script: Use hkdf crate for HKDF in WebCrypto
#40650
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Signed-off-by: Kingsley Yung <kingsley@kkoyung.dev>
Signed-off-by: Kingsley Yung <kingsley@kkoyung.dev>
TimvdLippe
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Nov 15, 2025
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Another big chunk of passing chunks 🎉
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We currently use the crate
aws-lc-rsfor HKDF in the WebCrypto API. When generating output bytes from the output of HKDF-Expand operation (OKM, Output Key Material), it enforces the requested output length must match the length of key type (see error condition ofOkm::fillat https://docs.rs/aws-lc-rs/1.14.1/aws_lc_rs/hkdf/struct.Okm.html#method.fill). However, according to the WebCrypto API specification, user should be allowed to choose the output length (https://w3c.github.io/webcrypto/#hkdf-operations-derive-bits). The restriction fromaws-lc-rscauses several HKDF-related WPT tests to fail.This patch switches to use a more flexible crate
hkdf(https://crates.io/crates/hkdf) for implementing HKDF in our WebCrypto API, and allowing variable length output. This helps to make those HKDF-related WPT tests pass.Testing: Pass some WPT tests that were expected to fail.