HttpsClientSession.h

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regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
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http://www.apache.org/licenses/LICENSE-2.0
 
Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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specific language governing permissions and limitations
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#pragma once
 
#include <iostream>
 
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/connect.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <boost/asio/ssl/error.hpp>
#include <boost/asio/ssl/stream.hpp>
 
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 ETP_NS
{
    // Performs an HTTP GET and stores the response
    class HttpsClientSession : public std::enable_shared_from_this<HttpsClientSession>
    {
        tcp::resolver resolver_;
        ssl::stream<tcp::socket> stream_;
        boost::beast::flat_buffer buffer_; // (Must persist between reads)
        http::request<http::empty_body> req_;
        http::request<http::empty_body> proxyHandshake;
        http::response<http::string_body> res_;
        http::response<http::empty_body> proxyHandshakeResponse;
        // use own response parser
        // NOTE: 200 response to a CONNECT request from a tunneling proxy do not carry a body
        http::response_parser<http::empty_body> http_proxy_handshake_parser;
 
    public:
        // Resolver and stream require an io_context
        explicit
            HttpsClientSession(boost::asio::io_context& ioc, ssl::context& ctx)
            : resolver_(ioc)
            , stream_(ioc, ctx)
            , http_proxy_handshake_parser(proxyHandshakeResponse)
        {
        }
 
        // Start the asynchronous operation
        void
            run(
                const std::string& etpServerHost,
                uint16_t etpServerPort,
                const std::string& etpServerTarget,
                int version,
                std::string authorization = "",
                const std::string& proxyHost = "",
                uint16_t proxyPort = 80,
                const std::string& proxyAuthorization = "")
        {
            size_t hostSizeWithNullTermChar = etpServerHost.size() + 1;
            char* copyHost = new char[hostSizeWithNullTermChar];
            std::memcpy(copyHost, etpServerHost.c_str(), hostSizeWithNullTermChar); // Copy host because it must be non const in SSL_set_tlsext_host_name
            // Set SNI Hostname (many hosts need this to handshake successfully)
            if (!SSL_set_tlsext_host_name(stream_.native_handle(), copyHost))
            {
                boost::system::error_code ec{ static_cast<int>(::ERR_get_error()), boost::asio::error::get_ssl_category() };
                std::cerr << ec.message() << "\n";
                delete[] copyHost;
                return;
            }
            delete[] copyHost;
 
            // Set up an HTTP GET request message
            req_.version(version);
            req_.method(http::verb::get);
            req_.target(etpServerTarget);
            req_.set(http::field::host, etpServerHost + ':' + std::to_string(etpServerPort));
            req_.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);
            if (!authorization.empty()) {
                req_.set(http::field::authorization, authorization);
            }
 
            if (!proxyHost.empty()) {
                proxyHandshake.version(version);
                proxyHandshake.method(http::verb::connect);
                proxyHandshake.target(etpServerHost + ':' + std::to_string(etpServerPort));
                proxyHandshake.set(http::field::host, etpServerHost + ':' + std::to_string(etpServerPort));
                if (!authorization.empty()) {
                    proxyHandshake.set(http::field::authorization, authorization);
                }
                if (!proxyAuthorization.empty()) {
                    proxyHandshake.set(http::field::proxy_authorization, proxyAuthorization);
                }
            }
 
            // Look up the domain name
            resolver_.async_resolve(
                proxyHost.empty() ? etpServerHost : proxyHost,
                std::to_string(proxyHost.empty() ? etpServerPort : proxyPort),
                std::bind(
                    &HttpsClientSession::on_resolve,
                    shared_from_this(),
                    std::placeholders::_1,
                    std::placeholders::_2));
        }
 
        void
            on_resolve(
                boost::system::error_code ec,
                tcp::resolver::results_type results)
        {
            if (ec) {
                std::cerr << "resolve : " << ec.message() << std::endl;
                return;
            }
 
            // Make the connection on the IP address we get from a lookup
            boost::asio::async_connect(
                stream_.next_layer(),
                results.begin(),
                results.end(),
                std::bind(
                    &HttpsClientSession::on_connect,
                    shared_from_this(),
                    std::placeholders::_1));
        }
 
        void
            on_connect(boost::system::error_code ec)
        {
            if (ec) {
                std::cerr << "connect : " << ec.message() << std::endl;
                return;
            }
 
            if (proxyHandshake.count(http::field::host) > 0) {
                // Send the handshake to the proxy
                http::async_write(stream_.next_layer(), proxyHandshake,
                    std::bind(
                        &HttpsClientSession::on_proxy_handshake_write,
                        shared_from_this(),
                        std::placeholders::_1,
                        std::placeholders::_2));
            }
            else {
                // Perform the SSL handshake
                stream_.async_handshake(
                    ssl::stream_base::client,
                    std::bind(
                        &HttpsClientSession::on_handshake,
                        shared_from_this(),
                        std::placeholders::_1));
            }
        }
 
        void
            on_proxy_handshake_write(
                boost::system::error_code ec,
                std::size_t bytes_transferred)
        {
            boost::ignore_unused(bytes_transferred);
 
            if (ec) {
                std::cerr << "Proxy handshake write : " << ec.message() << std::endl;
                return;
            }
 
            http_proxy_handshake_parser.skip(true); // see https://stackoverflow.com/a/49837467/10904212
 
            // Receive the HTTP response
            http::async_read(stream_.next_layer(), buffer_, http_proxy_handshake_parser,
                std::bind(
                    &HttpsClientSession::on_proxy_handshake_read,
                    shared_from_this(),
                    std::placeholders::_1,
                    std::placeholders::_2));
        }
 
        void
            on_proxy_handshake_read(
                boost::system::error_code ec,
                std::size_t bytes_transferred)
        {
            boost::ignore_unused(bytes_transferred);
            if (ec) {
                std::cerr << "read : " << ec.message() << std::endl;
                return;
            }
 
            // Perform the SSL handshake
            stream_.async_handshake(
                ssl::stream_base::client,
                std::bind(
                    &HttpsClientSession::on_handshake,
                    shared_from_this(),
                    std::placeholders::_1));
        }
 
        void
            on_handshake(boost::system::error_code ec)
        {
            if (ec) {
                std::cerr << "handshake : " << ec.message() << std::endl;
                return;
            }
 
            // Send the HTTP request to the remote host
            http::async_write(stream_, req_,
                std::bind(
                    &HttpsClientSession::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);
 
            if (ec) {
                std::cerr << "write : " << ec.message() << std::endl;
                return;
            }
 
            // Receive the HTTP response
            http::async_read(stream_, buffer_, res_,
                std::bind(
                    &HttpsClientSession::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);
 
            if (ec) {
                std::cerr << "read : " << ec.message() << std::endl;
                return;
            }
 
            // Force close
            boost::system::error_code closeEc;
            stream_.next_layer().close(closeEc);
            /*
            // Gracefully close the stream_
            stream_.async_shutdown(
                std::bind(
                    &HttpsClientSession::on_shutdown,
                    shared_from_this(),
                    std::placeholders::_1));
                    */
        }
 
        void
            on_shutdown(boost::system::error_code ec)
        {
            if (ec == boost::asio::error::eof)
            {
                // Rationale:
                // http://stackoverflow.com/questions/25587403/boost-asio-ssl-async-shutdown-always-finishes-with-an-error
                ec.assign(0, ec.category());
            }
            if (ec) {
                // Do nothing : https://stackoverflow.com/questions/25587403/boost-asio-ssl-async-shutdown-always-finishes-with-an-error
                //std::cerr << "shutdown : " << ec.message() << std::endl;
                return;
            }
 
            // If we get here then the connection is closed gracefully
        }
 
        const http::response<http::string_body>& getResponse() const {
            return res_;
        }
    };
}