LibreDrive and revocation list update protection

[VA1DER]

As I understand it, LibreDrive mode, when it is engaged on a drive, prevents a drive from updating its revocation list when it encounters a later MKB version on a loaded disc.

I have seen mention a couple times, though, that LibreDrive mode is only soft-loaded microcode that gets stored on the drive temporarily. That patched firmwares don't have it turned on all the time, they merely make the drive amenable to uploading the LibreDrive mode microcode.

So then, as I understand it, my drive is only protected from updating its revocation list from a newer MKB when MakeMKV is running and has enabled LibreDrive on the drive. Is this correct?

[SamuriHL]

As I understand it, LibreDrive mode, when it is engaged on a drive, prevents a drive from updating its revocation list when it encounters a later MKB version on a loaded disc.

No. It does not prevent that from happening...see below. It only ignores it when it's in LibreDrive mode.

I have seen mention a couple times, though, that LibreDrive mode is only soft-loaded microcode that gets stored on the drive temporarily. That patched firmwares don't have it turned on all the time, they merely make the drive amenable to uploading the LibreDrive mode microcode.

Correct.

So then, as I understand it, my drive is only protected from updating its revocation list from a newer MKB when MakeMKV is running and has enabled LibreDrive on the drive. Is this correct?

Yes. And in order to put the drive in LibreDrive mode, you have to insert the disc which then automatically updates the MKB revocation list on the drive. You can't prevent it. You can, however, with LibreDrive, ignore it.

[VA1DER]

Yes. And in order to put the drive in LibreDrive mode, you have to insert the disc which then automatically updates the MKB revocation list on the drive.

Hmmm. I thought the drive was in LibreDrive mode the moment you ran MakeMKV and selected the drive - hence the "Status: Enabled" message. So the drive still updates its revocation list and that can't be prevented. That changes my drive plans. I have an LG WH16NS60 which is UHD native. I wanted to be able to rip MKBv82 discs with it without having it update its revocation list.

I may not use it for ripping then. I just ripped my first UHD - The Abyss 4k (which from all accounts has posed problems for a lot of drives) with an old little Pioneer UD03 (cross-patched to UD04). Maybe I'll use this for my ripping and keep my UHD LG clean.

[EDIT] I just re-read mike admin's post on the subject to see where I misunderstood the process:

The moment you insert the disc into your drive, the drive checks if the list is newer than the one it knows about, and if it is, the drive re-flashes itself (updates firmware). With LibreDrive mode your drive just became immune to this nonsense.

So while he doesn't quite say the drive won't update itself, I think this wording strongly implies it. I would recommend changing this to read the drive is immune to the changed revocation list, not that it is immune to reflashing itself.

[SamuriHL]

The firmware for libredrive is loaded only after a disc is inserted and you then scan that disc with makemkv... Either by opening the disc in makemkv or activating libredrive from a commandline. Once the disc is inserted the mkb is updated.

As for mkb v82 that's not really a big deal. There's a publicly posted device key for it. If you use my keydb helper tool, as found in the uhd FAQ in the uhd section of the forum and follow the instructions I link to in that post for updating your keydb file with the device key then you can decrypt all your Blu-rays including mkb v82.

Sent from my SM-S938U1 using Tapatalk

[MartyMcNuts]

When LibreDrive mode is activated by MakeMKV, it puts the drive into a mode where:

The drive does not update its internal revocation list, even if it sees a newer MKB.

This is not true. The drive always checks it's revocation list and updates it when it sees a newer MKB. Libredrive does not stop that. The revocation is simply ignored when libredrive is enabled.

[SamuriHL]

How, exactly, do you think LibreDrive "stops the MKB revocation list from being updated" when you HAVE TO INSERT THE DISC BEFORE ACTIVATING LibreDrive??

[AstralWanderer]

So then, as I understand it, my drive is only protected from updating its revocation list from a newer MKB when MakeMKV is running and has enabled LibreDrive on the drive. Is this correct?

Going OT a little, mightn't it be possible to prevent revocation list updates by creating and inserting a disc with a fake zero-entry list dated far in the future? ("Greetings Earthlings! This is the AACS-LA from 2252 - surrender your antiquated artifacts at once!"). Or would this be impractical/unnecessary?

[keydb_helper]

Going OT a little, mightn't it be possible to prevent revocation list updates by creating and inserting a disc with a fake zero-entry list dated far in the future? ("Greetings Earthlings! This is the AACS-LA from 2252 - surrender your antiquated artifacts at once!"). Or would this be impractical/unnecessary?

MT1959 drives have the option of modifying the stored host certificate revocation list (HRL). But the HRL is digitally signed by the AACS LA and this signature is validated by the drive. If an invalid HRL is present and you patch the firmware to block updates to the HRL it can lead to AACS authentication issues with licensed playback software.

You can also zero out the stored HRL but it will be replaced the next time you load an AACS protected disc.

The easier option is to patch the firmware of MT1959 drives to effectively ignore the HRL for the purposes of host certificate revocation whilst allowing the HRL to be freely updated by newer MKB revisions.

[AstralWanderer]

MT1959 drives have the option of modifying the stored host certificate revocation list (HRL)...

Thanks for the detailed reply. Presumably zeroing the HRL would make sense for drives without the option of firmware patches (e.g. "domestic" players used with TV/home cinema setups), but the patches can do much more.