Annotation of src/usr.bin/ssh/ssh.1, Revision 1.234
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: .\"
1.59 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: .\"
1.93 deraadt 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.
1.59 deraadt 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: .\"
1.59 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,
32: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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: .\"
1.234 ! jmc 37: .\" $OpenBSD: ssh.1,v 1.233 2005/12/31 13:44:04 jmc Exp $
1.2 deraadt 38: .Dd September 25, 1999
39: .Dt SSH 1
40: .Os
41: .Sh NAME
42: .Nm ssh
1.96 deraadt 43: .Nd OpenSSH SSH client (remote login program)
1.2 deraadt 44: .Sh SYNOPSIS
45: .Nm ssh
1.191 djm 46: .Op Fl 1246AaCfgkMNnqsTtVvXxY
1.108 markus 47: .Op Fl b Ar bind_address
1.51 markus 48: .Op Fl c Ar cipher_spec
1.210 djm 49: .Oo Fl D\ \&
50: .Sm off
51: .Oo Ar bind_address : Oc
52: .Ar port
53: .Sm on
54: .Oc
1.2 deraadt 55: .Op Fl e Ar escape_char
1.176 jmc 56: .Op Fl F Ar configfile
1.211 jmc 57: .Bk -words
1.2 deraadt 58: .Op Fl i Ar identity_file
1.211 jmc 59: .Ek
1.202 jmc 60: .Oo Fl L\ \&
1.12 aaron 61: .Sm off
1.200 djm 62: .Oo Ar bind_address : Oc
1.202 jmc 63: .Ar port : host : hostport
1.12 aaron 64: .Sm on
65: .Oc
1.211 jmc 66: .Bk -words
1.176 jmc 67: .Op Fl l Ar login_name
1.211 jmc 68: .Ek
1.176 jmc 69: .Op Fl m Ar mac_spec
1.198 djm 70: .Op Fl O Ar ctl_cmd
1.176 jmc 71: .Op Fl o Ar option
72: .Op Fl p Ar port
1.202 jmc 73: .Oo Fl R\ \&
1.12 aaron 74: .Sm off
1.200 djm 75: .Oo Ar bind_address : Oc
1.202 jmc 76: .Ar port : host : hostport
1.12 aaron 77: .Sm on
78: .Oc
1.198 djm 79: .Op Fl S Ar ctl_path
1.216 jmc 80: .Bk -words
81: .Op Fl w Ar tunnel : Ns Ar tunnel
1.176 jmc 82: .Oo Ar user Ns @ Oc Ns Ar hostname
1.2 deraadt 83: .Op Ar command
1.216 jmc 84: .Ek
1.44 aaron 85: .Sh DESCRIPTION
1.2 deraadt 86: .Nm
1.96 deraadt 87: (SSH client) is a program for logging into a remote machine and for
1.40 aaron 88: executing commands on a remote machine.
1.176 jmc 89: It is intended to replace rlogin and rsh,
90: and provide secure encrypted communications between
1.40 aaron 91: two untrusted hosts over an insecure network.
1.176 jmc 92: X11 connections and arbitrary TCP/IP ports
93: can also be forwarded over the secure channel.
1.2 deraadt 94: .Pp
95: .Nm
1.44 aaron 96: connects and logs into the specified
1.176 jmc 97: .Ar hostname
98: (with optional
99: .Ar user
100: name).
1.1 deraadt 101: The user must prove
1.49 markus 102: his/her identity to the remote machine using one of several methods
1.221 jmc 103: depending on the protocol version used (see below).
1.49 markus 104: .Pp
1.176 jmc 105: If
106: .Ar command
107: is specified,
1.219 jmc 108: it is executed on the remote host instead of a login shell.
1.2 deraadt 109: .Pp
1.218 jmc 110: The options are as follows:
111: .Bl -tag -width Ds
112: .It Fl 1
113: Forces
1.2 deraadt 114: .Nm
1.218 jmc 115: to try protocol version 1 only.
116: .It Fl 2
117: Forces
1.2 deraadt 118: .Nm
1.218 jmc 119: to try protocol version 2 only.
120: .It Fl 4
121: Forces
1.2 deraadt 122: .Nm
1.218 jmc 123: to use IPv4 addresses only.
124: .It Fl 6
125: Forces
1.2 deraadt 126: .Nm
1.218 jmc 127: to use IPv6 addresses only.
128: .It Fl A
129: Enables forwarding of the authentication agent connection.
130: This can also be specified on a per-host basis in a configuration file.
1.2 deraadt 131: .Pp
1.218 jmc 132: Agent forwarding should be enabled with caution.
133: Users with the ability to bypass file permissions on the remote host
134: (for the agent's Unix-domain socket)
135: can access the local agent through the forwarded connection.
136: An attacker cannot obtain key material from the agent,
137: however they can perform operations on the keys that enable them to
138: authenticate using the identities loaded into the agent.
139: .It Fl a
140: Disables forwarding of the authentication agent connection.
141: .It Fl b Ar bind_address
142: Use
143: .Ar bind_address
144: on the local machine as the source address
145: of the connection.
146: Only useful on systems with more than one address.
147: .It Fl C
148: Requests compression of all data (including stdin, stdout, stderr, and
149: data for forwarded X11 and TCP/IP connections).
150: The compression algorithm is the same used by
151: .Xr gzip 1 ,
152: and the
153: .Dq level
154: can be controlled by the
155: .Cm CompressionLevel
156: option for protocol version 1.
157: Compression is desirable on modem lines and other
158: slow connections, but will only slow down things on fast networks.
159: The default value can be set on a host-by-host basis in the
160: configuration files; see the
161: .Cm Compression
162: option.
163: .It Fl c Ar cipher_spec
164: Selects the cipher specification for encrypting the session.
1.2 deraadt 165: .Pp
1.218 jmc 166: Protocol version 1 allows specification of a single cipher.
167: The supported values are
168: .Dq 3des ,
1.220 jmc 169: .Dq blowfish ,
1.218 jmc 170: and
171: .Dq des .
172: .Ar 3des
173: (triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
174: It is believed to be secure.
175: .Ar blowfish
176: is a fast block cipher; it appears very secure and is much faster than
177: .Ar 3des .
178: .Ar des
179: is only supported in the
1.2 deraadt 180: .Nm
1.218 jmc 181: client for interoperability with legacy protocol 1 implementations
182: that do not support the
183: .Ar 3des
184: cipher.
185: Its use is strongly discouraged due to cryptographic weaknesses.
186: The default is
187: .Dq 3des .
1.49 markus 188: .Pp
1.230 jmc 189: For protocol version 2,
1.218 jmc 190: .Ar cipher_spec
191: is a comma-separated list of ciphers
192: listed in order of preference.
1.230 jmc 193: The supported ciphers are:
194: 3des-cbc,
195: aes128-cbc,
196: aes192-cbc,
197: aes256-cbc,
198: aes128-ctr,
199: aes192-ctr,
200: aes256-ctr,
201: arcfour128,
202: arcfour256,
203: arcfour,
204: blowfish-cbc,
1.218 jmc 205: and
1.230 jmc 206: cast128-cbc.
1.220 jmc 207: The default is:
208: .Bd -literal -offset indent
209: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,
210: arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,
211: aes192-ctr,aes256-ctr
1.218 jmc 212: .Ed
213: .It Fl D Xo
214: .Sm off
215: .Oo Ar bind_address : Oc
216: .Ar port
217: .Sm on
218: .Xc
219: Specifies a local
220: .Dq dynamic
221: application-level port forwarding.
222: This works by allocating a socket to listen to
223: .Ar port
224: on the local side, optionally bound to the specified
225: .Ar bind_address .
226: Whenever a connection is made to this port, the
227: connection is forwarded over the secure channel, and the application
228: protocol is then used to determine where to connect to from the
229: remote machine.
230: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.107 markus 231: .Nm
1.218 jmc 232: will act as a SOCKS server.
233: Only root can forward privileged ports.
234: Dynamic port forwardings can also be specified in the configuration file.
1.49 markus 235: .Pp
1.218 jmc 236: IPv6 addresses can be specified with an alternative syntax:
237: .Sm off
238: .Xo
239: .Op Ar bind_address No /
240: .Ar port
241: .Xc
242: .Sm on
243: or by enclosing the address in square brackets.
244: Only the superuser can forward privileged ports.
245: By default, the local port is bound in accordance with the
246: .Cm GatewayPorts
247: setting.
248: However, an explicit
249: .Ar bind_address
250: may be used to bind the connection to a specific address.
251: The
252: .Ar bind_address
253: of
254: .Dq localhost
255: indicates that the listening port be bound for local use only, while an
256: empty address or
257: .Sq *
258: indicates that the port should be available from all interfaces.
1.229 jmc 259: .It Fl e Ar escape_char
1.218 jmc 260: Sets the escape character for sessions with a pty (default:
261: .Ql ~ ) .
262: The escape character is only recognized at the beginning of a line.
263: The escape character followed by a dot
264: .Pq Ql \&.
265: closes the connection;
266: followed by control-Z suspends the connection;
267: and followed by itself sends the escape character once.
268: Setting the character to
1.2 deraadt 269: .Dq none
1.218 jmc 270: disables any escapes and makes the session fully transparent.
271: .It Fl F Ar configfile
272: Specifies an alternative per-user configuration file.
273: If a configuration file is given on the command line,
274: the system-wide configuration file
275: .Pq Pa /etc/ssh/ssh_config
276: will be ignored.
277: The default for the per-user configuration file is
278: .Pa ~/.ssh/config .
279: .It Fl f
280: Requests
281: .Nm
282: to go to background just before command execution.
283: This is useful if
1.176 jmc 284: .Nm
1.218 jmc 285: is going to ask for passwords or passphrases, but the user
286: wants it in the background.
287: This implies
288: .Fl n .
289: The recommended way to start X11 programs at a remote site is with
290: something like
291: .Ic ssh -f host xterm .
292: .It Fl g
293: Allows remote hosts to connect to local forwarded ports.
294: .It Fl I Ar smartcard_device
1.229 jmc 295: Specify the device
1.176 jmc 296: .Nm
1.218 jmc 297: should use to communicate with a smartcard used for storing the user's
298: private RSA key.
1.229 jmc 299: This option is only available if support for smartcard devices
300: is compiled in (default is no support).
1.218 jmc 301: .It Fl i Ar identity_file
302: Selects a file from which the identity (private key) for
303: RSA or DSA authentication is read.
304: The default is
305: .Pa ~/.ssh/identity
306: for protocol version 1, and
307: .Pa ~/.ssh/id_rsa
1.149 jakob 308: and
1.218 jmc 309: .Pa ~/.ssh/id_dsa
310: for protocol version 2.
311: Identity files may also be specified on
312: a per-host basis in the configuration file.
313: It is possible to have multiple
314: .Fl i
315: options (and multiple identities specified in
316: configuration files).
317: .It Fl k
318: Disables forwarding (delegation) of GSSAPI credentials to the server.
319: .It Fl L Xo
320: .Sm off
321: .Oo Ar bind_address : Oc
322: .Ar port : host : hostport
323: .Sm on
324: .Xc
325: Specifies that the given port on the local (client) host is to be
326: forwarded to the given host and port on the remote side.
327: This works by allocating a socket to listen to
328: .Ar port
329: on the local side, optionally bound to the specified
330: .Ar bind_address .
331: Whenever a connection is made to this port, the
332: connection is forwarded over the secure channel, and a connection is
333: made to
334: .Ar host
335: port
336: .Ar hostport
337: from the remote machine.
338: Port forwardings can also be specified in the configuration file.
339: IPv6 addresses can be specified with an alternative syntax:
340: .Sm off
341: .Xo
342: .Op Ar bind_address No /
343: .Ar port No / Ar host No /
344: .Ar hostport
345: .Xc
346: .Sm on
347: or by enclosing the address in square brackets.
348: Only the superuser can forward privileged ports.
349: By default, the local port is bound in accordance with the
350: .Cm GatewayPorts
351: setting.
352: However, an explicit
353: .Ar bind_address
354: may be used to bind the connection to a specific address.
1.2 deraadt 355: The
1.218 jmc 356: .Ar bind_address
357: of
358: .Dq localhost
359: indicates that the listening port be bound for local use only, while an
360: empty address or
361: .Sq *
362: indicates that the port should be available from all interfaces.
363: .It Fl l Ar login_name
364: Specifies the user to log in as on the remote machine.
365: This also may be specified on a per-host basis in the configuration file.
366: .It Fl M
367: Places the
368: .Nm
369: client into
370: .Dq master
371: mode for connection sharing.
1.231 stevesk 372: Multiple
373: .Fl M
374: options places
375: .Nm
376: into
377: .Dq master
378: mode with confirmation required before slave connections are accepted.
1.218 jmc 379: Refer to the description of
380: .Cm ControlMaster
381: in
382: .Xr ssh_config 5
383: for details.
384: .It Fl m Ar mac_spec
385: Additionally, for protocol version 2 a comma-separated list of MAC
386: (message authentication code) algorithms can
387: be specified in order of preference.
388: See the
389: .Cm MACs
390: keyword for more information.
391: .It Fl N
392: Do not execute a remote command.
393: This is useful for just forwarding ports
394: (protocol version 2 only).
395: .It Fl n
396: Redirects stdin from
397: .Pa /dev/null
398: (actually, prevents reading from stdin).
399: This must be used when
1.2 deraadt 400: .Nm
1.218 jmc 401: is run in the background.
402: A common trick is to use this to run X11 programs on a remote machine.
403: For example,
404: .Ic ssh -n shadows.cs.hut.fi emacs &
405: will start an emacs on shadows.cs.hut.fi, and the X11
406: connection will be automatically forwarded over an encrypted channel.
407: The
1.2 deraadt 408: .Nm
1.218 jmc 409: program will be put in the background.
410: (This does not work if
1.2 deraadt 411: .Nm
1.218 jmc 412: needs to ask for a password or passphrase; see also the
413: .Fl f
414: option.)
415: .It Fl O Ar ctl_cmd
416: Control an active connection multiplexing master process.
417: When the
418: .Fl O
419: option is specified, the
420: .Ar ctl_cmd
421: argument is interpreted and passed to the master process.
422: Valid commands are:
423: .Dq check
424: (check that the master process is running) and
425: .Dq exit
426: (request the master to exit).
427: .It Fl o Ar option
428: Can be used to give options in the format used in the configuration file.
429: This is useful for specifying options for which there is no separate
430: command-line flag.
431: For full details of the options listed below, and their possible values, see
432: .Xr ssh_config 5 .
1.2 deraadt 433: .Pp
1.218 jmc 434: .Bl -tag -width Ds -offset indent -compact
435: .It AddressFamily
436: .It BatchMode
437: .It BindAddress
438: .It ChallengeResponseAuthentication
439: .It CheckHostIP
440: .It Cipher
441: .It Ciphers
442: .It ClearAllForwardings
443: .It Compression
444: .It CompressionLevel
445: .It ConnectionAttempts
446: .It ConnectTimeout
447: .It ControlMaster
448: .It ControlPath
449: .It DynamicForward
450: .It EscapeChar
451: .It ForwardAgent
452: .It ForwardX11
453: .It ForwardX11Trusted
454: .It GatewayPorts
455: .It GlobalKnownHostsFile
456: .It GSSAPIAuthentication
457: .It GSSAPIDelegateCredentials
458: .It HashKnownHosts
459: .It Host
460: .It HostbasedAuthentication
461: .It HostKeyAlgorithms
462: .It HostKeyAlias
463: .It HostName
464: .It IdentityFile
465: .It IdentitiesOnly
466: .It KbdInteractiveDevices
467: .It LocalCommand
468: .It LocalForward
469: .It LogLevel
470: .It MACs
471: .It NoHostAuthenticationForLocalhost
472: .It NumberOfPasswordPrompts
473: .It PasswordAuthentication
474: .It PermitLocalCommand
475: .It Port
476: .It PreferredAuthentications
477: .It Protocol
478: .It ProxyCommand
479: .It PubkeyAuthentication
480: .It RemoteForward
481: .It RhostsRSAAuthentication
482: .It RSAAuthentication
483: .It SendEnv
484: .It ServerAliveInterval
485: .It ServerAliveCountMax
486: .It SmartcardDevice
487: .It StrictHostKeyChecking
488: .It TCPKeepAlive
489: .It Tunnel
490: .It TunnelDevice
491: .It UsePrivilegedPort
492: .It User
493: .It UserKnownHostsFile
494: .It VerifyHostKeyDNS
495: .It XAuthLocation
496: .El
497: .It Fl p Ar port
498: Port to connect to on the remote host.
499: This can be specified on a
500: per-host basis in the configuration file.
501: .It Fl q
502: Quiet mode.
503: Causes all warning and diagnostic messages to be suppressed.
504: .It Fl R Xo
505: .Sm off
506: .Oo Ar bind_address : Oc
507: .Ar port : host : hostport
508: .Sm on
509: .Xc
510: Specifies that the given port on the remote (server) host is to be
511: forwarded to the given host and port on the local side.
512: This works by allocating a socket to listen to
513: .Ar port
514: on the remote side, and whenever a connection is made to this port, the
515: connection is forwarded over the secure channel, and a connection is
516: made to
517: .Ar host
518: port
519: .Ar hostport
520: from the local machine.
1.2 deraadt 521: .Pp
1.218 jmc 522: Port forwardings can also be specified in the configuration file.
523: Privileged ports can be forwarded only when
524: logging in as root on the remote machine.
525: IPv6 addresses can be specified by enclosing the address in square braces or
526: using an alternative syntax:
527: .Sm off
528: .Xo
529: .Op Ar bind_address No /
530: .Ar host No / Ar port No /
531: .Ar hostport
532: .Xc .
533: .Sm on
1.194 jakob 534: .Pp
1.218 jmc 535: By default, the listening socket on the server will be bound to the loopback
536: interface only.
537: This may be overriden by specifying a
538: .Ar bind_address .
539: An empty
540: .Ar bind_address ,
541: or the address
542: .Ql * ,
543: indicates that the remote socket should listen on all interfaces.
544: Specifying a remote
545: .Ar bind_address
546: will only succeed if the server's
547: .Cm GatewayPorts
548: option is enabled (see
549: .Xr sshd_config 5 ) .
550: .It Fl S Ar ctl_path
551: Specifies the location of a control socket for connection sharing.
552: Refer to the description of
553: .Cm ControlPath
554: and
555: .Cm ControlMaster
556: in
557: .Xr ssh_config 5
558: for details.
559: .It Fl s
560: May be used to request invocation of a subsystem on the remote system.
561: Subsystems are a feature of the SSH2 protocol which facilitate the use
562: of SSH as a secure transport for other applications (eg.\&
563: .Xr sftp 1 ) .
564: The subsystem is specified as the remote command.
565: .It Fl T
566: Disable pseudo-tty allocation.
567: .It Fl t
568: Force pseudo-tty allocation.
569: This can be used to execute arbitrary
570: screen-based programs on a remote machine, which can be very useful,
571: e.g., when implementing menu services.
572: Multiple
573: .Fl t
574: options force tty allocation, even if
1.194 jakob 575: .Nm
1.218 jmc 576: has no local tty.
577: .It Fl V
578: Display the version number and exit.
579: .It Fl v
580: Verbose mode.
581: Causes
1.176 jmc 582: .Nm
1.218 jmc 583: to print debugging messages about its progress.
584: This is helpful in
585: debugging connection, authentication, and configuration problems.
586: Multiple
587: .Fl v
588: options increase the verbosity.
589: The maximum is 3.
590: .It Fl w Ar tunnel : Ns Ar tunnel
591: Requests a
592: .Xr tun 4
1.228 jmc 593: device on the client
594: (first
595: .Ar tunnel
596: arg)
597: and server
598: (second
599: .Ar tunnel
600: arg).
601: The devices may be specified by numerical ID or the keyword
602: .Dq any ,
603: which uses the next available tunnel device.
604: See also the
1.218 jmc 605: .Cm Tunnel
606: directive in
607: .Xr ssh_config 5 .
608: .It Fl X
609: Enables X11 forwarding.
1.54 markus 610: This can also be specified on a per-host basis in a configuration file.
1.165 stevesk 611: .Pp
1.218 jmc 612: X11 forwarding should be enabled with caution.
1.168 jmc 613: Users with the ability to bypass file permissions on the remote host
1.218 jmc 614: (for the user's X authorization database)
615: can access the local X11 display through the forwarded connection.
616: An attacker may then be able to perform activities such as keystroke monitoring.
617: .Pp
618: For this reason, X11 forwarding is subjected to X11 SECURITY extension
619: restrictions by default.
620: Please refer to the
621: .Nm
622: .Fl Y
623: option and the
624: .Cm ForwardX11Trusted
625: directive in
626: .Xr ssh_config 5
627: for more information.
628: .It Fl x
629: Disables X11 forwarding.
630: .It Fl Y
631: Enables trusted X11 forwarding.
632: Trusted X11 forwardings are not subjected to the X11 SECURITY extension
633: controls.
634: .El
1.224 jmc 635: .Pp
636: .Nm
637: may additionally obtain configuration data from
638: a per-user configuration file and a system-wide configuration file.
639: The file format and configuration options are described in
640: .Xr ssh_config 5 .
641: .Pp
642: .Nm
643: exits with the exit status of the remote command or with 255
644: if an error occurred.
1.222 jmc 645: .Sh AUTHENTICATION
646: The OpenSSH SSH client supports OpenSSH protocols 1 and 2.
647: Protocol 2 is the default, with
648: .Nm
649: falling back to protocol 1 if it detects protocol 2 is unsupported.
650: These settings may be altered using the
651: .Cm Protocol
652: option in
653: .Xr ssh_config 5 ,
654: or enforced using the
655: .Fl 1
656: and
657: .Fl 2
658: options (see above).
659: Both protocols support similar authentication methods,
660: but protocol 2 is preferred since
661: it provides additional mechanisms for confidentiality
662: (the traffic is encrypted using AES, 3DES, Blowfish, CAST128, or Arcfour)
663: and integrity (hmac-md5, hmac-sha1, hmac-ripemd160).
664: Protocol 1 lacks a strong mechanism for ensuring the
665: integrity of the connection.
666: .Pp
667: The methods available for authentication are:
668: host-based authentication,
669: public key authentication,
670: challenge-response authentication,
671: and password authentication.
672: Authentication methods are tried in the order specified above,
673: though protocol 2 has a configuration option to change the default order:
674: .Cm PreferredAuthentications .
675: .Pp
676: Host-based authentication works as follows:
1.218 jmc 677: If the machine the user logs in from is listed in
678: .Pa /etc/hosts.equiv
679: or
680: .Pa /etc/shosts.equiv
681: on the remote machine, and the user names are
682: the same on both sides, or if the files
683: .Pa ~/.rhosts
684: or
685: .Pa ~/.shosts
686: exist in the user's home directory on the
687: remote machine and contain a line containing the name of the client
688: machine and the name of the user on that machine, the user is
1.222 jmc 689: considered for login.
690: Additionally, the server
691: .Em must
692: be able to verify the client's
693: host key (see the description of
1.218 jmc 694: .Pa /etc/ssh/ssh_known_hosts
1.189 dtucker 695: and
1.222 jmc 696: .Pa ~/.ssh/known_hosts ,
697: below)
698: for login to be permitted.
1.218 jmc 699: This authentication method closes security holes due to IP
1.222 jmc 700: spoofing, DNS spoofing, and routing spoofing.
1.218 jmc 701: [Note to the administrator:
702: .Pa /etc/hosts.equiv ,
703: .Pa ~/.rhosts ,
704: and the rlogin/rsh protocol in general, are inherently insecure and should be
705: disabled if security is desired.]
1.189 dtucker 706: .Pp
1.222 jmc 707: Public key authentication works as follows:
708: The scheme is based on public-key cryptography,
709: using cryptosystems
710: where encryption and decryption are done using separate keys,
711: and it is unfeasible to derive the decryption key from the encryption key.
1.218 jmc 712: The idea is that each user creates a public/private
713: key pair for authentication purposes.
714: The server knows the public key, and only the user knows the private key.
1.222 jmc 715: .Nm
716: implements public key authentication protocol automatically,
717: using either the RSA or DSA algorithms.
718: Protocol 1 is restricted to using only RSA keys,
719: but protocol 2 may use either.
720: The
721: .Sx HISTORY
722: section of
723: .Xr ssl 8
724: contains a brief discussion of the two algorithms.
1.210 djm 725: .Pp
1.218 jmc 726: The file
727: .Pa ~/.ssh/authorized_keys
728: lists the public keys that are permitted for logging in.
729: When the user logs in, the
1.2 deraadt 730: .Nm
1.218 jmc 731: program tells the server which key pair it would like to use for
732: authentication.
1.222 jmc 733: The client proves that it has access to the private key
734: and the server checks that the corresponding public key
735: is authorized to accept the account.
1.218 jmc 736: .Pp
1.222 jmc 737: The user creates his/her key pair by running
1.218 jmc 738: .Xr ssh-keygen 1 .
739: This stores the private key in
1.207 djm 740: .Pa ~/.ssh/identity
1.222 jmc 741: (protocol 1),
742: .Pa ~/.ssh/id_dsa
743: (protocol 2 DSA),
744: or
745: .Pa ~/.ssh/id_rsa
746: (protocol 2 RSA)
1.218 jmc 747: and stores the public key in
748: .Pa ~/.ssh/identity.pub
1.222 jmc 749: (protocol 1),
750: .Pa ~/.ssh/id_dsa.pub
751: (protocol 2 DSA),
752: or
753: .Pa ~/.ssh/id_rsa.pub
754: (protocol 2 RSA)
1.218 jmc 755: in the user's home directory.
1.222 jmc 756: The user should then copy the public key
1.218 jmc 757: to
758: .Pa ~/.ssh/authorized_keys
1.222 jmc 759: in his/her home directory on the remote machine.
760: The
1.218 jmc 761: .Pa authorized_keys
762: file corresponds to the conventional
763: .Pa ~/.rhosts
764: file, and has one key
1.222 jmc 765: per line, though the lines can be very long.
1.218 jmc 766: After this, the user can log in without giving the password.
767: .Pp
1.222 jmc 768: The most convenient way to use public key authentication may be with an
1.218 jmc 769: authentication agent.
770: See
771: .Xr ssh-agent 1
772: for more information.
773: .Pp
1.222 jmc 774: Challenge-response authentication works as follows:
775: The server sends an arbitrary
776: .Qq challenge
777: text, and prompts for a response.
778: Protocol 2 allows multiple challenges and responses;
779: protocol 1 is restricted to just one challenge/response.
780: Examples of challenge-response authentication include
781: BSD Authentication (see
782: .Xr login.conf 5 )
783: and PAM (some non-OpenBSD systems).
784: .Pp
785: Finally, if other authentication methods fail,
1.218 jmc 786: .Nm
787: prompts the user for a password.
788: The password is sent to the remote
789: host for checking; however, since all communications are encrypted,
790: the password cannot be seen by someone listening on the network.
1.232 jmc 791: .Pp
792: .Nm
793: automatically maintains and checks a database containing
794: identification for all hosts it has ever been used with.
795: Host keys are stored in
796: .Pa ~/.ssh/known_hosts
797: in the user's home directory.
798: Additionally, the file
799: .Pa /etc/ssh/ssh_known_hosts
800: is automatically checked for known hosts.
801: Any new hosts are automatically added to the user's file.
802: If a host's identification ever changes,
803: .Nm
804: warns about this and disables password authentication to prevent
805: server spoofing or man-in-the-middle attacks,
806: which could otherwise be used to circumvent the encryption.
807: The
808: .Cm StrictHostKeyChecking
809: option can be used to control logins to machines whose
810: host key is not known or has changed.
811: .Pp
812: .Nm
813: can be configured to verify host identification using fingerprint resource
814: records (SSHFP) published in DNS.
815: The
816: .Cm VerifyHostKeyDNS
817: option can be used to control how DNS lookups are performed.
818: SSHFP resource records can be generated using
819: .Xr ssh-keygen 1 .
820: .Pp
1.218 jmc 821: When the user's identity has been accepted by the server, the server
822: either executes the given command, or logs into the machine and gives
823: the user a normal shell on the remote machine.
824: All communication with
825: the remote command or shell will be automatically encrypted.
826: .Pp
827: If a pseudo-terminal has been allocated (normal login session), the
828: user may use the escape characters noted below.
829: .Pp
830: If no pseudo-tty has been allocated,
831: the session is transparent and can be used to reliably transfer binary data.
832: On most systems, setting the escape character to
833: .Dq none
834: will also make the session transparent even if a tty is used.
835: .Pp
836: The session terminates when the command or shell on the remote
837: machine exits and all X11 and TCP/IP connections have been closed.
1.223 jmc 838: .Sh ESCAPE CHARACTERS
1.218 jmc 839: When a pseudo-terminal has been requested,
1.2 deraadt 840: .Nm
1.218 jmc 841: supports a number of functions through the use of an escape character.
842: .Pp
843: A single tilde character can be sent as
844: .Ic ~~
845: or by following the tilde by a character other than those described below.
846: The escape character must always follow a newline to be interpreted as
847: special.
848: The escape character can be changed in configuration files using the
849: .Cm EscapeChar
850: configuration directive or on the command line by the
851: .Fl e
852: option.
853: .Pp
854: The supported escapes (assuming the default
855: .Ql ~ )
856: are:
857: .Bl -tag -width Ds
858: .It Cm ~.
859: Disconnect.
860: .It Cm ~^Z
861: Background
1.234 ! jmc 862: .Nm .
1.218 jmc 863: .It Cm ~#
864: List forwarded connections.
865: .It Cm ~&
866: Background
1.2 deraadt 867: .Nm
1.218 jmc 868: at logout when waiting for forwarded connection / X11 sessions to terminate.
869: .It Cm ~?
870: Display a list of escape characters.
871: .It Cm ~B
872: Send a BREAK to the remote system
873: (only useful for SSH protocol version 2 and if the peer supports it).
874: .It Cm ~C
875: Open command line.
876: Currently this allows the addition of port forwardings using the
877: .Fl L
878: and
879: .Fl R
1.225 jmc 880: options (see above).
1.218 jmc 881: It also allows the cancellation of existing remote port-forwardings
882: using
883: .Fl KR Ar hostport .
884: .Ic !\& Ns Ar command
885: allows the user to execute a local command if the
886: .Ic PermitLocalCommand
887: option is enabled in
1.176 jmc 888: .Xr ssh_config 5 .
1.218 jmc 889: Basic help is available, using the
890: .Fl h
891: option.
892: .It Cm ~R
893: Request rekeying of the connection
894: (only useful for SSH protocol version 2 and if the peer supports it).
1.176 jmc 895: .El
1.223 jmc 896: .Sh X11 AND TCP FORWARDING
1.218 jmc 897: If the
898: .Cm ForwardX11
899: variable is set to
900: .Dq yes
901: (or see the description of the
1.227 jmc 902: .Fl X ,
903: .Fl x ,
1.218 jmc 904: and
1.227 jmc 905: .Fl Y
1.226 jmc 906: options above)
1.218 jmc 907: and the user is using X11 (the
908: .Ev DISPLAY
909: environment variable is set), the connection to the X11 display is
910: automatically forwarded to the remote side in such a way that any X11
911: programs started from the shell (or command) will go through the
912: encrypted channel, and the connection to the real X server will be made
1.176 jmc 913: from the local machine.
1.218 jmc 914: The user should not manually set
915: .Ev DISPLAY .
916: Forwarding of X11 connections can be
917: configured on the command line or in configuration files.
918: .Pp
919: The
920: .Ev DISPLAY
921: value set by
922: .Nm
923: will point to the server machine, but with a display number greater than zero.
924: This is normal, and happens because
925: .Nm
926: creates a
927: .Dq proxy
928: X server on the server machine for forwarding the
929: connections over the encrypted channel.
1.200 djm 930: .Pp
1.218 jmc 931: .Nm
932: will also automatically set up Xauthority data on the server machine.
933: For this purpose, it will generate a random authorization cookie,
934: store it in Xauthority on the server, and verify that any forwarded
935: connections carry this cookie and replace it by the real cookie when
936: the connection is opened.
937: The real authentication cookie is never
938: sent to the server machine (and no cookies are sent in the plain).
1.200 djm 939: .Pp
1.218 jmc 940: If the
941: .Cm ForwardAgent
942: variable is set to
943: .Dq yes
944: (or see the description of the
945: .Fl A
1.191 djm 946: and
1.218 jmc 947: .Fl a
1.226 jmc 948: options above) and
1.218 jmc 949: the user is using an authentication agent, the connection to the agent
950: is automatically forwarded to the remote side.
951: .Pp
952: Forwarding of arbitrary TCP/IP connections over the secure channel can
953: be specified either on the command line or in a configuration file.
954: One possible application of TCP/IP forwarding is a secure connection to an
955: electronic purse; another is going through firewalls.
1.2 deraadt 956: .Sh ENVIRONMENT
957: .Nm
1.1 deraadt 958: will normally set the following environment variables:
1.176 jmc 959: .Bl -tag -width LOGNAME
1.2 deraadt 960: .It Ev DISPLAY
961: The
962: .Ev DISPLAY
1.40 aaron 963: variable indicates the location of the X11 server.
1.44 aaron 964: It is automatically set by
1.2 deraadt 965: .Nm
966: to point to a value of the form
1.233 jmc 967: .Dq hostname:n ,
968: where
969: .Dq hostname
970: indicates the host where the shell runs, and
971: .Sq n
972: is an integer \*(Ge 1.
1.40 aaron 973: .Nm
974: uses this special value to forward X11 connections over the secure
975: channel.
1.107 markus 976: The user should normally not set
977: .Ev DISPLAY
978: explicitly, as that
1.1 deraadt 979: will render the X11 connection insecure (and will require the user to
980: manually copy any required authorization cookies).
1.2 deraadt 981: .It Ev HOME
1.1 deraadt 982: Set to the path of the user's home directory.
1.2 deraadt 983: .It Ev LOGNAME
984: Synonym for
1.12 aaron 985: .Ev USER ;
986: set for compatibility with systems that use this variable.
1.2 deraadt 987: .It Ev MAIL
1.129 stevesk 988: Set to the path of the user's mailbox.
1.40 aaron 989: .It Ev PATH
1.2 deraadt 990: Set to the default
991: .Ev PATH ,
992: as specified when compiling
1.234 ! jmc 993: .Nm .
1.118 markus 994: .It Ev SSH_ASKPASS
995: If
996: .Nm
997: needs a passphrase, it will read the passphrase from the current
998: terminal if it was run from a terminal.
999: If
1000: .Nm
1001: does not have a terminal associated with it but
1002: .Ev DISPLAY
1003: and
1004: .Ev SSH_ASKPASS
1005: are set, it will execute the program specified by
1006: .Ev SSH_ASKPASS
1007: and open an X11 window to read the passphrase.
1008: This is particularly useful when calling
1009: .Nm
1010: from a
1.196 jmc 1011: .Pa .xsession
1.118 markus 1012: or related script.
1013: (Note that on some machines it
1014: may be necessary to redirect the input from
1015: .Pa /dev/null
1016: to make this work.)
1.18 markus 1017: .It Ev SSH_AUTH_SOCK
1.233 jmc 1018: Identifies the path of a
1019: .Ux Ns -domain
1020: socket used to communicate with the agent.
1.166 stevesk 1021: .It Ev SSH_CONNECTION
1022: Identifies the client and server ends of the connection.
1.40 aaron 1023: The variable contains
1.233 jmc 1024: four space-separated values: client IP address, client port number,
1025: server IP address, and server port number.
1.73 markus 1026: .It Ev SSH_ORIGINAL_COMMAND
1.233 jmc 1027: This variable contains the original command line if a forced command
1.73 markus 1028: is executed.
1029: It can be used to extract the original arguments.
1.2 deraadt 1030: .It Ev SSH_TTY
1.1 deraadt 1031: This is set to the name of the tty (path to the device) associated
1.40 aaron 1032: with the current shell or command.
1033: If the current session has no tty,
1.1 deraadt 1034: this variable is not set.
1.2 deraadt 1035: .It Ev TZ
1.214 jmc 1036: This variable is set to indicate the present time zone if it
1.56 deraadt 1037: was set when the daemon was started (i.e., the daemon passes the value
1.1 deraadt 1038: on to new connections).
1.2 deraadt 1039: .It Ev USER
1.1 deraadt 1040: Set to the name of the user logging in.
1.2 deraadt 1041: .El
1042: .Pp
1.44 aaron 1043: Additionally,
1.2 deraadt 1044: .Nm
1.44 aaron 1045: reads
1.207 djm 1046: .Pa ~/.ssh/environment ,
1.2 deraadt 1047: and adds lines of the format
1048: .Dq VARNAME=value
1.233 jmc 1049: to the environment if the file exists and users are allowed to
1.161 marc 1050: change their environment.
1.176 jmc 1051: For more information, see the
1.161 marc 1052: .Cm PermitUserEnvironment
1.162 stevesk 1053: option in
1.161 marc 1054: .Xr sshd_config 5 .
1.2 deraadt 1055: .Sh FILES
1.36 markus 1056: .Bl -tag -width Ds
1.207 djm 1057: .It Pa ~/.ssh/known_hosts
1.129 stevesk 1058: Records host keys for all hosts the user has logged into that are not
1.2 deraadt 1059: in
1.147 deraadt 1060: .Pa /etc/ssh/ssh_known_hosts .
1.2 deraadt 1061: See
1062: .Xr sshd 8 .
1.207 djm 1063: .It Pa ~/.ssh/identity, ~/.ssh/id_dsa, ~/.ssh/id_rsa
1.102 itojun 1064: Contains the authentication identity of the user.
1065: They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
1.48 markus 1066: These files
1067: contain sensitive data and should be readable by the user but not
1.15 markus 1068: accessible by others (read/write/execute).
1069: Note that
1070: .Nm
1.48 markus 1071: ignores a private key file if it is accessible by others.
1.15 markus 1072: It is possible to specify a passphrase when
1.1 deraadt 1073: generating the key; the passphrase will be used to encrypt the
1.8 deraadt 1074: sensitive part of this file using 3DES.
1.207 djm 1075: .It Pa ~/.ssh/identity.pub, ~/.ssh/id_dsa.pub, ~/.ssh/id_rsa.pub
1.1 deraadt 1076: Contains the public key for authentication (public part of the
1.40 aaron 1077: identity file in human-readable form).
1.48 markus 1078: The contents of the
1.207 djm 1079: .Pa ~/.ssh/identity.pub
1.176 jmc 1080: file should be added to the file
1.207 djm 1081: .Pa ~/.ssh/authorized_keys
1.2 deraadt 1082: on all machines
1.137 deraadt 1083: where the user wishes to log in using protocol version 1 RSA authentication.
1.48 markus 1084: The contents of the
1.207 djm 1085: .Pa ~/.ssh/id_dsa.pub
1.102 itojun 1086: and
1.207 djm 1087: .Pa ~/.ssh/id_rsa.pub
1.48 markus 1088: file should be added to
1.207 djm 1089: .Pa ~/.ssh/authorized_keys
1.48 markus 1090: on all machines
1.137 deraadt 1091: where the user wishes to log in using protocol version 2 DSA/RSA authentication.
1.48 markus 1092: These files are not
1.40 aaron 1093: sensitive and can (but need not) be readable by anyone.
1.48 markus 1094: These files are
1.84 markus 1095: never used automatically and are not necessary; they are only provided for
1.1 deraadt 1096: the convenience of the user.
1.207 djm 1097: .It Pa ~/.ssh/config
1.40 aaron 1098: This is the per-user configuration file.
1.158 stevesk 1099: The file format and configuration options are described in
1100: .Xr ssh_config 5 .
1.183 djm 1101: Because of the potential for abuse, this file must have strict permissions:
1102: read/write for the user, and not accessible by others.
1.207 djm 1103: .It Pa ~/.ssh/authorized_keys
1.115 markus 1104: Lists the public keys (RSA/DSA) that can be used for logging in as this user.
1.40 aaron 1105: The format of this file is described in the
1.2 deraadt 1106: .Xr sshd 8
1.40 aaron 1107: manual page.
1.176 jmc 1108: In the simplest form the format is the same as the
1109: .Pa .pub
1.116 markus 1110: identity files.
1.48 markus 1111: This file is not highly sensitive, but the recommended
1112: permissions are read/write for the user, and not accessible by others.
1.147 deraadt 1113: .It Pa /etc/ssh/ssh_known_hosts
1.40 aaron 1114: Systemwide list of known host keys.
1.116 markus 1115: This file should be prepared by the
1.1 deraadt 1116: system administrator to contain the public host keys of all machines in the
1.40 aaron 1117: organization.
1118: This file should be world-readable.
1119: This file contains
1.1 deraadt 1120: public keys, one per line, in the following format (fields separated
1.116 markus 1121: by spaces): system name, public key and optional comment field.
1.40 aaron 1122: When different names are used
1.1 deraadt 1123: for the same machine, all such names should be listed, separated by
1.40 aaron 1124: commas.
1.176 jmc 1125: The format is described in the
1.2 deraadt 1126: .Xr sshd 8
1.1 deraadt 1127: manual page.
1.2 deraadt 1128: .Pp
1.1 deraadt 1129: The canonical system name (as returned by name servers) is used by
1.2 deraadt 1130: .Xr sshd 8
1.1 deraadt 1131: to verify the client host when logging in; other names are needed because
1.2 deraadt 1132: .Nm
1.1 deraadt 1133: does not convert the user-supplied name to a canonical name before
1134: checking the key, because someone with access to the name servers
1135: would then be able to fool host authentication.
1.147 deraadt 1136: .It Pa /etc/ssh/ssh_config
1.40 aaron 1137: Systemwide configuration file.
1.158 stevesk 1138: The file format and configuration options are described in
1139: .Xr ssh_config 5 .
1.147 deraadt 1140: .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key
1.141 markus 1141: These three files contain the private parts of the host keys
1142: and are used for
1143: .Cm RhostsRSAAuthentication
1144: and
1145: .Cm HostbasedAuthentication .
1.155 stevesk 1146: If the protocol version 1
1147: .Cm RhostsRSAAuthentication
1.157 deraadt 1148: method is used,
1.155 stevesk 1149: .Nm
1150: must be setuid root, since the host key is readable only by root.
1151: For protocol version 2,
1152: .Nm
1153: uses
1154: .Xr ssh-keysign 8
1155: to access the host keys for
1156: .Cm HostbasedAuthentication .
1157: This eliminates the requirement that
1158: .Nm
1159: be setuid root when that authentication method is used.
1160: By default
1.141 markus 1161: .Nm
1.155 stevesk 1162: is not setuid root.
1.207 djm 1163: .It Pa ~/.rhosts
1.2 deraadt 1164: This file is used in
1.195 markus 1165: .Cm RhostsRSAAuthentication
1166: and
1167: .Cm HostbasedAuthentication
1.2 deraadt 1168: authentication to list the
1.40 aaron 1169: host/user pairs that are permitted to log in.
1170: (Note that this file is
1.1 deraadt 1171: also used by rlogin and rsh, which makes using this file insecure.)
1172: Each line of the file contains a host name (in the canonical form
1173: returned by name servers), and then a user name on that host,
1.40 aaron 1174: separated by a space.
1.92 markus 1175: On some machines this file may need to be
1.1 deraadt 1176: world-readable if the user's home directory is on a NFS partition,
1177: because
1.2 deraadt 1178: .Xr sshd 8
1.40 aaron 1179: reads it as root.
1180: Additionally, this file must be owned by the user,
1181: and must not have write permissions for anyone else.
1182: The recommended
1.1 deraadt 1183: permission for most machines is read/write for the user, and not
1184: accessible by others.
1.2 deraadt 1185: .Pp
1.195 markus 1186: Note that
1.2 deraadt 1187: .Xr sshd 8
1.195 markus 1188: allows authentication only in combination with client host key
1189: authentication before permitting log in.
1.137 deraadt 1190: If the server machine does not have the client's host key in
1.147 deraadt 1191: .Pa /etc/ssh/ssh_known_hosts ,
1.137 deraadt 1192: it can be stored in
1.207 djm 1193: .Pa ~/.ssh/known_hosts .
1.2 deraadt 1194: The easiest way to do this is to
1.1 deraadt 1195: connect back to the client from the server machine using ssh; this
1.48 markus 1196: will automatically add the host key to
1.207 djm 1197: .Pa ~/.ssh/known_hosts .
1198: .It Pa ~/.shosts
1.2 deraadt 1199: This file is used exactly the same way as
1.176 jmc 1200: .Pa .rhosts .
1.2 deraadt 1201: The purpose for
1.195 markus 1202: having this file is to be able to use
1203: .Cm RhostsRSAAuthentication
1204: and
1205: .Cm HostbasedAuthentication
1206: authentication without permitting login with
1.176 jmc 1207: .Xr rlogin
1.2 deraadt 1208: or
1209: .Xr rsh 1 .
1210: .It Pa /etc/hosts.equiv
1211: This file is used during
1.195 markus 1212: .Cm RhostsRSAAuthentication
1213: and
1214: .Cm HostbasedAuthentication
1.173 jmc 1215: authentication.
1.40 aaron 1216: It contains
1.176 jmc 1217: canonical hosts names, one per line (the full format is described in the
1.2 deraadt 1218: .Xr sshd 8
1.40 aaron 1219: manual page).
1220: If the client host is found in this file, login is
1.1 deraadt 1221: automatically permitted provided client and server user names are the
1.40 aaron 1222: same.
1.195 markus 1223: Additionally, successful client host key authentication is required.
1.40 aaron 1224: This file should only be writable by root.
1.2 deraadt 1225: .It Pa /etc/shosts.equiv
1.44 aaron 1226: This file is processed exactly as
1.2 deraadt 1227: .Pa /etc/hosts.equiv .
1.1 deraadt 1228: This file may be useful to permit logins using
1.2 deraadt 1229: .Nm
1.1 deraadt 1230: but not using rsh/rlogin.
1.147 deraadt 1231: .It Pa /etc/ssh/sshrc
1.1 deraadt 1232: Commands in this file are executed by
1.2 deraadt 1233: .Nm
1.1 deraadt 1234: when the user logs in just before the user's shell (or command) is started.
1235: See the
1.2 deraadt 1236: .Xr sshd 8
1.1 deraadt 1237: manual page for more information.
1.207 djm 1238: .It Pa ~/.ssh/rc
1.1 deraadt 1239: Commands in this file are executed by
1.2 deraadt 1240: .Nm
1.1 deraadt 1241: when the user logs in just before the user's shell (or command) is
1242: started.
1.44 aaron 1243: See the
1.2 deraadt 1244: .Xr sshd 8
1.1 deraadt 1245: manual page for more information.
1.207 djm 1246: .It Pa ~/.ssh/environment
1.31 markus 1247: Contains additional definitions for environment variables, see section
1248: .Sx ENVIRONMENT
1249: above.
1.58 itojun 1250: .El
1.2 deraadt 1251: .Sh SEE ALSO
1.176 jmc 1252: .Xr gzip 1 ,
1.2 deraadt 1253: .Xr rsh 1 ,
1254: .Xr scp 1 ,
1.83 djm 1255: .Xr sftp 1 ,
1.2 deraadt 1256: .Xr ssh-add 1 ,
1257: .Xr ssh-agent 1 ,
1258: .Xr ssh-keygen 1 ,
1259: .Xr telnet 1 ,
1.176 jmc 1260: .Xr hosts.equiv 5 ,
1.159 stevesk 1261: .Xr ssh_config 5 ,
1.160 naddy 1262: .Xr ssh-keysign 8 ,
1.87 itojun 1263: .Xr sshd 8
1.106 markus 1264: .Rs
1265: .%A T. Ylonen
1266: .%A T. Kivinen
1267: .%A M. Saarinen
1268: .%A T. Rinne
1269: .%A S. Lehtinen
1270: .%T "SSH Protocol Architecture"
1.150 markus 1271: .%N draft-ietf-secsh-architecture-12.txt
1272: .%D January 2002
1.106 markus 1273: .%O work in progress material
1274: .Re
1.173 jmc 1275: .Sh AUTHORS
1276: OpenSSH is a derivative of the original and free
1277: ssh 1.2.12 release by Tatu Ylonen.
1278: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1279: Theo de Raadt and Dug Song
1280: removed many bugs, re-added newer features and
1281: created OpenSSH.
1282: Markus Friedl contributed the support for SSH
1283: protocol versions 1.5 and 2.0.
![[BACK]](/icons/back.gif){kind=icon}
Return to ssh.1 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh