Kjell Tore Guttormsen
6e9b8168e3
v0.3.0 made the untrusted upload path unusable: measured on both doors, an ordinary remote image fail_secure'd and an ordinary link/autolink/refdef quarantined, so only documents without external references persisted. Two independent defects compounded; neither fix works alone: 1. `markdown-image: HIGH` fired on any external image. The exfil primitive is a URL that moves bytes outward, not an image. `is_ordinary_url` now grades on shape - http(s)/protocol-relative, no query, no userinfo, no percent-escape, no opaque host label or path segment -> LOW; anything data-carrying keeps the carrier's severity. raw-html and data: URIs stay HIGH unconditionally. Opacity reuses entropy's primitives; floors calibrated against real doc URLs (worst legit token H=4.08, exfil segments 4.36-4.54) and frozen in calibration. 2. The quarantine_default floor fired on ANY finding, a premise that broke when every ordinary link became a finding. It now fires at MEDIUM+ - a no-op for every detector that shipped before 0.3.0 (no LOW/INFO exists), which is what makes this a patch rather than a minor. The corpus blind spot that let this pass 522 green tests is closed: the FP corpus carries realistic markdown and is asserted on the OUTPUT gate under PRESET_USER_UPLOAD, with a counter-corpus of exfil-shaped URLs that must still block. Beaconing and short opaque segments are conceded in LIMITATIONS and asserted by the coverage matrix rather than papered over. No new public API; no new preset (0.4.0 work); allow_reserved default unchanged.
240 lines
14 KiB
Markdown
240 lines
14 KiB
Markdown
# llm-ingestion-guard
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**Write-time ingestion is the trust boundary that query-time guardrails
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structurally cannot see.** When untrusted content passes through an LLM
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enrichment/summarization/extraction step into a *persisted* artifact — a RAG
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corpus, a knowledge base, an LLM wiki — the poisoned result is read *later* by a
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downstream agent as **trusted context**. That agent's guardrail never sees where
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the content came from. The only place the provenance still exists is the write.
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This library packages that write-time contract — sanitize → fence → tool-less
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quarantined transform → per-stage capability isolation → scan-before-commit →
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fail-secure — as composable, stdlib-first, framework-agnostic code. It is the
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write-time **sibling** of query-time tools (LLM Guard, NeMo Guardrails, Rebuff,
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Vigil), not a competitor: those harden material as it enters the model; this
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hardens it as it is committed for a *later* reader. Where existing OSS tooling is
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mostly single-stage *detectors* — a risk verdict, with quarantine, capability
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isolation, scan-before-persist, and fail-secure left to the integrator — this
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packages the full contract as code. (Neighbours surveyed in
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[`docs/BRIEF.md`](docs/BRIEF.md) §11.)
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**Why an LLM wiki (e.g. Google OKF) needs this specifically.** OKF and
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second-brain formats have no schema registry, no central authority, and no
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signing — a bundle's claimed origin is not verifiable at the format level. So
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*your ingestion pipeline is the trust boundary*: provenance must be stamped by you
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at write time, never assumed from the format. Any pipeline ingesting external data
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into an agent-read store has this shape; an OKF wiki is its canonical form — which
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is why the guard ships a first-class OKF adapter (below).
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**Status:** `v0.3`, alpha. The stdlib-only core — its detector, contract, and
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OKF-adapter modules plus the top-level wiring — is built and tested, exercised by
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an end-to-end showcase and adversarial + false-positive corpora. The public API
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may still change. There are real limitations, stated plainly below; read them.
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## Install
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Not on PyPI. The guard is distributed from its Forgejo origin — pin a release tag:
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```bash
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pip install "llm-ingestion-guard @ git+https://git.fromaitochitta.com/open/llm-ingestion-pipeline-security.git@v0.3.1"
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```
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The `open/` mirror is anonymously readable, so CI needs no deploy key, token, or
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other credential. The core is stdlib-only with zero dependencies, so nothing else
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resolves. Optional ML/judge detectors live behind extras (`[ml]`, `[judge]`) and
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are not required — the core is deterministic and dependency-free.
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**Tags are the stable contract.** Every release is version-synced before tagging,
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and published tags are never moved.
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Two consequences worth knowing before you depend on this:
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- A git URL is a PEP 508 *direct reference*: it pins one exact tag, not a range
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like `>=0.2,<0.3`. Real range pinning — and therefore automatic pickup of patch
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releases — arrives with a Forgejo PyPI registry, which becomes the durable
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channel at the first patch release or the second downstream consumer, whichever
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comes first. The distribution name (`llm-ingestion-guard`) and the version
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scheme are unchanged by that move, so pins written today keep their meaning.
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- **Vendoring the source into a consumer is not supported.** It severs the patch
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channel that a shared security dependency exists to provide: a copied guard
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keeps running the vulnerabilities the original has already fixed.
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## Quickstart — the two bookends
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The library never makes the model call itself. It gives you the two library-side
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halves around your own **tool-less** transform:
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```python
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from llm_ingestion_guard import (
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prepare_input, screen_output, Disposition, PRESET_USER_UPLOAD,
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)
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prepared = prepare_input(untrusted_content) # sanitize + fence
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enriched = your_model(prepared.fenced) # tool-less — YOUR call
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decision = screen_output(enriched, PRESET_USER_UPLOAD) # scan + dispose
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if decision.disposition is Disposition.FAIL_SECURE:
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alert(gate_code=decision.reasons) # minimal payload, no content
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raise SystemExit # halt — never persist
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```
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`screen_output` fails **closed**: if the scanner itself errors on crafted input,
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the disposition is `FAIL_SECURE`, never a silent persist. Pass
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`transform_failed=True` when your model call raised or fell back — a scan hit
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together with a transform failure is treated as a probable forced-fallback attack
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and halts regardless of trust tier.
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Every primitive is also exported for pipelines that compose the checklist
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themselves — `sanitize`, `scan_lexicon`, `scan_entropy`, `scan_output`,
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`scan_active_content`, `neutralize`, the `decide` / `guard` disposition
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machinery, and the contract asserters `assert_tool_less` /
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`assert_credential_allowlist` / `scoped_env`. See
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[the end-to-end showcase](tests/test_showcase.py) for a full worked pipeline.
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## OKF / LLM-wiki support (shipped)
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For a bundle-shaped store, the `okf` submodule sits **on top of** the
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format-agnostic core: it knows OKF structure (frontmatter, paths, links,
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`resource`, bundles) and feeds scannable regions into the same `sanitize` /
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`scan_output` / disposition machinery — no YAML/format awareness leaks into the
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core. Two ingestion modes:
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- **(a) Own enrichment output** — your agent writes concepts. Run the two bookends
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above per concept before commit.
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- **(b) Received external bundle** — you merge a whole third-party OKF bundle.
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`import_bundle` iterates concept-by-concept and runs the full per-concept gate:
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```python
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from llm_ingestion_guard.okf import import_bundle, Origin, Channel
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# bundle: {concept_path -> raw document text}, e.g. {"tables/users.md": "---\n..."}
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result = import_bundle(bundle, origin=Origin.EXTERNAL, channel=Channel.AUTOMATIC)
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for c in result.concepts:
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if c.error: # hard reject: bad path, unsafe frontmatter, non-https resource
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skip(c.path) # disposition is FAIL_SECURE; do not merge this concept
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# result.disposition = most-severe across concepts
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# result.links = the cross-link graph (dangling/rejected/resolved edges)
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# result.log() = the log.md body (one provenance-stamped line per concept)
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```
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Per-concept gates: **path / reserved-name** (rejects `..` traversal and reserved
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`index.md`/`log.md` shadowing); **frontmatter parse-safety** — a strict,
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reject-by-default loader that refuses anchors, aliases, and explicit tags *by
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construction*, so a billion-laughs alias expansion or a `!!python/object` coercion
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cannot occur (it is deliberately **not** a general YAML engine, whose own features
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are the attack surface); **`resource` https-allowlist** (hard-rejects
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`data:`/`javascript:`/`file:` before commit — a reject-gate, not defang);
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**whole-concept scan** (frontmatter *values* + body through `scan_output`);
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**cross-link graph** (surfaces dangling targets, the dormant-injection signal, and
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rejects bundle-escaping links); **provenance stamping** (`Origin` × `Channel` →
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tier + disposition, emitted to `log.md`).
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## What it protects against
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Concrete attack classes, grouped by OWASP LLM Top-10 (2025) anchor. Every row is
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driven by a **live payload** in the coverage matrix — run it to watch all 126 pass
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in your own environment:
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```bash
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python -m llm_ingestion_guard.coverage # 126/126 classes; exit 0 = all as documented
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```
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| Anchor | Attack classes it stops (representative) |
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|---|---|
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| **LLM01 · prompt injection** | 83 instruction-override lexicon classes (ignore / forget / disregard / suspend-constraints, role-play, jailbreak, …); hidden carriers — zero-width stego, BIDI override, Unicode-tag stego, HTML-comment, `data:` URI — stripped on input **and** re-checked at the persist gate; high-entropy base64/hex blobs; an injection hidden inside a base64 blob (decoded, then re-scanned) |
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| **LLM02 · sensitive-info disclosure** | Secret egress in output — AWS keys, tokens, private keys, the credential set; a base64-*wrapped* secret (decoded → `decoded:egress:*`) |
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| **LLM05 · improper output handling** | Zero-click exfil carriers (EchoLeak, CVE-2025-32711) — markdown-image auto-fetch, inline / reference / autolink links, raw active HTML, standalone `data:` URIs; non-`https` `resource` URLs |
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| **LLM06 · excessive agency** | A tool surface on the quarantined transform; credential use beyond the per-stage allowlist; capability isolation (`scoped_env`) |
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| **LLM10 · fail-secure** | Forced-fallback attack (scan hit + transform failure → halt); compound weak-signal escalation; an un-scannable artifact fails **closed** — never a silent persist |
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| **OKF structure (T1–T6)** | Body + frontmatter-value injection; YAML anchor / merge / nested / block DoS (parse-safety); `resource` allowlist; path traversal / reserved-name shadow; cross-link graph; provenance stamping |
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| **Container / upload layer** | CSV/XLSX formula-injection (lead `= + - @`); zip-slip path escape; zip-bomb size cap; symlink refusal *(upload front-end — see the showcase)* |
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The manifest ([`coverage.py`](src/llm_ingestion_guard/coverage.py)) is the single
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source of truth for
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[`tests/test_coverage_matrix.py`](tests/test_coverage_matrix.py), which asserts
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total recall over every class, that every documented gap still holds (a closed gap
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fails the test), and that every lexicon pattern has a case — so the matrix cannot
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fall behind the code. The four classes it deliberately does **not** stop are called
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out in [Honest limitations](#honest-limitations).
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## The reusable contract (adopt-this checklist)
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The actual product is this checklist, encoded as code you wire in order:
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1. **Sanitize before fence.** Strip carrier classes (zero-width, BIDI,
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Unicode-tag, HTML comment, `data:`) from untrusted input first.
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2. **Fence untrusted input.** Spotlight-mark it in a randomized per-call
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delimiter; strip attacker fence markers from the payload.
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3. **Tool-less transform.** Call the model with zero tools. A successful
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injection then has nothing to act with.
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4. **Per-stage capability isolation.** The enrichment stage holds only the model
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key; the publish stage holds only the publish credential; no stage holds both.
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5. **Treat output as data.** Parse to a frozen schema; reject on structural
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violation. The output never reaches a shell, git, or a filesystem path.
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6. **Scan output before persist.** Run the lexicon + entropy + active-content
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scan over the emitted text. Verbatim-carried payloads, model-emitted
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instructions, and zero-click exfil carriers (EchoLeak-class markdown
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images/links, raw active HTML, `data:` URIs) are caught here; `neutralize`
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additionally defangs them, opt-in.
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7. **Fail-secure on compound signals.** Injection hit + transform failure = halt
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+ alert, never a silent verbatim commit.
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8. **Minimal alert payloads.** Alert with a gate code + run ID, never content.
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Steps 1-2 are `prepare_input`; steps 6-7 are `screen_output`; steps 3-5 are
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yours; the contract asserters harden step 3-4.
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## Honest limitations
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Conceding these plainly is itself a control — it prevents the false assurance that
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a green scan means safe content. The highest-impact items:
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- **The contract carries the security, not the lexicon.** Pattern detection is
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bypassable in isolation (character-injection, novel phrasings); the tool-less
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transform + capability isolation + fail-secure are the wall.
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- **Semantic / factual poisoning is invisible.** A false claim in clean prose
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carries no suspicious token — the highest-impact gap for a wiki. Needs a `[judge]`
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plugged into the `grounding` seam.
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- **Text-only, extracted-text-only.** The core parses no files; OCR-embedded
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instructions, macros, and multimodal stego are out of scope. `.pdf` is refused as
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unsupported, not half-scanned.
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- **A lone HIGH in *trusted* prose disposes to WARN**, and **insider in-place
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edits** are outside the untrusted-content threat model — run genuinely untrusted
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sources as untrusted.
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- **Active-content severity grades on URL shape, not construct type.** A URL that
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only *names* a remote document is LOW; one that can carry a value outward keeps
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HIGH/MEDIUM. The conceded hole: a bare-path image on a hostile host still *fetches*
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when rendered, so pure beaconing (reader IP, timing) is not graded.
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- **Six documented gaps** the coverage matrix keeps honest: hex-wrapped secret
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egress, semantic poisoning, trusted-prose lone-HIGH, lexicon dedup (`count=1`),
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pure beaconing, and short opaque URL segments.
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**Full list — 18 items, each with the mechanism, plus the out-of-scope boundary:**
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[`docs/LIMITATIONS.md`](docs/LIMITATIONS.md).
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## Out-of-scope (documented boundary)
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Embedding/vector-layer defenses (OWASP LLM08, downstream of persist); multimodal
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steganography; query-time / runtime guardrails; semantic factuality verification.
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## Design & threat model
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- [Design brief](docs/BRIEF.md) — what this repo contains and why.
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- [Build plan](docs/PLAN.md) — module build order and the reuse map.
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- [Adoption brief](docs/ADOPTION-BRIEF.md) — wiring the guard into an OKF
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second-brain / LLM wiki, and a checklist for *when* to include it.
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The contract is extracted from a working reference implementation (the
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`claude-code-llm-wiki` Stage B enrichment pipeline). Threat-model anchors: OWASP
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LLM Top-10 2025 (LLM01/02/04/05/06 strongest, LLM08 boundary, LLM09/10),
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PoisonedRAG, guardrail-evasion (arXiv 2504.11168), EchoLeak (CVE-2025-32711).
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## License
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MIT — see [LICENSE](LICENSE).
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