fix(aes-gcm): reject empty nonces - #885
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Zero-length nonces violate NIST SP 800-38D and expose the GHASH authentication key when encrypting an empty message. Reject them at the type level and cover the invariant with a compile-fail example. Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
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This is probably a good idea in general but it's also imposing a new bound on a generic parameter, which is a breaking change: anyone using it in a generic context will need to propagate this bound. |
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As a temporary solution we could panic on empty nonces. I doubt that anyone uses the crate with them, so it should not affect anyone while serving as a guard against misuse. |
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Summary
Running the Wycheproof AES-GCM vectors exposed failures for the
ZeroLengthIvcases. A zero-length nonce violates NIST SP 800-38D and can disclose the GHASH authentication key.Changes
NonceSizebound requiring non-zero nonce sizes.AesGcmimplementation, preventing bypasses.AesGcm<Aes128, U0>.Tests
Tests pass.