Kjell Tore Guttormsen
2d98d6809d
The scanners cap by truncating: they return findings, so reading a prefix costs detection in the tail and nothing else. The three transform surfaces return *content*, where the same move is not available — a shortened document is silent data loss, and a transformed prefix followed by an untransformed tail is a bypass, since the attacker chooses where in the document the payload sits. So they fail secure instead. Above MAX_INPUT_CHARS (1 000 000) sanitize, fence and neutralize raise OversizeInputError. sanitize is step 1 of prepare_input and only ever removes, so that one refusal bounds the whole input path. OversizeInputError subclasses ContractViolation: a pipeline already bracketing its quarantined stage keeps failing closed rather than meeting a type it has never heard of. It inherits the alert-routable property too — sizes in the message, refusing surface in details, no input in either. Invariant now pinned across all three: returned text is always fully transformed, or not returned at all. Still uncapped and recorded in LIMITATIONS: scan_active_content called directly (through scan_output it inherits that cap) and the okf link graph. Both are detection-shaped, so truncate-and-flag transfers unchanged — mechanical, not policy. 699 tests (+23), coverage 128/128 + 6/6, ReDoS sweep 0 candidates / 150.
105 lines
4.4 KiB
Python
105 lines
4.4 KiB
Python
"""Tests for the input-size cap on the TRANSFORM surfaces (OWASP LLM10).
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The scan surfaces (``scan_lexicon`` / ``scan_output``) cap by *truncating*: they
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read the prefix, emit an ``oversize-input`` finding, and return findings only.
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That trade does not transfer here. ``sanitize`` / ``fence`` / ``neutralize``
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return **content**, so truncating would either drop user data silently or hand
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back a tail that never went through the transform — a one-line bypass, since an
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attacker controls where in the document the payload sits.
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So these three fail *secure* instead. The invariant under test:
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returned text is ALWAYS fully transformed, or not returned at all.
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"""
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import inspect
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import pytest
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from llm_ingestion_guard import prepare_input
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from llm_ingestion_guard.calibration import MAX_INPUT_CHARS
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from llm_ingestion_guard.contract import ContractViolation, OversizeInputError
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from llm_ingestion_guard.fence import fence
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from llm_ingestion_guard.neutralize import neutralize
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from llm_ingestion_guard.sanitize import sanitize
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# Every transform surface, called through a uniform (text, max) shim so the
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# invariant is asserted once per surface rather than restated three times.
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TRANSFORMS = (
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("sanitize", lambda text, cap: sanitize(text, max_input_chars=cap)),
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("fence", lambda text, cap: fence(text, max_input_chars=cap)),
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("neutralize", lambda text, cap: neutralize(text, max_input_chars=cap)),
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)
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@pytest.mark.parametrize("name,call", TRANSFORMS, ids=[n for n, _ in TRANSFORMS])
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def test_oversize_input_is_rejected(name, call):
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with pytest.raises(OversizeInputError):
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call("a" * 101, 100)
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@pytest.mark.parametrize("name,call", TRANSFORMS, ids=[n for n, _ in TRANSFORMS])
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def test_input_exactly_at_the_cap_is_accepted(name, call):
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# The cap is the largest accepted size, not the smallest rejected one.
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result = call("a" * 100, 100)
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assert result.text is not None
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@pytest.mark.parametrize("name,call", TRANSFORMS, ids=[n for n, _ in TRANSFORMS])
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def test_rejection_is_a_contract_violation(name, call):
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# Subclass, so a pipeline with a broad `except ContractViolation` around its
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# quarantined stage keeps failing closed instead of meeting a new exception
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# type it has never heard of.
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with pytest.raises(ContractViolation) as exc:
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call("a" * 101, 100)
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assert exc.value.code == "oversize-input"
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@pytest.mark.parametrize("name,call", TRANSFORMS, ids=[n for n, _ in TRANSFORMS])
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def test_error_carries_sizes_never_content(name, call):
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# Same alert-safety property ContractViolation already promises: the raised
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# object must be routable to an alert channel without leaking the payload.
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secret = "CANARYVALUE"
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with pytest.raises(OversizeInputError) as exc:
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call(secret * 100, 100)
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assert secret not in str(exc.value)
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assert not any(secret in d for d in exc.value.details)
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assert "101" not in exc.value.details # details name the surface, not sizes
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assert name in exc.value.details
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@pytest.mark.parametrize("name,call", TRANSFORMS, ids=[n for n, _ in TRANSFORMS])
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def test_error_reports_both_the_size_and_the_cap(name, call):
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with pytest.raises(OversizeInputError) as exc:
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call("a" * 101, 100)
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message = str(exc.value)
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assert "101" in message and "100" in message
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@pytest.mark.parametrize("name,call", TRANSFORMS, ids=[n for n, _ in TRANSFORMS])
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def test_under_cap_is_unchanged_by_the_guard(name, call):
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# The cap must not perturb the ordinary path: clean prose still round-trips
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# the way each surface's own tests already pin.
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result = call("ordinary prose", 100)
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assert "ordinary prose" in result.text
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@pytest.mark.parametrize(
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"func", [sanitize, fence, neutralize], ids=["sanitize", "fence", "neutralize"]
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)
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def test_default_cap_comes_from_calibration(func):
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# Calibration numbers live in ONE module; a literal re-typed at a call site
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# is the drift this pins against.
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default = inspect.signature(func).parameters["max_input_chars"].default
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assert default == MAX_INPUT_CHARS
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def test_prepare_input_inherits_the_cap():
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# The input path is sanitize -> fence, and step 1 is where the document
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# arrives, so the whole path is bounded by sanitize's guard alone.
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with pytest.raises(OversizeInputError):
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prepare_input("a" * (MAX_INPUT_CHARS + 1))
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def test_prepare_input_accepts_a_document_at_the_cap():
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result = prepare_input("a" * MAX_INPUT_CHARS)
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assert result.fenced
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