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fix(policy): read policy.json only from the caller's own working tree

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loadPolicy() read .llm-security/policy.json from whatever root it was
given, and every scanner passes the SCANNED TARGET: scan-orchestrator
(policyRoot = resolve(args.target)), entropy-scanner (thresholds and
suppression patterns), signature-scanner (sig.custom_rules_path and
enabled_families), trigger-scanner (phrase lists) and ast-taint-scanner
(enabled, python_path). A foreign/cloned target could raise its own
entropy thresholds, disable SIG families, supply its own SIG ruleset or
name the interpreter the AST scanner spawns — configuring the scan of
itself. Same defect class as S3b's .llm-security-ignore fix.

Chosen: move isOwnWorkingTree() to scanners/lib/own-working-tree.mjs (one
copy, reused by the orchestrator's ignore-file check) and make
loadPolicy() refuse an EXPLICIT root that is not the caller's own tree —
defaults plus one stderr line, same form as S3b — because one rule in one
function covers every scanner and a future call site cannot forget it.
The IMPLICIT root (CLAUDE_PROJECT_ROOT/cwd, what every hook uses) is the
caller's own project by construction and is read as before.
entropy-scanner's calibration.policy_source no longer reports an ignored
file as its source.

New tests/scanners/policy-scope.test.mjs was red on 0d37f5a (foreign
target: entropy finding silenced, custom SIG rule loaded, findings differ
from the same tree without policy.json, no stderr line) and is green now;
its own-tree scenario (known-positive) is green before and after. The 15
existing policy tests that placed own-tree fixtures under os.tmpdir() now
use tests/helpers/own-tree.mjs (fixture under $HOME, cwd set to it).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Kjell Tore Guttormsen 2026-09-22 20:15:17 +02:00
commit 6d0f3c31fc
Signed by: ktg
SSH key fingerprint: SHA256:JakMjO6FTBBzN0Bhfj9saOoEjaFxlSdYuZQQpM/lF9Q
12 changed files with 364 additions and 50 deletions
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6
scanners/entropy-scanner.mjs
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@ -17,6 +17,7 @@ import { finding, scannerResult } from './lib/output.mjs';
import { SEVERITY } from './lib/severity.mjs';
import { shannonEntropy, extractStringLiterals, isBase64Like, isHexBlob, redact } from './lib/string-utils.mjs';
import { loadPolicy } from './lib/policy-loader.mjs';
import { isOwnWorkingTree } from './lib/own-working-tree.mjs';
// ---------------------------------------------------------------------------
// File-extension suppression (context-aware, v7.0.0+)
@ -569,10 +570,11 @@ export async function scan(targetPath, discovery) {
// Best-effort — on any error we fall back to built-in defaults. Provenance
// tracked via file-existence check, not by comparing merged values (defaults
// always include an entropy section so a value-based check would always
// report 'policy.json').
// report 'policy.json'). S3c: a foreign target's policy.json is not read by
// loadPolicy(), so it is not reported as the source either.
let policySource = 'defaults';
try {
if (existsSync(join(targetPath, '.llm-security', 'policy.json'))) {
if (existsSync(join(targetPath, '.llm-security', 'policy.json')) && isOwnWorkingTree(targetPath)) {
policySource = 'policy.json';
}
const policy = loadPolicy(targetPath);