181 lines
13 KiB
Markdown
181 lines
13 KiB
Markdown
# llm-security-commons
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Runtime-neutral core for LLM and agent security detection: detector data, normative contracts and a conformance corpus that several runtimes can share.
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[](LICENSE)
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Detection logic gets reimplemented every time it crosses a language boundary, and the
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copies drift: the Node scanner flags a zero-width carrier the Python guard misses, and
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nobody notices until an incident. This repository holds the part that should never have
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been copied — the pattern tables, the code-point carriers, the calibration thresholds, the
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finding contract, and a fixture corpus with expected verdicts — so that two independent
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implementations can be held to the same answer on the same input.
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It is for anyone building or maintaining a detector for prompt injection, secret egress,
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unicode-carrier smuggling or active content in untrusted text, on any runtime.
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**It holds no runnable code.** Data, specifications and fixtures only.
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## Install
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Nothing to install — this repository is **vendored into consumers**, not installed.
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As a `git subtree` (recommended: history is preserved and upgrades are a single command):
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```bash
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git subtree add --prefix vendor/commons \
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https://git.fromaitochitta.com/open/llm-security-commons.git v0.4.3 --squash
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# later, to move to a newer tag
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git subtree pull --prefix vendor/commons \
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https://git.fromaitochitta.com/open/llm-security-commons.git <newer-tag> --squash
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```
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Or pin a tag and copy — `fork-and-own` is an explicitly supported path:
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```bash
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git clone --depth 1 --branch v0.4.3 \
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https://git.fromaitochitta.com/open/llm-security-commons.git
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```
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Always vendor **a tag**, never `main`. The tag is what a conformance result can be
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attributed to.
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## Requirements
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A JSON parser and the ability to read a text file. That is the entire dependency surface,
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and keeping it that small is the point.
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## What it does
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| Path | Contents |
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| --- | --- |
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| [`lexicon/injection-lexicon.json`](lexicon/injection-lexicon.json) | Prompt-injection pattern lexicon: 83 patterns in four **severity** families (`critical`, `high`, `medium`, `hybrid`), each with a stable `id` and per-runtime aliases. The thematic class (`override:`, `evasion:`, `hitl-trap:`, …) is the id prefix, not the family. |
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| [`codepoints/carriers.json`](codepoints/carriers.json) | Invisible and deceptive carriers: zero-width characters, BIDI controls, Unicode Tag block ranges, and the homoglyph map. |
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| [`signatures/secret-egress.json`](signatures/secret-egress.json) | Credential and token shapes that must never leave a machine, in a portable regex dialect. |
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| [`signatures/malware-signatures.json`](signatures/malware-signatures.json) | Known-bad **identity** for the malicious-code class (`SIG`): seven tight signatures over four families — PHP webshells, reverse shells, cryptominers, offensive tooling. Seven signatures are not malware coverage, and the file says so. |
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| [`signatures/active-content.json`](signatures/active-content.json) | Active content that renders or fetches on its own — Markdown images, links, reference definitions and autolinks, `data:` URIs, active HTML. The EchoLeak class. |
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| [`calibration/calibration.json`](calibration/calibration.json) | The numbers a detector must not invent: risk-score tier constants, verdict thresholds, risk-band cutoffs, posture grade thresholds. Transcribed from a prose summary, not differentially verified — the file says so itself. |
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| [`mapping/owasp-map.json`](mapping/owasp-map.json) | Finding-id prefix → OWASP taxonomy entry (LLM / ASI / AST / MCP). |
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| [`schema/finding.schema.json`](schema/finding.schema.json) | **Normative.** The finding contract — closed against its producer, ten properties — plus the SARIF output profile. The JSONL profile is recorded as `not applicable`, with the reason. |
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| [`schema/conformance-declaration.schema.json`](schema/conformance-declaration.schema.json) | **Normative.** The shape a runtime publishes alongside a conformance result: which commons tables it implements, the commons commit it measured, and the four verdict counts. Required by the corpus spec §1.1; not validated by anything here, because nothing here runs. |
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| [`spec/conformance-corpus.md`](spec/conformance-corpus.md) | **Normative.** How to read the corpus: what a case is, why `input.txt` is bytes rather than text, what `exact-within-scope` requires of a runtime, and how a runtime declares its table set so a case scoped outside it reads as `not-applicable` rather than as a failure. |
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| [`conformance/`](conformance/) | 90 cases. One directory per case: `input.txt` in, `expected.json` out. Ground truth. 84 cover the injection lexicon — 83 one per pattern, both seeding runtimes measured producing the same verdict on all 83, plus one variant case gating a pattern form against its predecessor. Six cover active content and are measured against the one runtime that implements that table — `not-applicable` for the other, not failing. See [`conformance/manifest.json`](conformance/manifest.json). |
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| `spec/decode-pipeline.md` | **Planned, still not shipped as of v0.4.3.** The decode order, in RFC 2119 language. Two runtimes that decode in different orders will disagree on identical input. Writing it needs the decode implementation, which is engine code and has not been supplied — and a normative spec guessed from a data dump would be worse than an absent one. |
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| [`docs/extraction-plan.md`](docs/extraction-plan.md) | Informative: where each file was seeded from, and what v0.1.0 promised. |
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| [`docs/lexicon-port-divergence.md`](docs/lexicon-port-divergence.md) | Informative: a measured disagreement between two ports of the injection lexicon — 13 patterns that behave differently, in both directions. Most of it is still open, and the two rows that closed in v0.4.0 closed because the runtime that owns the value decided, not because this document found them wrong. |
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Every JSON file carries a top-level `version`. Every normative specification carries a
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`Status: normative` marker. Rows marked **Planned** are named here because the layout is
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part of the contract, but the file does not exist yet — they are not links, and nothing in
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v0.4.3 depends on them.
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Each data file records its own provenance and, in `verified`, how strongly it is backed.
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`calibration/calibration.json` is currently the one file that says `false`: it was
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transcribed from a prose summary rather than diffed against a running implementation.
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### How a consumer proves it conforms
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Run every `conformance/<case>/input.txt` through your detector and compare the finding ids
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to `expected.json` — exactly, but only within the data files the case names in `scope`.
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[`spec/conformance-corpus.md`](spec/conformance-corpus.md) is the normative reading;
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the short version is that a runtime must raise every listed finding and no other finding
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*from the same table*, and that what it does with tables outside the case's scope is not
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compared.
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Disagreement means your runtime is wrong, or the fixture is — and the fixture only changes
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in its own commit, with the reason written down.
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There is **no CI in this organisation** and nothing runs that comparison automatically. It
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runs in each consumer's own test suite, against a pinned tag.
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The corpus covers two tables, and they do not carry equal weight — treating them as one
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number would misreport both:
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- `lexicon/injection-lexicon.json` — 84 cases over 83 patterns. Both seeding runtimes
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implement it and both ratified its id space. One pattern carries a second, variant case;
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see `case_id_derivation.variant_suffix` in the manifest.
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- `signatures/active-content.json` — 6 cases. One runtime implements it. For a runtime that
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does not, these cases are **`not-applicable`**, a third verdict beside pass and fail: a
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runtime declares which commons data files it implements, and a case scoped outside that
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set was never addressed to it. See [§1.1](spec/conformance-corpus.md) — and note that
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`not-applicable` says the corpus did not ask, never that the runtime is blind.
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Four cases remain unshipped, for the carrier and secret-egress tables, and neither is
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blocked on effort. Carriers has no *ratified* id space: six labels exist to adopt verbatim
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from one runtime, but adopting them would hand the other an id asserting a strip it does not
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perform, and publishing a single alias would force that runtime's declared table set to widen
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— turning three cases it cannot reach from `not-applicable` into failures. Put to both
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runtimes as a decision request on 2026-08-11; unanswered. Secret egress is not an id question at all — the two
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runtimes carry *different tables*, 19 entries against 25, cut at different granularities.
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`conformance/manifest.json` records both blockers under `scope_planned.blockers`, measured,
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so the gap is visible rather than inferred.
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## Non-goals
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- **Not a scanner.** There is no engine here, and there will not be one. If you are looking
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for something to run, you want a consumer — `llm-security` for Claude Code.
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- **Not a framework or a library.** No package manifest, no dependencies, no build.
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- **Not a general-purpose Unicode or regex toolkit.** The tables cover what the detection
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classes need, not the standard.
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- **Not a vulnerability feed.** No CVEs, no advisories, nothing time-sensitive. Everything
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here is offline and deterministic.
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- **Not a policy engine.** `calibration.json` publishes the thresholds; deciding what to do
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when one is crossed belongs to the consumer.
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- **Not the place to fix a consumer's behaviour.** Data extracted from an implementation is
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kept behaviour-identical on purpose. A disagreement is reported to that implementation
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and decided there, where it is tested.
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## Known limitations
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- **Coverage is the union of what the seed implementations detected**, not of what exists.
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A class absent from the tables above has not been shown to work anywhere.
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- **The corpus is narrower than the data.** `conformance/` constrains two of the seven data
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files. The other five are published, provenance-checked and unfixtured: a runtime can
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pass every case and still read `calibration.json` wrongly. Passing the corpus is evidence
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about the injection lexicon and about active content, and about nothing else.
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- **A pass count is unreadable without the declared table set.** A runtime implementing one
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table and a runtime implementing four can print the same number. `not-applicable` cases
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must be reported, not dropped from the denominator — `76/83` and `76 passed, 6
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not-applicable` describe different runtimes.
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- **The six active-content cases prove less than the 83.** Their payloads come from the only
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runtime that implements the table, so no second implementation's agreement could be
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measured. They pin one runtime's behaviour as a contract a future implementer can be held
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to; they are not cross-runtime agreement.
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- **Regex portability is a real risk.** Pattern data is written for a common subset, but
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engines differ (lookbehind, named groups, Unicode property escapes). A consumer whose
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engine rejects a pattern must report it rather than silently skip it — a skipped pattern
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is an invisible false negative.
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- **Fixtures prove agreement, not correctness.** Two runtimes passing the same corpus agree
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with each other and with the fixture author. A wrong `expected.json` makes both wrong
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identically.
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- **The homoglyph map is finite.** Confusable coverage is a long tail; absence from the map
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is not evidence a character is safe.
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## Contributing
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[CONVENTIONS.md](CONVENTIONS.md) is the whole rule set a change here is held to: the charter
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(nothing runs, and why that is load-bearing rather than fussy), the file conventions, when a
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detection value is allowed to move, how the two version numbers work, and the four offline
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checks that stand in for the CI this organisation does not have.
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It also answers the question the forge surface raises on its own: **pull requests are switched
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off, deliberately.** This repository is vendored into independent runtimes that pin a tag, so a
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change to detection data changes what they *find* — that has to be coordinated with each
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consumer before it exists, which a merge button cannot do. Fork-and-own is the supported path;
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a wrong entry is reported privately.
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## Reporting a wrong entry
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A wrong code point or a mis-escaped regex here is a silent false negative in every runtime
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that reads it, so it is a security report even though nothing runs. Send it privately — see
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[SECURITY.md](SECURITY.md), which also explains why a confirmed defect in extracted data is
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decided in the runtime it came from before it is changed here.
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## Changelog
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See [CHANGELOG.md](CHANGELOG.md).
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## License
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MIT — see [LICENSE](LICENSE). Fork-and-own is an intended use, not a tolerated one.
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