src/auth.rs


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use hmac::{Hmac, Mac};
use rand::{rngs::OsRng, RngCore};
use sha2::Sha256;

// Generate a random nonce
pub fn generate_nonce() -> String {
    let mut bytes = [0u8; 16];
    OsRng.fill_bytes(&mut bytes);
    hex::encode(bytes)
}

// Calculate HMAC using the shared secret
pub fn calculate_hmac(secret: &str, data: &str) -> String {
    type HmacSha256 = Hmac<Sha256>;
    let mut mac = HmacSha256::new_from_slice(secret.as_bytes())
        .expect("HMAC can take key of any size");
    
    mac.update(data.as_bytes());
    let result = mac.finalize();
    let code_bytes = result.into_bytes();
    
    hex::encode(code_bytes)
}

// Verify an HMAC token
pub fn verify_hmac(secret: &str, data: &str, expected: &str) -> bool {
    let calculated = calculate_hmac(secret, data);
    calculated == expected
}