Annotation of src/usr.bin/ssh/sshd_config.5, Revision 1.22
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: .\"
1.22 ! markus 37: .\" $OpenBSD: sshd_config.5,v 1.21 2003/07/22 13:35:22 markus Exp $
1.1 stevesk 38: .Dd September 25, 1999
39: .Dt SSHD_CONFIG 5
40: .Os
41: .Sh NAME
42: .Nm sshd_config
43: .Nd OpenSSH SSH daemon configuration file
44: .Sh SYNOPSIS
45: .Bl -tag -width Ds -compact
46: .It Pa /etc/ssh/sshd_config
47: .El
48: .Sh DESCRIPTION
49: .Nm sshd
50: reads configuration data from
51: .Pa /etc/ssh/sshd_config
52: (or the file specified with
53: .Fl f
54: on the command line).
55: The file contains keyword-argument pairs, one per line.
56: Lines starting with
57: .Ql #
58: and empty lines are interpreted as comments.
59: .Pp
60: The possible
61: keywords and their meanings are as follows (note that
62: keywords are case-insensitive and arguments are case-sensitive):
63: .Bl -tag -width Ds
64: .It Cm AllowGroups
65: This keyword can be followed by a list of group name patterns, separated
66: by spaces.
67: If specified, login is allowed only for users whose primary
68: group or supplementary group list matches one of the patterns.
69: .Ql \&*
70: and
1.16 mouring 71: .Ql \&?
1.1 stevesk 72: can be used as
73: wildcards in the patterns.
74: Only group names are valid; a numerical group ID is not recognized.
75: By default, login is allowed for all groups.
76: .Pp
77: .It Cm AllowTcpForwarding
78: Specifies whether TCP forwarding is permitted.
79: The default is
80: .Dq yes .
81: Note that disabling TCP forwarding does not improve security unless
82: users are also denied shell access, as they can always install their
83: own forwarders.
84: .Pp
85: .It Cm AllowUsers
86: This keyword can be followed by a list of user name patterns, separated
87: by spaces.
1.14 jmc 88: If specified, login is allowed only for user names that
1.1 stevesk 89: match one of the patterns.
90: .Ql \&*
91: and
1.16 mouring 92: .Ql \&?
1.1 stevesk 93: can be used as
94: wildcards in the patterns.
95: Only user names are valid; a numerical user ID is not recognized.
96: By default, login is allowed for all users.
97: If the pattern takes the form USER@HOST then USER and HOST
98: are separately checked, restricting logins to particular
99: users from particular hosts.
100: .Pp
101: .It Cm AuthorizedKeysFile
102: Specifies the file that contains the public keys that can be used
103: for user authentication.
104: .Cm AuthorizedKeysFile
105: may contain tokens of the form %T which are substituted during connection
1.17 jmc 106: set-up.
107: The following tokens are defined: %% is replaced by a literal '%',
1.1 stevesk 108: %h is replaced by the home directory of the user being authenticated and
109: %u is replaced by the username of that user.
110: After expansion,
111: .Cm AuthorizedKeysFile
112: is taken to be an absolute path or one relative to the user's home
113: directory.
114: The default is
115: .Dq .ssh/authorized_keys .
116: .It Cm Banner
117: In some jurisdictions, sending a warning message before authentication
118: may be relevant for getting legal protection.
119: The contents of the specified file are sent to the remote user before
120: authentication is allowed.
121: This option is only available for protocol version 2.
122: By default, no banner is displayed.
123: .Pp
124: .It Cm ChallengeResponseAuthentication
125: Specifies whether challenge response authentication is allowed.
126: All authentication styles from
127: .Xr login.conf 5
128: are supported.
129: The default is
130: .Dq yes .
131: .It Cm Ciphers
132: Specifies the ciphers allowed for protocol version 2.
133: Multiple ciphers must be comma-separated.
134: The default is
135: .Pp
136: .Bd -literal
137: ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
1.20 djm 138: aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr''
1.1 stevesk 139: .Ed
140: .It Cm ClientAliveInterval
141: Sets a timeout interval in seconds after which if no data has been received
142: from the client,
143: .Nm sshd
144: will send a message through the encrypted
145: channel to request a response from the client.
146: The default
147: is 0, indicating that these messages will not be sent to the client.
148: This option applies to protocol version 2 only.
149: .It Cm ClientAliveCountMax
150: Sets the number of client alive messages (see above) which may be
151: sent without
152: .Nm sshd
1.17 jmc 153: receiving any messages back from the client.
154: If this threshold is reached while client alive messages are being sent,
1.1 stevesk 155: .Nm sshd
1.17 jmc 156: will disconnect the client, terminating the session.
157: It is important to note that the use of client alive messages is very
158: different from
1.1 stevesk 159: .Cm KeepAlive
1.17 jmc 160: (below).
161: The client alive messages are sent through the encrypted channel
162: and therefore will not be spoofable.
163: The TCP keepalive option enabled by
1.1 stevesk 164: .Cm KeepAlive
1.17 jmc 165: is spoofable.
166: The client alive mechanism is valuable when the client or
1.1 stevesk 167: server depend on knowing when a connection has become inactive.
168: .Pp
1.17 jmc 169: The default value is 3.
170: If
1.1 stevesk 171: .Cm ClientAliveInterval
172: (above) is set to 15, and
173: .Cm ClientAliveCountMax
174: is left at the default, unresponsive ssh clients
175: will be disconnected after approximately 45 seconds.
1.3 markus 176: .It Cm Compression
177: Specifies whether compression is allowed.
178: The argument must be
179: .Dq yes
180: or
181: .Dq no .
182: The default is
183: .Dq yes .
1.1 stevesk 184: .It Cm DenyGroups
185: This keyword can be followed by a list of group name patterns, separated
186: by spaces.
187: Login is disallowed for users whose primary group or supplementary
188: group list matches one of the patterns.
189: .Ql \&*
190: and
1.16 mouring 191: .Ql \&?
1.1 stevesk 192: can be used as
193: wildcards in the patterns.
194: Only group names are valid; a numerical group ID is not recognized.
195: By default, login is allowed for all groups.
196: .Pp
197: .It Cm DenyUsers
198: This keyword can be followed by a list of user name patterns, separated
199: by spaces.
200: Login is disallowed for user names that match one of the patterns.
201: .Ql \&*
202: and
1.16 mouring 203: .Ql \&?
1.1 stevesk 204: can be used as wildcards in the patterns.
205: Only user names are valid; a numerical user ID is not recognized.
206: By default, login is allowed for all users.
207: If the pattern takes the form USER@HOST then USER and HOST
208: are separately checked, restricting logins to particular
209: users from particular hosts.
210: .It Cm GatewayPorts
211: Specifies whether remote hosts are allowed to connect to ports
212: forwarded for the client.
213: By default,
214: .Nm sshd
1.15 jmc 215: binds remote port forwardings to the loopback address.
216: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 217: .Cm GatewayPorts
218: can be used to specify that
219: .Nm sshd
220: should bind remote port forwardings to the wildcard address,
221: thus allowing remote hosts to connect to forwarded ports.
222: The argument must be
223: .Dq yes
224: or
225: .Dq no .
226: The default is
227: .Dq no .
228: .It Cm HostbasedAuthentication
229: Specifies whether rhosts or /etc/hosts.equiv authentication together
230: with successful public key client host authentication is allowed
231: (hostbased authentication).
232: This option is similar to
233: .Cm RhostsRSAAuthentication
234: and applies to protocol version 2 only.
235: The default is
236: .Dq no .
237: .It Cm HostKey
238: Specifies a file containing a private host key
239: used by SSH.
240: The default is
241: .Pa /etc/ssh/ssh_host_key
242: for protocol version 1, and
243: .Pa /etc/ssh/ssh_host_rsa_key
244: and
245: .Pa /etc/ssh/ssh_host_dsa_key
246: for protocol version 2.
247: Note that
248: .Nm sshd
249: will refuse to use a file if it is group/world-accessible.
250: It is possible to have multiple host key files.
251: .Dq rsa1
252: keys are used for version 1 and
253: .Dq dsa
254: or
255: .Dq rsa
256: are used for version 2 of the SSH protocol.
257: .It Cm IgnoreRhosts
258: Specifies that
259: .Pa .rhosts
260: and
261: .Pa .shosts
262: files will not be used in
263: .Cm RhostsRSAAuthentication
264: or
265: .Cm HostbasedAuthentication .
266: .Pp
267: .Pa /etc/hosts.equiv
268: and
269: .Pa /etc/shosts.equiv
270: are still used.
271: The default is
272: .Dq yes .
273: .It Cm IgnoreUserKnownHosts
274: Specifies whether
275: .Nm sshd
276: should ignore the user's
277: .Pa $HOME/.ssh/known_hosts
278: during
279: .Cm RhostsRSAAuthentication
280: or
281: .Cm HostbasedAuthentication .
282: The default is
283: .Dq no .
284: .It Cm KeepAlive
285: Specifies whether the system should send TCP keepalive messages to the
286: other side.
287: If they are sent, death of the connection or crash of one
288: of the machines will be properly noticed.
289: However, this means that
290: connections will die if the route is down temporarily, and some people
291: find it annoying.
292: On the other hand, if keepalives are not sent,
293: sessions may hang indefinitely on the server, leaving
294: .Dq ghost
295: users and consuming server resources.
296: .Pp
297: The default is
298: .Dq yes
299: (to send keepalives), and the server will notice
300: if the network goes down or the client host crashes.
301: This avoids infinitely hanging sessions.
302: .Pp
303: To disable keepalives, the value should be set to
304: .Dq no .
305: .It Cm KerberosAuthentication
306: Specifies whether Kerberos authentication is allowed.
307: This can be in the form of a Kerberos ticket, or if
308: .Cm PasswordAuthentication
309: is yes, the password provided by the user will be validated through
310: the Kerberos KDC.
311: To use this option, the server needs a
312: Kerberos servtab which allows the verification of the KDC's identity.
313: Default is
314: .Dq no .
315: .It Cm KerberosOrLocalPasswd
316: If set then if password authentication through Kerberos fails then
317: the password will be validated via any additional local mechanism
318: such as
319: .Pa /etc/passwd .
320: Default is
321: .Dq yes .
322: .It Cm KerberosTgtPassing
323: Specifies whether a Kerberos TGT may be forwarded to the server.
324: Default is
1.21 markus 325: .Dq no .
1.1 stevesk 326: .It Cm KerberosTicketCleanup
327: Specifies whether to automatically destroy the user's ticket cache
328: file on logout.
329: Default is
330: .Dq yes .
331: .It Cm KeyRegenerationInterval
332: In protocol version 1, the ephemeral server key is automatically regenerated
333: after this many seconds (if it has been used).
334: The purpose of regeneration is to prevent
335: decrypting captured sessions by later breaking into the machine and
336: stealing the keys.
337: The key is never stored anywhere.
338: If the value is 0, the key is never regenerated.
339: The default is 3600 (seconds).
340: .It Cm ListenAddress
341: Specifies the local addresses
342: .Nm sshd
343: should listen on.
344: The following forms may be used:
345: .Pp
346: .Bl -item -offset indent -compact
347: .It
348: .Cm ListenAddress
349: .Sm off
350: .Ar host No | Ar IPv4_addr No | Ar IPv6_addr
351: .Sm on
352: .It
353: .Cm ListenAddress
354: .Sm off
355: .Ar host No | Ar IPv4_addr No : Ar port
356: .Sm on
357: .It
358: .Cm ListenAddress
359: .Sm off
360: .Oo
361: .Ar host No | Ar IPv6_addr Oc : Ar port
362: .Sm on
363: .El
364: .Pp
365: If
366: .Ar port
367: is not specified,
368: .Nm sshd
369: will listen on the address and all prior
370: .Cm Port
1.17 jmc 371: options specified.
372: The default is to listen on all local addresses.
1.15 jmc 373: Multiple
1.1 stevesk 374: .Cm ListenAddress
1.17 jmc 375: options are permitted.
376: Additionally, any
1.1 stevesk 377: .Cm Port
378: options must precede this option for non port qualified addresses.
379: .It Cm LoginGraceTime
380: The server disconnects after this time if the user has not
381: successfully logged in.
382: If the value is 0, there is no time limit.
1.12 stevesk 383: The default is 120 seconds.
1.1 stevesk 384: .It Cm LogLevel
385: Gives the verbosity level that is used when logging messages from
386: .Nm sshd .
387: The possible values are:
388: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2 and DEBUG3.
1.15 jmc 389: The default is INFO.
390: DEBUG and DEBUG1 are equivalent.
391: DEBUG2 and DEBUG3 each specify higher levels of debugging output.
392: Logging with a DEBUG level violates the privacy of users and is not recommended.
1.1 stevesk 393: .It Cm MACs
394: Specifies the available MAC (message authentication code) algorithms.
395: The MAC algorithm is used in protocol version 2
396: for data integrity protection.
397: Multiple algorithms must be comma-separated.
398: The default is
399: .Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 .
400: .It Cm MaxStartups
401: Specifies the maximum number of concurrent unauthenticated connections to the
402: .Nm sshd
403: daemon.
404: Additional connections will be dropped until authentication succeeds or the
405: .Cm LoginGraceTime
406: expires for a connection.
407: The default is 10.
408: .Pp
409: Alternatively, random early drop can be enabled by specifying
410: the three colon separated values
411: .Dq start:rate:full
412: (e.g., "10:30:60").
413: .Nm sshd
414: will refuse connection attempts with a probability of
415: .Dq rate/100
416: (30%)
417: if there are currently
418: .Dq start
419: (10)
420: unauthenticated connections.
421: The probability increases linearly and all connection attempts
422: are refused if the number of unauthenticated connections reaches
423: .Dq full
424: (60).
425: .It Cm PasswordAuthentication
426: Specifies whether password authentication is allowed.
427: The default is
428: .Dq yes .
429: .It Cm PermitEmptyPasswords
430: When password authentication is allowed, it specifies whether the
431: server allows login to accounts with empty password strings.
432: The default is
433: .Dq no .
434: .It Cm PermitRootLogin
435: Specifies whether root can login using
436: .Xr ssh 1 .
437: The argument must be
438: .Dq yes ,
439: .Dq without-password ,
440: .Dq forced-commands-only
441: or
442: .Dq no .
443: The default is
444: .Dq yes .
445: .Pp
446: If this option is set to
447: .Dq without-password
448: password authentication is disabled for root.
449: .Pp
450: If this option is set to
451: .Dq forced-commands-only
452: root login with public key authentication will be allowed,
453: but only if the
454: .Ar command
455: option has been specified
456: (which may be useful for taking remote backups even if root login is
1.17 jmc 457: normally not allowed).
458: All other authentication methods are disabled for root.
1.1 stevesk 459: .Pp
460: If this option is set to
461: .Dq no
462: root is not allowed to login.
1.6 markus 463: .It Cm PermitUserEnvironment
464: Specifies whether
465: .Pa ~/.ssh/environment
1.9 stevesk 466: and
1.6 markus 467: .Cm environment=
468: options in
469: .Pa ~/.ssh/authorized_keys
1.9 stevesk 470: are processed by
471: .Nm sshd .
1.6 markus 472: The default is
473: .Dq no .
1.9 stevesk 474: Enabling environment processing may enable users to bypass access
475: restrictions in some configurations using mechanisms such as
476: .Ev LD_PRELOAD .
1.1 stevesk 477: .It Cm PidFile
1.4 stevesk 478: Specifies the file that contains the process ID of the
1.1 stevesk 479: .Nm sshd
480: daemon.
481: The default is
482: .Pa /var/run/sshd.pid .
483: .It Cm Port
484: Specifies the port number that
485: .Nm sshd
486: listens on.
487: The default is 22.
488: Multiple options of this type are permitted.
489: See also
490: .Cm ListenAddress .
491: .It Cm PrintLastLog
492: Specifies whether
493: .Nm sshd
494: should print the date and time when the user last logged in.
495: The default is
496: .Dq yes .
497: .It Cm PrintMotd
498: Specifies whether
499: .Nm sshd
500: should print
501: .Pa /etc/motd
502: when a user logs in interactively.
503: (On some systems it is also printed by the shell,
504: .Pa /etc/profile ,
505: or equivalent.)
506: The default is
507: .Dq yes .
508: .It Cm Protocol
509: Specifies the protocol versions
510: .Nm sshd
1.5 stevesk 511: supports.
1.1 stevesk 512: The possible values are
513: .Dq 1
514: and
515: .Dq 2 .
516: Multiple versions must be comma-separated.
517: The default is
518: .Dq 2,1 .
1.5 stevesk 519: Note that the order of the protocol list does not indicate preference,
520: because the client selects among multiple protocol versions offered
521: by the server.
522: Specifying
523: .Dq 2,1
524: is identical to
525: .Dq 1,2 .
1.1 stevesk 526: .It Cm PubkeyAuthentication
527: Specifies whether public key authentication is allowed.
528: The default is
529: .Dq yes .
530: Note that this option applies to protocol version 2 only.
531: .Cm RhostsRSAAuthentication
532: should be used
533: instead, because it performs RSA-based host authentication in addition
534: to normal rhosts or /etc/hosts.equiv authentication.
535: The default is
536: .Dq no .
537: This option applies to protocol version 1 only.
538: .It Cm RhostsRSAAuthentication
539: Specifies whether rhosts or /etc/hosts.equiv authentication together
540: with successful RSA host authentication is allowed.
541: The default is
542: .Dq no .
543: This option applies to protocol version 1 only.
544: .It Cm RSAAuthentication
545: Specifies whether pure RSA authentication is allowed.
546: The default is
547: .Dq yes .
548: This option applies to protocol version 1 only.
549: .It Cm ServerKeyBits
550: Defines the number of bits in the ephemeral protocol version 1 server key.
551: The minimum value is 512, and the default is 768.
552: .It Cm StrictModes
553: Specifies whether
554: .Nm sshd
555: should check file modes and ownership of the
556: user's files and home directory before accepting login.
557: This is normally desirable because novices sometimes accidentally leave their
558: directory or files world-writable.
559: The default is
560: .Dq yes .
561: .It Cm Subsystem
562: Configures an external subsystem (e.g., file transfer daemon).
563: Arguments should be a subsystem name and a command to execute upon subsystem
564: request.
565: The command
566: .Xr sftp-server 8
567: implements the
568: .Dq sftp
569: file transfer subsystem.
570: By default no subsystems are defined.
571: Note that this option applies to protocol version 2 only.
572: .It Cm SyslogFacility
573: Gives the facility code that is used when logging messages from
574: .Nm sshd .
575: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
576: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
577: The default is AUTH.
1.18 markus 578: .It Cm UseDNS
579: Specifies whether
580: .Nm sshd
581: should lookup the remote host name and check that
582: the resolved host name for the remote IP address maps back to the
583: very same IP address.
584: The default is
585: .Dq yes .
1.1 stevesk 586: .It Cm UseLogin
587: Specifies whether
588: .Xr login 1
589: is used for interactive login sessions.
590: The default is
591: .Dq no .
592: Note that
593: .Xr login 1
594: is never used for remote command execution.
595: Note also, that if this is enabled,
596: .Cm X11Forwarding
597: will be disabled because
598: .Xr login 1
599: does not know how to handle
600: .Xr xauth 1
1.15 jmc 601: cookies.
602: If
1.1 stevesk 603: .Cm UsePrivilegeSeparation
604: is specified, it will be disabled after authentication.
605: .It Cm UsePrivilegeSeparation
606: Specifies whether
607: .Nm sshd
1.2 stevesk 608: separates privileges by creating an unprivileged child process
1.15 jmc 609: to deal with incoming network traffic.
610: After successful authentication, another process will be created that has
611: the privilege of the authenticated user.
612: The goal of privilege separation is to prevent privilege
1.1 stevesk 613: escalation by containing any corruption within the unprivileged processes.
614: The default is
615: .Dq yes .
616: .It Cm X11DisplayOffset
617: Specifies the first display number available for
618: .Nm sshd Ns 's
619: X11 forwarding.
620: This prevents
621: .Nm sshd
622: from interfering with real X11 servers.
623: The default is 10.
624: .It Cm X11Forwarding
625: Specifies whether X11 forwarding is permitted.
1.13 stevesk 626: The argument must be
627: .Dq yes
628: or
629: .Dq no .
1.1 stevesk 630: The default is
631: .Dq no .
1.13 stevesk 632: .Pp
633: When X11 forwarding is enabled, there may be additional exposure to
634: the server and to client displays if the
635: .Nm sshd
636: proxy display is configured to listen on the wildcard address (see
637: .Cm X11UseLocalhost
638: below), however this is not the default.
639: Additionally, the authentication spoofing and authentication data
640: verification and substitution occur on the client side.
641: The security risk of using X11 forwarding is that the client's X11
642: display server may be exposed to attack when the ssh client requests
643: forwarding (see the warnings for
644: .Cm ForwardX11
645: in
1.19 jmc 646: .Xr ssh_config 5 ) .
1.13 stevesk 647: A system administrator may have a stance in which they want to
648: protect clients that may expose themselves to attack by unwittingly
649: requesting X11 forwarding, which can warrant a
650: .Dq no
651: setting.
652: .Pp
653: Note that disabling X11 forwarding does not prevent users from
654: forwarding X11 traffic, as users can always install their own forwarders.
1.1 stevesk 655: X11 forwarding is automatically disabled if
656: .Cm UseLogin
657: is enabled.
658: .It Cm X11UseLocalhost
659: Specifies whether
660: .Nm sshd
661: should bind the X11 forwarding server to the loopback address or to
1.15 jmc 662: the wildcard address.
663: By default,
1.1 stevesk 664: .Nm sshd
665: binds the forwarding server to the loopback address and sets the
666: hostname part of the
667: .Ev DISPLAY
668: environment variable to
669: .Dq localhost .
1.8 stevesk 670: This prevents remote hosts from connecting to the proxy display.
1.1 stevesk 671: However, some older X11 clients may not function with this
672: configuration.
673: .Cm X11UseLocalhost
674: may be set to
675: .Dq no
676: to specify that the forwarding server should be bound to the wildcard
677: address.
678: The argument must be
679: .Dq yes
680: or
681: .Dq no .
682: The default is
683: .Dq yes .
684: .It Cm XAuthLocation
1.11 stevesk 685: Specifies the full pathname of the
1.1 stevesk 686: .Xr xauth 1
687: program.
688: The default is
689: .Pa /usr/X11R6/bin/xauth .
690: .El
691: .Ss Time Formats
692: .Nm sshd
693: command-line arguments and configuration file options that specify time
694: may be expressed using a sequence of the form:
695: .Sm off
1.7 stevesk 696: .Ar time Op Ar qualifier ,
1.1 stevesk 697: .Sm on
698: where
699: .Ar time
700: is a positive integer value and
701: .Ar qualifier
702: is one of the following:
703: .Pp
704: .Bl -tag -width Ds -compact -offset indent
705: .It Cm <none>
706: seconds
707: .It Cm s | Cm S
708: seconds
709: .It Cm m | Cm M
710: minutes
711: .It Cm h | Cm H
712: hours
713: .It Cm d | Cm D
714: days
715: .It Cm w | Cm W
716: weeks
717: .El
718: .Pp
719: Each member of the sequence is added together to calculate
720: the total time value.
721: .Pp
722: Time format examples:
723: .Pp
724: .Bl -tag -width Ds -compact -offset indent
725: .It 600
726: 600 seconds (10 minutes)
727: .It 10m
728: 10 minutes
729: .It 1h30m
730: 1 hour 30 minutes (90 minutes)
731: .El
732: .Sh FILES
733: .Bl -tag -width Ds
734: .It Pa /etc/ssh/sshd_config
735: Contains configuration data for
736: .Nm sshd .
737: This file should be writable by root only, but it is recommended
738: (though not necessary) that it be world-readable.
739: .El
1.19 jmc 740: .Sh SEE ALSO
741: .Xr sshd 8
1.1 stevesk 742: .Sh AUTHORS
743: OpenSSH is a derivative of the original and free
744: ssh 1.2.12 release by Tatu Ylonen.
745: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
746: Theo de Raadt and Dug Song
747: removed many bugs, re-added newer features and
748: created OpenSSH.
749: Markus Friedl contributed the support for SSH
750: protocol versions 1.5 and 2.0.
751: Niels Provos and Markus Friedl contributed support
752: for privilege separation.
![[BACK]](/icons/back.gif){kind=icon}
Return to sshd_config.5 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh