Add comments

.gitignore

@@ -1 +1,3 @@
 /target
+
+Cargo.lock

Cargo.toml

@@ -12,3 +12,6 @@ binascii = { version = "0.1", default-features = false, features = ["decode"] }
 [profile.release]
 lto = true
 panic = "abort"
+strip = true
+opt-level = "z"
+codegen-units = 1

build.sh

@@ -1,2 +1 @@
 cargo build -Z build-std=core --target avr-atmega328p.json --release
-avr-objcopy -O ihex -R .eeprom target/avr-atmega328p/release/rustytoken.elf rustytoken.hex

src/main.rs

@@ -1,23 +1,27 @@
-// #![no_std]
+#![no_std]
-// #![no_main]
+#![no_main]
 
 mod crypto;
 
 use arduino_hal::hal::usart::BaudrateArduinoExt;
 use arduino_hal::prelude::*;
 use arduino_hal::{delay_ms, Usart};
-use binascii::b32decode;
 use crypto::hmac_sha1;
-use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
-// use panic_halt as _;
+use panic_halt as _;
 
 const INTERVAL: u64 = 30;
+const SECRET_KEY_MAX_LEN: u8 = 32;
 
 fn process_secret<'a>(secret: &str, output: &mut [u8]) -> usize {
-    let mut result = [0u8; 32];
+    // RFC 6238 Doesn't specify a max length for the secret keys, So I chose 32
+    // You can change the max length by modifying the const
+    let mut result = [0u8; SECRET_KEY_MAX_LEN];
     let mut inc = 0;
-    let offset = 8 - (secret.len() % 8);
+    let offset = match 8 - (secret.len() % 8) {
+        8 => 0,
+        n => n,
+    };
 
     for c in secret.chars() {
         result[inc] = c.to_ascii_uppercase() as u8;
@@ -30,73 +34,63 @@ fn process_secret<'a>(secret: &str, output: &mut [u8]) -> usize {
 
     let decoded = match binascii::b32decode(&result[..inc], output).ok() {
         Some(bytes) => bytes,
-        None => "".as_bytes(),
+        None => "".as_bytes(), // TODO: Implement a way to display errors
     };
     decoded.len()
 }
 
-fn generate_otp_token(private_key: &str, actual_time: u64) -> u64 {
+fn generate_otp_token(private_key: &str, actual_time: u64) -> u32 {
-    let mut output = [0u8; 200];
+    let mut output = [0u8; 50];
     let private_key_len = process_secret(private_key, &mut output);
 
     let interval = actual_time / INTERVAL;
     let msg = interval.to_be_bytes();
 
-    println!("key:\n{private_key:?}");
-    println!("msg:\n{msg:?}");
-
     let mut hmac_digest = [0u8; 20];
     hmac_sha1(&output[..private_key_len], &msg, &mut hmac_digest);
-    println!("{:?}", hmac_digest);
 
     let start = (hmac_digest[19] & 0xF) as usize;
-    println!("Start before process: {}", hmac_digest[19]);
-    println!("start: {start}");
     let bytes: [u8; 4] = hmac_digest[start..start + 4].try_into().unwrap();
-    println!("bytes: {bytes:?}");
 
     let raw_token = u32::from_be_bytes(bytes);
-    println!("raw token: {raw_token}");
+    ((raw_token & 0x7F_FF_FF_FF) % 1_000_000) as u32
-    ((raw_token & 0x7F_FF_FF_FF) % 1_000_000) as u64
 }
 
-fn main() {
+fn token_to_bytes(mut token: u32, output: &mut [u8]) {
-    // let now = SystemTime::now();
+    let mut inc = 0;
-    // let elapsed = now.duration_since(UNIX_EPOCH).unwrap();
+    while token > 0 {
-    // let seconds = elapsed.as_secs();
+        output[inc] = (token % 10) as u8 + b'0';
-    // println!("seconds: {seconds}");
+        token /= 10;
+        inc += 1;
+    }
+    output.reverse()
+}
 
-    // let otp_token = generate_otp_token("holaaaaamundo", seconds);
+#[arduino_hal::entry]
+fn main() -> ! {
+    let dp = arduino_hal::Peripherals::take().unwrap();
+    let pins = arduino_hal::pins!(dp);
 
-    // println!("{:06}", otp_token);
+    let mut led = pins.d13.into_output();
-    // std::thread::sleep(Duration::from_secs(1));
+    let mut serial = Usart::new(
+        dp.USART0,
+        pins.d0,
+        pins.d1.into_output(),
+        BaudrateArduinoExt::into_baudrate(9600),
+    );
+
+    // let token = generate_otp_token("holaaaaamundo", 1680155315);
+    let token = generate_otp_token("FS7J22EHLLSOGKUVJKV2XE7FTIX24JAJ", 1680155315);
+    let mut output = [0u8; 6];
+    token_to_bytes(token, &mut output);
+
+    for b in output {
+        serial.write_byte(b);
+    }
+    serial.write_byte('\n' as u8);
 
     loop {
-        let now = SystemTime::now();
+        led.toggle();
-        let elapsed = now.duration_since(UNIX_EPOCH).unwrap();
+        delay_ms(1000);
-        let seconds = elapsed.as_secs();
-
-        let otp_token = generate_otp_token("holaaaaamundo", seconds);
-        println!("{:06}", otp_token);
-        std::thread::sleep(Duration::from_secs(1));
     }
 }
-
-// #[arduino_hal::entry]
-// fn main() -> ! {
-//     let dp = arduino_hal::Peripherals::take().unwrap();
-//     let pins = arduino_hal::pins!(dp);
-//
-//     let mut led = pins.d13.into_output();
-//     let mut serial = Usart::new(
-//         dp.USART0,
-//         pins.d0,
-//         pins.d1.into_output(),
-//         BaudrateArduinoExt::into_baudrate(9600),
-//     );
-//
-//     loop {
-//         led.toggle();
-//         delay_ms(1000);
-//     }
-// }

upload.sh

@@ -1 +1 @@
-avrdude -p atmega328p -c arduino -P /dev/ttyACM0 -U flash:w:rustytoken.hex:i
+avrdude -p atmega328p -c arduino -P /dev/ttyACM0 -U flash:w:target/avr-atmega328p/release/rustytoken.elf:e