mcp-shell-server

import shlex from typing import Dict, List, Tuple, Union class CommandPreProcessor: """ Pre-processes and validates shell commands before execution """ def preprocess_command(self, command: List[str]) -> List[str]: """ Preprocess the command to handle cases where '|' is attached to a command. """ preprocessed_command = [] for token in command: if token in ["||", "&&", ";"]: # Special shell operators preprocessed_command.append(token) elif "|" in token and token != "|": parts = token.split("|") preprocessed_command.extend( [part.strip() for part in parts if part.strip()] ) preprocessed_command.append("|") else: preprocessed_command.append(token) return preprocessed_command def clean_command(self, command: List[str]) -> List[str]: """ Clean command by trimming whitespace from each part. Removes empty strings but preserves arguments that are meant to be spaces. Args: command (List[str]): Original command and its arguments Returns: List[str]: Cleaned command """ return [arg for arg in command if arg] # Remove empty strings def create_shell_command(self, command: List[str]) -> str: """ Create a shell command string from a list of arguments. Handles wildcards and arguments properly. """ if not command: return "" escaped_args = [] for arg in command: if arg.isspace(): # Wrap space-only arguments in single quotes escaped_args.append(f"'{arg}'") else: # Properly escape all arguments including those with wildcards escaped_args.append(shlex.quote(arg.strip())) return " ".join(escaped_args) def split_pipe_commands(self, command: List[str]) -> List[List[str]]: """ Split commands by pipe operator into separate commands. Args: command (List[str]): Command and its arguments with pipe operators Returns: List[List[str]]: List of commands split by pipe operator """ commands: List[List[str]] = [] current_command: List[str] = [] for arg in command: if arg.strip() == "|": if current_command: commands.append(current_command) current_command = [] else: current_command.append(arg) if current_command: commands.append(current_command) return commands def parse_command( self, command: List[str] ) -> Tuple[List[str], Dict[str, Union[None, str, bool]]]: """ Parse command and extract redirections. """ cmd = [] redirects: Dict[str, Union[None, str, bool]] = { "stdin": None, "stdout": None, "stdout_append": False, } i = 0 while i < len(command): token = command[i] # Shell operators check if token in ["|", ";", "&&", "||"]: raise ValueError(f"Unexpected shell operator: {token}") # Output redirection if token in [">", ">>"]: if i + 1 >= len(command): raise ValueError("Missing path for output redirection") if i + 1 < len(command) and command[i + 1] in [">", ">>", "<"]: raise ValueError("Invalid redirection target: operator found") path = command[i + 1] redirects["stdout"] = path redirects["stdout_append"] = token == ">>" i += 2 continue # Input redirection if token == "<": if i + 1 >= len(command): raise ValueError("Missing path for input redirection") path = command[i + 1] redirects["stdin"] = path i += 2 continue cmd.append(token) i += 1 return cmd, redirects