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#![no_std]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![doc(
html_logo_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg",
html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg"
)]
#![deny(unsafe_code)]
#![warn(missing_docs, rust_2018_idioms)]
pub use aead::{self, AeadInPlace, Error, NewAead};
use block_cipher::{
consts::{U0, U16},
generic_array::functional::FunctionalSequence,
generic_array::{ArrayLength, GenericArray},
Block, BlockCipher, Key, NewBlockCipher,
};
use cmac::crypto_mac::NewMac;
use cmac::{Cmac, Mac};
use ctr::stream_cipher::{FromBlockCipher, SyncStreamCipher};
pub const A_MAX: u64 = 1 << 36;
pub const P_MAX: u64 = 1 << 36;
pub const C_MAX: u64 = (1 << 36) + 16;
pub type Tag = GenericArray<u8, U16>;
#[derive(Clone)]
pub struct Eax<Cipher>
where
Cipher: BlockCipher<BlockSize = U16> + NewBlockCipher + Clone,
Cipher::ParBlocks: ArrayLength<Block<Cipher>>,
{
key: Key<Cipher>,
}
impl<Cipher> NewAead for Eax<Cipher>
where
Cipher: BlockCipher<BlockSize = U16> + NewBlockCipher + Clone,
Cipher::ParBlocks: ArrayLength<Block<Cipher>>,
{
type KeySize = Cipher::KeySize;
fn new(key: &Key<Cipher>) -> Self {
Self { key: key.clone() }
}
}
impl<Cipher> AeadInPlace for Eax<Cipher>
where
Cipher: BlockCipher<BlockSize = U16> + NewBlockCipher + Clone,
Cipher::ParBlocks: ArrayLength<Block<Cipher>>,
{
type NonceSize = Cipher::BlockSize;
type TagSize = <Cmac<Cipher> as Mac>::OutputSize;
type CiphertextOverhead = U0;
fn encrypt_in_place_detached(
&self,
nonce: &GenericArray<u8, Self::NonceSize>,
associated_data: &[u8],
buffer: &mut [u8],
) -> Result<Tag, Error> {
if buffer.len() as u64 > P_MAX || associated_data.len() as u64 > A_MAX {
return Err(Error);
}
let n = Self::cmac_with_iv(&self.key, 0, nonce);
let h = Self::cmac_with_iv(&self.key, 1, associated_data);
let mut cipher = ctr::Ctr128::<Cipher>::from_block_cipher(Cipher::new(&self.key), &n);
cipher.apply_keystream(buffer);
let c = Self::cmac_with_iv(&self.key, 2, buffer);
Ok(n.zip(h, |a, b| a ^ b).zip(c, |a, b| a ^ b))
}
fn decrypt_in_place_detached(
&self,
nonce: &GenericArray<u8, Self::NonceSize>,
associated_data: &[u8],
buffer: &mut [u8],
tag: &Tag,
) -> Result<(), Error> {
if buffer.len() as u64 > C_MAX || associated_data.len() as u64 > A_MAX {
return Err(Error);
}
let n = Self::cmac_with_iv(&self.key, 0, nonce);
let h = Self::cmac_with_iv(&self.key, 1, associated_data);
let c = Self::cmac_with_iv(&self.key, 2, buffer);
let expected_tag = n.zip(h, |a, b| a ^ b).zip(c, |a, b| a ^ b);
let expected_tag = &expected_tag[..tag.len()];
use subtle::ConstantTimeEq;
if expected_tag.ct_eq(tag).unwrap_u8() == 1 {
let mut cipher = ctr::Ctr128::<Cipher>::from_block_cipher(Cipher::new(&self.key), &n);
cipher.apply_keystream(buffer);
Ok(())
} else {
Err(Error)
}
}
}
impl<Cipher> Eax<Cipher>
where
Cipher: BlockCipher<BlockSize = U16> + NewBlockCipher + Clone,
Cipher::ParBlocks: ArrayLength<Block<Cipher>>,
{
fn cmac_with_iv(
key: &GenericArray<u8, Cipher::KeySize>,
iv: u8,
data: &[u8],
) -> GenericArray<u8, <Cmac<Cipher> as Mac>::OutputSize> {
let mut mac = Cmac::<Cipher>::new(key);
mac.update(&[0; 15]);
mac.update(&[iv]);
mac.update(data);
mac.finalize().into_bytes()
}
}