m2pack-secure/mcp_server.mjs

import { spawnSync } from "node:child_process";
import { existsSync } from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { z } from "zod";

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);
const defaultBinary = path.join(__dirname, "build", "m2pack");

function resolveBinary() {
  const envBinary = process.env.M2PACK_BINARY;
  if (envBinary && existsSync(envBinary)) {
    return envBinary;
  }
  if (existsSync(defaultBinary)) {
    return defaultBinary;
  }
  return "m2pack";
}

function runCli(args) {
  const binary = resolveBinary();
  const proc = spawnSync(binary, [...args, "--json"], {
    cwd: __dirname,
    encoding: "utf-8",
  });

  if (proc.error) {
    throw new Error(`m2pack failed to start: ${proc.error.message}`);
  }

  if (proc.status !== 0) {
    const detail = (proc.stderr || proc.stdout || `exit code ${proc.status}`).trim();
    throw new Error(`m2pack failed: ${detail}`);
  }

  const stdout = proc.stdout.trim();
  if (!stdout) {
    return { ok: true };
  }

  try {
    return JSON.parse(stdout);
  } catch (error) {
    throw new Error(`m2pack returned non-JSON output: ${stdout}`);
  }
}

function toolResult(payload) {
  return {
    content: [{ type: "text", text: JSON.stringify(payload, null, 2) }],
    structuredContent: payload,
  };
}

const server = new McpServer({
  name: "m2pack-secure",
  version: "0.1.0",
});

server.tool(
  "pack_keygen",
  "Generate a new master content key and Ed25519 signing keypair.",
  {
    out_dir: z.string(),
  },
  async ({ out_dir }) => toolResult(runCli(["keygen", "--out-dir", out_dir])),
);

server.tool(
  "pack_build",
  "Build an .m2p archive from a source directory.",
  {
    input_dir: z.string(),
    output_archive: z.string(),
    key_file: z.string(),
    signing_secret_key_file: z.string(),
  },
  async ({ input_dir, output_archive, key_file, signing_secret_key_file }) =>
    toolResult(
      runCli([
        "build",
        "--input",
        input_dir,
        "--output",
        output_archive,
        "--key",
        key_file,
        "--sign-secret-key",
        signing_secret_key_file,
      ]),
    ),
);

server.tool(
  "pack_list",
  "List entries in an .m2p archive.",
  {
    archive: z.string(),
  },
  async ({ archive }) => toolResult(runCli(["list", "--archive", archive])),
);

server.tool(
  "pack_verify",
  "Verify archive manifest integrity and optionally decrypt all entries.",
  {
    archive: z.string(),
    public_key_file: z.string().optional(),
    key_file: z.string().optional(),
  },
  async ({ archive, public_key_file, key_file }) => {
    const args = ["verify", "--archive", archive];
    if (public_key_file) {
      args.push("--public-key", public_key_file);
    }
    if (key_file) {
      args.push("--key", key_file);
    }
    return toolResult(runCli(args));
  },
);

server.tool(
  "pack_extract",
  "Extract an .m2p archive into a directory.",
  {
    archive: z.string(),
    output_dir: z.string(),
    key_file: z.string(),
  },
  async ({ archive, output_dir, key_file }) =>
    toolResult(
      runCli([
        "extract",
        "--archive",
        archive,
        "--output",
        output_dir,
        "--key",
        key_file,
      ]),
    ),
);

server.tool(
  "pack_export_client_config",
  "Generate M2PackKeys.h for the Windows client tree.",
  {
    key_file: z.string(),
    public_key_file: z.string(),
    output_header: z.string(),
  },
  async ({ key_file, public_key_file, output_header }) =>
    toolResult(
      runCli([
        "export-client-config",
        "--key",
        key_file,
        "--public-key",
        public_key_file,
        "--output",
        output_header,
      ]),
    ),
);

server.tool(
  "pack_binary_info",
  "Report which m2pack binary the server will execute.",
  {},
  async () =>
    toolResult({
      ok: true,
      binary: resolveBinary(),
      repo_root: __dirname,
    }),
);

async function main() {
  const transport = new StdioServerTransport();
  await server.connect(transport);
}

main().catch((error) => {
  console.error(error);
  process.exit(1);
});