[bostik]

If there's anything we've seen, over and over again, it's that theoretical and infeasible attacks eventually become, in order:

1) possible

2) feasible; and

3) reliable to the point of weaponization

It may take 5 years. It may take 20 years. It will invariably require a huge amount of other research, only some of which will appear relevant. Then all of a sudden the intermediate pieces are all understood and the first practical attack becomes possible.

Even if this attack only works against an ideal target, it still shows a new way of thinking about particular attacks.

> Any read pattern that hammers a particular location will trigger garbage collection or data rewrite to a fresh location.

I can't help thinking that you may have inadvertantly outlined how an eventual practical attack will be performed. This wouldn't be the first time a mitigation method is abused to prepare an attack either - what if you had statistical methods at your disposal to predict how the SSD's wear-leveling redirects your writes? Could you arrange for the cells to be rotated in and out in a reliably determinable pattern?

I'm not discounting your doubts, btw. I'm just pointing out that dismissing the attack due to its current sophistication (or lack thereof) feels shortsighted.

[fpgaminer]

> If there's anything we've seen, over and over again, it's that theoretical and infeasible attacks eventually become, in order:

In general, yes it's always good to keep in mind that just as technology progresses exponentially, technological attacks also progress exponentially.

BUT, theoretical attack -> weaponized attack is hardly an axiom. To take a page out of history which I believe is apropos, let us recall the old myth of recovering data from an erased hard drive.

Way back in yonder years it was widely believed that three letter agencies could take any hard drive that had been erased, and recover all the data by carefully analyzing the residual magnetic flux. A single erase, the theory went, wasn't enough to fully wipe the magnetic signal.

The idea was so pervasive that security obsessed peoples would wipe their drives 6, 7, maybe even 8 times just to be sure. That'll stop those three letter agencies!

Well, as time went on it turned out the theoretical attack became less plausible and less feasible! We have no evidence that such a technique was _ever_ used. And while, in theory, it _may_ have been possible when the myth started, the relentless march of platter density rendered it less and less feasible as time went on.

It's hard to know what attacks will follow the exponential curve upward towards weaponization, and which will follow it downward to obscurity. Best to just keep your wits about you, I say.

[ericseppanen]

I don't think we can assume that all impractical attacks will eventually become feasable.

There are some things that are not just hard, but computationally infeasable. Triggering random bit errors and expecting to pass both the LDPC error correction as well as the extra checksum probably falls in this category.

I'm afraid I don't follow your suggestion that triggering SSD GC could somehow result in some other attack. This is simply the firmware automatically repairing the damage you were attempting to inflict. I don't see an additional attack vector here.

Since flash is already an unreliable media, hardware & firmware already works very hard to conceal and silently repair any errors before they accumulate to a data corruption scenario. This is very different from a rowhammer-type attack because there is an active CPU that already works to prevent this type of damage when it occurs naturally (or due to a naive workload that reads hot locations often).

[bostik]

> I'm afraid I don't follow your suggestion that triggering SSD GC could somehow result in some other attack.

I was thinking more of the wear-leveling of the NAND cells. (Sibling comment from wtallis points out that the entire technology is being phased out so that's pretty much covered then.)

What I had in mind was a write-spray to identifiable locations. Wear-leveling cycles cells out from active to inactive, and from inactive back to active. If you could prepare a whole bunch of cells with suitable patterns, AND had a way to get occasional cells cycled in uninitialised - then having predictable control over "where"[ß] a cell is cycled back in could allow to target the reads and writes to perform the attack.

We don't need control over which cells are cycled in if majority of incoming cells already have our data on them from their previous active incarnation.

ß: There is indirection above the physical cells and their addressing. I just don't know how many layers.

[ericseppanen]

That's not how SSDs work. You would never be exposed to uninitialized flash pages; they are unlinked from the logical address space until after the block gets erased and programmed with fresh data. Wear leveling doesn't change that process at all.

[wtallis]

> It may take 5 years. It may take 20 years. It will invariably require a huge amount of other research, only some of which will appear relevant. Then all of a sudden the intermediate pieces are all understood and the first practical attack becomes possible.

Except that the NAND flash that's vulnerable to these attacks is being phased out of production as quickly as the fabs can be converted. Coming up with more plausible ways to obtain the oracular knowledge necessary to properly target this attack is of no use if the underlying storage medium no longer has the failure mechanism that's being exploited.