Cloud Armor WAF Patrol MCP

cloudarmor-mcp

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MCP server for Google Cloud Armor WAF log patrol — deny summaries per rule, home-region false-positive checks, and preview (dry-run) rule review, straight from Cloud Logging.

Built for a daily "is the WAF healthy?" patrol: one daily_brief call answers what did we block, did we block anyone we shouldn't have, and are the preview rules ready to promote.

Documentation: https://shigechika.github.io/cloudarmor-mcp/

Tools

All tools are read-only. Counts are hard-capped (default 2000 entries per query) and a capped result is reported as >= N (capped), never as an exact total.

Setup

1. Least-privilege service account

Create a service account with roles/logging.viewer only and download a key. Unlike human accounts, service accounts are not subject to organization re-authentication policies, so an unattended patrol never silently expires.

gcloud iam service-accounts create waf-log-viewer --project=YOUR_PROJECT
gcloud projects add-iam-policy-binding YOUR_PROJECT \
  --member=serviceAccount:waf-log-viewer@YOUR_PROJECT.iam.gserviceaccount.com \
  --role=roles/logging.viewer
gcloud iam service-accounts keys create key.json \
  --iam-account=waf-log-viewer@YOUR_PROJECT.iam.gserviceaccount.com

2. Install

pip install cloudarmor-mcp
# or
uv tool install cloudarmor-mcp

3. Environment variables

4. Optional rules INI

Keep your rule numbering out of prompts and give the reports human-readable labels:

[rules]
101 = block non-home deep-path crawlers
500 = AutoDiscover probe block
1002 = OWASP LFI protection

[home]
; home-region DENYs on these priorities are expected, not false positives
known_normal_priorities = 500, 600

5. Claude Code (plugin)

This repository doubles as a single-plugin marketplace, so Claude Code can install the server for you:

/plugin marketplace add shigechika/cloudarmor-mcp
/plugin install cloudarmor-mcp@cloudarmor-mcp

The plugin launches uvx cloudarmor-mcp and reads the same environment variables described in Environment variables above; export them before starting Claude Code. GOOGLE_APPLICATION_CREDENTIALS still has to point at a service-account key file that exists on your own machine — the plugin can't ship or fetch that file for you, so this server can't be fully configured through the plugin's own settings alone.

uvx must be on the PATH of the process that runs Claude Code — a login shell usually has it, but a GUI-launched app may not; install uv system-wide if the plugin fails to start.

6. Claude Code (manual)

claude mcp add cloudarmor -- cloudarmor-mcp

with the environment variables above in the server's env.

CLI

cloudarmor-mcp --version   # print version
cloudarmor-mcp --check     # config + API probe (exit 0 when healthy)
cloudarmor-mcp --brief     # print daily_brief to stdout (cron / smoke tests)

Exporting one day of DENY entries (batch)

cloudarmor-mcp deny-export --date 2026-09-22 --tz Asia/Tokyo > out.tmp && mv out.tmp 2026-09-22.json

Writes one JSON document to stdout with one record per DENY log entry of that calendar day ([00:00, 24:00) in --tz, default UTC): the enforced and preview policy verdicts (policy, priority, action, outcome, rule_ids), source IP, region code and ASN as Cloud Armor logged them, method, host, path (query string dropped — only its length is kept), status, User-Agent (200 chars) and backend. --kind both (default) fetches entries where either policy says DENY in a single query, so a request that matched a preview rule and was denied appears once with both sections filled. --backend a,b overrides CLOUDARMOR_BACKEND_SERVICES.

This and traffic-export (below) are the only outputs of the package that contain per-request log data; it is meant for an operator batch on the same host that aggregates the day itself. The document ends with count, fetched, malformed and capped: when capped is true the export stopped at --max-entries (default 200000; CLOUDARMOR_MAX_ENTRIES does not apply) and is a prefix of the day, oldest first. Records are streamed, so memory does not grow with the day, and pages are fetched at most one per 1.2 s to stay under the Cloud Logging read quota (60 requests per minute), so a day with 200,000 entries takes a few minutes. A day that has not ended yet is refused. Run it some minutes after local midnight — Cloud Logging entries arrive with a delay — and write to a temporary file first: on a query failure the exit code is 1 and stdout may hold an unterminated document.

Exporting a sampled day of all requests (batch)

cloudarmor-mcp traffic-export --date 2026-09-22 --tz Asia/Tokyo --sample 0.01 > out.tmp && mv out.tmp 2026-09-22.json

Same document layout and record fields as deny-export, but for every load-balancer request of the day — allowed, denied and served from the CDN cache — thinned by Cloud Logging's sample(insertId, RATE) (--sample, default 0.01). The sample is a hash of each entry's insertId, so it is spread evenly over the day and the same rate selects the same entries on every run; scale counts by 1 / sample to estimate the day — but not when capped is true: entries are read oldest first, so a capped export covers only the early part of the day (lower --sample or raise --max-entries instead). Each record adds cache_hit. When no backend security policy evaluated a request (a CDN cache hit, for example) it has enforced: null and no region code or ASN; use cache_hit, not enforced, to tell cache hits apart. The header carries sample instead of kind. Use it to see who visits — browsers, crawlers, AI agents — which the DENY logs cannot show. The per-request caveats of deny-export apply: the records include legitimate visitors' addresses.

Reading the report

• Enforced DENY by rule — your normal blocking volume. Sudden shifts in the mix are worth a look.
• Home-region DENY — requests from your own country/region that were blocked. Legitimate users and legitimate crawlers being denied show up here; scanner traffic that happens to originate locally will too, so the known_normal_priorities list keeps expected rules (e.g. an AutoDiscover block) out of the suspicious list.
• Preview DENY — rules in dry-run. A preview rule that stays free of home-region hits over time is a candidate for promotion to enforce.

License

MIT