5 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
7 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
8 .\" All rights reserved
10 .\" Created: Sat Apr 22 21:55:14 1995 ylo
14 .Dd September 25, 1999
19 .Nd secure shell daemon
24 .Op Fl f Ar config_file
25 .Op Fl g Ar login_grace_time
26 .Op Fl h Ar host_key_file
27 .Op Fl k Ar key_gen_time
30 .Op Fl V Ar client_protocol_id
33 (Secure Shell Daemon) is the daemon program for
35 Together these programs replace rlogin and rsh, and
36 provide secure encrypted communications between two untrusted hosts
37 over an insecure network.
38 The programs are intended to be as easy to
39 install and use as possible.
42 is the daemon that listens for connections from clients.
43 It is normally started at boot from
46 daemon for each incoming connection.
47 The forked daemons handle
48 key exchange, encryption, authentication, command execution,
50 This implementation of
52 supports both SSH protocol version 1 and 2 simultaneously.
56 .Ss SSH protocol version 1
58 Each host has a host-specific RSA key
59 (normally 1024 bits) used to identify the host.
61 the daemon starts, it generates a server RSA key (normally 768 bits).
62 This key is normally regenerated every hour if it has been used, and
63 is never stored on disk.
65 Whenever a client connects the daemon responds with its public
67 The client compares the
68 RSA host key against its own database to verify that it has not changed.
69 The client then generates a 256 bit random number.
71 random number using both the host key and the server key, and sends
72 the encrypted number to the server.
73 Both sides then use this
74 random number as a session key which is used to encrypt all further
75 communications in the session.
76 The rest of the session is encrypted
77 using a conventional cipher, currently Blowfish or 3DES, with 3DES
78 being used by default.
79 The client selects the encryption algorithm
80 to use from those offered by the server.
82 Next, the server and the client enter an authentication dialog.
83 The client tries to authenticate itself using
87 authentication combined with RSA host
88 authentication, RSA challenge-response authentication, or password
91 Rhosts authentication is normally disabled
92 because it is fundamentally insecure, but can be enabled in the server
93 configuration file if desired.
94 System security is not improved unless
100 are disabled (thus completely disabling
106 .Ss SSH protocol version 2
108 Version 2 works similarly:
109 Each host has a host-specific DSA key used to identify the host.
110 However, when the daemon starts, it does not generate a server key.
111 Forward security is provided through a Diffie-Hellman key agreement.
112 This key agreement results in a shared session key.
113 The rest of the session is encrypted
114 using a symmetric cipher, currently
115 Blowfish, 3DES or CAST128 in CBC mode or Arcfour.
116 The client selects the encryption algorithm
117 to use from those offered by the server.
118 Additionally, session integrity is provided
119 through a cryptographic message authentication code
120 (hmac-sha1 or hmac-md5).
122 Protocol version 2 provides a public key based
123 user authentication method (DSAAuthentication)
124 and conventional password authentication.
126 .Ss Command execution and data forwarding
128 If the client successfully authenticates itself, a dialog for
129 preparing the session is entered.
130 At this time the client may request
131 things like allocating a pseudo-tty, forwarding X11 connections,
132 forwarding TCP/IP connections, or forwarding the authentication agent
133 connection over the secure channel.
135 Finally, the client either requests a shell or execution of a command.
136 The sides then enter session mode.
137 In this mode, either side may send
138 data at any time, and such data is forwarded to/from the shell or
139 command on the server side, and the user terminal in the client side.
141 When the user program terminates and all forwarded X11 and other
142 connections have been closed, the server sends command exit status to
143 the client, and both sides exit.
146 can be configured using command-line options or a configuration
148 Command-line options override values specified in the
152 rereads its configuration file when it receives a hangup signal,
155 The options are as follows:
158 Specifies the number of bits in the server key (default 768).
162 The server sends verbose debug output to the system
163 log, and does not put itself in the background.
164 The server also will not fork and will only process one connection.
165 This option is only intended for debugging for the server.
166 .It Fl f Ar configuration_file
167 Specifies the name of the configuration file.
169 .Pa /etc/sshd_config .
171 refuses to start if there is no configuration file.
172 .It Fl g Ar login_grace_time
173 Gives the grace time for clients to authenticate themselves (default
175 If the client fails to authenticate the user within
176 this many seconds, the server disconnects and exits.
177 A value of zero indicates no limit.
178 .It Fl h Ar host_key_file
179 Specifies the file from which the RSA host key is read (default
180 .Pa /etc/ssh_host_key ) .
181 This option must be given if
183 is not run as root (as the normal
184 host file is normally not readable by anyone but root).
188 is being run from inetd.
191 from inetd because it needs to generate the server key before it can
192 respond to the client, and this may take tens of seconds.
193 Clients would have to wait too long if the key was regenerated every time.
194 However, with small key sizes (e.g., 512) using
198 .It Fl k Ar key_gen_time
199 Specifies how often the server key is regenerated (default 3600
200 seconds, or one hour).
201 The motivation for regenerating the key fairly
202 often is that the key is not stored anywhere, and after about an hour,
203 it becomes impossible to recover the key for decrypting intercepted
204 communications even if the machine is cracked into or physically
206 A value of zero indicates that the key will never be regenerated.
208 Specifies the port on which the server listens for connections
212 Nothing is sent to the system log.
213 Normally the beginning,
214 authentication, and termination of each connection is logged.
216 This option is used to specify the size of the field
219 structure that holds the remote host name.
220 If the resolved host name is longer than
222 the dotted decimal value will be used instead.
223 This allows hosts with very long host names that
224 overflow this field to still be uniquely identified.
227 indicates that only dotted decimal addresses
228 should be put into the
232 Do not print an error message if RSA support is missing.
233 .It Fl V Ar client_protocol_id
234 SSH2 compatibility mode.
235 When this option is specified
237 assumes the client has sent the supplied version string
239 Protocol Version Identification Exchange.
243 to use IPv4 addresses only.
247 to use IPv6 addresses only.
249 .Sh CONFIGURATION FILE
251 reads configuration data from
253 (or the file specified with
255 on the command line).
256 The file contains keyword-value pairs, one per line.
259 and empty lines are interpreted as comments.
261 The following keywords are possible.
263 .It Cm AFSTokenPassing
264 Specifies whether an AFS token may be forwarded to the server.
268 This keyword can be followed by a number of group names, separated
270 If specified, login is allowed only for users whose primary
271 group matches one of the patterns.
276 wildcards in the patterns.
277 Only group names are valid; a numerical group ID isn't recognized.
278 By default login is allowed regardless of the primary group.
281 This keyword can be followed by a number of user names, separated
283 If specified, login is allowed only for users names that
284 match one of the patterns.
289 wildcards in the patterns.
290 Only user names are valid; a numerical user ID isn't recognized.
291 By default login is allowed regardless of the user name.
294 Specifies the ciphers allowed for protocol version 2.
295 Multiple ciphers must be comma-separated.
297 .Dq 3des-cbc,blowfish-cbc,arcfour,cast128-cbc .
301 should check for new mail for interactive logins.
305 This keyword can be followed by a number of group names, separated
307 Users whose primary group matches one of the patterns
308 aren't allowed to log in.
313 wildcards in the patterns.
314 Only group names are valid; a numerical group ID isn't recognized.
315 By default login is allowed regardless of the primary group.
318 This keyword can be followed by a number of user names, separated
320 Login is disallowed for user names that match one of the patterns.
324 can be used as wildcards in the patterns.
325 Only user names are valid; a numerical user ID isn't recognized.
326 By default login is allowed regardless of the user name.
327 .It Cm DSAAuthentication
328 Specifies whether DSA authentication is allowed.
331 Note that this option applies to protocol version 2 only.
333 Specifies whether remote hosts are allowed to connect to ports
334 forwarded for the client.
342 Specifies the file containing the private DSA host key (default
343 .Pa /etc/ssh_host_dsa_key )
344 used by SSH protocol 2.0.
347 disables protocol 2.0 if this file is group/world-accessible.
349 Specifies the file containing the private RSA host key (default
350 .Pa /etc/ssh_host_key )
351 used by SSH protocols 1.3 and 1.5.
354 disables protocols 1.3 and 1.5 if this file is group/world-accessible.
360 files will not be used in authentication.
363 .Pa /etc/shosts.equiv
367 .It Cm IgnoreUserKnownHosts
370 should ignore the user's
371 .Pa $HOME/.ssh/known_hosts
373 .Cm RhostsRSAAuthentication .
377 Specifies whether the system should send keepalive messages to the
379 If they are sent, death of the connection or crash of one
380 of the machines will be properly noticed.
381 However, this means that
382 connections will die if the route is down temporarily, and some people
384 On the other hand, if keepalives are not sent,
385 sessions may hang indefinitely on the server, leaving
387 users and consuming server resources.
391 (to send keepalives), and the server will notice
392 if the network goes down or the client host reboots.
393 This avoids infinitely hanging sessions.
395 To disable keepalives, the value should be set to
397 in both the server and the client configuration files.
398 .It Cm KerberosAuthentication
399 Specifies whether Kerberos authentication is allowed.
400 This can be in the form of a Kerberos ticket, or if
401 .Cm PasswordAuthentication
402 is yes, the password provided by the user will be validated through
403 the Kerberos KDC. To use this option, the server needs a
404 Kerberos servtab which allows the verification of the KDC's identity.
407 .It Cm KerberosOrLocalPasswd
408 If set then if password authentication through Kerberos fails then
409 the password will be validated via any additional local mechanism
415 .It Cm KerberosTgtPassing
416 Specifies whether a Kerberos TGT may be forwarded to the server.
419 as this only works when the Kerberos KDC is actually an AFS kaserver.
420 .It Cm KerberosTicketCleanup
421 Specifies whether to automatically destroy the user's ticket cache
425 .It Cm KeyRegenerationInterval
426 The server key is automatically regenerated after this many seconds
427 (if it has been used).
428 The purpose of regeneration is to prevent
429 decrypting captured sessions by later breaking into the machine and
431 The key is never stored anywhere.
432 If the value is 0, the key is never regenerated.
433 The default is 3600 (seconds).
435 Specifies what local address
438 The default is to listen to all local addresses.
439 Multiple options of this type are permitted.
442 options must precede this option.
443 .It Cm LoginGraceTime
444 The server disconnects after this time if the user has not
445 successfully logged in.
446 If the value is 0, there is no time limit.
447 The default is 600 (seconds).
449 Gives the verbosity level that is used when logging messages from
451 The possible values are:
452 QUIET, FATAL, ERROR, INFO, VERBOSE and DEBUG.
454 Logging with level DEBUG violates the privacy of users
455 and is not recommended.
457 Specifies the maximum number of concurrent unauthenticated connections to the
460 Additional connections will be dropped until authentication succeeds or the
462 expires for a connection.
465 Alternatively, random early drop can be enabled by specifying
466 the three colon separated values
470 will refuse connection attempts with a probabillity of
473 if there are currently
476 unauthenticated connections.
477 The probabillity increases linearly and all connection attempts
478 are refused if the number of unauthenticated connections reaches
481 .It Cm PasswordAuthentication
482 Specifies whether password authentication is allowed.
485 Note that this option applies to both protocol versions 1 and 2.
486 .It Cm PermitEmptyPasswords
487 When password authentication is allowed, it specifies whether the
488 server allows login to accounts with empty password strings.
491 .It Cm PermitRootLogin
492 Specifies whether the root can log in using
501 If this options is set to
503 only password authentication is disabled for root.
505 Root login with RSA authentication when the
508 specified will be allowed regardless of the value of this setting
509 (which may be useful for taking remote backups even if root login is
510 normally not allowed).
512 Specifies the file that contains the process identifier of the
516 .Pa /var/run/sshd.pid .
518 Specifies the port number that
522 Multiple options of this type are permitted.
528 when a user logs in interactively.
529 (On some systems it is also printed by the shell,
535 Specifies the protocol versions
538 The possible values are
542 Multiple versions must be comma-separated.
547 Random number generation uses other techniques.
548 .It Cm RhostsAuthentication
549 Specifies whether authentication using rhosts or /etc/hosts.equiv
551 Normally, this method should not be permitted because it is insecure.
552 .Cm RhostsRSAAuthentication
554 instead, because it performs RSA-based host authentication in addition
555 to normal rhosts or /etc/hosts.equiv authentication.
558 .It Cm RhostsRSAAuthentication
559 Specifies whether rhosts or /etc/hosts.equiv authentication together
560 with successful RSA host authentication is allowed.
563 .It Cm RSAAuthentication
564 Specifies whether pure RSA authentication is allowed.
567 Note that this option applies to protocol version 1 only.
569 Defines the number of bits in the server key.
570 The minimum value is 512, and the default is 768.
571 .It Cm SkeyAuthentication
574 authentication is allowed.
577 Note that s/key authentication is enabled only if
578 .Cm PasswordAuthentication
583 should check file modes and ownership of the
584 user's files and home directory before accepting login.
585 This is normally desirable because novices sometimes accidentally leave their
586 directory or files world-writable.
590 Configures an external subsystem (e.g. file transfer daemon).
591 Arguments should be a subsystem name and a command to execute upon subsystem request.
596 file transfer subsystem.
597 By default no subsystems are defined.
598 Note that this option applies to protocol version 2 only.
599 .It Cm SyslogFacility
600 Gives the facility code that is used when logging messages from
602 The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
603 LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
608 is used for interactive login sessions.
611 is never used for remote command execution.
614 .It Cm X11DisplayOffset
615 Specifies the first display number available for
620 from interfering with real X11 servers.
623 Specifies whether X11 forwarding is permitted.
626 Note that disabling X11 forwarding does not improve security in any
627 way, as users can always install their own forwarders.
629 Specifies the location of the
633 .Pa /usr/X11R6/bin/xauth .
636 When a user successfully logs in,
639 .Bl -enum -offset indent
641 If the login is on a tty, and no command has been specified,
642 prints last login time and
644 (unless prevented in the configuration file or by
645 .Pa $HOME/.hushlogin ;
650 If the login is on a tty, records login time.
654 if it exists, prints contents and quits
657 Changes to run with normal user privileges.
659 Sets up basic environment.
662 .Pa $HOME/.ssh/environment
665 Changes to user's home directory.
669 exists, runs it; else if
672 it; otherwise runs xauth.
675 files are given the X11
676 authentication protocol and cookie in standard input.
678 Runs user's shell or command.
680 .Sh AUTHORIZED_KEYS FILE FORMAT
682 .Pa $HOME/.ssh/authorized_keys
683 file lists the RSA keys that are
684 permitted for RSA authentication in SSH protocols 1.3 and 1.5
686 .Pa $HOME/.ssh/authorized_keys2
687 file lists the DSA keys that are
688 permitted for DSA authentication in SSH protocol 2.0.
689 Each line of the file contains one
690 key (empty lines and lines starting with a
694 Each line consists of the following fields, separated by
695 spaces: options, bits, exponent, modulus, comment.
697 is optional; its presence is determined by whether the line starts
698 with a number or not (the option field never starts with a number).
699 The bits, exponent, modulus and comment fields give the RSA key; the
700 comment field is not used for anything (but may be convenient for the
701 user to identify the key).
703 Note that lines in this file are usually several hundred bytes long
704 (because of the size of the RSA key modulus).
705 You don't want to type them in; instead, copy the
709 The options (if present) consist of comma-separated option
711 No spaces are permitted, except within double quotes.
712 The following option specifications are supported:
714 .It Cm from="pattern-list"
715 Specifies that in addition to RSA authentication, the canonical name
716 of the remote host must be present in the comma-separated list of
722 The list may also contain
723 patterns negated by prefixing them with
725 if the canonical host name matches a negated pattern, the key is not accepted.
727 of this option is to optionally increase security: RSA authentication
728 by itself does not trust the network or name servers or anything (but
729 the key); however, if somebody somehow steals the key, the key
730 permits an intruder to log in from anywhere in the world.
731 This additional option makes using a stolen key more difficult (name
732 servers and/or routers would have to be compromised in addition to
734 .It Cm command="command"
735 Specifies that the command is executed whenever this key is used for
737 The command supplied by the user (if any) is ignored.
738 The command is run on a pty if the connection requests a pty;
739 otherwise it is run without a tty.
740 A quote may be included in the command by quoting it with a backslash.
741 This option might be useful
742 to restrict certain RSA keys to perform just a specific operation.
743 An example might be a key that permits remote backups but nothing else.
744 Note that the client may specify TCP/IP and/or X11
745 forwarding unless they are explicitly prohibited.
746 .It Cm environment="NAME=value"
747 Specifies that the string is to be added to the environment when
748 logging in using this key.
749 Environment variables set this way
750 override other default environment values.
751 Multiple options of this type are permitted.
752 .It Cm no-port-forwarding
753 Forbids TCP/IP forwarding when this key is used for authentication.
754 Any port forward requests by the client will return an error.
755 This might be used, e.g., in connection with the
758 .It Cm no-X11-forwarding
759 Forbids X11 forwarding when this key is used for authentication.
760 Any X11 forward requests by the client will return an error.
761 .It Cm no-agent-forwarding
762 Forbids authentication agent forwarding when this key is used for
765 Prevents tty allocation (a request to allocate a pty will fail).
768 1024 33 12121.\|.\|.\|312314325 ylo@foo.bar
770 from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula
772 command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi
773 .Sh SSH_KNOWN_HOSTS FILE FORMAT
775 .Pa /etc/ssh_known_hosts ,
776 .Pa /etc/ssh_known_hosts2 ,
777 .Pa $HOME/.ssh/known_hosts ,
779 .Pa $HOME/.ssh/known_hosts2
780 files contain host public keys for all known hosts.
781 The global file should
782 be prepared by the administrator (optional), and the per-user file is
783 maintained automatically: whenever the user connects from an unknown host
784 its key is added to the per-user file.
786 Each line in these files contains the following fields: hostnames,
787 bits, exponent, modulus, comment.
788 The fields are separated by spaces.
790 Hostnames is a comma-separated list of patterns ('*' and '?' act as
791 wildcards); each pattern in turn is matched against the canonical host
792 name (when authenticating a client) or against the user-supplied
793 name (when authenticating a server).
794 A pattern may also be preceded by
796 to indicate negation: if the host name matches a negated
797 pattern, it is not accepted (by that line) even if it matched another
800 Bits, exponent, and modulus are taken directly from the RSA host key; they
801 can be obtained, e.g., from
802 .Pa /etc/ssh_host_key.pub .
803 The optional comment field continues to the end of the line, and is not used.
807 and empty lines are ignored as comments.
809 When performing host authentication, authentication is accepted if any
810 matching line has the proper key.
811 It is thus permissible (but not
812 recommended) to have several lines or different host keys for the same
814 This will inevitably happen when short forms of host names
815 from different domains are put in the file.
817 that the files contain conflicting information; authentication is
818 accepted if valid information can be found from either file.
820 Note that the lines in these files are typically hundreds of characters
821 long, and you definitely don't want to type in the host keys by hand.
822 Rather, generate them by a script
824 .Pa /etc/ssh_host_key.pub
825 and adding the host names at the front.
827 closenet,closenet.hut.fi,.\|.\|.\|,130.233.208.41 1024 37 159.\|.\|.93 closenet.hut.fi
830 .It Pa /etc/sshd_config
831 Contains configuration data for
833 This file should be writable by root only, but it is recommended
834 (though not necessary) that it be world-readable.
835 .It Pa /etc/ssh_host_key
836 Contains the private part of the host key.
837 This file should only be owned by root, readable only by root, and not
838 accessible to others.
841 does not start if this file is group/world-accessible.
842 .It Pa /etc/ssh_host_key.pub
843 Contains the public part of the host key.
844 This file should be world-readable but writable only by
846 Its contents should match the private part.
848 really used for anything; it is only provided for the convenience of
849 the user so its contents can be copied to known hosts files.
850 These two files are created using
852 .It Pa /var/run/sshd.pid
853 Contains the process ID of the
855 listening for connections (if there are several daemons running
856 concurrently for different ports, this contains the pid of the one
858 The content of this file is not sensitive; it can be world-readable.
859 .It Pa $HOME/.ssh/authorized_keys
860 Lists the RSA keys that can be used to log into the user's account.
861 This file must be readable by root (which may on some machines imply
862 it being world-readable if the user's home directory resides on an NFS
864 It is recommended that it not be accessible by others.
865 The format of this file is described above.
866 Users will place the contents of their
868 files into this file, as described in
870 .It Pa $HOME/.ssh/authorized_keys2
871 Lists the DSA keys that can be used to log into the user's account.
872 This file must be readable by root (which may on some machines imply
873 it being world-readable if the user's home directory resides on an NFS
875 It is recommended that it not be accessible by others.
876 The format of this file is described above.
877 Users will place the contents of their
879 files into this file, as described in
881 .It Pa "/etc/ssh_known_hosts" and "$HOME/.ssh/known_hosts"
882 These files are consulted when using rhosts with RSA host
883 authentication to check the public key of the host.
884 The key must be listed in one of these files to be accepted.
885 The client uses the same files
886 to verify that the remote host is the one it intended to connect.
887 These files should be writable only by root/the owner.
888 .Pa /etc/ssh_known_hosts
889 should be world-readable, and
890 .Pa $HOME/.ssh/known_hosts
891 can but need not be world-readable.
895 refuses to let anyone except root log in.
896 The contents of the file
897 are displayed to anyone trying to log in, and non-root connections are
899 The file should be world-readable.
900 .It Pa /etc/hosts.allow, /etc/hosts.deny
903 support, tcp-wrappers access controls may be defined here as described in
906 This file contains host-username pairs, separated by a space, one per
908 The given user on the corresponding host is permitted to log in
910 The same file is used by rlogind and rshd.
912 be writable only by the user; it is recommended that it not be
913 accessible by others.
915 If is also possible to use netgroups in the file.
917 name may be of the form +@groupname to specify all hosts or all users
921 this file is exactly the same as for
923 However, this file is
924 not used by rlogin and rshd, so using this permits access using SSH only.
925 .It Pa /etc/hosts.equiv
926 This file is used during
929 In the simplest form, this file contains host names, one per line.
931 those hosts are permitted to log in without a password, provided they
932 have the same user name on both machines.
933 The host name may also be
934 followed by a user name; such users are permitted to log in as
936 user on this machine (except root).
937 Additionally, the syntax
939 can be used to specify netgroups.
940 Negated entries start with
943 If the client host/user is successfully matched in this file, login is
944 automatically permitted provided the client and server user names are the
946 Additionally, successful RSA host authentication is normally required.
947 This file must be writable only by root; it is recommended
948 that it be world-readable.
950 .Sy "Warning: It is almost never a good idea to use user names in"
952 Beware that it really means that the named user(s) can log in as
954 which includes bin, daemon, adm, and other accounts that own critical
955 binaries and directories.
956 Using a user name practically grants the user root access.
957 The only valid use for user names that I can think
958 of is in negative entries.
960 Note that this warning also applies to rsh/rlogin.
961 .It Pa /etc/shosts.equiv
962 This is processed exactly as
963 .Pa /etc/hosts.equiv .
964 However, this file may be useful in environments that want to run both
966 .It Pa $HOME/.ssh/environment
967 This file is read into the environment at login (if it exists).
968 It can only contain empty lines, comment lines (that start with
970 and assignment lines of the form name=value.
971 The file should be writable
972 only by the user; it need not be readable by anyone else.
974 If this file exists, it is run with /bin/sh after reading the
975 environment files but before starting the user's shell or command.
976 If X11 spoofing is in use, this will receive the "proto cookie" pair in
984 The primary purpose of this file is to run any initialization routines
985 which may be needed before the user's home directory becomes
986 accessible; AFS is a particular example of such an environment.
988 This file will probably contain some initialization code followed by
989 something similar to: "if read proto cookie; then echo add $DISPLAY
990 $proto $cookie | xauth -q -; fi".
992 If this file does not exist,
995 does not exist either, xauth is used to store the cookie.
997 This file should be writable only by the user, and need not be
998 readable by anyone else.
1002 This can be used to specify
1003 machine-specific login-time initializations globally.
1004 This file should be writable only by root, and should be world-readable.
1008 is a derivative of the original (free) ssh 1.2.12 release by Tatu Ylonen,
1009 but with bugs removed and newer features re-added.
1011 1.2.12 release, newer versions of the original ssh bore successively
1012 more restrictive licenses, and thus demand for a free version was born.
1014 This version of OpenSSH
1017 has all components of a restrictive nature (i.e., patents)
1018 directly removed from the source code; any licensed or patented components
1022 has been updated to support SSH protocol 1.5 and 2, making it compatible with
1023 all other SSH clients and servers.
1025 contains added support for
1027 authentication and ticket passing.
1029 supports one-time password authentication with
1033 OpenSSH has been created by Aaron Campbell, Bob Beck, Markus Friedl,
1034 Niels Provos, Theo de Raadt, and Dug Song.
1036 The support for SSH protocol 2 was written by Markus Friedl.