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authorColin Watson <cjwatson@debian.org>2004-03-01 02:25:32 +0000
committerColin Watson <cjwatson@debian.org>2004-03-01 02:25:32 +0000
commitea8116a11e3de70036dbc665ccb0d486cf89cac9 (patch)
treed73ccdff78d8608e156465af42e6a1b3527fb2d6 /sshd.8
parente39b311381a5609cc05acf298c42fba196dc524b (diff)
parentf5bda272678ec6dccaa5f29379cf60cb855018e8 (diff)
Merge 3.8p1 to the trunk. This builds and runs, but I haven't tested it
extensively yet. ProtocolKeepAlives is now just a compatibility alias for ServerAliveInterval.
Diffstat (limited to 'sshd.8')
-rw-r--r--sshd.885
1 files changed, 43 insertions, 42 deletions
diff --git a/sshd.8 b/sshd.8
index 27b1a3cf6..460263e92 100644
--- a/sshd.8
+++ b/sshd.8
@@ -34,7 +34,7 @@
34.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 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. 35.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36.\" 36.\"
37.\" $OpenBSD: sshd.8,v 1.199 2003/08/13 08:46:31 markus Exp $ 37.\" $OpenBSD: sshd.8,v 1.200 2003/10/08 08:27:36 jmc Exp $
38.Dd September 25, 1999 38.Dd September 25, 1999
39.Dt SSHD 8 39.Dt SSHD 8
40.Os 40.Os
@@ -44,7 +44,7 @@
44.Sh SYNOPSIS 44.Sh SYNOPSIS
45.Nm sshd 45.Nm sshd
46.Bk -words 46.Bk -words
47.Op Fl deiqtD46 47.Op Fl 46Ddeiqt
48.Op Fl b Ar bits 48.Op Fl b Ar bits
49.Op Fl f Ar config_file 49.Op Fl f Ar config_file
50.Op Fl g Ar login_grace_time 50.Op Fl g Ar login_grace_time
@@ -78,9 +78,7 @@ This implementation of
78supports both SSH protocol version 1 and 2 simultaneously. 78supports both SSH protocol version 1 and 2 simultaneously.
79.Nm 79.Nm
80works as follows: 80works as follows:
81.Pp
82.Ss SSH protocol version 1 81.Ss SSH protocol version 1
83.Pp
84Each host has a host-specific RSA key 82Each host has a host-specific RSA key
85(normally 1024 bits) used to identify the host. 83(normally 1024 bits) used to identify the host.
86Additionally, when 84Additionally, when
@@ -92,7 +90,7 @@ Whenever a client connects, the daemon responds with its public
92host and server keys. 90host and server keys.
93The client compares the 91The client compares the
94RSA host key against its own database to verify that it has not changed. 92RSA host key against its own database to verify that it has not changed.
95The client then generates a 256 bit random number. 93The client then generates a 256-bit random number.
96It encrypts this 94It encrypts this
97random number using both the host key and the server key, and sends 95random number using both the host key and the server key, and sends
98the encrypted number to the server. 96the encrypted number to the server.
@@ -107,9 +105,9 @@ to use from those offered by the server.
107.Pp 105.Pp
108Next, the server and the client enter an authentication dialog. 106Next, the server and the client enter an authentication dialog.
109The client tries to authenticate itself using 107The client tries to authenticate itself using
110.Pa .rhosts 108.Em .rhosts
111authentication, 109authentication,
112.Pa .rhosts 110.Em .rhosts
113authentication combined with RSA host 111authentication combined with RSA host
114authentication, RSA challenge-response authentication, or password 112authentication, RSA challenge-response authentication, or password
115based authentication. 113based authentication.
@@ -137,7 +135,8 @@ or
137.Ql \&*NP\&* 135.Ql \&*NP\&*
138). 136).
139.Pp 137.Pp
140Rhosts authentication is normally disabled 138.Em rhosts
139authentication is normally disabled
141because it is fundamentally insecure, but can be enabled in the server 140because it is fundamentally insecure, but can be enabled in the server
142configuration file if desired. 141configuration file if desired.
143System security is not improved unless 142System security is not improved unless
@@ -150,9 +149,7 @@ are disabled (thus completely disabling
150and 149and
151.Xr rsh 150.Xr rsh
152into the machine). 151into the machine).
153.Pp
154.Ss SSH protocol version 2 152.Ss SSH protocol version 2
155.Pp
156Version 2 works similarly: 153Version 2 works similarly:
157Each host has a host-specific key (RSA or DSA) used to identify the host. 154Each host has a host-specific key (RSA or DSA) used to identify the host.
158However, when the daemon starts, it does not generate a server key. 155However, when the daemon starts, it does not generate a server key.
@@ -160,7 +157,7 @@ Forward security is provided through a Diffie-Hellman key agreement.
160This key agreement results in a shared session key. 157This key agreement results in a shared session key.
161.Pp 158.Pp
162The rest of the session is encrypted using a symmetric cipher, currently 159The rest of the session is encrypted using a symmetric cipher, currently
163128 bit AES, Blowfish, 3DES, CAST128, Arcfour, 192 bit AES, or 256 bit AES. 160128-bit AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES.
164The client selects the encryption algorithm 161The client selects the encryption algorithm
165to use from those offered by the server. 162to use from those offered by the server.
166Additionally, session integrity is provided 163Additionally, session integrity is provided
@@ -171,9 +168,7 @@ Protocol version 2 provides a public key based
171user (PubkeyAuthentication) or 168user (PubkeyAuthentication) or
172client host (HostbasedAuthentication) authentication method, 169client host (HostbasedAuthentication) authentication method,
173conventional password authentication and challenge response based methods. 170conventional password authentication and challenge response based methods.
174.Pp
175.Ss Command execution and data forwarding 171.Ss Command execution and data forwarding
176.Pp
177If the client successfully authenticates itself, a dialog for 172If the client successfully authenticates itself, a dialog for
178preparing the session is entered. 173preparing the session is entered.
179At this time the client may request 174At this time the client may request
@@ -192,8 +187,9 @@ connections have been closed, the server sends command exit status to
192the client, and both sides exit. 187the client, and both sides exit.
193.Pp 188.Pp
194.Nm 189.Nm
195can be configured using command-line options or a configuration 190can be configured using command-line options or a configuration file
196file. 191(by default
192.Xr sshd_config 5 ) .
197Command-line options override values specified in the 193Command-line options override values specified in the
198configuration file. 194configuration file.
199.Pp 195.Pp
@@ -205,9 +201,23 @@ by executing itself with the name it was started as, i.e.,
205.Pp 201.Pp
206The options are as follows: 202The options are as follows:
207.Bl -tag -width Ds 203.Bl -tag -width Ds
204.It Fl 4
205Forces
206.Nm
207to use IPv4 addresses only.
208.It Fl 6
209Forces
210.Nm
211to use IPv6 addresses only.
208.It Fl b Ar bits 212.It Fl b Ar bits
209Specifies the number of bits in the ephemeral protocol version 1 213Specifies the number of bits in the ephemeral protocol version 1
210server key (default 768). 214server key (default 768).
215.It Fl D
216When this option is specified,
217.Nm
218will not detach and does not become a daemon.
219This allows easy monitoring of
220.Nm sshd .
211.It Fl d 221.It Fl d
212Debug mode. 222Debug mode.
213The server sends verbose debug output to the system 223The server sends verbose debug output to the system
@@ -267,7 +277,7 @@ be feasible.
267Specifies how often the ephemeral protocol version 1 server key is 277Specifies how often the ephemeral protocol version 1 server key is
268regenerated (default 3600 seconds, or one hour). 278regenerated (default 3600 seconds, or one hour).
269The motivation for regenerating the key fairly 279The motivation for regenerating the key fairly
270often is that the key is not stored anywhere, and after about an hour, 280often is that the key is not stored anywhere, and after about an hour
271it becomes impossible to recover the key for decrypting intercepted 281it becomes impossible to recover the key for decrypting intercepted
272communications even if the machine is cracked into or physically 282communications even if the machine is cracked into or physically
273seized. 283seized.
@@ -276,6 +286,8 @@ A value of zero indicates that the key will never be regenerated.
276Can be used to give options in the format used in the configuration file. 286Can be used to give options in the format used in the configuration file.
277This is useful for specifying options for which there is no separate 287This is useful for specifying options for which there is no separate
278command-line flag. 288command-line flag.
289For full details of the options, and their values, see
290.Xr sshd_config 5 .
279.It Fl p Ar port 291.It Fl p Ar port
280Specifies the port on which the server listens for connections 292Specifies the port on which the server listens for connections
281(default 22). 293(default 22).
@@ -328,20 +340,6 @@ USER@HOST pattern in
328.Cm AllowUsers 340.Cm AllowUsers
329or 341or
330.Cm DenyUsers . 342.Cm DenyUsers .
331.It Fl D
332When this option is specified
333.Nm
334will not detach and does not become a daemon.
335This allows easy monitoring of
336.Nm sshd .
337.It Fl 4
338Forces
339.Nm
340to use IPv4 addresses only.
341.It Fl 6
342Forces
343.Nm
344to use IPv6 addresses only.
345.El 343.El
346.Sh CONFIGURATION FILE 344.Sh CONFIGURATION FILE
347.Nm 345.Nm
@@ -378,9 +376,9 @@ Changes to run with normal user privileges.
378.It 376.It
379Sets up basic environment. 377Sets up basic environment.
380.It 378.It
381Reads 379Reads the file
382.Pa $HOME/.ssh/environment 380.Pa $HOME/.ssh/environment ,
383if it exists and users are allowed to change their environment. 381if it exists, and users are allowed to change their environment.
384See the 382See the
385.Cm PermitUserEnvironment 383.Cm PermitUserEnvironment
386option in 384option in
@@ -519,7 +517,7 @@ Limit local
519port forwarding such that it may only connect to the specified host and 517port forwarding such that it may only connect to the specified host and
520port. 518port.
521IPv6 addresses can be specified with an alternative syntax: 519IPv6 addresses can be specified with an alternative syntax:
522.Ar host/port . 520.Ar host Ns / Ns Ar port .
523Multiple 521Multiple
524.Cm permitopen 522.Cm permitopen
525options may be applied separated by commas. 523options may be applied separated by commas.
@@ -527,13 +525,13 @@ No pattern matching is performed on the specified hostnames,
527they must be literal domains or addresses. 525they must be literal domains or addresses.
528.El 526.El
529.Ss Examples 527.Ss Examples
5301024 33 12121.\|.\|.\|312314325 ylo@foo.bar 5281024 33 12121...312314325 ylo@foo.bar
531.Pp 529.Pp
532from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula 530from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23...2334 ylo@niksula
533.Pp 531.Pp
534command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi 532command="dump /home",no-pty,no-port-forwarding 1024 33 23...2323 backup.hut.fi
535.Pp 533.Pp
536permitopen="10.2.1.55:80",permitopen="10.2.1.56:25" 1024 33 23.\|.\|.\|2323 534permitopen="10.2.1.55:80",permitopen="10.2.1.56:25" 1024 33 23...2323
537.Sh SSH_KNOWN_HOSTS FILE FORMAT 535.Sh SSH_KNOWN_HOSTS FILE FORMAT
538The 536The
539.Pa /etc/ssh/ssh_known_hosts 537.Pa /etc/ssh/ssh_known_hosts
@@ -591,7 +589,7 @@ or by taking
591and adding the host names at the front. 589and adding the host names at the front.
592.Ss Examples 590.Ss Examples
593.Bd -literal 591.Bd -literal
594closenet,.\|.\|.\|,130.233.208.41 1024 37 159.\|.\|.93 closenet.hut.fi 592closenet,...,130.233.208.41 1024 37 159...93 closenet.hut.fi
595cvs.openbsd.org,199.185.137.3 ssh-rsa AAAA1234.....= 593cvs.openbsd.org,199.185.137.3 ssh-rsa AAAA1234.....=
596.Ed 594.Ed
597.Sh FILES 595.Sh FILES
@@ -650,7 +648,7 @@ and/or
650.Pa id_rsa.pub 648.Pa id_rsa.pub
651files into this file, as described in 649files into this file, as described in
652.Xr ssh-keygen 1 . 650.Xr ssh-keygen 1 .
653.It Pa "/etc/ssh/ssh_known_hosts" and "$HOME/.ssh/known_hosts" 651.It Pa "/etc/ssh/ssh_known_hosts", "$HOME/.ssh/known_hosts"
654These files are consulted when using rhosts with RSA host 652These files are consulted when using rhosts with RSA host
655authentication or protocol version 2 hostbased authentication 653authentication or protocol version 2 hostbased authentication
656to check the public key of the host. 654to check the public key of the host.
@@ -684,7 +682,7 @@ The file must
684be writable only by the user; it is recommended that it not be 682be writable only by the user; it is recommended that it not be
685accessible by others. 683accessible by others.
686.Pp 684.Pp
687If is also possible to use netgroups in the file. 685It is also possible to use netgroups in the file.
688Either host or user 686Either host or user
689name may be of the form +@groupname to specify all hosts or all users 687name may be of the form +@groupname to specify all hosts or all users
690in the group. 688in the group.
@@ -696,7 +694,7 @@ However, this file is
696not used by rlogin and rshd, so using this permits access using SSH only. 694not used by rlogin and rshd, so using this permits access using SSH only.
697.It Pa /etc/hosts.equiv 695.It Pa /etc/hosts.equiv
698This file is used during 696This file is used during
699.Pa .rhosts 697.Em rhosts
700authentication. 698authentication.
701In the simplest form, this file contains host names, one per line. 699In the simplest form, this file contains host names, one per line.
702Users on 700Users on
@@ -803,9 +801,12 @@ This file should be writable only by root, and should be world-readable.
803.Xr ssh-add 1 , 801.Xr ssh-add 1 ,
804.Xr ssh-agent 1 , 802.Xr ssh-agent 1 ,
805.Xr ssh-keygen 1 , 803.Xr ssh-keygen 1 ,
804.Xr chroot 2 ,
805.Xr hosts_access 5 ,
806.Xr login.conf 5 , 806.Xr login.conf 5 ,
807.Xr moduli 5 , 807.Xr moduli 5 ,
808.Xr sshd_config 5 , 808.Xr sshd_config 5 ,
809.Xr inetd 8 ,
809.Xr sftp-server 8 810.Xr sftp-server 8
810.Rs 811.Rs
811.%A T. Ylonen 812.%A T. Ylonen