WebServer.cpp

#include "WebServer.h"

#include "index.hpp"
#include "detect_ssl.hpp"
#include "server_certificate.hpp"
#include "ssl_stream.hpp"
#include "root_certificates.hpp"

#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/websocket.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/bind_executor.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <boost/asio/signal_set.hpp>
#include <boost/asio/ssl/stream.hpp>
#include <boost/asio/strand.hpp>
#include <boost/asio/steady_timer.hpp>
#include <boost/make_unique.hpp>
#include <boost/config.hpp>
#include <algorithm>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <memory>
#include <string>
#include <thread>
#include <vector>
#include <iostream>
#include "Serialize.h"

using tcp = boost::asio::ip::tcp;               // from <boost/asio/ip/tcp.hpp>
namespace ssl = boost::asio::ssl;               // from <boost/asio/ssl.hpp>
namespace http = boost::beast::http;            // from <boost/beast/http.hpp>
namespace websocket = boost::beast::websocket;  // from <boost/beast/websocket.hpp>

// Report a failure
void
fail(boost::system::error_code ec, char const* what)
{
    std::cerr << what << ": " << ec.message() << "\n";
}

// Handles a plain WebSocket connection
struct plain_websocket_session : std::enable_shared_from_this<plain_websocket_session> {
    websocket::stream<tcp::socket> ws_;
    bool close_ = false;
    size_t callback_id;
    WebBroker& web_broker;
    boost::beast::multi_buffer buffer_;
    char ping_state_ = 0;

    boost::asio::strand<boost::asio::io_context::executor_type> strand_;
    boost::asio::steady_timer timer_;

    // Start the asynchronous operation
    template<class Body, class Allocator>
    void
    do_accept(http::request<Body, http::basic_fields<Allocator>> req)
    {
        // Set the control callback. This will be called
        // on every incoming ping, pong, and close frame.
        ws_.control_callback(
            std::bind(
                &plain_websocket_session::on_control_callback,
                this,
                std::placeholders::_1,
                std::placeholders::_2));

        // Set the timer
        timer_.expires_after(std::chrono::seconds(15));

        // Accept the websocket handshake
        ws_.async_accept(
            req,
            boost::asio::bind_executor(
                strand_,
                std::bind(
                    &plain_websocket_session::on_accept,
                    shared_from_this(),
                    std::placeholders::_1)));
    }

    void write(const std::string& x) {
      ws_.write(boost::asio::buffer(x));
    }

    void
    on_accept(boost::system::error_code ec)
    {
        // Happens when the timer closes the socket
        if(ec == boost::asio::error::operation_aborted)
            return;

        if(ec)
            return fail(ec, "accept");

        // Read a message
        do_read();
    }

    // Called when the timer expires.
    void
    on_timer(boost::system::error_code ec)
    {
        if(ec && ec != boost::asio::error::operation_aborted)
            return fail(ec, "timer");

        // See if the timer really expired since the deadline may have moved.
        if(timer_.expiry() <= std::chrono::steady_clock::now())
        {
            // If this is the first time the timer expired,
            // send a ping to see if the other end is there.
            if(ws_.is_open() && ping_state_ == 0)
            {
                // Note that we are sending a ping
                ping_state_ = 1;

                // Set the timer
                timer_.expires_after(std::chrono::seconds(15));

                // Now send the ping
                ws_.async_ping({},
                    boost::asio::bind_executor(
                        strand_,
                        std::bind(
                            &plain_websocket_session::on_ping,
                            shared_from_this(),
                            std::placeholders::_1)));
            }
            else
            {
                // The timer expired while trying to handshake,
                // or we sent a ping and it never completed or
                // we never got back a control frame, so close.

                do_timeout();
                return;
            }
        }

        // Wait on the timer
        timer_.async_wait(
            boost::asio::bind_executor(
                strand_,
                std::bind(
                    &plain_websocket_session::on_timer,
                    shared_from_this(),
                    std::placeholders::_1)));
    }

    // Called to indicate activity from the remote peer
    void
    activity()
    {
        // Note that the connection is alive
        ping_state_ = 0;

        // Set the timer
        timer_.expires_after(std::chrono::seconds(15));
    }

    // Called after a ping is sent.
    void
    on_ping(boost::system::error_code ec)
    {
        // Happens when the timer closes the socket
        if(ec == boost::asio::error::operation_aborted)
            return;

        if(ec)
            return fail(ec, "ping");

        // Note that the ping was sent.
        if(ping_state_ == 1)
        {
            ping_state_ = 2;
        }
        else
        {
            // ping_state_ could have been set to 0
            // if an incoming control frame was received
            // at exactly the same time we sent a ping.
            BOOST_ASSERT(ping_state_ == 0);
        }
    }

    void
    on_control_callback(
        websocket::frame_type kind,
        boost::beast::string_view payload)
    {
        boost::ignore_unused(kind, payload);

        // Note that there is activity
        activity();
    }

    void
    do_read()
    {
        // Read a message into our buffer
        ws_.async_read(
            buffer_,
            boost::asio::bind_executor(
                strand_,
                std::bind(
                    &plain_websocket_session::on_read,
                    shared_from_this(),
                    std::placeholders::_1,
                    std::placeholders::_2)));
    }

    void
    on_read(
        boost::system::error_code ec,
        std::size_t bytes_transferred)
    {
        boost::ignore_unused(bytes_transferred);

        // Happens when the timer closes the socket
        if(ec == boost::asio::error::operation_aborted)
            return;

        // This indicates that the websocket_session was closed
        if(ec == websocket::error::closed)
            return;

        if(ec)
            fail(ec, "read");

        // Note that there is activity
        activity();

        // Echo the message
        ws_.text(ws_.got_text());
        ws_.async_write(
            buffer_.data(),
            boost::asio::bind_executor(
                strand_,
                std::bind(
                    &plain_websocket_session::on_write,
                    shared_from_this(),
                    std::placeholders::_1,
                    std::placeholders::_2)));
    }

    void
    on_write(
        boost::system::error_code ec,
        std::size_t bytes_transferred)
    {
        boost::ignore_unused(bytes_transferred);

        // Happens when the timer closes the socket
        if(ec == boost::asio::error::operation_aborted)
            return;

        if(ec)
            return fail(ec, "write");

        // Clear the buffer
        buffer_.consume(buffer_.size());

        // Do another read
        do_read();
    }
    explicit plain_websocket_session(tcp::socket socket, WebBroker& web_broker)
      :  strand_(socket.get_executor())
        , timer_(socket.get_executor().context(), (std::chrono::steady_clock::time_point::max)()),
        ws_{ std::move(socket) },
        web_broker{ web_broker },
        callback_id{ web_broker.register_callback([&](const std::string& x){ write(x); }) }{
    }

    ~plain_websocket_session() {
      web_broker.unregister_callback(callback_id);
    }

    websocket::stream<tcp::socket>&
    ws()
    {
        return ws_;
    }

    // Start the asynchronous operation
    template<class Body, class Allocator>
    void
    run(http::request<Body, http::basic_fields<Allocator>> req)
    {
        // Run the timer. The timer is operated
        // continuously, this simplifies the code.
        on_timer({});

        // Accept the WebSocket upgrade request
        do_accept(std::move(req));
    }

    void
    do_timeout()
    {
        // This is so the close can have a timeout
        if(close_)
            return;
        close_ = true;

        // Set the timer
        timer_.expires_after(std::chrono::seconds(15));

        // Close the WebSocket Connection
        ws_.async_close(
            websocket::close_code::normal,
            boost::asio::bind_executor(
                strand_,
                std::bind(
                    &plain_websocket_session::on_close,
                    shared_from_this(),
                    std::placeholders::_1)));
    }

    void
    on_close(boost::system::error_code ec)
    {
        // Happens when close times out
        if(ec == boost::asio::error::operation_aborted)
            return;

        if(ec)
            return fail(ec, "close");

        // At this point the connection is gracefully closed
    }
};

template<class Derived>
class http_session
{
    // Access the derived class, this is part of
    // the Curiously Recurring Template Pattern idiom.
    Derived&
    derived()
    {
        return static_cast<Derived&>(*this);
    }

    // This queue is used for HTTP pipelining.
    class queue
    {
        enum
        {
            // Maximum number of responses we will queue
            limit = 8
        };

        // The type-erased, saved work item
        struct work
        {
            virtual ~work() = default;
            virtual void operator()() = 0;
        };

        http_session& self_;
        std::vector<std::unique_ptr<work>> items_;

    public:
        explicit
        queue(http_session& self)
            : self_(self)
        {
            static_assert(limit > 0, "queue limit must be positive");
            items_.reserve(limit);
        }

        // Returns `true` if we have reached the queue limit
        bool
        is_full() const
        {
            return items_.size() >= limit;
        }

        // Called when a message finishes sending
        // Returns `true` if the caller should initiate a read
        bool
        on_write()
        {
            BOOST_ASSERT(! items_.empty());
            auto const was_full = is_full();
            items_.erase(items_.begin());
            if(! items_.empty())
                (*items_.front())();
            return was_full;
        }

        // Called by the HTTP handler to send a response.
        template<bool isRequest, class Body, class Fields>
        void
        operator()(http::message<isRequest, Body, Fields>&& msg)
        {
            // This holds a work item
            struct work_impl : work
            {
                http_session& self_;
                http::message<isRequest, Body, Fields> msg_;

                work_impl(
                    http_session& self,
                    http::message<isRequest, Body, Fields>&& msg)
                    : self_(self)
                    , msg_(std::move(msg))
                {
                }

                void
                operator()()
                {
                    http::async_write(
                        self_.derived().stream(),
                        msg_,
                        boost::asio::bind_executor(
                            self_.strand_,
                            std::bind(
                                &http_session::on_write,
                                self_.derived().shared_from_this(),
                                std::placeholders::_1,
                                msg_.need_eof())));
                }
            };

            // Allocate and store the work
            items_.push_back(
                boost::make_unique<work_impl>(self_, std::move(msg)));

            // If there was no previous work, start this one
            if(items_.size() == 1)
                (*items_.front())();
        }
    };
    Store& store;
    WebBroker& web_broker;
    http::request<http::string_body> req_;
    queue queue_;

    http::response<http::string_body> bad_request(boost::beast::string_view why) {
      http::response<http::string_body> res{ http::status::bad_request, req_.version() };
      res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
      res.set(http::field::content_type, "text/html");
      res.keep_alive(req_.keep_alive());
      res.body() = why.to_string();
      res.prepare_payload();
      return res;
    };

    http::response<http::string_body> not_found(boost::beast::string_view target) {
      http::response<http::string_body> res{ http::status::not_found, req_.version() };
      res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
      res.set(http::field::content_type, "text/html");
      res.keep_alive(req_.keep_alive());
      res.body() = "The resource '" + target.to_string() + "' was not found.";
      res.prepare_payload();
      return res;
    };

    http::response<http::string_body> server_error(boost::beast::string_view what) {
      http::response<http::string_body> res{ http::status::internal_server_error, req_.version() };
      res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
      res.set(http::field::content_type, "text/html");
      res.keep_alive(req_.keep_alive());
      res.body() = "An error occurred: '" + what.to_string() + "'";
      res.prepare_payload();
      return res;
    };

protected:
    boost::asio::steady_timer timer_;
    boost::asio::strand<boost::asio::io_context::executor_type> strand_;
    boost::beast::flat_buffer buffer_;

public:
    http_session(
        boost::asio::io_context& ioc,
        boost::beast::flat_buffer buffer,
        Store& store,
        WebBroker& web_broker)
        : store{ store }
        , web_broker{ web_broker }
        , queue_(*this)
        , timer_(ioc, (std::chrono::steady_clock::time_point::max)())
        , strand_(ioc.get_executor())
        , buffer_(std::move(buffer))
    {
    }

    void
    do_read()
    {
        // Set the timer
        timer_.expires_after(std::chrono::seconds(15));

        // Make the request empty before reading,
        // otherwise the operation behavior is undefined.
        req_ = {};

        // Read a request
        http::async_read(
            derived().stream(),
            buffer_,
            req_,
            boost::asio::bind_executor(
                strand_,
                std::bind(
                    &http_session::on_read,
                    derived().shared_from_this(),
                    std::placeholders::_1)));
    }

    // Called when the timer expires.
    void
    on_timer(boost::system::error_code ec)
    {
        if(ec && ec != boost::asio::error::operation_aborted)
            return fail(ec, "timer");

        // Verify that the timer really expired since the deadline may have moved.
        if(timer_.expiry() <= std::chrono::steady_clock::now())
            return derived().do_timeout();

        // Wait on the timer
        timer_.async_wait(
            boost::asio::bind_executor(
                strand_,
                std::bind(
                    &http_session::on_timer,
                    derived().shared_from_this(),
                    std::placeholders::_1)));
    }

    void index() {
      if (req_.method() == http::verb::head) {
        http::response<http::empty_body> res{ http::status::ok, req_.version() };
        res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
        res.set(http::field::content_type, "text/html");
        res.content_length(index_body.size());
        res.keep_alive(req_.keep_alive());
        return queue_(std::move(res));
      }

      http::response<http::string_body> res{
        std::piecewise_construct,
        std::make_tuple(index_body),
        std::make_tuple(http::status::ok, req_.version()) };
      res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
      res.set(http::field::content_type, "text/html");
      res.content_length(index_body.size());
      res.keep_alive(req_.keep_alive());
      return queue_(std::move(res));
    }

    void json_response(std::string body) {
      if (req_.method() == http::verb::head) {
        http::response<http::empty_body> res{ http::status::ok, req_.version() };
        res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
        res.set(http::field::content_type, "application/json");
        res.content_length(body.size());
        res.keep_alive(req_.keep_alive());
        return queue_(std::move(res));
      }

      http::response<http::string_body> res{
        std::piecewise_construct,
        std::make_tuple(body),
        std::make_tuple(http::status::ok, req_.version()) };
      res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
      res.set(http::field::content_type, "application/json");
      res.content_length(body.size());
      res.keep_alive(req_.keep_alive());
      return queue_(std::move(res));
    }

    void handle_request() {
      if (req_.method() != http::verb::get && req_.method() != http::verb::head)
        return queue_(bad_request("Unknown HTTP-method"));
      if (req_.target() == "/") return index();
      if (req_.target() == "/dns") return json_response(serialize(store.dns_requests()));
      if (req_.target() == "/connections") return json_response(serialize(store.connections()));
      if (req_.target() == "/requests") return json_response(serialize(store.requests()));
      if (req_.target() == "/netflows") return json_response(serialize(store.netflows()));
      return queue_(bad_request("Not found."));
    }

    void
    on_read(boost::system::error_code ec)
    {
        // Happens when the timer closes the socket
        if(ec == boost::asio::error::operation_aborted)
            return;

        // This means they closed the connection
        if(ec == http::error::end_of_stream)
            return derived().do_eof();

        if(ec)
            return fail(ec, "read");

        // See if it is a WebSocket Upgrade
        if(websocket::is_upgrade(req_)) {
          std::make_shared<plain_websocket_session>(derived().release_stream(), web_broker)->run(std::move(req_));
          return;
        }

        // Send the response
        handle_request();

        // If we aren't at the queue limit, try to pipeline another request
        if(! queue_.is_full())
            do_read();
    }

    void
    on_write(boost::system::error_code ec, bool close)
    {
        // Happens when the timer closes the socket
        if(ec == boost::asio::error::operation_aborted)
            return;

        if(ec)
            return fail(ec, "write");

        if(close)
        {
            // This means we should close the connection, usually because
            // the response indicated the "Connection: close" semantic.
            return derived().do_eof();
        }

        // Inform the queue that a write completed
        if(queue_.on_write())
        {
            // Read another request
            do_read();
        }
    }
};

// Handles a plain HTTP connection
class plain_http_session
    : public http_session<plain_http_session>
    , public std::enable_shared_from_this<plain_http_session>
{
    tcp::socket socket_;
    boost::asio::strand<
        boost::asio::io_context::executor_type> strand_;
    Store& store;
    WebBroker& web_broker;
public:
    // Create the http_session
    plain_http_session(
        tcp::socket socket,
        boost::beast::flat_buffer buffer,
        Store& store,
        WebBroker& web_broker)
        : http_session<plain_http_session>(
            socket.get_executor().context(),
            std::move(buffer),
            store, web_broker)
        , socket_(std::move(socket))
        , strand_(socket_.get_executor())
        , store{ store }
        , web_broker{ web_broker }
    {
    }

    // Called by the base class
    tcp::socket&
    stream()
    {
        return socket_;
    }

    // Called by the base class
    tcp::socket
    release_stream()
    {
        return std::move(socket_);
    }

    // Start the asynchronous operation
    void
    run()
    {
        // Run the timer. The timer is operated
        // continuously, this simplifies the code.
        on_timer({});

        do_read();
    }

    void
    do_eof()
    {
        // Send a TCP shutdown
        boost::system::error_code ec;
        socket_.shutdown(tcp::socket::shutdown_send, ec);

        // At this point the connection is closed gracefully
    }

    void
    do_timeout()
    {
        // Closing the socket cancels all outstanding operations. They
        // will complete with boost::asio::error::operation_aborted
        boost::system::error_code ec;
        socket_.shutdown(tcp::socket::shutdown_both, ec);
        socket_.close(ec);
    }
};

// Detects SSL handshakes
class detect_session : public std::enable_shared_from_this<detect_session>
{
    tcp::socket socket_;
    ssl::context& ctx_;
    boost::asio::strand<
        boost::asio::io_context::executor_type> strand_;
    boost::beast::flat_buffer buffer_;
    Store& store;
    WebBroker& web_broker;
public:
    explicit
    detect_session(
        tcp::socket socket,
        ssl::context& ctx,
        Store& store,
        WebBroker& web_broker)
        : socket_(std::move(socket))
        , ctx_(ctx)
        , strand_(socket_.get_executor())
        , store{ store }
        , web_broker{ web_broker }
    {
    }

    // Launch the detector
    void
    run()
    {
        async_detect_ssl(
            socket_,
            buffer_,
            boost::asio::bind_executor(
                strand_,
                std::bind(
                    &detect_session::on_detect,
                    shared_from_this(),
                    std::placeholders::_1,
                    std::placeholders::_2)));

    }

    void
    on_detect(boost::system::error_code ec, boost::tribool result)
    {
        if(ec)
            return fail(ec, "detect");

        std::make_shared<plain_http_session>(
            std::move(socket_),
            std::move(buffer_),
            store,
            web_broker)->run();
    }
};

// Accepts incoming connections and launches the sessions
class listener : public std::enable_shared_from_this<listener>
{
    ssl::context& ctx_;
    tcp::acceptor acceptor_;
    tcp::socket socket_;
    Store& store;
    WebBroker& web_broker;
public:
    listener(
        boost::asio::io_context& ioc,
        ssl::context& ctx,
        tcp::endpoint endpoint,
        Store& store,
        WebBroker& web_broker)
        : ctx_(ctx)
        , acceptor_(ioc)
        , socket_(ioc)
        , store{ store }
        , web_broker{ web_broker }
    {
        boost::system::error_code ec;

        // Open the acceptor
        acceptor_.open(endpoint.protocol(), ec);
        if(ec)
        {
            fail(ec, "open");
            return;
        }

        // Allow address reuse
        acceptor_.set_option(boost::asio::socket_base::reuse_address(true));
        if(ec)
        {
            fail(ec, "set_option");
            return;
        }

        // Bind to the server address
        acceptor_.bind(endpoint, ec);
        if(ec)
        {
            fail(ec, "bind");
            return;
        }

        // Start listening for connections
        acceptor_.listen(
            boost::asio::socket_base::max_listen_connections, ec);
        if(ec)
        {
            fail(ec, "listen");
            return;
        }
    }

    // Start accepting incoming connections
    void
    run()
    {
        if(! acceptor_.is_open())
            return;
        do_accept();
    }

    void
    do_accept()
    {
        acceptor_.async_accept(
            socket_,
            std::bind(
                &listener::on_accept,
                shared_from_this(),
                std::placeholders::_1));
    }

    void
    on_accept(boost::system::error_code ec)
    {
        if(ec)
        {
            fail(ec, "accept");
        }
        else
        {
            // Create the detector http_session and run it
            std::make_shared<detect_session>(
                std::move(socket_),
                ctx_,
                store,
                web_broker)->run();
        }

        // Accept another connection
        do_accept();
    }
};

WebServer::WebServer(Store& store, WebBroker& web_broker, boost::asio::io_context& io_context, 
  const std::string& address, uint16_t port) : store{ store }, web_broker{ web_broker } {
  ssl::context ctx{ssl::context::sslv23};
  load_server_certificate(ctx);
  auto ip = boost::asio::ip::make_address(address);
  std::make_shared<listener>(
      io_context,
      ctx,
      tcp::endpoint{ip, port},
      store,
      web_broker)->run();
}