Annotation of src/usr.bin/ssh/ssh.1, Revision 1.191
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: .\"
1.191 ! djm 37: .\" $OpenBSD: ssh.1,v 1.190 2004/06/13 15:03:02 djm 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
1.176 jmc 49: .Op Fl D Ar port
1.2 deraadt 50: .Op Fl e Ar escape_char
1.176 jmc 51: .Op Fl F Ar configfile
1.2 deraadt 52: .Op Fl i Ar identity_file
1.176 jmc 53: .Bk -words
1.12 aaron 54: .Oo Fl L Xo
55: .Sm off
1.33 markus 56: .Ar port :
1.12 aaron 57: .Ar host :
58: .Ar hostport
59: .Sm on
60: .Xc
61: .Oc
1.168 jmc 62: .Ek
1.176 jmc 63: .Op Fl l Ar login_name
64: .Op Fl m Ar mac_spec
65: .Op Fl o Ar option
1.168 jmc 66: .Bk -words
1.176 jmc 67: .Op Fl p Ar port
68: .Ek
1.12 aaron 69: .Oo Fl R Xo
70: .Sm off
1.33 markus 71: .Ar port :
1.12 aaron 72: .Ar host :
73: .Ar hostport
74: .Sm on
75: .Xc
76: .Oc
1.191 ! djm 77: .Op Fl S Ar ctl_path
1.176 jmc 78: .Oo Ar user Ns @ Oc Ns Ar hostname
1.2 deraadt 79: .Op Ar command
1.44 aaron 80: .Sh DESCRIPTION
1.2 deraadt 81: .Nm
1.96 deraadt 82: (SSH client) is a program for logging into a remote machine and for
1.40 aaron 83: executing commands on a remote machine.
1.176 jmc 84: It is intended to replace rlogin and rsh,
85: and provide secure encrypted communications between
1.40 aaron 86: two untrusted hosts over an insecure network.
1.176 jmc 87: X11 connections and arbitrary TCP/IP ports
88: can also be forwarded over the secure channel.
1.2 deraadt 89: .Pp
90: .Nm
1.44 aaron 91: connects and logs into the specified
1.176 jmc 92: .Ar hostname
93: (with optional
94: .Ar user
95: name).
1.1 deraadt 96: The user must prove
1.49 markus 97: his/her identity to the remote machine using one of several methods
1.176 jmc 98: depending on the protocol version used.
1.49 markus 99: .Pp
1.176 jmc 100: If
101: .Ar command
102: is specified,
103: .Ar command
104: is executed on the remote host instead of a login shell.
1.49 markus 105: .Ss SSH protocol version 1
1.1 deraadt 106: First, if the machine the user logs in from is listed in
1.2 deraadt 107: .Pa /etc/hosts.equiv
1.1 deraadt 108: or
1.2 deraadt 109: .Pa /etc/shosts.equiv
1.1 deraadt 110: on the remote machine, and the user names are
111: the same on both sides, the user is immediately permitted to log in.
1.44 aaron 112: Second, if
1.176 jmc 113: .Pa .rhosts
1.1 deraadt 114: or
1.176 jmc 115: .Pa .shosts
1.1 deraadt 116: exists in the user's home directory on the
117: remote machine and contains a line containing the name of the client
118: machine and the name of the user on that machine, the user is
1.40 aaron 119: permitted to log in.
120: This form of authentication alone is normally not
1.1 deraadt 121: allowed by the server because it is not secure.
1.2 deraadt 122: .Pp
1.107 markus 123: The second authentication method is the
1.176 jmc 124: .Em rhosts
1.1 deraadt 125: or
1.176 jmc 126: .Em hosts.equiv
1.40 aaron 127: method combined with RSA-based host authentication.
128: It means that if the login would be permitted by
1.49 markus 129: .Pa $HOME/.rhosts ,
130: .Pa $HOME/.shosts ,
1.2 deraadt 131: .Pa /etc/hosts.equiv ,
1.1 deraadt 132: or
1.2 deraadt 133: .Pa /etc/shosts.equiv ,
1.11 deraadt 134: and if additionally the server can verify the client's
1.44 aaron 135: host key (see
1.147 deraadt 136: .Pa /etc/ssh/ssh_known_hosts
1.23 markus 137: and
138: .Pa $HOME/.ssh/known_hosts
1.1 deraadt 139: in the
1.2 deraadt 140: .Sx FILES
1.176 jmc 141: section), only then is login permitted.
1.40 aaron 142: This authentication method closes security holes due to IP
143: spoofing, DNS spoofing and routing spoofing.
144: [Note to the administrator:
1.2 deraadt 145: .Pa /etc/hosts.equiv ,
1.49 markus 146: .Pa $HOME/.rhosts ,
1.1 deraadt 147: and the rlogin/rsh protocol in general, are inherently insecure and should be
148: disabled if security is desired.]
1.2 deraadt 149: .Pp
1.44 aaron 150: As a third authentication method,
1.2 deraadt 151: .Nm
1.1 deraadt 152: supports RSA based authentication.
153: The scheme is based on public-key cryptography: there are cryptosystems
154: where encryption and decryption are done using separate keys, and it
155: is not possible to derive the decryption key from the encryption key.
1.40 aaron 156: RSA is one such system.
1.44 aaron 157: The idea is that each user creates a public/private
1.40 aaron 158: key pair for authentication purposes.
159: The server knows the public key, and only the user knows the private key.
1.176 jmc 160: .Pp
1.44 aaron 161: The file
1.2 deraadt 162: .Pa $HOME/.ssh/authorized_keys
1.176 jmc 163: lists the public keys that are permitted for logging in.
1.40 aaron 164: When the user logs in, the
1.2 deraadt 165: .Nm
1.1 deraadt 166: program tells the server which key pair it would like to use for
1.40 aaron 167: authentication.
1.176 jmc 168: The server checks if this key is permitted, and if so,
169: sends the user (actually the
1.2 deraadt 170: .Nm
1.1 deraadt 171: program running on behalf of the user) a challenge, a random number,
1.40 aaron 172: encrypted by the user's public key.
1.176 jmc 173: The challenge can only be decrypted using the proper private key.
174: The user's client then decrypts the challenge using the private key,
175: proving that he/she knows the private key
176: but without disclosing it to the server.
1.2 deraadt 177: .Pp
178: .Nm
1.40 aaron 179: implements the RSA authentication protocol automatically.
180: The user creates his/her RSA key pair by running
1.2 deraadt 181: .Xr ssh-keygen 1 .
1.44 aaron 182: This stores the private key in
1.49 markus 183: .Pa $HOME/.ssh/identity
1.176 jmc 184: and stores the public key in
1.49 markus 185: .Pa $HOME/.ssh/identity.pub
1.40 aaron 186: in the user's home directory.
187: The user should then copy the
1.2 deraadt 188: .Pa identity.pub
1.44 aaron 189: to
1.49 markus 190: .Pa $HOME/.ssh/authorized_keys
1.44 aaron 191: in his/her home directory on the remote machine (the
1.2 deraadt 192: .Pa authorized_keys
1.44 aaron 193: file corresponds to the conventional
1.49 markus 194: .Pa $HOME/.rhosts
1.1 deraadt 195: file, and has one key
1.40 aaron 196: per line, though the lines can be very long).
197: After this, the user can log in without giving the password.
1.176 jmc 198: RSA authentication is much more secure than
199: .Em rhosts
200: authentication.
1.2 deraadt 201: .Pp
1.1 deraadt 202: The most convenient way to use RSA authentication may be with an
1.40 aaron 203: authentication agent.
204: See
1.2 deraadt 205: .Xr ssh-agent 1
1.1 deraadt 206: for more information.
1.2 deraadt 207: .Pp
1.44 aaron 208: If other authentication methods fail,
1.2 deraadt 209: .Nm
1.40 aaron 210: prompts the user for a password.
211: The password is sent to the remote
1.1 deraadt 212: host for checking; however, since all communications are encrypted,
213: the password cannot be seen by someone listening on the network.
1.49 markus 214: .Ss SSH protocol version 2
1.176 jmc 215: When a user connects using protocol version 2,
1.145 markus 216: similar authentication methods are available.
1.107 markus 217: Using the default values for
218: .Cm PreferredAuthentications ,
1.123 markus 219: the client will try to authenticate first using the hostbased method;
1.176 jmc 220: if this method fails, public key authentication is attempted,
221: and finally if this method fails, keyboard-interactive and
1.123 markus 222: password authentication are tried.
1.49 markus 223: .Pp
224: The public key method is similar to RSA authentication described
1.107 markus 225: in the previous section and allows the RSA or DSA algorithm to be used:
1.102 itojun 226: The client uses his private key,
1.49 markus 227: .Pa $HOME/.ssh/id_dsa
1.102 itojun 228: or
229: .Pa $HOME/.ssh/id_rsa ,
1.49 markus 230: to sign the session identifier and sends the result to the server.
231: The server checks whether the matching public key is listed in
1.115 markus 232: .Pa $HOME/.ssh/authorized_keys
1.49 markus 233: and grants access if both the key is found and the signature is correct.
234: The session identifier is derived from a shared Diffie-Hellman value
235: and is only known to the client and the server.
236: .Pp
1.176 jmc 237: If public key authentication fails or is not available, a password
238: can be sent encrypted to the remote host to prove the user's identity.
1.107 markus 239: .Pp
240: Additionally,
241: .Nm
242: supports hostbased or challenge response authentication.
1.49 markus 243: .Pp
244: Protocol 2 provides additional mechanisms for confidentiality
1.189 dtucker 245: (the traffic is encrypted using AES, 3DES, Blowfish, CAST128 or Arcfour)
246: and integrity (hmac-md5, hmac-sha1, hmac-ripemd160).
1.49 markus 247: Note that protocol 1 lacks a strong mechanism for ensuring the
248: integrity of the connection.
249: .Ss Login session and remote execution
1.1 deraadt 250: When the user's identity has been accepted by the server, the server
251: either executes the given command, or logs into the machine and gives
1.40 aaron 252: the user a normal shell on the remote machine.
253: All communication with
1.1 deraadt 254: the remote command or shell will be automatically encrypted.
1.2 deraadt 255: .Pp
1.1 deraadt 256: If a pseudo-terminal has been allocated (normal login session), the
1.104 djm 257: user may use the escape characters noted below.
1.2 deraadt 258: .Pp
1.176 jmc 259: If no pseudo-tty has been allocated,
260: the session is transparent and can be used to reliably transfer binary data.
1.40 aaron 261: On most systems, setting the escape character to
1.2 deraadt 262: .Dq none
263: will also make the session transparent even if a tty is used.
264: .Pp
1.71 djm 265: The session terminates when the command or shell on the remote
1.92 markus 266: machine exits and all X11 and TCP/IP connections have been closed.
1.176 jmc 267: The exit status of the remote program is returned as the exit status of
1.2 deraadt 268: .Nm ssh .
1.104 djm 269: .Ss Escape Characters
1.176 jmc 270: When a pseudo-terminal has been requested,
271: .Nm
272: supports a number of functions through the use of an escape character.
1.104 djm 273: .Pp
274: A single tilde character can be sent as
275: .Ic ~~
1.119 stevesk 276: or by following the tilde by a character other than those described below.
1.104 djm 277: The escape character must always follow a newline to be interpreted as
278: special.
279: The escape character can be changed in configuration files using the
280: .Cm EscapeChar
1.117 itojun 281: configuration directive or on the command line by the
1.104 djm 282: .Fl e
283: option.
284: .Pp
285: The supported escapes (assuming the default
286: .Ql ~ )
287: are:
288: .Bl -tag -width Ds
289: .It Cm ~.
1.176 jmc 290: Disconnect.
1.104 djm 291: .It Cm ~^Z
1.176 jmc 292: Background
293: .Nm ssh .
1.104 djm 294: .It Cm ~#
1.176 jmc 295: List forwarded connections.
1.104 djm 296: .It Cm ~&
1.176 jmc 297: Background
298: .Nm
299: at logout when waiting for forwarded connection / X11 sessions to terminate.
1.104 djm 300: .It Cm ~?
1.176 jmc 301: Display a list of escape characters.
1.170 markus 302: .It Cm ~B
1.176 jmc 303: Send a BREAK to the remote system
304: (only useful for SSH protocol version 2 and if the peer supports it).
1.149 jakob 305: .It Cm ~C
1.186 djm 306: Open command line.
307: Currently this allows the addition of port forwardings using the
1.149 jakob 308: .Fl L
309: and
310: .Fl R
1.186 djm 311: options (see below).
1.188 jmc 312: It also allows the cancellation of existing remote port-forwardings
1.186 djm 313: using
314: .Fl KR Ar hostport .
1.187 djm 315: Basic help is available, using the
316: .Fl h
1.186 djm 317: option.
1.104 djm 318: .It Cm ~R
1.176 jmc 319: Request rekeying of the connection
320: (only useful for SSH protocol version 2 and if the peer supports it).
1.104 djm 321: .El
1.49 markus 322: .Ss X11 and TCP forwarding
1.110 deraadt 323: If the
324: .Cm ForwardX11
325: variable is set to
326: .Dq yes
1.176 jmc 327: (or see the description of the
1.110 deraadt 328: .Fl X
329: and
330: .Fl x
331: options described later)
332: and the user is using X11 (the
1.2 deraadt 333: .Ev DISPLAY
1.1 deraadt 334: environment variable is set), the connection to the X11 display is
335: automatically forwarded to the remote side in such a way that any X11
336: programs started from the shell (or command) will go through the
337: encrypted channel, and the connection to the real X server will be made
1.40 aaron 338: from the local machine.
339: The user should not manually set
1.2 deraadt 340: .Ev DISPLAY .
1.1 deraadt 341: Forwarding of X11 connections can be
342: configured on the command line or in configuration files.
1.2 deraadt 343: .Pp
344: The
1.44 aaron 345: .Ev DISPLAY
1.2 deraadt 346: value set by
347: .Nm
1.176 jmc 348: will point to the server machine, but with a display number greater than zero.
1.40 aaron 349: This is normal, and happens because
1.2 deraadt 350: .Nm
351: creates a
352: .Dq proxy
353: X server on the server machine for forwarding the
1.1 deraadt 354: connections over the encrypted channel.
1.2 deraadt 355: .Pp
356: .Nm
1.1 deraadt 357: will also automatically set up Xauthority data on the server machine.
358: For this purpose, it will generate a random authorization cookie,
359: store it in Xauthority on the server, and verify that any forwarded
360: connections carry this cookie and replace it by the real cookie when
1.40 aaron 361: the connection is opened.
362: The real authentication cookie is never
1.1 deraadt 363: sent to the server machine (and no cookies are sent in the plain).
1.2 deraadt 364: .Pp
1.163 stevesk 365: If the
366: .Cm ForwardAgent
367: variable is set to
368: .Dq yes
1.176 jmc 369: (or see the description of the
1.163 stevesk 370: .Fl A
371: and
372: .Fl a
1.168 jmc 373: options described later) and
1.163 stevesk 374: the user is using an authentication agent, the connection to the agent
375: is automatically forwarded to the remote side.
1.2 deraadt 376: .Pp
1.1 deraadt 377: Forwarding of arbitrary TCP/IP connections over the secure channel can
1.120 stevesk 378: be specified either on the command line or in a configuration file.
1.40 aaron 379: One possible application of TCP/IP forwarding is a secure connection to an
1.92 markus 380: electronic purse; another is going through firewalls.
1.49 markus 381: .Ss Server authentication
1.2 deraadt 382: .Nm
1.49 markus 383: automatically maintains and checks a database containing
1.40 aaron 384: identifications for all hosts it has ever been used with.
1.116 markus 385: Host keys are stored in
1.49 markus 386: .Pa $HOME/.ssh/known_hosts
1.40 aaron 387: in the user's home directory.
1.116 markus 388: Additionally, the file
1.147 deraadt 389: .Pa /etc/ssh/ssh_known_hosts
1.116 markus 390: is automatically checked for known hosts.
1.40 aaron 391: Any new hosts are automatically added to the user's file.
1.176 jmc 392: If a host's identification ever changes,
1.2 deraadt 393: .Nm
1.1 deraadt 394: warns about this and disables password authentication to prevent a
1.40 aaron 395: trojan horse from getting the user's password.
1.176 jmc 396: Another purpose of this mechanism is to prevent man-in-the-middle attacks
397: which could otherwise be used to circumvent the encryption.
1.40 aaron 398: The
1.2 deraadt 399: .Cm StrictHostKeyChecking
1.158 stevesk 400: option can be used to prevent logins to machines whose
1.1 deraadt 401: host key is not known or has changed.
1.65 aaron 402: .Pp
403: The options are as follows:
1.2 deraadt 404: .Bl -tag -width Ds
1.176 jmc 405: .It Fl 1
406: Forces
407: .Nm
408: to try protocol version 1 only.
409: .It Fl 2
410: Forces
411: .Nm
412: to try protocol version 2 only.
413: .It Fl 4
414: Forces
415: .Nm
416: to use IPv4 addresses only.
417: .It Fl 6
418: Forces
419: .Nm
420: to use IPv6 addresses only.
1.54 markus 421: .It Fl A
422: Enables forwarding of the authentication agent connection.
423: This can also be specified on a per-host basis in a configuration file.
1.165 stevesk 424: .Pp
1.168 jmc 425: Agent forwarding should be enabled with caution.
426: Users with the ability to bypass file permissions on the remote host
427: (for the agent's Unix-domain socket)
428: can access the local agent through the forwarded connection.
429: An attacker cannot obtain key material from the agent,
1.165 stevesk 430: however they can perform operations on the keys that enable them to
431: authenticate using the identities loaded into the agent.
1.176 jmc 432: .It Fl a
433: Disables forwarding of the authentication agent connection.
1.108 markus 434: .It Fl b Ar bind_address
435: Specify the interface to transmit from on machines with multiple
436: interfaces or aliased addresses.
1.176 jmc 437: .It Fl C
438: Requests compression of all data (including stdin, stdout, stderr, and
439: data for forwarded X11 and TCP/IP connections).
440: The compression algorithm is the same used by
441: .Xr gzip 1 ,
442: and the
443: .Dq level
444: can be controlled by the
445: .Cm CompressionLevel
446: option for protocol version 1.
447: Compression is desirable on modem lines and other
448: slow connections, but will only slow down things on fast networks.
449: The default value can be set on a host-by-host basis in the
450: configuration files; see the
451: .Cm Compression
452: option.
1.189 dtucker 453: .It Fl c Ar cipher_spec
454: Selects the cipher specification for encrypting the session.
455: .Pp
456: Protocol version 1 allows specification of a single cipher.
457: The suported values are
458: .Dq 3des ,
459: .Dq blowfish
460: and
461: .Dq des .
1.2 deraadt 462: .Ar 3des
1.189 dtucker 463: (triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
1.44 aaron 464: It is believed to be secure.
1.5 deraadt 465: .Ar blowfish
1.176 jmc 466: is a fast block cipher; it appears very secure and is much faster than
1.40 aaron 467: .Ar 3des .
1.131 stevesk 468: .Ar des
469: is only supported in the
470: .Nm
471: client for interoperability with legacy protocol 1 implementations
472: that do not support the
473: .Ar 3des
1.168 jmc 474: cipher.
475: Its use is strongly discouraged due to cryptographic weaknesses.
1.189 dtucker 476: The default is
477: .Dq 3des .
478: .Pp
479: For protocol version 2
480: .Ar cipher_spec
481: is a comma-separated list of ciphers
482: listed in order of preference.
483: The supported ciphers are
484: .Dq 3des-cbc ,
485: .Dq aes128-cbc ,
486: .Dq aes192-cbc ,
487: .Dq aes256-cbc ,
488: .Dq aes128-ctr ,
489: .Dq aes192-ctr ,
490: .Dq aes256-ctr ,
491: .Dq arcfour ,
492: .Dq blowfish-cbc ,
493: and
494: .Dq cast128-cbc .
495: The default is
496: .Bd -literal
497: ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
498: aes192-cbc,aes256-cbc''
499: .Ed
1.176 jmc 500: .It Fl D Ar port
501: Specifies a local
502: .Dq dynamic
503: application-level port forwarding.
504: This works by allocating a socket to listen to
505: .Ar port
506: on the local side, and whenever a connection is made to this port, the
507: connection is forwarded over the secure channel, and the application
508: protocol is then used to determine where to connect to from the
509: remote machine.
510: Currently the SOCKS4 and SOCKS5 protocols are supported, and
511: .Nm
512: will act as a SOCKS server.
513: Only root can forward privileged ports.
514: Dynamic port forwardings can also be specified in the configuration file.
515: .It Fl e Ar ch | ^ch | none
1.2 deraadt 516: Sets the escape character for sessions with a pty (default:
517: .Ql ~ ) .
1.40 aaron 518: The escape character is only recognized at the beginning of a line.
519: The escape character followed by a dot
1.2 deraadt 520: .Pq Ql \&.
1.176 jmc 521: closes the connection;
522: followed by control-Z suspends the connection;
523: and followed by itself sends the escape character once.
1.40 aaron 524: Setting the character to
1.2 deraadt 525: .Dq none
526: disables any escapes and makes the session fully transparent.
1.176 jmc 527: .It Fl F Ar configfile
528: Specifies an alternative per-user configuration file.
529: If a configuration file is given on the command line,
530: the system-wide configuration file
531: .Pq Pa /etc/ssh/ssh_config
532: will be ignored.
533: The default for the per-user configuration file is
534: .Pa $HOME/.ssh/config .
1.2 deraadt 535: .It Fl f
536: Requests
537: .Nm
1.40 aaron 538: to go to background just before command execution.
539: This is useful if
1.2 deraadt 540: .Nm
541: is going to ask for passwords or passphrases, but the user
1.40 aaron 542: wants it in the background.
1.44 aaron 543: This implies
1.2 deraadt 544: .Fl n .
1.1 deraadt 545: The recommended way to start X11 programs at a remote site is with
1.2 deraadt 546: something like
547: .Ic ssh -f host xterm .
1.34 markus 548: .It Fl g
549: Allows remote hosts to connect to local forwarded ports.
1.176 jmc 550: .It Fl I Ar smartcard_device
551: Specifies which smartcard device to use.
552: The argument is the device
553: .Nm
554: should use to communicate with a smartcard used for storing the user's
555: private RSA key.
1.2 deraadt 556: .It Fl i Ar identity_file
1.144 stevesk 557: Selects a file from which the identity (private key) for
1.68 markus 558: RSA or DSA authentication is read.
1.144 stevesk 559: The default is
1.49 markus 560: .Pa $HOME/.ssh/identity
1.144 stevesk 561: for protocol version 1, and
562: .Pa $HOME/.ssh/id_rsa
563: and
564: .Pa $HOME/.ssh/id_dsa
565: for protocol version 2.
1.40 aaron 566: Identity files may also be specified on
567: a per-host basis in the configuration file.
568: It is possible to have multiple
1.2 deraadt 569: .Fl i
570: options (and multiple identities specified in
1.1 deraadt 571: configuration files).
1.2 deraadt 572: .It Fl k
1.179 dtucker 573: Disables forwarding (delegation) of GSSAPI credentials to the server.
1.176 jmc 574: .It Fl L Xo
575: .Sm off
576: .Ar port : host : hostport
577: .Sm on
578: .Xc
579: Specifies that the given port on the local (client) host is to be
580: forwarded to the given host and port on the remote side.
581: This works by allocating a socket to listen to
582: .Ar port
583: on the local side, and whenever a connection is made to this port, the
584: connection is forwarded over the secure channel, and a connection is
585: made to
586: .Ar host
587: port
588: .Ar hostport
589: from the remote machine.
590: Port forwardings can also be specified in the configuration file.
591: Only root can forward privileged ports.
592: IPv6 addresses can be specified with an alternative syntax:
593: .Sm off
594: .Xo
595: .Ar port No / Ar host No /
596: .Ar hostport .
597: .Xc
598: .Sm on
1.2 deraadt 599: .It Fl l Ar login_name
1.40 aaron 600: Specifies the user to log in as on the remote machine.
601: This also may be specified on a per-host basis in the configuration file.
1.91 markus 602: .It Fl m Ar mac_spec
603: Additionally, for protocol version 2 a comma-separated list of MAC
604: (message authentication code) algorithms can
605: be specified in order of preference.
606: See the
607: .Cm MACs
608: keyword for more information.
1.190 djm 609: .It Fl M
610: Places the
611: .Nm
612: client into
613: .Dq master
614: mode for connection sharing.
615: Refer to the description of
616: .Cm ControlMaster
617: in
618: .Xr ssh_config 5
619: for details.
1.176 jmc 620: .It Fl N
621: Do not execute a remote command.
622: This is useful for just forwarding ports
623: (protocol version 2 only).
1.2 deraadt 624: .It Fl n
625: Redirects stdin from
626: .Pa /dev/null
627: (actually, prevents reading from stdin).
1.1 deraadt 628: This must be used when
1.2 deraadt 629: .Nm
1.40 aaron 630: is run in the background.
631: A common trick is to use this to run X11 programs on a remote machine.
632: For example,
1.2 deraadt 633: .Ic ssh -n shadows.cs.hut.fi emacs &
634: will start an emacs on shadows.cs.hut.fi, and the X11
1.1 deraadt 635: connection will be automatically forwarded over an encrypted channel.
636: The
1.2 deraadt 637: .Nm
1.1 deraadt 638: program will be put in the background.
639: (This does not work if
1.2 deraadt 640: .Nm
641: needs to ask for a password or passphrase; see also the
642: .Fl f
643: option.)
644: .It Fl o Ar option
1.127 stevesk 645: Can be used to give options in the format used in the configuration file.
1.1 deraadt 646: This is useful for specifying options for which there is no separate
1.40 aaron 647: command-line flag.
1.176 jmc 648: For full details of the options listed below, and their possible values, see
649: .Xr ssh_config 5 .
650: .Pp
651: .Bl -tag -width Ds -offset indent -compact
652: .It AddressFamily
653: .It BatchMode
654: .It BindAddress
655: .It ChallengeResponseAuthentication
656: .It CheckHostIP
657: .It Cipher
658: .It Ciphers
659: .It ClearAllForwardings
660: .It Compression
661: .It CompressionLevel
662: .It ConnectionAttempts
1.185 dtucker 663: .It ConnectTimeout
1.190 djm 664: .It ControlMaster
665: .It ControlPath
1.176 jmc 666: .It DynamicForward
667: .It EscapeChar
668: .It ForwardAgent
669: .It ForwardX11
1.178 markus 670: .It ForwardX11Trusted
1.176 jmc 671: .It GatewayPorts
672: .It GlobalKnownHostsFile
673: .It GSSAPIAuthentication
674: .It GSSAPIDelegateCredentials
675: .It Host
676: .It HostbasedAuthentication
677: .It HostKeyAlgorithms
678: .It HostKeyAlias
679: .It HostName
680: .It IdentityFile
1.182 markus 681: .It IdentitiesOnly
1.176 jmc 682: .It LocalForward
683: .It LogLevel
684: .It MACs
685: .It NoHostAuthenticationForLocalhost
686: .It NumberOfPasswordPrompts
687: .It PasswordAuthentication
688: .It Port
689: .It PreferredAuthentications
690: .It Protocol
691: .It ProxyCommand
692: .It PubkeyAuthentication
693: .It RemoteForward
694: .It RhostsRSAAuthentication
695: .It RSAAuthentication
1.184 jmc 696: .It SendEnv
1.181 markus 697: .It ServerAliveInterval
698: .It ServerAliveCountMax
1.176 jmc 699: .It SmartcardDevice
700: .It StrictHostKeyChecking
1.180 markus 701: .It TCPKeepAlive
1.176 jmc 702: .It UsePrivilegedPort
703: .It User
704: .It UserKnownHostsFile
705: .It VerifyHostKeyDNS
706: .It XAuthLocation
707: .El
1.2 deraadt 708: .It Fl p Ar port
1.40 aaron 709: Port to connect to on the remote host.
710: This can be specified on a
1.1 deraadt 711: per-host basis in the configuration file.
1.2 deraadt 712: .It Fl q
1.40 aaron 713: Quiet mode.
714: Causes all warning and diagnostic messages to be suppressed.
1.176 jmc 715: .It Fl R Xo
716: .Sm off
717: .Ar port : host : hostport
718: .Sm on
719: .Xc
720: Specifies that the given port on the remote (server) host is to be
721: forwarded to the given host and port on the local side.
722: This works by allocating a socket to listen to
723: .Ar port
724: on the remote side, and whenever a connection is made to this port, the
725: connection is forwarded over the secure channel, and a connection is
726: made to
727: .Ar host
728: port
729: .Ar hostport
730: from the local machine.
731: Port forwardings can also be specified in the configuration file.
732: Privileged ports can be forwarded only when
733: logging in as root on the remote machine.
734: IPv6 addresses can be specified with an alternative syntax:
735: .Sm off
736: .Xo
737: .Ar port No / Ar host No /
738: .Ar hostport .
739: .Xc
740: .Sm on
1.191 ! djm 741: .It Fl S Ar ctl_path
! 742: Specifies the location of a control socket for for connection sharing.
1.190 djm 743: Refer to the description of
1.191 ! djm 744: .Cm ControlPath
! 745: and
1.190 djm 746: .Cm ControlMaster
747: in
748: .Xr ssh_config 5
749: for details.
1.80 djm 750: .It Fl s
1.172 jmc 751: May be used to request invocation of a subsystem on the remote system.
752: Subsystems are a feature of the SSH2 protocol which facilitate the use
1.176 jmc 753: of SSH as a secure transport for other applications (eg.\&
754: .Xr sftp 1 ) .
1.172 jmc 755: The subsystem is specified as the remote command.
1.176 jmc 756: .It Fl T
757: Disable pseudo-tty allocation.
1.2 deraadt 758: .It Fl t
1.40 aaron 759: Force pseudo-tty allocation.
1.43 brad 760: This can be used to execute arbitrary
1.40 aaron 761: screen-based programs on a remote machine, which can be very useful,
762: e.g., when implementing menu services.
1.73 markus 763: Multiple
764: .Fl t
765: options force tty allocation, even if
766: .Nm
767: has no local tty.
1.176 jmc 768: .It Fl V
769: Display the version number and exit.
1.2 deraadt 770: .It Fl v
1.40 aaron 771: Verbose mode.
772: Causes
1.2 deraadt 773: .Nm
1.40 aaron 774: to print debugging messages about its progress.
775: This is helpful in
1.1 deraadt 776: debugging connection, authentication, and configuration problems.
1.73 markus 777: Multiple
778: .Fl v
1.169 naddy 779: options increase the verbosity.
780: The maximum is 3.
1.2 deraadt 781: .It Fl X
1.1 deraadt 782: Enables X11 forwarding.
1.54 markus 783: This can also be specified on a per-host basis in a configuration file.
1.165 stevesk 784: .Pp
1.168 jmc 785: X11 forwarding should be enabled with caution.
786: Users with the ability to bypass file permissions on the remote host
787: (for the user's X authorization database)
788: can access the local X11 display through the forwarded connection.
789: An attacker may then be able to perform activities such as keystroke monitoring.
1.176 jmc 790: .It Fl x
791: Disables X11 forwarding.
1.178 markus 792: .It Fl Y
793: Enables trusted X11 forwarding.
1.2 deraadt 794: .El
795: .Sh CONFIGURATION FILES
796: .Nm
1.158 stevesk 797: may additionally obtain configuration data from
798: a per-user configuration file and a system-wide configuration file.
799: The file format and configuration options are described in
800: .Xr ssh_config 5 .
1.2 deraadt 801: .Sh ENVIRONMENT
802: .Nm
1.1 deraadt 803: will normally set the following environment variables:
1.176 jmc 804: .Bl -tag -width LOGNAME
1.2 deraadt 805: .It Ev DISPLAY
806: The
807: .Ev DISPLAY
1.40 aaron 808: variable indicates the location of the X11 server.
1.44 aaron 809: It is automatically set by
1.2 deraadt 810: .Nm
811: to point to a value of the form
812: .Dq hostname:n
813: where hostname indicates
1.176 jmc 814: the host where the shell runs, and n is an integer \*(Ge 1.
1.40 aaron 815: .Nm
816: uses this special value to forward X11 connections over the secure
817: channel.
1.107 markus 818: The user should normally not set
819: .Ev DISPLAY
820: explicitly, as that
1.1 deraadt 821: will render the X11 connection insecure (and will require the user to
822: manually copy any required authorization cookies).
1.2 deraadt 823: .It Ev HOME
1.1 deraadt 824: Set to the path of the user's home directory.
1.2 deraadt 825: .It Ev LOGNAME
826: Synonym for
1.12 aaron 827: .Ev USER ;
828: set for compatibility with systems that use this variable.
1.2 deraadt 829: .It Ev MAIL
1.129 stevesk 830: Set to the path of the user's mailbox.
1.40 aaron 831: .It Ev PATH
1.2 deraadt 832: Set to the default
833: .Ev PATH ,
834: as specified when compiling
1.12 aaron 835: .Nm ssh .
1.118 markus 836: .It Ev SSH_ASKPASS
837: If
838: .Nm
839: needs a passphrase, it will read the passphrase from the current
840: terminal if it was run from a terminal.
841: If
842: .Nm
843: does not have a terminal associated with it but
844: .Ev DISPLAY
845: and
846: .Ev SSH_ASKPASS
847: are set, it will execute the program specified by
848: .Ev SSH_ASKPASS
849: and open an X11 window to read the passphrase.
850: This is particularly useful when calling
851: .Nm
852: from a
853: .Pa .Xsession
854: or related script.
855: (Note that on some machines it
856: may be necessary to redirect the input from
857: .Pa /dev/null
858: to make this work.)
1.18 markus 859: .It Ev SSH_AUTH_SOCK
1.129 stevesk 860: Identifies the path of a unix-domain socket used to communicate with the
1.17 markus 861: agent.
1.166 stevesk 862: .It Ev SSH_CONNECTION
863: Identifies the client and server ends of the connection.
1.40 aaron 864: The variable contains
1.166 stevesk 865: four space-separated values: client ip-address, client port number,
866: server ip-address and server port number.
1.73 markus 867: .It Ev SSH_ORIGINAL_COMMAND
868: The variable contains the original command line if a forced command
869: is executed.
870: It can be used to extract the original arguments.
1.2 deraadt 871: .It Ev SSH_TTY
1.1 deraadt 872: This is set to the name of the tty (path to the device) associated
1.40 aaron 873: with the current shell or command.
874: If the current session has no tty,
1.1 deraadt 875: this variable is not set.
1.2 deraadt 876: .It Ev TZ
1.1 deraadt 877: The timezone variable is set to indicate the present timezone if it
1.56 deraadt 878: was set when the daemon was started (i.e., the daemon passes the value
1.1 deraadt 879: on to new connections).
1.2 deraadt 880: .It Ev USER
1.1 deraadt 881: Set to the name of the user logging in.
1.2 deraadt 882: .El
883: .Pp
1.44 aaron 884: Additionally,
1.2 deraadt 885: .Nm
1.44 aaron 886: reads
887: .Pa $HOME/.ssh/environment ,
1.2 deraadt 888: and adds lines of the format
889: .Dq VARNAME=value
1.161 marc 890: to the environment if the file exists and if users are allowed to
891: change their environment.
1.176 jmc 892: For more information, see the
1.161 marc 893: .Cm PermitUserEnvironment
1.162 stevesk 894: option in
1.161 marc 895: .Xr sshd_config 5 .
1.2 deraadt 896: .Sh FILES
1.36 markus 897: .Bl -tag -width Ds
1.116 markus 898: .It Pa $HOME/.ssh/known_hosts
1.129 stevesk 899: Records host keys for all hosts the user has logged into that are not
1.2 deraadt 900: in
1.147 deraadt 901: .Pa /etc/ssh/ssh_known_hosts .
1.2 deraadt 902: See
903: .Xr sshd 8 .
1.102 itojun 904: .It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa, $HOME/.ssh/id_rsa
905: Contains the authentication identity of the user.
906: They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
1.48 markus 907: These files
908: contain sensitive data and should be readable by the user but not
1.15 markus 909: accessible by others (read/write/execute).
910: Note that
911: .Nm
1.48 markus 912: ignores a private key file if it is accessible by others.
1.15 markus 913: It is possible to specify a passphrase when
1.1 deraadt 914: generating the key; the passphrase will be used to encrypt the
1.8 deraadt 915: sensitive part of this file using 3DES.
1.102 itojun 916: .It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub, $HOME/.ssh/id_rsa.pub
1.1 deraadt 917: Contains the public key for authentication (public part of the
1.40 aaron 918: identity file in human-readable form).
1.48 markus 919: The contents of the
920: .Pa $HOME/.ssh/identity.pub
1.176 jmc 921: file should be added to the file
1.2 deraadt 922: .Pa $HOME/.ssh/authorized_keys
923: on all machines
1.137 deraadt 924: where the user wishes to log in using protocol version 1 RSA authentication.
1.48 markus 925: The contents of the
926: .Pa $HOME/.ssh/id_dsa.pub
1.102 itojun 927: and
928: .Pa $HOME/.ssh/id_rsa.pub
1.48 markus 929: file should be added to
1.115 markus 930: .Pa $HOME/.ssh/authorized_keys
1.48 markus 931: on all machines
1.137 deraadt 932: where the user wishes to log in using protocol version 2 DSA/RSA authentication.
1.48 markus 933: These files are not
1.40 aaron 934: sensitive and can (but need not) be readable by anyone.
1.48 markus 935: These files are
1.84 markus 936: never used automatically and are not necessary; they are only provided for
1.1 deraadt 937: the convenience of the user.
1.2 deraadt 938: .It Pa $HOME/.ssh/config
1.40 aaron 939: This is the per-user configuration file.
1.158 stevesk 940: The file format and configuration options are described in
941: .Xr ssh_config 5 .
1.183 djm 942: Because of the potential for abuse, this file must have strict permissions:
943: read/write for the user, and not accessible by others.
1.2 deraadt 944: .It Pa $HOME/.ssh/authorized_keys
1.115 markus 945: Lists the public keys (RSA/DSA) that can be used for logging in as this user.
1.40 aaron 946: The format of this file is described in the
1.2 deraadt 947: .Xr sshd 8
1.40 aaron 948: manual page.
1.176 jmc 949: In the simplest form the format is the same as the
950: .Pa .pub
1.116 markus 951: identity files.
1.48 markus 952: This file is not highly sensitive, but the recommended
953: permissions are read/write for the user, and not accessible by others.
1.147 deraadt 954: .It Pa /etc/ssh/ssh_known_hosts
1.40 aaron 955: Systemwide list of known host keys.
1.116 markus 956: This file should be prepared by the
1.1 deraadt 957: system administrator to contain the public host keys of all machines in the
1.40 aaron 958: organization.
959: This file should be world-readable.
960: This file contains
1.1 deraadt 961: public keys, one per line, in the following format (fields separated
1.116 markus 962: by spaces): system name, public key and optional comment field.
1.40 aaron 963: When different names are used
1.1 deraadt 964: for the same machine, all such names should be listed, separated by
1.40 aaron 965: commas.
1.176 jmc 966: The format is described in the
1.2 deraadt 967: .Xr sshd 8
1.1 deraadt 968: manual page.
1.2 deraadt 969: .Pp
1.1 deraadt 970: The canonical system name (as returned by name servers) is used by
1.2 deraadt 971: .Xr sshd 8
1.1 deraadt 972: to verify the client host when logging in; other names are needed because
1.2 deraadt 973: .Nm
1.1 deraadt 974: does not convert the user-supplied name to a canonical name before
975: checking the key, because someone with access to the name servers
976: would then be able to fool host authentication.
1.147 deraadt 977: .It Pa /etc/ssh/ssh_config
1.40 aaron 978: Systemwide configuration file.
1.158 stevesk 979: The file format and configuration options are described in
980: .Xr ssh_config 5 .
1.147 deraadt 981: .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key
1.141 markus 982: These three files contain the private parts of the host keys
983: and are used for
984: .Cm RhostsRSAAuthentication
985: and
986: .Cm HostbasedAuthentication .
1.155 stevesk 987: If the protocol version 1
988: .Cm RhostsRSAAuthentication
1.157 deraadt 989: method is used,
1.155 stevesk 990: .Nm
991: must be setuid root, since the host key is readable only by root.
992: For protocol version 2,
993: .Nm
994: uses
995: .Xr ssh-keysign 8
996: to access the host keys for
997: .Cm HostbasedAuthentication .
998: This eliminates the requirement that
999: .Nm
1000: be setuid root when that authentication method is used.
1001: By default
1.141 markus 1002: .Nm
1.155 stevesk 1003: is not setuid root.
1.2 deraadt 1004: .It Pa $HOME/.rhosts
1005: This file is used in
1.176 jmc 1006: .Em rhosts
1.2 deraadt 1007: authentication to list the
1.40 aaron 1008: host/user pairs that are permitted to log in.
1009: (Note that this file is
1.1 deraadt 1010: also used by rlogin and rsh, which makes using this file insecure.)
1011: Each line of the file contains a host name (in the canonical form
1012: returned by name servers), and then a user name on that host,
1.40 aaron 1013: separated by a space.
1.92 markus 1014: On some machines this file may need to be
1.1 deraadt 1015: world-readable if the user's home directory is on a NFS partition,
1016: because
1.2 deraadt 1017: .Xr sshd 8
1.40 aaron 1018: reads it as root.
1019: Additionally, this file must be owned by the user,
1020: and must not have write permissions for anyone else.
1021: The recommended
1.1 deraadt 1022: permission for most machines is read/write for the user, and not
1023: accessible by others.
1.2 deraadt 1024: .Pp
1.1 deraadt 1025: Note that by default
1.2 deraadt 1026: .Xr sshd 8
1.1 deraadt 1027: will be installed so that it requires successful RSA host
1.176 jmc 1028: authentication before permitting
1029: .Em rhosts
1030: authentication.
1.137 deraadt 1031: If the server machine does not have the client's host key in
1.147 deraadt 1032: .Pa /etc/ssh/ssh_known_hosts ,
1.137 deraadt 1033: it can be stored in
1.2 deraadt 1034: .Pa $HOME/.ssh/known_hosts .
1035: The easiest way to do this is to
1.1 deraadt 1036: connect back to the client from the server machine using ssh; this
1.48 markus 1037: will automatically add the host key to
1.2 deraadt 1038: .Pa $HOME/.ssh/known_hosts .
1039: .It Pa $HOME/.shosts
1040: This file is used exactly the same way as
1.176 jmc 1041: .Pa .rhosts .
1.2 deraadt 1042: The purpose for
1.1 deraadt 1043: having this file is to be able to use rhosts authentication with
1.2 deraadt 1044: .Nm
1045: without permitting login with
1.176 jmc 1046: .Xr rlogin
1.2 deraadt 1047: or
1048: .Xr rsh 1 .
1049: .It Pa /etc/hosts.equiv
1050: This file is used during
1.176 jmc 1051: .Em rhosts
1.173 jmc 1052: authentication.
1.40 aaron 1053: It contains
1.176 jmc 1054: canonical hosts names, one per line (the full format is described in the
1.2 deraadt 1055: .Xr sshd 8
1.40 aaron 1056: manual page).
1057: If the client host is found in this file, login is
1.1 deraadt 1058: automatically permitted provided client and server user names are the
1.40 aaron 1059: same.
1060: Additionally, successful RSA host authentication is normally
1061: required.
1062: This file should only be writable by root.
1.2 deraadt 1063: .It Pa /etc/shosts.equiv
1.44 aaron 1064: This file is processed exactly as
1.2 deraadt 1065: .Pa /etc/hosts.equiv .
1.1 deraadt 1066: This file may be useful to permit logins using
1.2 deraadt 1067: .Nm
1.1 deraadt 1068: but not using rsh/rlogin.
1.147 deraadt 1069: .It Pa /etc/ssh/sshrc
1.1 deraadt 1070: Commands in this file are executed by
1.2 deraadt 1071: .Nm
1.1 deraadt 1072: when the user logs in just before the user's shell (or command) is started.
1073: See the
1.2 deraadt 1074: .Xr sshd 8
1.1 deraadt 1075: manual page for more information.
1.2 deraadt 1076: .It Pa $HOME/.ssh/rc
1.1 deraadt 1077: Commands in this file are executed by
1.2 deraadt 1078: .Nm
1.1 deraadt 1079: when the user logs in just before the user's shell (or command) is
1080: started.
1.44 aaron 1081: See the
1.2 deraadt 1082: .Xr sshd 8
1.1 deraadt 1083: manual page for more information.
1.31 markus 1084: .It Pa $HOME/.ssh/environment
1085: Contains additional definitions for environment variables, see section
1086: .Sx ENVIRONMENT
1087: above.
1.58 itojun 1088: .El
1.145 markus 1089: .Sh DIAGNOSTICS
1090: .Nm
1091: exits with the exit status of the remote command or with 255
1092: if an error occurred.
1.2 deraadt 1093: .Sh SEE ALSO
1.176 jmc 1094: .Xr gzip 1 ,
1.2 deraadt 1095: .Xr rsh 1 ,
1096: .Xr scp 1 ,
1.83 djm 1097: .Xr sftp 1 ,
1.2 deraadt 1098: .Xr ssh-add 1 ,
1099: .Xr ssh-agent 1 ,
1100: .Xr ssh-keygen 1 ,
1101: .Xr telnet 1 ,
1.176 jmc 1102: .Xr hosts.equiv 5 ,
1.159 stevesk 1103: .Xr ssh_config 5 ,
1.160 naddy 1104: .Xr ssh-keysign 8 ,
1.87 itojun 1105: .Xr sshd 8
1.106 markus 1106: .Rs
1107: .%A T. Ylonen
1108: .%A T. Kivinen
1109: .%A M. Saarinen
1110: .%A T. Rinne
1111: .%A S. Lehtinen
1112: .%T "SSH Protocol Architecture"
1.150 markus 1113: .%N draft-ietf-secsh-architecture-12.txt
1114: .%D January 2002
1.106 markus 1115: .%O work in progress material
1116: .Re
1.173 jmc 1117: .Sh AUTHORS
1118: OpenSSH is a derivative of the original and free
1119: ssh 1.2.12 release by Tatu Ylonen.
1120: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1121: Theo de Raadt and Dug Song
1122: removed many bugs, re-added newer features and
1123: created OpenSSH.
1124: Markus Friedl contributed the support for SSH
1125: protocol versions 1.5 and 2.0.
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