Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.36
1.1 stevesk 1: .\" -*- nroff -*-
2: .\"
3: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: .\" All rights reserved
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7: .\" As far as I am concerned, the code I have written for this software
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9: .\" software must be clearly marked as such, and if the derived work is
10: .\" incompatible with the protocol description in the RFC file, it must be
11: .\" called by a name other than "ssh" or "Secure Shell".
12: .\"
13: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
14: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
15: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
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1.36 ! djm 37: .\" $OpenBSD: ssh_config.5,v 1.35 2004/06/13 14:01:42 dtucker Exp $
1.1 stevesk 38: .Dd September 25, 1999
39: .Dt SSH_CONFIG 5
40: .Os
41: .Sh NAME
42: .Nm ssh_config
43: .Nd OpenSSH SSH client configuration files
44: .Sh SYNOPSIS
45: .Bl -tag -width Ds -compact
46: .It Pa $HOME/.ssh/config
47: .It Pa /etc/ssh/ssh_config
48: .El
49: .Sh DESCRIPTION
50: .Nm ssh
51: obtains configuration data from the following sources in
52: the following order:
1.2 stevesk 53: .Bl -enum -offset indent -compact
54: .It
55: command-line options
56: .It
57: user's configuration file
58: .Pq Pa $HOME/.ssh/config
59: .It
60: system-wide configuration file
61: .Pq Pa /etc/ssh/ssh_config
62: .El
1.1 stevesk 63: .Pp
64: For each parameter, the first obtained value
65: will be used.
66: The configuration files contain sections bracketed by
67: .Dq Host
68: specifications, and that section is only applied for hosts that
69: match one of the patterns given in the specification.
70: The matched host name is the one given on the command line.
71: .Pp
72: Since the first obtained value for each parameter is used, more
73: host-specific declarations should be given near the beginning of the
74: file, and general defaults at the end.
75: .Pp
76: The configuration file has the following format:
77: .Pp
78: Empty lines and lines starting with
79: .Ql #
80: are comments.
81: .Pp
82: Otherwise a line is of the format
83: .Dq keyword arguments .
84: Configuration options may be separated by whitespace or
85: optional whitespace and exactly one
86: .Ql = ;
87: the latter format is useful to avoid the need to quote whitespace
88: when specifying configuration options using the
89: .Nm ssh ,
90: .Nm scp
91: and
92: .Nm sftp
93: .Fl o
94: option.
95: .Pp
96: The possible
97: keywords and their meanings are as follows (note that
98: keywords are case-insensitive and arguments are case-sensitive):
99: .Bl -tag -width Ds
100: .It Cm Host
101: Restricts the following declarations (up to the next
102: .Cm Host
103: keyword) to be only for those hosts that match one of the patterns
104: given after the keyword.
105: .Ql \&*
106: and
1.20 jmc 107: .Ql \&?
1.1 stevesk 108: can be used as wildcards in the
109: patterns.
110: A single
111: .Ql \&*
112: as a pattern can be used to provide global
113: defaults for all hosts.
114: The host is the
115: .Ar hostname
116: argument given on the command line (i.e., the name is not converted to
117: a canonicalized host name before matching).
1.10 djm 118: .It Cm AddressFamily
1.11 jmc 119: Specifies which address family to use when connecting.
120: Valid arguments are
1.10 djm 121: .Dq any ,
122: .Dq inet
123: (Use IPv4 only) or
124: .Dq inet6
125: (Use IPv6 only.)
1.1 stevesk 126: .It Cm BatchMode
127: If set to
128: .Dq yes ,
129: passphrase/password querying will be disabled.
130: This option is useful in scripts and other batch jobs where no user
131: is present to supply the password.
132: The argument must be
133: .Dq yes
134: or
135: .Dq no .
136: The default is
137: .Dq no .
138: .It Cm BindAddress
139: Specify the interface to transmit from on machines with multiple
140: interfaces or aliased addresses.
141: Note that this option does not work if
142: .Cm UsePrivilegedPort
143: is set to
144: .Dq yes .
145: .It Cm ChallengeResponseAuthentication
146: Specifies whether to use challenge response authentication.
147: The argument to this keyword must be
148: .Dq yes
149: or
150: .Dq no .
151: The default is
152: .Dq yes .
153: .It Cm CheckHostIP
154: If this flag is set to
155: .Dq yes ,
156: ssh will additionally check the host IP address in the
157: .Pa known_hosts
158: file.
159: This allows ssh to detect if a host key changed due to DNS spoofing.
160: If the option is set to
161: .Dq no ,
162: the check will not be executed.
163: The default is
164: .Dq yes .
165: .It Cm Cipher
166: Specifies the cipher to use for encrypting the session
167: in protocol version 1.
168: Currently,
169: .Dq blowfish ,
170: .Dq 3des ,
171: and
172: .Dq des
173: are supported.
174: .Ar des
175: is only supported in the
176: .Nm ssh
177: client for interoperability with legacy protocol 1 implementations
178: that do not support the
179: .Ar 3des
1.7 jmc 180: cipher.
181: Its use is strongly discouraged due to cryptographic weaknesses.
1.1 stevesk 182: The default is
183: .Dq 3des .
184: .It Cm Ciphers
185: Specifies the ciphers allowed for protocol version 2
186: in order of preference.
187: Multiple ciphers must be comma-separated.
1.35 dtucker 188: The supported ciphers are
189: .Dq 3des-cbc ,
190: .Dq aes128-cbc ,
191: .Dq aes192-cbc ,
192: .Dq aes256-cbc ,
193: .Dq aes128-ctr ,
194: .Dq aes192-ctr ,
195: .Dq aes256-ctr ,
196: .Dq arcfour ,
197: .Dq blowfish-cbc ,
198: and
199: .Dq cast128-cbc .
1.1 stevesk 200: The default is
201: .Bd -literal
202: ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
203: aes192-cbc,aes256-cbc''
204: .Ed
205: .It Cm ClearAllForwardings
206: Specifies that all local, remote and dynamic port forwardings
207: specified in the configuration files or on the command line be
1.7 jmc 208: cleared.
209: This option is primarily useful when used from the
1.1 stevesk 210: .Nm ssh
211: command line to clear port forwardings set in
212: configuration files, and is automatically set by
213: .Xr scp 1
214: and
215: .Xr sftp 1 .
216: The argument must be
217: .Dq yes
218: or
219: .Dq no .
220: The default is
221: .Dq no .
222: .It Cm Compression
223: Specifies whether to use compression.
224: The argument must be
225: .Dq yes
226: or
227: .Dq no .
228: The default is
229: .Dq no .
230: .It Cm CompressionLevel
231: Specifies the compression level to use if compression is enabled.
232: The argument must be an integer from 1 (fast) to 9 (slow, best).
233: The default level is 6, which is good for most applications.
234: The meaning of the values is the same as in
235: .Xr gzip 1 .
236: Note that this option applies to protocol version 1 only.
237: .It Cm ConnectionAttempts
238: Specifies the number of tries (one per second) to make before exiting.
239: The argument must be an integer.
240: This may be useful in scripts if the connection sometimes fails.
241: The default is 1.
1.9 djm 242: .It Cm ConnectTimeout
243: Specifies the timeout (in seconds) used when connecting to the ssh
1.11 jmc 244: server, instead of using the default system TCP timeout.
245: This value is used only when the target is down or really unreachable,
246: not when it refuses the connection.
1.1 stevesk 247: .It Cm DynamicForward
248: Specifies that a TCP/IP port on the local machine be forwarded
249: over the secure channel, and the application
250: protocol is then used to determine where to connect to from the
1.7 jmc 251: remote machine.
252: The argument must be a port number.
1.15 markus 253: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.1 stevesk 254: .Nm ssh
1.15 markus 255: will act as a SOCKS server.
1.1 stevesk 256: Multiple forwardings may be specified, and
1.7 jmc 257: additional forwardings can be given on the command line.
258: Only the superuser can forward privileged ports.
1.36 ! djm 259: .It Cm ControlMaster
! 260: Enables the sharing of multiple sessions over a single network connection.
! 261: When set to
! 262: .Dq yes
! 263: .Nm ssh
! 264: will listen for connections on a control socket specified using the
! 265: .Cm ControlPath
! 266: argument.
! 267: Additional sessions can connect to this socket using the same
! 268: .Cm ControlPath
! 269: with
! 270: .Cm ControlMaster
! 271: set to
! 272: .Dq no
! 273: (the default.)
! 274: These sessions will reuse the master instance's network connection rather
! 275: than initiating new ones.
! 276: .It Cm ControlPath
! 277: Specify a the path to the control socket used for connection sharing.
! 278: See
! 279: .Cm ControlMaster
! 280: above.
1.14 markus 281: .It Cm EnableSSHKeysign
282: Setting this option to
283: .Dq yes
284: in the global client configuration file
285: .Pa /etc/ssh/ssh_config
286: enables the use of the helper program
287: .Xr ssh-keysign 8
288: during
289: .Cm HostbasedAuthentication .
290: The argument must be
291: .Dq yes
292: or
293: .Dq no .
294: The default is
295: .Dq no .
1.23 jmc 296: This option should be placed in the non-hostspecific section.
1.14 markus 297: See
298: .Xr ssh-keysign 8
299: for more information.
1.1 stevesk 300: .It Cm EscapeChar
301: Sets the escape character (default:
302: .Ql ~ ) .
303: The escape character can also
304: be set on the command line.
305: The argument should be a single character,
306: .Ql ^
307: followed by a letter, or
308: .Dq none
309: to disable the escape
310: character entirely (making the connection transparent for binary
311: data).
312: .It Cm ForwardAgent
313: Specifies whether the connection to the authentication agent (if any)
314: will be forwarded to the remote machine.
315: The argument must be
316: .Dq yes
317: or
318: .Dq no .
319: The default is
320: .Dq no .
1.3 stevesk 321: .Pp
1.7 jmc 322: Agent forwarding should be enabled with caution.
323: Users with the ability to bypass file permissions on the remote host
324: (for the agent's Unix-domain socket)
325: can access the local agent through the forwarded connection.
326: An attacker cannot obtain key material from the agent,
1.3 stevesk 327: however they can perform operations on the keys that enable them to
328: authenticate using the identities loaded into the agent.
1.1 stevesk 329: .It Cm ForwardX11
330: Specifies whether X11 connections will be automatically redirected
331: over the secure channel and
332: .Ev DISPLAY
333: set.
334: The argument must be
335: .Dq yes
336: or
337: .Dq no .
338: The default is
339: .Dq no .
1.3 stevesk 340: .Pp
1.7 jmc 341: X11 forwarding should be enabled with caution.
342: Users with the ability to bypass file permissions on the remote host
1.22 markus 343: (for the user's X11 authorization database)
1.7 jmc 344: can access the local X11 display through the forwarded connection.
1.22 markus 345: An attacker may then be able to perform activities such as keystroke monitoring
346: if the
347: .Cm ForwardX11Trusted
348: option is also enabled.
349: .It Cm ForwardX11Trusted
1.34 jmc 350: If this option is set to
1.22 markus 351: .Dq yes
352: then remote X11 clients will have full access to the original X11 display.
353: If this option is set to
354: .Dq no
355: then remote X11 clients will be considered untrusted and prevented
356: from stealing or tampering with data belonging to trusted X11
357: clients.
358: .Pp
359: The default is
360: .Dq no .
361: .Pp
362: See the X11 SECURITY extension specification for full details on
363: the restrictions imposed on untrusted clients.
1.1 stevesk 364: .It Cm GatewayPorts
365: Specifies whether remote hosts are allowed to connect to local
366: forwarded ports.
367: By default,
368: .Nm ssh
1.7 jmc 369: binds local port forwardings to the loopback address.
370: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 371: .Cm GatewayPorts
372: can be used to specify that
373: .Nm ssh
374: should bind local port forwardings to the wildcard address,
375: thus allowing remote hosts to connect to forwarded ports.
376: The argument must be
377: .Dq yes
378: or
379: .Dq no .
380: The default is
381: .Dq no .
382: .It Cm GlobalKnownHostsFile
383: Specifies a file to use for the global
384: host key database instead of
385: .Pa /etc/ssh/ssh_known_hosts .
1.18 markus 386: .It Cm GSSAPIAuthentication
1.27 markus 387: Specifies whether user authentication based on GSSAPI is allowed.
1.20 jmc 388: The default is
1.21 markus 389: .Dq no .
1.18 markus 390: Note that this option applies to protocol version 2 only.
391: .It Cm GSSAPIDelegateCredentials
392: Forward (delegate) credentials to the server.
393: The default is
394: .Dq no .
395: Note that this option applies to protocol version 2 only.
1.1 stevesk 396: .It Cm HostbasedAuthentication
397: Specifies whether to try rhosts based authentication with public key
398: authentication.
399: The argument must be
400: .Dq yes
401: or
402: .Dq no .
403: The default is
404: .Dq no .
405: This option applies to protocol version 2 only and
406: is similar to
407: .Cm RhostsRSAAuthentication .
408: .It Cm HostKeyAlgorithms
409: Specifies the protocol version 2 host key algorithms
410: that the client wants to use in order of preference.
411: The default for this option is:
412: .Dq ssh-rsa,ssh-dss .
413: .It Cm HostKeyAlias
414: Specifies an alias that should be used instead of the
415: real host name when looking up or saving the host key
416: in the host key database files.
417: This option is useful for tunneling ssh connections
418: or for multiple servers running on a single host.
419: .It Cm HostName
420: Specifies the real host name to log into.
421: This can be used to specify nicknames or abbreviations for hosts.
422: Default is the name given on the command line.
423: Numeric IP addresses are also permitted (both on the command line and in
424: .Cm HostName
425: specifications).
426: .It Cm IdentityFile
427: Specifies a file from which the user's RSA or DSA authentication identity
1.11 jmc 428: is read.
429: The default is
1.1 stevesk 430: .Pa $HOME/.ssh/identity
431: for protocol version 1, and
432: .Pa $HOME/.ssh/id_rsa
433: and
434: .Pa $HOME/.ssh/id_dsa
435: for protocol version 2.
436: Additionally, any identities represented by the authentication agent
437: will be used for authentication.
438: The file name may use the tilde
439: syntax to refer to a user's home directory.
440: It is possible to have
441: multiple identity files specified in configuration files; all these
442: identities will be tried in sequence.
1.29 markus 443: .It Cm IdentitiesOnly
444: Specifies that
445: .Nm ssh
446: should only use the authentication identity files configured in the
1.31 jmc 447: .Nm
1.29 markus 448: files,
449: even if the
450: .Nm ssh-agent
451: offers more identities.
452: The argument to this keyword must be
453: .Dq yes
454: or
455: .Dq no .
456: This option is intented for situations where
457: .Nm ssh-agent
458: offers many different identities.
459: The default is
460: .Dq no .
1.1 stevesk 461: .It Cm LocalForward
462: Specifies that a TCP/IP port on the local machine be forwarded over
463: the secure channel to the specified host and port from the remote machine.
464: The first argument must be a port number, and the second must be
465: .Ar host:port .
466: IPv6 addresses can be specified with an alternative syntax:
467: .Ar host/port .
468: Multiple forwardings may be specified, and additional
469: forwardings can be given on the command line.
470: Only the superuser can forward privileged ports.
471: .It Cm LogLevel
472: Gives the verbosity level that is used when logging messages from
473: .Nm ssh .
474: The possible values are:
475: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2 and DEBUG3.
1.7 jmc 476: The default is INFO.
477: DEBUG and DEBUG1 are equivalent.
478: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 479: .It Cm MACs
480: Specifies the MAC (message authentication code) algorithms
481: in order of preference.
482: The MAC algorithm is used in protocol version 2
483: for data integrity protection.
484: Multiple algorithms must be comma-separated.
485: The default is
486: .Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 .
487: .It Cm NoHostAuthenticationForLocalhost
488: This option can be used if the home directory is shared across machines.
489: In this case localhost will refer to a different machine on each of
490: the machines and the user will get many warnings about changed host keys.
491: However, this option disables host authentication for localhost.
492: The argument to this keyword must be
493: .Dq yes
494: or
495: .Dq no .
496: The default is to check the host key for localhost.
497: .It Cm NumberOfPasswordPrompts
498: Specifies the number of password prompts before giving up.
499: The argument to this keyword must be an integer.
500: Default is 3.
501: .It Cm PasswordAuthentication
502: Specifies whether to use password authentication.
503: The argument to this keyword must be
504: .Dq yes
505: or
506: .Dq no .
507: The default is
508: .Dq yes .
509: .It Cm Port
510: Specifies the port number to connect on the remote host.
511: Default is 22.
512: .It Cm PreferredAuthentications
513: Specifies the order in which the client should try protocol 2
1.11 jmc 514: authentication methods.
515: This allows a client to prefer one method (e.g.
1.1 stevesk 516: .Cm keyboard-interactive )
517: over another method (e.g.
518: .Cm password )
519: The default for this option is:
520: .Dq hostbased,publickey,keyboard-interactive,password .
521: .It Cm Protocol
522: Specifies the protocol versions
523: .Nm ssh
524: should support in order of preference.
525: The possible values are
526: .Dq 1
527: and
528: .Dq 2 .
529: Multiple versions must be comma-separated.
530: The default is
531: .Dq 2,1 .
532: This means that
533: .Nm ssh
534: tries version 2 and falls back to version 1
535: if version 2 is not available.
536: .It Cm ProxyCommand
537: Specifies the command to use to connect to the server.
538: The command
539: string extends to the end of the line, and is executed with
540: .Pa /bin/sh .
541: In the command string,
542: .Ql %h
543: will be substituted by the host name to
544: connect and
545: .Ql %p
546: by the port.
547: The command can be basically anything,
548: and should read from its standard input and write to its standard output.
549: It should eventually connect an
550: .Xr sshd 8
551: server running on some machine, or execute
552: .Ic sshd -i
553: somewhere.
554: Host key management will be done using the
555: HostName of the host being connected (defaulting to the name typed by
556: the user).
1.7 jmc 557: Setting the command to
558: .Dq none
1.6 markus 559: disables this option entirely.
1.1 stevesk 560: Note that
561: .Cm CheckHostIP
562: is not available for connects with a proxy command.
563: .Pp
564: .It Cm PubkeyAuthentication
565: Specifies whether to try public key authentication.
566: The argument to this keyword must be
567: .Dq yes
568: or
569: .Dq no .
570: The default is
571: .Dq yes .
572: This option applies to protocol version 2 only.
573: .It Cm RemoteForward
574: Specifies that a TCP/IP port on the remote machine be forwarded over
575: the secure channel to the specified host and port from the local machine.
576: The first argument must be a port number, and the second must be
577: .Ar host:port .
578: IPv6 addresses can be specified with an alternative syntax:
579: .Ar host/port .
580: Multiple forwardings may be specified, and additional
581: forwardings can be given on the command line.
582: Only the superuser can forward privileged ports.
583: .It Cm RhostsRSAAuthentication
584: Specifies whether to try rhosts based authentication with RSA host
585: authentication.
586: The argument must be
587: .Dq yes
588: or
589: .Dq no .
590: The default is
591: .Dq no .
592: This option applies to protocol version 1 only and requires
593: .Nm ssh
594: to be setuid root.
595: .It Cm RSAAuthentication
596: Specifies whether to try RSA authentication.
597: The argument to this keyword must be
598: .Dq yes
599: or
600: .Dq no .
601: RSA authentication will only be
602: attempted if the identity file exists, or an authentication agent is
603: running.
604: The default is
605: .Dq yes .
606: Note that this option applies to protocol version 1 only.
1.32 djm 607: .It Cm SendEnv
608: Specifies what variables from the local
609: .Xr environ 7
610: should be sent to the server.
611: Note that environment passing is only supported for protocol 2, the
1.33 djm 612: server must also support it, and the server must be configured to
613: accept these environment variables.
1.32 djm 614: Refer to
615: .Cm AcceptEnv
616: in
617: .Xr sshd_config 5
618: for how to configure the server.
619: Variables are specified by name, which may contain the wildcard characters
620: .Ql \&*
621: and
622: .Ql \&? .
1.33 djm 623: Multiple environment variables may be separated by whitespace or spread
1.32 djm 624: across multiple
625: .Cm SendEnv
626: directives.
627: The default is not to send any environment variables.
1.28 markus 628: .It Cm ServerAliveInterval
629: Sets a timeout interval in seconds after which if no data has been received
630: from the server,
631: .Nm ssh
632: will send a message through the encrypted
633: channel to request a response from the server.
634: The default
635: is 0, indicating that these messages will not be sent to the server.
636: This option applies to protocol version 2 only.
637: .It Cm ServerAliveCountMax
638: Sets the number of server alive messages (see above) which may be
639: sent without
640: .Nm ssh
641: receiving any messages back from the server.
642: If this threshold is reached while server alive messages are being sent,
643: .Nm ssh
644: will disconnect from the server, terminating the session.
645: It is important to note that the use of server alive messages is very
646: different from
647: .Cm TCPKeepAlive
648: (below).
649: The server alive messages are sent through the encrypted channel
650: and therefore will not be spoofable.
651: The TCP keepalive option enabled by
652: .Cm TCPKeepAlive
653: is spoofable.
654: The server alive mechanism is valuable when the client or
655: server depend on knowing when a connection has become inactive.
656: .Pp
657: The default value is 3.
658: If, for example,
659: .Cm ServerAliveInterval
660: (above) is set to 15, and
661: .Cm ServerAliveCountMax
662: is left at the default, if the server becomes unresponsive ssh
663: will disconnect after approximately 45 seconds.
1.1 stevesk 664: .It Cm SmartcardDevice
1.11 jmc 665: Specifies which smartcard device to use.
666: The argument to this keyword is the device
1.1 stevesk 667: .Nm ssh
668: should use to communicate with a smartcard used for storing the user's
1.11 jmc 669: private RSA key.
670: By default, no device is specified and smartcard support is not activated.
1.1 stevesk 671: .It Cm StrictHostKeyChecking
672: If this flag is set to
673: .Dq yes ,
674: .Nm ssh
675: will never automatically add host keys to the
676: .Pa $HOME/.ssh/known_hosts
677: file, and refuses to connect to hosts whose host key has changed.
678: This provides maximum protection against trojan horse attacks,
679: however, can be annoying when the
680: .Pa /etc/ssh/ssh_known_hosts
681: file is poorly maintained, or connections to new hosts are
682: frequently made.
683: This option forces the user to manually
684: add all new hosts.
685: If this flag is set to
686: .Dq no ,
687: .Nm ssh
688: will automatically add new host keys to the
689: user known hosts files.
690: If this flag is set to
691: .Dq ask ,
692: new host keys
693: will be added to the user known host files only after the user
694: has confirmed that is what they really want to do, and
695: .Nm ssh
696: will refuse to connect to hosts whose host key has changed.
697: The host keys of
698: known hosts will be verified automatically in all cases.
699: The argument must be
700: .Dq yes ,
701: .Dq no
702: or
703: .Dq ask .
704: The default is
705: .Dq ask .
1.26 markus 706: .It Cm TCPKeepAlive
707: Specifies whether the system should send TCP keepalive messages to the
708: other side.
709: If they are sent, death of the connection or crash of one
710: of the machines will be properly noticed.
711: However, this means that
712: connections will die if the route is down temporarily, and some people
713: find it annoying.
714: .Pp
715: The default is
716: .Dq yes
717: (to send TCP keepalive messages), and the client will notice
718: if the network goes down or the remote host dies.
719: This is important in scripts, and many users want it too.
720: .Pp
721: To disable TCP keepalive messages, the value should be set to
722: .Dq no .
1.1 stevesk 723: .It Cm UsePrivilegedPort
724: Specifies whether to use a privileged port for outgoing connections.
725: The argument must be
726: .Dq yes
727: or
728: .Dq no .
729: The default is
730: .Dq no .
1.4 stevesk 731: If set to
732: .Dq yes
733: .Nm ssh
734: must be setuid root.
1.1 stevesk 735: Note that this option must be set to
736: .Dq yes
1.17 markus 737: for
1.1 stevesk 738: .Cm RhostsRSAAuthentication
1.17 markus 739: with older servers.
1.1 stevesk 740: .It Cm User
741: Specifies the user to log in as.
742: This can be useful when a different user name is used on different machines.
743: This saves the trouble of
744: having to remember to give the user name on the command line.
745: .It Cm UserKnownHostsFile
746: Specifies a file to use for the user
747: host key database instead of
748: .Pa $HOME/.ssh/known_hosts .
1.8 jakob 749: .It Cm VerifyHostKeyDNS
750: Specifies whether to verify the remote key using DNS and SSHFP resource
751: records.
1.24 jakob 752: If this option is set to
753: .Dq yes ,
1.25 jmc 754: the client will implicitly trust keys that match a secure fingerprint
1.24 jakob 755: from DNS.
756: Insecure fingerprints will be handled as if this option was set to
757: .Dq ask .
758: If this option is set to
759: .Dq ask ,
760: information on fingerprint match will be displayed, but the user will still
761: need to confirm new host keys according to the
762: .Cm StrictHostKeyChecking
763: option.
764: The argument must be
765: .Dq yes ,
766: .Dq no
1.25 jmc 767: or
768: .Dq ask .
1.8 jakob 769: The default is
770: .Dq no .
1.12 jakob 771: Note that this option applies to protocol version 2 only.
1.1 stevesk 772: .It Cm XAuthLocation
1.5 stevesk 773: Specifies the full pathname of the
1.1 stevesk 774: .Xr xauth 1
775: program.
776: The default is
777: .Pa /usr/X11R6/bin/xauth .
778: .El
779: .Sh FILES
780: .Bl -tag -width Ds
781: .It Pa $HOME/.ssh/config
782: This is the per-user configuration file.
783: The format of this file is described above.
784: This file is used by the
785: .Nm ssh
786: client.
1.30 djm 787: Because of the potential for abuse, this file must have strict permissions:
788: read/write for the user, and not accessible by others.
1.1 stevesk 789: .It Pa /etc/ssh/ssh_config
790: Systemwide configuration file.
791: This file provides defaults for those
792: values that are not specified in the user's configuration file, and
793: for those users who do not have a configuration file.
794: This file must be world-readable.
795: .El
1.13 jmc 796: .Sh SEE ALSO
797: .Xr ssh 1
1.1 stevesk 798: .Sh AUTHORS
799: OpenSSH is a derivative of the original and free
800: ssh 1.2.12 release by Tatu Ylonen.
801: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
802: Theo de Raadt and Dug Song
803: removed many bugs, re-added newer features and
804: created OpenSSH.
805: Markus Friedl contributed the support for SSH
806: protocol versions 1.5 and 2.0.