Annotation of src/usr.bin/ssh/sshd_config.5, Revision 1.148
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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29: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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1.148 ! djm 36: .\" $OpenBSD: sshd_config.5,v 1.147 2012/10/31 08:04:50 jmc Exp $
! 37: .Dd $Mdocdate: October 31 2012 $
1.1 stevesk 38: .Dt SSHD_CONFIG 5
39: .Os
40: .Sh NAME
41: .Nm sshd_config
42: .Nd OpenSSH SSH daemon configuration file
43: .Sh SYNOPSIS
1.71 jmc 44: .Nm /etc/ssh/sshd_config
1.1 stevesk 45: .Sh DESCRIPTION
1.53 jmc 46: .Xr sshd 8
1.1 stevesk 47: reads configuration data from
48: .Pa /etc/ssh/sshd_config
49: (or the file specified with
50: .Fl f
51: on the command line).
52: The file contains keyword-argument pairs, one per line.
53: Lines starting with
54: .Ql #
55: and empty lines are interpreted as comments.
1.56 dtucker 56: Arguments may optionally be enclosed in double quotes
57: .Pq \&"
58: in order to represent arguments containing spaces.
1.1 stevesk 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
1.30 djm 64: .It Cm AcceptEnv
65: Specifies what environment variables sent by the client will be copied into
66: the session's
67: .Xr environ 7 .
68: See
69: .Cm SendEnv
70: in
71: .Xr ssh_config 5
72: for how to configure the client.
1.31 djm 73: Note that environment passing is only supported for protocol 2.
1.30 djm 74: Variables are specified by name, which may contain the wildcard characters
1.51 jmc 75: .Ql *
1.30 djm 76: and
77: .Ql \&? .
1.31 djm 78: Multiple environment variables may be separated by whitespace or spread
1.30 djm 79: across multiple
80: .Cm AcceptEnv
81: directives.
1.31 djm 82: Be warned that some environment variables could be used to bypass restricted
1.30 djm 83: user environments.
84: For this reason, care should be taken in the use of this directive.
85: The default is not to accept any environment variables.
1.37 djm 86: .It Cm AddressFamily
87: Specifies which address family should be used by
1.53 jmc 88: .Xr sshd 8 .
1.37 djm 89: Valid arguments are
90: .Dq any ,
91: .Dq inet
1.52 jmc 92: (use IPv4 only), or
1.37 djm 93: .Dq inet6
94: (use IPv6 only).
95: The default is
96: .Dq any .
1.89 jmc 97: .It Cm AllowAgentForwarding
98: Specifies whether
99: .Xr ssh-agent 1
100: forwarding is permitted.
101: The default is
102: .Dq yes .
103: Note that disabling agent forwarding does not improve security
104: unless users are also denied shell access, as they can always install
105: their own forwarders.
1.1 stevesk 106: .It Cm AllowGroups
107: This keyword can be followed by a list of group name patterns, separated
108: by spaces.
109: If specified, login is allowed only for users whose primary
110: group or supplementary group list matches one of the patterns.
111: Only group names are valid; a numerical group ID is not recognized.
112: By default, login is allowed for all groups.
1.54 jmc 113: The allow/deny directives are processed in the following order:
114: .Cm DenyUsers ,
115: .Cm AllowUsers ,
116: .Cm DenyGroups ,
117: and finally
118: .Cm AllowGroups .
1.49 jmc 119: .Pp
120: See
121: .Sx PATTERNS
122: in
123: .Xr ssh_config 5
124: for more information on patterns.
1.1 stevesk 125: .It Cm AllowTcpForwarding
126: Specifies whether TCP forwarding is permitted.
127: The default is
128: .Dq yes .
129: Note that disabling TCP forwarding does not improve security unless
130: users are also denied shell access, as they can always install their
131: own forwarders.
132: .It Cm AllowUsers
133: This keyword can be followed by a list of user name patterns, separated
134: by spaces.
1.14 jmc 135: If specified, login is allowed only for user names that
1.1 stevesk 136: match one of the patterns.
137: Only user names are valid; a numerical user ID is not recognized.
138: By default, login is allowed for all users.
139: If the pattern takes the form USER@HOST then USER and HOST
140: are separately checked, restricting logins to particular
141: users from particular hosts.
1.54 jmc 142: The allow/deny directives are processed in the following order:
143: .Cm DenyUsers ,
144: .Cm AllowUsers ,
145: .Cm DenyGroups ,
146: and finally
147: .Cm AllowGroups .
1.49 jmc 148: .Pp
149: See
150: .Sx PATTERNS
151: in
152: .Xr ssh_config 5
153: for more information on patterns.
1.146 djm 154: .It Cm AuthorizedKeysCommand
1.147 jmc 155: Specifies a program to be used to look up the user's public keys.
1.146 djm 156: The program will be invoked with a single argument of the username
157: being authenticated, and should produce on standard output zero or
1.147 jmc 158: more lines of authorized_keys output (see
159: .Sx AUTHORIZED_KEYS
160: in
161: .Xr sshd 8 ) .
1.146 djm 162: If a key supplied by AuthorizedKeysCommand does not successfully authenticate
163: and authorize the user then public key authentication continues using the usual
164: .Cm AuthorizedKeysFile
165: files.
166: By default, no AuthorizedKeysCommand is run.
167: .It Cm AuthorizedKeysCommandUser
168: Specifies the user under whose account the AuthorizedKeysCommand is run.
169: It is recommended to use a dedicated user that has no other role on the host
170: than running authorized keys commands.
1.1 stevesk 171: .It Cm AuthorizedKeysFile
172: Specifies the file that contains the public keys that can be used
173: for user authentication.
1.124 djm 174: The format is described in the
175: .Sx AUTHORIZED_KEYS FILE FORMAT
176: section of
177: .Xr sshd 8 .
1.1 stevesk 178: .Cm AuthorizedKeysFile
179: may contain tokens of the form %T which are substituted during connection
1.52 jmc 180: setup.
1.17 jmc 181: The following tokens are defined: %% is replaced by a literal '%',
1.52 jmc 182: %h is replaced by the home directory of the user being authenticated, and
1.1 stevesk 183: %u is replaced by the username of that user.
184: After expansion,
185: .Cm AuthorizedKeysFile
186: is taken to be an absolute path or one relative to the user's home
187: directory.
1.133 jmc 188: Multiple files may be listed, separated by whitespace.
189: The default is
190: .Dq .ssh/authorized_keys .ssh/authorized_keys2 .
1.121 djm 191: .It Cm AuthorizedPrincipalsFile
192: Specifies a file that lists principal names that are accepted for
193: certificate authentication.
194: When using certificates signed by a key listed in
195: .Cm TrustedUserCAKeys ,
196: this file lists names, one of which must appear in the certificate for it
197: to be accepted for authentication.
1.125 jmc 198: Names are listed one per line preceded by key options (as described
1.124 djm 199: in
200: .Sx AUTHORIZED_KEYS FILE FORMAT
201: in
1.125 jmc 202: .Xr sshd 8 ) .
1.124 djm 203: Empty lines and comments starting with
1.121 djm 204: .Ql #
205: are ignored.
206: .Pp
207: .Cm AuthorizedPrincipalsFile
208: may contain tokens of the form %T which are substituted during connection
209: setup.
210: The following tokens are defined: %% is replaced by a literal '%',
211: %h is replaced by the home directory of the user being authenticated, and
212: %u is replaced by the username of that user.
213: After expansion,
214: .Cm AuthorizedPrincipalsFile
215: is taken to be an absolute path or one relative to the user's home
216: directory.
217: .Pp
1.138 djm 218: The default is
219: .Dq none ,
220: i.e. not to use a principals file \(en in this case, the username
1.121 djm 221: of the user must appear in a certificate's principals list for it to be
222: accepted.
223: Note that
224: .Cm AuthorizedPrincipalsFile
225: is only used when authentication proceeds using a CA listed in
226: .Cm TrustedUserCAKeys
227: and is not consulted for certification authorities trusted via
228: .Pa ~/.ssh/authorized_keys ,
229: though the
230: .Cm principals=
231: key option offers a similar facility (see
232: .Xr sshd 8
233: for details).
1.1 stevesk 234: .It Cm Banner
235: The contents of the specified file are sent to the remote user before
236: authentication is allowed.
1.78 djm 237: If the argument is
238: .Dq none
239: then no banner is displayed.
1.1 stevesk 240: This option is only available for protocol version 2.
241: By default, no banner is displayed.
242: .It Cm ChallengeResponseAuthentication
1.50 jmc 243: Specifies whether challenge-response authentication is allowed.
1.1 stevesk 244: All authentication styles from
245: .Xr login.conf 5
246: are supported.
247: The default is
248: .Dq yes .
1.80 djm 249: .It Cm ChrootDirectory
1.113 stevesk 250: Specifies the pathname of a directory to
1.80 djm 251: .Xr chroot 2
252: to after authentication.
1.113 stevesk 253: All components of the pathname must be root-owned directories that are
1.80 djm 254: not writable by any other user or group.
1.106 stevesk 255: After the chroot,
256: .Xr sshd 8
257: changes the working directory to the user's home directory.
1.80 djm 258: .Pp
1.113 stevesk 259: The pathname may contain the following tokens that are expanded at runtime once
1.80 djm 260: the connecting user has been authenticated: %% is replaced by a literal '%',
261: %h is replaced by the home directory of the user being authenticated, and
262: %u is replaced by the username of that user.
263: .Pp
264: The
265: .Cm ChrootDirectory
266: must contain the necessary files and directories to support the
1.103 stevesk 267: user's session.
1.80 djm 268: For an interactive session this requires at least a shell, typically
269: .Xr sh 1 ,
270: and basic
271: .Pa /dev
272: nodes such as
273: .Xr null 4 ,
274: .Xr zero 4 ,
275: .Xr stdin 4 ,
276: .Xr stdout 4 ,
277: .Xr stderr 4 ,
278: .Xr arandom 4
279: and
280: .Xr tty 4
281: devices.
282: For file transfer sessions using
1.105 jmc 283: .Dq sftp ,
1.80 djm 284: no additional configuration of the environment is necessary if the
1.105 jmc 285: in-process sftp server is used,
286: though sessions which use logging do require
1.104 stevesk 287: .Pa /dev/log
288: inside the chroot directory (see
289: .Xr sftp-server 8
1.81 jmc 290: for details).
1.80 djm 291: .Pp
292: The default is not to
293: .Xr chroot 2 .
1.1 stevesk 294: .It Cm Ciphers
295: Specifies the ciphers allowed for protocol version 2.
296: Multiple ciphers must be comma-separated.
1.34 dtucker 297: The supported ciphers are
298: .Dq 3des-cbc ,
299: .Dq aes128-cbc ,
300: .Dq aes192-cbc ,
301: .Dq aes256-cbc ,
302: .Dq aes128-ctr ,
303: .Dq aes192-ctr ,
304: .Dq aes256-ctr ,
1.43 djm 305: .Dq arcfour128 ,
306: .Dq arcfour256 ,
1.34 dtucker 307: .Dq arcfour ,
308: .Dq blowfish-cbc ,
309: and
310: .Dq cast128-cbc .
1.52 jmc 311: The default is:
312: .Bd -literal -offset 3n
1.100 naddy 313: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
314: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
315: aes256-cbc,arcfour
1.1 stevesk 316: .Ed
317: .It Cm ClientAliveCountMax
1.48 jmc 318: Sets the number of client alive messages (see below) which may be
1.1 stevesk 319: sent without
1.52 jmc 320: .Xr sshd 8
1.17 jmc 321: receiving any messages back from the client.
322: If this threshold is reached while client alive messages are being sent,
1.52 jmc 323: sshd will disconnect the client, terminating the session.
1.17 jmc 324: It is important to note that the use of client alive messages is very
325: different from
1.27 markus 326: .Cm TCPKeepAlive
1.17 jmc 327: (below).
328: The client alive messages are sent through the encrypted channel
329: and therefore will not be spoofable.
330: The TCP keepalive option enabled by
1.27 markus 331: .Cm TCPKeepAlive
1.17 jmc 332: is spoofable.
333: The client alive mechanism is valuable when the client or
1.1 stevesk 334: server depend on knowing when a connection has become inactive.
335: .Pp
1.17 jmc 336: The default value is 3.
337: If
1.1 stevesk 338: .Cm ClientAliveInterval
1.48 jmc 339: (see below) is set to 15, and
1.1 stevesk 340: .Cm ClientAliveCountMax
1.52 jmc 341: is left at the default, unresponsive SSH clients
1.1 stevesk 342: will be disconnected after approximately 45 seconds.
1.57 markus 343: This option applies to protocol version 2 only.
1.42 djm 344: .It Cm ClientAliveInterval
345: Sets a timeout interval in seconds after which if no data has been received
346: from the client,
1.52 jmc 347: .Xr sshd 8
1.42 djm 348: will send a message through the encrypted
349: channel to request a response from the client.
350: The default
351: is 0, indicating that these messages will not be sent to the client.
352: This option applies to protocol version 2 only.
1.3 markus 353: .It Cm Compression
1.44 markus 354: Specifies whether compression is allowed, or delayed until
355: the user has authenticated successfully.
1.3 markus 356: The argument must be
1.44 markus 357: .Dq yes ,
358: .Dq delayed ,
1.3 markus 359: or
360: .Dq no .
361: The default is
1.44 markus 362: .Dq delayed .
1.1 stevesk 363: .It Cm DenyGroups
364: This keyword can be followed by a list of group name patterns, separated
365: by spaces.
366: Login is disallowed for users whose primary group or supplementary
367: group list matches one of the patterns.
368: Only group names are valid; a numerical group ID is not recognized.
369: By default, login is allowed for all groups.
1.54 jmc 370: The allow/deny directives are processed in the following order:
371: .Cm DenyUsers ,
372: .Cm AllowUsers ,
373: .Cm DenyGroups ,
374: and finally
375: .Cm AllowGroups .
1.49 jmc 376: .Pp
377: See
378: .Sx PATTERNS
379: in
380: .Xr ssh_config 5
381: for more information on patterns.
1.1 stevesk 382: .It Cm DenyUsers
383: This keyword can be followed by a list of user name patterns, separated
384: by spaces.
385: Login is disallowed for user names that match one of the patterns.
386: Only user names are valid; a numerical user ID is not recognized.
387: By default, login is allowed for all users.
388: If the pattern takes the form USER@HOST then USER and HOST
389: are separately checked, restricting logins to particular
390: users from particular hosts.
1.54 jmc 391: The allow/deny directives are processed in the following order:
392: .Cm DenyUsers ,
393: .Cm AllowUsers ,
394: .Cm DenyGroups ,
395: and finally
396: .Cm AllowGroups .
1.49 jmc 397: .Pp
398: See
399: .Sx PATTERNS
400: in
401: .Xr ssh_config 5
402: for more information on patterns.
1.67 dtucker 403: .It Cm ForceCommand
404: Forces the execution of the command specified by
405: .Cm ForceCommand ,
1.84 djm 406: ignoring any command supplied by the client and
407: .Pa ~/.ssh/rc
408: if present.
1.67 dtucker 409: The command is invoked by using the user's login shell with the -c option.
410: This applies to shell, command, or subsystem execution.
411: It is most useful inside a
412: .Cm Match
413: block.
414: The command originally supplied by the client is available in the
415: .Ev SSH_ORIGINAL_COMMAND
416: environment variable.
1.82 djm 417: Specifying a command of
418: .Dq internal-sftp
419: will force the use of an in-process sftp server that requires no support
420: files when used with
421: .Cm ChrootDirectory .
1.1 stevesk 422: .It Cm GatewayPorts
423: Specifies whether remote hosts are allowed to connect to ports
424: forwarded for the client.
425: By default,
1.52 jmc 426: .Xr sshd 8
1.15 jmc 427: binds remote port forwardings to the loopback address.
428: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 429: .Cm GatewayPorts
1.52 jmc 430: can be used to specify that sshd
1.39 djm 431: should allow remote port forwardings to bind to non-loopback addresses, thus
432: allowing other hosts to connect.
433: The argument may be
434: .Dq no
435: to force remote port forwardings to be available to the local host only,
1.1 stevesk 436: .Dq yes
1.39 djm 437: to force remote port forwardings to bind to the wildcard address, or
438: .Dq clientspecified
439: to allow the client to select the address to which the forwarding is bound.
1.1 stevesk 440: The default is
441: .Dq no .
1.23 markus 442: .It Cm GSSAPIAuthentication
1.25 markus 443: Specifies whether user authentication based on GSSAPI is allowed.
1.26 djm 444: The default is
1.23 markus 445: .Dq no .
446: Note that this option applies to protocol version 2 only.
447: .It Cm GSSAPICleanupCredentials
448: Specifies whether to automatically destroy the user's credentials cache
449: on logout.
450: The default is
451: .Dq yes .
452: Note that this option applies to protocol version 2 only.
1.1 stevesk 453: .It Cm HostbasedAuthentication
454: Specifies whether rhosts or /etc/hosts.equiv authentication together
455: with successful public key client host authentication is allowed
1.50 jmc 456: (host-based authentication).
1.1 stevesk 457: This option is similar to
458: .Cm RhostsRSAAuthentication
459: and applies to protocol version 2 only.
1.70 dtucker 460: The default is
461: .Dq no .
462: .It Cm HostbasedUsesNameFromPacketOnly
463: Specifies whether or not the server will attempt to perform a reverse
464: name lookup when matching the name in the
465: .Pa ~/.shosts ,
466: .Pa ~/.rhosts ,
467: and
468: .Pa /etc/hosts.equiv
469: files during
470: .Cm HostbasedAuthentication .
471: A setting of
472: .Dq yes
473: means that
474: .Xr sshd 8
475: uses the name supplied by the client rather than
476: attempting to resolve the name from the TCP connection itself.
1.1 stevesk 477: The default is
478: .Dq no .
1.117 djm 479: .It Cm HostCertificate
480: Specifies a file containing a public host certificate.
481: The certificate's public key must match a private host key already specified
482: by
483: .Cm HostKey .
484: The default behaviour of
485: .Xr sshd 8
486: is not to load any certificates.
1.1 stevesk 487: .It Cm HostKey
488: Specifies a file containing a private host key
489: used by SSH.
490: The default is
491: .Pa /etc/ssh/ssh_host_key
492: for protocol version 1, and
1.126 djm 493: .Pa /etc/ssh/ssh_host_dsa_key ,
494: .Pa /etc/ssh/ssh_host_ecdsa_key
495: and
1.1 stevesk 496: .Pa /etc/ssh/ssh_host_rsa_key
497: for protocol version 2.
498: Note that
1.52 jmc 499: .Xr sshd 8
1.1 stevesk 500: will refuse to use a file if it is group/world-accessible.
501: It is possible to have multiple host key files.
502: .Dq rsa1
503: keys are used for version 1 and
1.126 djm 504: .Dq dsa ,
505: .Dq ecdsa
1.1 stevesk 506: or
507: .Dq rsa
508: are used for version 2 of the SSH protocol.
509: .It Cm IgnoreRhosts
510: Specifies that
511: .Pa .rhosts
512: and
513: .Pa .shosts
514: files will not be used in
515: .Cm RhostsRSAAuthentication
516: or
517: .Cm HostbasedAuthentication .
518: .Pp
519: .Pa /etc/hosts.equiv
520: and
521: .Pa /etc/shosts.equiv
522: are still used.
523: The default is
524: .Dq yes .
525: .It Cm IgnoreUserKnownHosts
526: Specifies whether
1.52 jmc 527: .Xr sshd 8
1.1 stevesk 528: should ignore the user's
1.41 djm 529: .Pa ~/.ssh/known_hosts
1.1 stevesk 530: during
531: .Cm RhostsRSAAuthentication
532: or
533: .Cm HostbasedAuthentication .
534: The default is
535: .Dq no .
1.129 djm 536: .It Cm IPQoS
537: Specifies the IPv4 type-of-service or DSCP class for the connection.
538: Accepted values are
539: .Dq af11 ,
540: .Dq af12 ,
541: .Dq af13 ,
1.136 djm 542: .Dq af21 ,
1.129 djm 543: .Dq af22 ,
544: .Dq af23 ,
545: .Dq af31 ,
546: .Dq af32 ,
547: .Dq af33 ,
548: .Dq af41 ,
549: .Dq af42 ,
550: .Dq af43 ,
551: .Dq cs0 ,
552: .Dq cs1 ,
553: .Dq cs2 ,
554: .Dq cs3 ,
555: .Dq cs4 ,
556: .Dq cs5 ,
557: .Dq cs6 ,
558: .Dq cs7 ,
559: .Dq ef ,
560: .Dq lowdelay ,
561: .Dq throughput ,
562: .Dq reliability ,
563: or a numeric value.
1.131 djm 564: This option may take one or two arguments, separated by whitespace.
1.129 djm 565: If one argument is specified, it is used as the packet class unconditionally.
566: If two values are specified, the first is automatically selected for
567: interactive sessions and the second for non-interactive sessions.
568: The default is
569: .Dq lowdelay
570: for interactive sessions and
571: .Dq throughput
572: for non-interactive sessions.
1.1 stevesk 573: .It Cm KerberosAuthentication
1.24 markus 574: Specifies whether the password provided by the user for
1.1 stevesk 575: .Cm PasswordAuthentication
1.24 markus 576: will be validated through the Kerberos KDC.
1.1 stevesk 577: To use this option, the server needs a
578: Kerberos servtab which allows the verification of the KDC's identity.
1.52 jmc 579: The default is
1.29 dtucker 580: .Dq no .
581: .It Cm KerberosGetAFSToken
1.45 djm 582: If AFS is active and the user has a Kerberos 5 TGT, attempt to acquire
1.29 dtucker 583: an AFS token before accessing the user's home directory.
1.52 jmc 584: The default is
1.1 stevesk 585: .Dq no .
586: .It Cm KerberosOrLocalPasswd
1.52 jmc 587: If password authentication through Kerberos fails then
1.1 stevesk 588: the password will be validated via any additional local mechanism
589: such as
590: .Pa /etc/passwd .
1.52 jmc 591: The default is
1.1 stevesk 592: .Dq yes .
593: .It Cm KerberosTicketCleanup
594: Specifies whether to automatically destroy the user's ticket cache
595: file on logout.
1.52 jmc 596: The default is
1.1 stevesk 597: .Dq yes .
1.127 djm 598: .It Cm KexAlgorithms
599: Specifies the available KEX (Key Exchange) algorithms.
600: Multiple algorithms must be comma-separated.
601: The default is
602: .Dq ecdh-sha2-nistp256 ,
603: .Dq ecdh-sha2-nistp384 ,
604: .Dq ecdh-sha2-nistp521 ,
1.130 jmc 605: .Dq diffie-hellman-group-exchange-sha256 ,
1.127 djm 606: .Dq diffie-hellman-group-exchange-sha1 ,
607: .Dq diffie-hellman-group14-sha1 ,
608: .Dq diffie-hellman-group1-sha1 .
1.1 stevesk 609: .It Cm KeyRegenerationInterval
610: In protocol version 1, the ephemeral server key is automatically regenerated
611: after this many seconds (if it has been used).
612: The purpose of regeneration is to prevent
613: decrypting captured sessions by later breaking into the machine and
614: stealing the keys.
615: The key is never stored anywhere.
616: If the value is 0, the key is never regenerated.
617: The default is 3600 (seconds).
618: .It Cm ListenAddress
619: Specifies the local addresses
1.52 jmc 620: .Xr sshd 8
1.1 stevesk 621: should listen on.
622: The following forms may be used:
623: .Pp
624: .Bl -item -offset indent -compact
625: .It
626: .Cm ListenAddress
627: .Sm off
628: .Ar host No | Ar IPv4_addr No | Ar IPv6_addr
629: .Sm on
630: .It
631: .Cm ListenAddress
632: .Sm off
633: .Ar host No | Ar IPv4_addr No : Ar port
634: .Sm on
635: .It
636: .Cm ListenAddress
637: .Sm off
638: .Oo
639: .Ar host No | Ar IPv6_addr Oc : Ar port
640: .Sm on
641: .El
642: .Pp
643: If
644: .Ar port
645: is not specified,
1.52 jmc 646: sshd will listen on the address and all prior
1.1 stevesk 647: .Cm Port
1.17 jmc 648: options specified.
649: The default is to listen on all local addresses.
1.15 jmc 650: Multiple
1.1 stevesk 651: .Cm ListenAddress
1.17 jmc 652: options are permitted.
653: Additionally, any
1.1 stevesk 654: .Cm Port
1.52 jmc 655: options must precede this option for non-port qualified addresses.
1.1 stevesk 656: .It Cm LoginGraceTime
657: The server disconnects after this time if the user has not
658: successfully logged in.
659: If the value is 0, there is no time limit.
1.12 stevesk 660: The default is 120 seconds.
1.1 stevesk 661: .It Cm LogLevel
662: Gives the verbosity level that is used when logging messages from
1.53 jmc 663: .Xr sshd 8 .
1.1 stevesk 664: The possible values are:
1.52 jmc 665: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.15 jmc 666: The default is INFO.
667: DEBUG and DEBUG1 are equivalent.
668: DEBUG2 and DEBUG3 each specify higher levels of debugging output.
669: Logging with a DEBUG level violates the privacy of users and is not recommended.
1.1 stevesk 670: .It Cm MACs
671: Specifies the available MAC (message authentication code) algorithms.
672: The MAC algorithm is used in protocol version 2
673: for data integrity protection.
674: Multiple algorithms must be comma-separated.
1.52 jmc 675: The default is:
1.77 jmc 676: .Bd -literal -offset indent
1.145 markus 677: hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,
1.144 naddy 678: hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,
679: hmac-sha1-96,hmac-md5-96
1.77 jmc 680: .Ed
1.60 dtucker 681: .It Cm Match
1.61 jmc 682: Introduces a conditional block.
1.65 dtucker 683: If all of the criteria on the
1.60 dtucker 684: .Cm Match
1.65 dtucker 685: line are satisfied, the keywords on the following lines override those
686: set in the global section of the config file, until either another
1.60 dtucker 687: .Cm Match
1.65 dtucker 688: line or the end of the file.
1.91 djm 689: .Pp
1.61 jmc 690: The arguments to
1.60 dtucker 691: .Cm Match
1.65 dtucker 692: are one or more criteria-pattern pairs.
1.60 dtucker 693: The available criteria are
694: .Cm User ,
1.69 dtucker 695: .Cm Group ,
1.60 dtucker 696: .Cm Host ,
1.139 dtucker 697: .Cm LocalAddress ,
698: .Cm LocalPort ,
1.60 dtucker 699: and
700: .Cm Address .
1.91 djm 701: The match patterns may consist of single entries or comma-separated
702: lists and may use the wildcard and negation operators described in the
1.92 djm 703: .Sx PATTERNS
1.91 djm 704: section of
1.92 djm 705: .Xr ssh_config 5 .
1.91 djm 706: .Pp
707: The patterns in an
708: .Cm Address
709: criteria may additionally contain addresses to match in CIDR
1.93 jmc 710: address/masklen format, e.g.\&
1.91 djm 711: .Dq 192.0.2.0/24
712: or
713: .Dq 3ffe:ffff::/32 .
714: Note that the mask length provided must be consistent with the address -
715: it is an error to specify a mask length that is too long for the address
1.93 jmc 716: or one with bits set in this host portion of the address.
717: For example,
1.91 djm 718: .Dq 192.0.2.0/33
719: and
1.93 jmc 720: .Dq 192.0.2.0/8
1.91 djm 721: respectively.
722: .Pp
1.60 dtucker 723: Only a subset of keywords may be used on the lines following a
724: .Cm Match
725: keyword.
726: Available keywords are
1.142 jmc 727: .Cm AcceptEnv ,
1.99 okan 728: .Cm AllowAgentForwarding ,
1.142 jmc 729: .Cm AllowGroups ,
1.62 dtucker 730: .Cm AllowTcpForwarding ,
1.141 markus 731: .Cm AllowUsers ,
1.146 djm 732: .Cm AuthorizedKeysCommand ,
733: .Cm AuthorizedKeysCommandUser ,
1.147 jmc 734: .Cm AuthorizedKeysFile ,
1.123 djm 735: .Cm AuthorizedPrincipalsFile ,
1.72 dtucker 736: .Cm Banner ,
1.85 djm 737: .Cm ChrootDirectory ,
1.141 markus 738: .Cm DenyGroups ,
739: .Cm DenyUsers ,
1.67 dtucker 740: .Cm ForceCommand ,
1.142 jmc 741: .Cm GatewayPorts ,
1.141 markus 742: .Cm GSSAPIAuthentication ,
1.87 djm 743: .Cm HostbasedAuthentication ,
1.123 djm 744: .Cm HostbasedUsesNameFromPacketOnly ,
1.74 jmc 745: .Cm KbdInteractiveAuthentication ,
1.72 dtucker 746: .Cm KerberosAuthentication ,
1.95 dtucker 747: .Cm MaxAuthTries ,
1.94 dtucker 748: .Cm MaxSessions ,
1.72 dtucker 749: .Cm PasswordAuthentication ,
1.97 djm 750: .Cm PermitEmptyPasswords ,
1.66 dtucker 751: .Cm PermitOpen ,
1.79 dtucker 752: .Cm PermitRootLogin ,
1.123 djm 753: .Cm PermitTunnel ,
1.107 dtucker 754: .Cm PubkeyAuthentication ,
1.142 jmc 755: .Cm RhostsRSAAuthentication ,
1.141 markus 756: .Cm RSAAuthentication ,
1.66 dtucker 757: .Cm X11DisplayOffset ,
1.101 djm 758: .Cm X11Forwarding
1.60 dtucker 759: and
1.102 djm 760: .Cm X11UseLocalHost .
1.33 dtucker 761: .It Cm MaxAuthTries
762: Specifies the maximum number of authentication attempts permitted per
1.35 jmc 763: connection.
764: Once the number of failures reaches half this value,
765: additional failures are logged.
766: The default is 6.
1.90 djm 767: .It Cm MaxSessions
768: Specifies the maximum number of open sessions permitted per network connection.
769: The default is 10.
1.1 stevesk 770: .It Cm MaxStartups
771: Specifies the maximum number of concurrent unauthenticated connections to the
1.52 jmc 772: SSH daemon.
1.1 stevesk 773: Additional connections will be dropped until authentication succeeds or the
774: .Cm LoginGraceTime
775: expires for a connection.
776: The default is 10.
777: .Pp
778: Alternatively, random early drop can be enabled by specifying
779: the three colon separated values
780: .Dq start:rate:full
1.51 jmc 781: (e.g. "10:30:60").
1.53 jmc 782: .Xr sshd 8
1.1 stevesk 783: will refuse connection attempts with a probability of
784: .Dq rate/100
785: (30%)
786: if there are currently
787: .Dq start
788: (10)
789: unauthenticated connections.
790: The probability increases linearly and all connection attempts
791: are refused if the number of unauthenticated connections reaches
792: .Dq full
793: (60).
794: .It Cm PasswordAuthentication
795: Specifies whether password authentication is allowed.
796: The default is
797: .Dq yes .
798: .It Cm PermitEmptyPasswords
799: When password authentication is allowed, it specifies whether the
800: server allows login to accounts with empty password strings.
801: The default is
802: .Dq no .
1.62 dtucker 803: .It Cm PermitOpen
804: Specifies the destinations to which TCP port forwarding is permitted.
805: The forwarding specification must be one of the following forms:
806: .Pp
807: .Bl -item -offset indent -compact
808: .It
809: .Cm PermitOpen
810: .Sm off
811: .Ar host : port
812: .Sm on
813: .It
814: .Cm PermitOpen
815: .Sm off
816: .Ar IPv4_addr : port
817: .Sm on
818: .It
819: .Cm PermitOpen
820: .Sm off
821: .Ar \&[ IPv6_addr \&] : port
822: .Sm on
823: .El
824: .Pp
1.68 dtucker 825: Multiple forwards may be specified by separating them with whitespace.
1.62 dtucker 826: An argument of
827: .Dq any
828: can be used to remove all restrictions and permit any forwarding requests.
1.140 dtucker 829: An argument of
830: .Dq none
831: can be used to prohibit all forwarding requests.
1.63 jmc 832: By default all port forwarding requests are permitted.
1.1 stevesk 833: .It Cm PermitRootLogin
1.38 jmc 834: Specifies whether root can log in using
1.1 stevesk 835: .Xr ssh 1 .
836: The argument must be
837: .Dq yes ,
838: .Dq without-password ,
1.52 jmc 839: .Dq forced-commands-only ,
1.1 stevesk 840: or
841: .Dq no .
842: The default is
843: .Dq yes .
844: .Pp
845: If this option is set to
1.52 jmc 846: .Dq without-password ,
1.1 stevesk 847: password authentication is disabled for root.
848: .Pp
849: If this option is set to
1.52 jmc 850: .Dq forced-commands-only ,
1.1 stevesk 851: root login with public key authentication will be allowed,
852: but only if the
853: .Ar command
854: option has been specified
855: (which may be useful for taking remote backups even if root login is
1.17 jmc 856: normally not allowed).
857: All other authentication methods are disabled for root.
1.1 stevesk 858: .Pp
859: If this option is set to
1.52 jmc 860: .Dq no ,
1.38 jmc 861: root is not allowed to log in.
1.46 reyk 862: .It Cm PermitTunnel
863: Specifies whether
864: .Xr tun 4
865: device forwarding is allowed.
1.47 reyk 866: The argument must be
867: .Dq yes ,
1.58 stevesk 868: .Dq point-to-point
869: (layer 3),
870: .Dq ethernet
871: (layer 2), or
1.47 reyk 872: .Dq no .
1.58 stevesk 873: Specifying
874: .Dq yes
875: permits both
876: .Dq point-to-point
877: and
878: .Dq ethernet .
1.46 reyk 879: The default is
880: .Dq no .
1.6 markus 881: .It Cm PermitUserEnvironment
882: Specifies whether
883: .Pa ~/.ssh/environment
1.9 stevesk 884: and
1.6 markus 885: .Cm environment=
886: options in
887: .Pa ~/.ssh/authorized_keys
1.9 stevesk 888: are processed by
1.52 jmc 889: .Xr sshd 8 .
1.6 markus 890: The default is
891: .Dq no .
1.9 stevesk 892: Enabling environment processing may enable users to bypass access
893: restrictions in some configurations using mechanisms such as
894: .Ev LD_PRELOAD .
1.1 stevesk 895: .It Cm PidFile
1.4 stevesk 896: Specifies the file that contains the process ID of the
1.53 jmc 897: SSH daemon.
1.1 stevesk 898: The default is
899: .Pa /var/run/sshd.pid .
900: .It Cm Port
901: Specifies the port number that
1.52 jmc 902: .Xr sshd 8
1.1 stevesk 903: listens on.
904: The default is 22.
905: Multiple options of this type are permitted.
906: See also
907: .Cm ListenAddress .
908: .It Cm PrintLastLog
909: Specifies whether
1.52 jmc 910: .Xr sshd 8
1.36 jaredy 911: should print the date and time of the last user login when a user logs
912: in interactively.
1.1 stevesk 913: The default is
914: .Dq yes .
915: .It Cm PrintMotd
916: Specifies whether
1.52 jmc 917: .Xr sshd 8
1.1 stevesk 918: should print
919: .Pa /etc/motd
920: when a user logs in interactively.
921: (On some systems it is also printed by the shell,
922: .Pa /etc/profile ,
923: or equivalent.)
924: The default is
925: .Dq yes .
926: .It Cm Protocol
927: Specifies the protocol versions
1.52 jmc 928: .Xr sshd 8
1.5 stevesk 929: supports.
1.1 stevesk 930: The possible values are
1.52 jmc 931: .Sq 1
1.1 stevesk 932: and
1.52 jmc 933: .Sq 2 .
1.1 stevesk 934: Multiple versions must be comma-separated.
935: The default is
1.109 jmc 936: .Sq 2 .
1.5 stevesk 937: Note that the order of the protocol list does not indicate preference,
938: because the client selects among multiple protocol versions offered
939: by the server.
940: Specifying
941: .Dq 2,1
942: is identical to
943: .Dq 1,2 .
1.1 stevesk 944: .It Cm PubkeyAuthentication
945: Specifies whether public key authentication is allowed.
946: The default is
947: .Dq yes .
948: Note that this option applies to protocol version 2 only.
1.118 djm 949: .It Cm RevokedKeys
950: Specifies a list of revoked public keys.
951: Keys listed in this file will be refused for public key authentication.
952: Note that if this file is not readable, then public key authentication will
953: be refused for all users.
1.1 stevesk 954: .It Cm RhostsRSAAuthentication
955: Specifies whether rhosts or /etc/hosts.equiv authentication together
956: with successful RSA host authentication is allowed.
957: The default is
958: .Dq no .
959: This option applies to protocol version 1 only.
960: .It Cm RSAAuthentication
961: Specifies whether pure RSA authentication is allowed.
962: The default is
963: .Dq yes .
964: This option applies to protocol version 1 only.
965: .It Cm ServerKeyBits
966: Defines the number of bits in the ephemeral protocol version 1 server key.
1.96 djm 967: The minimum value is 512, and the default is 1024.
1.1 stevesk 968: .It Cm StrictModes
969: Specifies whether
1.52 jmc 970: .Xr sshd 8
1.1 stevesk 971: should check file modes and ownership of the
972: user's files and home directory before accepting login.
973: This is normally desirable because novices sometimes accidentally leave their
974: directory or files world-writable.
975: The default is
976: .Dq yes .
1.112 djm 977: Note that this does not apply to
978: .Cm ChrootDirectory ,
979: whose permissions and ownership are checked unconditionally.
1.1 stevesk 980: .It Cm Subsystem
1.51 jmc 981: Configures an external subsystem (e.g. file transfer daemon).
1.59 djm 982: Arguments should be a subsystem name and a command (with optional arguments)
983: to execute upon subsystem request.
1.80 djm 984: .Pp
1.1 stevesk 985: The command
986: .Xr sftp-server 8
987: implements the
988: .Dq sftp
989: file transfer subsystem.
1.80 djm 990: .Pp
991: Alternately the name
992: .Dq internal-sftp
993: implements an in-process
994: .Dq sftp
995: server.
996: This may simplify configurations using
997: .Cm ChrootDirectory
998: to force a different filesystem root on clients.
999: .Pp
1.1 stevesk 1000: By default no subsystems are defined.
1001: Note that this option applies to protocol version 2 only.
1002: .It Cm SyslogFacility
1003: Gives the facility code that is used when logging messages from
1.53 jmc 1004: .Xr sshd 8 .
1.1 stevesk 1005: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1006: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1007: The default is AUTH.
1.27 markus 1008: .It Cm TCPKeepAlive
1009: Specifies whether the system should send TCP keepalive messages to the
1010: other side.
1011: If they are sent, death of the connection or crash of one
1012: of the machines will be properly noticed.
1013: However, this means that
1014: connections will die if the route is down temporarily, and some people
1015: find it annoying.
1016: On the other hand, if TCP keepalives are not sent,
1017: sessions may hang indefinitely on the server, leaving
1018: .Dq ghost
1019: users and consuming server resources.
1020: .Pp
1021: The default is
1022: .Dq yes
1023: (to send TCP keepalive messages), and the server will notice
1024: if the network goes down or the client host crashes.
1025: This avoids infinitely hanging sessions.
1026: .Pp
1027: To disable TCP keepalive messages, the value should be set to
1028: .Dq no .
1.118 djm 1029: .It Cm TrustedUserCAKeys
1030: Specifies a file containing public keys of certificate authorities that are
1.120 djm 1031: trusted to sign user certificates for authentication.
1.119 jmc 1032: Keys are listed one per line; empty lines and comments starting with
1.118 djm 1033: .Ql #
1034: are allowed.
1035: If a certificate is presented for authentication and has its signing CA key
1036: listed in this file, then it may be used for authentication for any user
1037: listed in the certificate's principals list.
1038: Note that certificates that lack a list of principals will not be permitted
1039: for authentication using
1040: .Cm TrustedUserCAKeys .
1.119 jmc 1041: For more details on certificates, see the
1.118 djm 1042: .Sx CERTIFICATES
1043: section in
1044: .Xr ssh-keygen 1 .
1.18 markus 1045: .It Cm UseDNS
1046: Specifies whether
1.52 jmc 1047: .Xr sshd 8
1.40 jmc 1048: should look up the remote host name and check that
1.18 markus 1049: the resolved host name for the remote IP address maps back to the
1050: very same IP address.
1051: The default is
1052: .Dq yes .
1.1 stevesk 1053: .It Cm UseLogin
1054: Specifies whether
1055: .Xr login 1
1056: is used for interactive login sessions.
1057: The default is
1058: .Dq no .
1059: Note that
1060: .Xr login 1
1061: is never used for remote command execution.
1062: Note also, that if this is enabled,
1063: .Cm X11Forwarding
1064: will be disabled because
1065: .Xr login 1
1066: does not know how to handle
1067: .Xr xauth 1
1.15 jmc 1068: cookies.
1069: If
1.1 stevesk 1070: .Cm UsePrivilegeSeparation
1071: is specified, it will be disabled after authentication.
1072: .It Cm UsePrivilegeSeparation
1073: Specifies whether
1.52 jmc 1074: .Xr sshd 8
1.2 stevesk 1075: separates privileges by creating an unprivileged child process
1.15 jmc 1076: to deal with incoming network traffic.
1077: After successful authentication, another process will be created that has
1078: the privilege of the authenticated user.
1079: The goal of privilege separation is to prevent privilege
1.1 stevesk 1080: escalation by containing any corruption within the unprivileged processes.
1081: The default is
1082: .Dq yes .
1.134 djm 1083: If
1084: .Cm UsePrivilegeSeparation
1085: is set to
1086: .Dq sandbox
1087: then the pre-authentication unprivileged process is subject to additional
1088: restrictions.
1.137 djm 1089: .It Cm VersionAddendum
1090: Optionally specifies additional text to append to the SSH protocol banner
1091: sent by the server upon connection.
1092: The default is
1093: .Dq none .
1.1 stevesk 1094: .It Cm X11DisplayOffset
1095: Specifies the first display number available for
1.52 jmc 1096: .Xr sshd 8 Ns 's
1.1 stevesk 1097: X11 forwarding.
1.52 jmc 1098: This prevents sshd from interfering with real X11 servers.
1.1 stevesk 1099: The default is 10.
1100: .It Cm X11Forwarding
1101: Specifies whether X11 forwarding is permitted.
1.13 stevesk 1102: The argument must be
1103: .Dq yes
1104: or
1105: .Dq no .
1.1 stevesk 1106: The default is
1107: .Dq no .
1.13 stevesk 1108: .Pp
1109: When X11 forwarding is enabled, there may be additional exposure to
1110: the server and to client displays if the
1.52 jmc 1111: .Xr sshd 8
1.13 stevesk 1112: proxy display is configured to listen on the wildcard address (see
1113: .Cm X11UseLocalhost
1.52 jmc 1114: below), though this is not the default.
1.13 stevesk 1115: Additionally, the authentication spoofing and authentication data
1116: verification and substitution occur on the client side.
1117: The security risk of using X11 forwarding is that the client's X11
1.52 jmc 1118: display server may be exposed to attack when the SSH client requests
1.13 stevesk 1119: forwarding (see the warnings for
1120: .Cm ForwardX11
1121: in
1.19 jmc 1122: .Xr ssh_config 5 ) .
1.13 stevesk 1123: A system administrator may have a stance in which they want to
1124: protect clients that may expose themselves to attack by unwittingly
1125: requesting X11 forwarding, which can warrant a
1126: .Dq no
1127: setting.
1128: .Pp
1129: Note that disabling X11 forwarding does not prevent users from
1130: forwarding X11 traffic, as users can always install their own forwarders.
1.1 stevesk 1131: X11 forwarding is automatically disabled if
1132: .Cm UseLogin
1133: is enabled.
1134: .It Cm X11UseLocalhost
1135: Specifies whether
1.52 jmc 1136: .Xr sshd 8
1.1 stevesk 1137: should bind the X11 forwarding server to the loopback address or to
1.15 jmc 1138: the wildcard address.
1139: By default,
1.52 jmc 1140: sshd binds the forwarding server to the loopback address and sets the
1.1 stevesk 1141: hostname part of the
1142: .Ev DISPLAY
1143: environment variable to
1144: .Dq localhost .
1.8 stevesk 1145: This prevents remote hosts from connecting to the proxy display.
1.1 stevesk 1146: However, some older X11 clients may not function with this
1147: configuration.
1148: .Cm X11UseLocalhost
1149: may be set to
1150: .Dq no
1151: to specify that the forwarding server should be bound to the wildcard
1152: address.
1153: The argument must be
1154: .Dq yes
1155: or
1156: .Dq no .
1157: The default is
1158: .Dq yes .
1159: .It Cm XAuthLocation
1.11 stevesk 1160: Specifies the full pathname of the
1.1 stevesk 1161: .Xr xauth 1
1162: program.
1163: The default is
1164: .Pa /usr/X11R6/bin/xauth .
1165: .El
1.55 jmc 1166: .Sh TIME FORMATS
1.53 jmc 1167: .Xr sshd 8
1.1 stevesk 1168: command-line arguments and configuration file options that specify time
1169: may be expressed using a sequence of the form:
1170: .Sm off
1.7 stevesk 1171: .Ar time Op Ar qualifier ,
1.1 stevesk 1172: .Sm on
1173: where
1174: .Ar time
1175: is a positive integer value and
1176: .Ar qualifier
1177: is one of the following:
1178: .Pp
1179: .Bl -tag -width Ds -compact -offset indent
1.64 jmc 1180: .It Aq Cm none
1.1 stevesk 1181: seconds
1182: .It Cm s | Cm S
1183: seconds
1184: .It Cm m | Cm M
1185: minutes
1186: .It Cm h | Cm H
1187: hours
1188: .It Cm d | Cm D
1189: days
1190: .It Cm w | Cm W
1191: weeks
1192: .El
1193: .Pp
1194: Each member of the sequence is added together to calculate
1195: the total time value.
1196: .Pp
1197: Time format examples:
1198: .Pp
1199: .Bl -tag -width Ds -compact -offset indent
1200: .It 600
1201: 600 seconds (10 minutes)
1202: .It 10m
1203: 10 minutes
1204: .It 1h30m
1205: 1 hour 30 minutes (90 minutes)
1206: .El
1207: .Sh FILES
1208: .Bl -tag -width Ds
1209: .It Pa /etc/ssh/sshd_config
1210: Contains configuration data for
1.53 jmc 1211: .Xr sshd 8 .
1.1 stevesk 1212: This file should be writable by root only, but it is recommended
1213: (though not necessary) that it be world-readable.
1214: .El
1.19 jmc 1215: .Sh SEE ALSO
1216: .Xr sshd 8
1.1 stevesk 1217: .Sh AUTHORS
1218: OpenSSH is a derivative of the original and free
1219: ssh 1.2.12 release by Tatu Ylonen.
1220: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1221: Theo de Raadt and Dug Song
1222: removed many bugs, re-added newer features and
1223: created OpenSSH.
1224: Markus Friedl contributed the support for SSH
1225: protocol versions 1.5 and 2.0.
1226: Niels Provos and Markus Friedl contributed support
1227: for privilege separation.
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