fix(ms-ai-architect): G6 Layer B — unicode/carrier-scan kjører pre-write via temp-fil (lukker ingestion-brief §8-akseptansegap, TDD) [skip-docs]

scripts/kb-update/lib/adversarial-detect.mjs

@@ -23,7 +23,9 @@
 // pattern as scripts/kb-eval/score-skill.mjs.
 
 import { fileURLToPath } from 'node:url';
-import { dirname, resolve, basename } from 'node:path';
+import { dirname, resolve, basename, join } from 'node:path';
+import { mkdtempSync, writeFileSync, rmSync } from 'node:fs';
+import { tmpdir } from 'node:os';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 
@@ -80,7 +82,9 @@ const ENCODED_MIN_ENTROPY = 4.0;
  *               driven with a single-file discovery so no charset is re-derived here.
  *
  * @param {string} content — the candidate file content
- * @param {{path?: string}} [opts] — path is required for unicode detection (the scanner reads it)
+ * @param {{path?: string}} [opts] — optional on-disk path; when absent the unicode scan runs
+ *   PRE-WRITE against a temp file materialized from `content` (the ingestion gate), so unicode
+ *   coverage no longer depends on the file already existing on disk
  * @returns {Promise<Array<{class: string, subtype?: string, severity: string, line: number, evidence: string}>>}
  */
 export async function detectAdversarial(content, opts = {}) {
@@ -108,8 +112,22 @@ export async function detectAdversarial(content, opts = {}) {
   }
 
   // --- unicode (disk-based scanner; needs a real path) ---
-  if (opts.path) {
-    const discovery = { files: [{ absPath: resolve(opts.path), relPath: basename(opts.path) }] };
+  // The llm-security unicode scanner reads a file off disk. When a caller passes content
+  // WITHOUT a path — the pre-write ingestion gate: scan the COMPOSED artefact before it is
+  // ever written — materialize a temp file so the SAME scanner runs pre-write. This closes
+  // the ingestion-brief §8 acceptance test (zero-width/bidi rejected BEFORE write); the old
+  // `if (opts.path)` guard skipped unicode entirely on the content path, leaving pre-write
+  // carriers undetected. Fail-closed posture is unchanged — a scanner error still propagates
+  // as a throw → the caller BLOCKs.
+  let scanPath = opts.path;
+  let tmpDir = null;
+  try {
+    if (!scanPath) {
+      tmpDir = mkdtempSync(join(tmpdir(), 'kb-adv-'));
+      scanPath = join(tmpDir, 'candidate.md');
+      writeFileSync(scanPath, String(content ?? ''), 'utf8');
+    }
+    const discovery = { files: [{ absPath: resolve(scanPath), relPath: basename(scanPath) }] };
     const res = await unicodeScan('.', discovery);
     for (const f of res.findings || []) {
       findings.push({
@@ -120,6 +138,8 @@ export async function detectAdversarial(content, opts = {}) {
         evidence: f.evidence || f.title || 'unicode anomaly',
       });
     }
+  } finally {
+    if (tmpDir) rmSync(tmpDir, { recursive: true, force: true });
   }
 
   return findings;

tests/kb-update/test-scan-adversarial-content.test.mjs

@@ -11,7 +11,11 @@
 
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
+import { mkdtempSync, writeFileSync, rmSync, readdirSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
 import { scanPaths } from '../../scripts/kb-update/scan-adversarial-content.mjs';
+import { detectAdversarial } from '../../scripts/kb-update/lib/adversarial-detect.mjs';
 
 const CLEAN = '# T\n\n**Source:** https://learn.microsoft.com/azure/x\n\nProse.\n';
 
@@ -80,3 +84,52 @@ test('scanPaths — no paths → ok:true (nothing to gate)', async () => {
   assert.equal(r.ok, true);
   assert.deepEqual(r.results, []);
 });
+
+// --- detectAdversarial: pre-write unicode scan (G6 Layer B bugfix, ingestion-brief §8) ----
+// Unlike the scanPaths tests above (fake detectors, never touch disk/llm-security), these
+// exercise the REAL bridge. The bug: the disk-based unicode scanner only ran when opts.path
+// was supplied, so a candidate scanned as CONTENT (the pre-write ingestion gate) got zero
+// unicode coverage — violating the committed §8 acceptance test (zero-width/bidi rejected
+// BEFORE write). The fix materialises a temp file so the same scanner runs pre-write. These
+// tests are skipped when the llm-security sibling is absent (fresh clone) so the maintainer
+// suite stays green either way.
+let llmSecurityAvailable = false;
+try {
+  await detectAdversarial('probe'); // loads the detectors; throws LLM_SECURITY_UNAVAILABLE if absent
+  llmSecurityAvailable = true;
+} catch { /* sibling not resolvable — the integration tests below skip */ }
+
+const ZW_BIDI = 'Ren tekst​ med zero-width og ‮ bidi override.\n';
+const PLAIN = 'Helt ren prosatekst uten anomalier.\n';
+const advTmpDirs = () => readdirSync(tmpdir()).filter((n) => n.startsWith('kb-adv-'));
+
+test('detectAdversarial flags zero-width/bidi in content WITHOUT a path (pre-write §8)', { skip: !llmSecurityAvailable }, async () => {
+  const findings = await detectAdversarial(ZW_BIDI);
+  const unicode = findings.filter((f) => f.class === 'unicode');
+  assert.ok(unicode.length >= 2, `expected ≥2 unicode findings pre-write, got ${JSON.stringify(findings)}`);
+  assert.ok(unicode.some((f) => f.subtype === 'zero-width'), 'zero-width carrier must be caught pre-write');
+  assert.ok(unicode.some((f) => f.subtype === 'bidi'), 'bidi override must be caught pre-write');
+});
+
+test('detectAdversarial returns no unicode findings for clean content WITHOUT a path', { skip: !llmSecurityAvailable }, async () => {
+  const findings = await detectAdversarial(PLAIN);
+  assert.equal(findings.filter((f) => f.class === 'unicode').length, 0);
+});
+
+test('detectAdversarial disk-path route is unchanged (regression)', { skip: !llmSecurityAvailable }, async () => {
+  const d = mkdtempSync(join(tmpdir(), 'kbreg-'));
+  const p = join(d, 'candidate.md');
+  try {
+    writeFileSync(p, ZW_BIDI, 'utf8');
+    const viaPath = await detectAdversarial(ZW_BIDI, { path: p });
+    assert.ok(viaPath.filter((f) => f.class === 'unicode').length >= 2, 'explicit-path route must still flag unicode');
+  } finally {
+    rmSync(d, { recursive: true, force: true });
+  }
+});
+
+test('detectAdversarial cleans up its pre-write temp file (no leak)', { skip: !llmSecurityAvailable }, async () => {
+  const before = advTmpDirs().length;
+  await detectAdversarial(ZW_BIDI);
+  assert.equal(advTmpDirs().length, before, 'pre-write temp dir must be removed in finally');
+});