SensorgnomeServer

(C) 2019 John Brzustowski

License: GPL2 or greater.

A server for the sensorgnome project.

Intro

This server manages a growing set of networked sensorgnome receivers.

Functions

• [register sensorgnomes](# register)
• manage messages from SGs:
  • store
  • forward
• provide SG status to clients
• manage sync of SGs to motus.org (i.e. download and process raw data)
• manage remote access to SGs (i.e. let users interact directly with an SG)
• allow sensorgnomes from trusted IP addresses to self-register
• allow sensorgnomes from untrusted IP addresses to self-register if they provide credentials; e.g. from motus.org and/or sensorgnome.org
• allow remotely changing on-board tag database
• allow remotely changing on-board deployment.txt configuration file

Message Channels

Messages arrive on these channels:

• signed datagrams sent to a public UDP port (59022)

  • the signature proves the message originated from the specified sensorgnome
  • the SG uses its server-issued public/private key pair to sign

• unsigned datagrams sent to a local UDP port (59023); the datagrams are sent from an SG local port mapped through ssh to the server's port 59023

• streams sent to a local TCP port (59024); streams come from an SG via ssh. On the SG, we'd be doing:

    ssh -f -N -L 59024:localhost:59024 sg_remote@sensorgnome.org

to map local port 59024 to server port 59024, and then output on the SG would use cat /etc/hostname - | nc -u localhost 59024 instead of ssh ...; this sends the serial number as the first line, then copies all output from the sensorgnome's uploader.js to the server socket

• the factory ssh keys used by SGs to login before registering connect to a local unix domain port dedicated to registration Protocol: SG> SERNO[,name,password] (12-character serno followed by optional name, password) SRV> FAILED (if serial number not valid) SRV> FAILED (if serial number already registered and name,password not valid credentials) SRV> PORT\nPUBKEY\nPRIVKEY (otherwise); these might be new credentials or existing ones

Note that some BBKs are running a special release that allows them to send signed datagrams, but unfortunately we hardcoded the host address to 131.162.131.200 in uploader.js

Status Page

• this server regenerates a simple markdown page whenever an event triggers it
• the hugo server detects a change to the markdown file and regenerates static html
• page is public and currently served from new.sensorgnome.org

Status Server

• this server listens on port 50025 for TCP connections, and replies to these commands:
  • who: list of serno,port for connected receivers
  • ports: list of port of connected receivers
  • serno: list of serno of connected receivers
  • status: json-formated status of all active receivers, connected or not. active means connected at least once since the server was launched

Registration Server

• login via ssh to port 59022 with the factory keys forces the command "nc localhost 59026", which communicates with this server's registration listener on port 59026

Individual version changes

BBBK 2015-08-27

• e.g. SG-5113BBBK2853 (BSC HQ)
• uploader.js:
  • command is now nc localhost 59024
  • pushStartupInfo() now sends serno as first line on stream
• maintain_ssh_tunnel: map localhost:59024 to sensorgnome.org:59024
• new file /etc/network/if-up.d/init_ssh_tunnel runs maintain_ssh_tunnel when a non-local, non-usb interface comes up:

BBBK 2017-03-06

• same changes as above

Receivers completed

• SG-1614BBBK1666
• SG-1614BBBK1807

Clean up of tunnel vs. streaming

• ultimate new setup on server side:
  • TCP port 59022: sshd_sg, as before
  • UDP port 59022: accept signed datagrams from the network, as before but now in same program
  • UDP port 59023: accept unsigned datagrams from localhost (TBD).
  • TCP port 59024: accept streams over an ssh (and thus authenticated) connection; the stream begins with the SG's serial number

This way:

• datagrams authenticated by embedded signature, when needed (i.e. sent from arbitrary hosts which are not using ssh)
• datagrams authenticated by virtue of arriving over authenticated channel (ssh) and not signed (first
• no race conditions between mapping ports and running a program over ssh (see jbrzusto/openssh-portable#1)

But this requires retooling SG-side code to include the serno on all messages sent over the authenticated channel.

/home/bone/proj/bonedongle/master/uploader.js

The the child process is now

nc -u localhost 59024

rather than

usr/bin/ssh -T -o ControlMaster=auto", -o ControlPath=/tmp/sgremote", -o ServerAliveInterval=5", -o ServerAliveCountMax=3",-i /home/bone/.ssh/id_dsa", -p 59022", sg_remote@sensorgnome.org", /home/sg_remote/code/sg_remote

We also modify the first line of startup-info sent by the uploader to simply be the SG's serial number (e.g. SG-1234BBBK5678) to identify the stream:

Uploader.prototype.pushStartupInfo = function() {
    var ts = (new Date()).getTime()/1000;
    this.child.stdin.write( "SG-" + Machine.machineID + "\n" + "M," + ts + ",machineID," + Machine.machineID + "\n" +
                            "M," + ts + ",bootCount," + Machine.bootCount + "\n");
};

/etc/hosts

Change to hardwire new sensorgnome.org address:

sed -i -e '/sensorgnome.org/d' /etc/hosts
echo 108.63.14.166 sensorgnome.org >> /etc/hosts
sed -i -e '/StrictHostKeyChecking/s/^.*$/StrictHostKeyChecking no/' /etc/ssh/ssh_config

/home/bone/proj/bonedongle/scripts/maintain_ssh_tunnel

Drop use of autossh (since we're running from a cronjob anyway) and map streaming port:

# maintain a reverse tunnel portmap to sensorgnome.org
# run every 5 minutes from /etc/cron.d
#
# map server:TUNNEL_PORT -> localhost:22  (ssh reverse tunnel)
# map localhost:59024 -> server:59024     (message streaming)

TUNNEL_PORT_FILE=/home/bone/.ssh/tunnel_port
UNIQUE_KEY_FILE=/home/bone/.ssh/id_dsa
REMOTE_USER=sg_remote
REMOTE_HOST=sensorgnome.org
REMOTE_SSH_PORT=59022
REMOTE_STREAM_PORT=59024
LOCAL_STREAM_PORT=59024

if [[ -f $TUNNEL_PORT_FILE ]]; then
    read TUNNEL_PORT < $TUNNEL_PORT_FILE
    ssh -f -N -T \
        -L$LOCAL_STREAM_PORT:localhost:$REMOTE_STREAM_PORT \
        -R$TUNNEL_PORT:localhost:22 \
        -o ControlMaster=auto \
        -o ControlPath=/tmp/sgremote \
        -o ServerAliveInterval=5 \
        -o ServerAliveCountMax=3 \
        -i $UNIQUE_KEY_FILE \
        -p $REMOTE_SSH_PORT \
        $REMOTE_USER@$REMOTE_HOST
fi

/etc/network/if-up.d/init_ssh_tunnel

This file attempts to set up a tunnel as soon a non-local network interface comes up:

#!/bin/bash
#
# initiate an ssh tunnel without waiting for cron
#
if [[ "$IFACE" != "usb0" && "$IFACE" != "lo" ]]; then
        /home/bone/proj/bonedongle/scripts/maintain_ssh_tunnel
fi
exit 0

Also note that some BBKs are running a special release that allows them to send signed datagrams, but unfortunately we hardcoded the host address to 131.162.131.200 in uploader.js