.TH SSH2 1
.SH NAME
ssh, sshsession, rsa2ssh2 \- encrypted login and copy with foreign systems via SSHv2
.SH SYNOPSIS
.B ssh
[
.B -adIiKkmrvx
] [
.B -l
.I user
] [
.B -n
.I dir
] [
.B -z
.I attribute=value
]
system
[
.I cmd
[
.I args
] ]
.PP
.B aux/sshsession
[
.B -t
] [
.B -n
.I namespace
] [
.B -R
.I dir
] [
.B -r
.I dir
] [
.B -s
.I command
] [
.B -S
.I srvpt
]
.PP
.B rsa2ssh2
[
.I file
]
.SH DESCRIPTION
These programs collectively implement communication via SSH v2 over TCP.
All of the encryption, authentication, and SSH protocol are handled by
.IR ssh (4).
.PP
.I Ssh
dials a remote
.I system
and runs a shell (or some other command) there.
.L "ssh root@hannibal"
will result in a command prompt on the machine
.B hannibal
logged in as
.BR root .
If
.I ssh
does not find an SSH server in
.BR /net ,
it runs
.I netssh
(see
.IR ssh (4))
to start one.
.I Ssh
dials the remote SSH server and exchanges encryption keys with
the server using Diffie-Hellman key exchange.
.PP
A
.B clone
file and
.B connect
message protocol
similar to that of
.IR ip (3)
creates a session in the established connection.
In the course of session creation,
.I ssh
first attempts to authenticate the user with the server using
public key authentication.
If that fails, it prompts for a password, and attempts to
authenticate with password authentication.
It also passes across the value of the environment variable
.B TERM
as would be set if
.I ssh
is run inside of
.IR vt (1).
.LP
Per
.IR con (1),
typing a control-\e will result in a
.B >>>
prompt.
There are currently only four commands that can be issued at that prompt:
.B c
to continue the session,
.B h
to print a list of the available commands,
.B r
to toggle the suppression of carriage returns, and
.B q
to close the session.
.LP
Options are:
.TF "-i -
.TP
.B -a -v -x
No-ops included for compatibility with
.I scp
(see
.IR ssh1 (1)).
.TP
.B -d
Increase the amount of debugging output.
.TP
.B -i -I
Sets
.I ssh
to interactive
.RB ( -i )
or non-interactive
.RI ( -I )
mode.
This determines whether the user is prompted for a password
if none is found in factotum.
Without either of these options,
.I ssh
uses interactive mode if run in a term window.
.TP
.B -k
Skip the attempt to authenticate using public key authentication.
.TP
.B -K
Don't fall back to password authentication.
If the public key authentication fails,
.I ssh
will exit.
.TP
.B -l
Use
.I user
name on the remote system
(deprecated).
.TP
.B -m
Remove the special meaning of control-\e.
This is needed by
.I scp
to prevent that character in files being copied from triggering the
special command mode.
.TP
.B -n
Specify the network directory of an alternate network to use.
The default is
.BR /net .
.TP
.B -r
Strip carriage return characters coming from the remote system.
This will normally be desired when running in a
.IR rio (1)
window or from within
.IR win (1)
in
.IR acme (1).
It is normally not used when running
.I ssh
from within
.IR vt (1).
.TP
.B -z
Used to specify which of several possible keys to use.
.PD
.
.SS "Server-side Daemon"
.I Sshsession
implements the server side of an SSH connection
and is suitable for running by
.IR listen (8)
or
.IR listen1 ;
it is not normally run directly by the user.
Like
.IR ssh ,
it does all of its SSH communication through
.IR ssh (4).
.I Sshsession
starts a shell or a requested command when a remote
system authenticates and requests a new connection and session.
.LP
A system-wide SSH listener can be run by creating a file
.BR /rc/bin/service.auth/ssh22
that invokes
.IR sshsession :
.IP
.EX
#!/bin/rc
# ssh22
exec aux/sshsession $3 >>/sys/log/sshdebug >[2=1]
.EE
.LP
.ne 3
then ensuring that
.B /rc/bin/cpurc
contains
.IP
.EX
netssh -s ssh
aux/listen -t /rc/bin/service.auth -d /rc/bin/service ssh
.EE
.LP
When invoked with no options,
.I sshsession
runs as an SSH server.
Options are:
.TF -S
.TP
.B -n
Use a
.I namespace
other than the default
.B /lib/namespace
when starting the shell or running the requested command.
.TP
.B -r
Run the SSH session in
.IR dir .
.TP
.B -R
Like
.B -r
but also prevent any arguments, in the command to be executed,
from accessing files outside this directory;
primarily used to limit what
.I scp
can access.
.TP
.B -s
Execute
.I command
instead of
.BR /bin/rc .
.TP
.B -S
Create
.BI /srv/ srvpt
if an SSH server is not already mounted in
.BR /net .
.TP
.B -t
Trust
.I sshsession
and run it in the same namespace as the
.I listen
that started it.
.PD
.LP
A private SSH listener can be run by starting
.I netssh
(see
.IR ssh (4))
then running
.IR listen1 :
.IP
.EX
if (! test -e /net/ssh) netssh -s ssh
aux/listen1 -t 'ssh!*!2222' aux/sshsession
.EE
.
.SS Keys
.I Rsa2ssh2
converts an RSA key to one suitable for use with SSH v2 on Unix systems.
The following command will extract the public part of the key and add it to the
.B authorized_keys
file on a remote Unix system:
.IP
.EX
grep 'proto=rsa' /mnt/factotum/ctl | rsa2ssh2 |
	ssh2 user@unix 'cat >>.ssh/authorized_keys'
.EE
.SH FILES
.TF /sys/lib/ssh/keyring
.TP
.B /sys/lib/ssh/keyring
System-wide known host public keys.
.TP
.B $home/lib/keyring
Per-user known host public keys.
.TP
.B /env/nosshkeyverify
.SH SOURCE
.B /sys/src/cmd/ssh2
.SH "SEE ALSO"
.IR con (1),
.IR cpu (1),
.IR secstore (1),
.IR ssh1 (1),
.IR vt (1),
.IR factotum (4),
.IR ssh (4),
.IR listen (8),
.br
RFCs 4250, 4251, 4252, 4253, 4254, and 4419
.SH BUGS
.I Sshsession
shouldn't have to run as the host owner and using
.IR factotum (4)
correctly would permit this.
.PP
The SSH v2 protocol is a classic second system:
over-engineered,
overly complicated,
misdesigned
and
jammed full of pointless goodies.