boost_beast/example/http/client/sync-ssl/http_client_sync_ssl.cpp

//
// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/boostorg/beast
//

//------------------------------------------------------------------------------
//
// Example: HTTP SSL client, synchronous
//
//------------------------------------------------------------------------------

#include "example/common/root_certificates.hpp"

#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/ssl.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>
#include <cstdlib>
#include <iostream>
#include <string>

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

// Performs an HTTP GET and prints the response
int main(int argc, char** argv)
{
    try
    {
        // Check command line arguments.
        if(argc != 4 && argc != 5)
        {
            std::cerr <<
                "Usage: http-client-sync-ssl <host> <port> <target> [<HTTP version: 1.0 or 1.1(default)>]\n" <<
                "Example:\n" <<
                "    http-client-sync-ssl www.example.com 443 /\n" <<
                "    http-client-sync-ssl www.example.com 443 / 1.0\n";
            return EXIT_FAILURE;
        }
        auto const host = argv[1];
        auto const port = argv[2];
        auto const target = argv[3];
        int version = argc == 5 && !std::strcmp("1.0", argv[4]) ? 10 : 11;

        // The io_context is required for all I/O
        net::io_context ioc;

        // The SSL context is required, and holds certificates
        ssl::context ctx(ssl::context::tlsv12_client);

        // This holds the root certificate used for verification
        load_root_certificates(ctx);

        // Verify the remote server's certificate
        ctx.set_verify_mode(ssl::verify_peer);

            // These objects perform our I/O
        tcp::resolver resolver(ioc);
        beast::ssl_stream<beast::tcp_stream> stream(ioc, ctx);

        // Set SNI Hostname (many hosts need this to handshake successfully)
        if(! SSL_set_tlsext_host_name(stream.native_handle(), host))
        {
            beast::error_code ec{static_cast<int>(::ERR_get_error()), net::error::get_ssl_category()};
            throw beast::system_error{ec};
        }

        // Look up the domain name
        auto const results = resolver.resolve(host, port);

        // Make the connection on the IP address we get from a lookup
        beast::get_lowest_layer(stream).connect(results);

        // Perform the SSL handshake
        stream.handshake(ssl::stream_base::client);

        // Set up an HTTP GET request message
        http::request<http::string_body> req{http::verb::get, target, version};
        req.set(http::field::host, host);
        req.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);

        // Send the HTTP request to the remote host
        http::write(stream, req);

        // This buffer is used for reading and must be persisted
        beast::flat_buffer buffer;

        // Declare a container to hold the response
        http::response<http::dynamic_body> res;

        // Receive the HTTP response
        http::read(stream, buffer, res);

        // Write the message to standard out
        std::cout << res << std::endl;

        // Gracefully close the stream
        beast::error_code ec;
        stream.shutdown(ec);

        // ssl::error::stream_truncated, also known as an SSL "short read",
        // indicates the peer closed the connection without performing the
        // required closing handshake (for example, Google does this to
        // improve performance). Generally this can be a security issue,
        // but if your communication protocol is self-terminated (as
        // it is with both HTTP and WebSocket) then you may simply
        // ignore the lack of close_notify.
        //
        // https://github.com/boostorg/beast/issues/38
        //
        // https://security.stackexchange.com/questions/91435/how-to-handle-a-malicious-ssl-tls-shutdown
        //
        // When a short read would cut off the end of an HTTP message,
        // Beast returns the error beast::http::error::partial_message.
        // Therefore, if we see a short read here, it has occurred
        // after the message has been completed, so it is safe to ignore it.

        if(ec != net::ssl::error::stream_truncated)
            throw beast::system_error{ec};
    }
    catch(std::exception const& e)
    {
        std::cerr << "Error: " << e.what() << std::endl;
        return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
}