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diff --git a/rand/rand_chacha/src/chacha.rs b/rand/rand_chacha/src/chacha.rs
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-// Copyright 2018 Developers of the Rand project.
-// Copyright 2014 The Rust Project Developers.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or https://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::fmt;
-use rand_core::{CryptoRng, RngCore, SeedableRng, Error, le};
-use rand_core::block::{BlockRngCore, BlockRng};
-
-const SEED_WORDS: usize = 8; // 8 words for the 256-bit key
-const STATE_WORDS: usize = 16;
-
-/// A cryptographically secure random number generator that uses the ChaCha
-/// algorithm.
-///
-/// ChaCha is a stream cipher designed by Daniel J. Bernstein[^1], that we use
-/// as an RNG. It is an improved variant of the Salsa20 cipher family, which was
-/// selected as one of the "stream ciphers suitable for widespread adoption" by
-/// eSTREAM[^2].
-///
-/// ChaCha uses add-rotate-xor (ARX) operations as its basis. These are safe
-/// against timing attacks, although that is mostly a concern for ciphers and
-/// not for RNGs. Also it is very suitable for SIMD implementation.
-/// Here we do not provide a SIMD implementation yet, except for what is
-/// provided by auto-vectorisation.
-///
-/// With the ChaCha algorithm it is possible to choose the number of rounds the
-/// core algorithm should run. The number of rounds is a tradeoff between
-/// performance and security, where 8 rounds is the minimum potentially
-/// secure configuration, and 20 rounds is widely used as a conservative choice.
-/// We use 20 rounds in this implementation, but hope to allow type-level
-/// configuration in the future.
-///
-/// We use a 64-bit counter and 64-bit stream identifier as in Bernstein's
-/// implementation[^1] except that we use a stream identifier in place of a
-/// nonce. A 64-bit counter over 64-byte (16 word) blocks allows 1 ZiB of output
-/// before cycling, and the stream identifier allows 2<sup>64</sup> unique
-/// streams of output per seed. Both counter and stream are initialized to zero
-/// but may be set via [`set_word_pos`] and [`set_stream`].
-///
-/// The word layout is:
-///
-/// ```text
-/// constant constant constant constant
-/// seed seed seed seed
-/// seed seed seed seed
-/// counter counter stream_id stream_id
-/// ```
-///
-/// This implementation uses an output buffer of sixteen `u32` words, and uses
-/// [`BlockRng`] to implement the [`RngCore`] methods.
-///
-/// [^1]: D. J. Bernstein, [*ChaCha, a variant of Salsa20*](
-/// https://cr.yp.to/chacha.html)
-///
-/// [^2]: [eSTREAM: the ECRYPT Stream Cipher Project](
-/// http://www.ecrypt.eu.org/stream/)
-///
-/// [`set_word_pos`]: #method.set_word_pos
-/// [`set_stream`]: #method.set_stream
-/// [`BlockRng`]: ../rand_core/block/struct.BlockRng.html
-/// [`RngCore`]: ../rand_core/trait.RngCore.html
-#[derive(Clone, Debug)]
-pub struct ChaChaRng(BlockRng<ChaChaCore>);
-
-impl RngCore for ChaChaRng {
- #[inline]
- fn next_u32(&mut self) -> u32 {
- self.0.next_u32()
- }
-
- #[inline]
- fn next_u64(&mut self) -> u64 {
- self.0.next_u64()
- }
-
- #[inline]
- fn fill_bytes(&mut self, dest: &mut [u8]) {
- self.0.fill_bytes(dest)
- }
-
- #[inline]
- fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
- self.0.try_fill_bytes(dest)
- }
-}
-
-impl SeedableRng for ChaChaRng {
- type Seed = <ChaChaCore as SeedableRng>::Seed;
-
- fn from_seed(seed: Self::Seed) -> Self {
- ChaChaRng(BlockRng::<ChaChaCore>::from_seed(seed))
- }
-
- fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
- BlockRng::<ChaChaCore>::from_rng(rng).map(ChaChaRng)
- }
-}
-
-impl CryptoRng for ChaChaRng {}
-
-impl ChaChaRng {
- /// Get the offset from the start of the stream, in 32-bit words.
- ///
- /// Since the generated blocks are 16 words (2<sup>4</sup>) long and the
- /// counter is 64-bits, the offset is a 68-bit number. Sub-word offsets are
- /// not supported, hence the result can simply be multiplied by 4 to get a
- /// byte-offset.
- ///
- /// Note: this function is currently only available with Rust 1.26 or later.
- #[cfg(all(rustc_1_26, not(target_os = "emscripten")))]
- pub fn get_word_pos(&self) -> u128 {
- let mut c = (self.0.core.state[13] as u64) << 32
- | (self.0.core.state[12] as u64);
- let mut index = self.0.index();
- // c is the end of the last block generated, unless index is at end
- if index >= STATE_WORDS {
- index = 0;
- } else {
- c = c.wrapping_sub(1);
- }
- ((c as u128) << 4) | (index as u128)
- }
-
- /// Set the offset from the start of the stream, in 32-bit words.
- ///
- /// As with `get_word_pos`, we use a 68-bit number. Since the generator
- /// simply cycles at the end of its period (1 ZiB), we ignore the upper
- /// 60 bits.
- ///
- /// Note: this function is currently only available with Rust 1.26 or later.
- #[cfg(all(rustc_1_26, not(target_os = "emscripten")))]
- pub fn set_word_pos(&mut self, word_offset: u128) {
- let index = (word_offset as usize) & 0xF;
- let counter = (word_offset >> 4) as u64;
- self.0.core.state[12] = counter as u32;
- self.0.core.state[13] = (counter >> 32) as u32;
- if index != 0 {
- self.0.generate_and_set(index); // also increments counter
- } else {
- self.0.reset();
- }
- }
-
- /// Set the stream number.
- ///
- /// This is initialized to zero; 2<sup>64</sup> unique streams of output
- /// are available per seed/key.
- ///
- /// Note that in order to reproduce ChaCha output with a specific 64-bit
- /// nonce, one can convert that nonce to a `u64` in little-endian fashion
- /// and pass to this function. In theory a 96-bit nonce can be used by
- /// passing the last 64-bits to this function and using the first 32-bits as
- /// the most significant half of the 64-bit counter (which may be set
- /// indirectly via `set_word_pos`), but this is not directly supported.
- pub fn set_stream(&mut self, stream: u64) {
- let index = self.0.index();
- self.0.core.state[14] = stream as u32;
- self.0.core.state[15] = (stream >> 32) as u32;
- if index < STATE_WORDS {
- // we need to regenerate a partial result buffer
- {
- // reverse of counter adjustment in generate()
- if self.0.core.state[12] == 0 {
- self.0.core.state[13] = self.0.core.state[13].wrapping_sub(1);
- }
- self.0.core.state[12] = self.0.core.state[12].wrapping_sub(1);
- }
- self.0.generate_and_set(index);
- }
- }
-}
-
-/// The core of `ChaChaRng`, used with `BlockRng`.
-#[derive(Clone)]
-pub struct ChaChaCore {
- state: [u32; STATE_WORDS],
-}
-
-// Custom Debug implementation that does not expose the internal state
-impl fmt::Debug for ChaChaCore {
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- write!(f, "ChaChaCore {{}}")
- }
-}
-
-macro_rules! quarter_round{
- ($a: expr, $b: expr, $c: expr, $d: expr) => {{
- $a = $a.wrapping_add($b); $d ^= $a; $d = $d.rotate_left(16);
- $c = $c.wrapping_add($d); $b ^= $c; $b = $b.rotate_left(12);
- $a = $a.wrapping_add($b); $d ^= $a; $d = $d.rotate_left( 8);
- $c = $c.wrapping_add($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]);
- }}
-}
-
-impl BlockRngCore for ChaChaCore {
- type Item = u32;
- type Results = [u32; STATE_WORDS];
-
- fn generate(&mut self, results: &mut Self::Results) {
- // For some reason extracting this part into a separate function
- // improves performance by 50%.
- fn core(results: &mut [u32; STATE_WORDS],
- state: &[u32; STATE_WORDS])
- {
- let mut tmp = *state;
- let rounds = 20;
- for _ in 0..rounds / 2 {
- double_round!(tmp);
- }
- for i in 0..STATE_WORDS {
- results[i] = tmp[i].wrapping_add(state[i]);
- }
- }
-
- core(results, &self.state);
-
- // update 64-bit counter
- self.state[12] = self.state[12].wrapping_add(1);
- if self.state[12] != 0 { return; };
- self.state[13] = self.state[13].wrapping_add(1);
- }
-}
-
-impl SeedableRng for ChaChaCore {
- type Seed = [u8; SEED_WORDS*4];
-
- fn from_seed(seed: Self::Seed) -> Self {
- let mut seed_le = [0u32; SEED_WORDS];
- le::read_u32_into(&seed, &mut seed_le);
- Self {
- state: [0x61707865, 0x3320646E, 0x79622D32, 0x6B206574, // constants
- seed_le[0], seed_le[1], seed_le[2], seed_le[3], // seed
- seed_le[4], seed_le[5], seed_le[6], seed_le[7], // seed
- 0, 0, 0, 0], // counter
- }
- }
-}
-
-impl CryptoRng for ChaChaCore {}
-
-impl From<ChaChaCore> for ChaChaRng {
- fn from(core: ChaChaCore) -> Self {
- ChaChaRng(BlockRng::new(core))
- }
-}
-
-#[cfg(test)]
-mod test {
- use ::rand_core::{RngCore, SeedableRng};
- use super::ChaChaRng;
-
- #[test]
- fn test_chacha_construction() {
- let seed = [0,0,0,0,0,0,0,0,
- 1,0,0,0,0,0,0,0,
- 2,0,0,0,0,0,0,0,
- 3,0,0,0,0,0,0,0];
- let mut rng1 = ChaChaRng::from_seed(seed);
- assert_eq!(rng1.next_u32(), 137206642);
-
- let mut rng2 = ChaChaRng::from_rng(rng1).unwrap();
- assert_eq!(rng2.next_u32(), 1325750369);
- }
-
- #[test]
- fn test_chacha_true_values_a() {
- // Test vectors 1 and 2 from
- // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
- let seed = [0u8; 32];
- let mut rng = ChaChaRng::from_seed(seed);
-
- let mut results = [0u32; 16];
- for i in results.iter_mut() { *i = rng.next_u32(); }
- let expected = [0xade0b876, 0x903df1a0, 0xe56a5d40, 0x28bd8653,
- 0xb819d2bd, 0x1aed8da0, 0xccef36a8, 0xc70d778b,
- 0x7c5941da, 0x8d485751, 0x3fe02477, 0x374ad8b8,
- 0xf4b8436a, 0x1ca11815, 0x69b687c3, 0x8665eeb2];
- assert_eq!(results, expected);
-
- for i in results.iter_mut() { *i = rng.next_u32(); }
- let expected = [0xbee7079f, 0x7a385155, 0x7c97ba98, 0x0d082d73,
- 0xa0290fcb, 0x6965e348, 0x3e53c612, 0xed7aee32,
- 0x7621b729, 0x434ee69c, 0xb03371d5, 0xd539d874,
- 0x281fed31, 0x45fb0a51, 0x1f0ae1ac, 0x6f4d794b];
- assert_eq!(results, expected);
- }
-
- #[test]
- fn test_chacha_true_values_b() {
- // Test vector 3 from
- // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
- let seed = [0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 1];
- let mut rng = ChaChaRng::from_seed(seed);
-
- // Skip block 0
- for _ in 0..16 { rng.next_u32(); }
-
- let mut results = [0u32; 16];
- for i in results.iter_mut() { *i = rng.next_u32(); }
- let expected = [0x2452eb3a, 0x9249f8ec, 0x8d829d9b, 0xddd4ceb1,
- 0xe8252083, 0x60818b01, 0xf38422b8, 0x5aaa49c9,
- 0xbb00ca8e, 0xda3ba7b4, 0xc4b592d1, 0xfdf2732f,
- 0x4436274e, 0x2561b3c8, 0xebdd4aa6, 0xa0136c00];
- assert_eq!(results, expected);
- }
-
- #[test]
- #[cfg(all(rustc_1_26, not(target_os = "emscripten")))]
- fn test_chacha_true_values_c() {
- // Test vector 4 from
- // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
- let seed = [0, 0xff, 0, 0, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0];
- let expected = [0xfb4dd572, 0x4bc42ef1, 0xdf922636, 0x327f1394,
- 0xa78dea8f, 0x5e269039, 0xa1bebbc1, 0xcaf09aae,
- 0xa25ab213, 0x48a6b46c, 0x1b9d9bcb, 0x092c5be6,
- 0x546ca624, 0x1bec45d5, 0x87f47473, 0x96f0992e];
- let expected_end = 3 * 16;
- let mut results = [0u32; 16];
-
- // Test block 2 by skipping block 0 and 1
- let mut rng1 = ChaChaRng::from_seed(seed);
- for _ in 0..32 { rng1.next_u32(); }
- for i in results.iter_mut() { *i = rng1.next_u32(); }
- assert_eq!(results, expected);
- assert_eq!(rng1.get_word_pos(), expected_end);
-
- // Test block 2 by using `set_word_pos`
- let mut rng2 = ChaChaRng::from_seed(seed);
- rng2.set_word_pos(2 * 16);
- for i in results.iter_mut() { *i = rng2.next_u32(); }
- assert_eq!(results, expected);
- assert_eq!(rng2.get_word_pos(), expected_end);
-
- // Test skipping behaviour with other types
- let mut buf = [0u8; 32];
- rng2.fill_bytes(&mut buf[..]);
- assert_eq!(rng2.get_word_pos(), expected_end + 8);
- rng2.fill_bytes(&mut buf[0..25]);
- assert_eq!(rng2.get_word_pos(), expected_end + 15);
- rng2.next_u64();
- assert_eq!(rng2.get_word_pos(), expected_end + 17);
- rng2.next_u32();
- rng2.next_u64();
- assert_eq!(rng2.get_word_pos(), expected_end + 20);
- rng2.fill_bytes(&mut buf[0..1]);
- assert_eq!(rng2.get_word_pos(), expected_end + 21);
- }
-
- #[test]
- fn test_chacha_multiple_blocks() {
- let seed = [0,0,0,0, 1,0,0,0, 2,0,0,0, 3,0,0,0, 4,0,0,0, 5,0,0,0, 6,0,0,0, 7,0,0,0];
- let mut rng = ChaChaRng::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 results = [0u32; 16];
- for i in results.iter_mut() {
- *i = rng.next_u32();
- for _ in 0..16 {
- rng.next_u32();
- }
- }
- let expected = [0xf225c81a, 0x6ab1be57, 0x04d42951, 0x70858036,
- 0x49884684, 0x64efec72, 0x4be2d186, 0x3615b384,
- 0x11cfa18e, 0xd3c50049, 0x75c775f6, 0x434c6530,
- 0x2c5bad8f, 0x898881dc, 0x5f1c86d9, 0xc1f8e7f4];
- assert_eq!(results, expected);
- }
-
- #[test]
- fn test_chacha_true_bytes() {
- let seed = [0u8; 32];
- let mut rng = ChaChaRng::from_seed(seed);
- let mut results = [0u8; 32];
- rng.fill_bytes(&mut results);
- let expected = [118, 184, 224, 173, 160, 241, 61, 144,
- 64, 93, 106, 229, 83, 134, 189, 40,
- 189, 210, 25, 184, 160, 141, 237, 26,
- 168, 54, 239, 204, 139, 119, 13, 199];
- assert_eq!(results, expected);
- }
-
- #[test]
- fn test_chacha_nonce() {
- // Test vector 5 from
- // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
- // Although we do not support setting a nonce, we try it here anyway so
- // we can use this test vector.
- let seed = [0u8; 32];
- let mut rng = ChaChaRng::from_seed(seed);
- // 96-bit nonce in LE order is: 0,0,0,0, 0,0,0,0, 0,0,0,2
- rng.set_stream(2u64 << (24 + 32));
-
- let mut results = [0u32; 16];
- for i in results.iter_mut() { *i = rng.next_u32(); }
- let expected = [0x374dc6c2, 0x3736d58c, 0xb904e24a, 0xcd3f93ef,
- 0x88228b1a, 0x96a4dfb3, 0x5b76ab72, 0xc727ee54,
- 0x0e0e978a, 0xf3145c95, 0x1b748ea8, 0xf786c297,
- 0x99c28f5f, 0x628314e8, 0x398a19fa, 0x6ded1b53];
- assert_eq!(results, expected);
- }
-
- #[test]
- fn test_chacha_clone_streams() {
- let seed = [0,0,0,0, 1,0,0,0, 2,0,0,0, 3,0,0,0, 4,0,0,0, 5,0,0,0, 6,0,0,0, 7,0,0,0];
- let mut rng = ChaChaRng::from_seed(seed);
- let mut clone = rng.clone();
- for _ in 0..16 {
- assert_eq!(rng.next_u64(), clone.next_u64());
- }
-
- rng.set_stream(51);
- for _ in 0..7 {
- assert!(rng.next_u32() != clone.next_u32());
- }
- clone.set_stream(51); // switch part way through block
- for _ in 7..16 {
- assert_eq!(rng.next_u32(), clone.next_u32());
- }
- }
-}
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