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use crate::{Cipher, CryptoError, Digest, CryptoErrorKind};
use crate::cmac::const_tables::{RB_128, RB_64, RB_32, RB_48, RB_96, RB_160, RB_192, RB_224, RB_256, RB_320, RB_384, RB_448, RB_512, RB_768, RB_1024, RB_2048};
pub struct CMAC<C> {
k1: Vec<u8>,
k2: Vec<u8>,
data: Vec<u8>,
nonce: Vec<u8>,
is_check: bool,
cipher: C,
}
impl<C: 'static + Cipher> CMAC<C> {
fn shl_one(l: &Vec<u8>, k1: &mut Vec<u8>) {
k1.clear();
let mut cur = (*l.first().unwrap()) << 1;
l.iter().skip(1).for_each(|&a| {
cur |= a >> 7;
k1.push(cur);
cur = a << 1;
});
k1.push(cur);
}
fn subkey_gen(c: &C, k1: &mut Vec<u8>, k2: &mut Vec<u8>, rb: &[u8]) -> Result<(), CryptoError> {
let block_len = c.block_size().unwrap();
k1.resize(block_len, 0);
c.encrypt(k2, k1.as_slice()).map(|_|{})?;
Self::shl_one(k2, k1);
if (k2.first().unwrap() >> 7) > 0 {
k1.iter_mut().zip(rb.iter()).for_each(|(a, &b)| {
*a ^= b;
});
}
Self::shl_one(k1, k2);
if (k1.first().unwrap() >> 7) > 0 {
k2.iter_mut().zip(rb.iter()).for_each(|(a, &b)| {
*a ^= b;
});
}
Ok(())
}
fn block_size_to_rb(block_size: usize) -> Option<u32> {
match block_size {
4 => Some(RB_32),
6 => Some(RB_48),
8 => Some(RB_64),
12 => Some(RB_96),
16 => Some(RB_128),
20 => Some(RB_160),
24 => Some(RB_192),
28 => Some(RB_224),
32 => Some(RB_256),
40 => Some(RB_320),
48 => Some(RB_384),
56 => Some(RB_448),
64 => Some(RB_512),
96 => Some(RB_768),
128 => Some(RB_1024),
256 => Some(RB_2048),
_ => None,
}
}
pub fn is_support(c: &C) -> bool {
match c.block_size() {
Some(b) => Self::block_size_to_rb(b).is_some(),
None => false,
}
}
pub fn new(c: C) -> Result<Self, CryptoError> {
let (b, rb) = if Self::is_support(&c) {
let b = c.block_size().unwrap();
let x = Self::block_size_to_rb(b).unwrap();
let mut buf = Vec::with_capacity(b);
buf.resize(b, 0u8);
buf.iter_mut().rev().zip(x.to_le_bytes().iter()).for_each(|(a, &b)| {
*a = b;
});
(b, buf)
} else {
return Err(CryptoError::new(CryptoErrorKind::InvalidParameter, format!("Does not support the block size of {}", std::any::type_name::<C>())));
};
let (mut k1, mut k2) = (Vec::with_capacity(b), Vec::with_capacity(b));
let mut nonce = Vec::new();
nonce.resize(b, 0);
Self::subkey_gen(&c, &mut k1, &mut k2, rb.as_slice()).map(|_| {Self {
k1,
k2,
nonce,
data: Vec::with_capacity(b),
is_check: false,
cipher: c,
}})
}
}
impl<C: Cipher> Digest for CMAC<C> {
fn block_size(&self) -> Option<usize> {
self.cipher.block_size()
}
fn bits_len(&self) -> usize {
self.cipher.block_size().unwrap() << 3
}
fn write(&mut self, data: &[u8]) {
let b = self.block_size().unwrap();
if self.is_check {
self.nonce.clear();
self.nonce.resize(b, 0);
self.is_check = false;
}
let mut data = if (data.len() + self.data.len()) < b {
self.data.extend_from_slice(data);
&data[data.len()..]
} else {
let len = b - self.data.len();
self.data.extend_from_slice(&data[..len]);
&data[len..]
};
if (self.data.len() + data.len()) > b {
self.data.iter_mut().zip(self.nonce.iter()).for_each(|(a, &b)| {
*a ^= b;
});
self.cipher.encrypt(&mut self.nonce, self.data.as_slice()).unwrap();
while data.len() > b {
let txt = &data[..b];
self.data.iter_mut().zip(self.nonce.iter().zip(txt.iter())).for_each(|(a, (&b, &c))| {
*a = b ^ c;
});
self.cipher.encrypt(&mut self.nonce, self.data.as_slice()).unwrap();
data = &data[b..];
}
}
if !data.is_empty() {
self.data.clear();
self.data.extend_from_slice(data);
}
}
fn checksum(&mut self, digest: &mut Vec<u8>) {
if !self.is_check {
let b = self.block_size().unwrap();
if self.data.len() == b {
self.data.iter_mut().zip(self.nonce.iter().zip(self.k1.iter())).for_each(|(a, (&b, &c))| {
*a = ((*a) ^ c) ^ b;
});
} else {
self.data.push(0x80);
self.data.resize(b, 0);
self.data.iter_mut().zip(self.nonce.iter().zip(self.k2.iter())).for_each(|(a, (&b, &c))| {
*a = ((*a) ^ c) ^ b;
});
}
self.cipher.encrypt(&mut self.nonce, self.data.as_slice()).unwrap();
self.data.clear();
self.is_check = true;
}
digest.clear();
digest.extend(self.nonce.iter());
}
fn reset(&mut self) {
let b = self.block_size().unwrap();
self.nonce.clear();
self.nonce.resize(b, 0);
self.data.clear();
self.is_check = false;
}
}