If a winsock2 socket is non-blocking, would an SSL object associated with it also exhibit non-blocking behavior?

Question

I'm asking this question because I am unsure whether an SSL object treats a socket as a sink/source for messages like it does with a BIO object. My gut is telling me yes, but I'm not certain.

Goal: I am integrating a SSL authentication into already existing TCP code. Rather than calling the conventional send()/receive(), I would like to direct the messages through OpenSSL's SSL_read()/SSL_write() instead. My other requirement is that communication is non-blocking and data can be partially sent.

Here's how I've associated the SSL object with the socket (Server code).

SSL_Init(std::wstring &peer_hostname, SOCKET sock){
        //...
        //Initialize SSL structure
                ssl = SSL_new(context);
                if (ssl == NULL){
                    mr = APPZRETURN(E_FAIL, L"%ls (%d) : SSL_new failed. Unable to create SSL structure", __FUNCTIONW__, __LINE__);
                }

                //Agent uses winsock class, but OpenSSL uses unix socket. Surpressed warning added here for 4244. It works
                if (SSL_set_fd(ssl, sock) == 0){    //set file descriptor for ssl
                    //Operation failed
                    return -1;
        }
        //...
        int status = SSL_accept(ssl);   
        SSL_set_mode(ssl, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER|SSL_MODE_ENABLE_PARTIAL_WRITE);
        //...
    }

According to the documentation for SSL_read() [ https://www.openssl.org/docs/ssl/SSL_read.html] , the SSL is non-blocking if the underlying BIO is non-blocking. If my assumption is correct, does that mean if the socket is non-blocking, the SSL is as well?

Extension of my Question : Is a winsock tcp socket non-blocking by default (assuming I have created a TCP socket, but have not called ioctlsocket and set non-blocking mode)

Thank you for taking the time to read this. It's much appreciated.

Answer 1

If my assumption is correct, does that mean if the socket is non-blocking, the SSL is as well?

Yes.

Is a winsock tcp socket non-blocking by default (assuming I have created a TCP socket, but have not called ioctlsocket and set non-blocking mode)

Unix sockets are by default blocking. Haven't used Winsock. But am sure Winsock should be by default blocking.

Answer 2

try following code:

   SSL_set_fd(ss, sock);
retry:
   int ret = SSL_accept(ssl);
   if (ret != 1) {
      int err = SSL_get_error(ssl, ret);
      if (err == SSL_ERROR_WANT_READ || SSL_ERROR_WANT_WRITE) {
         // maybe need some sleep or select
         goto retry;
      }
   }