Open_Ultra_SAST/src/openultrasast/model/config_value.py

"""Constant abstraction for the configuration families (model-grounded-detection, Req 6.3).

The third arbiter form, and the simplest. A configuration bug has no flow to follow and no guard to dominate:
``CORS(app, origins="*")`` is dangerous because of the value it is *set to*. So the model evaluates the
setting's arguments against the closed permissive set from the obligation facts.

    ENTAILED      a security setting is passed a literal in the permissive set — the model can read the value
    CORROBORATED  the setting's argument is computed, so constant abstraction cannot decide it; whether the
                  computed value is permissive is the residual the judge asks about
    (none)        every literal argument is outside the permissive set, or the call is not a known setting
"""

from __future__ import annotations

from collections.abc import Mapping, Sequence

from ..cpg.backend import CpgResult
from .ladder import Rung, Verdict
from .specs import ConfigSpec


def request_params(spec: ConfigSpec, *, function: str = "", file: str = "") -> dict[str, object]:
    """The query parameters this arbiter sends. Shared with the batcher; see the note in `taint.request_params`.

    ``file`` scopes the answer to one source file. A region with no enclosing function sends ``function=""``,
    which without this matches the whole repository and gets that answer attributed to it -- one permissive
    literal in `app.py` became eight identical entailed findings in eight files that do not contain it. Empty
    means unscoped, which is what the single-region pair path still uses.
    """
    return {"settings": spec.settings, "function": function, "file": file}


def verdict(cpg: CpgResult, spec: ConfigSpec, *, function: str = "", file: str = "") -> Verdict | None:
    """The verdict for a security setting in ``function``, or ``None`` when nothing is established."""
    rows = cpg.run("config", request_params(spec, function=function, file=file))
    settings = _settings(rows, spec, function=function)
    if not settings:
        return None

    # Both abstractions read the same literal: a permissive flag ("*", True) and a weak algorithm ("md5").
    permissive = {value.strip().strip("'\"").lower() for value in spec.permissive}
    permissive |= {value.strip().strip("'\"").lower() for value in spec.weak_algorithms}
    for row in settings:
        literals = row["literals"]
        if not isinstance(literals, list):
            continue
        for literal in literals:
            if str(literal).strip().strip("'\"").lower() in permissive:
                return Verdict(
                    rung=Rung.ENTAILED,
                    family=spec.family,
                    witness=f"{row['setting']} (line {row['line']}): permissive literal {literal}",
                )

    # A setting whose value the model could not read. Not safe, not decided.
    computed = [row for row in settings if not row["literals"]]  # type: ignore[truthy-iterable]
    if computed:
        row = computed[0]
        return Verdict(
            rung=Rung.CORROBORATED,
            family=spec.family,
            witness=f"{row['setting']} (line {row['line']}): value is computed, not a literal the model can evaluate",
        )
    return None


def _settings(rows: object, spec: ConfigSpec, *, function: str) -> list[dict[str, object]]:
    """Rows for calls this spec actually names. A non-list (an engine failure) yields nothing."""
    if not isinstance(rows, Sequence) or isinstance(rows, (str, bytes)):
        return []
    kept: list[dict[str, object]] = []
    for row in rows:
        if not isinstance(row, Mapping):
            continue
        setting = str(row.get("setting", ""))
        if not any(name in setting for name in spec.settings):
            continue  # a permissive literal passed to something that is not a security setting is not a bug
        if function and str(row.get("method", "")) != function:
            continue
        literals = row.get("literalArgs")
        kept.append(
            {
                "setting": setting[:200],
                "line": str(row.get("line", "")),
                "method": str(row.get("method", "")),
                "literals": [str(v) for v in literals] if isinstance(literals, Sequence) and not isinstance(literals, str) else [],
            }
        )
    # Deterministic order: the first row decides, so it must not depend on engine ordering.
    return sorted(kept, key=lambda row: (str(row["method"]), str(row["line"]), str(row["setting"])))


__all__ = ["request_params", "verdict"]