Ssl: Copy the on-demand cert loading bool from default config

Otherwise individual sockets will still load system certificates when
a chain doesn't match against the configured CA certificates.
That's not intended behavior, since specifically setting the CA
certificates means you don't want the system certificates to be used.

Follow-up to/amends ada2c573c1a25f8d96577734968fe317ddfa292a

This is potentially a breaking change because now, if you ever add a
CA to the default config, it will disable loading system certificates
on demand for all sockets. And the only way to re-enable it is to
create a null-QSslConfiguration and set it as the new default.

Change-Id: Ic3b2ab125c0cdd58ad654af1cb36173960ce2d1e
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
(cherry picked from commit 57ba6260c0801055b7188fdaa1818b940590f5f1)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/network/ssl/qsslsocket.cpp

@@ -2007,6 +2007,10 @@ QSslSocketPrivate::QSslSocketPrivate()
     , flushTriggered(false)
 {
     QSslConfigurationPrivate::deepCopyDefaultConfiguration(&configuration);
+    // If the global configuration doesn't allow root certificates to be loaded
+    // on demand then we have to disable it for this socket as well.
+    if (!configuration.allowRootCertOnDemandLoading)
+        allowRootCertOnDemandLoading = false;
 
     const auto *tlsBackend = tlsBackendInUse();
     if (!tlsBackend) {
@@ -2312,6 +2316,7 @@ void QSslConfigurationPrivate::deepCopyDefaultConfiguration(QSslConfigurationPri
     ptr->sessionProtocol = global->sessionProtocol;
     ptr->ciphers = global->ciphers;
     ptr->caCertificates = global->caCertificates;
+    ptr->allowRootCertOnDemandLoading = global->allowRootCertOnDemandLoading;
     ptr->protocol = global->protocol;
     ptr->peerVerifyMode = global->peerVerifyMode;
     ptr->peerVerifyDepth = global->peerVerifyDepth;

tests/manual/network/ssl/client-auth/tst_manual_ssl_client_auth.cpp

@@ -16,6 +16,9 @@
 // but the other side presents a certificate signed by a different CA.
 constexpr bool TestServerPresentsIncorrectCa = false;
 constexpr bool TestClientPresentsIncorrectCa = true;
+// Decides whether or not to put the root CA into the global ssl configuration
+// or into the socket's specific ssl configuration.
+constexpr bool UseGlobalConfiguration = true;
 
 class ServerThread : public QThread
 {
@@ -26,8 +29,10 @@ public:
         QSslServer server;
 
         QSslConfiguration config = server.sslConfiguration();
+        if (!UseGlobalConfiguration) {
             QList<QSslCertificate> certs = QSslCertificate::fromPath(QStringLiteral(":/rootCA.pem"));
             config.setCaCertificates(certs);
+        }
         config.setLocalCertificate(QSslCertificate::fromPath(QStringLiteral(":/127.0.0.1.pem"))
                                            .first());
         QFile keyFile(QStringLiteral(":/127.0.0.1-key.pem"));
@@ -73,6 +78,12 @@ int main(int argc, char **argv)
     if (!QFileInfo(u":/rootCA.pem"_s).exists())
         qFatal("rootCA.pem not found. Did you run generate.sh in the certs directory?");
 
+    if (UseGlobalConfiguration) {
+        QSslConfiguration config = QSslConfiguration::defaultConfiguration();
+        config.setCaCertificates(QSslCertificate::fromPath(u":/rootCA.pem"_s));
+        QSslConfiguration::setDefaultConfiguration(config);
+    }
+
     ServerThread serverThread;
     serverThread.start();
 
@@ -88,12 +99,19 @@ int main(int argc, char **argv)
         keyFileName = u":/accepted-client-key.pem"_s;
     }
     config.setLocalCertificate(QSslCertificate::fromPath(certificatePath).first());
-    if (TestServerPresentsIncorrectCa) // true: Verify server using incorrect CA: should fail
+    if (!UseGlobalConfiguration && TestServerPresentsIncorrectCa) {
+        // Verify server using incorrect CA: should fail
         config.setCaCertificates(QSslCertificate::fromPath(u":/rootCA.pem"_s));
+    } else if (UseGlobalConfiguration && !TestServerPresentsIncorrectCa) {
+        // Verify server using correct CA, we need to explicitly set the
+        // system CAs when the global config is overridden.
+        config.setCaCertificates(QSslConfiguration::systemCaCertificates());
+    }
     QFile keyFile(keyFileName);
     if (!keyFile.open(QIODevice::ReadOnly))
         qFatal("Failed to open key file");
     config.setPrivateKey(QSslKey(&keyFile, QSsl::Rsa));
+
     socket.setSslConfiguration(config);
 
     QObject::connect(&socket, &QSslSocket::encrypted, []() { qDebug() << "[c] encrypted"; });