Shoring up SSHd configuration

Published on Oct 18, 2016

I recently came across a useful tool on GitHub called ssh-audit. It’s a small Python script that connects to an SSH server, gathers a bunch of information, and then highlights any problems it has detected. The problems it reports range from potentially weak algorithms right up to know remote code execution vulnerabilities.

This is the kind of output you get when running ssh-audit. In this particular example, I’m looking at GitHub’s SSH server and have filtered the output to just warnings and failures:

A pair of Yubikeys
A pair of Yubikeys

I recently noticed that I’d accidentally lost my previous GPG private key — whoops. It was on a drive that I’d since formatted and used for a fair amount of time, so there’s no hope of getting it back (but, on the plus side, there’s also no risk of anyone else getting their hands on it). I could have created a new one in a few seconds and been done with it, but I decided to treat it as an exercise in doing things properly.

Background: GPG? Yubikey?

GPG or GnuPG is short for Gnu Privacy Guard, which is a suite of applications that provide cryptographic privacy and authentication functionality. At a basic level, it works in a similar way to HTTPS certificates: each user has a public key which is shared widely, and a private key that is unique to them. You can use someone else’s public key to encrypt messages so only they can see them, and use your own private key to sign content so that others can verify it came from you.

A Yubikey is a small hardware device that offers two-factor authentication. Most Yubikey models also act as smartcards and allow you to store OpenPGP credentials on them.

Why you should be using HTTPS

Published on Jun 17, 2016

The EFF's HTTPS Everywhere logo
The EFF's HTTPS Everywhere logo

One of my favourite hobbyhorses recently has been the use of HTTPS, or lack thereof. HTTPS is the thing that makes the little padlock appear in your browser, and has existed for over 20 years. In the past, that little padlock was the exclusive preserve of banks and other ‘high security’ establishments; over time its use has gradually expanded to most (but not all) websites that handle user information, and the time is now right for it to become ubiquitous.

Why use HTTPS?

There are numerous advantages to using HTTPS, both for the users of a website and for the operator:

Privacy

The most obvious advantage is that HTTPS gives your users additional privacy. An insecure (HTTP) request can potentially be read by anyone on the same network, or the network operators, or anyone who happens to operate a network along the path between the user and the server.

Users on shared WiFi networks (such as those in coffee shops, hotels, or offices) are particularly vulnerable to passive sniffing by anyone else on that network. If the network is open (as is frequently the case) then anyone in radio range can see exactly what the user is up to.

The Docker project logo
The Docker project logo

Over the past few weeks I’ve gradually been migrating services from running in LXC containers to Docker containers. It takes a while to get into the right mindset for Docker - thinking of containers as basically immutable - especially when you’re coming from a background of running things without containers, or in “full” VM-like containers. Once you’ve got your head around that, though, it opens up a lot of opportunities: Docker doesn’t just provide a container platform, it turns software into discrete units with a defined interface.

With all of your software suddenly having a common interface, it becomes trivial to automate a lot of things that would be tedious or complicated otherwise. You don’t need to manage port forwards because the containers just declare their ports, for example. You can also apply labels to the application containers, and then query the labels through Docker’s API.

A WeMo Insight Switch
A WeMo Insight Switch

I recently picked up a couple of Belkin’s WeMo Insight Switches to monitor power usage for my PC and networking equipment. WeMo is Belkin’s home automation brand, and the switches allow you to toggle power on and off with an app, and monitor power usage.

The WeMo Android app is pretty dismal. It’s slow, doesn’t look great, and crashed about a dozen times during the setup process for each of my two switches. It also doesn’t provide much information at all about power: you can see average power draw and current power draw, and that’s basically it.

Belkin has provided an option to e-mail yourself a spreadsheet with historical power data, and can even do it on a regularly scheduled basis, but that’s not really a nice solution if you want up-to-date power stats. Even if you were happy with data arriving in batch, having to get hold of an e-mail attachment and parse out a weirdly formatted spreadsheet doesn’t make for easy automation. It also relies on Belkin supporting the service indefinitely, which isn’t necessarily going to happen.