Thin Client - Thin Crypto Bypassing Full-Disk Encryption Across 3 Thin Clients - wo Breaking a Cipher

Thin clients run full operating systems and hold Wi-Fi keys, 802.1X certificates, admin password hashes and VDI configuration, yet their disk encryption is often tied to the TPM. The speaker examined three vendors: IGEL OS (formerly Eagle), HP ThinPro and Dell ThinOS, across several major versions. Because the TPM releases its key only after the bootloader and kernel load, those early boot stages were the main target.

IGEL had a sound design that seals keys to PCR values, but a boot menu entry and an unsigned configuration partition let the speaker reach a root shell. A missing signature file also dropped the device to a GRUB prompt. HP ThinPro measured only part of the boot chain, so the unseal script could be modified to write out the key. Dell's older ThinOS releases had weaker schemes: an administrator password was obfuscated with a reused XOR key that could be recovered from SPI flash, and a key derived from hardware identifiers was used in place of measurement. ThinOS 9 also wrote crash dumps unencrypted. ThinOS 10 released its key from TPM storage with no policy at all, and a later PCR 7 fix could be sidestepped with another Canonical-signed USB stick.

The main lesson is that automatically unsealed disk encryption is hard to get right, and TPM-only protection fails when the boot partition is not measured. The speaker urged assessors to read the boot scripts rather than assume encryption is effective. At the time of the talk, the HP issue was reported as unpatched.