Kjell Tore Guttormsen
5397ba15a1
Pre-release hardening from an independent adversarial review; each fixed test-first (failing test -> fix -> green). 214 tests pass. - entropy (M1): decode-and-rescan now runs BEFORE false-positive suppression, so an SRI/media-prefixed injection blob is still decoded and lexicon-rescanned. Suppression gates only the entropy finding, never the decode. - output/disposition (M3): the invisible-carrier invariant now holds on the persist gate. scan_output flags zero-width/BIDI presence and disposition treats those + lexicon:unicode-tags-present as any-tier carriers, so a carrier in model output fails secure even under a trusted policy. - contract (M2): assert_credential_allowlist catches a bare <PROVIDER>_KEY (e.g. STRIPE_KEY) that the old regex silently missed (fail-open). Deliberately broad: also flags PARTITION_KEY/SORT_KEY as loud, allowlistable FPs -- fail-loud beats fail-silent for an isolation control. - disposition (m6): guard runs decide inside its guarded block -> total fail-closed even on a malformed report. - output (m4): egress placeholder suppression anchors word markers (example, todo, ...) to a word boundary, closing a fail-open where a real secret merely containing such a word was suppressed. Docs: CHANGELOG Security subsection; README honest-limit for lexicon dedup (m5, documented tradeoff, not fixed). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01HyRCQMocjZ6SmSQ6JidJ2k
305 lines
15 KiB
Python
305 lines
15 KiB
Python
"""output — the report-only OUTPUT gate (compose + secret egress).
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Query-time guardrails guard the answer; this guards the *persisted artifact*.
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``output`` is the last gate before model output is written to a wiki, doc, or
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knowledge base: it scans the emitted text and reports what must not be persisted.
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It is **report-only** (design principles 3 & 4) — it never mutates the text.
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Mutation is ``neutralize``'s separate, opt-in job; disposition (WARN /
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QUARANTINE_REVIEW / FAIL_SECURE) is the caller's, decided from this ``Report``.
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It composes the existing detectors over the output and adds the egress layer the
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input-side scanners do not cover:
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1. :func:`~llm_ingestion_guard.lexicon.scan_lexicon` over the output — injection
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strings the model reproduced into the artifact (RAG poisoning).
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2. :func:`~llm_ingestion_guard.entropy.scan_entropy` over the output — encoded /
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high-entropy carrier blobs.
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3. **Decode-and-rescan** — every base64 blob ``entropy`` decoded to printable
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text is fed back through ``scan_lexicon``. This is what turns "a blob is
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present" into "an injection is hidden *inside* this blob". Findings from the
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decoded plaintext are re-labelled ``decoded:<label>`` and carry the blob's
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offset in the original text. (Scope: base64 only — ``entropy`` exposes
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decoded plaintext for base64, not hex; a base64-*wrapped secret* is a
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documented gap, since decode-rescan feeds the lexicon, not the egress set.)
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4. **Secret / credential egress** (:func:`scan_secret_egress`, OWASP LLM02 —
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Sensitive Information Disclosure) — cloud/provider API keys, PEM private-key
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headers, DB connection strings, JWTs, and labelled password/secret/api-key
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assignments, with false-positive suppression for placeholders and variable
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references. Ported from the ``llm-security`` ``knowledge/secrets-patterns.md``
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seed. Classic PII (email / national-ID / card numbers) is intentionally out
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of scope for v1 — high false-positive risk, not in the seed.
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5. **Invisible carrier presence** (:func:`_scan_invisible_carriers`) — zero-width
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and BIDI override/isolate characters in the emitted artifact. Output is
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report-only and never sanitized, so this is the persist-gate analogue of
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``sanitize``'s input-side stripping; disposition treats the labels as
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any-tier carriers. Unicode-tag / PUA stego is already surfaced by step 1.
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**Security property (this module specifically).** A finding's ``evidence`` never
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contains the secret value it matched — only a human description and the match
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length. The report is meant to be logged; it must not become the leak.
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**Self-safety (OWASP LLM10).** The output is capped once to ``max_scan_chars``
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and a single ``output:oversize-input`` finding is emitted if it was truncated;
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every sub-scanner then sees bounded input. The egress patterns are linear
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(anchored prefixes / negated character classes — no nested quantifiers).
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"""
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from __future__ import annotations
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import re
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from dataclasses import dataclass, replace
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from typing import Optional, Union
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from .entropy import scan_entropy
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from .lexicon import MAX_SCAN_CHARS, scan_lexicon
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from .report import Finding, Report, Severity, Source
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# --- secret / credential egress patterns (OWASP LLM02) ----------------------
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# Ported from knowledge/secrets-patterns.md. ``value_group`` names the capturing
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# group holding the matched secret *value*: when set, value-based false-positive
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# suppression (placeholder / variable-ref / all-same-char / short) is applied to
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# it — these are the low-specificity "labelled" patterns the seed warns about.
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# When ``value_group`` is None the pattern is a high-specificity token (a unique
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# prefix + length) with, per the seed, no known false positives; it is always
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# reported. PEM headers use ``-{5}`` rather than five literal dashes so neither
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# this source nor a scanned example trips a secret scanner on the module itself.
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@dataclass(frozen=True)
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class _SecretPattern:
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id: str
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regex: re.Pattern[str]
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severity: Severity
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desc: str
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value_group: Optional[Union[int, str]] = None
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def _p(pattern: str, flags: int = 0) -> re.Pattern[str]:
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return re.compile(pattern, flags)
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_I = re.IGNORECASE
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_SECRET_PATTERNS: list[_SecretPattern] = [
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# --- cloud / provider keys (high-specificity: always reported) ----------
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_SecretPattern("aws-access-key-id", _p(r"\bAKIA[0-9A-Z]{16}\b"),
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Severity.CRITICAL, "AWS access key ID"),
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_SecretPattern("gcp-api-key", _p(r"\bAIza[0-9A-Za-z_\-]{35}\b"),
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Severity.HIGH, "Google Cloud / Firebase API key"),
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_SecretPattern("gcp-service-account-json", _p(r'"type"\s*:\s*"service_account"'),
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Severity.CRITICAL, "GCP service-account credential marker"),
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_SecretPattern("github-pat-classic", _p(r"\bghp_[A-Za-z0-9]{36}\b"),
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Severity.CRITICAL, "GitHub classic personal access token"),
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_SecretPattern("github-pat-fine-grained", _p(r"\bgithub_pat_[A-Za-z0-9_]{82}\b"),
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Severity.CRITICAL, "GitHub fine-grained personal access token"),
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_SecretPattern("github-oauth-token", _p(r"\bgho_[A-Za-z0-9]{36}\b"),
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Severity.CRITICAL, "GitHub OAuth access token"),
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_SecretPattern("github-server-token", _p(r"\bghs_[A-Za-z0-9]{36}\b"),
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Severity.HIGH, "GitHub App / Actions token"),
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_SecretPattern("npm-token", _p(r"\bnpm_[A-Za-z0-9]{36}\b"),
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Severity.CRITICAL, "npm automation / publish token"),
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_SecretPattern("openai-api-key-legacy",
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_p(r"\bsk-[A-Za-z0-9]{20}T3BlbkFJ[A-Za-z0-9]{20}\b"),
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Severity.CRITICAL, "OpenAI API key (legacy format)"),
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_SecretPattern("openai-project-key", _p(r"\bsk-proj-[A-Za-z0-9\-_]{40,}\b"),
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Severity.CRITICAL, "OpenAI project-scoped API key"),
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_SecretPattern("anthropic-api-key", _p(r"\bsk-ant-api03-[A-Za-z0-9\-_]{93}\b"),
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Severity.CRITICAL, "Anthropic Claude API key"),
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_SecretPattern("azure-storage-key", _p(r"AccountKey=([A-Za-z0-9+/]{86}==)", _I),
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Severity.CRITICAL, "Azure Storage account key"),
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# --- PEM private-key headers (header alone is sufficient to flag) --------
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_SecretPattern("rsa-private-key", _p(r"-{5}BEGIN RSA PRIVATE KEY-{5}"),
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Severity.CRITICAL, "PEM RSA private key header"),
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_SecretPattern("ec-private-key",
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_p(r"-{5}BEGIN (?:EC|DSA|OPENSSH|ENCRYPTED) PRIVATE KEY-{5}"),
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Severity.CRITICAL, "PEM EC/DSA/OpenSSH private key header"),
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_SecretPattern("pkcs8-private-key", _p(r"-{5}BEGIN PRIVATE KEY-{5}"),
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Severity.CRITICAL, "PEM PKCS#8 private key header"),
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# --- DB connection strings (suppress placeholder passwords) -------------
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_SecretPattern("postgres-connstr",
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_p(r"postgres(?:ql)?://[^:@\s]+:(?P<val>[^@\s]+)@[^\s'\"]+"),
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Severity.CRITICAL, "PostgreSQL connection string with credentials",
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value_group="val"),
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_SecretPattern("mongodb-connstr",
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_p(r"mongodb(?:\+srv)?://[^:@\s]+:(?P<val>[^@\s]+)@[^\s'\"]+"),
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Severity.CRITICAL, "MongoDB connection string with credentials",
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value_group="val"),
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_SecretPattern("mysql-connstr",
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_p(r"mysql(?:2)?://[^:@\s]+:(?P<val>[^@\s]+)@[^\s'\"]+"),
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Severity.CRITICAL, "MySQL/MariaDB connection string with credentials",
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value_group="val"),
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_SecretPattern("redis-connstr", _p(r"redis://:(?P<val>[^@\s]+)@[^\s'\"]+"),
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Severity.HIGH, "Redis connection string with password",
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value_group="val"),
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# --- JWT (high false-positive rate -> MEDIUM, flag for review) ----------
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_SecretPattern("jwt-token",
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_p(r"\beyJ[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+\b"),
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Severity.MEDIUM, "JSON Web Token"),
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# --- labelled / generic (value-based FP suppression applied) ------------
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_SecretPattern("generic-api-key",
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_p(r"\bapi[_\-]?key\s*[:=]\s*[\"']([A-Za-z0-9\-._]{16,64})[\"']", _I),
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Severity.HIGH, "generic api_key assignment", value_group=1),
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_SecretPattern("bearer-token",
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_p(r"Authorization\s*[:=]\s*[\"']?Bearer\s+([A-Za-z0-9\-._~+/]+=*)", _I),
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Severity.HIGH, "Bearer token in Authorization header", value_group=1),
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_SecretPattern("azure-client-secret",
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_p(r"client[_\-]?secret[\"'\s]*[:=][\"'\s]*([A-Za-z0-9~._\-]{34,40})", _I),
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Severity.CRITICAL, "Azure AD client secret", value_group=1),
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_SecretPattern("config-password",
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_p(r"(?:^|[\s,;{(])\bpass(?:word|wd)?\s*[:=]\s*[\"']([^\"'$<>{}\s]{6,})[\"']", _I),
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Severity.HIGH, "password assignment", value_group=1),
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_SecretPattern("config-secret",
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_p(r"(?:^|[\s,;{(])\bsecret\b\s*[:=]\s*[\"']([^\"'$<>{}\s]{8,})[\"']", _I),
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Severity.HIGH, "secret assignment", value_group=1),
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]
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# Value fragments that mark a placeholder / template rather than a real secret.
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# Structural markers are legitimate anywhere in the value (a template fragment
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# like ``<your-key>`` or ``your-api-key-here``), so they match as a substring.
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_PLACEHOLDER_STRUCTURAL = ("your-", "your_", "<", ">", "***")
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# Word markers are matched on a word boundary, NOT as a bare substring: a real
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# secret that merely *contains* one ("todoAppSecretKey12" contains "todo") must
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# not be suppressed — that would be a fail-open egress miss. Genuine placeholders
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# ("example-secret", "changeme") still match at their boundaries.
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_PLACEHOLDER_WORDS = (
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"example", "placeholder", "replace", "changeme",
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"xxx", "todo", "fixme", "dummy", "sample",
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)
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_PLACEHOLDER_WORD_RE = re.compile(
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r"\b(?:" + "|".join(_PLACEHOLDER_WORDS) + r")\b", re.IGNORECASE
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)
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_VARREF_TOKENS = ("${", "$(", "%{", "env[", "os.environ", "process.env")
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def _is_fp_value(value: str) -> bool:
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"""True if ``value`` is a placeholder / variable ref / trivial, not a secret."""
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low = value.lower()
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if any(token in low for token in _PLACEHOLDER_STRUCTURAL):
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return True
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if _PLACEHOLDER_WORD_RE.search(value):
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return True
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if any(token in low for token in _VARREF_TOKENS):
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return True
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if len(set(value)) == 1: # all-same-character (e.g. "xxxxxxxx")
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return True
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if len(value) < 8: # too short for a generic-pattern secret
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return True
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return False
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def scan_secret_egress(text: str, source: Source = Source.OUTPUT) -> Report:
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"""Scan ``text`` for secret/credential egress; report-only, evidence-safe.
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Each finding is labelled ``egress:<id>`` with OWASP ``LLM02``. Evidence is a
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human description plus the match length — never the secret value itself.
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"""
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report = Report()
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for pattern in _SECRET_PATTERNS:
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for match in pattern.regex.finditer(text):
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if pattern.value_group is not None:
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value = match.group(pattern.value_group)
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if value is None or _is_fp_value(value):
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continue
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report.add(
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Finding(
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label=f"egress:{pattern.id}",
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severity=pattern.severity,
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source=source,
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detector="output",
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offset=match.start(),
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owasp="LLM02",
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# Length only — the evidence must never carry the secret.
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evidence=f"{pattern.desc} (match len {len(match.group(0))})",
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)
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)
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return report
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# --- invisible carrier presence (BRIEF §4.7) --------------------------------
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# The output-gate analogue of sanitize's input-side stripping: model output is
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# report-only and never sanitized, so an invisible carrier reaching the persist
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# gate must be flagged here. Zero-width / soft-hyphen and BIDI override/isolate
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# code points; Unicode-tag / PUA stego is already surfaced by scan_lexicon
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# (``lexicon:unicode-tags-present``), so it is not repeated. Disposition treats
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# these labels as any-tier carriers (FAIL_SECURE regardless of trust).
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_ZERO_WIDTH_CPS = frozenset({0x200B, 0x200C, 0x200D, 0xFEFF, 0x00AD})
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_BIDI_CPS = frozenset({0x202A, 0x202B, 0x202C, 0x202D, 0x202E, 0x2066, 0x2067, 0x2068, 0x2069})
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def _scan_invisible_carriers(text: str, source: Source) -> Report:
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"""Flag invisible zero-width / BIDI carriers present in ``text`` (report-only)."""
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report = Report()
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zero_width = sum(1 for ch in text if ord(ch) in _ZERO_WIDTH_CPS)
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bidi = sum(1 for ch in text if ord(ch) in _BIDI_CPS)
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if zero_width:
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report.add(Finding(
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label="output:zero-width-present", severity=Severity.HIGH,
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source=source, detector="output", count=zero_width, owasp="LLM01",
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evidence="invisible zero-width/soft-hyphen characters present",
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))
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if bidi:
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report.add(Finding(
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label="output:bidi-present", severity=Severity.HIGH,
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source=source, detector="output", count=bidi, owasp="LLM01",
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evidence="BIDI override/isolate characters present",
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))
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return report
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def scan_output(
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text: str,
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source: Source = Source.OUTPUT,
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max_scan_chars: int = MAX_SCAN_CHARS,
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) -> Report:
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"""Scan model OUTPUT before persist; return the merged, report-only findings.
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Composes lexicon + entropy + decode-and-rescan + secret egress over ``text``.
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Never mutates ``text``. Bounds runtime by capping the scanned length once.
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"""
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report = Report()
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truncated = len(text) > max_scan_chars
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scan_text = text[:max_scan_chars] if truncated else text
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if truncated:
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report.add(
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Finding(
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label="output:oversize-input",
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severity=Severity.MEDIUM,
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source=source,
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detector="output",
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count=len(text),
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owasp="LLM10",
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evidence=f"output {len(text)} chars exceeds cap {max_scan_chars}; scanned prefix only",
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)
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)
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# 1. Injection strings the model reproduced into the artifact. scan_text is
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# already <= cap, so the lexicon will not emit a second oversize finding.
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report.extend(scan_lexicon(scan_text, source, max_scan_chars).findings)
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# 2. Encoded / high-entropy carrier blobs, plus the decoded plaintext blobs.
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entropy_result = scan_entropy(scan_text, source)
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report.extend(entropy_result.report.findings)
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# 3. Decode-and-rescan: run the lexicon over each decoded blob's plaintext,
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# re-labelled so the finding is attributable to the hiding blob.
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for blob in entropy_result.decoded:
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hidden = scan_lexicon(blob.decoded, source, max_scan_chars)
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for finding in hidden.findings:
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report.add(
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replace(
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finding,
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label=f"decoded:{finding.label}",
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offset=blob.offset,
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evidence=f"{finding.evidence} (in base64 blob @ {blob.offset})",
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)
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)
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# 4. Secret / credential egress (OWASP LLM02).
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report.extend(scan_secret_egress(scan_text, source).findings)
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# 5. Invisible carriers present in the artifact (zero-width / BIDI). Output
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# is never sanitized, so this is the persist-gate carrier signal; the
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# unicode-tag case is already covered by the lexicon scan in step 1.
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report.extend(_scan_invisible_carriers(scan_text, source).findings)
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return report
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