Annotation of src/usr.bin/ssh/ssh.1, Revision 1.200
1.1 deraadt 1: .\" -*- nroff -*-
2: .\"
3: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: .\" All rights reserved
6: .\"
1.59 deraadt 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".
12: .\"
1.93 deraadt 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.
1.59 deraadt 16: .\"
17: .\" Redistribution and use in source and binary forms, with or without
18: .\" modification, are permitted provided that the following conditions
19: .\" are met:
20: .\" 1. Redistributions of source code must retain the above copyright
21: .\" notice, this list of conditions and the following disclaimer.
22: .\" 2. Redistributions in binary form must reproduce the above copyright
23: .\" notice, this list of conditions and the following disclaimer in the
24: .\" documentation and/or other materials provided with the distribution.
1.1 deraadt 25: .\"
1.59 deraadt 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.
1.1 deraadt 36: .\"
1.200 ! djm 37: .\" $OpenBSD: ssh.1,v 1.199 2004/11/07 17:42:36 jmc Exp $
1.2 deraadt 38: .Dd September 25, 1999
39: .Dt SSH 1
40: .Os
41: .Sh NAME
42: .Nm ssh
1.96 deraadt 43: .Nd OpenSSH SSH client (remote login program)
1.2 deraadt 44: .Sh SYNOPSIS
45: .Nm ssh
1.191 djm 46: .Op Fl 1246AaCfgkMNnqsTtVvXxY
1.108 markus 47: .Op Fl b Ar bind_address
1.51 markus 48: .Op Fl c Ar cipher_spec
1.193 jmc 49: .Bk -words
1.176 jmc 50: .Op Fl D Ar port
1.2 deraadt 51: .Op Fl e Ar escape_char
1.176 jmc 52: .Op Fl F Ar configfile
1.2 deraadt 53: .Op Fl i Ar identity_file
1.12 aaron 54: .Oo Fl L Xo
55: .Sm off
1.200 ! djm 56: .Oo Ar bind_address : Oc
1.33 markus 57: .Ar port :
1.12 aaron 58: .Ar host :
59: .Ar hostport
60: .Sm on
61: .Xc
62: .Oc
1.176 jmc 63: .Op Fl l Ar login_name
64: .Op Fl m Ar mac_spec
1.198 djm 65: .Op Fl O Ar ctl_cmd
1.176 jmc 66: .Op Fl o Ar option
1.168 jmc 67: .Bk -words
1.176 jmc 68: .Op Fl p Ar port
69: .Ek
1.12 aaron 70: .Oo Fl R Xo
71: .Sm off
1.200 ! djm 72: .Oo Ar bind_address : Oc
1.33 markus 73: .Ar port :
1.12 aaron 74: .Ar host :
75: .Ar hostport
76: .Sm on
77: .Xc
78: .Oc
1.198 djm 79: .Op Fl S Ar ctl_path
1.176 jmc 80: .Oo Ar user Ns @ Oc Ns Ar hostname
1.2 deraadt 81: .Op Ar command
1.44 aaron 82: .Sh DESCRIPTION
1.2 deraadt 83: .Nm
1.96 deraadt 84: (SSH client) is a program for logging into a remote machine and for
1.40 aaron 85: executing commands on a remote machine.
1.176 jmc 86: It is intended to replace rlogin and rsh,
87: and provide secure encrypted communications between
1.40 aaron 88: two untrusted hosts over an insecure network.
1.176 jmc 89: X11 connections and arbitrary TCP/IP ports
90: can also be forwarded over the secure channel.
1.2 deraadt 91: .Pp
92: .Nm
1.44 aaron 93: connects and logs into the specified
1.176 jmc 94: .Ar hostname
95: (with optional
96: .Ar user
97: name).
1.1 deraadt 98: The user must prove
1.49 markus 99: his/her identity to the remote machine using one of several methods
1.176 jmc 100: depending on the protocol version used.
1.49 markus 101: .Pp
1.176 jmc 102: If
103: .Ar command
104: is specified,
105: .Ar command
106: is executed on the remote host instead of a login shell.
1.49 markus 107: .Ss SSH protocol version 1
1.195 markus 108: The first authentication method is the
109: .Em rhosts
110: or
111: .Em hosts.equiv
112: method combined with RSA-based host authentication.
113: If the machine the user logs in from is listed in
1.2 deraadt 114: .Pa /etc/hosts.equiv
1.1 deraadt 115: or
1.2 deraadt 116: .Pa /etc/shosts.equiv
1.1 deraadt 117: on the remote machine, and the user names are
1.195 markus 118: the same on both sides, or if the files
119: .Pa $HOME/.rhosts
1.1 deraadt 120: or
1.195 markus 121: .Pa $HOME/.shosts
122: exist in the user's home directory on the
123: remote machine and contain a line containing the name of the client
1.1 deraadt 124: machine and the name of the user on that machine, the user is
1.195 markus 125: considered for log in.
126: Additionally, if the server can verify the client's
1.44 aaron 127: host key (see
1.147 deraadt 128: .Pa /etc/ssh/ssh_known_hosts
1.23 markus 129: and
130: .Pa $HOME/.ssh/known_hosts
1.1 deraadt 131: in the
1.2 deraadt 132: .Sx FILES
1.176 jmc 133: section), only then is login permitted.
1.40 aaron 134: This authentication method closes security holes due to IP
135: spoofing, DNS spoofing and routing spoofing.
136: [Note to the administrator:
1.2 deraadt 137: .Pa /etc/hosts.equiv ,
1.49 markus 138: .Pa $HOME/.rhosts ,
1.1 deraadt 139: and the rlogin/rsh protocol in general, are inherently insecure and should be
140: disabled if security is desired.]
1.2 deraadt 141: .Pp
1.195 markus 142: As a second authentication method,
1.2 deraadt 143: .Nm
1.1 deraadt 144: supports RSA based authentication.
145: The scheme is based on public-key cryptography: there are cryptosystems
146: where encryption and decryption are done using separate keys, and it
147: is not possible to derive the decryption key from the encryption key.
1.40 aaron 148: RSA is one such system.
1.44 aaron 149: The idea is that each user creates a public/private
1.40 aaron 150: key pair for authentication purposes.
151: The server knows the public key, and only the user knows the private key.
1.176 jmc 152: .Pp
1.44 aaron 153: The file
1.2 deraadt 154: .Pa $HOME/.ssh/authorized_keys
1.176 jmc 155: lists the public keys that are permitted for logging in.
1.40 aaron 156: When the user logs in, the
1.2 deraadt 157: .Nm
1.1 deraadt 158: program tells the server which key pair it would like to use for
1.40 aaron 159: authentication.
1.176 jmc 160: The server checks if this key is permitted, and if so,
161: sends the user (actually the
1.2 deraadt 162: .Nm
1.1 deraadt 163: program running on behalf of the user) a challenge, a random number,
1.40 aaron 164: encrypted by the user's public key.
1.176 jmc 165: The challenge can only be decrypted using the proper private key.
166: The user's client then decrypts the challenge using the private key,
167: proving that he/she knows the private key
168: but without disclosing it to the server.
1.2 deraadt 169: .Pp
170: .Nm
1.40 aaron 171: implements the RSA authentication protocol automatically.
172: The user creates his/her RSA key pair by running
1.2 deraadt 173: .Xr ssh-keygen 1 .
1.44 aaron 174: This stores the private key in
1.49 markus 175: .Pa $HOME/.ssh/identity
1.176 jmc 176: and stores the public key in
1.49 markus 177: .Pa $HOME/.ssh/identity.pub
1.40 aaron 178: in the user's home directory.
179: The user should then copy the
1.2 deraadt 180: .Pa identity.pub
1.44 aaron 181: to
1.49 markus 182: .Pa $HOME/.ssh/authorized_keys
1.44 aaron 183: in his/her home directory on the remote machine (the
1.2 deraadt 184: .Pa authorized_keys
1.44 aaron 185: file corresponds to the conventional
1.49 markus 186: .Pa $HOME/.rhosts
1.1 deraadt 187: file, and has one key
1.40 aaron 188: per line, though the lines can be very long).
189: After this, the user can log in without giving the password.
1.2 deraadt 190: .Pp
1.1 deraadt 191: The most convenient way to use RSA authentication may be with an
1.40 aaron 192: authentication agent.
193: See
1.2 deraadt 194: .Xr ssh-agent 1
1.1 deraadt 195: for more information.
1.2 deraadt 196: .Pp
1.44 aaron 197: If other authentication methods fail,
1.2 deraadt 198: .Nm
1.40 aaron 199: prompts the user for a password.
200: The password is sent to the remote
1.1 deraadt 201: host for checking; however, since all communications are encrypted,
202: the password cannot be seen by someone listening on the network.
1.49 markus 203: .Ss SSH protocol version 2
1.176 jmc 204: When a user connects using protocol version 2,
1.145 markus 205: similar authentication methods are available.
1.107 markus 206: Using the default values for
207: .Cm PreferredAuthentications ,
1.123 markus 208: the client will try to authenticate first using the hostbased method;
1.176 jmc 209: if this method fails, public key authentication is attempted,
210: and finally if this method fails, keyboard-interactive and
1.123 markus 211: password authentication are tried.
1.49 markus 212: .Pp
213: The public key method is similar to RSA authentication described
1.107 markus 214: in the previous section and allows the RSA or DSA algorithm to be used:
1.102 itojun 215: The client uses his private key,
1.49 markus 216: .Pa $HOME/.ssh/id_dsa
1.102 itojun 217: or
218: .Pa $HOME/.ssh/id_rsa ,
1.49 markus 219: to sign the session identifier and sends the result to the server.
220: The server checks whether the matching public key is listed in
1.115 markus 221: .Pa $HOME/.ssh/authorized_keys
1.49 markus 222: and grants access if both the key is found and the signature is correct.
223: The session identifier is derived from a shared Diffie-Hellman value
224: and is only known to the client and the server.
225: .Pp
1.176 jmc 226: If public key authentication fails or is not available, a password
227: can be sent encrypted to the remote host to prove the user's identity.
1.107 markus 228: .Pp
229: Additionally,
230: .Nm
231: supports hostbased or challenge response authentication.
1.49 markus 232: .Pp
233: Protocol 2 provides additional mechanisms for confidentiality
1.189 dtucker 234: (the traffic is encrypted using AES, 3DES, Blowfish, CAST128 or Arcfour)
235: and integrity (hmac-md5, hmac-sha1, hmac-ripemd160).
1.49 markus 236: Note that protocol 1 lacks a strong mechanism for ensuring the
237: integrity of the connection.
238: .Ss Login session and remote execution
1.1 deraadt 239: When the user's identity has been accepted by the server, the server
240: either executes the given command, or logs into the machine and gives
1.40 aaron 241: the user a normal shell on the remote machine.
242: All communication with
1.1 deraadt 243: the remote command or shell will be automatically encrypted.
1.2 deraadt 244: .Pp
1.1 deraadt 245: If a pseudo-terminal has been allocated (normal login session), the
1.104 djm 246: user may use the escape characters noted below.
1.2 deraadt 247: .Pp
1.176 jmc 248: If no pseudo-tty has been allocated,
249: the session is transparent and can be used to reliably transfer binary data.
1.40 aaron 250: On most systems, setting the escape character to
1.2 deraadt 251: .Dq none
252: will also make the session transparent even if a tty is used.
253: .Pp
1.71 djm 254: The session terminates when the command or shell on the remote
1.92 markus 255: machine exits and all X11 and TCP/IP connections have been closed.
1.176 jmc 256: The exit status of the remote program is returned as the exit status of
1.2 deraadt 257: .Nm ssh .
1.104 djm 258: .Ss Escape Characters
1.176 jmc 259: When a pseudo-terminal has been requested,
260: .Nm
261: supports a number of functions through the use of an escape character.
1.104 djm 262: .Pp
263: A single tilde character can be sent as
264: .Ic ~~
1.119 stevesk 265: or by following the tilde by a character other than those described below.
1.104 djm 266: The escape character must always follow a newline to be interpreted as
267: special.
268: The escape character can be changed in configuration files using the
269: .Cm EscapeChar
1.117 itojun 270: configuration directive or on the command line by the
1.104 djm 271: .Fl e
272: option.
273: .Pp
274: The supported escapes (assuming the default
275: .Ql ~ )
276: are:
277: .Bl -tag -width Ds
278: .It Cm ~.
1.176 jmc 279: Disconnect.
1.104 djm 280: .It Cm ~^Z
1.176 jmc 281: Background
282: .Nm ssh .
1.104 djm 283: .It Cm ~#
1.176 jmc 284: List forwarded connections.
1.104 djm 285: .It Cm ~&
1.176 jmc 286: Background
287: .Nm
288: at logout when waiting for forwarded connection / X11 sessions to terminate.
1.104 djm 289: .It Cm ~?
1.176 jmc 290: Display a list of escape characters.
1.170 markus 291: .It Cm ~B
1.176 jmc 292: Send a BREAK to the remote system
293: (only useful for SSH protocol version 2 and if the peer supports it).
1.149 jakob 294: .It Cm ~C
1.186 djm 295: Open command line.
296: Currently this allows the addition of port forwardings using the
1.149 jakob 297: .Fl L
298: and
299: .Fl R
1.186 djm 300: options (see below).
1.188 jmc 301: It also allows the cancellation of existing remote port-forwardings
1.186 djm 302: using
303: .Fl KR Ar hostport .
1.187 djm 304: Basic help is available, using the
305: .Fl h
1.186 djm 306: option.
1.104 djm 307: .It Cm ~R
1.176 jmc 308: Request rekeying of the connection
309: (only useful for SSH protocol version 2 and if the peer supports it).
1.104 djm 310: .El
1.49 markus 311: .Ss X11 and TCP forwarding
1.110 deraadt 312: If the
313: .Cm ForwardX11
314: variable is set to
315: .Dq yes
1.176 jmc 316: (or see the description of the
1.110 deraadt 317: .Fl X
318: and
319: .Fl x
320: options described later)
321: and the user is using X11 (the
1.2 deraadt 322: .Ev DISPLAY
1.1 deraadt 323: environment variable is set), the connection to the X11 display is
324: automatically forwarded to the remote side in such a way that any X11
325: programs started from the shell (or command) will go through the
326: encrypted channel, and the connection to the real X server will be made
1.40 aaron 327: from the local machine.
328: The user should not manually set
1.2 deraadt 329: .Ev DISPLAY .
1.1 deraadt 330: Forwarding of X11 connections can be
331: configured on the command line or in configuration files.
1.2 deraadt 332: .Pp
333: The
1.44 aaron 334: .Ev DISPLAY
1.2 deraadt 335: value set by
336: .Nm
1.176 jmc 337: will point to the server machine, but with a display number greater than zero.
1.40 aaron 338: This is normal, and happens because
1.2 deraadt 339: .Nm
340: creates a
341: .Dq proxy
342: X server on the server machine for forwarding the
1.1 deraadt 343: connections over the encrypted channel.
1.2 deraadt 344: .Pp
345: .Nm
1.1 deraadt 346: will also automatically set up Xauthority data on the server machine.
347: For this purpose, it will generate a random authorization cookie,
348: store it in Xauthority on the server, and verify that any forwarded
349: connections carry this cookie and replace it by the real cookie when
1.40 aaron 350: the connection is opened.
351: The real authentication cookie is never
1.1 deraadt 352: sent to the server machine (and no cookies are sent in the plain).
1.2 deraadt 353: .Pp
1.163 stevesk 354: If the
355: .Cm ForwardAgent
356: variable is set to
357: .Dq yes
1.176 jmc 358: (or see the description of the
1.163 stevesk 359: .Fl A
360: and
361: .Fl a
1.168 jmc 362: options described later) and
1.163 stevesk 363: the user is using an authentication agent, the connection to the agent
364: is automatically forwarded to the remote side.
1.2 deraadt 365: .Pp
1.1 deraadt 366: Forwarding of arbitrary TCP/IP connections over the secure channel can
1.120 stevesk 367: be specified either on the command line or in a configuration file.
1.40 aaron 368: One possible application of TCP/IP forwarding is a secure connection to an
1.92 markus 369: electronic purse; another is going through firewalls.
1.49 markus 370: .Ss Server authentication
1.2 deraadt 371: .Nm
1.49 markus 372: automatically maintains and checks a database containing
1.40 aaron 373: identifications for all hosts it has ever been used with.
1.116 markus 374: Host keys are stored in
1.49 markus 375: .Pa $HOME/.ssh/known_hosts
1.40 aaron 376: in the user's home directory.
1.116 markus 377: Additionally, the file
1.147 deraadt 378: .Pa /etc/ssh/ssh_known_hosts
1.116 markus 379: is automatically checked for known hosts.
1.40 aaron 380: Any new hosts are automatically added to the user's file.
1.176 jmc 381: If a host's identification ever changes,
1.2 deraadt 382: .Nm
1.1 deraadt 383: warns about this and disables password authentication to prevent a
1.40 aaron 384: trojan horse from getting the user's password.
1.176 jmc 385: Another purpose of this mechanism is to prevent man-in-the-middle attacks
386: which could otherwise be used to circumvent the encryption.
1.40 aaron 387: The
1.2 deraadt 388: .Cm StrictHostKeyChecking
1.158 stevesk 389: option can be used to prevent logins to machines whose
1.1 deraadt 390: host key is not known or has changed.
1.194 jakob 391: .Pp
392: .Nm
393: can be configured to verify host identification using fingerprint resource
394: records (SSHFP) published in DNS.
395: The
396: .Cm VerifyHostKeyDNS
397: option can be used to control how DNS lookups are performed.
398: SSHFP resource records can be generated using
399: .Xr ssh-keygen 1 .
1.65 aaron 400: .Pp
401: The options are as follows:
1.2 deraadt 402: .Bl -tag -width Ds
1.176 jmc 403: .It Fl 1
404: Forces
405: .Nm
406: to try protocol version 1 only.
407: .It Fl 2
408: Forces
409: .Nm
410: to try protocol version 2 only.
411: .It Fl 4
412: Forces
413: .Nm
414: to use IPv4 addresses only.
415: .It Fl 6
416: Forces
417: .Nm
418: to use IPv6 addresses only.
1.54 markus 419: .It Fl A
420: Enables forwarding of the authentication agent connection.
421: This can also be specified on a per-host basis in a configuration file.
1.165 stevesk 422: .Pp
1.168 jmc 423: Agent forwarding should be enabled with caution.
424: Users with the ability to bypass file permissions on the remote host
425: (for the agent's Unix-domain socket)
426: can access the local agent through the forwarded connection.
427: An attacker cannot obtain key material from the agent,
1.165 stevesk 428: however they can perform operations on the keys that enable them to
429: authenticate using the identities loaded into the agent.
1.176 jmc 430: .It Fl a
431: Disables forwarding of the authentication agent connection.
1.108 markus 432: .It Fl b Ar bind_address
433: Specify the interface to transmit from on machines with multiple
434: interfaces or aliased addresses.
1.176 jmc 435: .It Fl C
436: Requests compression of all data (including stdin, stdout, stderr, and
437: data for forwarded X11 and TCP/IP connections).
438: The compression algorithm is the same used by
439: .Xr gzip 1 ,
440: and the
441: .Dq level
442: can be controlled by the
443: .Cm CompressionLevel
444: option for protocol version 1.
445: Compression is desirable on modem lines and other
446: slow connections, but will only slow down things on fast networks.
447: The default value can be set on a host-by-host basis in the
448: configuration files; see the
449: .Cm Compression
450: option.
1.189 dtucker 451: .It Fl c Ar cipher_spec
452: Selects the cipher specification for encrypting the session.
453: .Pp
454: Protocol version 1 allows specification of a single cipher.
455: The suported values are
456: .Dq 3des ,
457: .Dq blowfish
458: and
459: .Dq des .
1.2 deraadt 460: .Ar 3des
1.189 dtucker 461: (triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
1.44 aaron 462: It is believed to be secure.
1.5 deraadt 463: .Ar blowfish
1.176 jmc 464: is a fast block cipher; it appears very secure and is much faster than
1.40 aaron 465: .Ar 3des .
1.131 stevesk 466: .Ar des
467: is only supported in the
468: .Nm
469: client for interoperability with legacy protocol 1 implementations
470: that do not support the
471: .Ar 3des
1.168 jmc 472: cipher.
473: Its use is strongly discouraged due to cryptographic weaknesses.
1.189 dtucker 474: The default is
475: .Dq 3des .
476: .Pp
477: For protocol version 2
478: .Ar cipher_spec
479: is a comma-separated list of ciphers
480: listed in order of preference.
481: The supported ciphers are
482: .Dq 3des-cbc ,
483: .Dq aes128-cbc ,
484: .Dq aes192-cbc ,
485: .Dq aes256-cbc ,
486: .Dq aes128-ctr ,
487: .Dq aes192-ctr ,
488: .Dq aes256-ctr ,
489: .Dq arcfour ,
490: .Dq blowfish-cbc ,
491: and
492: .Dq cast128-cbc .
493: The default is
494: .Bd -literal
495: ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
496: aes192-cbc,aes256-cbc''
497: .Ed
1.176 jmc 498: .It Fl D Ar port
499: Specifies a local
500: .Dq dynamic
501: application-level port forwarding.
502: This works by allocating a socket to listen to
503: .Ar port
504: on the local side, and whenever a connection is made to this port, the
505: connection is forwarded over the secure channel, and the application
506: protocol is then used to determine where to connect to from the
507: remote machine.
508: Currently the SOCKS4 and SOCKS5 protocols are supported, and
509: .Nm
510: will act as a SOCKS server.
511: Only root can forward privileged ports.
512: Dynamic port forwardings can also be specified in the configuration file.
513: .It Fl e Ar ch | ^ch | none
1.2 deraadt 514: Sets the escape character for sessions with a pty (default:
515: .Ql ~ ) .
1.40 aaron 516: The escape character is only recognized at the beginning of a line.
517: The escape character followed by a dot
1.2 deraadt 518: .Pq Ql \&.
1.176 jmc 519: closes the connection;
520: followed by control-Z suspends the connection;
521: and followed by itself sends the escape character once.
1.40 aaron 522: Setting the character to
1.2 deraadt 523: .Dq none
524: disables any escapes and makes the session fully transparent.
1.176 jmc 525: .It Fl F Ar configfile
526: Specifies an alternative per-user configuration file.
527: If a configuration file is given on the command line,
528: the system-wide configuration file
529: .Pq Pa /etc/ssh/ssh_config
530: will be ignored.
531: The default for the per-user configuration file is
532: .Pa $HOME/.ssh/config .
1.2 deraadt 533: .It Fl f
534: Requests
535: .Nm
1.40 aaron 536: to go to background just before command execution.
537: This is useful if
1.2 deraadt 538: .Nm
539: is going to ask for passwords or passphrases, but the user
1.40 aaron 540: wants it in the background.
1.44 aaron 541: This implies
1.2 deraadt 542: .Fl n .
1.1 deraadt 543: The recommended way to start X11 programs at a remote site is with
1.2 deraadt 544: something like
545: .Ic ssh -f host xterm .
1.34 markus 546: .It Fl g
547: Allows remote hosts to connect to local forwarded ports.
1.176 jmc 548: .It Fl I Ar smartcard_device
549: Specifies which smartcard device to use.
550: The argument is the device
551: .Nm
552: should use to communicate with a smartcard used for storing the user's
553: private RSA key.
1.2 deraadt 554: .It Fl i Ar identity_file
1.144 stevesk 555: Selects a file from which the identity (private key) for
1.68 markus 556: RSA or DSA authentication is read.
1.144 stevesk 557: The default is
1.49 markus 558: .Pa $HOME/.ssh/identity
1.144 stevesk 559: for protocol version 1, and
560: .Pa $HOME/.ssh/id_rsa
561: and
562: .Pa $HOME/.ssh/id_dsa
563: for protocol version 2.
1.40 aaron 564: Identity files may also be specified on
565: a per-host basis in the configuration file.
566: It is possible to have multiple
1.2 deraadt 567: .Fl i
568: options (and multiple identities specified in
1.1 deraadt 569: configuration files).
1.2 deraadt 570: .It Fl k
1.179 dtucker 571: Disables forwarding (delegation) of GSSAPI credentials to the server.
1.176 jmc 572: .It Fl L Xo
573: .Sm off
1.200 ! djm 574: .Oo Ar bind_address : Oc
1.176 jmc 575: .Ar port : host : hostport
576: .Sm on
577: .Xc
578: Specifies that the given port on the local (client) host is to be
579: forwarded to the given host and port on the remote side.
580: This works by allocating a socket to listen to
581: .Ar port
1.200 ! djm 582: on the local side, optionally bound to the specified
! 583: .Ar bind_address .
! 584: Whenever a connection is made to this port, the
1.176 jmc 585: connection is forwarded over the secure channel, and a connection is
586: made to
587: .Ar host
588: port
589: .Ar hostport
590: from the remote machine.
591: Port forwardings can also be specified in the configuration file.
592: IPv6 addresses can be specified with an alternative syntax:
593: .Sm off
594: .Xo
1.200 ! djm 595: .Oo Ar bind_address / Oc
1.176 jmc 596: .Ar port No / Ar host No /
1.200 ! djm 597: .Ar hostport
1.176 jmc 598: .Xc
599: .Sm on
1.200 ! djm 600: or by enclosing the address in square brackets.
! 601: Only the superuser can forward privileged ports.
! 602: By default, the local port is bound in accordance with the
! 603: .Cm GatewayPorts
! 604: setting.
! 605: However, an explicit
! 606: .Ar bind_address
! 607: may be used to bind the connection to a specific address.
! 608: The
! 609: .Ar bind_address
! 610: of
! 611: .Dq localhost
! 612: indicates that the listening port be bound for local use only, while an
! 613: empty address or
! 614: .Dq *
! 615: indicates that the port should be available from all interfaces.
1.2 deraadt 616: .It Fl l Ar login_name
1.40 aaron 617: Specifies the user to log in as on the remote machine.
618: This also may be specified on a per-host basis in the configuration file.
1.190 djm 619: .It Fl M
620: Places the
621: .Nm
622: client into
623: .Dq master
624: mode for connection sharing.
625: Refer to the description of
626: .Cm ControlMaster
627: in
628: .Xr ssh_config 5
629: for details.
1.193 jmc 630: .It Fl m Ar mac_spec
631: Additionally, for protocol version 2 a comma-separated list of MAC
632: (message authentication code) algorithms can
633: be specified in order of preference.
634: See the
635: .Cm MACs
636: keyword for more information.
1.176 jmc 637: .It Fl N
638: Do not execute a remote command.
639: This is useful for just forwarding ports
640: (protocol version 2 only).
1.2 deraadt 641: .It Fl n
642: Redirects stdin from
643: .Pa /dev/null
644: (actually, prevents reading from stdin).
1.1 deraadt 645: This must be used when
1.2 deraadt 646: .Nm
1.40 aaron 647: is run in the background.
648: A common trick is to use this to run X11 programs on a remote machine.
649: For example,
1.2 deraadt 650: .Ic ssh -n shadows.cs.hut.fi emacs &
651: will start an emacs on shadows.cs.hut.fi, and the X11
1.1 deraadt 652: connection will be automatically forwarded over an encrypted channel.
653: The
1.2 deraadt 654: .Nm
1.1 deraadt 655: program will be put in the background.
656: (This does not work if
1.2 deraadt 657: .Nm
658: needs to ask for a password or passphrase; see also the
659: .Fl f
660: option.)
1.199 jmc 661: .It Fl O Ar ctl_cmd
662: Control an active connection multiplexing master process.
663: When the
664: .Fl O
665: option is specified, the
666: .Ar ctl_cmd
667: argument is interpreted and passed to the master process.
668: Valid commands are:
669: .Dq check
670: (check that the master process is running) and
671: .Dq exit
672: (request the master to exit).
1.2 deraadt 673: .It Fl o Ar option
1.127 stevesk 674: Can be used to give options in the format used in the configuration file.
1.1 deraadt 675: This is useful for specifying options for which there is no separate
1.40 aaron 676: command-line flag.
1.176 jmc 677: For full details of the options listed below, and their possible values, see
678: .Xr ssh_config 5 .
679: .Pp
680: .Bl -tag -width Ds -offset indent -compact
681: .It AddressFamily
682: .It BatchMode
683: .It BindAddress
684: .It ChallengeResponseAuthentication
685: .It CheckHostIP
686: .It Cipher
687: .It Ciphers
688: .It ClearAllForwardings
689: .It Compression
690: .It CompressionLevel
691: .It ConnectionAttempts
1.185 dtucker 692: .It ConnectTimeout
1.190 djm 693: .It ControlMaster
694: .It ControlPath
1.176 jmc 695: .It DynamicForward
696: .It EscapeChar
697: .It ForwardAgent
698: .It ForwardX11
1.178 markus 699: .It ForwardX11Trusted
1.176 jmc 700: .It GatewayPorts
701: .It GlobalKnownHostsFile
702: .It GSSAPIAuthentication
703: .It GSSAPIDelegateCredentials
704: .It Host
705: .It HostbasedAuthentication
706: .It HostKeyAlgorithms
707: .It HostKeyAlias
708: .It HostName
709: .It IdentityFile
1.182 markus 710: .It IdentitiesOnly
1.197 djm 711: .It KbdInteractiveDevices
1.176 jmc 712: .It LocalForward
713: .It LogLevel
714: .It MACs
715: .It NoHostAuthenticationForLocalhost
716: .It NumberOfPasswordPrompts
717: .It PasswordAuthentication
718: .It Port
719: .It PreferredAuthentications
720: .It Protocol
721: .It ProxyCommand
722: .It PubkeyAuthentication
723: .It RemoteForward
724: .It RhostsRSAAuthentication
725: .It RSAAuthentication
1.184 jmc 726: .It SendEnv
1.181 markus 727: .It ServerAliveInterval
728: .It ServerAliveCountMax
1.176 jmc 729: .It SmartcardDevice
730: .It StrictHostKeyChecking
1.180 markus 731: .It TCPKeepAlive
1.176 jmc 732: .It UsePrivilegedPort
733: .It User
734: .It UserKnownHostsFile
735: .It VerifyHostKeyDNS
736: .It XAuthLocation
737: .El
1.2 deraadt 738: .It Fl p Ar port
1.40 aaron 739: Port to connect to on the remote host.
740: This can be specified on a
1.1 deraadt 741: per-host basis in the configuration file.
1.2 deraadt 742: .It Fl q
1.40 aaron 743: Quiet mode.
744: Causes all warning and diagnostic messages to be suppressed.
1.176 jmc 745: .It Fl R Xo
746: .Sm off
1.200 ! djm 747: .Oo Ar bind_address : Oc
1.176 jmc 748: .Ar port : host : hostport
749: .Sm on
750: .Xc
751: Specifies that the given port on the remote (server) host is to be
752: forwarded to the given host and port on the local side.
753: This works by allocating a socket to listen to
754: .Ar port
755: on the remote side, and whenever a connection is made to this port, the
756: connection is forwarded over the secure channel, and a connection is
757: made to
758: .Ar host
759: port
760: .Ar hostport
761: from the local machine.
1.200 ! djm 762: .Pp
1.176 jmc 763: Port forwardings can also be specified in the configuration file.
764: Privileged ports can be forwarded only when
765: logging in as root on the remote machine.
1.200 ! djm 766: IPv6 addresses can be specified by enclosing the address in square braces or
! 767: using an alternative syntax:
! 768: .Xo
1.176 jmc 769: .Sm off
1.200 ! djm 770: .Oo Ar bind_address / Oc
! 771: .Ar host/port/hostport
1.176 jmc 772: .Sm on
1.200 ! djm 773: .Xc .
! 774: .Pp
! 775: By default, the listening socket on the server will be bound to the loopback
! 776: interface only.
! 777: This may be overriden by specifying a
! 778: .Ar bind_address .
! 779: An empty
! 780: .Ar bind_address ,
! 781: or the address
! 782: .Ql *
! 783: indicates that the remote socket should listen on all interfaces.
! 784: Specifying a remote
! 785: .Ar bind_address
! 786: will only succeed if the server's
! 787: .Cm GatewayPorts
! 788: option is enabled (see
! 789: .Xr sshd_config 5 ).
1.198 djm 790: .It Fl S Ar ctl_path
1.193 jmc 791: Specifies the location of a control socket for connection sharing.
1.190 djm 792: Refer to the description of
1.191 djm 793: .Cm ControlPath
794: and
1.190 djm 795: .Cm ControlMaster
796: in
797: .Xr ssh_config 5
798: for details.
1.80 djm 799: .It Fl s
1.172 jmc 800: May be used to request invocation of a subsystem on the remote system.
801: Subsystems are a feature of the SSH2 protocol which facilitate the use
1.176 jmc 802: of SSH as a secure transport for other applications (eg.\&
803: .Xr sftp 1 ) .
1.172 jmc 804: The subsystem is specified as the remote command.
1.176 jmc 805: .It Fl T
806: Disable pseudo-tty allocation.
1.2 deraadt 807: .It Fl t
1.40 aaron 808: Force pseudo-tty allocation.
1.43 brad 809: This can be used to execute arbitrary
1.40 aaron 810: screen-based programs on a remote machine, which can be very useful,
811: e.g., when implementing menu services.
1.73 markus 812: Multiple
813: .Fl t
814: options force tty allocation, even if
815: .Nm
816: has no local tty.
1.176 jmc 817: .It Fl V
818: Display the version number and exit.
1.2 deraadt 819: .It Fl v
1.40 aaron 820: Verbose mode.
821: Causes
1.2 deraadt 822: .Nm
1.40 aaron 823: to print debugging messages about its progress.
824: This is helpful in
1.1 deraadt 825: debugging connection, authentication, and configuration problems.
1.73 markus 826: Multiple
827: .Fl v
1.169 naddy 828: options increase the verbosity.
829: The maximum is 3.
1.2 deraadt 830: .It Fl X
1.1 deraadt 831: Enables X11 forwarding.
1.54 markus 832: This can also be specified on a per-host basis in a configuration file.
1.165 stevesk 833: .Pp
1.168 jmc 834: X11 forwarding should be enabled with caution.
835: Users with the ability to bypass file permissions on the remote host
836: (for the user's X authorization database)
837: can access the local X11 display through the forwarded connection.
838: An attacker may then be able to perform activities such as keystroke monitoring.
1.176 jmc 839: .It Fl x
840: Disables X11 forwarding.
1.178 markus 841: .It Fl Y
842: Enables trusted X11 forwarding.
1.2 deraadt 843: .El
844: .Sh CONFIGURATION FILES
845: .Nm
1.158 stevesk 846: may additionally obtain configuration data from
847: a per-user configuration file and a system-wide configuration file.
848: The file format and configuration options are described in
849: .Xr ssh_config 5 .
1.2 deraadt 850: .Sh ENVIRONMENT
851: .Nm
1.1 deraadt 852: will normally set the following environment variables:
1.176 jmc 853: .Bl -tag -width LOGNAME
1.2 deraadt 854: .It Ev DISPLAY
855: The
856: .Ev DISPLAY
1.40 aaron 857: variable indicates the location of the X11 server.
1.44 aaron 858: It is automatically set by
1.2 deraadt 859: .Nm
860: to point to a value of the form
861: .Dq hostname:n
862: where hostname indicates
1.176 jmc 863: the host where the shell runs, and n is an integer \*(Ge 1.
1.40 aaron 864: .Nm
865: uses this special value to forward X11 connections over the secure
866: channel.
1.107 markus 867: The user should normally not set
868: .Ev DISPLAY
869: explicitly, as that
1.1 deraadt 870: will render the X11 connection insecure (and will require the user to
871: manually copy any required authorization cookies).
1.2 deraadt 872: .It Ev HOME
1.1 deraadt 873: Set to the path of the user's home directory.
1.2 deraadt 874: .It Ev LOGNAME
875: Synonym for
1.12 aaron 876: .Ev USER ;
877: set for compatibility with systems that use this variable.
1.2 deraadt 878: .It Ev MAIL
1.129 stevesk 879: Set to the path of the user's mailbox.
1.40 aaron 880: .It Ev PATH
1.2 deraadt 881: Set to the default
882: .Ev PATH ,
883: as specified when compiling
1.12 aaron 884: .Nm ssh .
1.118 markus 885: .It Ev SSH_ASKPASS
886: If
887: .Nm
888: needs a passphrase, it will read the passphrase from the current
889: terminal if it was run from a terminal.
890: If
891: .Nm
892: does not have a terminal associated with it but
893: .Ev DISPLAY
894: and
895: .Ev SSH_ASKPASS
896: are set, it will execute the program specified by
897: .Ev SSH_ASKPASS
898: and open an X11 window to read the passphrase.
899: This is particularly useful when calling
900: .Nm
901: from a
1.196 jmc 902: .Pa .xsession
1.118 markus 903: or related script.
904: (Note that on some machines it
905: may be necessary to redirect the input from
906: .Pa /dev/null
907: to make this work.)
1.18 markus 908: .It Ev SSH_AUTH_SOCK
1.129 stevesk 909: Identifies the path of a unix-domain socket used to communicate with the
1.17 markus 910: agent.
1.166 stevesk 911: .It Ev SSH_CONNECTION
912: Identifies the client and server ends of the connection.
1.40 aaron 913: The variable contains
1.166 stevesk 914: four space-separated values: client ip-address, client port number,
915: server ip-address and server port number.
1.73 markus 916: .It Ev SSH_ORIGINAL_COMMAND
917: The variable contains the original command line if a forced command
918: is executed.
919: It can be used to extract the original arguments.
1.2 deraadt 920: .It Ev SSH_TTY
1.1 deraadt 921: This is set to the name of the tty (path to the device) associated
1.40 aaron 922: with the current shell or command.
923: If the current session has no tty,
1.1 deraadt 924: this variable is not set.
1.2 deraadt 925: .It Ev TZ
1.1 deraadt 926: The timezone variable is set to indicate the present timezone if it
1.56 deraadt 927: was set when the daemon was started (i.e., the daemon passes the value
1.1 deraadt 928: on to new connections).
1.2 deraadt 929: .It Ev USER
1.1 deraadt 930: Set to the name of the user logging in.
1.2 deraadt 931: .El
932: .Pp
1.44 aaron 933: Additionally,
1.2 deraadt 934: .Nm
1.44 aaron 935: reads
936: .Pa $HOME/.ssh/environment ,
1.2 deraadt 937: and adds lines of the format
938: .Dq VARNAME=value
1.161 marc 939: to the environment if the file exists and if users are allowed to
940: change their environment.
1.176 jmc 941: For more information, see the
1.161 marc 942: .Cm PermitUserEnvironment
1.162 stevesk 943: option in
1.161 marc 944: .Xr sshd_config 5 .
1.2 deraadt 945: .Sh FILES
1.36 markus 946: .Bl -tag -width Ds
1.116 markus 947: .It Pa $HOME/.ssh/known_hosts
1.129 stevesk 948: Records host keys for all hosts the user has logged into that are not
1.2 deraadt 949: in
1.147 deraadt 950: .Pa /etc/ssh/ssh_known_hosts .
1.2 deraadt 951: See
952: .Xr sshd 8 .
1.102 itojun 953: .It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa, $HOME/.ssh/id_rsa
954: Contains the authentication identity of the user.
955: They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
1.48 markus 956: These files
957: contain sensitive data and should be readable by the user but not
1.15 markus 958: accessible by others (read/write/execute).
959: Note that
960: .Nm
1.48 markus 961: ignores a private key file if it is accessible by others.
1.15 markus 962: It is possible to specify a passphrase when
1.1 deraadt 963: generating the key; the passphrase will be used to encrypt the
1.8 deraadt 964: sensitive part of this file using 3DES.
1.102 itojun 965: .It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub, $HOME/.ssh/id_rsa.pub
1.1 deraadt 966: Contains the public key for authentication (public part of the
1.40 aaron 967: identity file in human-readable form).
1.48 markus 968: The contents of the
969: .Pa $HOME/.ssh/identity.pub
1.176 jmc 970: file should be added to the file
1.2 deraadt 971: .Pa $HOME/.ssh/authorized_keys
972: on all machines
1.137 deraadt 973: where the user wishes to log in using protocol version 1 RSA authentication.
1.48 markus 974: The contents of the
975: .Pa $HOME/.ssh/id_dsa.pub
1.102 itojun 976: and
977: .Pa $HOME/.ssh/id_rsa.pub
1.48 markus 978: file should be added to
1.115 markus 979: .Pa $HOME/.ssh/authorized_keys
1.48 markus 980: on all machines
1.137 deraadt 981: where the user wishes to log in using protocol version 2 DSA/RSA authentication.
1.48 markus 982: These files are not
1.40 aaron 983: sensitive and can (but need not) be readable by anyone.
1.48 markus 984: These files are
1.84 markus 985: never used automatically and are not necessary; they are only provided for
1.1 deraadt 986: the convenience of the user.
1.2 deraadt 987: .It Pa $HOME/.ssh/config
1.40 aaron 988: This is the per-user configuration file.
1.158 stevesk 989: The file format and configuration options are described in
990: .Xr ssh_config 5 .
1.183 djm 991: Because of the potential for abuse, this file must have strict permissions:
992: read/write for the user, and not accessible by others.
1.2 deraadt 993: .It Pa $HOME/.ssh/authorized_keys
1.115 markus 994: Lists the public keys (RSA/DSA) that can be used for logging in as this user.
1.40 aaron 995: The format of this file is described in the
1.2 deraadt 996: .Xr sshd 8
1.40 aaron 997: manual page.
1.176 jmc 998: In the simplest form the format is the same as the
999: .Pa .pub
1.116 markus 1000: identity files.
1.48 markus 1001: This file is not highly sensitive, but the recommended
1002: permissions are read/write for the user, and not accessible by others.
1.147 deraadt 1003: .It Pa /etc/ssh/ssh_known_hosts
1.40 aaron 1004: Systemwide list of known host keys.
1.116 markus 1005: This file should be prepared by the
1.1 deraadt 1006: system administrator to contain the public host keys of all machines in the
1.40 aaron 1007: organization.
1008: This file should be world-readable.
1009: This file contains
1.1 deraadt 1010: public keys, one per line, in the following format (fields separated
1.116 markus 1011: by spaces): system name, public key and optional comment field.
1.40 aaron 1012: When different names are used
1.1 deraadt 1013: for the same machine, all such names should be listed, separated by
1.40 aaron 1014: commas.
1.176 jmc 1015: The format is described in the
1.2 deraadt 1016: .Xr sshd 8
1.1 deraadt 1017: manual page.
1.2 deraadt 1018: .Pp
1.1 deraadt 1019: The canonical system name (as returned by name servers) is used by
1.2 deraadt 1020: .Xr sshd 8
1.1 deraadt 1021: to verify the client host when logging in; other names are needed because
1.2 deraadt 1022: .Nm
1.1 deraadt 1023: does not convert the user-supplied name to a canonical name before
1024: checking the key, because someone with access to the name servers
1025: would then be able to fool host authentication.
1.147 deraadt 1026: .It Pa /etc/ssh/ssh_config
1.40 aaron 1027: Systemwide configuration file.
1.158 stevesk 1028: The file format and configuration options are described in
1029: .Xr ssh_config 5 .
1.147 deraadt 1030: .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key
1.141 markus 1031: These three files contain the private parts of the host keys
1032: and are used for
1033: .Cm RhostsRSAAuthentication
1034: and
1035: .Cm HostbasedAuthentication .
1.155 stevesk 1036: If the protocol version 1
1037: .Cm RhostsRSAAuthentication
1.157 deraadt 1038: method is used,
1.155 stevesk 1039: .Nm
1040: must be setuid root, since the host key is readable only by root.
1041: For protocol version 2,
1042: .Nm
1043: uses
1044: .Xr ssh-keysign 8
1045: to access the host keys for
1046: .Cm HostbasedAuthentication .
1047: This eliminates the requirement that
1048: .Nm
1049: be setuid root when that authentication method is used.
1050: By default
1.141 markus 1051: .Nm
1.155 stevesk 1052: is not setuid root.
1.2 deraadt 1053: .It Pa $HOME/.rhosts
1054: This file is used in
1.195 markus 1055: .Cm RhostsRSAAuthentication
1056: and
1057: .Cm HostbasedAuthentication
1.2 deraadt 1058: authentication to list the
1.40 aaron 1059: host/user pairs that are permitted to log in.
1060: (Note that this file is
1.1 deraadt 1061: also used by rlogin and rsh, which makes using this file insecure.)
1062: Each line of the file contains a host name (in the canonical form
1063: returned by name servers), and then a user name on that host,
1.40 aaron 1064: separated by a space.
1.92 markus 1065: On some machines this file may need to be
1.1 deraadt 1066: world-readable if the user's home directory is on a NFS partition,
1067: because
1.2 deraadt 1068: .Xr sshd 8
1.40 aaron 1069: reads it as root.
1070: Additionally, this file must be owned by the user,
1071: and must not have write permissions for anyone else.
1072: The recommended
1.1 deraadt 1073: permission for most machines is read/write for the user, and not
1074: accessible by others.
1.2 deraadt 1075: .Pp
1.195 markus 1076: Note that
1.2 deraadt 1077: .Xr sshd 8
1.195 markus 1078: allows authentication only in combination with client host key
1079: authentication before permitting log in.
1.137 deraadt 1080: If the server machine does not have the client's host key in
1.147 deraadt 1081: .Pa /etc/ssh/ssh_known_hosts ,
1.137 deraadt 1082: it can be stored in
1.2 deraadt 1083: .Pa $HOME/.ssh/known_hosts .
1084: The easiest way to do this is to
1.1 deraadt 1085: connect back to the client from the server machine using ssh; this
1.48 markus 1086: will automatically add the host key to
1.2 deraadt 1087: .Pa $HOME/.ssh/known_hosts .
1088: .It Pa $HOME/.shosts
1089: This file is used exactly the same way as
1.176 jmc 1090: .Pa .rhosts .
1.2 deraadt 1091: The purpose for
1.195 markus 1092: having this file is to be able to use
1093: .Cm RhostsRSAAuthentication
1094: and
1095: .Cm HostbasedAuthentication
1096: authentication without permitting login with
1.176 jmc 1097: .Xr rlogin
1.2 deraadt 1098: or
1099: .Xr rsh 1 .
1100: .It Pa /etc/hosts.equiv
1101: This file is used during
1.195 markus 1102: .Cm RhostsRSAAuthentication
1103: and
1104: .Cm HostbasedAuthentication
1.173 jmc 1105: authentication.
1.40 aaron 1106: It contains
1.176 jmc 1107: canonical hosts names, one per line (the full format is described in the
1.2 deraadt 1108: .Xr sshd 8
1.40 aaron 1109: manual page).
1110: If the client host is found in this file, login is
1.1 deraadt 1111: automatically permitted provided client and server user names are the
1.40 aaron 1112: same.
1.195 markus 1113: Additionally, successful client host key authentication is required.
1.40 aaron 1114: This file should only be writable by root.
1.2 deraadt 1115: .It Pa /etc/shosts.equiv
1.44 aaron 1116: This file is processed exactly as
1.2 deraadt 1117: .Pa /etc/hosts.equiv .
1.1 deraadt 1118: This file may be useful to permit logins using
1.2 deraadt 1119: .Nm
1.1 deraadt 1120: but not using rsh/rlogin.
1.147 deraadt 1121: .It Pa /etc/ssh/sshrc
1.1 deraadt 1122: Commands in this file are executed by
1.2 deraadt 1123: .Nm
1.1 deraadt 1124: when the user logs in just before the user's shell (or command) is started.
1125: See the
1.2 deraadt 1126: .Xr sshd 8
1.1 deraadt 1127: manual page for more information.
1.2 deraadt 1128: .It Pa $HOME/.ssh/rc
1.1 deraadt 1129: Commands in this file are executed by
1.2 deraadt 1130: .Nm
1.1 deraadt 1131: when the user logs in just before the user's shell (or command) is
1132: started.
1.44 aaron 1133: See the
1.2 deraadt 1134: .Xr sshd 8
1.1 deraadt 1135: manual page for more information.
1.31 markus 1136: .It Pa $HOME/.ssh/environment
1137: Contains additional definitions for environment variables, see section
1138: .Sx ENVIRONMENT
1139: above.
1.58 itojun 1140: .El
1.145 markus 1141: .Sh DIAGNOSTICS
1142: .Nm
1143: exits with the exit status of the remote command or with 255
1144: if an error occurred.
1.2 deraadt 1145: .Sh SEE ALSO
1.176 jmc 1146: .Xr gzip 1 ,
1.2 deraadt 1147: .Xr rsh 1 ,
1148: .Xr scp 1 ,
1.83 djm 1149: .Xr sftp 1 ,
1.2 deraadt 1150: .Xr ssh-add 1 ,
1151: .Xr ssh-agent 1 ,
1152: .Xr ssh-keygen 1 ,
1153: .Xr telnet 1 ,
1.176 jmc 1154: .Xr hosts.equiv 5 ,
1.159 stevesk 1155: .Xr ssh_config 5 ,
1.160 naddy 1156: .Xr ssh-keysign 8 ,
1.87 itojun 1157: .Xr sshd 8
1.106 markus 1158: .Rs
1159: .%A T. Ylonen
1160: .%A T. Kivinen
1161: .%A M. Saarinen
1162: .%A T. Rinne
1163: .%A S. Lehtinen
1164: .%T "SSH Protocol Architecture"
1.150 markus 1165: .%N draft-ietf-secsh-architecture-12.txt
1166: .%D January 2002
1.106 markus 1167: .%O work in progress material
1168: .Re
1.173 jmc 1169: .Sh AUTHORS
1170: OpenSSH is a derivative of the original and free
1171: ssh 1.2.12 release by Tatu Ylonen.
1172: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1173: Theo de Raadt and Dug Song
1174: removed many bugs, re-added newer features and
1175: created OpenSSH.
1176: Markus Friedl contributed the support for SSH
1177: protocol versions 1.5 and 2.0.
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