| name | phx:deps-audit |
| description | Audit Hex deps for supply-chain security risk — bidi chars, compile-time exec, maintainer changes, typosquats, CVEs. Use after mix deps.update, when checking if a package upgrade is safe, or reviewing mix.lock PR diffs. |
| effort | medium |
| argument-hint | [--base <ref> | --preview [pkg...]] [--quick] [--json] [--sarif <path>] [--ci] [--strict] [--no-differential] [--no-llm | --llm] [--trace] |
| allowed-tools | Read, Grep, Glob, Bash, WebFetch |
Hex Dependency Audit
Non-mutating supply-chain audit for Hex packages. Runs an 8-rule MVP catalogue
against changed packages, enriches with Hex API metadata, wraps existing tools
(mix hex.audit, mix_audit, OSV-Scanner), and emits a triage table.
When to Use
- After
mix deps.update or mix deps.get brought in new versions
- On PRs that touch
mix.lock (pre-merge gate)
- Before manually updating a single package (
--preview <pkg>)
- When investigating a dependency you don't recognize
Iron Laws
- NEVER claim a diff is clean without inspecting it. Run all 8 rules
on the unpacked NEW tarball. "Looks fine" without a tool run is a false
pass. Always write
.claude/deps-audit/last-run.json — its absence
is evidence the audit didn't actually run.
- NEVER install
mix_audit / osv-scanner — even if asked. Detect,
warn with install instructions, skip cleanly if missing. If the user
says "install it," respond with the install command (e.g.,
mix deps.add mix_audit --only dev) and do not execute it. The
audit skill is non-mutating; mix.exs / mix.lock are off-limits
regardless of consent.
- NEVER promote a finding to BLOCK without rule citation. Every finding
shows
rule_id, severity, file:line, snippet, message. No
handwaving.
- NEVER fetch from Hex API without rate-limiting. Cap at 5 req/sec.
Cache metadata 7 days, top-500 list 1 day.
- NEVER run the audit on already-committed lock changes silently —
tell the user which mode (A/B/C) is active and which
(old, new) pairs
resolved.
- LLM triage only above threshold. Native rules + Semgrep + YARA
are deterministic. The
hex-deps-triager agent runs only when score
10 (1 BLOCK or 3+ WARNs), and its verdicts are advisory — never
auto-suppress a finding without human review.
Operating Modes
| Mode | Trigger | Old source | New source |
|---|
| B (default) | /phx:deps-audit | git show HEAD:mix.lock | working mix.lock |
| C (PR) | /phx:deps-audit --base main | git show <ref>:mix.lock | working mix.lock |
| A (preview) | /phx:deps-audit --preview httpoison | locked version | Hex API latest |
See ${CLAUDE_SKILL_DIR}/references/operating-modes.md for full resolver logic.
Execution Flow
Default = full 8-rule scan with streaming progress. --quick opts out
to CVE + retirement only. See ${CLAUDE_SKILL_DIR}/references/execution-flow.md.
Step 1: Resolve the diff
Parse the mix.lock Erlang term format for both old and new sources. Emit a
list of {pkg, old_version, new_version} tuples. Surface
new-only and removed-only packages separately (a removed package is not
audited; a brand-new package gets old_version = nil and skips diff-only
rules).
See ${CLAUDE_SKILL_DIR}/references/diff-resolver.md for shell + mix run -e snippets per mode and the JSON output contract.
Step 2: Fetch tarballs (per-run tmpdir)
For each (pkg, old, new):
mix hex.package fetch <pkg> <old> --unpack -o ${AUDIT_TMPDIR}/tarballs/<pkg>/<old>/
mix hex.package fetch <pkg> <new> --unpack -o ${AUDIT_TMPDIR}/tarballs/<pkg>/<new>/
All ephemeral artifacts live under ${AUDIT_TMPDIR} (driver-owned, removed
on exit). See ${CLAUDE_SKILL_DIR}/references/audit-tmpdir.md and
${CLAUDE_SKILL_DIR}/references/tarball-fetcher.md.
Step 3: Run the 8 MVP rules on each NEW tarball
| # | Rule | Sev | Method |
|---|
| 1 | Bidi Unicode control chars in .ex/.exs/.erl | BLOCK | grep |
| 2 | Code.eval_* / :erlang.apply with non-literal MFA at module scope | BLOCK | AST (Sourceror or regex+scope) |
| 3 | System.cmd / :os.cmd / Port.open at compile time | BLOCK | AST |
| 4 | :erlang.binary_to_term/1 on literal without :safe | BLOCK | AST |
| 5 | New :git/:path dep in mix.exs (vs old) | BLOCK | AST diff |
| 6 | Maintainer change between versions | BLOCK | Hex API |
| 7 | Base64 blobs >256 chars outside priv/static/, test/fixtures/, assets/ | WARN | regex |
| 8 | Levenshtein ≤2 from top-500 + download delta >1000× | BLOCK | Hex API + fuzzy |
Full catalogue (35 rules, MVP marked) in ${CLAUDE_SKILL_DIR}/references/heuristics.md.
Bash + mix run -e implementations for all 8 MVP rules in
${CLAUDE_SKILL_DIR}/references/rules-impl.md (single-pass NEW + diff rules +
Hex API rules, with run_all_rules master loop).
Step 4: External tool wrappers (parallel)
mix hex.audit — retired-package check, always availablemix_audit — CVE check via GHSA, if installed (else warn + skip; do NOT install)osv-scanner — CVE check via OSV.dev, if installed (else warn + skip; do NOT install)
See ${CLAUDE_SKILL_DIR}/references/external-tools.md for detection, output parsing, and severity mapping per tool.
Step 5: Hex API enrichment (per package)
GET /api/packages/:name — owners, downloads, inserted_atGET /api/packages/:name/releases/:version — per-release publisher- Compute:
days_since_publish, owner_age_days, download_velocity
Cap at 5 req/sec. Per-run cache under ${AUDIT_TMPDIR}/hex-api/.
See ${CLAUDE_SKILL_DIR}/references/hex-api.md for endpoint contracts,
caching strategy, Rule 6/8 detection, and Levenshtein implementation.
Step 5.5: Apply hex_vet.exs ledger (if present)
If hex_vet.exs exists at project root, vetted-version findings are
downgraded to INFO. Unvetted versions retain their severity.
Lock-vs-ledger disagreement: lock wins. See the deps-vet skill's
hex-vet schema doc for the "Lock-vs-ledger disagreement" section.
Use /phx:deps-vet <pkg> <version> (separate skill) to add entries.
Step 5.7: Differential subtract
When run with DIFFERENTIAL=1 (default), findings that existed in the
OLD tarball are downgraded to INFO. Net-new signals reach the renderer
at full severity. See ${CLAUDE_SKILL_DIR}/references/differential.md.
Step 5.8: LLM triage (when score > threshold)
For packages where the aggregate score exceeds 10, the
hex-deps-triager sonnet agent reads finding + diff windows and
produces structured verdicts (confidence, verdict, rationale,
fp_reasons[]). A context-supervisor (haiku) consolidates verdicts
across packages into triage/consolidated.md. Main skill reads only
the consolidated file.
See ${CLAUDE_SKILL_DIR}/references/llm-triage.md.
Step 6: Score & render
Per-package weighted sum: BLOCK = 10, WARN = 3, INFO = 1.
Risk band: 0 clean · 1–5 low · 6–15 medium · 16+ high.
Output:
- Stdout: markdown table —
pkg | old → new | risk | findings | diff.hex.pm | maintainer-change plus a per-package detail section for any non-clean row.
- Sidecar (MANDATORY): Write
.claude/deps-audit/last-run.json. The Phase 3 gate reads this; an audit that doesn't write it is a no-op for the gate. Always emit, even on clean runs.
--json flag emits JSON to stdout instead of markdown. See
${CLAUDE_SKILL_DIR}/references/output-renderer.md for table format,
sidecar schema, exit-code rubric, and --quiet mode.
Out of scope / Phase 3 surface
- NEVER modify
mix.lock, mix.exs, or any project file (non-mutating)
- NEVER auto-install missing tools (warn + skip)
- Gate
mix deps.{get,update,compile} via deps-audit-gate.sh. See references/hook.md.
- Prompt for
/phx:compound after BLOCK findings — corpus self-feeds.
- Emit SARIF 2.1.0 via
--sarif <path> and gate CI via --ci.
References
${CLAUDE_SKILL_DIR}/references/heuristics.md — full 35-rule catalogue${CLAUDE_SKILL_DIR}/references/rules-impl.md — bash + mix run -e for the 8 MVP rules${CLAUDE_SKILL_DIR}/references/operating-modes.md — Mode A/B/C resolver${CLAUDE_SKILL_DIR}/references/diff-resolver.md — shell snippets, lock parser${CLAUDE_SKILL_DIR}/references/tarball-fetcher.md — fetch wrapper, parallel cap, cache prune${CLAUDE_SKILL_DIR}/references/external-tools.md — mix_audit, osv-scanner wrappers${CLAUDE_SKILL_DIR}/references/hex-api.md — endpoint contracts, rate limit, Rule 6/8${CLAUDE_SKILL_DIR}/references/output-renderer.md — markdown, JSON v1, exit codes, SARIF${CLAUDE_SKILL_DIR}/references/testing.md — smoke runner, fixture matrix${CLAUDE_SKILL_DIR}/references/differential.md / llm-triage.md — Phase 2 NDJSON subtract + triager${CLAUDE_SKILL_DIR}/references/semgrep.md / yara.md — Phase 2 precision layers (soft deps)${CLAUDE_SKILL_DIR}/references/cassettes.md / sarif.md / hook.md / ci-integration.md — Phase 3 surface${CLAUDE_SKILL_DIR}/references/trusted-publishers.md / skill-checklist.md — upstream + eval${CLAUDE_SKILL_DIR}/references/audit-tmpdir.md — Phase 5 per-run ephemeral storage contract${CLAUDE_SKILL_DIR}/references/execution-flow.md / differential-cve.md — Phase 5 default scan + CVE diff
