4 ms·

Slap ROM Patcher

27 points by apsec112 2mo ago

yjftsjthsd-h 2mo ago
> It is written in Haskell and Rust and this made getting it to work nicely in the browser, interesting I imagine. What motivated using that combination?
- nyuutsu 2mo ago
  (author; wife posted the thread) Haskell is cool and I wanted to play with it. Rust is cool enough, has libraries Haskell doesn't, can be faster, and is a way to stick the unavoidably imperative parts under the bed. Browser was not in the original vision but turned out to be surprisingly painless-ish. Haskell can compile to wasm. Avoiding C-backed crates on vibes / for no particular reason happened to be quite helpful.
gblargg 2mo ago
Doesn't the undo functionality cause it to store copyrighted data from the original ROM in the patch?
- deleted 2mo ago
  [deleted]
- infinite_spin 2mo ago
  I think it's similar to adding a note to a book, and then removing that note, leaving you with a the original book. That scenario doesn't violate copyright law as far as I'm aware.
  - Dylan16807 2mo ago
    That's not how patching a rom works. You directly replace data and the formats that let you undo have to put a copy of the original data in the patch file. So yes it is a risk.
    - choo-t 2mo ago
      You don't need a copy of the original data, you can simply store your change as a XOR so undoing it mean XORing it again.
      - Retr0id 2mo ago
        However, if your change involves zeroing something out, you're back to storing the original data again.
        Retr0id 2mo ago
        Slightly silly idea to solve this: Hash all non-patched areas of the file to produce a key. Use the key to encrypt your XOR value. Thus the key can only be derived by someone who has either the original file, or the patched version.
    - Joker_vD 2mo ago
      So? Since when has making backups of the copyrighted stuff that you have the right to use been made illegal?
      - SideQuark 2mo ago
        Employing anti-protection methods to do to has been illegal since 1996 WIPO treaties, and then much more strongly in the 2002 DMCA. So around 30 years now.
        WhiteDawn 2mo ago
        In fairness, games didn’t start employing encryption on the content till the 7th generation. So unless you’re applying ips patches to a 360 game you’re not breaking any DRM Playing the title you backed up and patched is a different matter entirely
        SideQuark 2mo ago
- nyuutsu 2mo ago
  (Author here, my wife posted this thread; it has no bearing on the question but I am told it is good to disclaim.) You could quibble about what counts but the core is "yeah". Ppf3-with-undo stores literal "hey, we expect byte n to be 'foo'. on apply, replace it with 'bar'. on undo, put 'foo' back. remember: the copyrighted byte is 'foo'". Touch every byte in some way and your undo data is the entire original. Some patches literally touch one byte. Their undo is, indirectly or indirectly, a recipe for retrieving one byte of copyrighted data. Is that fragmentary enough that it is entirely in the clear? I have no idea.
  - gblargg 2mo ago
    For some reason an XOR scheme escaped me. It's the perfect way, doesn't take any extra space over the size of the modified regions, and avoids even storing the copyrighted work of the ROM patch author. You could distribute the patch without anyone's permission (maybe)! Just include a strong checksum of the affected regions to be sure you're starting with the correct version, and checksums of the resulting data to give the same guarantee for reversing the process.
teroshan 2mo ago
I recently stumbled upon https://www.hackdex.app/ https://www.hackdex.app/ which is a lovely website dedicated to Pokémon ROM hacks. It's a really vibrant scene, with a lot of different hacks that go all the way to fully-fledged games, but because it's so rich it can be a pain to find what is available and what the latest version of a given ROM hack is. This website has a neat feature where you upload any base Pokémon ROM file, and it filters all available ROM hacks that are compatible with it via a neat UI. And of course it offers you a one-click download (well, in-local-storage-patch) to the given ROM hack. Source code: https://github.com/Hackdex-App/hackdex-website https://github.com/Hackdex-App/hackdex-website
- saghm 2mo ago
  Quick clarification: I'm pretty sure there's no uploading at all; it uses local storage for the filtering too, which is important because uploading a ROM tends to be risky legally
  - teroshan 2mo ago
    Absolutely, I should have made it more explicit, thanks for clarifying it. That's what makes this possible and legally compliant.
    - saghm 2mo ago
      I was pretty sure you understood based on how you described it! This stuff is very easy for people less technical to get confused about though (which is not at all their fault!), and from what I've seen in the subreddit where I found out about Hackdex, it seems like there was a lot of confusion about it early on, so I figure it's better to be on the safe side.
matheusmoreira 2mo ago
> nyuu.page Is this in any way related to byuu, the SNES emulator author?
- deleted 2mo ago
  [deleted]
- 22c 2mo ago
  No it's not related, sadly Byuu passed away several years ago.

27 points by apsec112 2mo ago

> It is written in Haskell and Rust and this made getting it to work nicely in the browser, interesting I imagine. What motivated using that combination?

nyuutsu 2mo ago
(author; wife posted the thread) Haskell is cool and I wanted to play with it. Rust is cool enough, has libraries Haskell doesn't, can be faster, and is a way to stick the unavoidably imperative parts under the bed. Browser was not in the original vision but turned out to be surprisingly painless-ish. Haskell can compile to wasm. Avoiding C-backed crates on vibes / for no particular reason happened to be quite helpful.

gblargg 2mo ago

Doesn't the undo functionality cause it to store copyrighted data from the original ROM in the patch?

deleted 2mo ago
[deleted]
infinite_spin 2mo ago
I think it's similar to adding a note to a book, and then removing that note, leaving you with a the original book. That scenario doesn't violate copyright law as far as I'm aware.
- Dylan16807 2mo ago
  That's not how patching a rom works. You directly replace data and the formats that let you undo have to put a copy of the original data in the patch file. So yes it is a risk.
  - choo-t 2mo ago
    You don't need a copy of the original data, you can simply store your change as a XOR so undoing it mean XORing it again.
    - Retr0id 2mo ago
      However, if your change involves zeroing something out, you're back to storing the original data again.
      - Retr0id 2mo ago
        Slightly silly idea to solve this: Hash all non-patched areas of the file to produce a key. Use the key to encrypt your XOR value. Thus the key can only be derived by someone who has either the original file, or the patched version.
  - Joker_vD 2mo ago
    So? Since when has making backups of the copyrighted stuff that you have the right to use been made illegal?
    - SideQuark 2mo ago
      Employing anti-protection methods to do to has been illegal since 1996 WIPO treaties, and then much more strongly in the 2002 DMCA. So around 30 years now.
      - WhiteDawn 2mo ago
        In fairness, games didn’t start employing encryption on the content till the 7th generation. So unless you’re applying ips patches to a 360 game you’re not breaking any DRM Playing the title you backed up and patched is a different matter entirely
        SideQuark 2mo ago
nyuutsu 2mo ago
(Author here, my wife posted this thread; it has no bearing on the question but I am told it is good to disclaim.) You could quibble about what counts but the core is "yeah". Ppf3-with-undo stores literal "hey, we expect byte n to be 'foo'. on apply, replace it with 'bar'. on undo, put 'foo' back. remember: the copyrighted byte is 'foo'". Touch every byte in some way and your undo data is the entire original. Some patches literally touch one byte. Their undo is, indirectly or indirectly, a recipe for retrieving one byte of copyrighted data. Is that fragmentary enough that it is entirely in the clear? I have no idea.
- gblargg 2mo ago
  For some reason an XOR scheme escaped me. It's the perfect way, doesn't take any extra space over the size of the modified regions, and avoids even storing the copyrighted work of the ROM patch author. You could distribute the patch without anyone's permission (maybe)! Just include a strong checksum of the affected regions to be sure you're starting with the correct version, and checksums of the resulting data to give the same guarantee for reversing the process.

teroshan 2mo ago

I recently stumbled upon https://www.hackdex.app/ https://www.hackdex.app/ which is a lovely website dedicated to Pokémon ROM hacks. It's a really vibrant scene, with a lot of different hacks that go all the way to fully-fledged games, but because it's so rich it can be a pain to find what is available and what the latest version of a given ROM hack is. This website has a neat feature where you upload any base Pokémon ROM file, and it filters all available ROM hacks that are compatible with it via a neat UI. And of course it offers you a one-click download (well, in-local-storage-patch) to the given ROM hack. Source code: https://github.com/Hackdex-App/hackdex-website https://github.com/Hackdex-App/hackdex-website

saghm 2mo ago
Quick clarification: I'm pretty sure there's no uploading at all; it uses local storage for the filtering too, which is important because uploading a ROM tends to be risky legally
- teroshan 2mo ago
  Absolutely, I should have made it more explicit, thanks for clarifying it. That's what makes this possible and legally compliant.
  - saghm 2mo ago
    I was pretty sure you understood based on how you described it! This stuff is very easy for people less technical to get confused about though (which is not at all their fault!), and from what I've seen in the subreddit where I found out about Hackdex, it seems like there was a lot of confusion about it early on, so I figure it's better to be on the safe side.

matheusmoreira 2mo ago

> nyuu.page Is this in any way related to byuu, the SNES emulator author?

deleted 2mo ago
[deleted]
22c 2mo ago
No it's not related, sadly Byuu passed away several years ago.