embedded-trainings-2020/boards/dongle/puzzle-nousb.rs

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#![deny(unused_must_use)]
#![no_main]
#![no_std]
use hal::{
led,
radio::{self, Channel, Packet},
};
use heapless::{consts, LinearMap};
use panic_abort as _;
static FROM: &[u8] = &[
// <redacted>
];
static TO: &[u8] = &[
// <redacted>
];
// store the secret rather than the plaintext -- otherwise `strings $elf` will reveal the answer
static SECRET: &[u8] = b"<redacted>";
#[no_mangle]
fn main() -> ! {
let (mut rtx, mut rrx) = radio::claim(Channel::_26);
let led = led::Green;
let mut dict = LinearMap::<_, _, consts::U128>::new();
for (&from, &to) in FROM.iter().zip(TO.iter()) {
dict.insert(from, to).ok();
}
let task = async {
let mut packet = Packet::new().await;
let mut on = true;
loop {
let crcres = rrx.read(&mut packet).await;
// toggle LED on each new packet
if on {
led.on();
} else {
led.off();
}
on = !on;
if crcres.is_ok() {
if packet.is_empty() {
packet.copy_from_slice(SECRET);
} else if packet.len() == 1 {
let p = packet[0];
let c = dict.get(&p).unwrap_or(&p);
packet.copy_from_slice(&[*c]);
} else {
// encrypt
for slot in packet.iter_mut() {
if let Some(c) = dict.get(slot) {
*slot = *c;
}
}
let matches = &packet[..] == SECRET;
packet.copy_from_slice(if matches {
led::Blue.on();
b"correct"
} else {
led::Blue.off();
b"incorrect"
});
}
rtx.write(&packet).await.ok();
}
}
};
executor::run!(task)
}