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Damien Miller32aa1441999-10-29 09:15:49 +10001.\" -*- nroff -*-
2.\"
Damien Miller32aa1441999-10-29 09:15:49 +10003.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
Damien Miller32aa1441999-10-29 09:15:49 +10004.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5.\" All rights reserved
6.\"
Damien Millere4340be2000-09-16 13:29:08 +11007.\" 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".
Damien Miller32aa1441999-10-29 09:15:49 +100012.\"
Ben Lindstrom92a2e382001-03-05 06:59:27 +000013.\" 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.
Damien Millere4340be2000-09-16 13:29:08 +110016.\"
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.
25.\"
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.
Damien Miller32aa1441999-10-29 09:15:49 +100036.\"
Ben Lindstrom89b0bd62001-03-29 00:27:11 +000037.\" $OpenBSD: ssh.1,v 1.100 2001/03/26 15:47:59 stevesk Exp $
Damien Miller32aa1441999-10-29 09:15:49 +100038.Dd September 25, 1999
39.Dt SSH 1
40.Os
41.Sh NAME
42.Nm ssh
Ben Lindstromd58eb5f2001-03-07 06:07:22 +000043.Nd OpenSSH SSH client (remote login program)
Damien Miller32aa1441999-10-29 09:15:49 +100044.Sh SYNOPSIS
45.Nm ssh
46.Op Fl l Ar login_name
47.Op Ar hostname | user@hostname
48.Op Ar command
49.Pp
50.Nm ssh
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +000051.Op Fl afgknqstvxACNPTX1246
Damien Miller30c3d422000-05-09 11:02:59 +100052.Op Fl c Ar cipher_spec
Damien Miller32aa1441999-10-29 09:15:49 +100053.Op Fl e Ar escape_char
54.Op Fl i Ar identity_file
55.Op Fl l Ar login_name
Ben Lindstrom06b33aa2001-02-15 03:01:59 +000056.Op Fl m Ar mac_spec
Damien Miller32aa1441999-10-29 09:15:49 +100057.Op Fl o Ar option
58.Op Fl p Ar port
59.Oo Fl L Xo
60.Sm off
Damien Miller32aa1441999-10-29 09:15:49 +100061.Ar port :
Damien Miller396691a2000-01-20 22:44:08 +110062.Ar host :
Damien Miller32aa1441999-10-29 09:15:49 +100063.Ar hostport
64.Sm on
65.Xc
66.Oc
67.Oo Fl R Xo
68.Sm off
Damien Miller32aa1441999-10-29 09:15:49 +100069.Ar port :
Damien Miller396691a2000-01-20 22:44:08 +110070.Ar host :
Damien Miller32aa1441999-10-29 09:15:49 +100071.Ar hostport
72.Sm on
73.Xc
74.Oc
75.Op Ar hostname | user@hostname
76.Op Ar command
Damien Miller22c77262000-04-13 12:26:34 +100077.Sh DESCRIPTION
Damien Miller32aa1441999-10-29 09:15:49 +100078.Nm
Ben Lindstromd58eb5f2001-03-07 06:07:22 +000079(SSH client) is a program for logging into a remote machine and for
Damien Miller7684ee12000-03-17 23:40:15 +110080executing commands on a remote machine.
81It is intended to replace
Damien Miller32aa1441999-10-29 09:15:49 +100082rlogin and rsh, and provide secure encrypted communications between
Damien Miller7684ee12000-03-17 23:40:15 +110083two untrusted hosts over an insecure network.
84X11 connections and
Damien Miller32aa1441999-10-29 09:15:49 +100085arbitrary TCP/IP ports can also be forwarded over the secure channel.
86.Pp
87.Nm
Damien Miller22c77262000-04-13 12:26:34 +100088connects and logs into the specified
Damien Miller32aa1441999-10-29 09:15:49 +100089.Ar hostname .
90The user must prove
Damien Millere247cc42000-05-07 12:03:14 +100091his/her identity to the remote machine using one of several methods
92depending on the protocol version used:
93.Pp
94.Ss SSH protocol version 1
Damien Miller32aa1441999-10-29 09:15:49 +100095.Pp
96First, if the machine the user logs in from is listed in
97.Pa /etc/hosts.equiv
98or
Damien Miller886c63a2000-01-20 23:13:36 +110099.Pa /etc/shosts.equiv
Damien Miller32aa1441999-10-29 09:15:49 +1000100on the remote machine, and the user names are
101the same on both sides, the user is immediately permitted to log in.
Damien Miller22c77262000-04-13 12:26:34 +1000102Second, if
Damien Miller32aa1441999-10-29 09:15:49 +1000103.Pa \&.rhosts
104or
105.Pa \&.shosts
106exists in the user's home directory on the
107remote machine and contains a line containing the name of the client
108machine and the name of the user on that machine, the user is
Damien Miller7684ee12000-03-17 23:40:15 +1100109permitted to log in.
110This form of authentication alone is normally not
Damien Miller32aa1441999-10-29 09:15:49 +1000111allowed by the server because it is not secure.
112.Pp
113The second (and primary) authentication method is the
114.Pa rhosts
115or
116.Pa hosts.equiv
Damien Miller7684ee12000-03-17 23:40:15 +1100117method combined with RSA-based host authentication.
118It means that if the login would be permitted by
Damien Millere247cc42000-05-07 12:03:14 +1000119.Pa $HOME/.rhosts ,
120.Pa $HOME/.shosts ,
Damien Miller32aa1441999-10-29 09:15:49 +1000121.Pa /etc/hosts.equiv ,
122or
Damien Miller886c63a2000-01-20 23:13:36 +1100123.Pa /etc/shosts.equiv ,
Damien Miller32aa1441999-10-29 09:15:49 +1000124and if additionally the server can verify the client's
Damien Miller22c77262000-04-13 12:26:34 +1000125host key (see
Damien Miller886c63a2000-01-20 23:13:36 +1100126.Pa /etc/ssh_known_hosts
Damien Miller33e511e1999-11-11 11:43:13 +1100127and
128.Pa $HOME/.ssh/known_hosts
Damien Miller32aa1441999-10-29 09:15:49 +1000129in the
130.Sx FILES
Damien Miller7684ee12000-03-17 23:40:15 +1100131section), only then login is permitted.
132This authentication method closes security holes due to IP
133spoofing, DNS spoofing and routing spoofing.
134[Note to the administrator:
Damien Miller32aa1441999-10-29 09:15:49 +1000135.Pa /etc/hosts.equiv ,
Damien Millere247cc42000-05-07 12:03:14 +1000136.Pa $HOME/.rhosts ,
Damien Miller32aa1441999-10-29 09:15:49 +1000137and the rlogin/rsh protocol in general, are inherently insecure and should be
138disabled if security is desired.]
139.Pp
Damien Miller22c77262000-04-13 12:26:34 +1000140As a third authentication method,
Damien Miller32aa1441999-10-29 09:15:49 +1000141.Nm
142supports RSA based authentication.
143The scheme is based on public-key cryptography: there are cryptosystems
144where encryption and decryption are done using separate keys, and it
145is not possible to derive the decryption key from the encryption key.
Damien Miller7684ee12000-03-17 23:40:15 +1100146RSA is one such system.
Damien Miller22c77262000-04-13 12:26:34 +1000147The idea is that each user creates a public/private
Damien Miller7684ee12000-03-17 23:40:15 +1100148key pair for authentication purposes.
149The server knows the public key, and only the user knows the private key.
Damien Miller22c77262000-04-13 12:26:34 +1000150The file
Damien Miller32aa1441999-10-29 09:15:49 +1000151.Pa $HOME/.ssh/authorized_keys
152lists the public keys that are permitted for logging
Damien Miller7684ee12000-03-17 23:40:15 +1100153in.
154When the user logs in, the
Damien Miller32aa1441999-10-29 09:15:49 +1000155.Nm
156program tells the server which key pair it would like to use for
Damien Miller7684ee12000-03-17 23:40:15 +1100157authentication.
158The server checks if this key is permitted, and if
Damien Miller32aa1441999-10-29 09:15:49 +1000159so, sends the user (actually the
160.Nm
161program running on behalf of the user) a challenge, a random number,
Damien Miller7684ee12000-03-17 23:40:15 +1100162encrypted by the user's public key.
163The challenge can only be
164decrypted using the proper private key.
165The user's client then decrypts the
Damien Miller32aa1441999-10-29 09:15:49 +1000166challenge using the private key, proving that he/she knows the private
167key but without disclosing it to the server.
168.Pp
169.Nm
Damien Miller7684ee12000-03-17 23:40:15 +1100170implements the RSA authentication protocol automatically.
171The user creates his/her RSA key pair by running
Damien Miller32aa1441999-10-29 09:15:49 +1000172.Xr ssh-keygen 1 .
Damien Miller22c77262000-04-13 12:26:34 +1000173This stores the private key in
Damien Millere247cc42000-05-07 12:03:14 +1000174.Pa $HOME/.ssh/identity
Damien Miller32aa1441999-10-29 09:15:49 +1000175and the public key in
Damien Millere247cc42000-05-07 12:03:14 +1000176.Pa $HOME/.ssh/identity.pub
Damien Miller7684ee12000-03-17 23:40:15 +1100177in the user's home directory.
178The user should then copy the
Damien Miller32aa1441999-10-29 09:15:49 +1000179.Pa identity.pub
Damien Miller22c77262000-04-13 12:26:34 +1000180to
Damien Millere247cc42000-05-07 12:03:14 +1000181.Pa $HOME/.ssh/authorized_keys
Damien Miller22c77262000-04-13 12:26:34 +1000182in his/her home directory on the remote machine (the
Damien Miller32aa1441999-10-29 09:15:49 +1000183.Pa authorized_keys
Damien Miller22c77262000-04-13 12:26:34 +1000184file corresponds to the conventional
Damien Millere247cc42000-05-07 12:03:14 +1000185.Pa $HOME/.rhosts
Damien Miller32aa1441999-10-29 09:15:49 +1000186file, and has one key
Damien Miller7684ee12000-03-17 23:40:15 +1100187per line, though the lines can be very long).
188After this, the user can log in without giving the password.
189RSA authentication is much
Damien Miller32aa1441999-10-29 09:15:49 +1000190more secure than rhosts authentication.
191.Pp
192The most convenient way to use RSA authentication may be with an
Damien Miller7684ee12000-03-17 23:40:15 +1100193authentication agent.
194See
Damien Miller32aa1441999-10-29 09:15:49 +1000195.Xr ssh-agent 1
196for more information.
197.Pp
Damien Miller22c77262000-04-13 12:26:34 +1000198If other authentication methods fail,
Damien Miller32aa1441999-10-29 09:15:49 +1000199.Nm
Damien Miller7684ee12000-03-17 23:40:15 +1100200prompts the user for a password.
201The password is sent to the remote
Damien Miller32aa1441999-10-29 09:15:49 +1000202host for checking; however, since all communications are encrypted,
203the password cannot be seen by someone listening on the network.
204.Pp
Damien Millere247cc42000-05-07 12:03:14 +1000205.Ss SSH protocol version 2
206.Pp
207When a user connects using the protocol version 2
208different authentication methods are available:
209At first, the client attempts to authenticate using the public key method.
210If this method fails password authentication is tried.
211.Pp
212The public key method is similar to RSA authentication described
Damien Miller0bc1bd82000-11-13 22:57:25 +1100213in the previous section except that the DSA or RSA algorithm is used
214instead.
215The client uses his private key
Damien Millere247cc42000-05-07 12:03:14 +1000216.Pa $HOME/.ssh/id_dsa
217to sign the session identifier and sends the result to the server.
218The server checks whether the matching public key is listed in
219.Pa $HOME/.ssh/authorized_keys2
220and grants access if both the key is found and the signature is correct.
221The session identifier is derived from a shared Diffie-Hellman value
222and is only known to the client and the server.
223.Pp
224If public key authentication fails or is not available a password
225can be sent encrypted to the remote host for proving the user's identity.
226This protocol 2 implementation does not yet support Kerberos or
227S/Key authentication.
228.Pp
229Protocol 2 provides additional mechanisms for confidentiality
Damien Miller30c3d422000-05-09 11:02:59 +1000230(the traffic is encrypted using 3DES, Blowfish, CAST128 or Arcfour)
Ben Lindstromec26fb12001-03-06 01:05:23 +0000231and integrity (hmac-md5, hmac-sha1).
Damien Millere247cc42000-05-07 12:03:14 +1000232Note that protocol 1 lacks a strong mechanism for ensuring the
233integrity of the connection.
234.Pp
235.Ss Login session and remote execution
236.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000237When the user's identity has been accepted by the server, the server
238either executes the given command, or logs into the machine and gives
Damien Miller7684ee12000-03-17 23:40:15 +1100239the user a normal shell on the remote machine.
240All communication with
Damien Miller32aa1441999-10-29 09:15:49 +1000241the remote command or shell will be automatically encrypted.
242.Pp
243If a pseudo-terminal has been allocated (normal login session), the
244user can disconnect with
245.Ic ~. ,
246and suspend
247.Nm
248with
249.Ic ~^Z .
250All forwarded connections can be listed with
Damien Miller22c77262000-04-13 12:26:34 +1000251.Ic ~#
Damien Miller32aa1441999-10-29 09:15:49 +1000252and if
253the session blocks waiting for forwarded X11 or TCP/IP
254connections to terminate, it can be backgrounded with
255.Ic ~&
256(this should not be used while the user shell is active, as it can cause the
Damien Miller7684ee12000-03-17 23:40:15 +1100257shell to hang).
258All available escapes can be listed with
Damien Miller32aa1441999-10-29 09:15:49 +1000259.Ic ~? .
260.Pp
261A single tilde character can be sent as
262.Ic ~~
263(or by following the tilde by a character other than those described above).
264The escape character must always follow a newline to be interpreted as
Damien Miller7684ee12000-03-17 23:40:15 +1100265special.
266The escape character can be changed in configuration files
267or on the command line.
Damien Miller32aa1441999-10-29 09:15:49 +1000268.Pp
269If no pseudo tty has been allocated, the
270session is transparent and can be used to reliably transfer binary
Damien Miller7684ee12000-03-17 23:40:15 +1100271data.
272On most systems, setting the escape character to
Damien Miller32aa1441999-10-29 09:15:49 +1000273.Dq none
274will also make the session transparent even if a tty is used.
275.Pp
Ben Lindstroma6885612000-12-09 03:45:32 +0000276The session terminates when the command or shell on the remote
Ben Lindstromebd888d2001-03-05 05:49:29 +0000277machine exits and all X11 and TCP/IP connections have been closed.
Damien Miller32aa1441999-10-29 09:15:49 +1000278The exit status of the remote program is returned as the exit status
279of
280.Nm ssh .
281.Pp
Damien Millere247cc42000-05-07 12:03:14 +1000282.Ss X11 and TCP forwarding
283.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000284If the user is using X11 (the
285.Ev DISPLAY
286environment variable is set), the connection to the X11 display is
287automatically forwarded to the remote side in such a way that any X11
288programs started from the shell (or command) will go through the
289encrypted channel, and the connection to the real X server will be made
Damien Miller7684ee12000-03-17 23:40:15 +1100290from the local machine.
291The user should not manually set
Damien Miller32aa1441999-10-29 09:15:49 +1000292.Ev DISPLAY .
293Forwarding of X11 connections can be
294configured on the command line or in configuration files.
295.Pp
296The
Damien Miller22c77262000-04-13 12:26:34 +1000297.Ev DISPLAY
Damien Miller32aa1441999-10-29 09:15:49 +1000298value set by
299.Nm
300will point to the server machine, but with a display number greater
Damien Miller7684ee12000-03-17 23:40:15 +1100301than zero.
302This is normal, and happens because
Damien Miller32aa1441999-10-29 09:15:49 +1000303.Nm
304creates a
305.Dq proxy
306X server on the server machine for forwarding the
307connections over the encrypted channel.
308.Pp
309.Nm
310will also automatically set up Xauthority data on the server machine.
311For this purpose, it will generate a random authorization cookie,
312store it in Xauthority on the server, and verify that any forwarded
313connections carry this cookie and replace it by the real cookie when
Damien Miller7684ee12000-03-17 23:40:15 +1100314the connection is opened.
315The real authentication cookie is never
Damien Miller32aa1441999-10-29 09:15:49 +1000316sent to the server machine (and no cookies are sent in the plain).
317.Pp
318If the user is using an authentication agent, the connection to the agent
319is automatically forwarded to the remote side unless disabled on
320command line or in a configuration file.
321.Pp
322Forwarding of arbitrary TCP/IP connections over the secure channel can
Damien Miller7684ee12000-03-17 23:40:15 +1100323be specified either on command line or in a configuration file.
324One possible application of TCP/IP forwarding is a secure connection to an
Ben Lindstromebd888d2001-03-05 05:49:29 +0000325electronic purse; another is going through firewalls.
Damien Miller32aa1441999-10-29 09:15:49 +1000326.Pp
Damien Millere247cc42000-05-07 12:03:14 +1000327.Ss Server authentication
328.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000329.Nm
Damien Millere247cc42000-05-07 12:03:14 +1000330automatically maintains and checks a database containing
Damien Miller7684ee12000-03-17 23:40:15 +1100331identifications for all hosts it has ever been used with.
Damien Millere247cc42000-05-07 12:03:14 +1000332RSA host keys are stored in
333.Pa $HOME/.ssh/known_hosts
334and
Damien Miller0bc1bd82000-11-13 22:57:25 +1100335host keys used in the protocol version 2 are stored in
Damien Millere247cc42000-05-07 12:03:14 +1000336.Pa $HOME/.ssh/known_hosts2
Damien Miller7684ee12000-03-17 23:40:15 +1100337in the user's home directory.
Damien Millere247cc42000-05-07 12:03:14 +1000338Additionally, the files
Damien Miller886c63a2000-01-20 23:13:36 +1100339.Pa /etc/ssh_known_hosts
Damien Millere247cc42000-05-07 12:03:14 +1000340and
341.Pa /etc/ssh_known_hosts2
342are automatically checked for known hosts.
Damien Miller7684ee12000-03-17 23:40:15 +1100343Any new hosts are automatically added to the user's file.
344If a host's identification
Damien Miller32aa1441999-10-29 09:15:49 +1000345ever changes,
346.Nm
347warns about this and disables password authentication to prevent a
Damien Miller7684ee12000-03-17 23:40:15 +1100348trojan horse from getting the user's password.
349Another purpose of
Damien Miller32aa1441999-10-29 09:15:49 +1000350this mechanism is to prevent man-in-the-middle attacks which could
Damien Miller7684ee12000-03-17 23:40:15 +1100351otherwise be used to circumvent the encryption.
352The
Damien Miller32aa1441999-10-29 09:15:49 +1000353.Cm StrictHostKeyChecking
354option (see below) can be used to prevent logins to machines whose
355host key is not known or has changed.
Damien Miller0bc1bd82000-11-13 22:57:25 +1100356.Pp
357The options are as follows:
Damien Miller32aa1441999-10-29 09:15:49 +1000358.Bl -tag -width Ds
359.It Fl a
Damien Miller450a7a12000-03-26 13:04:51 +1000360Disables forwarding of the authentication agent connection.
Damien Millerb1715dc2000-05-30 13:44:51 +1000361.It Fl A
362Enables forwarding of the authentication agent connection.
363This can also be specified on a per-host basis in a configuration file.
Damien Miller32aa1441999-10-29 09:15:49 +1000364.It Fl c Ar blowfish|3des
Damien Miller22c77262000-04-13 12:26:34 +1000365Selects the cipher to use for encrypting the session.
Damien Miller32aa1441999-10-29 09:15:49 +1000366.Ar 3des
Damien Miller7684ee12000-03-17 23:40:15 +1100367is used by default.
Damien Miller22c77262000-04-13 12:26:34 +1000368It is believed to be secure.
Damien Miller32aa1441999-10-29 09:15:49 +1000369.Ar 3des
370(triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
371It is presumably more secure than the
372.Ar des
Damien Miller69b69aa2000-10-28 14:19:58 +1100373cipher which is no longer fully supported in
Damien Miller30c3d422000-05-09 11:02:59 +1000374.Nm ssh .
Damien Miller32aa1441999-10-29 09:15:49 +1000375.Ar blowfish
376is a fast block cipher, it appears very secure and is much faster than
Damien Miller7684ee12000-03-17 23:40:15 +1100377.Ar 3des .
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +0000378.It Fl c Ar cipher_spec
Damien Miller30c3d422000-05-09 11:02:59 +1000379Additionally, for protocol version 2 a comma-separated list of ciphers can
Damien Miller874d77b2000-10-14 16:23:11 +1100380be specified in order of preference.
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +0000381See
382.Cm Ciphers
383for more information.
Damien Miller32aa1441999-10-29 09:15:49 +1000384.It Fl e Ar ch|^ch|none
385Sets the escape character for sessions with a pty (default:
386.Ql ~ ) .
Damien Miller7684ee12000-03-17 23:40:15 +1100387The escape character is only recognized at the beginning of a line.
388The escape character followed by a dot
Damien Miller32aa1441999-10-29 09:15:49 +1000389.Pq Ql \&.
390closes the connection, followed
391by control-Z suspends the connection, and followed by itself sends the
Damien Miller7684ee12000-03-17 23:40:15 +1100392escape character once.
393Setting the character to
Damien Miller32aa1441999-10-29 09:15:49 +1000394.Dq none
395disables any escapes and makes the session fully transparent.
396.It Fl f
397Requests
398.Nm
Damien Miller7684ee12000-03-17 23:40:15 +1100399to go to background just before command execution.
400This is useful if
Damien Miller32aa1441999-10-29 09:15:49 +1000401.Nm
402is going to ask for passwords or passphrases, but the user
Damien Miller7684ee12000-03-17 23:40:15 +1100403wants it in the background.
Damien Miller22c77262000-04-13 12:26:34 +1000404This implies
Damien Miller32aa1441999-10-29 09:15:49 +1000405.Fl n .
406The recommended way to start X11 programs at a remote site is with
407something like
408.Ic ssh -f host xterm .
Damien Miller396691a2000-01-20 22:44:08 +1100409.It Fl g
410Allows remote hosts to connect to local forwarded ports.
Damien Miller32aa1441999-10-29 09:15:49 +1000411.It Fl i Ar identity_file
Damien Miller22c77262000-04-13 12:26:34 +1000412Selects the file from which the identity (private key) for
Damien Miller0bc1bd82000-11-13 22:57:25 +1100413RSA or DSA authentication is read.
Damien Miller22c77262000-04-13 12:26:34 +1000414Default is
Damien Millere247cc42000-05-07 12:03:14 +1000415.Pa $HOME/.ssh/identity
Damien Miller7684ee12000-03-17 23:40:15 +1100416in the user's home directory.
417Identity files may also be specified on
418a per-host basis in the configuration file.
419It is possible to have multiple
Damien Miller32aa1441999-10-29 09:15:49 +1000420.Fl i
421options (and multiple identities specified in
422configuration files).
Damien Miller32aa1441999-10-29 09:15:49 +1000423.It Fl k
Damien Miller450a7a12000-03-26 13:04:51 +1000424Disables forwarding of Kerberos tickets and AFS tokens.
425This may also be specified on a per-host basis in the configuration file.
Damien Miller32aa1441999-10-29 09:15:49 +1000426.It Fl l Ar login_name
Damien Miller7684ee12000-03-17 23:40:15 +1100427Specifies the user to log in as on the remote machine.
428This also may be specified on a per-host basis in the configuration file.
Ben Lindstrom06b33aa2001-02-15 03:01:59 +0000429.It Fl m Ar mac_spec
430Additionally, for protocol version 2 a comma-separated list of MAC
431(message authentication code) algorithms can
432be specified in order of preference.
433See the
434.Cm MACs
435keyword for more information.
Damien Miller32aa1441999-10-29 09:15:49 +1000436.It Fl n
437Redirects stdin from
438.Pa /dev/null
439(actually, prevents reading from stdin).
440This must be used when
441.Nm
Damien Miller7684ee12000-03-17 23:40:15 +1100442is run in the background.
443A common trick is to use this to run X11 programs on a remote machine.
444For example,
Damien Miller32aa1441999-10-29 09:15:49 +1000445.Ic ssh -n shadows.cs.hut.fi emacs &
446will start an emacs on shadows.cs.hut.fi, and the X11
447connection will be automatically forwarded over an encrypted channel.
448The
449.Nm
450program will be put in the background.
451(This does not work if
452.Nm
453needs to ask for a password or passphrase; see also the
454.Fl f
455option.)
Damien Millerdcb6ecd2000-05-17 22:34:22 +1000456.It Fl N
457Do not execute a remote command.
Ben Lindstromc72745a2000-12-02 19:03:54 +0000458This is useful if you just want to forward ports
Damien Millerdcb6ecd2000-05-17 22:34:22 +1000459(protocol version 2 only).
Damien Miller32aa1441999-10-29 09:15:49 +1000460.It Fl o Ar option
461Can be used to give options in the format used in the config file.
462This is useful for specifying options for which there is no separate
Damien Miller7684ee12000-03-17 23:40:15 +1100463command-line flag.
464The option has the same format as a line in the configuration file.
Damien Miller32aa1441999-10-29 09:15:49 +1000465.It Fl p Ar port
Damien Miller7684ee12000-03-17 23:40:15 +1100466Port to connect to on the remote host.
467This can be specified on a
Damien Miller32aa1441999-10-29 09:15:49 +1000468per-host basis in the configuration file.
469.It Fl P
470Use a non-privileged port for outgoing connections.
471This can be used if your firewall does
472not permit connections from privileged ports.
Damien Millera34a28b1999-12-14 10:47:15 +1100473Note that this option turns off
Damien Miller32aa1441999-10-29 09:15:49 +1000474.Cm RhostsAuthentication
475and
Kevin Stevesfcec7f82000-12-15 19:55:48 +0000476.Cm RhostsRSAAuthentication
477for older servers.
Damien Miller32aa1441999-10-29 09:15:49 +1000478.It Fl q
Damien Miller7684ee12000-03-17 23:40:15 +1100479Quiet mode.
480Causes all warning and diagnostic messages to be suppressed.
481Only fatal errors are displayed.
Damien Miller832562e2001-01-30 09:30:01 +1100482.It Fl s
483May be used to request invocation of a subsystem on the remote system. Subsystems are a feature of the SSH2 protocol which facilitate the use
484of SSH as a secure transport for other application (eg. sftp). The
485subsystem is specified as the remote command.
Damien Miller32aa1441999-10-29 09:15:49 +1000486.It Fl t
Damien Miller7684ee12000-03-17 23:40:15 +1100487Force pseudo-tty allocation.
Damien Miller450a7a12000-03-26 13:04:51 +1000488This can be used to execute arbitrary
Damien Miller7684ee12000-03-17 23:40:15 +1100489screen-based programs on a remote machine, which can be very useful,
490e.g., when implementing menu services.
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000491Multiple
492.Fl t
493options force tty allocation, even if
494.Nm
495has no local tty.
Damien Millerdcb6ecd2000-05-17 22:34:22 +1000496.It Fl T
Ben Lindstromc72745a2000-12-02 19:03:54 +0000497Disable pseudo-tty allocation.
Damien Miller32aa1441999-10-29 09:15:49 +1000498.It Fl v
Damien Miller7684ee12000-03-17 23:40:15 +1100499Verbose mode.
500Causes
Damien Miller32aa1441999-10-29 09:15:49 +1000501.Nm
Damien Miller7684ee12000-03-17 23:40:15 +1100502to print debugging messages about its progress.
503This is helpful in
Damien Miller32aa1441999-10-29 09:15:49 +1000504debugging connection, authentication, and configuration problems.
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000505Multiple
506.Fl v
507options increases the verbosity.
Damien Miller874d77b2000-10-14 16:23:11 +1100508Maximum is 3.
Damien Miller32aa1441999-10-29 09:15:49 +1000509.It Fl x
Damien Miller7684ee12000-03-17 23:40:15 +1100510Disables X11 forwarding.
Damien Miller32aa1441999-10-29 09:15:49 +1000511.It Fl X
512Enables X11 forwarding.
Damien Millerb1715dc2000-05-30 13:44:51 +1000513This can also be specified on a per-host basis in a configuration file.
Damien Miller32aa1441999-10-29 09:15:49 +1000514.It Fl C
515Requests compression of all data (including stdin, stdout, stderr, and
Damien Miller7684ee12000-03-17 23:40:15 +1100516data for forwarded X11 and TCP/IP connections).
517The compression algorithm is the same used by
Damien Miller396691a2000-01-20 22:44:08 +1100518.Xr gzip 1 ,
519and the
Damien Miller32aa1441999-10-29 09:15:49 +1000520.Dq level
521can be controlled by the
522.Cm CompressionLevel
Damien Miller7684ee12000-03-17 23:40:15 +1100523option (see below).
524Compression is desirable on modem lines and other
Damien Miller32aa1441999-10-29 09:15:49 +1000525slow connections, but will only slow down things on fast networks.
526The default value can be set on a host-by-host basis in the
527configuration files; see the
528.Cm Compress
529option below.
530.It Fl L Ar port:host:hostport
531Specifies that the given port on the local (client) host is to be
Damien Miller7684ee12000-03-17 23:40:15 +1100532forwarded to the given host and port on the remote side.
533This works by allocating a socket to listen to
Damien Miller32aa1441999-10-29 09:15:49 +1000534.Ar port
535on the local side, and whenever a connection is made to this port, the
536connection is forwarded over the secure channel, and a connection is
537made to
Damien Miller34132e52000-01-14 15:45:46 +1100538.Ar host
539port
540.Ar hostport
Damien Miller7684ee12000-03-17 23:40:15 +1100541from the remote machine.
542Port forwardings can also be specified in the configuration file.
543Only root can forward privileged ports.
Damien Miller34132e52000-01-14 15:45:46 +1100544IPv6 addresses can be specified with an alternative syntax:
545.Ar port/host/hostport
Damien Miller32aa1441999-10-29 09:15:49 +1000546.It Fl R Ar port:host:hostport
547Specifies that the given port on the remote (server) host is to be
Damien Miller7684ee12000-03-17 23:40:15 +1100548forwarded to the given host and port on the local side.
549This works by allocating a socket to listen to
Damien Miller32aa1441999-10-29 09:15:49 +1000550.Ar port
551on the remote side, and whenever a connection is made to this port, the
552connection is forwarded over the secure channel, and a connection is
553made to
Damien Miller34132e52000-01-14 15:45:46 +1100554.Ar host
555port
556.Ar hostport
Damien Miller7684ee12000-03-17 23:40:15 +1100557from the local machine.
558Port forwardings can also be specified in the configuration file.
559Privileged ports can be forwarded only when
Damien Miller32aa1441999-10-29 09:15:49 +1000560logging in as root on the remote machine.
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +0000561.It Fl 1
562Forces
563.Nm
564to try protocol version 1 only.
Damien Miller4af51302000-04-16 11:18:38 +1000565.It Fl 2
566Forces
567.Nm
Damien Millere247cc42000-05-07 12:03:14 +1000568to try protocol version 2 only.
Damien Miller34132e52000-01-14 15:45:46 +1100569.It Fl 4
570Forces
571.Nm
572to use IPv4 addresses only.
573.It Fl 6
574Forces
575.Nm
576to use IPv6 addresses only.
Damien Miller32aa1441999-10-29 09:15:49 +1000577.El
578.Sh CONFIGURATION FILES
579.Nm
580obtains configuration data from the following sources (in this order):
581command line options, user's configuration file
582.Pq Pa $HOME/.ssh/config ,
583and system-wide configuration file
Damien Miller886c63a2000-01-20 23:13:36 +1100584.Pq Pa /etc/ssh_config .
Damien Miller32aa1441999-10-29 09:15:49 +1000585For each parameter, the first obtained value
Damien Miller7684ee12000-03-17 23:40:15 +1100586will be used.
587The configuration files contain sections bracketed by
588.Dq Host
589specifications, and that section is only applied for hosts that
590match one of the patterns given in the specification.
591The matched host name is the one given on the command line.
Damien Miller32aa1441999-10-29 09:15:49 +1000592.Pp
593Since the first obtained value for each parameter is used, more
594host-specific declarations should be given near the beginning of the
595file, and general defaults at the end.
596.Pp
597The configuration file has the following format:
598.Pp
599Empty lines and lines starting with
600.Ql #
601are comments.
602.Pp
603Otherwise a line is of the format
604.Dq keyword arguments .
605The possible
606keywords and their meanings are as follows (note that the
607configuration files are case-sensitive):
608.Bl -tag -width Ds
609.It Cm Host
610Restricts the following declarations (up to the next
611.Cm Host
612keyword) to be only for those hosts that match one of the patterns
613given after the keyword.
614.Ql \&*
615and
616.Ql ?
617can be used as wildcards in the
Damien Miller7684ee12000-03-17 23:40:15 +1100618patterns.
619A single
Damien Miller32aa1441999-10-29 09:15:49 +1000620.Ql \&*
621as a pattern can be used to provide global
Damien Miller7684ee12000-03-17 23:40:15 +1100622defaults for all hosts.
623The host is the
Damien Miller32aa1441999-10-29 09:15:49 +1000624.Ar hostname
625argument given on the command line (i.e., the name is not converted to
626a canonicalized host name before matching).
627.It Cm AFSTokenPassing
Damien Miller450a7a12000-03-26 13:04:51 +1000628Specifies whether to pass AFS tokens to remote host.
629The argument to this keyword must be
Damien Miller32aa1441999-10-29 09:15:49 +1000630.Dq yes
631or
632.Dq no .
633.It Cm BatchMode
634If set to
635.Dq yes ,
Damien Miller7684ee12000-03-17 23:40:15 +1100636passphrase/password querying will be disabled.
637This option is useful in scripts and other batch jobs where you have no
638user to supply the password.
639The argument must be
Damien Miller32aa1441999-10-29 09:15:49 +1000640.Dq yes
641or
642.Dq no .
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000643The default is
644.Dq no .
Damien Miller396691a2000-01-20 22:44:08 +1100645.It Cm CheckHostIP
646If this flag is set to
647.Dq yes ,
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000648ssh will additionally check the host IP address in the
Damien Miller396691a2000-01-20 22:44:08 +1100649.Pa known_hosts
Damien Miller450a7a12000-03-26 13:04:51 +1000650file.
651This allows ssh to detect if a host key changed due to DNS spoofing.
Damien Miller396691a2000-01-20 22:44:08 +1100652If the option is set to
653.Dq no ,
654the check will not be executed.
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000655The default is
656.Dq yes .
Damien Miller32aa1441999-10-29 09:15:49 +1000657.It Cm Cipher
Damien Miller50a41ed2000-10-16 12:14:42 +1100658Specifies the cipher to use for encrypting the session
Damien Miller69b69aa2000-10-28 14:19:58 +1100659in protocol version 1.
Damien Miller7684ee12000-03-17 23:40:15 +1100660Currently,
Damien Miller69b69aa2000-10-28 14:19:58 +1100661.Dq blowfish
Damien Miller32aa1441999-10-29 09:15:49 +1000662and
663.Dq 3des
Damien Miller7684ee12000-03-17 23:40:15 +1100664are supported.
665The default is
Damien Miller32aa1441999-10-29 09:15:49 +1000666.Dq 3des .
Damien Miller22c77262000-04-13 12:26:34 +1000667.It Cm Ciphers
668Specifies the ciphers allowed for protocol version 2
669in order of preference.
670Multiple ciphers must be comma-separated.
671The default is
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +0000672.Pp
673.Bd -literal
Ben Lindstromec26fb12001-03-06 01:05:23 +0000674 ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +0000675 aes192-cbc,aes256-cbc,rijndael128-cbc,rijndael192-cbc,
676 rijndael256-cbc,rijndael-cbc@lysator.liu.se''
677.Ed
Damien Miller32aa1441999-10-29 09:15:49 +1000678.It Cm Compression
Damien Miller7684ee12000-03-17 23:40:15 +1100679Specifies whether to use compression.
680The argument must be
Damien Miller32aa1441999-10-29 09:15:49 +1000681.Dq yes
682or
683.Dq no .
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000684The default is
685.Dq no .
Damien Miller32aa1441999-10-29 09:15:49 +1000686.It Cm CompressionLevel
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000687Specifies the compression level to use if compression is enabled.
Damien Miller7684ee12000-03-17 23:40:15 +1100688The argument must be an integer from 1 (fast) to 9 (slow, best).
689The default level is 6, which is good for most applications.
690The meaning of the values is the same as in
Damien Miller396691a2000-01-20 22:44:08 +1100691.Xr gzip 1 .
Damien Miller32aa1441999-10-29 09:15:49 +1000692.It Cm ConnectionAttempts
693Specifies the number of tries (one per second) to make before falling
Damien Miller7684ee12000-03-17 23:40:15 +1100694back to rsh or exiting.
695The argument must be an integer.
696This may be useful in scripts if the connection sometimes fails.
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000697The default is 4.
Damien Miller0bc1bd82000-11-13 22:57:25 +1100698.It Cm PubkeyAuthentication
699Specifies whether to try public key authentication.
Damien Millere247cc42000-05-07 12:03:14 +1000700The argument to this keyword must be
701.Dq yes
702or
703.Dq no .
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000704The default is
705.Dq yes .
Damien Millere247cc42000-05-07 12:03:14 +1000706Note that this option applies to protocol version 2 only.
Damien Miller32aa1441999-10-29 09:15:49 +1000707.It Cm EscapeChar
708Sets the escape character (default:
709.Ql ~ ) .
710The escape character can also
Damien Miller7684ee12000-03-17 23:40:15 +1100711be set on the command line.
712The argument should be a single character,
Damien Miller32aa1441999-10-29 09:15:49 +1000713.Ql ^
714followed by a letter, or
715.Dq none
716to disable the escape
717character entirely (making the connection transparent for binary
718data).
Damien Miller22c77262000-04-13 12:26:34 +1000719.It Cm FallBackToRsh
Damien Miller32aa1441999-10-29 09:15:49 +1000720Specifies that if connecting via
721.Nm
722fails due to a connection refused error (there is no
723.Xr sshd 8
Damien Miller22c77262000-04-13 12:26:34 +1000724listening on the remote host),
Damien Miller32aa1441999-10-29 09:15:49 +1000725.Xr rsh 1
726should automatically be used instead (after a suitable warning about
Damien Miller7684ee12000-03-17 23:40:15 +1100727the session being unencrypted).
728The argument must be
Damien Miller32aa1441999-10-29 09:15:49 +1000729.Dq yes
730or
731.Dq no .
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000732The default is
733.Dq no .
Damien Miller32aa1441999-10-29 09:15:49 +1000734.It Cm ForwardAgent
735Specifies whether the connection to the authentication agent (if any)
Damien Miller7684ee12000-03-17 23:40:15 +1100736will be forwarded to the remote machine.
737The argument must be
Damien Miller32aa1441999-10-29 09:15:49 +1000738.Dq yes
739or
740.Dq no .
Damien Millerb1715dc2000-05-30 13:44:51 +1000741The default is
742.Dq no .
Damien Miller32aa1441999-10-29 09:15:49 +1000743.It Cm ForwardX11
744Specifies whether X11 connections will be automatically redirected
Damien Miller22c77262000-04-13 12:26:34 +1000745over the secure channel and
Damien Miller32aa1441999-10-29 09:15:49 +1000746.Ev DISPLAY
Damien Miller7684ee12000-03-17 23:40:15 +1100747set.
Damien Miller22c77262000-04-13 12:26:34 +1000748The argument must be
Damien Miller32aa1441999-10-29 09:15:49 +1000749.Dq yes
750or
751.Dq no .
Damien Miller98c7ad62000-03-09 21:27:49 +1100752The default is
753.Dq no .
Damien Miller32aa1441999-10-29 09:15:49 +1000754.It Cm GatewayPorts
755Specifies whether remote hosts are allowed to connect to local
756forwarded ports.
757The argument must be
758.Dq yes
759or
760.Dq no .
761The default is
762.Dq no .
763.It Cm GlobalKnownHostsFile
Ben Lindstrom1e621742001-03-06 01:10:53 +0000764Specifies a file to use for the protocol version 1 global
765host key database instead of
Damien Miller886c63a2000-01-20 23:13:36 +1100766.Pa /etc/ssh_known_hosts .
Ben Lindstrom1e621742001-03-06 01:10:53 +0000767.It Cm GlobalKnownHostsFile2
768Specifies a file to use for the protocol version 2 global
769host key database instead of
770.Pa /etc/ssh_known_hosts2 .
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000771.It Cm HostKeyAlias
772Specifies an alias that should be used instead of the
773real host name when looking up or saving the host key
Damien Miller33804262001-02-04 23:20:18 +1100774in the known_hosts files.
775This option is useful for tunneling ssh connections
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000776or if you have multiple servers running on a single host.
Damien Miller32aa1441999-10-29 09:15:49 +1000777.It Cm HostName
Damien Miller7684ee12000-03-17 23:40:15 +1100778Specifies the real host name to log into.
779This can be used to specify nicknames or abbreviations for hosts.
780Default is the name given on the command line.
781Numeric IP addresses are also permitted (both on the command line and in
Damien Miller32aa1441999-10-29 09:15:49 +1000782.Cm HostName
783specifications).
784.It Cm IdentityFile
785Specifies the file from which the user's RSA authentication identity
786is read (default
Damien Millere247cc42000-05-07 12:03:14 +1000787.Pa $HOME/.ssh/identity
Damien Miller32aa1441999-10-29 09:15:49 +1000788in the user's home directory).
789Additionally, any identities represented by the authentication agent
Damien Miller7684ee12000-03-17 23:40:15 +1100790will be used for authentication.
791The file name may use the tilde
792syntax to refer to a user's home directory.
793It is possible to have
Damien Miller32aa1441999-10-29 09:15:49 +1000794multiple identity files specified in configuration files; all these
795identities will be tried in sequence.
796.It Cm KeepAlive
797Specifies whether the system should send keepalive messages to the
Damien Miller7684ee12000-03-17 23:40:15 +1100798other side.
799If they are sent, death of the connection or crash of one
800of the machines will be properly noticed.
801However, this means that
Damien Miller32aa1441999-10-29 09:15:49 +1000802connections will die if the route is down temporarily, and some people
Damien Miller450a7a12000-03-26 13:04:51 +1000803find it annoying.
Damien Miller32aa1441999-10-29 09:15:49 +1000804.Pp
805The default is
806.Dq yes
807(to send keepalives), and the client will notice
Damien Miller7684ee12000-03-17 23:40:15 +1100808if the network goes down or the remote host dies.
809This is important in scripts, and many users want it too.
Damien Miller32aa1441999-10-29 09:15:49 +1000810.Pp
811To disable keepalives, the value should be set to
812.Dq no
813in both the server and the client configuration files.
814.It Cm KerberosAuthentication
Damien Miller450a7a12000-03-26 13:04:51 +1000815Specifies whether Kerberos authentication will be used.
816The argument to this keyword must be
Damien Miller32aa1441999-10-29 09:15:49 +1000817.Dq yes
818or
819.Dq no .
820.It Cm KerberosTgtPassing
Damien Miller450a7a12000-03-26 13:04:51 +1000821Specifies whether a Kerberos TGT will be forwarded to the server.
822This will only work if the Kerberos server is actually an AFS kaserver.
823The argument to this keyword must be
Damien Miller32aa1441999-10-29 09:15:49 +1000824.Dq yes
825or
826.Dq no .
827.It Cm LocalForward
828Specifies that a TCP/IP port on the local machine be forwarded over
Damien Miller7684ee12000-03-17 23:40:15 +1100829the secure channel to given host:port from the remote machine.
830The first argument must be a port number, and the second must be
831host:port.
832Multiple forwardings may be specified, and additional
833forwardings can be given on the command line.
834Only the superuser can forward privileged ports.
Damien Miller5ce662a1999-11-11 17:57:39 +1100835.It Cm LogLevel
836Gives the verbosity level that is used when logging messages from
837.Nm ssh .
838The possible values are:
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000839QUIET, FATAL, ERROR, INFO, VERBOSE and DEBUG.
840The default is INFO.
Ben Lindstrom06b33aa2001-02-15 03:01:59 +0000841.It Cm MACs
842Specifies the MAC (message authentication code) algorithms
843in order of preference.
844The MAC algorithm is used in protocol version 2
845for data integrity protection.
846Multiple algorithms must be comma-separated.
847The default is
848.Pp
849.Bd -literal
Ben Lindstromec26fb12001-03-06 01:05:23 +0000850 ``hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@openssh.com,
Ben Lindstrom06b33aa2001-02-15 03:01:59 +0000851 hmac-sha1-96,hmac-md5-96''
852.Ed
Damien Miller32aa1441999-10-29 09:15:49 +1000853.It Cm NumberOfPasswordPrompts
Damien Miller450a7a12000-03-26 13:04:51 +1000854Specifies the number of password prompts before giving up.
855The argument to this keyword must be an integer.
856Default is 3.
Damien Miller396691a2000-01-20 22:44:08 +1100857.It Cm PasswordAuthentication
Damien Miller7684ee12000-03-17 23:40:15 +1100858Specifies whether to use password authentication.
859The argument to this keyword must be
Damien Miller396691a2000-01-20 22:44:08 +1100860.Dq yes
861or
862.Dq no .
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000863The default is
864.Dq yes .
Damien Millere247cc42000-05-07 12:03:14 +1000865Note that this option applies to both protocol version 1 and 2.
Damien Miller32aa1441999-10-29 09:15:49 +1000866.It Cm Port
Damien Miller7684ee12000-03-17 23:40:15 +1100867Specifies the port number to connect on the remote host.
868Default is 22.
Damien Miller1e42f302001-03-19 23:59:11 +1100869.It Cm PreferredAuthentications
870Specifies the order in which the client should try protocol 2
871authentication methods. This allows a client to prefer one method (e.g.
872.Cm keyboard-interactive )
873over another method (e.g.
874.Cm password )
875The default for this option is:
876.Dq publickey, password, keyboard-interactive
Damien Miller22c77262000-04-13 12:26:34 +1000877.It Cm Protocol
878Specifies the protocol versions
879.Nm
880should support in order of preference.
881The possible values are
882.Dq 1
883and
884.Dq 2 .
885Multiple versions must be comma-separated.
886The default is
Damien Millere247cc42000-05-07 12:03:14 +1000887.Dq 1,2 .
888This means that
889.Nm
890tries version 1 and falls back to version 2
Damien Miller30c3d422000-05-09 11:02:59 +1000891if version 1 is not available.
Damien Miller32aa1441999-10-29 09:15:49 +1000892.It Cm ProxyCommand
Damien Miller7684ee12000-03-17 23:40:15 +1100893Specifies the command to use to connect to the server.
894The command
895string extends to the end of the line, and is executed with
896.Pa /bin/sh .
897In the command string,
898.Ql %h
899will be substituted by the host name to
900connect and
901.Ql %p
902by the port.
903The command can be basically anything,
904and should read from its standard input and write to its standard output.
905It should eventually connect an
Damien Miller32aa1441999-10-29 09:15:49 +1000906.Xr sshd 8
907server running on some machine, or execute
908.Ic sshd -i
Damien Miller7684ee12000-03-17 23:40:15 +1100909somewhere.
910Host key management will be done using the
Damien Miller32aa1441999-10-29 09:15:49 +1000911HostName of the host being connected (defaulting to the name typed by
912the user).
Damien Milleraae6c611999-12-06 11:47:28 +1100913Note that
914.Cm CheckHostIP
915is not available for connects with a proxy command.
Damien Miller32aa1441999-10-29 09:15:49 +1000916.Pp
917.It Cm RemoteForward
918Specifies that a TCP/IP port on the remote machine be forwarded over
Damien Miller7684ee12000-03-17 23:40:15 +1100919the secure channel to given host:port from the local machine.
920The first argument must be a port number, and the second must be
921host:port.
922Multiple forwardings may be specified, and additional
923forwardings can be given on the command line.
924Only the superuser can forward privileged ports.
Damien Miller32aa1441999-10-29 09:15:49 +1000925.It Cm RhostsAuthentication
Damien Miller7684ee12000-03-17 23:40:15 +1100926Specifies whether to try rhosts based authentication.
927Note that this
Damien Miller32aa1441999-10-29 09:15:49 +1000928declaration only affects the client side and has no effect whatsoever
Damien Miller7684ee12000-03-17 23:40:15 +1100929on security.
930Disabling rhosts authentication may reduce
Damien Miller32aa1441999-10-29 09:15:49 +1000931authentication time on slow connections when rhosts authentication is
Damien Miller7684ee12000-03-17 23:40:15 +1100932not used.
933Most servers do not permit RhostsAuthentication because it
934is not secure (see RhostsRSAAuthentication).
935The argument to this keyword must be
Damien Miller32aa1441999-10-29 09:15:49 +1000936.Dq yes
937or
938.Dq no .
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000939The default is
940.Dq yes .
Damien Miller32aa1441999-10-29 09:15:49 +1000941.It Cm RhostsRSAAuthentication
942Specifies whether to try rhosts based authentication with RSA host
Damien Miller7684ee12000-03-17 23:40:15 +1100943authentication.
Damien Miller7684ee12000-03-17 23:40:15 +1100944The argument must be
Damien Miller32aa1441999-10-29 09:15:49 +1000945.Dq yes
946or
947.Dq no .
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000948The default is
949.Dq yes .
Damien Miller32aa1441999-10-29 09:15:49 +1000950.It Cm RSAAuthentication
Damien Miller7684ee12000-03-17 23:40:15 +1100951Specifies whether to try RSA authentication.
952The argument to this keyword must be
Damien Miller32aa1441999-10-29 09:15:49 +1000953.Dq yes
954or
955.Dq no .
956RSA authentication will only be
957attempted if the identity file exists, or an authentication agent is
958running.
Ben Lindstrom89b0bd62001-03-29 00:27:11 +0000959The default is
960.Dq yes .
Damien Millere247cc42000-05-07 12:03:14 +1000961Note that this option applies to protocol version 1 only.
Damien Miller33804262001-02-04 23:20:18 +1100962.It Cm ChallengeResponseAuthentication
963Specifies whether to use challenge response authentication.
964Currently there is only support for
Damien Miller95def091999-11-25 00:26:21 +1100965.Xr skey 1
Damien Miller7684ee12000-03-17 23:40:15 +1100966authentication.
967The argument to this keyword must be
Damien Miller95def091999-11-25 00:26:21 +1100968.Dq yes
969or
970.Dq no .
971The default is
972.Dq no .
Damien Miller32aa1441999-10-29 09:15:49 +1000973.It Cm StrictHostKeyChecking
974If this flag is set to
Damien Miller22c77262000-04-13 12:26:34 +1000975.Dq yes ,
Damien Miller32aa1441999-10-29 09:15:49 +1000976.Nm
Ben Lindstromeb930d42001-01-29 08:37:08 +0000977will never automatically add host keys to the
Damien Miller32aa1441999-10-29 09:15:49 +1000978.Pa $HOME/.ssh/known_hosts
Damien Millere247cc42000-05-07 12:03:14 +1000979and
980.Pa $HOME/.ssh/known_hosts2
Ben Lindstromeb930d42001-01-29 08:37:08 +0000981files, and refuses to connect to hosts whose host key has changed.
Damien Miller7684ee12000-03-17 23:40:15 +1100982This provides maximum protection against trojan horse attacks.
983However, it can be somewhat annoying if you don't have good
Damien Miller886c63a2000-01-20 23:13:36 +1100984.Pa /etc/ssh_known_hosts
Damien Millere247cc42000-05-07 12:03:14 +1000985and
986.Pa /etc/ssh_known_hosts2
Damien Miller32aa1441999-10-29 09:15:49 +1000987files installed and frequently
Ben Lindstromeb930d42001-01-29 08:37:08 +0000988connect to new hosts.
989This option forces the user to manually
990add all new hosts.
991If this flag is set to
992.Dq no ,
993.Nm
994will automatically add new host keys to the
995user known hosts files.
996If this flag is set to
997.Dq ask ,
998new host keys
999will be added to the user known host files only after the user
1000has confirmed that is what they really want to do, and
1001.Nm
1002will refuse to connect to hosts whose host key has changed.
Damien Miller7684ee12000-03-17 23:40:15 +11001003The host keys of
Ben Lindstromeb930d42001-01-29 08:37:08 +00001004known hosts will be verified automatically in all cases.
Damien Miller7684ee12000-03-17 23:40:15 +11001005The argument must be
Ben Lindstromeb930d42001-01-29 08:37:08 +00001006.Dq yes ,
1007.Dq no
Damien Miller32aa1441999-10-29 09:15:49 +10001008or
Ben Lindstromeb930d42001-01-29 08:37:08 +00001009.Dq ask .
1010The default is
1011.Dq ask .
Damien Miller32aa1441999-10-29 09:15:49 +10001012.It Cm UsePrivilegedPort
1013Specifies whether to use a privileged port for outgoing connections.
1014The argument must be
1015.Dq yes
1016or
1017.Dq no .
1018The default is
Ben Lindstromcebc8582001-03-08 03:39:10 +00001019.Dq no .
Damien Miller32aa1441999-10-29 09:15:49 +10001020Note that setting this option to
1021.Dq no
Damien Millera34a28b1999-12-14 10:47:15 +11001022turns off
Damien Miller32aa1441999-10-29 09:15:49 +10001023.Cm RhostsAuthentication
1024and
Kevin Stevesfcec7f82000-12-15 19:55:48 +00001025.Cm RhostsRSAAuthentication
1026for older servers.
Damien Miller396691a2000-01-20 22:44:08 +11001027.It Cm User
Damien Miller7684ee12000-03-17 23:40:15 +11001028Specifies the user to log in as.
1029This can be useful if you have a different user name on different machines.
1030This saves the trouble of
Damien Miller396691a2000-01-20 22:44:08 +11001031having to remember to give the user name on the command line.
1032.It Cm UserKnownHostsFile
Ben Lindstrom1e621742001-03-06 01:10:53 +00001033Specifies a file to use for the protocol version 1 user
1034host key database instead of
Damien Miller396691a2000-01-20 22:44:08 +11001035.Pa $HOME/.ssh/known_hosts .
Ben Lindstrom1e621742001-03-06 01:10:53 +00001036.It Cm UserKnownHostsFile2
1037Specifies a file to use for the protocol version 2 user
1038host key database instead of
1039.Pa $HOME/.ssh/known_hosts2 .
Damien Miller32aa1441999-10-29 09:15:49 +10001040.It Cm UseRsh
Damien Miller7684ee12000-03-17 23:40:15 +11001041Specifies that rlogin/rsh should be used for this host.
1042It is possible that the host does not at all support the
Damien Miller32aa1441999-10-29 09:15:49 +10001043.Nm
Damien Miller7684ee12000-03-17 23:40:15 +11001044protocol.
1045This causes
Damien Miller32aa1441999-10-29 09:15:49 +10001046.Nm
Damien Miller7684ee12000-03-17 23:40:15 +11001047to immediately execute
Damien Miller32aa1441999-10-29 09:15:49 +10001048.Xr rsh 1 .
1049All other options (except
1050.Cm HostName )
Damien Miller7684ee12000-03-17 23:40:15 +11001051are ignored if this has been specified.
1052The argument must be
Damien Miller32aa1441999-10-29 09:15:49 +10001053.Dq yes
1054or
1055.Dq no .
Damien Millerd3a18572000-06-07 19:55:44 +10001056.It Cm XAuthLocation
1057Specifies the location of the
1058.Xr xauth 1
1059program.
1060The default is
1061.Pa /usr/X11R6/bin/xauth .
Damien Miller7b28dc52000-09-05 13:34:53 +11001062.El
Damien Miller32aa1441999-10-29 09:15:49 +10001063.Sh ENVIRONMENT
1064.Nm
1065will normally set the following environment variables:
1066.Bl -tag -width Ds
1067.It Ev DISPLAY
1068The
1069.Ev DISPLAY
Damien Miller7684ee12000-03-17 23:40:15 +11001070variable indicates the location of the X11 server.
Damien Miller22c77262000-04-13 12:26:34 +10001071It is automatically set by
Damien Miller32aa1441999-10-29 09:15:49 +10001072.Nm
1073to point to a value of the form
1074.Dq hostname:n
1075where hostname indicates
Damien Miller7684ee12000-03-17 23:40:15 +11001076the host where the shell runs, and n is an integer >= 1.
1077.Nm
1078uses this special value to forward X11 connections over the secure
1079channel.
1080The user should normally not set DISPLAY explicitly, as that
Damien Miller32aa1441999-10-29 09:15:49 +10001081will render the X11 connection insecure (and will require the user to
1082manually copy any required authorization cookies).
1083.It Ev HOME
1084Set to the path of the user's home directory.
1085.It Ev LOGNAME
1086Synonym for
1087.Ev USER ;
1088set for compatibility with systems that use this variable.
1089.It Ev MAIL
1090Set to point the user's mailbox.
Damien Miller7684ee12000-03-17 23:40:15 +11001091.It Ev PATH
Damien Miller32aa1441999-10-29 09:15:49 +10001092Set to the default
1093.Ev PATH ,
1094as specified when compiling
1095.Nm ssh .
1096.It Ev SSH_AUTH_SOCK
1097indicates the path of a unix-domain socket used to communicate with the
1098agent.
1099.It Ev SSH_CLIENT
Damien Miller7684ee12000-03-17 23:40:15 +11001100Identifies the client end of the connection.
1101The variable contains
Damien Miller32aa1441999-10-29 09:15:49 +10001102three space-separated values: client ip-address, client port number,
1103and server port number.
Ben Lindstrom4dccfa52000-12-28 16:40:05 +00001104.It Ev SSH_ORIGINAL_COMMAND
1105The variable contains the original command line if a forced command
1106is executed.
1107It can be used to extract the original arguments.
Damien Miller32aa1441999-10-29 09:15:49 +10001108.It Ev SSH_TTY
1109This is set to the name of the tty (path to the device) associated
Damien Miller7684ee12000-03-17 23:40:15 +11001110with the current shell or command.
1111If the current session has no tty,
Damien Miller32aa1441999-10-29 09:15:49 +10001112this variable is not set.
1113.It Ev TZ
1114The timezone variable is set to indicate the present timezone if it
Damien Miller942da032000-08-18 13:59:06 +10001115was set when the daemon was started (i.e., the daemon passes the value
Damien Miller32aa1441999-10-29 09:15:49 +10001116on to new connections).
1117.It Ev USER
1118Set to the name of the user logging in.
1119.El
1120.Pp
Damien Miller22c77262000-04-13 12:26:34 +10001121Additionally,
Damien Miller32aa1441999-10-29 09:15:49 +10001122.Nm
Damien Miller22c77262000-04-13 12:26:34 +10001123reads
1124.Pa $HOME/.ssh/environment ,
Damien Miller32aa1441999-10-29 09:15:49 +10001125and adds lines of the format
1126.Dq VARNAME=value
1127to the environment.
1128.Sh FILES
Damien Miller98c7ad62000-03-09 21:27:49 +11001129.Bl -tag -width Ds
Ben Lindstrom1e621742001-03-06 01:10:53 +00001130.It Pa $HOME/.ssh/known_hosts, $HOME/.ssh/known_hosts2
Damien Miller32aa1441999-10-29 09:15:49 +10001131Records host keys for all hosts the user has logged into (that are not
1132in
Ben Lindstrom1e621742001-03-06 01:10:53 +00001133.Pa /etc/ssh_known_hosts
1134for protocol version 1 or
1135.Pa /etc/ssh_known_hosts2
1136for protocol version 2).
Damien Miller32aa1441999-10-29 09:15:49 +10001137See
1138.Xr sshd 8 .
Damien Millere247cc42000-05-07 12:03:14 +10001139.It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa
1140Contains the RSA and the DSA authentication identity of the user.
1141These files
1142contain sensitive data and should be readable by the user but not
Damien Miller32aa1441999-10-29 09:15:49 +10001143accessible by others (read/write/execute).
1144Note that
1145.Nm
Damien Millere247cc42000-05-07 12:03:14 +10001146ignores a private key file if it is accessible by others.
Damien Miller32aa1441999-10-29 09:15:49 +10001147It is possible to specify a passphrase when
1148generating the key; the passphrase will be used to encrypt the
1149sensitive part of this file using 3DES.
Damien Millere247cc42000-05-07 12:03:14 +10001150.It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub
Damien Miller32aa1441999-10-29 09:15:49 +10001151Contains the public key for authentication (public part of the
Damien Miller7684ee12000-03-17 23:40:15 +11001152identity file in human-readable form).
Damien Millere247cc42000-05-07 12:03:14 +10001153The contents of the
1154.Pa $HOME/.ssh/identity.pub
1155file should be added to
Damien Miller32aa1441999-10-29 09:15:49 +10001156.Pa $HOME/.ssh/authorized_keys
1157on all machines
Damien Miller7684ee12000-03-17 23:40:15 +11001158where you wish to log in using RSA authentication.
Damien Millere247cc42000-05-07 12:03:14 +10001159The contents of the
1160.Pa $HOME/.ssh/id_dsa.pub
1161file should be added to
1162.Pa $HOME/.ssh/authorized_keys2
1163on all machines
1164where you wish to log in using DSA authentication.
1165These files are not
Damien Miller7684ee12000-03-17 23:40:15 +11001166sensitive and can (but need not) be readable by anyone.
Damien Millere247cc42000-05-07 12:03:14 +10001167These files are
Kevin Steves3c034ae2001-02-05 13:47:11 +00001168never used automatically and are not necessary; they are only provided for
Damien Miller32aa1441999-10-29 09:15:49 +10001169the convenience of the user.
1170.It Pa $HOME/.ssh/config
Damien Miller7684ee12000-03-17 23:40:15 +11001171This is the per-user configuration file.
1172The format of this file is described above.
1173This file is used by the
Damien Miller32aa1441999-10-29 09:15:49 +10001174.Nm
Damien Miller7684ee12000-03-17 23:40:15 +11001175client.
1176This file does not usually contain any sensitive information,
Damien Miller32aa1441999-10-29 09:15:49 +10001177but the recommended permissions are read/write for the user, and not
1178accessible by others.
1179.It Pa $HOME/.ssh/authorized_keys
Damien Miller7684ee12000-03-17 23:40:15 +11001180Lists the RSA keys that can be used for logging in as this user.
1181The format of this file is described in the
Damien Miller32aa1441999-10-29 09:15:49 +10001182.Xr sshd 8
Damien Miller7684ee12000-03-17 23:40:15 +11001183manual page.
1184In the simplest form the format is the same as the .pub
Damien Miller32aa1441999-10-29 09:15:49 +10001185identity files (that is, each line contains the number of bits in
1186modulus, public exponent, modulus, and comment fields, separated by
Damien Miller7684ee12000-03-17 23:40:15 +11001187spaces).
1188This file is not highly sensitive, but the recommended
Damien Miller32aa1441999-10-29 09:15:49 +10001189permissions are read/write for the user, and not accessible by others.
Damien Millere247cc42000-05-07 12:03:14 +10001190.It Pa $HOME/.ssh/authorized_keys2
Damien Miller0bc1bd82000-11-13 22:57:25 +11001191Lists the public keys (DSA/RSA) that can be used for logging in as this user.
Damien Millere247cc42000-05-07 12:03:14 +10001192This file is not highly sensitive, but the recommended
1193permissions are read/write for the user, and not accessible by others.
1194.It Pa /etc/ssh_known_hosts, /etc/ssh_known_hosts2
Damien Miller7684ee12000-03-17 23:40:15 +11001195Systemwide list of known host keys.
Damien Millere247cc42000-05-07 12:03:14 +10001196.Pa /etc/ssh_known_hosts
1197contains RSA and
1198.Pa /etc/ssh_known_hosts2
Damien Miller0bc1bd82000-11-13 22:57:25 +11001199contains DSA or RSA keys for protocol version 2.
Damien Millere247cc42000-05-07 12:03:14 +10001200These files should be prepared by the
Damien Miller32aa1441999-10-29 09:15:49 +10001201system administrator to contain the public host keys of all machines in the
Damien Miller7684ee12000-03-17 23:40:15 +11001202organization.
1203This file should be world-readable.
1204This file contains
Damien Miller32aa1441999-10-29 09:15:49 +10001205public keys, one per line, in the following format (fields separated
1206by spaces): system name, number of bits in modulus, public exponent,
Damien Miller7684ee12000-03-17 23:40:15 +11001207modulus, and optional comment field.
1208When different names are used
Damien Miller32aa1441999-10-29 09:15:49 +10001209for the same machine, all such names should be listed, separated by
Damien Miller7684ee12000-03-17 23:40:15 +11001210commas.
1211The format is described on the
Damien Miller32aa1441999-10-29 09:15:49 +10001212.Xr sshd 8
1213manual page.
1214.Pp
1215The canonical system name (as returned by name servers) is used by
1216.Xr sshd 8
1217to verify the client host when logging in; other names are needed because
1218.Nm
1219does not convert the user-supplied name to a canonical name before
1220checking the key, because someone with access to the name servers
1221would then be able to fool host authentication.
Damien Miller886c63a2000-01-20 23:13:36 +11001222.It Pa /etc/ssh_config
Damien Miller7684ee12000-03-17 23:40:15 +11001223Systemwide configuration file.
1224This file provides defaults for those
Damien Miller32aa1441999-10-29 09:15:49 +10001225values that are not specified in the user's configuration file, and
Damien Miller7684ee12000-03-17 23:40:15 +11001226for those users who do not have a configuration file.
1227This file must be world-readable.
Damien Miller32aa1441999-10-29 09:15:49 +10001228.It Pa $HOME/.rhosts
1229This file is used in
1230.Pa \&.rhosts
1231authentication to list the
Damien Miller7684ee12000-03-17 23:40:15 +11001232host/user pairs that are permitted to log in.
1233(Note that this file is
Damien Miller32aa1441999-10-29 09:15:49 +10001234also used by rlogin and rsh, which makes using this file insecure.)
1235Each line of the file contains a host name (in the canonical form
1236returned by name servers), and then a user name on that host,
Damien Miller7684ee12000-03-17 23:40:15 +11001237separated by a space.
Ben Lindstromebd888d2001-03-05 05:49:29 +00001238On some machines this file may need to be
Damien Miller32aa1441999-10-29 09:15:49 +10001239world-readable if the user's home directory is on a NFS partition,
1240because
1241.Xr sshd 8
Damien Miller7684ee12000-03-17 23:40:15 +11001242reads it as root.
1243Additionally, this file must be owned by the user,
1244and must not have write permissions for anyone else.
1245The recommended
Damien Miller32aa1441999-10-29 09:15:49 +10001246permission for most machines is read/write for the user, and not
1247accessible by others.
1248.Pp
1249Note that by default
1250.Xr sshd 8
1251will be installed so that it requires successful RSA host
Damien Miller7684ee12000-03-17 23:40:15 +11001252authentication before permitting \s+2.\s0rhosts authentication.
1253If your server machine does not have the client's host key in
Damien Miller886c63a2000-01-20 23:13:36 +11001254.Pa /etc/ssh_known_hosts ,
Damien Miller32aa1441999-10-29 09:15:49 +10001255you can store it in
1256.Pa $HOME/.ssh/known_hosts .
1257The easiest way to do this is to
1258connect back to the client from the server machine using ssh; this
Damien Millere247cc42000-05-07 12:03:14 +10001259will automatically add the host key to
Damien Miller32aa1441999-10-29 09:15:49 +10001260.Pa $HOME/.ssh/known_hosts .
1261.It Pa $HOME/.shosts
1262This file is used exactly the same way as
1263.Pa \&.rhosts .
1264The purpose for
1265having this file is to be able to use rhosts authentication with
1266.Nm
1267without permitting login with
1268.Xr rlogin 1
1269or
1270.Xr rsh 1 .
1271.It Pa /etc/hosts.equiv
1272This file is used during
Damien Miller7684ee12000-03-17 23:40:15 +11001273.Pa \&.rhosts authentication.
1274It contains
Damien Miller32aa1441999-10-29 09:15:49 +10001275canonical hosts names, one per line (the full format is described on
1276the
1277.Xr sshd 8
Damien Miller7684ee12000-03-17 23:40:15 +11001278manual page).
1279If the client host is found in this file, login is
Damien Miller32aa1441999-10-29 09:15:49 +10001280automatically permitted provided client and server user names are the
Damien Miller7684ee12000-03-17 23:40:15 +11001281same.
1282Additionally, successful RSA host authentication is normally
1283required.
1284This file should only be writable by root.
Damien Miller886c63a2000-01-20 23:13:36 +11001285.It Pa /etc/shosts.equiv
Damien Miller22c77262000-04-13 12:26:34 +10001286This file is processed exactly as
Damien Miller32aa1441999-10-29 09:15:49 +10001287.Pa /etc/hosts.equiv .
1288This file may be useful to permit logins using
1289.Nm
1290but not using rsh/rlogin.
Damien Miller886c63a2000-01-20 23:13:36 +11001291.It Pa /etc/sshrc
Damien Miller32aa1441999-10-29 09:15:49 +10001292Commands in this file are executed by
1293.Nm
1294when the user logs in just before the user's shell (or command) is started.
1295See the
1296.Xr sshd 8
1297manual page for more information.
1298.It Pa $HOME/.ssh/rc
1299Commands in this file are executed by
1300.Nm
1301when the user logs in just before the user's shell (or command) is
1302started.
Damien Miller22c77262000-04-13 12:26:34 +10001303See the
Damien Miller32aa1441999-10-29 09:15:49 +10001304.Xr sshd 8
1305manual page for more information.
Damien Miller4f0fa561999-12-26 14:24:41 +11001306.It Pa $HOME/.ssh/environment
1307Contains additional definitions for environment variables, see section
1308.Sx ENVIRONMENT
1309above.
Damien Miller7b28dc52000-09-05 13:34:53 +11001310.El
Damien Miller0bc1bd82000-11-13 22:57:25 +11001311.Sh AUTHORS
Ben Lindstrom035782e2001-01-29 08:34:16 +00001312OpenSSH is a derivative of the original and free
1313ssh 1.2.12 release by Tatu Ylonen.
1314Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1315Theo de Raadt and Dug Song
1316removed many bugs, re-added newer features and
1317created OpenSSH.
1318Markus Friedl contributed the support for SSH
1319protocol versions 1.5 and 2.0.
Damien Miller32aa1441999-10-29 09:15:49 +10001320.Sh SEE ALSO
1321.Xr rlogin 1 ,
1322.Xr rsh 1 ,
1323.Xr scp 1 ,
Damien Miller33804262001-02-04 23:20:18 +11001324.Xr sftp 1 ,
Damien Miller32aa1441999-10-29 09:15:49 +10001325.Xr ssh-add 1 ,
1326.Xr ssh-agent 1 ,
1327.Xr ssh-keygen 1 ,
1328.Xr telnet 1 ,
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +00001329.Xr sshd 8