Refactor WLAN PSK retrieval code

- Reduce platform specific code in ImageWriter class,
  and move that to seperate classes.
- Use API calls to get current SSID on Windows and Linux instead
  of launching command line utilities.

src/linux/networkmanagerapi.cpp

@@ -4,30 +4,76 @@
  */
 
 #include "networkmanagerapi.h"
+#include <QDebug>
+#include <QNetworkInterface>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/ioctl.h>
+#include <linux/wireless.h>
+
+#ifndef QT_NO_DBUS
 #include <QDBusMetaType>
 #include <QDBusInterface>
 #include <QDBusReply>
-#include <QDebug>
+#endif
 
 typedef QMap<QString, QVariantMap> VariantMapMap;
 Q_DECLARE_METATYPE(VariantMapMap)
 
-NetworkManagerApi::NetworkManagerApi(QObject *parent)
-    : QObject{parent}
+NetworkManagerApi::NetworkManagerApi()
 {
-
+#ifndef QT_NO_DBUS
+    qDBusRegisterMetaType<VariantMapMap>();
+#endif
 }
 
-QString NetworkManagerApi::getPSK()
+QByteArray NetworkManagerApi::getSSID()
 {
-    qDBusRegisterMetaType<VariantMapMap>();
+    QByteArray ssid;
+    const auto interfaces = QNetworkInterface::allInterfaces();
+
+    for (const auto &interface : interfaces)
+    {
+        if (interface.type() == interface.Wifi)
+        {
+            ssid = _getSSIDofInterface(interface.name().toLatin1());
+            if (!ssid.isEmpty())
+                break;
+        }
+    }
+
+    return ssid;
+}
+
+QByteArray NetworkManagerApi::_getSSIDofInterface(const QByteArray &iface)
+{
+    char ssid[IW_ESSID_MAX_SIZE+1] = {0};
+    struct iwreq iw = {0};
+    int s = ::socket(AF_INET, SOCK_DGRAM, 0);
+
+    if (s == -1)
+        return QByteArray();
+
+    strncpy(iw.ifr_ifrn.ifrn_name, iface.data(), sizeof(iw.ifr_ifrn.ifrn_name));
+    iw.u.essid.pointer = ssid;
+    iw.u.essid.length = IW_ESSID_MAX_SIZE;
+    ::ioctl(s, SIOCGIWESSID, &iw);
+    ::close(s);
+
+    return QByteArray(ssid);
+}
+
+QByteArray NetworkManagerApi::getPSK()
+{
+#ifndef QT_NO_DBUS
     QDBusInterface nm("org.freedesktop.NetworkManager", "/org/freedesktop/NetworkManager",
                       "org.freedesktop.NetworkManager", QDBusConnection::systemBus());
 
     if (!nm.isValid())
     {
         qDebug() << "NetworkManager not available";
-        return QString();
+        return QByteArray();
     }
 
     const auto activeConnections = nm.property("ActiveConnections").value<QList<QDBusObjectPath>>();
@@ -52,8 +98,18 @@ QString NetworkManagerApi::getPSK()
             continue;
         QVariantMap secrets = reply.value().value("802-11-wireless-security");
         if (secrets.contains("psk"))
-            return secrets.value("psk").toString();
+            return secrets.value("psk").toByteArray();
     }
+#endif
 
-    return QString();
+    return QByteArray();
+}
+
+WlanCredentials *WlanCredentials::_instance = NULL;
+WlanCredentials *WlanCredentials::instance()
+{
+    if (!_instance)
+        _instance = new NetworkManagerApi();
+
+    return _instance;
 }

src/linux/networkmanagerapi.h

@@ -6,17 +6,17 @@
  * Copyright (C) 2022 Raspberry Pi Ltd
  */
 
-#include <QObject>
+#include "wlancredentials.h"
 
-class NetworkManagerApi : public QObject
+class NetworkManagerApi : public WlanCredentials
 {
-    Q_OBJECT
 public:
-    explicit NetworkManagerApi(QObject *parent = nullptr);
-    QString getPSK();
-
-signals:
+    NetworkManagerApi();
+    virtual QByteArray getSSID();
+    virtual QByteArray getPSK();
 
+protected:
+    QByteArray _getSSIDofInterface(const QByteArray &iface);
 };
 
 #endif // NETWORKMANAGERAPI_H