glm-5.2
dd1ca1de70
Spec the vault crate from its existing implementation. The vault is stable (implementation exists); this spec documents what IS so the implementation-sync agent can reconcile source drift. New spec documents (crates/vault/): - README.md — crate index, security constraints, public API - mnemonic-derivation.md — BIP39, SLIP-0010, BIP-0032, derivation paths - encryption.md — AES-256-GCM, EncryptedData, key versioning, salt - service.md — VaultServiceHandle lifecycle, actor dispatch, cache - protocol.md — VaultProtocol irpc messages, DerivedKey redaction New ADRs: - ADR-018: Vault as standalone crate (zero alknet deps; own types/errors) - ADR-019: Vault assembly-layer-only access (CLI is sole caller) New open questions: - OQ-20: Salt/KDF Phase B (open, low priority — salt field reserved) - OQ-21: Remote vault administration (deferred — needs ADR if ever needed) - OQ-22: Key rotation mechanism (open, low priority — workflow not specced) Spec-vs-source drift explicitly flagged (for the sync agent): - rand::random() used for IVs instead of OsRng (security-critical) - unwrap() on every RwLock acquisition (must use unwrap_or_else) - ADR-038 / OQ-SVC-03 references in source comments are stale (old numbering) - VaultServiceActor::spawn returns a non-functional second actor (source bug) - KeyVersionMismatch error variant is defined but unused in v1
162 lines
7.3 KiB
Markdown
162 lines
7.3 KiB
Markdown
# ADR-018: Vault as Standalone Crate
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## Status
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Accepted
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## Context
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alknet-vault provides BIP39 mnemonic generation, SLIP-0010 Ed25519 HD key
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derivation, BIP-0032 secp256k1 derivation (feature-gated), and AES-256-GCM
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encryption. It holds the master seed — the root of trust for all derived keys
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and encrypted credentials in the alknet system.
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The question is: what does alknet-vault depend on? The candidates:
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1. **Depend on alknet-core** for shared types (errors, maybe Identity). This
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pulls QUIC, quinn, iroh, rustls, and tokio runtime dependencies into the
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vault's dependency tree.
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2. **Stand alone** — zero alknet crate dependencies. The vault defines its own
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types, its own error enum, its own irpc protocol. Other crates depend on
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the vault; the vault depends on nothing in alknet.
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This is a one-way door. Once the vault depends on alknet-core, reversing it
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requires removing that dependency from every type, error conversion, and
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test — and the longer it stays, the more entangled it becomes.
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### Why standalone matters
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The vault is used in contexts where QUIC networking does not exist:
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- **CLI tools**: a key-derivation utility that derives an identity key from a
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mnemonic without starting a network endpoint.
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- **Test harnesses**: integration tests in other crates derive test keys
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without spinning up a QUIC endpoint.
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- **WASM key derivation**: a future WASM target that derives keys in a browser
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(the BiStream trait in ADR-007 preserves this door at the transport layer;
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the vault's independence preserves it at the secret layer).
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- **Embedded assembly**: a binary that only needs the vault to decrypt a
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config file at startup, with no networking at all.
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If the vault depends on alknet-core, all of these contexts pull in quinn,
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iroh, rustls, and tokio — none of which they need. The vault's job is
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cryptographic derivation and encryption. It has no networking concern.
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### What the vault provides without alknet-core
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The vault defines its own types and traits:
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- `Mnemonic`, `Seed` — BIP39 root material
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- `ExtendedPrivKey` (Ed25519), `Secp256k1ExtendedPrivKey` (Ethereum) —
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derived key material
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- `DerivedKey`, `KeyType` — protocol-level key representation
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- `EncryptedData`, `EncryptionKey` — AES-256-GCM blobs
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- `VaultServiceHandle`, `VaultServiceActor` — runtime API
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- `VaultProtocol` — irpc message enum (in-process dispatch)
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- `VaultServiceError` — its own error enum (string-wrapped sub-errors; the
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vault doesn't share an error type with alknet-core)
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The `VaultProtocol` uses irpc directly (see ADR-005), not through alknet-call.
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This is consistent: irpc is a lightweight framing library, not an alknet
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crate. The vault's irpc usage is an in-process dispatch mechanism, not a
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network-exposed service.
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## Decision
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**alknet-vault has zero alknet crate dependencies.** It depends only on
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external crates (`bip39`, `ed25519-bip32`, `aes-gcm`, `sha2`, `hmac`,
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`secp256k1`, `irpc`, `tokio` for the actor's sync primitives, `serde`,
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`zeroize`, `thiserror`, `base64`, `rand`).
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The vault does not depend on:
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- `alknet-core` — no shared types, no `Identity`, no `AuthContext`
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- `alknet-call` — no `OperationSpec`, no `OperationContext`, no call protocol
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- `alknet-vault` does not implement `ProtocolHandler` — it has no ALPN (see
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ADR-019)
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Dependency flow is strictly one-directional:
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```
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alknet-vault (standalone)
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↑
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alknet (CLI binary) — the only crate that depends on alknet-vault
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```
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No handler crate depends on alknet-vault directly. Handlers receive derived
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material through capabilities injected by the assembly layer (ADR-014). The
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CLI binary is the sole integration point (ADR-008, ADR-019).
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### Type independence
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The vault defines its own types and does not share types with alknet-core:
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- `VaultServiceError` is the vault's error enum. It is `Serialize`/`Deserialize`
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(for irpc dispatch) and wraps sub-errors as strings. It does not implement
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`From` for alknet-core error types — the CLI binary converts at the
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assembly boundary.
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- `DerivedKey` is the vault's key representation. It is not shared with
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alknet-core's `Identity` type. The CLI binary extracts the bytes it needs
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(private key for signing, public key for TLS identity) and constructs the
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alknet-core types at the assembly layer.
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- `EncryptedData` is the vault's encrypted blob format. It is shared with
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`alknet-storage` (a future crate) by type-level agreement, not by a crate
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dependency — both crates must agree on the serialization format (see
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[encryption.md](../crates/vault/encryption.md)).
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## Consequences
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**Positive:**
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- The vault compiles and runs without QUIC, quinn, iroh, rustls, or a tokio
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runtime (the `VaultServiceHandle` works with just `std::sync::RwLock`; the
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actor uses `tokio::sync::mpsc` but that's a lightweight dependency).
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- CLI tools, test harnesses, and future WASM targets can use the vault for key
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derivation without pulling in networking crates.
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- The vault's API surface is stable — changes to alknet-core types don't
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force a vault recompile, and changes to vault types don't force a
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handler recompile (the CLI is the only consumer).
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- No circular dependency risk. The dependency graph is a strict DAG.
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- The vault can be published and used independently of alknet — it's a
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general-purpose local key vault, not an alknet-specific component.
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**Negative:**
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- The vault cannot share types with alknet-core. If a type wants to be shared
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(e.g., a future `Fingerprint` type), it must live in alknet-core and the
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vault must define its own equivalent, or a new shared crate must be
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created. This is a feature, not a bug — it forces explicit boundaries.
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- The CLI binary must convert between vault types and alknet-core types at
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the assembly boundary. This is a small amount of glue code (extract bytes
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from `DerivedKey`, construct alknet-core types). See ADR-019.
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- The vault's `VaultServiceError` is separate from alknet-core's
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`HandlerError`. The CLI binary maps vault errors to handler errors or
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startup failures. This is expected — the vault is a library, not a
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handler.
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## Assumptions
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1. **The vault's API is consumed by one component (the CLI binary) in the
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alknet system.** If a future use case requires multiple crates to depend
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on the vault directly, the dependency flow still holds — they depend on
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the vault, the vault depends on nothing. The standalone property is
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preserved.
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2. **Shared types between the vault and other crates are agreed by type-level
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compatibility, not by a crate dependency.** `EncryptedData` is the example:
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both the vault and `alknet-storage` (future) must agree on the
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serialization format. This is documented in the type's spec, not enforced
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by the type system across crates.
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3. **The vault's error type does not need to integrate with alknet-core's
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error handling.** The vault returns `VaultServiceError`; the CLI binary
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handles it at the assembly boundary. If a future use case requires
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propagating vault errors through alknet-core's error types, the CLI
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converts at the boundary.
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## References
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- ADR-003: Crate decomposition (alknet-vault is standalone)
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- ADR-005: irpc as call protocol foundation (vault uses irpc directly)
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- ADR-008: Vault integration point (CLI-embedded, assembly-layer only)
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- ADR-014: Secret material flow and capability injection
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- ADR-019: Vault assembly-layer-only access
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- [crates/vault/README.md](../crates/vault/README.md)
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- Implementation: `crates/alknet-vault/` |