use nettle_sys::{
chacha_ctx, nettle_chacha_crypt, nettle_chacha_set_key,
nettle_chacha_set_nonce,
};
use std::cmp::min;
use std::mem::{MaybeUninit, transmute};
use crate::{Error, Result};
pub struct ChaCha {
context: Box<chacha_ctx>,
}
impl_zeroing_drop_for!(ChaCha);
impl ChaCha {
pub const BLOCK_SIZE: usize = ::nettle_sys::CHACHA_BLOCK_SIZE as usize;
pub const KEY_SIZE: usize = ::nettle_sys::CHACHA_KEY_SIZE as usize;
pub const NONCE_SIZE: usize = ::nettle_sys::CHACHA_NONCE_SIZE as usize;
pub fn with_key_and_nonce(key: &[u8], nonce: &[u8]) -> Result<Self> {
if key.len() != ChaCha::KEY_SIZE {
return Err(Error::InvalidArgument { argument_name: "key" });
}
if nonce.len() != ChaCha::NONCE_SIZE {
return Err(Error::InvalidArgument { argument_name: "nonce" });
}
let context = unsafe {
let mut ctx = Box::new(MaybeUninit::uninit());
nettle_chacha_set_key(ctx.as_mut_ptr(), key.as_ptr());
nettle_chacha_set_nonce(ctx.as_mut_ptr(), nonce.as_ptr());
transmute(ctx)
};
Ok(ChaCha { context })
}
pub fn crypt(&mut self, dst: &mut [u8], src: &[u8]) {
unsafe {
nettle_chacha_crypt(
self.context.as_mut() as *mut _,
min(src.len(), dst.len()),
dst.as_mut_ptr(),
src.as_ptr(),
)
};
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn set_key_and_nonce() {
let key = vec![0; 32];
let nonce = vec![1; 8];
let _ = ChaCha::with_key_and_nonce(&key, &nonce).unwrap();
}
#[test]
fn round_trip() {
let key = vec![0; 32];
let nonce = vec![1; 8];
let input = vec![
0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x10, 0x11,
0x12, 0x13, 0x14, 0x15, 0x16,
];
let mut cipher = vec![0; 16];
let mut output = vec![0; 16];
let mut enc = ChaCha::with_key_and_nonce(&key, &nonce).unwrap();
let mut dec = ChaCha::with_key_and_nonce(&key, &nonce).unwrap();
enc.crypt(&mut cipher, &input);
dec.crypt(&mut output, &cipher);
assert_eq!(output, input);
}
}