3 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 .\" All rights reserved
7 .\" As far as I am concerned, the code I have written for this software
8 .\" can be used freely for any purpose. Any derived versions of this
9 .\" software must be clearly marked as such, and if the derived work is
10 .\" incompatible with the protocol description in the RFC file, it must be
11 .\" called by a name other than "ssh" or "Secure Shell".
13 .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
14 .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
15 .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
17 .\" Redistribution and use in source and binary forms, with or without
18 .\" modification, are permitted provided that the following conditions
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.
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.
37 .\" $OpenBSD: ssh.1,v 1.181 2003/12/16 15:49:51 markus Exp $
39 .Dd September 25, 1999
44 .Nd OpenSSH SSH client (remote login program)
47 .Op Fl 1246AaCfgkNnqsTtVvXxY
48 .Op Fl b Ar bind_address
49 .Op Fl c Ar cipher_spec
51 .Op Fl e Ar escape_char
52 .Op Fl F Ar configfile
53 .Op Fl i Ar identity_file
64 .Op Fl l Ar login_name
78 .Oo Ar user Ns @ Oc Ns Ar hostname
82 (SSH client) is a program for logging into a remote machine and for
83 executing commands on a remote machine.
84 It is intended to replace rlogin and rsh,
85 and provide secure encrypted communications between
86 two untrusted hosts over an insecure network.
87 X11 connections and arbitrary TCP/IP ports
88 can also be forwarded over the secure channel.
91 connects and logs into the specified
97 his/her identity to the remote machine using one of several methods
98 depending on the protocol version used.
104 is executed on the remote host instead of a login shell.
105 .Ss SSH protocol version 1
106 First, if the machine the user logs in from is listed in
109 .Pa /etc/ssh/shosts.equiv
110 on the remote machine, and the user names are
111 the same on both sides, the user is immediately permitted to log in.
116 exists in the user's home directory on the
117 remote machine and contains a line containing the name of the client
118 machine and the name of the user on that machine, the user is
120 This form of authentication alone is normally not
121 allowed by the server because it is not secure.
123 The second authentication method is the
127 method combined with RSA-based host authentication.
128 It means that if the login would be permitted by
131 .Pa /etc/hosts.equiv ,
133 .Pa /etc/ssh/shosts.equiv ,
134 and if additionally the server can verify the client's
136 .Pa /etc/ssh/ssh_known_hosts
138 .Pa $HOME/.ssh/known_hosts
141 section), only then is login permitted.
142 This authentication method closes security holes due to IP
143 spoofing, DNS spoofing and routing spoofing.
144 [Note to the administrator:
145 .Pa /etc/hosts.equiv ,
147 and the rlogin/rsh protocol in general, are inherently insecure and should be
148 disabled if security is desired.]
150 As a third authentication method,
152 supports RSA based authentication.
153 The scheme is based on public-key cryptography: there are cryptosystems
154 where encryption and decryption are done using separate keys, and it
155 is not possible to derive the decryption key from the encryption key.
156 RSA is one such system.
157 The idea is that each user creates a public/private
158 key pair for authentication purposes.
159 The server knows the public key, and only the user knows the private key.
162 .Pa $HOME/.ssh/authorized_keys
163 lists the public keys that are permitted for logging in.
164 When the user logs in, the
166 program tells the server which key pair it would like to use for
168 The server checks if this key is permitted, and if so,
169 sends the user (actually the
171 program running on behalf of the user) a challenge, a random number,
172 encrypted by the user's public key.
173 The challenge can only be decrypted using the proper private key.
174 The user's client then decrypts the challenge using the private key,
175 proving that he/she knows the private key
176 but without disclosing it to the server.
179 implements the RSA authentication protocol automatically.
180 The user creates his/her RSA key pair by running
182 This stores the private key in
183 .Pa $HOME/.ssh/identity
184 and stores the public key in
185 .Pa $HOME/.ssh/identity.pub
186 in the user's home directory.
187 The user should then copy the
190 .Pa $HOME/.ssh/authorized_keys
191 in his/her home directory on the remote machine (the
193 file corresponds to the conventional
195 file, and has one key
196 per line, though the lines can be very long).
197 After this, the user can log in without giving the password.
198 RSA authentication is much more secure than
202 The most convenient way to use RSA authentication may be with an
203 authentication agent.
206 for more information.
208 If other authentication methods fail,
210 prompts the user for a password.
211 The password is sent to the remote
212 host for checking; however, since all communications are encrypted,
213 the password cannot be seen by someone listening on the network.
214 .Ss SSH protocol version 2
215 When a user connects using protocol version 2,
216 similar authentication methods are available.
217 Using the default values for
218 .Cm PreferredAuthentications ,
219 the client will try to authenticate first using the hostbased method;
220 if this method fails, public key authentication is attempted,
221 and finally if this method fails, keyboard-interactive and
222 password authentication are tried.
224 The public key method is similar to RSA authentication described
225 in the previous section and allows the RSA or DSA algorithm to be used:
226 The client uses his private key,
227 .Pa $HOME/.ssh/id_dsa
229 .Pa $HOME/.ssh/id_rsa ,
230 to sign the session identifier and sends the result to the server.
231 The server checks whether the matching public key is listed in
232 .Pa $HOME/.ssh/authorized_keys
233 and grants access if both the key is found and the signature is correct.
234 The session identifier is derived from a shared Diffie-Hellman value
235 and is only known to the client and the server.
237 If public key authentication fails or is not available, a password
238 can be sent encrypted to the remote host to prove the user's identity.
242 supports hostbased or challenge response authentication.
244 Protocol 2 provides additional mechanisms for confidentiality
245 (the traffic is encrypted using 3DES, Blowfish, CAST128 or Arcfour)
246 and integrity (hmac-md5, hmac-sha1).
247 Note that protocol 1 lacks a strong mechanism for ensuring the
248 integrity of the connection.
249 .Ss Login session and remote execution
250 When the user's identity has been accepted by the server, the server
251 either executes the given command, or logs into the machine and gives
252 the user a normal shell on the remote machine.
253 All communication with
254 the remote command or shell will be automatically encrypted.
256 If a pseudo-terminal has been allocated (normal login session), the
257 user may use the escape characters noted below.
259 If no pseudo-tty has been allocated,
260 the session is transparent and can be used to reliably transfer binary data.
261 On most systems, setting the escape character to
263 will also make the session transparent even if a tty is used.
265 The session terminates when the command or shell on the remote
266 machine exits and all X11 and TCP/IP connections have been closed.
267 The exit status of the remote program is returned as the exit status of
269 .Ss Escape Characters
270 When a pseudo-terminal has been requested,
272 supports a number of functions through the use of an escape character.
274 A single tilde character can be sent as
276 or by following the tilde by a character other than those described below.
277 The escape character must always follow a newline to be interpreted as
279 The escape character can be changed in configuration files using the
281 configuration directive or on the command line by the
285 The supported escapes (assuming the default
295 List forwarded connections.
299 at logout when waiting for forwarded connection / X11 sessions to terminate.
301 Display a list of escape characters.
303 Send a BREAK to the remote system
304 (only useful for SSH protocol version 2 and if the peer supports it).
306 Open command line (only useful for adding port forwardings using the
312 Request rekeying of the connection
313 (only useful for SSH protocol version 2 and if the peer supports it).
315 .Ss X11 and TCP forwarding
320 (or see the description of the
324 options described later)
325 and the user is using X11 (the
327 environment variable is set), the connection to the X11 display is
328 automatically forwarded to the remote side in such a way that any X11
329 programs started from the shell (or command) will go through the
330 encrypted channel, and the connection to the real X server will be made
331 from the local machine.
332 The user should not manually set
334 Forwarding of X11 connections can be
335 configured on the command line or in configuration files.
336 Take note that X11 forwarding can represent a security hazard.
342 will point to the server machine, but with a display number greater than zero.
343 This is normal, and happens because
347 X server on the server machine for forwarding the
348 connections over the encrypted channel.
351 will also automatically set up Xauthority data on the server machine.
352 For this purpose, it will generate a random authorization cookie,
353 store it in Xauthority on the server, and verify that any forwarded
354 connections carry this cookie and replace it by the real cookie when
355 the connection is opened.
356 The real authentication cookie is never
357 sent to the server machine (and no cookies are sent in the plain).
363 (or see the description of the
367 options described later) and
368 the user is using an authentication agent, the connection to the agent
369 is automatically forwarded to the remote side.
371 Forwarding of arbitrary TCP/IP connections over the secure channel can
372 be specified either on the command line or in a configuration file.
373 One possible application of TCP/IP forwarding is a secure connection to an
374 electronic purse; another is going through firewalls.
375 .Ss Server authentication
377 automatically maintains and checks a database containing
378 identifications for all hosts it has ever been used with.
379 Host keys are stored in
380 .Pa $HOME/.ssh/known_hosts
381 in the user's home directory.
382 Additionally, the file
383 .Pa /etc/ssh/ssh_known_hosts
384 is automatically checked for known hosts.
385 Any new hosts are automatically added to the user's file.
386 If a host's identification ever changes,
388 warns about this and disables password authentication to prevent a
389 trojan horse from getting the user's password.
390 Another purpose of this mechanism is to prevent man-in-the-middle attacks
391 which could otherwise be used to circumvent the encryption.
393 .Cm StrictHostKeyChecking
394 option can be used to prevent logins to machines whose
395 host key is not known or has changed.
397 The options are as follows:
402 to try protocol version 1 only.
406 to try protocol version 2 only.
410 to use IPv4 addresses only.
414 to use IPv6 addresses only.
416 Enables forwarding of the authentication agent connection.
417 This can also be specified on a per-host basis in a configuration file.
419 Agent forwarding should be enabled with caution.
420 Users with the ability to bypass file permissions on the remote host
421 (for the agent's Unix-domain socket)
422 can access the local agent through the forwarded connection.
423 An attacker cannot obtain key material from the agent,
424 however they can perform operations on the keys that enable them to
425 authenticate using the identities loaded into the agent.
427 Disables forwarding of the authentication agent connection.
428 .It Fl b Ar bind_address
429 Specify the interface to transmit from on machines with multiple
430 interfaces or aliased addresses.
432 Requests compression of all data (including stdin, stdout, stderr, and
433 data for forwarded X11 and TCP/IP connections).
434 The compression algorithm is the same used by
438 can be controlled by the
440 option for protocol version 1.
441 Compression is desirable on modem lines and other
442 slow connections, but will only slow down things on fast networks.
443 The default value can be set on a host-by-host basis in the
444 configuration files; see the
447 .It Fl c Ar blowfish | 3des | des
448 Selects the cipher to use for encrypting the session.
451 It is believed to be secure.
453 (triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
455 is a fast block cipher; it appears very secure and is much faster than
458 is only supported in the
460 client for interoperability with legacy protocol 1 implementations
461 that do not support the
464 Its use is strongly discouraged due to cryptographic weaknesses.
465 .It Fl c Ar cipher_spec
466 Additionally, for protocol version 2 a comma-separated list of ciphers can
467 be specified in order of preference.
470 for more information.
474 application-level port forwarding.
475 This works by allocating a socket to listen to
477 on the local side, and whenever a connection is made to this port, the
478 connection is forwarded over the secure channel, and the application
479 protocol is then used to determine where to connect to from the
481 Currently the SOCKS4 and SOCKS5 protocols are supported, and
483 will act as a SOCKS server.
484 Only root can forward privileged ports.
485 Dynamic port forwardings can also be specified in the configuration file.
486 .It Fl e Ar ch | ^ch | none
487 Sets the escape character for sessions with a pty (default:
489 The escape character is only recognized at the beginning of a line.
490 The escape character followed by a dot
492 closes the connection;
493 followed by control-Z suspends the connection;
494 and followed by itself sends the escape character once.
495 Setting the character to
497 disables any escapes and makes the session fully transparent.
498 .It Fl F Ar configfile
499 Specifies an alternative per-user configuration file.
500 If a configuration file is given on the command line,
501 the system-wide configuration file
502 .Pq Pa /etc/ssh/ssh_config
504 The default for the per-user configuration file is
505 .Pa $HOME/.ssh/config .
509 to go to background just before command execution.
512 is going to ask for passwords or passphrases, but the user
513 wants it in the background.
516 The recommended way to start X11 programs at a remote site is with
518 .Ic ssh -f host xterm .
520 Allows remote hosts to connect to local forwarded ports.
521 .It Fl I Ar smartcard_device
522 Specifies which smartcard device to use.
523 The argument is the device
525 should use to communicate with a smartcard used for storing the user's
527 .It Fl i Ar identity_file
528 Selects a file from which the identity (private key) for
529 RSA or DSA authentication is read.
531 .Pa $HOME/.ssh/identity
532 for protocol version 1, and
533 .Pa $HOME/.ssh/id_rsa
535 .Pa $HOME/.ssh/id_dsa
536 for protocol version 2.
537 Identity files may also be specified on
538 a per-host basis in the configuration file.
539 It is possible to have multiple
541 options (and multiple identities specified in
542 configuration files).
544 Disables forwarding (delegation) of GSSAPI credentials to the server.
547 .Ar port : host : hostport
550 Specifies that the given port on the local (client) host is to be
551 forwarded to the given host and port on the remote side.
552 This works by allocating a socket to listen to
554 on the local side, and whenever a connection is made to this port, the
555 connection is forwarded over the secure channel, and a connection is
560 from the remote machine.
561 Port forwardings can also be specified in the configuration file.
562 Only root can forward privileged ports.
563 IPv6 addresses can be specified with an alternative syntax:
566 .Ar port No / Ar host No /
570 .It Fl l Ar login_name
571 Specifies the user to log in as on the remote machine.
572 This also may be specified on a per-host basis in the configuration file.
574 Additionally, for protocol version 2 a comma-separated list of MAC
575 (message authentication code) algorithms can
576 be specified in order of preference.
579 keyword for more information.
581 Do not execute a remote command.
582 This is useful for just forwarding ports
583 (protocol version 2 only).
587 (actually, prevents reading from stdin).
588 This must be used when
590 is run in the background.
591 A common trick is to use this to run X11 programs on a remote machine.
593 .Ic ssh -n shadows.cs.hut.fi emacs &
594 will start an emacs on shadows.cs.hut.fi, and the X11
595 connection will be automatically forwarded over an encrypted channel.
598 program will be put in the background.
599 (This does not work if
601 needs to ask for a password or passphrase; see also the
605 Can be used to give options in the format used in the configuration file.
606 This is useful for specifying options for which there is no separate
608 For full details of the options listed below, and their possible values, see
611 .Bl -tag -width Ds -offset indent -compact
615 .It ChallengeResponseAuthentication
619 .It ClearAllForwardings
622 .It ConnectionAttempts
623 .It ConnectionTimeout
628 .It ForwardX11Trusted
630 .It GlobalKnownHostsFile
631 .It GSSAPIAuthentication
632 .It GSSAPIDelegateCredentials
634 .It HostbasedAuthentication
635 .It HostKeyAlgorithms
642 .It NoHostAuthenticationForLocalhost
643 .It NumberOfPasswordPrompts
644 .It PasswordAuthentication
646 .It PreferredAuthentications
649 .It PubkeyAuthentication
651 .It RhostsRSAAuthentication
652 .It RSAAuthentication
653 .It ServerAliveInterval
654 .It ServerAliveCountMax
656 .It StrictHostKeyChecking
658 .It UsePrivilegedPort
660 .It UserKnownHostsFile
665 Port to connect to on the remote host.
666 This can be specified on a
667 per-host basis in the configuration file.
670 Causes all warning and diagnostic messages to be suppressed.
673 .Ar port : host : hostport
676 Specifies that the given port on the remote (server) host is to be
677 forwarded to the given host and port on the local side.
678 This works by allocating a socket to listen to
680 on the remote side, and whenever a connection is made to this port, the
681 connection is forwarded over the secure channel, and a connection is
686 from the local machine.
687 Port forwardings can also be specified in the configuration file.
688 Privileged ports can be forwarded only when
689 logging in as root on the remote machine.
690 IPv6 addresses can be specified with an alternative syntax:
693 .Ar port No / Ar host No /
698 May be used to request invocation of a subsystem on the remote system.
699 Subsystems are a feature of the SSH2 protocol which facilitate the use
700 of SSH as a secure transport for other applications (eg.\&
702 The subsystem is specified as the remote command.
704 Disable pseudo-tty allocation.
706 Force pseudo-tty allocation.
707 This can be used to execute arbitrary
708 screen-based programs on a remote machine, which can be very useful,
709 e.g., when implementing menu services.
712 options force tty allocation, even if
716 Display the version number and exit.
721 to print debugging messages about its progress.
723 debugging connection, authentication, and configuration problems.
726 options increase the verbosity.
729 Enables X11 forwarding.
730 This can also be specified on a per-host basis in a configuration file.
732 X11 forwarding should be enabled with caution.
733 Users with the ability to bypass file permissions on the remote host
734 (for the user's X authorization database)
735 can access the local X11 display through the forwarded connection.
736 An attacker may then be able to perform activities such as keystroke monitoring.
738 Disables X11 forwarding.
740 Enables trusted X11 forwarding.
742 .Sh CONFIGURATION FILES
744 may additionally obtain configuration data from
745 a per-user configuration file and a system-wide configuration file.
746 The file format and configuration options are described in
750 will normally set the following environment variables:
751 .Bl -tag -width LOGNAME
755 variable indicates the location of the X11 server.
756 It is automatically set by
758 to point to a value of the form
760 where hostname indicates
761 the host where the shell runs, and n is an integer \*(Ge 1.
763 uses this special value to forward X11 connections over the secure
765 The user should normally not set
768 will render the X11 connection insecure (and will require the user to
769 manually copy any required authorization cookies).
771 Set to the path of the user's home directory.
775 set for compatibility with systems that use this variable.
777 Set to the path of the user's mailbox.
781 as specified when compiling
786 needs a passphrase, it will read the passphrase from the current
787 terminal if it was run from a terminal.
790 does not have a terminal associated with it but
794 are set, it will execute the program specified by
796 and open an X11 window to read the passphrase.
797 This is particularly useful when calling
802 (Note that on some machines it
803 may be necessary to redirect the input from
807 Identifies the path of a unix-domain socket used to communicate with the
809 .It Ev SSH_CONNECTION
810 Identifies the client and server ends of the connection.
811 The variable contains
812 four space-separated values: client ip-address, client port number,
813 server ip-address and server port number.
814 .It Ev SSH_ORIGINAL_COMMAND
815 The variable contains the original command line if a forced command
817 It can be used to extract the original arguments.
819 This is set to the name of the tty (path to the device) associated
820 with the current shell or command.
821 If the current session has no tty,
822 this variable is not set.
824 The timezone variable is set to indicate the present timezone if it
825 was set when the daemon was started (i.e., the daemon passes the value
826 on to new connections).
828 Set to the name of the user logging in.
834 .Pa $HOME/.ssh/environment ,
835 and adds lines of the format
837 to the environment if the file exists and if users are allowed to
838 change their environment.
839 For more information, see the
840 .Cm PermitUserEnvironment
845 .It Pa $HOME/.ssh/known_hosts
846 Records host keys for all hosts the user has logged into that are not
848 .Pa /etc/ssh/ssh_known_hosts .
851 .It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa, $HOME/.ssh/id_rsa
852 Contains the authentication identity of the user.
853 They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
855 contain sensitive data and should be readable by the user but not
856 accessible by others (read/write/execute).
859 ignores a private key file if it is accessible by others.
860 It is possible to specify a passphrase when
861 generating the key; the passphrase will be used to encrypt the
862 sensitive part of this file using 3DES.
863 .It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub, $HOME/.ssh/id_rsa.pub
864 Contains the public key for authentication (public part of the
865 identity file in human-readable form).
867 .Pa $HOME/.ssh/identity.pub
868 file should be added to the file
869 .Pa $HOME/.ssh/authorized_keys
871 where the user wishes to log in using protocol version 1 RSA authentication.
873 .Pa $HOME/.ssh/id_dsa.pub
875 .Pa $HOME/.ssh/id_rsa.pub
876 file should be added to
877 .Pa $HOME/.ssh/authorized_keys
879 where the user wishes to log in using protocol version 2 DSA/RSA authentication.
881 sensitive and can (but need not) be readable by anyone.
883 never used automatically and are not necessary; they are only provided for
884 the convenience of the user.
885 .It Pa $HOME/.ssh/config
886 This is the per-user configuration file.
887 The file format and configuration options are described in
889 .It Pa $HOME/.ssh/authorized_keys
890 Lists the public keys (RSA/DSA) that can be used for logging in as this user.
891 The format of this file is described in the
894 In the simplest form the format is the same as the
897 This file is not highly sensitive, but the recommended
898 permissions are read/write for the user, and not accessible by others.
899 .It Pa /etc/ssh/ssh_known_hosts
900 Systemwide list of known host keys.
901 This file should be prepared by the
902 system administrator to contain the public host keys of all machines in the
904 This file should be world-readable.
906 public keys, one per line, in the following format (fields separated
907 by spaces): system name, public key and optional comment field.
908 When different names are used
909 for the same machine, all such names should be listed, separated by
911 The format is described in the
915 The canonical system name (as returned by name servers) is used by
917 to verify the client host when logging in; other names are needed because
919 does not convert the user-supplied name to a canonical name before
920 checking the key, because someone with access to the name servers
921 would then be able to fool host authentication.
922 .It Pa /etc/ssh/ssh_config
923 Systemwide configuration file.
924 The file format and configuration options are described in
926 .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key
927 These three files contain the private parts of the host keys
929 .Cm RhostsRSAAuthentication
931 .Cm HostbasedAuthentication .
932 If the protocol version 1
933 .Cm RhostsRSAAuthentication
936 must be setuid root, since the host key is readable only by root.
937 For protocol version 2,
941 to access the host keys for
942 .Cm HostbasedAuthentication .
943 This eliminates the requirement that
945 be setuid root when that authentication method is used.
952 authentication to list the
953 host/user pairs that are permitted to log in.
954 (Note that this file is
955 also used by rlogin and rsh, which makes using this file insecure.)
956 Each line of the file contains a host name (in the canonical form
957 returned by name servers), and then a user name on that host,
958 separated by a space.
959 On some machines this file may need to be
960 world-readable if the user's home directory is on a NFS partition,
964 Additionally, this file must be owned by the user,
965 and must not have write permissions for anyone else.
967 permission for most machines is read/write for the user, and not
968 accessible by others.
972 will be installed so that it requires successful RSA host
973 authentication before permitting
976 If the server machine does not have the client's host key in
977 .Pa /etc/ssh/ssh_known_hosts ,
979 .Pa $HOME/.ssh/known_hosts .
980 The easiest way to do this is to
981 connect back to the client from the server machine using ssh; this
982 will automatically add the host key to
983 .Pa $HOME/.ssh/known_hosts .
985 This file is used exactly the same way as
988 having this file is to be able to use rhosts authentication with
990 without permitting login with
994 .It Pa /etc/hosts.equiv
995 This file is used during
999 canonical hosts names, one per line (the full format is described in the
1002 If the client host is found in this file, login is
1003 automatically permitted provided client and server user names are the
1005 Additionally, successful RSA host authentication is normally
1007 This file should only be writable by root.
1008 .It Pa /etc/ssh/shosts.equiv
1009 This file is processed exactly as
1010 .Pa /etc/hosts.equiv .
1011 This file may be useful to permit logins using
1013 but not using rsh/rlogin.
1014 .It Pa /etc/ssh/sshrc
1015 Commands in this file are executed by
1017 when the user logs in just before the user's shell (or command) is started.
1020 manual page for more information.
1021 .It Pa $HOME/.ssh/rc
1022 Commands in this file are executed by
1024 when the user logs in just before the user's shell (or command) is
1028 manual page for more information.
1029 .It Pa $HOME/.ssh/environment
1030 Contains additional definitions for environment variables, see section
1036 exits with the exit status of the remote command or with 255
1037 if an error occurred.
1057 .%T "SSH Protocol Architecture"
1058 .%N draft-ietf-secsh-architecture-12.txt
1060 .%O work in progress material
1063 OpenSSH is a derivative of the original and free
1064 ssh 1.2.12 release by Tatu Ylonen.
1065 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1066 Theo de Raadt and Dug Song
1067 removed many bugs, re-added newer features and
1069 Markus Friedl contributed the support for SSH
1070 protocol versions 1.5 and 2.0.
projects / FreeBSD / FreeBSD.git / blob