Island: Handle IP address collisions when updating Machine on agent reg

monkey/monkey_island/cc/island_event_handlers/handle_agent_registration.py

@@ -1,6 +1,6 @@
 from contextlib import suppress
 from ipaddress import IPv4Address, IPv4Interface
-from typing import Optional
+from typing import List, Optional
 
 from common import AgentRegistrationData
 from common.network.network_utils import address_to_ip_port
@@ -84,11 +84,21 @@ class handle_agent_registration:
     def _update_network_interfaces(
         self, machine: Machine, agent_registration_data: AgentRegistrationData
     ):
-        updated_network_interfaces = set(machine.network_interfaces)
+        updated_network_interfaces: List[IPv4Interface] = []
-        updated_network_interfaces = updated_network_interfaces.union(
+        agent_registration_data_ips = set(
-            agent_registration_data.network_interfaces
+            map(lambda iface: iface.ip, agent_registration_data.network_interfaces)
         )
 
+        # Prefer interfaces provided by the AgentRegistrationData to those in the Machine record.
+        # The AgentRegistrationData was collected while running on the machine, whereas the Machine
+        # data may have only been collected from a scan. For example, the Machine and
+        # AgentRedistrationData may have the same IP with a different subnet mask.
+        for interface in machine.network_interfaces:
+            if interface.ip not in agent_registration_data_ips:
+                updated_network_interfaces.append(interface)
+
+        updated_network_interfaces.extend(agent_registration_data.network_interfaces)
+
         machine.network_interfaces = sorted(updated_network_interfaces)
 
     def _add_agent(self, agent_registration_data: AgentRegistrationData, machine: Machine):

monkey/tests/unit_tests/monkey_island/cc/island_event_handlers/test_handle_agent_registration.py

@@ -201,3 +201,35 @@ def test_add_node_connection__unknown_server(handler, machine_repository, node_r
     node_repository.upsert_communication.assert_called_with(
         MACHINE.id, SEED_ID, CommunicationType.CC
     )
+
+
+def test_machine_interfaces_updated(handler, machine_repository):
+    existing_machine = Machine(
+        id=SEED_ID,
+        hardware_id=AGENT_REGISTRATION_DATA.machine_hardware_id,
+        network_interfaces=[IPv4Interface("192.168.1.2/32"), IPv4Interface("192.168.1.5/32")],
+    )
+    machine_repository.get_machine_by_hardware_id = MagicMock(return_value=existing_machine)
+    agent_registration_data = AgentRegistrationData(
+        id=AGENT_ID,
+        machine_hardware_id=MACHINE.hardware_id,
+        start_time=0,
+        parent_id=None,
+        cc_server="192.168.1.1:5000",
+        network_interfaces=[
+            IPv4Interface("192.168.1.2/24"),
+            IPv4Interface("192.168.1.3/16"),
+            IPv4Interface("192.168.1.4/24"),
+        ],
+    )
+    expected_network_interfaces = tuple(
+        sorted(
+            (*agent_registration_data.network_interfaces, existing_machine.network_interfaces[-1])
+        )
+    )
+
+    handler(agent_registration_data)
+    updated_machine = machine_repository.upsert_machine.call_args_list[0][0][0]
+    actual_network_interfaces = updated_machine.network_interfaces
+
+    assert actual_network_interfaces == expected_network_interfaces