The CTS Tablet's Apparent Lack of USB Port

At first blush, the CTS tablets appear not to have a USB port. Instead, the tablets have a five pin magnetic port for charging and no port for I/O or accessories.

The breakaway magnetic charger has the obvious benefit that it prevents unintentional damage to USB ports and cords. GTL, the tablet's vendor, however, claims that this USB-less design has two additional advantages:

First, they claim that allowing USB chargers would allow incarcerated individuals to use the chargers with contraband cellphones. Though perhaps true, CDCR allows USB chargers for watches, clippers and other devices. Indeed, USB chargers are quickly becoming ubiquitous. The evidence for this claimed advantage seems thin.

Second, GTL claims that allowing USB accessories has undescribed security risks. Other tablets for incarcerated individuals from vendors such as Securus, Walkenhorsts, and Union Supply have been hacked using USB-based attacks. It is likely that GTL's security concerns about USB are related to these hacks.

Nevertheless, GTL's concerns are unfounded. The attacks on other tablets by incarcerated individuals did not leverage vulnerabilities in USB, but unsecured services such as ADB, MTP, and mass storage. These services can all be disabled without disabling USB.

Moreover, Android has the capability of allowing USB access only to specified classes of accessories (e.g. input devices versus storage devices), accessories by specific manufacturers, or even particular accessories. Given this capability, it is possible to allow USB access for keyboards, switches, or other accessibility accessories without raising security concerns.

In any case, the CTS tablet actually does contain a USB-C connector behind the magnetic power port.