Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.6.2.3
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
6: .\"
7: .\" As far as I am concerned, the code I have written for this software
8: .\" can be used freely for any purpose. Any derived versions of this
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.
16: .\"
17: .\" Redistribution and use in source and binary forms, with or without
18: .\" modification, are permitted provided that the following conditions
19: .\" are met:
20: .\" 1. Redistributions of source code must retain the above copyright
21: .\" notice, this list of conditions and the following disclaimer.
22: .\" 2. Redistributions in binary form must reproduce the above copyright
23: .\" notice, this list of conditions and the following disclaimer in the
24: .\" documentation and/or other materials provided with the distribution.
25: .\"
26: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36: .\"
1.6.2.3 ! brad 37: .\" $OpenBSD: ssh_config.5,v 1.28 2003/12/16 15:49:51 markus 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
1.6.2.2 brad 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).
1.6.2.2 brad 118: .It Cm AddressFamily
119: Specifies which address family to use when connecting.
120: Valid arguments are
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
1.6.2.1 margarid 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.
188: The default is
189: .Bd -literal
190: ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
191: aes192-cbc,aes256-cbc''
192: .Ed
193: .It Cm ClearAllForwardings
194: Specifies that all local, remote and dynamic port forwardings
195: specified in the configuration files or on the command line be
1.6.2.1 margarid 196: cleared.
197: This option is primarily useful when used from the
1.1 stevesk 198: .Nm ssh
199: command line to clear port forwardings set in
200: configuration files, and is automatically set by
201: .Xr scp 1
202: and
203: .Xr sftp 1 .
204: The argument must be
205: .Dq yes
206: or
207: .Dq no .
208: The default is
209: .Dq no .
210: .It Cm Compression
211: Specifies whether to use compression.
212: The argument must be
213: .Dq yes
214: or
215: .Dq no .
216: The default is
217: .Dq no .
218: .It Cm CompressionLevel
219: Specifies the compression level to use if compression is enabled.
220: The argument must be an integer from 1 (fast) to 9 (slow, best).
221: The default level is 6, which is good for most applications.
222: The meaning of the values is the same as in
223: .Xr gzip 1 .
224: Note that this option applies to protocol version 1 only.
225: .It Cm ConnectionAttempts
226: Specifies the number of tries (one per second) to make before exiting.
227: The argument must be an integer.
228: This may be useful in scripts if the connection sometimes fails.
229: The default is 1.
1.6.2.2 brad 230: .It Cm ConnectTimeout
231: Specifies the timeout (in seconds) used when connecting to the ssh
232: server, instead of using the default system TCP timeout.
233: This value is used only when the target is down or really unreachable,
234: not when it refuses the connection.
1.1 stevesk 235: .It Cm DynamicForward
236: Specifies that a TCP/IP port on the local machine be forwarded
237: over the secure channel, and the application
238: protocol is then used to determine where to connect to from the
1.6.2.1 margarid 239: remote machine.
240: The argument must be a port number.
1.6.2.2 brad 241: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.1 stevesk 242: .Nm ssh
1.6.2.2 brad 243: will act as a SOCKS server.
1.1 stevesk 244: Multiple forwardings may be specified, and
1.6.2.1 margarid 245: additional forwardings can be given on the command line.
246: Only the superuser can forward privileged ports.
1.6.2.2 brad 247: .It Cm EnableSSHKeysign
248: Setting this option to
249: .Dq yes
250: in the global client configuration file
251: .Pa /etc/ssh/ssh_config
252: enables the use of the helper program
253: .Xr ssh-keysign 8
254: during
255: .Cm HostbasedAuthentication .
256: The argument must be
257: .Dq yes
258: or
259: .Dq no .
260: The default is
261: .Dq no .
1.6.2.3 ! brad 262: This option should be placed in the non-hostspecific section.
1.6.2.2 brad 263: See
264: .Xr ssh-keysign 8
265: for more information.
1.1 stevesk 266: .It Cm EscapeChar
267: Sets the escape character (default:
268: .Ql ~ ) .
269: The escape character can also
270: be set on the command line.
271: The argument should be a single character,
272: .Ql ^
273: followed by a letter, or
274: .Dq none
275: to disable the escape
276: character entirely (making the connection transparent for binary
277: data).
278: .It Cm ForwardAgent
279: Specifies whether the connection to the authentication agent (if any)
280: will be forwarded to the remote machine.
281: The argument must be
282: .Dq yes
283: or
284: .Dq no .
285: The default is
286: .Dq no .
1.3 stevesk 287: .Pp
1.6.2.1 margarid 288: Agent forwarding should be enabled with caution.
289: Users with the ability to bypass file permissions on the remote host
290: (for the agent's Unix-domain socket)
291: can access the local agent through the forwarded connection.
292: An attacker cannot obtain key material from the agent,
1.3 stevesk 293: however they can perform operations on the keys that enable them to
294: authenticate using the identities loaded into the agent.
1.1 stevesk 295: .It Cm ForwardX11
296: Specifies whether X11 connections will be automatically redirected
297: over the secure channel and
298: .Ev DISPLAY
299: set.
300: The argument must be
301: .Dq yes
302: or
303: .Dq no .
304: The default is
305: .Dq no .
1.3 stevesk 306: .Pp
1.6.2.1 margarid 307: X11 forwarding should be enabled with caution.
308: Users with the ability to bypass file permissions on the remote host
1.6.2.3 ! brad 309: (for the user's X11 authorization database)
1.6.2.1 margarid 310: can access the local X11 display through the forwarded connection.
1.6.2.3 ! brad 311: An attacker may then be able to perform activities such as keystroke monitoring
! 312: if the
! 313: .Cm ForwardX11Trusted
! 314: option is also enabled.
! 315: .It Cm ForwardX11Trusted
! 316: If the this option is set to
! 317: .Dq yes
! 318: then remote X11 clients will have full access to the original X11 display.
! 319: If this option is set to
! 320: .Dq no
! 321: then remote X11 clients will be considered untrusted and prevented
! 322: from stealing or tampering with data belonging to trusted X11
! 323: clients.
! 324: .Pp
! 325: The default is
! 326: .Dq no .
! 327: .Pp
! 328: See the X11 SECURITY extension specification for full details on
! 329: the restrictions imposed on untrusted clients.
1.1 stevesk 330: .It Cm GatewayPorts
331: Specifies whether remote hosts are allowed to connect to local
332: forwarded ports.
333: By default,
334: .Nm ssh
1.6.2.1 margarid 335: binds local port forwardings to the loopback address.
336: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 337: .Cm GatewayPorts
338: can be used to specify that
339: .Nm ssh
340: should bind local port forwardings to the wildcard address,
341: thus allowing remote hosts to connect to forwarded ports.
342: The argument must be
343: .Dq yes
344: or
345: .Dq no .
346: The default is
347: .Dq no .
348: .It Cm GlobalKnownHostsFile
349: Specifies a file to use for the global
350: host key database instead of
351: .Pa /etc/ssh/ssh_known_hosts .
1.6.2.2 brad 352: .It Cm GSSAPIAuthentication
1.6.2.3 ! brad 353: Specifies whether user authentication based on GSSAPI is allowed.
1.6.2.2 brad 354: The default is
1.6.2.3 ! brad 355: .Dq no .
1.6.2.2 brad 356: Note that this option applies to protocol version 2 only.
357: .It Cm GSSAPIDelegateCredentials
358: Forward (delegate) credentials to the server.
359: The default is
360: .Dq no .
361: Note that this option applies to protocol version 2 only.
1.1 stevesk 362: .It Cm HostbasedAuthentication
363: Specifies whether to try rhosts based authentication with public key
364: authentication.
365: The argument must be
366: .Dq yes
367: or
368: .Dq no .
369: The default is
370: .Dq no .
371: This option applies to protocol version 2 only and
372: is similar to
373: .Cm RhostsRSAAuthentication .
374: .It Cm HostKeyAlgorithms
375: Specifies the protocol version 2 host key algorithms
376: that the client wants to use in order of preference.
377: The default for this option is:
378: .Dq ssh-rsa,ssh-dss .
379: .It Cm HostKeyAlias
380: Specifies an alias that should be used instead of the
381: real host name when looking up or saving the host key
382: in the host key database files.
383: This option is useful for tunneling ssh connections
384: or for multiple servers running on a single host.
385: .It Cm HostName
386: Specifies the real host name to log into.
387: This can be used to specify nicknames or abbreviations for hosts.
388: Default is the name given on the command line.
389: Numeric IP addresses are also permitted (both on the command line and in
390: .Cm HostName
391: specifications).
392: .It Cm IdentityFile
393: Specifies a file from which the user's RSA or DSA authentication identity
1.6.2.2 brad 394: is read.
395: The default is
1.1 stevesk 396: .Pa $HOME/.ssh/identity
397: for protocol version 1, and
398: .Pa $HOME/.ssh/id_rsa
399: and
400: .Pa $HOME/.ssh/id_dsa
401: for protocol version 2.
402: Additionally, any identities represented by the authentication agent
403: will be used for authentication.
404: The file name may use the tilde
405: syntax to refer to a user's home directory.
406: It is possible to have
407: multiple identity files specified in configuration files; all these
408: identities will be tried in sequence.
409: .It Cm LocalForward
410: Specifies that a TCP/IP port on the local machine be forwarded over
411: the secure channel to the specified host and port from the remote machine.
412: The first argument must be a port number, and the second must be
413: .Ar host:port .
414: IPv6 addresses can be specified with an alternative syntax:
415: .Ar host/port .
416: Multiple forwardings may be specified, and additional
417: forwardings can be given on the command line.
418: Only the superuser can forward privileged ports.
419: .It Cm LogLevel
420: Gives the verbosity level that is used when logging messages from
421: .Nm ssh .
422: The possible values are:
423: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2 and DEBUG3.
1.6.2.1 margarid 424: The default is INFO.
425: DEBUG and DEBUG1 are equivalent.
426: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 427: .It Cm MACs
428: Specifies the MAC (message authentication code) algorithms
429: in order of preference.
430: The MAC algorithm is used in protocol version 2
431: for data integrity protection.
432: Multiple algorithms must be comma-separated.
433: The default is
434: .Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 .
435: .It Cm NoHostAuthenticationForLocalhost
436: This option can be used if the home directory is shared across machines.
437: In this case localhost will refer to a different machine on each of
438: the machines and the user will get many warnings about changed host keys.
439: However, this option disables host authentication for localhost.
440: The argument to this keyword must be
441: .Dq yes
442: or
443: .Dq no .
444: The default is to check the host key for localhost.
445: .It Cm NumberOfPasswordPrompts
446: Specifies the number of password prompts before giving up.
447: The argument to this keyword must be an integer.
448: Default is 3.
449: .It Cm PasswordAuthentication
450: Specifies whether to use password authentication.
451: The argument to this keyword must be
452: .Dq yes
453: or
454: .Dq no .
455: The default is
456: .Dq yes .
457: .It Cm Port
458: Specifies the port number to connect on the remote host.
459: Default is 22.
460: .It Cm PreferredAuthentications
461: Specifies the order in which the client should try protocol 2
1.6.2.2 brad 462: authentication methods.
463: This allows a client to prefer one method (e.g.
1.1 stevesk 464: .Cm keyboard-interactive )
465: over another method (e.g.
466: .Cm password )
467: The default for this option is:
468: .Dq hostbased,publickey,keyboard-interactive,password .
469: .It Cm Protocol
470: Specifies the protocol versions
471: .Nm ssh
472: should support in order of preference.
473: The possible values are
474: .Dq 1
475: and
476: .Dq 2 .
477: Multiple versions must be comma-separated.
478: The default is
479: .Dq 2,1 .
480: This means that
481: .Nm ssh
482: tries version 2 and falls back to version 1
483: if version 2 is not available.
484: .It Cm ProxyCommand
485: Specifies the command to use to connect to the server.
486: The command
487: string extends to the end of the line, and is executed with
488: .Pa /bin/sh .
489: In the command string,
490: .Ql %h
491: will be substituted by the host name to
492: connect and
493: .Ql %p
494: by the port.
495: The command can be basically anything,
496: and should read from its standard input and write to its standard output.
497: It should eventually connect an
498: .Xr sshd 8
499: server running on some machine, or execute
500: .Ic sshd -i
501: somewhere.
502: Host key management will be done using the
503: HostName of the host being connected (defaulting to the name typed by
504: the user).
1.6.2.1 margarid 505: Setting the command to
506: .Dq none
1.6 markus 507: disables this option entirely.
1.1 stevesk 508: Note that
509: .Cm CheckHostIP
510: is not available for connects with a proxy command.
511: .Pp
512: .It Cm PubkeyAuthentication
513: Specifies whether to try public key authentication.
514: The argument to this keyword must be
515: .Dq yes
516: or
517: .Dq no .
518: The default is
519: .Dq yes .
520: This option applies to protocol version 2 only.
521: .It Cm RemoteForward
522: Specifies that a TCP/IP port on the remote machine be forwarded over
523: the secure channel to the specified host and port from the local machine.
524: The first argument must be a port number, and the second must be
525: .Ar host:port .
526: IPv6 addresses can be specified with an alternative syntax:
527: .Ar host/port .
528: Multiple forwardings may be specified, and additional
529: forwardings can be given on the command line.
530: Only the superuser can forward privileged ports.
531: .It Cm RhostsRSAAuthentication
532: Specifies whether to try rhosts based authentication with RSA host
533: authentication.
534: The argument must be
535: .Dq yes
536: or
537: .Dq no .
538: The default is
539: .Dq no .
540: This option applies to protocol version 1 only and requires
541: .Nm ssh
542: to be setuid root.
543: .It Cm RSAAuthentication
544: Specifies whether to try RSA authentication.
545: The argument to this keyword must be
546: .Dq yes
547: or
548: .Dq no .
549: RSA authentication will only be
550: attempted if the identity file exists, or an authentication agent is
551: running.
552: The default is
553: .Dq yes .
554: Note that this option applies to protocol version 1 only.
1.6.2.3 ! brad 555: .It Cm ServerAliveInterval
! 556: Sets a timeout interval in seconds after which if no data has been received
! 557: from the server,
! 558: .Nm ssh
! 559: will send a message through the encrypted
! 560: channel to request a response from the server.
! 561: The default
! 562: is 0, indicating that these messages will not be sent to the server.
! 563: This option applies to protocol version 2 only.
! 564: .It Cm ServerAliveCountMax
! 565: Sets the number of server alive messages (see above) which may be
! 566: sent without
! 567: .Nm ssh
! 568: receiving any messages back from the server.
! 569: If this threshold is reached while server alive messages are being sent,
! 570: .Nm ssh
! 571: will disconnect from the server, terminating the session.
! 572: It is important to note that the use of server alive messages is very
! 573: different from
! 574: .Cm TCPKeepAlive
! 575: (below).
! 576: The server alive messages are sent through the encrypted channel
! 577: and therefore will not be spoofable.
! 578: The TCP keepalive option enabled by
! 579: .Cm TCPKeepAlive
! 580: is spoofable.
! 581: The server alive mechanism is valuable when the client or
! 582: server depend on knowing when a connection has become inactive.
! 583: .Pp
! 584: The default value is 3.
! 585: If, for example,
! 586: .Cm ServerAliveInterval
! 587: (above) is set to 15, and
! 588: .Cm ServerAliveCountMax
! 589: is left at the default, if the server becomes unresponsive ssh
! 590: will disconnect after approximately 45 seconds.
1.1 stevesk 591: .It Cm SmartcardDevice
1.6.2.2 brad 592: Specifies which smartcard device to use.
593: The argument to this keyword is the device
1.1 stevesk 594: .Nm ssh
595: should use to communicate with a smartcard used for storing the user's
1.6.2.2 brad 596: private RSA key.
597: By default, no device is specified and smartcard support is not activated.
1.1 stevesk 598: .It Cm StrictHostKeyChecking
599: If this flag is set to
600: .Dq yes ,
601: .Nm ssh
602: will never automatically add host keys to the
603: .Pa $HOME/.ssh/known_hosts
604: file, and refuses to connect to hosts whose host key has changed.
605: This provides maximum protection against trojan horse attacks,
606: however, can be annoying when the
607: .Pa /etc/ssh/ssh_known_hosts
608: file is poorly maintained, or connections to new hosts are
609: frequently made.
610: This option forces the user to manually
611: add all new hosts.
612: If this flag is set to
613: .Dq no ,
614: .Nm ssh
615: will automatically add new host keys to the
616: user known hosts files.
617: If this flag is set to
618: .Dq ask ,
619: new host keys
620: will be added to the user known host files only after the user
621: has confirmed that is what they really want to do, and
622: .Nm ssh
623: will refuse to connect to hosts whose host key has changed.
624: The host keys of
625: known hosts will be verified automatically in all cases.
626: The argument must be
627: .Dq yes ,
628: .Dq no
629: or
630: .Dq ask .
631: The default is
632: .Dq ask .
1.6.2.3 ! brad 633: .It Cm TCPKeepAlive
! 634: Specifies whether the system should send TCP keepalive messages to the
! 635: other side.
! 636: If they are sent, death of the connection or crash of one
! 637: of the machines will be properly noticed.
! 638: However, this means that
! 639: connections will die if the route is down temporarily, and some people
! 640: find it annoying.
! 641: .Pp
! 642: The default is
! 643: .Dq yes
! 644: (to send TCP keepalive messages), and the client will notice
! 645: if the network goes down or the remote host dies.
! 646: This is important in scripts, and many users want it too.
! 647: .Pp
! 648: To disable TCP keepalive messages, the value should be set to
! 649: .Dq no .
1.1 stevesk 650: .It Cm UsePrivilegedPort
651: Specifies whether to use a privileged port for outgoing connections.
652: The argument must be
653: .Dq yes
654: or
655: .Dq no .
656: The default is
657: .Dq no .
1.4 stevesk 658: If set to
659: .Dq yes
660: .Nm ssh
661: must be setuid root.
1.1 stevesk 662: Note that this option must be set to
663: .Dq yes
1.6.2.2 brad 664: for
1.1 stevesk 665: .Cm RhostsRSAAuthentication
1.6.2.2 brad 666: with older servers.
1.1 stevesk 667: .It Cm User
668: Specifies the user to log in as.
669: This can be useful when a different user name is used on different machines.
670: This saves the trouble of
671: having to remember to give the user name on the command line.
672: .It Cm UserKnownHostsFile
673: Specifies a file to use for the user
674: host key database instead of
675: .Pa $HOME/.ssh/known_hosts .
1.6.2.2 brad 676: .It Cm VerifyHostKeyDNS
677: Specifies whether to verify the remote key using DNS and SSHFP resource
678: records.
1.6.2.3 ! brad 679: If this option is set to
! 680: .Dq yes ,
! 681: the client will implicitly trust keys that match a secure fingerprint
! 682: from DNS.
! 683: Insecure fingerprints will be handled as if this option was set to
! 684: .Dq ask .
! 685: If this option is set to
! 686: .Dq ask ,
! 687: information on fingerprint match will be displayed, but the user will still
! 688: need to confirm new host keys according to the
! 689: .Cm StrictHostKeyChecking
! 690: option.
! 691: The argument must be
! 692: .Dq yes ,
! 693: .Dq no
! 694: or
! 695: .Dq ask .
1.6.2.2 brad 696: The default is
697: .Dq no .
698: Note that this option applies to protocol version 2 only.
1.1 stevesk 699: .It Cm XAuthLocation
1.5 stevesk 700: Specifies the full pathname of the
1.1 stevesk 701: .Xr xauth 1
702: program.
703: The default is
704: .Pa /usr/X11R6/bin/xauth .
705: .El
706: .Sh FILES
707: .Bl -tag -width Ds
708: .It Pa $HOME/.ssh/config
709: This is the per-user configuration file.
710: The format of this file is described above.
711: This file is used by the
712: .Nm ssh
713: client.
714: This file does not usually contain any sensitive information,
715: but the recommended permissions are read/write for the user, and not
716: accessible by others.
717: .It Pa /etc/ssh/ssh_config
718: Systemwide configuration file.
719: This file provides defaults for those
720: values that are not specified in the user's configuration file, and
721: for those users who do not have a configuration file.
722: This file must be world-readable.
723: .El
1.6.2.2 brad 724: .Sh SEE ALSO
725: .Xr ssh 1
1.1 stevesk 726: .Sh AUTHORS
727: OpenSSH is a derivative of the original and free
728: ssh 1.2.12 release by Tatu Ylonen.
729: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
730: Theo de Raadt and Dug Song
731: removed many bugs, re-added newer features and
732: created OpenSSH.
733: Markus Friedl contributed the support for SSH
734: protocol versions 1.5 and 2.0.