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 1.194 2004/08/12 21:41:13 jakob Exp $
39 .Dd September 25, 1999
44 .Nd OpenSSH SSH client (remote login program)
47 .Op Fl 1246AaCfgkMNnqsTtVvXxY
48 .Op Fl b Ar bind_address
49 .Op Fl c Ar cipher_spec
52 .Op Fl e Ar escape_char
53 .Op Fl F Ar configfile
54 .Op Fl i Ar identity_file
64 .Op Fl l Ar login_name
79 .Oo Ar user Ns @ Oc Ns Ar hostname
83 (SSH client) is a program for logging into a remote machine and for
84 executing commands on a remote machine.
85 It is intended to replace rlogin and rsh,
86 and provide secure encrypted communications between
87 two untrusted hosts over an insecure network.
88 X11 connections and arbitrary TCP/IP ports
89 can also be forwarded over the secure channel.
92 connects and logs into the specified
98 his/her identity to the remote machine using one of several methods
99 depending on the protocol version used.
105 is executed on the remote host instead of a login shell.
106 .Ss SSH protocol version 1
107 First, if the machine the user logs in from is listed in
110 .Pa /etc/ssh/shosts.equiv
111 on the remote machine, and the user names are
112 the same on both sides, the user is immediately permitted to log in.
117 exists in the user's home directory on the
118 remote machine and contains a line containing the name of the client
119 machine and the name of the user on that machine, the user is
121 This form of authentication alone is normally not
122 allowed by the server because it is not secure.
124 The second authentication method is the
128 method combined with RSA-based host authentication.
129 It means that if the login would be permitted by
132 .Pa /etc/hosts.equiv ,
134 .Pa /etc/ssh/shosts.equiv ,
135 and if additionally the server can verify the client's
137 .Pa /etc/ssh/ssh_known_hosts
139 .Pa $HOME/.ssh/known_hosts
142 section), only then is login permitted.
143 This authentication method closes security holes due to IP
144 spoofing, DNS spoofing and routing spoofing.
145 [Note to the administrator:
146 .Pa /etc/hosts.equiv ,
148 and the rlogin/rsh protocol in general, are inherently insecure and should be
149 disabled if security is desired.]
151 As a third authentication method,
153 supports RSA based authentication.
154 The scheme is based on public-key cryptography: there are cryptosystems
155 where encryption and decryption are done using separate keys, and it
156 is not possible to derive the decryption key from the encryption key.
157 RSA is one such system.
158 The idea is that each user creates a public/private
159 key pair for authentication purposes.
160 The server knows the public key, and only the user knows the private key.
163 .Pa $HOME/.ssh/authorized_keys
164 lists the public keys that are permitted for logging in.
165 When the user logs in, the
167 program tells the server which key pair it would like to use for
169 The server checks if this key is permitted, and if so,
170 sends the user (actually the
172 program running on behalf of the user) a challenge, a random number,
173 encrypted by the user's public key.
174 The challenge can only be decrypted using the proper private key.
175 The user's client then decrypts the challenge using the private key,
176 proving that he/she knows the private key
177 but without disclosing it to the server.
180 implements the RSA authentication protocol automatically.
181 The user creates his/her RSA key pair by running
183 This stores the private key in
184 .Pa $HOME/.ssh/identity
185 and stores the public key in
186 .Pa $HOME/.ssh/identity.pub
187 in the user's home directory.
188 The user should then copy the
191 .Pa $HOME/.ssh/authorized_keys
192 in his/her home directory on the remote machine (the
194 file corresponds to the conventional
196 file, and has one key
197 per line, though the lines can be very long).
198 After this, the user can log in without giving the password.
199 RSA authentication is much more secure than
203 The most convenient way to use RSA authentication may be with an
204 authentication agent.
207 for more information.
209 If other authentication methods fail,
211 prompts the user for a password.
212 The password is sent to the remote
213 host for checking; however, since all communications are encrypted,
214 the password cannot be seen by someone listening on the network.
215 .Ss SSH protocol version 2
216 When a user connects using protocol version 2,
217 similar authentication methods are available.
218 Using the default values for
219 .Cm PreferredAuthentications ,
220 the client will try to authenticate first using the hostbased method;
221 if this method fails, public key authentication is attempted,
222 and finally if this method fails, keyboard-interactive and
223 password authentication are tried.
225 The public key method is similar to RSA authentication described
226 in the previous section and allows the RSA or DSA algorithm to be used:
227 The client uses his private key,
228 .Pa $HOME/.ssh/id_dsa
230 .Pa $HOME/.ssh/id_rsa ,
231 to sign the session identifier and sends the result to the server.
232 The server checks whether the matching public key is listed in
233 .Pa $HOME/.ssh/authorized_keys
234 and grants access if both the key is found and the signature is correct.
235 The session identifier is derived from a shared Diffie-Hellman value
236 and is only known to the client and the server.
238 If public key authentication fails or is not available, a password
239 can be sent encrypted to the remote host to prove the user's identity.
243 supports hostbased or challenge response authentication.
245 Protocol 2 provides additional mechanisms for confidentiality
246 (the traffic is encrypted using AES, 3DES, Blowfish, CAST128 or Arcfour)
247 and integrity (hmac-md5, hmac-sha1, hmac-ripemd160).
248 Note that protocol 1 lacks a strong mechanism for ensuring the
249 integrity of the connection.
250 .Ss Login session and remote execution
251 When the user's identity has been accepted by the server, the server
252 either executes the given command, or logs into the machine and gives
253 the user a normal shell on the remote machine.
254 All communication with
255 the remote command or shell will be automatically encrypted.
257 If a pseudo-terminal has been allocated (normal login session), the
258 user may use the escape characters noted below.
260 If no pseudo-tty has been allocated,
261 the session is transparent and can be used to reliably transfer binary data.
262 On most systems, setting the escape character to
264 will also make the session transparent even if a tty is used.
266 The session terminates when the command or shell on the remote
267 machine exits and all X11 and TCP/IP connections have been closed.
268 The exit status of the remote program is returned as the exit status of
270 .Ss Escape Characters
271 When a pseudo-terminal has been requested,
273 supports a number of functions through the use of an escape character.
275 A single tilde character can be sent as
277 or by following the tilde by a character other than those described below.
278 The escape character must always follow a newline to be interpreted as
280 The escape character can be changed in configuration files using the
282 configuration directive or on the command line by the
286 The supported escapes (assuming the default
296 List forwarded connections.
300 at logout when waiting for forwarded connection / X11 sessions to terminate.
302 Display a list of escape characters.
304 Send a BREAK to the remote system
305 (only useful for SSH protocol version 2 and if the peer supports it).
308 Currently this allows the addition of port forwardings using the
313 It also allows the cancellation of existing remote port-forwardings
316 Basic help is available, using the
320 Request rekeying of the connection
321 (only useful for SSH protocol version 2 and if the peer supports it).
323 .Ss X11 and TCP forwarding
328 (or see the description of the
332 options described later)
333 and the user is using X11 (the
335 environment variable is set), the connection to the X11 display is
336 automatically forwarded to the remote side in such a way that any X11
337 programs started from the shell (or command) will go through the
338 encrypted channel, and the connection to the real X server will be made
339 from the local machine.
340 The user should not manually set
342 Forwarding of X11 connections can be
343 configured on the command line or in configuration files.
349 will point to the server machine, but with a display number greater than zero.
350 This is normal, and happens because
354 X server on the server machine for forwarding the
355 connections over the encrypted channel.
358 will also automatically set up Xauthority data on the server machine.
359 For this purpose, it will generate a random authorization cookie,
360 store it in Xauthority on the server, and verify that any forwarded
361 connections carry this cookie and replace it by the real cookie when
362 the connection is opened.
363 The real authentication cookie is never
364 sent to the server machine (and no cookies are sent in the plain).
370 (or see the description of the
374 options described later) and
375 the user is using an authentication agent, the connection to the agent
376 is automatically forwarded to the remote side.
378 Forwarding of arbitrary TCP/IP connections over the secure channel can
379 be specified either on the command line or in a configuration file.
380 One possible application of TCP/IP forwarding is a secure connection to an
381 electronic purse; another is going through firewalls.
382 .Ss Server authentication
384 automatically maintains and checks a database containing
385 identifications for all hosts it has ever been used with.
386 Host keys are stored in
387 .Pa $HOME/.ssh/known_hosts
388 in the user's home directory.
389 Additionally, the file
390 .Pa /etc/ssh/ssh_known_hosts
391 is automatically checked for known hosts.
392 Any new hosts are automatically added to the user's file.
393 If a host's identification ever changes,
395 warns about this and disables password authentication to prevent a
396 trojan horse from getting the user's password.
397 Another purpose of this mechanism is to prevent man-in-the-middle attacks
398 which could otherwise be used to circumvent the encryption.
400 .Cm StrictHostKeyChecking
401 option can be used to prevent logins to machines whose
402 host key is not known or has changed.
405 can be configured to verify host identification using fingerprint resource
406 records (SSHFP) published in DNS.
409 option can be used to control how DNS lookups are performed.
410 SSHFP resource records can be generated using
413 The options are as follows:
418 to try protocol version 1 only.
422 to try protocol version 2 only.
426 to use IPv4 addresses only.
430 to use IPv6 addresses only.
432 Enables forwarding of the authentication agent connection.
433 This can also be specified on a per-host basis in a configuration file.
435 Agent forwarding should be enabled with caution.
436 Users with the ability to bypass file permissions on the remote host
437 (for the agent's Unix-domain socket)
438 can access the local agent through the forwarded connection.
439 An attacker cannot obtain key material from the agent,
440 however they can perform operations on the keys that enable them to
441 authenticate using the identities loaded into the agent.
443 Disables forwarding of the authentication agent connection.
444 .It Fl b Ar bind_address
445 Specify the interface to transmit from on machines with multiple
446 interfaces or aliased addresses.
448 Requests compression of all data (including stdin, stdout, stderr, and
449 data for forwarded X11 and TCP/IP connections).
450 The compression algorithm is the same used by
454 can be controlled by the
456 option for protocol version 1.
457 Compression is desirable on modem lines and other
458 slow connections, but will only slow down things on fast networks.
459 The default value can be set on a host-by-host basis in the
460 configuration files; see the
463 .It Fl c Ar cipher_spec
464 Selects the cipher specification for encrypting the session.
466 Protocol version 1 allows specification of a single cipher.
467 The suported values are
473 (triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
474 It is believed to be secure.
476 is a fast block cipher; it appears very secure and is much faster than
479 is only supported in the
481 client for interoperability with legacy protocol 1 implementations
482 that do not support the
485 Its use is strongly discouraged due to cryptographic weaknesses.
489 For protocol version 2
491 is a comma-separated list of ciphers
492 listed in order of preference.
493 The supported ciphers are
507 ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
508 aes192-cbc,aes256-cbc''
513 application-level port forwarding.
514 This works by allocating a socket to listen to
516 on the local side, and whenever a connection is made to this port, the
517 connection is forwarded over the secure channel, and the application
518 protocol is then used to determine where to connect to from the
520 Currently the SOCKS4 and SOCKS5 protocols are supported, and
522 will act as a SOCKS server.
523 Only root can forward privileged ports.
524 Dynamic port forwardings can also be specified in the configuration file.
525 .It Fl e Ar ch | ^ch | none
526 Sets the escape character for sessions with a pty (default:
528 The escape character is only recognized at the beginning of a line.
529 The escape character followed by a dot
531 closes the connection;
532 followed by control-Z suspends the connection;
533 and followed by itself sends the escape character once.
534 Setting the character to
536 disables any escapes and makes the session fully transparent.
537 .It Fl F Ar configfile
538 Specifies an alternative per-user configuration file.
539 If a configuration file is given on the command line,
540 the system-wide configuration file
541 .Pq Pa /etc/ssh/ssh_config
543 The default for the per-user configuration file is
544 .Pa $HOME/.ssh/config .
548 to go to background just before command execution.
551 is going to ask for passwords or passphrases, but the user
552 wants it in the background.
555 The recommended way to start X11 programs at a remote site is with
557 .Ic ssh -f host xterm .
559 Allows remote hosts to connect to local forwarded ports.
560 .It Fl I Ar smartcard_device
561 Specifies which smartcard device to use.
562 The argument is the device
564 should use to communicate with a smartcard used for storing the user's
566 .It Fl i Ar identity_file
567 Selects a file from which the identity (private key) for
568 RSA or DSA authentication is read.
570 .Pa $HOME/.ssh/identity
571 for protocol version 1, and
572 .Pa $HOME/.ssh/id_rsa
574 .Pa $HOME/.ssh/id_dsa
575 for protocol version 2.
576 Identity files may also be specified on
577 a per-host basis in the configuration file.
578 It is possible to have multiple
580 options (and multiple identities specified in
581 configuration files).
583 Disables forwarding (delegation) of GSSAPI credentials to the server.
586 .Ar port : host : hostport
589 Specifies that the given port on the local (client) host is to be
590 forwarded to the given host and port on the remote side.
591 This works by allocating a socket to listen to
593 on the local side, and whenever a connection is made to this port, the
594 connection is forwarded over the secure channel, and a connection is
599 from the remote machine.
600 Port forwardings can also be specified in the configuration file.
601 Only root can forward privileged ports.
602 IPv6 addresses can be specified with an alternative syntax:
605 .Ar port No / Ar host No /
609 .It Fl l Ar login_name
610 Specifies the user to log in as on the remote machine.
611 This also may be specified on a per-host basis in the configuration file.
617 mode for connection sharing.
618 Refer to the description of
624 Additionally, for protocol version 2 a comma-separated list of MAC
625 (message authentication code) algorithms can
626 be specified in order of preference.
629 keyword for more information.
631 Do not execute a remote command.
632 This is useful for just forwarding ports
633 (protocol version 2 only).
637 (actually, prevents reading from stdin).
638 This must be used when
640 is run in the background.
641 A common trick is to use this to run X11 programs on a remote machine.
643 .Ic ssh -n shadows.cs.hut.fi emacs &
644 will start an emacs on shadows.cs.hut.fi, and the X11
645 connection will be automatically forwarded over an encrypted channel.
648 program will be put in the background.
649 (This does not work if
651 needs to ask for a password or passphrase; see also the
655 Can be used to give options in the format used in the configuration file.
656 This is useful for specifying options for which there is no separate
658 For full details of the options listed below, and their possible values, see
661 .Bl -tag -width Ds -offset indent -compact
665 .It ChallengeResponseAuthentication
669 .It ClearAllForwardings
672 .It ConnectionAttempts
680 .It ForwardX11Trusted
682 .It GlobalKnownHostsFile
683 .It GSSAPIAuthentication
684 .It GSSAPIDelegateCredentials
686 .It HostbasedAuthentication
687 .It HostKeyAlgorithms
695 .It NoHostAuthenticationForLocalhost
696 .It NumberOfPasswordPrompts
697 .It PasswordAuthentication
699 .It PreferredAuthentications
702 .It PubkeyAuthentication
704 .It RhostsRSAAuthentication
705 .It RSAAuthentication
707 .It ServerAliveInterval
708 .It ServerAliveCountMax
710 .It StrictHostKeyChecking
712 .It UsePrivilegedPort
714 .It UserKnownHostsFile
719 Port to connect to on the remote host.
720 This can be specified on a
721 per-host basis in the configuration file.
724 Causes all warning and diagnostic messages to be suppressed.
727 .Ar port : host : hostport
730 Specifies that the given port on the remote (server) host is to be
731 forwarded to the given host and port on the local side.
732 This works by allocating a socket to listen to
734 on the remote side, and whenever a connection is made to this port, the
735 connection is forwarded over the secure channel, and a connection is
740 from the local machine.
741 Port forwardings can also be specified in the configuration file.
742 Privileged ports can be forwarded only when
743 logging in as root on the remote machine.
744 IPv6 addresses can be specified with an alternative syntax:
747 .Ar port No / Ar host No /
752 Specifies the location of a control socket for connection sharing.
753 Refer to the description of
761 May be used to request invocation of a subsystem on the remote system.
762 Subsystems are a feature of the SSH2 protocol which facilitate the use
763 of SSH as a secure transport for other applications (eg.\&
765 The subsystem is specified as the remote command.
767 Disable pseudo-tty allocation.
769 Force pseudo-tty allocation.
770 This can be used to execute arbitrary
771 screen-based programs on a remote machine, which can be very useful,
772 e.g., when implementing menu services.
775 options force tty allocation, even if
779 Display the version number and exit.
784 to print debugging messages about its progress.
786 debugging connection, authentication, and configuration problems.
789 options increase the verbosity.
792 Enables X11 forwarding.
793 This can also be specified on a per-host basis in a configuration file.
795 X11 forwarding should be enabled with caution.
796 Users with the ability to bypass file permissions on the remote host
797 (for the user's X authorization database)
798 can access the local X11 display through the forwarded connection.
799 An attacker may then be able to perform activities such as keystroke monitoring.
801 Disables X11 forwarding.
803 Enables trusted X11 forwarding.
805 .Sh CONFIGURATION FILES
807 may additionally obtain configuration data from
808 a per-user configuration file and a system-wide configuration file.
809 The file format and configuration options are described in
813 will normally set the following environment variables:
814 .Bl -tag -width LOGNAME
818 variable indicates the location of the X11 server.
819 It is automatically set by
821 to point to a value of the form
823 where hostname indicates
824 the host where the shell runs, and n is an integer \*(Ge 1.
826 uses this special value to forward X11 connections over the secure
828 The user should normally not set
831 will render the X11 connection insecure (and will require the user to
832 manually copy any required authorization cookies).
834 Set to the path of the user's home directory.
838 set for compatibility with systems that use this variable.
840 Set to the path of the user's mailbox.
844 as specified when compiling
849 needs a passphrase, it will read the passphrase from the current
850 terminal if it was run from a terminal.
853 does not have a terminal associated with it but
857 are set, it will execute the program specified by
859 and open an X11 window to read the passphrase.
860 This is particularly useful when calling
865 (Note that on some machines it
866 may be necessary to redirect the input from
870 Identifies the path of a unix-domain socket used to communicate with the
872 .It Ev SSH_CONNECTION
873 Identifies the client and server ends of the connection.
874 The variable contains
875 four space-separated values: client ip-address, client port number,
876 server ip-address and server port number.
877 .It Ev SSH_ORIGINAL_COMMAND
878 The variable contains the original command line if a forced command
880 It can be used to extract the original arguments.
882 This is set to the name of the tty (path to the device) associated
883 with the current shell or command.
884 If the current session has no tty,
885 this variable is not set.
887 The timezone variable is set to indicate the present timezone if it
888 was set when the daemon was started (i.e., the daemon passes the value
889 on to new connections).
891 Set to the name of the user logging in.
897 .Pa $HOME/.ssh/environment ,
898 and adds lines of the format
900 to the environment if the file exists and if users are allowed to
901 change their environment.
902 For more information, see the
903 .Cm PermitUserEnvironment
908 .It Pa $HOME/.ssh/known_hosts
909 Records host keys for all hosts the user has logged into that are not
911 .Pa /etc/ssh/ssh_known_hosts .
914 .It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa, $HOME/.ssh/id_rsa
915 Contains the authentication identity of the user.
916 They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
918 contain sensitive data and should be readable by the user but not
919 accessible by others (read/write/execute).
922 ignores a private key file if it is accessible by others.
923 It is possible to specify a passphrase when
924 generating the key; the passphrase will be used to encrypt the
925 sensitive part of this file using 3DES.
926 .It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub, $HOME/.ssh/id_rsa.pub
927 Contains the public key for authentication (public part of the
928 identity file in human-readable form).
930 .Pa $HOME/.ssh/identity.pub
931 file should be added to the file
932 .Pa $HOME/.ssh/authorized_keys
934 where the user wishes to log in using protocol version 1 RSA authentication.
936 .Pa $HOME/.ssh/id_dsa.pub
938 .Pa $HOME/.ssh/id_rsa.pub
939 file should be added to
940 .Pa $HOME/.ssh/authorized_keys
942 where the user wishes to log in using protocol version 2 DSA/RSA authentication.
944 sensitive and can (but need not) be readable by anyone.
946 never used automatically and are not necessary; they are only provided for
947 the convenience of the user.
948 .It Pa $HOME/.ssh/config
949 This is the per-user configuration file.
950 The file format and configuration options are described in
952 Because of the potential for abuse, this file must have strict permissions:
953 read/write for the user, and not accessible by others.
954 .It Pa $HOME/.ssh/authorized_keys
955 Lists the public keys (RSA/DSA) that can be used for logging in as this user.
956 The format of this file is described in the
959 In the simplest form the format is the same as the
962 This file is not highly sensitive, but the recommended
963 permissions are read/write for the user, and not accessible by others.
964 .It Pa /etc/ssh/ssh_known_hosts
965 Systemwide list of known host keys.
966 This file should be prepared by the
967 system administrator to contain the public host keys of all machines in the
969 This file should be world-readable.
971 public keys, one per line, in the following format (fields separated
972 by spaces): system name, public key and optional comment field.
973 When different names are used
974 for the same machine, all such names should be listed, separated by
976 The format is described in the
980 The canonical system name (as returned by name servers) is used by
982 to verify the client host when logging in; other names are needed because
984 does not convert the user-supplied name to a canonical name before
985 checking the key, because someone with access to the name servers
986 would then be able to fool host authentication.
987 .It Pa /etc/ssh/ssh_config
988 Systemwide configuration file.
989 The file format and configuration options are described in
991 .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key
992 These three files contain the private parts of the host keys
994 .Cm RhostsRSAAuthentication
996 .Cm HostbasedAuthentication .
997 If the protocol version 1
998 .Cm RhostsRSAAuthentication
1001 must be setuid root, since the host key is readable only by root.
1002 For protocol version 2,
1006 to access the host keys for
1007 .Cm HostbasedAuthentication .
1008 This eliminates the requirement that
1010 be setuid root when that authentication method is used.
1014 .It Pa $HOME/.rhosts
1015 This file is used in
1017 authentication to list the
1018 host/user pairs that are permitted to log in.
1019 (Note that this file is
1020 also used by rlogin and rsh, which makes using this file insecure.)
1021 Each line of the file contains a host name (in the canonical form
1022 returned by name servers), and then a user name on that host,
1023 separated by a space.
1024 On some machines this file may need to be
1025 world-readable if the user's home directory is on a NFS partition,
1029 Additionally, this file must be owned by the user,
1030 and must not have write permissions for anyone else.
1032 permission for most machines is read/write for the user, and not
1033 accessible by others.
1035 Note that by default
1037 will be installed so that it requires successful RSA host
1038 authentication before permitting
1041 If the server machine does not have the client's host key in
1042 .Pa /etc/ssh/ssh_known_hosts ,
1044 .Pa $HOME/.ssh/known_hosts .
1045 The easiest way to do this is to
1046 connect back to the client from the server machine using ssh; this
1047 will automatically add the host key to
1048 .Pa $HOME/.ssh/known_hosts .
1049 .It Pa $HOME/.shosts
1050 This file is used exactly the same way as
1053 having this file is to be able to use rhosts authentication with
1055 without permitting login with
1059 .It Pa /etc/hosts.equiv
1060 This file is used during
1064 canonical hosts names, one per line (the full format is described in the
1067 If the client host is found in this file, login is
1068 automatically permitted provided client and server user names are the
1070 Additionally, successful RSA host authentication is normally
1072 This file should only be writable by root.
1073 .It Pa /etc/ssh/shosts.equiv
1074 This file is processed exactly as
1075 .Pa /etc/hosts.equiv .
1076 This file may be useful to permit logins using
1078 but not using rsh/rlogin.
1079 .It Pa /etc/ssh/sshrc
1080 Commands in this file are executed by
1082 when the user logs in just before the user's shell (or command) is started.
1085 manual page for more information.
1086 .It Pa $HOME/.ssh/rc
1087 Commands in this file are executed by
1089 when the user logs in just before the user's shell (or command) is
1093 manual page for more information.
1094 .It Pa $HOME/.ssh/environment
1095 Contains additional definitions for environment variables, see section
1101 exits with the exit status of the remote command or with 255
1102 if an error occurred.
1122 .%T "SSH Protocol Architecture"
1123 .%N draft-ietf-secsh-architecture-12.txt
1125 .%O work in progress material
1128 OpenSSH is a derivative of the original and free
1129 ssh 1.2.12 release by Tatu Ylonen.
1130 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1131 Theo de Raadt and Dug Song
1132 removed many bugs, re-added newer features and
1134 Markus Friedl contributed the support for SSH
1135 protocol versions 1.5 and 2.0.
projects / FreeBSD / FreeBSD.git / blob