Ensure that only podman and docker container runtimes can be used

dangerzone/container_utils.py

@@ -21,6 +21,8 @@ class Runtime(object):
 
         if settings.custom_runtime_specified():
             self.path = Path(settings.get("container_runtime"))
+            if not self.path.exists():
+                raise errors.UnsupportedContainerRuntime(self.path)
             self.name = self.path.stem
         else:
             self.name = self.get_default_runtime_name()
@@ -29,6 +31,9 @@ class Runtime(object):
                 raise errors.NoContainerTechException(self.name)
             self.path = Path(binary_path)
 
+        if self.name not in ("podman", "docker"):
+            raise errors.UnsupportedContainerRuntime(self.name)
+
     @staticmethod
     def get_default_runtime_name() -> str:
         return "podman" if platform.system() == "Linux" else "docker"

dangerzone/errors.py

@@ -140,3 +140,7 @@ class NotAvailableContainerTechException(Exception):
         self.error = error
         self.container_tech = container_tech
         super().__init__(f"{container_tech} is not available")
+
+
+class UnsupportedContainerRuntime(Exception):
+    pass

tests/test_container_utils.py

@@ -1,20 +1,21 @@
 from pathlib import Path
 
+import pytest
 from pytest_mock import MockerFixture
 
+from dangerzone import errors
 from dangerzone.container_utils import Runtime
 from dangerzone.settings import Settings
 
 
 def test_get_runtime_name_from_settings(mocker: MockerFixture, tmp_path: Path) -> None:
     mocker.patch("dangerzone.settings.get_config_dir", return_value=tmp_path)
+    mocker.patch("dangerzone.container_utils.Path.exists", return_value=True)
 
     settings = Settings()
-    settings.set(
-        "container_runtime", "/opt/somewhere/new-kid-on-the-block", autosave=True
-    )
+    settings.set("container_runtime", "/opt/somewhere/docker", autosave=True)
 
-    assert Runtime().name == "new-kid-on-the-block"
+    assert Runtime().name == "docker"
 
 
 def test_get_runtime_name_linux(mocker: MockerFixture, tmp_path: Path) -> None:
@@ -46,3 +47,14 @@ def test_get_runtime_name_non_linux(mocker: MockerFixture, tmp_path: Path) -> No
     assert runtime.name == "docker"
     assert runtime.path == Path("/usr/bin/docker")
     assert Runtime().name == "docker"
+
+
+def test_get_unsupported_runtime_name(mocker: MockerFixture, tmp_path: Path):
+    mocker.patch("dangerzone.settings.get_config_dir", return_value=tmp_path)
+    settings = Settings()
+    settings.set(
+        "container_runtime", "/opt/somewhere/new-kid-on-the-block", autosave=True
+    )
+
+    with pytest.raises(errors.UnsupportedContainerRuntime):
+        assert Runtime().name == "new-kid-on-the-block"