.TH SSH 1
.SH NAME
ssh, sshserve \- secure login from/to Brazil or Plan 9
.SH SYNOPSIS
.B ssh
[
.B \-v
]
[
.B \-r
]
[
.B \-u
.I user
]
.I hostname
[
.I command
[
.I arguments
...]]
.PP
.B scp
[host:]file [host:]file
.br
.B scp
[host:]file ... [host:]dir
.PP
.B sshserve
.I address
.SH DESCRIPTION
.I Ssh
allows authenticated login over an encrypted channel to hosts that
support the ssh protocol (see the RFC listed below for encryption and
authentication details).
.LP
.I Ssh
takes the host name of the machine to connect to as its mandatory argument.
It may be specified as a domain name or an IP address.
Normally, login is attempted using the user name from /dev/user.
The
.B \-v
(verbose) flag gives feedback during the connection and authentication proces. 
The
.B \-r
flag strips carriage returns. 
The
.B \-u
flag allows login under a different name.
.LP
If no command is specified, an interactive shell is started on the remote
host.
Otherwise, the command is executed with its arguments.
.LP
Ssh establishes a connection with an ssh daemon on the remote host.
The daemon sends to ssh its RSA public host key and session key.
Using these, ssh sends a session key which, presumably, only the
daemon can decipher.  After this, both sides start encrypting their
data with this session key.  The encryption algorithm preferred by
Plan9 ssh for data transfer is RC4, with triple-DES (which isn't
really triple DES but a somewhat doubtful variation on it) as
backup.  (All ssh implementations are required to be able to do 3DES.)
.LP
When the daemon's host key has been received,
.I ssh
looks it up in $home/lib/keyring and in /sys/lib/ssh/keyring.  If
the key is found there, and it matches the received key,
.I ssh
is satisfied.  If not,
.ssh
reports this and offers to add the key to $home/lib/keyring.
.LP
Over the encrypted channel,
.I ssh
attempts to convince the daemon to accept the call.  It may prompt for
the password on the remote host \- note that this password will be sent
over the
.I encrypted
channel.  This is safe, provided one is indeed connected to the intended
host.
.LP
The preferred way to authenticate the user, however, is the
challenge/response system used by
.I netkey .
.I Ssh
users on other systems than Plan 9 should enable \s-2TIS_A\s0uthentication.
.LP
When the connection is established, the command given in the remaining
arguments, or the shell, is started up on the remote host.
.sp 1
.I Scp
uses
.I ssh
to copy files from one host to another.  A remote file is identified by
a host name, a colon and a file name (no spaces).
.I Scp
can copy files from remote hosts and to remote hosts.
.sp 1
.I Sshserve
is the server that services
.I ssh
calls from remote hosts.  On Plan9 and Brazil, it always requires either
a response to a challenge (netkey), or a password.  The password is
protected by encryption as it travels from the remote host to
.I sshserve .
.SH FILES
.TF /sys/lib/ssh/hostkey.public
.TP
.B /sys/lib/ssh/hostkey.public
Public key for the host on which the program runs.
.TP
.B /sys/lib/ssh/hostkey.secret
Secret key for the host on which the program runs.  This file must
be owned and be readable by bootes only.
.TP
.B /sys/lib/ssh/keyring
System keyring file containing public keys for remote ssh clients and servers.
.TP
.B /usr/\fIuser\fP/lib/keyring
Personal keyring file containing public keys for remote ssh clients and
servers.
.SH SOURCE
.B /sys/src/cmd/ssh
.SH "SEE ALSO"
.IR /sys/src/cmd/ssh/RFC*
.IR Auth(6)
.SH BUGS
This program was written (and partially copied) by Sape Mullender.