layer-crypto 0.5.0

// Copyright (c) Ankit Chaubey <ankitchaubey.dev@gmail.com>
// SPDX-License-Identifier: MIT OR Apache-2.0

// NOTE:
// The "Layer" project is no longer maintained or supported.
// Its original purpose for personal SDK/APK experimentation and learning
// has been fulfilled.
//
// Please use Ferogram instead:
// https://github.com/ankit-chaubey/ferogram
// Ferogram will receive future updates and development, although progress
// may be slower.
//
// Ferogram is an async Telegram MTProto client library written in Rust.
// Its implementation follows the behaviour of the official Telegram clients,
// particularly Telegram Desktop and TDLib, and aims to provide a clean and
// modern async interface for building Telegram clients and tools.

//! AES-IGE (Infinite Garble Extension): used by Telegram's MTProto.

#![allow(deprecated)]

use aes::Aes256;
use aes::cipher::generic_array::GenericArray;
use aes::cipher::{BlockDecrypt, BlockEncrypt, KeyInit};

/// Encrypt `buffer` in-place with AES-256-IGE.
/// `buffer.len()` must be a multiple of 16.
pub fn ige_encrypt(buffer: &mut [u8], key: &[u8; 32], iv: &[u8; 32]) {
    assert_eq!(buffer.len() % 16, 0);
    let cipher = Aes256::new(GenericArray::from_slice(key));

    let mut iv1: [u8; 16] = iv[..16].try_into().unwrap();
    let mut iv2: [u8; 16] = iv[16..].try_into().unwrap();
    let mut next_iv2 = [0u8; 16];

    for block in buffer.chunks_mut(16) {
        next_iv2.copy_from_slice(block);
        for i in 0..16 {
            block[i] ^= iv1[i];
        }
        cipher.encrypt_block(GenericArray::from_mut_slice(block));
        for i in 0..16 {
            block[i] ^= iv2[i];
        }
        iv1.copy_from_slice(block);
        std::mem::swap(&mut iv2, &mut next_iv2);
    }
}

/// Decrypt `buffer` in-place with AES-256-IGE.
/// `buffer.len()` must be a multiple of 16.
pub fn ige_decrypt(buffer: &mut [u8], key: &[u8; 32], iv: &[u8; 32]) {
    assert_eq!(buffer.len() % 16, 0);
    let cipher = Aes256::new(GenericArray::from_slice(key));

    let mut iv1: [u8; 16] = iv[..16].try_into().unwrap();
    let mut iv2: [u8; 16] = iv[16..].try_into().unwrap();
    let mut next_iv1 = [0u8; 16];

    for block in buffer.chunks_mut(16) {
        next_iv1.copy_from_slice(block);
        for i in 0..16 {
            block[i] ^= iv2[i];
        }
        cipher.decrypt_block(GenericArray::from_mut_slice(block));
        for i in 0..16 {
            block[i] ^= iv1[i];
        }
        std::mem::swap(&mut iv1, &mut next_iv1);
        iv2.copy_from_slice(block);
    }
}