Add Bearer auth, rewrite example server, add README

- lmcp.lua: optional Bearer token auth via conf file or explicit token - lmcp.lua: CORS Authorization header allowed - example_server.lua: rewritten with non-blocking shell, file ops, search - README.md: usage, auth config, Claude Code integration, tool examples Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-11 19:15:27 +02:00
parent 2bd661a8c9
commit abd9db30f2
3 changed files with 221 additions and 50 deletions
@@ -0,0 +1,109 @@
+# lmcp — Lightweight MCP Server in Lua
+
+A minimal [Model Context Protocol](https://modelcontextprotocol.io/) server in pure Lua. ~350 lines, 2.4MB RSS, zero compiled dependencies beyond Lua + LuaSocket.
+
+## Features
+
+- MCP 2025-03-26 protocol (JSON-RPC over HTTP)
+- Tool registration with JSON Schema validation
+- Optional Bearer token authentication (config file or explicit)
+- SSE and plain JSON response modes
+- Non-blocking shell execution with timeout
+- Runs on any Linux with Lua 5.4 + LuaSocket
+
+## Quick Start
+
+```sh
+# Install dependencies (Debian/Ubuntu)
+apt install lua5.4 lua-socket
+
+# Or use a self-contained archive (see releases)
+tar xzf lmcp-linux-amd64.tar.gz
+export PATH=$PWD/lmcp-linux-amd64/bin:$PATH
+
+# Run
+lua5.4 example_server.lua
+# lmcp: my-tools v0.1.0 listening on 0.0.0.0:8080/mcp
+```
+
+## Files
+
+| File | Description |
+|------|-------------|
+| `lmcp.lua` | Core library — HTTP server, JSON-RPC, MCP protocol, auth |
+| `json.lua` | Minimal JSON encoder/decoder (bundled, no external dep) |
+| `example_server.lua` | Example server with shell, read/write file, list/search tools |
+
+## Authentication
+
+To require a Bearer token, create an `lmcp.conf` next to your server:
+
+```
+.godparticle = your-secret-token-here
+```
+
+Then reference it when creating the server:
+
+```lua
+local server = lmcp.new("my-tools", {
+    port = 8080,
+    conf = dir .. "lmcp.conf",
+})
+```
+
+Clients must send `Authorization: Bearer <token>` on every request. OPTIONS (CORS preflight) is exempt.
+
+You can also set the token directly:
+
+```lua
+local server = lmcp.new("my-tools", {
+    auth_token = "my-secret-token",
+})
+```
+
+## Claude Code Integration
+
+Add to `~/.claude/settings.json`:
+
+```json
+{
+  "mcpServers": {
+    "my-host": {
+      "type": "url",
+      "url": "http://my-host:8080/mcp",
+      "headers": {
+        "Authorization": "Bearer your-token-here"
+      }
+    }
+  }
+}
+```
+
+## Adding Tools
+
+```lua
+server:tool("greet", "Say hello to someone.", {
+    type = "object",
+    properties = {
+        name = { type = "string", description = "Who to greet" },
+    },
+    required = { "name" },
+}, function(args)
+    return "Hello, " .. args.name .. "!"
+end)
+```
+
+Tool handlers return a string (wrapped as text content) or a table (encoded as JSON). Errors thrown via `error()` are caught and returned as MCP error responses.
+
+## Self-Contained Archives
+
+Pre-built archives with Lua 5.4 + LuaSocket for Linux:
+
+- `lmcp-linux-amd64.tar.gz` — x86_64
+- `lmcp-linux-aarch64.tar.gz` — ARM64 (Pi 5, RK3588, etc.)
+
+These include the Lua interpreter and LuaSocket shared library so no system packages are needed.
+
+## License
+
+MIT
@@ -1,73 +1,100 @@
 #!/usr/bin/env lua
-- Example lmcp server — shell tools
-- Usage: lua example_server.lua [port]
+-- Example lmcp server — customize tools for your host
+local dir = arg[0]:match("(.*/)")  or "./"
+package.path = package.path .. ";" .. dir .. "?.lua"
+local lmcp = require("lmcp")

-local dir = arg[0]:match('(.*/)')  or './'
-package.path = package.path .. ';' .. dir .. '?.lua'
-
-local lmcp = require('lmcp')
-
-local server = lmcp.new("example-tools", {
-    port = tonumber(arg[1]) or 8080,
+local server = lmcp.new("my-tools", {
+    port = tonumber(os.getenv("LMCP_PORT")) or 8080,
+    -- Optional: Bearer token auth from config file
+    -- conf = dir .. "lmcp.conf",
+    -- Or set directly:
+    -- auth_token = "my-secret-token",
 })

-server:tool("shell", "Execute a shell command", {
+-- Non-blocking shell execution with timeout
+local function run(cmd, timeout_sec)
+    timeout_sec = timeout_sec or 120
+    local base = os.tmpname()
+    local out_file = base .. ".out"
+    local done_file = base .. ".done"
+    local sh_cmd = string.format("(%s) > '%s' 2>&1; echo $? > '%s'", cmd, out_file, done_file)
+    os.execute("sh -c ' " .. sh_cmd .. " ' &")
+    local elapsed = 0
+    local interval = 50
+    while elapsed < timeout_sec * 1000 do
+        local f = io.open(done_file, "r")
+        if f then f:close(); break end
+        if interval < 1000 then
+            os.execute("sleep 0." .. string.format("%03d", interval))
+        else
+            os.execute("sleep " .. math.ceil(interval / 1000))
+        end
+        elapsed = elapsed + interval
+        if interval < 2000 then interval = math.floor(interval * 1.5) end
+    end
+    local f = io.open(out_file, "r")
+    local output = f and f:read("*a") or ""
+    if f then f:close() end
+    os.remove(out_file); os.remove(done_file); os.remove(base)
+    if elapsed >= timeout_sec * 1000 then return "Error: timed out after " .. timeout_sec .. "s" end
+    return output ~= "" and output or "(no output)"
+end
+
+-- Register tools
+server:tool("shell", "Execute a shell command.", {
    type = "object",
    properties = {
-        command = { type = "string", description = "Shell command to execute" },
-        timeout = { type = "integer", description = "Timeout in seconds", default = 30 },
+        command = { type = "string" },
+        cwd = { type = "string" },
+        timeout = { type = "integer", default = 120 },
    },
    required = { "command" },
-}, function(args)
-    local handle = io.popen(args.command .. ' 2>&1', 'r')
-    if not handle then return "Error: could not execute command" end
-    local result = handle:read('*a')
-    handle:close()
-    return result ~= '' and result or '(no output)'
+}, function(a)
+    local c = a.command
+    if a.cwd then c = "cd \"" .. a.cwd .. "\" && " .. c end
+    return run(c, a.timeout or 120)
 end)

-server:tool("read_file", "Read a file", {
+server:tool("read_file", "Read a file.", {
    type = "object",
-    properties = {
-        path = { type = "string", description = "File path to read" },
-    },
+    properties = { path = { type = "string" } },
    required = { "path" },
-}, function(args)
-    local f = io.open(args.path, 'r')
-    if not f then return "Error: could not open " .. args.path end
-    local content = f:read('*a')
-    f:close()
-    return content
+}, function(a)
+    local f = io.open(a.path, "r")
+    if not f then return "Error: could not read " .. a.path end
+    local c = f:read("*a"); f:close(); return c
 end)

-server:tool("write_file", "Write content to a file", {
+server:tool("write_file", "Write content to a file.", {
    type = "object",
-    properties = {
-        path = { type = "string", description = "File path to write" },
-        content = { type = "string", description = "Content to write" },
-    },
+    properties = { path = { type = "string" }, content = { type = "string" } },
    required = { "path", "content" },
-}, function(args)
-    local f = io.open(args.path, 'w')
-    if not f then return "Error: could not open " .. args.path .. " for writing" end
-    f:write(args.content)
-    f:close()
-    return string.format("Written %d bytes to %s", #args.content, args.path)
+}, function(a)
+    local f = io.open(a.path, "w")
+    if not f then return "Error: could not write " .. a.path end
+    f:write(a.content); f:close()
+    return string.format("Written %d bytes to %s", #a.content, a.path)
 end)

-server:tool("list_dir", "List directory contents", {
+server:tool("list_dir", "List directory contents.", {
+    type = "object",
+    properties = { path = { type = "string", default = "." } },
+}, function(a)
+    return run("ls -la '" .. (a.path or ".") .. "'", 10)
+end)
+
+server:tool("search_files", "Search for files by name.", {
    type = "object",
    properties = {
-        path = { type = "string", description = "Directory path", default = "." },
+        pattern = { type = "string" },
+        path = { type = "string", default = "/" },
+        max_depth = { type = "integer", default = 4 },
    },
-}, function(args)
-    local path = args.path or '.'
-    local handle = io.popen('ls -1 ' .. path:gsub("'", "'\\''") .. ' 2>&1')
-    if not handle then return "Error: could not list " .. path end
-    local result = handle:read('*a')
-    handle:close()
-    return result
+    required = { "pattern" },
+}, function(a)
+    return run(string.format("find '%s' -maxdepth %d -name '%s' 2>/dev/null",
+        a.path or "/", a.max_depth or 4, a.pattern), 30)
 end)

-io.stderr:write("Starting lmcp example server...\n")
 server:run()
@@ -7,6 +7,19 @@ local json = require('json')
 local lmcp = {}
 lmcp.__index = lmcp

+-- Read auth token from config file if present
+local function read_conf(path)
+    local conf = {}
+    local f = io.open(path, 'r')
+    if not f then return conf end
+    for line in f:lines() do
+        local k, v = line:match('^%s*(%S+)%s*=%s*(.-)%s*$')
+        if k and not k:match('^#') then conf[k] = v end
+    end
+    f:close()
+    return conf
+end
+
 -- Protocol constants
 local MCP_VERSION = "2025-03-26"
 local JSONRPC = "2.0"
@@ -20,6 +33,13 @@ function lmcp.new(name, opts)
    self.port = opts.port or 8080
    self.tools = {}
    self._session_id = nil
+    -- Auth: explicit opt > conf file > nil (no auth)
+    if opts.auth_token then
+        self._auth_token = opts.auth_token
+    elseif opts.conf then
+        local conf = read_conf(opts.conf)
+        self._auth_token = conf['.godparticle']
+    end
    return self
 end

@@ -178,6 +198,20 @@ function lmcp:serve_request(client)
    local path = req.path
    local accept = req.headers['accept'] or ''

+    -- Auth check (skip for OPTIONS, already handled above)
+    if self._auth_token and req.method ~= 'OPTIONS' then
+        local auth = req.headers['authorization'] or ''
+        local token = auth:match('^Bearer%s+(.+)$')
+        if token ~= self._auth_token then
+            send_response(client, '401 Unauthorized',
+                { ['Content-Type'] = 'application/json',
+                  ['WWW-Authenticate'] = 'Bearer' },
+                '{"error":"unauthorized"}')
+            client:close()
+            return
+        end
+    end
+
    -- GET /mcp — SSE endpoint (for session establishment)
    if req.method == 'GET' and path:match('^/mcp') then
        -- SSE stream — send headers and keep alive briefly
@@ -261,7 +295,7 @@ function lmcp:serve_request(client)
        send_response(client, '204 No Content', {
            ['Access-Control-Allow-Origin'] = '*',
            ['Access-Control-Allow-Methods'] = 'GET, POST, OPTIONS',
-            ['Access-Control-Allow-Headers'] = 'Content-Type, Accept',
+            ['Access-Control-Allow-Headers'] = 'Content-Type, Accept, Authorization',
        }, '')
        client:close()
        return
@@ -307,3 +341,4 @@ function lmcp:run()
 end

 return lmcp
+