fix: overflow-safe activation interval validation in key_gen#45
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tcoratger merged 3 commits intoleanEthereum:mainfrom Apr 3, 2026
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The previous bounds check `activation_epoch + num_active_epochs <= Self::LIFETIME as usize` had two defects: 1. The usize addition can wrap in release builds, silently passing the check with bogus values (e.g. usize::MAX + 2 wraps to 1). 2. `Self::LIFETIME as usize` truncates on 32-bit targets when LOG_LIFETIME == 32 (1u64 << 32 becomes 0), making the check vacuous. Fix both by performing the entire validation in u64 space via checked_add, comparing directly against Self::LIFETIME without any usize cast. Also adds: - Compile-time assertion that LOG_LIFETIME <= 32, since sign() and verify() take epoch as u32. - Explicit rejection of num_active_epochs == 0, which previously passed validation but caused expand_activation_time() to silently invent a non-empty key range. Partially addresses leanEthereum#37.
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Apr 2, 2026
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LGTM, just small comment
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
The bounds check in
key_gen()had two defects:usize wrapping:
activation_epoch + num_active_epochscan wrap in release builds, silently passing the check (e.g.usize::MAX + 2wraps to1).32-bit truncation:
Self::LIFETIME as usizetruncates whenLOG_LIFETIME == 32on 32-bit targets (1u64 << 32becomes0), making the validation vacuous.This PR fixes both by performing the entire validation in
u64space viachecked_add, comparing directly againstSelf::LIFETIMEwithout anyusizecast.Also adds:
LOG_LIFETIME <= 32, sincesign()andverify()takeepoch: u32.num_active_epochs == 0, which previously passed validation but causedexpand_activation_time()to silently invent a non-empty key range.Partially addresses #37.
Test plan
cargo +nightly test— 119 passed, 0 failed, 1 ignored (pre-existing)cargo +nightly clippy --all-targets— zero warningscargo +nightly fmt --check— clean