Mac: open preferences for user if Imager is not allowed access

Normally the system will prompt the user to allow Imager access
to removable volumes.
Open preferences and ask user to allow Imager manually in a
corner case in which this does not occur.

downloadthread.cpp

@@ -171,8 +171,17 @@ bool DownloadThread::_openAndPrepareDevice()
 #ifdef Q_OS_DARWIN
     _filename.replace("/dev/disk", "/dev/rdisk");
 
-    if (!_file.authOpen(_filename)) {
-        emit error(tr("Error running authopen to gain access to disk device '%1'").arg(QString(_filename)));
+    auto authopenresult = _file.authOpen(_filename);
+
+    if (authopenresult == _file.authOpenCancelled) {
+        /* User cancelled authentication */
+        emit error(tr("Authentication cancelled"));
+        return false;
+    } else if (authopenresult == _file.authOpenError) {
+        QString msg = tr("Error running authopen to gain access to disk device '%1'").arg(QString(_filename));
+        msg += "<br>"+tr("Please verify if 'Raspberry Pi Imager' is allowed access to 'removable volumes' in privacy settings (under 'files and folders' or alternatively give it 'full disk access').");
+        QProcess::execute("open x-apple.systempreferences:com.apple.preference.security?Privacy_AllFiles");
+        emit error(msg);
         return false;
     }
 #else

mac/macfile.cpp

@@ -22,7 +22,7 @@ bool MacFile::isSequential() const
     return false;
 }
 
-bool MacFile::authOpen(const QByteArray &filename)
+MacFile::authOpenResult MacFile::authOpen(const QByteArray &filename)
 {
     int fd = -1;
 
@@ -34,13 +34,13 @@ bool MacFile::authOpen(const QByteArray &filename)
             kAuthorizationFlagPreAuthorize;
     AuthorizationRef authRef;
     if (AuthorizationCreate(&rights, nullptr, flags, &authRef) != 0)
-        return false;
+        return authOpenCancelled;
 
     AuthorizationExternalForm externalForm;
     if (AuthorizationMakeExternalForm(authRef, &externalForm) != 0)
     {
         AuthorizationFree(authRef, 0);
-        return false;
+        return authOpenError;
     }
 
     const char *cmd = "/usr/libexec/authopen";
@@ -110,17 +110,17 @@ bool MacFile::authOpen(const QByteArray &filename)
         if (wpid == -1)
         {
             qDebug() << "waitpid() failed executing authopen";
-            return false;
+            return authOpenError;
         }
         if (WEXITSTATUS(status))
         {
             qDebug() << "authopen returned failure code" << WEXITSTATUS(status);
-            return false;
+            return authOpenError;
         }
 
         qDebug() << "fd received:" << fd;
     }
     AuthorizationFree(authRef, 0);
 
-    return open(fd, QIODevice::ReadWrite | QIODevice::ExistingOnly | QIODevice::Unbuffered, QFileDevice::AutoCloseHandle);
+    return open(fd, QIODevice::ReadWrite | QIODevice::ExistingOnly | QIODevice::Unbuffered, QFileDevice::AutoCloseHandle) ? authOpenSuccess : authOpenError;
 }

mac/macfile.h

@@ -12,9 +12,11 @@ class MacFile : public QFile
 {
     Q_OBJECT
 public:
+    enum authOpenResult {authOpenCancelled, authOpenSuccess, authOpenError };
+
     MacFile(QObject *parent = nullptr);
     virtual bool isSequential() const;
-    bool authOpen(const QByteArray &filename);
+    authOpenResult authOpen(const QByteArray &filename);
 };
 
 #endif // MACFILE_H