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// Copyright 2015-2018 Parity Technologies (UK) Ltd.
// This file is part of Tetsy.

// Tetsy is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Tetsy is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Tetsy.  If not, see <http://www.gnu.org/licenses/>.

//! Crypto utils used by ethstore and network.

pub mod aes;
pub mod error;
pub mod scrypt;
pub mod digest;
pub mod hmac;
pub mod pbkdf2;
#[cfg(feature = "publickey")]
pub mod publickey;

pub use crate::error::Error;

use tiny_keccak::Keccak;
use subtle::ConstantTimeEq;

pub const KEY_LENGTH: usize = 32;
pub const KEY_ITERATIONS: usize = 10240;
pub const KEY_LENGTH_AES: usize = KEY_LENGTH / 2;

/// Default authenticated data to use (in RPC).
pub const DEFAULT_MAC: [u8; 2] = [0, 0];

pub trait Keccak256<T> {
	fn keccak256(&self) -> T where T: Sized;
}

impl<T> Keccak256<[u8; 32]> for T where T: AsRef<[u8]> {
	fn keccak256(&self) -> [u8; 32] {
		let mut keccak = Keccak::new_keccak256();
		let mut result = [0u8; 32];
		keccak.update(self.as_ref());
		keccak.finalize(&mut result);
		result
	}
}

pub fn derive_key_iterations(password: &[u8], salt: &[u8], c: u32) -> (Vec<u8>, Vec<u8>) {
	let mut derived_key = [0u8; KEY_LENGTH];
	pbkdf2::sha256(c, pbkdf2::Salt(salt), pbkdf2::Secret(password), &mut derived_key);
	let derived_right_bits = &derived_key[0..KEY_LENGTH_AES];
	let derived_left_bits = &derived_key[KEY_LENGTH_AES..KEY_LENGTH];
	(derived_right_bits.to_vec(), derived_left_bits.to_vec())
}

pub fn derive_mac(derived_left_bits: &[u8], cipher_text: &[u8]) -> Vec<u8> {
	let mut mac = vec![0u8; KEY_LENGTH_AES + cipher_text.len()];
	mac[0..KEY_LENGTH_AES].copy_from_slice(derived_left_bits);
	mac[KEY_LENGTH_AES..cipher_text.len() + KEY_LENGTH_AES].copy_from_slice(cipher_text);
	mac
}

pub fn is_equal(a: &[u8], b: &[u8]) -> bool {
	a.ct_eq(b).into()
}

#[cfg(test)]
mod test {
	use super::*;

	#[test]
	fn can_test_for_equality() {
		let a = b"abc";
		let b = b"abc";
		let c = b"efg";
		assert!(is_equal(a, b));
		assert!(!is_equal(a, c));
	}
}