fix: reject non-canonical ASN.1 lengths - #44
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Summary
Fixes CAT finding
a35a941e-3a1a-45a5-a71f-c1a8ebcf5065.CertManagerkeys cached certificates bykeccak256(cert), so the verifier must reject alternate byte encodings of the same signed X.509 certificate. Trailing certificate bytes are already rejected onmain; this PR closes the remaining non-canonical ASN.1 length-encoding path.This change updates
Asn1Decode.readNodeLengthto enforce DER length rules:0x80);Self Review
Reviewed the final diff before opening this PR. The production change is scoped to ASN.1 length decoding, so all certificate parsing paths get the same DER canonicalization. Existing canonical AWS Nitro certificates continue to verify, while a real Nitro CA cert re-encoded with a non-minimal outer SEQUENCE length now reverts before
_saveVerifiedcan write a new cache entry.Tests
forge test --match-path test/Asn1Decode.t.sol -vvvforge test --match-test test_HintedCACertRejectsNonCanonicalOuterLength -vvvforge test