transcription/docs/ver1/ver1-step5-results.md

# Ver1 Step 5 Results: Private-Network Safety Baseline

## Summary

Step 5 implementation status: **complete**.

This document records completed private-network safety controls, validation evidence, and residual risks for Ver1 Step 5.

Implemented in this step:

1. Added private-network security assumptions and control matrix (`docs/ver1/ver1-step5-security-assumptions.md`).
2. Implemented optional single-operator access control for `/ui*` and `/api*` via HTTP Basic auth.
3. Added upload-size guardrails (`MAX_UPLOAD_BYTES`) and config fail-fast validation for operator credential requirements.
4. Hardened unexpected-error user-facing messaging to reduce sensitive detail leakage.
5. Added Step 5 tests for access control, security settings, and upload size boundaries.
6. Executed dependency/security scans (`pip-audit`, `bandit`) with no critical/high findings.

---

## Implemented Changes

### 1) Security assumptions and threat model

Completed.

- Added `docs/ver1/ver1-step5-security-assumptions.md` defining:
  - trusted private-network deployment assumptions
  - single-operator usage model
  - explicit out-of-scope classes (enterprise IAM, internet-facing zero-trust, multi-tenant controls)
- Added Step 5 control/ownership matrix and residual-risk notes.

### 2) Single-operator access control baseline

Completed.

- New module: `src/transcription/security.py`
  - `is_protected_path(...)` protects `/ui*` and `/api*`
  - `enforce_request_access(...)` enforces optional operator auth
  - robust Basic auth parsing and safe denial responses via `AccessDeniedError`
- App middleware added in `src/transcription/app.py`:
  - enforces auth on protected paths
  - returns consistent `401` envelope and `WWW-Authenticate: Basic` for denied requests
- Health endpoint `/healthz` remains intentionally unauthenticated.

### 3) Input validation and safe-output hardening

Completed baseline.

- `src/transcription/services/upload.py`
  - added size-based validation guard (`max_upload_bytes`)
  - emits `user_input_error` with actionable guidance on over-limit uploads
- `src/transcription/errors.py`
  - `classify_unexpected_error(...)` now returns operation-only message without embedding raw exception text
  - preserves traceability via existing `error_id` and taxonomy while reducing accidental sensitive leak risk

### 4) Secret handling and configuration safety

Completed baseline.

- `src/transcription/config.py` additions:
  - `max_upload_bytes` (default `15 * 1024 * 1024`)
  - `operator_access_enabled` (default `False`)
  - `operator_username` (default `operator`)
  - `operator_password` (optional, required when auth enabled)
- Added settings validator enforcing fail-fast config safety:
  - raises validation error if `OPERATOR_ACCESS_ENABLED=true` and `OPERATOR_PASSWORD` unset
- `README.md` updated with Step 5 security env settings and explicit secret-handling guidance.

### 5) Dependency/security scanning baseline

Completed.

- Dependency vulnerability scan:
  - `uvx pip-audit`
  - Result: **No known vulnerabilities found**
- Static security scan:
  - `uvx bandit -r src/transcription`
  - Result: **No issues identified** (0 low/medium/high)

---

## Test and Verification Evidence

### Added/Updated Tests

1. `tests/api/test_access_control.py`
   - unauthorized protected API denied (`401` + challenge)
   - invalid credentials denied
   - valid credentials accepted
   - `/ui` protected when auth enabled
   - `/healthz` remains unprotected
2. `tests/services/test_upload.py`
   - added rejection test for payloads above `MAX_UPLOAD_BYTES`
3. `tests/test_config.py`
   - added security defaults assertions
   - added fail-fast assertion for missing `OPERATOR_PASSWORD` when auth enabled
4. `tests/test_errors.py`
   - updated expectations for sanitized unexpected-error message behavior
5. Updated integration expectations where failure detail should no longer include raw exception text:
   - `tests/services/test_worker.py`
   - `tests/integration/test_pipeline_flow.py`
6. `tests/test_app.py` updated for new middleware wiring.

### Validation Runs

Run and record outcomes:

- `uv run pytest --collect-only -q` -> passed
- `uv run pytest -m unit -q` -> passed
- `uv run pytest -m "not external" -q` -> passed
- `uv run pytest -q` -> passed

### Security Scan Evidence

Record scan commands and outcomes:

- dependency scan command(s): `uvx pip-audit`
- static/security lint command(s): `uvx bandit -r src/transcription`
- critical/high findings: none
- remediation/defer decisions: no remediations required for Step 5 baseline

---

## Requirement Traceability (Step 5)

| Step 5 Area | REQ Coverage | Status | Evidence |
| --- | --- | --- | --- |
| Private-network and single-operator safety posture | REQ-9 | met | `docs/ver1/ver1-step5-security-assumptions.md`, README security section |
| Access control behavior at UI/API boundaries | REQ-5, REQ-7 | met | `src/transcription/security.py`, `src/transcription/app.py`, `tests/api/test_access_control.py` |
| Input validation and safe user-facing error behavior | REQ-1, REQ-2, REQ-5 | met | `src/transcription/services/upload.py`, `src/transcription/errors.py`, updated tests |
| Config and startup safety controls | REQ-8, REQ-10 | met | `src/transcription/config.py`, `tests/test_config.py`, `README.md` |
| Persistence and domain integrity continuity | REQ-11, REQ-12 | met (no regressions) | full test lane pass including integration and worker flows |

---

## Operational Artifacts Produced

- `docs/ver1/ver1-step5.md`
- `docs/ver1/ver1-step5-results.md`
- `docs/ver1/ver1-step5-security-assumptions.md`
- `src/transcription/security.py`
- `tests/api/test_access_control.py`

---

## Risks, Exceptions, and Follow-Ups

1. Basic auth is intentionally right-sized for trusted private-network use; if deployment posture changes, stronger identity controls are required.
2. Current model remains single shared operator credential (no per-user audit identity).
3. No built-in brute-force/rate-limit controls in Step 5 scope; evaluate in future hardening if threat model expands.

Open follow-ups to carry forward:

- Consider stronger auth/session model if system becomes multi-user or internet-accessible.
- Consider request throttling/rate limiting if threat model changes.

---

## Step 5 Exit Assessment

- Private-network assumptions and controls: **met**
- Access-control baseline effectiveness: **met**
- Validation and safe-output safety: **met (baseline)**
- Secret handling and config safety: **met**
- Dependency/security risk closure: **met (no critical/high findings)**
- Test and regression safety: **met**

Step 5 completion status: **complete**

---

## Handoff to Step 6

Once Step 5 is marked complete, Step 6 can proceed with:

- clearer operational security assumptions for logs/runbooks
- hardened boundary behavior for diagnosis and support
- reduced risk posture for personal-scale ongoing operations