bash.cpp

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// SPDX-License-Identifier: Apache-2.0
#include <entropic/mcp/servers/bash.h>
#include <entropic/mcp/tool_base.h>
#include <entropic/mcp/server_base.h>
#include <entropic/types/logging.h>
 
#include <nlohmann/json.hpp>
 
#include <array>
#include <cstdio>
#include <filesystem>
#include <stdexcept>
#include <string>
 
static auto logger = entropic::log::get("mcp.bash");
 
namespace entropic {
 
// ── working_dir validation ──────────────────────────────────────
 
static bool is_safe_cwd(const std::string& cwd) {
    static constexpr const char* unsafe_chars = ";&|`$<>\n\r\\\"'*?(){}[]";
    if (cwd.find_first_of(unsafe_chars) != std::string::npos) {
        return false;
    }
    std::error_code ec;
    return std::filesystem::is_directory(cwd, ec);
}
 
static std::pair<std::string, int> run_popen(
    const std::string& full_cmd) {
 
    FILE* pipe = popen(full_cmd.c_str(), "r");  // NOLINT
    if (pipe == nullptr) {
        return {"Failed to open process", -1};
    }
 
    std::string output;
    std::array<char, 4096> buf{};
    while (fgets(buf.data(), buf.size(), pipe) != nullptr) {
        output += buf.data();
    }
 
    int status = pclose(pipe);  // NOLINT
    int exit_code = WEXITSTATUS(status);
    return {output, exit_code};
}
 
// ── ExecuteTool ─────────────────────────────────────────────────
 
class ExecuteTool : public ToolBase {
public:
    ExecuteTool(ToolDefinition def, BashServer& server)
        : ToolBase(std::move(def)), server_(server) {}
 
    ServerResponse execute(const std::string& args_json) override;
 
private:
    BashServer& server_;
};
 
ServerResponse ExecuteTool::execute(const std::string& args_json) {
    auto args = nlohmann::json::parse(args_json);
    std::string command = args.at("command").get<std::string>();
 
    std::string cwd = args.value(
        "working_dir", server_.working_dir().string());
 
    logger->info("[bash.execute] cmd='{}' cwd='{}'", command, cwd);
 
    if (!is_safe_cwd(cwd)) {
        logger->warn("Rejected unsafe working_dir: '{}'", cwd);
        return {"Error: working_dir is not an existing directory or "
                "contains shell metacharacters", {}};
    }
 
    std::string full_cmd =
        "cd " + cwd + " && " + command + " 2>&1";
 
    auto [output, exit_code] = run_popen(full_cmd);
    logger->info("Bash: exit={}, stdout={} chars, cmd='{}'",
                 exit_code, output.size(), command);
 
    nlohmann::json result;
    result["exit_code"] = exit_code;
    result["output"] = output;
    return {result.dump(), {}};
}
 
// ── BashServer ──────────────────────────────────────────────────
 
BashServer::BashServer(
    const std::filesystem::path& working_dir,
    const std::string& data_dir,
    int timeout)
    : MCPServerBase("bash")
    , working_dir_(working_dir)
    , timeout_(timeout) {
 
    auto def = load_tool_definition(
        "execute", "bash", data_dir + "/tools");
 
    execute_tool_ = std::make_unique<ExecuteTool>(
        std::move(def), *this);
 
    register_tool(execute_tool_.get());
 
    logger->info("BashServer initialized: cwd='{}' timeout={}s",
                 working_dir_.string(), timeout_);
}
 
BashServer::~BashServer() = default;
 
std::string
BashServer::get_permission_pattern(const std::string& tool_name, const std::string& args_json) const {
 
    std::string base_cmd = "unknown";
    try {
        auto args = nlohmann::json::parse(args_json);
        std::string cmd = args.at("command").get<std::string>();
        auto space = cmd.find(' ');
        base_cmd = (space != std::string::npos)
            ? cmd.substr(0, space) : cmd;
    } catch (const std::exception& e) {
        logger->warn("Failed to parse command for permission: {}",
                     e.what());
    }
    return tool_name + ":" + base_cmd + " *";
}
 
bool BashServer::set_working_dir(const std::string& path) {
    working_dir_ = path;
    logger->info("Working directory set to: {}", path);
    return true;
}
 
const std::filesystem::path& BashServer::working_dir() const {
    return working_dir_;
}
 
int BashServer::timeout() const {
    return timeout_;
}
 
} // namespace entropic