msd-core/scripts/npm-audit-baseline.cjs

#!/usr/bin/env node
'use strict';

/**
 * #4196: npm-audit baseline diff.
 *
 * The #3588 gate (tests/npm-integrity-gate.test.cjs) used to fail on ANY
 * advisory present in the production tree, regardless of whether the PR
 * being checked introduced it. Because npm's advisory database updates
 * continuously and independently of repo state, that made the gate fail
 * for reasons no PR caused -- see #4196 for the incident where PR #4188
 * passed this gate at merge time and failed it ~15 minutes later on the
 * identical commit, purely because a new advisory was disclosed in the
 * interim.
 *
 * This module computes which vulnerable packages are NEW relative to a
 * baseline tree (typically the PR's target branch), so the gate blocks a
 * PR only for advisories it actually introduces -- a pre-existing advisory
 * in an untouched transitive dependency no longer blocks unrelated work.
 */

const fs = require('node:fs');
const os = require('node:os');
const path = require('node:path');
const { execFileSync } = require('node:child_process');

const AUDIT_TIMEOUT_MS = 180_000;

const AUDIT_DIFF_REASON = Object.freeze({
  OK_NO_NEW_VULNERABILITIES: 'ok_no_new_vulnerabilities',
  FAIL_NEW_VULNERABLE_PACKAGE: 'fail_new_vulnerable_package',
});

/**
 * Pure diff: which package names are vulnerable in `headVulnerabilities`
 * but were NOT already vulnerable in `baselineVulnerabilities`.
 *
 * Both args are the `.vulnerabilities` object from `npm audit --json`
 * (keyed by package name). Matched by package NAME only -- not by the
 * specific advisory ID or severity -- so a package that stays vulnerable
 * across a *different* newly-disclosed advisory for the same package is
 * still "pre-existing", not new. A package whose vulnerability *worsens*
 * while remaining the same package name is deliberately NOT flagged here;
 * that tradeoff keeps the predicate simple and matched to the #4196
 * incident shape (a transitive dependency neither side of the diff
 * touched). Severity escalation on an already-known-vulnerable package is
 * exactly the kind of thing the scheduled Dependabot channel should catch
 * instead (see #4196, PR #4200's auto-merge workflow).
 */
function diffNewVulnerablePackages(baselineVulnerabilities, headVulnerabilities) {
  const baselineNames = new Set(Object.keys(baselineVulnerabilities || {}));
  return Object.keys(headVulnerabilities || {}).filter((name) => !baselineNames.has(name));
}

/**
 * Typed verdict wrapping diffNewVulnerablePackages. `ok: false` means the
 * diff (head vs baseline) is non-empty -- this PR/push introduced at
 * least one newly-vulnerable package.
 */
function evaluateAuditDiff({ baselineVulnerabilities, headVulnerabilities }) {
  const newlyIntroduced = diffNewVulnerablePackages(baselineVulnerabilities, headVulnerabilities);
  if (newlyIntroduced.length > 0) {
    return { ok: false, reason: AUDIT_DIFF_REASON.FAIL_NEW_VULNERABLE_PACKAGE, newlyIntroduced };
  }
  return {
    ok: true,
    reason: AUDIT_DIFF_REASON.OK_NO_NEW_VULNERABILITIES,
    preExisting: Object.keys(headVulnerabilities || {}),
  };
}

/**
 * Runs `npm audit --package-lock-only --omit=dev --json` in `cwd` and
 * returns the parsed JSON, or `null` if `cwd` has no package.json or no
 * package-lock.json (not an auditable tree -- callers treat this as
 * "skip"/"no baseline available", not an error).
 *
 * `--package-lock-only` deliberately avoids requiring `node_modules/` to
 * be installed: it lets a baseline tree be audited from nothing but an
 * extracted package.json + package-lock.json (see extractBaselineTree),
 * without a second full `npm ci`.
 */
function runPackageLockAudit(cwd) {
  if (!fs.existsSync(path.join(cwd, 'package.json'))) return null;
  if (!fs.existsSync(path.join(cwd, 'package-lock.json'))) return null;
  const isWindows = process.platform === 'win32';
  const npmCandidates = isWindows ? ['npm.cmd', 'npm'] : ['npm'];
  const args = ['audit', '--package-lock-only', '--omit=dev', '--json'];
  let out;
  let lastErr = null;
  for (const npmCmd of npmCandidates) {
    try {
      out = execFileSync(
        npmCmd,
        args,
        {
          cwd,
          encoding: 'utf-8',
          stdio: ['ignore', 'pipe', 'pipe'],
          timeout: AUDIT_TIMEOUT_MS,
          shell: isWindows,
        },
      );
      lastErr = null;
      break;
    } catch (e) {
      // `npm audit` exits non-zero when advisories are present; the JSON is
      // still on stdout in that case. Recover and let the caller classify —
      // but only when stdout actually CARRIES the JSON: an audit that was
      // killed or aborted can exit non-zero with EMPTY stdout, and accepting
      // the empty string here surfaces as a bare `SyntaxError: Unexpected
      // end of JSON input` at the parse below, hiding the captured error
      // (observed on CI 2026-09-03, both lanes; cause undetermined).
      const recovered = e && typeof e.stdout !== 'undefined' && e.stdout !== null
        ? (Buffer.isBuffer(e.stdout) ? e.stdout.toString('utf-8') : String(e.stdout))
        : '';
      if (recovered.trim()) {
        out = recovered;
        lastErr = null;
        break;
      }
      lastErr = e;
    }
  }
  if (!out || !out.trim()) {
    const detail = lastErr
      ? [lastErr.stdout, lastErr.stderr, String(lastErr.message)].filter(Boolean).join('\n').slice(0, 500)
      : '(no error captured)';
    throw new Error(
      `npm audit --json produced no output in ${cwd}. ` +
        `Detail from the failed invocation:\n${detail}`
    );
  }
  if (lastErr) throw lastErr;
  const parsed = JSON.parse(out);
  if (parsed && parsed.metadata && parsed.metadata.vulnerabilities) {
    return parsed;
  }
  throw new Error(`Unexpected npm audit JSON shape in ${cwd}: missing metadata.vulnerabilities`);
}

/**
 * Extracts package.json + package-lock.json (optionally under `subdir`,
 * e.g. 'sdk') from `ref` at git object level into a fresh temp directory --
 * no working-tree checkout, no `node_modules` install. Returns the temp
 * dir path, or `null` if `ref` cannot be resolved locally (e.g. a shallow
 * clone that never fetched it) or either file is absent at that ref --
 * callers treat `null` as "no baseline available", not an error.
 */
function extractBaselineTree(ref, repoRoot, subdir = '') {
  const rel = (name) => (subdir ? path.posix.join(subdir, name) : name);
  let pkgJson;
  let lockJson;
  try {
    pkgJson = execFileSync('git', ['show', `${ref}:${rel('package.json')}`], {
      cwd: repoRoot,
      encoding: 'utf-8',
      stdio: ['ignore', 'pipe', 'ignore'],
    });
    lockJson = execFileSync('git', ['show', `${ref}:${rel('package-lock.json')}`], {
      cwd: repoRoot,
      encoding: 'utf-8',
      stdio: ['ignore', 'pipe', 'ignore'],
    });
  } catch {
    return null;
  }
  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-audit-baseline-'));
  fs.writeFileSync(path.join(dir, 'package.json'), pkgJson);
  fs.writeFileSync(path.join(dir, 'package-lock.json'), lockJson);
  return dir;
}

// All-zeros is git's documented sentinel for "this ref did not exist
// before this push" (a brand-new branch's first push) -- never a real
// commit to diff against.
const NULL_SHA = '0000000000000000000000000000000000000000';

/**
 * Resolves the git ref to diff against, in priority order:
 *   1. AUDIT_BASELINE_REF env var -- the primary mechanism. CI sets this
 *      explicitly (see .github/workflows/test.yml) to github.event.pull_
 *      request.base.sha on a pull_request event, or github.event.before on
 *      a push event -- both pinned, race-free values Git/GitHub track for
 *      exactly this purpose. Prefer this over anything below whenever the
 *      caller can provide it.
 *   2. GITHUB_BASE_REF (GitHub Actions sets this on pull_request events)
 *      resolved against the LIVE origin/<branch> tip. Only reached if
 *      AUDIT_BASELINE_REF wasn't set -- e.g. a workflow that forgot to
 *      wire it. origin/<branch> can advance mid-run (see the GSD_EMITTED_
 *      BASE precedent in test.yml), so this is a degraded fallback, not
 *      the intended path for pull_request events in this repo's own CI.
 *   3. On a `push` event, `HEAD~1` -- correct ONLY when the push added
 *      exactly one commit (true for a squash-merge or a single ordinary
 *      commit). This repo also allows rebase-merge (allow_rebase_merge:
 *      true), which can land a PR as several discrete commits in one
 *      push -- HEAD~1 then lands on an EARLIER commit in the same push,
 *      which may already contain a vulnerable package that commit itself
 *      introduced, silently marking it "pre-existing". CI never reaches
 *      this branch (AUDIT_BASELINE_REF is always set by test.yml for
 *      push events); it exists only for out-of-band invocations (e.g.
 *      gsd-test) that don't set any of the above.
 *   4. `origin/next`, else a plain local branch named `next` (gsd-test's
 *      sandbox fetches the base as a local branch, not a remote-tracking
 *      ref -- see gsd-test-merges-into-LOCAL-base-branch in this repo's
 *      own operational notes), if either exists locally (this repo's
 *      integration branch -- matches DEFAULT_BASE in
 *      scripts/changeset/lint.cjs).
 * Returns '' if none resolve -- callers fall back to strict zero-tolerance
 * rather than silently skipping the gate.
 */
function resolveBaselineRef(repoRoot) {
  if (process.env.AUDIT_BASELINE_REF) return process.env.AUDIT_BASELINE_REF;
  if (process.env.GITHUB_BASE_REF) return `origin/${process.env.GITHUB_BASE_REF}`;
  if (process.env.GITHUB_EVENT_NAME === 'push') {
    try {
      const parent = execFileSync('git', ['rev-parse', '--verify', 'HEAD~1'], {
        cwd: repoRoot,
        encoding: 'utf-8',
        stdio: ['ignore', 'pipe', 'ignore'],
      }).trim();
      if (parent && parent !== NULL_SHA) return parent;
    } catch {
      // not enough history; fall through
    }
  }
  try {
    execFileSync('git', ['rev-parse', '--verify', 'origin/next'], {
      cwd: repoRoot,
      stdio: 'ignore',
    });
    return 'origin/next';
  } catch {
    // fall through to a plain local branch
  }
  try {
    execFileSync('git', ['rev-parse', '--verify', 'next'], {
      cwd: repoRoot,
      stdio: 'ignore',
    });
    return 'next';
  } catch {
    return '';
  }
}

module.exports = {
  AUDIT_DIFF_REASON,
  diffNewVulnerablePackages,
  evaluateAuditDiff,
  runPackageLockAudit,
  extractBaselineTree,
  resolveBaselineRef,
  NULL_SHA,
};