DriveCrypt Security Model bypass exploiting wrong BIOS API
The password checking routine of DriveCrypt fails to sanitize the
BIOS keyboard buffer before AND after reading passwords.
Secu Star's DriveCrypt Plus Pack v3.9 (possibly other versions also)
DriveCrypt's pre-boot authentication routines use the BIOS API to
read user input via the keyboard. The BIOS internally copies the
keystrokes in a RAM structure called the BIOS Keyboard buffer
inside the BIOS Data Area. This buffer is not flushed after use,
resulting in potential plain text password leakage once the OS
is fully booted, assuming the attacker can read the password at
physical memory location 0x40:0x1e. It is also possible for a root
user to reboot the computer by incrementing the BIOS keyboard
buffer in spite of the full disk encryption.
1) Plain text password disclosure.
Required privileges to perform this operation are OS dependant,
from unprivileged users under Windows (any), to root under most
2) A privileged attacker able to write to the MBR and knowing the
password (for instance thanks to 1), is able to reboot the computer
in spite of the password prompted at boot time (and in spite of
disk encryption) by initializing the BIOS keyboard buffer with the
correct password (using an intermediary bootloader that will in turn
Full Technical Whitepaper
No Response from vendor in spite of multiple solicitations.
This vulnerability was discovered by Security Researcher
Jonathan Brossard from iViZ Techno Solutions Pvt. Ltd.
First private disclosure to vendor on July 15th 2008
First Public disclosure at Defcon 16 on August 10th 2008
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