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WAF & Smart-Firewall Rule Generation for Agentic LLMs

An MCP server that lets an LLM author, validate, and test Wirefilter WAF and Smart Firewall rules — grounded in live schema and real CVE exploit templates instead of guesswork.

What it does:

• Validates rules against a real engine — expressions are checked (and optionally test-matched) through the Wirefilter rules-validator API, so the model gets real pass/fail feedback, not a hallucinated opinion
• Grounds generation in live schema — serves the authoritative actions / expressions / fields / functions / operators / values straight from the rules-validator, so rules use fields that actually exist
• Pulls real exploit context — fetches CVE-indexed Nuclei templates from multiple sources (Nuclei Open Source via GitHub, Nuclei Paid via the ProjectDiscovery API) to inform CVE-driven rule generation
• Self-updating — periodically refreshes the Wirefilter context and CVE template repositories in the background

Runs anywhere Python 3.12+ runs · ships as a Claude Desktop bundle, a stdio MCP server, or an HTTP container

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Quick start

Claude Desktop (bundle)

# Prerequisites: uv, and mcpb (npm install -g @anthropic-ai/mcpb)
mcpb pack          # produces gen0sec-mcp-server.mcpb

Open the generated gen0sec-mcp-server.mcpb file — Claude Desktop installs it in about a minute, after which the tools, resources, and prompts are available.

Cursor IDE — local (stdio)

Add to ~/.cursor/mcp.json (%USERPROFILE%\.cursor\mcp.json on Windows):

{
  "mcpServers": {
    "waf-rule-mcp": {
      "command": "uv",
      "args": [
        "run",
        "--project", "/absolute/path/to/mcp-server",
        "/absolute/path/to/mcp-server/server/main.py"
      ],
      "env": {
        "WAF_VALIDATION_API_URL": "https://public.gen0sec.com/v1/waf/validate"
      }
    }
  }
}

WAF_VALIDATION_API_URL is optional — if unset, the value from server/config.yaml is used. Restart Cursor to apply.

Docker (HTTP)

docker build -t waf-rule-mcp .
docker run -p 8000:8000 waf-rule-mcp

Then point your MCP client at it:

{
  "mcpServers": {
    "waf-rule-mcp": { "url": "http://localhost:8000" }
  }
}

The WAF rule validation API must be reachable for the validation tools to work. Set its URL via WAF_VALIDATION_API_URL or server/config.yaml.

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MCP surface

Tools

Tool	Purpose
fetch_cve_vulnerability_template	Retrieve a CVE-indexed vulnerability template from a preferred source (Nuclei Open Source or Nuclei Paid API)
fetch_cve_from_all_sources	Fetch a CVE template from all enabled sources for cross-source comparison
list_cve_sources	List the registered CVE source plugins and their status
validate_waf_expression	Validate a Wirefilter rule expression (rule_type selects the scheme)
validate_waf_expression_with_tests	Validate a Wirefilter rule and match it against test data (mock data if none given)
get_waf_context	Fetch WAF context from Wirefilter docs: actions, expressions, fields, functions, operators, values
get_rule_fields	Fetch the live, authoritative Wirefilter field/function schema directly from the rules-validator

Resources

URI	Reference
wafcontext://actions	Actions available in the Rules language
wafcontext://expressions	Expressions available in the Rules language
wafcontext://fields	Fields available in the Rules language
wafcontext://functions	Functions available in the Rules language
wafcontext://operators	Operators available in the Rules language
wafcontext://values	Values available in the Rules language

Prompts

Prompt	Generates a rule from…
natural_waf_rule_generation_prompt	a natural-language description
cve_waf_rule_generation_prompt	a CVE index
smart_firewall_rule_generation_prompt	a natural-language description, as an L3/L4 + JA4 Smart Firewall rule (no http.* fields; block/allow actions)

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Architecture

flowchart TD
    LLM([Agentic LLM / MCP client]) <--> MCP

    subgraph MCP[Gen0Sec WAF Rule MCP Server]
        T[Tools]
        R["Resources<br/>wafcontext://*"]
        P[Prompts]
        RU[Resource updater<br/>periodic refresh]
    end

    T -->|validate / fields| RV[Wirefilter rules-validator API]
    R -->|live schema| RV
    T -->|CVE templates| CS

    subgraph CS[CVE sources]
        N1[Nuclei Open Source<br/>GitHub]
        N2[Nuclei Paid<br/>ProjectDiscovery API]
    end

    RU -.refreshes.-> CS
    RU -.refreshes.-> RV

Loading

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Documentation

Gen0Sec Docs	Product documentation and guides
server/config.yaml	Validation API URL, CVE source toggles, update intervals
manifest.json	Claude Desktop bundle manifest and user-configurable options
Wirefilter	The rule expression language this server targets

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Thank you!

• Cloudflare for Wirefilter
• ProjectDiscovery for the Nuclei templates