ssh-agent was in the news recently due to the matrix.org compromise. The main takeaway from that incident was that one should avoid the ForwardAgent (or -A) functionality when ProxyCommand can do and consider multi-factor authentication on the server-side, for example using libpam-google-authenticator or libpam-yubico.

That said, there are also two options to ssh-add that can help reduce the risk of someone else with elevated privileges hijacking your agent to make use of your ssh credentials.

Prompt before each use of a key

The first option is -c which will require you to confirm each use of your ssh key by pressing Enter when a graphical prompt shows up.

Simply install an ssh-askpass frontend like ssh-askpass-gnome:

apt install ssh-askpass-gnome

and then use this to when adding your key to the agent:

ssh-add -c ~/.ssh/key

Automatically removing keys after a timeout

ssh-add -D will remove all identities (i.e. keys) from your ssh agent, but requires that you remember to run it manually once you're done.

That's where the second option comes in. Specifying -t when adding a key will automatically remove that key from the agent after a while.

For example, I have found that this setting works well at work:

ssh-add -t 10h ~/.ssh/key

where I don't want to have to type my ssh password everytime I push a git branch.

At home on the other hand, my use of ssh is more sporadic and so I don't mind a shorter timeout:

ssh-add -t 4h ~/.ssh/key

Making these options the default

I couldn't find a configuration file to make these settings the default and so I ended up putting the following line in my ~/.bash_aliases:

alias ssh-add='ssh-add -c -t 4h'

so that I can continue to use ssh-add as normal and have not remember to include these extra options.

I recently acquired an AnyTone AT-D878UV DMR radio which is unfortunately not supported by chirp, my usual go-to free software package for programming amateur radios.

Instead, I had to setup a Windows 10 virtual machine so that I could setup the radio using the manufacturer's computer programming software (CPS).

Install VirtualBox

Install VirtualBox:

apt install virtualbox virtualbox-guest-additions-iso

and add your user account to the vboxusers group:

adduser francois vboxusers

to make filesharing before the host and the guest work.

Finally, reboot to ensure that group membership and kernel modules are all set.

Create a Windows 10 virtual machine

Create a new Windows 10 virtual machine within VirtualBox. Then, download Windows 10 from Microsoft then start the virtual machine mounting the .iso file as an optical drive.

Follow the instructions to install Windows 10, paying attention to the various privacy options you will be offered.

Once Windows is installed, mount the host's /usr/share/virtualbox/VBoxGuestAdditions.iso as a virtual optical drive and install the VirtualBox guest additions.

Installing the CPS

With Windows fully setup, it's time to download the latest version of the computer programming software.

Unpack the downloaded file and then install it as Admin (right-click on the .exe).

Do NOT install the GD driver update or the USB driver, they do not appear to be necessary.

Program the radio

First, you'll want to download from the radio to get a starting configuration that you can change.

To do this:

1. Turn the radio on and wait until it has finished booting.
2. Plug the USB programming cable onto the computer and the radio.
3. From the CPS menu choose "Set COM port".
4. From the CPS menu choose "Read from radio".

Save this original codeplug to a file as a backup in case you need to easily reset back to the factory settings.

To program the radio, follow this handy third-party guide since it's much better than the official manual.

You should be able to use the "Write to radio" menu option without any problems once you're done creating your codeplug.