Annotation of src/usr.bin/ssh/sshd.8, Revision 1.51.2.4
1.1 deraadt 1: .\" -*- nroff -*-
2: .\"
3: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: .\" All rights reserved
6: .\"
1.51.2.3 jason 7: .\" As far as I am concerned, the code I have written for this software
8: .\" can be used freely for any purpose. Any derived versions of this
9: .\" software must be clearly marked as such, and if the derived work is
10: .\" incompatible with the protocol description in the RFC file, it must be
11: .\" called by a name other than "ssh" or "Secure Shell".
12: .\"
13: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
14: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
15: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
16: .\"
17: .\" Redistribution and use in source and binary forms, with or without
18: .\" modification, are permitted provided that the following conditions
19: .\" are met:
20: .\" 1. Redistributions of source code must retain the above copyright
21: .\" notice, this list of conditions and the following disclaimer.
22: .\" 2. Redistributions in binary form must reproduce the above copyright
23: .\" notice, this list of conditions and the following disclaimer in the
24: .\" documentation and/or other materials provided with the distribution.
1.1 deraadt 25: .\"
1.51.2.3 jason 26: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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34: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 deraadt 36: .\"
1.51.2.4! jason 37: .\" $OpenBSD: sshd.8,v 1.95 2001/02/17 23:48:48 deraadt Exp $
1.2 deraadt 38: .Dd September 25, 1999
39: .Dt SSHD 8
40: .Os
41: .Sh NAME
42: .Nm sshd
1.51.2.4! jason 43: .Nd OpenSSH secure shell daemon
1.2 deraadt 44: .Sh SYNOPSIS
45: .Nm sshd
1.51.2.4! jason 46: .Op Fl diqD46
1.2 deraadt 47: .Op Fl b Ar bits
48: .Op Fl f Ar config_file
49: .Op Fl g Ar login_grace_time
50: .Op Fl h Ar host_key_file
51: .Op Fl k Ar key_gen_time
52: .Op Fl p Ar port
1.51.2.2 jason 53: .Op Fl u Ar len
1.26 markus 54: .Op Fl V Ar client_protocol_id
1.40 aaron 55: .Sh DESCRIPTION
1.2 deraadt 56: .Nm
1.40 aaron 57: (Secure Shell Daemon) is the daemon program for
1.2 deraadt 58: .Xr ssh 1 .
1.42 hugh 59: Together these programs replace rlogin and rsh, and
1.1 deraadt 60: provide secure encrypted communications between two untrusted hosts
1.36 aaron 61: over an insecure network.
62: The programs are intended to be as easy to
1.1 deraadt 63: install and use as possible.
1.2 deraadt 64: .Pp
65: .Nm
1.36 aaron 66: is the daemon that listens for connections from clients.
1.40 aaron 67: It is normally started at boot from
1.2 deraadt 68: .Pa /etc/rc .
69: It forks a new
1.36 aaron 70: daemon for each incoming connection.
71: The forked daemons handle
1.1 deraadt 72: key exchange, encryption, authentication, command execution,
73: and data exchange.
1.49 markus 74: This implementation of
75: .Nm
76: supports both SSH protocol version 1 and 2 simultaneously.
1.2 deraadt 77: .Nm
1.36 aaron 78: works as follows.
1.49 markus 79: .Pp
80: .Ss SSH protocol version 1
81: .Pp
1.36 aaron 82: Each host has a host-specific RSA key
83: (normally 1024 bits) used to identify the host.
84: Additionally, when
1.1 deraadt 85: the daemon starts, it generates a server RSA key (normally 768 bits).
86: This key is normally regenerated every hour if it has been used, and
87: is never stored on disk.
1.2 deraadt 88: .Pp
1.42 hugh 89: Whenever a client connects the daemon responds with its public
90: host and server keys.
1.36 aaron 91: The client compares the
1.49 markus 92: RSA host key against its own database to verify that it has not changed.
1.36 aaron 93: The client then generates a 256 bit random number.
94: It encrypts this
1.1 deraadt 95: random number using both the host key and the server key, and sends
1.36 aaron 96: the encrypted number to the server.
1.42 hugh 97: Both sides then use this
1.1 deraadt 98: random number as a session key which is used to encrypt all further
1.36 aaron 99: communications in the session.
100: The rest of the session is encrypted
1.42 hugh 101: using a conventional cipher, currently Blowfish or 3DES, with 3DES
1.39 deraadt 102: being used by default.
1.36 aaron 103: The client selects the encryption algorithm
1.5 deraadt 104: to use from those offered by the server.
1.2 deraadt 105: .Pp
1.36 aaron 106: Next, the server and the client enter an authentication dialog.
107: The client tries to authenticate itself using
1.2 deraadt 108: .Pa .rhosts
109: authentication,
110: .Pa .rhosts
111: authentication combined with RSA host
1.1 deraadt 112: authentication, RSA challenge-response authentication, or password
113: based authentication.
1.2 deraadt 114: .Pp
1.1 deraadt 115: Rhosts authentication is normally disabled
116: because it is fundamentally insecure, but can be enabled in the server
1.36 aaron 117: configuration file if desired.
118: System security is not improved unless
1.2 deraadt 119: .Xr rshd 8 ,
120: .Xr rlogind 8 ,
121: .Xr rexecd 8 ,
122: and
123: .Xr rexd 8
1.1 deraadt 124: are disabled (thus completely disabling
1.2 deraadt 125: .Xr rlogin 1
1.1 deraadt 126: and
1.2 deraadt 127: .Xr rsh 1
1.42 hugh 128: into the machine).
1.2 deraadt 129: .Pp
1.49 markus 130: .Ss SSH protocol version 2
131: .Pp
1.51.2.2 jason 132: Version 2 works similarly:
1.49 markus 133: Each host has a host-specific DSA key used to identify the host.
134: However, when the daemon starts, it does not generate a server key.
135: Forward security is provided through a Diffie-Hellman key agreement.
136: This key agreement results in a shared session key.
137: The rest of the session is encrypted
138: using a symmetric cipher, currently
139: Blowfish, 3DES or CAST128 in CBC mode or Arcfour.
140: The client selects the encryption algorithm
141: to use from those offered by the server.
142: Additionally, session integrity is provided
1.51 hugh 143: through a cryptographic message authentication code
1.49 markus 144: (hmac-sha1 or hmac-md5).
145: .Pp
146: Protocol version 2 provides a public key based
1.51.2.4! jason 147: user authentication method (PubkeyAuthentication)
1.49 markus 148: and conventional password authentication.
149: .Pp
150: .Ss Command execution and data forwarding
151: .Pp
1.1 deraadt 152: If the client successfully authenticates itself, a dialog for
1.36 aaron 153: preparing the session is entered.
154: At this time the client may request
1.1 deraadt 155: things like allocating a pseudo-tty, forwarding X11 connections,
156: forwarding TCP/IP connections, or forwarding the authentication agent
157: connection over the secure channel.
1.2 deraadt 158: .Pp
1.1 deraadt 159: Finally, the client either requests a shell or execution of a command.
1.36 aaron 160: The sides then enter session mode.
161: In this mode, either side may send
1.1 deraadt 162: data at any time, and such data is forwarded to/from the shell or
163: command on the server side, and the user terminal in the client side.
1.2 deraadt 164: .Pp
1.1 deraadt 165: When the user program terminates and all forwarded X11 and other
166: connections have been closed, the server sends command exit status to
167: the client, and both sides exit.
1.2 deraadt 168: .Pp
169: .Nm
1.1 deraadt 170: can be configured using command-line options or a configuration
1.36 aaron 171: file.
172: Command-line options override values specified in the
1.1 deraadt 173: configuration file.
1.25 markus 174: .Pp
175: .Nm
176: rereads its configuration file when it receives a hangup signal,
177: .Dv SIGHUP .
1.18 aaron 178: .Pp
179: The options are as follows:
1.2 deraadt 180: .Bl -tag -width Ds
181: .It Fl b Ar bits
1.1 deraadt 182: Specifies the number of bits in the server key (default 768).
1.2 deraadt 183: .Pp
184: .It Fl d
1.36 aaron 185: Debug mode.
186: The server sends verbose debug output to the system
187: log, and does not put itself in the background.
188: The server also will not fork and will only process one connection.
189: This option is only intended for debugging for the server.
1.51.2.3 jason 190: Multiple -d options increases the debugging level.
191: Maximum is 3.
1.2 deraadt 192: .It Fl f Ar configuration_file
1.36 aaron 193: Specifies the name of the configuration file.
194: The default is
1.2 deraadt 195: .Pa /etc/sshd_config .
1.16 markus 196: .Nm
197: refuses to start if there is no configuration file.
1.2 deraadt 198: .It Fl g Ar login_grace_time
1.1 deraadt 199: Gives the grace time for clients to authenticate themselves (default
1.51.2.4! jason 200: 600 seconds).
1.36 aaron 201: If the client fails to authenticate the user within
202: this many seconds, the server disconnects and exits.
203: A value of zero indicates no limit.
1.2 deraadt 204: .It Fl h Ar host_key_file
1.51.2.4! jason 205: Specifies the file from which the host key is read (default
1.2 deraadt 206: .Pa /etc/ssh_host_key ) .
1.7 markus 207: This option must be given if
208: .Nm
209: is not run as root (as the normal
1.1 deraadt 210: host file is normally not readable by anyone but root).
1.51.2.4! jason 211: It is possible to have multiple host key files for
! 212: the different protocol versions.
1.2 deraadt 213: .It Fl i
1.7 markus 214: Specifies that
215: .Nm
1.40 aaron 216: is being run from inetd.
1.7 markus 217: .Nm
218: is normally not run
1.1 deraadt 219: from inetd because it needs to generate the server key before it can
1.36 aaron 220: respond to the client, and this may take tens of seconds.
221: Clients would have to wait too long if the key was regenerated every time.
1.35 aaron 222: However, with small key sizes (e.g., 512) using
1.7 markus 223: .Nm
224: from inetd may
1.1 deraadt 225: be feasible.
1.2 deraadt 226: .It Fl k Ar key_gen_time
1.1 deraadt 227: Specifies how often the server key is regenerated (default 3600
1.36 aaron 228: seconds, or one hour).
229: The motivation for regenerating the key fairly
1.1 deraadt 230: often is that the key is not stored anywhere, and after about an hour,
231: it becomes impossible to recover the key for decrypting intercepted
232: communications even if the machine is cracked into or physically
1.36 aaron 233: seized.
234: A value of zero indicates that the key will never be regenerated.
1.2 deraadt 235: .It Fl p Ar port
1.1 deraadt 236: Specifies the port on which the server listens for connections
237: (default 22).
1.2 deraadt 238: .It Fl q
1.36 aaron 239: Quiet mode.
240: Nothing is sent to the system log.
241: Normally the beginning,
1.1 deraadt 242: authentication, and termination of each connection is logged.
1.51.2.2 jason 243: .It Fl u Ar len
244: This option is used to specify the size of the field
245: in the
246: .Li utmp
247: structure that holds the remote host name.
248: If the resolved host name is longer than
249: .Ar len ,
250: the dotted decimal value will be used instead.
251: This allows hosts with very long host names that
252: overflow this field to still be uniquely identified.
253: Specifying
254: .Fl u0
255: indicates that only dotted decimal addresses
256: should be put into the
257: .Pa utmp
258: file.
1.51.2.4! jason 259: .It Fl D
! 260: When this option is specified
! 261: .Nm
! 262: will not detach and does not become a daemon.
! 263: This allows easy monitoring of
! 264: .Nm sshd .
1.26 markus 265: .It Fl V Ar client_protocol_id
1.51.2.3 jason 266: SSH-2 compatibility mode.
1.42 hugh 267: When this option is specified
1.26 markus 268: .Nm
1.42 hugh 269: assumes the client has sent the supplied version string
1.26 markus 270: and skips the
271: Protocol Version Identification Exchange.
1.51.2.3 jason 272: This option is not intended to be called directly.
1.29 markus 273: .It Fl 4
274: Forces
275: .Nm
276: to use IPv4 addresses only.
277: .It Fl 6
278: Forces
279: .Nm
280: to use IPv6 addresses only.
1.2 deraadt 281: .El
282: .Sh CONFIGURATION FILE
283: .Nm
1.40 aaron 284: reads configuration data from
1.2 deraadt 285: .Pa /etc/sshd_config
286: (or the file specified with
287: .Fl f
1.36 aaron 288: on the command line).
289: The file contains keyword-value pairs, one per line.
290: Lines starting with
1.2 deraadt 291: .Ql #
1.1 deraadt 292: and empty lines are interpreted as comments.
1.2 deraadt 293: .Pp
1.1 deraadt 294: The following keywords are possible.
1.2 deraadt 295: .Bl -tag -width Ds
296: .It Cm AFSTokenPassing
1.36 aaron 297: Specifies whether an AFS token may be forwarded to the server.
298: Default is
1.2 deraadt 299: .Dq yes .
1.11 markus 300: .It Cm AllowGroups
1.51.2.4! jason 301: This keyword can be followed by a list of group names, separated
1.36 aaron 302: by spaces.
303: If specified, login is allowed only for users whose primary
1.51.2.4! jason 304: group or supplementary group list matches one of the patterns.
1.11 markus 305: .Ql \&*
306: and
307: .Ql ?
308: can be used as
1.36 aaron 309: wildcards in the patterns.
1.51.2.2 jason 310: Only group names are valid; a numerical group ID isn't recognized.
1.51.2.4! jason 311: By default login is allowed regardless of the group list.
1.3 dugsong 312: .Pp
1.51.2.3 jason 313: .It Cm AllowTcpForwarding
314: Specifies whether TCP forwarding is permitted.
315: The default is
316: .Dq yes .
317: Note that disabling TCP forwarding does not improve security unless
318: users are also denied shell access, as they can always install their
319: own forwarders.
320: .Pp
1.11 markus 321: .It Cm AllowUsers
1.51.2.4! jason 322: This keyword can be followed by a list of user names, separated
1.36 aaron 323: by spaces.
324: If specified, login is allowed only for users names that
1.11 markus 325: match one of the patterns.
326: .Ql \&*
327: and
328: .Ql ?
329: can be used as
1.36 aaron 330: wildcards in the patterns.
1.51.2.2 jason 331: Only user names are valid; a numerical user ID isn't recognized.
1.36 aaron 332: By default login is allowed regardless of the user name.
1.11 markus 333: .Pp
1.51.2.4! jason 334: .It Cm Banner
! 335: In some jurisdictions, sending a warning message before authentication
! 336: may be relevant for getting legal protection.
! 337: The contents of the specified file are sent to the remote user before
! 338: authentication is allowed.
! 339: This option is only available for protocol version 2.
! 340: .Pp
1.41 markus 341: .It Cm Ciphers
342: Specifies the ciphers allowed for protocol version 2.
343: Multiple ciphers must be comma-separated.
344: The default is
1.51.2.4! jason 345: .Dq 3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes128-cbc .
1.8 markus 346: .It Cm CheckMail
347: Specifies whether
348: .Nm
349: should check for new mail for interactive logins.
350: The default is
351: .Dq no .
1.11 markus 352: .It Cm DenyGroups
353: This keyword can be followed by a number of group names, separated
1.36 aaron 354: by spaces.
1.51.2.4! jason 355: Users whose primary group or supplementary group list matches
! 356: one of the patterns aren't allowed to log in.
1.11 markus 357: .Ql \&*
358: and
359: .Ql ?
360: can be used as
1.36 aaron 361: wildcards in the patterns.
1.51.2.2 jason 362: Only group names are valid; a numerical group ID isn't recognized.
1.51.2.4! jason 363: By default login is allowed regardless of the group list.
1.11 markus 364: .Pp
365: .It Cm DenyUsers
366: This keyword can be followed by a number of user names, separated
1.36 aaron 367: by spaces.
368: Login is disallowed for user names that match one of the patterns.
1.11 markus 369: .Ql \&*
370: and
371: .Ql ?
1.36 aaron 372: can be used as wildcards in the patterns.
1.51.2.2 jason 373: Only user names are valid; a numerical user ID isn't recognized.
1.36 aaron 374: By default login is allowed regardless of the user name.
1.51.2.4! jason 375: .It Cm PubkeyAuthentication
! 376: Specifies whether public key authentication is allowed.
1.49 markus 377: The default is
378: .Dq yes .
379: Note that this option applies to protocol version 2 only.
1.47 markus 380: .It Cm GatewayPorts
381: Specifies whether remote hosts are allowed to connect to ports
382: forwarded for the client.
383: The argument must be
384: .Dq yes
385: or
386: .Dq no .
387: The default is
388: .Dq no .
1.2 deraadt 389: .It Cm HostKey
1.51.2.4! jason 390: Specifies the file containing the private host keys (default
1.46 markus 391: .Pa /etc/ssh_host_key )
1.51.2.4! jason 392: used by SSH protocol versions 1 and 2.
1.9 markus 393: Note that
394: .Nm
1.51.2.4! jason 395: will refuse to use a file if it is group/world-accessible.
! 396: It is possible to have multiple host key files.
! 397: .Dq rsa1
! 398: keys are used for version 1 and
! 399: .Dq dsa
! 400: or
! 401: .Dq rsa
! 402: are used for version 2 of the SSH protocol.
1.2 deraadt 403: .It Cm IgnoreRhosts
1.34 markus 404: Specifies that
405: .Pa .rhosts
1.40 aaron 406: and
1.34 markus 407: .Pa .shosts
408: files will not be used in authentication.
1.2 deraadt 409: .Pa /etc/hosts.equiv
1.1 deraadt 410: and
1.40 aaron 411: .Pa /etc/shosts.equiv
1.36 aaron 412: are still used.
1.40 aaron 413: The default is
1.34 markus 414: .Dq yes .
1.24 markus 415: .It Cm IgnoreUserKnownHosts
416: Specifies whether
417: .Nm
418: should ignore the user's
419: .Pa $HOME/.ssh/known_hosts
1.45 markus 420: during
1.24 markus 421: .Cm RhostsRSAAuthentication .
422: The default is
1.2 deraadt 423: .Dq no .
424: .It Cm KeepAlive
1.1 deraadt 425: Specifies whether the system should send keepalive messages to the
1.36 aaron 426: other side.
427: If they are sent, death of the connection or crash of one
428: of the machines will be properly noticed.
429: However, this means that
1.1 deraadt 430: connections will die if the route is down temporarily, and some people
1.36 aaron 431: find it annoying.
1.51 hugh 432: On the other hand, if keepalives are not sent,
1.2 deraadt 433: sessions may hang indefinitely on the server, leaving
434: .Dq ghost
435: users and consuming server resources.
436: .Pp
437: The default is
438: .Dq yes
439: (to send keepalives), and the server will notice
1.36 aaron 440: if the network goes down or the client host reboots.
441: This avoids infinitely hanging sessions.
1.2 deraadt 442: .Pp
443: To disable keepalives, the value should be set to
444: .Dq no
445: in both the server and the client configuration files.
446: .It Cm KerberosAuthentication
1.36 aaron 447: Specifies whether Kerberos authentication is allowed.
448: This can be in the form of a Kerberos ticket, or if
1.7 markus 449: .Cm PasswordAuthentication
1.1 deraadt 450: is yes, the password provided by the user will be validated through
1.51.2.3 jason 451: the Kerberos KDC.
452: To use this option, the server needs a
1.51.2.2 jason 453: Kerberos servtab which allows the verification of the KDC's identity.
1.36 aaron 454: Default is
1.3 dugsong 455: .Dq yes .
1.2 deraadt 456: .It Cm KerberosOrLocalPasswd
1.1 deraadt 457: If set then if password authentication through Kerberos fails then
458: the password will be validated via any additional local mechanism
1.2 deraadt 459: such as
1.51.2.3 jason 460: .Pa /etc/passwd .
1.36 aaron 461: Default is
1.20 dugsong 462: .Dq yes .
1.2 deraadt 463: .It Cm KerberosTgtPassing
1.1 deraadt 464: Specifies whether a Kerberos TGT may be forwarded to the server.
1.40 aaron 465: Default is
1.3 dugsong 466: .Dq no ,
467: as this only works when the Kerberos KDC is actually an AFS kaserver.
1.2 deraadt 468: .It Cm KerberosTicketCleanup
1.7 markus 469: Specifies whether to automatically destroy the user's ticket cache
1.36 aaron 470: file on logout.
471: Default is
1.3 dugsong 472: .Dq yes .
1.2 deraadt 473: .It Cm KeyRegenerationInterval
1.1 deraadt 474: The server key is automatically regenerated after this many seconds
1.36 aaron 475: (if it has been used).
476: The purpose of regeneration is to prevent
1.1 deraadt 477: decrypting captured sessions by later breaking into the machine and
1.36 aaron 478: stealing the keys.
479: The key is never stored anywhere.
480: If the value is 0, the key is never regenerated.
481: The default is 3600 (seconds).
1.7 markus 482: .It Cm ListenAddress
483: Specifies what local address
484: .Nm
485: should listen on.
486: The default is to listen to all local addresses.
1.28 markus 487: Multiple options of this type are permitted.
488: Additionally, the
489: .Cm Ports
490: options must precede this option.
1.2 deraadt 491: .It Cm LoginGraceTime
1.1 deraadt 492: The server disconnects after this time if the user has not
1.36 aaron 493: successfully logged in.
494: If the value is 0, there is no time limit.
1.1 deraadt 495: The default is 600 (seconds).
1.23 markus 496: .It Cm LogLevel
497: Gives the verbosity level that is used when logging messages from
498: .Nm sshd .
499: The possible values are:
1.27 markus 500: QUIET, FATAL, ERROR, INFO, VERBOSE and DEBUG.
1.23 markus 501: The default is INFO.
502: Logging with level DEBUG violates the privacy of users
503: and is not recommended.
1.51.2.4! jason 504: .It Cm MACs
! 505: Specifies the available MAC (message authentication code) algorithms.
! 506: The MAC algorithm is used in protocol version 2
! 507: for data integrity protection.
! 508: Multiple algorithms must be comma-separated.
! 509: The default is
! 510: .Pp
! 511: .Bd -literal
! 512: ``hmac-sha1,hmac-md5,hmac-ripemd160,hmac-ripemd160@openssh.com,
! 513: hmac-sha1-96,hmac-md5-96''
! 514: .Ed
1.51.2.2 jason 515: .It Cm MaxStartups
516: Specifies the maximum number of concurrent unauthenticated connections to the
517: .Nm
518: daemon.
519: Additional connections will be dropped until authentication succeeds or the
520: .Cm LoginGraceTime
521: expires for a connection.
522: The default is 10.
523: .Pp
524: Alternatively, random early drop can be enabled by specifying
525: the three colon separated values
526: .Dq start:rate:full
1.51.2.3 jason 527: (e.g., "10:30:60").
1.51.2.2 jason 528: .Nm
1.51.2.4! jason 529: will refuse connection attempts with a probability of
1.51.2.2 jason 530: .Dq rate/100
531: (30%)
532: if there are currently
533: .Dq start
534: (10)
535: unauthenticated connections.
1.51.2.4! jason 536: The probability increases linearly and all connection attempts
1.51.2.2 jason 537: are refused if the number of unauthenticated connections reaches
538: .Dq full
539: (60).
1.2 deraadt 540: .It Cm PasswordAuthentication
1.1 deraadt 541: Specifies whether password authentication is allowed.
1.2 deraadt 542: The default is
543: .Dq yes .
1.51.2.2 jason 544: Note that this option applies to both protocol versions 1 and 2.
1.2 deraadt 545: .It Cm PermitEmptyPasswords
1.1 deraadt 546: When password authentication is allowed, it specifies whether the
1.36 aaron 547: server allows login to accounts with empty password strings.
548: The default is
1.34 markus 549: .Dq no .
1.2 deraadt 550: .It Cm PermitRootLogin
1.1 deraadt 551: Specifies whether the root can log in using
1.2 deraadt 552: .Xr ssh 1 .
1.15 markus 553: The argument must be
554: .Dq yes ,
1.51.2.4! jason 555: .Dq without-password ,
! 556: .Dq forced-commands-only
1.15 markus 557: or
558: .Dq no .
1.2 deraadt 559: The default is
560: .Dq yes .
1.51.2.4! jason 561: .Pp
! 562: If this option is set to
1.15 markus 563: .Dq without-password
1.51.2.4! jason 564: password authentication is disabled for root.
1.2 deraadt 565: .Pp
1.51.2.4! jason 566: If this option is set to
! 567: .Dq forced-commands-only
! 568: root login with public key authentication will be allowed,
! 569: but only if the
1.2 deraadt 570: .Ar command
1.51.2.4! jason 571: option has been specified
1.1 deraadt 572: (which may be useful for taking remote backups even if root login is
1.51.2.4! jason 573: normally not allowed). All other authentication methods are disabled
! 574: for root.
1.43 markus 575: .It Cm PidFile
576: Specifies the file that contains the process identifier of the
577: .Nm
578: daemon.
579: The default is
580: .Pa /var/run/sshd.pid .
1.2 deraadt 581: .It Cm Port
1.1 deraadt 582: Specifies the port number that
1.2 deraadt 583: .Nm
1.36 aaron 584: listens on.
585: The default is 22.
1.28 markus 586: Multiple options of this type are permitted.
1.2 deraadt 587: .It Cm PrintMotd
1.1 deraadt 588: Specifies whether
1.2 deraadt 589: .Nm
1.40 aaron 590: should print
1.2 deraadt 591: .Pa /etc/motd
1.36 aaron 592: when a user logs in interactively.
593: (On some systems it is also printed by the shell,
1.2 deraadt 594: .Pa /etc/profile ,
1.36 aaron 595: or equivalent.)
596: The default is
1.2 deraadt 597: .Dq yes .
1.41 markus 598: .It Cm Protocol
599: Specifies the protocol versions
600: .Nm
601: should support.
602: The possible values are
603: .Dq 1
604: and
605: .Dq 2 .
606: Multiple versions must be comma-separated.
607: The default is
608: .Dq 1 .
1.2 deraadt 609: .It Cm RandomSeed
1.36 aaron 610: Obsolete.
611: Random number generation uses other techniques.
1.51.2.4! jason 612: .It Cm ReverseMappingCheck
! 613: Specifies whether
! 614: .Nm
! 615: should try to verify the remote host name and check that
! 616: the resolved host name for the remote IP address maps back to the
! 617: very same IP address.
! 618: The default is
! 619: .Dq no .
1.2 deraadt 620: .It Cm RhostsAuthentication
1.1 deraadt 621: Specifies whether authentication using rhosts or /etc/hosts.equiv
1.36 aaron 622: files is sufficient.
623: Normally, this method should not be permitted because it is insecure.
1.7 markus 624: .Cm RhostsRSAAuthentication
625: should be used
1.1 deraadt 626: instead, because it performs RSA-based host authentication in addition
627: to normal rhosts or /etc/hosts.equiv authentication.
1.2 deraadt 628: The default is
629: .Dq no .
630: .It Cm RhostsRSAAuthentication
1.1 deraadt 631: Specifies whether rhosts or /etc/hosts.equiv authentication together
1.36 aaron 632: with successful RSA host authentication is allowed.
633: The default is
1.34 markus 634: .Dq no .
1.2 deraadt 635: .It Cm RSAAuthentication
1.36 aaron 636: Specifies whether pure RSA authentication is allowed.
637: The default is
1.2 deraadt 638: .Dq yes .
1.49 markus 639: Note that this option applies to protocol version 1 only.
1.2 deraadt 640: .It Cm ServerKeyBits
1.36 aaron 641: Defines the number of bits in the server key.
642: The minimum value is 512, and the default is 768.
1.51.2.4! jason 643: .It Cm ChallengeResponseAuthentication
1.7 markus 644: Specifies whether
1.51.2.4! jason 645: challenge reponse
1.36 aaron 646: authentication is allowed.
1.51.2.4! jason 647: Currently there is only support for
! 648: .Xr skey 1
! 649: authentication.
1.36 aaron 650: The default is
1.7 markus 651: .Dq yes .
1.2 deraadt 652: .It Cm StrictModes
1.12 markus 653: Specifies whether
654: .Nm
655: should check file modes and ownership of the
1.36 aaron 656: user's files and home directory before accepting login.
657: This is normally desirable because novices sometimes accidentally leave their
658: directory or files world-writable.
659: The default is
1.7 markus 660: .Dq yes .
1.51.2.2 jason 661: .It Cm Subsystem
1.51.2.3 jason 662: Configures an external subsystem (e.g., file transfer daemon).
663: Arguments should be a subsystem name and a command to execute upon subsystem
664: request.
665: The command
666: .Xr sftp-server 8
667: implements the
668: .Dq sftp
669: file transfer subsystem.
1.51.2.2 jason 670: By default no subsystems are defined.
671: Note that this option applies to protocol version 2 only.
1.2 deraadt 672: .It Cm SyslogFacility
1.1 deraadt 673: Gives the facility code that is used when logging messages from
1.2 deraadt 674: .Nm sshd .
1.1 deraadt 675: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1.36 aaron 676: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
677: The default is AUTH.
1.10 markus 678: .It Cm UseLogin
679: Specifies whether
680: .Xr login 1
1.51.2.1 jason 681: is used for interactive login sessions.
682: Note that
683: .Xr login 1
1.51.2.2 jason 684: is never used for remote command execution.
1.36 aaron 685: The default is
1.10 markus 686: .Dq no .
1.6 aaron 687: .It Cm X11DisplayOffset
688: Specifies the first display number available for
689: .Nm sshd Ns 's
1.36 aaron 690: X11 forwarding.
691: This prevents
1.6 aaron 692: .Nm
693: from interfering with real X11 servers.
1.34 markus 694: The default is 10.
1.30 markus 695: .It Cm X11Forwarding
1.36 aaron 696: Specifies whether X11 forwarding is permitted.
697: The default is
1.34 markus 698: .Dq no .
1.30 markus 699: Note that disabling X11 forwarding does not improve security in any
700: way, as users can always install their own forwarders.
1.51.2.1 jason 701: .It Cm XAuthLocation
702: Specifies the location of the
703: .Xr xauth 1
704: program.
705: The default is
706: .Pa /usr/X11R6/bin/xauth .
1.2 deraadt 707: .El
708: .Sh LOGIN PROCESS
1.1 deraadt 709: When a user successfully logs in,
1.2 deraadt 710: .Nm
1.1 deraadt 711: does the following:
1.2 deraadt 712: .Bl -enum -offset indent
713: .It
1.1 deraadt 714: If the login is on a tty, and no command has been specified,
1.40 aaron 715: prints last login time and
1.2 deraadt 716: .Pa /etc/motd
1.1 deraadt 717: (unless prevented in the configuration file or by
1.2 deraadt 718: .Pa $HOME/.hushlogin ;
719: see the
1.40 aaron 720: .Sx FILES
1.2 deraadt 721: section).
722: .It
1.1 deraadt 723: If the login is on a tty, records login time.
1.2 deraadt 724: .It
725: Checks
726: .Pa /etc/nologin ;
727: if it exists, prints contents and quits
1.1 deraadt 728: (unless root).
1.2 deraadt 729: .It
1.1 deraadt 730: Changes to run with normal user privileges.
1.2 deraadt 731: .It
1.1 deraadt 732: Sets up basic environment.
1.2 deraadt 733: .It
734: Reads
735: .Pa $HOME/.ssh/environment
736: if it exists.
737: .It
1.1 deraadt 738: Changes to user's home directory.
1.2 deraadt 739: .It
740: If
741: .Pa $HOME/.ssh/rc
742: exists, runs it; else if
743: .Pa /etc/sshrc
744: exists, runs
1.36 aaron 745: it; otherwise runs xauth.
746: The
1.2 deraadt 747: .Dq rc
748: files are given the X11
1.1 deraadt 749: authentication protocol and cookie in standard input.
1.2 deraadt 750: .It
1.1 deraadt 751: Runs user's shell or command.
1.2 deraadt 752: .El
753: .Sh AUTHORIZED_KEYS FILE FORMAT
1.40 aaron 754: The
1.2 deraadt 755: .Pa $HOME/.ssh/authorized_keys
1.1 deraadt 756: file lists the RSA keys that are
1.44 deraadt 757: permitted for RSA authentication in SSH protocols 1.3 and 1.5
1.51 hugh 758: Similarly, the
1.44 deraadt 759: .Pa $HOME/.ssh/authorized_keys2
1.51.2.4! jason 760: file lists the DSA and RSA keys that are
! 761: permitted for public key authentication (PubkeyAuthentication)
! 762: in SSH protocol 2.0.
! 763: .Pp
1.36 aaron 764: Each line of the file contains one
1.2 deraadt 765: key (empty lines and lines starting with a
766: .Ql #
767: are ignored as
1.36 aaron 768: comments).
1.51.2.4! jason 769: Each RSA public key consists of the following fields, separated by
1.36 aaron 770: spaces: options, bits, exponent, modulus, comment.
1.51.2.4! jason 771: Each protocol version 2 public key consists of:
! 772: options, keytype, base64 encoded key, comment.
! 773: The options fields
! 774: are optional; its presence is determined by whether the line starts
1.1 deraadt 775: with a number or not (the option field never starts with a number).
1.51.2.4! jason 776: The bits, exponent, modulus and comment fields give the RSA key for
! 777: protocol version 1; the
1.1 deraadt 778: comment field is not used for anything (but may be convenient for the
779: user to identify the key).
1.51.2.4! jason 780: For protocol version 2 the keytype is
! 781: .Dq ssh-dss
! 782: or
! 783: .Dq ssh-rsa .
1.2 deraadt 784: .Pp
1.1 deraadt 785: Note that lines in this file are usually several hundred bytes long
1.36 aaron 786: (because of the size of the RSA key modulus).
787: You don't want to type them in; instead, copy the
1.2 deraadt 788: .Pa identity.pub
1.51.2.4! jason 789: or the
! 790: .Pa id_dsa.pub
1.1 deraadt 791: file and edit it.
1.2 deraadt 792: .Pp
1.51.2.2 jason 793: The options (if present) consist of comma-separated option
1.36 aaron 794: specifications.
795: No spaces are permitted, except within double quotes.
1.1 deraadt 796: The following option specifications are supported:
1.2 deraadt 797: .Bl -tag -width Ds
798: .It Cm from="pattern-list"
1.1 deraadt 799: Specifies that in addition to RSA authentication, the canonical name
800: of the remote host must be present in the comma-separated list of
1.36 aaron 801: patterns
802: .Pf ( Ql *
803: and
804: .Ql ?
805: serve as wildcards).
806: The list may also contain
807: patterns negated by prefixing them with
808: .Ql ! ;
809: if the canonical host name matches a negated pattern, the key is not accepted.
810: The purpose
1.1 deraadt 811: of this option is to optionally increase security: RSA authentication
812: by itself does not trust the network or name servers or anything (but
813: the key); however, if somebody somehow steals the key, the key
1.36 aaron 814: permits an intruder to log in from anywhere in the world.
815: This additional option makes using a stolen key more difficult (name
1.1 deraadt 816: servers and/or routers would have to be compromised in addition to
817: just the key).
1.2 deraadt 818: .It Cm command="command"
1.1 deraadt 819: Specifies that the command is executed whenever this key is used for
1.36 aaron 820: authentication.
821: The command supplied by the user (if any) is ignored.
1.1 deraadt 822: The command is run on a pty if the connection requests a pty;
1.36 aaron 823: otherwise it is run without a tty.
1.51.2.4! jason 824: Note that if you want a 8-bit clean channel,
! 825: you must not request a pty or should specify
! 826: .Cm no-pty .
1.36 aaron 827: A quote may be included in the command by quoting it with a backslash.
828: This option might be useful
829: to restrict certain RSA keys to perform just a specific operation.
830: An example might be a key that permits remote backups but nothing else.
1.51 hugh 831: Note that the client may specify TCP/IP and/or X11
832: forwarding unless they are explicitly prohibited.
1.2 deraadt 833: .It Cm environment="NAME=value"
1.1 deraadt 834: Specifies that the string is to be added to the environment when
1.36 aaron 835: logging in using this key.
836: Environment variables set this way
837: override other default environment values.
838: Multiple options of this type are permitted.
1.2 deraadt 839: .It Cm no-port-forwarding
1.1 deraadt 840: Forbids TCP/IP forwarding when this key is used for authentication.
1.36 aaron 841: Any port forward requests by the client will return an error.
842: This might be used, e.g., in connection with the
1.2 deraadt 843: .Cm command
1.1 deraadt 844: option.
1.2 deraadt 845: .It Cm no-X11-forwarding
1.1 deraadt 846: Forbids X11 forwarding when this key is used for authentication.
847: Any X11 forward requests by the client will return an error.
1.2 deraadt 848: .It Cm no-agent-forwarding
1.1 deraadt 849: Forbids authentication agent forwarding when this key is used for
850: authentication.
1.2 deraadt 851: .It Cm no-pty
1.1 deraadt 852: Prevents tty allocation (a request to allocate a pty will fail).
1.2 deraadt 853: .El
854: .Ss Examples
1.1 deraadt 855: 1024 33 12121.\|.\|.\|312314325 ylo@foo.bar
1.2 deraadt 856: .Pp
1.1 deraadt 857: from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula
1.2 deraadt 858: .Pp
1.1 deraadt 859: command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi
1.2 deraadt 860: .Sh SSH_KNOWN_HOSTS FILE FORMAT
1.40 aaron 861: The
1.44 deraadt 862: .Pa /etc/ssh_known_hosts ,
863: .Pa /etc/ssh_known_hosts2 ,
864: .Pa $HOME/.ssh/known_hosts ,
1.40 aaron 865: and
1.44 deraadt 866: .Pa $HOME/.ssh/known_hosts2
1.36 aaron 867: files contain host public keys for all known hosts.
868: The global file should
1.37 brad 869: be prepared by the administrator (optional), and the per-user file is
1.51.2.2 jason 870: maintained automatically: whenever the user connects from an unknown host
1.36 aaron 871: its key is added to the per-user file.
1.2 deraadt 872: .Pp
1.1 deraadt 873: Each line in these files contains the following fields: hostnames,
1.36 aaron 874: bits, exponent, modulus, comment.
875: The fields are separated by spaces.
1.2 deraadt 876: .Pp
1.1 deraadt 877: Hostnames is a comma-separated list of patterns ('*' and '?' act as
878: wildcards); each pattern in turn is matched against the canonical host
879: name (when authenticating a client) or against the user-supplied
1.36 aaron 880: name (when authenticating a server).
881: A pattern may also be preceded by
1.2 deraadt 882: .Ql !
883: to indicate negation: if the host name matches a negated
1.1 deraadt 884: pattern, it is not accepted (by that line) even if it matched another
885: pattern on the line.
1.2 deraadt 886: .Pp
1.49 markus 887: Bits, exponent, and modulus are taken directly from the RSA host key; they
1.2 deraadt 888: can be obtained, e.g., from
889: .Pa /etc/ssh_host_key.pub .
1.1 deraadt 890: The optional comment field continues to the end of the line, and is not used.
1.2 deraadt 891: .Pp
892: Lines starting with
893: .Ql #
894: and empty lines are ignored as comments.
895: .Pp
1.1 deraadt 896: When performing host authentication, authentication is accepted if any
1.36 aaron 897: matching line has the proper key.
898: It is thus permissible (but not
1.1 deraadt 899: recommended) to have several lines or different host keys for the same
1.36 aaron 900: names.
901: This will inevitably happen when short forms of host names
902: from different domains are put in the file.
903: It is possible
1.1 deraadt 904: that the files contain conflicting information; authentication is
905: accepted if valid information can be found from either file.
1.2 deraadt 906: .Pp
1.1 deraadt 907: Note that the lines in these files are typically hundreds of characters
908: long, and you definitely don't want to type in the host keys by hand.
1.6 aaron 909: Rather, generate them by a script
1.40 aaron 910: or by taking
1.2 deraadt 911: .Pa /etc/ssh_host_key.pub
1.1 deraadt 912: and adding the host names at the front.
1.2 deraadt 913: .Ss Examples
1.1 deraadt 914: closenet,closenet.hut.fi,.\|.\|.\|,130.233.208.41 1024 37 159.\|.\|.93 closenet.hut.fi
1.2 deraadt 915: .Sh FILES
916: .Bl -tag -width Ds
917: .It Pa /etc/sshd_config
1.1 deraadt 918: Contains configuration data for
1.2 deraadt 919: .Nm sshd .
1.1 deraadt 920: This file should be writable by root only, but it is recommended
921: (though not necessary) that it be world-readable.
1.2 deraadt 922: .It Pa /etc/ssh_host_key
1.7 markus 923: Contains the private part of the host key.
1.1 deraadt 924: This file should only be owned by root, readable only by root, and not
925: accessible to others.
1.14 markus 926: Note that
927: .Nm
928: does not start if this file is group/world-accessible.
1.2 deraadt 929: .It Pa /etc/ssh_host_key.pub
1.7 markus 930: Contains the public part of the host key.
931: This file should be world-readable but writable only by
1.36 aaron 932: root.
933: Its contents should match the private part.
934: This file is not
1.1 deraadt 935: really used for anything; it is only provided for the convenience of
936: the user so its contents can be copied to known hosts files.
1.7 markus 937: These two files are created using
938: .Xr ssh-keygen 1 .
1.51.2.4! jason 939: .It Pa /etc/primes
! 940: Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange".
1.2 deraadt 941: .It Pa /var/run/sshd.pid
942: Contains the process ID of the
943: .Nm
1.1 deraadt 944: listening for connections (if there are several daemons running
945: concurrently for different ports, this contains the pid of the one
1.36 aaron 946: started last).
1.51.2.2 jason 947: The content of this file is not sensitive; it can be world-readable.
1.2 deraadt 948: .It Pa $HOME/.ssh/authorized_keys
1.1 deraadt 949: Lists the RSA keys that can be used to log into the user's account.
950: This file must be readable by root (which may on some machines imply
951: it being world-readable if the user's home directory resides on an NFS
1.36 aaron 952: volume).
953: It is recommended that it not be accessible by others.
954: The format of this file is described above.
1.44 deraadt 955: Users will place the contents of their
956: .Pa identity.pub
957: files into this file, as described in
958: .Xr ssh-keygen 1 .
959: .It Pa $HOME/.ssh/authorized_keys2
960: Lists the DSA keys that can be used to log into the user's account.
961: This file must be readable by root (which may on some machines imply
962: it being world-readable if the user's home directory resides on an NFS
963: volume).
964: It is recommended that it not be accessible by others.
965: The format of this file is described above.
966: Users will place the contents of their
967: .Pa id_dsa.pub
968: files into this file, as described in
969: .Xr ssh-keygen 1 .
1.22 markus 970: .It Pa "/etc/ssh_known_hosts" and "$HOME/.ssh/known_hosts"
971: These files are consulted when using rhosts with RSA host
1.36 aaron 972: authentication to check the public key of the host.
973: The key must be listed in one of these files to be accepted.
1.22 markus 974: The client uses the same files
1.51.2.2 jason 975: to verify that the remote host is the one it intended to connect.
1.36 aaron 976: These files should be writable only by root/the owner.
1.2 deraadt 977: .Pa /etc/ssh_known_hosts
978: should be world-readable, and
979: .Pa $HOME/.ssh/known_hosts
980: can but need not be world-readable.
1.6 aaron 981: .It Pa /etc/nologin
1.40 aaron 982: If this file exists,
1.2 deraadt 983: .Nm
1.36 aaron 984: refuses to let anyone except root log in.
985: The contents of the file
1.1 deraadt 986: are displayed to anyone trying to log in, and non-root connections are
1.36 aaron 987: refused.
988: The file should be world-readable.
1.19 dugsong 989: .It Pa /etc/hosts.allow, /etc/hosts.deny
990: If compiled with
991: .Sy LIBWRAP
992: support, tcp-wrappers access controls may be defined here as described in
993: .Xr hosts_access 5 .
1.6 aaron 994: .It Pa $HOME/.rhosts
1.1 deraadt 995: This file contains host-username pairs, separated by a space, one per
1.36 aaron 996: line.
997: The given user on the corresponding host is permitted to log in
998: without password.
999: The same file is used by rlogind and rshd.
1.6 aaron 1000: The file must
1.1 deraadt 1001: be writable only by the user; it is recommended that it not be
1002: accessible by others.
1.2 deraadt 1003: .Pp
1.36 aaron 1004: If is also possible to use netgroups in the file.
1005: Either host or user
1.1 deraadt 1006: name may be of the form +@groupname to specify all hosts or all users
1007: in the group.
1.2 deraadt 1008: .It Pa $HOME/.shosts
1009: For ssh,
1010: this file is exactly the same as for
1011: .Pa .rhosts .
1012: However, this file is
1013: not used by rlogin and rshd, so using this permits access using SSH only.
1.51.2.2 jason 1014: .It Pa /etc/hosts.equiv
1.2 deraadt 1015: This file is used during
1016: .Pa .rhosts
1.36 aaron 1017: authentication.
1018: In the simplest form, this file contains host names, one per line.
1019: Users on
1.1 deraadt 1020: those hosts are permitted to log in without a password, provided they
1.36 aaron 1021: have the same user name on both machines.
1022: The host name may also be
1.1 deraadt 1023: followed by a user name; such users are permitted to log in as
1.2 deraadt 1024: .Em any
1.36 aaron 1025: user on this machine (except root).
1026: Additionally, the syntax
1.2 deraadt 1027: .Dq +@group
1.36 aaron 1028: can be used to specify netgroups.
1029: Negated entries start with
1.2 deraadt 1030: .Ql \&- .
1031: .Pp
1.1 deraadt 1032: If the client host/user is successfully matched in this file, login is
1033: automatically permitted provided the client and server user names are the
1.36 aaron 1034: same.
1035: Additionally, successful RSA host authentication is normally required.
1036: This file must be writable only by root; it is recommended
1.1 deraadt 1037: that it be world-readable.
1.2 deraadt 1038: .Pp
1.6 aaron 1039: .Sy "Warning: It is almost never a good idea to use user names in"
1.2 deraadt 1040: .Pa hosts.equiv .
1.1 deraadt 1041: Beware that it really means that the named user(s) can log in as
1.2 deraadt 1042: .Em anybody ,
1.1 deraadt 1043: which includes bin, daemon, adm, and other accounts that own critical
1.36 aaron 1044: binaries and directories.
1045: Using a user name practically grants the user root access.
1046: The only valid use for user names that I can think
1.1 deraadt 1047: of is in negative entries.
1.2 deraadt 1048: .Pp
1049: Note that this warning also applies to rsh/rlogin.
1050: .It Pa /etc/shosts.equiv
1.1 deraadt 1051: This is processed exactly as
1.2 deraadt 1052: .Pa /etc/hosts.equiv .
1.1 deraadt 1053: However, this file may be useful in environments that want to run both
1.2 deraadt 1054: rsh/rlogin and ssh.
1.6 aaron 1055: .It Pa $HOME/.ssh/environment
1.36 aaron 1056: This file is read into the environment at login (if it exists).
1057: It can only contain empty lines, comment lines (that start with
1.2 deraadt 1058: .Ql # ) ,
1.36 aaron 1059: and assignment lines of the form name=value.
1060: The file should be writable
1.6 aaron 1061: only by the user; it need not be readable by anyone else.
1.2 deraadt 1062: .It Pa $HOME/.ssh/rc
1.1 deraadt 1063: If this file exists, it is run with /bin/sh after reading the
1.36 aaron 1064: environment files but before starting the user's shell or command.
1065: If X11 spoofing is in use, this will receive the "proto cookie" pair in
1.2 deraadt 1066: standard input (and
1067: .Ev DISPLAY
1.36 aaron 1068: in environment).
1069: This must call
1.2 deraadt 1070: .Xr xauth 1
1071: in that case.
1072: .Pp
1.1 deraadt 1073: The primary purpose of this file is to run any initialization routines
1074: which may be needed before the user's home directory becomes
1075: accessible; AFS is a particular example of such an environment.
1.2 deraadt 1076: .Pp
1.1 deraadt 1077: This file will probably contain some initialization code followed by
1078: something similar to: "if read proto cookie; then echo add $DISPLAY
1079: $proto $cookie | xauth -q -; fi".
1.2 deraadt 1080: .Pp
1081: If this file does not exist,
1082: .Pa /etc/sshrc
1083: is run, and if that
1.1 deraadt 1084: does not exist either, xauth is used to store the cookie.
1.2 deraadt 1085: .Pp
1.1 deraadt 1086: This file should be writable only by the user, and need not be
1087: readable by anyone else.
1.2 deraadt 1088: .It Pa /etc/sshrc
1089: Like
1090: .Pa $HOME/.ssh/rc .
1091: This can be used to specify
1.36 aaron 1092: machine-specific login-time initializations globally.
1093: This file should be writable only by root, and should be world-readable.
1.51.2.2 jason 1094: .El
1.51.2.4! jason 1095: .Sh AUTHORS
! 1096: OpenSSH is a derivative of the original and free
! 1097: ssh 1.2.12 release by Tatu Ylonen.
! 1098: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
! 1099: Theo de Raadt and Dug Song
! 1100: removed many bugs, re-added newer features and
! 1101: created OpenSSH.
! 1102: Markus Friedl contributed the support for SSH
! 1103: protocol versions 1.5 and 2.0.
1.2 deraadt 1104: .Sh SEE ALSO
1105: .Xr scp 1 ,
1.51.2.4! jason 1106: .Xr sftp 1 ,
1.51.2.3 jason 1107: .Xr sftp-server 8 ,
1.2 deraadt 1108: .Xr ssh 1 ,
1.5 deraadt 1109: .Xr ssh-add 1 ,
1.2 deraadt 1110: .Xr ssh-agent 1 ,
1.5 deraadt 1111: .Xr ssh-keygen 1 ,
1.38 deraadt 1112: .Xr rlogin 1 ,
1113: .Xr rsh 1
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