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