Linux distros that use NetworkManager: prefill WLAN PSK

Only supported when NetworkManager is used on the Linux distro
as wpa_supplicant itself does not support reading PSKs through
DBus, only setting them.

Closes #457

src/linux/networkmanagerapi.cpp

@@ -0,0 +1,59 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright (C) 2022 Raspberry Pi Ltd
+ */
+
+#include "networkmanagerapi.h"
+#include <QDBusMetaType>
+#include <QDBusInterface>
+#include <QDBusReply>
+#include <QDebug>
+
+typedef QMap<QString, QVariantMap> VariantMapMap;
+Q_DECLARE_METATYPE(VariantMapMap)
+
+NetworkManagerApi::NetworkManagerApi(QObject *parent)
+    : QObject{parent}
+{
+
+}
+
+QString NetworkManagerApi::getPSK()
+{
+    qDBusRegisterMetaType<VariantMapMap>();
+    QDBusInterface nm("org.freedesktop.NetworkManager", "/org/freedesktop/NetworkManager",
+                      "org.freedesktop.NetworkManager", QDBusConnection::systemBus());
+
+    if (!nm.isValid())
+    {
+        qDebug() << "NetworkManager not available";
+        return QString();
+    }
+
+    const auto activeConnections = nm.property("ActiveConnections").value<QList<QDBusObjectPath>>();
+    for (const QDBusObjectPath &activeConnection : activeConnections)
+    {
+        QString activeConnectionPath = activeConnection.path();
+        if (activeConnectionPath.isEmpty())
+            continue;
+        QDBusInterface ac("org.freedesktop.NetworkManager", activeConnectionPath,
+                          "org.freedesktop.NetworkManager.Connection.Active", QDBusConnection::systemBus());
+        if (!ac.isValid())
+            continue;
+        QString settingsPath = ac.property("Connection").value<QDBusObjectPath>().path();
+        if (settingsPath.isEmpty())
+            continue;
+        QDBusInterface settings("org.freedesktop.NetworkManager", settingsPath,
+                          "org.freedesktop.NetworkManager.Settings.Connection", QDBusConnection::systemBus());
+        if (!settings.isValid())
+            continue;
+        QDBusReply<VariantMapMap> reply = settings.call("GetSecrets", "802-11-wireless-security");
+        if (!reply.isValid())
+            continue;
+        QVariantMap secrets = reply.value().value("802-11-wireless-security");
+        if (secrets.contains("psk"))
+            return secrets.value("psk").toString();
+    }
+
+    return QString();
+}

src/linux/networkmanagerapi.h

@@ -0,0 +1,22 @@
+#ifndef NETWORKMANAGERAPI_H
+#define NETWORKMANAGERAPI_H
+
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright (C) 2022 Raspberry Pi Ltd
+ */
+
+#include <QObject>
+
+class NetworkManagerApi : public QObject
+{
+    Q_OBJECT
+public:
+    explicit NetworkManagerApi(QObject *parent = nullptr);
+    QString getPSK();
+
+signals:
+
+};
+
+#endif // NETWORKMANAGERAPI_H