Fix wrong container runtime detection on Linux

Use "podman" when on Linux, and "docker" otherwise.
Show what the error was when the command failed.

dangerzone/gui/__init__.py

@@ -5,7 +5,7 @@
 import signal
 import sys
 import typing
-from typing import Dict, List, Optional
+from typing import List, Optional
 
 import click
 import colorama

dangerzone/gui/main_window.py

@@ -10,14 +10,18 @@
 # FIXME: See https://github.com/freedomofpress/dangerzone/issues/320 for more details.
 if typing.TYPE_CHECKING:
  from PySide2 import QtCore, QtGui, QtSvg, QtWidgets
- from PySide2.QtWidgets import QAction
+ from PySide2.QtCore import Qt
+ from PySide2.QtWidgets import QAction, QTextEdit
 else:
  try:
  from PySide6 import QtCore, QtGui, QtSvg, QtWidgets
+ from PySide6.QtCore import Qt
  from PySide6.QtGui import QAction
+ from PySide6.QtWidgets import QTextEdit
  except ImportError:
  from PySide2 import QtCore, QtGui, QtSvg, QtWidgets
- from PySide2.QtWidgets import QAction
+ from PySide2.QtWidgets import QAction, QTextEdit
+ from PySide2.QtCore import Qt
 
 from .. import errors
 from ..document import SAFE_EXTENSION, Document
@@ -434,10 +438,29 @@ def __init__(self, dangerzone: DangerzoneGui) -> None:
  self.buttons = QtWidgets.QWidget()
  self.buttons.setLayout(buttons_layout)
 
+ # Error
+ self.error_text = QTextEdit()
+ self.error_text.setReadOnly(True)
+ self.error_text.setStyleSheet(
+ """
+ QTextEdit {
+ font-family: Consolas, Monospace;
+ font-size: 12px;
+ background-color: #fff;
+ color: #000;
+ padding: 10px;
+ }
+ """
+ )
+ self.error_text.setVisible(False)
+ # Enable copying
+ self.error_text.setTextInteractionFlags(Qt.TextSelectableByMouse)
+
  # Layout
  layout = QtWidgets.QVBoxLayout()
  layout.addStretch()
  layout.addWidget(self.label)
+ layout.addWidget(self.error_text)
  layout.addStretch()
  layout.addWidget(self.buttons)
  layout.addStretch()
@@ -448,49 +471,84 @@ def __init__(self, dangerzone: DangerzoneGui) -> None:
 
  def check_state(self) -> None:
  state: Optional[str] = None
+ error: Optional[str] = None
 
  try:
  if isinstance( # Sanity check
  self.dangerzone.isolation_provider, Container
  ):
  container_runtime = self.dangerzone.isolation_provider.get_runtime()
+ runtime_name = self.dangerzone.isolation_provider.get_runtime_name()
  except NoContainerTechException as e:
  log.error(str(e))
  state = "not_installed"
 
  else:
- # Can we run `docker image ls` without an error
+ # Can we run `docker/podman image ls` without an error
  with subprocess.Popen(
  [container_runtime, "image", "ls"],
  stdout=subprocess.DEVNULL,
- stderr=subprocess.DEVNULL,
+ stderr=subprocess.PIPE,
  startupinfo=get_subprocess_startupinfo(),
  ) as p:
- p.communicate()
+ _, stderr = p.communicate()
  if p.returncode != 0:
- log.error("Docker is not running")
+ log.error(f"{runtime_name} is not running")
  state = "not_running"
+ error = stderr.decode()
  else:
  # Always try installing the container
  state = "install_container"
 
  # Update the state
- self.state_change(state)
+ self.state_change(state, error)
 
- def state_change(self, state: str) -> None:
+ def state_change(self, state: str, error: str | None = None) -> None:
  if state == "not_installed":
- self.label.setText(
- "<strong>Dangerzone Requires Docker Desktop</strong><br><br><a href='https://www.docker.com/products/docker-desktop'>Download Docker Desktop</a>, install it, and open it."
- )
+ if platform.system() == "Linux":
+ self.label.setText(
+ (
+ "<strong>Dangerzone requires Podman</strong><br><br>"
+ "Install it and retry."
+ )
+ )
+ else:
+ self.label.setText(
+ (
+ "<strong>Dangerzone requires Docker Desktop</strong><br><br>"
+ "<a href='https://www.docker.com/products/docker-desktop'>Download Docker Desktop</a>"
+ ", install it, and open it."
+ )
+ )
  self.buttons.show()
  elif state == "not_running":
- self.label.setText(
- "<strong>Dangerzone Requires Docker Desktop</strong><br><br>Docker is installed but isn't running.<br><br>Open Docker and make sure it's running in the background."
- )
+ if platform.system() == "Linux":
+ # "not_running" here means that the `podman image ls` command failed.
+ message = (
+ "<strong>Dangerzone requires Podman</strong><br><br>"
+ "Podman is installed but cannot run properly. See errors below"
+ )
+ if error:
+ self.error_text.setPlainText(error)
+ self.error_text.setVisible(True)
+
+ self.label.setText(message)
+
+ else:
+ self.label.setText(
+ (
+ "<strong>Dangerzone requires Docker Desktop</strong><br><br>"
+ "Docker is installed but isn't running.<br><br>"
+ "Open Docker and make sure it's running in the background."
+ )
+ )
  self.buttons.show()
  else:
  self.label.setText(
- "Installing the Dangerzone container image.<br><br>This might take a few minutes..."
+ (
+ "Installing the Dangerzone container image.<br><br>"
+ "This might take a few minutes..."
+ )
  )
  self.buttons.hide()
  self.install_container_t = InstallContainerThread(self.dangerzone)

dangerzone/isolation_provider/container.py

@@ -242,7 +242,7 @@ def assert_field_type(self, val: Any, _type: object) -> None:
  # `int`.
  #
  # See https://stackoverflow.com/a/37888668
- if not type(val) == _type:
+ if type(val) is not _type:
  raise ValueError("Status field has incorrect type")
 
  def parse_progress_trusted(self, document: Document, line: str) -> None: