git:20260511.548e3d1 to git:20260515.6be9f59

---

name: mcp-security-auditor

description: "On-demand audit of MCP usage. Reads .aura/security/mcp-audit.jsonl, surfaces blocked calls, rate-limit hits, suspicious input patterns. Companion to mcp-call-gate hook (which produces the audit log)."

when_to_use: "/aura-frog:mcp audit, security review, post-incident forensics on MCP calls"

allowed-tools: Read, Glob, Grep, Bash

effort: low

user-invocable: false

---

# MCP Security Auditor

**STATUS — v3.7.0-rc.1.** Read-only auditor; does not enforce — that's `mcp-call-gate.cjs`'s job.

## Behavior

1. Read `.aura/security/mcp-audit.jsonl` (append-only; produced by `hooks/mcp-call-gate.cjs`)

2. Group entries by:

- Agent → MCP server → method

- Time bucket (last 1h / 24h / session)

- Status (success / blocked / rate-limited)

3. Project to TOON (via `scripts/json-to-toon.cjs --schema generic` or custom fields) — NEVER load raw JSONL into context

4. Surface findings categorized as:

- **Blocked calls** (`BLOCKED:true`) — deserve investigation

- **Rate-limit warnings** — soft (80%) or hard (100%) hits

- **Suspicious patterns** — destructive SQL detected, large output (>10KB), high frequency

## What this skill does NOT do

- Does NOT enforce — `mcp-call-gate.cjs` is the enforcement layer

- Does NOT mutate the audit log (append-only by design)

- Does NOT call MCPs itself (read-only on the audit file)

- Does NOT proxy MCP calls — the gate hook intercepts at PreToolUse

- Does NOT decide policy — `rules/agent/mcp-security-policy.md` is authoritative

## Audit log schema (per spec §23.2)

```jsonl

{"ts":"2026-05-07T...","agent":"architect","mcp":"context7","method":"query","input":{"q":"React hooks"},"output_size_bytes":4521,"latency_ms":234,"success":true}

{"ts":"2026-05-07T...","agent":"backend","mcp":"postgres","method":"query","input":{"sql":"DROP TABLE users"},"BLOCKED":true,"reason":"destructive_op_blocked"}

{"ts":"2026-05-07T...","agent":"frontend","mcp":"figma","method":"download_image","input":{"url":"..."},"success":true,"rate_limit":"80%_warn"}

```

Sanitized input fields per `scripts/security/sanitize-mcp-input.sh`:

- Authorization headers stripped

- Tokens/secrets replaced with `[REDACTED]`

- Content-Length > 1KB → truncated with `... [N more bytes]`

## Output (TOON)

```toon

mcp_audit_summary{window,total_calls,blocked,rate_limit_hits,top_agent,top_mcp}:

24h,142,3,2,architect,context7

blocked[3]{ts,agent,mcp,reason}:

2026-05-07T10:30,backend,postgres,destructive_op_blocked

2026-05-07T11:45,frontend,figma,allowlist_violation

2026-05-07T12:10,architect,redis,destructive_op_blocked

```

## Retention (per spec §23.2)

`AF_MCP_AUDIT_RETENTION_DAYS=30` (default) — older entries are pruned by a session-start sweep (NOT this skill).

## Tie-Ins

- **Spec:** §9.10, §23 (MCP security)

- **Hook:** `hooks/mcp-call-gate.cjs` — sole writer of `.aura/security/mcp-audit.jsonl`

- **Script:** `scripts/security/sanitize-mcp-input.sh` — sanitization run by the gate before logging

- **Rule:** `rules/agent/mcp-security-policy.md` — authoritative policy

- **Rule:** `rules/agent/db-access-policy.md` — DB-specific subset (architect/tdd-engineer only, read-only default, destructive ops blocked)

- **Command:** `/aura-frog:mcp audit` — primary user-facing entry to this skill

- **Skill:** Reuses `scripts/json-to-toon.cjs` to project the JSONL into context-friendly TOON