56290a0044
This commit is an implementation of [RFC 503][rfc] which is a stabilization story for the prelude. Most of the RFC was directly applied, removing reexports. Some reexports are kept around, however: * `range` remains until range syntax has landed to reduce churn. * `Path` and `GenericPath` remain until path reform lands. This is done to prevent many imports of `GenericPath` which will soon be removed. * All `io` traits remain until I/O reform lands so imports can be rewritten all at once to `std::io::prelude::*`. This is a breaking change because many prelude reexports have been removed, and the RFC can be consulted for the exact list of removed reexports, as well as to find the locations of where to import them. [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0503-prelude-stabilization.md [breaking-change] Closes #20068
288 lines
9.4 KiB
Rust
288 lines
9.4 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! The ChaCha random number generator.
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use core::prelude::*;
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use core::num::Int;
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use {Rng, SeedableRng, Rand};
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const KEY_WORDS : uint = 8; // 8 words for the 256-bit key
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const STATE_WORDS : uint = 16;
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const CHACHA_ROUNDS: uint = 20; // Cryptographically secure from 8 upwards as of this writing
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/// A random number generator that uses the ChaCha20 algorithm [1].
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///
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/// The ChaCha algorithm is widely accepted as suitable for
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/// cryptographic purposes, but this implementation has not been
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/// verified as such. Prefer a generator like `OsRng` that defers to
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/// the operating system for cases that need high security.
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///
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/// [1]: D. J. Bernstein, [*ChaCha, a variant of
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/// Salsa20*](http://cr.yp.to/chacha.html)
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#[deriving(Copy)]
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pub struct ChaChaRng {
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buffer: [u32; STATE_WORDS], // Internal buffer of output
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state: [u32; STATE_WORDS], // Initial state
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index: uint, // Index into state
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}
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static EMPTY: ChaChaRng = ChaChaRng {
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buffer: [0; STATE_WORDS],
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state: [0; STATE_WORDS],
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index: STATE_WORDS
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};
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macro_rules! quarter_round{
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($a: expr, $b: expr, $c: expr, $d: expr) => {{
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$a += $b; $d ^= $a; $d = $d.rotate_left(16);
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$c += $d; $b ^= $c; $b = $b.rotate_left(12);
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$a += $b; $d ^= $a; $d = $d.rotate_left( 8);
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$c += $d; $b ^= $c; $b = $b.rotate_left( 7);
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}}
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}
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macro_rules! double_round{
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($x: expr) => {{
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// Column round
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quarter_round!($x[ 0], $x[ 4], $x[ 8], $x[12]);
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quarter_round!($x[ 1], $x[ 5], $x[ 9], $x[13]);
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quarter_round!($x[ 2], $x[ 6], $x[10], $x[14]);
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quarter_round!($x[ 3], $x[ 7], $x[11], $x[15]);
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// Diagonal round
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quarter_round!($x[ 0], $x[ 5], $x[10], $x[15]);
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quarter_round!($x[ 1], $x[ 6], $x[11], $x[12]);
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quarter_round!($x[ 2], $x[ 7], $x[ 8], $x[13]);
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quarter_round!($x[ 3], $x[ 4], $x[ 9], $x[14]);
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}}
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}
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#[inline]
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fn core(output: &mut [u32; STATE_WORDS], input: &[u32; STATE_WORDS]) {
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*output = *input;
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for _ in range(0, CHACHA_ROUNDS / 2) {
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double_round!(output);
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}
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for i in range(0, STATE_WORDS) {
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output[i] += input[i];
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}
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}
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impl ChaChaRng {
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/// Create an ChaCha random number generator using the default
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/// fixed key of 8 zero words.
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pub fn new_unseeded() -> ChaChaRng {
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let mut rng = EMPTY;
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rng.init(&[0; KEY_WORDS]);
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rng
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}
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/// Sets the internal 128-bit ChaCha counter to
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/// a user-provided value. This permits jumping
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/// arbitrarily ahead (or backwards) in the pseudorandom stream.
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///
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/// Since the nonce words are used to extend the counter to 128 bits,
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/// users wishing to obtain the conventional ChaCha pseudorandom stream
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/// associated with a particular nonce can call this function with
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/// arguments `0, desired_nonce`.
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pub fn set_counter(&mut self, counter_low: u64, counter_high: u64) {
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self.state[12] = (counter_low >> 0) as u32;
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self.state[13] = (counter_low >> 32) as u32;
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self.state[14] = (counter_high >> 0) as u32;
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self.state[15] = (counter_high >> 32) as u32;
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self.index = STATE_WORDS; // force recomputation
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}
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/// Initializes `self.state` with the appropriate key and constants
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///
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/// We deviate slightly from the ChaCha specification regarding
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/// the nonce, which is used to extend the counter to 128 bits.
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/// This is provably as strong as the original cipher, though,
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/// since any distinguishing attack on our variant also works
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/// against ChaCha with a chosen-nonce. See the XSalsa20 [1]
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/// security proof for a more involved example of this.
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///
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/// The modified word layout is:
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/// ```text
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/// constant constant constant constant
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/// key key key key
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/// key key key key
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/// counter counter counter counter
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/// ```
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/// [1]: Daniel J. Bernstein. [*Extending the Salsa20
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/// nonce.*](http://cr.yp.to/papers.html#xsalsa)
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fn init(&mut self, key: &[u32; KEY_WORDS]) {
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self.state[0] = 0x61707865;
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self.state[1] = 0x3320646E;
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self.state[2] = 0x79622D32;
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self.state[3] = 0x6B206574;
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for i in range(0, KEY_WORDS) {
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self.state[4+i] = key[i];
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}
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self.state[12] = 0;
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self.state[13] = 0;
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self.state[14] = 0;
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self.state[15] = 0;
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self.index = STATE_WORDS;
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}
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/// Refill the internal output buffer (`self.buffer`)
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fn update(&mut self) {
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core(&mut self.buffer, &self.state);
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self.index = 0;
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// update 128-bit counter
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self.state[12] += 1;
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if self.state[12] != 0 { return };
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self.state[13] += 1;
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if self.state[13] != 0 { return };
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self.state[14] += 1;
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if self.state[14] != 0 { return };
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self.state[15] += 1;
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}
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}
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impl Rng for ChaChaRng {
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#[inline]
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fn next_u32(&mut self) -> u32 {
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if self.index == STATE_WORDS {
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self.update();
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}
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let value = self.buffer[self.index % STATE_WORDS];
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self.index += 1;
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value
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}
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}
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impl<'a> SeedableRng<&'a [u32]> for ChaChaRng {
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fn reseed(&mut self, seed: &'a [u32]) {
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// reset state
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self.init(&[0u32; KEY_WORDS]);
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// set key in place
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let key = self.state.slice_mut(4, 4+KEY_WORDS);
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for (k, s) in key.iter_mut().zip(seed.iter()) {
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*k = *s;
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}
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}
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/// Create a ChaCha generator from a seed,
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/// obtained from a variable-length u32 array.
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/// Only up to 8 words are used; if less than 8
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/// words are used, the remaining are set to zero.
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fn from_seed(seed: &'a [u32]) -> ChaChaRng {
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let mut rng = EMPTY;
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rng.reseed(seed);
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rng
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}
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}
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impl Rand for ChaChaRng {
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fn rand<R: Rng>(other: &mut R) -> ChaChaRng {
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let mut key : [u32; KEY_WORDS] = [0; KEY_WORDS];
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for word in key.iter_mut() {
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*word = other.gen();
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}
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SeedableRng::from_seed(key.as_slice())
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}
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}
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#[cfg(test)]
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mod test {
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use std::prelude::v1::*;
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use core::iter::order;
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use {Rng, SeedableRng};
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use super::ChaChaRng;
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#[test]
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fn test_rng_rand_seeded() {
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let s = ::test::rng().gen_iter::<u32>().take(8).collect::<Vec<u32>>();
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let mut ra: ChaChaRng = SeedableRng::from_seed(s.as_slice());
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let mut rb: ChaChaRng = SeedableRng::from_seed(s.as_slice());
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assert!(order::equals(ra.gen_ascii_chars().take(100),
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rb.gen_ascii_chars().take(100)));
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}
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#[test]
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fn test_rng_seeded() {
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let seed : &[_] = &[0,1,2,3,4,5,6,7];
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let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
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let mut rb: ChaChaRng = SeedableRng::from_seed(seed);
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assert!(order::equals(ra.gen_ascii_chars().take(100),
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rb.gen_ascii_chars().take(100)));
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}
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#[test]
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fn test_rng_reseed() {
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let s = ::test::rng().gen_iter::<u32>().take(8).collect::<Vec<u32>>();
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let mut r: ChaChaRng = SeedableRng::from_seed(s.as_slice());
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let string1: String = r.gen_ascii_chars().take(100).collect();
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r.reseed(s.as_slice());
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let string2: String = r.gen_ascii_chars().take(100).collect();
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assert_eq!(string1, string2);
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}
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#[test]
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fn test_rng_true_values() {
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// Test vectors 1 and 2 from
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// http://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
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let seed : &[_] = &[0u32; 8];
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let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
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let v = Vec::from_fn(16, |_| ra.next_u32());
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assert_eq!(v,
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vec!(0xade0b876, 0x903df1a0, 0xe56a5d40, 0x28bd8653,
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0xb819d2bd, 0x1aed8da0, 0xccef36a8, 0xc70d778b,
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0x7c5941da, 0x8d485751, 0x3fe02477, 0x374ad8b8,
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0xf4b8436a, 0x1ca11815, 0x69b687c3, 0x8665eeb2));
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let v = Vec::from_fn(16, |_| ra.next_u32());
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assert_eq!(v,
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vec!(0xbee7079f, 0x7a385155, 0x7c97ba98, 0x0d082d73,
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0xa0290fcb, 0x6965e348, 0x3e53c612, 0xed7aee32,
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0x7621b729, 0x434ee69c, 0xb03371d5, 0xd539d874,
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0x281fed31, 0x45fb0a51, 0x1f0ae1ac, 0x6f4d794b));
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let seed : &[_] = &[0,1,2,3,4,5,6,7];
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let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
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// Store the 17*i-th 32-bit word,
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// i.e., the i-th word of the i-th 16-word block
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let mut v : Vec<u32> = Vec::new();
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for _ in range(0u, 16) {
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v.push(ra.next_u32());
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for _ in range(0u, 16) {
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ra.next_u32();
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}
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}
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assert_eq!(v,
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vec!(0xf225c81a, 0x6ab1be57, 0x04d42951, 0x70858036,
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0x49884684, 0x64efec72, 0x4be2d186, 0x3615b384,
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0x11cfa18e, 0xd3c50049, 0x75c775f6, 0x434c6530,
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0x2c5bad8f, 0x898881dc, 0x5f1c86d9, 0xc1f8e7f4));
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}
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}
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