85 lines
2.2 KiB
Rust
85 lines
2.2 KiB
Rust
//! ChaCha variant-specific configurations.
|
|
|
|
mod sealed {
|
|
pub trait Sealed {}
|
|
}
|
|
|
|
/// A trait that distinguishes some ChaCha variants. Contains configurations
|
|
/// for "Legacy" DJB variant and the IETF variant.
|
|
pub trait Variant: sealed::Sealed {
|
|
/// The counter's type.
|
|
#[cfg(not(feature = "cipher"))]
|
|
type Counter: Copy;
|
|
|
|
/// The counter's type.
|
|
#[cfg(feature = "cipher")]
|
|
type Counter: cipher::StreamCipherCounter;
|
|
|
|
/// Takes a slice of `state[12..NONCE_INDEX]` to convert it into
|
|
/// `Self::Counter`.
|
|
fn get_block_pos(row: &[u32]) -> Self::Counter;
|
|
|
|
/// Breaks down the `Self::Counter` type into a u32 array for setting the
|
|
/// block pos.
|
|
fn set_block_pos(row: &mut [u32], pos: Self::Counter);
|
|
|
|
/// A helper method for calculating the remaining blocks using these types
|
|
fn remaining_blocks(block_pos: Self::Counter) -> Option<usize>;
|
|
}
|
|
|
|
/// IETF ChaCha configuration to use a 32-bit counter and 96-bit nonce.
|
|
#[derive(Clone, Copy, Debug)]
|
|
pub enum Ietf {}
|
|
|
|
impl sealed::Sealed for Ietf {}
|
|
|
|
impl Variant for Ietf {
|
|
type Counter = u32;
|
|
|
|
#[inline(always)]
|
|
fn get_block_pos(row: &[u32]) -> u32 {
|
|
row[0]
|
|
}
|
|
|
|
#[inline(always)]
|
|
fn set_block_pos(row: &mut [u32], pos: u32) {
|
|
row[0] = pos;
|
|
}
|
|
|
|
#[inline(always)]
|
|
fn remaining_blocks(block_pos: u32) -> Option<usize> {
|
|
let remaining = u32::MAX - block_pos;
|
|
remaining.try_into().ok()
|
|
}
|
|
}
|
|
|
|
/// DJB variant specific features: 64-bit counter and 64-bit nonce.
|
|
#[cfg(any(feature = "legacy", feature = "rng"))]
|
|
#[derive(Clone, Copy, Debug)]
|
|
pub enum Legacy {}
|
|
|
|
#[cfg(any(feature = "legacy", feature = "rng"))]
|
|
impl sealed::Sealed for Legacy {}
|
|
|
|
#[cfg(any(feature = "legacy", feature = "rng"))]
|
|
impl Variant for Legacy {
|
|
type Counter = u64;
|
|
|
|
#[inline(always)]
|
|
fn get_block_pos(row: &[u32]) -> u64 {
|
|
(u64::from(row[1]) << 32) | u64::from(row[0])
|
|
}
|
|
|
|
#[inline(always)]
|
|
fn set_block_pos(row: &mut [u32], pos: u64) {
|
|
row[0] = (pos & 0xFFFF_FFFF) as u32;
|
|
row[1] = (pos >> 32) as u32;
|
|
}
|
|
|
|
#[inline(always)]
|
|
fn remaining_blocks(block_pos: u64) -> Option<usize> {
|
|
let remaining = u64::MAX - block_pos;
|
|
remaining.try_into().ok()
|
|
}
|
|
}
|