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Today I did a little pointer exercise using Rust.

This is what we are going to do:

Allocate a new instance of `Point` struct on the heap
Change values of Point instance inside `Box<T>`
Inspect the memory addr of the `Box<T>` and the values of primitive types by using existing scope reference of the current stack (safe)
Inspect the memory addr of the `Box<T>` and the values of primitive types by reading from raw memory by address as u32 (unsafe)
Read point as `Point` from memory by raw pointer address into stack variable (unsafe) (values are copied)

1. Allocate a new instance of `Point` struct on the heap


use std::ptr;

struct Point {
    x: u8,
    y: u8,
    z: u8,
}

fn main() {
    let mut point = Box::new(Point { x: 0, y: 0, z: 0 });
}

2. Change values of Point instance inside `Box<T>`


point.x = u8::max_value(); //   0
point.y = u8::min_value(); // 255
point.z = u8::max_value(); //   0

3. Inspect the memory addr of the `Box<T>` and the values of primitive types by using existing scope reference of the current stack (safe)


// get raw memory address of `Box<Point>`:
// &point: get reference to `point`
// as *const Box<Point>: cast reference into raw pointer of type T
// as usize: cast raw pointer of type T into usize
let mem_addr_of_box = &point as *const Box<Point> as usize;

// get raw memory address of `Point`:
// &*point: get reference to `Point` by dereferenceing instance of `Box<Point>` first
// as *const Point: cast reference into raw pointer of type T
// as usize: cast raw pointer of type T into usize
let mem_addr_of_point_inside_box = &*point as *const Point as usize;

let x = point.x;
let y = point.y;
let z = point.z;

4. Inspect the memory addr of the `Box<T>` and the values of primitive types by reading from raw memory by address as u32 (unsafe)


// get raw memory address of `Box<Point>` from the current scope.
let addr = &point as *const Box<Point>;

// cast raw pointer of type T into usize
let mem_addr_of_box = addr as usize;

// perform unsafe raw memory read of `Box<Point>` resulting in raw pointer to `Point`.
// as *const usize: casing into usize because addr is a memory address
let mem_addr_of_point = unsafe { ptr::read(addr as *const usize) };

// perform unsafe raw memory read of `Point` as type `u32`:
// read(...) as *const u32: read `Point` as u32 to inspect binary value & layout
//                          u32 is sufficient as 3x u8 fit inside a u32
let point_value = unsafe { ptr::read_unaligned(ptr::read(addr as *const usize) as *const u32) };

5. Read point as `Point` from memory by raw pointer address into stack variable (unsafe) (values are copied)


// perform unsafe raw memory read of `Box<Point>` -> `Point` as type `Point`.
let point = unsafe { ptr::read(ptr::read(addr as *const usize) as *const Point) };

// get raw memory address of `Point`:
// as *const Point: cast reference into raw pointer of type T
// as usize: cast raw pointer of type T into usize
let mem_addr_of_point = &point as *const Point as usize;

let x = point.x;
let y = point.y;
let z = point.z;

And here is an example of how that could look like in action
Code Snippet

[JavaScript things 😆]

[The "date" shell command 😍]

I tools i love, today "date":


date --rfc-email --date="aug 15 10am"
# Mon, 15 Aug 2022 10:00:00 +0200

date --rfc-email --date="+2 weeks"
# Fri, 12 Aug 2022 16:17:48 +0200

date --rfc-email --date="next monday 1600"
# Mon, 01 Aug 2022 16:00:00 +0200

# convert the current day of the month + one month at 9pm local time to est
TZ="EST" date --rfc-email --date="next month 2100 Z+0200"
# Mon, 29 Aug 2022 14:00:00 -0500

I use this almost daily 😄

[DNSSEC; second attempt]

Some quite some time ago i wrote about DNSSEC Quick Zone Setup with BIND.

While it worked, i didn't had it active for long. Mainly because all the manual work in keeping the signatures up-to-date.

At the time i either didn't knew about BIND9's "inline-signing yes;" and "auto-dnssec maintain;" or they didn't exist back then^^

And ow was the time i revisit the topic and "try again" on finding a better solution. And well, i think i did \o/

So far i've configured DNSSEC for one of my domains and will see how this approach is keeping up in the following months.
I'll plan on writing more about DNSSEC and how my new setup works.

Until then i have a WIP document with some notes i've took along the way.

DNSSEC Notes

PS: I totally fell in love with Asciidoc / Asciidoctor.
Maybe it's also time to re-write my blogging software, too.

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