Annotation of src/usr.bin/ssh/sshd_config.5, Revision 1.276
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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1.276 ! djm 36: .\" $OpenBSD: sshd_config.5,v 1.275 2018/06/09 03:18:11 djm Exp $
1.274 djm 37: .Dd $Mdocdate: June 9 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
663: as a comma-separated pattern list.
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,
678: ssh-rsa-cert-v01@openssh.com,
679: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.220 djm 680: ssh-ed25519,ssh-rsa
1.206 markus 681: .Ed
682: .Pp
1.237 jmc 683: The list of available key types may also be obtained using
684: .Qq ssh -Q key .
1.1 stevesk 685: .It Cm HostbasedAuthentication
686: Specifies whether rhosts or /etc/hosts.equiv authentication together
687: with successful public key client host authentication is allowed
1.50 jmc 688: (host-based authentication).
1.70 dtucker 689: The default is
1.237 jmc 690: .Cm no .
1.70 dtucker 691: .It Cm HostbasedUsesNameFromPacketOnly
692: Specifies whether or not the server will attempt to perform a reverse
693: name lookup when matching the name in the
694: .Pa ~/.shosts ,
695: .Pa ~/.rhosts ,
696: and
697: .Pa /etc/hosts.equiv
698: files during
699: .Cm HostbasedAuthentication .
700: A setting of
1.237 jmc 701: .Cm yes
1.70 dtucker 702: means that
703: .Xr sshd 8
704: uses the name supplied by the client rather than
705: attempting to resolve the name from the TCP connection itself.
1.1 stevesk 706: The default is
1.237 jmc 707: .Cm no .
1.117 djm 708: .It Cm HostCertificate
709: Specifies a file containing a public host certificate.
710: The certificate's public key must match a private host key already specified
711: by
712: .Cm HostKey .
713: The default behaviour of
714: .Xr sshd 8
715: is not to load any certificates.
1.1 stevesk 716: .It Cm HostKey
717: Specifies a file containing a private host key
718: used by SSH.
1.229 naddy 719: The defaults are
1.169 naddy 720: .Pa /etc/ssh/ssh_host_ecdsa_key ,
721: .Pa /etc/ssh/ssh_host_ed25519_key
1.126 djm 722: and
1.229 naddy 723: .Pa /etc/ssh/ssh_host_rsa_key .
1.206 markus 724: .Pp
1.1 stevesk 725: Note that
1.52 jmc 726: .Xr sshd 8
1.206 markus 727: will refuse to use a file if it is group/world-accessible
728: and that the
729: .Cm HostKeyAlgorithms
730: option restricts which of the keys are actually used by
731: .Xr sshd 8 .
732: .Pp
1.1 stevesk 733: It is possible to have multiple host key files.
1.162 markus 734: It is also possible to specify public host key files instead.
735: In this case operations on the private key will be delegated
736: to an
737: .Xr ssh-agent 1 .
738: .It Cm HostKeyAgent
739: Identifies the UNIX-domain socket used to communicate
740: with an agent that has access to the private host keys.
1.223 markus 741: If the string
1.237 jmc 742: .Qq SSH_AUTH_SOCK
1.162 markus 743: is specified, the location of the socket will be read from the
744: .Ev SSH_AUTH_SOCK
745: environment variable.
1.206 markus 746: .It Cm HostKeyAlgorithms
1.219 jmc 747: Specifies the host key algorithms
1.206 markus 748: that the server offers.
749: The default for this option is:
750: .Bd -literal -offset 3n
751: ecdsa-sha2-nistp256-cert-v01@openssh.com,
752: ecdsa-sha2-nistp384-cert-v01@openssh.com,
753: ecdsa-sha2-nistp521-cert-v01@openssh.com,
754: ssh-ed25519-cert-v01@openssh.com,
755: ssh-rsa-cert-v01@openssh.com,
756: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.220 djm 757: ssh-ed25519,ssh-rsa
1.206 markus 758: .Ed
759: .Pp
1.237 jmc 760: The list of available key types may also be obtained using
761: .Qq ssh -Q key .
1.1 stevesk 762: .It Cm IgnoreRhosts
763: Specifies that
764: .Pa .rhosts
765: and
766: .Pa .shosts
767: files will not be used in
768: .Cm HostbasedAuthentication .
769: .Pp
770: .Pa /etc/hosts.equiv
771: and
772: .Pa /etc/shosts.equiv
773: are still used.
774: The default is
1.237 jmc 775: .Cm yes .
1.1 stevesk 776: .It Cm IgnoreUserKnownHosts
777: Specifies whether
1.52 jmc 778: .Xr sshd 8
1.1 stevesk 779: should ignore the user's
1.41 djm 780: .Pa ~/.ssh/known_hosts
1.1 stevesk 781: during
1.261 djm 782: .Cm HostbasedAuthentication
783: and use only the system-wide known hosts file
784: .Pa /etc/ssh/known_hosts .
1.1 stevesk 785: The default is
1.237 jmc 786: .Cm no .
1.129 djm 787: .It Cm IPQoS
788: Specifies the IPv4 type-of-service or DSCP class for the connection.
789: Accepted values are
1.237 jmc 790: .Cm af11 ,
791: .Cm af12 ,
792: .Cm af13 ,
793: .Cm af21 ,
794: .Cm af22 ,
795: .Cm af23 ,
796: .Cm af31 ,
797: .Cm af32 ,
798: .Cm af33 ,
799: .Cm af41 ,
800: .Cm af42 ,
801: .Cm af43 ,
802: .Cm cs0 ,
803: .Cm cs1 ,
804: .Cm cs2 ,
805: .Cm cs3 ,
806: .Cm cs4 ,
807: .Cm cs5 ,
808: .Cm cs6 ,
809: .Cm cs7 ,
810: .Cm ef ,
811: .Cm lowdelay ,
812: .Cm throughput ,
813: .Cm reliability ,
1.250 djm 814: a numeric value, or
815: .Cm none
816: to use the operating system default.
1.131 djm 817: This option may take one or two arguments, separated by whitespace.
1.129 djm 818: If one argument is specified, it is used as the packet class unconditionally.
819: If two values are specified, the first is automatically selected for
820: interactive sessions and the second for non-interactive sessions.
821: The default is
1.264 job 822: .Cm af21
1.265 jmc 823: (Low-Latency Data)
1.129 djm 824: for interactive sessions and
1.264 job 825: .Cm cs1
1.265 jmc 826: (Lower Effort)
1.129 djm 827: for non-interactive sessions.
1.171 jmc 828: .It Cm KbdInteractiveAuthentication
829: Specifies whether to allow keyboard-interactive authentication.
830: The argument to this keyword must be
1.237 jmc 831: .Cm yes
1.171 jmc 832: or
1.237 jmc 833: .Cm no .
1.171 jmc 834: The default is to use whatever value
835: .Cm ChallengeResponseAuthentication
836: is set to
837: (by default
1.237 jmc 838: .Cm yes ) .
1.1 stevesk 839: .It Cm KerberosAuthentication
1.24 markus 840: Specifies whether the password provided by the user for
1.1 stevesk 841: .Cm PasswordAuthentication
1.24 markus 842: will be validated through the Kerberos KDC.
1.1 stevesk 843: To use this option, the server needs a
844: Kerberos servtab which allows the verification of the KDC's identity.
1.52 jmc 845: The default is
1.237 jmc 846: .Cm no .
1.29 dtucker 847: .It Cm KerberosGetAFSToken
1.45 djm 848: If AFS is active and the user has a Kerberos 5 TGT, attempt to acquire
1.29 dtucker 849: an AFS token before accessing the user's home directory.
1.52 jmc 850: The default is
1.237 jmc 851: .Cm no .
1.1 stevesk 852: .It Cm KerberosOrLocalPasswd
1.52 jmc 853: If password authentication through Kerberos fails then
1.1 stevesk 854: the password will be validated via any additional local mechanism
855: such as
856: .Pa /etc/passwd .
1.52 jmc 857: The default is
1.237 jmc 858: .Cm yes .
1.1 stevesk 859: .It Cm KerberosTicketCleanup
860: Specifies whether to automatically destroy the user's ticket cache
861: file on logout.
1.52 jmc 862: The default is
1.237 jmc 863: .Cm yes .
1.127 djm 864: .It Cm KexAlgorithms
865: Specifies the available KEX (Key Exchange) algorithms.
866: Multiple algorithms must be comma-separated.
1.208 djm 867: Alternately if the specified value begins with a
868: .Sq +
869: character, then the specified methods will be appended to the default set
870: instead of replacing them.
1.242 djm 871: If the specified value begins with a
872: .Sq -
873: character, then the specified methods (including wildcards) will be removed
874: from the default set instead of replacing them.
1.173 naddy 875: The supported algorithms are:
876: .Pp
877: .Bl -item -compact -offset indent
878: .It
1.234 djm 879: curve25519-sha256
880: .It
1.173 naddy 881: curve25519-sha256@libssh.org
882: .It
883: diffie-hellman-group1-sha1
884: .It
885: diffie-hellman-group14-sha1
886: .It
1.263 djm 887: diffie-hellman-group14-sha256
888: .It
889: diffie-hellman-group16-sha512
890: .It
891: diffie-hellman-group18-sha512
892: .It
1.173 naddy 893: diffie-hellman-group-exchange-sha1
894: .It
895: diffie-hellman-group-exchange-sha256
896: .It
897: ecdh-sha2-nistp256
898: .It
899: ecdh-sha2-nistp384
900: .It
901: ecdh-sha2-nistp521
902: .El
903: .Pp
904: The default is:
1.170 dtucker 905: .Bd -literal -offset indent
1.234 djm 906: curve25519-sha256,curve25519-sha256@libssh.org,
1.170 dtucker 907: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
908: diffie-hellman-group-exchange-sha256,
1.263 djm 909: diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,
910: diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
1.170 dtucker 911: .Ed
1.188 djm 912: .Pp
1.237 jmc 913: The list of available key exchange algorithms may also be obtained using
914: .Qq ssh -Q kex .
1.1 stevesk 915: .It Cm ListenAddress
916: Specifies the local addresses
1.52 jmc 917: .Xr sshd 8
1.1 stevesk 918: should listen on.
919: The following forms may be used:
920: .Pp
921: .Bl -item -offset indent -compact
922: .It
923: .Cm ListenAddress
924: .Sm off
1.259 jmc 925: .Ar hostname | address
1.1 stevesk 926: .Sm on
1.260 jmc 927: .Op Cm rdomain Ar domain
1.1 stevesk 928: .It
929: .Cm ListenAddress
930: .Sm off
1.259 jmc 931: .Ar hostname : port
1.1 stevesk 932: .Sm on
1.260 jmc 933: .Op Cm rdomain Ar domain
1.256 djm 934: .It
935: .Cm ListenAddress
936: .Sm off
1.259 jmc 937: .Ar IPv4_address : port
1.256 djm 938: .Sm on
1.260 jmc 939: .Op Cm rdomain Ar domain
1.1 stevesk 940: .It
941: .Cm ListenAddress
942: .Sm off
1.259 jmc 943: .Oo Ar hostname | address Oc : Ar port
1.1 stevesk 944: .Sm on
1.260 jmc 945: .Op Cm rdomain Ar domain
1.1 stevesk 946: .El
947: .Pp
1.256 djm 948: The optional
949: .Cm rdomain
950: qualifier requests
951: .Xr sshd 8
952: listen in an explicit routing domain.
1.1 stevesk 953: If
954: .Ar port
955: is not specified,
1.200 dtucker 956: sshd will listen on the address and all
1.1 stevesk 957: .Cm Port
1.17 jmc 958: options specified.
1.256 djm 959: The default is to listen on all local addresses on the current default
960: routing domain.
1.15 jmc 961: Multiple
1.1 stevesk 962: .Cm ListenAddress
1.17 jmc 963: options are permitted.
1.256 djm 964: For more information on routing domains, see
1.259 jmc 965: .Xr rdomain 4 .
1.1 stevesk 966: .It Cm LoginGraceTime
967: The server disconnects after this time if the user has not
968: successfully logged in.
969: If the value is 0, there is no time limit.
1.12 stevesk 970: The default is 120 seconds.
1.1 stevesk 971: .It Cm LogLevel
972: Gives the verbosity level that is used when logging messages from
1.53 jmc 973: .Xr sshd 8 .
1.1 stevesk 974: The possible values are:
1.52 jmc 975: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1.15 jmc 976: The default is INFO.
977: DEBUG and DEBUG1 are equivalent.
978: DEBUG2 and DEBUG3 each specify higher levels of debugging output.
979: Logging with a DEBUG level violates the privacy of users and is not recommended.
1.1 stevesk 980: .It Cm MACs
981: Specifies the available MAC (message authentication code) algorithms.
1.219 jmc 982: The MAC algorithm is used for data integrity protection.
1.1 stevesk 983: Multiple algorithms must be comma-separated.
1.208 djm 984: If the specified value begins with a
985: .Sq +
986: character, then the specified algorithms will be appended to the default set
987: instead of replacing them.
1.242 djm 988: If the specified value begins with a
989: .Sq -
990: character, then the specified algorithms (including wildcards) will be removed
991: from the default set instead of replacing them.
1.208 djm 992: .Pp
1.152 markus 993: The algorithms that contain
1.237 jmc 994: .Qq -etm
1.152 markus 995: calculate the MAC after encryption (encrypt-then-mac).
996: These are considered safer and their use recommended.
1.173 naddy 997: The supported MACs are:
998: .Pp
999: .Bl -item -compact -offset indent
1000: .It
1001: hmac-md5
1002: .It
1003: hmac-md5-96
1004: .It
1005: hmac-sha1
1006: .It
1007: hmac-sha1-96
1008: .It
1009: hmac-sha2-256
1010: .It
1011: hmac-sha2-512
1012: .It
1013: umac-64@openssh.com
1014: .It
1015: umac-128@openssh.com
1016: .It
1017: hmac-md5-etm@openssh.com
1018: .It
1019: hmac-md5-96-etm@openssh.com
1020: .It
1021: hmac-sha1-etm@openssh.com
1022: .It
1023: hmac-sha1-96-etm@openssh.com
1024: .It
1025: hmac-sha2-256-etm@openssh.com
1026: .It
1027: hmac-sha2-512-etm@openssh.com
1028: .It
1029: umac-64-etm@openssh.com
1030: .It
1031: umac-128-etm@openssh.com
1032: .El
1033: .Pp
1.52 jmc 1034: The default is:
1.77 jmc 1035: .Bd -literal -offset indent
1.152 markus 1036: umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1037: hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1.217 djm 1038: hmac-sha1-etm@openssh.com,
1.173 naddy 1039: umac-64@openssh.com,umac-128@openssh.com,
1.217 djm 1040: hmac-sha2-256,hmac-sha2-512,hmac-sha1
1.77 jmc 1041: .Ed
1.188 djm 1042: .Pp
1.237 jmc 1043: The list of available MAC algorithms may also be obtained using
1044: .Qq ssh -Q mac .
1.60 dtucker 1045: .It Cm Match
1.61 jmc 1046: Introduces a conditional block.
1.65 dtucker 1047: If all of the criteria on the
1.60 dtucker 1048: .Cm Match
1.65 dtucker 1049: line are satisfied, the keywords on the following lines override those
1050: set in the global section of the config file, until either another
1.60 dtucker 1051: .Cm Match
1.65 dtucker 1052: line or the end of the file.
1.172 djm 1053: If a keyword appears in multiple
1054: .Cm Match
1.177 sobrado 1055: blocks that are satisfied, only the first instance of the keyword is
1.172 djm 1056: applied.
1.91 djm 1057: .Pp
1.61 jmc 1058: The arguments to
1.60 dtucker 1059: .Cm Match
1.163 dtucker 1060: are one or more criteria-pattern pairs or the single token
1061: .Cm All
1062: which matches all criteria.
1.60 dtucker 1063: The available criteria are
1064: .Cm User ,
1.69 dtucker 1065: .Cm Group ,
1.60 dtucker 1066: .Cm Host ,
1.139 dtucker 1067: .Cm LocalAddress ,
1068: .Cm LocalPort ,
1.258 djm 1069: .Cm RDomain ,
1.60 dtucker 1070: and
1.258 djm 1071: .Cm Address
1072: (with
1073: .Cm RDomain
1074: representing the
1075: .Xr rdomain 4
1076: on which the connection was received.)
1077: .Pp
1.91 djm 1078: The match patterns may consist of single entries or comma-separated
1079: lists and may use the wildcard and negation operators described in the
1.237 jmc 1080: .Sx PATTERNS
1081: section of
1.92 djm 1082: .Xr ssh_config 5 .
1.91 djm 1083: .Pp
1084: The patterns in an
1085: .Cm Address
1086: criteria may additionally contain addresses to match in CIDR
1.237 jmc 1087: address/masklen format,
1088: such as 192.0.2.0/24 or 2001:db8::/32.
1.91 djm 1089: Note that the mask length provided must be consistent with the address -
1090: it is an error to specify a mask length that is too long for the address
1.93 jmc 1091: or one with bits set in this host portion of the address.
1.237 jmc 1092: For example, 192.0.2.0/33 and 192.0.2.0/8, respectively.
1.91 djm 1093: .Pp
1.60 dtucker 1094: Only a subset of keywords may be used on the lines following a
1095: .Cm Match
1096: keyword.
1097: Available keywords are
1.142 jmc 1098: .Cm AcceptEnv ,
1.99 okan 1099: .Cm AllowAgentForwarding ,
1.142 jmc 1100: .Cm AllowGroups ,
1.193 djm 1101: .Cm AllowStreamLocalForwarding ,
1.62 dtucker 1102: .Cm AllowTcpForwarding ,
1.141 markus 1103: .Cm AllowUsers ,
1.149 djm 1104: .Cm AuthenticationMethods ,
1.146 djm 1105: .Cm AuthorizedKeysCommand ,
1106: .Cm AuthorizedKeysCommandUser ,
1.147 jmc 1107: .Cm AuthorizedKeysFile ,
1.214 djm 1108: .Cm AuthorizedPrincipalsCommand ,
1109: .Cm AuthorizedPrincipalsCommandUser ,
1.123 djm 1110: .Cm AuthorizedPrincipalsFile ,
1.72 dtucker 1111: .Cm Banner ,
1.85 djm 1112: .Cm ChrootDirectory ,
1.238 markus 1113: .Cm ClientAliveCountMax ,
1114: .Cm ClientAliveInterval ,
1.141 markus 1115: .Cm DenyGroups ,
1116: .Cm DenyUsers ,
1.67 dtucker 1117: .Cm ForceCommand ,
1.194 djm 1118: .Cm GatewayPorts ,
1.193 djm 1119: .Cm GSSAPIAuthentication ,
1.189 djm 1120: .Cm HostbasedAcceptedKeyTypes ,
1.87 djm 1121: .Cm HostbasedAuthentication ,
1.123 djm 1122: .Cm HostbasedUsesNameFromPacketOnly ,
1.193 djm 1123: .Cm IPQoS ,
1.74 jmc 1124: .Cm KbdInteractiveAuthentication ,
1.72 dtucker 1125: .Cm KerberosAuthentication ,
1.245 djm 1126: .Cm LogLevel ,
1.95 dtucker 1127: .Cm MaxAuthTries ,
1.94 dtucker 1128: .Cm MaxSessions ,
1.72 dtucker 1129: .Cm PasswordAuthentication ,
1.97 djm 1130: .Cm PermitEmptyPasswords ,
1.271 djm 1131: .Cm PermitListen ,
1.66 dtucker 1132: .Cm PermitOpen ,
1.79 dtucker 1133: .Cm PermitRootLogin ,
1.164 djm 1134: .Cm PermitTTY ,
1.123 djm 1135: .Cm PermitTunnel ,
1.174 djm 1136: .Cm PermitUserRC ,
1.189 djm 1137: .Cm PubkeyAcceptedKeyTypes ,
1.107 dtucker 1138: .Cm PubkeyAuthentication ,
1.159 dtucker 1139: .Cm RekeyLimit ,
1.193 djm 1140: .Cm RevokedKeys ,
1.257 djm 1141: .Cm RDomain ,
1.274 djm 1142: .Cm SetEnv ,
1.193 djm 1143: .Cm StreamLocalBindMask ,
1144: .Cm StreamLocalBindUnlink ,
1145: .Cm TrustedUserCAKeys ,
1.66 dtucker 1146: .Cm X11DisplayOffset ,
1.101 djm 1147: .Cm X11Forwarding
1.60 dtucker 1148: and
1.102 djm 1149: .Cm X11UseLocalHost .
1.33 dtucker 1150: .It Cm MaxAuthTries
1151: Specifies the maximum number of authentication attempts permitted per
1.35 jmc 1152: connection.
1153: Once the number of failures reaches half this value,
1154: additional failures are logged.
1155: The default is 6.
1.90 djm 1156: .It Cm MaxSessions
1.216 djm 1157: Specifies the maximum number of open shell, login or subsystem (e.g. sftp)
1158: sessions permitted per network connection.
1159: Multiple sessions may be established by clients that support connection
1160: multiplexing.
1161: Setting
1162: .Cm MaxSessions
1163: to 1 will effectively disable session multiplexing, whereas setting it to 0
1164: will prevent all shell, login and subsystem sessions while still permitting
1165: forwarding.
1.90 djm 1166: The default is 10.
1.1 stevesk 1167: .It Cm MaxStartups
1168: Specifies the maximum number of concurrent unauthenticated connections to the
1.52 jmc 1169: SSH daemon.
1.1 stevesk 1170: Additional connections will be dropped until authentication succeeds or the
1171: .Cm LoginGraceTime
1172: expires for a connection.
1.156 dtucker 1173: The default is 10:30:100.
1.1 stevesk 1174: .Pp
1175: Alternatively, random early drop can be enabled by specifying
1176: the three colon separated values
1.237 jmc 1177: start:rate:full (e.g. "10:30:60").
1.53 jmc 1178: .Xr sshd 8
1.237 jmc 1179: will refuse connection attempts with a probability of rate/100 (30%)
1180: if there are currently start (10) unauthenticated connections.
1.1 stevesk 1181: The probability increases linearly and all connection attempts
1.237 jmc 1182: are refused if the number of unauthenticated connections reaches full (60).
1.1 stevesk 1183: .It Cm PasswordAuthentication
1184: Specifies whether password authentication is allowed.
1185: The default is
1.237 jmc 1186: .Cm yes .
1.1 stevesk 1187: .It Cm PermitEmptyPasswords
1188: When password authentication is allowed, it specifies whether the
1189: server allows login to accounts with empty password strings.
1190: The default is
1.237 jmc 1191: .Cm no .
1.271 djm 1192: .It Cm PermitListen
1193: Specifies the addresses/ports on which a remote TCP port forwarding may listen.
1194: The listen specification must be one of the following forms:
1195: .Pp
1196: .Bl -item -offset indent -compact
1197: .It
1198: .Cm PermitListen
1199: .Sm off
1.276 ! djm 1200: .Ar port
1.271 djm 1201: .Sm on
1202: .It
1203: .Cm PermitListen
1204: .Sm off
1.276 ! djm 1205: .Ar host : port
1.271 djm 1206: .Sm on
1207: .El
1208: .Pp
1209: Multiple permissions may be specified by separating them with whitespace.
1210: An argument of
1211: .Cm any
1212: can be used to remove all restrictions and permit any listen requests.
1213: An argument of
1214: .Cm none
1215: can be used to prohibit all listen requests.
1216: The host name may contain wildcards as described in the PATTERNS section in
1217: .Xr ssh_config 5 .
1218: The wildcard
1219: .Sq *
1220: can also be used in place of a port number to allow all ports.
1221: By default all port forwarding listen requests are permitted.
1.272 jmc 1222: Note that the
1.271 djm 1223: .Cm GatewayPorts
1224: option may further restrict which addresses may be listened on.
1.276 ! djm 1225: Note also that
! 1226: .Xr ssh 1
! 1227: will request a listen host of
! 1228: .Dq localhost
! 1229: if no listen host was specifically requested, and this this name is
! 1230: treated differently to explict localhost addresses of
! 1231: .Dq 127.0.0.1
! 1232: and
! 1233: .Dq ::1 .
1.62 dtucker 1234: .It Cm PermitOpen
1235: Specifies the destinations to which TCP port forwarding is permitted.
1236: The forwarding specification must be one of the following forms:
1237: .Pp
1238: .Bl -item -offset indent -compact
1239: .It
1240: .Cm PermitOpen
1241: .Sm off
1242: .Ar host : port
1243: .Sm on
1244: .It
1245: .Cm PermitOpen
1246: .Sm off
1247: .Ar IPv4_addr : port
1248: .Sm on
1249: .It
1250: .Cm PermitOpen
1251: .Sm off
1252: .Ar \&[ IPv6_addr \&] : port
1253: .Sm on
1254: .El
1255: .Pp
1.68 dtucker 1256: Multiple forwards may be specified by separating them with whitespace.
1.62 dtucker 1257: An argument of
1.237 jmc 1258: .Cm any
1.62 dtucker 1259: can be used to remove all restrictions and permit any forwarding requests.
1.140 dtucker 1260: An argument of
1.237 jmc 1261: .Cm none
1.140 dtucker 1262: can be used to prohibit all forwarding requests.
1.227 jmc 1263: The wildcard
1.237 jmc 1264: .Sq *
1.227 jmc 1265: can be used for host or port to allow all hosts or ports, respectively.
1.63 jmc 1266: By default all port forwarding requests are permitted.
1.1 stevesk 1267: .It Cm PermitRootLogin
1.38 jmc 1268: Specifies whether root can log in using
1.1 stevesk 1269: .Xr ssh 1 .
1270: The argument must be
1.237 jmc 1271: .Cm yes ,
1272: .Cm prohibit-password ,
1273: .Cm forced-commands-only ,
1.1 stevesk 1274: or
1.237 jmc 1275: .Cm no .
1.1 stevesk 1276: The default is
1.237 jmc 1277: .Cm prohibit-password .
1.1 stevesk 1278: .Pp
1279: If this option is set to
1.237 jmc 1280: .Cm prohibit-password
1.255 jmc 1281: (or its deprecated alias,
1282: .Cm without-password ) ,
1.210 deraadt 1283: password and keyboard-interactive authentication are disabled for root.
1.1 stevesk 1284: .Pp
1285: If this option is set to
1.237 jmc 1286: .Cm forced-commands-only ,
1.1 stevesk 1287: root login with public key authentication will be allowed,
1288: but only if the
1289: .Ar command
1290: option has been specified
1291: (which may be useful for taking remote backups even if root login is
1.17 jmc 1292: normally not allowed).
1293: All other authentication methods are disabled for root.
1.1 stevesk 1294: .Pp
1295: If this option is set to
1.237 jmc 1296: .Cm no ,
1.38 jmc 1297: root is not allowed to log in.
1.231 jmc 1298: .It Cm PermitTTY
1299: Specifies whether
1300: .Xr pty 4
1301: allocation is permitted.
1302: The default is
1.237 jmc 1303: .Cm yes .
1.46 reyk 1304: .It Cm PermitTunnel
1305: Specifies whether
1306: .Xr tun 4
1307: device forwarding is allowed.
1.47 reyk 1308: The argument must be
1.237 jmc 1309: .Cm yes ,
1310: .Cm point-to-point
1.58 stevesk 1311: (layer 3),
1.237 jmc 1312: .Cm ethernet
1.58 stevesk 1313: (layer 2), or
1.237 jmc 1314: .Cm no .
1.58 stevesk 1315: Specifying
1.237 jmc 1316: .Cm yes
1.58 stevesk 1317: permits both
1.237 jmc 1318: .Cm point-to-point
1.58 stevesk 1319: and
1.237 jmc 1320: .Cm ethernet .
1.46 reyk 1321: The default is
1.237 jmc 1322: .Cm no .
1.178 djm 1323: .Pp
1324: Independent of this setting, the permissions of the selected
1325: .Xr tun 4
1326: device must allow access to the user.
1.6 markus 1327: .It Cm PermitUserEnvironment
1328: Specifies whether
1329: .Pa ~/.ssh/environment
1.9 stevesk 1330: and
1.6 markus 1331: .Cm environment=
1332: options in
1333: .Pa ~/.ssh/authorized_keys
1.9 stevesk 1334: are processed by
1.52 jmc 1335: .Xr sshd 8 .
1.6 markus 1336: The default is
1.237 jmc 1337: .Cm no .
1.9 stevesk 1338: Enabling environment processing may enable users to bypass access
1339: restrictions in some configurations using mechanisms such as
1340: .Ev LD_PRELOAD .
1.174 djm 1341: .It Cm PermitUserRC
1342: Specifies whether any
1343: .Pa ~/.ssh/rc
1344: file is executed.
1345: The default is
1.237 jmc 1346: .Cm yes .
1.1 stevesk 1347: .It Cm PidFile
1.4 stevesk 1348: Specifies the file that contains the process ID of the
1.195 dtucker 1349: SSH daemon, or
1.237 jmc 1350: .Cm none
1.195 dtucker 1351: to not write one.
1.1 stevesk 1352: The default is
1353: .Pa /var/run/sshd.pid .
1354: .It Cm Port
1355: Specifies the port number that
1.52 jmc 1356: .Xr sshd 8
1.1 stevesk 1357: listens on.
1358: The default is 22.
1359: Multiple options of this type are permitted.
1360: See also
1361: .Cm ListenAddress .
1362: .It Cm PrintLastLog
1363: Specifies whether
1.52 jmc 1364: .Xr sshd 8
1.36 jaredy 1365: should print the date and time of the last user login when a user logs
1366: in interactively.
1.1 stevesk 1367: The default is
1.237 jmc 1368: .Cm yes .
1.1 stevesk 1369: .It Cm PrintMotd
1370: Specifies whether
1.52 jmc 1371: .Xr sshd 8
1.1 stevesk 1372: should print
1373: .Pa /etc/motd
1374: when a user logs in interactively.
1375: (On some systems it is also printed by the shell,
1376: .Pa /etc/profile ,
1377: or equivalent.)
1378: The default is
1.237 jmc 1379: .Cm yes .
1.189 djm 1380: .It Cm PubkeyAcceptedKeyTypes
1381: Specifies the key types that will be accepted for public key authentication
1382: as a comma-separated pattern list.
1.208 djm 1383: Alternately if the specified value begins with a
1384: .Sq +
1385: character, then the specified key types will be appended to the default set
1386: instead of replacing them.
1.242 djm 1387: If the specified value begins with a
1388: .Sq -
1389: character, then the specified key types (including wildcards) will be removed
1390: from the default set instead of replacing them.
1.206 markus 1391: The default for this option is:
1392: .Bd -literal -offset 3n
1393: ecdsa-sha2-nistp256-cert-v01@openssh.com,
1394: ecdsa-sha2-nistp384-cert-v01@openssh.com,
1395: ecdsa-sha2-nistp521-cert-v01@openssh.com,
1396: ssh-ed25519-cert-v01@openssh.com,
1397: ssh-rsa-cert-v01@openssh.com,
1398: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1.220 djm 1399: ssh-ed25519,ssh-rsa
1.206 markus 1400: .Ed
1401: .Pp
1.237 jmc 1402: The list of available key types may also be obtained using
1403: .Qq ssh -Q key .
1.1 stevesk 1404: .It Cm PubkeyAuthentication
1405: Specifies whether public key authentication is allowed.
1406: The default is
1.237 jmc 1407: .Cm yes .
1.159 dtucker 1408: .It Cm RekeyLimit
1409: Specifies the maximum amount of data that may be transmitted before the
1410: session key is renegotiated, optionally followed a maximum amount of
1411: time that may pass before the session key is renegotiated.
1412: The first argument is specified in bytes and may have a suffix of
1413: .Sq K ,
1414: .Sq M ,
1415: or
1416: .Sq G
1417: to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1418: The default is between
1419: .Sq 1G
1420: and
1421: .Sq 4G ,
1422: depending on the cipher.
1423: The optional second value is specified in seconds and may use any of the
1424: units documented in the
1425: .Sx TIME FORMATS
1.160 jmc 1426: section.
1.159 dtucker 1427: The default value for
1428: .Cm RekeyLimit
1429: is
1.237 jmc 1430: .Cm default none ,
1.159 dtucker 1431: which means that rekeying is performed after the cipher's default amount
1432: of data has been sent or received and no time based rekeying is done.
1.118 djm 1433: .It Cm RevokedKeys
1.195 dtucker 1434: Specifies revoked public keys file, or
1.237 jmc 1435: .Cm none
1.195 dtucker 1436: to not use one.
1.118 djm 1437: Keys listed in this file will be refused for public key authentication.
1438: Note that if this file is not readable, then public key authentication will
1439: be refused for all users.
1.154 djm 1440: Keys may be specified as a text file, listing one public key per line, or as
1441: an OpenSSH Key Revocation List (KRL) as generated by
1.155 jmc 1442: .Xr ssh-keygen 1 .
1.161 jmc 1443: For more information on KRLs, see the KEY REVOCATION LISTS section in
1.154 djm 1444: .Xr ssh-keygen 1 .
1.257 djm 1445: .It Cm RDomain
1446: Specifies an explicit routing domain that is applied after authentication
1447: has completed.
1.259 jmc 1448: The user session, as well and any forwarded or listening IP sockets,
1449: will be bound to this
1.257 djm 1450: .Xr rdomain 4 .
1451: If the routing domain is set to
1452: .Cm \&%D ,
1.259 jmc 1453: then the domain in which the incoming connection was received will be applied.
1.274 djm 1454: .It Cm SetEnv
1455: Specifies one or more environment variables to set in child sessions started
1456: by
1457: .Xr sshd 8
1458: as
1459: .Dq NAME=VALUE .
1460: The environment value may be quoted (e.g. if it contains whitespace
1461: characters).
1462: Environment variables set by
1463: .Cm SetEnv
1464: override the default environment and any variables specified by the user
1465: via
1466: .Cm AcceptEnv
1467: or
1468: .Cm PermitUserEnvironment .
1.175 millert 1469: .It Cm StreamLocalBindMask
1470: Sets the octal file creation mode mask
1471: .Pq umask
1472: used when creating a Unix-domain socket file for local or remote
1473: port forwarding.
1474: This option is only used for port forwarding to a Unix-domain socket file.
1475: .Pp
1476: The default value is 0177, which creates a Unix-domain socket file that is
1477: readable and writable only by the owner.
1478: Note that not all operating systems honor the file mode on Unix-domain
1479: socket files.
1480: .It Cm StreamLocalBindUnlink
1481: Specifies whether to remove an existing Unix-domain socket file for local
1482: or remote port forwarding before creating a new one.
1483: If the socket file already exists and
1484: .Cm StreamLocalBindUnlink
1485: is not enabled,
1486: .Nm sshd
1487: will be unable to forward the port to the Unix-domain socket file.
1488: This option is only used for port forwarding to a Unix-domain socket file.
1489: .Pp
1490: The argument must be
1.237 jmc 1491: .Cm yes
1.175 millert 1492: or
1.237 jmc 1493: .Cm no .
1.175 millert 1494: The default is
1.237 jmc 1495: .Cm no .
1.1 stevesk 1496: .It Cm StrictModes
1497: Specifies whether
1.52 jmc 1498: .Xr sshd 8
1.1 stevesk 1499: should check file modes and ownership of the
1500: user's files and home directory before accepting login.
1501: This is normally desirable because novices sometimes accidentally leave their
1502: directory or files world-writable.
1503: The default is
1.237 jmc 1504: .Cm yes .
1.112 djm 1505: Note that this does not apply to
1506: .Cm ChrootDirectory ,
1507: whose permissions and ownership are checked unconditionally.
1.1 stevesk 1508: .It Cm Subsystem
1.51 jmc 1509: Configures an external subsystem (e.g. file transfer daemon).
1.59 djm 1510: Arguments should be a subsystem name and a command (with optional arguments)
1511: to execute upon subsystem request.
1.80 djm 1512: .Pp
1.1 stevesk 1513: The command
1.237 jmc 1514: .Cm sftp-server
1515: implements the SFTP file transfer subsystem.
1.80 djm 1516: .Pp
1517: Alternately the name
1.237 jmc 1518: .Cm internal-sftp
1519: implements an in-process SFTP server.
1.80 djm 1520: This may simplify configurations using
1521: .Cm ChrootDirectory
1522: to force a different filesystem root on clients.
1523: .Pp
1.1 stevesk 1524: By default no subsystems are defined.
1525: .It Cm SyslogFacility
1526: Gives the facility code that is used when logging messages from
1.53 jmc 1527: .Xr sshd 8 .
1.1 stevesk 1528: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1529: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1530: The default is AUTH.
1.27 markus 1531: .It Cm TCPKeepAlive
1532: Specifies whether the system should send TCP keepalive messages to the
1533: other side.
1534: If they are sent, death of the connection or crash of one
1535: of the machines will be properly noticed.
1536: However, this means that
1537: connections will die if the route is down temporarily, and some people
1538: find it annoying.
1539: On the other hand, if TCP keepalives are not sent,
1540: sessions may hang indefinitely on the server, leaving
1.237 jmc 1541: .Qq ghost
1.27 markus 1542: users and consuming server resources.
1543: .Pp
1544: The default is
1.237 jmc 1545: .Cm yes
1.27 markus 1546: (to send TCP keepalive messages), and the server will notice
1547: if the network goes down or the client host crashes.
1548: This avoids infinitely hanging sessions.
1549: .Pp
1550: To disable TCP keepalive messages, the value should be set to
1.237 jmc 1551: .Cm no .
1.118 djm 1552: .It Cm TrustedUserCAKeys
1553: Specifies a file containing public keys of certificate authorities that are
1.195 dtucker 1554: trusted to sign user certificates for authentication, or
1.237 jmc 1555: .Cm none
1.195 dtucker 1556: to not use one.
1.119 jmc 1557: Keys are listed one per line; empty lines and comments starting with
1.118 djm 1558: .Ql #
1559: are allowed.
1560: If a certificate is presented for authentication and has its signing CA key
1561: listed in this file, then it may be used for authentication for any user
1562: listed in the certificate's principals list.
1563: Note that certificates that lack a list of principals will not be permitted
1564: for authentication using
1565: .Cm TrustedUserCAKeys .
1.161 jmc 1566: For more details on certificates, see the CERTIFICATES section in
1.118 djm 1567: .Xr ssh-keygen 1 .
1.18 markus 1568: .It Cm UseDNS
1569: Specifies whether
1.52 jmc 1570: .Xr sshd 8
1.207 djm 1571: should look up the remote host name, and to check that
1.18 markus 1572: the resolved host name for the remote IP address maps back to the
1573: very same IP address.
1.207 djm 1574: .Pp
1575: If this option is set to
1.237 jmc 1576: .Cm no
1.207 djm 1577: (the default) then only addresses and not host names may be used in
1.221 djm 1578: .Pa ~/.ssh/authorized_keys
1.207 djm 1579: .Cm from
1580: and
1.211 jmc 1581: .Nm
1.207 djm 1582: .Cm Match
1583: .Cm Host
1584: directives.
1.137 djm 1585: .It Cm VersionAddendum
1586: Optionally specifies additional text to append to the SSH protocol banner
1587: sent by the server upon connection.
1588: The default is
1.237 jmc 1589: .Cm none .
1.1 stevesk 1590: .It Cm X11DisplayOffset
1591: Specifies the first display number available for
1.52 jmc 1592: .Xr sshd 8 Ns 's
1.1 stevesk 1593: X11 forwarding.
1.52 jmc 1594: This prevents sshd from interfering with real X11 servers.
1.1 stevesk 1595: The default is 10.
1596: .It Cm X11Forwarding
1597: Specifies whether X11 forwarding is permitted.
1.13 stevesk 1598: The argument must be
1.237 jmc 1599: .Cm yes
1.13 stevesk 1600: or
1.237 jmc 1601: .Cm no .
1.1 stevesk 1602: The default is
1.237 jmc 1603: .Cm no .
1.13 stevesk 1604: .Pp
1605: When X11 forwarding is enabled, there may be additional exposure to
1606: the server and to client displays if the
1.52 jmc 1607: .Xr sshd 8
1.13 stevesk 1608: proxy display is configured to listen on the wildcard address (see
1.237 jmc 1609: .Cm X11UseLocalhost ) ,
1610: though this is not the default.
1.13 stevesk 1611: Additionally, the authentication spoofing and authentication data
1612: verification and substitution occur on the client side.
1613: The security risk of using X11 forwarding is that the client's X11
1.52 jmc 1614: display server may be exposed to attack when the SSH client requests
1.13 stevesk 1615: forwarding (see the warnings for
1616: .Cm ForwardX11
1617: in
1.19 jmc 1618: .Xr ssh_config 5 ) .
1.13 stevesk 1619: A system administrator may have a stance in which they want to
1620: protect clients that may expose themselves to attack by unwittingly
1621: requesting X11 forwarding, which can warrant a
1.237 jmc 1622: .Cm no
1.13 stevesk 1623: setting.
1624: .Pp
1625: Note that disabling X11 forwarding does not prevent users from
1626: forwarding X11 traffic, as users can always install their own forwarders.
1.1 stevesk 1627: .It Cm X11UseLocalhost
1628: Specifies whether
1.52 jmc 1629: .Xr sshd 8
1.1 stevesk 1630: should bind the X11 forwarding server to the loopback address or to
1.15 jmc 1631: the wildcard address.
1632: By default,
1.52 jmc 1633: sshd binds the forwarding server to the loopback address and sets the
1.1 stevesk 1634: hostname part of the
1635: .Ev DISPLAY
1636: environment variable to
1.237 jmc 1637: .Cm localhost .
1.8 stevesk 1638: This prevents remote hosts from connecting to the proxy display.
1.1 stevesk 1639: However, some older X11 clients may not function with this
1640: configuration.
1641: .Cm X11UseLocalhost
1642: may be set to
1.237 jmc 1643: .Cm no
1.1 stevesk 1644: to specify that the forwarding server should be bound to the wildcard
1645: address.
1646: The argument must be
1.237 jmc 1647: .Cm yes
1.1 stevesk 1648: or
1.237 jmc 1649: .Cm no .
1.1 stevesk 1650: The default is
1.237 jmc 1651: .Cm yes .
1.1 stevesk 1652: .It Cm XAuthLocation
1.11 stevesk 1653: Specifies the full pathname of the
1.1 stevesk 1654: .Xr xauth 1
1.195 dtucker 1655: program, or
1.237 jmc 1656: .Cm none
1.195 dtucker 1657: to not use one.
1.1 stevesk 1658: The default is
1659: .Pa /usr/X11R6/bin/xauth .
1660: .El
1.55 jmc 1661: .Sh TIME FORMATS
1.53 jmc 1662: .Xr sshd 8
1.1 stevesk 1663: command-line arguments and configuration file options that specify time
1664: may be expressed using a sequence of the form:
1665: .Sm off
1.7 stevesk 1666: .Ar time Op Ar qualifier ,
1.1 stevesk 1667: .Sm on
1668: where
1669: .Ar time
1670: is a positive integer value and
1671: .Ar qualifier
1672: is one of the following:
1673: .Pp
1674: .Bl -tag -width Ds -compact -offset indent
1.64 jmc 1675: .It Aq Cm none
1.1 stevesk 1676: seconds
1677: .It Cm s | Cm S
1678: seconds
1679: .It Cm m | Cm M
1680: minutes
1681: .It Cm h | Cm H
1682: hours
1683: .It Cm d | Cm D
1684: days
1685: .It Cm w | Cm W
1686: weeks
1687: .El
1688: .Pp
1689: Each member of the sequence is added together to calculate
1690: the total time value.
1691: .Pp
1692: Time format examples:
1693: .Pp
1694: .Bl -tag -width Ds -compact -offset indent
1695: .It 600
1696: 600 seconds (10 minutes)
1697: .It 10m
1698: 10 minutes
1699: .It 1h30m
1700: 1 hour 30 minutes (90 minutes)
1701: .El
1.235 jmc 1702: .Sh TOKENS
1703: Arguments to some keywords can make use of tokens,
1704: which are expanded at runtime:
1705: .Pp
1706: .Bl -tag -width XXXX -offset indent -compact
1707: .It %%
1708: A literal
1709: .Sq % .
1.257 djm 1710: .It \&%D
1711: The routing domain in which the incoming connection was received.
1.235 jmc 1712: .It %F
1713: The fingerprint of the CA key.
1714: .It %f
1715: The fingerprint of the key or certificate.
1716: .It %h
1717: The home directory of the user.
1718: .It %i
1719: The key ID in the certificate.
1720: .It %K
1721: The base64-encoded CA key.
1722: .It %k
1723: The base64-encoded key or certificate for authentication.
1724: .It %s
1725: The serial number of the certificate.
1726: .It \&%T
1727: The type of the CA key.
1728: .It %t
1729: The key or certificate type.
1.268 jmc 1730: .It \&%U
1731: The numeric user ID of the target user.
1.235 jmc 1732: .It %u
1733: The username.
1734: .El
1735: .Pp
1736: .Cm AuthorizedKeysCommand
1.270 jmc 1737: accepts the tokens %%, %f, %h, %k, %t, %U, and %u.
1.235 jmc 1738: .Pp
1739: .Cm AuthorizedKeysFile
1.270 jmc 1740: accepts the tokens %%, %h, %U, and %u.
1.235 jmc 1741: .Pp
1742: .Cm AuthorizedPrincipalsCommand
1.270 jmc 1743: accepts the tokens %%, %F, %f, %h, %i, %K, %k, %s, %T, %t, %U, and %u.
1.235 jmc 1744: .Pp
1745: .Cm AuthorizedPrincipalsFile
1.270 jmc 1746: accepts the tokens %%, %h, %U, and %u.
1.235 jmc 1747: .Pp
1748: .Cm ChrootDirectory
1.270 jmc 1749: accepts the tokens %%, %h, %U, and %u.
1.257 djm 1750: .Pp
1751: .Cm RoutingDomain
1752: accepts the token %D.
1.1 stevesk 1753: .Sh FILES
1754: .Bl -tag -width Ds
1755: .It Pa /etc/ssh/sshd_config
1756: Contains configuration data for
1.53 jmc 1757: .Xr sshd 8 .
1.1 stevesk 1758: This file should be writable by root only, but it is recommended
1759: (though not necessary) that it be world-readable.
1760: .El
1.19 jmc 1761: .Sh SEE ALSO
1.237 jmc 1762: .Xr sftp-server 8 ,
1.19 jmc 1763: .Xr sshd 8
1.1 stevesk 1764: .Sh AUTHORS
1.237 jmc 1765: .An -nosplit
1.1 stevesk 1766: OpenSSH is a derivative of the original and free
1.237 jmc 1767: ssh 1.2.12 release by
1768: .An Tatu Ylonen .
1769: .An Aaron Campbell , Bob Beck , Markus Friedl , Niels Provos ,
1770: .An Theo de Raadt
1771: and
1772: .An Dug Song
1.1 stevesk 1773: removed many bugs, re-added newer features and
1774: created OpenSSH.
1.237 jmc 1775: .An Markus Friedl
1776: contributed the support for SSH protocol versions 1.5 and 2.0.
1777: .An Niels Provos
1778: and
1779: .An Markus Friedl
1780: contributed support for privilege separation.
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