waf-mcp-remote

A drop-in wrapper around mcp-remote that intercepts generic WAF blocking responses and converts them into valid MCP JSON-RPC SSE error events.
It wraps the original mcp-remote CLI under the hood and currently supports only Streamable HTTP protocol (not HTTP+SSE).

Note: This project is experimental—use it at your own risk.

Why is this necessary?

When a Web Application Firewall (WAF) flags a request to your MCP streaming endpoint, it typically returns an HTML block page.
That breaks any client expecting a continuous JSON-RPC SSE stream, causing errors or hangs.

waf-mcp-remote:

1. Catches WAF responses: Detects non-JSON HTML block pages.
2. Suppresses the block page: Terminates the HTML response.
3. Emits a JSON-RPC error event: Sends a clean SSE-compatible JSON-RPC error so your client and AI analytics can handle it gracefully.

Use it to test or adopt MCP streaming without disabling your WAF or confusing end users.

Installation

npm install -g @f5devcentral/waf-mcp-remote

Or via npx:

npx @f5devcentral/waf-mcp-remote <server-url> [options]

Environment Variables

You can set these environment variables to configure waf-mcp-remote:

• WAF_STATUS_CODE: Override the WAF block status code (default: 0).
• WAF_RESPONSE_PATTERN: Regex pattern to match against WAF block page content (default: \bYour support ID is:? ([\w-]+)\b).
• WAF_RESPONSE_PATTERN_FLAGS: Regex flags for the WAF response pattern (default: ``).

Usage

Replace calls to mcp-remote in your MCP client config with waf-mcp-remote. Example for a JSON config:

{
  "mcpServers": {
    "protected-remote": {
      "command": "npx",
      "args": [
        "@f5devcentral/waf-mcp-remote",
        "https://remote.mcp.server/mcp"
      ],
      "env": {
        "WAF_STATUS_CODE": "403",
        "NODE_TLS_REJECT_UNAUTHORIZED": "0"
      }
    }
  }
}

CLI Options

All flags from mcp-remote still apply. In addition, waf-mcp-remote supports:

• --debug : Enable verbose logs (~/.mcp-auth/{server_hash}_debug.log).
• --header : Add custom headers to each request (e.g. --header "Authorization: Bearer $TOKEN").
• --allow-http : Permit HTTP (non-HTTPS) endpoints in trusted networks.

Tip: With npx, pass -y to auto-accept installations: npx -y @f5devcentral/waf-mcp-remote <url>.

Transport Strategies

Control HTTP vs SSE order just like mcp-remote:

npx @f5devcentral/waf-mcp-remote https://example/stream --transport <mode>

• http-only (default)
• http-first (convert to http-only)
• sse-first (not supported)
• sse-only (not supported)

OAuth Configuration

Use any standard mcp-remote OAuth flags:

• --static-oauth-client-metadata : JSON string or @-file path
• --static-oauth-client-info : via MCP_REMOTE_CLIENT_ID/MCP_REMOTE_CLIENT_SECRET
• --host : Override OAuth callback host
• Append a port after the URL to change redirect port

Troubleshooting

• Silent client: Ensure you’re targeting an HTTP stream endpoint (not SSE).

• Unexpected HTML: Confirm your WAF’s block page isn’t non-standard.

• State issues: Clear auth state with:

  rm -rf ~/.mcp-auth

• Node version: Requires Node.js 18+.

Contributing

Feel free to open issues or PRs in the waf-mcp-remote repo. Contributions welcome!

Wraps mcp-remote - add WAF-aware streaming to your MCP clients in one command.