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 1.186 2004/05/21 11:33:11 djm Exp $
38 .Dd September 25, 1999
43 .Nd OpenSSH SSH client (remote login program)
46 .Op Fl 1246AaCfgkNnqsTtVvXxY
47 .Op Fl b Ar bind_address
48 .Op Fl c Ar cipher_spec
50 .Op Fl e Ar escape_char
51 .Op Fl F Ar configfile
52 .Op Fl i Ar identity_file
63 .Op Fl l Ar login_name
77 .Oo Ar user Ns @ Oc Ns Ar hostname
81 (SSH client) is a program for logging into a remote machine and for
82 executing commands on a remote machine.
83 It is intended to replace rlogin and rsh,
84 and provide secure encrypted communications between
85 two untrusted hosts over an insecure network.
86 X11 connections and arbitrary TCP/IP ports
87 can also be forwarded over the secure channel.
90 connects and logs into the specified
96 his/her identity to the remote machine using one of several methods
97 depending on the protocol version used.
103 is executed on the remote host instead of a login shell.
104 .Ss SSH protocol version 1
105 First, if the machine the user logs in from is listed in
108 .Pa /etc/shosts.equiv
109 on the remote machine, and the user names are
110 the same on both sides, the user is immediately permitted to log in.
115 exists in the user's home directory on the
116 remote machine and contains a line containing the name of the client
117 machine and the name of the user on that machine, the user is
119 This form of authentication alone is normally not
120 allowed by the server because it is not secure.
122 The second authentication method is the
126 method combined with RSA-based host authentication.
127 It means that if the login would be permitted by
130 .Pa /etc/hosts.equiv ,
132 .Pa /etc/shosts.equiv ,
133 and if additionally the server can verify the client's
135 .Pa /etc/ssh/ssh_known_hosts
137 .Pa $HOME/.ssh/known_hosts
140 section), only then is login permitted.
141 This authentication method closes security holes due to IP
142 spoofing, DNS spoofing and routing spoofing.
143 [Note to the administrator:
144 .Pa /etc/hosts.equiv ,
146 and the rlogin/rsh protocol in general, are inherently insecure and should be
147 disabled if security is desired.]
149 As a third authentication method,
151 supports RSA based authentication.
152 The scheme is based on public-key cryptography: there are cryptosystems
153 where encryption and decryption are done using separate keys, and it
154 is not possible to derive the decryption key from the encryption key.
155 RSA is one such system.
156 The idea is that each user creates a public/private
157 key pair for authentication purposes.
158 The server knows the public key, and only the user knows the private key.
161 .Pa $HOME/.ssh/authorized_keys
162 lists the public keys that are permitted for logging in.
163 When the user logs in, the
165 program tells the server which key pair it would like to use for
167 The server checks if this key is permitted, and if so,
168 sends the user (actually the
170 program running on behalf of the user) a challenge, a random number,
171 encrypted by the user's public key.
172 The challenge can only be decrypted using the proper private key.
173 The user's client then decrypts the challenge using the private key,
174 proving that he/she knows the private key
175 but without disclosing it to the server.
178 implements the RSA authentication protocol automatically.
179 The user creates his/her RSA key pair by running
181 This stores the private key in
182 .Pa $HOME/.ssh/identity
183 and stores the public key in
184 .Pa $HOME/.ssh/identity.pub
185 in the user's home directory.
186 The user should then copy the
189 .Pa $HOME/.ssh/authorized_keys
190 in his/her home directory on the remote machine (the
192 file corresponds to the conventional
194 file, and has one key
195 per line, though the lines can be very long).
196 After this, the user can log in without giving the password.
197 RSA authentication is much more secure than
201 The most convenient way to use RSA authentication may be with an
202 authentication agent.
205 for more information.
207 If other authentication methods fail,
209 prompts the user for a password.
210 The password is sent to the remote
211 host for checking; however, since all communications are encrypted,
212 the password cannot be seen by someone listening on the network.
213 .Ss SSH protocol version 2
214 When a user connects using protocol version 2,
215 similar authentication methods are available.
216 Using the default values for
217 .Cm PreferredAuthentications ,
218 the client will try to authenticate first using the hostbased method;
219 if this method fails, public key authentication is attempted,
220 and finally if this method fails, keyboard-interactive and
221 password authentication are tried.
223 The public key method is similar to RSA authentication described
224 in the previous section and allows the RSA or DSA algorithm to be used:
225 The client uses his private key,
226 .Pa $HOME/.ssh/id_dsa
228 .Pa $HOME/.ssh/id_rsa ,
229 to sign the session identifier and sends the result to the server.
230 The server checks whether the matching public key is listed in
231 .Pa $HOME/.ssh/authorized_keys
232 and grants access if both the key is found and the signature is correct.
233 The session identifier is derived from a shared Diffie-Hellman value
234 and is only known to the client and the server.
236 If public key authentication fails or is not available, a password
237 can be sent encrypted to the remote host to prove the user's identity.
241 supports hostbased or challenge response authentication.
243 Protocol 2 provides additional mechanisms for confidentiality
244 (the traffic is encrypted using 3DES, Blowfish, CAST128 or Arcfour)
245 and integrity (hmac-md5, hmac-sha1).
246 Note that protocol 1 lacks a strong mechanism for ensuring the
247 integrity of the connection.
248 .Ss Login session and remote execution
249 When the user's identity has been accepted by the server, the server
250 either executes the given command, or logs into the machine and gives
251 the user a normal shell on the remote machine.
252 All communication with
253 the remote command or shell will be automatically encrypted.
255 If a pseudo-terminal has been allocated (normal login session), the
256 user may use the escape characters noted below.
258 If no pseudo-tty has been allocated,
259 the session is transparent and can be used to reliably transfer binary data.
260 On most systems, setting the escape character to
262 will also make the session transparent even if a tty is used.
264 The session terminates when the command or shell on the remote
265 machine exits and all X11 and TCP/IP connections have been closed.
266 The exit status of the remote program is returned as the exit status of
268 .Ss Escape Characters
269 When a pseudo-terminal has been requested,
271 supports a number of functions through the use of an escape character.
273 A single tilde character can be sent as
275 or by following the tilde by a character other than those described below.
276 The escape character must always follow a newline to be interpreted as
278 The escape character can be changed in configuration files using the
280 configuration directive or on the command line by the
284 The supported escapes (assuming the default
294 List forwarded connections.
298 at logout when waiting for forwarded connection / X11 sessions to terminate.
300 Display a list of escape characters.
302 Send a BREAK to the remote system
303 (only useful for SSH protocol version 2 and if the peer supports it).
306 Currently this allows the addition of port forwardings using the
311 It also allows the cancellation of existing remote port-forwardings
314 Basic help is available, using the
318 Request rekeying of the connection
319 (only useful for SSH protocol version 2 and if the peer supports it).
321 .Ss X11 and TCP forwarding
326 (or see the description of the
330 options described later)
331 and the user is using X11 (the
333 environment variable is set), the connection to the X11 display is
334 automatically forwarded to the remote side in such a way that any X11
335 programs started from the shell (or command) will go through the
336 encrypted channel, and the connection to the real X server will be made
337 from the local machine.
338 The user should not manually set
340 Forwarding of X11 connections can be
341 configured on the command line or in configuration files.
347 will point to the server machine, but with a display number greater than zero.
348 This is normal, and happens because
352 X server on the server machine for forwarding the
353 connections over the encrypted channel.
356 will also automatically set up Xauthority data on the server machine.
357 For this purpose, it will generate a random authorization cookie,
358 store it in Xauthority on the server, and verify that any forwarded
359 connections carry this cookie and replace it by the real cookie when
360 the connection is opened.
361 The real authentication cookie is never
362 sent to the server machine (and no cookies are sent in the plain).
368 (or see the description of the
372 options described later) and
373 the user is using an authentication agent, the connection to the agent
374 is automatically forwarded to the remote side.
376 Forwarding of arbitrary TCP/IP connections over the secure channel can
377 be specified either on the command line or in a configuration file.
378 One possible application of TCP/IP forwarding is a secure connection to an
379 electronic purse; another is going through firewalls.
380 .Ss Server authentication
382 automatically maintains and checks a database containing
383 identifications for all hosts it has ever been used with.
384 Host keys are stored in
385 .Pa $HOME/.ssh/known_hosts
386 in the user's home directory.
387 Additionally, the file
388 .Pa /etc/ssh/ssh_known_hosts
389 is automatically checked for known hosts.
390 Any new hosts are automatically added to the user's file.
391 If a host's identification ever changes,
393 warns about this and disables password authentication to prevent a
394 trojan horse from getting the user's password.
395 Another purpose of this mechanism is to prevent man-in-the-middle attacks
396 which could otherwise be used to circumvent the encryption.
398 .Cm StrictHostKeyChecking
399 option can be used to prevent logins to machines whose
400 host key is not known or has changed.
402 The options are as follows:
407 to try protocol version 1 only.
411 to try protocol version 2 only.
415 to use IPv4 addresses only.
419 to use IPv6 addresses only.
421 Enables forwarding of the authentication agent connection.
422 This can also be specified on a per-host basis in a configuration file.
424 Agent forwarding should be enabled with caution.
425 Users with the ability to bypass file permissions on the remote host
426 (for the agent's Unix-domain socket)
427 can access the local agent through the forwarded connection.
428 An attacker cannot obtain key material from the agent,
429 however they can perform operations on the keys that enable them to
430 authenticate using the identities loaded into the agent.
432 Disables forwarding of the authentication agent connection.
433 .It Fl b Ar bind_address
434 Specify the interface to transmit from on machines with multiple
435 interfaces or aliased addresses.
437 Requests compression of all data (including stdin, stdout, stderr, and
438 data for forwarded X11 and TCP/IP connections).
439 The compression algorithm is the same used by
443 can be controlled by the
445 option for protocol version 1.
446 Compression is desirable on modem lines and other
447 slow connections, but will only slow down things on fast networks.
448 The default value can be set on a host-by-host basis in the
449 configuration files; see the
452 .It Fl c Ar blowfish | 3des | des
453 Selects the cipher to use for encrypting the session.
456 It is believed to be secure.
458 (triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
460 is a fast block cipher; it appears very secure and is much faster than
463 is only supported in the
465 client for interoperability with legacy protocol 1 implementations
466 that do not support the
469 Its use is strongly discouraged due to cryptographic weaknesses.
470 .It Fl c Ar cipher_spec
471 Additionally, for protocol version 2 a comma-separated list of ciphers can
472 be specified in order of preference.
475 for more information.
479 application-level port forwarding.
480 This works by allocating a socket to listen to
482 on the local side, and whenever a connection is made to this port, the
483 connection is forwarded over the secure channel, and the application
484 protocol is then used to determine where to connect to from the
486 Currently the SOCKS4 and SOCKS5 protocols are supported, and
488 will act as a SOCKS server.
489 Only root can forward privileged ports.
490 Dynamic port forwardings can also be specified in the configuration file.
491 .It Fl e Ar ch | ^ch | none
492 Sets the escape character for sessions with a pty (default:
494 The escape character is only recognized at the beginning of a line.
495 The escape character followed by a dot
497 closes the connection;
498 followed by control-Z suspends the connection;
499 and followed by itself sends the escape character once.
500 Setting the character to
502 disables any escapes and makes the session fully transparent.
503 .It Fl F Ar configfile
504 Specifies an alternative per-user configuration file.
505 If a configuration file is given on the command line,
506 the system-wide configuration file
507 .Pq Pa /etc/ssh/ssh_config
509 The default for the per-user configuration file is
510 .Pa $HOME/.ssh/config .
514 to go to background just before command execution.
517 is going to ask for passwords or passphrases, but the user
518 wants it in the background.
521 The recommended way to start X11 programs at a remote site is with
523 .Ic ssh -f host xterm .
525 Allows remote hosts to connect to local forwarded ports.
526 .It Fl I Ar smartcard_device
527 Specifies which smartcard device to use.
528 The argument is the device
530 should use to communicate with a smartcard used for storing the user's
532 .It Fl i Ar identity_file
533 Selects a file from which the identity (private key) for
534 RSA or DSA authentication is read.
536 .Pa $HOME/.ssh/identity
537 for protocol version 1, and
538 .Pa $HOME/.ssh/id_rsa
540 .Pa $HOME/.ssh/id_dsa
541 for protocol version 2.
542 Identity files may also be specified on
543 a per-host basis in the configuration file.
544 It is possible to have multiple
546 options (and multiple identities specified in
547 configuration files).
549 Disables forwarding (delegation) of GSSAPI credentials to the server.
552 .Ar port : host : hostport
555 Specifies that the given port on the local (client) host is to be
556 forwarded to the given host and port on the remote side.
557 This works by allocating a socket to listen to
559 on the local side, and whenever a connection is made to this port, the
560 connection is forwarded over the secure channel, and a connection is
565 from the remote machine.
566 Port forwardings can also be specified in the configuration file.
567 Only root can forward privileged ports.
568 IPv6 addresses can be specified with an alternative syntax:
571 .Ar port No / Ar host No /
575 .It Fl l Ar login_name
576 Specifies the user to log in as on the remote machine.
577 This also may be specified on a per-host basis in the configuration file.
579 Additionally, for protocol version 2 a comma-separated list of MAC
580 (message authentication code) algorithms can
581 be specified in order of preference.
584 keyword for more information.
586 Do not execute a remote command.
587 This is useful for just forwarding ports
588 (protocol version 2 only).
592 (actually, prevents reading from stdin).
593 This must be used when
595 is run in the background.
596 A common trick is to use this to run X11 programs on a remote machine.
598 .Ic ssh -n shadows.cs.hut.fi emacs &
599 will start an emacs on shadows.cs.hut.fi, and the X11
600 connection will be automatically forwarded over an encrypted channel.
603 program will be put in the background.
604 (This does not work if
606 needs to ask for a password or passphrase; see also the
610 Can be used to give options in the format used in the configuration file.
611 This is useful for specifying options for which there is no separate
613 For full details of the options listed below, and their possible values, see
616 .Bl -tag -width Ds -offset indent -compact
620 .It ChallengeResponseAuthentication
624 .It ClearAllForwardings
627 .It ConnectionAttempts
633 .It ForwardX11Trusted
635 .It GlobalKnownHostsFile
636 .It GSSAPIAuthentication
637 .It GSSAPIDelegateCredentials
639 .It HostbasedAuthentication
640 .It HostKeyAlgorithms
648 .It NoHostAuthenticationForLocalhost
649 .It NumberOfPasswordPrompts
650 .It PasswordAuthentication
652 .It PreferredAuthentications
655 .It PubkeyAuthentication
657 .It RhostsRSAAuthentication
658 .It RSAAuthentication
660 .It ServerAliveInterval
661 .It ServerAliveCountMax
663 .It StrictHostKeyChecking
665 .It UsePrivilegedPort
667 .It UserKnownHostsFile
672 Port to connect to on the remote host.
673 This can be specified on a
674 per-host basis in the configuration file.
677 Causes all warning and diagnostic messages to be suppressed.
680 .Ar port : host : hostport
683 Specifies that the given port on the remote (server) host is to be
684 forwarded to the given host and port on the local side.
685 This works by allocating a socket to listen to
687 on the remote side, and whenever a connection is made to this port, the
688 connection is forwarded over the secure channel, and a connection is
693 from the local machine.
694 Port forwardings can also be specified in the configuration file.
695 Privileged ports can be forwarded only when
696 logging in as root on the remote machine.
697 IPv6 addresses can be specified with an alternative syntax:
700 .Ar port No / Ar host No /
705 May be used to request invocation of a subsystem on the remote system.
706 Subsystems are a feature of the SSH2 protocol which facilitate the use
707 of SSH as a secure transport for other applications (eg.\&
709 The subsystem is specified as the remote command.
711 Disable pseudo-tty allocation.
713 Force pseudo-tty allocation.
714 This can be used to execute arbitrary
715 screen-based programs on a remote machine, which can be very useful,
716 e.g., when implementing menu services.
719 options force tty allocation, even if
723 Display the version number and exit.
728 to print debugging messages about its progress.
730 debugging connection, authentication, and configuration problems.
733 options increase the verbosity.
736 Enables X11 forwarding.
737 This can also be specified on a per-host basis in a configuration file.
739 X11 forwarding should be enabled with caution.
740 Users with the ability to bypass file permissions on the remote host
741 (for the user's X authorization database)
742 can access the local X11 display through the forwarded connection.
743 An attacker may then be able to perform activities such as keystroke monitoring.
745 Disables X11 forwarding.
747 Enables trusted X11 forwarding.
749 .Sh CONFIGURATION FILES
751 may additionally obtain configuration data from
752 a per-user configuration file and a system-wide configuration file.
753 The file format and configuration options are described in
757 will normally set the following environment variables:
758 .Bl -tag -width LOGNAME
762 variable indicates the location of the X11 server.
763 It is automatically set by
765 to point to a value of the form
767 where hostname indicates
768 the host where the shell runs, and n is an integer \*(Ge 1.
770 uses this special value to forward X11 connections over the secure
772 The user should normally not set
775 will render the X11 connection insecure (and will require the user to
776 manually copy any required authorization cookies).
778 Set to the path of the user's home directory.
782 set for compatibility with systems that use this variable.
784 Set to the path of the user's mailbox.
788 as specified when compiling
793 needs a passphrase, it will read the passphrase from the current
794 terminal if it was run from a terminal.
797 does not have a terminal associated with it but
801 are set, it will execute the program specified by
803 and open an X11 window to read the passphrase.
804 This is particularly useful when calling
809 (Note that on some machines it
810 may be necessary to redirect the input from
814 Identifies the path of a unix-domain socket used to communicate with the
816 .It Ev SSH_CONNECTION
817 Identifies the client and server ends of the connection.
818 The variable contains
819 four space-separated values: client ip-address, client port number,
820 server ip-address and server port number.
821 .It Ev SSH_ORIGINAL_COMMAND
822 The variable contains the original command line if a forced command
824 It can be used to extract the original arguments.
826 This is set to the name of the tty (path to the device) associated
827 with the current shell or command.
828 If the current session has no tty,
829 this variable is not set.
831 The timezone variable is set to indicate the present timezone if it
832 was set when the daemon was started (i.e., the daemon passes the value
833 on to new connections).
835 Set to the name of the user logging in.
841 .Pa $HOME/.ssh/environment ,
842 and adds lines of the format
844 to the environment if the file exists and if users are allowed to
845 change their environment.
846 For more information, see the
847 .Cm PermitUserEnvironment
852 .It Pa $HOME/.ssh/known_hosts
853 Records host keys for all hosts the user has logged into that are not
855 .Pa /etc/ssh/ssh_known_hosts .
858 .It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa, $HOME/.ssh/id_rsa
859 Contains the authentication identity of the user.
860 They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
862 contain sensitive data and should be readable by the user but not
863 accessible by others (read/write/execute).
866 ignores a private key file if it is accessible by others.
867 It is possible to specify a passphrase when
868 generating the key; the passphrase will be used to encrypt the
869 sensitive part of this file using 3DES.
870 .It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub, $HOME/.ssh/id_rsa.pub
871 Contains the public key for authentication (public part of the
872 identity file in human-readable form).
874 .Pa $HOME/.ssh/identity.pub
875 file should be added to the file
876 .Pa $HOME/.ssh/authorized_keys
878 where the user wishes to log in using protocol version 1 RSA authentication.
880 .Pa $HOME/.ssh/id_dsa.pub
882 .Pa $HOME/.ssh/id_rsa.pub
883 file should be added to
884 .Pa $HOME/.ssh/authorized_keys
886 where the user wishes to log in using protocol version 2 DSA/RSA authentication.
888 sensitive and can (but need not) be readable by anyone.
890 never used automatically and are not necessary; they are only provided for
891 the convenience of the user.
892 .It Pa $HOME/.ssh/config
893 This is the per-user configuration file.
894 The file format and configuration options are described in
896 Because of the potential for abuse, this file must have strict permissions:
897 read/write for the user, and not accessible by others.
898 .It Pa $HOME/.ssh/authorized_keys
899 Lists the public keys (RSA/DSA) that can be used for logging in as this user.
900 The format of this file is described in the
903 In the simplest form the format is the same as the
906 This file is not highly sensitive, but the recommended
907 permissions are read/write for the user, and not accessible by others.
908 .It Pa /etc/ssh/ssh_known_hosts
909 Systemwide list of known host keys.
910 This file should be prepared by the
911 system administrator to contain the public host keys of all machines in the
913 This file should be world-readable.
915 public keys, one per line, in the following format (fields separated
916 by spaces): system name, public key and optional comment field.
917 When different names are used
918 for the same machine, all such names should be listed, separated by
920 The format is described in the
924 The canonical system name (as returned by name servers) is used by
926 to verify the client host when logging in; other names are needed because
928 does not convert the user-supplied name to a canonical name before
929 checking the key, because someone with access to the name servers
930 would then be able to fool host authentication.
931 .It Pa /etc/ssh/ssh_config
932 Systemwide configuration file.
933 The file format and configuration options are described in
935 .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key
936 These three files contain the private parts of the host keys
938 .Cm RhostsRSAAuthentication
940 .Cm HostbasedAuthentication .
941 If the protocol version 1
942 .Cm RhostsRSAAuthentication
945 must be setuid root, since the host key is readable only by root.
946 For protocol version 2,
950 to access the host keys for
951 .Cm HostbasedAuthentication .
952 This eliminates the requirement that
954 be setuid root when that authentication method is used.
961 authentication to list the
962 host/user pairs that are permitted to log in.
963 (Note that this file is
964 also used by rlogin and rsh, which makes using this file insecure.)
965 Each line of the file contains a host name (in the canonical form
966 returned by name servers), and then a user name on that host,
967 separated by a space.
968 On some machines this file may need to be
969 world-readable if the user's home directory is on a NFS partition,
973 Additionally, this file must be owned by the user,
974 and must not have write permissions for anyone else.
976 permission for most machines is read/write for the user, and not
977 accessible by others.
981 will be installed so that it requires successful RSA host
982 authentication before permitting
985 If the server machine does not have the client's host key in
986 .Pa /etc/ssh/ssh_known_hosts ,
988 .Pa $HOME/.ssh/known_hosts .
989 The easiest way to do this is to
990 connect back to the client from the server machine using ssh; this
991 will automatically add the host key to
992 .Pa $HOME/.ssh/known_hosts .
994 This file is used exactly the same way as
997 having this file is to be able to use rhosts authentication with
999 without permitting login with
1003 .It Pa /etc/hosts.equiv
1004 This file is used during
1008 canonical hosts names, one per line (the full format is described in the
1011 If the client host is found in this file, login is
1012 automatically permitted provided client and server user names are the
1014 Additionally, successful RSA host authentication is normally
1016 This file should only be writable by root.
1017 .It Pa /etc/shosts.equiv
1018 This file is processed exactly as
1019 .Pa /etc/hosts.equiv .
1020 This file may be useful to permit logins using
1022 but not using rsh/rlogin.
1023 .It Pa /etc/ssh/sshrc
1024 Commands in this file are executed by
1026 when the user logs in just before the user's shell (or command) is started.
1029 manual page for more information.
1030 .It Pa $HOME/.ssh/rc
1031 Commands in this file are executed by
1033 when the user logs in just before the user's shell (or command) is
1037 manual page for more information.
1038 .It Pa $HOME/.ssh/environment
1039 Contains additional definitions for environment variables, see section
1045 exits with the exit status of the remote command or with 255
1046 if an error occurred.
1066 .%T "SSH Protocol Architecture"
1067 .%N draft-ietf-secsh-architecture-12.txt
1069 .%O work in progress material
1072 OpenSSH is a derivative of the original and free
1073 ssh 1.2.12 release by Tatu Ylonen.
1074 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1075 Theo de Raadt and Dug Song
1076 removed many bugs, re-added newer features and
1078 Markus Friedl contributed the support for SSH
1079 protocol versions 1.5 and 2.0.
andersk / openssh.git / blob