test(fuzz): add coverage for derive_encrypt and key_derivation parsing#402
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mmorrissette-devolutions wants to merge 2 commits into
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test(fuzz): add coverage for derive_encrypt and key_derivation parsing#402mmorrissette-devolutions wants to merge 2 commits into
mmorrissette-devolutions wants to merge 2 commits into
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Add three fuzz targets covering untrusted-byte paths that previously had no coverage: - kdf_encrypted_data_deserialization: KdfEncryptedData::try_from(&[u8]) - derivation_parameters_deserialization: DerivationParameters::try_from(&[u8]) - decrypt_with_password: encrypt/decrypt round-trip via KdfEncryptedData, with Argon2 parameters clamped to keep key derivation cheap enough for fuzzing. CI discovers targets via `cargo fuzz list`, so no workflow change is needed.
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A SecretKey requires exactly 32 raw bytes, so an arbitrary Argon2 output length (previously clamped to 1..128) made encrypt_with_password_and_aad fail before the decrypt path for ~127/128 of inputs. Pin the length to 32 so the password-decrypt path is actually exercised; arbitrary output lengths remain covered by the derive_key_argon2 target.
Sébastien Duquette (sduquette-devolutions)
approved these changes
Jun 19, 2026
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Summary
Adds fuzz coverage for three untrusted-byte paths in the
derive_encryptandkey_derivationmodules that previously had no fuzz target.The
derive_encryptmodule was entirely unfuzzed, andDerivationParametersdeserialization — another publicTryFrom<&[u8]>parser of attacker-controllable bytes — had no coverage.New targets
kdf_encrypted_data_deserializationKdfEncryptedData::try_from(&[u8])derivation_parameters_deserializationDerivationParameters::try_from(&[u8])decrypt_with_passwordencrypt_with_password_and_aad→decrypt_with_password_and_aadround-tripFor
decrypt_with_password, the Argon2 parameters are clamped (length/lanes/memory/iterations + small salt, same approach as the existingderive_key_argon2target) so key derivation stays cheap enough for fuzzing — an unclampedArbitraryvalue could request billions of iterations and blow the per-target time budget.The CI action discovers targets via
cargo fuzz list, so no workflow change is needed.Testing
Built and ran all three targets in WSL (nightly + cargo-fuzz 0.13.1), no crashes:
kdf_encrypted_data_deserialization— 18.6M runsderivation_parameters_deserialization— 19.4M runsdecrypt_with_password— full KDF round-trip, no timeout