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
16In 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.
17
18It'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.
19
20Even 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.
21
22Be 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.
23
24**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.
25
26Now that all [script kiddies][script-kid] have left the room, let's proceed with the post.
27
28## Exact Value scanning
29
30<details open><summary>Cheat Engine Tutorial: Step 2</summary>
31
32> Now that you have opened the tutorial with Cheat Engine let's get on with the next step.
33>
34> You can see at the bottom of this window is the text Health: xxx. Each time you click 'Hit me' your health gets decreased.
35>
36> To get to the next step you have to find this value and change it to 1000
37>
38> 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.
39>
40> 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
41>
42> 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.....)
43>
44> 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.
45>
46> If everything went ok the next button should become enabled, and you're ready for the next step.
47>
48> 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'
49
50</details>
51
52## Our First Scan
53
54The Cheat Engine tutorial talks about "value types" and "scan types" like "exact value".
55
56The **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.
57
58When 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`.
59
60The **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.
61
62What'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.
63
64We 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.
65
66```rust
67pub fn read_memory(&self, addr: usize, n: usize) -> io::Result<Vec<u8>> {
68 todo!()
69}
70```
71
72Much 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.
73
74The 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:
75
76```rust
77let mut buffer = Vec::<u8>::with_capacity(n);
78let mut read = 0;
79
80// SAFETY: the buffer points to valid memory, and the buffer size is correctly set.
81if unsafe {
82 winapi::um::memoryapi::ReadProcessMemory(
83 self.handle.as_ptr(),
84 addr as *const _,
85 buffer.as_mut_ptr().cast(),
86 buffer.capacity(),
87 &mut read,
88 )
89} == FALSE
90{
91 Err(io::Error::last_os_error())
92} else {
93 // SAFETY: the call succeeded and `read` contains the amount of bytes written.
94 unsafe { buffer.set_len(read as usize) };
95 Ok(buffer)
96}
97```
98
99Great! 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.
100
101I 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?
102
103## Memory regions
104
105The 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.
106
107We need to query for the memory regions allocated to the program. For this purpose we can use [`VirtualQueryEx`][vquery].
108
109> Retrieves information about a range of pages within the virtual address space of a specified process.
110
111We have enumerated things before, and this function is not all that different.
112
113```rust
114fn memory_regions(&self) -> io::Result<winapi::um::winnt::MEMORY_BASIC_INFORMATION> {
115 let mut info = MaybeUninit::uninit();
116
117 // SAFETY: the info structure points to valid memory.
118 let written = unsafe {
119 winapi::um::memoryapi::VirtualQueryEx(
120 self.handle.as_ptr(),
121 std::ptr::null(),
122 info.as_mut_ptr(),
123 mem::size_of::<winapi::um::winnt::MEMORY_BASIC_INFORMATION>(),
124 )
125 };
126 if written == 0 {
127 Err(io::Error::last_os_error())
128 } else {
129 // SAFETY: a non-zero amount was written to the structure
130 Ok(unsafe { info.assume_init() })
131 }
132}
133```
134
135We 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`:
136
137```rust
138dbg!(process.memory_regions());
139```
140
141```
142>cargo run
143Compiling memo v0.1.0
144
145error[E0277]: `winapi::um::winnt::MEMORY_BASIC_INFORMATION` doesn't implement `std::fmt::Debug`
146 --> src\main.rs:185:5
147 |
148185 | dbg!(process.memory_regions());
149 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `winapi::um::winnt::MEMORY_BASIC_INFORMATION` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
150```
151
152That'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:
153
154```
155eprintln!(
156 "Region:
157 BaseAddress: {:?}
158 AllocationBase: {:?}
159 AllocationProtect: {:?}
160 RegionSize: {:?}
161 State: {:?}
162 Protect: {:?}
163 Type: {:?}",
164 region.BaseAddress,
165 region.AllocationBase,
166 region.AllocationProtect,
167 region.RegionSize,
168 region.State,
169 region.Protect,
170 region.Type,
171);
172```
173
174Hopefully we don't need to do this often:
175
176```
177>cargo run
178 Compiling memo v0.1.0
179 Finished dev [unoptimized + debuginfo] target(s) in 0.60s
180 Running `target\debug\memo.exe`
181
182Region:
183 BaseAddress: 0x0
184 AllocationBase: 0x0
185 AllocationProtect: 0
186 RegionSize: 65536
187 State: 65536
188 Protect: 1
189 Type: 0
190```
191
192Awesome! 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]:
193
194> 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.
195
196Now 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]:
197
198```rust
199pub fn memory_regions(&self) -> Vec<winapi::um::winnt::MEMORY_BASIC_INFORMATION> {
200 let mut base = 0;
201 let mut regions = Vec::new();
202 let mut info = MaybeUninit::uninit();
203
204 loop {
205 // SAFETY: the info structure points to valid memory.
206 let written = unsafe {
207 winapi::um::memoryapi::VirtualQueryEx(
208 self.handle.as_ptr(),
209 base as *const _,
210 info.as_mut_ptr(),
211 mem::size_of::<winapi::um::winnt::MEMORY_BASIC_INFORMATION>(),
212 )
213 };
214 if written == 0 {
215 break regions;
216 }
217 // SAFETY: a non-zero amount was written to the structure
218 let info = unsafe { info.assume_init() };
219 base = info.BaseAddress as usize + info.RegionSize;
220 regions.push(info);
221 }
222}
223```
224
225`RegionSize` is:
226
227> The size of the region beginning at the base address in which all pages have identical attributes, in bytes.
228
229…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:
230
231```rust
232dbg!(process.memory_regions().len());
233```
234
235```
236>cargo run
237 Compiling memo v0.1.0
238 Finished dev [unoptimized + debuginfo] target(s) in 0.63s
239 Running `target\debug\memo.exe`
240
241[src\main.rs:189] process.memory_regions().len() = 367
242```
243
244That's a lot of pages!
245
246## Protection levels
247
248Let's try to narrow the amount of pages down. How many pages aren't `PAGE_NOACCESS`?
249
250```rust
251dbg!(process
252 .memory_regions()
253 .into_iter()
254 .filter(|p| p.Protect != winapi::um::winnt::PAGE_NOACCESS)
255 .count());
256```
257
258```
259295
260```
261
262Still 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?
263
264```rust
265dbg!(process
266 .memory_regions()
267 .into_iter()
268 .filter(|p| p.Protect != winapi::um::winnt::PAGE_NOACCESS)
269 .map(|p| p.RegionSize)
270 .sum::<usize>());
271```
272
273```
2744480434176
275```
276
277Wait, 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:
278
279
280```rust
281let mask = winnt::PAGE_EXECUTE_READWRITE
282 | winnt::PAGE_EXECUTE_WRITECOPY
283 | winnt::PAGE_READWRITE
284 | winnt::PAGE_WRITECOPY;
285
286dbg!(process
287 .memory_regions()
288 .into_iter()
289 .filter(|p| (p.Protect & mask) != 0)
290 .map(|p| p.RegionSize)
291 .sum::<usize>());
292```
293
294Each 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.
295
296Don'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.
297
298```
2992580480
300```
301
302Hey, that's close to the value shown by the Task Manager! A handfull of megabytes is a lot more manageable than 4 entire gigabytes.
303
304## Actually running our First Scan
305
306Okay, 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:
307
308```rust
309let regions = process
310 .memory_regions()
311 .into_iter()
312 .filter(|p| (p.Protect & mask) != 0)
313 .collect::<Vec<_>>();
314
315println!("Scanning {} memory regions", regions.len());
316
317regions.into_iter().for_each(|region| {
318 match process.read_memory(region.BaseAddress as _, region.RegionSize) {
319 Ok(memory) => todo!(),
320 Err(err) => eprintln!(
321 "Failed to read {} bytes at {:?}: {}",
322 region.RegionSize, region.BaseAddress, err,
323 ),
324 }
325})
326```
327
328All 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.
329
330```rust
331let target: i32 = ...;
332let target = target.to_ne_bytes();
333
334// -snip-
335
336// inside the Ok match, replacing the todo!() -- this is where the first scan happens
337Ok(memory) => memory
338 .windows(target.len())
339 .enumerate()
340 .for_each(|(offset, window)| {
341 if window == target {
342 println!(
343 "Found exact value at [{:?}+{:x}]",
344 region.BaseAddress, offset
345 );
346 }
347 })
348```
349
350We 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.
351
352This is enough to find the value in the process' memory!
353
354```
355Found exact value at [0x10000+aec]
356Failed to read 12288 bytes at 0x13f8000: Only part of a ReadProcessMemory or WriteProcessMemory request was completed. (os error 299)
357Found exact value at [0x14f0000+3188]
358Found exact value at [0x14f0000+ac74]
359...
360Found exact value at [0x10030e000+1816]
361Found exact value at [0x7ff8f7b93000+441a]
362...
363Found exact value at [0x7ff8fb381000+4023]
364```
365
366The 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.
367
368Attentive 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.
369
370We can perform a fast scan ourselves with [`step_by`][stepby][^5]:
371
372```rust
373memory
374 .windows(target.len())
375 .enumerate()
376 .step_by(4)
377 .for_each(...)
378```
379
380As a bonus, over half the addresses are gone, so we have less results to worry about[^6].
381
382## Next Scan
383
384The 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.
385
386For 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.
387
388Let's do that:
389
390```rust
391// new vector to hold the locations, before getting into `memory.windows`' for-each
392let mut locations = Vec::with_capacity(regions.len());
393
394// -snip-
395
396// updating the `println!("Found exact value...")` to store the location instead.
397if window == target {
398 locations.push(region.BaseAddress as usize + offset);
399}
400
401// -snip-
402
403// performing a second scan on the locations the first scan found.
404let target: i32 = ...;
405let target = target.to_ne_bytes();
406locations.retain(|addr| match process.read_memory(*addr, target.len()) {
407 Ok(memory) => memory == target,
408 Err(_) => false,
409});
410
411println!("Now have {} locations", locations.len());
412```
413
414We 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:
415
416```
417Scanning 98 memory regions
418Which exact value to scan for?: 100
419Failed to read 12288 bytes at 0x13f8000: Only part of a ReadProcessMemory or WriteProcessMemory request was completed. (os error 299)
420...
421Found 49 locations
422Which exact value to scan for next?: 99
423Now have 1 locations
424```
425
426Sweet! 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.
427
428For good measure, we'll wrap our `retain` in a `while` loop[^8]:
429
430```rust
431while locations.len() != 1 {
432 let target: i32 = ...;
433 let target = target.to_ne_bytes();
434 locations.retain(...);
435}
436```
437
438## Modifying memory
439
440Now 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:
441
442```rust
443pub fn write_memory(&self, addr: usize, value: &[u8]) -> io::Result<usize> {
444 let mut written = 0;
445
446 // SAFETY: the input value buffer points to valid memory.
447 if unsafe {
448 winapi::um::memoryapi::WriteProcessMemory(
449 self.handle.as_ptr(),
450 addr as *mut _,
451 value.as_ptr().cast(),
452 value.len(),
453 &mut written,
454 )
455 } == FALSE
456 {
457 Err(io::Error::last_os_error())
458 } else {
459 Ok(written)
460 }
461}
462```
463
464Similar 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.
465
466```rust
467let new_value: i32 = ...;
468locations
469 .into_iter()
470 .for_each(|addr| match process.write_memory(addr, &new_value) {
471 Ok(n) => eprintln!("Written {} bytes to [{:x}]", n, addr),
472 Err(e) => eprintln!("Failed to write to [{:x}]: {}", addr, e),
473 });
474```
475
476And just like that:
477
478```
479Now have 1 location(s)
480Enter new memory value: 1000
481Failed to write to [15d8b90]: Access is denied. (os error 5)
482```
483
484…oh noes. Oh yeah. The documentation, which I totally didn't forget to read, mentions:
485
486> The handle must have `PROCESS_VM_WRITE` and `PROCESS_VM_OPERATION` access to the process.
487
488We 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:
489
490```rust
491winapi::um::processthreadsapi::OpenProcess(
492 winnt::PROCESS_QUERY_INFORMATION
493 | winnt::PROCESS_VM_READ
494 | winnt::PROCESS_VM_WRITE
495 | winnt::PROCESS_VM_OPERATION,
496 FALSE,
497 pid,
498)
499```
500
501Behold:
502
503```
504Now have 1 location(s)
505Enter new memory value: 1000
506Written 4 bytes to [15d8b90]
507```
508
509![Tutorial complete with memo][completion]
510
511Isn't that active *Next* button just beautiful?
512
513## Finale
514
515This 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.
516
517And we're not even done. The current tutorial has nine steps, and three additional graphical levels.
518
519In the next post, 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!
520
521Remember 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.
522
523### Footnotes
524
525[^1]: I did in fact use an online tool to spell it out for me.
526
527[^2]: 16 GiB is good enough for my needs. I don't think I'll ever upgrade to 16 EiB.
528
529[^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.
530
531[^4]: Another option is to [`GetSystemInfo`][getsysinfo] to determine the `lpMinimumApplicationAddress` and `lpMaximumApplicationAddress` and only work within bounds.
532
533[^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.
534
535[^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.
536
537[^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.
538
539[^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!
540
541[^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.
542
543[script-kid]: https://www.urbandictionary.com/define.php?term=script%20kiddie
544[readmem]: https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-readprocessmemory
545[exbibytes]: https://en.wikipedia.org/wiki/Orders_of_magnitude_(data)
546[vquery]: https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-virtualqueryex
547[prdebug]: https://github.com/retep998/winapi-rs/issues/548#issuecomment-355278090
548[memprot]: https://docs.microsoft.com/en-us/windows/win32/memory/memory-protection-constants
549[getsysinfo]: https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsysteminfo
550[slicewin]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.windows
551[tone]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.to_ne_bytes
552[stepby]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.step_by
553[writemem]: https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-writeprocessmemory
554[completion]: https://user-images.githubusercontent.com/6297805/107829541-3f4f2d00-6d8a-11eb-87c4-e2f2d505afbc.png
555[code]: https://github.com/lonami/memo