@m_sea_bass/relpath-filesystem-mcp
Version:
Secure MCP Filesystem Server with relative path support
547 lines (537 loc) • 25.7 kB
JavaScript
import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { CallToolRequestSchema, ListToolsRequestSchema, ToolSchema, } from "@modelcontextprotocol/sdk/types.js";
import fs from "fs/promises";
import path from "path";
import os from 'os';
import { z } from "zod";
import { zodToJsonSchema } from "zod-to-json-schema";
import { createTwoFilesPatch } from 'diff';
import { minimatch } from 'minimatch';
// Command line argument parsing
const args = process.argv.slice(2);
if (args.length === 0) {
console.error("Usage: mcp-server-filesystem <base-directory>");
process.exit(1);
}
// Normalize all paths consistently
function normalizePath(p) {
return path.normalize(p);
}
function expandHome(filepath) {
if (filepath.startsWith('~/') || filepath === '~') {
return path.join(os.homedir(), filepath.slice(1));
}
return filepath;
}
// Store base directory in normalized form (single directory only)
const baseDirectory = normalizePath(path.resolve(expandHome(args[0])));
// Validate that base directory exists and is accessible
try {
const stats = await fs.stat(expandHome(args[0]));
if (!stats.isDirectory()) {
console.error(`Error: ${args[0]} is not a directory`);
process.exit(1);
}
}
catch (error) {
console.error(`Error accessing directory ${args[0]}:`, error);
process.exit(1);
}
// Relative path resolution utility
function resolveRelativePath(relativePath) {
// Security check: Prevent path traversal attacks
if (relativePath.includes('..')) {
throw new Error('Path traversal attack detected: ".." is not allowed');
}
// Absolute path check: Only relative paths accepted
if (path.isAbsolute(relativePath)) {
throw new Error('Absolute paths are not allowed. Use relative paths only.');
}
// Resolve against base directory
const resolvedPath = path.resolve(baseDirectory, relativePath);
// Final security check: Prevent access outside base directory
if (!resolvedPath.startsWith(baseDirectory)) {
throw new Error('Access outside base directory is not allowed');
}
return resolvedPath;
}
// Security utilities - Redesigned for relative path handling
async function validatePath(requestedPath) {
// Use new relative path resolution with security checks
const resolvedPath = resolveRelativePath(requestedPath);
// Handle symlinks by checking their real path
try {
const realPath = await fs.realpath(resolvedPath);
const normalizedReal = normalizePath(realPath);
// Ensure symlink target is still within base directory
if (!normalizedReal.startsWith(baseDirectory)) {
throw new Error("Access denied - symlink target outside base directory");
}
return realPath;
}
catch (error) {
// For new files that don't exist yet, verify parent directory
const parentDir = path.dirname(resolvedPath);
try {
const realParentPath = await fs.realpath(parentDir);
const normalizedParent = normalizePath(realParentPath);
// Ensure parent directory is within base directory
if (!normalizedParent.startsWith(baseDirectory)) {
throw new Error("Access denied - parent directory outside base directory");
}
return resolvedPath;
}
catch {
throw new Error(`Parent directory does not exist: ${parentDir}`);
}
}
}
// Schema definitions
const ReadFileArgsSchema = z.object({
path: z.string().describe('Relative path from base directory'),
});
const ReadMultipleFilesArgsSchema = z.object({
paths: z.array(z.string().describe('Relative path from base directory')),
});
const WriteFileArgsSchema = z.object({
path: z.string().describe('Relative path from base directory'),
content: z.string(),
});
const EditOperation = z.object({
oldText: z.string().describe('Text to search for - must match exactly'),
newText: z.string().describe('Text to replace with')
});
const EditFileArgsSchema = z.object({
path: z.string().describe('Relative path from base directory'),
edits: z.array(EditOperation),
dryRun: z.boolean().default(false).describe('Preview changes using git-style diff format')
});
const CreateDirectoryArgsSchema = z.object({
path: z.string().describe('Relative path from base directory'),
});
const ListDirectoryArgsSchema = z.object({
path: z.string().describe('Relative path from base directory'),
});
const DirectoryTreeArgsSchema = z.object({
path: z.string().describe('Relative path from base directory'),
});
const MoveFileArgsSchema = z.object({
source: z.string().describe('Relative path from base directory'),
destination: z.string().describe('Relative path from base directory'),
});
const SearchFilesArgsSchema = z.object({
path: z.string().describe('Relative path from base directory'),
pattern: z.string(),
excludePatterns: z.array(z.string()).optional().default([])
});
const GetFileInfoArgsSchema = z.object({
path: z.string().describe('Relative path from base directory'),
});
const ToolInputSchema = ToolSchema.shape.inputSchema;
// Server setup
const server = new Server({
name: "secure-filesystem-server",
version: "0.2.0",
}, {
capabilities: {
tools: {},
},
});
// Tool implementations
async function getFileStats(filePath) {
const stats = await fs.stat(filePath);
return {
size: stats.size,
created: stats.birthtime,
modified: stats.mtime,
accessed: stats.atime,
isDirectory: stats.isDirectory(),
isFile: stats.isFile(),
permissions: stats.mode.toString(8).slice(-3),
};
}
async function searchFiles(rootPath, pattern, excludePatterns = []) {
const results = [];
async function search(currentPath) {
const entries = await fs.readdir(currentPath, { withFileTypes: true });
for (const entry of entries) {
const fullPath = path.join(currentPath, entry.name);
try {
// Validate path using relative path from base directory
const relativePath = path.relative(baseDirectory, fullPath);
await validatePath(relativePath);
// Check if path matches any exclude pattern
const shouldExclude = excludePatterns.some(pattern => {
const globPattern = pattern.includes('*') ? pattern : `**/${pattern}/**`;
return minimatch(relativePath, globPattern, { dot: true });
});
if (shouldExclude) {
continue;
}
if (entry.name.toLowerCase().includes(pattern.toLowerCase())) {
results.push(relativePath);
}
if (entry.isDirectory()) {
await search(fullPath);
}
}
catch (error) {
// Skip invalid paths during search
continue;
}
}
}
await search(rootPath);
return results;
}
// file editing and diffing utilities
function normalizeLineEndings(text) {
return text.replace(/\r\n/g, '\n');
}
function createUnifiedDiff(originalContent, newContent, filepath = 'file') {
// Ensure consistent line endings for diff
const normalizedOriginal = normalizeLineEndings(originalContent);
const normalizedNew = normalizeLineEndings(newContent);
return createTwoFilesPatch(filepath, filepath, normalizedOriginal, normalizedNew, 'original', 'modified');
}
async function applyFileEdits(filePath, edits, dryRun = false) {
// Read file content and normalize line endings
const content = normalizeLineEndings(await fs.readFile(filePath, 'utf-8'));
// Apply edits sequentially
let modifiedContent = content;
for (const edit of edits) {
const normalizedOld = normalizeLineEndings(edit.oldText);
const normalizedNew = normalizeLineEndings(edit.newText);
// If exact match exists, use it
if (modifiedContent.includes(normalizedOld)) {
modifiedContent = modifiedContent.replace(normalizedOld, normalizedNew);
continue;
}
// Otherwise, try line-by-line matching with flexibility for whitespace
const oldLines = normalizedOld.split('\n');
const contentLines = modifiedContent.split('\n');
let matchFound = false;
for (let i = 0; i <= contentLines.length - oldLines.length; i++) {
const potentialMatch = contentLines.slice(i, i + oldLines.length);
// Compare lines with normalized whitespace
const isMatch = oldLines.every((oldLine, j) => {
const contentLine = potentialMatch[j];
return oldLine.trim() === contentLine.trim();
});
if (isMatch) {
// Preserve original indentation of first line
const originalIndent = contentLines[i].match(/^\s*/)?.[0] || '';
const newLines = normalizedNew.split('\n').map((line, j) => {
if (j === 0)
return originalIndent + line.trimStart();
// For subsequent lines, try to preserve relative indentation
const oldIndent = oldLines[j]?.match(/^\s*/)?.[0] || '';
const newIndent = line.match(/^\s*/)?.[0] || '';
if (oldIndent && newIndent) {
const relativeIndent = newIndent.length - oldIndent.length;
return originalIndent + ' '.repeat(Math.max(0, relativeIndent)) + line.trimStart();
}
return line;
});
contentLines.splice(i, oldLines.length, ...newLines);
modifiedContent = contentLines.join('\n');
matchFound = true;
break;
}
}
if (!matchFound) {
throw new Error(`Could not find exact match for edit:\n${edit.oldText}`);
}
}
// Create unified diff with relative path
const relativePath = path.relative(baseDirectory, filePath);
const diff = createUnifiedDiff(content, modifiedContent, relativePath);
// Format diff with appropriate number of backticks
let numBackticks = 3;
while (diff.includes('`'.repeat(numBackticks))) {
numBackticks++;
}
const formattedDiff = `${'`'.repeat(numBackticks)}diff\n${diff}${'`'.repeat(numBackticks)}\n\n`;
if (!dryRun) {
await fs.writeFile(filePath, modifiedContent, 'utf-8');
}
return formattedDiff;
}
// Tool handlers
server.setRequestHandler(ListToolsRequestSchema, async () => {
return {
tools: [
{
name: "read_file",
description: "Read the complete contents of a file from the file system. " +
"Handles various text encodings and provides detailed error messages " +
"if the file cannot be read. Use this tool when you need to examine " +
"the contents of a single file. Only works within allowed directories.",
inputSchema: zodToJsonSchema(ReadFileArgsSchema),
},
{
name: "read_multiple_files",
description: "Read the contents of multiple files simultaneously. This is more " +
"efficient than reading files one by one when you need to analyze " +
"or compare multiple files. Each file's content is returned with its " +
"path as a reference. Failed reads for individual files won't stop " +
"the entire operation. Only works within allowed directories.",
inputSchema: zodToJsonSchema(ReadMultipleFilesArgsSchema),
},
{
name: "write_file",
description: "Create a new file or completely overwrite an existing file with new content. " +
"Use with caution as it will overwrite existing files without warning. " +
"Handles text content with proper encoding. Only works within allowed directories.",
inputSchema: zodToJsonSchema(WriteFileArgsSchema),
},
{
name: "edit_file",
description: "Make line-based edits to a text file. Each edit replaces exact line sequences " +
"with new content. Returns a git-style diff showing the changes made. " +
"Only works within allowed directories.",
inputSchema: zodToJsonSchema(EditFileArgsSchema),
},
{
name: "create_directory",
description: "Create a new directory or ensure a directory exists. Can create multiple " +
"nested directories in one operation. If the directory already exists, " +
"this operation will succeed silently. Perfect for setting up directory " +
"structures for projects or ensuring required paths exist. Only works within allowed directories.",
inputSchema: zodToJsonSchema(CreateDirectoryArgsSchema),
},
{
name: "list_directory",
description: "Get a detailed listing of all files and directories in a specified path. " +
"Results clearly distinguish between files and directories with [FILE] and [DIR] " +
"prefixes. This tool is essential for understanding directory structure and " +
"finding specific files within a directory. Only works within allowed directories.",
inputSchema: zodToJsonSchema(ListDirectoryArgsSchema),
},
{
name: "directory_tree",
description: "Get a recursive tree view of files and directories as a JSON structure. " +
"Each entry includes 'name', 'type' (file/directory), and 'children' for directories. " +
"Files have no children array, while directories always have a children array (which may be empty). " +
"The output is formatted with 2-space indentation for readability. Only works within allowed directories.",
inputSchema: zodToJsonSchema(DirectoryTreeArgsSchema),
},
{
name: "move_file",
description: "Move or rename files and directories. Can move files between directories " +
"and rename them in a single operation. If the destination exists, the " +
"operation will fail. Works across different directories and can be used " +
"for simple renaming within the same directory. Both source and destination must be within allowed directories.",
inputSchema: zodToJsonSchema(MoveFileArgsSchema),
},
{
name: "search_files",
description: "Recursively search for files and directories matching a pattern. " +
"Searches through all subdirectories from the starting path. The search " +
"is case-insensitive and matches partial names. Returns full paths to all " +
"matching items. Great for finding files when you don't know their exact location. " +
"Only searches within allowed directories.",
inputSchema: zodToJsonSchema(SearchFilesArgsSchema),
},
{
name: "get_file_info",
description: "Retrieve detailed metadata about a file or directory. Returns comprehensive " +
"information including size, creation time, last modified time, permissions, " +
"and type. This tool is perfect for understanding file characteristics " +
"without reading the actual content. Only works within allowed directories.",
inputSchema: zodToJsonSchema(GetFileInfoArgsSchema),
},
{
name: "list_allowed_directory",
description: "Returns the base directory that this server is allowed to access. " +
"All file operations work with relative paths from this base directory.",
inputSchema: {
type: "object",
properties: {},
required: [],
},
},
],
};
});
server.setRequestHandler(CallToolRequestSchema, async (request) => {
try {
const { name, arguments: args } = request.params;
switch (name) {
case "read_file": {
const parsed = ReadFileArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for read_file: ${parsed.error}`);
}
const validPath = await validatePath(parsed.data.path);
const content = await fs.readFile(validPath, "utf-8");
return {
content: [{ type: "text", text: content }],
};
}
case "read_multiple_files": {
const parsed = ReadMultipleFilesArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for read_multiple_files: ${parsed.error}`);
}
const results = await Promise.all(parsed.data.paths.map(async (filePath) => {
try {
const validPath = await validatePath(filePath);
const content = await fs.readFile(validPath, "utf-8");
return `${filePath}:\n${content}\n`;
}
catch (error) {
const errorMessage = error instanceof Error ? error.message : String(error);
return `${filePath}: Error - ${errorMessage}`;
}
}));
return {
content: [{ type: "text", text: results.join("\n---\n") }],
};
}
case "write_file": {
const parsed = WriteFileArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for write_file: ${parsed.error}`);
}
const validPath = await validatePath(parsed.data.path);
await fs.writeFile(validPath, parsed.data.content, "utf-8");
return {
content: [{ type: "text", text: `Successfully wrote to ${parsed.data.path}` }],
};
}
case "edit_file": {
const parsed = EditFileArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for edit_file: ${parsed.error}`);
}
const validPath = await validatePath(parsed.data.path);
const result = await applyFileEdits(validPath, parsed.data.edits, parsed.data.dryRun);
return {
content: [{ type: "text", text: result }],
};
}
case "create_directory": {
const parsed = CreateDirectoryArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for create_directory: ${parsed.error}`);
}
const validPath = await validatePath(parsed.data.path);
await fs.mkdir(validPath, { recursive: true });
return {
content: [{ type: "text", text: `Successfully created directory ${parsed.data.path}` }],
};
}
case "list_directory": {
const parsed = ListDirectoryArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for list_directory: ${parsed.error}`);
}
const validPath = await validatePath(parsed.data.path);
const entries = await fs.readdir(validPath, { withFileTypes: true });
const formatted = entries
.map((entry) => `${entry.isDirectory() ? "[DIR]" : "[FILE]"} ${entry.name}`)
.join("\n");
return {
content: [{ type: "text", text: formatted }],
};
}
case "directory_tree": {
const parsed = DirectoryTreeArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for directory_tree: ${parsed.error}`);
}
async function buildTree(currentPath) {
const validPath = await validatePath(currentPath);
const entries = await fs.readdir(validPath, { withFileTypes: true });
const result = [];
for (const entry of entries) {
const entryData = {
name: entry.name,
type: entry.isDirectory() ? 'directory' : 'file'
};
if (entry.isDirectory()) {
const subPath = path.join(currentPath, entry.name);
entryData.children = await buildTree(subPath);
}
result.push(entryData);
}
return result;
}
const treeData = await buildTree(parsed.data.path);
return {
content: [{
type: "text",
text: JSON.stringify(treeData, null, 2)
}],
};
}
case "move_file": {
const parsed = MoveFileArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for move_file: ${parsed.error}`);
}
const validSourcePath = await validatePath(parsed.data.source);
const validDestPath = await validatePath(parsed.data.destination);
await fs.rename(validSourcePath, validDestPath);
return {
content: [{ type: "text", text: `Successfully moved ${parsed.data.source} to ${parsed.data.destination}` }],
};
}
case "search_files": {
const parsed = SearchFilesArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for search_files: ${parsed.error}`);
}
const validPath = await validatePath(parsed.data.path);
const results = await searchFiles(validPath, parsed.data.pattern, parsed.data.excludePatterns);
return {
content: [{ type: "text", text: results.length > 0 ? results.join("\n") : "No matches found" }],
};
}
case "get_file_info": {
const parsed = GetFileInfoArgsSchema.safeParse(args);
if (!parsed.success) {
throw new Error(`Invalid arguments for get_file_info: ${parsed.error}`);
}
const validPath = await validatePath(parsed.data.path);
const info = await getFileStats(validPath);
return {
content: [{ type: "text", text: Object.entries(info)
.map(([key, value]) => `${key}: ${value}`)
.join("\n") }],
};
}
case "list_allowed_directory": {
return {
content: [{
type: "text",
text: `Base directory:\n${baseDirectory}`
}],
};
}
default:
throw new Error(`Unknown tool: ${name}`);
}
}
catch (error) {
const errorMessage = error instanceof Error ? error.message : String(error);
return {
content: [{ type: "text", text: `Error: ${errorMessage}` }],
isError: true,
};
}
});
// Start server
async function runServer() {
const transport = new StdioServerTransport();
await server.connect(transport);
console.error("Secure MCP Filesystem Server running on stdio");
console.error("Base directory:", baseDirectory);
}
runServer().catch((error) => {
console.error("Fatal error running server:", error);
process.exit(1);
});