relay

Jump

Jump is an external jump server for admin (ssh) access to remote machines that are not served with a conventional private-network-side jump machine. Jump provides a secure external relay for ssh sessions, that works together with clients on the host (remote) and client (local) machines.

Relay is a set of tools and services to let you to host remote lab experiments, without opening firewall ports.

• Secure login shell relay, host adapter and client for end-to-end encrypted admin access without a jumpserver
• Works with experiments behind firewalls and NAT because all communications are relayed
• No need to open firewall ports, or get public IPv4 addresses.

Background

Institutional networks vary in their ability to provide admin access to machines, so this jump server alternative allows a more convenient administrative option.

Status

We've got over 100 experiments under management at the present time - many in our latest in our new 1:6 scale ISO containers:

Overview

This repo provides the jump command for relaying ssh connections, with the following sub-commands

1. jump host runs on the experiment to connect to the shell relay to provide secured ssh connections to the experiment
2. jump relay runs in the cloud (to connect experiments and administrators)
3. jump client runs on the administrators' systems to connect to the shell relay

Status client

The status client pkg/status is useful for obtaining status information from another golang service, as per the example below from status.

import (	
   jc "github.com/practable/jump/pkg/status"
)

<snip>
			iat := time.Now()
			nbf := time.Now()
			exp := time.Now().Add(s.Config.ReconnectJumpEvery)
			log.WithFields(log.Fields{"iat": iat, "nbf": nbf, "exp": exp}).Trace("Token times")
			aud := s.Config.SchemeJump + "://" + path.Join(s.Config.HostJump, s.Config.BasepathJump)
			bid := "status-server"
			connectionType := "connect"
			scopes := []string{"stats"}
			topic := "stats"
			token, err := token.New(iat, nbf, exp, scopes, aud, bid, connectionType, s.Config.SecretJump, topic)
			log.Tracef("token: [%s]", token)
			if err != nil {
				log.WithField("error", err.Error()).Error("Jump stats token generation failed")
				time.Sleep(5 * time.Second) //rate-limit retries if there is a long standing issue
				break
			}
			ctxStats, cancel := context.WithTimeout(ctx, s.Config.ReconnectJumpEvery)
			to := aud + "/api/v1/" + connectionType + "/" + topic
			log.Tracef("to: [%s]", to)
			j.Connect(ctxStats, to, token)
			cancel() // call to save leaking, even though cancelled before getting to here
<snip>

It can be mocked in testing by eliminating the call to connect to, and just passing populated []Report{} to the Status channel.

s := New()

go func() {
	s.Status <- []Report{Report{Topic: "test00"}}
}()

mockReport := <-s.Status:

More information

Additonal documentation (in various states of completeness) can be found on the following components here:

1. jump relay
2. jump host

References

[1] Timothy D. Drysdale (corresponding author), Simon Kelley, Anne-Marie Scott, Victoria Dishon, Andrew Weightman, Richard James Lewis & Stephen Watts (2020) Opinion piece: non-traditional practical work for traditional campuses, Higher Education Pedagogies, 5:1, 210-222, DOI: 10.1080/23752696.2020.1816845

[2] David P. Reid, Joshua Burridge, David B. Lowe, and Timothy D. Drysdale (corresponding author), Open-source remote laboratory experiments for controls engineering education, International Journal of Mechanical Engineering Education, Accepted 22 Jan 2022.