Harden: gate /api/export behind an admin token (closed by default)

/api/export returns every subscriber's Ki/OPc and was reachable unauthenticated
by any WiFi client (and directly, since Flask binds 0.0.0.0). It now requires
server.admin_token via the X-Admin-Token header (constant-time compare) and is
disabled entirely when no token is configured.

Add admin_token to config.yaml.example. Tests: +2 (disabled/401/200); 86 pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CHANGELOG.md

@@ -8,6 +8,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Security
+- `/api/export` (dumps every subscriber's Ki/OPc) now requires an admin token
+  (`server.admin_token`, sent as `X-Admin-Token`, constant-time compared) and
+  is disabled by default. Previously any WiFi client could pull all credentials
+  unauthenticated.
 - Profile download URLs now use an unguessable capability token
   (`secrets.token_urlsafe`) instead of the sequential subscriber id. Profiles
   contain Ki/OPc, so the old `/api/profile/<int>` scheme let anyone on the WiFi

config.yaml.example

@@ -15,6 +15,7 @@ server:
   host: "0.0.0.0"
   port: 5000
   debug: false
+  admin_token: ""    # set a secret to enable /api/export (sent as X-Admin-Token); empty = export disabled
 
 database:
   path: "/opt/esim-provisioning/data/subscribers.db"

server/app.py

@@ -93,6 +93,9 @@ def create_app(config_path: str = CONFIG_PATH) -> Flask:
     rl_cfg = cfg["rate_limiting"]
     window_hours = rl_cfg["window_hours"]
 
+    # Optional admin token guarding /api/export; unset means export is disabled.
+    admin_token = cfg.get("server", {}).get("admin_token") or ""
+
     # ------------------------------------------------------------------
     # Routes
     # ------------------------------------------------------------------
@@ -194,6 +197,14 @@ def create_app(config_path: str = CONFIG_PATH) -> Flask:
 
     @app.route("/api/export")
     def export():
+        # This endpoint dumps every subscriber's Ki/OPc, so it is gated behind
+        # an admin token and defaults closed (disabled unless configured).
+        if not admin_token:
+            return jsonify({"error": "Export disabled (server.admin_token not set)"}), 403
+        provided = request.headers.get("X-Admin-Token", "")
+        if not secrets.compare_digest(provided, admin_token):
+            return jsonify({"error": "Unauthorized"}), 401
+
         conn = get_connection(db_path)
         try:
             subscribers = export_all(conn)

tests/test_app.py

@@ -6,13 +6,14 @@ import yaml
 from server.app import create_app
 
 
-def _write_config(tmp_path):
+def _write_config(tmp_path, admin_token=""):
     cfg = {
         "network": {"mcc": "302", "mnc": "720", "plmn": "302720",
                     "op_key": "63bfa50ee6523365ff14c1f45f88737d"},
         "wifi": {"ssid": "Emergency-5G", "channel": 6, "ip": "192.168.4.1",
                  "subnet": "192.168.4.0/24", "dhcp_range": "192.168.4.10,192.168.4.250"},
-        "server": {"host": "0.0.0.0", "port": 5000, "debug": False},
+        "server": {"host": "0.0.0.0", "port": 5000, "debug": False,
+                   "admin_token": admin_token},
         "database": {"path": str(tmp_path / "subscribers.db")},
         "rate_limiting": {"max_profiles_per_mac": 1, "window_hours": 1},
         "core": {"type": "none", "mongodb_uri": "mongodb://localhost:27017",
@@ -32,6 +33,13 @@ def client(tmp_path):
     return app.test_client()
 
 
+@pytest.fixture
+def admin_client(tmp_path):
+    app = create_app(_write_config(tmp_path, admin_token="s3cret-token"))
+    app.config.update(TESTING=True)
+    return app.test_client()
+
+
 class TestRoutes:
     def test_index_redirects_to_activate(self, client):
         r = client.get("/")
@@ -43,8 +51,20 @@ class TestRoutes:
         assert data["status"] == "ok"
         assert data["core_adapter"] == "none"
 
-    def test_export_empty(self, client):
-        data = client.get("/api/export").get_json()
+    def test_export_disabled_without_admin_token(self, client):
+        # No server.admin_token configured -> export is disabled.
+        assert client.get("/api/export").status_code == 403
+
+    def test_export_requires_matching_token(self, admin_client):
+        assert admin_client.get("/api/export").status_code == 401
+        assert admin_client.get(
+            "/api/export", headers={"X-Admin-Token": "wrong"}
+        ).status_code == 401
+
+    def test_export_with_valid_token(self, admin_client):
+        r = admin_client.get("/api/export", headers={"X-Admin-Token": "s3cret-token"})
+        assert r.status_code == 200
+        data = r.get_json()
         assert data["count"] == 0
         assert data["subscribers"] == []