LEDMatrix/test/test_composer_code_injection.py

"""The composer generates Python that the plugin loader imports and executes.

/api/install writes the generated manager.py into plugins_dir and the loader
imports it, so anything the payload can splice into that source runs on the
device. The ast.parse check in _generate_plugin_files rejects only *invalid*
syntax -- an injected `import os` is perfectly valid and passed it.

Two ways in, both confirmed against the code before it was fixed:

  metadata.name = a name containing a triple-quote, a newline, then
                  `import os; PWNED = os.getuid()`, then another triple-quote
      -> closes the module docstring; the rest became module-level statements
         (spelled out rather than shown literally -- writing the payload into
         this docstring closes *this* file's docstring, which is the bug)

  element x     = '0 or __import__("os").system("id")'
      -> f-string interpolated it verbatim: x=0 or __import__("os").system("id")
"""
import ast
import sys
from pathlib import Path

import pytest

sys.path.insert(0, str(Path(__file__).resolve().parent.parent))

from web_interface.blueprints import composer as C  # noqa: E402

BASE_META = {"id": "test-plugin", "name": "Clock", "author": "a",
             "version": "1.0.0", "description": "d"}

#: Values that terminate a Python expression and start a new statement.
EXPR_PAYLOADS = [
    '0 or __import__("os").system("id")',
    '0);import os;os.system("id");(',
    '__import__("subprocess").run(["id"])',
    "0 if False else exec('x=1')",
    "1e999", "nan", "0x41", "0__0",
]

#: Values that close a string literal in the generated source.
LITERAL_PAYLOADS = [
    'Clock"""\nimport os; PWNED = os.getuid()\n"""',
    "Clock'''\nimport os\n'''",
    'Clock" + __import__("os").system("id") + "',
    "Clock\\", "Clock\nimport os",
]


def _payload(**over):
    # dataModel.configVars is the key _generate_plugin_files reads; "config_vars"
    # was never looked at, so anything passed through it tested nothing.
    p = {"metadata": dict(BASE_META), "elements": [],
         "dataModel": {"configVars": over.pop("config_vars", [])}}
    p["metadata"].update(over.pop("metadata", {}))
    p.update(over)
    return p


def _generated(payload):
    return C._generate_plugin_files(payload)["manager.py"]


def _module_level_code(src):
    """Statements at module level that are not the docstring/imports/classes."""
    tree = ast.parse(src)
    out = []
    for node in tree.body:
        if isinstance(node, (ast.ClassDef, ast.FunctionDef, ast.ImportFrom)):
            continue
        if isinstance(node, ast.Expr) and isinstance(node.value, ast.Constant):
            continue  # the docstring
        out.append(ast.unparse(node))
    return out


@pytest.mark.parametrize("payload", LITERAL_PAYLOADS)
def test_a_name_that_breaks_out_of_a_literal_is_refused(payload):
    with pytest.raises(C.ComposerInputError):
        _generated(_payload(metadata={"name": payload}))


#: Types with a drawing branch in manager.py.j2. An injection test using any
#: other type proves nothing: _preprocess_elements drops it, so its values
#: never reach the generated source and every assertion passes trivially.
#: This test previously used "line", which has never had a branch.
RENDERED_GEOMETRY_CASES = [
    ("rectangle", {"x": 0, "y": 0, "width": 10, "height": 8}),
    ("arc", {"x": 0, "y": 0, "width": 24, "height": 24}),
    ("ellipse", {"x": 0, "y": 0, "width": 24, "height": 12}),
    ("rounded_rectangle", {"x": 0, "y": 0, "width": 24, "height": 10}),
    ("gauge", {"x": 0, "y": 0, "width": 32, "height": 32}),
]


@pytest.mark.parametrize("etype,base", RENDERED_GEOMETRY_CASES)
@pytest.mark.parametrize("evil", EXPR_PAYLOADS)
@pytest.mark.parametrize("field", ["x", "y", "width", "height"])
def test_a_non_numeric_geometry_value_cannot_reach_the_source(etype, base, evil, field):
    """width/height were interpolated raw into the generated source.

    p['x2_expr'] = f"({x_expr}) + {w}" with w straight off the payload, so a
    rectangle with width='0 or __import__("os").system("id")' produced

        [0, 0, (0) + 0 or __import__("os").system("id"), (0) + 8],

    in a manager.py that /api/install writes to disk and the loader imports.
    """
    el = {"type": etype, "id": "e1", **base}
    el[field] = evil
    src = _generated(_payload(elements=[el]))
    assert "__import__" not in src, f"{etype}.{field}={evil!r} reached the generated source"
    assert "os.system" not in src
    assert not _module_level_code(src), \
        f"{etype}.{field}={evil!r} produced module-level statements: {_module_level_code(src)}"


def test_every_injection_case_uses_a_type_that_actually_renders():
    """Guards against the whole suite quietly going vacuous again.

    An element type with no template branch is dropped before generation, so
    an injection test written against one asserts nothing and still passes.
    """
    used = {etype for etype, _ in RENDERED_GEOMETRY_CASES}
    missing = used - set(C._RENDERABLE_ELEMENT_TYPES)
    assert not missing, f"injection tests use non-rendering types: {sorted(missing)}"


@pytest.mark.parametrize("evil", EXPR_PAYLOADS)
@pytest.mark.parametrize("channel", ["r", "g", "b"])
def test_a_non_numeric_colour_channel_cannot_reach_the_source(evil, channel):
    el = {"type": "text", "id": "t1", "x": 0, "y": 0, "text": "hi",
          "font": "press_start", "r": 255, "g": 255, "b": 255}
    el[channel] = evil
    src = _generated(_payload(elements=[el]))
    assert "__import__" not in src and "os.system" not in src
    assert not _module_level_code(src)


def test_colour_channels_are_clamped_to_a_byte():
    el = {"type": "text", "id": "t1", "x": 0, "y": 0, "text": "hi",
          "font": "press_start", "r": 99999, "g": -5, "b": 128}
    src = _generated(_payload(elements=[el]))
    assert "(255, 0, 128)" in src, "channels were not clamped to 0-255"


def test_the_generated_module_still_has_no_top_level_statements():
    """The clean case: a normal payload produces only imports and a class."""
    el = {"type": "text", "id": "t1", "x": 4, "y": 4, "text": "hi",
          "font": "press_start", "r": 1, "g": 2, "b": 3}
    src = _generated(_payload(elements=[el]))
    assert not _module_level_code(src)
    assert "(1, 2, 3)" in src


# --- config variable keys ---------------------------------------------------

def _with_key(key):
    return {"metadata": dict(BASE_META), "elements": [],
            "dataModel": {"configVars": [{"key": key, "type": "string",
                                          "default": "x", "label": "L"}]}}


@pytest.mark.parametrize("key", ["class", "def", "import", "None", "True",
                                 "lambda", "pass", "match", "case"])
def test_a_keyword_config_key_is_named_in_the_error(key):
    """ast.parse already rejected these, but as an unhelpful line number.

    "Generated code has a syntax error: invalid syntax (line 17)" tells the
    user nothing about which field to fix.
    """
    with pytest.raises(C.ComposerInputError) as exc:
        _generated(_with_key(key))
    assert key in str(exc.value) and "keyword" in str(exc.value).lower()


@pytest.mark.parametrize("key", ["config", "logger", "display_manager",
                                 "cache_manager", "plugin_id", "enabled",
                                 "self", "update", "display"])
def test_a_reserved_attribute_config_key_is_refused(key):
    """These generate *valid* Python that silently clobbers plugin state.

    The worst is `config`: the assignment lands right after super().__init__(),
    so `self.config = config.get("config", "x")` replaces the plugin's config
    dict with a string and every later self.config.get(...) fails at runtime.
    """
    with pytest.raises(C.ComposerInputError) as exc:
        _generated(_with_key(key))
    assert key in str(exc.value) and "reserved" in str(exc.value).lower()


@pytest.mark.parametrize("key", ["brightness", "my_var", "_private", "x1",
                                 "update_interval_seconds"])
def test_ordinary_config_keys_are_still_accepted(key):
    src = _generated(_with_key(key))
    assert f"self.{key} = config.get(" in src


def test_the_generated_config_assignment_does_not_precede_super_init():
    """Guards the reasoning behind the reserved list, not just the list."""
    src = _generated(_with_key("brightness"))
    body = src.splitlines()
    super_at = next(i for i, line in enumerate(body) if "super().__init__(" in line)
    assign_at = next(i for i, line in enumerate(body)
                     if "self.brightness = config.get(" in line)
    assert assign_at > super_at, (
        "config vars are assigned before super().__init__(); the reserved-name "
        "list assumes they land after it")


# --- optional keys ----------------------------------------------------------

@pytest.mark.parametrize("el_type,missing", [
    ("text", "text"), ("text", "text2"), ("clock", "format"),
])
def test_an_element_missing_an_optional_key_does_not_500(el_type, missing):
    """`p` is a copy of the raw element, so an absent key stays absent.

    The defaults were applied to locals only, so manager.py.j2 rendered
    `{{ el.text | tojson }}` over a jinja2.Undefined and tojson raised
    TypeError -- which no handler catches, making a missing key a 500 rather
    than a validation error or a sensible default.
    """
    el = {"type": el_type, "id": "e1", "x": 0, "y": 0, "font": "press_start"}
    src = _generated(_payload(elements=[el]))
    ast.parse(src)          # must still be valid Python
    assert "Undefined" not in src


def test_a_clock_without_a_format_uses_the_documented_default():
    el = {"type": "clock", "id": "c1", "x": 0, "y": 0, "font": "press_start"}
    src = _generated(_payload(elements=[el]))
    assert '"%H:%M"' in src, "the %H:%M default did not reach the generated source"