Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.169
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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1.169 ! djm 36: .\" $OpenBSD: ssh_config.5,v 1.168 2013/08/20 06:56:07 jmc Exp $
1.168 jmc 37: .Dd $Mdocdate: August 20 2013 $
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
1.1 stevesk 65: .Dq Host
66: specifications, and that section is only applied for hosts that
67: match one of the patterns given in the specification.
68: The matched host name is the one given on the command line.
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
1.1 stevesk 74: The configuration file has the following format:
75: .Pp
76: Empty lines and lines starting with
77: .Ql #
78: are comments.
79: Otherwise a line is of the format
80: .Dq keyword arguments .
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.
1.88 dtucker 92: Arguments may optionally be enclosed in double quotes
93: .Pq \&"
94: in order to represent arguments containing spaces.
1.1 stevesk 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.
112: The host is the
113: .Ar hostname
1.83 jmc 114: argument given on the command line (i.e. the name is not converted to
1.1 stevesk 115: a canonicalized host name before matching).
1.148 djm 116: .Pp
117: A pattern entry may be negated by prefixing it with an exclamation mark
118: .Pq Sq !\& .
119: If a negated entry is matched, then the
120: .Cm Host
121: entry is ignored, regardless of whether any other patterns on the line
122: match.
123: Negated matches are therefore useful to provide exceptions for wildcard
124: matches.
1.81 jmc 125: .Pp
126: See
127: .Sx PATTERNS
128: for more information on patterns.
1.169 ! djm 129: .It Cm Match
! 130: Restricts the following declarations (up to the next
! 131: .Cm Host
! 132: or
! 133: .Cm Match
! 134: keyword) to be used only when the conditions following the
! 135: .Cm Match
! 136: keyword are satisfied.
! 137: Match conditions are specified using one or more keyword/criteria pairs.
! 138: The available keywords are:
! 139: .Cm command ,
! 140: .Cm host ,
! 141: .Cm originalhost ,
! 142: .Cm user ,
! 143: and
! 144: .Cm localuser .
! 145: .Pp
! 146: The criteria for the
! 147: .Cm command
! 148: keyword is a path to a command that is executed.
! 149: If the command returns a zero exit status then the condition is considered true.
! 150: Commands containing whitespace characters must be quoted.
! 151: .Pp
! 152: The other keywords' criteria must be single entries or comma-separated
! 153: lists and may use the wildcard and negation operators described in the
! 154: .Sx PATTERNS
! 155: section.
! 156: The criteria for the
! 157: .Cm host
! 158: keyword are matched against the target hostname, after any substitution
! 159: by the
! 160: .Cm Hostname
! 161: option.
! 162: The
! 163: .Cm originalhost
! 164: keyword matches against the hostname as it was specified on the command-line.
! 165: The
! 166: .Cm user
! 167: keyword matches against the target username on the remote host.
! 168: The
! 169: .Cm localuser
! 170: keyword matches against the name of the local user running
! 171: .Xr ssh 1
! 172: (this keyword may be useful in system-wide
! 173: .Nm
! 174: files).
1.10 djm 175: .It Cm AddressFamily
1.11 jmc 176: Specifies which address family to use when connecting.
177: Valid arguments are
1.10 djm 178: .Dq any ,
179: .Dq inet
1.84 jmc 180: (use IPv4 only), or
1.10 djm 181: .Dq inet6
1.40 jmc 182: (use IPv6 only).
1.1 stevesk 183: .It Cm BatchMode
184: If set to
185: .Dq yes ,
186: passphrase/password querying will be disabled.
187: This option is useful in scripts and other batch jobs where no user
188: is present to supply the password.
189: The argument must be
190: .Dq yes
191: or
192: .Dq no .
193: The default is
194: .Dq no .
195: .It Cm BindAddress
1.60 dtucker 196: Use the specified address on the local machine as the source address of
1.61 jmc 197: the connection.
198: Only useful on systems with more than one address.
1.1 stevesk 199: Note that this option does not work if
200: .Cm UsePrivilegedPort
201: is set to
202: .Dq yes .
203: .It Cm ChallengeResponseAuthentication
1.82 jmc 204: Specifies whether to use challenge-response authentication.
1.1 stevesk 205: The argument to this keyword must be
206: .Dq yes
207: or
208: .Dq no .
209: The default is
210: .Dq yes .
211: .It Cm CheckHostIP
212: If this flag is set to
213: .Dq yes ,
1.84 jmc 214: .Xr ssh 1
215: will additionally check the host IP address in the
1.1 stevesk 216: .Pa known_hosts
217: file.
218: This allows ssh to detect if a host key changed due to DNS spoofing.
1.107 grunk 219: If the option is set to
1.1 stevesk 220: .Dq no ,
221: the check will not be executed.
222: The default is
223: .Dq yes .
224: .It Cm Cipher
225: Specifies the cipher to use for encrypting the session
226: in protocol version 1.
227: Currently,
228: .Dq blowfish ,
229: .Dq 3des ,
230: and
231: .Dq des
232: are supported.
233: .Ar des
234: is only supported in the
1.84 jmc 235: .Xr ssh 1
1.1 stevesk 236: client for interoperability with legacy protocol 1 implementations
237: that do not support the
238: .Ar 3des
1.7 jmc 239: cipher.
240: Its use is strongly discouraged due to cryptographic weaknesses.
1.1 stevesk 241: The default is
242: .Dq 3des .
243: .It Cm Ciphers
244: Specifies the ciphers allowed for protocol version 2
245: in order of preference.
246: Multiple ciphers must be comma-separated.
1.35 dtucker 247: The supported ciphers are
248: .Dq 3des-cbc ,
249: .Dq aes128-cbc ,
250: .Dq aes192-cbc ,
251: .Dq aes256-cbc ,
252: .Dq aes128-ctr ,
253: .Dq aes192-ctr ,
254: .Dq aes256-ctr ,
1.161 markus 255: .Dq aes128-gcm@openssh.com ,
256: .Dq aes256-gcm@openssh.com ,
1.54 djm 257: .Dq arcfour128 ,
258: .Dq arcfour256 ,
1.35 dtucker 259: .Dq arcfour ,
260: .Dq blowfish-cbc ,
261: and
262: .Dq cast128-cbc .
1.84 jmc 263: The default is:
264: .Bd -literal -offset 3n
1.116 naddy 265: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
1.161 markus 266: aes128-gcm@openssh.com,aes256-gcm@openssh.com,
1.116 naddy 267: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
268: aes256-cbc,arcfour
1.1 stevesk 269: .Ed
270: .It Cm ClearAllForwardings
1.84 jmc 271: Specifies that all local, remote, and dynamic port forwardings
1.1 stevesk 272: specified in the configuration files or on the command line be
1.7 jmc 273: cleared.
274: This option is primarily useful when used from the
1.84 jmc 275: .Xr ssh 1
1.1 stevesk 276: command line to clear port forwardings set in
277: configuration files, and is automatically set by
278: .Xr scp 1
279: and
280: .Xr sftp 1 .
281: The argument must be
282: .Dq yes
283: or
284: .Dq no .
285: The default is
286: .Dq no .
287: .It Cm Compression
288: Specifies whether to use compression.
289: The argument must be
290: .Dq yes
291: or
292: .Dq no .
293: The default is
294: .Dq no .
295: .It Cm CompressionLevel
296: Specifies the compression level to use if compression is enabled.
297: The argument must be an integer from 1 (fast) to 9 (slow, best).
298: The default level is 6, which is good for most applications.
299: The meaning of the values is the same as in
300: .Xr gzip 1 .
301: Note that this option applies to protocol version 1 only.
302: .It Cm ConnectionAttempts
303: Specifies the number of tries (one per second) to make before exiting.
304: The argument must be an integer.
305: This may be useful in scripts if the connection sometimes fails.
306: The default is 1.
1.9 djm 307: .It Cm ConnectTimeout
1.84 jmc 308: Specifies the timeout (in seconds) used when connecting to the
309: SSH server, instead of using the default system TCP timeout.
1.11 jmc 310: This value is used only when the target is down or really unreachable,
311: not when it refuses the connection.
1.36 djm 312: .It Cm ControlMaster
313: Enables the sharing of multiple sessions over a single network connection.
314: When set to
1.84 jmc 315: .Dq yes ,
316: .Xr ssh 1
1.36 djm 317: will listen for connections on a control socket specified using the
318: .Cm ControlPath
319: argument.
320: Additional sessions can connect to this socket using the same
321: .Cm ControlPath
322: with
323: .Cm ControlMaster
324: set to
325: .Dq no
1.38 jmc 326: (the default).
1.64 jmc 327: These sessions will try to reuse the master instance's network connection
1.63 djm 328: rather than initiating new ones, but will fall back to connecting normally
329: if the control socket does not exist, or is not listening.
330: .Pp
1.37 djm 331: Setting this to
332: .Dq ask
1.84 jmc 333: will cause ssh
1.37 djm 334: to listen for control connections, but require confirmation using the
335: .Ev SSH_ASKPASS
336: program before they are accepted (see
337: .Xr ssh-add 1
1.38 jmc 338: for details).
1.51 jakob 339: If the
340: .Cm ControlPath
1.84 jmc 341: cannot be opened,
342: ssh will continue without connecting to a master instance.
1.58 djm 343: .Pp
344: X11 and
1.59 jmc 345: .Xr ssh-agent 1
1.58 djm 346: forwarding is supported over these multiplexed connections, however the
1.70 stevesk 347: display and agent forwarded will be the one belonging to the master
1.59 jmc 348: connection i.e. it is not possible to forward multiple displays or agents.
1.56 djm 349: .Pp
350: Two additional options allow for opportunistic multiplexing: try to use a
351: master connection but fall back to creating a new one if one does not already
352: exist.
353: These options are:
354: .Dq auto
355: and
356: .Dq autoask .
357: The latter requires confirmation like the
358: .Dq ask
359: option.
1.36 djm 360: .It Cm ControlPath
1.55 djm 361: Specify the path to the control socket used for connection sharing as described
362: in the
1.36 djm 363: .Cm ControlMaster
1.57 djm 364: section above or the string
365: .Dq none
366: to disable connection sharing.
1.55 djm 367: In the path,
1.147 djm 368: .Ql %L
369: will be substituted by the first component of the local host name,
1.77 djm 370: .Ql %l
1.147 djm 371: will be substituted by the local host name (including any domain name),
1.55 djm 372: .Ql %h
373: will be substituted by the target host name,
1.150 jmc 374: .Ql %n
375: will be substituted by the original target host name
376: specified on the command line,
1.55 djm 377: .Ql %p
1.147 djm 378: the port,
1.55 djm 379: .Ql %r
1.147 djm 380: by the remote login username, and
381: .Ql %u
382: by the username of the user running
383: .Xr ssh 1 .
1.56 djm 384: It is recommended that any
385: .Cm ControlPath
386: used for opportunistic connection sharing include
1.78 jmc 387: at least %h, %p, and %r.
1.56 djm 388: This ensures that shared connections are uniquely identified.
1.137 djm 389: .It Cm ControlPersist
390: When used in conjunction with
391: .Cm ControlMaster ,
392: specifies that the master connection should remain open
393: in the background (waiting for future client connections)
394: after the initial client connection has been closed.
395: If set to
396: .Dq no ,
397: then the master connection will not be placed into the background,
398: and will close as soon as the initial client connection is closed.
399: If set to
400: .Dq yes ,
401: then the master connection will remain in the background indefinitely
402: (until killed or closed via a mechanism such as the
403: .Xr ssh 1
404: .Dq Fl O No exit
405: option).
406: If set to a time in seconds, or a time in any of the formats documented in
407: .Xr sshd_config 5 ,
408: then the backgrounded master connection will automatically terminate
409: after it has remained idle (with no client connections) for the
410: specified time.
1.38 jmc 411: .It Cm DynamicForward
1.74 jmc 412: Specifies that a TCP port on the local machine be forwarded
1.38 jmc 413: over the secure channel, and the application
414: protocol is then used to determine where to connect to from the
415: remote machine.
1.62 djm 416: .Pp
417: The argument must be
418: .Sm off
419: .Oo Ar bind_address : Oc Ar port .
420: .Sm on
1.138 djm 421: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.62 djm 422: By default, the local port is bound in accordance with the
423: .Cm GatewayPorts
424: setting.
425: However, an explicit
426: .Ar bind_address
427: may be used to bind the connection to a specific address.
428: The
429: .Ar bind_address
430: of
431: .Dq localhost
432: indicates that the listening port be bound for local use only, while an
433: empty address or
434: .Sq *
435: indicates that the port should be available from all interfaces.
436: .Pp
1.38 jmc 437: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.84 jmc 438: .Xr ssh 1
1.38 jmc 439: will act as a SOCKS server.
440: Multiple forwardings may be specified, and
441: additional forwardings can be given on the command line.
442: Only the superuser can forward privileged ports.
1.14 markus 443: .It Cm EnableSSHKeysign
444: Setting this option to
445: .Dq yes
446: in the global client configuration file
447: .Pa /etc/ssh/ssh_config
448: enables the use of the helper program
449: .Xr ssh-keysign 8
450: during
451: .Cm HostbasedAuthentication .
452: The argument must be
453: .Dq yes
454: or
455: .Dq no .
456: The default is
457: .Dq no .
1.23 jmc 458: This option should be placed in the non-hostspecific section.
1.14 markus 459: See
460: .Xr ssh-keysign 8
461: for more information.
1.1 stevesk 462: .It Cm EscapeChar
463: Sets the escape character (default:
464: .Ql ~ ) .
465: The escape character can also
466: be set on the command line.
467: The argument should be a single character,
468: .Ql ^
469: followed by a letter, or
470: .Dq none
471: to disable the escape
472: character entirely (making the connection transparent for binary
473: data).
1.96 markus 474: .It Cm ExitOnForwardFailure
475: Specifies whether
476: .Xr ssh 1
477: should terminate the connection if it cannot set up all requested
1.102 stevesk 478: dynamic, tunnel, local, and remote port forwardings.
1.96 markus 479: The argument must be
480: .Dq yes
481: or
482: .Dq no .
483: The default is
484: .Dq no .
1.1 stevesk 485: .It Cm ForwardAgent
486: Specifies whether the connection to the authentication agent (if any)
487: will be forwarded to the remote machine.
488: The argument must be
489: .Dq yes
490: or
491: .Dq no .
492: The default is
493: .Dq no .
1.3 stevesk 494: .Pp
1.7 jmc 495: Agent forwarding should be enabled with caution.
496: Users with the ability to bypass file permissions on the remote host
497: (for the agent's Unix-domain socket)
498: can access the local agent through the forwarded connection.
499: An attacker cannot obtain key material from the agent,
1.3 stevesk 500: however they can perform operations on the keys that enable them to
501: authenticate using the identities loaded into the agent.
1.1 stevesk 502: .It Cm ForwardX11
503: Specifies whether X11 connections will be automatically redirected
504: over the secure channel and
505: .Ev DISPLAY
506: set.
507: The argument must be
508: .Dq yes
509: or
510: .Dq no .
511: The default is
512: .Dq no .
1.3 stevesk 513: .Pp
1.7 jmc 514: X11 forwarding should be enabled with caution.
515: Users with the ability to bypass file permissions on the remote host
1.22 markus 516: (for the user's X11 authorization database)
1.7 jmc 517: can access the local X11 display through the forwarded connection.
1.22 markus 518: An attacker may then be able to perform activities such as keystroke monitoring
519: if the
520: .Cm ForwardX11Trusted
521: option is also enabled.
1.134 djm 522: .It Cm ForwardX11Timeout
1.135 jmc 523: Specify a timeout for untrusted X11 forwarding
524: using the format described in the
1.166 jmc 525: TIME FORMATS section of
1.134 djm 526: .Xr sshd_config 5 .
527: X11 connections received by
528: .Xr ssh 1
529: after this time will be refused.
530: The default is to disable untrusted X11 forwarding after twenty minutes has
531: elapsed.
1.22 markus 532: .It Cm ForwardX11Trusted
1.34 jmc 533: If this option is set to
1.84 jmc 534: .Dq yes ,
535: remote X11 clients will have full access to the original X11 display.
1.42 djm 536: .Pp
1.22 markus 537: If this option is set to
1.84 jmc 538: .Dq no ,
539: remote X11 clients will be considered untrusted and prevented
1.22 markus 540: from stealing or tampering with data belonging to trusted X11
541: clients.
1.42 djm 542: Furthermore, the
543: .Xr xauth 1
544: token used for the session will be set to expire after 20 minutes.
545: Remote clients will be refused access after this time.
1.22 markus 546: .Pp
547: The default is
548: .Dq no .
549: .Pp
550: See the X11 SECURITY extension specification for full details on
551: the restrictions imposed on untrusted clients.
1.1 stevesk 552: .It Cm GatewayPorts
553: Specifies whether remote hosts are allowed to connect to local
554: forwarded ports.
555: By default,
1.84 jmc 556: .Xr ssh 1
1.7 jmc 557: binds local port forwardings to the loopback address.
558: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 559: .Cm GatewayPorts
1.84 jmc 560: can be used to specify that ssh
1.1 stevesk 561: should bind local port forwardings to the wildcard address,
562: thus allowing remote hosts to connect to forwarded ports.
563: The argument must be
564: .Dq yes
565: or
566: .Dq no .
567: The default is
568: .Dq no .
569: .It Cm GlobalKnownHostsFile
1.151 djm 570: Specifies one or more files to use for the global
571: host key database, separated by whitespace.
572: The default is
573: .Pa /etc/ssh/ssh_known_hosts ,
574: .Pa /etc/ssh/ssh_known_hosts2 .
1.18 markus 575: .It Cm GSSAPIAuthentication
1.27 markus 576: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 577: The default is
1.21 markus 578: .Dq no .
1.18 markus 579: Note that this option applies to protocol version 2 only.
580: .It Cm GSSAPIDelegateCredentials
581: Forward (delegate) credentials to the server.
582: The default is
583: .Dq no .
584: Note that this option applies to protocol version 2 only.
1.44 djm 585: .It Cm HashKnownHosts
586: Indicates that
1.84 jmc 587: .Xr ssh 1
1.44 djm 588: should hash host names and addresses when they are added to
1.50 djm 589: .Pa ~/.ssh/known_hosts .
1.44 djm 590: These hashed names may be used normally by
1.84 jmc 591: .Xr ssh 1
1.44 djm 592: and
1.84 jmc 593: .Xr sshd 8 ,
1.44 djm 594: but they do not reveal identifying information should the file's contents
595: be disclosed.
596: The default is
597: .Dq no .
1.97 jmc 598: Note that existing names and addresses in known hosts files
599: will not be converted automatically,
600: but may be manually hashed using
1.45 djm 601: .Xr ssh-keygen 1 .
1.1 stevesk 602: .It Cm HostbasedAuthentication
603: Specifies whether to try rhosts based authentication with public key
604: authentication.
605: The argument must be
606: .Dq yes
607: or
608: .Dq no .
609: The default is
610: .Dq no .
611: This option applies to protocol version 2 only and
612: is similar to
613: .Cm RhostsRSAAuthentication .
614: .It Cm HostKeyAlgorithms
615: Specifies the protocol version 2 host key algorithms
616: that the client wants to use in order of preference.
617: The default for this option is:
1.139 djm 618: .Bd -literal -offset 3n
619: ecdsa-sha2-nistp256-cert-v01@openssh.com,
620: ecdsa-sha2-nistp384-cert-v01@openssh.com,
621: ecdsa-sha2-nistp521-cert-v01@openssh.com,
622: ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,
623: ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,
624: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
625: ssh-rsa,ssh-dss
626: .Ed
1.145 djm 627: .Pp
628: If hostkeys are known for the destination host then this default is modified
629: to prefer their algorithms.
1.1 stevesk 630: .It Cm HostKeyAlias
631: Specifies an alias that should be used instead of the
632: real host name when looking up or saving the host key
633: in the host key database files.
1.84 jmc 634: This option is useful for tunneling SSH connections
1.1 stevesk 635: or for multiple servers running on a single host.
636: .It Cm HostName
637: Specifies the real host name to log into.
638: This can be used to specify nicknames or abbreviations for hosts.
1.136 djm 639: If the hostname contains the character sequence
640: .Ql %h ,
1.150 jmc 641: then this will be replaced with the host name specified on the command line
1.136 djm 642: (this is useful for manipulating unqualified names).
1.84 jmc 643: The default is the name given on the command line.
1.1 stevesk 644: Numeric IP addresses are also permitted (both on the command line and in
645: .Cm HostName
646: specifications).
1.29 markus 647: .It Cm IdentitiesOnly
648: Specifies that
1.84 jmc 649: .Xr ssh 1
1.29 markus 650: should only use the authentication identity files configured in the
1.31 jmc 651: .Nm
1.29 markus 652: files,
1.84 jmc 653: even if
654: .Xr ssh-agent 1
1.159 djm 655: or a
656: .Cm PKCS11Provider
1.29 markus 657: offers more identities.
658: The argument to this keyword must be
659: .Dq yes
660: or
661: .Dq no .
1.84 jmc 662: This option is intended for situations where ssh-agent
1.29 markus 663: offers many different identities.
664: The default is
665: .Dq no .
1.67 jmc 666: .It Cm IdentityFile
1.155 dtucker 667: Specifies a file from which the user's DSA, ECDSA or RSA authentication
1.139 djm 668: identity is read.
1.67 jmc 669: The default is
670: .Pa ~/.ssh/identity
671: for protocol version 1, and
1.139 djm 672: .Pa ~/.ssh/id_dsa ,
673: .Pa ~/.ssh/id_ecdsa
674: and
1.67 jmc 675: .Pa ~/.ssh/id_rsa
676: for protocol version 2.
677: Additionally, any identities represented by the authentication agent
1.165 djm 678: will be used for authentication unless
679: .Cm IdentitiesOnly
680: is set.
1.129 djm 681: .Xr ssh 1
682: will try to load certificate information from the filename obtained by
683: appending
684: .Pa -cert.pub
685: to the path of a specified
686: .Cm IdentityFile .
1.90 djm 687: .Pp
1.67 jmc 688: The file name may use the tilde
1.91 jmc 689: syntax to refer to a user's home directory or one of the following
1.90 djm 690: escape characters:
691: .Ql %d
692: (local user's home directory),
693: .Ql %u
694: (local user name),
695: .Ql %l
696: (local host name),
697: .Ql %h
698: (remote host name) or
1.92 djm 699: .Ql %r
1.90 djm 700: (remote user name).
701: .Pp
1.67 jmc 702: It is possible to have
703: multiple identity files specified in configuration files; all these
704: identities will be tried in sequence.
1.152 djm 705: Multiple
706: .Cm IdentityFile
707: directives will add to the list of identities tried (this behaviour
708: differs from that of other configuration directives).
1.165 djm 709: .Pp
710: .Cm IdentityFile
711: may be used in conjunction with
712: .Cm IdentitiesOnly
713: to select which identities in an agent are offered during authentication.
1.164 jmc 714: .It Cm IgnoreUnknown
715: Specifies a pattern-list of unknown options to be ignored if they are
716: encountered in configuration parsing.
717: This may be used to suppress errors if
718: .Nm
719: contains options that are unrecognised by
720: .Xr ssh 1 .
721: It is recommended that
722: .Cm IgnoreUnknown
723: be listed early in the configuration file as it will not be applied
724: to unknown options that appear before it.
1.143 djm 725: .It Cm IPQoS
726: Specifies the IPv4 type-of-service or DSCP class for connections.
727: Accepted values are
728: .Dq af11 ,
729: .Dq af12 ,
730: .Dq af13 ,
1.154 djm 731: .Dq af21 ,
1.143 djm 732: .Dq af22 ,
733: .Dq af23 ,
734: .Dq af31 ,
735: .Dq af32 ,
736: .Dq af33 ,
737: .Dq af41 ,
738: .Dq af42 ,
739: .Dq af43 ,
740: .Dq cs0 ,
741: .Dq cs1 ,
742: .Dq cs2 ,
743: .Dq cs3 ,
744: .Dq cs4 ,
745: .Dq cs5 ,
746: .Dq cs6 ,
747: .Dq cs7 ,
748: .Dq ef ,
749: .Dq lowdelay ,
750: .Dq throughput ,
751: .Dq reliability ,
752: or a numeric value.
1.146 djm 753: This option may take one or two arguments, separated by whitespace.
1.143 djm 754: If one argument is specified, it is used as the packet class unconditionally.
755: If two values are specified, the first is automatically selected for
756: interactive sessions and the second for non-interactive sessions.
757: The default is
758: .Dq lowdelay
759: for interactive sessions and
760: .Dq throughput
761: for non-interactive sessions.
1.103 djm 762: .It Cm KbdInteractiveAuthentication
763: Specifies whether to use keyboard-interactive authentication.
764: The argument to this keyword must be
765: .Dq yes
766: or
767: .Dq no .
768: The default is
769: .Dq yes .
1.39 djm 770: .It Cm KbdInteractiveDevices
771: Specifies the list of methods to use in keyboard-interactive authentication.
772: Multiple method names must be comma-separated.
773: The default is to use the server specified list.
1.85 jmc 774: The methods available vary depending on what the server supports.
775: For an OpenSSH server,
776: it may be zero or more of:
777: .Dq bsdauth ,
778: .Dq pam ,
779: and
780: .Dq skey .
1.140 djm 781: .It Cm KexAlgorithms
782: Specifies the available KEX (Key Exchange) algorithms.
783: Multiple algorithms must be comma-separated.
1.141 jmc 784: The default is:
785: .Bd -literal -offset indent
786: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
787: diffie-hellman-group-exchange-sha256,
788: diffie-hellman-group-exchange-sha1,
789: diffie-hellman-group14-sha1,
790: diffie-hellman-group1-sha1
791: .Ed
1.65 reyk 792: .It Cm LocalCommand
793: Specifies a command to execute on the local machine after successfully
794: connecting to the server.
795: The command string extends to the end of the line, and is executed with
1.105 jmc 796: the user's shell.
1.109 dtucker 797: The following escape character substitutions will be performed:
798: .Ql %d
799: (local user's home directory),
800: .Ql %h
801: (remote host name),
802: .Ql %l
803: (local host name),
804: .Ql %n
805: (host name as provided on the command line),
806: .Ql %p
807: (remote port),
808: .Ql %r
809: (remote user name) or
810: .Ql %u
811: (local user name).
1.123 djm 812: .Pp
813: The command is run synchronously and does not have access to the
814: session of the
815: .Xr ssh 1
816: that spawned it.
817: It should not be used for interactive commands.
818: .Pp
1.65 reyk 819: This directive is ignored unless
820: .Cm PermitLocalCommand
821: has been enabled.
1.1 stevesk 822: .It Cm LocalForward
1.74 jmc 823: Specifies that a TCP port on the local machine be forwarded over
1.1 stevesk 824: the secure channel to the specified host and port from the remote machine.
1.49 jmc 825: The first argument must be
1.43 djm 826: .Sm off
1.49 jmc 827: .Oo Ar bind_address : Oc Ar port
1.43 djm 828: .Sm on
1.49 jmc 829: and the second argument must be
830: .Ar host : Ns Ar hostport .
1.138 djm 831: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.46 jmc 832: Multiple forwardings may be specified, and additional forwardings can be
1.43 djm 833: given on the command line.
1.1 stevesk 834: Only the superuser can forward privileged ports.
1.43 djm 835: By default, the local port is bound in accordance with the
836: .Cm GatewayPorts
837: setting.
838: However, an explicit
839: .Ar bind_address
840: may be used to bind the connection to a specific address.
841: The
842: .Ar bind_address
843: of
844: .Dq localhost
1.46 jmc 845: indicates that the listening port be bound for local use only, while an
846: empty address or
847: .Sq *
1.43 djm 848: indicates that the port should be available from all interfaces.
1.1 stevesk 849: .It Cm LogLevel
850: Gives the verbosity level that is used when logging messages from
1.84 jmc 851: .Xr ssh 1 .
1.1 stevesk 852: The possible values are:
1.84 jmc 853: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.7 jmc 854: The default is INFO.
855: DEBUG and DEBUG1 are equivalent.
856: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 857: .It Cm MACs
858: Specifies the MAC (message authentication code) algorithms
859: in order of preference.
860: The MAC algorithm is used in protocol version 2
861: for data integrity protection.
862: Multiple algorithms must be comma-separated.
1.160 markus 863: The algorithms that contain
864: .Dq -etm
865: calculate the MAC after encryption (encrypt-then-mac).
866: These are considered safer and their use recommended.
1.84 jmc 867: The default is:
1.101 jmc 868: .Bd -literal -offset indent
1.160 markus 869: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,
870: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
871: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
872: hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,
873: hmac-md5-96-etm@openssh.com,
1.158 markus 874: hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,
1.157 naddy 875: hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,
876: hmac-sha1-96,hmac-md5-96
1.101 jmc 877: .Ed
1.1 stevesk 878: .It Cm NoHostAuthenticationForLocalhost
879: This option can be used if the home directory is shared across machines.
880: In this case localhost will refer to a different machine on each of
881: the machines and the user will get many warnings about changed host keys.
882: However, this option disables host authentication for localhost.
883: The argument to this keyword must be
884: .Dq yes
885: or
886: .Dq no .
887: The default is to check the host key for localhost.
888: .It Cm NumberOfPasswordPrompts
889: Specifies the number of password prompts before giving up.
890: The argument to this keyword must be an integer.
1.84 jmc 891: The default is 3.
1.1 stevesk 892: .It Cm PasswordAuthentication
893: Specifies whether to use password authentication.
894: The argument to this keyword must be
895: .Dq yes
896: or
897: .Dq no .
898: The default is
899: .Dq yes .
1.65 reyk 900: .It Cm PermitLocalCommand
901: Allow local command execution via the
902: .Ic LocalCommand
903: option or using the
1.66 jmc 904: .Ic !\& Ns Ar command
1.65 reyk 905: escape sequence in
906: .Xr ssh 1 .
907: The argument must be
908: .Dq yes
909: or
910: .Dq no .
911: The default is
912: .Dq no .
1.127 markus 913: .It Cm PKCS11Provider
914: Specifies which PKCS#11 provider to use.
1.144 jmc 915: The argument to this keyword is the PKCS#11 shared library
1.127 markus 916: .Xr ssh 1
1.128 markus 917: should use to communicate with a PKCS#11 token providing the user's
1.127 markus 918: private RSA key.
1.67 jmc 919: .It Cm Port
920: Specifies the port number to connect on the remote host.
1.84 jmc 921: The default is 22.
1.1 stevesk 922: .It Cm PreferredAuthentications
923: Specifies the order in which the client should try protocol 2
1.11 jmc 924: authentication methods.
1.48 jmc 925: This allows a client to prefer one method (e.g.\&
1.1 stevesk 926: .Cm keyboard-interactive )
1.48 jmc 927: over another method (e.g.\&
1.131 jmc 928: .Cm password ) .
929: The default is:
930: .Bd -literal -offset indent
931: gssapi-with-mic,hostbased,publickey,
932: keyboard-interactive,password
933: .Ed
1.1 stevesk 934: .It Cm Protocol
935: Specifies the protocol versions
1.84 jmc 936: .Xr ssh 1
1.1 stevesk 937: should support in order of preference.
938: The possible values are
1.84 jmc 939: .Sq 1
1.1 stevesk 940: and
1.84 jmc 941: .Sq 2 .
1.1 stevesk 942: Multiple versions must be comma-separated.
1.120 markus 943: When this option is set to
1.121 jmc 944: .Dq 2,1
1.120 markus 945: .Nm ssh
946: will try version 2 and fall back to version 1
947: if version 2 is not available.
1.1 stevesk 948: The default is
1.121 jmc 949: .Sq 2 .
1.1 stevesk 950: .It Cm ProxyCommand
951: Specifies the command to use to connect to the server.
952: The command
953: string extends to the end of the line, and is executed with
1.105 jmc 954: the user's shell.
1.133 jmc 955: In the command string, any occurrence of
1.1 stevesk 956: .Ql %h
957: will be substituted by the host name to
1.132 djm 958: connect,
1.1 stevesk 959: .Ql %p
1.133 jmc 960: by the port, and
961: .Ql %r
1.132 djm 962: by the remote user name.
1.1 stevesk 963: The command can be basically anything,
964: and should read from its standard input and write to its standard output.
965: It should eventually connect an
966: .Xr sshd 8
967: server running on some machine, or execute
968: .Ic sshd -i
969: somewhere.
970: Host key management will be done using the
971: HostName of the host being connected (defaulting to the name typed by
972: the user).
1.7 jmc 973: Setting the command to
974: .Dq none
1.6 markus 975: disables this option entirely.
1.1 stevesk 976: Note that
977: .Cm CheckHostIP
978: is not available for connects with a proxy command.
1.52 djm 979: .Pp
980: This directive is useful in conjunction with
981: .Xr nc 1
982: and its proxy support.
1.53 jmc 983: For example, the following directive would connect via an HTTP proxy at
1.52 djm 984: 192.0.2.0:
985: .Bd -literal -offset 3n
986: ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
987: .Ed
1.167 djm 988: .It Cm ProxyUseFdpass
1.168 jmc 989: Specifies that
1.167 djm 990: .Cm ProxyCommand
991: will pass a connected file descriptor back to
1.168 jmc 992: .Xr ssh 1
1.167 djm 993: instead of continuing to execute and pass data.
994: The default is
995: .Dq no .
1.1 stevesk 996: .It Cm PubkeyAuthentication
997: Specifies whether to try public key authentication.
998: The argument to this keyword must be
999: .Dq yes
1000: or
1001: .Dq no .
1002: The default is
1003: .Dq yes .
1004: This option applies to protocol version 2 only.
1.75 dtucker 1005: .It Cm RekeyLimit
1006: Specifies the maximum amount of data that may be transmitted before the
1.162 dtucker 1007: session key is renegotiated, optionally followed a maximum amount of
1008: time that may pass before the session key is renegotiated.
1009: The first argument is specified in bytes and may have a suffix of
1.76 jmc 1010: .Sq K ,
1011: .Sq M ,
1.75 dtucker 1012: or
1.76 jmc 1013: .Sq G
1.75 dtucker 1014: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1015: The default is between
1.84 jmc 1016: .Sq 1G
1.75 dtucker 1017: and
1.84 jmc 1018: .Sq 4G ,
1.75 dtucker 1019: depending on the cipher.
1.162 dtucker 1020: The optional second value is specified in seconds and may use any of the
1021: units documented in the
1.166 jmc 1022: TIME FORMATS section of
1.162 dtucker 1023: .Xr sshd_config 5 .
1024: The default value for
1025: .Cm RekeyLimit
1026: is
1027: .Dq default none ,
1028: which means that rekeying is performed after the cipher's default amount
1029: of data has been sent or received and no time based rekeying is done.
1.76 jmc 1030: This option applies to protocol version 2 only.
1.1 stevesk 1031: .It Cm RemoteForward
1.74 jmc 1032: Specifies that a TCP port on the remote machine be forwarded over
1.1 stevesk 1033: the secure channel to the specified host and port from the local machine.
1.49 jmc 1034: The first argument must be
1.43 djm 1035: .Sm off
1.49 jmc 1036: .Oo Ar bind_address : Oc Ar port
1.43 djm 1037: .Sm on
1.49 jmc 1038: and the second argument must be
1039: .Ar host : Ns Ar hostport .
1.138 djm 1040: IPv6 addresses can be specified by enclosing addresses in square brackets.
1.1 stevesk 1041: Multiple forwardings may be specified, and additional
1042: forwardings can be given on the command line.
1.113 stevesk 1043: Privileged ports can be forwarded only when
1044: logging in as root on the remote machine.
1.118 jmc 1045: .Pp
1.117 djm 1046: If the
1047: .Ar port
1048: argument is
1049: .Ql 0 ,
1050: the listen port will be dynamically allocated on the server and reported
1051: to the client at run time.
1.43 djm 1052: .Pp
1053: If the
1054: .Ar bind_address
1055: is not specified, the default is to only bind to loopback addresses.
1056: If the
1057: .Ar bind_address
1058: is
1059: .Ql *
1060: or an empty string, then the forwarding is requested to listen on all
1061: interfaces.
1062: Specifying a remote
1063: .Ar bind_address
1.46 jmc 1064: will only succeed if the server's
1065: .Cm GatewayPorts
1.43 djm 1066: option is enabled (see
1.46 jmc 1067: .Xr sshd_config 5 ) .
1.149 djm 1068: .It Cm RequestTTY
1069: Specifies whether to request a pseudo-tty for the session.
1070: The argument may be one of:
1071: .Dq no
1072: (never request a TTY),
1073: .Dq yes
1074: (always request a TTY when standard input is a TTY),
1075: .Dq force
1076: (always request a TTY) or
1077: .Dq auto
1078: (request a TTY when opening a login session).
1079: This option mirrors the
1080: .Fl t
1081: and
1082: .Fl T
1083: flags for
1084: .Xr ssh 1 .
1.1 stevesk 1085: .It Cm RhostsRSAAuthentication
1086: Specifies whether to try rhosts based authentication with RSA host
1087: authentication.
1088: The argument must be
1089: .Dq yes
1090: or
1091: .Dq no .
1092: The default is
1093: .Dq no .
1094: This option applies to protocol version 1 only and requires
1.84 jmc 1095: .Xr ssh 1
1.1 stevesk 1096: to be setuid root.
1097: .It Cm RSAAuthentication
1098: Specifies whether to try RSA authentication.
1099: The argument to this keyword must be
1100: .Dq yes
1101: or
1102: .Dq no .
1103: RSA authentication will only be
1104: attempted if the identity file exists, or an authentication agent is
1105: running.
1106: The default is
1107: .Dq yes .
1108: Note that this option applies to protocol version 1 only.
1.32 djm 1109: .It Cm SendEnv
1110: Specifies what variables from the local
1111: .Xr environ 7
1112: should be sent to the server.
1.84 jmc 1113: Note that environment passing is only supported for protocol 2.
1114: The server must also support it, and the server must be configured to
1.33 djm 1115: accept these environment variables.
1.32 djm 1116: Refer to
1117: .Cm AcceptEnv
1118: in
1119: .Xr sshd_config 5
1120: for how to configure the server.
1.80 jmc 1121: Variables are specified by name, which may contain wildcard characters.
1.33 djm 1122: Multiple environment variables may be separated by whitespace or spread
1.32 djm 1123: across multiple
1124: .Cm SendEnv
1125: directives.
1126: The default is not to send any environment variables.
1.81 jmc 1127: .Pp
1128: See
1129: .Sx PATTERNS
1130: for more information on patterns.
1.28 markus 1131: .It Cm ServerAliveCountMax
1.73 jmc 1132: Sets the number of server alive messages (see below) which may be
1.28 markus 1133: sent without
1.84 jmc 1134: .Xr ssh 1
1.28 markus 1135: receiving any messages back from the server.
1136: If this threshold is reached while server alive messages are being sent,
1.84 jmc 1137: ssh will disconnect from the server, terminating the session.
1.28 markus 1138: It is important to note that the use of server alive messages is very
1139: different from
1140: .Cm TCPKeepAlive
1141: (below).
1142: The server alive messages are sent through the encrypted channel
1143: and therefore will not be spoofable.
1144: The TCP keepalive option enabled by
1145: .Cm TCPKeepAlive
1146: is spoofable.
1147: The server alive mechanism is valuable when the client or
1148: server depend on knowing when a connection has become inactive.
1149: .Pp
1150: The default value is 3.
1151: If, for example,
1152: .Cm ServerAliveInterval
1.84 jmc 1153: (see below) is set to 15 and
1.28 markus 1154: .Cm ServerAliveCountMax
1.84 jmc 1155: is left at the default, if the server becomes unresponsive,
1156: ssh will disconnect after approximately 45 seconds.
1.89 markus 1157: This option applies to protocol version 2 only.
1.67 jmc 1158: .It Cm ServerAliveInterval
1159: Sets a timeout interval in seconds after which if no data has been received
1160: from the server,
1.84 jmc 1161: .Xr ssh 1
1.67 jmc 1162: will send a message through the encrypted
1163: channel to request a response from the server.
1164: The default
1165: is 0, indicating that these messages will not be sent to the server.
1166: This option applies to protocol version 2 only.
1.1 stevesk 1167: .It Cm StrictHostKeyChecking
1168: If this flag is set to
1169: .Dq yes ,
1.84 jmc 1170: .Xr ssh 1
1.1 stevesk 1171: will never automatically add host keys to the
1.50 djm 1172: .Pa ~/.ssh/known_hosts
1.1 stevesk 1173: file, and refuses to connect to hosts whose host key has changed.
1174: This provides maximum protection against trojan horse attacks,
1.84 jmc 1175: though it can be annoying when the
1.1 stevesk 1176: .Pa /etc/ssh/ssh_known_hosts
1.84 jmc 1177: file is poorly maintained or when connections to new hosts are
1.1 stevesk 1178: frequently made.
1179: This option forces the user to manually
1180: add all new hosts.
1181: If this flag is set to
1182: .Dq no ,
1.84 jmc 1183: ssh will automatically add new host keys to the
1.1 stevesk 1184: user known hosts files.
1185: If this flag is set to
1186: .Dq ask ,
1187: new host keys
1188: will be added to the user known host files only after the user
1189: has confirmed that is what they really want to do, and
1.84 jmc 1190: ssh will refuse to connect to hosts whose host key has changed.
1.1 stevesk 1191: The host keys of
1192: known hosts will be verified automatically in all cases.
1193: The argument must be
1194: .Dq yes ,
1.84 jmc 1195: .Dq no ,
1.1 stevesk 1196: or
1197: .Dq ask .
1198: The default is
1199: .Dq ask .
1.26 markus 1200: .It Cm TCPKeepAlive
1201: Specifies whether the system should send TCP keepalive messages to the
1202: other side.
1203: If they are sent, death of the connection or crash of one
1204: of the machines will be properly noticed.
1205: However, this means that
1206: connections will die if the route is down temporarily, and some people
1207: find it annoying.
1208: .Pp
1209: The default is
1210: .Dq yes
1211: (to send TCP keepalive messages), and the client will notice
1212: if the network goes down or the remote host dies.
1213: This is important in scripts, and many users want it too.
1214: .Pp
1215: To disable TCP keepalive messages, the value should be set to
1216: .Dq no .
1.65 reyk 1217: .It Cm Tunnel
1.95 stevesk 1218: Request
1.65 reyk 1219: .Xr tun 4
1.69 jmc 1220: device forwarding between the client and the server.
1.65 reyk 1221: The argument must be
1.68 reyk 1222: .Dq yes ,
1.95 stevesk 1223: .Dq point-to-point
1224: (layer 3),
1225: .Dq ethernet
1226: (layer 2),
1.65 reyk 1227: or
1228: .Dq no .
1.95 stevesk 1229: Specifying
1230: .Dq yes
1231: requests the default tunnel mode, which is
1232: .Dq point-to-point .
1.65 reyk 1233: The default is
1234: .Dq no .
1235: .It Cm TunnelDevice
1.95 stevesk 1236: Specifies the
1.65 reyk 1237: .Xr tun 4
1.95 stevesk 1238: devices to open on the client
1239: .Pq Ar local_tun
1240: and the server
1241: .Pq Ar remote_tun .
1242: .Pp
1243: The argument must be
1244: .Sm off
1245: .Ar local_tun Op : Ar remote_tun .
1246: .Sm on
1247: The devices may be specified by numerical ID or the keyword
1248: .Dq any ,
1249: which uses the next available tunnel device.
1250: If
1251: .Ar remote_tun
1252: is not specified, it defaults to
1253: .Dq any .
1254: The default is
1255: .Dq any:any .
1.72 jmc 1256: .It Cm UsePrivilegedPort
1257: Specifies whether to use a privileged port for outgoing connections.
1258: The argument must be
1259: .Dq yes
1260: or
1261: .Dq no .
1262: The default is
1263: .Dq no .
1264: If set to
1.84 jmc 1265: .Dq yes ,
1266: .Xr ssh 1
1.72 jmc 1267: must be setuid root.
1268: Note that this option must be set to
1269: .Dq yes
1270: for
1271: .Cm RhostsRSAAuthentication
1272: with older servers.
1.1 stevesk 1273: .It Cm User
1274: Specifies the user to log in as.
1275: This can be useful when a different user name is used on different machines.
1276: This saves the trouble of
1277: having to remember to give the user name on the command line.
1278: .It Cm UserKnownHostsFile
1.151 djm 1279: Specifies one or more files to use for the user
1280: host key database, separated by whitespace.
1281: The default is
1282: .Pa ~/.ssh/known_hosts ,
1283: .Pa ~/.ssh/known_hosts2 .
1.8 jakob 1284: .It Cm VerifyHostKeyDNS
1285: Specifies whether to verify the remote key using DNS and SSHFP resource
1286: records.
1.24 jakob 1287: If this option is set to
1288: .Dq yes ,
1.25 jmc 1289: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 1290: from DNS.
1291: Insecure fingerprints will be handled as if this option was set to
1292: .Dq ask .
1293: If this option is set to
1294: .Dq ask ,
1295: information on fingerprint match will be displayed, but the user will still
1296: need to confirm new host keys according to the
1297: .Cm StrictHostKeyChecking
1298: option.
1299: The argument must be
1300: .Dq yes ,
1.84 jmc 1301: .Dq no ,
1.25 jmc 1302: or
1303: .Dq ask .
1.8 jakob 1304: The default is
1305: .Dq no .
1.12 jakob 1306: Note that this option applies to protocol version 2 only.
1.84 jmc 1307: .Pp
1.166 jmc 1308: See also VERIFYING HOST KEYS in
1.84 jmc 1309: .Xr ssh 1 .
1.111 grunk 1310: .It Cm VisualHostKey
1311: If this flag is set to
1312: .Dq yes ,
1313: an ASCII art representation of the remote host key fingerprint is
1.114 stevesk 1314: printed in addition to the hex fingerprint string at login and
1315: for unknown host keys.
1.111 grunk 1316: If this flag is set to
1317: .Dq no ,
1.114 stevesk 1318: no fingerprint strings are printed at login and
1319: only the hex fingerprint string will be printed for unknown host keys.
1.111 grunk 1320: The default is
1321: .Dq no .
1.1 stevesk 1322: .It Cm XAuthLocation
1.5 stevesk 1323: Specifies the full pathname of the
1.1 stevesk 1324: .Xr xauth 1
1325: program.
1326: The default is
1327: .Pa /usr/X11R6/bin/xauth .
1328: .El
1.86 jmc 1329: .Sh PATTERNS
1330: A
1331: .Em pattern
1332: consists of zero or more non-whitespace characters,
1333: .Sq *
1334: (a wildcard that matches zero or more characters),
1335: or
1336: .Sq ?\&
1337: (a wildcard that matches exactly one character).
1338: For example, to specify a set of declarations for any host in the
1339: .Dq .co.uk
1340: set of domains,
1341: the following pattern could be used:
1342: .Pp
1343: .Dl Host *.co.uk
1344: .Pp
1345: The following pattern
1346: would match any host in the 192.168.0.[0-9] network range:
1347: .Pp
1348: .Dl Host 192.168.0.?
1349: .Pp
1350: A
1351: .Em pattern-list
1352: is a comma-separated list of patterns.
1353: Patterns within pattern-lists may be negated
1354: by preceding them with an exclamation mark
1355: .Pq Sq !\& .
1356: For example,
1357: to allow a key to be used from anywhere within an organisation
1358: except from the
1359: .Dq dialup
1360: pool,
1361: the following entry (in authorized_keys) could be used:
1362: .Pp
1363: .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1.1 stevesk 1364: .Sh FILES
1365: .Bl -tag -width Ds
1.50 djm 1366: .It Pa ~/.ssh/config
1.1 stevesk 1367: This is the per-user configuration file.
1368: The format of this file is described above.
1.84 jmc 1369: This file is used by the SSH client.
1.30 djm 1370: Because of the potential for abuse, this file must have strict permissions:
1371: read/write for the user, and not accessible by others.
1.1 stevesk 1372: .It Pa /etc/ssh/ssh_config
1373: Systemwide configuration file.
1374: This file provides defaults for those
1375: values that are not specified in the user's configuration file, and
1376: for those users who do not have a configuration file.
1377: This file must be world-readable.
1378: .El
1.13 jmc 1379: .Sh SEE ALSO
1380: .Xr ssh 1
1.1 stevesk 1381: .Sh AUTHORS
1382: OpenSSH is a derivative of the original and free
1383: ssh 1.2.12 release by Tatu Ylonen.
1384: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1385: Theo de Raadt and Dug Song
1386: removed many bugs, re-added newer features and
1387: created OpenSSH.
1388: Markus Friedl contributed the support for SSH
1389: protocol versions 1.5 and 2.0.
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