Boost Asio SSL Certification on iOS

Question

In another answer of mine you can see a simple SSL client.

In this code you'll quickly note verify_certificate which you can use to (additionally) verify the server certificate.

Sidenote

Note that I don't know which libraries are underlying the Asio SSL implementation iOS, but keep in mind verifying (or even pinning) theserver certificate could be rather useless. It would only verify the authenticity of the certificate presented. In the light of yesterday's security debacle I don't think this helps much, because unless properly patched the server could have presented a valid certificate, but still use unrelated encryption keys - this still allows a MiTM scenario

Just noting this in case your question is somehow related to this situration

From A: HTTPS POST request with boost asio

#define DEMO_USING_SSL
#define BOOST_ASIO_ENABLE_HANDLER_TRACKING

#include <iostream>
#include <iomanip>
#include <boost/bind.hpp>
#include <boost/asio.hpp>
#include <boost/asio/ssl.hpp>

class client
{
public:
  client(boost::asio::io_service& io_service,
      boost::asio::ssl::context& context,
      boost::asio::ip::tcp::resolver::iterator endpoint_iterator)
    : socket_(io_service
#ifdef DEMO_USING_SSL
            , context)
  {
    socket_.set_verify_mode(boost::asio::ssl::verify_peer);
    socket_.set_verify_callback(
        boost::bind(&client::verify_certificate, this, _1, _2));
#else
            )
  {
      (void) context;
#endif

    boost::asio::async_connect(socket_.lowest_layer(), endpoint_iterator,
        boost::bind(&client::handle_connect, this,
          boost::asio::placeholders::error));
  }

  bool verify_certificate(bool preverified,
      boost::asio::ssl::verify_context& ctx)
  {
      // The verify callback can be used to check whether the certificate that is
      // being presented is valid for the peer. For example, RFC 2818 describes
      // the steps involved in doing this for HTTPS. Consult the OpenSSL
      // documentation for more details. Note that the callback is called once
      // for each certificate in the certificate chain, starting from the root
      // certificate authority.

      // In this example we will simply print the certificate's subject name.
      char subject_name[256];
      X509* cert = X509_STORE_CTX_get_current_cert(ctx.native_handle());
      X509_NAME_oneline(X509_get_subject_name(cert), subject_name, 256);
      std::cout << "Verifying " << subject_name << "\n";

      return preverified;
  }

  void handle_connect(const boost::system::error_code& error)
  {
#ifdef DEMO_USING_SSL
      if (!error)
      {
          socket_.async_handshake(boost::asio::ssl::stream_base::client,
                  boost::bind(&client::handle_handshake, this,
                      boost::asio::placeholders::error));
      }
      else
      {
          std::cout << "Connect failed: " << error.message() << "\n";
      }
#else
      handle_handshake(error);
#endif
  }

  void handle_handshake(const boost::system::error_code& error)
  {
      if (!error)
      {
          std::cout << "Enter message: ";
          static char const raw[] = "POST / HTTP/1.1\r\nHost: www.example.com\r\nConnection: close\r\n\r\n";

          static_assert(sizeof(raw)<=sizeof(request_), "too large");

          size_t request_length = strlen(raw);
          std::copy(raw, raw+request_length, request_);

          {
              // used this for debugging:
              std::ostream hexos(std::cout.rdbuf());
              for(auto it = raw; it != raw+request_length; ++it)
                  hexos << std::hex << std::setw(2) << std::setfill('0') << std::showbase << ((short unsigned) *it) << " ";
              std::cout << "\n";
          }

          boost::asio::async_write(socket_,
                  boost::asio::buffer(request_, request_length),
                  boost::bind(&client::handle_write, this,
                      boost::asio::placeholders::error,
                      boost::asio::placeholders::bytes_transferred));
      }
      else
      {
          std::cout << "Handshake failed: " << error.message() << "\n";
      }
  }

  void handle_write(const boost::system::error_code& error,
      size_t /*bytes_transferred*/)
  {
      if (!error)
      {
          std::cout << "starting read loop\n";
          boost::asio::async_read_until(socket_,
                  //boost::asio::buffer(reply_, sizeof(reply_)),
                  reply_, '\n',
                  boost::bind(&client::handle_read, this,
                      boost::asio::placeholders::error,
                      boost::asio::placeholders::bytes_transferred));
      }
      else
      {
          std::cout << "Write failed: " << error.message() << "\n";
      }
  }

  void handle_read(const boost::system::error_code& error, size_t /*bytes_transferred*/)
  {
      if (!error)
      {
          std::cout << "Reply: " << &reply_ << "\n";
      }
      else
      {
          std::cout << "Read failed: " << error.message() << "\n";
      }
  }

private:
#ifdef DEMO_USING_SSL
  boost::asio::ssl::stream<boost::asio::ip::tcp::socket> socket_;
#else
  boost::asio::ip::tcp::socket socket_;
#endif
  char request_[1024];
  boost::asio::streambuf reply_;
};

int main(int argc, char* argv[])
{
    try
    {
        if (argc != 3)
        {
            std::cerr << "Usage: client <host> <port>\n";
            return 1;
        }

        boost::asio::io_service io_service;

        boost::asio::ip::tcp::resolver resolver(io_service);
        boost::asio::ip::tcp::resolver::query query(argv[1], argv[2]);
        boost::asio::ip::tcp::resolver::iterator iterator = resolver.resolve(query);

        boost::asio::ssl::context ctx(boost::asio::ssl::context::sslv23);
        ctx.set_default_verify_paths();

        client c(io_service, ctx, iterator);

        io_service.run();
    }
    catch (std::exception& e)
    {
        std::cerr << "Exception: " << e.what() << "\n";
    }

    return 0;
}