first totp POC

.gitignore

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+/target

Cargo.toml

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+[package]
+name = "rust-totp"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+actix-web = "4"
+base32 = "0.5.1"
+chrono = "0.4.37"
+futures-util = "0.3.30"
+hmac = "0.12.1"
+hmac-sha1 = "0.2.2"
+sha1 = "0.10.6"

src/main.rs

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+mod totp;
+use totp::*;
+
+fn main() {
+    let mut totpdata = totp::TOTPData {
+        time_validity:30,
+        seed: String::from("JBSWY3DPEHPK3PXP"),
+        last_totp: 0,
+        generation_time: 0,
+        issuer: String::from("you"),
+        digits: 6
+    };
+    let opt = totpdata.get_totp();
+    println!("{:0width$}", opt, width = totpdata.digits as usize);
+}

src/totp.rs

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+use std::time::{SystemTime, UNIX_EPOCH};
+use sha1::Sha1;
+use hmac::{Hmac, Mac};
+use base32::Alphabet;
+
+type HmacSha1 = Hmac<Sha1>;
+
+pub trait TOTP{
+    fn get_totp(&mut self) -> u32;
+    fn set_new_totp(&mut self, now: &u64);
+}
+
+pub struct TOTPData{
+    pub time_validity: u64,
+    pub seed: String,
+    pub last_totp: u32,
+    pub generation_time: u64,
+    pub issuer: String,
+    pub digits: u32
+}
+
+impl TOTP for TOTPData {
+    fn get_totp(&mut self) -> u32 {
+        let now:u64 = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .expect("")
+            .as_secs();
+
+        if self.generation_time + self.time_validity < now {
+            self.set_new_totp(&now);
+        }
+        return self.last_totp.clone();
+    }
+
+    fn set_new_totp(&mut self, now: &u64) {
+        let t = (now/self.time_validity).to_be_bytes();
+        self.generation_time = now.clone();
+        let key = base32::decode(Alphabet::Rfc4648 {padding: false}, self.seed.as_str()).expect("Invalid Base32 encoding");
+        let mut mac = HmacSha1::new_from_slice(&key).expect("HMAC can take key of any size");
+        mac.update(&t);
+        let result = mac.finalize().into_bytes();
+        let offset = (result[result.len() -1] & 0x0F) as usize;
+        let truncated_hash = &result[offset..offset+4];
+        let binary_code = ((truncated_hash[0] as u32) << 24)
+            | ((truncated_hash[1] as u32) << 16)
+            | ((truncated_hash[2] as u32) << 8)
+            | (truncated_hash[3] as u32);
+        let otp = (binary_code & 0x7FFFFFFF) % 10_u32.pow(self.digits); 
+        self.last_totp = otp
+    }
+}
+