rust-nex/prudpv0/src/crypto/friends_secure.rs

use hmac::Mac;
use rc4::{Rc4, StreamCipher};
use rnex_core::prudp::{
    encryption::EncryptionPair,
    types_flags::{TypesFlags, types::DATA},
};
use typenum::U32;

use crate::crypto::{
    Crypto, CryptoInstance,
    common_crypto::common_checksum,
    friends_common::{ACCESS_KEY, HmacMd5},
};

pub struct SecureInstance {
    pair: EncryptionPair<Rc4<U32>>,
    uid: u32,
    self_signat: [u8; 4],
    remote_signat: [u8; 4],
}

impl CryptoInstance for SecureInstance {
    fn decrypt_incoming(&mut self, data: &mut [u8]) {
        self.pair.recv.apply_keystream(data);
    }
    fn encrypt_outgoing(&mut self, data: &mut [u8]) {
        self.pair.send.apply_keystream(data);
    }
    fn get_user_id(&self) -> u32 {
        self.uid
    }
    fn generate_signature(&self, types_flags: TypesFlags, data: &[u8]) -> [u8; 4] {
        if types_flags.get_types() == DATA {
            if data.len() == 0 {
                [0x78, 0x56, 0x34, 0x12]
            } else {
                let mut hmac = <HmacMd5 as Mac>::new_from_slice(ACCESS_KEY.as_bytes())
                    .expect("unable to create hmac md5");
                hmac.update(data);
                hmac.finalize().into_bytes()[0..4].try_into().unwrap()
            }
        } else {
            self.self_signat
        }
    }
}

pub struct Secure();

impl Crypto for Secure {
    type Instance = SecureInstance;
    fn new() -> Self {
        Self()
    }
    fn calculate_checksum(&self, data: &[u8]) -> u8 {
        common_checksum(ACCESS_KEY, data)
    }
    fn instantiate(
        &self,
        data: &[u8],
        self_signat: [u8; 4],
        remote_signat: [u8; 4],
    ) -> Self::Instance {
        todo!()
    }
}