dMZX Forums: Decryption should maybe validate before actually offering the option -> MegaZeux Bugs -> Tracker

Legacy world decryption will offer to decrypt pretty much anything that looks remotely like an encrypted file, that is, anything with its protection method byte between 1 and 3 inclusive. This includes anything from otherwise valid worlds with only a few unfortunately-positioned corrupt bytes to completely corrupt worlds to things that aren't even a world at all. It should be fairly simple to decrypt the world in memory up through the palette, global robot offset, and SFX list and check them before even displaying the option since those sections can be fairly good signs of an invalid world.

This isn't particularly urgent though.

Updating status to: Awaiting Feedback
Updating severity to: 3 - Medium

I've implemented a very basic version of this in GIT 67657a2a that only checks the world version (which is never encrypted). This is good enough to prevent MZX from decrypting backup1.mzx from the issue linked above and a test world I made that's valid except for its protection byte being set. This also lets MZX fail when attempting to load an encrypted 1.x world (of which Terryn just recovered two <3), which store the password slightly differently and gets corrupted if modern MZX tries to decrypt it.

I think this is probably good enough but if a world with this issue pops up again and gets through this check more safeties can be added. Adding this requires computing the password during the initial validation pass, which isn't that big of a deal.

Updating status to: Fixed
Issue fixed in: 2.93

As of GIT 1d5202cf, decryption is automatically performed into a memory buffer or temporary file and thus this is no longer much of a concern.