--- /dev/null
+// Copyright 2018 Developers of the Rand project.
+//
+// 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.
+
+#[cfg(not(feature = "std"))] use core;
+#[cfg(feature = "std")] use std as core;
+
+use self::core::fmt;
+use crate::guts::ChaCha;
+use rand_core::block::{BlockRng, BlockRngCore};
+use rand_core::{CryptoRng, Error, RngCore, SeedableRng};
+
+const STREAM_PARAM_NONCE: u32 = 1;
+const STREAM_PARAM_BLOCK: u32 = 0;
+
+pub struct Array64<T>([T; 64]);
+impl<T> Default for Array64<T>
+where T: Default
+{
+ #[rustfmt::skip]
+ fn default() -> Self {
+ Self([
+ T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+ T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+ T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+ T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+ T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+ T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+ T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+ T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+ ])
+ }
+}
+impl<T> AsRef<[T]> for Array64<T> {
+ fn as_ref(&self) -> &[T] {
+ &self.0
+ }
+}
+impl<T> AsMut<[T]> for Array64<T> {
+ fn as_mut(&mut self) -> &mut [T] {
+ &mut self.0
+ }
+}
+impl<T> Clone for Array64<T>
+where T: Copy + Default
+{
+ fn clone(&self) -> Self {
+ let mut new = Self::default();
+ new.0.copy_from_slice(&self.0);
+ new
+ }
+}
+impl<T> fmt::Debug for Array64<T> {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ write!(f, "Array64 {{}}")
+ }
+}
+
+macro_rules! chacha_impl {
+ ($ChaChaXCore:ident, $ChaChaXRng:ident, $rounds:expr, $doc:expr) => {
+ #[doc=$doc]
+ #[derive(Clone)]
+ pub struct $ChaChaXCore {
+ state: ChaCha,
+ }
+
+ // Custom Debug implementation that does not expose the internal state
+ impl fmt::Debug for $ChaChaXCore {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ write!(f, "ChaChaXCore {{}}")
+ }
+ }
+
+ impl BlockRngCore for $ChaChaXCore {
+ type Item = u32;
+ type Results = Array64<u32>;
+ #[inline]
+ fn generate(&mut self, r: &mut Self::Results) {
+ // Fill slice of words by writing to equivalent slice of bytes, then fixing endianness.
+ self.state.refill4($rounds, unsafe {
+ &mut *(&mut *r as *mut Array64<u32> as *mut [u8; 256])
+ });
+ for x in r.as_mut() {
+ *x = x.to_le();
+ }
+ }
+ }
+
+ impl SeedableRng for $ChaChaXCore {
+ type Seed = [u8; 32];
+ #[inline]
+ fn from_seed(seed: Self::Seed) -> Self {
+ $ChaChaXCore { state: ChaCha::new(&seed, &[0u8; 8]) }
+ }
+ }
+
+ impl CryptoRng for $ChaChaXCore {}
+
+ /// 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. We provide a SIMD
+ /// implementation to support high throughput on a variety of common hardware platforms.
+ ///
+ /// 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 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 the `set_word_pos` and `set_stream` methods.
+ ///
+ /// 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/)
+ #[derive(Clone, Debug)]
+ pub struct $ChaChaXRng {
+ rng: BlockRng<$ChaChaXCore>,
+ }
+
+ impl SeedableRng for $ChaChaXRng {
+ type Seed = [u8; 32];
+ #[inline]
+ fn from_seed(seed: Self::Seed) -> Self {
+ let core = $ChaChaXCore::from_seed(seed);
+ Self {
+ rng: BlockRng::new(core),
+ }
+ }
+ }
+
+ impl RngCore for $ChaChaXRng {
+ #[inline]
+ fn next_u32(&mut self) -> u32 {
+ self.rng.next_u32()
+ }
+ #[inline]
+ fn next_u64(&mut self) -> u64 {
+ self.rng.next_u64()
+ }
+ #[inline]
+ fn fill_bytes(&mut self, bytes: &mut [u8]) {
+ self.rng.fill_bytes(bytes)
+ }
+ #[inline]
+ fn try_fill_bytes(&mut self, bytes: &mut [u8]) -> Result<(), Error> {
+ self.rng.try_fill_bytes(bytes)
+ }
+ }
+
+ impl $ChaChaXRng {
+ // The buffer is a 4-block window, i.e. it is always at a block-aligned position in the
+ // stream but if the stream has been seeked it may not be self-aligned.
+
+ /// 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.
+ #[inline]
+ pub fn get_word_pos(&self) -> u128 {
+ let mut block = u128::from(self.rng.core.state.get_stream_param(STREAM_PARAM_BLOCK));
+ // counter is incremented *after* filling buffer
+ block -= 4;
+ (block << 4) + self.rng.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.
+ #[inline]
+ pub fn set_word_pos(&mut self, word_offset: u128) {
+ let block = (word_offset >> 4) as u64;
+ self.rng
+ .core
+ .state
+ .set_stream_param(STREAM_PARAM_BLOCK, block);
+ self.rng.generate_and_set((word_offset & 15) as usize);
+ }
+
+ /// 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.
+ #[inline]
+ pub fn set_stream(&mut self, stream: u64) {
+ self.rng
+ .core
+ .state
+ .set_stream_param(STREAM_PARAM_NONCE, stream);
+ if self.rng.index() != 64 {
+ let wp = self.get_word_pos();
+ self.set_word_pos(wp);
+ }
+ }
+ }
+
+ impl CryptoRng for $ChaChaXRng {}
+
+ impl From<$ChaChaXCore> for $ChaChaXRng {
+ fn from(core: $ChaChaXCore) -> Self {
+ $ChaChaXRng {
+ rng: BlockRng::new(core),
+ }
+ }
+ }
+ }
+}
+
+chacha_impl!(ChaCha20Core, ChaCha20Rng, 10, "ChaCha with 20 rounds");
+chacha_impl!(ChaCha12Core, ChaCha12Rng, 6, "ChaCha with 12 rounds");
+chacha_impl!(ChaCha8Core, ChaCha8Rng, 4, "ChaCha with 8 rounds");
+
+#[cfg(test)]
+mod test {
+ use rand_core::{RngCore, SeedableRng};
+
+ type ChaChaRng = super::ChaCha20Rng;
+
+ #[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]
+ 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());
+ }
+ }
+}
projects / rustc.git / blobdiff