4 ms·
I'm interested in how this was fixed. Is the update an EFI update which disables DMA or does it with IOMMU? Or is the memory just overwritten on boot? I'm als
by ysleepy 10y ago
I'm interested in how this was fixed.
Is the update an EFI update which disables DMA or does it with IOMMU? Or is the memory just overwritten on boot?
I'm also quite surprised they leave the password in memory in multiple locations. - Assuming the password is only used to derive the KEK for the actual key.
- dom0 10y agoThis interests me, too. I can only assume, since disabling DMA would imply a huge performance hit (and quite likely many broken devices?), that the update enables the IOMMU right from the system start, probably directly in the firmware, and has nothing/only a whitelist mapped, with further mappings only explicitly enabled by drivers?
- astrodust 10y agoI wonder if the chipset can't do a sort of DMA emulation, or DMA with conditions versus the sort of free-for-all stuff you'd see with things like FireWire.
- dom0 10y agoThat's what an IOMMU does. Without an IOMMU devices on extension buses directly address physical memory. With an MMU the host CPU creates a virtual address space for devices and can thus limit access to the main memory (conveniently also allows passing devices to VM guests), much like virtual memory for processes/VMs.
- deleted 10y ago[deleted]
- feld 10y agoThis exact command: sudo firmwarepasswd -setpasswd -setmode command enter in a password to lock down Option ROM, reboot. Now you're protected. source, the hacker-now-Apple-developer: https://twitter.com/XenoKovah/status/809418554428657666 https://twitter.com/XenoKovah/status/809418554428657666