1CONCH(1) BSD General Commands Manual CONCH(1)
2
4 conch — Conch SSH client
5
7 conch [-AaCfINnrsTtVvx] [-c cipher_spec] [-e escape_char]
8 [-i identity_file] [-K connection_spec] [-L port:host:hostport]
9 [-l user] [-m mac_spec] [-o openssh_option] [-p port]
10 [-R port:host:hostport] [user@] hostname [command]
11
13 conch is a SSHv2 client for logging into a remote machine and executing
14 commands. It provides encrypted and secure communications across a pos‐
15 sibly insecure network. Arbitrary TCP/IP ports can also be forwarded
16 over the secure connection.
17 conch connects and logs into hostname (as user or the current username).
19 The user must prove her/his identity through a public-key or a password.
20 Alternatively, if a connection is already open to a server, a new shell
21 can be opened over the connection without having to reauthenticate.
22 If command is specified, command is executed instead of a shell. If the
24 -s option is given, command is treated as an SSHv2 subsystem name.
25 Authentication
27 Conch supports the public-key, keyboard-interactive, and password authen‐
28 tications.
29 The public-key method allows the RSA or DSA algorithm to be used. The
31 client uses his/her private key, $HOME/.ssh/id_rsa or $HOME/.ssh/id_dsa
32 to sign the session identifier, known only by the client and server. The
33 server checks that the matching public key is valid for the user, and
34 that the signature is correct.
35 If public-key authentication fails, conch can authenticate by sending an
37 encrypted password over the connection.
38 Connection sharing
40 conch has the ability to multiplex multiple shells, commands and TCP/IP
41 ports over the same secure connection. To disable multiplexing for a
42 connection, use the -I flag.
43 The -K option determines how the client connects to the remote host. It
45 is a comma-separated list of the methods to use, in order of preference.
46 The two connection methods are ‘unix’ (for connecting over a multiplexed
47 connection) and ‘direct’ (to connect directly). To disable connecting
48 over a multiplexed connection, do not include ‘unix’ in the preference
49 list.
50 As an example of how connection sharing works, to speed up CVS over SSH:
52 conch --noshell --fork -l cvs_user cvs_host
54 set CVS_RSH=conch
55 Now, when CVS connects to cvs_host as cvs_user, instead of making a new
57 connection to the server, conch will add a new channel to the existing
58 connection. This saves the cost of repeatedly negotiating the cryptogra‐
59 phy and authentication.
60 The options are as follows:
62 -A Enables authentication agent forwarding.
64 -a Disables authentication agent forwarding (default).
66 -C Enable compression.
68 -c cipher_spec
70 Selects encryption algorithms to be used for this connection, as
71 a comma-separated list of ciphers in order of preference. The
72 list that conch supports is (in order of default preference):
73 aes256-ctr, aes256-cbc, aes192-ctr, aes192-cbc, aes128-ctr,
74 aes128-cbc, cast128-ctr, cast128-cbc, blowfish-ctr, blowfish,
75 idea-ctr, idea-cbc, 3des-ctr, 3des-cbc.
76 -e ch | ^ch | none
78 Sets the escape character for sessions with a PTY (default: ‘~’).
79 The escape character is only recognized at the beginning of a
80 line (after a newline). The escape character followed by a dot
81 (‘.’) closes the connection; followed by ^Z suspends the connec‐
82 tion; and followed by the escape character sends the escape char‐
83 acter once. Setting the character to “none” disables any
84 escapes.
85 -f Fork to background after authentication.
87 -I Do not allow connection sharing over this connection.
89 -i identity_spec
91 The file from which the identity (private key) for RSA or DSA
92 authentication is read. The defaults are $HOME/.ssh/id_rsa and
93 $HOME/.ssh/id_dsa. It is possible to use this option more than
94 once to use more than one private key.
95 -K connection_spec
97 Selects methods for connection to the server, as a comma-sepa‐
98 rated list of methods in order of preference. See Connection
99 sharing for more information.
100 -L port:host:hostport
102 Specifies that the given port on the client host is to be for‐
103 warded to the given host and port on the remote side. This allo‐
104 cates a socket to listen to port on the local side, and when con‐
105 nections are made to that socket, they are forwarded over the
106 secure channel and a connection is made to host port hostport
107 from the remote machine. Only root can forward privieged ports.
108 -l user
110 Log in using this username.
111 -m mac_spec
113 Selects MAC (message authentication code) algorithms, as a comma-
114 separated list in order of preference. The list that conch sup‐
115 ports is (in order of preference): hmac-sha1, hmac-md5.
116 -N Do not execute a shell or command.
118 -n Redirect input from /dev/null.
120 -o openssh_option
122 Ignored OpenSSH options.
123 -p port
125 The port to connect to on the server.
126 -R port:host:hostport
128 Specifies that the given port on the remote host is to be for‐
129 warded to the given host and port on the local side. This allo‐
130 cates a socket to listen to port on the remote side, and when
131 connections are made to that socket, they are forwarded over the
132 secure channel and a connection is made to host port hostport
133 from the client host. Only root can forward privieged ports.
134 -s Reconnect to the server if the connection is lost.
136 -s Invoke command (mandatory) as a SSHv2 subsystem.
138 -T Do not allocate a TTY.
140 -t Allocate a TTY even if command is given.
142 -V Display version number only.
144 -v Log to stderr.
146 -x Disable X11 connection forwarding (default).
148
150 Written by Paul Swartz <z3p@twistedmatrix.com>.
151
153 To report a bug, visit http://twistedmatrix.com/bugs/
154
156 Copyright © 2002-2008 Twisted Matrix Laboratories.
157 This is free software; see the source for copying conditions. There is
158 NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
159 PURPOSE.
160
162 ssh(1)
163BSD May 22, 2004 BSD