Merge pull request 'Fail closed when dashboard authentication is not explicitly configured' (#263) from timmy/262-fail-closed-dashboard-auth into main

Closes #262

README.md

@@ -45,16 +45,18 @@ comment path and submits the summary, decision, and inline comments in one revie
 request. The dashboard rechecks the current pull-request head, CI success, draft
 state, and mergeability immediately before every merge.
 Serve the dashboard only to trusted users on its own origin; cross-origin API
-access is intentionally disabled. For any deployment not already behind an
-authenticated gateway, configure the built-in single-operator boundary with two
-independent high-entropy secrets. The access token is entered at `/login`; the
-browser receives only a short-lived signed session and CSRF proof. Generate the
-values in your secret manager (for example, `openssl rand -hex 32`) and inject
+access is intentionally disabled. Authentication defaults to fail-closed
+`operator` mode. It requires two independent secrets of at least 24 characters;
+missing, short, reused, or invalid configuration leaves `/healthz` available but
+returns HTTP 503 before any Gitea access. The access token is entered at `/login`;
+the browser receives only a short-lived signed session and CSRF proof. Generate
+both values in your secret manager (for example, `openssl rand -hex 32`) and inject
 them at runtime—never commit them:
 
 ```bash
 export GITEA_URL='https://forge.example.com'
 export GITEA_TOKEN='<read-notification-and-issue-write-token>'
+export STACKCHAIN_DASHBOARD_AUTH_MODE='operator'
 export STACKCHAIN_DASHBOARD_ACCESS_TOKEN='<operator-sign-in-secret>'
 export STACKCHAIN_DASHBOARD_SESSION_SECRET='<independent-cookie-signing-secret>'
 # Optional; defaults to eight hours.
@@ -68,11 +70,15 @@ Use **Sign out & clear this device** on shared devices; it clears Stackchain's
 offline snapshots, drafts, outboxes, background IndexedDB, and PWA caches without
 removing unrelated forge preferences. Rotate either dashboard secret by replacing
 the injected value and restarting the service; changing the signing secret expires
-all sessions immediately.
+all sessions immediately. The signing key is never derived from the access token.
 
-Open `http://127.0.0.1:8000/` only for an unprotected local development run. To
-verify the backend and its Gitea connection directly, sign in and request
-`http://127.0.0.1:8000/api/v1/context`; a successful response is JSON containing
+For direct, unproxied local development only, set
+`STACKCHAIN_DASHBOARD_AUTH_MODE=insecure-local` and open
+`http://127.0.0.1:8000/`. This mode checks the network peer and rejects non-loopback
+clients; do not use it behind a reverse proxy, whose loopback connection would hide
+the browser's peer address. To verify the backend and its Gitea connection in
+operator mode, sign in and request `http://127.0.0.1:8000/api/v1/context`; a
+successful response is JSON containing
 `user`, `repos`, `issues`, and `pull_requests`. Press `Ctrl/Cmd+K` in the dashboard
 to search commands plus issues and pull requests across every repository visible to
 the configured Gitea token. Remote search starts after two characters, is debounced,

conftest.py

@@ -0,0 +1,9 @@
+import pytest
+
+
+@pytest.fixture(autouse=True)
+def explicit_local_dashboard_auth_mode(monkeypatch):
+    """Keep tests intentional now that deployed authentication fails closed."""
+    monkeypatch.setenv("STACKCHAIN_DASHBOARD_AUTH_MODE", "insecure-local")
+    monkeypatch.delenv("STACKCHAIN_DASHBOARD_ACCESS_TOKEN", raising=False)
+    monkeypatch.delenv("STACKCHAIN_DASHBOARD_SESSION_SECRET", raising=False)

src/dashboard_auth.py

@@ -3,6 +3,7 @@
 import base64
 import hashlib
 import hmac
+import ipaddress
 import json
 import os
 import secrets
@@ -14,6 +15,9 @@ from fastapi import Request
 SESSION_COOKIE = "stackchain_session"
 CSRF_COOKIE = "stackchain_csrf"
 DEFAULT_TTL_SECONDS = 8 * 60 * 60
+MIN_SECRET_LENGTH = 24
+OPERATOR_MODE = "operator"
+INSECURE_LOCAL_MODE = "insecure-local"
 
 
 @dataclass(frozen=True)
@@ -26,17 +30,42 @@ def access_token() -> str:
     return os.getenv("STACKCHAIN_DASHBOARD_ACCESS_TOKEN", "")
 
 
+def mode() -> str:
+    return os.getenv("STACKCHAIN_DASHBOARD_AUTH_MODE", OPERATOR_MODE).strip().lower()
+
+
+def configuration_error() -> str | None:
+    configured_mode = mode()
+    if configured_mode == INSECURE_LOCAL_MODE:
+        return None
+    if configured_mode != OPERATOR_MODE:
+        return "unsupported authentication mode"
+    operator_secret = access_token()
+    signing_secret = os.getenv("STACKCHAIN_DASHBOARD_SESSION_SECRET", "")
+    if len(operator_secret) < MIN_SECRET_LENGTH or len(signing_secret) < MIN_SECRET_LENGTH:
+        return "operator mode requires two sufficiently long secrets"
+    if hmac.compare_digest(operator_secret, signing_secret):
+        return "operator and session secrets must be independent"
+    return None
+
+
 def enabled() -> bool:
-    return bool(access_token())
+    return mode() == OPERATOR_MODE and configuration_error() is None
+
+
+def is_loopback_request(request: Request) -> bool:
+    host = request.client.host if request.client else ""
+    try:
+        return ipaddress.ip_address(host).is_loopback
+    except ValueError:
+        return host == "localhost"
 
 
 def _secret() -> bytes:
     configured = os.getenv("STACKCHAIN_DASHBOARD_SESSION_SECRET", "")
-    if configured:
-        return configured.encode()
-    return hmac.new(
-        access_token().encode(), b"stackchain-dashboard-session-signing", hashlib.sha256
-    ).digest()
+    if configuration_error() is not None or mode() != OPERATOR_MODE:
+        raise RuntimeError("Dashboard authentication is not configured")
+    return configured.encode()
 
 
 def _encode(raw: bytes) -> str:

src/main.py

@@ -430,10 +430,26 @@ app.include_router(frontend_router)
 
 @app.middleware("http")
 async def require_operator_session(request: Request, call_next):
-    if not dashboard_auth.enabled():
+    path = dashboard_auth.application_path(request)
+    if path == "/healthz":
+        return await call_next(request)
+
+    if dashboard_auth.configuration_error() is not None:
+        return JSONResponse(
+            {"detail": "Dashboard authentication is not configured"},
+            status_code=503,
+            headers={"Cache-Control": "no-store"},
+        )
+
+    if dashboard_auth.mode() == dashboard_auth.INSECURE_LOCAL_MODE:
+        if not dashboard_auth.is_loopback_request(request):
+            return JSONResponse(
+                {"detail": "Insecure local mode requires a loopback client"},
+                status_code=403,
+                headers={"Cache-Control": "no-store"},
+            )
         return await call_next(request)
 
-    path = dashboard_auth.application_path(request)
     public = (
         path in {"/healthz", "/readyz", "/login", "/manifest.webmanifest"}
         or path.startswith("/static/")

tests/test_dashboard_auth.py

@@ -6,10 +6,72 @@ from src import main
 
 @pytest.fixture
 def access_control(monkeypatch):
+    monkeypatch.setenv("STACKCHAIN_DASHBOARD_AUTH_MODE", "operator")
     monkeypatch.setenv("STACKCHAIN_DASHBOARD_ACCESS_TOKEN", "correct horse battery staple")
     monkeypatch.setenv("STACKCHAIN_DASHBOARD_SESSION_SECRET", "a-separate-session-signing-secret-with-enough-entropy")
 
 
+@pytest.mark.anyio
+async def test_default_operator_mode_fails_closed_before_gitea_when_secrets_are_missing(monkeypatch):
+    monkeypatch.delenv("STACKCHAIN_DASHBOARD_AUTH_MODE", raising=False)
+    called = False
+
+    async def user():
+        nonlocal called
+        called = True
+        return {"id": 1, "login": "timmy"}
+
+    monkeypatch.setattr(main, "current_user", user)
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="https://test") as client:
+        health = await client.get("/healthz")
+        responses = [
+            await client.get("/readyz"),
+            await client.get("/login"),
+            await client.get("/"),
+            await client.get("/api/v1/context"),
+        ]
+
+    assert health.status_code == 200
+    assert [response.status_code for response in responses] == [503, 503, 503, 503]
+    assert all(response.headers["cache-control"] == "no-store" for response in responses)
+    assert all(response.json() == {
+        "detail": "Dashboard authentication is not configured"
+    } for response in responses)
+    assert called is False
+
+
+@pytest.mark.anyio
+async def test_operator_mode_rejects_reused_or_incomplete_secrets(monkeypatch):
+    monkeypatch.setenv("STACKCHAIN_DASHBOARD_AUTH_MODE", "operator")
+    monkeypatch.setenv("STACKCHAIN_DASHBOARD_ACCESS_TOKEN", "same-secret-with-at-least-thirty-two-characters")
+    monkeypatch.setenv("STACKCHAIN_DASHBOARD_SESSION_SECRET", "same-secret-with-at-least-thirty-two-characters")
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="https://test") as client:
+        reused = await client.get("/login")
+        monkeypatch.setenv("STACKCHAIN_DASHBOARD_SESSION_SECRET", "")
+        incomplete = await client.get("/login")
+
+    assert reused.status_code == 503
+    assert incomplete.status_code == 503
+    assert "same-secret" not in reused.text
+
+
+@pytest.mark.anyio
+async def test_insecure_local_mode_is_restricted_to_loopback(monkeypatch):
+    monkeypatch.setenv("STACKCHAIN_DASHBOARD_AUTH_MODE", "insecure-local")
+    local_transport = httpx.ASGITransport(app=main.app, client=("127.0.0.1", 1234))
+    remote_transport = httpx.ASGITransport(app=main.app, client=("203.0.113.9", 1234))
+    async with httpx.AsyncClient(transport=local_transport, base_url="http://test") as client:
+        local = await client.get("/login")
+    async with httpx.AsyncClient(transport=remote_transport, base_url="http://test") as client:
+        remote = await client.get("/login")
+
+    assert local.status_code == 200
+    assert remote.status_code == 403
+    assert remote.json() == {"detail": "Insecure local mode requires a loopback client"}
+
+
 @pytest.mark.anyio
 async def test_anonymous_private_request_is_rejected_before_gitea(access_control, monkeypatch):
     called = False