Annotation of src/usr.bin/ssh/sshd_config.5, Revision 1.280
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.
28: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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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1.280 ! djm 36: .\" $OpenBSD: sshd_config.5,v 1.279 2018/07/03 11:39:54 djm Exp $
1.279 djm 37: .Dd $Mdocdate: July 3 2018 $
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 DESCRIPTION
1.53 jmc 44: .Xr sshd 8
1.1 stevesk 45: reads configuration data from
46: .Pa /etc/ssh/sshd_config
47: (or the file specified with
48: .Fl f
49: on the command line).
50: The file contains keyword-argument pairs, one per line.
1.254 benno 51: For each keyword, the first obtained value will be used.
1.1 stevesk 52: Lines starting with
53: .Ql #
54: and empty lines are interpreted as comments.
1.56 dtucker 55: Arguments may optionally be enclosed in double quotes
56: .Pq \&"
57: in order to represent arguments containing spaces.
1.1 stevesk 58: .Pp
59: The possible
60: keywords and their meanings are as follows (note that
61: keywords are case-insensitive and arguments are case-sensitive):
62: .Bl -tag -width Ds
1.30 djm 63: .It Cm AcceptEnv
64: Specifies what environment variables sent by the client will be copied into
65: the session's
66: .Xr environ 7 .
67: See
68: .Cm SendEnv
1.273 djm 69: and
70: .Cm SetEnv
1.30 djm 71: in
72: .Xr ssh_config 5
73: for how to configure the client.
1.219 jmc 74: The
1.197 dtucker 75: .Ev TERM
1.275 djm 76: environment variable is always accepted whenever the client
1.204 djm 77: requests a pseudo-terminal as it is required by the protocol.
1.30 djm 78: Variables are specified by name, which may contain the wildcard characters
1.51 jmc 79: .Ql *
1.30 djm 80: and
81: .Ql \&? .
1.31 djm 82: Multiple environment variables may be separated by whitespace or spread
1.30 djm 83: across multiple
84: .Cm AcceptEnv
85: directives.
1.31 djm 86: Be warned that some environment variables could be used to bypass restricted
1.30 djm 87: user environments.
88: For this reason, care should be taken in the use of this directive.
89: The default is not to accept any environment variables.
1.37 djm 90: .It Cm AddressFamily
91: Specifies which address family should be used by
1.53 jmc 92: .Xr sshd 8 .
1.37 djm 93: Valid arguments are
1.237 jmc 94: .Cm any
95: (the default),
96: .Cm inet
1.52 jmc 97: (use IPv4 only), or
1.237 jmc 98: .Cm inet6
1.37 djm 99: (use IPv6 only).
1.89 jmc 100: .It Cm AllowAgentForwarding
101: Specifies whether
102: .Xr ssh-agent 1
103: forwarding is permitted.
104: The default is
1.237 jmc 105: .Cm yes .
1.89 jmc 106: Note that disabling agent forwarding does not improve security
107: unless users are also denied shell access, as they can always install
108: their own forwarders.
1.1 stevesk 109: .It Cm AllowGroups
110: This keyword can be followed by a list of group name patterns, separated
111: by spaces.
112: If specified, login is allowed only for users whose primary
113: group or supplementary group list matches one of the patterns.
114: Only group names are valid; a numerical group ID is not recognized.
115: By default, login is allowed for all groups.
1.54 jmc 116: The allow/deny directives are processed in the following order:
117: .Cm DenyUsers ,
118: .Cm AllowUsers ,
119: .Cm DenyGroups ,
120: and finally
121: .Cm AllowGroups .
1.49 jmc 122: .Pp
1.161 jmc 123: See PATTERNS in
1.49 jmc 124: .Xr ssh_config 5
125: for more information on patterns.
1.231 jmc 126: .It Cm AllowStreamLocalForwarding
127: Specifies whether StreamLocal (Unix-domain socket) forwarding is permitted.
1.150 djm 128: The available options are
1.237 jmc 129: .Cm yes
130: (the default)
1.150 djm 131: or
1.237 jmc 132: .Cm all
1.231 jmc 133: to allow StreamLocal forwarding,
1.237 jmc 134: .Cm no
1.231 jmc 135: to prevent all StreamLocal forwarding,
1.237 jmc 136: .Cm local
1.150 djm 137: to allow local (from the perspective of
1.151 jmc 138: .Xr ssh 1 )
139: forwarding only or
1.237 jmc 140: .Cm remote
1.150 djm 141: to allow remote forwarding only.
1.231 jmc 142: Note that disabling StreamLocal forwarding does not improve security unless
1.1 stevesk 143: users are also denied shell access, as they can always install their
144: own forwarders.
1.231 jmc 145: .It Cm AllowTcpForwarding
146: Specifies whether TCP forwarding is permitted.
1.175 millert 147: The available options are
1.237 jmc 148: .Cm yes
149: (the default)
1.175 millert 150: or
1.237 jmc 151: .Cm all
1.231 jmc 152: to allow TCP forwarding,
1.237 jmc 153: .Cm no
1.231 jmc 154: to prevent all TCP forwarding,
1.237 jmc 155: .Cm local
1.175 millert 156: to allow local (from the perspective of
157: .Xr ssh 1 )
158: forwarding only or
1.237 jmc 159: .Cm remote
1.175 millert 160: to allow remote forwarding only.
1.231 jmc 161: Note that disabling TCP forwarding does not improve security unless
1.175 millert 162: users are also denied shell access, as they can always install their
163: own forwarders.
1.1 stevesk 164: .It Cm AllowUsers
165: This keyword can be followed by a list of user name patterns, separated
166: by spaces.
1.14 jmc 167: If specified, login is allowed only for user names that
1.1 stevesk 168: match one of the patterns.
169: Only user names are valid; a numerical user ID is not recognized.
170: By default, login is allowed for all users.
171: If the pattern takes the form USER@HOST then USER and HOST
172: are separately checked, restricting logins to particular
173: users from particular hosts.
1.222 jmc 174: HOST criteria may additionally contain addresses to match in CIDR
175: address/masklen format.
1.54 jmc 176: The allow/deny directives are processed in the following order:
177: .Cm DenyUsers ,
178: .Cm AllowUsers ,
179: .Cm DenyGroups ,
180: and finally
181: .Cm AllowGroups .
1.49 jmc 182: .Pp
1.161 jmc 183: See PATTERNS in
1.49 jmc 184: .Xr ssh_config 5
185: for more information on patterns.
1.149 djm 186: .It Cm AuthenticationMethods
187: Specifies the authentication methods that must be successfully completed
188: for a user to be granted access.
189: This option must be followed by one or more comma-separated lists of
1.224 djm 190: authentication method names, or by the single string
1.237 jmc 191: .Cm any
1.224 djm 192: to indicate the default behaviour of accepting any single authentication
1.225 jmc 193: method.
1.237 jmc 194: If the default is overridden, then successful authentication requires
1.224 djm 195: completion of every method in at least one of these lists.
1.149 djm 196: .Pp
1.237 jmc 197: For example,
198: .Qq publickey,password publickey,keyboard-interactive
1.149 djm 199: would require the user to complete public key authentication, followed by
200: either password or keyboard interactive authentication.
201: Only methods that are next in one or more lists are offered at each stage,
1.237 jmc 202: so for this example it would not be possible to attempt password or
1.149 djm 203: keyboard-interactive authentication before public key.
1.157 markus 204: .Pp
205: For keyboard interactive authentication it is also possible to
206: restrict authentication to a specific device by appending a
207: colon followed by the device identifier
1.237 jmc 208: .Cm bsdauth ,
209: .Cm pam ,
1.157 markus 210: or
1.237 jmc 211: .Cm skey ,
1.157 markus 212: depending on the server configuration.
213: For example,
1.237 jmc 214: .Qq keyboard-interactive:bsdauth
1.157 markus 215: would restrict keyboard interactive authentication to the
1.237 jmc 216: .Cm bsdauth
1.157 markus 217: device.
1.185 djm 218: .Pp
1.237 jmc 219: If the publickey method is listed more than once,
1.185 djm 220: .Xr sshd 8
221: verifies that keys that have been used successfully are not reused for
222: subsequent authentications.
1.237 jmc 223: For example,
224: .Qq publickey,publickey
225: requires successful authentication using two different public keys.
1.181 djm 226: .Pp
1.149 djm 227: Note that each authentication method listed should also be explicitly enabled
228: in the configuration.
1.251 djm 229: .Pp
230: The available authentication methods are:
231: .Qq gssapi-with-mic ,
232: .Qq hostbased ,
233: .Qq keyboard-interactive ,
234: .Qq none
235: (used for access to password-less accounts when
1.266 jmc 236: .Cm PermitEmptyPasswords
1.251 djm 237: is enabled),
238: .Qq password
239: and
240: .Qq publickey .
1.146 djm 241: .It Cm AuthorizedKeysCommand
1.147 jmc 242: Specifies a program to be used to look up the user's public keys.
1.201 djm 243: The program must be owned by root, not writable by group or others and
244: specified by an absolute path.
245: Arguments to
246: .Cm AuthorizedKeysCommand
1.235 jmc 247: accept the tokens described in the
248: .Sx TOKENS
249: section.
250: If no arguments are specified then the username of the target user is used.
1.201 djm 251: .Pp
252: The program should produce on standard output zero or
1.235 jmc 253: more lines of authorized_keys output (see
254: .Sx AUTHORIZED_KEYS
255: in
1.147 jmc 256: .Xr sshd 8 ) .
1.235 jmc 257: If a key supplied by
258: .Cm AuthorizedKeysCommand
259: does not successfully authenticate
1.146 djm 260: and authorize the user then public key authentication continues using the usual
261: .Cm AuthorizedKeysFile
262: files.
1.237 jmc 263: By default, no
264: .Cm AuthorizedKeysCommand
265: is run.
1.146 djm 266: .It Cm AuthorizedKeysCommandUser
1.237 jmc 267: Specifies the user under whose account the
268: .Cm AuthorizedKeysCommand
269: is run.
1.146 djm 270: It is recommended to use a dedicated user that has no other role on the host
271: than running authorized keys commands.
1.186 djm 272: If
1.181 djm 273: .Cm AuthorizedKeysCommand
1.186 djm 274: is specified but
275: .Cm AuthorizedKeysCommandUser
276: is not, then
277: .Xr sshd 8
278: will refuse to start.
1.1 stevesk 279: .It Cm AuthorizedKeysFile
1.235 jmc 280: Specifies the file that contains the public keys used for user authentication.
1.124 djm 281: The format is described in the
1.235 jmc 282: .Sx AUTHORIZED_KEYS FILE FORMAT
1.124 djm 283: section of
284: .Xr sshd 8 .
1.235 jmc 285: Arguments to
1.1 stevesk 286: .Cm AuthorizedKeysFile
1.235 jmc 287: accept the tokens described in the
288: .Sx TOKENS
289: section.
1.1 stevesk 290: After expansion,
291: .Cm AuthorizedKeysFile
292: is taken to be an absolute path or one relative to the user's home
293: directory.
1.133 jmc 294: Multiple files may be listed, separated by whitespace.
1.212 djm 295: Alternately this option may be set to
1.237 jmc 296: .Cm none
1.212 djm 297: to skip checking for user keys in files.
1.133 jmc 298: The default is
1.237 jmc 299: .Qq .ssh/authorized_keys .ssh/authorized_keys2 .
1.202 djm 300: .It Cm AuthorizedPrincipalsCommand
301: Specifies a program to be used to generate the list of allowed
302: certificate principals as per
303: .Cm AuthorizedPrincipalsFile .
304: The program must be owned by root, not writable by group or others and
305: specified by an absolute path.
306: Arguments to
307: .Cm AuthorizedPrincipalsCommand
1.235 jmc 308: accept the tokens described in the
309: .Sx TOKENS
310: section.
311: If no arguments are specified then the username of the target user is used.
1.202 djm 312: .Pp
313: The program should produce on standard output zero or
314: more lines of
315: .Cm AuthorizedPrincipalsFile
316: output.
317: If either
318: .Cm AuthorizedPrincipalsCommand
319: or
320: .Cm AuthorizedPrincipalsFile
321: is specified, then certificates offered by the client for authentication
322: must contain a principal that is listed.
1.235 jmc 323: By default, no
324: .Cm AuthorizedPrincipalsCommand
325: is run.
1.202 djm 326: .It Cm AuthorizedPrincipalsCommandUser
1.235 jmc 327: Specifies the user under whose account the
328: .Cm AuthorizedPrincipalsCommand
329: is run.
1.202 djm 330: It is recommended to use a dedicated user that has no other role on the host
331: than running authorized principals commands.
332: If
333: .Cm AuthorizedPrincipalsCommand
334: is specified but
335: .Cm AuthorizedPrincipalsCommandUser
336: is not, then
337: .Xr sshd 8
338: will refuse to start.
1.121 djm 339: .It Cm AuthorizedPrincipalsFile
340: Specifies a file that lists principal names that are accepted for
341: certificate authentication.
342: When using certificates signed by a key listed in
343: .Cm TrustedUserCAKeys ,
344: this file lists names, one of which must appear in the certificate for it
345: to be accepted for authentication.
1.235 jmc 346: Names are listed one per line preceded by key options (as described in
347: .Sx AUTHORIZED_KEYS FILE FORMAT
348: in
1.125 jmc 349: .Xr sshd 8 ) .
1.124 djm 350: Empty lines and comments starting with
1.121 djm 351: .Ql #
352: are ignored.
353: .Pp
1.235 jmc 354: Arguments to
1.121 djm 355: .Cm AuthorizedPrincipalsFile
1.235 jmc 356: accept the tokens described in the
357: .Sx TOKENS
358: section.
1.121 djm 359: After expansion,
360: .Cm AuthorizedPrincipalsFile
1.235 jmc 361: is taken to be an absolute path or one relative to the user's home directory.
1.138 djm 362: The default is
1.237 jmc 363: .Cm none ,
1.138 djm 364: i.e. not to use a principals file \(en in this case, the username
1.121 djm 365: of the user must appear in a certificate's principals list for it to be
366: accepted.
1.235 jmc 367: .Pp
1.121 djm 368: Note that
369: .Cm AuthorizedPrincipalsFile
370: is only used when authentication proceeds using a CA listed in
371: .Cm TrustedUserCAKeys
372: and is not consulted for certification authorities trusted via
373: .Pa ~/.ssh/authorized_keys ,
374: though the
375: .Cm principals=
376: key option offers a similar facility (see
377: .Xr sshd 8
378: for details).
1.1 stevesk 379: .It Cm Banner
380: The contents of the specified file are sent to the remote user before
381: authentication is allowed.
1.78 djm 382: If the argument is
1.237 jmc 383: .Cm none
1.78 djm 384: then no banner is displayed.
1.1 stevesk 385: By default, no banner is displayed.
386: .It Cm ChallengeResponseAuthentication
1.50 jmc 387: Specifies whether challenge-response authentication is allowed.
1.1 stevesk 388: All authentication styles from
389: .Xr login.conf 5
390: are supported.
391: The default is
1.237 jmc 392: .Cm yes .
1.80 djm 393: .It Cm ChrootDirectory
1.113 stevesk 394: Specifies the pathname of a directory to
1.80 djm 395: .Xr chroot 2
396: to after authentication.
1.190 deraadt 397: At session startup
398: .Xr sshd 8
399: checks that all components of the pathname are root-owned directories
400: which are not writable by any other user or group.
1.106 stevesk 401: After the chroot,
402: .Xr sshd 8
403: changes the working directory to the user's home directory.
1.235 jmc 404: Arguments to
405: .Cm ChrootDirectory
406: accept the tokens described in the
407: .Sx TOKENS
408: section.
1.80 djm 409: .Pp
410: The
411: .Cm ChrootDirectory
412: must contain the necessary files and directories to support the
1.103 stevesk 413: user's session.
1.80 djm 414: For an interactive session this requires at least a shell, typically
415: .Xr sh 1 ,
416: and basic
417: .Pa /dev
418: nodes such as
419: .Xr null 4 ,
420: .Xr zero 4 ,
421: .Xr stdin 4 ,
422: .Xr stdout 4 ,
423: .Xr stderr 4 ,
1.180 jmc 424: and
1.80 djm 425: .Xr tty 4
426: devices.
1.237 jmc 427: For file transfer sessions using SFTP
428: no additional configuration of the environment is necessary if the in-process
429: sftp-server is used,
1.176 schwarze 430: though sessions which use logging may require
1.104 stevesk 431: .Pa /dev/log
1.176 schwarze 432: inside the chroot directory on some operating systems (see
1.104 stevesk 433: .Xr sftp-server 8
1.81 jmc 434: for details).
1.190 deraadt 435: .Pp
1.191 jmc 436: For safety, it is very important that the directory hierarchy be
1.190 deraadt 437: prevented from modification by other processes on the system (especially
438: those outside the jail).
439: Misconfiguration can lead to unsafe environments which
440: .Xr sshd 8
441: cannot detect.
1.80 djm 442: .Pp
1.215 djm 443: The default is
1.237 jmc 444: .Cm none ,
1.215 djm 445: indicating not to
1.80 djm 446: .Xr chroot 2 .
1.1 stevesk 447: .It Cm Ciphers
1.219 jmc 448: Specifies the ciphers allowed.
1.1 stevesk 449: Multiple ciphers must be comma-separated.
1.208 djm 450: If the specified value begins with a
451: .Sq +
452: character, then the specified ciphers will be appended to the default set
453: instead of replacing them.
1.242 djm 454: If the specified value begins with a
455: .Sq -
456: character, then the specified ciphers (including wildcards) will be removed
457: from the default set instead of replacing them.
1.208 djm 458: .Pp
1.167 djm 459: The supported ciphers are:
460: .Pp
1.173 naddy 461: .Bl -item -compact -offset indent
462: .It
463: 3des-cbc
464: .It
465: aes128-cbc
466: .It
467: aes192-cbc
468: .It
469: aes256-cbc
470: .It
471: aes128-ctr
472: .It
473: aes192-ctr
474: .It
475: aes256-ctr
476: .It
477: aes128-gcm@openssh.com
478: .It
479: aes256-gcm@openssh.com
480: .It
481: chacha20-poly1305@openssh.com
482: .El
1.167 djm 483: .Pp
1.52 jmc 484: The default is:
1.173 naddy 485: .Bd -literal -offset indent
1.211 jmc 486: chacha20-poly1305@openssh.com,
1.173 naddy 487: aes128-ctr,aes192-ctr,aes256-ctr,
1.211 jmc 488: aes128-gcm@openssh.com,aes256-gcm@openssh.com
1.1 stevesk 489: .Ed
1.167 djm 490: .Pp
1.237 jmc 491: The list of available ciphers may also be obtained using
492: .Qq ssh -Q cipher .
1.1 stevesk 493: .It Cm ClientAliveCountMax
1.237 jmc 494: Sets the number of client alive messages which may be sent without
1.52 jmc 495: .Xr sshd 8
1.17 jmc 496: receiving any messages back from the client.
497: If this threshold is reached while client alive messages are being sent,
1.52 jmc 498: sshd will disconnect the client, terminating the session.
1.17 jmc 499: It is important to note that the use of client alive messages is very
500: different from
1.237 jmc 501: .Cm TCPKeepAlive .
1.17 jmc 502: The client alive messages are sent through the encrypted channel
503: and therefore will not be spoofable.
504: The TCP keepalive option enabled by
1.27 markus 505: .Cm TCPKeepAlive
1.17 jmc 506: is spoofable.
507: The client alive mechanism is valuable when the client or
1.1 stevesk 508: server depend on knowing when a connection has become inactive.
509: .Pp
1.17 jmc 510: The default value is 3.
511: If
1.1 stevesk 512: .Cm ClientAliveInterval
1.237 jmc 513: is set to 15, and
1.1 stevesk 514: .Cm ClientAliveCountMax
1.52 jmc 515: is left at the default, unresponsive SSH clients
1.1 stevesk 516: will be disconnected after approximately 45 seconds.
1.42 djm 517: .It Cm ClientAliveInterval
518: Sets a timeout interval in seconds after which if no data has been received
519: from the client,
1.52 jmc 520: .Xr sshd 8
1.42 djm 521: will send a message through the encrypted
522: channel to request a response from the client.
523: The default
524: is 0, indicating that these messages will not be sent to the client.
1.3 markus 525: .It Cm Compression
1.236 djm 526: Specifies whether compression is enabled after
1.44 markus 527: the user has authenticated successfully.
1.3 markus 528: The argument must be
1.237 jmc 529: .Cm yes ,
530: .Cm delayed
1.236 djm 531: (a legacy synonym for
1.237 jmc 532: .Cm yes )
1.3 markus 533: or
1.237 jmc 534: .Cm no .
1.3 markus 535: The default is
1.237 jmc 536: .Cm yes .
1.1 stevesk 537: .It Cm DenyGroups
538: This keyword can be followed by a list of group name patterns, separated
539: by spaces.
540: Login is disallowed for users whose primary group or supplementary
541: group list matches one of the patterns.
542: Only group names are valid; a numerical group ID is not recognized.
543: By default, login is allowed for all groups.
1.54 jmc 544: The allow/deny directives are processed in the following order:
545: .Cm DenyUsers ,
546: .Cm AllowUsers ,
547: .Cm DenyGroups ,
548: and finally
549: .Cm AllowGroups .
1.49 jmc 550: .Pp
1.161 jmc 551: See PATTERNS in
1.49 jmc 552: .Xr ssh_config 5
553: for more information on patterns.
1.1 stevesk 554: .It Cm DenyUsers
555: This keyword can be followed by a list of user name patterns, separated
556: by spaces.
557: Login is disallowed for user names that match one of the patterns.
558: Only user names are valid; a numerical user ID is not recognized.
559: By default, login is allowed for all users.
560: If the pattern takes the form USER@HOST then USER and HOST
561: are separately checked, restricting logins to particular
562: users from particular hosts.
1.222 jmc 563: HOST criteria may additionally contain addresses to match in CIDR
564: address/masklen format.
1.54 jmc 565: The allow/deny directives are processed in the following order:
566: .Cm DenyUsers ,
567: .Cm AllowUsers ,
568: .Cm DenyGroups ,
569: and finally
570: .Cm AllowGroups .
1.49 jmc 571: .Pp
1.161 jmc 572: See PATTERNS in
1.49 jmc 573: .Xr ssh_config 5
574: for more information on patterns.
1.239 djm 575: .It Cm DisableForwarding
576: Disables all forwarding features, including X11,
577: .Xr ssh-agent 1 ,
578: TCP and StreamLocal.
579: This option overrides all other forwarding-related options and may
580: simplify restricted configurations.
1.246 djm 581: .It Cm ExposeAuthInfo
1.253 jmc 582: Writes a temporary file containing a list of authentication methods and
1.246 djm 583: public credentials (e.g. keys) used to authenticate the user.
1.247 jmc 584: The location of the file is exposed to the user session through the
1.248 djm 585: .Ev SSH_USER_AUTH
1.247 jmc 586: environment variable.
1.253 jmc 587: The default is
588: .Cm no .
1.183 djm 589: .It Cm FingerprintHash
590: Specifies the hash algorithm used when logging key fingerprints.
591: Valid options are:
1.237 jmc 592: .Cm md5
1.183 djm 593: and
1.237 jmc 594: .Cm sha256 .
1.183 djm 595: The default is
1.237 jmc 596: .Cm sha256 .
1.67 dtucker 597: .It Cm ForceCommand
598: Forces the execution of the command specified by
599: .Cm ForceCommand ,
1.84 djm 600: ignoring any command supplied by the client and
601: .Pa ~/.ssh/rc
602: if present.
1.67 dtucker 603: The command is invoked by using the user's login shell with the -c option.
604: This applies to shell, command, or subsystem execution.
605: It is most useful inside a
606: .Cm Match
607: block.
608: The command originally supplied by the client is available in the
609: .Ev SSH_ORIGINAL_COMMAND
610: environment variable.
1.82 djm 611: Specifying a command of
1.237 jmc 612: .Cm internal-sftp
613: will force the use of an in-process SFTP server that requires no support
1.82 djm 614: files when used with
615: .Cm ChrootDirectory .
1.215 djm 616: The default is
1.237 jmc 617: .Cm none .
1.1 stevesk 618: .It Cm GatewayPorts
619: Specifies whether remote hosts are allowed to connect to ports
620: forwarded for the client.
621: By default,
1.52 jmc 622: .Xr sshd 8
1.15 jmc 623: binds remote port forwardings to the loopback address.
624: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 625: .Cm GatewayPorts
1.52 jmc 626: can be used to specify that sshd
1.39 djm 627: should allow remote port forwardings to bind to non-loopback addresses, thus
628: allowing other hosts to connect.
629: The argument may be
1.237 jmc 630: .Cm no
1.39 djm 631: to force remote port forwardings to be available to the local host only,
1.237 jmc 632: .Cm yes
1.39 djm 633: to force remote port forwardings to bind to the wildcard address, or
1.237 jmc 634: .Cm clientspecified
1.39 djm 635: to allow the client to select the address to which the forwarding is bound.
1.1 stevesk 636: The default is
1.237 jmc 637: .Cm no .
1.23 markus 638: .It Cm GSSAPIAuthentication
1.25 markus 639: Specifies whether user authentication based on GSSAPI is allowed.
1.26 djm 640: The default is
1.237 jmc 641: .Cm no .
1.23 markus 642: .It Cm GSSAPICleanupCredentials
643: Specifies whether to automatically destroy the user's credentials cache
644: on logout.
645: The default is
1.237 jmc 646: .Cm yes .
1.203 djm 647: .It Cm GSSAPIStrictAcceptorCheck
648: Determines whether to be strict about the identity of the GSSAPI acceptor
649: a client authenticates against.
650: If set to
1.237 jmc 651: .Cm yes
652: then the client must authenticate against the host
1.203 djm 653: service on the current hostname.
654: If set to
1.237 jmc 655: .Cm no
1.203 djm 656: then the client may authenticate against any service key stored in the
657: machine's default store.
658: This facility is provided to assist with operation on multi homed machines.
659: The default is
1.237 jmc 660: .Cm yes .
1.189 djm 661: .It Cm HostbasedAcceptedKeyTypes
662: Specifies the key types that will be accepted for hostbased authentication
1.280 ! djm 663: as a list of comma-separated patterns.
1.208 djm 664: Alternately if the specified value begins with a
665: .Sq +
666: character, then the specified key types will be appended to the default set
667: instead of replacing them.
1.242 djm 668: If the specified value begins with a
669: .Sq -
670: character, then the specified key types (including wildcards) will be removed
671: from the default set instead of replacing them.
1.206 markus 672: The default for this option is:
673: .Bd -literal -offset 3n
674: ecdsa-sha2-nistp256-cert-v01@openssh.com,
675: ecdsa-sha2-nistp384-cert-v01@openssh.com,
676: ecdsa-sha2-nistp521-cert-v01@openssh.com,
677: ssh-ed25519-cert-v01@openssh.com,
1.279 djm 678: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.206 markus 679: ssh-rsa-cert-v01@openssh.com,
680: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.279 djm 681: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.206 markus 682: .Ed
683: .Pp
1.237 jmc 684: The list of available key types may also be obtained using
685: .Qq ssh -Q key .
1.1 stevesk 686: .It Cm HostbasedAuthentication
687: Specifies whether rhosts or /etc/hosts.equiv authentication together
688: with successful public key client host authentication is allowed
1.50 jmc 689: (host-based authentication).
1.70 dtucker 690: The default is
1.237 jmc 691: .Cm no .
1.70 dtucker 692: .It Cm HostbasedUsesNameFromPacketOnly
693: Specifies whether or not the server will attempt to perform a reverse
694: name lookup when matching the name in the
695: .Pa ~/.shosts ,
696: .Pa ~/.rhosts ,
697: and
698: .Pa /etc/hosts.equiv
699: files during
700: .Cm HostbasedAuthentication .
701: A setting of
1.237 jmc 702: .Cm yes
1.70 dtucker 703: means that
704: .Xr sshd 8
705: uses the name supplied by the client rather than
706: attempting to resolve the name from the TCP connection itself.
1.1 stevesk 707: The default is
1.237 jmc 708: .Cm no .
1.117 djm 709: .It Cm HostCertificate
710: Specifies a file containing a public host certificate.
711: The certificate's public key must match a private host key already specified
712: by
713: .Cm HostKey .
714: The default behaviour of
715: .Xr sshd 8
716: is not to load any certificates.
1.1 stevesk 717: .It Cm HostKey
718: Specifies a file containing a private host key
719: used by SSH.
1.229 naddy 720: The defaults are
1.169 naddy 721: .Pa /etc/ssh/ssh_host_ecdsa_key ,
722: .Pa /etc/ssh/ssh_host_ed25519_key
1.126 djm 723: and
1.229 naddy 724: .Pa /etc/ssh/ssh_host_rsa_key .
1.206 markus 725: .Pp
1.1 stevesk 726: Note that
1.52 jmc 727: .Xr sshd 8
1.206 markus 728: will refuse to use a file if it is group/world-accessible
729: and that the
730: .Cm HostKeyAlgorithms
731: option restricts which of the keys are actually used by
732: .Xr sshd 8 .
733: .Pp
1.1 stevesk 734: It is possible to have multiple host key files.
1.162 markus 735: It is also possible to specify public host key files instead.
736: In this case operations on the private key will be delegated
737: to an
738: .Xr ssh-agent 1 .
739: .It Cm HostKeyAgent
740: Identifies the UNIX-domain socket used to communicate
741: with an agent that has access to the private host keys.
1.223 markus 742: If the string
1.237 jmc 743: .Qq SSH_AUTH_SOCK
1.162 markus 744: is specified, the location of the socket will be read from the
745: .Ev SSH_AUTH_SOCK
746: environment variable.
1.206 markus 747: .It Cm HostKeyAlgorithms
1.219 jmc 748: Specifies the host key algorithms
1.206 markus 749: that the server offers.
750: The default for this option is:
751: .Bd -literal -offset 3n
752: ecdsa-sha2-nistp256-cert-v01@openssh.com,
753: ecdsa-sha2-nistp384-cert-v01@openssh.com,
754: ecdsa-sha2-nistp521-cert-v01@openssh.com,
755: ssh-ed25519-cert-v01@openssh.com,
1.279 djm 756: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.206 markus 757: ssh-rsa-cert-v01@openssh.com,
758: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.279 djm 759: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.206 markus 760: .Ed
761: .Pp
1.237 jmc 762: The list of available key types may also be obtained using
763: .Qq ssh -Q key .
1.1 stevesk 764: .It Cm IgnoreRhosts
765: Specifies that
766: .Pa .rhosts
767: and
768: .Pa .shosts
769: files will not be used in
770: .Cm HostbasedAuthentication .
771: .Pp
772: .Pa /etc/hosts.equiv
773: and
774: .Pa /etc/shosts.equiv
775: are still used.
776: The default is
1.237 jmc 777: .Cm yes .
1.1 stevesk 778: .It Cm IgnoreUserKnownHosts
779: Specifies whether
1.52 jmc 780: .Xr sshd 8
1.1 stevesk 781: should ignore the user's
1.41 djm 782: .Pa ~/.ssh/known_hosts
1.1 stevesk 783: during
1.261 djm 784: .Cm HostbasedAuthentication
785: and use only the system-wide known hosts file
786: .Pa /etc/ssh/known_hosts .
1.1 stevesk 787: The default is
1.237 jmc 788: .Cm no .
1.129 djm 789: .It Cm IPQoS
790: Specifies the IPv4 type-of-service or DSCP class for the connection.
791: Accepted values are
1.237 jmc 792: .Cm af11 ,
793: .Cm af12 ,
794: .Cm af13 ,
795: .Cm af21 ,
796: .Cm af22 ,
797: .Cm af23 ,
798: .Cm af31 ,
799: .Cm af32 ,
800: .Cm af33 ,
801: .Cm af41 ,
802: .Cm af42 ,
803: .Cm af43 ,
804: .Cm cs0 ,
805: .Cm cs1 ,
806: .Cm cs2 ,
807: .Cm cs3 ,
808: .Cm cs4 ,
809: .Cm cs5 ,
810: .Cm cs6 ,
811: .Cm cs7 ,
812: .Cm ef ,
813: .Cm lowdelay ,
814: .Cm throughput ,
815: .Cm reliability ,
1.250 djm 816: a numeric value, or
817: .Cm none
818: to use the operating system default.
1.131 djm 819: This option may take one or two arguments, separated by whitespace.
1.129 djm 820: If one argument is specified, it is used as the packet class unconditionally.
821: If two values are specified, the first is automatically selected for
822: interactive sessions and the second for non-interactive sessions.
823: The default is
1.264 job 824: .Cm af21
1.265 jmc 825: (Low-Latency Data)
1.129 djm 826: for interactive sessions and
1.264 job 827: .Cm cs1
1.265 jmc 828: (Lower Effort)
1.129 djm 829: for non-interactive sessions.
1.171 jmc 830: .It Cm KbdInteractiveAuthentication
831: Specifies whether to allow keyboard-interactive authentication.
832: The argument to this keyword must be
1.237 jmc 833: .Cm yes
1.171 jmc 834: or
1.237 jmc 835: .Cm no .
1.171 jmc 836: The default is to use whatever value
837: .Cm ChallengeResponseAuthentication
838: is set to
839: (by default
1.237 jmc 840: .Cm yes ) .
1.1 stevesk 841: .It Cm KerberosAuthentication
1.24 markus 842: Specifies whether the password provided by the user for
1.1 stevesk 843: .Cm PasswordAuthentication
1.24 markus 844: will be validated through the Kerberos KDC.
1.1 stevesk 845: To use this option, the server needs a
846: Kerberos servtab which allows the verification of the KDC's identity.
1.52 jmc 847: The default is
1.237 jmc 848: .Cm no .
1.29 dtucker 849: .It Cm KerberosGetAFSToken
1.45 djm 850: If AFS is active and the user has a Kerberos 5 TGT, attempt to acquire
1.29 dtucker 851: an AFS token before accessing the user's home directory.
1.52 jmc 852: The default is
1.237 jmc 853: .Cm no .
1.1 stevesk 854: .It Cm KerberosOrLocalPasswd
1.52 jmc 855: If password authentication through Kerberos fails then
1.1 stevesk 856: the password will be validated via any additional local mechanism
857: such as
858: .Pa /etc/passwd .
1.52 jmc 859: The default is
1.237 jmc 860: .Cm yes .
1.1 stevesk 861: .It Cm KerberosTicketCleanup
862: Specifies whether to automatically destroy the user's ticket cache
863: file on logout.
1.52 jmc 864: The default is
1.237 jmc 865: .Cm yes .
1.127 djm 866: .It Cm KexAlgorithms
867: Specifies the available KEX (Key Exchange) algorithms.
868: Multiple algorithms must be comma-separated.
1.208 djm 869: Alternately if the specified value begins with a
870: .Sq +
871: character, then the specified methods will be appended to the default set
872: instead of replacing them.
1.242 djm 873: If the specified value begins with a
874: .Sq -
875: character, then the specified methods (including wildcards) will be removed
876: from the default set instead of replacing them.
1.173 naddy 877: The supported algorithms are:
878: .Pp
879: .Bl -item -compact -offset indent
880: .It
1.234 djm 881: curve25519-sha256
882: .It
1.173 naddy 883: curve25519-sha256@libssh.org
884: .It
885: diffie-hellman-group1-sha1
886: .It
887: diffie-hellman-group14-sha1
888: .It
1.263 djm 889: diffie-hellman-group14-sha256
890: .It
891: diffie-hellman-group16-sha512
892: .It
893: diffie-hellman-group18-sha512
894: .It
1.173 naddy 895: diffie-hellman-group-exchange-sha1
896: .It
897: diffie-hellman-group-exchange-sha256
898: .It
899: ecdh-sha2-nistp256
900: .It
901: ecdh-sha2-nistp384
902: .It
903: ecdh-sha2-nistp521
904: .El
905: .Pp
906: The default is:
1.170 dtucker 907: .Bd -literal -offset indent
1.234 djm 908: curve25519-sha256,curve25519-sha256@libssh.org,
1.170 dtucker 909: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
910: diffie-hellman-group-exchange-sha256,
1.263 djm 911: diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,
912: diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
1.170 dtucker 913: .Ed
1.188 djm 914: .Pp
1.237 jmc 915: The list of available key exchange algorithms may also be obtained using
916: .Qq ssh -Q kex .
1.1 stevesk 917: .It Cm ListenAddress
918: Specifies the local addresses
1.52 jmc 919: .Xr sshd 8
1.1 stevesk 920: should listen on.
921: The following forms may be used:
922: .Pp
923: .Bl -item -offset indent -compact
924: .It
925: .Cm ListenAddress
926: .Sm off
1.259 jmc 927: .Ar hostname | address
1.1 stevesk 928: .Sm on
1.260 jmc 929: .Op Cm rdomain Ar domain
1.1 stevesk 930: .It
931: .Cm ListenAddress
932: .Sm off
1.259 jmc 933: .Ar hostname : port
1.1 stevesk 934: .Sm on
1.260 jmc 935: .Op Cm rdomain Ar domain
1.256 djm 936: .It
937: .Cm ListenAddress
938: .Sm off
1.259 jmc 939: .Ar IPv4_address : port
1.256 djm 940: .Sm on
1.260 jmc 941: .Op Cm rdomain Ar domain
1.1 stevesk 942: .It
943: .Cm ListenAddress
944: .Sm off
1.259 jmc 945: .Oo Ar hostname | address Oc : Ar port
1.1 stevesk 946: .Sm on
1.260 jmc 947: .Op Cm rdomain Ar domain
1.1 stevesk 948: .El
949: .Pp
1.256 djm 950: The optional
951: .Cm rdomain
952: qualifier requests
953: .Xr sshd 8
954: listen in an explicit routing domain.
1.1 stevesk 955: If
956: .Ar port
957: is not specified,
1.200 dtucker 958: sshd will listen on the address and all
1.1 stevesk 959: .Cm Port
1.17 jmc 960: options specified.
1.256 djm 961: The default is to listen on all local addresses on the current default
962: routing domain.
1.15 jmc 963: Multiple
1.1 stevesk 964: .Cm ListenAddress
1.17 jmc 965: options are permitted.
1.256 djm 966: For more information on routing domains, see
1.259 jmc 967: .Xr rdomain 4 .
1.1 stevesk 968: .It Cm LoginGraceTime
969: The server disconnects after this time if the user has not
970: successfully logged in.
971: If the value is 0, there is no time limit.
1.12 stevesk 972: The default is 120 seconds.
1.1 stevesk 973: .It Cm LogLevel
974: Gives the verbosity level that is used when logging messages from
1.53 jmc 975: .Xr sshd 8 .
1.1 stevesk 976: The possible values are:
1.52 jmc 977: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.15 jmc 978: The default is INFO.
979: DEBUG and DEBUG1 are equivalent.
980: DEBUG2 and DEBUG3 each specify higher levels of debugging output.
981: Logging with a DEBUG level violates the privacy of users and is not recommended.
1.1 stevesk 982: .It Cm MACs
983: Specifies the available MAC (message authentication code) algorithms.
1.219 jmc 984: The MAC algorithm is used for data integrity protection.
1.1 stevesk 985: Multiple algorithms must be comma-separated.
1.208 djm 986: If the specified value begins with a
987: .Sq +
988: character, then the specified algorithms will be appended to the default set
989: instead of replacing them.
1.242 djm 990: If the specified value begins with a
991: .Sq -
992: character, then the specified algorithms (including wildcards) will be removed
993: from the default set instead of replacing them.
1.208 djm 994: .Pp
1.152 markus 995: The algorithms that contain
1.237 jmc 996: .Qq -etm
1.152 markus 997: calculate the MAC after encryption (encrypt-then-mac).
998: These are considered safer and their use recommended.
1.173 naddy 999: The supported MACs are:
1000: .Pp
1001: .Bl -item -compact -offset indent
1002: .It
1003: hmac-md5
1004: .It
1005: hmac-md5-96
1006: .It
1007: hmac-sha1
1008: .It
1009: hmac-sha1-96
1010: .It
1011: hmac-sha2-256
1012: .It
1013: hmac-sha2-512
1014: .It
1015: umac-64@openssh.com
1016: .It
1017: umac-128@openssh.com
1018: .It
1019: hmac-md5-etm@openssh.com
1020: .It
1021: hmac-md5-96-etm@openssh.com
1022: .It
1023: hmac-sha1-etm@openssh.com
1024: .It
1025: hmac-sha1-96-etm@openssh.com
1026: .It
1027: hmac-sha2-256-etm@openssh.com
1028: .It
1029: hmac-sha2-512-etm@openssh.com
1030: .It
1031: umac-64-etm@openssh.com
1032: .It
1033: umac-128-etm@openssh.com
1034: .El
1035: .Pp
1.52 jmc 1036: The default is:
1.77 jmc 1037: .Bd -literal -offset indent
1.152 markus 1038: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1039: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.217 djm 1040: hmac-sha1-etm@openssh.com,
1.173 naddy 1041: umac-64@openssh.com,umac-128@openssh.com,
1.217 djm 1042: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.77 jmc 1043: .Ed
1.188 djm 1044: .Pp
1.237 jmc 1045: The list of available MAC algorithms may also be obtained using
1046: .Qq ssh -Q mac .
1.60 dtucker 1047: .It Cm Match
1.61 jmc 1048: Introduces a conditional block.
1.65 dtucker 1049: If all of the criteria on the
1.60 dtucker 1050: .Cm Match
1.65 dtucker 1051: line are satisfied, the keywords on the following lines override those
1052: set in the global section of the config file, until either another
1.60 dtucker 1053: .Cm Match
1.65 dtucker 1054: line or the end of the file.
1.172 djm 1055: If a keyword appears in multiple
1056: .Cm Match
1.177 sobrado 1057: blocks that are satisfied, only the first instance of the keyword is
1.172 djm 1058: applied.
1.91 djm 1059: .Pp
1.61 jmc 1060: The arguments to
1.60 dtucker 1061: .Cm Match
1.163 dtucker 1062: are one or more criteria-pattern pairs or the single token
1063: .Cm All
1064: which matches all criteria.
1.60 dtucker 1065: The available criteria are
1066: .Cm User ,
1.69 dtucker 1067: .Cm Group ,
1.60 dtucker 1068: .Cm Host ,
1.139 dtucker 1069: .Cm LocalAddress ,
1070: .Cm LocalPort ,
1.258 djm 1071: .Cm RDomain ,
1.60 dtucker 1072: and
1.258 djm 1073: .Cm Address
1074: (with
1075: .Cm RDomain
1076: representing the
1077: .Xr rdomain 4
1078: on which the connection was received.)
1079: .Pp
1.91 djm 1080: The match patterns may consist of single entries or comma-separated
1081: lists and may use the wildcard and negation operators described in the
1.237 jmc 1082: .Sx PATTERNS
1083: section of
1.92 djm 1084: .Xr ssh_config 5 .
1.91 djm 1085: .Pp
1086: The patterns in an
1087: .Cm Address
1088: criteria may additionally contain addresses to match in CIDR
1.237 jmc 1089: address/masklen format,
1090: such as 192.0.2.0/24 or 2001:db8::/32.
1.91 djm 1091: Note that the mask length provided must be consistent with the address -
1092: it is an error to specify a mask length that is too long for the address
1.93 jmc 1093: or one with bits set in this host portion of the address.
1.237 jmc 1094: For example, 192.0.2.0/33 and 192.0.2.0/8, respectively.
1.91 djm 1095: .Pp
1.60 dtucker 1096: Only a subset of keywords may be used on the lines following a
1097: .Cm Match
1098: keyword.
1099: Available keywords are
1.142 jmc 1100: .Cm AcceptEnv ,
1.99 okan 1101: .Cm AllowAgentForwarding ,
1.142 jmc 1102: .Cm AllowGroups ,
1.193 djm 1103: .Cm AllowStreamLocalForwarding ,
1.62 dtucker 1104: .Cm AllowTcpForwarding ,
1.141 markus 1105: .Cm AllowUsers ,
1.149 djm 1106: .Cm AuthenticationMethods ,
1.146 djm 1107: .Cm AuthorizedKeysCommand ,
1108: .Cm AuthorizedKeysCommandUser ,
1.147 jmc 1109: .Cm AuthorizedKeysFile ,
1.214 djm 1110: .Cm AuthorizedPrincipalsCommand ,
1111: .Cm AuthorizedPrincipalsCommandUser ,
1.123 djm 1112: .Cm AuthorizedPrincipalsFile ,
1.72 dtucker 1113: .Cm Banner ,
1.85 djm 1114: .Cm ChrootDirectory ,
1.238 markus 1115: .Cm ClientAliveCountMax ,
1116: .Cm ClientAliveInterval ,
1.141 markus 1117: .Cm DenyGroups ,
1118: .Cm DenyUsers ,
1.67 dtucker 1119: .Cm ForceCommand ,
1.194 djm 1120: .Cm GatewayPorts ,
1.193 djm 1121: .Cm GSSAPIAuthentication ,
1.189 djm 1122: .Cm HostbasedAcceptedKeyTypes ,
1.87 djm 1123: .Cm HostbasedAuthentication ,
1.123 djm 1124: .Cm HostbasedUsesNameFromPacketOnly ,
1.193 djm 1125: .Cm IPQoS ,
1.74 jmc 1126: .Cm KbdInteractiveAuthentication ,
1.72 dtucker 1127: .Cm KerberosAuthentication ,
1.245 djm 1128: .Cm LogLevel ,
1.95 dtucker 1129: .Cm MaxAuthTries ,
1.94 dtucker 1130: .Cm MaxSessions ,
1.72 dtucker 1131: .Cm PasswordAuthentication ,
1.97 djm 1132: .Cm PermitEmptyPasswords ,
1.271 djm 1133: .Cm PermitListen ,
1.66 dtucker 1134: .Cm PermitOpen ,
1.79 dtucker 1135: .Cm PermitRootLogin ,
1.164 djm 1136: .Cm PermitTTY ,
1.123 djm 1137: .Cm PermitTunnel ,
1.174 djm 1138: .Cm PermitUserRC ,
1.189 djm 1139: .Cm PubkeyAcceptedKeyTypes ,
1.107 dtucker 1140: .Cm PubkeyAuthentication ,
1.159 dtucker 1141: .Cm RekeyLimit ,
1.193 djm 1142: .Cm RevokedKeys ,
1.257 djm 1143: .Cm RDomain ,
1.274 djm 1144: .Cm SetEnv ,
1.193 djm 1145: .Cm StreamLocalBindMask ,
1146: .Cm StreamLocalBindUnlink ,
1147: .Cm TrustedUserCAKeys ,
1.66 dtucker 1148: .Cm X11DisplayOffset ,
1.101 djm 1149: .Cm X11Forwarding
1.60 dtucker 1150: and
1.102 djm 1151: .Cm X11UseLocalHost .
1.33 dtucker 1152: .It Cm MaxAuthTries
1153: Specifies the maximum number of authentication attempts permitted per
1.35 jmc 1154: connection.
1155: Once the number of failures reaches half this value,
1156: additional failures are logged.
1157: The default is 6.
1.90 djm 1158: .It Cm MaxSessions
1.216 djm 1159: Specifies the maximum number of open shell, login or subsystem (e.g. sftp)
1160: sessions permitted per network connection.
1161: Multiple sessions may be established by clients that support connection
1162: multiplexing.
1163: Setting
1164: .Cm MaxSessions
1165: to 1 will effectively disable session multiplexing, whereas setting it to 0
1166: will prevent all shell, login and subsystem sessions while still permitting
1167: forwarding.
1.90 djm 1168: The default is 10.
1.1 stevesk 1169: .It Cm MaxStartups
1170: Specifies the maximum number of concurrent unauthenticated connections to the
1.52 jmc 1171: SSH daemon.
1.1 stevesk 1172: Additional connections will be dropped until authentication succeeds or the
1173: .Cm LoginGraceTime
1174: expires for a connection.
1.156 dtucker 1175: The default is 10:30:100.
1.1 stevesk 1176: .Pp
1177: Alternatively, random early drop can be enabled by specifying
1178: the three colon separated values
1.237 jmc 1179: start:rate:full (e.g. "10:30:60").
1.53 jmc 1180: .Xr sshd 8
1.237 jmc 1181: will refuse connection attempts with a probability of rate/100 (30%)
1182: if there are currently start (10) unauthenticated connections.
1.1 stevesk 1183: The probability increases linearly and all connection attempts
1.237 jmc 1184: are refused if the number of unauthenticated connections reaches full (60).
1.1 stevesk 1185: .It Cm PasswordAuthentication
1186: Specifies whether password authentication is allowed.
1187: The default is
1.237 jmc 1188: .Cm yes .
1.1 stevesk 1189: .It Cm PermitEmptyPasswords
1190: When password authentication is allowed, it specifies whether the
1191: server allows login to accounts with empty password strings.
1192: The default is
1.237 jmc 1193: .Cm no .
1.271 djm 1194: .It Cm PermitListen
1195: Specifies the addresses/ports on which a remote TCP port forwarding may listen.
1196: The listen specification must be one of the following forms:
1197: .Pp
1198: .Bl -item -offset indent -compact
1199: .It
1200: .Cm PermitListen
1201: .Sm off
1.276 djm 1202: .Ar port
1.271 djm 1203: .Sm on
1204: .It
1205: .Cm PermitListen
1206: .Sm off
1.276 djm 1207: .Ar host : port
1.271 djm 1208: .Sm on
1209: .El
1210: .Pp
1211: Multiple permissions may be specified by separating them with whitespace.
1212: An argument of
1213: .Cm any
1214: can be used to remove all restrictions and permit any listen requests.
1215: An argument of
1216: .Cm none
1217: can be used to prohibit all listen requests.
1218: The host name may contain wildcards as described in the PATTERNS section in
1219: .Xr ssh_config 5 .
1220: The wildcard
1221: .Sq *
1222: can also be used in place of a port number to allow all ports.
1223: By default all port forwarding listen requests are permitted.
1.272 jmc 1224: Note that the
1.271 djm 1225: .Cm GatewayPorts
1226: option may further restrict which addresses may be listened on.
1.276 djm 1227: Note also that
1228: .Xr ssh 1
1229: will request a listen host of
1230: .Dq localhost
1231: if no listen host was specifically requested, and this this name is
1.277 jmc 1232: treated differently to explicit localhost addresses of
1.276 djm 1233: .Dq 127.0.0.1
1234: and
1235: .Dq ::1 .
1.62 dtucker 1236: .It Cm PermitOpen
1237: Specifies the destinations to which TCP port forwarding is permitted.
1238: The forwarding specification must be one of the following forms:
1239: .Pp
1240: .Bl -item -offset indent -compact
1241: .It
1242: .Cm PermitOpen
1243: .Sm off
1244: .Ar host : port
1245: .Sm on
1246: .It
1247: .Cm PermitOpen
1248: .Sm off
1249: .Ar IPv4_addr : port
1250: .Sm on
1251: .It
1252: .Cm PermitOpen
1253: .Sm off
1254: .Ar \&[ IPv6_addr \&] : port
1255: .Sm on
1256: .El
1257: .Pp
1.68 dtucker 1258: Multiple forwards may be specified by separating them with whitespace.
1.62 dtucker 1259: An argument of
1.237 jmc 1260: .Cm any
1.62 dtucker 1261: can be used to remove all restrictions and permit any forwarding requests.
1.140 dtucker 1262: An argument of
1.237 jmc 1263: .Cm none
1.140 dtucker 1264: can be used to prohibit all forwarding requests.
1.227 jmc 1265: The wildcard
1.237 jmc 1266: .Sq *
1.227 jmc 1267: can be used for host or port to allow all hosts or ports, respectively.
1.63 jmc 1268: By default all port forwarding requests are permitted.
1.1 stevesk 1269: .It Cm PermitRootLogin
1.38 jmc 1270: Specifies whether root can log in using
1.1 stevesk 1271: .Xr ssh 1 .
1272: The argument must be
1.237 jmc 1273: .Cm yes ,
1274: .Cm prohibit-password ,
1275: .Cm forced-commands-only ,
1.1 stevesk 1276: or
1.237 jmc 1277: .Cm no .
1.1 stevesk 1278: The default is
1.237 jmc 1279: .Cm prohibit-password .
1.1 stevesk 1280: .Pp
1281: If this option is set to
1.237 jmc 1282: .Cm prohibit-password
1.255 jmc 1283: (or its deprecated alias,
1284: .Cm without-password ) ,
1.210 deraadt 1285: password and keyboard-interactive authentication are disabled for root.
1.1 stevesk 1286: .Pp
1287: If this option is set to
1.237 jmc 1288: .Cm forced-commands-only ,
1.1 stevesk 1289: root login with public key authentication will be allowed,
1290: but only if the
1291: .Ar command
1292: option has been specified
1293: (which may be useful for taking remote backups even if root login is
1.17 jmc 1294: normally not allowed).
1295: All other authentication methods are disabled for root.
1.1 stevesk 1296: .Pp
1297: If this option is set to
1.237 jmc 1298: .Cm no ,
1.38 jmc 1299: root is not allowed to log in.
1.231 jmc 1300: .It Cm PermitTTY
1301: Specifies whether
1302: .Xr pty 4
1303: allocation is permitted.
1304: The default is
1.237 jmc 1305: .Cm yes .
1.46 reyk 1306: .It Cm PermitTunnel
1307: Specifies whether
1308: .Xr tun 4
1309: device forwarding is allowed.
1.47 reyk 1310: The argument must be
1.237 jmc 1311: .Cm yes ,
1312: .Cm point-to-point
1.58 stevesk 1313: (layer 3),
1.237 jmc 1314: .Cm ethernet
1.58 stevesk 1315: (layer 2), or
1.237 jmc 1316: .Cm no .
1.58 stevesk 1317: Specifying
1.237 jmc 1318: .Cm yes
1.58 stevesk 1319: permits both
1.237 jmc 1320: .Cm point-to-point
1.58 stevesk 1321: and
1.237 jmc 1322: .Cm ethernet .
1.46 reyk 1323: The default is
1.237 jmc 1324: .Cm no .
1.178 djm 1325: .Pp
1326: Independent of this setting, the permissions of the selected
1327: .Xr tun 4
1328: device must allow access to the user.
1.6 markus 1329: .It Cm PermitUserEnvironment
1330: Specifies whether
1331: .Pa ~/.ssh/environment
1.9 stevesk 1332: and
1.6 markus 1333: .Cm environment=
1334: options in
1335: .Pa ~/.ssh/authorized_keys
1.9 stevesk 1336: are processed by
1.52 jmc 1337: .Xr sshd 8 .
1.278 djm 1338: Valid options are
1339: .Cm yes ,
1340: .Cm no
1341: or a pattern-list specifying which environment variable names to accept
1342: (for example
1343: .Qq LANG,LC_* ) .
1.6 markus 1344: The default is
1.237 jmc 1345: .Cm no .
1.9 stevesk 1346: Enabling environment processing may enable users to bypass access
1347: restrictions in some configurations using mechanisms such as
1348: .Ev LD_PRELOAD .
1.174 djm 1349: .It Cm PermitUserRC
1350: Specifies whether any
1351: .Pa ~/.ssh/rc
1352: file is executed.
1353: The default is
1.237 jmc 1354: .Cm yes .
1.1 stevesk 1355: .It Cm PidFile
1.4 stevesk 1356: Specifies the file that contains the process ID of the
1.195 dtucker 1357: SSH daemon, or
1.237 jmc 1358: .Cm none
1.195 dtucker 1359: to not write one.
1.1 stevesk 1360: The default is
1361: .Pa /var/run/sshd.pid .
1362: .It Cm Port
1363: Specifies the port number that
1.52 jmc 1364: .Xr sshd 8
1.1 stevesk 1365: listens on.
1366: The default is 22.
1367: Multiple options of this type are permitted.
1368: See also
1369: .Cm ListenAddress .
1370: .It Cm PrintLastLog
1371: Specifies whether
1.52 jmc 1372: .Xr sshd 8
1.36 jaredy 1373: should print the date and time of the last user login when a user logs
1374: in interactively.
1.1 stevesk 1375: The default is
1.237 jmc 1376: .Cm yes .
1.1 stevesk 1377: .It Cm PrintMotd
1378: Specifies whether
1.52 jmc 1379: .Xr sshd 8
1.1 stevesk 1380: should print
1381: .Pa /etc/motd
1382: when a user logs in interactively.
1383: (On some systems it is also printed by the shell,
1384: .Pa /etc/profile ,
1385: or equivalent.)
1386: The default is
1.237 jmc 1387: .Cm yes .
1.189 djm 1388: .It Cm PubkeyAcceptedKeyTypes
1389: Specifies the key types that will be accepted for public key authentication
1.280 ! djm 1390: as a list of comma-separated patterns.
1.208 djm 1391: Alternately if the specified value begins with a
1392: .Sq +
1393: character, then the specified key types will be appended to the default set
1394: instead of replacing them.
1.242 djm 1395: If the specified value begins with a
1396: .Sq -
1397: character, then the specified key types (including wildcards) will be removed
1398: from the default set instead of replacing them.
1.206 markus 1399: The default for this option is:
1400: .Bd -literal -offset 3n
1401: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1402: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1403: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1404: ssh-ed25519-cert-v01@openssh.com,
1.279 djm 1405: rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
1.206 markus 1406: ssh-rsa-cert-v01@openssh.com,
1407: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.279 djm 1408: ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
1.206 markus 1409: .Ed
1410: .Pp
1.237 jmc 1411: The list of available key types may also be obtained using
1412: .Qq ssh -Q key .
1.1 stevesk 1413: .It Cm PubkeyAuthentication
1414: Specifies whether public key authentication is allowed.
1415: The default is
1.237 jmc 1416: .Cm yes .
1.159 dtucker 1417: .It Cm RekeyLimit
1418: Specifies the maximum amount of data that may be transmitted before the
1419: session key is renegotiated, optionally followed a maximum amount of
1420: time that may pass before the session key is renegotiated.
1421: The first argument is specified in bytes and may have a suffix of
1422: .Sq K ,
1423: .Sq M ,
1424: or
1425: .Sq G
1426: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1427: The default is between
1428: .Sq 1G
1429: and
1430: .Sq 4G ,
1431: depending on the cipher.
1432: The optional second value is specified in seconds and may use any of the
1433: units documented in the
1434: .Sx TIME FORMATS
1.160 jmc 1435: section.
1.159 dtucker 1436: The default value for
1437: .Cm RekeyLimit
1438: is
1.237 jmc 1439: .Cm default none ,
1.159 dtucker 1440: which means that rekeying is performed after the cipher's default amount
1441: of data has been sent or received and no time based rekeying is done.
1.118 djm 1442: .It Cm RevokedKeys
1.195 dtucker 1443: Specifies revoked public keys file, or
1.237 jmc 1444: .Cm none
1.195 dtucker 1445: to not use one.
1.118 djm 1446: Keys listed in this file will be refused for public key authentication.
1447: Note that if this file is not readable, then public key authentication will
1448: be refused for all users.
1.154 djm 1449: Keys may be specified as a text file, listing one public key per line, or as
1450: an OpenSSH Key Revocation List (KRL) as generated by
1.155 jmc 1451: .Xr ssh-keygen 1 .
1.161 jmc 1452: For more information on KRLs, see the KEY REVOCATION LISTS section in
1.154 djm 1453: .Xr ssh-keygen 1 .
1.257 djm 1454: .It Cm RDomain
1455: Specifies an explicit routing domain that is applied after authentication
1456: has completed.
1.259 jmc 1457: The user session, as well and any forwarded or listening IP sockets,
1458: will be bound to this
1.257 djm 1459: .Xr rdomain 4 .
1460: If the routing domain is set to
1461: .Cm \&%D ,
1.259 jmc 1462: then the domain in which the incoming connection was received will be applied.
1.274 djm 1463: .It Cm SetEnv
1464: Specifies one or more environment variables to set in child sessions started
1465: by
1466: .Xr sshd 8
1467: as
1468: .Dq NAME=VALUE .
1469: The environment value may be quoted (e.g. if it contains whitespace
1470: characters).
1471: Environment variables set by
1472: .Cm SetEnv
1473: override the default environment and any variables specified by the user
1474: via
1475: .Cm AcceptEnv
1476: or
1477: .Cm PermitUserEnvironment .
1.175 millert 1478: .It Cm StreamLocalBindMask
1479: Sets the octal file creation mode mask
1480: .Pq umask
1481: used when creating a Unix-domain socket file for local or remote
1482: port forwarding.
1483: This option is only used for port forwarding to a Unix-domain socket file.
1484: .Pp
1485: The default value is 0177, which creates a Unix-domain socket file that is
1486: readable and writable only by the owner.
1487: Note that not all operating systems honor the file mode on Unix-domain
1488: socket files.
1489: .It Cm StreamLocalBindUnlink
1490: Specifies whether to remove an existing Unix-domain socket file for local
1491: or remote port forwarding before creating a new one.
1492: If the socket file already exists and
1493: .Cm StreamLocalBindUnlink
1494: is not enabled,
1495: .Nm sshd
1496: will be unable to forward the port to the Unix-domain socket file.
1497: This option is only used for port forwarding to a Unix-domain socket file.
1498: .Pp
1499: The argument must be
1.237 jmc 1500: .Cm yes
1.175 millert 1501: or
1.237 jmc 1502: .Cm no .
1.175 millert 1503: The default is
1.237 jmc 1504: .Cm no .
1.1 stevesk 1505: .It Cm StrictModes
1506: Specifies whether
1.52 jmc 1507: .Xr sshd 8
1.1 stevesk 1508: should check file modes and ownership of the
1509: user's files and home directory before accepting login.
1510: This is normally desirable because novices sometimes accidentally leave their
1511: directory or files world-writable.
1512: The default is
1.237 jmc 1513: .Cm yes .
1.112 djm 1514: Note that this does not apply to
1515: .Cm ChrootDirectory ,
1516: whose permissions and ownership are checked unconditionally.
1.1 stevesk 1517: .It Cm Subsystem
1.51 jmc 1518: Configures an external subsystem (e.g. file transfer daemon).
1.59 djm 1519: Arguments should be a subsystem name and a command (with optional arguments)
1520: to execute upon subsystem request.
1.80 djm 1521: .Pp
1.1 stevesk 1522: The command
1.237 jmc 1523: .Cm sftp-server
1524: implements the SFTP file transfer subsystem.
1.80 djm 1525: .Pp
1526: Alternately the name
1.237 jmc 1527: .Cm internal-sftp
1528: implements an in-process SFTP server.
1.80 djm 1529: This may simplify configurations using
1530: .Cm ChrootDirectory
1531: to force a different filesystem root on clients.
1532: .Pp
1.1 stevesk 1533: By default no subsystems are defined.
1534: .It Cm SyslogFacility
1535: Gives the facility code that is used when logging messages from
1.53 jmc 1536: .Xr sshd 8 .
1.1 stevesk 1537: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1538: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1539: The default is AUTH.
1.27 markus 1540: .It Cm TCPKeepAlive
1541: Specifies whether the system should send TCP keepalive messages to the
1542: other side.
1543: If they are sent, death of the connection or crash of one
1544: of the machines will be properly noticed.
1545: However, this means that
1546: connections will die if the route is down temporarily, and some people
1547: find it annoying.
1548: On the other hand, if TCP keepalives are not sent,
1549: sessions may hang indefinitely on the server, leaving
1.237 jmc 1550: .Qq ghost
1.27 markus 1551: users and consuming server resources.
1552: .Pp
1553: The default is
1.237 jmc 1554: .Cm yes
1.27 markus 1555: (to send TCP keepalive messages), and the server will notice
1556: if the network goes down or the client host crashes.
1557: This avoids infinitely hanging sessions.
1558: .Pp
1559: To disable TCP keepalive messages, the value should be set to
1.237 jmc 1560: .Cm no .
1.118 djm 1561: .It Cm TrustedUserCAKeys
1562: Specifies a file containing public keys of certificate authorities that are
1.195 dtucker 1563: trusted to sign user certificates for authentication, or
1.237 jmc 1564: .Cm none
1.195 dtucker 1565: to not use one.
1.119 jmc 1566: Keys are listed one per line; empty lines and comments starting with
1.118 djm 1567: .Ql #
1568: are allowed.
1569: If a certificate is presented for authentication and has its signing CA key
1570: listed in this file, then it may be used for authentication for any user
1571: listed in the certificate's principals list.
1572: Note that certificates that lack a list of principals will not be permitted
1573: for authentication using
1574: .Cm TrustedUserCAKeys .
1.161 jmc 1575: For more details on certificates, see the CERTIFICATES section in
1.118 djm 1576: .Xr ssh-keygen 1 .
1.18 markus 1577: .It Cm UseDNS
1578: Specifies whether
1.52 jmc 1579: .Xr sshd 8
1.207 djm 1580: should look up the remote host name, and to check that
1.18 markus 1581: the resolved host name for the remote IP address maps back to the
1582: very same IP address.
1.207 djm 1583: .Pp
1584: If this option is set to
1.237 jmc 1585: .Cm no
1.207 djm 1586: (the default) then only addresses and not host names may be used in
1.221 djm 1587: .Pa ~/.ssh/authorized_keys
1.207 djm 1588: .Cm from
1589: and
1.211 jmc 1590: .Nm
1.207 djm 1591: .Cm Match
1592: .Cm Host
1593: directives.
1.137 djm 1594: .It Cm VersionAddendum
1595: Optionally specifies additional text to append to the SSH protocol banner
1596: sent by the server upon connection.
1597: The default is
1.237 jmc 1598: .Cm none .
1.1 stevesk 1599: .It Cm X11DisplayOffset
1600: Specifies the first display number available for
1.52 jmc 1601: .Xr sshd 8 Ns 's
1.1 stevesk 1602: X11 forwarding.
1.52 jmc 1603: This prevents sshd from interfering with real X11 servers.
1.1 stevesk 1604: The default is 10.
1605: .It Cm X11Forwarding
1606: Specifies whether X11 forwarding is permitted.
1.13 stevesk 1607: The argument must be
1.237 jmc 1608: .Cm yes
1.13 stevesk 1609: or
1.237 jmc 1610: .Cm no .
1.1 stevesk 1611: The default is
1.237 jmc 1612: .Cm no .
1.13 stevesk 1613: .Pp
1614: When X11 forwarding is enabled, there may be additional exposure to
1615: the server and to client displays if the
1.52 jmc 1616: .Xr sshd 8
1.13 stevesk 1617: proxy display is configured to listen on the wildcard address (see
1.237 jmc 1618: .Cm X11UseLocalhost ) ,
1619: though this is not the default.
1.13 stevesk 1620: Additionally, the authentication spoofing and authentication data
1621: verification and substitution occur on the client side.
1622: The security risk of using X11 forwarding is that the client's X11
1.52 jmc 1623: display server may be exposed to attack when the SSH client requests
1.13 stevesk 1624: forwarding (see the warnings for
1625: .Cm ForwardX11
1626: in
1.19 jmc 1627: .Xr ssh_config 5 ) .
1.13 stevesk 1628: A system administrator may have a stance in which they want to
1629: protect clients that may expose themselves to attack by unwittingly
1630: requesting X11 forwarding, which can warrant a
1.237 jmc 1631: .Cm no
1.13 stevesk 1632: setting.
1633: .Pp
1634: Note that disabling X11 forwarding does not prevent users from
1635: forwarding X11 traffic, as users can always install their own forwarders.
1.1 stevesk 1636: .It Cm X11UseLocalhost
1637: Specifies whether
1.52 jmc 1638: .Xr sshd 8
1.1 stevesk 1639: should bind the X11 forwarding server to the loopback address or to
1.15 jmc 1640: the wildcard address.
1641: By default,
1.52 jmc 1642: sshd binds the forwarding server to the loopback address and sets the
1.1 stevesk 1643: hostname part of the
1644: .Ev DISPLAY
1645: environment variable to
1.237 jmc 1646: .Cm localhost .
1.8 stevesk 1647: This prevents remote hosts from connecting to the proxy display.
1.1 stevesk 1648: However, some older X11 clients may not function with this
1649: configuration.
1650: .Cm X11UseLocalhost
1651: may be set to
1.237 jmc 1652: .Cm no
1.1 stevesk 1653: to specify that the forwarding server should be bound to the wildcard
1654: address.
1655: The argument must be
1.237 jmc 1656: .Cm yes
1.1 stevesk 1657: or
1.237 jmc 1658: .Cm no .
1.1 stevesk 1659: The default is
1.237 jmc 1660: .Cm yes .
1.1 stevesk 1661: .It Cm XAuthLocation
1.11 stevesk 1662: Specifies the full pathname of the
1.1 stevesk 1663: .Xr xauth 1
1.195 dtucker 1664: program, or
1.237 jmc 1665: .Cm none
1.195 dtucker 1666: to not use one.
1.1 stevesk 1667: The default is
1668: .Pa /usr/X11R6/bin/xauth .
1669: .El
1.55 jmc 1670: .Sh TIME FORMATS
1.53 jmc 1671: .Xr sshd 8
1.1 stevesk 1672: command-line arguments and configuration file options that specify time
1673: may be expressed using a sequence of the form:
1674: .Sm off
1.7 stevesk 1675: .Ar time Op Ar qualifier ,
1.1 stevesk 1676: .Sm on
1677: where
1678: .Ar time
1679: is a positive integer value and
1680: .Ar qualifier
1681: is one of the following:
1682: .Pp
1683: .Bl -tag -width Ds -compact -offset indent
1.64 jmc 1684: .It Aq Cm none
1.1 stevesk 1685: seconds
1686: .It Cm s | Cm S
1687: seconds
1688: .It Cm m | Cm M
1689: minutes
1690: .It Cm h | Cm H
1691: hours
1692: .It Cm d | Cm D
1693: days
1694: .It Cm w | Cm W
1695: weeks
1696: .El
1697: .Pp
1698: Each member of the sequence is added together to calculate
1699: the total time value.
1700: .Pp
1701: Time format examples:
1702: .Pp
1703: .Bl -tag -width Ds -compact -offset indent
1704: .It 600
1705: 600 seconds (10 minutes)
1706: .It 10m
1707: 10 minutes
1708: .It 1h30m
1709: 1 hour 30 minutes (90 minutes)
1710: .El
1.235 jmc 1711: .Sh TOKENS
1712: Arguments to some keywords can make use of tokens,
1713: which are expanded at runtime:
1714: .Pp
1715: .Bl -tag -width XXXX -offset indent -compact
1716: .It %%
1717: A literal
1718: .Sq % .
1.257 djm 1719: .It \&%D
1720: The routing domain in which the incoming connection was received.
1.235 jmc 1721: .It %F
1722: The fingerprint of the CA key.
1723: .It %f
1724: The fingerprint of the key or certificate.
1725: .It %h
1726: The home directory of the user.
1727: .It %i
1728: The key ID in the certificate.
1729: .It %K
1730: The base64-encoded CA key.
1731: .It %k
1732: The base64-encoded key or certificate for authentication.
1733: .It %s
1734: The serial number of the certificate.
1735: .It \&%T
1736: The type of the CA key.
1737: .It %t
1738: The key or certificate type.
1.268 jmc 1739: .It \&%U
1740: The numeric user ID of the target user.
1.235 jmc 1741: .It %u
1742: The username.
1743: .El
1744: .Pp
1745: .Cm AuthorizedKeysCommand
1.270 jmc 1746: accepts the tokens %%, %f, %h, %k, %t, %U, and %u.
1.235 jmc 1747: .Pp
1748: .Cm AuthorizedKeysFile
1.270 jmc 1749: accepts the tokens %%, %h, %U, and %u.
1.235 jmc 1750: .Pp
1751: .Cm AuthorizedPrincipalsCommand
1.270 jmc 1752: accepts the tokens %%, %F, %f, %h, %i, %K, %k, %s, %T, %t, %U, and %u.
1.235 jmc 1753: .Pp
1754: .Cm AuthorizedPrincipalsFile
1.270 jmc 1755: accepts the tokens %%, %h, %U, and %u.
1.235 jmc 1756: .Pp
1757: .Cm ChrootDirectory
1.270 jmc 1758: accepts the tokens %%, %h, %U, and %u.
1.257 djm 1759: .Pp
1760: .Cm RoutingDomain
1761: accepts the token %D.
1.1 stevesk 1762: .Sh FILES
1763: .Bl -tag -width Ds
1764: .It Pa /etc/ssh/sshd_config
1765: Contains configuration data for
1.53 jmc 1766: .Xr sshd 8 .
1.1 stevesk 1767: This file should be writable by root only, but it is recommended
1768: (though not necessary) that it be world-readable.
1769: .El
1.19 jmc 1770: .Sh SEE ALSO
1.237 jmc 1771: .Xr sftp-server 8 ,
1.19 jmc 1772: .Xr sshd 8
1.1 stevesk 1773: .Sh AUTHORS
1.237 jmc 1774: .An -nosplit
1.1 stevesk 1775: OpenSSH is a derivative of the original and free
1.237 jmc 1776: ssh 1.2.12 release by
1777: .An Tatu Ylonen .
1778: .An Aaron Campbell , Bob Beck , Markus Friedl , Niels Provos ,
1779: .An Theo de Raadt
1780: and
1781: .An Dug Song
1.1 stevesk 1782: removed many bugs, re-added newer features and
1783: created OpenSSH.
1.237 jmc 1784: .An Markus Friedl
1785: contributed the support for SSH protocol versions 1.5 and 2.0.
1786: .An Niels Provos
1787: and
1788: .An Markus Friedl
1789: contributed support for privilege separation.