347 lines
6.6 KiB
Text
347 lines
6.6 KiB
Text
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.TH SSH 1
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.SH NAME
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ssh, sshnet, scp, sshserve \- secure login and file copy from/to Unix or Plan 9
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.SH SYNOPSIS
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.B ssh
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[
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.B -CfiImPpRrw
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]
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[
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.B -A
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.I authlist
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]
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[
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.B -c
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.I cipherlist
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]
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[
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.B -[lu]
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.I user
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]
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.RI [ user\fB@ ] host
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[
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.I cmd
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[
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.I args
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\&... ]]
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.PP
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.B sshnet
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[
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.B -A
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.I authlist
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]
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[
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.B -c
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.I cipherlist
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]
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[
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.B -m
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.I mtpt
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]
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[
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.B -s
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.I service
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]
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.RI [ user\fB@ ] host
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.PP
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.B scp
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[host:]file [host:]file
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.br
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.B scp
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[host:]file ... [host:]dir
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.PP
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.B aux/sshserve
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[
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.B -p
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]
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.I address
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.SH DESCRIPTION
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.I Ssh
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allows authenticated login over an encrypted channel to hosts that
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support the ssh protocol (see the RFCs listed below for encryption and
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authentication details).
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.LP
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.I Ssh
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takes the host name of the machine to connect to as its mandatory argument.
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It may be specified as a domain name or an IP address.
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Normally, login is attempted using the user name from /dev/user.
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.PP
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Command-line options are:
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.TP
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.B -C
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force input to be read in cooked mode:
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``line at a time'' with local echo.
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.TP
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.B -f
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enable agent forwarding.
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With this flag,
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.I ssh
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uses SSH's agent forwarding protocol to allow
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programs running on the remote server to
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interact with
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.IR factotum (4)
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to perform RSA authentication.
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.TP
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.B -i
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force interactive mode.
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In interactive mode,
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.I ssh
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prompts for passwords and confirmations of
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new host keys when necessary.
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(In non-interactive mode, password requests
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are rejected and unrecognized host keys are
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cause for disconnecting.)
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By default,
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.I ssh
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runs in interactive mode only when its
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input file descriptor is
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.BR /dev/cons .
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.TP
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.B -I
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force non-interactive mode.
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.TP
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.B -m
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disable the
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.RB control- \e
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menu, described below.
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.TP
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.B -p
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force pseudoterminal request.
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The
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.I ssh
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protocol, grounded in Unix tradition,
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differentiates between connections
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that request controlling pseudoterminals
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and those that do not.
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By default,
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.I ssh
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requests a pseudoterminal only when no
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.I command
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is given.
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.TP
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.B -P
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force no pseudoterminal request.
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.TP
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.B -r
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strip carriage returns.
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.TP
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.B -R
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put the allocated pseudoterminal, if any, in raw mode.
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.TP
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.B -w
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notify the remote side whenever the window changes size.
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.TP
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.BR - [ lu ] "\fI user
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specify user name.
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This option is deprecated in favor of the
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.IB user @ hostname
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syntax.
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.TP
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.B "-A\fI authlist
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specify an ordered space-separated list of authentication protocols to try.
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The full set of authentication protocols is
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.B rsa
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(RSA using
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.IR factotum (4)
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to moderate key usage),
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.B password
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(use a password gathered from factotum),
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and
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.B tis
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(challenge-response).
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The default list is all three in that order.
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.TP
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.B "-c\fI cipherlist
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specify an ordered space-separated list of allowed ciphers to use when encrypting the channel.
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The full set of ciphers is
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.B des
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(standard DES),
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.B 3des
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(a somewhat doubtful variation on triple DES),
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.B blowfish
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(Bruce Schneier's Blowfish),
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.B rc4
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(RC4),
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and
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.B none
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(no encryption).
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The default cipher list is
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.B blowfish
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.B rc4
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.BR 3des .
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.PD
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.PP
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The
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.RB control\- \e
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character is a local escape, as in
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.IR con (1).
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It prompts with
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.BR >>> .
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Legitimate responses to the prompt are
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.TP
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.B q
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Exit.
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.TP
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.B .
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Return from the escape.
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.TP
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.B !cmd
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Run the command with the network connection as its
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standard input and standard output.
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Standard error will go to the screen.
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.TP
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.B r
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Toggle printing of carriage returns.
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.PD
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.LP
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If no command is specified,
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a login session is started on the remote
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host.
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Otherwise, the command is executed with its arguments.
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.LP
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.I Ssh
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establishes a connection with an ssh daemon on the remote host.
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The daemon sends to
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.I ssh
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its RSA public host key and session key.
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Using these,
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.I ssh
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sends a session key which, presumably, only the
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daemon can decipher. After this, both sides start encrypting their
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data with this session key.
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.LP
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When the daemon's host key has been received,
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.I ssh
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looks it up in
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.B $home/lib/keyring
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and in
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.BR /sys/lib/ssh/keyring .
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If
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the key is found there, and it matches the received key,
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.I ssh
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is satisfied. If not,
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.I ssh
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reports this and offers to add the key to
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.BR $home/lib/keyring .
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.LP
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Over the encrypted channel,
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.I ssh
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attempts to convince the daemon to accept the call
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using the listed authentication protocols
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(see the
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.B -A
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option above).
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.LP
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The preferred way to authenticate is a
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.IR netkey -style
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challenge/response or via a SecurID token.
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.I Ssh
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users on other systems than Plan 9 should enable \s-2TIS_A\s0uthentication.
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.LP
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When the connection is authenticated, the given command line,
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(by default, a login shell) is executed on the remote host.
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.sp 1
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The SSH protocol allows clients to make outgoing TCP calls via the server.
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.I Sshnet
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establishes an SSH connection and, rather than execute a remote command,
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presents the remote server's TCP stack as a network stack
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(see the discussion of TCP in
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.IR ip (3))
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mounted at
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.I mtpt
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(default
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.BR /net ),
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optionally posting a 9P service
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descriptor for the new file system as
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.IB /srv/ service \fR.
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The
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.B -A
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and
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.B -c
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arguments are as in
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.IR ssh .
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.sp 1
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.I Scp
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uses
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.I ssh
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to copy files from one host to another. A remote file is identified by
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a host name, a colon and a file name (no spaces).
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.I Scp
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can copy files from remote hosts and to remote hosts.
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.sp 1
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.I Sshserve
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is the server that services
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.I ssh
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calls from remote hosts.
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The
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.B -A
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and
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.B -c
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options set valid authentication methods and ciphers
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as in
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.IR ssh ,
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except that there is no
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.B rsa
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authentication method.
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Unlike in
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.IR ssh ,
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the list is not ordered: the server presents a set and the client makes the choice.
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The default sets are
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.B tis
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and
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.B blowfish
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.B rc4
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.BR 3des .
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By default, users start with the namespace defined in
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.BR /lib/namespace .
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Users in group
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.B noworld
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in
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.B /adm/users
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start with the namespace defined in
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.BR /lib/namespace.noworld .
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.I Sshserve
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does not provide the TCP forwarding functionality used
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by
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.IR sshnet ,
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because many Unix clients present
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this capability in an insecure manner.
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.PP
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.I Sshserve
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requires that
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.IR factotum (4)
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hold the host key,
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identified by having attributes
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.B proto=rsa
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.BR service=sshserve .
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To generate a host key:
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.IP
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.EX
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auth/rsagen -t 'service=sshserve' >/mnt/factotum/ctl
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.EE
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.LP
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To extract the public part of the host key in the form
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used by SSH key rings:
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.IP
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.EX
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grep 'service=sshserve' /mnt/factotum/ctl | auth/rsa2ssh
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.EE
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.SH FILES
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.TP
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.B /sys/lib/ssh/keyring
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System key ring file containing public keys for remote ssh clients and servers.
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.TP
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.B /usr/\fIuser\fP/lib/keyring
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Personal key ring file containing public keys for remote ssh clients and
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servers.
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.SH SOURCE
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.B /sys/src/cmd/ssh
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.SH "SEE ALSO"
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.B /lib/rfc/rfc425[0-6]
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.br
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.IR factotum (4),
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.IR authsrv (6),
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.IR rsa (8)
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.SH BUGS
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Only version 1 of the SSH protocol is implemented.
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