SSH2(1) SSH2(1)
NAME
ssh2, sshsession, rsa2ssh2 - encrypted login and copy with
foreign systems via SSHv2
SYNOPSIS
ssh2 [ -adIiKkmrvx ] [ -l user ] [ -n dir ] [ -z
attribute=value ] system [ cmd [ args ] ]
aux/sshsession [ -t ] [ -n namespace ] [ -R dir ] [ -r dir ]
[ -s command ] [ -S srvpt ]
rsa2ssh2 [ file ]
DESCRIPTION
These programs collectively implement communication via SSH
v2 over TCP. All of the encryption, authentication, and SSH
protocol are handled by ssh(4).
Ssh2 dials a remote system and runs a shell (or some other
command) there. `ssh2 root@hannibal' will result in a com-
mand prompt on the machine hannibal logged in as root. If
ssh2 does not find an SSH server in /net, it runs netssh
(see ssh(4)) to start one. Ssh2 dials the remote SSH server
and exchanges encryption keys with the server using Diffie-
Hellman key exchange.
A clone file and connect message protocol similar to that of
ip(3) creates a session in the established connection. In
the course of session creation, ssh2 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
TERM as would be set if ssh2 is run inside of vt(1).
Per con(1), typing a control-\ will result in a >>> prompt.
There are currently only four commands that can be issued at
that prompt: c to continue the session, h to print a list of
the available commands, r to toggle the suppression of car-
riage returns, and q to close the session.
Options are:
-a -v -x
No-ops included for compatibility with scp (see
ssh1(1)).
-d Increase the amount of debugging output.
-i -I Sets ssh2 to interactive (-i) or non-interactive (-I)
mode. This determines whether the user is prompted
for a password if none is found in factotum. Without
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either of these options, ssh2 uses interactive mode if
run in a term window.
-k Skip the attempt to authenticate using public key
authentication.
-K Don't fall back to password authentication. If the
public key authentication fails, ssh2 will exit.
-l Use user name on the remote system (deprecated).
-m Remove the special meaning of control-\. This is
needed by scp to prevent that character in files being
copied from triggering the special command mode.
-n Specify the network directory of an alternate network
to use. The default is /net.
-r Strip carriage return characters coming from the
remote system. This will normally be desired when
running in a rio(1) window or from within win(1) in
acme(1). It is normally not used when running ssh2
from within vt(1).
-z Used to specify which of several possible keys to use.
Server-side Daemon
Sshsession implements the server side of an SSH connection
and is suitable for running by listen(8) or listen1; it is
not normally run directly by the user. Like ssh2, it does
all of its SSH communication through ssh(4). Sshsession
starts a shell or a requested command when a remote system
authenticates and requests a new connection and session.
A system-wide SSH listener can be run by creating a file
/rc/bin/service.auth/ssh22 that invokes sshsession:
#!/bin/rc
# ssh22
exec aux/sshsession $3 >>/sys/log/sshdebug >[2=1]
then ensuring that /rc/bin/cpurc contains
netssh -s ssh
aux/listen -t /rc/bin/service.auth -d /rc/bin/service ssh
When invoked with no options, sshsession runs as an SSH
server. Options are:
-n Use a namespace other than the default /lib/namespace
when starting the shell or running the requested com-
mand.
-r Run the SSH session in dir.
-R Like -r but also prevent any arguments, in the command
to be executed, from accessing files outside this direc-
tory; primarily used to limit what scp can access.
-s Execute command instead of /bin/rc.
-S Create /srv/srvpt if an SSH server is not already
mounted in /net.
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-t Trust sshsession and run it in the same namespace as the
listen that started it.
A private SSH listener can be run by starting netssh (see
ssh(4)) then running listen1:
if (! test -e /net/ssh) netssh -s ssh
aux/listen1 -t 'ssh!*!2222' aux/sshsession
Keys
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 authorized_keys
file on a remote Unix system:
grep 'proto=rsa' /mnt/factotum/ctl | rsa2ssh2 |
ssh2 user@unix 'cat >>.ssh/authorized_keys'
FILES
/sys/lib/ssh/keyring System-wide known host public keys.
$home/lib/keyring Per-user known host public keys.
/env/nosshkeyverify
SOURCE
/sys/src/cmd/ssh2
SEE ALSO
con(1), cpu(1), secstore(1), ssh1(1), vt(1), factotum(4),
ssh(4), listen(8),
RFCs 4250, 4251, 4252, 4253, 4254, and 4419
BUGS
Sshsession shouldn't have to run as the host owner and using
factotum(4) correctly would permit this.
The SSH v2 protocol is a classic second system: over-
engineered, overly complicated, misdesigned and jammed full
of pointless goodies.
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