A secure Model Context Protocol (MCP) server implementation for executing controlled command-line operations with comprehensive security features.

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Table of Contents

1. Overview
2. Features
3. Configuration
4. Available Tools
   • run_command
   • show_security_rules
5. Security Features
6. Error Handling

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Overview

This MCP server enables secure command-line execution with robust security measures including command whitelisting, path validation, and execution controls. Perfect for providing controlled CLI access to LLM applications while maintaining security.

Features

• 🔒 Secure command execution with strict validation
• ⚙️ Configurable command and flag whitelisting with 'all' option
• 🛡️ Path traversal prevention and validation
• 🚫 Shell operator injection protection
• ⏱️ Execution timeouts and length limits
• 📝 Detailed error reporting
• 🔄 Async operation support
• 🎯 Working directory restriction and validation

Configuration

Configure the server using environment variables:

| Variable | Description | Default | |---------------------|------------------------------------------------------|-------------------| | ALLOWED_DIR | Base directory for command execution (Required) | None (Required) | | ALLOWED_COMMANDS | Comma-separated list of allowed commands or 'all' | ls,cat,pwd | | ALLOWED_FLAGS | Comma-separated list of allowed flags or 'all' | -l,-a,--help | | MAX_COMMAND_LENGTH| Maximum command string length | 1024 | | COMMAND_TIMEOUT | Command execution timeout (seconds) | 30 |

Note: Setting ALLOWED_COMMANDS or ALLOWED_FLAGS to 'all' will allow any command or flag respectively.

Available Tools

run_command

Executes whitelisted CLI commands within allowed directories.

Input Schema:

Security Notes:

• Shell operators (&&, |, >, >>) are not supported
• Commands must be whitelisted unless ALLOWED_COMMANDS='all'
• Flags must be whitelisted unless ALLOWED_FLAGS='all'
• All paths are validated to be within ALLOWED_DIR

show_security_rules

Displays current security configuration and restrictions, including:

• Working directory
• Allowed commands
• Allowed flags
• Security limits (max command length and timeout)

Security Features

• ✅ Command whitelist enforcement with 'all' option
• ✅ Flag validation with 'all' option
• ✅ Path traversal prevention and normalization
• ✅ Shell operator blocking
• ✅ Command length limits
• ✅ Execution timeouts
• ✅ Working directory restrictions
• ✅ Symlink resolution and validation

Error Handling

The server provides detailed error messages for:

• Security violations (CommandSecurityError)
• Command timeouts (CommandTimeoutError)
• Invalid command formats
• Path security violations
• Execution failures (CommandExecutionError)
• General command errors (CommandError)