Add dependency-aware module ordering

docs/development.md

@@ -21,6 +21,24 @@ make check
 
 Run these tests before making new commits or opening pull requests.
 
+## Module dependencies
+
+Modules can require other modules to run first by declaring their classes in
+`dependencies`. The command runner uses a stable topological ordering, so the
+existing module list order is preserved wherever dependency constraints allow.
+
+```python
+class DependentModule(MVTModule):
+    dependencies = (PrerequisiteModule,)
+
+    def run(self):
+        prerequisite_results = self.get_dependency_results(PrerequisiteModule)
+```
+
+Selecting a single module also runs its transitive dependencies. If a dependency
+is unavailable or the dependency graph contains a cycle, the command logs a
+warning and does not run any modules.
+
 ## Profiling
 
 Some MVT modules extract and process significant amounts of data during the analysis process or while checking results against known indicators. Care must be

src/mvt/common/command.py

@@ -8,6 +8,7 @@ import logging
 import os
 import sys
 from datetime import datetime
+from heapq import heappop, heappush
 from typing import Any, Optional
 
 from rich.console import Console
@@ -18,6 +19,7 @@ from .alerts import AlertLevel, AlertStore
 from .config import settings
 from .indicators import Indicators
 from .module import EncryptedBackupError, MVTModule, run_module, save_timeline
+from .module_types import ModuleTimeline
 from .utils import (
     CustomJSONEncoder,
     convert_datetime_to_iso,
@@ -44,7 +46,7 @@ class Command:
         disable_indicator_check: bool = False,
     ) -> None:
         self.name = ""
-        self.modules: list[Any] = []
+        self.modules: list[type[MVTModule]] = []
 
         self.target_path = target_path
         self.results_path = results_path
@@ -63,10 +65,10 @@ class Command:
 
         # This list will contain all executed modules.
         # We can use this to reference e.g. self.executed[0].results.
-        self.executed: list[Any] = []
+        self.executed: list[MVTModule] = []
         self.hashes = hashes
         self.hash_values: list[dict[str, Any]] = []
-        self.timeline: list[dict[str, Any]] = []
+        self.timeline: ModuleTimeline = []
 
         # Load IOCs
         self._create_storage()
@@ -258,20 +260,84 @@ class Command:
         console.print("")
         console.print(panel)
 
+    def _ordered_modules(self) -> Optional[list[type[MVTModule]]]:
+        """Return enabled modules in stable topological order."""
+        module_indexes = {module: index for index, module in enumerate(self.modules)}
+
+        if self.module_name:
+            selected = [
+                module for module in self.modules if module.__name__ == self.module_name
+            ]
+        else:
+            selected = [module for module in self.modules if module.enabled]
+
+        required = set(selected)
+        pending = list(selected)
+        while pending:
+            module = pending.pop()
+            for dependency in module.dependencies:
+                if dependency not in module_indexes:
+                    self.log.warning(
+                        "Module %s depends on unavailable module %s. "
+                        "No modules will be run.",
+                        module.__name__,
+                        dependency.__name__,
+                    )
+                    return None
+                if dependency not in required:
+                    required.add(dependency)
+                    pending.append(dependency)
+
+        dependents: dict[type[MVTModule], list[type[MVTModule]]] = {
+            module: [] for module in required
+        }
+        indegree = {module: 0 for module in required}
+        for module in required:
+            for dependency in module.dependencies:
+                if dependency not in required:
+                    continue
+                dependents[dependency].append(module)
+                indegree[module] += 1
+
+        ready: list[tuple[int, type[MVTModule]]] = []
+        for module, count in indegree.items():
+            if count == 0:
+                heappush(ready, (module_indexes[module], module))
+
+        ordered = []
+        while ready:
+            _, module = heappop(ready)
+            ordered.append(module)
+            for dependent in dependents[module]:
+                indegree[dependent] -= 1
+                if indegree[dependent] == 0:
+                    heappush(ready, (module_indexes[dependent], dependent))
+
+        if len(ordered) != len(required):
+            cyclic_modules = sorted(
+                (module.__name__ for module, count in indegree.items() if count > 0)
+            )
+            self.log.warning(
+                "Circular module dependency detected involving: %s. "
+                "No modules will be run.",
+                ", ".join(cyclic_modules),
+            )
+            return None
+
+        return ordered
+
     def run(self) -> None:
+        ordered_modules = self._ordered_modules()
+        if ordered_modules is None:
+            return
+
         try:
             self.init()
         except NotImplementedError:
             pass
 
-        for module in self.modules:
-            if self.module_name and module.__name__ != self.module_name:
-                continue
-
-            if not module.enabled and not (
-                self.module_name and module.__name__ == self.module_name
-            ):
-                continue
+        executed_by_type: dict[type[MVTModule], MVTModule] = {}
+        for module in ordered_modules:
 
             # FIXME: do we need the logger here
             module_logger = logging.getLogger(module.__module__)
@@ -282,6 +348,10 @@ class Command:
                 module_options=self.module_options,
                 log=module_logger,
             )
+            m.dependency_modules = {
+                dependency: executed_by_type[dependency]
+                for dependency in module.dependencies
+            }
 
             if self.iocs.total_ioc_count:
                 m.indicators = self.iocs
@@ -305,6 +375,7 @@ class Command:
                 return
 
             self.executed.append(m)
+            executed_by_type[module] = m
             self.timeline.extend(m.timeline)
             self.alertstore.extend(m.alertstore.alerts)
 

src/mvt/common/module.py

@@ -9,7 +9,7 @@ import logging
 import os
 import re
 from dataclasses import asdict, is_dataclass
-from typing import Any, Dict, Optional
+from typing import Any, Dict, Optional, Sequence
 
 from .alerts import AlertStore
 from .indicators import Indicators
@@ -43,6 +43,7 @@ class MVTModule:
 
     enabled: bool = True
     slug: Optional[str] = None
+    dependencies: Sequence[type["MVTModule"]] = ()
 
     def __init__(
         self,
@@ -71,6 +72,7 @@ class MVTModule:
         self.file_path: Optional[str] = file_path
         self.target_path: Optional[str] = target_path
         self.results_path: Optional[str] = results_path
+        self.serial: Optional[str] = None
         self.module_options: Optional[Dict[str, Any]] = (
             module_options if module_options else {}
         )
@@ -81,6 +83,13 @@ class MVTModule:
 
         self.results: ModuleResults = results if results else []
         self.timeline: ModuleTimeline = []
+        self.dependency_modules: Dict[type["MVTModule"], "MVTModule"] = {}
+
+    def get_dependency_results(
+        self, module_class: type["MVTModule"]
+    ) -> ModuleResults:
+        """Return the results produced by a prerequisite module."""
+        return self.dependency_modules[module_class].results
 
     @classmethod
     def from_json(cls, json_path: str, log: logging.Logger):

tests/common/test_command.py

@@ -4,11 +4,59 @@
 #   https://license.mvt.re/1.1/
 
 import json
+import logging
 
 from mvt.common.command import Command
+from mvt.common.module import MVTModule
+
+
+class RecordingModule(MVTModule):
+    run_order = []
+
+    def run(self):
+        self.run_order.append(self.__class__.__name__)
+
+    def check_indicators(self):
+        pass
+
+
+class FirstModule(RecordingModule):
+    def run(self):
+        super().run()
+        self.results = ["first"]
+
+
+class SecondModule(RecordingModule):
+    dependencies = (FirstModule,)
+
+    def run(self):
+        super().run()
+        self.results = self.get_dependency_results(FirstModule) + ["second"]
+
+
+class ThirdModule(RecordingModule):
+    dependencies = (SecondModule,)
+
+
+class IndependentModule(RecordingModule):
+    pass
+
+
+class RecordingCommand(Command):
+    def init(self):
+        self.initialized = True
+
+    def module_init(self, module):
+        pass
+
+    def finish(self):
+        pass
 
 
 class TestCommand:
+    def setup_method(self):
+        RecordingModule.run_order = []
+
     def test_store_alerts_handles_bytes(self, tmp_path):
         cmd = Command(results_path=str(tmp_path))
         cmd.alertstore.medium(
@@ -21,3 +69,66 @@ class TestCommand:
 
         alerts = json.loads((tmp_path / "alerts.json").read_text())
         assert alerts[0]["event"]["payload"] == "\\xa8\\xa9"
+
+    def test_modules_run_in_stable_topological_order(self):
+        cmd = RecordingCommand()
+        cmd.modules = [ThirdModule, IndependentModule, SecondModule, FirstModule]
+
+        cmd.run()
+
+        assert RecordingModule.run_order == [
+            "IndependentModule",
+            "FirstModule",
+            "SecondModule",
+            "ThirdModule",
+        ]
+        second = next(module for module in cmd.executed if isinstance(module, SecondModule))
+        assert second.results == ["first", "second"]
+
+    def test_selected_module_runs_transitive_dependencies(self):
+        cmd = RecordingCommand(module_name="ThirdModule")
+        cmd.modules = [ThirdModule, SecondModule, FirstModule, IndependentModule]
+
+        cmd.run()
+
+        assert RecordingModule.run_order == [
+            "FirstModule",
+            "SecondModule",
+            "ThirdModule",
+        ]
+
+    def test_circular_dependency_warns_and_stops(self, caplog):
+        class CircularOne(RecordingModule):
+            pass
+
+        class CircularTwo(RecordingModule):
+            dependencies = (CircularOne,)
+
+        CircularOne.dependencies = (CircularTwo,)
+
+        cmd = RecordingCommand()
+        cmd.modules = [CircularOne, CircularTwo]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == []
+        assert not hasattr(cmd, "initialized")
+        assert "Circular module dependency detected" in caplog.text
+
+    def test_unavailable_dependency_warns_and_stops(self, caplog):
+        class UnavailableModule(RecordingModule):
+            pass
+
+        class DependentModule(RecordingModule):
+            dependencies = (UnavailableModule,)
+
+        cmd = RecordingCommand()
+        cmd.modules = [DependentModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == []
+        assert not hasattr(cmd, "initialized")
+        assert "depends on unavailable module UnavailableModule" in caplog.text