Annotation of src/usr.bin/ssh/ssh.1, Revision 1.182.2.1
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: .\"
1.182.2.1! brad 37: .\" $OpenBSD: ssh.1,v 1.194 2004/08/12 21:41:13 jakob 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
1.182.2.1! brad 46: .Op Fl 1246AaCfgkMNnqsTtVvXxY
1.108 markus 47: .Op Fl b Ar bind_address
1.51 markus 48: .Op Fl c Ar cipher_spec
1.182.2.1! brad 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
1.33 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
1.182.2.1! brad 77: .Op Fl S Ar ctl
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
1.182.2.1! brad 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
1.182.2.1! brad 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
1.182.2.1! brad 311: options (see below).
! 312: It also allows the cancellation of existing remote port-forwardings
! 313: using
! 314: .Fl KR Ar hostport .
! 315: Basic help is available, using the
! 316: .Fl h
! 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
1.182.2.1! brad 403: .Nm
! 404: can be configured to verify host identification using fingerprint resource
! 405: records (SSHFP) published in DNS.
! 406: The
! 407: .Cm VerifyHostKeyDNS
! 408: option can be used to control how DNS lookups are performed.
! 409: SSHFP resource records can be generated using
! 410: .Xr ssh-keygen 1 .
! 411: .Pp
1.65 aaron 412: The options are as follows:
1.2 deraadt 413: .Bl -tag -width Ds
1.176 jmc 414: .It Fl 1
415: Forces
416: .Nm
417: to try protocol version 1 only.
418: .It Fl 2
419: Forces
420: .Nm
421: to try protocol version 2 only.
422: .It Fl 4
423: Forces
424: .Nm
425: to use IPv4 addresses only.
426: .It Fl 6
427: Forces
428: .Nm
429: to use IPv6 addresses only.
1.54 markus 430: .It Fl A
431: Enables forwarding of the authentication agent connection.
432: This can also be specified on a per-host basis in a configuration file.
1.165 stevesk 433: .Pp
1.168 jmc 434: Agent forwarding should be enabled with caution.
435: Users with the ability to bypass file permissions on the remote host
436: (for the agent's Unix-domain socket)
437: can access the local agent through the forwarded connection.
438: An attacker cannot obtain key material from the agent,
1.165 stevesk 439: however they can perform operations on the keys that enable them to
440: authenticate using the identities loaded into the agent.
1.176 jmc 441: .It Fl a
442: Disables forwarding of the authentication agent connection.
1.108 markus 443: .It Fl b Ar bind_address
444: Specify the interface to transmit from on machines with multiple
445: interfaces or aliased addresses.
1.176 jmc 446: .It Fl C
447: Requests compression of all data (including stdin, stdout, stderr, and
448: data for forwarded X11 and TCP/IP connections).
449: The compression algorithm is the same used by
450: .Xr gzip 1 ,
451: and the
452: .Dq level
453: can be controlled by the
454: .Cm CompressionLevel
455: option for protocol version 1.
456: Compression is desirable on modem lines and other
457: slow connections, but will only slow down things on fast networks.
458: The default value can be set on a host-by-host basis in the
459: configuration files; see the
460: .Cm Compression
461: option.
1.182.2.1! brad 462: .It Fl c Ar cipher_spec
! 463: Selects the cipher specification for encrypting the session.
! 464: .Pp
! 465: Protocol version 1 allows specification of a single cipher.
! 466: The suported values are
! 467: .Dq 3des ,
! 468: .Dq blowfish
! 469: and
! 470: .Dq des .
1.5 deraadt 471: .Ar 3des
472: (triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
1.182.2.1! brad 473: It is believed to be secure.
1.5 deraadt 474: .Ar blowfish
1.176 jmc 475: is a fast block cipher; it appears very secure and is much faster than
1.40 aaron 476: .Ar 3des .
1.131 stevesk 477: .Ar des
478: is only supported in the
479: .Nm
480: client for interoperability with legacy protocol 1 implementations
481: that do not support the
482: .Ar 3des
1.168 jmc 483: cipher.
484: Its use is strongly discouraged due to cryptographic weaknesses.
1.182.2.1! brad 485: The default is
! 486: .Dq 3des .
! 487: .Pp
! 488: For protocol version 2
! 489: .Ar cipher_spec
! 490: is a comma-separated list of ciphers
! 491: listed in order of preference.
! 492: The supported ciphers are
! 493: .Dq 3des-cbc ,
! 494: .Dq aes128-cbc ,
! 495: .Dq aes192-cbc ,
! 496: .Dq aes256-cbc ,
! 497: .Dq aes128-ctr ,
! 498: .Dq aes192-ctr ,
! 499: .Dq aes256-ctr ,
! 500: .Dq arcfour ,
! 501: .Dq blowfish-cbc ,
! 502: and
! 503: .Dq cast128-cbc .
! 504: The default is
! 505: .Bd -literal
! 506: ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
! 507: aes192-cbc,aes256-cbc''
! 508: .Ed
1.176 jmc 509: .It Fl D Ar port
510: Specifies a local
511: .Dq dynamic
512: application-level port forwarding.
513: This works by allocating a socket to listen to
514: .Ar port
515: on the local side, and whenever a connection is made to this port, the
516: connection is forwarded over the secure channel, and the application
517: protocol is then used to determine where to connect to from the
518: remote machine.
519: Currently the SOCKS4 and SOCKS5 protocols are supported, and
520: .Nm
521: will act as a SOCKS server.
522: Only root can forward privileged ports.
523: Dynamic port forwardings can also be specified in the configuration file.
524: .It Fl e Ar ch | ^ch | none
1.2 deraadt 525: Sets the escape character for sessions with a pty (default:
526: .Ql ~ ) .
1.40 aaron 527: The escape character is only recognized at the beginning of a line.
528: The escape character followed by a dot
1.2 deraadt 529: .Pq Ql \&.
1.176 jmc 530: closes the connection;
531: followed by control-Z suspends the connection;
532: and followed by itself sends the escape character once.
1.40 aaron 533: Setting the character to
1.2 deraadt 534: .Dq none
535: disables any escapes and makes the session fully transparent.
1.176 jmc 536: .It Fl F Ar configfile
537: Specifies an alternative per-user configuration file.
538: If a configuration file is given on the command line,
539: the system-wide configuration file
540: .Pq Pa /etc/ssh/ssh_config
541: will be ignored.
542: The default for the per-user configuration file is
543: .Pa $HOME/.ssh/config .
1.2 deraadt 544: .It Fl f
545: Requests
546: .Nm
1.40 aaron 547: to go to background just before command execution.
548: This is useful if
1.2 deraadt 549: .Nm
550: is going to ask for passwords or passphrases, but the user
1.40 aaron 551: wants it in the background.
1.44 aaron 552: This implies
1.2 deraadt 553: .Fl n .
1.1 deraadt 554: The recommended way to start X11 programs at a remote site is with
1.2 deraadt 555: something like
556: .Ic ssh -f host xterm .
1.34 markus 557: .It Fl g
558: Allows remote hosts to connect to local forwarded ports.
1.176 jmc 559: .It Fl I Ar smartcard_device
560: Specifies which smartcard device to use.
561: The argument is the device
562: .Nm
563: should use to communicate with a smartcard used for storing the user's
564: private RSA key.
1.2 deraadt 565: .It Fl i Ar identity_file
1.144 stevesk 566: Selects a file from which the identity (private key) for
1.68 markus 567: RSA or DSA authentication is read.
1.144 stevesk 568: The default is
1.49 markus 569: .Pa $HOME/.ssh/identity
1.144 stevesk 570: for protocol version 1, and
571: .Pa $HOME/.ssh/id_rsa
572: and
573: .Pa $HOME/.ssh/id_dsa
574: for protocol version 2.
1.40 aaron 575: Identity files may also be specified on
576: a per-host basis in the configuration file.
577: It is possible to have multiple
1.2 deraadt 578: .Fl i
579: options (and multiple identities specified in
1.1 deraadt 580: configuration files).
1.2 deraadt 581: .It Fl k
1.179 dtucker 582: Disables forwarding (delegation) of GSSAPI credentials to the server.
1.176 jmc 583: .It Fl L Xo
584: .Sm off
585: .Ar port : host : hostport
586: .Sm on
587: .Xc
588: Specifies that the given port on the local (client) host is to be
589: forwarded to the given host and port on the remote side.
590: This works by allocating a socket to listen to
591: .Ar port
592: on the local side, and whenever a connection is made to this port, the
593: connection is forwarded over the secure channel, and a connection is
594: made to
595: .Ar host
596: port
597: .Ar hostport
598: from the remote machine.
599: Port forwardings can also be specified in the configuration file.
600: Only root can forward privileged ports.
601: IPv6 addresses can be specified with an alternative syntax:
602: .Sm off
603: .Xo
604: .Ar port No / Ar host No /
605: .Ar hostport .
606: .Xc
607: .Sm on
1.2 deraadt 608: .It Fl l Ar login_name
1.40 aaron 609: Specifies the user to log in as on the remote machine.
610: This also may be specified on a per-host basis in the configuration file.
1.182.2.1! brad 611: .It Fl M
! 612: Places the
! 613: .Nm
! 614: client into
! 615: .Dq master
! 616: mode for connection sharing.
! 617: Refer to the description of
! 618: .Cm ControlMaster
! 619: in
! 620: .Xr ssh_config 5
! 621: for details.
1.91 markus 622: .It Fl m Ar mac_spec
623: Additionally, for protocol version 2 a comma-separated list of MAC
624: (message authentication code) algorithms can
625: be specified in order of preference.
626: See the
627: .Cm MACs
628: keyword for more information.
1.176 jmc 629: .It Fl N
630: Do not execute a remote command.
631: This is useful for just forwarding ports
632: (protocol version 2 only).
1.2 deraadt 633: .It Fl n
634: Redirects stdin from
635: .Pa /dev/null
636: (actually, prevents reading from stdin).
1.1 deraadt 637: This must be used when
1.2 deraadt 638: .Nm
1.40 aaron 639: is run in the background.
640: A common trick is to use this to run X11 programs on a remote machine.
641: For example,
1.2 deraadt 642: .Ic ssh -n shadows.cs.hut.fi emacs &
643: will start an emacs on shadows.cs.hut.fi, and the X11
1.1 deraadt 644: connection will be automatically forwarded over an encrypted channel.
645: The
1.2 deraadt 646: .Nm
1.1 deraadt 647: program will be put in the background.
648: (This does not work if
1.2 deraadt 649: .Nm
650: needs to ask for a password or passphrase; see also the
651: .Fl f
652: option.)
653: .It Fl o Ar option
1.127 stevesk 654: Can be used to give options in the format used in the configuration file.
1.1 deraadt 655: This is useful for specifying options for which there is no separate
1.40 aaron 656: command-line flag.
1.176 jmc 657: For full details of the options listed below, and their possible values, see
658: .Xr ssh_config 5 .
659: .Pp
660: .Bl -tag -width Ds -offset indent -compact
661: .It AddressFamily
662: .It BatchMode
663: .It BindAddress
664: .It ChallengeResponseAuthentication
665: .It CheckHostIP
666: .It Cipher
667: .It Ciphers
668: .It ClearAllForwardings
669: .It Compression
670: .It CompressionLevel
671: .It ConnectionAttempts
1.182.2.1! brad 672: .It ConnectTimeout
! 673: .It ControlMaster
! 674: .It ControlPath
1.176 jmc 675: .It DynamicForward
676: .It EscapeChar
677: .It ForwardAgent
678: .It ForwardX11
1.178 markus 679: .It ForwardX11Trusted
1.176 jmc 680: .It GatewayPorts
681: .It GlobalKnownHostsFile
682: .It GSSAPIAuthentication
683: .It GSSAPIDelegateCredentials
684: .It Host
685: .It HostbasedAuthentication
686: .It HostKeyAlgorithms
687: .It HostKeyAlias
688: .It HostName
689: .It IdentityFile
1.182 markus 690: .It IdentitiesOnly
1.176 jmc 691: .It LocalForward
692: .It LogLevel
693: .It MACs
694: .It NoHostAuthenticationForLocalhost
695: .It NumberOfPasswordPrompts
696: .It PasswordAuthentication
697: .It Port
698: .It PreferredAuthentications
699: .It Protocol
700: .It ProxyCommand
701: .It PubkeyAuthentication
702: .It RemoteForward
703: .It RhostsRSAAuthentication
704: .It RSAAuthentication
1.182.2.1! brad 705: .It SendEnv
1.181 markus 706: .It ServerAliveInterval
707: .It ServerAliveCountMax
1.176 jmc 708: .It SmartcardDevice
709: .It StrictHostKeyChecking
1.180 markus 710: .It TCPKeepAlive
1.176 jmc 711: .It UsePrivilegedPort
712: .It User
713: .It UserKnownHostsFile
714: .It VerifyHostKeyDNS
715: .It XAuthLocation
716: .El
1.2 deraadt 717: .It Fl p Ar port
1.40 aaron 718: Port to connect to on the remote host.
719: This can be specified on a
1.1 deraadt 720: per-host basis in the configuration file.
1.2 deraadt 721: .It Fl q
1.40 aaron 722: Quiet mode.
723: Causes all warning and diagnostic messages to be suppressed.
1.176 jmc 724: .It Fl R Xo
725: .Sm off
726: .Ar port : host : hostport
727: .Sm on
728: .Xc
729: Specifies that the given port on the remote (server) host is to be
730: forwarded to the given host and port on the local side.
731: This works by allocating a socket to listen to
732: .Ar port
733: on the remote side, and whenever a connection is made to this port, the
734: connection is forwarded over the secure channel, and a connection is
735: made to
736: .Ar host
737: port
738: .Ar hostport
739: from the local machine.
740: Port forwardings can also be specified in the configuration file.
741: Privileged ports can be forwarded only when
742: logging in as root on the remote machine.
743: IPv6 addresses can be specified with an alternative syntax:
744: .Sm off
745: .Xo
746: .Ar port No / Ar host No /
747: .Ar hostport .
748: .Xc
749: .Sm on
1.182.2.1! brad 750: .It Fl S Ar ctl
! 751: Specifies the location of a control socket for connection sharing.
! 752: Refer to the description of
! 753: .Cm ControlPath
! 754: and
! 755: .Cm ControlMaster
! 756: in
! 757: .Xr ssh_config 5
! 758: for details.
1.80 djm 759: .It Fl s
1.172 jmc 760: May be used to request invocation of a subsystem on the remote system.
761: Subsystems are a feature of the SSH2 protocol which facilitate the use
1.176 jmc 762: of SSH as a secure transport for other applications (eg.\&
763: .Xr sftp 1 ) .
1.172 jmc 764: The subsystem is specified as the remote command.
1.176 jmc 765: .It Fl T
766: Disable pseudo-tty allocation.
1.2 deraadt 767: .It Fl t
1.40 aaron 768: Force pseudo-tty allocation.
1.43 brad 769: This can be used to execute arbitrary
1.40 aaron 770: screen-based programs on a remote machine, which can be very useful,
771: e.g., when implementing menu services.
1.73 markus 772: Multiple
773: .Fl t
774: options force tty allocation, even if
775: .Nm
776: has no local tty.
1.176 jmc 777: .It Fl V
778: Display the version number and exit.
1.2 deraadt 779: .It Fl v
1.40 aaron 780: Verbose mode.
781: Causes
1.2 deraadt 782: .Nm
1.40 aaron 783: to print debugging messages about its progress.
784: This is helpful in
1.1 deraadt 785: debugging connection, authentication, and configuration problems.
1.73 markus 786: Multiple
787: .Fl v
1.169 naddy 788: options increase the verbosity.
789: The maximum is 3.
1.2 deraadt 790: .It Fl X
1.1 deraadt 791: Enables X11 forwarding.
1.54 markus 792: This can also be specified on a per-host basis in a configuration file.
1.165 stevesk 793: .Pp
1.168 jmc 794: X11 forwarding should be enabled with caution.
795: Users with the ability to bypass file permissions on the remote host
796: (for the user's X authorization database)
797: can access the local X11 display through the forwarded connection.
798: An attacker may then be able to perform activities such as keystroke monitoring.
1.176 jmc 799: .It Fl x
800: Disables X11 forwarding.
1.178 markus 801: .It Fl Y
802: Enables trusted X11 forwarding.
1.2 deraadt 803: .El
804: .Sh CONFIGURATION FILES
805: .Nm
1.158 stevesk 806: may additionally obtain configuration data from
807: a per-user configuration file and a system-wide configuration file.
808: The file format and configuration options are described in
809: .Xr ssh_config 5 .
1.2 deraadt 810: .Sh ENVIRONMENT
811: .Nm
1.1 deraadt 812: will normally set the following environment variables:
1.176 jmc 813: .Bl -tag -width LOGNAME
1.2 deraadt 814: .It Ev DISPLAY
815: The
816: .Ev DISPLAY
1.40 aaron 817: variable indicates the location of the X11 server.
1.44 aaron 818: It is automatically set by
1.2 deraadt 819: .Nm
820: to point to a value of the form
821: .Dq hostname:n
822: where hostname indicates
1.176 jmc 823: the host where the shell runs, and n is an integer \*(Ge 1.
1.40 aaron 824: .Nm
825: uses this special value to forward X11 connections over the secure
826: channel.
1.107 markus 827: The user should normally not set
828: .Ev DISPLAY
829: explicitly, as that
1.1 deraadt 830: will render the X11 connection insecure (and will require the user to
831: manually copy any required authorization cookies).
1.2 deraadt 832: .It Ev HOME
1.1 deraadt 833: Set to the path of the user's home directory.
1.2 deraadt 834: .It Ev LOGNAME
835: Synonym for
1.12 aaron 836: .Ev USER ;
837: set for compatibility with systems that use this variable.
1.2 deraadt 838: .It Ev MAIL
1.129 stevesk 839: Set to the path of the user's mailbox.
1.40 aaron 840: .It Ev PATH
1.2 deraadt 841: Set to the default
842: .Ev PATH ,
843: as specified when compiling
1.12 aaron 844: .Nm ssh .
1.118 markus 845: .It Ev SSH_ASKPASS
846: If
847: .Nm
848: needs a passphrase, it will read the passphrase from the current
849: terminal if it was run from a terminal.
850: If
851: .Nm
852: does not have a terminal associated with it but
853: .Ev DISPLAY
854: and
855: .Ev SSH_ASKPASS
856: are set, it will execute the program specified by
857: .Ev SSH_ASKPASS
858: and open an X11 window to read the passphrase.
859: This is particularly useful when calling
860: .Nm
861: from a
862: .Pa .Xsession
863: or related script.
864: (Note that on some machines it
865: may be necessary to redirect the input from
866: .Pa /dev/null
867: to make this work.)
1.18 markus 868: .It Ev SSH_AUTH_SOCK
1.129 stevesk 869: Identifies the path of a unix-domain socket used to communicate with the
1.17 markus 870: agent.
1.166 stevesk 871: .It Ev SSH_CONNECTION
872: Identifies the client and server ends of the connection.
1.40 aaron 873: The variable contains
1.166 stevesk 874: four space-separated values: client ip-address, client port number,
875: server ip-address and server port number.
1.73 markus 876: .It Ev SSH_ORIGINAL_COMMAND
877: The variable contains the original command line if a forced command
878: is executed.
879: It can be used to extract the original arguments.
1.2 deraadt 880: .It Ev SSH_TTY
1.1 deraadt 881: This is set to the name of the tty (path to the device) associated
1.40 aaron 882: with the current shell or command.
883: If the current session has no tty,
1.1 deraadt 884: this variable is not set.
1.2 deraadt 885: .It Ev TZ
1.1 deraadt 886: The timezone variable is set to indicate the present timezone if it
1.56 deraadt 887: was set when the daemon was started (i.e., the daemon passes the value
1.1 deraadt 888: on to new connections).
1.2 deraadt 889: .It Ev USER
1.1 deraadt 890: Set to the name of the user logging in.
1.2 deraadt 891: .El
892: .Pp
1.44 aaron 893: Additionally,
1.2 deraadt 894: .Nm
1.44 aaron 895: reads
896: .Pa $HOME/.ssh/environment ,
1.2 deraadt 897: and adds lines of the format
898: .Dq VARNAME=value
1.161 marc 899: to the environment if the file exists and if users are allowed to
900: change their environment.
1.176 jmc 901: For more information, see the
1.161 marc 902: .Cm PermitUserEnvironment
1.162 stevesk 903: option in
1.161 marc 904: .Xr sshd_config 5 .
1.2 deraadt 905: .Sh FILES
1.36 markus 906: .Bl -tag -width Ds
1.116 markus 907: .It Pa $HOME/.ssh/known_hosts
1.129 stevesk 908: Records host keys for all hosts the user has logged into that are not
1.2 deraadt 909: in
1.147 deraadt 910: .Pa /etc/ssh/ssh_known_hosts .
1.2 deraadt 911: See
912: .Xr sshd 8 .
1.102 itojun 913: .It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa, $HOME/.ssh/id_rsa
914: Contains the authentication identity of the user.
915: They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
1.48 markus 916: These files
917: contain sensitive data and should be readable by the user but not
1.15 markus 918: accessible by others (read/write/execute).
919: Note that
920: .Nm
1.48 markus 921: ignores a private key file if it is accessible by others.
1.15 markus 922: It is possible to specify a passphrase when
1.1 deraadt 923: generating the key; the passphrase will be used to encrypt the
1.8 deraadt 924: sensitive part of this file using 3DES.
1.102 itojun 925: .It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub, $HOME/.ssh/id_rsa.pub
1.1 deraadt 926: Contains the public key for authentication (public part of the
1.40 aaron 927: identity file in human-readable form).
1.48 markus 928: The contents of the
929: .Pa $HOME/.ssh/identity.pub
1.176 jmc 930: file should be added to the file
1.2 deraadt 931: .Pa $HOME/.ssh/authorized_keys
932: on all machines
1.137 deraadt 933: where the user wishes to log in using protocol version 1 RSA authentication.
1.48 markus 934: The contents of the
935: .Pa $HOME/.ssh/id_dsa.pub
1.102 itojun 936: and
937: .Pa $HOME/.ssh/id_rsa.pub
1.48 markus 938: file should be added to
1.115 markus 939: .Pa $HOME/.ssh/authorized_keys
1.48 markus 940: on all machines
1.137 deraadt 941: where the user wishes to log in using protocol version 2 DSA/RSA authentication.
1.48 markus 942: These files are not
1.40 aaron 943: sensitive and can (but need not) be readable by anyone.
1.48 markus 944: These files are
1.84 markus 945: never used automatically and are not necessary; they are only provided for
1.1 deraadt 946: the convenience of the user.
1.2 deraadt 947: .It Pa $HOME/.ssh/config
1.40 aaron 948: This is the per-user configuration file.
1.158 stevesk 949: The file format and configuration options are described in
950: .Xr ssh_config 5 .
1.182.2.1! brad 951: Because of the potential for abuse, this file must have strict permissions:
! 952: read/write for the user, and not accessible by others.
1.2 deraadt 953: .It Pa $HOME/.ssh/authorized_keys
1.115 markus 954: Lists the public keys (RSA/DSA) that can be used for logging in as this user.
1.40 aaron 955: The format of this file is described in the
1.2 deraadt 956: .Xr sshd 8
1.40 aaron 957: manual page.
1.176 jmc 958: In the simplest form the format is the same as the
959: .Pa .pub
1.116 markus 960: identity files.
1.48 markus 961: This file is not highly sensitive, but the recommended
962: permissions are read/write for the user, and not accessible by others.
1.147 deraadt 963: .It Pa /etc/ssh/ssh_known_hosts
1.40 aaron 964: Systemwide list of known host keys.
1.116 markus 965: This file should be prepared by the
1.1 deraadt 966: system administrator to contain the public host keys of all machines in the
1.40 aaron 967: organization.
968: This file should be world-readable.
969: This file contains
1.1 deraadt 970: public keys, one per line, in the following format (fields separated
1.116 markus 971: by spaces): system name, public key and optional comment field.
1.40 aaron 972: When different names are used
1.1 deraadt 973: for the same machine, all such names should be listed, separated by
1.40 aaron 974: commas.
1.176 jmc 975: The format is described in the
1.2 deraadt 976: .Xr sshd 8
1.1 deraadt 977: manual page.
1.2 deraadt 978: .Pp
1.1 deraadt 979: The canonical system name (as returned by name servers) is used by
1.2 deraadt 980: .Xr sshd 8
1.1 deraadt 981: to verify the client host when logging in; other names are needed because
1.2 deraadt 982: .Nm
1.1 deraadt 983: does not convert the user-supplied name to a canonical name before
984: checking the key, because someone with access to the name servers
985: would then be able to fool host authentication.
1.147 deraadt 986: .It Pa /etc/ssh/ssh_config
1.40 aaron 987: Systemwide configuration file.
1.158 stevesk 988: The file format and configuration options are described in
989: .Xr ssh_config 5 .
1.147 deraadt 990: .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key
1.141 markus 991: These three files contain the private parts of the host keys
992: and are used for
993: .Cm RhostsRSAAuthentication
994: and
995: .Cm HostbasedAuthentication .
1.155 stevesk 996: If the protocol version 1
997: .Cm RhostsRSAAuthentication
1.157 deraadt 998: method is used,
1.155 stevesk 999: .Nm
1000: must be setuid root, since the host key is readable only by root.
1001: For protocol version 2,
1002: .Nm
1003: uses
1004: .Xr ssh-keysign 8
1005: to access the host keys for
1006: .Cm HostbasedAuthentication .
1007: This eliminates the requirement that
1008: .Nm
1009: be setuid root when that authentication method is used.
1010: By default
1.141 markus 1011: .Nm
1.155 stevesk 1012: is not setuid root.
1.2 deraadt 1013: .It Pa $HOME/.rhosts
1014: This file is used in
1.176 jmc 1015: .Em rhosts
1.2 deraadt 1016: authentication to list the
1.40 aaron 1017: host/user pairs that are permitted to log in.
1018: (Note that this file is
1.1 deraadt 1019: also used by rlogin and rsh, which makes using this file insecure.)
1020: Each line of the file contains a host name (in the canonical form
1021: returned by name servers), and then a user name on that host,
1.40 aaron 1022: separated by a space.
1.92 markus 1023: On some machines this file may need to be
1.1 deraadt 1024: world-readable if the user's home directory is on a NFS partition,
1025: because
1.2 deraadt 1026: .Xr sshd 8
1.40 aaron 1027: reads it as root.
1028: Additionally, this file must be owned by the user,
1029: and must not have write permissions for anyone else.
1030: The recommended
1.1 deraadt 1031: permission for most machines is read/write for the user, and not
1032: accessible by others.
1.2 deraadt 1033: .Pp
1.1 deraadt 1034: Note that by default
1.2 deraadt 1035: .Xr sshd 8
1.1 deraadt 1036: will be installed so that it requires successful RSA host
1.176 jmc 1037: authentication before permitting
1038: .Em rhosts
1039: authentication.
1.137 deraadt 1040: If the server machine does not have the client's host key in
1.147 deraadt 1041: .Pa /etc/ssh/ssh_known_hosts ,
1.137 deraadt 1042: it can be stored in
1.2 deraadt 1043: .Pa $HOME/.ssh/known_hosts .
1044: The easiest way to do this is to
1.1 deraadt 1045: connect back to the client from the server machine using ssh; this
1.48 markus 1046: will automatically add the host key to
1.2 deraadt 1047: .Pa $HOME/.ssh/known_hosts .
1048: .It Pa $HOME/.shosts
1049: This file is used exactly the same way as
1.176 jmc 1050: .Pa .rhosts .
1.2 deraadt 1051: The purpose for
1.1 deraadt 1052: having this file is to be able to use rhosts authentication with
1.2 deraadt 1053: .Nm
1054: without permitting login with
1.176 jmc 1055: .Xr rlogin
1.2 deraadt 1056: or
1057: .Xr rsh 1 .
1058: .It Pa /etc/hosts.equiv
1059: This file is used during
1.176 jmc 1060: .Em rhosts
1.173 jmc 1061: authentication.
1.40 aaron 1062: It contains
1.176 jmc 1063: canonical hosts names, one per line (the full format is described in the
1.2 deraadt 1064: .Xr sshd 8
1.40 aaron 1065: manual page).
1066: If the client host is found in this file, login is
1.1 deraadt 1067: automatically permitted provided client and server user names are the
1.40 aaron 1068: same.
1069: Additionally, successful RSA host authentication is normally
1070: required.
1071: This file should only be writable by root.
1.2 deraadt 1072: .It Pa /etc/shosts.equiv
1.44 aaron 1073: This file is processed exactly as
1.2 deraadt 1074: .Pa /etc/hosts.equiv .
1.1 deraadt 1075: This file may be useful to permit logins using
1.2 deraadt 1076: .Nm
1.1 deraadt 1077: but not using rsh/rlogin.
1.147 deraadt 1078: .It Pa /etc/ssh/sshrc
1.1 deraadt 1079: Commands in this file are executed by
1.2 deraadt 1080: .Nm
1.1 deraadt 1081: when the user logs in just before the user's shell (or command) is started.
1082: See the
1.2 deraadt 1083: .Xr sshd 8
1.1 deraadt 1084: manual page for more information.
1.2 deraadt 1085: .It Pa $HOME/.ssh/rc
1.1 deraadt 1086: Commands in this file are executed by
1.2 deraadt 1087: .Nm
1.1 deraadt 1088: when the user logs in just before the user's shell (or command) is
1089: started.
1.44 aaron 1090: See the
1.2 deraadt 1091: .Xr sshd 8
1.1 deraadt 1092: manual page for more information.
1.31 markus 1093: .It Pa $HOME/.ssh/environment
1094: Contains additional definitions for environment variables, see section
1095: .Sx ENVIRONMENT
1096: above.
1.58 itojun 1097: .El
1.145 markus 1098: .Sh DIAGNOSTICS
1099: .Nm
1100: exits with the exit status of the remote command or with 255
1101: if an error occurred.
1.2 deraadt 1102: .Sh SEE ALSO
1.176 jmc 1103: .Xr gzip 1 ,
1.2 deraadt 1104: .Xr rsh 1 ,
1105: .Xr scp 1 ,
1.83 djm 1106: .Xr sftp 1 ,
1.2 deraadt 1107: .Xr ssh-add 1 ,
1108: .Xr ssh-agent 1 ,
1109: .Xr ssh-keygen 1 ,
1110: .Xr telnet 1 ,
1.176 jmc 1111: .Xr hosts.equiv 5 ,
1.159 stevesk 1112: .Xr ssh_config 5 ,
1.160 naddy 1113: .Xr ssh-keysign 8 ,
1.87 itojun 1114: .Xr sshd 8
1.106 markus 1115: .Rs
1116: .%A T. Ylonen
1117: .%A T. Kivinen
1118: .%A M. Saarinen
1119: .%A T. Rinne
1120: .%A S. Lehtinen
1121: .%T "SSH Protocol Architecture"
1.150 markus 1122: .%N draft-ietf-secsh-architecture-12.txt
1123: .%D January 2002
1.106 markus 1124: .%O work in progress material
1125: .Re
1.173 jmc 1126: .Sh AUTHORS
1127: OpenSSH is a derivative of the original and free
1128: ssh 1.2.12 release by Tatu Ylonen.
1129: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1130: Theo de Raadt and Dug Song
1131: removed many bugs, re-added newer features and
1132: created OpenSSH.
1133: Markus Friedl contributed the support for SSH
1134: protocol versions 1.5 and 2.0.
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