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// Copyright 2019 The CryptoCorrosion Contributors
// Copyright 2020 Developers of the Rand project.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! The ChaCha random number generator.
use ppv_lite86::{dispatch, dispatch_light128};
pub use ppv_lite86::Machine;
use ppv_lite86::{vec128_storage, ArithOps, BitOps32, LaneWords4, MultiLane, StoreBytes, Vec4};
pub(crate) const BLOCK: usize = 64;
pub(crate) const BLOCK64: u64 = BLOCK as u64;
const LOG2_BUFBLOCKS: u64 = 2;
const BUFBLOCKS: u64 = 1 << LOG2_BUFBLOCKS;
pub(crate) const BUFSZ64: u64 = BLOCK64 * BUFBLOCKS;
pub(crate) const BUFSZ: usize = BUFSZ64 as usize;
const STREAM_PARAM_NONCE: u32 = 1;
const STREAM_PARAM_BLOCK: u32 = 0;
#[derive(Clone, PartialEq, Eq)]
pub struct ChaCha {
pub(crate) b: vec128_storage,
pub(crate) c: vec128_storage,
pub(crate) d: vec128_storage,
}
#[derive(Clone)]
pub struct State<V> {
pub(crate) a: V,
pub(crate) b: V,
pub(crate) c: V,
pub(crate) d: V,
}
#[inline(always)]
pub(crate) fn round<V: ArithOps + BitOps32>(mut x: State<V>) -> State<V> {
x.a += x.b;
x.d = (x.d ^ x.a).rotate_each_word_right16();
x.c += x.d;
x.b = (x.b ^ x.c).rotate_each_word_right20();
x.a += x.b;
x.d = (x.d ^ x.a).rotate_each_word_right24();
x.c += x.d;
x.b = (x.b ^ x.c).rotate_each_word_right25();
x
}
#[inline(always)]
pub(crate) fn diagonalize<V: LaneWords4>(mut x: State<V>) -> State<V> {
x.b = x.b.shuffle_lane_words3012();
x.c = x.c.shuffle_lane_words2301();
x.d = x.d.shuffle_lane_words1230();
x
}
#[inline(always)]
pub(crate) fn undiagonalize<V: LaneWords4>(mut x: State<V>) -> State<V> {
x.b = x.b.shuffle_lane_words1230();
x.c = x.c.shuffle_lane_words2301();
x.d = x.d.shuffle_lane_words3012();
x
}
impl ChaCha {
#[inline(always)]
pub fn new(key: &[u8; 32], nonce: &[u8]) -> Self {
init_chacha(key, nonce)
}
#[inline(always)]
fn pos64<M: Machine>(&self, m: M) -> u64 {
let d: M::u32x4 = m.unpack(self.d);
((d.extract(1) as u64) << 32) | d.extract(0) as u64
}
/// Produce 4 blocks of output, advancing the state
#[inline(always)]
pub fn refill4(&mut self, drounds: u32, out: &mut [u8; BUFSZ]) {
refill_wide(self, drounds, out)
}
#[inline(always)]
pub fn set_block_pos(&mut self, value: u64) {
set_stream_param(self, STREAM_PARAM_BLOCK, value)
}
#[inline(always)]
pub fn get_block_pos(&self) -> u64 {
get_stream_param(self, STREAM_PARAM_BLOCK)
}
#[inline(always)]
pub fn set_nonce(&mut self, value: u64) {
set_stream_param(self, STREAM_PARAM_NONCE, value)
}
#[inline(always)]
pub fn get_nonce(&self) -> u64 {
get_stream_param(self, STREAM_PARAM_NONCE)
}
#[inline(always)]
pub fn get_seed(&self) -> [u8; 32] {
get_seed(self)
}
}
#[allow(clippy::many_single_char_names)]
#[inline(always)]
fn refill_wide_impl<Mach: Machine>(
m: Mach, state: &mut ChaCha, drounds: u32, out: &mut [u8; BUFSZ],
) {
let k = m.vec([0x6170_7865, 0x3320_646e, 0x7962_2d32, 0x6b20_6574]);
let mut pos = state.pos64(m);
let d0: Mach::u32x4 = m.unpack(state.d);
pos = pos.wrapping_add(1);
let d1 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
pos = pos.wrapping_add(1);
let d2 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
pos = pos.wrapping_add(1);
let d3 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
let b = m.unpack(state.b);
let c = m.unpack(state.c);
let mut x = State {
a: Mach::u32x4x4::from_lanes([k, k, k, k]),
b: Mach::u32x4x4::from_lanes([b, b, b, b]),
c: Mach::u32x4x4::from_lanes([c, c, c, c]),
d: m.unpack(Mach::u32x4x4::from_lanes([d0, d1, d2, d3]).into()),
};
for _ in 0..drounds {
x = round(x);
x = undiagonalize(round(diagonalize(x)));
}
let mut pos = state.pos64(m);
let d0: Mach::u32x4 = m.unpack(state.d);
pos = pos.wrapping_add(1);
let d1 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
pos = pos.wrapping_add(1);
let d2 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
pos = pos.wrapping_add(1);
let d3 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
pos = pos.wrapping_add(1);
let d4 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
let (a, b, c, d) = (
x.a.to_lanes(),
x.b.to_lanes(),
x.c.to_lanes(),
x.d.to_lanes(),
);
let sb = m.unpack(state.b);
let sc = m.unpack(state.c);
let sd = [m.unpack(state.d), d1, d2, d3];
state.d = d4.into();
let mut words = out.chunks_exact_mut(16);
for ((((&a, &b), &c), &d), &sd) in a.iter().zip(&b).zip(&c).zip(&d).zip(&sd) {
(a + k).write_le(words.next().unwrap());
(b + sb).write_le(words.next().unwrap());
(c + sc).write_le(words.next().unwrap());
(d + sd).write_le(words.next().unwrap());
}
}
dispatch!(m, Mach, {
fn refill_wide(state: &mut ChaCha, drounds: u32, out: &mut [u8; BUFSZ]) {
refill_wide_impl(m, state, drounds, out);
}
});
// Single-block, rounds-only; shared by try_apply_keystream for tails shorter than BUFSZ
// and XChaCha's setup step.
dispatch!(m, Mach, {
fn refill_narrow_rounds(state: &mut ChaCha, drounds: u32) -> State<vec128_storage> {
let k: Mach::u32x4 = m.vec([0x6170_7865, 0x3320_646e, 0x7962_2d32, 0x6b20_6574]);
let mut x = State {
a: k,
b: m.unpack(state.b),
c: m.unpack(state.c),
d: m.unpack(state.d),
};
for _ in 0..drounds {
x = round(x);
x = undiagonalize(round(diagonalize(x)));
}
State {
a: x.a.into(),
b: x.b.into(),
c: x.c.into(),
d: x.d.into(),
}
}
});
dispatch_light128!(m, Mach, {
fn set_stream_param(state: &mut ChaCha, param: u32, value: u64) {
let d: Mach::u32x4 = m.unpack(state.d);
state.d = d
.insert((value >> 32) as u32, (param << 1) | 1)
.insert(value as u32, param << 1)
.into();
}
});
dispatch_light128!(m, Mach, {
fn get_stream_param(state: &ChaCha, param: u32) -> u64 {
let d: Mach::u32x4 = m.unpack(state.d);
((d.extract((param << 1) | 1) as u64) << 32) | d.extract(param << 1) as u64
}
});
dispatch_light128!(m, Mach, {
fn get_seed(state: &ChaCha) -> [u8; 32] {
let b: Mach::u32x4 = m.unpack(state.b);
let c: Mach::u32x4 = m.unpack(state.c);
let mut key = [0u8; 32];
b.write_le(&mut key[..16]);
c.write_le(&mut key[16..]);
key
}
});
fn read_u32le(xs: &[u8]) -> u32 {
assert_eq!(xs.len(), 4);
u32::from(xs[0]) | (u32::from(xs[1]) << 8) | (u32::from(xs[2]) << 16) | (u32::from(xs[3]) << 24)
}
dispatch_light128!(m, Mach, {
fn init_chacha(key: &[u8; 32], nonce: &[u8]) -> ChaCha {
let ctr_nonce = [
0,
if nonce.len() == 12 {
read_u32le(&nonce[0..4])
} else {
0
},
read_u32le(&nonce[nonce.len() - 8..nonce.len() - 4]),
read_u32le(&nonce[nonce.len() - 4..]),
];
let key0: Mach::u32x4 = m.read_le(&key[..16]);
let key1: Mach::u32x4 = m.read_le(&key[16..]);
ChaCha {
b: key0.into(),
c: key1.into(),
d: ctr_nonce.into(),
}
}
});
dispatch_light128!(m, Mach, {
fn init_chacha_x(key: &[u8; 32], nonce: &[u8; 24], rounds: u32) -> ChaCha {
let key0: Mach::u32x4 = m.read_le(&key[..16]);
let key1: Mach::u32x4 = m.read_le(&key[16..]);
let nonce0: Mach::u32x4 = m.read_le(&nonce[..16]);
let mut state = ChaCha {
b: key0.into(),
c: key1.into(),
d: nonce0.into(),
};
let x = refill_narrow_rounds(&mut state, rounds);
let ctr_nonce1 = [0, 0, read_u32le(&nonce[16..20]), read_u32le(&nonce[20..24])];
state.b = x.a;
state.c = x.d;
state.d = ctr_nonce1.into();
state
}
});