use aes::{Aes128, Aes192, Aes256};
use cmac::{Cmac, Mac, NewMac};
use std::{
cmp::min,
ops::DerefMut,
sync::{Arc, Mutex},
};
use tink_core::TinkError;
const RECOMMENDED_KEY_SIZE: usize = 32;
const AES_BLOCK_SIZE_IN_BYTES: usize = 16;
enum AesCmacVariant {
Aes128(Box<Cmac<Aes128>>),
Aes192(Box<Cmac<Aes192>>),
Aes256(Box<Cmac<Aes256>>),
}
#[derive(Clone)]
pub struct AesCmacPrf {
mac: Arc<Mutex<AesCmacVariant>>,
}
impl AesCmacPrf {
pub fn new(key: &[u8]) -> Result<AesCmacPrf, TinkError> {
let aes_cmac = match key.len() {
16 => AesCmacVariant::Aes128(Box::new(
Cmac::<Aes128>::new_from_slice(key).map_err(|_| "failed to create key")?,
)),
24 => AesCmacVariant::Aes192(Box::new(
Cmac::<Aes192>::new_from_slice(key).map_err(|_| "failed to create key")?,
)),
32 => AesCmacVariant::Aes256(Box::new(
Cmac::<Aes256>::new_from_slice(key).map_err(|_| "failed to create key")?,
)),
_ => return Err("AesCmacPrf: invalid key length for AES".into()),
};
Ok(AesCmacPrf {
mac: Arc::new(Mutex::new(aes_cmac)),
})
}
}
pub fn validate_aes_cmac_prf_params(key_size: usize) -> Result<(), TinkError> {
if key_size != RECOMMENDED_KEY_SIZE {
Err(format!(
"Recommended key size for AES-CMAC is {}, but {} given",
RECOMMENDED_KEY_SIZE, key_size
)
.into())
} else {
Ok(())
}
}
impl tink_core::Prf for AesCmacPrf {
fn compute_prf(&self, data: &[u8], output_length: usize) -> Result<Vec<u8>, TinkError> {
if output_length > AES_BLOCK_SIZE_IN_BYTES {
return Err(format!(
"AesCmacPrf: output_length must be between 0 and {}",
AES_BLOCK_SIZE_IN_BYTES
)
.into());
}
Ok(
match self
.mac
.lock()
.expect("internal lock corrupted") .deref_mut()
{
AesCmacVariant::Aes128(mac) => {
mac.update(data);
let result = mac.finalize_reset().into_bytes();
result[..min(result.len(), output_length)].to_vec()
}
AesCmacVariant::Aes192(mac) => {
mac.update(data);
let result = mac.finalize_reset().into_bytes();
result[..min(result.len(), output_length)].to_vec()
}
AesCmacVariant::Aes256(mac) => {
mac.update(data);
let result = mac.finalize_reset().into_bytes();
result[..min(result.len(), output_length)].to_vec()
}
},
)
}
}