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chacha20: fix big endian failure and test in CI #447

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Merged
tarcieri merged 4 commits into from
Aug 23, 2025
Merged

chacha20: fix big endian failure and test in CI #447

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e874bfb
revised big endian tests to use all features
nstilt1 Aug 23, 2025
4f46dfd
tried to fix the yml again... I'm new to this
nstilt1 Aug 23, 2025
7904e46
edited a comment in rng.rs
nstilt1 Aug 23, 2025
45dbb98
fix big endian generate() issue
nstilt1 Aug 23, 2025
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2 changes: 1 addition & 1 deletion .github/workflows/chacha20.yml
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Expand Up @@ -211,4 +211,4 @@ jobs:
toolchain: ${{ matrix.rust }}
targets: ${{ matrix.target }}
- uses: RustCrypto/actions/cross-install@master
- run: RUSTFLAGS="${{ matrix.rustflags }}" cross test --package chacha20 --target ${{ matrix.target }}
- run: RUSTFLAGS="${{ matrix.rustflags }}" cross test --package chacha20 --target ${{ matrix.target }} --all-features
6 changes: 5 additions & 1 deletion chacha20/src/rng.rs
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Expand Up @@ -362,6 +362,10 @@ macro_rules! impl_chacha_rng {
#[inline]
fn generate(&mut self, r: &mut Self::Results) {
self.0.generate(&mut r.0);
#[cfg(target_endian = "big")]
for word in r.0.iter_mut() {
*word = word.to_le();
}
Comment on lines +365 to +368
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@dhardy dhardy Aug 24, 2025

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I believe this is wrong: there is no type change here (u32 to u32) so there should be no endian-switch.

We also don't do this in rand_chacha.

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@nstilt1 nstilt1 Aug 25, 2025

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I dug through rand_chacha and ppv-lite86 for a few minutes and couldn't find anywhere with endian conversions regarding the output. But multiple tests fail on big endian. If you look closely, you can see that the bytes within the words are in reverse order. I don't know why they are in reverse order, but the tests pass as soon as to_le() is called on all of the words.

https://github.com/RustCrypto/stream-ciphers/actions/runs/17169966574/job/48717538576

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@nstilt1 nstilt1 Aug 26, 2025

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I might have found the problem. Line 48 of soft.rs converts each word to little endian. Big endian code will most likely be hitting the soft.rs backend. Even if this isn't the culprit, then this part of the code should be using conditional compilation. Will change the code and run a test right quick

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@nstilt1 nstilt1 Aug 26, 2025

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Yep... that was it

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@dhardy dhardy Aug 30, 2025

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Yeah, I'm pretty sure the backends shouldn't be doing any endian conversions.

}
}

Expand Down Expand Up @@ -1066,7 +1070,7 @@ pub(crate) mod tests {
tester_array = [0u8; LEN];
dest_pos = 0;

// test fill_bytes with lengths starting at N bytes, decreasing by 1,
// test fill_bytes with lengths starting at `N` bytes, decreasing by 1,
// down to 1 byte
for test_len in 1..=N {
let debug_start_word_pos = rng.get_word_pos();
Expand Down