fix(error): return TLS 1.2 PRF setup errors - #14
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thieman
marked this pull request as ready for review
June 23, 2026 19:27
tobz
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Jun 23, 2026
| output: &mut [u8; 48], | ||
| kx: Box<dyn ActiveKeyExchange>, | ||
| peer_pub_key: &[u8], | ||
| output: &mut [u8], |
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I'm not sure I understand why we're switching to a variable-length slice here... 🤔
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[GPT 5.5] This is shared with for_secret, whose rustls trait signature is already &mut [u8]. The for_key_exchange method still receives &mut [u8; 48]; before this PR it immediately called for_secret, which coerced that fixed array to the same slice type. So this does not broaden the key-exchange caller contract, it just avoids duplicating the CNG KDF implementation. I checked the PR diff and did not find another introduced fixed-array-output helper pattern that needs the same treatment.
tobz
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Jun 24, 2026
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Summary
Reduce panic surface in the TLS 1.2 PRF path:
rustls::Errorfrom the falliblePrf::for_key_exchangepath if CNG KDF setup or derivation fails.Prf::for_secretmethod, but route it through the same fallible helper and use an explicit invariantexpectmessage rather than opaque CNG unwraps.This PR intentionally avoids changing other infallible rustls trait implementations where the API has no
Resultreturn. Those sites need separate design/review if we want to preflight or restructure them.Testing
cargo fmt -- --checkcargo check --target x86_64-pc-windows-msvccargo check --target x86_64-pc-windows-msvc --no-default-featurescargo check --features fips --target x86_64-pc-windows-msvc(passes with pre-existingkx.rsdead-code warnings)cargo clippy --target x86_64-pc-windows-msvc -- -D warningsgit diff --checkWindows CI should run the unit tests. Local macOS cannot compile Windows-target test dependencies because
aws-lc-sysneeds Windows SDK headers.