how does a Qt application determines which openssl libs it uses?

Question

I'm on Ubuntu 16.04, running Qt5.3.0-rc and have OpenSsl 1.0.2g installed in /usr/bin. I've downloaded the latest OpenSsl 1.1.1c sources, build it and installed it in /usr/local/bin

which openssl returns the /usr/local/bin one

However, when I start a Qt application (from the same terminal window), It still seems to return the list of Ciphers of 1.0.2g

When running strace ./quicksecureclient 2>&1 | grep '^open(".*\.so"' | grep -i ssl, no ssl lib seems to be loaded.

So I think my first question is: "how does a Qt application determines which openssl libs it uses?"

The following Qt program lists only 4 PSK Ciphers (the same returned by /usr/bin/openssl ciphers -v 'ALL:eNULL' | grep PSK) while the 1.1.1 openssl returns 60 items

#include <QCoreApplication>

#include <QSslCipher>
#include <QSslConfiguration>
#include <QDebug>

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

    auto configuration = QSslConfiguration::defaultDtlsConfiguration();
    QList<QSslCipher> all_ciphers;
    all_ciphers = configuration.supportedCiphers();
    for(int i=0;i<all_ciphers.length();i++){
        if(all_ciphers[i].name().contains("PSK"))
                qDebug() << "Cipher " << all_ciphers[i].name();
    }
    qDebug() << "Ciphers: " << all_ciphers.length();
    return a.exec();
}

Edit1 I think it is hardcoded (defined when configuring/building Qt5): QSslSocket::sslLibraryBuildVersionString() prints out "OpenSSL 1.0.2k-fips 26 Jan 2017".
Given the incompatibility between 1.0 1nd 1.1 (as @LorinczyZsigmond pointed out), I currently think it is not possible to use OpenSSL 1.1 with Qt5 without rebuilding Qt from code

Try `ldd ./quicksecureclient` first. Mind you, openssl-1.0.n and openssl-1.1.1 aren't compatible, their shared libs have different major version numbers. — Lorinczy Zsigmond, Jun 08 '19 at 11:32
`ldd quicksecureclient` doesn't show a SSL library either. It does show libQt5Coap.so.5 and libQt5Network.so.5. I've added a simple example illustrating the problem. I'm not sure how to configure Qt to use a specific OpenSsl version — Marc Van Daele, Jun 08 '19 at 12:03

how does a Qt application determines which openssl libs it uses?

0 Answers0