embedded-trainings-2020/beginner/apps/src/bin/radio-puzzle-solution-2.rs
2020-06-24 16:38:01 +02:00

95 lines
2.5 KiB
Rust

#![deny(unused_must_use)]
#![no_main]
#![no_std]
use core::str;
use cortex_m_rt::entry;
use dk::ieee802154::{Channel, Packet};
use heapless::{consts, LinearMap};
use panic_log as _; // the panicking behavior
const TEN_MS: u32 = 10_000;
#[entry]
fn main() -> ! {
let board = dk::init().unwrap();
let mut radio = board.radio;
let mut timer = board.timer;
// puzzle.hex uses channel 25
radio.set_channel(Channel::_25);
/* # Build a dictionary */
let mut dict = LinearMap::<u8, u8, consts::U128>::new();
let mut packet = Packet::new();
for plainletter in 0..=127 {
packet.copy_from_slice(&[plainletter]);
radio.send(&packet);
if radio.recv_timeout(&mut packet, &mut timer, TEN_MS).is_ok() {
// response should be one byte large
if packet.len() == 1 {
let cipherletter = packet[0];
dict.insert(cipherletter, plainletter)
.expect("dictionary full");
} else {
log::error!("response packet was not a single byte");
dk::exit()
}
} else {
log::error!("no response or response packet was corrupted");
dk::exit()
}
}
/* # Retrieve the secret string */
packet.copy_from_slice(&[]); // empty packet
radio.send(&packet);
if radio.recv_timeout(&mut packet, &mut timer, TEN_MS).is_err() {
log::error!("no response or response packet was corrupted");
dk::exit()
}
log::info!(
"ciphertext: {}",
str::from_utf8(&packet).expect("packet was not valid UTF-8")
);
/* # Decrypt the string *in place* */
// NOTE *mutably* iterate over the bytes
for spot in packet.iter_mut() {
// `spot` has type `&mut u8` and lets you modify the contents of the packet
let cipherletter = *spot; // make a copy of the byte
let key = cipherletter;
let value = dict[&key];
let plainletter = value;
// overwrite the old value with the plainletter
*spot = plainletter;
}
log::info!(
"plaintext: {}",
str::from_utf8(&packet).expect("buffer contains non-UTF-8 data")
);
/* # Verify decrypted text */
radio.send(&packet);
if radio.recv_timeout(&mut packet, &mut timer, TEN_MS).is_err() {
log::error!("no response or response packet was corrupted");
dk::exit()
}
log::info!(
"Dongle response: {}",
str::from_utf8(&packet).expect("response was not UTF-8")
);
dk::exit()
}