Annotation of src/usr.bin/ssh/sshd.8, Revision 1.98
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: .\"
1.64 deraadt 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: .\"
1.64 deraadt 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: .\"
1.98 ! deraadt 37: .\" $OpenBSD: sshd.8,v 1.97 2001/03/02 06:21:01 deraadt Exp $
1.2 deraadt 38: .Dd September 25, 1999
39: .Dt SSHD 8
40: .Os
41: .Sh NAME
42: .Nm sshd
1.95 deraadt 43: .Nd OpenSSH secure shell daemon
1.2 deraadt 44: .Sh SYNOPSIS
45: .Nm sshd
1.85 markus 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
1.61 markus 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
1.58 deraadt 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
1.72 markus 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,
1.97 deraadt 177: .Dv SIGHUP ,
178: by executing itself with the name it was started as, ie.
179: .Pa /usr/sbin/sshd .
1.18 aaron 180: .Pp
181: The options are as follows:
1.2 deraadt 182: .Bl -tag -width Ds
183: .It Fl b Ar bits
1.1 deraadt 184: Specifies the number of bits in the server key (default 768).
1.2 deraadt 185: .Pp
186: .It Fl d
1.36 aaron 187: Debug mode.
188: The server sends verbose debug output to the system
189: log, and does not put itself in the background.
190: The server also will not fork and will only process one connection.
191: This option is only intended for debugging for the server.
1.67 aaron 192: Multiple -d options increases the debugging level.
193: Maximum is 3.
1.2 deraadt 194: .It Fl f Ar configuration_file
1.36 aaron 195: Specifies the name of the configuration file.
196: The default is
1.2 deraadt 197: .Pa /etc/sshd_config .
1.16 markus 198: .Nm
199: refuses to start if there is no configuration file.
1.2 deraadt 200: .It Fl g Ar login_grace_time
1.1 deraadt 201: Gives the grace time for clients to authenticate themselves (default
1.77 markus 202: 600 seconds).
1.36 aaron 203: If the client fails to authenticate the user within
204: this many seconds, the server disconnects and exits.
205: A value of zero indicates no limit.
1.2 deraadt 206: .It Fl h Ar host_key_file
1.75 markus 207: Specifies the file from which the host key is read (default
1.2 deraadt 208: .Pa /etc/ssh_host_key ) .
1.7 markus 209: This option must be given if
210: .Nm
211: is not run as root (as the normal
1.1 deraadt 212: host file is normally not readable by anyone but root).
1.75 markus 213: It is possible to have multiple host key files for
214: the different protocol versions.
1.2 deraadt 215: .It Fl i
1.7 markus 216: Specifies that
217: .Nm
1.40 aaron 218: is being run from inetd.
1.7 markus 219: .Nm
220: is normally not run
1.1 deraadt 221: from inetd because it needs to generate the server key before it can
1.36 aaron 222: respond to the client, and this may take tens of seconds.
223: Clients would have to wait too long if the key was regenerated every time.
1.35 aaron 224: However, with small key sizes (e.g., 512) using
1.7 markus 225: .Nm
226: from inetd may
1.1 deraadt 227: be feasible.
1.2 deraadt 228: .It Fl k Ar key_gen_time
1.1 deraadt 229: Specifies how often the server key is regenerated (default 3600
1.36 aaron 230: seconds, or one hour).
231: The motivation for regenerating the key fairly
1.1 deraadt 232: often is that the key is not stored anywhere, and after about an hour,
233: it becomes impossible to recover the key for decrypting intercepted
234: communications even if the machine is cracked into or physically
1.36 aaron 235: seized.
236: A value of zero indicates that the key will never be regenerated.
1.2 deraadt 237: .It Fl p Ar port
1.1 deraadt 238: Specifies the port on which the server listens for connections
239: (default 22).
1.2 deraadt 240: .It Fl q
1.36 aaron 241: Quiet mode.
242: Nothing is sent to the system log.
243: Normally the beginning,
1.1 deraadt 244: authentication, and termination of each connection is logged.
1.61 markus 245: .It Fl u Ar len
246: This option is used to specify the size of the field
247: in the
248: .Li utmp
249: structure that holds the remote host name.
250: If the resolved host name is longer than
251: .Ar len ,
252: the dotted decimal value will be used instead.
253: This allows hosts with very long host names that
254: overflow this field to still be uniquely identified.
255: Specifying
256: .Fl u0
257: indicates that only dotted decimal addresses
258: should be put into the
259: .Pa utmp
260: file.
1.74 markus 261: .It Fl D
262: When this option is specified
263: .Nm
264: will not detach and does not become a daemon.
265: This allows easy monitoring of
1.76 markus 266: .Nm sshd .
1.26 markus 267: .It Fl V Ar client_protocol_id
1.68 markus 268: SSH-2 compatibility mode.
1.42 hugh 269: When this option is specified
1.26 markus 270: .Nm
1.42 hugh 271: assumes the client has sent the supplied version string
1.26 markus 272: and skips the
273: Protocol Version Identification Exchange.
1.68 markus 274: This option is not intended to be called directly.
1.29 markus 275: .It Fl 4
276: Forces
277: .Nm
278: to use IPv4 addresses only.
279: .It Fl 6
280: Forces
281: .Nm
282: to use IPv6 addresses only.
1.2 deraadt 283: .El
284: .Sh CONFIGURATION FILE
285: .Nm
1.40 aaron 286: reads configuration data from
1.2 deraadt 287: .Pa /etc/sshd_config
288: (or the file specified with
289: .Fl f
1.36 aaron 290: on the command line).
291: The file contains keyword-value pairs, one per line.
292: Lines starting with
1.2 deraadt 293: .Ql #
1.1 deraadt 294: and empty lines are interpreted as comments.
1.2 deraadt 295: .Pp
1.1 deraadt 296: The following keywords are possible.
1.2 deraadt 297: .Bl -tag -width Ds
298: .It Cm AFSTokenPassing
1.36 aaron 299: Specifies whether an AFS token may be forwarded to the server.
300: Default is
1.2 deraadt 301: .Dq yes .
1.11 markus 302: .It Cm AllowGroups
1.92 deraadt 303: This keyword can be followed by a list of group names, separated
1.36 aaron 304: by spaces.
305: If specified, login is allowed only for users whose primary
1.81 markus 306: group or supplementary group list matches one of the patterns.
1.11 markus 307: .Ql \&*
308: and
309: .Ql ?
310: can be used as
1.36 aaron 311: wildcards in the patterns.
1.58 deraadt 312: Only group names are valid; a numerical group ID isn't recognized.
1.81 markus 313: By default login is allowed regardless of the group list.
1.3 dugsong 314: .Pp
1.69 markus 315: .It Cm AllowTcpForwarding
316: Specifies whether TCP forwarding is permitted.
317: The default is
318: .Dq yes .
319: Note that disabling TCP forwarding does not improve security unless
320: users are also denied shell access, as they can always install their
321: own forwarders.
322: .Pp
1.11 markus 323: .It Cm AllowUsers
1.92 deraadt 324: This keyword can be followed by a list of user names, separated
1.36 aaron 325: by spaces.
326: If specified, login is allowed only for users names that
1.11 markus 327: match one of the patterns.
328: .Ql \&*
329: and
330: .Ql ?
331: can be used as
1.36 aaron 332: wildcards in the patterns.
1.58 deraadt 333: Only user names are valid; a numerical user ID isn't recognized.
1.36 aaron 334: By default login is allowed regardless of the user name.
1.80 markus 335: .Pp
336: .It Cm Banner
337: In some jurisdictions, sending a warning message before authentication
338: may be relevant for getting legal protection.
339: The contents of the specified file are sent to the remote user before
340: authentication is allowed.
341: This option is only available for protocol version 2.
1.11 markus 342: .Pp
1.41 markus 343: .It Cm Ciphers
344: Specifies the ciphers allowed for protocol version 2.
345: Multiple ciphers must be comma-separated.
346: The default is
1.78 djm 347: .Dq 3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes128-cbc .
1.8 markus 348: .It Cm CheckMail
349: Specifies whether
350: .Nm
351: should check for new mail for interactive logins.
352: The default is
353: .Dq no .
1.11 markus 354: .It Cm DenyGroups
355: This keyword can be followed by a number of group names, separated
1.36 aaron 356: by spaces.
1.81 markus 357: Users whose primary group or supplementary group list matches
358: one of the patterns aren't allowed to log in.
1.11 markus 359: .Ql \&*
360: and
361: .Ql ?
362: can be used as
1.36 aaron 363: wildcards in the patterns.
1.58 deraadt 364: Only group names are valid; a numerical group ID isn't recognized.
1.81 markus 365: By default login is allowed regardless of the group list.
1.11 markus 366: .Pp
367: .It Cm DenyUsers
368: This keyword can be followed by a number of user names, separated
1.36 aaron 369: by spaces.
370: Login is disallowed for user names that match one of the patterns.
1.11 markus 371: .Ql \&*
372: and
373: .Ql ?
1.36 aaron 374: can be used as wildcards in the patterns.
1.58 deraadt 375: Only user names are valid; a numerical user ID isn't recognized.
1.36 aaron 376: By default login is allowed regardless of the user name.
1.72 markus 377: .It Cm PubkeyAuthentication
378: Specifies whether public key authentication is allowed.
1.49 markus 379: The default is
380: .Dq yes .
381: Note that this option applies to protocol version 2 only.
1.47 markus 382: .It Cm GatewayPorts
383: Specifies whether remote hosts are allowed to connect to ports
384: forwarded for the client.
385: The argument must be
386: .Dq yes
387: or
388: .Dq no .
389: The default is
390: .Dq no .
1.2 deraadt 391: .It Cm HostKey
1.72 markus 392: Specifies the file containing the private host keys (default
1.46 markus 393: .Pa /etc/ssh_host_key )
1.72 markus 394: used by SSH protocol versions 1 and 2.
1.9 markus 395: Note that
396: .Nm
1.83 markus 397: will refuse to use a file if it is group/world-accessible.
1.72 markus 398: It is possible to have multiple host key files.
399: .Dq rsa1
400: keys are used for version 1 and
401: .Dq dsa
402: or
403: .Dq rsa
404: are used for version 2 of the SSH protocol.
1.2 deraadt 405: .It Cm IgnoreRhosts
1.34 markus 406: Specifies that
407: .Pa .rhosts
1.40 aaron 408: and
1.34 markus 409: .Pa .shosts
410: files will not be used in authentication.
1.2 deraadt 411: .Pa /etc/hosts.equiv
1.1 deraadt 412: and
1.40 aaron 413: .Pa /etc/shosts.equiv
1.36 aaron 414: are still used.
1.40 aaron 415: The default is
1.34 markus 416: .Dq yes .
1.24 markus 417: .It Cm IgnoreUserKnownHosts
418: Specifies whether
419: .Nm
420: should ignore the user's
421: .Pa $HOME/.ssh/known_hosts
1.45 markus 422: during
1.24 markus 423: .Cm RhostsRSAAuthentication .
424: The default is
1.2 deraadt 425: .Dq no .
426: .It Cm KeepAlive
1.1 deraadt 427: Specifies whether the system should send keepalive messages to the
1.36 aaron 428: other side.
429: If they are sent, death of the connection or crash of one
430: of the machines will be properly noticed.
431: However, this means that
1.1 deraadt 432: connections will die if the route is down temporarily, and some people
1.36 aaron 433: find it annoying.
1.51 hugh 434: On the other hand, if keepalives are not sent,
1.2 deraadt 435: sessions may hang indefinitely on the server, leaving
436: .Dq ghost
437: users and consuming server resources.
438: .Pp
439: The default is
440: .Dq yes
441: (to send keepalives), and the server will notice
1.36 aaron 442: if the network goes down or the client host reboots.
443: This avoids infinitely hanging sessions.
1.2 deraadt 444: .Pp
445: To disable keepalives, the value should be set to
446: .Dq no
447: in both the server and the client configuration files.
448: .It Cm KerberosAuthentication
1.36 aaron 449: Specifies whether Kerberos authentication is allowed.
450: This can be in the form of a Kerberos ticket, or if
1.7 markus 451: .Cm PasswordAuthentication
1.1 deraadt 452: is yes, the password provided by the user will be validated through
1.67 aaron 453: the Kerberos KDC.
454: To use this option, the server needs a
1.59 provos 455: Kerberos servtab which allows the verification of the KDC's identity.
1.36 aaron 456: Default is
1.60 provos 457: .Dq yes .
1.2 deraadt 458: .It Cm KerberosOrLocalPasswd
1.1 deraadt 459: If set then if password authentication through Kerberos fails then
460: the password will be validated via any additional local mechanism
1.2 deraadt 461: such as
1.66 markus 462: .Pa /etc/passwd .
1.36 aaron 463: Default is
1.20 dugsong 464: .Dq yes .
1.2 deraadt 465: .It Cm KerberosTgtPassing
1.1 deraadt 466: Specifies whether a Kerberos TGT may be forwarded to the server.
1.40 aaron 467: Default is
1.3 dugsong 468: .Dq no ,
469: as this only works when the Kerberos KDC is actually an AFS kaserver.
1.2 deraadt 470: .It Cm KerberosTicketCleanup
1.7 markus 471: Specifies whether to automatically destroy the user's ticket cache
1.36 aaron 472: file on logout.
473: Default is
1.3 dugsong 474: .Dq yes .
1.2 deraadt 475: .It Cm KeyRegenerationInterval
1.1 deraadt 476: The server key is automatically regenerated after this many seconds
1.36 aaron 477: (if it has been used).
478: The purpose of regeneration is to prevent
1.1 deraadt 479: decrypting captured sessions by later breaking into the machine and
1.36 aaron 480: stealing the keys.
481: The key is never stored anywhere.
482: If the value is 0, the key is never regenerated.
483: The default is 3600 (seconds).
1.7 markus 484: .It Cm ListenAddress
485: Specifies what local address
486: .Nm
487: should listen on.
488: The default is to listen to all local addresses.
1.28 markus 489: Multiple options of this type are permitted.
490: Additionally, the
491: .Cm Ports
492: options must precede this option.
1.2 deraadt 493: .It Cm LoginGraceTime
1.1 deraadt 494: The server disconnects after this time if the user has not
1.36 aaron 495: successfully logged in.
496: If the value is 0, there is no time limit.
1.1 deraadt 497: The default is 600 (seconds).
1.23 markus 498: .It Cm LogLevel
499: Gives the verbosity level that is used when logging messages from
500: .Nm sshd .
501: The possible values are:
1.82 markus 502: QUIET, FATAL, ERROR, INFO, VERBOSE and DEBUG.
503: The default is INFO.
1.23 markus 504: Logging with level DEBUG violates the privacy of users
505: and is not recommended.
1.93 markus 506: .It Cm MACs
507: Specifies the available MAC (message authentication code) algorithms.
508: The MAC algorithm is used in protocol version 2
509: for data integrity protection.
510: Multiple algorithms must be comma-separated.
511: The default is
512: .Pp
513: .Bd -literal
514: ``hmac-sha1,hmac-md5,hmac-ripemd160,hmac-ripemd160@openssh.com,
515: hmac-sha1-96,hmac-md5-96''
516: .Ed
1.55 markus 517: .It Cm MaxStartups
518: Specifies the maximum number of concurrent unauthenticated connections to the
519: .Nm
520: daemon.
521: Additional connections will be dropped until authentication succeeds or the
522: .Cm LoginGraceTime
523: expires for a connection.
524: The default is 10.
1.57 markus 525: .Pp
526: Alternatively, random early drop can be enabled by specifying
527: the three colon separated values
528: .Dq start:rate:full
1.67 aaron 529: (e.g., "10:30:60").
1.57 markus 530: .Nm
1.86 stevesk 531: will refuse connection attempts with a probability of
1.57 markus 532: .Dq rate/100
533: (30%)
534: if there are currently
535: .Dq start
536: (10)
537: unauthenticated connections.
1.86 stevesk 538: The probability increases linearly and all connection attempts
1.57 markus 539: are refused if the number of unauthenticated connections reaches
540: .Dq full
541: (60).
1.2 deraadt 542: .It Cm PasswordAuthentication
1.1 deraadt 543: Specifies whether password authentication is allowed.
1.2 deraadt 544: The default is
545: .Dq yes .
1.58 deraadt 546: Note that this option applies to both protocol versions 1 and 2.
1.2 deraadt 547: .It Cm PermitEmptyPasswords
1.1 deraadt 548: When password authentication is allowed, it specifies whether the
1.36 aaron 549: server allows login to accounts with empty password strings.
550: The default is
1.34 markus 551: .Dq no .
1.2 deraadt 552: .It Cm PermitRootLogin
1.1 deraadt 553: Specifies whether the root can log in using
1.2 deraadt 554: .Xr ssh 1 .
1.15 markus 555: The argument must be
556: .Dq yes ,
1.94 markus 557: .Dq without-password ,
558: .Dq forced-commands-only
1.15 markus 559: or
560: .Dq no .
1.2 deraadt 561: The default is
562: .Dq yes .
1.94 markus 563: .Pp
564: If this option is set to
1.15 markus 565: .Dq without-password
1.94 markus 566: password authentication is disabled for root.
1.2 deraadt 567: .Pp
1.94 markus 568: If this option is set to
569: .Dq forced-commands-only
570: root login with public key authentication will be allowed,
571: but only if the
1.2 deraadt 572: .Ar command
1.94 markus 573: option has been specified
1.1 deraadt 574: (which may be useful for taking remote backups even if root login is
1.94 markus 575: normally not allowed). All other authentication methods are disabled
576: for root.
1.43 markus 577: .It Cm PidFile
578: Specifies the file that contains the process identifier of the
579: .Nm
580: daemon.
581: The default is
582: .Pa /var/run/sshd.pid .
1.2 deraadt 583: .It Cm Port
1.1 deraadt 584: Specifies the port number that
1.2 deraadt 585: .Nm
1.36 aaron 586: listens on.
587: The default is 22.
1.28 markus 588: Multiple options of this type are permitted.
1.2 deraadt 589: .It Cm PrintMotd
1.1 deraadt 590: Specifies whether
1.2 deraadt 591: .Nm
1.40 aaron 592: should print
1.2 deraadt 593: .Pa /etc/motd
1.36 aaron 594: when a user logs in interactively.
595: (On some systems it is also printed by the shell,
1.2 deraadt 596: .Pa /etc/profile ,
1.36 aaron 597: or equivalent.)
598: The default is
1.2 deraadt 599: .Dq yes .
1.41 markus 600: .It Cm Protocol
601: Specifies the protocol versions
602: .Nm
603: should support.
604: The possible values are
605: .Dq 1
606: and
607: .Dq 2 .
608: Multiple versions must be comma-separated.
609: The default is
610: .Dq 1 .
1.2 deraadt 611: .It Cm RandomSeed
1.36 aaron 612: Obsolete.
613: Random number generation uses other techniques.
1.87 markus 614: .It Cm ReverseMappingCheck
615: Specifies whether
616: .Nm
617: should try to verify the remote host name and check that
618: the resolved host name for the remote IP address maps back to the
619: very same IP address.
620: The default is
621: .Dq no .
1.2 deraadt 622: .It Cm RhostsAuthentication
1.1 deraadt 623: Specifies whether authentication using rhosts or /etc/hosts.equiv
1.36 aaron 624: files is sufficient.
625: Normally, this method should not be permitted because it is insecure.
1.7 markus 626: .Cm RhostsRSAAuthentication
627: should be used
1.1 deraadt 628: instead, because it performs RSA-based host authentication in addition
629: to normal rhosts or /etc/hosts.equiv authentication.
1.2 deraadt 630: The default is
631: .Dq no .
632: .It Cm RhostsRSAAuthentication
1.1 deraadt 633: Specifies whether rhosts or /etc/hosts.equiv authentication together
1.36 aaron 634: with successful RSA host authentication is allowed.
635: The default is
1.34 markus 636: .Dq no .
1.2 deraadt 637: .It Cm RSAAuthentication
1.36 aaron 638: Specifies whether pure RSA authentication is allowed.
639: The default is
1.2 deraadt 640: .Dq yes .
1.49 markus 641: Note that this option applies to protocol version 1 only.
1.2 deraadt 642: .It Cm ServerKeyBits
1.36 aaron 643: Defines the number of bits in the server key.
644: The minimum value is 512, and the default is 768.
1.88 markus 645: .It Cm ChallengeResponseAuthentication
1.7 markus 646: Specifies whether
1.88 markus 647: challenge reponse
648: authentication is allowed.
649: Currently there is only support for
1.40 aaron 650: .Xr skey 1
1.88 markus 651: authentication.
1.36 aaron 652: The default is
1.7 markus 653: .Dq yes .
1.2 deraadt 654: .It Cm StrictModes
1.12 markus 655: Specifies whether
656: .Nm
657: should check file modes and ownership of the
1.36 aaron 658: user's files and home directory before accepting login.
659: This is normally desirable because novices sometimes accidentally leave their
660: directory or files world-writable.
661: The default is
1.7 markus 662: .Dq yes .
1.54 jakob 663: .It Cm Subsystem
1.67 aaron 664: Configures an external subsystem (e.g., file transfer daemon).
665: Arguments should be a subsystem name and a command to execute upon subsystem
666: request.
1.63 markus 667: The command
668: .Xr sftp-server 8
669: implements the
670: .Dq sftp
671: file transfer subsystem.
1.54 jakob 672: By default no subsystems are defined.
673: Note that this option applies to protocol version 2 only.
1.2 deraadt 674: .It Cm SyslogFacility
1.1 deraadt 675: Gives the facility code that is used when logging messages from
1.2 deraadt 676: .Nm sshd .
1.1 deraadt 677: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1.36 aaron 678: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
679: The default is AUTH.
1.10 markus 680: .It Cm UseLogin
681: Specifies whether
682: .Xr login 1
1.53 markus 683: is used for interactive login sessions.
684: Note that
685: .Xr login 1
1.58 deraadt 686: is never used for remote command execution.
1.36 aaron 687: The default is
1.10 markus 688: .Dq no .
1.6 aaron 689: .It Cm X11DisplayOffset
690: Specifies the first display number available for
691: .Nm sshd Ns 's
1.36 aaron 692: X11 forwarding.
693: This prevents
1.6 aaron 694: .Nm
695: from interfering with real X11 servers.
1.34 markus 696: The default is 10.
1.30 markus 697: .It Cm X11Forwarding
1.36 aaron 698: Specifies whether X11 forwarding is permitted.
699: The default is
1.34 markus 700: .Dq no .
1.30 markus 701: Note that disabling X11 forwarding does not improve security in any
702: way, as users can always install their own forwarders.
1.52 markus 703: .It Cm XAuthLocation
704: Specifies the location of the
705: .Xr xauth 1
706: program.
707: The default is
708: .Pa /usr/X11R6/bin/xauth .
1.2 deraadt 709: .El
710: .Sh LOGIN PROCESS
1.1 deraadt 711: When a user successfully logs in,
1.2 deraadt 712: .Nm
1.1 deraadt 713: does the following:
1.2 deraadt 714: .Bl -enum -offset indent
715: .It
1.1 deraadt 716: If the login is on a tty, and no command has been specified,
1.40 aaron 717: prints last login time and
1.2 deraadt 718: .Pa /etc/motd
1.1 deraadt 719: (unless prevented in the configuration file or by
1.2 deraadt 720: .Pa $HOME/.hushlogin ;
721: see the
1.40 aaron 722: .Sx FILES
1.2 deraadt 723: section).
724: .It
1.1 deraadt 725: If the login is on a tty, records login time.
1.2 deraadt 726: .It
727: Checks
728: .Pa /etc/nologin ;
729: if it exists, prints contents and quits
1.1 deraadt 730: (unless root).
1.2 deraadt 731: .It
1.1 deraadt 732: Changes to run with normal user privileges.
1.2 deraadt 733: .It
1.1 deraadt 734: Sets up basic environment.
1.2 deraadt 735: .It
736: Reads
737: .Pa $HOME/.ssh/environment
738: if it exists.
739: .It
1.1 deraadt 740: Changes to user's home directory.
1.2 deraadt 741: .It
742: If
743: .Pa $HOME/.ssh/rc
744: exists, runs it; else if
745: .Pa /etc/sshrc
746: exists, runs
1.36 aaron 747: it; otherwise runs xauth.
748: The
1.2 deraadt 749: .Dq rc
750: files are given the X11
1.1 deraadt 751: authentication protocol and cookie in standard input.
1.2 deraadt 752: .It
1.1 deraadt 753: Runs user's shell or command.
1.2 deraadt 754: .El
755: .Sh AUTHORIZED_KEYS FILE FORMAT
1.40 aaron 756: The
1.2 deraadt 757: .Pa $HOME/.ssh/authorized_keys
1.1 deraadt 758: file lists the RSA keys that are
1.44 deraadt 759: permitted for RSA authentication in SSH protocols 1.3 and 1.5
1.51 hugh 760: Similarly, the
1.44 deraadt 761: .Pa $HOME/.ssh/authorized_keys2
1.75 markus 762: file lists the DSA and RSA keys that are
763: permitted for public key authentication (PubkeyAuthentication)
764: in SSH protocol 2.0.
765: .Pp
1.36 aaron 766: Each line of the file contains one
1.2 deraadt 767: key (empty lines and lines starting with a
768: .Ql #
769: are ignored as
1.36 aaron 770: comments).
1.75 markus 771: Each RSA public key consists of the following fields, separated by
1.36 aaron 772: spaces: options, bits, exponent, modulus, comment.
1.75 markus 773: Each protocol version 2 public key consists of:
774: options, keytype, base64 encoded key, comment.
775: The options fields
776: are optional; its presence is determined by whether the line starts
1.1 deraadt 777: with a number or not (the option field never starts with a number).
1.75 markus 778: The bits, exponent, modulus and comment fields give the RSA key for
779: protocol version 1; the
1.1 deraadt 780: comment field is not used for anything (but may be convenient for the
781: user to identify the key).
1.75 markus 782: For protocol version 2 the keytype is
783: .Dq ssh-dss
784: or
785: .Dq ssh-rsa .
1.2 deraadt 786: .Pp
1.1 deraadt 787: Note that lines in this file are usually several hundred bytes long
1.36 aaron 788: (because of the size of the RSA key modulus).
789: You don't want to type them in; instead, copy the
1.2 deraadt 790: .Pa identity.pub
1.75 markus 791: or the
792: .Pa id_dsa.pub
1.1 deraadt 793: file and edit it.
1.2 deraadt 794: .Pp
1.58 deraadt 795: The options (if present) consist of comma-separated option
1.36 aaron 796: specifications.
797: No spaces are permitted, except within double quotes.
1.1 deraadt 798: The following option specifications are supported:
1.2 deraadt 799: .Bl -tag -width Ds
800: .It Cm from="pattern-list"
1.1 deraadt 801: Specifies that in addition to RSA authentication, the canonical name
802: of the remote host must be present in the comma-separated list of
1.36 aaron 803: patterns
804: .Pf ( Ql *
805: and
806: .Ql ?
807: serve as wildcards).
808: The list may also contain
809: patterns negated by prefixing them with
810: .Ql ! ;
811: if the canonical host name matches a negated pattern, the key is not accepted.
812: The purpose
1.1 deraadt 813: of this option is to optionally increase security: RSA authentication
814: by itself does not trust the network or name servers or anything (but
815: the key); however, if somebody somehow steals the key, the key
1.36 aaron 816: permits an intruder to log in from anywhere in the world.
817: This additional option makes using a stolen key more difficult (name
1.1 deraadt 818: servers and/or routers would have to be compromised in addition to
819: just the key).
1.2 deraadt 820: .It Cm command="command"
1.1 deraadt 821: Specifies that the command is executed whenever this key is used for
1.36 aaron 822: authentication.
823: The command supplied by the user (if any) is ignored.
1.1 deraadt 824: The command is run on a pty if the connection requests a pty;
1.36 aaron 825: otherwise it is run without a tty.
1.89 markus 826: Note that if you want a 8-bit clean channel,
827: you must not request a pty or should specify
828: .Cm no-pty .
1.36 aaron 829: A quote may be included in the command by quoting it with a backslash.
830: This option might be useful
831: to restrict certain RSA keys to perform just a specific operation.
832: An example might be a key that permits remote backups but nothing else.
1.51 hugh 833: Note that the client may specify TCP/IP and/or X11
834: forwarding unless they are explicitly prohibited.
1.2 deraadt 835: .It Cm environment="NAME=value"
1.1 deraadt 836: Specifies that the string is to be added to the environment when
1.36 aaron 837: logging in using this key.
838: Environment variables set this way
839: override other default environment values.
840: Multiple options of this type are permitted.
1.2 deraadt 841: .It Cm no-port-forwarding
1.1 deraadt 842: Forbids TCP/IP forwarding when this key is used for authentication.
1.36 aaron 843: Any port forward requests by the client will return an error.
844: This might be used, e.g., in connection with the
1.2 deraadt 845: .Cm command
1.1 deraadt 846: option.
1.2 deraadt 847: .It Cm no-X11-forwarding
1.1 deraadt 848: Forbids X11 forwarding when this key is used for authentication.
849: Any X11 forward requests by the client will return an error.
1.2 deraadt 850: .It Cm no-agent-forwarding
1.1 deraadt 851: Forbids authentication agent forwarding when this key is used for
852: authentication.
1.2 deraadt 853: .It Cm no-pty
1.1 deraadt 854: Prevents tty allocation (a request to allocate a pty will fail).
1.2 deraadt 855: .El
856: .Ss Examples
1.1 deraadt 857: 1024 33 12121.\|.\|.\|312314325 ylo@foo.bar
1.2 deraadt 858: .Pp
1.1 deraadt 859: from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula
1.2 deraadt 860: .Pp
1.1 deraadt 861: command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi
1.2 deraadt 862: .Sh SSH_KNOWN_HOSTS FILE FORMAT
1.40 aaron 863: The
1.44 deraadt 864: .Pa /etc/ssh_known_hosts ,
865: .Pa /etc/ssh_known_hosts2 ,
866: .Pa $HOME/.ssh/known_hosts ,
1.40 aaron 867: and
1.44 deraadt 868: .Pa $HOME/.ssh/known_hosts2
1.36 aaron 869: files contain host public keys for all known hosts.
870: The global file should
1.37 brad 871: be prepared by the administrator (optional), and the per-user file is
1.58 deraadt 872: maintained automatically: whenever the user connects from an unknown host
1.36 aaron 873: its key is added to the per-user file.
1.2 deraadt 874: .Pp
1.1 deraadt 875: Each line in these files contains the following fields: hostnames,
1.36 aaron 876: bits, exponent, modulus, comment.
877: The fields are separated by spaces.
1.2 deraadt 878: .Pp
1.1 deraadt 879: Hostnames is a comma-separated list of patterns ('*' and '?' act as
880: wildcards); each pattern in turn is matched against the canonical host
881: name (when authenticating a client) or against the user-supplied
1.36 aaron 882: name (when authenticating a server).
883: A pattern may also be preceded by
1.2 deraadt 884: .Ql !
885: to indicate negation: if the host name matches a negated
1.1 deraadt 886: pattern, it is not accepted (by that line) even if it matched another
887: pattern on the line.
1.2 deraadt 888: .Pp
1.49 markus 889: Bits, exponent, and modulus are taken directly from the RSA host key; they
1.2 deraadt 890: can be obtained, e.g., from
891: .Pa /etc/ssh_host_key.pub .
1.1 deraadt 892: The optional comment field continues to the end of the line, and is not used.
1.2 deraadt 893: .Pp
894: Lines starting with
895: .Ql #
896: and empty lines are ignored as comments.
897: .Pp
1.1 deraadt 898: When performing host authentication, authentication is accepted if any
1.36 aaron 899: matching line has the proper key.
900: It is thus permissible (but not
1.1 deraadt 901: recommended) to have several lines or different host keys for the same
1.36 aaron 902: names.
903: This will inevitably happen when short forms of host names
904: from different domains are put in the file.
905: It is possible
1.1 deraadt 906: that the files contain conflicting information; authentication is
907: accepted if valid information can be found from either file.
1.2 deraadt 908: .Pp
1.1 deraadt 909: Note that the lines in these files are typically hundreds of characters
910: long, and you definitely don't want to type in the host keys by hand.
1.6 aaron 911: Rather, generate them by a script
1.40 aaron 912: or by taking
1.2 deraadt 913: .Pa /etc/ssh_host_key.pub
1.1 deraadt 914: and adding the host names at the front.
1.2 deraadt 915: .Ss Examples
1.1 deraadt 916: closenet,closenet.hut.fi,.\|.\|.\|,130.233.208.41 1024 37 159.\|.\|.93 closenet.hut.fi
1.2 deraadt 917: .Sh FILES
918: .Bl -tag -width Ds
919: .It Pa /etc/sshd_config
1.1 deraadt 920: Contains configuration data for
1.2 deraadt 921: .Nm sshd .
1.1 deraadt 922: This file should be writable by root only, but it is recommended
923: (though not necessary) that it be world-readable.
1.98 ! deraadt 924: .It Pa /etc/ssh_host_key, /etc/ssh_host_dsa_key, /etc/ssh_host_rsa_key
! 925: These three files contain the private parts of the
! 926: (SSH1, SSH2 DSA, and SSH2 RSA) host keys.
! 927: These files should only be owned by root, readable only by root, and not
1.1 deraadt 928: accessible to others.
1.14 markus 929: Note that
930: .Nm
931: does not start if this file is group/world-accessible.
1.98 ! deraadt 932: .It Pa /etc/ssh_host_key.pub, /etc/ssh_host_dsa_key.pub, /etc/ssh_host_rsa_key.pub
! 933: There three files contain the public parts of the
! 934: (SSH1, SSH2 DSA, and SSH2 RSA) host keys.
! 935: These files should be world-readable but writable only by
1.36 aaron 936: root.
1.98 ! deraadt 937: Their contents should match the respective private parts.
! 938: These files are not
! 939: really used for anything; they are provided for the convenience of
! 940: the user so their contents can be copied to known hosts files.
! 941: These files are created using
1.7 markus 942: .Xr ssh-keygen 1 .
1.73 provos 943: .It Pa /etc/primes
944: Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange".
1.2 deraadt 945: .It Pa /var/run/sshd.pid
946: Contains the process ID of the
947: .Nm
1.1 deraadt 948: listening for connections (if there are several daemons running
949: concurrently for different ports, this contains the pid of the one
1.36 aaron 950: started last).
1.58 deraadt 951: The content of this file is not sensitive; it can be world-readable.
1.2 deraadt 952: .It Pa $HOME/.ssh/authorized_keys
1.1 deraadt 953: Lists the RSA keys that can be used to log into the user's account.
954: This file must be readable by root (which may on some machines imply
955: it being world-readable if the user's home directory resides on an NFS
1.36 aaron 956: volume).
957: It is recommended that it not be accessible by others.
958: The format of this file is described above.
1.44 deraadt 959: Users will place the contents of their
960: .Pa identity.pub
961: files into this file, as described in
962: .Xr ssh-keygen 1 .
963: .It Pa $HOME/.ssh/authorized_keys2
964: Lists the DSA keys that can be used to log into the user's account.
965: This file must be readable by root (which may on some machines imply
966: it being world-readable if the user's home directory resides on an NFS
967: volume).
968: It is recommended that it not be accessible by others.
969: The format of this file is described above.
970: Users will place the contents of their
971: .Pa id_dsa.pub
972: files into this file, as described in
973: .Xr ssh-keygen 1 .
1.22 markus 974: .It Pa "/etc/ssh_known_hosts" and "$HOME/.ssh/known_hosts"
975: These files are consulted when using rhosts with RSA host
1.36 aaron 976: authentication to check the public key of the host.
977: The key must be listed in one of these files to be accepted.
1.22 markus 978: The client uses the same files
1.96 markus 979: to verify that it is connecting to the correct remote host.
1.36 aaron 980: These files should be writable only by root/the owner.
1.2 deraadt 981: .Pa /etc/ssh_known_hosts
982: should be world-readable, and
983: .Pa $HOME/.ssh/known_hosts
984: can but need not be world-readable.
1.6 aaron 985: .It Pa /etc/nologin
1.40 aaron 986: If this file exists,
1.2 deraadt 987: .Nm
1.36 aaron 988: refuses to let anyone except root log in.
989: The contents of the file
1.1 deraadt 990: are displayed to anyone trying to log in, and non-root connections are
1.36 aaron 991: refused.
992: The file should be world-readable.
1.19 dugsong 993: .It Pa /etc/hosts.allow, /etc/hosts.deny
994: If compiled with
995: .Sy LIBWRAP
996: support, tcp-wrappers access controls may be defined here as described in
997: .Xr hosts_access 5 .
1.6 aaron 998: .It Pa $HOME/.rhosts
1.1 deraadt 999: This file contains host-username pairs, separated by a space, one per
1.36 aaron 1000: line.
1001: The given user on the corresponding host is permitted to log in
1002: without password.
1003: The same file is used by rlogind and rshd.
1.6 aaron 1004: The file must
1.1 deraadt 1005: be writable only by the user; it is recommended that it not be
1006: accessible by others.
1.2 deraadt 1007: .Pp
1.36 aaron 1008: If is also possible to use netgroups in the file.
1009: Either host or user
1.1 deraadt 1010: name may be of the form +@groupname to specify all hosts or all users
1011: in the group.
1.2 deraadt 1012: .It Pa $HOME/.shosts
1013: For ssh,
1014: this file is exactly the same as for
1015: .Pa .rhosts .
1016: However, this file is
1017: not used by rlogin and rshd, so using this permits access using SSH only.
1.58 deraadt 1018: .It Pa /etc/hosts.equiv
1.2 deraadt 1019: This file is used during
1020: .Pa .rhosts
1.36 aaron 1021: authentication.
1022: In the simplest form, this file contains host names, one per line.
1023: Users on
1.1 deraadt 1024: those hosts are permitted to log in without a password, provided they
1.36 aaron 1025: have the same user name on both machines.
1026: The host name may also be
1.1 deraadt 1027: followed by a user name; such users are permitted to log in as
1.2 deraadt 1028: .Em any
1.36 aaron 1029: user on this machine (except root).
1030: Additionally, the syntax
1.2 deraadt 1031: .Dq +@group
1.36 aaron 1032: can be used to specify netgroups.
1033: Negated entries start with
1.2 deraadt 1034: .Ql \&- .
1035: .Pp
1.1 deraadt 1036: If the client host/user is successfully matched in this file, login is
1037: automatically permitted provided the client and server user names are the
1.36 aaron 1038: same.
1039: Additionally, successful RSA host authentication is normally required.
1040: This file must be writable only by root; it is recommended
1.1 deraadt 1041: that it be world-readable.
1.2 deraadt 1042: .Pp
1.6 aaron 1043: .Sy "Warning: It is almost never a good idea to use user names in"
1.2 deraadt 1044: .Pa hosts.equiv .
1.1 deraadt 1045: Beware that it really means that the named user(s) can log in as
1.2 deraadt 1046: .Em anybody ,
1.1 deraadt 1047: which includes bin, daemon, adm, and other accounts that own critical
1.36 aaron 1048: binaries and directories.
1049: Using a user name practically grants the user root access.
1050: The only valid use for user names that I can think
1.1 deraadt 1051: of is in negative entries.
1.2 deraadt 1052: .Pp
1053: Note that this warning also applies to rsh/rlogin.
1054: .It Pa /etc/shosts.equiv
1.1 deraadt 1055: This is processed exactly as
1.2 deraadt 1056: .Pa /etc/hosts.equiv .
1.1 deraadt 1057: However, this file may be useful in environments that want to run both
1.2 deraadt 1058: rsh/rlogin and ssh.
1.6 aaron 1059: .It Pa $HOME/.ssh/environment
1.36 aaron 1060: This file is read into the environment at login (if it exists).
1061: It can only contain empty lines, comment lines (that start with
1.2 deraadt 1062: .Ql # ) ,
1.36 aaron 1063: and assignment lines of the form name=value.
1064: The file should be writable
1.6 aaron 1065: only by the user; it need not be readable by anyone else.
1.2 deraadt 1066: .It Pa $HOME/.ssh/rc
1.1 deraadt 1067: If this file exists, it is run with /bin/sh after reading the
1.36 aaron 1068: environment files but before starting the user's shell or command.
1069: If X11 spoofing is in use, this will receive the "proto cookie" pair in
1.2 deraadt 1070: standard input (and
1071: .Ev DISPLAY
1.36 aaron 1072: in environment).
1073: This must call
1.2 deraadt 1074: .Xr xauth 1
1075: in that case.
1076: .Pp
1.1 deraadt 1077: The primary purpose of this file is to run any initialization routines
1078: which may be needed before the user's home directory becomes
1079: accessible; AFS is a particular example of such an environment.
1.2 deraadt 1080: .Pp
1.1 deraadt 1081: This file will probably contain some initialization code followed by
1082: something similar to: "if read proto cookie; then echo add $DISPLAY
1083: $proto $cookie | xauth -q -; fi".
1.2 deraadt 1084: .Pp
1085: If this file does not exist,
1086: .Pa /etc/sshrc
1087: is run, and if that
1.1 deraadt 1088: does not exist either, xauth is used to store the cookie.
1.2 deraadt 1089: .Pp
1.1 deraadt 1090: This file should be writable only by the user, and need not be
1091: readable by anyone else.
1.2 deraadt 1092: .It Pa /etc/sshrc
1093: Like
1094: .Pa $HOME/.ssh/rc .
1095: This can be used to specify
1.36 aaron 1096: machine-specific login-time initializations globally.
1097: This file should be writable only by root, and should be world-readable.
1.56 aaron 1098: .El
1.71 aaron 1099: .Sh AUTHORS
1.84 markus 1100: OpenSSH is a derivative of the original and free
1101: ssh 1.2.12 release by Tatu Ylonen.
1102: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1103: Theo de Raadt and Dug Song
1104: removed many bugs, re-added newer features and
1105: created OpenSSH.
1106: Markus Friedl contributed the support for SSH
1107: protocol versions 1.5 and 2.0.
1.2 deraadt 1108: .Sh SEE ALSO
1109: .Xr scp 1 ,
1.90 djm 1110: .Xr sftp 1 ,
1.63 markus 1111: .Xr sftp-server 8 ,
1.2 deraadt 1112: .Xr ssh 1 ,
1.5 deraadt 1113: .Xr ssh-add 1 ,
1.2 deraadt 1114: .Xr ssh-agent 1 ,
1.5 deraadt 1115: .Xr ssh-keygen 1 ,
1.38 deraadt 1116: .Xr rlogin 1 ,
1117: .Xr rsh 1
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