Feat/add generation of device tls cert

cos_registration_server/api/schema_status.py

@@ -13,8 +13,28 @@
 code_200_device = {200: DeviceSerializer}
 code_201_device = {201: DeviceSerializer}
 
+code_200_device_certificate = {
+    200: {
+        "type": "object",
+        "properties": {
+            "certificate": {
+                "type": "string",
+                "description": "PEM-encoded certificate",
+            },
+            "private_key": {
+                "type": "string",
+                "description": "PEM-encoded private key",
+            },
+        },
+    }
+}
+
 code_404_uid_not_found = {404: OpenApiResponse(description="UID not found")}
 
+code_404_device_certificate_not_found = {
+    404: OpenApiResponse(description="Device certificate not found")
+}
+
 code_200_grafana_dashboard = {200: GrafanaDashboardSerializer}
 code_201_grafana_dashboard = {201: GrafanaDashboardSerializer}
 

cos_registration_server/api/tests.py

@@ -1,6 +1,7 @@
 import json
 from datetime import datetime, timedelta
 from typing import Any, Dict, Set, Union
+from unittest.mock import Mock, patch
 
 import yaml
 from applications.models import (
@@ -523,6 +524,60 @@ def test_delete_device(self) -> None:
         self.assertEqual(response.status_code, 404)
 
 
+class DeviceCertificateViewTests(APITestCase):
+    def setUp(self) -> None:
+        self.device_uid = "robot-123"
+        self.device_address = "192.168.0.10"
+        self.url = reverse(
+            "api:device-certificate", kwargs={"uid": self.device_uid}
+        )
+
+    def create_device(self, **fields: Union[str, Set[str]]) -> HttpResponse:
+        data = {}
+        for field, value in fields.items():
+            data[field] = value
+        url = reverse("api:devices")
+        return self.client.post(url, data, format="json")
+
+    def test_get_certificate_success(self) -> None:
+        self.create_device(uid=self.device_uid, address=self.device_address)
+
+        response = self.client.get(self.url)
+
+        self.assertEqual(response.status_code, 200)
+        data = json.loads(response.content)
+        self.assertIn("certificate", data)
+        self.assertIn("private_key", data)
+
+    def test_get_certificate_device_not_found(self) -> None:
+        response = self.client.get(self.url)
+
+        self.assertEqual(response.status_code, 404)
+        self.assertIn("Device does not exist", str(response.data))
+
+    def test_get_certificate_no_address(self) -> None:
+        self.create_device(uid=self.device_uid, address="")
+
+        response = self.client.get(self.url)
+        self.assertEqual(response.status_code, 404)
+        self.assertIn("Device does not exist", str(response.data))
+
+    @patch("api.views.generate_tls_certificate")
+    def test_get_certificate_missing_cert_data(
+        self, mock_generate: Mock
+    ) -> None:
+        self.create_device(uid=self.device_uid, address=self.device_address)
+
+        mock_generate.return_value = {"certificate": "", "private_key": ""}
+
+        response = self.client.get(self.url)
+
+        self.assertEqual(response.status_code, 404)
+        self.assertIn(
+            "Certificate data for device not found", str(response.data)
+        )
+
+
 class GrafanaDashboardsViewTests(APITestCase):
     def setUp(self) -> None:
         self.url = reverse("api:grafana_dashboards")

cos_registration_server/api/urls.py

@@ -18,6 +18,11 @@
     path("v1/health/", views.HealthView.as_view(), name="health"),
     path("v1/devices/", views.DevicesView.as_view(), name="devices"),
     path("v1/devices/<str:uid>/", views.DeviceView.as_view(), name="device"),
+    path(
+        "v1/devices/<str:uid>/certificate",
+        views.DeviceCertificateView.as_view(),
+        name="device-certificate",
+    ),
     path(
         "v1/applications/grafana/dashboards/",
         views.GrafanaDashboardsView.as_view(),

cos_registration_server/api/utils.py

@@ -0,0 +1,52 @@
+"""API utils."""
+
+import ipaddress
+from datetime import datetime, timedelta
+
+from cryptography import x509
+from cryptography.hazmat.primitives import hashes, serialization
+from cryptography.hazmat.primitives.asymmetric import rsa
+from cryptography.x509.oid import NameOID
+
+
+def generate_tls_certificate(
+    device_uid: str, device_ip: str
+) -> dict[str, str]:
+    """Generate a self-signed TLS certificate with device IP in SAN.
+
+    device_uid: the uid of the device.
+    device_ip: the ip of the device.
+    """
+    private_key = rsa.generate_private_key(
+        public_exponent=65537, key_size=2048
+    )
+
+    subject = issuer = x509.Name(
+        [
+            x509.NameAttribute(NameOID.COMMON_NAME, device_uid),
+        ]
+    )
+
+    san_list = [x509.IPAddress(ipaddress.ip_address(device_ip))]
+
+    cert = (
+        x509.CertificateBuilder()
+        .subject_name(subject)
+        .issuer_name(issuer)
+        .public_key(private_key.public_key())
+        .serial_number(x509.random_serial_number())
+        .not_valid_before(datetime.utcnow())
+        .not_valid_after(datetime.utcnow() + timedelta(days=365))
+        .add_extension(x509.SubjectAlternativeName(san_list), critical=False)
+        .sign(private_key, hashes.SHA256())
+    )
+
+    private_key_pem = private_key.private_bytes(
+        encoding=serialization.Encoding.PEM,
+        format=serialization.PrivateFormat.PKCS8,
+        encryption_algorithm=serialization.NoEncryption(),
+    ).decode()
+
+    cert_pem = cert.public_bytes(encoding=serialization.Encoding.PEM).decode()
+
+    return {"certificate": cert_pem, "private_key": private_key_pem}

cos_registration_server/api/views.py

@@ -38,6 +38,8 @@
 from rest_framework.response import Response
 from rest_framework.views import APIView
 
+from .utils import generate_tls_certificate
+
 
 class HealthView(APIView):
     """Health API view."""
@@ -161,6 +163,50 @@ def delete(
         return super().delete(request, *args, **kwargs)
 
 
+class DeviceCertificateView(APIView):
+    """Device Certificate API view."""
+
+    @extend_schema(
+        summary="Generate and get a device TLS certificate",
+        description="Generate and retrieve TLS certificate and "
+        "private key for a device by UID",
+        responses={
+            **status.code_200_device_certificate,
+            **status.code_404_uid_not_found,
+            **status.code_404_device_certificate_not_found,
+        },
+    )
+    def get(
+        self,
+        request: Request,
+        uid: str,
+        *args: Tuple[Any],
+        **kwargs: Dict[str, Any],
+    ) -> Response:
+        """GET a device TLS certificate and private key."""
+        try:
+            device = Device.objects.get(uid=uid)
+        except Device.DoesNotExist:
+            raise NotFound("Device does not exist")
+
+        # If the device exists it will have an address,
+        # the serializer does not allow the creation of a device
+        # without an ip address.
+        cert_data = generate_tls_certificate(device.uid, device.address)
+
+        if not cert_data.get("certificate") or not cert_data.get(
+            "private_key"
+        ):
+            raise NotFound("Certificate data for device not found")
+
+        return Response(
+            {
+                "certificate": cert_data["certificate"],
+                "private_key": cert_data["private_key"],
+            }
+        )
+
+
 class GrafanaDashboardsView(ListCreateAPIView):  # type: ignore[type-arg]
     """GrafanaDashboards API view."""
 

cos_registration_server/openapi.yaml

@@ -938,6 +938,38 @@ paths:
           description: ''
         '404':
           description: UID not found
+  /api/v1/devices/{uid}/certificate:
+    get:
+      operationId: devices_certificate_retrieve
+      description: Generate and retrieve TLS certificate and private key for a device
+        by UID
+      summary: Generate and get a device TLS certificate
+      parameters:
+      - in: path
+        name: uid
+        schema:
+          type: string
+        required: true
+      tags:
+      - devices
+      security:
+      - {}
+      responses:
+        '200':
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  certificate:
+                    type: string
+                    description: PEM-encoded certificate
+                  private_key:
+                    type: string
+                    description: PEM-encoded private key
+          description: ''
+        '404':
+          description: Device certificate not found
   /api/v1/health/:
     get:
       operationId: health_retrieve

requirements.txt

@@ -7,3 +7,4 @@ whitenoise
 tzdata
 gunicorn
 pyyaml
+cryptography