing.
958: This may be used to suppress errors if
959: .Nm
960: contains options that are unrecognised by
961: .Xr ssh 1 .
962: It is recommended that
963: .Cm IgnoreUnknown
964: be listed early in the configuration file as it will not be applied
965: to unknown options that appear before it.
1.229 djm 966: .It Cm Include
967: Include the specified configuration file(s).
1.230 jmc 968: Multiple pathnames may be specified and each pathname may contain
1.281 kn 969: .Xr glob 7
1.229 djm 970: wildcards and, for user configurations, shell-like
1.240 jmc 971: .Sq ~
1.229 djm 972: references to user home directories.
973: Files without absolute paths are assumed to be in
974: .Pa ~/.ssh
1.230 jmc 975: if included in a user configuration file or
1.229 djm 976: .Pa /etc/ssh
977: if included from the system configuration file.
978: .Cm Include
979: directive may appear inside a
980: .Cm Match
981: or
982: .Cm Host
983: block
984: to perform conditional inclusion.
1.143 djm 985: .It Cm IPQoS
986: Specifies the IPv4 type-of-service or DSCP class for connections.
987: Accepted values are
1.240 jmc 988: .Cm af11 ,
989: .Cm af12 ,
990: .Cm af13 ,
991: .Cm af21 ,
992: .Cm af22 ,
993: .Cm af23 ,
994: .Cm af31 ,
995: .Cm af32 ,
996: .Cm af33 ,
997: .Cm af41 ,
998: .Cm af42 ,
999: .Cm af43 ,
1000: .Cm cs0 ,
1001: .Cm cs1 ,
1002: .Cm cs2 ,
1003: .Cm cs3 ,
1004: .Cm cs4 ,
1005: .Cm cs5 ,
1006: .Cm cs6 ,
1007: .Cm cs7 ,
1008: .Cm ef ,
1009: .Cm lowdelay ,
1010: .Cm throughput ,
1011: .Cm reliability ,
1.253 djm 1012: a numeric value, or
1013: .Cm none
1014: to use the operating system default.
1.146 djm 1015: This option may take one or two arguments, separated by whitespace.
1.143 djm 1016: If one argument is specified, it is used as the packet class unconditionally.
1017: If two values are specified, the first is automatically selected for
1018: interactive sessions and the second for non-interactive sessions.
1019: The default is
1.269 job 1020: .Cm af21
1.272 jmc 1021: (Low-Latency Data)
1.143 djm 1022: for interactive sessions and
1.269 job 1023: .Cm cs1
1.272 jmc 1024: (Lower Effort)
1.143 djm 1025: for non-interactive sessions.
1.103 djm 1026: .It Cm KbdInteractiveAuthentication
1027: Specifies whether to use keyboard-interactive authentication.
1028: The argument to this keyword must be
1.240 jmc 1029: .Cm yes
1030: (the default)
1.103 djm 1031: or
1.240 jmc 1032: .Cm no .
1.39 djm 1033: .It Cm KbdInteractiveDevices
1034: Specifies the list of methods to use in keyboard-interactive authentication.
1035: Multiple method names must be comma-separated.
1036: The default is to use the server specified list.
1.85 jmc 1037: The methods available vary depending on what the server supports.
1038: For an OpenSSH server,
1039: it may be zero or more of:
1.240 jmc 1040: .Cm bsdauth ,
1041: .Cm pam ,
1.85 jmc 1042: and
1.240 jmc 1043: .Cm skey .
1.140 djm 1044: .It Cm KexAlgorithms
1045: Specifies the available KEX (Key Exchange) algorithms.
1046: Multiple algorithms must be comma-separated.
1.299 ! kn 1047: If the specified list begins with a
1.214 djm 1048: .Sq +
1049: character, then the specified methods will be appended to the default set
1050: instead of replacing them.
1.299 ! kn 1051: If the specified list begins with a
1.241 djm 1052: .Sq -
1053: character, then the specified methods (including wildcards) will be removed
1054: from the default set instead of replacing them.
1.141 jmc 1055: The default is:
1056: .Bd -literal -offset indent
1.238 djm 1057: curve25519-sha256,curve25519-sha256@libssh.org,
1.141 jmc 1058: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1059: diffie-hellman-group-exchange-sha256,
1.266 djm 1060: diffie-hellman-group16-sha512,
1061: diffie-hellman-group18-sha512,
1062: diffie-hellman-group14-sha256,
1.212 djm 1063: diffie-hellman-group14-sha1
1.141 jmc 1064: .Ed
1.198 djm 1065: .Pp
1.240 jmc 1066: The list of available key exchange algorithms may also be obtained using
1067: .Qq ssh -Q kex .
1.65 reyk 1068: .It Cm LocalCommand
1069: Specifies a command to execute on the local machine after successfully
1070: connecting to the server.
1071: The command string extends to the end of the line, and is executed with
1.105 jmc 1072: the user's shell.
1.239 jmc 1073: Arguments to
1074: .Cm LocalCommand
1075: accept the tokens described in the
1076: .Sx TOKENS
1077: section.
1.123 djm 1078: .Pp
1079: The command is run synchronously and does not have access to the
1080: session of the
1081: .Xr ssh 1
1082: that spawned it.
1083: It should not be used for interactive commands.
1084: .Pp
1.65 reyk 1085: This directive is ignored unless
1086: .Cm PermitLocalCommand
1087: has been enabled.
1.1 stevesk 1088: .It Cm LocalForward
1.74 jmc 1089: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 1090: the secure channel to the specified host and port from the remote machine.
1.49 jmc 1091: The first argument must be
1.43 djm 1092: .Sm off
1.49 jmc 1093: .Oo Ar bind_address : Oc Ar port
1.43 djm 1094: .Sm on
1.49 jmc 1095: and the second argument must be
1096: .Ar host : Ns Ar hostport .
1.138 djm 1097: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 1098: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 1099: given on the command line.
1.1 stevesk 1100: Only the superuser can forward privileged ports.
1.43 djm 1101: By default, the local port is bound in accordance with the
1102: .Cm GatewayPorts
1103: setting.
1104: However, an explicit
1105: .Ar bind_address
1106: may be used to bind the connection to a specific address.
1107: The
1108: .Ar bind_address
1109: of
1.240 jmc 1110: .Cm localhost
1.46 jmc 1111: indicates that the listening port be bound for local use only, while an
1112: empty address or
1113: .Sq *
1.43 djm 1114: indicates that the port should be available from all interfaces.
1.1 stevesk 1115: .It Cm LogLevel
1116: Gives the verbosity level that is used when logging messages from
1.84 jmc 1117: .Xr ssh 1 .
1.1 stevesk 1118: The possible values are:
1.84 jmc 1119: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 1120: The default is INFO.
1121: DEBUG and DEBUG1 are equivalent.
1122: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 1123: .It Cm MACs
1124: Specifies the MAC (message authentication code) algorithms
1125: in order of preference.
1.226 jmc 1126: The MAC algorithm is used for data integrity protection.
1.1 stevesk 1127: Multiple algorithms must be comma-separated.
1.299 ! kn 1128: If the specified list begins with a
1.214 djm 1129: .Sq +
1130: character, then the specified algorithms will be appended to the default set
1131: instead of replacing them.
1.299 ! kn 1132: If the specified list begins with a
1.241 djm 1133: .Sq -
1134: character, then the specified algorithms (including wildcards) will be removed
1135: from the default set instead of replacing them.
1.214 djm 1136: .Pp
1.160 markus 1137: The algorithms that contain
1.240 jmc 1138: .Qq -etm
1.160 markus 1139: calculate the MAC after encryption (encrypt-then-mac).
1140: These are considered safer and their use recommended.
1.214 djm 1141: .Pp
1.84 jmc 1142: The default is:
1.101 jmc 1143: .Bd -literal -offset indent
1.160 markus 1144: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1145: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.224 djm 1146: hmac-sha1-etm@openssh.com,
1.186 naddy 1147: umac-64@openssh.com,umac-128@openssh.com,
1.224 djm 1148: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.101 jmc 1149: .Ed
1.198 djm 1150: .Pp
1.240 jmc 1151: The list of available MAC algorithms may also be obtained using
1152: .Qq ssh -Q mac .
1.1 stevesk 1153: .It Cm NoHostAuthenticationForLocalhost
1.264 djm 1154: Disable host authentication for localhost (loopback addresses).
1.1 stevesk 1155: The argument to this keyword must be
1.240 jmc 1156: .Cm yes
1.1 stevesk 1157: or
1.242 jmc 1158: .Cm no
1.240 jmc 1159: (the default).
1.1 stevesk 1160: .It Cm NumberOfPasswordPrompts
1161: Specifies the number of password prompts before giving up.
1162: The argument to this keyword must be an integer.
1.84 jmc 1163: The default is 3.
1.1 stevesk 1164: .It Cm PasswordAuthentication
1165: Specifies whether to use password authentication.
1166: The argument to this keyword must be
1.240 jmc 1167: .Cm yes
1168: (the default)
1.1 stevesk 1169: or
1.240 jmc 1170: .Cm no .
1.65 reyk 1171: .It Cm PermitLocalCommand
1172: Allow local command execution via the
1173: .Ic LocalCommand
1174: option or using the
1.66 jmc 1175: .Ic !\& Ns Ar command
1.65 reyk 1176: escape sequence in
1177: .Xr ssh 1 .
1178: The argument must be
1.240 jmc 1179: .Cm yes
1.65 reyk 1180: or
1.240 jmc 1181: .Cm no
1182: (the default).
1.127 markus 1183: .It Cm PKCS11Provider
1.292 djm 1184: Specifies which PKCS#11 provider to use or
1185: .Cm none
1186: to indicate that no provider should be used (the default).
1187: The argument to this keyword is a path to the PKCS#11 shared library
1.127 markus 1188: .Xr ssh 1
1.292 djm 1189: should use to communicate with a PKCS#11 token providing keys for user
1190: authentication.
1.67 jmc 1191: .It Cm Port
1192: Specifies the port number to connect on the remote host.
1.84 jmc 1193: The default is 22.
1.1 stevesk 1194: .It Cm PreferredAuthentications
1.226 jmc 1195: Specifies the order in which the client should try authentication methods.
1.48 jmc 1196: This allows a client to prefer one method (e.g.\&
1.1 stevesk 1197: .Cm keyboard-interactive )
1.48 jmc 1198: over another method (e.g.\&
1.131 jmc 1199: .Cm password ) .
1200: The default is:
1201: .Bd -literal -offset indent
1202: gssapi-with-mic,hostbased,publickey,
1203: keyboard-interactive,password
1204: .Ed
1.1 stevesk 1205: .It Cm ProxyCommand
1206: Specifies the command to use to connect to the server.
1207: The command
1.190 djm 1208: string extends to the end of the line, and is executed
1209: using the user's shell
1210: .Ql exec
1211: directive to avoid a lingering shell process.
1212: .Pp
1.239 jmc 1213: Arguments to
1214: .Cm ProxyCommand
1215: accept the tokens described in the
1216: .Sx TOKENS
1217: section.
1.1 stevesk 1218: The command can be basically anything,
1219: and should read from its standard input and write to its standard output.
1220: It should eventually connect an
1221: .Xr sshd 8
1222: server running on some machine, or execute
1223: .Ic sshd -i
1224: somewhere.
1225: Host key management will be done using the
1.296 jmc 1226: .Cm Hostname
1227: of the host being connected (defaulting to the name typed by the user).
1.7 jmc 1228: Setting the command to
1.240 jmc 1229: .Cm none
1.6 markus 1230: disables this option entirely.
1.1 stevesk 1231: Note that
1232: .Cm CheckHostIP
1233: is not available for connects with a proxy command.
1.52 djm 1234: .Pp
1235: This directive is useful in conjunction with
1236: .Xr nc 1
1237: and its proxy support.
1.53 jmc 1238: For example, the following directive would connect via an HTTP proxy at
1.52 djm 1239: 192.0.2.0:
1240: .Bd -literal -offset 3n
1241: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1242: .Ed
1.233 djm 1243: .It Cm ProxyJump
1.260 millert 1244: Specifies one or more jump proxies as either
1.233 djm 1245: .Xo
1246: .Sm off
1.234 jmc 1247: .Op Ar user No @
1.233 djm 1248: .Ar host
1.234 jmc 1249: .Op : Ns Ar port
1.233 djm 1250: .Sm on
1.260 millert 1251: or an ssh URI
1.233 djm 1252: .Xc .
1.235 djm 1253: Multiple proxies may be separated by comma characters and will be visited
1.236 djm 1254: sequentially.
1.233 djm 1255: Setting this option will cause
1256: .Xr ssh 1
1257: to connect to the target host by first making a
1258: .Xr ssh 1
1259: connection to the specified
1260: .Cm ProxyJump
1261: host and then establishing a
1.234 jmc 1262: TCP forwarding to the ultimate target from there.
1.233 djm 1263: .Pp
1264: Note that this option will compete with the
1265: .Cm ProxyCommand
1266: option - whichever is specified first will prevent later instances of the
1267: other from taking effect.
1.289 djm 1268: .Pp
1269: Note also that the configuration for the destination host (either supplied
1270: via the command-line or the configuration file) is not generally applied
1271: to jump hosts.
1272: .Pa ~/.ssh/config
1273: should be used if specific configuration is required for jump hosts.
1.167 djm 1274: .It Cm ProxyUseFdpass
1.168 jmc 1275: Specifies that
1.167 djm 1276: .Cm ProxyCommand
1277: will pass a connected file descriptor back to
1.168 jmc 1278: .Xr ssh 1
1.167 djm 1279: instead of continuing to execute and pass data.
1280: The default is
1.240 jmc 1281: .Cm no .
1.213 markus 1282: .It Cm PubkeyAcceptedKeyTypes
1283: Specifies the key types that will be used for public key authentication
1.279 djm 1284: as a comma-separated list of patterns.
1.299 ! kn 1285: If the specified list begins with a
1.214 djm 1286: .Sq +
1287: character, then the key types after it will be appended to the default
1288: instead of replacing it.
1.299 ! kn 1289: If the specified list begins with a
1.241 djm 1290: .Sq -
1291: character, then the specified key types (including wildcards) will be removed
1292: from the default set instead of replacing them.
1.213 markus 1293: The default for this option is:
1294: .Bd -literal -offset 3n
1295: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1296: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1297: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1298: ssh-ed25519-cert-v01@openssh.com,
1.278 djm 1299: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.213 markus 1300: ssh-rsa-cert-v01@openssh.com,
1301: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.278 djm 1302: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.213 markus 1303: .Ed
1304: .Pp
1.240 jmc 1305: The list of available key types may also be obtained using
1306: .Qq ssh -Q key .
1.1 stevesk 1307: .It Cm PubkeyAuthentication
1308: Specifies whether to try public key authentication.
1309: The argument to this keyword must be
1.240 jmc 1310: .Cm yes
1311: (the default)
1.1 stevesk 1312: or
1.240 jmc 1313: .Cm no .
1.75 dtucker 1314: .It Cm RekeyLimit
1315: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1316: session key is renegotiated, optionally followed a maximum amount of
1317: time that may pass before the session key is renegotiated.
1318: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1319: .Sq K ,
1320: .Sq M ,
1.75 dtucker 1321: or
1.76 jmc 1322: .Sq G
1.75 dtucker 1323: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1324: The default is between
1.84 jmc 1325: .Sq 1G
1.75 dtucker 1326: and
1.84 jmc 1327: .Sq 4G ,
1.75 dtucker 1328: depending on the cipher.
1.162 dtucker 1329: The optional second value is specified in seconds and may use any of the
1.293 schwarze 1330: units documented in the TIME FORMATS section of
1.162 dtucker 1331: .Xr sshd_config 5 .
1332: The default value for
1333: .Cm RekeyLimit
1334: is
1.240 jmc 1335: .Cm default none ,
1.162 dtucker 1336: which means that rekeying is performed after the cipher's default amount
1337: of data has been sent or received and no time based rekeying is done.
1.249 bluhm 1338: .It Cm RemoteCommand
1339: Specifies a command to execute on the remote machine after successfully
1340: connecting to the server.
1341: The command string extends to the end of the line, and is executed with
1342: the user's shell.
1.250 jmc 1343: Arguments to
1344: .Cm RemoteCommand
1345: accept the tokens described in the
1346: .Sx TOKENS
1347: section.
1.1 stevesk 1348: .It Cm RemoteForward
1.74 jmc 1349: Specifies that a TCP port on the remote machine be forwarded over
1.256 markus 1350: the secure channel.
1.273 djm 1351: The remote port may either be forwarded to a specified host and port
1.256 markus 1352: from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
1353: client to connect to arbitrary destinations from the local machine.
1.49 jmc 1354: The first argument must be
1.43 djm 1355: .Sm off
1.49 jmc 1356: .Oo Ar bind_address : Oc Ar port
1.43 djm 1357: .Sm on
1.256 markus 1358: If forwarding to a specific destination then the second argument must be
1359: .Ar host : Ns Ar hostport ,
1360: otherwise if no destination argument is specified then the remote forwarding
1361: will be established as a SOCKS proxy.
1362: .Pp
1.138 djm 1363: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.1 stevesk 1364: Multiple forwardings may be specified, and additional
1365: forwardings can be given on the command line.
1.113 stevesk 1366: Privileged ports can be forwarded only when
1367: logging in as root on the remote machine.
1.118 jmc 1368: .Pp
1.117 djm 1369: If the
1370: .Ar port
1.240 jmc 1371: argument is 0,
1.117 djm 1372: the listen port will be dynamically allocated on the server and reported
1373: to the client at run time.
1.43 djm 1374: .Pp
1375: If the
1376: .Ar bind_address
1377: is not specified, the default is to only bind to loopback addresses.
1378: If the
1379: .Ar bind_address
1380: is
1381: .Ql *
1382: or an empty string, then the forwarding is requested to listen on all
1383: interfaces.
1384: Specifying a remote
1385: .Ar bind_address
1.46 jmc 1386: will only succeed if the server's
1387: .Cm GatewayPorts
1.43 djm 1388: option is enabled (see
1.46 jmc 1389: .Xr sshd_config 5 ) .
1.149 djm 1390: .It Cm RequestTTY
1391: Specifies whether to request a pseudo-tty for the session.
1392: The argument may be one of:
1.240 jmc 1393: .Cm no
1.149 djm 1394: (never request a TTY),
1.240 jmc 1395: .Cm yes
1.149 djm 1396: (always request a TTY when standard input is a TTY),
1.240 jmc 1397: .Cm force
1.149 djm 1398: (always request a TTY) or
1.240 jmc 1399: .Cm auto
1.149 djm 1400: (request a TTY when opening a login session).
1401: This option mirrors the
1402: .Fl t
1403: and
1404: .Fl T
1405: flags for
1406: .Xr ssh 1 .
1.196 djm 1407: .It Cm RevokedHostKeys
1408: Specifies revoked host public keys.
1409: Keys listed in this file will be refused for host authentication.
1410: Note that if this file does not exist or is not readable,
1411: then host authentication will be refused for all hosts.
1412: Keys may be specified as a text file, listing one public key per line, or as
1413: an OpenSSH Key Revocation List (KRL) as generated by
1414: .Xr ssh-keygen 1 .
1415: For more information on KRLs, see the KEY REVOCATION LISTS section in
1416: .Xr ssh-keygen 1 .
1.32 djm 1417: .It Cm SendEnv
1418: Specifies what variables from the local
1419: .Xr environ 7
1420: should be sent to the server.
1.84 jmc 1421: The server must also support it, and the server must be configured to
1.33 djm 1422: accept these environment variables.
1.207 dtucker 1423: Note that the
1424: .Ev TERM
1.208 jmc 1425: environment variable is always sent whenever a
1.207 dtucker 1426: pseudo-terminal is requested as it is required by the protocol.
1.32 djm 1427: Refer to
1428: .Cm AcceptEnv
1429: in
1430: .Xr sshd_config 5
1431: for how to configure the server.
1.80 jmc 1432: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1433: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1434: across multiple
1435: .Cm SendEnv
1436: directives.
1.81 jmc 1437: .Pp
1438: See
1439: .Sx PATTERNS
1440: for more information on patterns.
1.271 djm 1441: .Pp
1.272 jmc 1442: It is possible to clear previously set
1.271 djm 1443: .Cm SendEnv
1444: variable names by prefixing patterns with
1445: .Pa - .
1446: The default is not to send any environment variables.
1.28 markus 1447: .It Cm ServerAliveCountMax
1.73 jmc 1448: Sets the number of server alive messages (see below) which may be
1.28 markus 1449: sent without
1.84 jmc 1450: .Xr ssh 1
1.28 markus 1451: receiving any messages back from the server.
1452: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1453: ssh will disconnect from the server, terminating the session.
1.28 markus 1454: It is important to note that the use of server alive messages is very
1455: different from
1456: .Cm TCPKeepAlive
1457: (below).
1458: The server alive messages are sent through the encrypted channel
1459: and therefore will not be spoofable.
1460: The TCP keepalive option enabled by
1461: .Cm TCPKeepAlive
1462: is spoofable.
1463: The server alive mechanism is valuable when the client or
1.298 dtucker 1464: server depend on knowing when a connection has become unresponsive.
1.28 markus 1465: .Pp
1466: The default value is 3.
1467: If, for example,
1468: .Cm ServerAliveInterval
1.84 jmc 1469: (see below) is set to 15 and
1.28 markus 1470: .Cm ServerAliveCountMax
1.84 jmc 1471: is left at the default, if the server becomes unresponsive,
1472: ssh will disconnect after approximately 45 seconds.
1.67 jmc 1473: .It Cm ServerAliveInterval
1474: Sets a timeout interval in seconds after which if no data has been received
1475: from the server,
1.84 jmc 1476: .Xr ssh 1
1.67 jmc 1477: will send a message through the encrypted
1478: channel to request a response from the server.
1479: The default
1480: is 0, indicating that these messages will not be sent to the server.
1.277 jmc 1481: .It Cm SetEnv
1482: Directly specify one or more environment variables and their contents to
1483: be sent to the server.
1484: Similarly to
1485: .Cm SendEnv ,
1486: the server must be prepared to accept the environment variable.
1.191 millert 1487: .It Cm StreamLocalBindMask
1488: Sets the octal file creation mode mask
1489: .Pq umask
1490: used when creating a Unix-domain socket file for local or remote
1491: port forwarding.
1492: This option is only used for port forwarding to a Unix-domain socket file.
1493: .Pp
1494: The default value is 0177, which creates a Unix-domain socket file that is
1495: readable and writable only by the owner.
1496: Note that not all operating systems honor the file mode on Unix-domain
1497: socket files.
1498: .It Cm StreamLocalBindUnlink
1499: Specifies whether to remove an existing Unix-domain socket file for local
1500: or remote port forwarding before creating a new one.
1501: If the socket file already exists and
1502: .Cm StreamLocalBindUnlink
1503: is not enabled,
1504: .Nm ssh
1505: will be unable to forward the port to the Unix-domain socket file.
1506: This option is only used for port forwarding to a Unix-domain socket file.
1507: .Pp
1508: The argument must be
1.240 jmc 1509: .Cm yes
1.191 millert 1510: or
1.240 jmc 1511: .Cm no
1512: (the default).
1.1 stevesk 1513: .It Cm StrictHostKeyChecking
1514: If this flag is set to
1.240 jmc 1515: .Cm yes ,
1.84 jmc 1516: .Xr ssh 1
1.1 stevesk 1517: will never automatically add host keys to the
1.50 djm 1518: .Pa ~/.ssh/known_hosts
1.1 stevesk 1519: file, and refuses to connect to hosts whose host key has changed.
1.263 dtucker 1520: This provides maximum protection against man-in-the-middle (MITM) attacks,
1.84 jmc 1521: though it can be annoying when the
1.1 stevesk 1522: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1523: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1524: frequently made.
1525: This option forces the user to manually
1526: add all new hosts.
1.255 jmc 1527: .Pp
1.1 stevesk 1528: If this flag is set to
1.254 djm 1529: .Dq accept-new
1.255 jmc 1530: then ssh will automatically add new host keys to the user
1.254 djm 1531: known hosts files, but will not permit connections to hosts with
1532: changed host keys.
1533: If this flag is set to
1534: .Dq no
1535: or
1536: .Dq off ,
1.255 jmc 1537: ssh will automatically add new host keys to the user known hosts files
1538: and allow connections to hosts with changed hostkeys to proceed,
1539: subject to some restrictions.
1.1 stevesk 1540: If this flag is set to
1.240 jmc 1541: .Cm ask
1542: (the default),
1.1 stevesk 1543: new host keys
1544: will be added to the user known host files only after the user
1545: has confirmed that is what they really want to do, and
1.84 jmc 1546: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1547: The host keys of
1548: known hosts will be verified automatically in all cases.
1.244 jmc 1549: .It Cm SyslogFacility
1550: Gives the facility code that is used when logging messages from
1551: .Xr ssh 1 .
1552: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1553: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1554: The default is USER.
1.26 markus 1555: .It Cm TCPKeepAlive
1556: Specifies whether the system should send TCP keepalive messages to the
1557: other side.
1558: If they are sent, death of the connection or crash of one
1559: of the machines will be properly noticed.
1560: However, this means that
1561: connections will die if the route is down temporarily, and some people
1562: find it annoying.
1563: .Pp
1564: The default is
1.240 jmc 1565: .Cm yes
1.26 markus 1566: (to send TCP keepalive messages), and the client will notice
1567: if the network goes down or the remote host dies.
1568: This is important in scripts, and many users want it too.
1569: .Pp
1570: To disable TCP keepalive messages, the value should be set to
1.240 jmc 1571: .Cm no .
1.265 djm 1572: See also
1573: .Cm ServerAliveInterval
1574: for protocol-level keepalives.
1.65 reyk 1575: .It Cm Tunnel
1.95 stevesk 1576: Request
1.65 reyk 1577: .Xr tun 4
1.69 jmc 1578: device forwarding between the client and the server.
1.65 reyk 1579: The argument must be
1.240 jmc 1580: .Cm yes ,
1581: .Cm point-to-point
1.95 stevesk 1582: (layer 3),
1.240 jmc 1583: .Cm ethernet
1.95 stevesk 1584: (layer 2),
1.65 reyk 1585: or
1.240 jmc 1586: .Cm no
1587: (the default).
1.95 stevesk 1588: Specifying
1.240 jmc 1589: .Cm yes
1.95 stevesk 1590: requests the default tunnel mode, which is
1.240 jmc 1591: .Cm point-to-point .
1.65 reyk 1592: .It Cm TunnelDevice
1.95 stevesk 1593: Specifies the
1.65 reyk 1594: .Xr tun 4
1.95 stevesk 1595: devices to open on the client
1596: .Pq Ar local_tun
1597: and the server
1598: .Pq Ar remote_tun .
1599: .Pp
1600: The argument must be
1601: .Sm off
1602: .Ar local_tun Op : Ar remote_tun .
1603: .Sm on
1604: The devices may be specified by numerical ID or the keyword
1.240 jmc 1605: .Cm any ,
1.95 stevesk 1606: which uses the next available tunnel device.
1607: If
1608: .Ar remote_tun
1609: is not specified, it defaults to
1.240 jmc 1610: .Cm any .
1.95 stevesk 1611: The default is
1.240 jmc 1612: .Cm any:any .
1.201 djm 1613: .It Cm UpdateHostKeys
1.200 djm 1614: Specifies whether
1615: .Xr ssh 1
1616: should accept notifications of additional hostkeys from the server sent
1617: after authentication has completed and add them to
1618: .Cm UserKnownHostsFile .
1619: The argument must be
1.240 jmc 1620: .Cm yes ,
1621: .Cm no
1.204 djm 1622: (the default) or
1.240 jmc 1623: .Cm ask .
1.200 djm 1624: Enabling this option allows learning alternate hostkeys for a server
1.201 djm 1625: and supports graceful key rotation by allowing a server to send replacement
1626: public keys before old ones are removed.
1.200 djm 1627: Additional hostkeys are only accepted if the key used to authenticate the
1.220 sobrado 1628: host was already trusted or explicitly accepted by the user.
1.204 djm 1629: If
1630: .Cm UpdateHostKeys
1631: is set to
1.240 jmc 1632: .Cm ask ,
1.204 djm 1633: then the user is asked to confirm the modifications to the known_hosts file.
1.205 djm 1634: Confirmation is currently incompatible with
1635: .Cm ControlPersist ,
1636: and will be disabled if it is enabled.
1.200 djm 1637: .Pp
1638: Presently, only
1639: .Xr sshd 8
1640: from OpenSSH 6.8 and greater support the
1.240 jmc 1641: .Qq hostkeys@openssh.com
1.200 djm 1642: protocol extension used to inform the client of all the server's hostkeys.
1.1 stevesk 1643: .It Cm User
1644: Specifies the user to log in as.
1645: This can be useful when a different user name is used on different machines.
1646: This saves the trouble of
1647: having to remember to give the user name on the command line.
1648: .It Cm UserKnownHostsFile
1.151 djm 1649: Specifies one or more files to use for the user
1650: host key database, separated by whitespace.
1651: The default is
1652: .Pa ~/.ssh/known_hosts ,
1653: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1654: .It Cm VerifyHostKeyDNS
1655: Specifies whether to verify the remote key using DNS and SSHFP resource
1656: records.
1.24 jakob 1657: If this option is set to
1.240 jmc 1658: .Cm yes ,
1.25 jmc 1659: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1660: from DNS.
1661: Insecure fingerprints will be handled as if this option was set to
1.240 jmc 1662: .Cm ask .
1.24 jakob 1663: If this option is set to
1.240 jmc 1664: .Cm ask ,
1.24 jakob 1665: information on fingerprint match will be displayed, but the user will still
1666: need to confirm new host keys according to the
1667: .Cm StrictHostKeyChecking
1668: option.
1.8 jakob 1669: The default is
1.240 jmc 1670: .Cm no .
1.84 jmc 1671: .Pp
1.240 jmc 1672: See also
1673: .Sx VERIFYING HOST KEYS
1674: in
1.84 jmc 1675: .Xr ssh 1 .
1.111 grunk 1676: .It Cm VisualHostKey
1677: If this flag is set to
1.240 jmc 1678: .Cm yes ,
1.111 grunk 1679: an ASCII art representation of the remote host key fingerprint is
1.197 djm 1680: printed in addition to the fingerprint string at login and
1.114 stevesk 1681: for unknown host keys.
1.111 grunk 1682: If this flag is set to
1.240 jmc 1683: .Cm no
1684: (the default),
1.114 stevesk 1685: no fingerprint strings are printed at login and
1.197 djm 1686: only the fingerprint string will be printed for unknown host keys.
1.1 stevesk 1687: .It Cm XAuthLocation
1.5 stevesk 1688: Specifies the full pathname of the
1.1 stevesk 1689: .Xr xauth 1
1690: program.
1691: The default is
1692: .Pa /usr/X11R6/bin/xauth .
1693: .El
1.86 jmc 1694: .Sh PATTERNS
1695: A
1696: .Em pattern
1697: consists of zero or more non-whitespace characters,
1698: .Sq *
1699: (a wildcard that matches zero or more characters),
1700: or
1701: .Sq ?\&
1702: (a wildcard that matches exactly one character).
1703: For example, to specify a set of declarations for any host in the
1.240 jmc 1704: .Qq .co.uk
1.86 jmc 1705: set of domains,
1706: the following pattern could be used:
1707: .Pp
1708: .Dl Host *.co.uk
1709: .Pp
1710: The following pattern
1711: would match any host in the 192.168.0.[0-9] network range:
1712: .Pp
1713: .Dl Host 192.168.0.?
1714: .Pp
1715: A
1716: .Em pattern-list
1717: is a comma-separated list of patterns.
1718: Patterns within pattern-lists may be negated
1719: by preceding them with an exclamation mark
1720: .Pq Sq !\& .
1721: For example,
1.174 djm 1722: to allow a key to be used from anywhere within an organization
1.86 jmc 1723: except from the
1.240 jmc 1724: .Qq dialup
1.86 jmc 1725: pool,
1726: the following entry (in authorized_keys) could be used:
1727: .Pp
1728: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.258 djm 1729: .Pp
1730: Note that a negated match will never produce a positive result by itself.
1731: For example, attempting to match
1732: .Qq host3
1733: against the following pattern-list will fail:
1734: .Pp
1735: .Dl from=\&"!host1,!host2\&"
1736: .Pp
1737: The solution here is to include a term that will yield a positive match,
1738: such as a wildcard:
1739: .Pp
1740: .Dl from=\&"!host1,!host2,*\&"
1.239 jmc 1741: .Sh TOKENS
1742: Arguments to some keywords can make use of tokens,
1743: which are expanded at runtime:
1744: .Pp
1745: .Bl -tag -width XXXX -offset indent -compact
1746: .It %%
1747: A literal
1748: .Sq % .
1749: .It \&%C
1.257 jmc 1750: Hash of %l%h%p%r.
1.239 jmc 1751: .It %d
1752: Local user's home directory.
1753: .It %h
1754: The remote hostname.
1755: .It %i
1756: The local user ID.
1757: .It %L
1758: The local hostname.
1759: .It %l
1760: The local hostname, including the domain name.
1761: .It %n
1762: The original remote hostname, as given on the command line.
1763: .It %p
1764: The remote port.
1765: .It %r
1766: The remote username.
1.261 djm 1767: .It \&%T
1768: The local
1769: .Xr tun 4
1770: or
1771: .Xr tap 4
1772: network interface assigned if
1.262 jmc 1773: tunnel forwarding was requested, or
1774: .Qq NONE
1.261 djm 1775: otherwise.
1.239 jmc 1776: .It %u
1777: The local username.
1778: .El
1779: .Pp
1780: .Cm Match exec
1.274 djm 1781: accepts the tokens %%, %h, %i, %L, %l, %n, %p, %r, and %u.
1.239 jmc 1782: .Pp
1783: .Cm CertificateFile
1.275 jmc 1784: accepts the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1785: .Pp
1786: .Cm ControlPath
1787: accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
1788: .Pp
1.295 jmc 1789: .Cm Hostname
1.239 jmc 1790: accepts the tokens %% and %h.
1791: .Pp
1792: .Cm IdentityAgent
1793: and
1794: .Cm IdentityFile
1.275 jmc 1795: accept the tokens %%, %d, %h, %i, %l, %r, and %u.
1.239 jmc 1796: .Pp
1797: .Cm LocalCommand
1.275 jmc 1798: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, %T, and %u.
1.239 jmc 1799: .Pp
1800: .Cm ProxyCommand
1801: accepts the tokens %%, %h, %p, and %r.
1.250 jmc 1802: .Pp
1803: .Cm RemoteCommand
1.274 djm 1804: accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, and %u.
1.1 stevesk 1805: .Sh FILES
1806: .Bl -tag -width Ds
1.50 djm 1807: .It Pa ~/.ssh/config
1.1 stevesk 1808: This is the per-user configuration file.
1809: The format of this file is described above.
1.84 jmc 1810: This file is used by the SSH client.
1.30 djm 1811: Because of the potential for abuse, this file must have strict permissions:
1.290 jmc 1812: read/write for the user, and not writable by others.
1.1 stevesk 1813: .It Pa /etc/ssh/ssh_config
1814: Systemwide configuration file.
1815: This file provides defaults for those
1816: values that are not specified in the user's configuration file, and
1817: for those users who do not have a configuration file.
1818: This file must be world-readable.
1819: .El
1.13 jmc 1820: .Sh SEE ALSO
1821: .Xr ssh 1
1.1 stevesk 1822: .Sh AUTHORS
1.240 jmc 1823: .An -nosplit
1.1 stevesk 1824: OpenSSH is a derivative of the original and free
1.240 jmc 1825: ssh 1.2.12 release by
1826: .An Tatu Ylonen .
1827: .An Aaron Campbell , Bob Beck , Markus Friedl ,
1828: .An Niels Provos , Theo de Raadt
1829: and
1830: .An Dug Song
1.1 stevesk 1831: removed many bugs, re-added newer features and
1832: created OpenSSH.
1.240 jmc 1833: .An Markus Friedl
1834: contributed the support for SSH protocol versions 1.5 and 2.0.
![[BACK]](/icons/back.gif){kind=icon}
Return to ssh_config.5 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh