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Diffstat (limited to 'rand/rand_chacha/src/chacha.rs')
-rw-r--r-- | rand/rand_chacha/src/chacha.rs | 449 |
1 files changed, 0 insertions, 449 deletions
diff --git a/rand/rand_chacha/src/chacha.rs b/rand/rand_chacha/src/chacha.rs deleted file mode 100644 index 86f191e..0000000 --- a/rand/rand_chacha/src/chacha.rs +++ /dev/null @@ -1,449 +0,0 @@ -// 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()); - } - } -} |