The first programs were written in binary/hexadecimal, and only later did we invent coding languages to convert between human readable code and binary machine code.
So why can’t we just do the same thing in reverse? I hear a lot about devices from audio streaming to footware rendered useless by abandonware. Couldn’t a very smart person (or AI) just take the existing program and turn it into code?
It is not. idk who told you it was.
Disassembling an executable is trivial to do. Everything is open source if you can read assembly. Obfuscation be damned.
Well decompiling is only one step in the reverse engineering process. I would recommend taking a look at the Legend of Zelda: Ocarina of Time decompile projects. They reversed engineered the whole thing, which took years and was a team effort.
In the end they got perfectly readable source code, fully documented. And the most amazing thing is, when compiled with the right compiler and right flags, it recreates the original rom perfectly.
I would also recommend a YouTuber called Kaze. He’s been working on Mario 64 for years, re-writing large parts of the engine to get some pretty cool stuff going.
The hard part isn’t reading assembly. The hard part is figuring out why it’s doing what it’s doing with no comments or function names or anything useful to help.
This is like saying if you can read English you can understand an advanced math or physics paper written in English without having any knowledge or context of those subjects.
I’ve used a decompiler to peek at the source code of an app written in Visual Basic I wanted to recreate as a browser addon. It was mostly successful but some variable and function names were messed up.
Variable names, class names, package structure, method names, etc. won’t normally be maintained in the disassembled code. They are meaningless to the CPU, and just a series of memory addresses. In cases where you have method names being mentioned, it’s likely a syscall, and it’s calling a method from an existing library. I’m not familiar with VB, but at least in .Net and .Net Framework, this would be something like the System.Collections.Generic providing the implementation for List<string> and when .Sort() is called, it makes the syscall to that compiled .dll.
You could chuck it at an AI to reverse compile it into something readable.
Imagine being presented with an aircraft. You bloody well know what it does and you get permission to disassemble the whole thing to your heart’s content. How big of a task do you think it’d still be to be able to work out how the winged metal tube works and why it does what it does when it does it?
Exactly.
It’s not impossible, just very labour intensive and difficult. Compiling an abstract, high level language into machine code is not a reversible process. Even though there are already automated tools to “decompile” machine code back to a high level language, there is still a huge amount of information loss as nearly everything that made the code readable in the first place was stripped away in compilation. Comments? Gone. Function names? Gone. Class names? Gone. Type information? Probably also gone.
Working through the decompiled code to bring it back into something readable (and thus something that can be worked with) is not something a lone “very smart person” can do in any reasonable time. It takes likely a team of smart people months of work (if not years) to understand the entire structure, as well as every function and piece of logic in the entire program. Once they’ve done that, they can’t even use their work directly, since to publish reconstructed code is copyright infringement. Instead, they need to write extremely detailed documentation about every aspect of the program, to be handed to another, completely isolated person who will then write a new program based off the logic and APIs detailed in the documentation. Only at that point do they have a legally usable reverse engineered program that they can then distribute or modify as needed.
Doing this kind of reverse engineering takes a huge amount of effort and motivation, something that an app for 350 total sneakers is unlikely to warrant. AI can’t do it either, because they are incapable of the kind of novel deductive reasoning required for the task. Also, the CarThing has actually always been “open-source”, and people have already experimented with flashing custom firmware. You haven’t heard about it because people quickly realised there was no point - the CarThing is too underpowered to do much beyond its original use.
To build on/give some example about what you said with the comments and function names (programmers, excuse the sloppy pseudocode that’s about to follow, it’s been a long time since high school intro to computer science)
Let’s say in a video game, you run around collecting coins, and if you get 100 coins you earn an extra life
One small part of that code may look something like:
IF
newGame = TRUE
THEN
coinCount = 0
lifeCount = 3
coinModel.all.visibility = TRUE
//Players start a new game with 3 lives and 0 coins, and all coins are visible in the level
IF
playerModel.isTouching.coinModel.x = TRUE
THEN
coinModel.x.visibility = FALSE
coinCount++
//If the player character model touches one of the coin models, that coin model disappears, and the players coin count is increased by 1
IF
coinCount % 100 = 0
THEN
lifeCount++
//if that coin count is divisible evenly by 100, then the players life count is also increased by 1
Quick notes for people who have even less programming background than me
++ Is used by a lot of programming languages to increase a value by 1
% is often used as the “modulo” operator, which basically returns the remainder from division. So 10 % 2 = 0, because 10 is evenly divisible by 2, 10 % 3 = 1, because 10 is divisible by 3 but not evenly and leaves a remainder of 1
// Are comments, they don’t affect the code, they’re just there for human readability to make it more understandable, so you can explain why you did what you did for anyone who has to maintain the code after you, etc.
Hopefully, between the simple variable names and comments, those pseudocode blocks all pretty readable for laypeople, but if not
The first block basically detects if you’re starting a new game (IF newGame = TRUE)
If it is, then it resets your life counter to a default 3, and you start with 0 coins and sets all of the coins in the level to be visible so you can collect them
Otherwise it would carry over the values from your previous level, or save game, or whatever
The second block detects if you touch a coin (playerModel.isTouching.coinModel.x = TRUE)
If you do, that coin vanishes (coin.x.visibility = FALSE)
It also increases your coin count (coinCount++)
Then if your coin count is divisible evenly by 100 (coinCount % 100 = 0) it increases your life total (lifeCount++)
When the code gets compiled, that gets turned into machine code, basically all 1s and 0s that the computer can understand. The computer doesn’t care if you call a coin a coin or if you call it object1, it’s going to strip all of those human-readable elements out because it would just be a waste of storage and processing power to keep it in.
So when you recompile that, you don’t get any of the explanatory comments or the easy to read variable names, so you might end up with something looking kind of like this
IF
Variable1 = TRUE
THEN
Variable2 = 0
Variable3 = 3
object1.all.condition1 = TRUE
IF
object2.condition2.object1.x = TRUE
THEN
object1.x.condition1 = FALSE
variable2++
IF
variable2 % 100 = 0
THEN
variable3++
Which is a lot harder to understand. The code will still work, you could recompile it and run it, but if you want to make any changes, you’d basically need to comb through it, figure out what all the variables, objects, conditions, etc. are, and try to piece together why the programmers who originally wrote the code did it the way they did
And that’s of course a bit of an oversimplification, for various reasons it may not decompile and recompile exactly 1:1 with the original code, it’s almost like translating the same sentence back and forth between 2 languages with Google translate.
And even this little snippet of fairly simple and straightforward code would probably going to be backed up by dozens, if not hundreds or thousands of other lines of code just to make this bit work, defining what a coin is, the hit boxes, animations, how it determines if it’s a new game or or continuing a previous game, etc.
Thank you for adding this! If people want a real life example of the effect shown in this pseudocode, here is a side-by-side comparison of real production code I wrote and it’s decompiled counterpart:
override fun process(event: MapStateEvent) {
when(event) {
is MapStateEvent.LassoButtonClicked -> {
action(
MapStateAction.LassoButtonSelected(false),
MapStateAction.Transition(BrowseMapState::class.java)
)
}
is MapStateEvent.SaveSearchClicked -> {
save(event.name)
}
// Propagated from the previous level
is MapStateEvent.LassoCursorLifted -> {
load(event.line + event.line.first())
}
is MapStateEvent.ClusterClick -> {
when (val action = ClusterHelper.handleClick(event.cluster)) {
is ClusterHelper.Action.OpenBottomDialog ->
action(MapStateAction.OpenBottomDialog(action.items))
is ClusterHelper.Action.AnimateCamera ->
action(MapStateAction.AnimateCamera(action.animation))
}
}
is MapStateEvent.ClusterItemClick -> {
action(
MapStateAction.OpenItem(event.item.proposal)
)
}
else -> {}
}
}
decompiled:
public void c(@l j jVar) {
L.p(jVar, D.f10724I0);
if (jVar instanceof j.c) {
f(new i.h(false), new i.r(c.class, (j) null, 2, (C2498w) null));
} else if (jVar instanceof j.e) {
m(((j.e) jVar).f8620a);
} else if (jVar instanceof j.d) {
List<LatLng> list = ((j.d) jVar).f8619a;
j(I.A4(list, I.w2(list)));
} else if (jVar instanceof j.a) {
d.a a7 = d.f8573a.a(((j.a) jVar).f8616a);
if (a7 instanceof d.a.b) {
f(new i.j(((d.a.b) a7).f8575a));
} else if (a7 instanceof d.a.C0058a) {
f(new i.a(((d.a.C0058a) a7).f8574a));
}
} else if (jVar instanceof j.b) {
f(new i.k(((j.b) jVar).f8617a.f11799a));
}
}
keep in mind, this was buried in hundreds of unlabeled classes and functions. I was only able to find this in a short amount of time because I have the most intimate knowledge of the code possible, having written it myself.
Apps are huge and compilers optimize the fuck out of the code. Code optimization doesn’t always make sense so you need to have a detailed understanding of which compilers were used. There could be hundreds of libraries involved or even layers of obfuscation in some cases. Loops can be unwrapped, or other bits of code optimized for specific architectures. Some of the logic won’t appear logical.
Disassemblers can do a decent job converting code back to C/C++, but even then, you have to go through the code line by line converting function names and variable names back to something that can be referenced later as a meaningful name.
You aren’t wrong: All the code is there. It’s just a matter of putting all the human readable references back into anything you disassembled.
Waaaay back in the day, we could tear apps apart easily if they were small. There were only a few flavors of assembly and compilers were still fairly basic for what they were. Regardless, it wasn’t a small task.
I played around with cracking for a while just to learn about it and honestly, it was kinda easy before everything was offloaded to “the cloud”. It’s just a matter of tracing execution and finding a few critical comparisons or jumps to alter. Even then, it could take me a day or two just to walk through what was basically one or two functions.
