Qt C++ SSL/TLS server with Python client

Question

Qt version: 5.8.0

Python version: 2.7.13

OpenSSL version: OpenSSL 1.0.1c

Operating system: Windows 10

I'm trying to create an SSL/TLS server using Qt C++ and a client written in Python. I'm using the sslechoserver example project that shipped with Qt. For an example Python client, I'm using the one I got from this Python documentation : https://docs.python.org/2/library/ssl.html . I copied the cert from the above-mentioned server example and placed it next to the Python script and specified that in the test scripts I tried.

I have also tried various Python client examples I have found on the internet (like here: https://carlo-hamalainen.net/blog/2013/1/24/python-ssl-socket-echo-test-with-self-signed-certificate ), but none were able to fully connect to the Qt echo server (it never printed out Client connected: like it does when I use the sslechoclient example that also shipped with Qt). The client in the link above does work with the Python server from the same link, so I know it still works with something.

Qt C++ server code

sslechoserver.cpp

/****************************************************************************
**
** Copyright (C) 2016 Kurt Pattyn <pattyn.kurt@gmail.com>.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtWebSockets module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** BSD License Usage
** Alternatively, you may use this file under the terms of the BSD license
** as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
**   * Redistributions of source code must retain the above copyright
**     notice, this list of conditions and the following disclaimer.
**   * Redistributions in binary form must reproduce the above copyright
**     notice, this list of conditions and the following disclaimer in
**     the documentation and/or other materials provided with the
**     distribution.
**   * Neither the name of The Qt Company Ltd nor the names of its
**     contributors may be used to endorse or promote products derived
**     from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "sslechoserver.h"
#include "QtWebSockets/QWebSocketServer"
#include "QtWebSockets/QWebSocket"
#include <QtCore/QDebug>
#include <QtCore/QFile>
#include <QtNetwork/QSslCertificate>
#include <QtNetwork/QSslKey>

QT_USE_NAMESPACE

//! [constructor]
SslEchoServer::SslEchoServer(quint16 port, QObject *parent) :
    QObject(parent),
    m_pWebSocketServer(Q_NULLPTR)
{
    m_pWebSocketServer = new QWebSocketServer(QStringLiteral("SSL Echo Server"),
                                              QWebSocketServer::SecureMode,
                                              this);
    QSslConfiguration sslConfiguration;
    QFile certFile(QStringLiteral(":/localhost.cert"));
    QFile keyFile(QStringLiteral(":/localhost.key"));
    certFile.open(QIODevice::ReadOnly);
    keyFile.open(QIODevice::ReadOnly);
    QSslCertificate certificate(&certFile, QSsl::Pem);
    QSslKey sslKey(&keyFile, QSsl::Rsa, QSsl::Pem);
    certFile.close();
    keyFile.close();
    sslConfiguration.setPeerVerifyMode(QSslSocket::VerifyNone);
    sslConfiguration.setLocalCertificate(certificate);
    sslConfiguration.setPrivateKey(sslKey);
    sslConfiguration.setProtocol(QSsl::TlsV1SslV3);
//    sslConfiguration.setProtocol(QSsl::TlsV1_2OrLater);
    m_pWebSocketServer->setSslConfiguration(sslConfiguration);

    if (m_pWebSocketServer->listen(QHostAddress::Any, port))
    {
        qDebug() << "SSL Echo Server listening on port" << port;
        connect(m_pWebSocketServer, &QWebSocketServer::newConnection,
                this, &SslEchoServer::onNewConnection);
        connect(m_pWebSocketServer, &QWebSocketServer::sslErrors,
                this, &SslEchoServer::onSslErrors);
    }
}
//! [constructor]

SslEchoServer::~SslEchoServer()
{
    m_pWebSocketServer->close();
    qDeleteAll(m_clients.begin(), m_clients.end());
}

//! [onNewConnection]
void SslEchoServer::onNewConnection()
{
    QWebSocket *pSocket = m_pWebSocketServer->nextPendingConnection();

    qDebug() << "Client connected:" << pSocket->peerName() << pSocket->origin();

    connect(pSocket, &QWebSocket::textMessageReceived, this, &SslEchoServer::processTextMessage);
    connect(pSocket, &QWebSocket::binaryMessageReceived,
            this, &SslEchoServer::processBinaryMessage);
    connect(pSocket, &QWebSocket::disconnected, this, &SslEchoServer::socketDisconnected);

    m_clients << pSocket;
}
//! [onNewConnection]

//! [processTextMessage]
void SslEchoServer::processTextMessage(QString message)
{
    QWebSocket *pClient = qobject_cast<QWebSocket *>(sender());
    if (pClient)
    {
        pClient->sendTextMessage(message);
    }
}
//! [processTextMessage]

//! [processBinaryMessage]
void SslEchoServer::processBinaryMessage(QByteArray message)
{
    QWebSocket *pClient = qobject_cast<QWebSocket *>(sender());
    if (pClient)
    {
        pClient->sendBinaryMessage(message);
    }
}
//! [processBinaryMessage]

//! [socketDisconnected]
void SslEchoServer::socketDisconnected()
{
    qDebug() << "Client disconnected";
    QWebSocket *pClient = qobject_cast<QWebSocket *>(sender());
    if (pClient)
    {
        m_clients.removeAll(pClient);
        pClient->deleteLater();
    }
}

void SslEchoServer::onSslErrors(const QList<QSslError> &)
{
    qDebug() << "Ssl errors occurred";
}
//! [socketDisconnected]

sslechoserver.h

/****************************************************************************
**
** Copyright (C) 2016 Kurt Pattyn <pattyn.kurt@gmail.com>.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtWebSockets module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** BSD License Usage
** Alternatively, you may use this file under the terms of the BSD license
** as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
**   * Redistributions of source code must retain the above copyright
**     notice, this list of conditions and the following disclaimer.
**   * Redistributions in binary form must reproduce the above copyright
**     notice, this list of conditions and the following disclaimer in
**     the documentation and/or other materials provided with the
**     distribution.
**   * Neither the name of The Qt Company Ltd nor the names of its
**     contributors may be used to endorse or promote products derived
**     from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef SSLECHOSERVER_H
#define SSLECHOSERVER_H

#include <QtCore/QObject>
#include <QtCore/QList>
#include <QtCore/QByteArray>
#include <QtNetwork/QSslError>

QT_FORWARD_DECLARE_CLASS(QWebSocketServer)
QT_FORWARD_DECLARE_CLASS(QWebSocket)

class SslEchoServer : public QObject
{
    Q_OBJECT
public:
    explicit SslEchoServer(quint16 port, QObject *parent = Q_NULLPTR);
    virtual ~SslEchoServer();

private Q_SLOTS:
    void onNewConnection();
    void processTextMessage(QString message);
    void processBinaryMessage(QByteArray message);
    void socketDisconnected();
    void onSslErrors(const QList<QSslError> &errors);

private:
    QWebSocketServer *m_pWebSocketServer;
    QList<QWebSocket *> m_clients;
};

#endif //SSLECHOSERVER_H

main.cpp

/****************************************************************************
**
** Copyright (C) 2016 Kurt Pattyn <pattyn.kurt@gmail.com>.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtWebSockets module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** BSD License Usage
** Alternatively, you may use this file under the terms of the BSD license
** as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
**   * Redistributions of source code must retain the above copyright
**     notice, this list of conditions and the following disclaimer.
**   * Redistributions in binary form must reproduce the above copyright
**     notice, this list of conditions and the following disclaimer in
**     the documentation and/or other materials provided with the
**     distribution.
**   * Neither the name of The Qt Company Ltd nor the names of its
**     contributors may be used to endorse or promote products derived
**     from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include <QtCore/QCoreApplication>
#include "sslechoserver.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    SslEchoServer server(1234);

    Q_UNUSED(server);

    return a.exec();
}

Python client code (just one of the ones I tried)

import socket, ssl

context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
context.verify_mode = ssl.CERT_REQUIRED
context.check_hostname = True
context.load_verify_locations("localhost.cert")
# context.load_default_certs()

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ssl_sock = context.wrap_socket(s, server_hostname='localhost')
ssl_sock.connect(('localhost', 1234))

Answer 1

Turns out I had to make my Python client connect use wss . I installed Websocket (version 0.40 ) from https://pypi.python.org/pypi/websocket-client and used the example script below. I used Python 3.6.1 , but I think 2.7.x might work as well.

import websocket
import time
import ssl

if __name__ == "__main__":
    websocket.enableTrace(True)
    ws = websocket.WebSocket(sslopt={"ca_certs": "localhost.cert",
                                      "cert_reqs": ssl.CERT_REQUIRED})
    ws.connect("wss://localhost:1234")
    print ("Sending 'Hello, World'...")
    ws.send("Hello, World")
    print ("Sent")
    print ("Receiving...")
    result =  ws.recv()
    print ("Received '%s'" % result)
    ws.close()