---
status: draft
last_updated: 2026-09-11
---

# Open Questions

Centralized tracker for alktls. Promoted from Phase 0
(`docs/research/phase-0.md` OQ-TLS-01..08) on 2026-09-10. Statuses here
are authoritative; the Phase 0 doc's statuses are the historical record.

## Statuses at a glance

| OQ | Topic | Status | Priority |
|----|-------|--------|----------|
| OQ-TLS-01 | Config-type ownership | **resolved** (ADR-005) | high |
| OQ-TLS-02 | `SelfSigned` on the client path | resolved (documented behavior kept) | low |
| OQ-TLS-03 | `for_tcp_tls()` adoption | **resolved** (ADR-004) | medium |
| OQ-TLS-04 | Accessor borrow-vs-consume | **resolved** (ADR-004) | medium |
| OQ-TLS-05 | Test surface | **resolved** (ADR-006) | low |
| OQ-TLS-06 | ACME task shutdown surface | resolved (detached-only for v1) | low |
| OQ-TLS-07 | iroh key surface | **resolved** (ADR-005, byte access pinned) | low |
| OQ-TLS-08 | `quinn` → `noq` feature rename | **resolved** (ADR-003) | high |
| OQ-TLS-09 | Server-path proof-of-possession | **resolved** (ADR-008) | high |
| OQ-TLS-10 | RFC 7250 over TCP: cert-type negotiation gap | **resolved** (ADR-007) | high |

## Identity & types

### OQ-TLS-01: Where do the config types live, and what moves?

- **Origin**: docs/research/phase-0.md §Gaps #3
- **Status**: resolved (2026-09-10)
- **Priority**: high
- **Resolution**: alktls owns the identity types (`TlsIdentity`,
  `Ed25519SecretKey`, `AcmeDirectory`), the credential bundle
  (`ConnectionCredentials`, `RemoteIdentity`), and the fingerprint
  helpers. The auth layer (`PeerEntry`, `AuthPolicy`,
  `IdentityProvider`) stays out — peer-level identity is not TLS.
  Decision recorded in [ADR-005](decisions/005-config-types-move-into-alktls.md).
- **Cross-references**: ADR-001, ADR-005

### OQ-TLS-02: `SelfSigned` on the client path — encode or document?

- **Origin**: docs/research/phase-0.md §Gaps #4
- **Status**: resolved (2026-09-10)
- **Priority**: low
- **Resolution**: keep the current behavior (present nothing via
  `NoClientCertResolver`) and document it on the identity type and in
  the [client spec](client.md). Type-level enforcement (config error,
  like `Acme`) was rejected: `SelfSigned` as a *local* identity
  meaning "present nothing" is coherent — the dev cert exists for the
  server side, and presenting a self-signed client cert would add
  nothing the fingerprint path uses.
- **Consequences**: a future dev client-auth use case would need a
  type-level change (additive, not a one-way door).
- **Cross-references**: ADR-001 (identity model), client spec

### OQ-TLS-07: iroh relationship in the rewrite

- **Origin**: docs/research/phase-0.md OQ-TLS-07
- **Status**: resolved (2026-09-10)
- **Priority**: low
- **Resolution**: the requirement is pinned and verified —
  `Ed25519SecretKey` keeps 32-byte raw access (`from_bytes` /
  `as_bytes`) with the same byte-level surface iroh's
  `iroh_base::SecretKey` consumes (`from_bytes` / `to_bytes`; 32 raw
  bytes in/out — verified against iroh 1.1 in Phase 0). iroh stays
  key-not-config; no `for_iroh()`. The rewrite's iroh dial consumes
  the type alktls owns (ADR-005); no alktls-side work remains.
- **Cross-references**: ADR-003, ADR-005

## API surface

### OQ-TLS-03: `for_tcp_tls()` — adopt the spec accessor?

- **Origin**: docs/research/phase-0.md §Gaps #2
- **Status**: resolved (2026-09-10)
- **Priority**: medium
- **Resolution**: adopted — `for_tcp_tls(&self) ->
  tokio_rustls::TlsAcceptor`, feature-gated on `tcp`, infallible.
  Decision and rationale in [ADR-004](decisions/004-accessor-surface.md).
- **Cross-references**: ADR-004

### OQ-TLS-04: `for_quinn()` — `self` or `&self`?

- **Origin**: docs/research/phase-0.md OQ-TLS-04
- **Status**: resolved (2026-09-10)
- **Priority**: medium
- **Resolution**: server accessors take `&self` (one config feeds N
  transports — the ADR-082 story, directly expressible); client
  accessors consume `self` (per-dial build, zero-cost
  `into_rustls_config`). Full rationale in
  [ADR-004](decisions/004-accessor-surface.md).
- **Cross-references**: ADR-003, ADR-004

### OQ-TLS-08: `quinn` feature vs `noq` feature — and the MSRV floor

- **Origin**: docs/research/phase-0.md §Prior art: noq
- **Status**: resolved (2026-09-10)
- **Priority**: high
- **Resolution**: the feature is `noq` (no `quinn` feature ever
  published; rename is pre-consumer and free). noq 1.2 pinned
  (`"1.2"`, default-features off, `rustls` feature), bump
  deliberately. The MSRV half of the OQ was separately resolved the
  same day (ecosystem floor 1.88; `time` pin dropped). Decision in
  [ADR-003](decisions/003-noq-replaces-quinn.md).
- **Cross-references**: ADR-002, ADR-003, ADR-004

### OQ-TLS-09: Which layer owns proof-of-possession on the server path?

- **Origin**: docs/reviews/001-implementation-review.md §S-1 (the
  impersonation probe: a handshake with the victim's cert bytes + an
  attacker signer completes, and the server extracts the victim's
  fingerprint)
- **Status**: resolved (2026-09-11) — option (b),
  [ADR-008](decisions/008-server-path-possession-verification.md).
  [`VerifyPresentedCertVerifier`](decisions/008-server-path-possession-verification.md)
  is the default client-cert verifier on every `TlsServerConfig` path
  (including the ACME path — the verifier install is crate-side
  rustls, not rustls-acme's): request, don't require, **verify the
  CertificateVerify against the presented cert's public key**. The
  extracted fingerprint is possession-checked (attacker-supplied
  presentations fail the handshake —
  `tests/impersonation_posture.rs` pins both directions); who a
  fingerprint maps to remains the auth layer's concern (ADR-005).
  `AcceptAnyCertVerifier` stays public as the explicit no-pop escape
  hatch, its posture pinned by the same test file.
- **Cross-references**: src/server.rs (`VerifyPresentedCertVerifier`,
  `AcceptAnyCertVerifier`), src/client.rs (`FingerprintPinVerifier` —
  the routing being mirrored), ADR-008, review 001 §S-1, alknet
  ADR-034

### OQ-TLS-10: How do RFC 7250 raw-key peers negotiate over rustls-driven TCP+TLS?

- **Origin**: `tasks/handshake-tests.md` (review 001 §U-3 execution):
  the executed handshake suites found that the crate's own pin client
  cannot complete a handshake against the crate's own raw-key server,
  and a raw-key client resolver cannot present itself to
  `AcceptAnyCertVerifier` — both fail with rustls' HandshakeFailure
  alert (cert-type negotiation), not a verification outcome. Verified
  empirically and against the rustls 0.23.44 sources
  (`server/hs.rs::process_cert_type_extension`,
  `client/hs.rs::process_cert_type_extension`); pinned by
  `tests/handshake_behavior.rs`.
- **Status**: resolved (2026-09-11) — by deviation from alknet,
  [ADR-007](decisions/007-cert-type-negotiation.md). Option (b) plus a
  resolver change: `FingerprintPinVerifier::requires_raw_public_keys()`
  derives from the pin format (`ed25519:` → `true`, `SHA256:` →
  `false`), and `RawKeyClientCertResolver` presents the SPKI under the
  X.509 offer (`only_raw_public_keys() == false`). The gap was a bug in
  the prior art (alknet's code never delivered its spec's raw-key-over-
  TCP promise), not an alknet behavior to preserve — so the
  behavior-preservation invariant does not cover it. The two pin
  formats negotiate independently (per-connection verifier, never
  shared); fail-closed is preserved and strengthened (an `ed25519:`
  pin against an X.509 server aborts at negotiation, never a
  downgrade). The original "defer until the first consumer" rationale
  was circular — the crate is the component that must enable the
  raw-key-over-TCP consumer, and the fix required no API change.
- **Cross-references**: src/client.rs (`FingerprintPinVerifier`,
  `RawKeyClientCertResolver`), src/server.rs (`RawKeyCertResolver`,
  `AcceptAnyCertVerifier`), review 001 §N-4, ADR-007,
  iroh `iroh/src/tls/verifier.rs` (the working prior art)

## Quality / process

### OQ-TLS-05: Test surface for the invariants

- **Origin**: docs/research/phase-0.md §Gaps #5
- **Status**: resolved (2026-09-10)
- **Priority**: low
- **Resolution**: port the in-module seed tests AND add `tests/`
  integration tests for the cross-module surfaces; pin the exact
  nine-scheme list (regression-proof). Decision in
  [ADR-006](decisions/006-module-layout-and-tests.md).
- **Cross-references**: ADR-006

### OQ-TLS-06: Does the ACME state machine need a shutdown surface?

- **Origin**: docs/research/phase-0.md OQ-TLS-06
- **Status**: resolved (2026-09-10)
- **Priority**: low
- **Resolution**: detached-only — the handle is stored (keeping
  `TlsServerConfig` non-Clone) and never aborted; the ACME task runs
  for the process lifetime. Documented on the type.
- **Consequences**: a `shutdown()` (abort + await) surface would be
  additive and cheap if the rewrite's graceful-shutdown design wants
  one later — not a one-way door.
- **Cross-references**: ADR-001 (one-ACME-machine rule),
  [server.md](server.md)

## Deferred / Blocked

None — all recorded OQs are resolved. Future questions (e.g. the
raw-key-only server-verifier sibling if a foreign strict RFC 7250
server interop ever appears — see ADR-007 §Limits) get new OQ entries
rather than reopening these.