"""Command executor tools for MCP Claude Code. This module provides tools for executing shell commands and scripts with comprehensive error handling, permissions checking, and progress tracking. """ import asyncio import base64 import os import shlex import sys import tempfile from collections.abc import Awaitable, Callable from typing import final from mcp.server.fastmcp import Context as MCPContext from mcp.server.fastmcp import FastMCP from dev_mcp.tools.common.context import create_tool_context from dev_mcp.tools.common.permissions import PermissionManager @final class CommandResult: """Represents the result of a command execution.""" def __init__( self, return_code: int = 0, stdout: str = "", stderr: str = "", error_message: str | None = None, ): """Initialize a command result. Args: return_code: The command's return code (0 for success) stdout: Standard output from the command stderr: Standard error from the command error_message: Optional error message for failure cases """ self.return_code: int = return_code self.stdout: str = stdout self.stderr: str = stderr self.error_message: str | None = error_message @property def is_success(self) -> bool: """Check if the command executed successfully. Returns: True if the command succeeded, False otherwise """ return self.return_code == 0 def format_output(self, include_exit_code: bool = True) -> str: """Format the command output as a string. Args: include_exit_code: Whether to include the exit code in the output Returns: Formatted output string """ result_parts: list[str] = [] # Add error message if present if self.error_message: result_parts.append(f"Error: {self.error_message}") # Add exit code if requested and not zero (for non-errors) if include_exit_code and (self.return_code != 0 or not self.error_message): result_parts.append(f"Exit code: {self.return_code}") # Add stdout if present if self.stdout: result_parts.append(f"STDOUT:\n{self.stdout}") # Add stderr if present if self.stderr: result_parts.append(f"STDERR:\n{self.stderr}") # Join with newlines return "\n\n".join(result_parts) @final class CommandExecutor: """Command executor tools for MCP Claude Code. This class provides tools for executing shell commands and scripts with comprehensive error handling, permissions checking, and progress tracking. """ def __init__( self, permission_manager: PermissionManager, verbose: bool = False ) -> None: """Initialize command execution. Args: permission_manager: Permission manager for access control verbose: Enable verbose logging """ self.permission_manager: PermissionManager = permission_manager self.verbose: bool = verbose # Excluded commands or patterns self.excluded_commands: list[str] = ["rm"] # Map of supported interpreters with special handling self.special_interpreters: dict[ str, Callable[ [str, str, str | None, dict[str, str] | None, float | None], Awaitable[CommandResult], ], ] = { "fish": self._handle_fish_script, } def allow_command(self, command: str) -> None: """Allow a specific command that might otherwise be excluded. Args: command: The command to allow """ if command in self.excluded_commands: self.excluded_commands.remove(command) def deny_command(self, command: str) -> None: """Deny a specific command, adding it to the excluded list. Args: command: The command to deny """ if command not in self.excluded_commands: self.excluded_commands.append(command) def _log(self, message: str, data: object = None) -> None: """Log a message if verbose logging is enabled. Args: message: The message to log data: Optional data to include with the message """ if not self.verbose: return if data is not None: try: import json if isinstance(data, (dict, list)): data_str = json.dumps(data) else: data_str = str(data) print(f"DEBUG: {message}: {data_str}", file=sys.stderr) except Exception: print(f"DEBUG: {message}: {data}", file=sys.stderr) else: print(f"DEBUG: {message}", file=sys.stderr) def is_command_allowed(self, command: str) -> bool: """Check if a command is allowed based on exclusion lists. Args: command: The command to check Returns: True if the command is allowed, False otherwise """ # Check for empty commands try: args: list[str] = shlex.split(command) except ValueError as e: self._log(f"Command parsing error: {e}") return False if not args: return False base_command: str = args[0] # Check if base command is in exclusion list if base_command in self.excluded_commands: self._log(f"Command rejected (in exclusion list): {base_command}") return False return True async def execute_command( self, command: str, cwd: str | None = None, env: dict[str, str] | None = None, timeout: float | None = 60.0, use_login_shell: bool = True, ) -> CommandResult: """Execute a shell command with safety checks. Args: command: The command to execute cwd: Optional working directory env: Optional environment variables timeout: Optional timeout in seconds use_login_shell: Whether to use login shell. default true (loads ~/.zshrc, ~/.bashrc, etc.) Returns: CommandResult containing execution results """ self._log(f"Executing command: {command}") # Check if the command is allowed if not self.is_command_allowed(command): return CommandResult( return_code=1, error_message=f"Command not allowed: {command}" ) # Check working directory permissions if specified if cwd: if not os.path.isdir(cwd): return CommandResult( return_code=1, error_message=f"Working directory does not exist: {cwd}", ) if not self.permission_manager.is_path_allowed(cwd): return CommandResult( return_code=1, error_message=f"Working directory not allowed: {cwd}" ) # Set up environment command_env: dict[str, str] = os.environ.copy() if env: command_env.update(env) try: # Check if command uses shell features like &&, ||, |, etc. or $ for env vars shell_operators = ["&&", "||", "|", ";", ">", "<", "$(", "`", "$"] needs_shell = any(op in command for op in shell_operators) if needs_shell or use_login_shell: # Determine which shell to use shell_cmd = command if use_login_shell: # Get the user's login shell user_shell = os.environ.get("SHELL", "/bin/bash") shell_basename = os.path.basename(user_shell) self._log(f"Using login shell: {user_shell}") # Wrap command with appropriate shell invocation if shell_basename == "zsh": shell_cmd = f"{user_shell} -l -c '{command}'" elif shell_basename == "bash": shell_cmd = f"{user_shell} -l -c '{command}'" elif shell_basename == "fish": shell_cmd = f"{user_shell} -l -c '{command}'" else: # Default fallback shell_cmd = f"{user_shell} -c '{command}'" else: self._log( f"Using shell for command with shell operators: {command}" ) # Use shell for command execution process = await asyncio.create_subprocess_shell( shell_cmd, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE, cwd=cwd, env=command_env, ) else: # Split the command into arguments for regular commands args: list[str] = shlex.split(command) # Create and run the process without shell process = await asyncio.create_subprocess_exec( *args, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE, cwd=cwd, env=command_env, ) # Wait for the process to complete with timeout try: stdout_bytes, stderr_bytes = await asyncio.wait_for( process.communicate(), timeout=timeout ) return CommandResult( return_code=process.returncode or 0, stdout=stdout_bytes.decode("utf-8", errors="replace"), stderr=stderr_bytes.decode("utf-8", errors="replace"), ) except asyncio.TimeoutError: # Kill the process if it times out try: process.kill() except ProcessLookupError: pass # Process already terminated return CommandResult( return_code=-1, error_message=f"Command timed out after {timeout} seconds: {command}", ) except Exception as e: self._log(f"Command execution error: {str(e)}") return CommandResult( return_code=1, error_message=f"Error executing command: {str(e)}" ) async def execute_script( self, script: str, interpreter: str = "bash", cwd: str | None = None, env: dict[str, str] | None = None, timeout: float | None = 60.0, use_login_shell: bool = True, ) -> CommandResult: """Execute a script with the specified interpreter. Args: script: The script content to execute interpreter: The interpreter to use (bash, python, etc.) cwd: Optional working directory env: Optional environment variables timeout: Optional timeout in seconds Returns: CommandResult containing execution results """ self._log(f"Executing script with interpreter: {interpreter}") # Check working directory permissions if specified if cwd: if not os.path.isdir(cwd): return CommandResult( return_code=1, error_message=f"Working directory does not exist: {cwd}", ) if not self.permission_manager.is_path_allowed(cwd): return CommandResult( return_code=1, error_message=f"Working directory not allowed: {cwd}" ) # Check if we need special handling for this interpreter interpreter_name = interpreter.split()[0].lower() if interpreter_name in self.special_interpreters: self._log(f"Using special handler for interpreter: {interpreter_name}") special_handler = self.special_interpreters[interpreter_name] return await special_handler(interpreter, script, cwd, env, timeout) # Regular execution return await self._execute_script_with_stdin( interpreter, script, cwd, env, timeout, use_login_shell ) async def _execute_script_with_stdin( self, interpreter: str, script: str, cwd: str | None = None, env: dict[str, str] | None = None, timeout: float | None = 60.0, use_login_shell: bool = True, ) -> CommandResult: """Execute a script by passing it to stdin of the interpreter. Args: interpreter: The interpreter command script: The script content cwd: Optional working directory env: Optional environment variables timeout: Optional timeout in seconds Returns: CommandResult containing execution results """ # Set up environment command_env: dict[str, str] = os.environ.copy() if env: command_env.update(env) try: # Determine if we should use a login shell if use_login_shell: # Get the user's login shell user_shell = os.environ.get("SHELL", "/bin/bash") os.path.basename(user_shell) self._log(f"Using login shell for interpreter: {user_shell}") # Create command that pipes script to interpreter through login shell shell_cmd = f"{user_shell} -l -c '{interpreter}'" # Create and run the process with shell process = await asyncio.create_subprocess_shell( shell_cmd, stdin=asyncio.subprocess.PIPE, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE, cwd=cwd, env=command_env, ) else: # Parse the interpreter command to get arguments interpreter_parts = shlex.split(interpreter) # Create and run the process normally process = await asyncio.create_subprocess_exec( *interpreter_parts, stdin=asyncio.subprocess.PIPE, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE, cwd=cwd, env=command_env, ) # Wait for the process to complete with timeout try: script_bytes: bytes = script.encode("utf-8") stdout_bytes, stderr_bytes = await asyncio.wait_for( process.communicate(script_bytes), timeout=timeout ) return CommandResult( return_code=process.returncode or 0, stdout=stdout_bytes.decode("utf-8", errors="replace"), stderr=stderr_bytes.decode("utf-8", errors="replace"), ) except asyncio.TimeoutError: # Kill the process if it times out try: process.kill() except ProcessLookupError: pass # Process already terminated return CommandResult( return_code=-1, error_message=f"Script execution timed out after {timeout} seconds", ) except Exception as e: self._log(f"Script execution error: {str(e)}") return CommandResult( return_code=1, error_message=f"Error executing script: {str(e)}" ) async def _handle_fish_script( self, interpreter: str, script: str, cwd: str | None = None, env: dict[str, str] | None = None, timeout: float | None = 60.0, ) -> CommandResult: """Special handler for Fish shell scripts. The Fish shell has issues with piped input in some contexts, so we use a workaround that base64 encodes the script and decodes it in the pipeline. Args: interpreter: The fish interpreter command script: The fish script content cwd: Optional working directory env: Optional environment variables timeout: Optional timeout in seconds Returns: CommandResult containing execution results """ self._log("Using Fish shell workaround") # Set up environment command_env: dict[str, str] = os.environ.copy() if env: command_env.update(env) try: # Base64 encode the script to avoid stdin issues with Fish base64_script = base64.b64encode(script.encode("utf-8")).decode("utf-8") # Create a command that decodes the script and pipes it to fish command = f'{interpreter} -c "echo {base64_script} | base64 -d | fish"' self._log(f"Fish command: {command}") # Create and run the process process = await asyncio.create_subprocess_shell( command, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE, cwd=cwd, env=command_env, ) # Wait for the process to complete with timeout try: stdout_bytes, stderr_bytes = await asyncio.wait_for( process.communicate(), timeout=timeout ) return CommandResult( return_code=process.returncode or 0, stdout=stdout_bytes.decode("utf-8", errors="replace"), stderr=stderr_bytes.decode("utf-8", errors="replace"), ) except asyncio.TimeoutError: # Kill the process if it times out try: process.kill() except ProcessLookupError: pass # Process already terminated return CommandResult( return_code=-1, error_message=f"Fish script execution timed out after {timeout} seconds", ) except Exception as e: self._log(f"Fish script execution error: {str(e)}") return CommandResult( return_code=1, error_message=f"Error executing Fish script: {str(e)}" ) async def execute_script_from_file( self, script: str, language: str, cwd: str | None = None, env: dict[str, str] | None = None, timeout: float | None = 60.0, args: list[str] | None = None, use_login_shell: bool = True, ) -> CommandResult: """Execute a script by writing it to a temporary file and executing it. This is useful for languages where the script is too complex or long to pass via stdin, or for languages that have limitations with stdin. Args: script: The script content language: The script language (determines file extension and interpreter) cwd: Optional working directory env: Optional environment variables timeout: Optional timeout in seconds args: Optional command-line arguments use_login_shell: Whether to use login shell. default true (loads ~/.zshrc, ~/.bashrc, etc.) Returns: CommandResult containing execution results """ # Language to interpreter mapping language_map: dict[str, dict[str, str]] = { "python": { "command": "python", "extension": ".py", }, "javascript": { "command": "node", "extension": ".js", }, "typescript": { "command": "ts-node", "extension": ".ts", }, "bash": { "command": "bash", "extension": ".sh", }, "fish": { "command": "fish", "extension": ".fish", }, "ruby": { "command": "ruby", "extension": ".rb", }, "php": { "command": "php", "extension": ".php", }, "perl": { "command": "perl", "extension": ".pl", }, "r": { "command": "Rscript", "extension": ".R", }, } # Check if the language is supported if language not in language_map: return CommandResult( return_code=1, error_message=f"Unsupported language: {language}. Supported languages: {', '.join(language_map.keys())}", ) # Get language info language_info = language_map[language] command = language_info["command"] extension = language_info["extension"] # Set up environment command_env: dict[str, str] = os.environ.copy() if env: command_env.update(env) # Create a temporary file for the script with tempfile.NamedTemporaryFile( suffix=extension, mode="w", delete=False ) as temp: temp_path = temp.name _ = temp.write(script) # Explicitly ignore the return value try: # Determine if we should use a login shell if use_login_shell: # Get the user's login shell user_shell = os.environ.get("SHELL", "/bin/bash") os.path.basename(user_shell) self._log(f"Using login shell for script execution: {user_shell}") # Build the command including args cmd = f"{command} {temp_path}" if args: cmd += " " + " ".join(args) # Create command that runs script through login shell shell_cmd = f"{user_shell} -l -c '{cmd}'" self._log(f"Executing script from file with login shell: {shell_cmd}") # Create and run the process with shell process = await asyncio.create_subprocess_shell( shell_cmd, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE, cwd=cwd, env=command_env, ) else: # Build command arguments cmd_args = [command, temp_path] if args: cmd_args.extend(args) self._log(f"Executing script from file with: {' '.join(cmd_args)}") # Create and run the process normally process = await asyncio.create_subprocess_exec( *cmd_args, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE, cwd=cwd, env=command_env, ) # Wait for the process to complete with timeout try: stdout_bytes, stderr_bytes = await asyncio.wait_for( process.communicate(), timeout=timeout ) return CommandResult( return_code=process.returncode or 0, stdout=stdout_bytes.decode("utf-8", errors="replace"), stderr=stderr_bytes.decode("utf-8", errors="replace"), ) except asyncio.TimeoutError: # Kill the process if it times out try: process.kill() except ProcessLookupError: pass # Process already terminated return CommandResult( return_code=-1, error_message=f"Script execution timed out after {timeout} seconds", ) except Exception as e: self._log(f"Script file execution error: {str(e)}") return CommandResult( return_code=1, error_message=f"Error executing script: {str(e)}" ) finally: # Clean up temporary file try: os.unlink(temp_path) except Exception as e: self._log(f"Error cleaning up temporary file: {str(e)}") def get_available_languages(self) -> list[str]: """Get a list of available script languages. Returns: List of supported language names """ # Use the same language map as in execute_script_from_file method language_map = { "python": {"command": "python", "extension": ".py"}, "javascript": {"command": "node", "extension": ".js"}, "typescript": {"command": "ts-node", "extension": ".ts"}, "bash": {"command": "bash", "extension": ".sh"}, "fish": {"command": "fish", "extension": ".fish"}, "ruby": {"command": "ruby", "extension": ".rb"}, "php": {"command": "php", "extension": ".php"}, "perl": {"command": "perl", "extension": ".pl"}, "r": {"command": "Rscript", "extension": ".R"}, } return list(language_map.keys()) def register_tools(self, mcp_server: FastMCP) -> None: """Register command execution tools with the MCP server. Args: mcp_server: The FastMCP server instance """ # Run Command Tool @mcp_server.tool() async def run_command( command: str, cwd: str, ctx: MCPContext, use_login_shell: bool = True, ) -> str: """Execute a shell command. Args: command: The shell command to execute cwd: Working directory for the command use_login_shell: Whether to use login shell (loads ~/.zshrc, ~/.bashrc, etc.) Returns: The output of the command """ tool_ctx = create_tool_context(ctx) tool_ctx.set_tool_info("run_command") await tool_ctx.info(f"Executing command: {command}") # Check if command is allowed if not self.is_command_allowed(command): await tool_ctx.error(f"Command not allowed: {command}") return f"Error: Command not allowed: {command}" # Validate required cwd parameter if not cwd: await tool_ctx.error("Parameter 'cwd' is required but was None") return "Error: Parameter 'cwd' is required but was None" if cwd.strip() == "": await tool_ctx.error("Parameter 'cwd' cannot be empty") return "Error: Parameter 'cwd' cannot be empty" # Check if working directory is allowed if not self.permission_manager.is_path_allowed(cwd): await tool_ctx.error(f"Working directory not allowed: {cwd}") return f"Error: Working directory not allowed: {cwd}" # Check if working directory exists if not os.path.isdir(cwd): await tool_ctx.error(f"Working directory does not exist: {cwd}") return f"Error: Working directory does not exist: {cwd}" # Execute the command result: CommandResult = await self.execute_command( command, cwd=cwd, timeout=30.0, use_login_shell=use_login_shell ) # Report result if result.is_success: await tool_ctx.info("Command executed successfully") else: await tool_ctx.error( f"Command failed with exit code {result.return_code}" ) # Format the result if result.is_success: # For successful commands, just return stdout unless stderr has content if result.stderr: return f"Command executed successfully.\n\nSTDOUT:\n{result.stdout}\n\nSTDERR:\n{result.stderr}" return result.stdout else: # For failed commands, include all available information return result.format_output() # Run Script Tool @mcp_server.tool() async def run_script( script: str, cwd: str, ctx: MCPContext, interpreter: str = "bash", use_login_shell: bool = True, ) -> str: """Execute a script with the specified interpreter. Args: script: The script content to execute cwd: Working directory for script execution interpreter: The interpreter to use (bash, python, etc.) use_login_shell: Whether to use login shell (loads ~/.zshrc, ~/.bashrc, etc.) Returns: The output of the script """ tool_ctx = create_tool_context(ctx) tool_ctx.set_tool_info("run_script") # Validate script parameter if not script: await tool_ctx.error("Parameter 'script' is required but was None") return "Error: Parameter 'script' is required but was None" if script.strip() == "": await tool_ctx.error("Parameter 'script' cannot be empty") return "Error: Parameter 'script' cannot be empty" # interpreter can be None safely as it has a default value if not interpreter: interpreter = "bash" # Use default if None elif interpreter.strip() == "": await tool_ctx.error("Parameter 'interpreter' cannot be empty") return "Error: Parameter 'interpreter' cannot be empty" # Validate required cwd parameter if not cwd: await tool_ctx.error("Parameter 'cwd' is required but was None") return "Error: Parameter 'cwd' is required but was None" if cwd.strip() == "": await tool_ctx.error("Parameter 'cwd' cannot be empty") return "Error: Parameter 'cwd' cannot be empty" await tool_ctx.info(f"Executing script with interpreter: {interpreter}") # Validate required cwd parameter if not cwd: await tool_ctx.error("Parameter 'cwd' is required but was None") return "Error: Parameter 'cwd' is required but was None" if cwd.strip() == "": await tool_ctx.error("Parameter 'cwd' cannot be empty") return "Error: Parameter 'cwd' cannot be empty" # Check if working directory is allowed if not self.permission_manager.is_path_allowed(cwd): await tool_ctx.error(f"Working directory not allowed: {cwd}") return f"Error: Working directory not allowed: {cwd}" # Check if working directory exists if not os.path.isdir(cwd): await tool_ctx.error(f"Working directory does not exist: {cwd}") return f"Error: Working directory does not exist: {cwd}" # Execute the script result: CommandResult = await self.execute_script( script=script, interpreter=interpreter, cwd=cwd, # cwd is now a required parameter timeout=30.0, use_login_shell=use_login_shell, ) # Report result if result.is_success: await tool_ctx.info("Script executed successfully") else: await tool_ctx.error( f"Script execution failed with exit code {result.return_code}" ) # Format the result if result.is_success: # For successful scripts, just return stdout unless stderr has content if result.stderr: return f"Script executed successfully.\n\nSTDOUT:\n{result.stdout}\n\nSTDERR:\n{result.stderr}" return result.stdout else: # For failed scripts, include all available information return result.format_output() # Script tool for executing scripts in various languages @mcp_server.tool() async def script_tool( language: str, script: str, cwd: str, ctx: MCPContext, args: list[str] | None = None, use_login_shell: bool = True, ) -> str: """Execute a script in the specified language. Args: language: The programming language (python, javascript, etc.) script: The script code to execute cwd: Working directory for script execution args: Optional command-line arguments use_login_shell: Whether to use login shell (loads ~/.zshrc, ~/.bashrc, etc.) Returns: Script execution results """ tool_ctx = create_tool_context(ctx) tool_ctx.set_tool_info("script_tool") # Validate required parameters if not language: await tool_ctx.error("Parameter 'language' is required but was None") return "Error: Parameter 'language' is required but was None" if language.strip() == "": await tool_ctx.error("Parameter 'language' cannot be empty") return "Error: Parameter 'language' cannot be empty" if not script: await tool_ctx.error("Parameter 'script' is required but was None") return "Error: Parameter 'script' is required but was None" if script.strip() == "": await tool_ctx.error("Parameter 'script' cannot be empty") return "Error: Parameter 'script' cannot be empty" # args can be None as it's optional # Check for empty list but still allow None if args is not None and len(args) == 0: await tool_ctx.warning("Parameter 'args' is an empty list") # We don't return error for this as empty args is acceptable # Validate required cwd parameter if not cwd: await tool_ctx.error("Parameter 'cwd' is required but was None") return "Error: Parameter 'cwd' is required but was None" if cwd.strip() == "": await tool_ctx.error("Parameter 'cwd' cannot be empty") return "Error: Parameter 'cwd' cannot be empty" await tool_ctx.info(f"Executing {language} script") # Check if the language is supported if language not in self.get_available_languages(): await tool_ctx.error(f"Unsupported language: {language}") return f"Error: Unsupported language: {language}. Supported languages: {', '.join(self.get_available_languages())}" # Check if working directory is allowed if not self.permission_manager.is_path_allowed(cwd): await tool_ctx.error(f"Working directory not allowed: {cwd}") return f"Error: Working directory not allowed: {cwd}" # Check if working directory exists if not os.path.isdir(cwd): await tool_ctx.error(f"Working directory does not exist: {cwd}") return f"Error: Working directory does not exist: {cwd}" # Proceed with execution await tool_ctx.info(f"Executing {language} script in {cwd}") # Execute the script result = await self.execute_script_from_file( script=script, language=language, cwd=cwd, # cwd is now a required parameter timeout=30.0, args=args, use_login_shell=use_login_shell, ) # Report result if result.is_success: await tool_ctx.info(f"{language} script executed successfully") else: await tool_ctx.error( f"{language} script execution failed with exit code {result.return_code}" ) # Format the result if result.is_success: # Format the successful result output = f"{language} script executed successfully.\n\n" if result.stdout: output += f"STDOUT:\n{result.stdout}\n\n" if result.stderr: output += f"STDERR:\n{result.stderr}" return output.strip() else: # For failed scripts, include all available information return result.format_output()