Add qt.chromium.sandboxing setting and sandboxing test

doc/changelog.asciidoc

@@ -60,6 +60,7 @@ Added
   which shows relative tab numbers.
 - New `input.mode_override` option which allows overriding the current mode
   based on the new URL when navigating or switching tabs.
+- New `qt.chromium.sandboxing` setting which allows to disable Chromium's sandboxing (mainly intended for development and testing)
 
 Fixed
 ~~~~~

doc/help/settings.asciidoc

@@ -289,6 +289,7 @@
 |<<qt.args,qt.args>>|Additional arguments to pass to Qt, without leading `--`.
 |<<qt.chromium.low_end_device_mode,qt.chromium.low_end_device_mode>>|When to use Chromium's low-end device mode.
 |<<qt.chromium.process_model,qt.chromium.process_model>>|Which Chromium process model to use.
+|<<qt.chromium.sandboxing,qt.chromium.sandboxing>>|What sandboxing mechanisms in Chromium to use.
 |<<qt.environ,qt.environ>>|Additional environment variables to set.
 |<<qt.force_platform,qt.force_platform>>|Force a Qt platform to use.
 |<<qt.force_platformtheme,qt.force_platformtheme>>|Force a Qt platformtheme to use.
@@ -3814,6 +3815,30 @@ Valid values:
 
 Default: +pass:[process-per-site-instance]+
 
+[[qt.chromium.sandboxing]]
+=== qt.chromium.sandboxing
+What sandboxing mechanisms in Chromium to use.
+Chromium has various sandboxing layers, which should be enabled for normal browser usage. Mainly for testing and development, it's possible to disable individual sandboxing layers via this setting.
+Open `chrome://sandbox` to see the current sandbox status.
+Changing this setting is only recommended if you know what you're doing, as it **disables one of Chromium's security layers**. To avoid sandboxing being accidentally disabled persistently, this setting can only be set via `config.py`, not via `:set`.
+See the Chromium documentation for more details: - Linux: https://chromium.googlesource.com/chromium/src/+/HEAD/docs/linux/sandboxing.md - Windows: https://chromium.googlesource.com/chromium/src/+/HEAD/docs/design/sandbox.md - FAQ (Windows-centric): https://chromium.googlesource.com/chromium/src/+/HEAD/docs/design/sandbox_faq.md
+
+This setting requires a restart.
+
+This setting can only be set in config.py.
+
+This setting is only available with the QtWebEngine backend.
+
+Type: <<types,String>>
+
+Valid values:
+
+ * +enable-all+: Enable all available sandboxing mechanisms.
+ * +disable-seccomp-bpf+: Disable the Seccomp BPF filter sandbox (Linux only).
+ * +disable-all+: Disable all sandboxing (**not recommended!**).
+
+Default: +pass:[enable-all]+
+
 [[qt.environ]]
 === qt.environ
 Additional environment variables to set.

qutebrowser/config/configdata.yml

@@ -290,6 +290,36 @@ qt.chromium.low_end_device_mode:
     This improves the RAM usage of renderer processes, at the expense of
     performance.
 
+qt.chromium.sandboxing:
+  type:
+    name: String
+    valid_values:
+      - enable-all: Enable all available sandboxing mechanisms.
+      - disable-seccomp-bpf: Disable the Seccomp BPF filter sandbox (Linux only).
+      - disable-all: Disable all sandboxing (**not recommended!**).
+  default: enable-all
+  backend: QtWebEngine
+  restart: true
+  no_autoconfig: true  # due to it being dangerous
+  desc: >-
+    What sandboxing mechanisms in Chromium to use.
+
+    Chromium has various sandboxing layers, which should be enabled for normal
+    browser usage. Mainly for testing and development, it's possible to disable
+    individual sandboxing layers via this setting.
+
+    Open `chrome://sandbox` to see the current sandbox status.
+
+    Changing this setting is only recommended if you know what you're doing, as
+    it **disables one of Chromium's security layers**. To avoid sandboxing being
+    accidentally disabled persistently, this setting can only be set via
+    `config.py`, not via `:set`.
+
+    See the Chromium documentation for more details:
+    - Linux: https://chromium.googlesource.com/chromium/src/+/HEAD/docs/linux/sandboxing.md
+    - Windows: https://chromium.googlesource.com/chromium/src/+/HEAD/docs/design/sandbox.md
+    - FAQ (Windows-centric): https://chromium.googlesource.com/chromium/src/+/HEAD/docs/design/sandbox_faq.md
+
 qt.highdpi:
   type: Bool
   default: false

qutebrowser/config/qtargs.py

@@ -338,6 +338,11 @@ def _qtwebengine_settings_args(versions: version.WebEngineVersions) -> Iterator[
             True: '--force-prefers-reduced-motion',
             False: None,
         },
+        'qt.chromium.sandboxing': {
+            'enable-all': None,
+            'disable-seccomp-bpf': '--disable-seccomp-filter-sandbox',
+            'disable-all': '--no-sandbox',
+        }
     }
     qt_514_ver = utils.VersionNumber(5, 14)
 

tests/end2end/test_invocations.py

@@ -826,3 +826,48 @@ def test_json_logging_without_debug(request, quteproc_new, runtime_tmpdir):
     quteproc_new.exit_expected = True
     quteproc_new.start(args, env={'XDG_RUNTIME_DIR': str(runtime_tmpdir)})
     assert not quteproc_new.is_running()
+
+
+@pytest.mark.qtwebkit_skip
+@pytest.mark.parametrize('sandboxing, has_namespaces, has_seccomp, has_yama, expected_result', [
+    ('enable-all', True, True, True, "You are adequately sandboxed."),
+    ('disable-seccomp-bpf', True, False, True, "You are NOT adequately sandboxed."),
+    ('disable-all', False, False, False, "You are NOT adequately sandboxed."),
+])
+def test_sandboxing(
+        request, quteproc_new, sandboxing,
+        has_namespaces, has_seccomp, has_yama, expected_result,
+):
+    args = _base_args(request.config) + [
+        '--temp-basedir',
+        '-s', 'qt.chromium.sandboxing', sandboxing,
+    ]
+    quteproc_new.start(args)
+
+    quteproc_new.open_url('chrome://sandbox')
+    text = quteproc_new.get_content()
+    print(text)
+    header, *lines, empty, result = text.split("\n")
+
+    assert header == "Sandbox Status"
+    assert not empty
+
+    status = dict(line.split("\t") for line in lines)
+
+    bpf_text = "Seccomp-BPF sandbox"
+    yama_text = "Ptrace Protection with Yama LSM"
+    expected_status = {
+        "Layer 1 Sandbox": "Namespace" if has_namespaces else "None",
+
+        "PID namespaces": "Yes" if has_namespaces else "No",
+        "Network namespaces": "Yes" if has_namespaces else "No",
+
+        bpf_text: "Yes" if has_seccomp else "No",
+        f"{bpf_text} supports TSYNC": "Yes" if has_seccomp else "No",
+
+        f"{yama_text} (Broker)": "Yes" if has_yama else "No",
+        f"{yama_text} (Non-broker)": "No",
+    }
+
+    assert status == expected_status
+    assert result == expected_result

tests/unit/config/test_qtargs.py

@@ -277,6 +277,28 @@ class TestWebEngineArgs:
         else:
             assert arg in args
 
+    @pytest.mark.parametrize('sandboxing, arg', [
+        ('enable-all', None),
+        ('disable-seccomp-bpf', '--disable-seccomp-filter-sandbox'),
+        ('disable-all', '--no-sandbox'),
+    ])
+    def test_sandboxing(self, config_stub, parser, sandboxing, arg):
+        config_stub.val.qt.chromium.sandboxing = sandboxing
+        parsed = parser.parse_args([])
+        args = qtargs.qt_args(parsed)
+
+        remaining_flags = {
+            '--no-sandbox',
+            '--disable-seccomp-filter-sandbox',
+        }
+        if arg is not None:
+            remaining_flags.remove(arg)
+
+        if arg is not None:
+            assert arg in args
+
+        assert not set(args) & remaining_flags
+
     @pytest.mark.parametrize('qt_version, referer, arg', [
         # 'always' -> no arguments
         ('5.15.0', 'always', None),