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Wouldn't secure boot just prevent you from booting into the invalid MBR? At that point your files are already encrypted and your MBR already over-written, Secu

Wouldn't secure boot just prevent you from booting into the invalid MBR? At that point your files are already encrypted and your MBR already over-written, Secure boot is just preventing further exploitation.

sedachv 9y ago
You can get around UEFI Secure Boot by installing an old signed bootloader with known exploits (if I understand correctly this is why the "Secure Golden Key Boot" exploit of last year[1] cannot be patched without changing public keys in the UEFI firmware). Not only that, the code that is shared by most UEFI implementations is garbage[2] with a large attack surface; exploits against the firmware is a possibility. The primary function of UEFI Secure Boot is for Microsoft to prevent other operating systems from being installed on as many systems as they can get away with (right now there is no provision that end users should be allowed to disable Secure Boot on ARM devices, for example). The "security" functionality is an unworkable side-effect that provides a convenient fiction to accomplish that goal. [1] https://www.reddit.com/r/netsec/comments/4wybax/writeup_of_secure_boot_bypass_which_i_dub_secure/ https://www.reddit.com/r/netsec/comments/4wybax/writeup_of_s... [2] https://www.youtube.com/watch?v=V2aq5M3Q76U https://www.youtube.com/watch?v=V2aq5M3Q76U