.TH SIDEDOOR 1 2017-01-14
.SH NAME
sidedoor \- SSH connection daemon
.SH SYNOPSIS
\fBsidedoor\fP [\fISSH options\fP] [\fIuser\fP\fB@\fP]\fIhostname\fP
.SH DESCRIPTION
.PP
sidedoor maintains an SSH connection or tunnel
with a shell script daemon.

The primary use case is maintaining a remote port forward
to the local SSH server (or another port). Thus, the local
device can be accessed without using incoming connections
that may be blocked by a NAT or firewall or otherwise
impractical with mobile devices.

SSH clients can connect to the device via the reverse SSH proxy
that sidedoor tunnels to. This proxy server can be untrusted
and run by a third party or cloud service.

sidedoor enables SSH keepalives and retries SSH with
exponential backoff. In order to reconnect as soon as possible,
it resets the backoff when a network interface is brought up
(or changed).
.SH OPTIONS
See \fBssh\fP(1).
.SH SIGNALS
\fBSIGUSR1\fP resets the retry backoff, immediately retrying \fBssh\fP(1)
if it is not currently running.
.SH FILES
.TP
.I /etc/default/sidedoor
Arguments to pass to \fBsidedoor\fP when run as a service. See \fBssh\fP(1).
.TP
.I /etc/sidedoor/config
SSH client configuration file.
.TP
.I /etc/sidedoor/id_rsa
SSH private key to access the remote server.

\fBssh-keygen\fP(1) can generate this key
(press y when prompted to overwrite the existing file):

    $ sudo ssh-keygen -t rsa -N '' -f /etc/sidedoor/id_rsa

The corresponding public key \fIid_rsa.pub\fP will need to be included in
the remote user's \fI~/.ssh/authorized_keys\fP file.
.TP
.I /etc/sidedoor/known_hosts
SSH host key of the remote server.
.TP
.I /etc/sidedoor/authorized_keys
Optionally, SSH public key(s) with remote access to the local sidedoor user.

This is a symlink to \fI~sidedoor/.ssh/authorized_keys\fP.
The sidedoor-sudo package provides full root access to this user.
.TP
.I /etc/network/if-up.d/sidedoor
Sends \fBSIGUSR1\fP to reset the retry backoff on network state changes.
.SH SEE ALSO
.BR ssh (1),
.I /usr/share/doc/sidedoor/README.md.gz