llm-security-commons/README.md

# llm-security-commons

Runtime-neutral core for LLM and agent security detection: detector data, normative contracts and a conformance corpus that several runtimes can share.

[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](LICENSE)

Detection logic gets reimplemented every time it crosses a language boundary, and the
copies drift: the Node scanner flags a zero-width carrier the Python guard misses, and
nobody notices until an incident. This repository holds the part that should never have
been copied — the pattern tables, the code-point carriers, the calibration thresholds, the
finding contract, and a fixture corpus with expected verdicts — so that two independent
implementations can be held to the same answer on the same input.

It is for anyone building or maintaining a detector for prompt injection, secret egress,
unicode-carrier smuggling or active content in untrusted text, on any runtime.

**It holds no runnable code.** Data, specifications and fixtures only.

## Install

Nothing to install — this repository is **vendored into consumers**, not installed.

As a `git subtree` (recommended: history is preserved and upgrades are a single command):

```bash
git subtree add --prefix vendor/commons \
  https://git.fromaitochitta.com/open/llm-security-commons.git v0.1.0 --squash

# later, to move to a newer tag
git subtree pull --prefix vendor/commons \
  https://git.fromaitochitta.com/open/llm-security-commons.git v0.2.0 --squash
```

Or pin a tag and copy — `fork-and-own` is an explicitly supported path:

```bash
git clone --depth 1 --branch v0.1.0 \
  https://git.fromaitochitta.com/open/llm-security-commons.git
```

Always vendor **a tag**, never `main`. The tag is what a conformance result can be
attributed to.

## Requirements

A JSON parser and the ability to read a text file. That is the entire dependency surface,
and keeping it that small is the point.

## What it does

| Path | Contents |
| --- | --- |
| [`lexicon/injection-lexicon.json`](lexicon/injection-lexicon.json) | Prompt-injection pattern lexicon: instruction-override, exfiltration and role-confusion families with per-pattern ids. |
| [`codepoints/carriers.json`](codepoints/carriers.json) | Invisible and deceptive carriers: zero-width characters, BIDI controls, Unicode Tag block ranges, and the homoglyph map. |
| [`signatures/secret-egress.json`](signatures/secret-egress.json) | Credential and token shapes that must never leave a machine, in a portable regex dialect. |
| `signatures/malware-signatures.json` | **Planned, not in v0.1.0.** Signature set for the malicious-code class (`SIG`). The seed data has not been delivered yet. |
| [`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. |
| [`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. |
| [`mapping/owasp-map.json`](mapping/owasp-map.json) | Finding-id prefix → OWASP taxonomy entry (LLM / ASI / AST / MCP). |
| [`schema/finding.schema.json`](schema/finding.schema.json) | **Normative.** The finding contract, plus the SARIF and JSONL output profiles. |
| `spec/decode-pipeline.md` | **Planned, not in v0.1.0.** 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. |
| `conformance/` | **Planned, not in v0.1.0.** One directory per case: `input.txt` in, `expected.json` out. Ground truth. |
| [`docs/extraction-plan.md`](docs/extraction-plan.md) | Informative: where each file was seeded from, and what v0.1.0 promised. |

Every JSON file carries a top-level `version`. Every normative specification carries a
`Status: normative` marker. Rows marked **Planned** are named here because the layout is
part of the contract, but the file does not exist yet — they are not links, and nothing in
v0.1.0 depends on them.

Each data file records its own provenance and, in `verified`, how strongly it is backed.
`calibration/calibration.json` is currently the one file that says `false`: it was
transcribed from a prose summary rather than diffed against a running implementation.

### How a consumer proves it conforms

Run every `conformance/<case>/input.txt` through your detector, serialize the result per
[`schema/finding.schema.json`](schema/finding.schema.json), and compare to
`expected.json`. Disagreement means your runtime is wrong, or the fixture is — and the
fixture only changes in its own commit, with the reason written down.

There is **no CI in this organisation** and nothing runs that comparison automatically. It
runs in each consumer's own test suite, against a pinned tag.

## Non-goals

- **Not a scanner.** There is no engine here, and there will not be one. If you are looking
  for something to run, you want a consumer — `llm-security` for Claude Code.
- **Not a framework or a library.** No package manifest, no dependencies, no build.
- **Not a general-purpose Unicode or regex toolkit.** The tables cover what the detection
  classes need, not the standard.
- **Not a vulnerability feed.** No CVEs, no advisories, nothing time-sensitive. Everything
  here is offline and deterministic.
- **Not a policy engine.** `calibration.json` publishes the thresholds; deciding what to do
  when one is crossed belongs to the consumer.
- **Not the place to fix a consumer's behaviour.** Data extracted from an implementation is
  kept behaviour-identical on purpose. A disagreement is reported to that implementation
  and decided there, where it is tested.

## Known limitations

- **Coverage is the union of what the seed implementations detected**, not of what exists.
  A class absent from `conformance/` has not been shown to work anywhere.
- **Regex portability is a real risk.** Pattern data is written for a common subset, but
  engines differ (lookbehind, named groups, Unicode property escapes). A consumer whose
  engine rejects a pattern must report it rather than silently skip it — a skipped pattern
  is an invisible false negative.
- **Fixtures prove agreement, not correctness.** Two runtimes passing the same corpus agree
  with each other and with the fixture author. A wrong `expected.json` makes both wrong
  identically.
- **The homoglyph map is finite.** Confusable coverage is a long tail; absence from the map
  is not evidence a character is safe.

## Changelog

See [CHANGELOG.md](CHANGELOG.md).

## License

MIT — see [LICENSE](LICENSE). Fork-and-own is an intended use, not a tolerated one.