I’ve got a Yubikey, a little USB security key. It’s main intended use is for two-factor authentication, but I mostly use mine for its ability to act as a GPG smartcard. The Yubikey stores the private key I use to sign the code I write1 and some of the e-mails I send.

At home, this is easy - my PC dual-boots into an Ubuntu environment I use for writing code. At work, though, we have Windows computers. For development, we then use CentOS 7 VMs running through VirtualBox.

It took me quite a while to get my Yubikey working with the VM, so I’m documenting some of the steps I took here in the hope that they may be more broadly useful.

Adding GPG smart-card support to CentOS 7

Install the smart card daemon with: sudo yum install gnupg2-smime Ensure that the following files exist with the given contents: ~/.gnupg/gpg-agent.conf

default-cache-ttl 14400

max-cache-ttl 14400




reader-port "Yubico Yubikey 4 OTP+U2F+CCID 00 00"

Run sudo service pcscd start At this point, you may need to sudo killall gpg-agent and/or sudo killall scdaemon gpg –card-status should now start providing useful output.

Mapping a specific USB port to a VirtualBox VM

  1. Via the VirtualBox GUI, go to the settings page for your VM whilst the VM is halted.
  2. Enable the USB controller (1.1 worked for me; YMMV)
  3. To actually get anything passed through, you now need to add a filter. If you want to grab only a specific device, create the filter by selecting the appropriate option from the ‘+’ menu. Otherwise, use the ‘blue circle’ option.
  4. Now, to get a specific port, you need to find out the correct number to plug into the ‘port’ field in your new filter. "c:\Program Files\Oracle\VirtualBox\VBoxManage.exe" list usbhost is your friend here. With a device inserted into the desired port, start the dev VM, then run that command. You should see something like:
Host USB Devices:

UUID:               xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
VendorId:           0x1050 (1050)
ProductId:          0x0407 (0407)
Revision:           4.53 (0453)
Port:               0
USB version/speed:  2/Full
Manufacturer:       Yubico
Product:            Yubikey 4 OTP+U2F+CCID
Address:            \\?\usb#vid_80ee&pid_cafe#x&xxxxxx&x&4#{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
Current State:      Captured

The port number appears to be the number just before the final ‘#’ in the ‘Address’ - i.e. 4, here.

  1. Now, edit the filter, and add the port number. Note that you may need to pad the port number out to 4 digits with ‘0’s (i.e. my current filter is ‘0003’).

  1. Prompted by https://mikegerwitz.com/papers/git-horror-story.html ↩︎