chacha20: fix use of SSE4.1 intrinsic in SSE2 backend - #580
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newpavlov
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Aug 27, 2026
| if size_of::<V::Counter>() == 8 { | ||
| state[13] = _mm_extract_epi32(backend.v[3], 1) as u32; | ||
| } | ||
| _mm_storeu_si128(state_ptr.add(3), backend.v[3]); |
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This unnecessarily writes 64-96 bits which stay unmodified, but it results in a simpler code (especially considering that _mm_cvtsi128_si64 is not available on i686 targets) and it even may be miniscully more efficient since we directly write XMM register data.
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@tarcieri |
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@tarcieri |
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sure |
newpavlov
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The yanked versions contain UB in SSE2 backend, see #580.
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Glad to see that RustCrypto/utils#1513 helped catch UB :) |
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That much is definitely cool! |
This was referenced Aug 27, 2026
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MarcusKainth
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Aug 27, 2026
`chacha20` 0.10.0 and 0.10.1 were yanked from crates.io. The SSE2 backend of the RNG and legacy 64-bit-counter variants used `_mm_extract_epi32`, an SSE4.1 intrinsic, so a CPU with SSE2 and without SSE4.1 met an illegal instruction instead of a working fallback. 0.10.2 replaces it with `_mm_storeu_si128`, which is SSE2 (RustCrypto/stream-ciphers#580). Nothing about ciphertext, keys or nonces changes. The fault is portability, and the affected path is reachable only on x86_64 hardware predating SSE4.1. `deny.toml` sets `yanked = "deny"`, so the yank fails `make deny` on every branch until the lockfile moves. The crate reaches the shipped tree through `apache-avro` and `async-nats`, both by way of `rand` 0.10.2. THIRD-PARTY.md carries the version, so it is regenerated here. Changelog: none
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IceTDrinker
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Aug 28, 2026
- RustCrypto/stream-ciphers#583 (yank) - RustCrypto/stream-ciphers#580 (UB SSE2 backend) - RustCrypto/utils#1513 (MIRI stuff enabled)
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Closes #579