Open_Ultra_SAST/tests/test_model_taint.py

"""model-grounded-detection task 2.2: the taint verdict, and what separates entailed from corroborated.

An `ENTAILED` verdict is the static analogue of a reproduced crash: the CPG establishes the flow on its own and
the LLM's assertion is no longer load-bearing. `CORROBORATED` means a path exists but a sanitizer may break it,
so the judgement of sufficiency is the LLM's residual — checked against the graph, never averaged over runs.
"""

from __future__ import annotations

from pathlib import Path


def _cpg(rows: list[dict[str, object]]):  # type: ignore[no-untyped-def]
    from openultrasast.cpg.backend import CpgResult

    return CpgResult(cpg_path=Path("cpg.bin"), run=lambda query, params: rows)


def _spec():  # type: ignore[no-untyped-def]
    from openultrasast.model.specs import TaintSpec

    return TaintSpec(
        family="injection",
        language="python",
        sources=("request.args",),
        sinks=("os.system", "execute"),
        sanitizers=("escape", "quote"),
    )


def test_an_unsanitized_source_to_sink_path_is_entailed() -> None:
    from openultrasast.model.ladder import Rung
    from openultrasast.model.taint import verdict

    rows = [
        {"sink": "os.system(cmd)", "sinkLine": "4", "sinkMethod": "run", "source": "request.args['x']", "sanitized": False, "length": 3}
    ]
    answer = verdict(_cpg(rows), _spec(), function="run")
    assert answer is not None and answer.rung is Rung.ENTAILED
    assert answer.family == "injection"
    assert "request.args" in answer.witness and "os.system" in answer.witness, "the witness names the flow it found"


def test_a_path_through_a_sanitizer_is_corroborated_not_entailed() -> None:
    """The model saw the flow but cannot judge whether the sanitizer is sufficient. That residual is the LLM's."""
    from openultrasast.model.ladder import Rung
    from openultrasast.model.taint import verdict

    rows = [{"sink": "execute(q)", "sinkLine": "9", "sinkMethod": "run", "source": "request.args['q']", "sanitized": True, "length": 4}]
    answer = verdict(_cpg(rows), _spec(), function="run")
    assert answer is not None and answer.rung is Rung.CORROBORATED


def test_no_path_yields_no_verdict_so_the_caller_reports_suspicion() -> None:
    from openultrasast.model.taint import verdict

    assert verdict(_cpg([]), _spec(), function="run") is None


def test_a_query_that_failed_is_not_read_as_an_absence_of_flow() -> None:
    """`None` from the engine means "could not decide", which is not the same as "no path" — Req 4.3."""
    from openultrasast.cpg.backend import CpgResult
    from openultrasast.model.taint import verdict

    broken = CpgResult(cpg_path=Path("cpg.bin"), run=lambda query, params: None)
    assert verdict(broken, _spec(), function="run") is None


def test_the_verdict_is_restricted_to_the_labeled_function() -> None:
    from openultrasast.model.taint import verdict

    rows = [
        {
            "sink": "os.system(x)", "sinkLine": "40", "sinkMethod": "elsewhere",
            "source": "request.args['x']", "sanitized": False, "length": 2,
        }
    ]
    assert verdict(_cpg(rows), _spec(), function="run") is None, "a flow in another function does not judge this one"


def test_the_shortest_unsanitized_flow_wins_and_the_sequence_is_deterministic() -> None:
    """Req 6.4: two runs over one CPG give an identical verdict sequence, so there is nothing to average."""
    from openultrasast.model.ladder import Rung
    from openultrasast.model.taint import verdict

    rows = [
        {"sink": "os.system(a)", "sinkLine": "7", "sinkMethod": "run", "source": "request.args['b']", "sanitized": True, "length": 9},
        {"sink": "os.system(a)", "sinkLine": "7", "sinkMethod": "run", "source": "request.args['a']", "sanitized": False, "length": 2},
    ]
    first = verdict(_cpg(rows), _spec(), function="run")
    second = verdict(_cpg(rows), _spec(), function="run")
    assert first == second
    assert first is not None and first.rung is Rung.ENTAILED and "request.args['a']" in first.witness


def test_the_spec_drives_the_query_parameters() -> None:
    """The security modelling is ours; the traversal is the engine's. The spec is what crosses the seam."""
    from openultrasast.cpg.backend import CpgResult
    from openultrasast.model.taint import verdict

    seen: dict[str, object] = {}

    def run(query: str, params: dict[str, object]) -> object:
        seen["query"] = query
        seen.update(params)
        return []

    verdict(CpgResult(cpg_path=Path("cpg.bin"), run=run), _spec(), function="run")
    assert seen["query"] == "taint"
    assert seen["sources"] == ("request.args",)
    assert seen["sinks"] == ("os.system", "execute")
    assert seen["sanitizers"] == ("escape", "quote")
    assert seen["function"] == "run"


# --- the safe-shape test (task 2.3 finding) ------------------------------------------------------------
#
# Taint reachability alone does not distinguish a parameterised fix from an interpolated bug: the flow
# `request.args["name"] -> name -> execute` exists on BOTH sides of the canonical SQL pair.
#
#     vuln   db.execute("select ... '" + name + "'")      one argument, interpolated
#     fixed  db.execute("select ... = %s", (name,))       two arguments, bound
#
# What separates them is the SHAPE of the sink call, which is exactly what `TaintSpec.safe_shape_sinks`
# preserves. Without this test the model entails both sides and arbitrates nothing.


def _shape_spec():  # type: ignore[no-untyped-def]
    from openultrasast.model.specs import TaintSpec

    return TaintSpec(
        family="injection",
        language="python",
        sources=("request.args",),
        sinks=("execute",),
        sanitizers=(),
        safe_shape_sinks=("execute",),
    )


def test_a_parameterised_sink_call_is_not_a_vulnerability_even_though_the_flow_reaches_it() -> None:
    from openultrasast.model.taint import verdict

    rows = [{
        "sink": 'db.execute("select ... = %s", (name,))', "sinkLine": "5", "sinkMethod": "run",
        "source": "request.args['name']", "sanitized": False, "length": 4, "sinkArity": 2, "sinkArg0Literal": True,
    }]
    assert verdict(_cpg(rows), _shape_spec(), function="run") is None, "a bound query is the fix, not the bug"


def test_an_interpolated_sink_call_of_the_same_name_is_entailed() -> None:
    from openultrasast.model.ladder import Rung
    from openultrasast.model.taint import verdict

    rows = [{
        "sink": 'db.execute("select ... \'" + name + "\'")', "sinkLine": "5", "sinkMethod": "run",
        "source": "request.args['name']", "sanitized": False, "length": 4, "sinkArity": 1, "sinkArg0Literal": False,
    }]
    answer = verdict(_cpg(rows), _shape_spec(), function="run")
    assert answer is not None and answer.rung is Rung.ENTAILED


def test_the_shape_test_only_applies_to_sinks_declared_safe_in_that_shape() -> None:
    """`os.system(x)` with one argument is not "safe because it has one argument" -- the rule is per sink."""
    from openultrasast.model.ladder import Rung
    from openultrasast.model.taint import verdict

    rows = [{
        "sink": "os.system(full)", "sinkLine": "7", "sinkMethod": "run",
        "source": "request.args['cmd']", "sanitized": False, "length": 5, "sinkArity": 1, "sinkArg0Literal": False,
    }]
    answer = verdict(_cpg(rows), _spec(), function="run")  # os.system is not in safe_shape_sinks
    assert answer is not None and answer.rung is Rung.ENTAILED


def test_a_row_without_shape_fields_is_judged_on_the_flow_alone() -> None:
    """Older rows, or an engine that could not report arity, must not be silently treated as safe."""
    from openultrasast.model.ladder import Rung
    from openultrasast.model.taint import verdict

    rows = [{"sink": "db.execute(q)", "sinkLine": "5", "sinkMethod": "run", "source": "request.args['n']",
             "sanitized": False, "length": 3}]
    answer = verdict(_cpg(rows), _shape_spec(), function="run")
    assert answer is not None and answer.rung is Rung.ENTAILED