EVFS: encrypted vault container#69
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VaultFull, VaultLocked, SegmentNotFound, VaultCorrupted.
Module root with format, segment, and wal submodules.
VaultHeader (32B), SegmentEntry with generation counters and per-segment compression, SegmentIndex with best-fit allocator, free-region merging, padded serialization (64KB), layout constants, and 27 unit tests.
feat(evfs): vault format structures and segment index
HKDF domain-separated sub-keys (cipher/nonce/index), generation-aware nonce derivation, compress-then-encrypt pipeline with MIME-aware skip, BLAKE3 checksums with constant-time verification (subtle), CSPRNG pre-allocation in 64KB chunks, secure erase with fsync. 23 tests.
HKDF domain-separated sub-keys (cipher/nonce/index), generation-aware nonce derivation for both segments and index, compress-then-encrypt pipeline with MIME-aware skip, BLAKE3 checksums with constant-time verification (subtle), CSPRNG pre-allocation in 64KB chunks, secure erase with fsync, intermediate buffer zeroization. 26 tests.
…cryption feat(evfs): add per-segment encryption, checksums, and secure deletion
…recovery feat(evfs): WAL crash recovery and advisory file locking
- Add ENCRYPTED_INDEX_SIZE (INDEX_PAD_SIZE + 28) for on-disk layout
- Update DATA_REGION_OFFSET and shadow/WAL offsets accordingly
- Add total_vault_size() helper for vault file preallocation
- Add pub(super) aead_encrypt_random_nonce and aead_decrypt_with_stored_nonce
for index encryption without generation-based nonce derivation
- Add VaultHandle (opaque) holding file, keys, index, WAL, and lock
- Implement vault_create, vault_open, vault_write, vault_read,
vault_delete, vault_list, vault_capacity, vault_close
- Compress-then-encrypt pipeline with MIME-aware skip
- BLAKE3 checksum on original plaintext (pre-compression)
- Free-list allocation with best-fit search and adjacent merge
- WAL crash recovery with snapshot size validation
- Shadow index fallback when primary is corrupted
- Zeroize master key and plaintext data after use
- Safe usize cast for 32-bit platform compatibility
feat(evfs): implement Vault Rust API with VaultHandle
feat(evfs): add Dart VaultService wrapper and integration tests
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Summary
.vaultencrypted container with per-segment AEAD encryption (AES-256-GCM / ChaCha20-Poly1305), BLAKE3integrity checksums, and WAL-based crash recovery
— never stored directly
VaultServicewrapper and 17 integration tests covering the full Dart → FRB → Rust → FRB → Dartpipeline
Architecture
.vault file layout:
Header (32B) → Primary Index (64KB encrypted) → Data Region (segments + CSPRNG fill) → Shadow Index (64KB
encrypted)
{vault_path}.wal — undo journal for crash recovery
{vault_path}.lock — advisory flock
→ write segment → flush dual index → WAL commit
Key Design Decisions
HKDF(nonce_key, segment_index || generation)— generationincrements on every overwrite
OsRngbytessubtle::ConstantTimeEqfor nonce verification and checksum validationFiles Changed
rust/src/core/evfs/format.rsrust/src/core/evfs/segment.rsrust/src/core/evfs/wal.rsrust/src/api/evfs/mod.rslib/src/evfs/vault_service.dartlib/m_security.dartVaultServiceexportintegration_test/evfs_test.dartrust/src/frb_generated.rsRust Tests (248 total, all pass)
EVFS unit tests cover: header roundtrip, index serialization, allocation/deallocation/merge, generation counters,
key derivation domain separation, nonce uniqueness, segment encrypt/decrypt with all compression modes, MIME-aware
skip, index encryption, checksum verification, secure erase, pre-allocation, WAL entry roundtrip/CRC/recovery, file
locking
Integration Tests (17)
Core lifecycle (10): create/write/close/open/read roundtrip, multiple segments, overwrite, read nonexistent
throws, delete, vault full, wrong key, concurrent open locked, list names, capacity info
Compression (4): zstd auto-decompression, brotli auto-decompression, MIME-aware skip (.jpg), mixed algorithms
in same vault
Integrity & recovery (3): tampered segment detection, WAL crash recovery, corrupted primary index falls back to
shadow
Verification
cargo check --features compression— cleancargo clippy --features compression --all-targets— no warningsflutter analyze lib/ integration_test/— no issues