content/blog/woce-2.md (view raw)
1+++
2title = "Writing our own Cheat Engine: Exact Value scanning"
3date = 2021-02-12
4updated = 2021-02-19
5[taxonomies]
6category = ["sw"]
7tags = ["windows", "rust", "hacking"]
8+++
9
10This is part 2 on the *Writing our own Cheat Engine* series:
11
12* [Part 1: Introduction](/blog/woce-1) (start here if you're new to the series!)
13* Part 2: Exact Value scanning
14* [Part 3: Unknown initial value](/blog/woce-3)
15* [Part 4: Floating points](/blog/woce-4)
16
17In the introduction, we spent a good deal of time enumerating all running processes just so we could find out the pid we cared about. With the pid now in our hands, we can do pretty much anything to its corresponding process.
18
19It's now time to read the process' memory and write to it. If our process was a single-player game, this would enable us to do things like setting a very high value on the player's current health pool, making us invincible. This technique will often not work for multi-player games, because the server likely knows your true current health (the most you could probably do is make the client render an incorrect value). However, if the server is crappy and it trusts the client, then you're still free to mess around with your current health.
20
21Even if we don't want to write to the process' memory, reading is still very useful. Maybe you could enhance your experience by making a custom overlay that displays useful information, or something that makes noise if it detects the life is too low, or even simulating a keyboard event to automatically recover some mana when you're running low.
22
23Be warned about anti-cheat systems. Anything beyond a basic game is likely to have some protection measures in place, making the analysis more difficult (perhaps the values are scrambled in memory), or even pinging the server if it detects something fishy.
24
25**I am not responsible for any bans!** Use your brain before messing with online games, and don't ruin the fun for everyone else. If you get caught for cheating, I don't want to know about it.
26
27Now that all [script kiddies][script-kid] have left the room, let's proceed with the post.
28
29## Exact Value scanning
30
31<details open><summary>Cheat Engine Tutorial: Step 2</summary>
32
33> Now that you have opened the tutorial with Cheat Engine let's get on with the next step.
34>
35> You can see at the bottom of this window is the text Health: xxx. Each time you click 'Hit me' your health gets decreased.
36>
37> To get to the next step you have to find this value and change it to 1000
38>
39> To find the value there are different ways, but I'll tell you about the easiest, 'Exact Value': First make sure value type is set to at least 2-bytes or 4-bytes. 1-byte will also work, but you'll run into an easy to fix problem when you've found the address and want to change it. The 8-byte may perhaps works if the bytes after the address are 0, but I wouldn't take the bet. Single, double, and the other scans just don't work, because they store the value in a different way.
40>
41> When the value type is set correctly, make sure the scantype is set to 'Exact Value'. Then fill in the number your health is in the value box. And click 'First Scan'. After a while (if you have a extremely slow pc) the scan is done and the results are shown in the list on the left
42>
43> If you find more than 1 address and you don't know for sure which address it is, click 'Hit me', fill in the new health value into the value box, and click 'Next Scan'. Repeat this until you're sure you've found it. (that includes that there's only 1 address in the list.....)
44>
45> Now double click the address in the list on the left. This makes the address pop-up in the list at the bottom, showing you the current value. Double click the value, (or select it and press enter), and change the value to 1000.
46>
47> If everything went ok the next button should become enabled, and you're ready for the next step.
48>
49> Note: If you did anything wrong while scanning, click "New Scan" and repeat the scanning again. Also, try playing around with the value and click 'hit me'
50
51</details>
52
53## Our First Scan
54
55The Cheat Engine tutorial talks about "value types" and "scan types" like "exact value".
56
57The **value types** will help us narrow down *what* we're looking for. For example, the integer type `i32` is represented in memory as 32 bits, or 4 bytes. However, `f32` is *also* represented by 4 bytes, and so is `u32`. Or perhaps the 4 bytes represent RGBA values of a color! So any 4 bytes in memory can be interpreted in many ways, and it's up to us to decide which way we interpret the bytes in.
58
59When programming, numbers which are 32-bit wide are common, as they're a good (and fast) size to work with. Scanning for this type is often a good bet. For positive numbers, `i32` is represented the same as `u32` in memory, so even if the value turns out to not be signed, the scan is likely to work. Focusing on `i32` will save us from scanning for `f32` or even other types, like interpreting 8 bytes for `i64`, `f64`, or less bytes like `i16`.
60
61The **scan types** will help us narrow down *how* we're looking for a value. Scanning for an exact value means what you think it does: interpret all 4 bytes in the process' memory as our value type, and check if they exactly match our value. This will often yield a lot of candidates, but it will be enough to get us started. Variations of the exact scan include checking for all values below a threshold, above, in between, or even just… unknown.
62
63What's the point of scanning for unknown values if *everything* in memory is unknown? Sometimes you don't have a concrete value. Maybe your health pool is a bar and it nevers tell you how much health you actually have, just a visual indicator of your percentage left, even if the health is not stored as a percentage. As we will find later on, scanning for unknown values is more useful than it might appear at first.
64
65We can access the memory of our own program by guessing random pointers and trying to read from them. But Windows isolates the memory of each program, so no pointer we could ever guess will let us read from the memory of another process. Luckily for us, searching for "read process memory winapi" leads us to the [`ReadProcessMemory`][readmem] function. Spot on.
66
67```rust
68pub fn read_memory(&self, addr: usize, n: usize) -> io::Result<Vec<u8>> {
69 todo!()
70}
71```
72
73Much like trying to dereference a pointer pointing to released memory or even null, reading from an arbitrary address can fail for the same reasons (and more). We will want to signal this with `io::Result`. It's funny to note that, even though we're doing something that seems wildly unsafe (reading arbitrary memory, even if the other process is mutating it at the same time), the function is perfectly safe. If we cannot read something, it will return `Err`, but if it succeeds, it has taken a snapshot of the memory of the process, and the returned value will be correctly initialized.
74
75The function will be defined inside our `impl Process`, since it conveniently holds an open handle to the process in question. It takes `&self`, because we do not need to mutate anything in the `Process` instance. After adding the `memoryapi` feature to `Cargo.toml`, we can perform the call:
76
77```rust
78let mut buffer = Vec::<u8>::with_capacity(n);
79let mut read = 0;
80
81// SAFETY: the buffer points to valid memory, and the buffer size is correctly set.
82if unsafe {
83 winapi::um::memoryapi::ReadProcessMemory(
84 self.handle.as_ptr(),
85 addr as *const _,
86 buffer.as_mut_ptr().cast(),
87 buffer.capacity(),
88 &mut read,
89 )
90} == FALSE
91{
92 Err(io::Error::last_os_error())
93} else {
94 // SAFETY: the call succeeded and `read` contains the amount of bytes written.
95 unsafe { buffer.set_len(read as usize) };
96 Ok(buffer)
97}
98```
99
100Great! But the address space is somewhat large. 64 bits large. Eighteen quintillion, four hundred and forty-six quadrillion, seven hundred and forty-four trillion, seventy-three billion, seven hundred and nine million, five hundred and fifty-one thousand, six hundred and sixteen[^1] large. You gave up reading that, didn't you? Anyway, 18'446'744'073'709'551'616 is a *big* number.
101
102I am not willing to wait for the program to scan over so many values. I don't even have 16 [exbibytes] of RAM installed on my laptop yet[^2]! What's up with that?
103
104## Memory regions
105
106The program does not actually have all that memory allocated (surprise!). Random-guessing an address is extremely likely to point out to invalid memory. Reading from the start of the address space all the way to the end would not be any better. And we **need** to do better.
107
108We need to query for the memory regions allocated to the program. For this purpose we can use [`VirtualQueryEx`][vquery].
109
110> Retrieves information about a range of pages within the virtual address space of a specified process.
111
112We have enumerated things before, and this function is not all that different.
113
114```rust
115fn memory_regions(&self) -> io::Result<winapi::um::winnt::MEMORY_BASIC_INFORMATION> {
116 let mut info = MaybeUninit::uninit();
117
118 // SAFETY: the info structure points to valid memory.
119 let written = unsafe {
120 winapi::um::memoryapi::VirtualQueryEx(
121 self.handle.as_ptr(),
122 std::ptr::null(),
123 info.as_mut_ptr(),
124 mem::size_of::<winapi::um::winnt::MEMORY_BASIC_INFORMATION>(),
125 )
126 };
127 if written == 0 {
128 Err(io::Error::last_os_error())
129 } else {
130 // SAFETY: a non-zero amount was written to the structure
131 Ok(unsafe { info.assume_init() })
132 }
133}
134```
135
136We start with a base address of zero[^3] (`std::ptr::null()`), and ask the function to tell us what's in there. Let's try it out, with the `impl-debug` crate feature in `Cargo.toml`:
137
138```rust
139dbg!(process.memory_regions());
140```
141
142```
143>cargo run
144Compiling memo v0.1.0
145
146error[E0277]: `winapi::um::winnt::MEMORY_BASIC_INFORMATION` doesn't implement `std::fmt::Debug`
147 --> src\main.rs:185:5
148 |
149185 | dbg!(process.memory_regions());
150 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `winapi::um::winnt::MEMORY_BASIC_INFORMATION` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
151```
152
153That's annoying. It seems not everything has an `impl std::fmt::Debug`, and [you're supposed to send a PR][prdebug] if you want it to have debug, even if the `impl-debug` feature is set. I'm surprised they don't auto-generate all of this and have to rely on manually adding `Debug` as needed? Oh well, let's get rid of the feature and print it out ourselves:
154
155```
156eprintln!(
157 "Region:
158 BaseAddress: {:?}
159 AllocationBase: {:?}
160 AllocationProtect: {:?}
161 RegionSize: {:?}
162 State: {:?}
163 Protect: {:?}
164 Type: {:?}",
165 region.BaseAddress,
166 region.AllocationBase,
167 region.AllocationProtect,
168 region.RegionSize,
169 region.State,
170 region.Protect,
171 region.Type,
172);
173```
174
175Hopefully we don't need to do this often:
176
177```
178>cargo run
179 Compiling memo v0.1.0
180 Finished dev [unoptimized + debuginfo] target(s) in 0.60s
181 Running `target\debug\memo.exe`
182
183Region:
184 BaseAddress: 0x0
185 AllocationBase: 0x0
186 AllocationProtect: 0
187 RegionSize: 65536
188 State: 65536
189 Protect: 1
190 Type: 0
191```
192
193Awesome! There is a region at `null`, and the `AllocationProtect` of zero indicates that "the caller does not have access" when the region was created. However, `Protect` is `1`, and that is the *current* protection level. A value of one indicates [`PAGE_NOACCESS`][memprot]:
194
195> Disables all access to the committed region of pages. An attempt to read from, write to, or execute the committed region results in an access violation.
196
197Now that we know that the first region starts at 0 and has a size of 64 KiB, we can simply query for the page at `(current base + current size)` to fetch the next region. Essentially, we want to loop until it fails, after which we'll know there are no more pages[^4]:
198
199```rust
200pub fn memory_regions(&self) -> Vec<winapi::um::winnt::MEMORY_BASIC_INFORMATION> {
201 let mut base = 0;
202 let mut regions = Vec::new();
203 let mut info = MaybeUninit::uninit();
204
205 loop {
206 // SAFETY: the info structure points to valid memory.
207 let written = unsafe {
208 winapi::um::memoryapi::VirtualQueryEx(
209 self.handle.as_ptr(),
210 base as *const _,
211 info.as_mut_ptr(),
212 mem::size_of::<winapi::um::winnt::MEMORY_BASIC_INFORMATION>(),
213 )
214 };
215 if written == 0 {
216 break regions;
217 }
218 // SAFETY: a non-zero amount was written to the structure
219 let info = unsafe { info.assume_init() };
220 base = info.BaseAddress as usize + info.RegionSize;
221 regions.push(info);
222 }
223}
224```
225
226`RegionSize` is:
227
228> The size of the region beginning at the base address in which all pages have identical attributes, in bytes.
229
230…which also hints that the value we want is "base address", not the "allocation base". With these two values, we can essentially iterate over all the page ranges:
231
232```rust
233dbg!(process.memory_regions().len());
234```
235
236```
237>cargo run
238 Compiling memo v0.1.0
239 Finished dev [unoptimized + debuginfo] target(s) in 0.63s
240 Running `target\debug\memo.exe`
241
242[src\main.rs:189] process.memory_regions().len() = 367
243```
244
245That's a lot of pages!
246
247## Protection levels
248
249Let's try to narrow the amount of pages down. How many pages aren't `PAGE_NOACCESS`?
250
251```rust
252dbg!(process
253 .memory_regions()
254 .into_iter()
255 .filter(|p| p.Protect != winapi::um::winnt::PAGE_NOACCESS)
256 .count());
257```
258
259```
260295
261```
262
263Still a fair bit! Most likely, there are just a few interleaved `NOACCESS` pages, and the rest are allocated each with different protection levels. How much memory do we need to scan through?
264
265```rust
266dbg!(process
267 .memory_regions()
268 .into_iter()
269 .filter(|p| p.Protect != winapi::um::winnt::PAGE_NOACCESS)
270 .map(|p| p.RegionSize)
271 .sum::<usize>());
272```
273
274```
2754480434176
276```
277
278Wait, what? What do you mean over 4 GiB? The Task Manager claims that the Cheat Engine Tutorial is only using 2.1 MB worth of RAM! Perhaps we can narrow down the [protection levels][memprot] a bit more. If you look at the scan options in Cheat Engine, you will notice the "Memory Scan Options" groupbox. By default, it only scans for memory that is writable, and doesn't care if it's executable or not:
279
280
281```rust
282let mask = winnt::PAGE_EXECUTE_READWRITE
283 | winnt::PAGE_EXECUTE_WRITECOPY
284 | winnt::PAGE_READWRITE
285 | winnt::PAGE_WRITECOPY;
286
287dbg!(process
288 .memory_regions()
289 .into_iter()
290 .filter(|p| (p.Protect & mask) != 0)
291 .map(|p| p.RegionSize)
292 .sum::<usize>());
293```
294
295Each memory protection level has its own bit, so we can OR them all together to have a single mask. When ANDing this mask with the protection level, if any bit is set, it will be non-zero, meaning we want to keep this region.
296
297Don't ask me why there isn't a specific bit for "write", "read", "execute", and there are only bits for combinations. I guess this way Windows forbids certain combinations.
298
299```
3002580480
301```
302
303Hey, that's close to the value shown by the Task Manager! A handfull of megabytes is a lot more manageable than 4 entire gigabytes.
304
305## Actually running our First Scan
306
307Okay, we have all the memory regions from which the program can read, write, or execute. Now we also can read the memory in these regions:
308
309```rust
310let regions = process
311 .memory_regions()
312 .into_iter()
313 .filter(|p| (p.Protect & mask) != 0)
314 .collect::<Vec<_>>();
315
316println!("Scanning {} memory regions", regions.len());
317
318regions.into_iter().for_each(|region| {
319 match process.read_memory(region.BaseAddress as _, region.RegionSize) {
320 Ok(memory) => todo!(),
321 Err(err) => eprintln!(
322 "Failed to read {} bytes at {:?}: {}",
323 region.RegionSize, region.BaseAddress, err,
324 ),
325 }
326})
327```
328
329All that's left is for us to scan for a target value. To do this, we want to iterate over all the [`slice::windows`][slicewin] of size equal to the size of our scan type.
330
331```rust
332let target: i32 = ...;
333let target = target.to_ne_bytes();
334
335// -snip-
336
337// inside the Ok match, replacing the todo!() -- this is where the first scan happens
338Ok(memory) => memory
339 .windows(target.len())
340 .enumerate()
341 .for_each(|(offset, window)| {
342 if window == target {
343 println!(
344 "Found exact value at [{:?}+{:x}]",
345 region.BaseAddress, offset
346 );
347 }
348 })
349```
350
351We convert the 32-bit exact target value to its memory representation as a byte array in [native byte order][tone]. This way we can compare the target bytes with the window bytes. Another option is to interpret the window bytes as an `i32` with `from_be_bytes`, but `slice::windows` gives us slices of type `&[u8]`, and `from_be_bytes` wants an `[u8; 4]` array, so it's a bit more annoying to convert.
352
353This is enough to find the value in the process' memory!
354
355```
356Found exact value at [0x10000+aec]
357Failed to read 12288 bytes at 0x13f8000: Only part of a ReadProcessMemory or WriteProcessMemory request was completed. (os error 299)
358Found exact value at [0x14f0000+3188]
359Found exact value at [0x14f0000+ac74]
360...
361Found exact value at [0x10030e000+1816]
362Found exact value at [0x7ff8f7b93000+441a]
363...
364Found exact value at [0x7ff8fb381000+4023]
365```
366
367The tutorial starts out with health "100", which is what I scanned. Apparently, there are nearly a hundred of `100`-valued integers stored in the memory of the tutorial.
368
369Attentive readers will notice that some values are located at an offset modulo 4. In Cheat Engine, this is known as "Fast Scan", which is enabled by default with an alignment of 4. Most of the time, values are aligned in memory, and this alignment often corresponds with the size of the type itself. For 4-byte integers, it's common that they're 4-byte aligned.
370
371We can perform a fast scan ourselves with [`step_by`][stepby][^5]:
372
373```rust
374memory
375 .windows(target.len())
376 .enumerate()
377 .step_by(4)
378 .for_each(...)
379```
380
381As a bonus, over half the addresses are gone, so we have less results to worry about[^6].
382
383## Next Scan
384
385The first scan gave us way too many results. We have no way to tell which is the correct one, as they all have the same value. What we need to do is a *second* scan at the *locations we just found*. This way, we can get a second reading, and compare it against a new value. If it's the same, we're on good track, and if not, we can discard a location. Repeating this process lets us cut the hundreds of potential addresses to just a handful of them.
386
387For example, let's say we're scanning our current health of `100` in a game. This gives us over a hundred addresses that point to the value of `100`. If we go in-game and get hit[^7] by some enemy and get our health down to, say, `99` (we have a lot of defense), we can then read the memory at the hundred memory locations we found before. If this second reading is not `99`, we know the address does not actually point to our health pool and it just happened to also contain a `100` on the first scan. This address can be removed from the list of potential addresses pointing to our health.
388
389Let's do that:
390
391```rust
392// new vector to hold the locations, before getting into `memory.windows`' for-each
393let mut locations = Vec::with_capacity(regions.len());
394
395// -snip-
396
397// updating the `println!("Found exact value...")` to store the location instead.
398if window == target {
399 locations.push(region.BaseAddress as usize + offset);
400}
401
402// -snip-
403
404// performing a second scan on the locations the first scan found.
405let target: i32 = ...;
406let target = target.to_ne_bytes();
407locations.retain(|addr| match process.read_memory(*addr, target.len()) {
408 Ok(memory) => memory == target,
409 Err(_) => false,
410});
411
412println!("Now have {} locations", locations.len());
413```
414
415We create a vector to store all the locations the first scan finds, and then retain those that match a second target value. You may have noticed that we perform a memory read, and thus a call to the Windows API, for every single address. With a hundred locations to read from, this is not a big deal, but oftentimes you will have tens of thousands of addresses. For the time being, we will not worry about this inefficiency, but we will get back to it once it matters:
416
417```
418Scanning 98 memory regions
419Which exact value to scan for?: 100
420Failed to read 12288 bytes at 0x13f8000: Only part of a ReadProcessMemory or WriteProcessMemory request was completed. (os error 299)
421...
422Found 49 locations
423Which exact value to scan for next?: 99
424Now have 1 locations
425```
426
427Sweet! In a real-world scenario, you will likely need to perform these additional scans a couple of times, and even then, there may be more than one value left no matter what.
428
429For good measure, we'll wrap our `retain` in a `while` loop[^8]:
430
431```rust
432while locations.len() != 1 {
433 let target: i32 = ...;
434 let target = target.to_ne_bytes();
435 locations.retain(...);
436}
437```
438
439## Modifying memory
440
441Now that we have very likely locations pointing to our current health in memory, all that's left is writing our new desired value to gain infinite health[^9]. Much like how we're able to read memory with `ReadProcessMemory`, we can write to it with [`WriteProcessMemory`][writemem]. Its usage is straightforward:
442
443```rust
444pub fn write_memory(&self, addr: usize, value: &[u8]) -> io::Result<usize> {
445 let mut written = 0;
446
447 // SAFETY: the input value buffer points to valid memory.
448 if unsafe {
449 winapi::um::memoryapi::WriteProcessMemory(
450 self.handle.as_ptr(),
451 addr as *mut _,
452 value.as_ptr().cast(),
453 value.len(),
454 &mut written,
455 )
456 } == FALSE
457 {
458 Err(io::Error::last_os_error())
459 } else {
460 Ok(written)
461 }
462}
463```
464
465Similar to how writing to a file can return short, writing to a memory location could also return short. Here we mimic the API for writing files and return the number of bytes written. The documentation indicates that we could actually ignore the amount written by passing `ptr::null_mut()` as the last parameter, but it does no harm to retrieve the written count as well.
466
467```rust
468let new_value: i32 = ...;
469locations
470 .into_iter()
471 .for_each(|addr| match process.write_memory(addr, &new_value) {
472 Ok(n) => eprintln!("Written {} bytes to [{:x}]", n, addr),
473 Err(e) => eprintln!("Failed to write to [{:x}]: {}", addr, e),
474 });
475```
476
477And just like that:
478
479```
480Now have 1 location(s)
481Enter new memory value: 1000
482Failed to write to [15d8b90]: Access is denied. (os error 5)
483```
484
485…oh noes. Oh yeah. The documentation, which I totally didn't forget to read, mentions:
486
487> The handle must have `PROCESS_VM_WRITE` and `PROCESS_VM_OPERATION` access to the process.
488
489We currently open our process with `PROCESS_QUERY_INFORMATION` and `PROCESS_VM_READ`, which is enough for reading, but not for writing. Let's adjust `OpenProcess` to accomodate for our new requirements:
490
491```rust
492winapi::um::processthreadsapi::OpenProcess(
493 winnt::PROCESS_QUERY_INFORMATION
494 | winnt::PROCESS_VM_READ
495 | winnt::PROCESS_VM_WRITE
496 | winnt::PROCESS_VM_OPERATION,
497 FALSE,
498 pid,
499)
500```
501
502Behold:
503
504```
505Now have 1 location(s)
506Enter new memory value: 1000
507Written 4 bytes to [15d8b90]
508```
509
510![Tutorial complete with memo][completion]
511
512Isn't that active *Next* button just beautiful?
513
514## Finale
515
516This post somehow ended up being longer than part one, but look at what we've achieved! We completed a step of the Cheat Engine Tutorial *without using Cheat Engine*. Just pure Rust. Figuring out how a program works and reimplementing it yourself is a great way to learn what it's doing behind the scenes. And now that this code is yours, you can extend it as much as you like, without being constrained by Cheat Engine's UI. You can automate it as much as you want.
517
518And we're not even done. The current tutorial has nine steps, and three additional graphical levels.
519
520In the [next post](/blog/woce-3), we'll tackle the third step of the tutorial: Unknown initial value. This will pose a challenge, because with just 2 MiB of memory, storing all the 4-byte aligned locations would require 524288 addresses (`usize`, 8 bytes). This adds up to twice as much memory as the original program (4 MiB), but that's not our main concern, having to perform over five hundred thousand API calls is!
521
522Remember that you can [obtain the code for this post][code] over at my GitHub. You can run `git checkout step2` after cloning the repository to get the right version of the code.
523
524### Footnotes
525
526[^1]: I did in fact use an online tool to spell it out for me.
527
528[^2]: 16 GiB is good enough for my needs. I don't think I'll ever upgrade to 16 EiB.
529
530[^3]: Every address we query should have a corresponding region, even if it's not allocated or we do not have access. This is why we can query for the memory address zero to get its corresponding region.
531
532[^4]: Another option is to [`GetSystemInfo`][getsysinfo] to determine the `lpMinimumApplicationAddress` and `lpMaximumApplicationAddress` and only work within bounds.
533
534[^5]: Memory regions are page-aligned, which is a large power of two. Our alignment of 4 is much lower than this, so we're guaranteed to start off at an aligned address.
535
536[^6]: If it turns out that the value was actually misaligned, we will miss it. You will notice this if, after going through the whole process, there are no results. It could mean that either the value type is wrong, or the value type is misaligned. In the worst case, the value is not stored directly but is rather computed with something like `maximum - stored`, or XORed with some magic value, or a myriad other things.
537
538[^7]: You could do this without getting hit, and just keep on repeating the scan for the same value over and over again. This does work, but the results are suboptimal, because there are also many other values that didn't change. Scanning for a changed value is a better option.
539
540[^8]: You could actually just go ahead and try to modify the memory at the hundred addresses you just found, although don't be surprised if the program starts to misbehave!
541
542[^9]: Okay, we cannot fit infinity in an `i32`. However, we can fit sufficiently large numbers. Like `1000`, which is enough to complete the tutorial.
543
544[script-kid]: https://www.urbandictionary.com/define.php?term=script%20kiddie
545[readmem]: https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-readprocessmemory
546[exbibytes]: https://en.wikipedia.org/wiki/Orders_of_magnitude_(data)
547[vquery]: https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-virtualqueryex
548[prdebug]: https://github.com/retep998/winapi-rs/issues/548#issuecomment-355278090
549[memprot]: https://docs.microsoft.com/en-us/windows/win32/memory/memory-protection-constants
550[getsysinfo]: https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsysteminfo
551[slicewin]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.windows
552[tone]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.to_ne_bytes
553[stepby]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.step_by
554[writemem]: https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-writeprocessmemory
555[completion]: https://user-images.githubusercontent.com/6297805/107829541-3f4f2d00-6d8a-11eb-87c4-e2f2d505afbc.png
556[code]: https://github.com/lonami/memo