286 lines
9.3 KiB
Rust
286 lines
9.3 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
|
|
// file at the top-level directory of this distribution and at
|
|
// http://rust-lang.org/COPYRIGHT.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
|
// option. This file may not be copied, modified, or distributed
|
|
// except according to those terms.
|
|
|
|
//! The ChaCha random number generator.
|
|
|
|
use core::prelude::*;
|
|
|
|
use {Rng, SeedableRng, Rand};
|
|
|
|
const KEY_WORDS : uint = 8; // 8 words for the 256-bit key
|
|
const STATE_WORDS : uint = 16;
|
|
const CHACHA_ROUNDS: uint = 20; // Cryptographically secure from 8 upwards as of this writing
|
|
|
|
/// A random number generator that uses the ChaCha20 algorithm [1].
|
|
///
|
|
/// The ChaCha algorithm is widely accepted as suitable for
|
|
/// cryptographic purposes, but this implementation has not been
|
|
/// verified as such. Prefer a generator like `OsRng` that defers to
|
|
/// the operating system for cases that need high security.
|
|
///
|
|
/// [1]: D. J. Bernstein, [*ChaCha, a variant of
|
|
/// Salsa20*](http://cr.yp.to/chacha.html)
|
|
|
|
pub struct ChaChaRng {
|
|
buffer: [u32, ..STATE_WORDS], // Internal buffer of output
|
|
state: [u32, ..STATE_WORDS], // Initial state
|
|
index: uint, // Index into state
|
|
}
|
|
|
|
static EMPTY: ChaChaRng = ChaChaRng {
|
|
buffer: [0, ..STATE_WORDS],
|
|
state: [0, ..STATE_WORDS],
|
|
index: STATE_WORDS
|
|
};
|
|
|
|
|
|
macro_rules! quarter_round{
|
|
($a: expr, $b: expr, $c: expr, $d: expr) => {{
|
|
$a += $b; $d ^= $a; $d = $d.rotate_left(16);
|
|
$c += $d; $b ^= $c; $b = $b.rotate_left(12);
|
|
$a += $b; $d ^= $a; $d = $d.rotate_left( 8);
|
|
$c += $d; $b ^= $c; $b = $b.rotate_left( 7);
|
|
}}
|
|
}
|
|
|
|
macro_rules! double_round{
|
|
($x: expr) => {{
|
|
// Column round
|
|
quarter_round!($x[ 0], $x[ 4], $x[ 8], $x[12]);
|
|
quarter_round!($x[ 1], $x[ 5], $x[ 9], $x[13]);
|
|
quarter_round!($x[ 2], $x[ 6], $x[10], $x[14]);
|
|
quarter_round!($x[ 3], $x[ 7], $x[11], $x[15]);
|
|
// Diagonal round
|
|
quarter_round!($x[ 0], $x[ 5], $x[10], $x[15]);
|
|
quarter_round!($x[ 1], $x[ 6], $x[11], $x[12]);
|
|
quarter_round!($x[ 2], $x[ 7], $x[ 8], $x[13]);
|
|
quarter_round!($x[ 3], $x[ 4], $x[ 9], $x[14]);
|
|
}}
|
|
}
|
|
|
|
#[inline]
|
|
fn core(output: &mut [u32, ..STATE_WORDS], input: &[u32, ..STATE_WORDS]) {
|
|
*output = *input;
|
|
|
|
for _ in range(0, CHACHA_ROUNDS / 2) {
|
|
double_round!(output);
|
|
}
|
|
|
|
for i in range(0, STATE_WORDS) {
|
|
output[i] += input[i];
|
|
}
|
|
}
|
|
|
|
impl ChaChaRng {
|
|
|
|
/// Create an ChaCha random number generator using the default
|
|
/// fixed key of 8 zero words.
|
|
pub fn new_unseeded() -> ChaChaRng {
|
|
let mut rng = EMPTY;
|
|
rng.init(&[0, ..KEY_WORDS]);
|
|
rng
|
|
}
|
|
|
|
/// Sets the internal 128-bit ChaCha counter to
|
|
/// a user-provided value. This permits jumping
|
|
/// arbitrarily ahead (or backwards) in the pseudorandom stream.
|
|
///
|
|
/// Since the nonce words are used to extend the counter to 128 bits,
|
|
/// users wishing to obtain the conventional ChaCha pseudorandom stream
|
|
/// associated with a particular nonce can call this function with
|
|
/// arguments `0, desired_nonce`.
|
|
pub fn set_counter(&mut self, counter_low: u64, counter_high: u64) {
|
|
self.state[12] = (counter_low >> 0) as u32;
|
|
self.state[13] = (counter_low >> 32) as u32;
|
|
self.state[14] = (counter_high >> 0) as u32;
|
|
self.state[15] = (counter_high >> 32) as u32;
|
|
self.index = STATE_WORDS; // force recomputation
|
|
}
|
|
|
|
/// Initializes `self.state` with the appropriate key and constants
|
|
///
|
|
/// We deviate slightly from the ChaCha specification regarding
|
|
/// the nonce, which is used to extend the counter to 128 bits.
|
|
/// This is provably as strong as the original cipher, though,
|
|
/// since any distinguishing attack on our variant also works
|
|
/// against ChaCha with a chosen-nonce. See the XSalsa20 [1]
|
|
/// security proof for a more involved example of this.
|
|
///
|
|
/// The modified word layout is:
|
|
/// ```notrust
|
|
/// constant constant constant constant
|
|
/// key key key key
|
|
/// key key key key
|
|
/// counter counter counter counter
|
|
/// ```
|
|
/// [1]: Daniel J. Bernstein. [*Extending the Salsa20
|
|
/// nonce.*](http://cr.yp.to/papers.html#xsalsa)
|
|
fn init(&mut self, key: &[u32, ..KEY_WORDS]) {
|
|
self.state[0] = 0x61707865;
|
|
self.state[1] = 0x3320646E;
|
|
self.state[2] = 0x79622D32;
|
|
self.state[3] = 0x6B206574;
|
|
|
|
for i in range(0, KEY_WORDS) {
|
|
self.state[4+i] = key[i];
|
|
}
|
|
|
|
self.state[12] = 0;
|
|
self.state[13] = 0;
|
|
self.state[14] = 0;
|
|
self.state[15] = 0;
|
|
|
|
self.index = STATE_WORDS;
|
|
}
|
|
|
|
/// Refill the internal output buffer (`self.buffer`)
|
|
fn update(&mut self) {
|
|
core(&mut self.buffer, &self.state);
|
|
self.index = 0;
|
|
// update 128-bit counter
|
|
self.state[12] += 1;
|
|
if self.state[12] != 0 { return };
|
|
self.state[13] += 1;
|
|
if self.state[13] != 0 { return };
|
|
self.state[14] += 1;
|
|
if self.state[14] != 0 { return };
|
|
self.state[15] += 1;
|
|
}
|
|
}
|
|
|
|
impl Rng for ChaChaRng {
|
|
#[inline]
|
|
fn next_u32(&mut self) -> u32 {
|
|
if self.index == STATE_WORDS {
|
|
self.update();
|
|
}
|
|
|
|
let value = self.buffer[self.index % STATE_WORDS];
|
|
self.index += 1;
|
|
value
|
|
}
|
|
}
|
|
|
|
impl<'a> SeedableRng<&'a [u32]> for ChaChaRng {
|
|
|
|
fn reseed(&mut self, seed: &'a [u32]) {
|
|
// reset state
|
|
self.init(&[0u32, ..KEY_WORDS]);
|
|
// set key in place
|
|
let key = self.state.slice_mut(4, 4+KEY_WORDS);
|
|
for (k, s) in key.iter_mut().zip(seed.iter()) {
|
|
*k = *s;
|
|
}
|
|
}
|
|
|
|
/// Create a ChaCha generator from a seed,
|
|
/// obtained from a variable-length u32 array.
|
|
/// Only up to 8 words are used; if less than 8
|
|
/// words are used, the remaining are set to zero.
|
|
fn from_seed(seed: &'a [u32]) -> ChaChaRng {
|
|
let mut rng = EMPTY;
|
|
rng.reseed(seed);
|
|
rng
|
|
}
|
|
}
|
|
|
|
impl Rand for ChaChaRng {
|
|
fn rand<R: Rng>(other: &mut R) -> ChaChaRng {
|
|
let mut key : [u32, ..KEY_WORDS] = [0, ..KEY_WORDS];
|
|
for word in key.iter_mut() {
|
|
*word = other.gen();
|
|
}
|
|
SeedableRng::from_seed(key.as_slice())
|
|
}
|
|
}
|
|
|
|
|
|
#[cfg(test)]
|
|
mod test {
|
|
use std::prelude::*;
|
|
|
|
use core::iter::order;
|
|
use {Rng, SeedableRng};
|
|
use super::ChaChaRng;
|
|
|
|
#[test]
|
|
fn test_rng_rand_seeded() {
|
|
let s = ::test::rng().gen_iter::<u32>().take(8).collect::<Vec<u32>>();
|
|
let mut ra: ChaChaRng = SeedableRng::from_seed(s.as_slice());
|
|
let mut rb: ChaChaRng = SeedableRng::from_seed(s.as_slice());
|
|
assert!(order::equals(ra.gen_ascii_chars().take(100),
|
|
rb.gen_ascii_chars().take(100)));
|
|
}
|
|
|
|
#[test]
|
|
fn test_rng_seeded() {
|
|
let seed : &[_] = &[0,1,2,3,4,5,6,7];
|
|
let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
|
|
let mut rb: ChaChaRng = SeedableRng::from_seed(seed);
|
|
assert!(order::equals(ra.gen_ascii_chars().take(100),
|
|
rb.gen_ascii_chars().take(100)));
|
|
}
|
|
|
|
#[test]
|
|
fn test_rng_reseed() {
|
|
let s = ::test::rng().gen_iter::<u32>().take(8).collect::<Vec<u32>>();
|
|
let mut r: ChaChaRng = SeedableRng::from_seed(s.as_slice());
|
|
let string1: String = r.gen_ascii_chars().take(100).collect();
|
|
|
|
r.reseed(s.as_slice());
|
|
|
|
let string2: String = r.gen_ascii_chars().take(100).collect();
|
|
assert_eq!(string1, string2);
|
|
}
|
|
|
|
#[test]
|
|
fn test_rng_true_values() {
|
|
// Test vectors 1 and 2 from
|
|
// http://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
|
|
let seed : &[_] = &[0u32, ..8];
|
|
let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
|
|
|
|
let v = Vec::from_fn(16, |_| ra.next_u32());
|
|
assert_eq!(v,
|
|
vec!(0xade0b876, 0x903df1a0, 0xe56a5d40, 0x28bd8653,
|
|
0xb819d2bd, 0x1aed8da0, 0xccef36a8, 0xc70d778b,
|
|
0x7c5941da, 0x8d485751, 0x3fe02477, 0x374ad8b8,
|
|
0xf4b8436a, 0x1ca11815, 0x69b687c3, 0x8665eeb2));
|
|
|
|
let v = Vec::from_fn(16, |_| ra.next_u32());
|
|
assert_eq!(v,
|
|
vec!(0xbee7079f, 0x7a385155, 0x7c97ba98, 0x0d082d73,
|
|
0xa0290fcb, 0x6965e348, 0x3e53c612, 0xed7aee32,
|
|
0x7621b729, 0x434ee69c, 0xb03371d5, 0xd539d874,
|
|
0x281fed31, 0x45fb0a51, 0x1f0ae1ac, 0x6f4d794b));
|
|
|
|
|
|
let seed : &[_] = &[0,1,2,3,4,5,6,7];
|
|
let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
|
|
|
|
// Store the 17*i-th 32-bit word,
|
|
// i.e., the i-th word of the i-th 16-word block
|
|
let mut v : Vec<u32> = Vec::new();
|
|
for _ in range(0u, 16) {
|
|
v.push(ra.next_u32());
|
|
for _ in range(0u, 16) {
|
|
ra.next_u32();
|
|
}
|
|
}
|
|
|
|
assert_eq!(v,
|
|
vec!(0xf225c81a, 0x6ab1be57, 0x04d42951, 0x70858036,
|
|
0x49884684, 0x64efec72, 0x4be2d186, 0x3615b384,
|
|
0x11cfa18e, 0xd3c50049, 0x75c775f6, 0x434c6530,
|
|
0x2c5bad8f, 0x898881dc, 0x5f1c86d9, 0xc1f8e7f4));
|
|
}
|
|
}
|
|
|