Files
rosenpass/ciphers/src/subtle/incorrect_hmac_blake2b.rs
David Niehues a789f801ab fix formatting
2024-12-10 12:35:22 +01:00

68 lines
2.3 KiB
Rust

use anyhow::ensure;
use zeroize::Zeroizing;
use rosenpass_constant_time::xor;
use rosenpass_to::{ops::copy_slice, with_destination, To};
use crate::subtle::blake2b;
/// The key length, 32 bytes or 256 bits.
pub const KEY_LEN: usize = 32;
/// The minimal key length, identical to [KEY_LEN]
pub const KEY_MIN: usize = KEY_LEN;
/// The maximal key length, identical to [KEY_LEN]
pub const KEY_MAX: usize = KEY_LEN;
/// The minimal output length, see [blake2b::OUT_MIN]
pub const OUT_MIN: usize = blake2b::OUT_MIN;
/// The maximal output length, see [blake2b::OUT_MAX]
pub const OUT_MAX: usize = blake2b::OUT_MAX;
/// This is a woefully incorrect implementation of hmac_blake2b.
/// See <https://github.com/rosenpass/rosenpass/issues/68#issuecomment-1563612222>
///
/// It accepts 32 byte keys, exclusively.
///
/// This will be replaced, likely by Kekkac at some point soon.
/// <https://github.com/rosenpass/rosenpass/pull/145>
///
/// # Examples
///```rust
/// # use rosenpass_ciphers::subtle::incorrect_hmac_blake2b::hash;
/// use rosenpass_to::To;
/// let key: [u8; 32] = [0; 32];
/// let data: [u8; 32] = [255; 32];
/// // buffer for the hash output
/// let mut hash_data: [u8; 32] = [0u8; 32];
///
/// assert!(hash(&key, &data).to(&mut hash_data).is_ok(), "Hashing has to return OK result");
/// # let expected_hash: &[u8] = &[5, 152, 135, 141, 151, 106, 147, 8, 220, 95, 38, 66, 29, 33, 3,
/// 104, 250, 114, 131, 119, 27, 56, 59, 44, 11, 67, 230, 113, 112, 20, 80, 103];
/// # assert_eq!(hash_data, expected_hash);
///```
///
#[inline]
pub fn hash<'a>(key: &'a [u8], data: &'a [u8]) -> impl To<[u8], anyhow::Result<()>> + 'a {
const IPAD: [u8; KEY_LEN] = [0x36u8; KEY_LEN];
const OPAD: [u8; KEY_LEN] = [0x5Cu8; KEY_LEN];
with_destination(|out: &mut [u8]| {
// Not bothering with padding; the implementation
// uses appropriately sized keys.
ensure!(key.len() == KEY_LEN);
type Key = Zeroizing<[u8; KEY_LEN]>;
let mut tmp_key = Key::default();
copy_slice(key).to(tmp_key.as_mut());
xor(&IPAD).to(tmp_key.as_mut());
let mut outer_data = Key::default();
blake2b::hash(tmp_key.as_ref(), data).to(outer_data.as_mut())?;
copy_slice(key).to(tmp_key.as_mut());
xor(&OPAD).to(tmp_key.as_mut());
blake2b::hash(tmp_key.as_ref(), outer_data.as_ref()).to(out)?;
Ok(())
})
}