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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.\"
Damien Millerac7ef6a2005-06-16 13:19:06 +100037.\" $OpenBSD: sshd.8,v 1.208 2005/06/08 03:50:00 djm Exp $
Damien Miller32aa1441999-10-29 09:15:49 +100038.Dd September 25, 1999
39.Dt SSHD 8
40.Os
41.Sh NAME
42.Nm sshd
Ben Lindstromc65e6a02001-04-23 13:02:16 +000043.Nd OpenSSH SSH daemon
Damien Miller32aa1441999-10-29 09:15:49 +100044.Sh SYNOPSIS
45.Nm sshd
Damien Millerffadc582003-02-24 11:52:26 +110046.Bk -words
Darren Tucker1f203942003-10-15 15:50:42 +100047.Op Fl 46Ddeiqt
Damien Miller32aa1441999-10-29 09:15:49 +100048.Op Fl b Ar bits
49.Op Fl f Ar config_file
50.Op Fl g Ar login_grace_time
51.Op Fl h Ar host_key_file
52.Op Fl k Ar key_gen_time
Ben Lindstromade03f62001-12-06 18:22:17 +000053.Op Fl o Ar option
Damien Miller32aa1441999-10-29 09:15:49 +100054.Op Fl p Ar port
Damien Miller942da032000-08-18 13:59:06 +100055.Op Fl u Ar len
Damien Millerffadc582003-02-24 11:52:26 +110056.Ek
Damien Miller22c77262000-04-13 12:26:34 +100057.Sh DESCRIPTION
Damien Miller32aa1441999-10-29 09:15:49 +100058.Nm
Ben Lindstromd58eb5f2001-03-07 06:07:22 +000059(SSH Daemon) is the daemon program for
Damien Miller32aa1441999-10-29 09:15:49 +100060.Xr ssh 1 .
Damien Miller35dabd02000-05-01 21:10:33 +100061Together these programs replace rlogin and rsh, and
Damien Miller32aa1441999-10-29 09:15:49 +100062provide secure encrypted communications between two untrusted hosts
Damien Miller450a7a12000-03-26 13:04:51 +100063over an insecure network.
64The programs are intended to be as easy to
Damien Miller32aa1441999-10-29 09:15:49 +100065install and use as possible.
66.Pp
67.Nm
Damien Miller450a7a12000-03-26 13:04:51 +100068is the daemon that listens for connections from clients.
Damien Miller22c77262000-04-13 12:26:34 +100069It is normally started at boot from
Damien Miller32aa1441999-10-29 09:15:49 +100070.Pa /etc/rc .
71It forks a new
Damien Miller450a7a12000-03-26 13:04:51 +100072daemon for each incoming connection.
73The forked daemons handle
Damien Miller32aa1441999-10-29 09:15:49 +100074key exchange, encryption, authentication, command execution,
75and data exchange.
Damien Millere247cc42000-05-07 12:03:14 +100076This implementation of
77.Nm
78supports both SSH protocol version 1 and 2 simultaneously.
Damien Miller32aa1441999-10-29 09:15:49 +100079.Nm
Damien Millerffadc582003-02-24 11:52:26 +110080works as follows:
Damien Millere247cc42000-05-07 12:03:14 +100081.Ss SSH protocol version 1
Damien Miller450a7a12000-03-26 13:04:51 +100082Each host has a host-specific RSA key
Damien Millerac7ef6a2005-06-16 13:19:06 +100083(normally 2048 bits) used to identify the host.
Damien Miller450a7a12000-03-26 13:04:51 +100084Additionally, when
Damien Miller32aa1441999-10-29 09:15:49 +100085the daemon starts, it generates a server RSA key (normally 768 bits).
86This key is normally regenerated every hour if it has been used, and
87is never stored on disk.
88.Pp
Damien Millerffadc582003-02-24 11:52:26 +110089Whenever a client connects, the daemon responds with its public
Damien Miller35dabd02000-05-01 21:10:33 +100090host and server keys.
Damien Miller450a7a12000-03-26 13:04:51 +100091The client compares the
Damien Millere247cc42000-05-07 12:03:14 +100092RSA host key against its own database to verify that it has not changed.
Darren Tucker1f203942003-10-15 15:50:42 +100093The client then generates a 256-bit random number.
Damien Miller450a7a12000-03-26 13:04:51 +100094It encrypts this
Damien Miller32aa1441999-10-29 09:15:49 +100095random number using both the host key and the server key, and sends
Damien Miller450a7a12000-03-26 13:04:51 +100096the encrypted number to the server.
Damien Miller35dabd02000-05-01 21:10:33 +100097Both sides then use this
Damien Miller32aa1441999-10-29 09:15:49 +100098random number as a session key which is used to encrypt all further
Damien Miller450a7a12000-03-26 13:04:51 +100099communications in the session.
100The rest of the session is encrypted
Damien Miller35dabd02000-05-01 21:10:33 +1000101using a conventional cipher, currently Blowfish or 3DES, with 3DES
Damien Millerb38eff82000-04-01 11:09:21 +1000102being used by default.
Damien Miller450a7a12000-03-26 13:04:51 +1000103The client selects the encryption algorithm
Damien Miller32aa1441999-10-29 09:15:49 +1000104to use from those offered by the server.
105.Pp
Damien Miller450a7a12000-03-26 13:04:51 +1000106Next, the server and the client enter an authentication dialog.
107The client tries to authenticate itself using
Darren Tucker1f203942003-10-15 15:50:42 +1000108.Em .rhosts
Damien Miller32aa1441999-10-29 09:15:49 +1000109authentication combined with RSA host
110authentication, RSA challenge-response authentication, or password
111based authentication.
112.Pp
Darren Tuckere41bba52003-08-25 11:51:19 +1000113Regardless of the authentication type, the account is checked to
114ensure that it is accessible. An account is not accessible if it is
115locked, listed in
116.Cm DenyUsers
117or its group is listed in
118.Cm DenyGroups
119\&. The definition of a locked account is system dependant. Some platforms
120have their own account database (eg AIX) and some modify the passwd field (
121.Ql \&*LK\&*
122on Solaris,
123.Ql \&*
124on HP-UX, containing
125.Ql Nologin
126on Tru64 and a leading
127.Ql \&!!
128on Linux). If there is a requirement to disable password authentication
129for the account while allowing still public-key, then the passwd field
130should be set to something other than these values (eg
131.Ql NP
132or
133.Ql \&*NP\&*
134).
135.Pp
Ben Lindstromc57bbf12002-05-15 21:36:45 +0000136.Nm rshd ,
137.Nm rlogind ,
Damien Miller32aa1441999-10-29 09:15:49 +1000138and
Damien Millerffadc582003-02-24 11:52:26 +1100139.Nm rexecd
Damien Miller32aa1441999-10-29 09:15:49 +1000140are disabled (thus completely disabling
Ben Lindstromc57bbf12002-05-15 21:36:45 +0000141.Xr rlogin
Damien Miller32aa1441999-10-29 09:15:49 +1000142and
Ben Lindstromc57bbf12002-05-15 21:36:45 +0000143.Xr rsh
Damien Miller35dabd02000-05-01 21:10:33 +1000144into the machine).
Damien Millere247cc42000-05-07 12:03:14 +1000145.Ss SSH protocol version 2
Damien Miller942da032000-08-18 13:59:06 +1000146Version 2 works similarly:
Ben Lindstrom07d24dc2001-08-06 21:18:57 +0000147Each host has a host-specific key (RSA or DSA) used to identify the host.
Damien Millere247cc42000-05-07 12:03:14 +1000148However, when the daemon starts, it does not generate a server key.
149Forward security is provided through a Diffie-Hellman key agreement.
150This key agreement results in a shared session key.
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000151.Pp
Ben Lindstromfd2e05b2001-03-05 07:48:45 +0000152The rest of the session is encrypted using a symmetric cipher, currently
Darren Tucker1f203942003-10-15 15:50:42 +1000153128-bit AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES.
Damien Millere247cc42000-05-07 12:03:14 +1000154The client selects the encryption algorithm
155to use from those offered by the server.
156Additionally, session integrity is provided
Damien Miller30c3d422000-05-09 11:02:59 +1000157through a cryptographic message authentication code
Damien Millere247cc42000-05-07 12:03:14 +1000158(hmac-sha1 or hmac-md5).
159.Pp
160Protocol version 2 provides a public key based
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000161user (PubkeyAuthentication) or
162client host (HostbasedAuthentication) authentication method,
163conventional password authentication and challenge response based methods.
Damien Millere247cc42000-05-07 12:03:14 +1000164.Ss Command execution and data forwarding
Damien Miller32aa1441999-10-29 09:15:49 +1000165If the client successfully authenticates itself, a dialog for
Damien Miller450a7a12000-03-26 13:04:51 +1000166preparing the session is entered.
167At this time the client may request
Damien Miller32aa1441999-10-29 09:15:49 +1000168things like allocating a pseudo-tty, forwarding X11 connections,
169forwarding TCP/IP connections, or forwarding the authentication agent
170connection over the secure channel.
171.Pp
172Finally, the client either requests a shell or execution of a command.
Damien Miller450a7a12000-03-26 13:04:51 +1000173The sides then enter session mode.
174In this mode, either side may send
Damien Miller32aa1441999-10-29 09:15:49 +1000175data at any time, and such data is forwarded to/from the shell or
176command on the server side, and the user terminal in the client side.
177.Pp
178When the user program terminates and all forwarded X11 and other
179connections have been closed, the server sends command exit status to
180the client, and both sides exit.
181.Pp
182.Nm
Darren Tucker1f203942003-10-15 15:50:42 +1000183can be configured using command-line options or a configuration file
184(by default
185.Xr sshd_config 5 ) .
Damien Miller450a7a12000-03-26 13:04:51 +1000186Command-line options override values specified in the
Damien Miller32aa1441999-10-29 09:15:49 +1000187configuration file.
188.Pp
Damien Miller6162d121999-11-21 13:23:52 +1100189.Nm
190rereads its configuration file when it receives a hangup signal,
Ben Lindstrom49a098d2001-03-05 06:55:18 +0000191.Dv SIGHUP ,
Darren Tucker097e1e92004-05-02 22:15:08 +1000192by executing itself with the name and options it was started with, e.g.,
Ben Lindstrom49a098d2001-03-05 06:55:18 +0000193.Pa /usr/sbin/sshd .
Damien Miller6162d121999-11-21 13:23:52 +1100194.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000195The options are as follows:
196.Bl -tag -width Ds
Darren Tucker1f203942003-10-15 15:50:42 +1000197.It Fl 4
198Forces
199.Nm
200to use IPv4 addresses only.
201.It Fl 6
202Forces
203.Nm
204to use IPv6 addresses only.
Damien Miller32aa1441999-10-29 09:15:49 +1000205.It Fl b Ar bits
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000206Specifies the number of bits in the ephemeral protocol version 1
207server key (default 768).
Darren Tucker1f203942003-10-15 15:50:42 +1000208.It Fl D
209When this option is specified,
210.Nm
211will not detach and does not become a daemon.
212This allows easy monitoring of
213.Nm sshd .
Damien Miller32aa1441999-10-29 09:15:49 +1000214.It Fl d
Damien Miller450a7a12000-03-26 13:04:51 +1000215Debug mode.
216The server sends verbose debug output to the system
217log, and does not put itself in the background.
218The server also will not fork and will only process one connection.
219This option is only intended for debugging for the server.
Damien Millerffadc582003-02-24 11:52:26 +1100220Multiple
221.Fl d
222options increase the debugging level.
Damien Miller874d77b2000-10-14 16:23:11 +1100223Maximum is 3.
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000224.It Fl e
225When this option is specified,
226.Nm
227will send the output to the standard error instead of the system log.
Damien Miller32aa1441999-10-29 09:15:49 +1000228.It Fl f Ar configuration_file
Damien Miller450a7a12000-03-26 13:04:51 +1000229Specifies the name of the configuration file.
230The default is
Damien Miller05eda432002-02-10 18:32:28 +1100231.Pa /etc/ssh/sshd_config .
Damien Miller32aa1441999-10-29 09:15:49 +1000232.Nm
233refuses to start if there is no configuration file.
234.It Fl g Ar login_grace_time
235Gives the grace time for clients to authenticate themselves (default
Damien Millerc1348632002-09-05 14:35:14 +1000236120 seconds).
Damien Miller450a7a12000-03-26 13:04:51 +1000237If the client fails to authenticate the user within
238this many seconds, the server disconnects and exits.
239A value of zero indicates no limit.
Damien Miller32aa1441999-10-29 09:15:49 +1000240.It Fl h Ar host_key_file
Damien Miller7fc23732002-01-22 23:19:11 +1100241Specifies a file from which a host key is read.
Damien Miller32aa1441999-10-29 09:15:49 +1000242This option must be given if
243.Nm
244is not run as root (as the normal
Damien Miller7fc23732002-01-22 23:19:11 +1100245host key files are normally not readable by anyone but root).
246The default is
Damien Miller05eda432002-02-10 18:32:28 +1100247.Pa /etc/ssh/ssh_host_key
Damien Miller7fc23732002-01-22 23:19:11 +1100248for protocol version 1, and
Damien Miller05eda432002-02-10 18:32:28 +1100249.Pa /etc/ssh/ssh_host_rsa_key
Damien Miller7fc23732002-01-22 23:19:11 +1100250and
Damien Miller05eda432002-02-10 18:32:28 +1100251.Pa /etc/ssh/ssh_host_dsa_key
Damien Miller7fc23732002-01-22 23:19:11 +1100252for protocol version 2.
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000253It is possible to have multiple host key files for
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000254the different protocol versions and host key algorithms.
Damien Miller32aa1441999-10-29 09:15:49 +1000255.It Fl i
256Specifies that
257.Nm
Damien Millerffadc582003-02-24 11:52:26 +1100258is being run from
259.Xr inetd 8 .
Damien Miller32aa1441999-10-29 09:15:49 +1000260.Nm
261is normally not run
262from inetd because it needs to generate the server key before it can
Damien Miller450a7a12000-03-26 13:04:51 +1000263respond to the client, and this may take tens of seconds.
264Clients would have to wait too long if the key was regenerated every time.
Damien Miller7684ee12000-03-17 23:40:15 +1100265However, with small key sizes (e.g., 512) using
Damien Miller32aa1441999-10-29 09:15:49 +1000266.Nm
267from inetd may
268be feasible.
269.It Fl k Ar key_gen_time
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000270Specifies how often the ephemeral protocol version 1 server key is
271regenerated (default 3600 seconds, or one hour).
Damien Miller450a7a12000-03-26 13:04:51 +1000272The motivation for regenerating the key fairly
Darren Tucker1f203942003-10-15 15:50:42 +1000273often is that the key is not stored anywhere, and after about an hour
Damien Miller32aa1441999-10-29 09:15:49 +1000274it becomes impossible to recover the key for decrypting intercepted
275communications even if the machine is cracked into or physically
Damien Miller450a7a12000-03-26 13:04:51 +1000276seized.
277A value of zero indicates that the key will never be regenerated.
Ben Lindstromade03f62001-12-06 18:22:17 +0000278.It Fl o Ar option
279Can be used to give options in the format used in the configuration file.
280This is useful for specifying options for which there is no separate
281command-line flag.
Darren Tucker1f203942003-10-15 15:50:42 +1000282For full details of the options, and their values, see
283.Xr sshd_config 5 .
Damien Miller32aa1441999-10-29 09:15:49 +1000284.It Fl p Ar port
285Specifies the port on which the server listens for connections
286(default 22).
Damien Miller7d1ded42002-01-22 23:09:41 +1100287Multiple port options are permitted.
288Ports specified in the configuration file are ignored when a
289command-line port is specified.
Damien Miller32aa1441999-10-29 09:15:49 +1000290.It Fl q
Damien Miller450a7a12000-03-26 13:04:51 +1000291Quiet mode.
292Nothing is sent to the system log.
293Normally the beginning,
Damien Miller32aa1441999-10-29 09:15:49 +1000294authentication, and termination of each connection is logged.
Ben Lindstrom794325a2001-08-06 21:09:07 +0000295.It Fl t
296Test mode.
297Only check the validity of the configuration file and sanity of the keys.
Damien Miller9f0f5c62001-12-21 14:45:46 +1100298This is useful for updating
Ben Lindstrom794325a2001-08-06 21:09:07 +0000299.Nm
300reliably as configuration options may change.
Damien Miller942da032000-08-18 13:59:06 +1000301.It Fl u Ar len
302This option is used to specify the size of the field
303in the
304.Li utmp
305structure that holds the remote host name.
306If the resolved host name is longer than
307.Ar len ,
308the dotted decimal value will be used instead.
309This allows hosts with very long host names that
310overflow this field to still be uniquely identified.
311Specifying
312.Fl u0
313indicates that only dotted decimal addresses
314should be put into the
315.Pa utmp
316file.
Ben Lindstrom6f672c02001-09-12 17:51:55 +0000317.Fl u0
Damien Millerffadc582003-02-24 11:52:26 +1100318may also be used to prevent
Ben Lindstrom6f672c02001-09-12 17:51:55 +0000319.Nm
320from making DNS requests unless the authentication
321mechanism or configuration requires it.
322Authentication mechanisms that may require DNS include
Ben Lindstrom6f672c02001-09-12 17:51:55 +0000323.Cm RhostsRSAAuthentication ,
324.Cm HostbasedAuthentication
325and using a
326.Cm from="pattern-list"
327option in a key file.
Ben Lindstromea03db92002-03-05 01:38:57 +0000328Configuration options that require DNS include using a
329USER@HOST pattern in
330.Cm AllowUsers
331or
332.Cm DenyUsers .
Damien Miller32aa1441999-10-29 09:15:49 +1000333.El
334.Sh CONFIGURATION FILE
335.Nm
Damien Miller22c77262000-04-13 12:26:34 +1000336reads configuration data from
Damien Miller05eda432002-02-10 18:32:28 +1100337.Pa /etc/ssh/sshd_config
Damien Miller32aa1441999-10-29 09:15:49 +1000338(or the file specified with
339.Fl f
Damien Miller450a7a12000-03-26 13:04:51 +1000340on the command line).
Ben Lindstrom9f049032002-06-21 00:59:05 +0000341The file format and configuration options are described in
342.Xr sshd_config 5 .
Damien Miller32aa1441999-10-29 09:15:49 +1000343.Sh LOGIN PROCESS
344When a user successfully logs in,
345.Nm
346does the following:
347.Bl -enum -offset indent
348.It
349If the login is on a tty, and no command has been specified,
Damien Miller22c77262000-04-13 12:26:34 +1000350prints last login time and
Damien Miller32aa1441999-10-29 09:15:49 +1000351.Pa /etc/motd
352(unless prevented in the configuration file or by
Damien Miller167ea5d2005-05-26 12:04:02 +1000353.Pa ~/.hushlogin ;
Damien Miller32aa1441999-10-29 09:15:49 +1000354see the
Damien Miller22c77262000-04-13 12:26:34 +1000355.Sx FILES
Damien Miller32aa1441999-10-29 09:15:49 +1000356section).
357.It
358If the login is on a tty, records login time.
359.It
360Checks
361.Pa /etc/nologin ;
362if it exists, prints contents and quits
363(unless root).
364.It
365Changes to run with normal user privileges.
366.It
367Sets up basic environment.
368.It
Darren Tucker1f203942003-10-15 15:50:42 +1000369Reads the file
Damien Miller167ea5d2005-05-26 12:04:02 +1000370.Pa ~/.ssh/environment ,
Darren Tucker1f203942003-10-15 15:50:42 +1000371if it exists, and users are allowed to change their environment.
Ben Lindstrombd9bf382002-08-20 18:54:20 +0000372See the
Ben Lindstromdc7adf22002-08-20 18:38:02 +0000373.Cm PermitUserEnvironment
Ben Lindstrombd9bf382002-08-20 18:54:20 +0000374option in
Ben Lindstromdc7adf22002-08-20 18:38:02 +0000375.Xr sshd_config 5 .
Damien Miller32aa1441999-10-29 09:15:49 +1000376.It
377Changes to user's home directory.
378.It
379If
Damien Miller167ea5d2005-05-26 12:04:02 +1000380.Pa ~/.ssh/rc
Damien Miller32aa1441999-10-29 09:15:49 +1000381exists, runs it; else if
Damien Millerafcc2252002-02-10 18:32:55 +1100382.Pa /etc/ssh/sshrc
Damien Miller32aa1441999-10-29 09:15:49 +1000383exists, runs
Damien Miller450a7a12000-03-26 13:04:51 +1000384it; otherwise runs xauth.
385The
Damien Miller32aa1441999-10-29 09:15:49 +1000386.Dq rc
387files are given the X11
388authentication protocol and cookie in standard input.
389.It
390Runs user's shell or command.
391.El
392.Sh AUTHORIZED_KEYS FILE FORMAT
Damien Miller167ea5d2005-05-26 12:04:02 +1000393.Pa ~/.ssh/authorized_keys
Ben Lindstromf96704d2001-06-25 04:17:12 +0000394is the default file that lists the public keys that are
395permitted for RSA authentication in protocol version 1
396and for public key authentication (PubkeyAuthentication)
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000397in protocol version 2.
Ben Lindstromf96704d2001-06-25 04:17:12 +0000398.Cm AuthorizedKeysFile
Ben Lindstrombfb3a0e2001-06-05 20:25:05 +0000399may be used to specify an alternative file.
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000400.Pp
Damien Miller450a7a12000-03-26 13:04:51 +1000401Each line of the file contains one
Damien Miller32aa1441999-10-29 09:15:49 +1000402key (empty lines and lines starting with a
403.Ql #
404are ignored as
Damien Miller450a7a12000-03-26 13:04:51 +1000405comments).
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000406Each RSA public key consists of the following fields, separated by
Damien Miller450a7a12000-03-26 13:04:51 +1000407spaces: options, bits, exponent, modulus, comment.
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000408Each protocol version 2 public key consists of:
409options, keytype, base64 encoded key, comment.
Damien Millerb83df8d2002-09-04 16:24:55 +1000410The options field
411is optional; its presence is determined by whether the line starts
412with a number or not (the options field never starts with a number).
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000413The bits, exponent, modulus and comment fields give the RSA key for
414protocol version 1; the
Damien Miller32aa1441999-10-29 09:15:49 +1000415comment field is not used for anything (but may be convenient for the
416user to identify the key).
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000417For protocol version 2 the keytype is
418.Dq ssh-dss
419or
420.Dq ssh-rsa .
Damien Miller32aa1441999-10-29 09:15:49 +1000421.Pp
422Note that lines in this file are usually several hundred bytes long
Darren Tucker22cc7412004-12-06 22:47:41 +1100423(because of the size of the public key encoding) up to a limit of
4248 kilobytes, which permits DSA keys up to 8 kilobits and RSA
425keys up to 16 kilobits.
Damien Miller450a7a12000-03-26 13:04:51 +1000426You don't want to type them in; instead, copy the
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000427.Pa identity.pub ,
Ben Lindstrom4dccfa52000-12-28 16:40:05 +0000428.Pa id_dsa.pub
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000429or the
430.Pa id_rsa.pub
Damien Miller32aa1441999-10-29 09:15:49 +1000431file and edit it.
432.Pp
Ben Lindstrom0d0be022002-04-02 20:39:29 +0000433.Nm
434enforces a minimum RSA key modulus size for protocol 1
435and protocol 2 keys of 768 bits.
436.Pp
Damien Miller942da032000-08-18 13:59:06 +1000437The options (if present) consist of comma-separated option
Damien Miller450a7a12000-03-26 13:04:51 +1000438specifications.
439No spaces are permitted, except within double quotes.
Ben Lindstrom1c0fd092001-09-12 16:36:17 +0000440The following option specifications are supported (note
441that option keywords are case-insensitive):
Damien Miller32aa1441999-10-29 09:15:49 +1000442.Bl -tag -width Ds
443.It Cm from="pattern-list"
Damien Millerb83df8d2002-09-04 16:24:55 +1000444Specifies that in addition to public key authentication, the canonical name
Damien Miller32aa1441999-10-29 09:15:49 +1000445of the remote host must be present in the comma-separated list of
Damien Miller450a7a12000-03-26 13:04:51 +1000446patterns
Damien Miller31554322003-05-14 13:44:58 +1000447.Pf ( Ql \&*
Damien Miller450a7a12000-03-26 13:04:51 +1000448and
Damien Miller049245d2003-05-14 13:44:42 +1000449.Ql \&?
Damien Miller450a7a12000-03-26 13:04:51 +1000450serve as wildcards).
451The list may also contain
452patterns negated by prefixing them with
Damien Miller049245d2003-05-14 13:44:42 +1000453.Ql \&! ;
Damien Miller450a7a12000-03-26 13:04:51 +1000454if the canonical host name matches a negated pattern, the key is not accepted.
455The purpose
Damien Millerb83df8d2002-09-04 16:24:55 +1000456of this option is to optionally increase security: public key authentication
Damien Miller32aa1441999-10-29 09:15:49 +1000457by itself does not trust the network or name servers or anything (but
458the key); however, if somebody somehow steals the key, the key
Damien Miller450a7a12000-03-26 13:04:51 +1000459permits an intruder to log in from anywhere in the world.
460This additional option makes using a stolen key more difficult (name
Damien Miller32aa1441999-10-29 09:15:49 +1000461servers and/or routers would have to be compromised in addition to
462just the key).
463.It Cm command="command"
464Specifies that the command is executed whenever this key is used for
Damien Miller450a7a12000-03-26 13:04:51 +1000465authentication.
466The command supplied by the user (if any) is ignored.
Ben Lindstrom23124ea2001-09-14 23:14:25 +0000467The command is run on a pty if the client requests a pty;
Damien Miller450a7a12000-03-26 13:04:51 +1000468otherwise it is run without a tty.
Damien Millerffadc582003-02-24 11:52:26 +1100469If an 8-bit clean channel is required,
Ben Lindstrom594e2032001-09-12 18:35:30 +0000470one must not request a pty or should specify
Damien Miller33804262001-02-04 23:20:18 +1100471.Cm no-pty .
Damien Miller450a7a12000-03-26 13:04:51 +1000472A quote may be included in the command by quoting it with a backslash.
473This option might be useful
Damien Millerb83df8d2002-09-04 16:24:55 +1000474to restrict certain public keys to perform just a specific operation.
Damien Miller450a7a12000-03-26 13:04:51 +1000475An example might be a key that permits remote backups but nothing else.
Damien Miller30c3d422000-05-09 11:02:59 +1000476Note that the client may specify TCP/IP and/or X11
477forwarding unless they are explicitly prohibited.
Ben Lindstrom20daef72001-09-20 00:54:01 +0000478Note that this option applies to shell, command or subsystem execution.
Damien Miller32aa1441999-10-29 09:15:49 +1000479.It Cm environment="NAME=value"
480Specifies that the string is to be added to the environment when
Damien Miller450a7a12000-03-26 13:04:51 +1000481logging in using this key.
482Environment variables set this way
483override other default environment values.
484Multiple options of this type are permitted.
Ben Lindstrombd9bf382002-08-20 18:54:20 +0000485Environment processing is disabled by default and is
486controlled via the
487.Cm PermitUserEnvironment
488option.
Ben Lindstrom38b951c2001-12-06 17:47:47 +0000489This option is automatically disabled if
490.Cm UseLogin
491is enabled.
Damien Miller32aa1441999-10-29 09:15:49 +1000492.It Cm no-port-forwarding
493Forbids TCP/IP forwarding when this key is used for authentication.
Damien Miller450a7a12000-03-26 13:04:51 +1000494Any port forward requests by the client will return an error.
495This might be used, e.g., in connection with the
Damien Miller32aa1441999-10-29 09:15:49 +1000496.Cm command
497option.
498.It Cm no-X11-forwarding
499Forbids X11 forwarding when this key is used for authentication.
500Any X11 forward requests by the client will return an error.
501.It Cm no-agent-forwarding
502Forbids authentication agent forwarding when this key is used for
503authentication.
504.It Cm no-pty
505Prevents tty allocation (a request to allocate a pty will fail).
Damien Millera243fde2001-03-19 23:16:08 +1100506.It Cm permitopen="host:port"
Ben Lindstrom24643222001-06-25 05:08:11 +0000507Limit local
Damien Millera243fde2001-03-19 23:16:08 +1100508.Li ``ssh -L''
Ben Lindstrom4b3564e2001-04-10 02:41:56 +0000509port forwarding such that it may only connect to the specified host and
Ben Lindstromd71ba572001-09-12 18:03:31 +0000510port.
511IPv6 addresses can be specified with an alternative syntax:
Darren Tucker1f203942003-10-15 15:50:42 +1000512.Ar host Ns / Ns Ar port .
Ben Lindstromd71ba572001-09-12 18:03:31 +0000513Multiple
Damien Millera243fde2001-03-19 23:16:08 +1100514.Cm permitopen
Damien Millerfbf486b2003-05-23 18:44:23 +1000515options may be applied separated by commas.
516No pattern matching is performed on the specified hostnames,
517they must be literal domains or addresses.
Damien Miller32aa1441999-10-29 09:15:49 +1000518.El
519.Ss Examples
Darren Tucker1f203942003-10-15 15:50:42 +10005201024 33 12121...312314325 ylo@foo.bar
Damien Miller32aa1441999-10-29 09:15:49 +1000521.Pp
Darren Tucker1f203942003-10-15 15:50:42 +1000522from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23...2334 ylo@niksula
Damien Miller32aa1441999-10-29 09:15:49 +1000523.Pp
Darren Tucker1f203942003-10-15 15:50:42 +1000524command="dump /home",no-pty,no-port-forwarding 1024 33 23...2323 backup.hut.fi
Damien Millera243fde2001-03-19 23:16:08 +1100525.Pp
Darren Tucker1f203942003-10-15 15:50:42 +1000526permitopen="10.2.1.55:80",permitopen="10.2.1.56:25" 1024 33 23...2323
Damien Miller32aa1441999-10-29 09:15:49 +1000527.Sh SSH_KNOWN_HOSTS FILE FORMAT
Damien Miller22c77262000-04-13 12:26:34 +1000528The
Damien Millerffadc582003-02-24 11:52:26 +1100529.Pa /etc/ssh/ssh_known_hosts
Damien Miller22c77262000-04-13 12:26:34 +1000530and
Damien Miller167ea5d2005-05-26 12:04:02 +1000531.Pa ~/.ssh/known_hosts
Damien Miller450a7a12000-03-26 13:04:51 +1000532files contain host public keys for all known hosts.
533The global file should
534be prepared by the administrator (optional), and the per-user file is
Damien Miller942da032000-08-18 13:59:06 +1000535maintained automatically: whenever the user connects from an unknown host
Damien Miller450a7a12000-03-26 13:04:51 +1000536its key is added to the per-user file.
Damien Miller32aa1441999-10-29 09:15:49 +1000537.Pp
538Each line in these files contains the following fields: hostnames,
Damien Miller450a7a12000-03-26 13:04:51 +1000539bits, exponent, modulus, comment.
540The fields are separated by spaces.
Damien Miller32aa1441999-10-29 09:15:49 +1000541.Pp
Damien Miller31554322003-05-14 13:44:58 +1000542Hostnames is a comma-separated list of patterns
Damien Millerfbf486b2003-05-23 18:44:23 +1000543.Pf ( Ql \&*
544and
545.Ql \&?
Damien Miller049245d2003-05-14 13:44:42 +1000546act as
Damien Miller32aa1441999-10-29 09:15:49 +1000547wildcards); each pattern in turn is matched against the canonical host
548name (when authenticating a client) or against the user-supplied
Damien Miller450a7a12000-03-26 13:04:51 +1000549name (when authenticating a server).
550A pattern may also be preceded by
Damien Miller049245d2003-05-14 13:44:42 +1000551.Ql \&!
Damien Miller32aa1441999-10-29 09:15:49 +1000552to indicate negation: if the host name matches a negated
553pattern, it is not accepted (by that line) even if it matched another
554pattern on the line.
555.Pp
Damien Millere1776152005-03-01 21:47:37 +1100556Alternately, hostnames may be stored in a hashed form which hides host names
Damien Miller718fd4b2005-03-02 12:03:23 +1100557and addresses should the file's contents be disclosed.
558Hashed hostnames start with a
559.Ql |
Damien Millere1776152005-03-01 21:47:37 +1100560character.
561Only one hashed hostname may appear on a single line and none of the above
562negation or wildcard operators may be applied.
563.Pp
Damien Millere247cc42000-05-07 12:03:14 +1000564Bits, exponent, and modulus are taken directly from the RSA host key; they
Damien Miller32aa1441999-10-29 09:15:49 +1000565can be obtained, e.g., from
Damien Miller05eda432002-02-10 18:32:28 +1100566.Pa /etc/ssh/ssh_host_key.pub .
Damien Miller32aa1441999-10-29 09:15:49 +1000567The optional comment field continues to the end of the line, and is not used.
568.Pp
569Lines starting with
570.Ql #
571and empty lines are ignored as comments.
572.Pp
573When performing host authentication, authentication is accepted if any
Damien Miller450a7a12000-03-26 13:04:51 +1000574matching line has the proper key.
575It is thus permissible (but not
Damien Miller32aa1441999-10-29 09:15:49 +1000576recommended) to have several lines or different host keys for the same
Damien Miller450a7a12000-03-26 13:04:51 +1000577names.
578This will inevitably happen when short forms of host names
579from different domains are put in the file.
580It is possible
Damien Miller32aa1441999-10-29 09:15:49 +1000581that the files contain conflicting information; authentication is
582accepted if valid information can be found from either file.
583.Pp
584Note that the lines in these files are typically hundreds of characters
585long, and you definitely don't want to type in the host keys by hand.
586Rather, generate them by a script
Damien Miller22c77262000-04-13 12:26:34 +1000587or by taking
Damien Miller05eda432002-02-10 18:32:28 +1100588.Pa /etc/ssh/ssh_host_key.pub
Damien Miller32aa1441999-10-29 09:15:49 +1000589and adding the host names at the front.
590.Ss Examples
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000591.Bd -literal
Darren Tucker1f203942003-10-15 15:50:42 +1000592closenet,...,130.233.208.41 1024 37 159...93 closenet.hut.fi
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000593cvs.openbsd.org,199.185.137.3 ssh-rsa AAAA1234.....=
594.Ed
Damien Millere1776152005-03-01 21:47:37 +1100595.Bd -literal
596# A hashed hostname
597|1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa
598AAAA1234.....=
599.Ed
Damien Miller32aa1441999-10-29 09:15:49 +1000600.Sh FILES
601.Bl -tag -width Ds
Damien Miller05eda432002-02-10 18:32:28 +1100602.It Pa /etc/ssh/sshd_config
Damien Miller32aa1441999-10-29 09:15:49 +1000603Contains configuration data for
604.Nm sshd .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000605The file format and configuration options are described in
606.Xr sshd_config 5 .
Damien Miller05eda432002-02-10 18:32:28 +1100607.It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000608These three files contain the private parts of the host keys.
Ben Lindstromd7f5b512001-03-05 06:57:23 +0000609These files should only be owned by root, readable only by root, and not
Damien Miller32aa1441999-10-29 09:15:49 +1000610accessible to others.
611Note that
612.Nm
613does not start if this file is group/world-accessible.
Damien Miller05eda432002-02-10 18:32:28 +1100614.It Pa /etc/ssh/ssh_host_key.pub, /etc/ssh/ssh_host_dsa_key.pub, /etc/ssh/ssh_host_rsa_key.pub
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000615These three files contain the public parts of the host keys.
Ben Lindstromd7f5b512001-03-05 06:57:23 +0000616These files should be world-readable but writable only by
Damien Miller450a7a12000-03-26 13:04:51 +1000617root.
Ben Lindstromd7f5b512001-03-05 06:57:23 +0000618Their contents should match the respective private parts.
619These files are not
620really used for anything; they are provided for the convenience of
621the user so their contents can be copied to known hosts files.
622These files are created using
Damien Miller32aa1441999-10-29 09:15:49 +1000623.Xr ssh-keygen 1 .
Ben Lindstromae1c51c2001-06-25 04:14:59 +0000624.It Pa /etc/moduli
Damien Millere39cacc2000-11-29 12:18:44 +1100625Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange".
Damien Miller86247e22002-09-19 11:51:53 +1000626The file format is described in
627.Xr moduli 5 .
Ben Lindstrom624e3f22002-06-23 00:32:57 +0000628.It Pa /var/empty
629.Xr chroot 2
630directory used by
631.Nm
632during privilege separation in the pre-authentication phase.
633The directory should not contain any files and must be owned by root
634and not group or world-writable.
Damien Miller886c63a2000-01-20 23:13:36 +1100635.It Pa /var/run/sshd.pid
Damien Miller32aa1441999-10-29 09:15:49 +1000636Contains the process ID of the
637.Nm
638listening for connections (if there are several daemons running
Ben Lindstrom959de992002-06-23 00:35:25 +0000639concurrently for different ports, this contains the process ID of the one
Damien Miller450a7a12000-03-26 13:04:51 +1000640started last).
Damien Miller942da032000-08-18 13:59:06 +1000641The content of this file is not sensitive; it can be world-readable.
Damien Miller167ea5d2005-05-26 12:04:02 +1000642.It Pa ~/.ssh/authorized_keys
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000643Lists the public keys (RSA or DSA) that can be used to log into the user's account.
Damien Millere247cc42000-05-07 12:03:14 +1000644This file must be readable by root (which may on some machines imply
645it being world-readable if the user's home directory resides on an NFS
646volume).
647It is recommended that it not be accessible by others.
648The format of this file is described above.
649Users will place the contents of their
Ben Lindstromf96704d2001-06-25 04:17:12 +0000650.Pa identity.pub ,
Damien Millere247cc42000-05-07 12:03:14 +1000651.Pa id_dsa.pub
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000652and/or
653.Pa id_rsa.pub
Damien Millere247cc42000-05-07 12:03:14 +1000654files into this file, as described in
655.Xr ssh-keygen 1 .
Damien Miller167ea5d2005-05-26 12:04:02 +1000656.It Pa "/etc/ssh/ssh_known_hosts", "~/.ssh/known_hosts"
Damien Miller5ce662a1999-11-11 17:57:39 +1100657These files are consulted when using rhosts with RSA host
Ben Lindstromd6481ea2001-06-25 04:37:41 +0000658authentication or protocol version 2 hostbased authentication
659to check the public key of the host.
Damien Miller450a7a12000-03-26 13:04:51 +1000660The key must be listed in one of these files to be accepted.
Damien Miller33e511e1999-11-11 11:43:13 +1100661The client uses the same files
Ben Lindstromebd888d2001-03-05 05:49:29 +0000662to verify that it is connecting to the correct remote host.
Damien Miller450a7a12000-03-26 13:04:51 +1000663These files should be writable only by root/the owner.
Damien Miller05eda432002-02-10 18:32:28 +1100664.Pa /etc/ssh/ssh_known_hosts
Damien Miller32aa1441999-10-29 09:15:49 +1000665should be world-readable, and
Damien Miller167ea5d2005-05-26 12:04:02 +1000666.Pa ~/.ssh/known_hosts
Damien Millerffadc582003-02-24 11:52:26 +1100667can, but need not be, world-readable.
Damien Miller70a908e2005-03-01 21:17:09 +1100668.It Pa /etc/motd
669See
670.Xr motd 5 .
Damien Miller167ea5d2005-05-26 12:04:02 +1000671.It Pa ~/.hushlogin
Damien Miller70a908e2005-03-01 21:17:09 +1100672This file is used to suppress printing the last login time and
673.Pa /etc/motd ,
674if
675.Cm PrintLastLog
676and
677.Cm PrintMotd ,
678respectively,
679are enabled.
680It does not suppress printing of the banner specified by
681.Cm Banner .
Damien Miller32aa1441999-10-29 09:15:49 +1000682.It Pa /etc/nologin
Damien Miller22c77262000-04-13 12:26:34 +1000683If this file exists,
Damien Miller32aa1441999-10-29 09:15:49 +1000684.Nm
Damien Miller450a7a12000-03-26 13:04:51 +1000685refuses to let anyone except root log in.
686The contents of the file
Damien Miller32aa1441999-10-29 09:15:49 +1000687are displayed to anyone trying to log in, and non-root connections are
Damien Miller450a7a12000-03-26 13:04:51 +1000688refused.
689The file should be world-readable.
Damien Miller32aa1441999-10-29 09:15:49 +1000690.It Pa /etc/hosts.allow, /etc/hosts.deny
Ben Lindstrom6149a6c2001-10-03 17:15:32 +0000691Access controls that should be enforced by tcp-wrappers are defined here.
692Further details are described in
Damien Miller32aa1441999-10-29 09:15:49 +1000693.Xr hosts_access 5 .
Damien Miller167ea5d2005-05-26 12:04:02 +1000694.It Pa ~/.rhosts
Darren Tuckerdb693902004-08-29 16:37:24 +1000695This file is used during
696.Cm RhostsRSAAuthentication
697and
698.Cm HostbasedAuthentication
699and contains host-username pairs, separated by a space, one per
Damien Miller450a7a12000-03-26 13:04:51 +1000700line.
701The given user on the corresponding host is permitted to log in
Damien Millerffadc582003-02-24 11:52:26 +1100702without a password.
Damien Miller450a7a12000-03-26 13:04:51 +1000703The same file is used by rlogind and rshd.
Damien Miller32aa1441999-10-29 09:15:49 +1000704The file must
705be writable only by the user; it is recommended that it not be
706accessible by others.
707.Pp
Darren Tucker1f203942003-10-15 15:50:42 +1000708It is also possible to use netgroups in the file.
Damien Miller450a7a12000-03-26 13:04:51 +1000709Either host or user
Damien Miller32aa1441999-10-29 09:15:49 +1000710name may be of the form +@groupname to specify all hosts or all users
711in the group.
Damien Miller167ea5d2005-05-26 12:04:02 +1000712.It Pa ~/.shosts
Damien Miller32aa1441999-10-29 09:15:49 +1000713For ssh,
714this file is exactly the same as for
715.Pa .rhosts .
716However, this file is
717not used by rlogin and rshd, so using this permits access using SSH only.
Damien Miller942da032000-08-18 13:59:06 +1000718.It Pa /etc/hosts.equiv
Damien Miller32aa1441999-10-29 09:15:49 +1000719This file is used during
Darren Tuckerdb693902004-08-29 16:37:24 +1000720.Cm RhostsRSAAuthentication
721and
722.Cm HostbasedAuthentication
Damien Miller450a7a12000-03-26 13:04:51 +1000723authentication.
724In the simplest form, this file contains host names, one per line.
725Users on
Damien Miller32aa1441999-10-29 09:15:49 +1000726those hosts are permitted to log in without a password, provided they
Damien Miller450a7a12000-03-26 13:04:51 +1000727have the same user name on both machines.
728The host name may also be
Damien Miller32aa1441999-10-29 09:15:49 +1000729followed by a user name; such users are permitted to log in as
730.Em any
Damien Miller450a7a12000-03-26 13:04:51 +1000731user on this machine (except root).
732Additionally, the syntax
Damien Miller32aa1441999-10-29 09:15:49 +1000733.Dq +@group
Damien Miller450a7a12000-03-26 13:04:51 +1000734can be used to specify netgroups.
735Negated entries start with
Damien Miller32aa1441999-10-29 09:15:49 +1000736.Ql \&- .
737.Pp
738If the client host/user is successfully matched in this file, login is
739automatically permitted provided the client and server user names are the
Damien Miller450a7a12000-03-26 13:04:51 +1000740same.
Darren Tuckerdb693902004-08-29 16:37:24 +1000741Additionally, successful client host key authentication is required.
Damien Miller450a7a12000-03-26 13:04:51 +1000742This file must be writable only by root; it is recommended
Damien Miller32aa1441999-10-29 09:15:49 +1000743that it be world-readable.
744.Pp
745.Sy "Warning: It is almost never a good idea to use user names in"
746.Pa hosts.equiv .
747Beware that it really means that the named user(s) can log in as
748.Em anybody ,
749which includes bin, daemon, adm, and other accounts that own critical
Damien Miller450a7a12000-03-26 13:04:51 +1000750binaries and directories.
751Using a user name practically grants the user root access.
752The only valid use for user names that I can think
Damien Miller32aa1441999-10-29 09:15:49 +1000753of is in negative entries.
754.Pp
755Note that this warning also applies to rsh/rlogin.
Damien Miller886c63a2000-01-20 23:13:36 +1100756.It Pa /etc/shosts.equiv
Damien Miller32aa1441999-10-29 09:15:49 +1000757This is processed exactly as
758.Pa /etc/hosts.equiv .
759However, this file may be useful in environments that want to run both
760rsh/rlogin and ssh.
Damien Miller167ea5d2005-05-26 12:04:02 +1000761.It Pa ~/.ssh/environment
Damien Miller450a7a12000-03-26 13:04:51 +1000762This file is read into the environment at login (if it exists).
763It can only contain empty lines, comment lines (that start with
Damien Miller32aa1441999-10-29 09:15:49 +1000764.Ql # ) ,
Damien Miller450a7a12000-03-26 13:04:51 +1000765and assignment lines of the form name=value.
766The file should be writable
Damien Miller32aa1441999-10-29 09:15:49 +1000767only by the user; it need not be readable by anyone else.
Ben Lindstrombd9bf382002-08-20 18:54:20 +0000768Environment processing is disabled by default and is
769controlled via the
770.Cm PermitUserEnvironment
771option.
Damien Miller167ea5d2005-05-26 12:04:02 +1000772.It Pa ~/.ssh/rc
Damien Millerffadc582003-02-24 11:52:26 +1100773If this file exists, it is run with
774.Pa /bin/sh
775after reading the
Damien Miller450a7a12000-03-26 13:04:51 +1000776environment files but before starting the user's shell or command.
Ben Lindstroma11e2702002-04-05 22:18:48 +0000777It must not produce any output on stdout; stderr must be used
778instead.
779If X11 forwarding is in use, it will receive the "proto cookie" pair in
780its standard input (and
Damien Miller32aa1441999-10-29 09:15:49 +1000781.Ev DISPLAY
Ben Lindstroma11e2702002-04-05 22:18:48 +0000782in its environment).
783The script must call
Damien Miller32aa1441999-10-29 09:15:49 +1000784.Xr xauth 1
Ben Lindstroma11e2702002-04-05 22:18:48 +0000785because
786.Nm
787will not run xauth automatically to add X11 cookies.
Damien Miller32aa1441999-10-29 09:15:49 +1000788.Pp
789The primary purpose of this file is to run any initialization routines
790which may be needed before the user's home directory becomes
791accessible; AFS is a particular example of such an environment.
792.Pp
793This file will probably contain some initialization code followed by
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000794something similar to:
795.Bd -literal
Ben Lindstroma11e2702002-04-05 22:18:48 +0000796if read proto cookie && [ -n "$DISPLAY" ]; then
797 if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
798 # X11UseLocalhost=yes
Damien Millerdcbb6c22002-09-25 12:20:52 +1000799 echo add unix:`echo $DISPLAY |
Ben Lindstroma11e2702002-04-05 22:18:48 +0000800 cut -c11-` $proto $cookie
801 else
802 # X11UseLocalhost=no
Damien Millerdcbb6c22002-09-25 12:20:52 +1000803 echo add $DISPLAY $proto $cookie
804 fi | xauth -q -
Ben Lindstroma11e2702002-04-05 22:18:48 +0000805fi
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000806.Ed
Damien Miller32aa1441999-10-29 09:15:49 +1000807.Pp
808If this file does not exist,
Damien Miller05eda432002-02-10 18:32:28 +1100809.Pa /etc/ssh/sshrc
Damien Miller32aa1441999-10-29 09:15:49 +1000810is run, and if that
Ben Lindstroma11e2702002-04-05 22:18:48 +0000811does not exist either, xauth is used to add the cookie.
Damien Miller32aa1441999-10-29 09:15:49 +1000812.Pp
813This file should be writable only by the user, and need not be
814readable by anyone else.
Damien Miller05eda432002-02-10 18:32:28 +1100815.It Pa /etc/ssh/sshrc
Damien Miller32aa1441999-10-29 09:15:49 +1000816Like
Damien Miller167ea5d2005-05-26 12:04:02 +1000817.Pa ~/.ssh/rc .
Damien Miller32aa1441999-10-29 09:15:49 +1000818This can be used to specify
Damien Miller450a7a12000-03-26 13:04:51 +1000819machine-specific login-time initializations globally.
820This file should be writable only by root, and should be world-readable.
Damien Miller37023962000-07-11 17:31:38 +1000821.El
Damien Miller32aa1441999-10-29 09:15:49 +1000822.Sh SEE ALSO
Damien Miller32aa1441999-10-29 09:15:49 +1000823.Xr scp 1 ,
Damien Miller33804262001-02-04 23:20:18 +1100824.Xr sftp 1 ,
Damien Miller32aa1441999-10-29 09:15:49 +1000825.Xr ssh 1 ,
826.Xr ssh-add 1 ,
827.Xr ssh-agent 1 ,
828.Xr ssh-keygen 1 ,
Darren Tucker1f203942003-10-15 15:50:42 +1000829.Xr chroot 2 ,
830.Xr hosts_access 5 ,
Ben Lindstromc8e29ce2001-08-06 20:55:28 +0000831.Xr login.conf 5 ,
832.Xr moduli 5 ,
Ben Lindstrom9f049032002-06-21 00:59:05 +0000833.Xr sshd_config 5 ,
Darren Tucker1f203942003-10-15 15:50:42 +1000834.Xr inetd 8 ,
Ben Lindstromd2bf0d62001-06-25 04:10:54 +0000835.Xr sftp-server 8
Ben Lindstrom160ec622001-04-22 17:17:46 +0000836.Rs
837.%A T. Ylonen
838.%A T. Kivinen
839.%A M. Saarinen
840.%A T. Rinne
841.%A S. Lehtinen
842.%T "SSH Protocol Architecture"
Ben Lindstromf1813842002-03-27 17:18:31 +0000843.%N draft-ietf-secsh-architecture-12.txt
844.%D January 2002
Ben Lindstrom160ec622001-04-22 17:17:46 +0000845.%O work in progress material
846.Re
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000847.Rs
848.%A M. Friedl
849.%A N. Provos
850.%A W. A. Simpson
851.%T "Diffie-Hellman Group Exchange for the SSH Transport Layer Protocol"
Ben Lindstromf1813842002-03-27 17:18:31 +0000852.%N draft-ietf-secsh-dh-group-exchange-02.txt
853.%D January 2002
Ben Lindstromc65e6a02001-04-23 13:02:16 +0000854.%O work in progress material
855.Re
Damien Millerf1ce5052003-06-11 22:04:39 +1000856.Sh AUTHORS
857OpenSSH is a derivative of the original and free
858ssh 1.2.12 release by Tatu Ylonen.
859Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
860Theo de Raadt and Dug Song
861removed many bugs, re-added newer features and
862created OpenSSH.
863Markus Friedl contributed the support for SSH
864protocol versions 1.5 and 2.0.
865Niels Provos and Markus Friedl contributed support
866for privilege separation.