Annotation of src/usr.bin/ssh/ssh_config.5, Revision 1.14
1.1 stevesk 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: .\"
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: .\"
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.
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.
25: .\"
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.
36: .\"
1.14 ! markus 37: .\" $OpenBSD: ssh_config.5,v 1.13 2003/06/10 09:12:12 jmc Exp $
1.1 stevesk 38: .Dd September 25, 1999
39: .Dt SSH_CONFIG 5
40: .Os
41: .Sh NAME
42: .Nm ssh_config
43: .Nd OpenSSH SSH client configuration files
44: .Sh SYNOPSIS
45: .Bl -tag -width Ds -compact
46: .It Pa $HOME/.ssh/config
47: .It Pa /etc/ssh/ssh_config
48: .El
49: .Sh DESCRIPTION
50: .Nm ssh
51: obtains configuration data from the following sources in
52: the following order:
1.2 stevesk 53: .Bl -enum -offset indent -compact
54: .It
55: command-line options
56: .It
57: user's configuration file
58: .Pq Pa $HOME/.ssh/config
59: .It
60: system-wide configuration file
61: .Pq Pa /etc/ssh/ssh_config
62: .El
1.1 stevesk 63: .Pp
64: For each parameter, the first obtained value
65: will be used.
66: The configuration files contain sections bracketed by
67: .Dq Host
68: specifications, and that section is only applied for hosts that
69: match one of the patterns given in the specification.
70: The matched host name is the one given on the command line.
71: .Pp
72: Since the first obtained value for each parameter is used, more
73: host-specific declarations should be given near the beginning of the
74: file, and general defaults at the end.
75: .Pp
76: The configuration file has the following format:
77: .Pp
78: Empty lines and lines starting with
79: .Ql #
80: are comments.
81: .Pp
82: Otherwise a line is of the format
83: .Dq keyword arguments .
84: Configuration options may be separated by whitespace or
85: optional whitespace and exactly one
86: .Ql = ;
87: the latter format is useful to avoid the need to quote whitespace
88: when specifying configuration options using the
89: .Nm ssh ,
90: .Nm scp
91: and
92: .Nm sftp
93: .Fl o
94: option.
95: .Pp
96: The possible
97: keywords and their meanings are as follows (note that
98: keywords are case-insensitive and arguments are case-sensitive):
99: .Bl -tag -width Ds
100: .It Cm Host
101: Restricts the following declarations (up to the next
102: .Cm Host
103: keyword) to be only for those hosts that match one of the patterns
104: given after the keyword.
105: .Ql \&*
106: and
107: .Ql ?
108: can be used as wildcards in the
109: patterns.
110: A single
111: .Ql \&*
112: as a pattern can be used to provide global
113: defaults for all hosts.
114: The host is the
115: .Ar hostname
116: argument given on the command line (i.e., the name is not converted to
117: a canonicalized host name before matching).
1.10 djm 118: .It Cm AddressFamily
1.11 jmc 119: Specifies which address family to use when connecting.
120: Valid arguments are
1.10 djm 121: .Dq any ,
122: .Dq inet
123: (Use IPv4 only) or
124: .Dq inet6
125: (Use IPv6 only.)
1.1 stevesk 126: .It Cm AFSTokenPassing
127: Specifies whether to pass AFS tokens to remote host.
128: The argument to this keyword must be
129: .Dq yes
130: or
131: .Dq no .
132: This option applies to protocol version 1 only.
133: .It Cm BatchMode
134: If set to
135: .Dq yes ,
136: passphrase/password querying will be disabled.
137: This option is useful in scripts and other batch jobs where no user
138: is present to supply the password.
139: The argument must be
140: .Dq yes
141: or
142: .Dq no .
143: The default is
144: .Dq no .
145: .It Cm BindAddress
146: Specify the interface to transmit from on machines with multiple
147: interfaces or aliased addresses.
148: Note that this option does not work if
149: .Cm UsePrivilegedPort
150: is set to
151: .Dq yes .
152: .It Cm ChallengeResponseAuthentication
153: Specifies whether to use challenge response authentication.
154: The argument to this keyword must be
155: .Dq yes
156: or
157: .Dq no .
158: The default is
159: .Dq yes .
160: .It Cm CheckHostIP
161: If this flag is set to
162: .Dq yes ,
163: ssh will additionally check the host IP address in the
164: .Pa known_hosts
165: file.
166: This allows ssh to detect if a host key changed due to DNS spoofing.
167: If the option is set to
168: .Dq no ,
169: the check will not be executed.
170: The default is
171: .Dq yes .
172: .It Cm Cipher
173: Specifies the cipher to use for encrypting the session
174: in protocol version 1.
175: Currently,
176: .Dq blowfish ,
177: .Dq 3des ,
178: and
179: .Dq des
180: are supported.
181: .Ar des
182: is only supported in the
183: .Nm ssh
184: client for interoperability with legacy protocol 1 implementations
185: that do not support the
186: .Ar 3des
1.7 jmc 187: cipher.
188: Its use is strongly discouraged due to cryptographic weaknesses.
1.1 stevesk 189: The default is
190: .Dq 3des .
191: .It Cm Ciphers
192: Specifies the ciphers allowed for protocol version 2
193: in order of preference.
194: Multiple ciphers must be comma-separated.
195: The default is
196: .Pp
197: .Bd -literal
198: ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
199: aes192-cbc,aes256-cbc''
200: .Ed
201: .It Cm ClearAllForwardings
202: Specifies that all local, remote and dynamic port forwardings
203: specified in the configuration files or on the command line be
1.7 jmc 204: cleared.
205: This option is primarily useful when used from the
1.1 stevesk 206: .Nm ssh
207: command line to clear port forwardings set in
208: configuration files, and is automatically set by
209: .Xr scp 1
210: and
211: .Xr sftp 1 .
212: The argument must be
213: .Dq yes
214: or
215: .Dq no .
216: The default is
217: .Dq no .
218: .It Cm Compression
219: Specifies whether to use compression.
220: The argument must be
221: .Dq yes
222: or
223: .Dq no .
224: The default is
225: .Dq no .
226: .It Cm CompressionLevel
227: Specifies the compression level to use if compression is enabled.
228: The argument must be an integer from 1 (fast) to 9 (slow, best).
229: The default level is 6, which is good for most applications.
230: The meaning of the values is the same as in
231: .Xr gzip 1 .
232: Note that this option applies to protocol version 1 only.
233: .It Cm ConnectionAttempts
234: Specifies the number of tries (one per second) to make before exiting.
235: The argument must be an integer.
236: This may be useful in scripts if the connection sometimes fails.
237: The default is 1.
1.9 djm 238: .It Cm ConnectTimeout
239: Specifies the timeout (in seconds) used when connecting to the ssh
1.11 jmc 240: server, instead of using the default system TCP timeout.
241: This value is used only when the target is down or really unreachable,
242: not when it refuses the connection.
1.1 stevesk 243: .It Cm DynamicForward
244: Specifies that a TCP/IP port on the local machine be forwarded
245: over the secure channel, and the application
246: protocol is then used to determine where to connect to from the
1.7 jmc 247: remote machine.
248: The argument must be a port number.
1.1 stevesk 249: Currently the SOCKS4 protocol is supported, and
250: .Nm ssh
251: will act as a SOCKS4 server.
252: Multiple forwardings may be specified, and
1.7 jmc 253: additional forwardings can be given on the command line.
254: Only the superuser can forward privileged ports.
1.14 ! markus 255: .It Cm EnableSSHKeysign
! 256: Setting this option to
! 257: .Dq yes
! 258: in the global client configuration file
! 259: .Pa /etc/ssh/ssh_config
! 260: enables the use of the helper program
! 261: .Xr ssh-keysign 8
! 262: during
! 263: .Cm HostbasedAuthentication .
! 264: The argument must be
! 265: .Dq yes
! 266: or
! 267: .Dq no .
! 268: The default is
! 269: .Dq no .
! 270: See
! 271: .Xr ssh-keysign 8
! 272: for more information.
1.1 stevesk 273: .It Cm EscapeChar
274: Sets the escape character (default:
275: .Ql ~ ) .
276: The escape character can also
277: be set on the command line.
278: The argument should be a single character,
279: .Ql ^
280: followed by a letter, or
281: .Dq none
282: to disable the escape
283: character entirely (making the connection transparent for binary
284: data).
285: .It Cm ForwardAgent
286: Specifies whether the connection to the authentication agent (if any)
287: will be forwarded to the remote machine.
288: The argument must be
289: .Dq yes
290: or
291: .Dq no .
292: The default is
293: .Dq no .
1.3 stevesk 294: .Pp
1.7 jmc 295: Agent forwarding should be enabled with caution.
296: Users with the ability to bypass file permissions on the remote host
297: (for the agent's Unix-domain socket)
298: can access the local agent through the forwarded connection.
299: An attacker cannot obtain key material from the agent,
1.3 stevesk 300: however they can perform operations on the keys that enable them to
301: authenticate using the identities loaded into the agent.
1.1 stevesk 302: .It Cm ForwardX11
303: Specifies whether X11 connections will be automatically redirected
304: over the secure channel and
305: .Ev DISPLAY
306: set.
307: The argument must be
308: .Dq yes
309: or
310: .Dq no .
311: The default is
312: .Dq no .
1.3 stevesk 313: .Pp
1.7 jmc 314: X11 forwarding should be enabled with caution.
315: Users with the ability to bypass file permissions on the remote host
316: (for the user's X authorization database)
317: can access the local X11 display through the forwarded connection.
318: An attacker may then be able to perform activities such as keystroke monitoring.
1.1 stevesk 319: .It Cm GatewayPorts
320: Specifies whether remote hosts are allowed to connect to local
321: forwarded ports.
322: By default,
323: .Nm ssh
1.7 jmc 324: binds local port forwardings to the loopback address.
325: This prevents other remote hosts from connecting to forwarded ports.
1.1 stevesk 326: .Cm GatewayPorts
327: can be used to specify that
328: .Nm ssh
329: should bind local port forwardings to the wildcard address,
330: thus allowing remote hosts to connect to forwarded ports.
331: The argument must be
332: .Dq yes
333: or
334: .Dq no .
335: The default is
336: .Dq no .
337: .It Cm GlobalKnownHostsFile
338: Specifies a file to use for the global
339: host key database instead of
340: .Pa /etc/ssh/ssh_known_hosts .
341: .It Cm HostbasedAuthentication
342: Specifies whether to try rhosts based authentication with public key
343: authentication.
344: The argument must be
345: .Dq yes
346: or
347: .Dq no .
348: The default is
349: .Dq no .
350: This option applies to protocol version 2 only and
351: is similar to
352: .Cm RhostsRSAAuthentication .
353: .It Cm HostKeyAlgorithms
354: Specifies the protocol version 2 host key algorithms
355: that the client wants to use in order of preference.
356: The default for this option is:
357: .Dq ssh-rsa,ssh-dss .
358: .It Cm HostKeyAlias
359: Specifies an alias that should be used instead of the
360: real host name when looking up or saving the host key
361: in the host key database files.
362: This option is useful for tunneling ssh connections
363: or for multiple servers running on a single host.
364: .It Cm HostName
365: Specifies the real host name to log into.
366: This can be used to specify nicknames or abbreviations for hosts.
367: Default is the name given on the command line.
368: Numeric IP addresses are also permitted (both on the command line and in
369: .Cm HostName
370: specifications).
371: .It Cm IdentityFile
372: Specifies a file from which the user's RSA or DSA authentication identity
1.11 jmc 373: is read.
374: The default is
1.1 stevesk 375: .Pa $HOME/.ssh/identity
376: for protocol version 1, and
377: .Pa $HOME/.ssh/id_rsa
378: and
379: .Pa $HOME/.ssh/id_dsa
380: for protocol version 2.
381: Additionally, any identities represented by the authentication agent
382: will be used for authentication.
383: The file name may use the tilde
384: syntax to refer to a user's home directory.
385: It is possible to have
386: multiple identity files specified in configuration files; all these
387: identities will be tried in sequence.
388: .It Cm KeepAlive
389: Specifies whether the system should send TCP keepalive messages to the
390: other side.
391: If they are sent, death of the connection or crash of one
392: of the machines will be properly noticed.
393: However, this means that
394: connections will die if the route is down temporarily, and some people
395: find it annoying.
396: .Pp
397: The default is
398: .Dq yes
399: (to send keepalives), and the client will notice
400: if the network goes down or the remote host dies.
401: This is important in scripts, and many users want it too.
402: .Pp
403: To disable keepalives, the value should be set to
404: .Dq no .
405: .It Cm KerberosAuthentication
406: Specifies whether Kerberos authentication will be used.
407: The argument to this keyword must be
408: .Dq yes
409: or
410: .Dq no .
411: .It Cm KerberosTgtPassing
412: Specifies whether a Kerberos TGT will be forwarded to the server.
413: This will only work if the Kerberos server is actually an AFS kaserver.
414: The argument to this keyword must be
415: .Dq yes
416: or
417: .Dq no .
418: .It Cm LocalForward
419: Specifies that a TCP/IP port on the local machine be forwarded over
420: the secure channel to the specified host and port from the remote machine.
421: The first argument must be a port number, and the second must be
422: .Ar host:port .
423: IPv6 addresses can be specified with an alternative syntax:
424: .Ar host/port .
425: Multiple forwardings may be specified, and additional
426: forwardings can be given on the command line.
427: Only the superuser can forward privileged ports.
428: .It Cm LogLevel
429: Gives the verbosity level that is used when logging messages from
430: .Nm ssh .
431: The possible values are:
432: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2 and DEBUG3.
1.7 jmc 433: The default is INFO.
434: DEBUG and DEBUG1 are equivalent.
435: DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1.1 stevesk 436: .It Cm MACs
437: Specifies the MAC (message authentication code) algorithms
438: in order of preference.
439: The MAC algorithm is used in protocol version 2
440: for data integrity protection.
441: Multiple algorithms must be comma-separated.
442: The default is
443: .Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 .
444: .It Cm NoHostAuthenticationForLocalhost
445: This option can be used if the home directory is shared across machines.
446: In this case localhost will refer to a different machine on each of
447: the machines and the user will get many warnings about changed host keys.
448: However, this option disables host authentication for localhost.
449: The argument to this keyword must be
450: .Dq yes
451: or
452: .Dq no .
453: The default is to check the host key for localhost.
454: .It Cm NumberOfPasswordPrompts
455: Specifies the number of password prompts before giving up.
456: The argument to this keyword must be an integer.
457: Default is 3.
458: .It Cm PasswordAuthentication
459: Specifies whether to use password authentication.
460: The argument to this keyword must be
461: .Dq yes
462: or
463: .Dq no .
464: The default is
465: .Dq yes .
466: .It Cm Port
467: Specifies the port number to connect on the remote host.
468: Default is 22.
469: .It Cm PreferredAuthentications
470: Specifies the order in which the client should try protocol 2
1.11 jmc 471: authentication methods.
472: This allows a client to prefer one method (e.g.
1.1 stevesk 473: .Cm keyboard-interactive )
474: over another method (e.g.
475: .Cm password )
476: The default for this option is:
477: .Dq hostbased,publickey,keyboard-interactive,password .
478: .It Cm Protocol
479: Specifies the protocol versions
480: .Nm ssh
481: should support in order of preference.
482: The possible values are
483: .Dq 1
484: and
485: .Dq 2 .
486: Multiple versions must be comma-separated.
487: The default is
488: .Dq 2,1 .
489: This means that
490: .Nm ssh
491: tries version 2 and falls back to version 1
492: if version 2 is not available.
493: .It Cm ProxyCommand
494: Specifies the command to use to connect to the server.
495: The command
496: string extends to the end of the line, and is executed with
497: .Pa /bin/sh .
498: In the command string,
499: .Ql %h
500: will be substituted by the host name to
501: connect and
502: .Ql %p
503: by the port.
504: The command can be basically anything,
505: and should read from its standard input and write to its standard output.
506: It should eventually connect an
507: .Xr sshd 8
508: server running on some machine, or execute
509: .Ic sshd -i
510: somewhere.
511: Host key management will be done using the
512: HostName of the host being connected (defaulting to the name typed by
513: the user).
1.7 jmc 514: Setting the command to
515: .Dq none
1.6 markus 516: disables this option entirely.
1.1 stevesk 517: Note that
518: .Cm CheckHostIP
519: is not available for connects with a proxy command.
520: .Pp
521: .It Cm PubkeyAuthentication
522: Specifies whether to try public key authentication.
523: The argument to this keyword must be
524: .Dq yes
525: or
526: .Dq no .
527: The default is
528: .Dq yes .
529: This option applies to protocol version 2 only.
530: .It Cm RemoteForward
531: Specifies that a TCP/IP port on the remote machine be forwarded over
532: the secure channel to the specified host and port from the local machine.
533: The first argument must be a port number, and the second must be
534: .Ar host:port .
535: IPv6 addresses can be specified with an alternative syntax:
536: .Ar host/port .
537: Multiple forwardings may be specified, and additional
538: forwardings can be given on the command line.
539: Only the superuser can forward privileged ports.
540: .It Cm RhostsAuthentication
541: Specifies whether to try rhosts based authentication.
542: Note that this
543: declaration only affects the client side and has no effect whatsoever
544: on security.
545: Most servers do not permit RhostsAuthentication because it
546: is not secure (see
547: .Cm RhostsRSAAuthentication ) .
548: The argument to this keyword must be
549: .Dq yes
550: or
551: .Dq no .
552: The default is
553: .Dq no .
1.4 stevesk 554: This option applies to protocol version 1 only and requires
555: .Nm ssh
556: to be setuid root and
557: .Cm UsePrivilegedPort
558: to be set to
559: .Dq yes .
1.1 stevesk 560: .It Cm RhostsRSAAuthentication
561: Specifies whether to try rhosts based authentication with RSA host
562: authentication.
563: The argument must be
564: .Dq yes
565: or
566: .Dq no .
567: The default is
568: .Dq no .
569: This option applies to protocol version 1 only and requires
570: .Nm ssh
571: to be setuid root.
572: .It Cm RSAAuthentication
573: Specifies whether to try RSA authentication.
574: The argument to this keyword must be
575: .Dq yes
576: or
577: .Dq no .
578: RSA authentication will only be
579: attempted if the identity file exists, or an authentication agent is
580: running.
581: The default is
582: .Dq yes .
583: Note that this option applies to protocol version 1 only.
584: .It Cm SmartcardDevice
1.11 jmc 585: Specifies which smartcard device to use.
586: The argument to this keyword is the device
1.1 stevesk 587: .Nm ssh
588: should use to communicate with a smartcard used for storing the user's
1.11 jmc 589: private RSA key.
590: By default, no device is specified and smartcard support is not activated.
1.1 stevesk 591: .It Cm StrictHostKeyChecking
592: If this flag is set to
593: .Dq yes ,
594: .Nm ssh
595: will never automatically add host keys to the
596: .Pa $HOME/.ssh/known_hosts
597: file, and refuses to connect to hosts whose host key has changed.
598: This provides maximum protection against trojan horse attacks,
599: however, can be annoying when the
600: .Pa /etc/ssh/ssh_known_hosts
601: file is poorly maintained, or connections to new hosts are
602: frequently made.
603: This option forces the user to manually
604: add all new hosts.
605: If this flag is set to
606: .Dq no ,
607: .Nm ssh
608: will automatically add new host keys to the
609: user known hosts files.
610: If this flag is set to
611: .Dq ask ,
612: new host keys
613: will be added to the user known host files only after the user
614: has confirmed that is what they really want to do, and
615: .Nm ssh
616: will refuse to connect to hosts whose host key has changed.
617: The host keys of
618: known hosts will be verified automatically in all cases.
619: The argument must be
620: .Dq yes ,
621: .Dq no
622: or
623: .Dq ask .
624: The default is
625: .Dq ask .
626: .It Cm UsePrivilegedPort
627: Specifies whether to use a privileged port for outgoing connections.
628: The argument must be
629: .Dq yes
630: or
631: .Dq no .
632: The default is
633: .Dq no .
1.4 stevesk 634: If set to
635: .Dq yes
636: .Nm ssh
637: must be setuid root.
1.1 stevesk 638: Note that this option must be set to
639: .Dq yes
640: if
641: .Cm RhostsAuthentication
642: and
643: .Cm RhostsRSAAuthentication
644: authentications are needed with older servers.
645: .It Cm User
646: Specifies the user to log in as.
647: This can be useful when a different user name is used on different machines.
648: This saves the trouble of
649: having to remember to give the user name on the command line.
650: .It Cm UserKnownHostsFile
651: Specifies a file to use for the user
652: host key database instead of
653: .Pa $HOME/.ssh/known_hosts .
1.8 jakob 654: .It Cm VerifyHostKeyDNS
655: Specifies whether to verify the remote key using DNS and SSHFP resource
656: records.
657: The default is
658: .Dq no .
1.12 jakob 659: Note that this option applies to protocol version 2 only.
1.1 stevesk 660: .It Cm XAuthLocation
1.5 stevesk 661: Specifies the full pathname of the
1.1 stevesk 662: .Xr xauth 1
663: program.
664: The default is
665: .Pa /usr/X11R6/bin/xauth .
666: .El
667: .Sh FILES
668: .Bl -tag -width Ds
669: .It Pa $HOME/.ssh/config
670: This is the per-user configuration file.
671: The format of this file is described above.
672: This file is used by the
673: .Nm ssh
674: client.
675: This file does not usually contain any sensitive information,
676: but the recommended permissions are read/write for the user, and not
677: accessible by others.
678: .It Pa /etc/ssh/ssh_config
679: Systemwide configuration file.
680: This file provides defaults for those
681: values that are not specified in the user's configuration file, and
682: for those users who do not have a configuration file.
683: This file must be world-readable.
684: .El
1.13 jmc 685: .Sh SEE ALSO
686: .Xr ssh 1
1.1 stevesk 687: .Sh AUTHORS
688: OpenSSH is a derivative of the original and free
689: ssh 1.2.12 release by Tatu Ylonen.
690: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
691: Theo de Raadt and Dug Song
692: removed many bugs, re-added newer features and
693: created OpenSSH.
694: Markus Friedl contributed the support for SSH
695: protocol versions 1.5 and 2.0.