Users with limited use of their hands, such as people suffering from disabilities of the arm, shoulder, and hand (DASH), face challenges when authenticating with computer terminals, specially with publicly accessible terminals such as ATMs. A new glass wearable device was recently introduced by Google and it was immediately welcomed by groups of users, such as the ones described above, as Google Glass allows them to perform actions, like taking a photo, using only verbal commands. This paper investigates whether glass wearable devices can be used to authenticate users, both to grant access (one-time) and to maintain access (continuous), in similar hands-free fashion. We do so by designing and implementing Gauth, a system that enables users to authenticate with a service simply by issuing a voice command, while facing the computer terminal they are going to use to access the service. To achieve this goal, we create a physical communication channel from the terminal to the device using machine readable visual codes, like QR codes, and utilize the device's network adapter to communicate directly with a service. More importantly, we continuously authenticate the user accessing the terminal, exploiting the fact that a user operating a terminal is most likely facing it most of the time. We periodically issue authentication challenges, which are displayed as a QR code on the terminal, that cause the glass device to re-authenticate the user with an appropriate response. We evaluate our system to determine the technical limits of our approach.