Check for write permissions for some key files (#1972)

* check if an nds save file can be opened for writing

also add the ability to open a file in append mode

* fix multi-instance saves

also move the check for file writability into a separate function (probably uneeded?)

* implement check for gba roms

* move rom load error messages into the functions

also finish gba slot (oops)

* improve error string

* check write perms before saving path settings

* fix memory leak

* check for writability of firmware/nand/sds

* add secondary checks for nand/firmware

* add check for config file being writable

* Return the file write error as a QString to avoid the invalid char*
causing a garbled error message.

Qt wants it as QString either way.

10 files changed, 199 insertions, 50 deletions

diff --git a/src/Platform.h b/src/Platform.h
index 21b3d46..425c712 100644
--- a/src/Platform.h
+++ b/src/Platform.h
@@ -137,6 +137,11 @@ enum FileMode : unsigned {
     Text = 0b01'00'00,
 
     /**
+     * Opens a file in append mode.
+     */
+    Append = 0b10'00'00,
+
+    /**
      * Opens a file for reading and writing.
      * Equivalent to <tt>Read | Write</tt>.
      */
@@ -201,6 +206,13 @@ FileHandle* OpenLocalFile(const std::string& path, FileMode mode);
 bool FileExists(const std::string& name);
 bool LocalFileExists(const std::string& name);
 
+// Returns true if we have permission to write to the file.
+// Warning: Also creates the file if not present!
+bool CheckFileWritable(const std::string& filepath);
+
+// Same as above (CheckFileWritable()) but for local files.
+bool CheckLocalFileWritable(const std::string& filepath);
+
 /** Close a file opened with \c OpenFile.
  * @returns \c true if the file was closed successfully, false otherwise.
  * @post \c file is no longer valid and should not be used.
diff --git a/src/frontend/qt_sdl/Config.cpp b/src/frontend/qt_sdl/Config.cpp
index 215ad0b..2fdfc3b 100644
--- a/src/frontend/qt_sdl/Config.cpp
+++ b/src/frontend/qt_sdl/Config.cpp
@@ -378,7 +378,7 @@ ConfigEntry ConfigFile[] =
 };
 
 
-void LoadFile(int inst)
+bool LoadFile(int inst, int actualinst)
 {
     Platform::FileHandle* f;
     if (inst > 0)
@@ -386,11 +386,17 @@ void LoadFile(int inst)
         char name[100] = {0};
         snprintf(name, 99, kUniqueConfigFile, inst+1);
         f = Platform::OpenLocalFile(name, Platform::FileMode::ReadText);
+
+        if (!Platform::CheckLocalFileWritable(name)) return false;
     }
     else
+    {
         f = Platform::OpenLocalFile(kConfigFile, Platform::FileMode::ReadText);
 
-    if (!f) return;
+        if (actualinst == 0 && !Platform::CheckLocalFileWritable(kConfigFile)) return false;
+    }
+
+    if (!f) return true;
 
     char linebuf[1024];
     char entryname[32];
@@ -425,9 +431,10 @@ void LoadFile(int inst)
     }
 
     CloseFile(f);
+    return true;
 }
 
-void Load()
+bool Load()
 {
 
     for (ConfigEntry* entry = &ConfigFile[0]; entry->Value; entry++)
@@ -440,12 +447,14 @@ void Load()
         case 3: *(int64_t*)entry->Value = std::get<int64_t>(entry->Default); break;
         }
     }
-
-    LoadFile(0);
-
+    
     int inst = Platform::InstanceID();
+
+    bool ret = LoadFile(0, inst);
     if (inst > 0)
-        LoadFile(inst);
+        ret = LoadFile(inst, inst);
+
+    return ret;
 }
 
 void Save()
diff --git a/src/frontend/qt_sdl/Config.h b/src/frontend/qt_sdl/Config.h
index 1893065..722384a 100644
--- a/src/frontend/qt_sdl/Config.h
+++ b/src/frontend/qt_sdl/Config.h
@@ -204,7 +204,7 @@ extern bool GdbARM7BreakOnStartup;
 extern bool GdbARM9BreakOnStartup;
 
 
-void Load();
+bool Load();
 void Save();
 
 }
diff --git a/src/frontend/qt_sdl/EmuSettingsDialog.cpp b/src/frontend/qt_sdl/EmuSettingsDialog.cpp
index 0a834a6..ca9c671 100644
--- a/src/frontend/qt_sdl/EmuSettingsDialog.cpp
+++ b/src/frontend/qt_sdl/EmuSettingsDialog.cpp
@@ -380,6 +380,12 @@ void EmuSettingsDialog::on_btnFirmwareBrowse_clicked()
 
     if (file.isEmpty()) return;
 
+    if (!Platform::CheckFileWritable(file.toStdString()))
+    {
+        QMessageBox::critical(this, "melonDS", "Unable to write to firmware file.\nPlease check file/folder write permissions.");
+        return;
+    }
+
     updateLastBIOSFolder(file);
 
     ui->txtFirmwarePath->setText(file);
@@ -436,6 +442,12 @@ void EmuSettingsDialog::on_btnDLDISDBrowse_clicked()
 
     if (file.isEmpty()) return;
 
+    if (!Platform::CheckFileWritable(file.toStdString()))
+    {
+        QMessageBox::critical(this, "melonDS", "Unable to write to DLDI SD image.\nPlease check file/folder write permissions.");
+        return;
+    }
+
     updateLastBIOSFolder(file);
 
     ui->txtDLDISDPath->setText(file);
@@ -468,6 +480,13 @@ void EmuSettingsDialog::on_btnDSiFirmwareBrowse_clicked()
 
     if (file.isEmpty()) return;
 
+    if (!Platform::CheckFileWritable(file.toStdString()))
+    {
+        QMessageBox::critical(this, "melonDS", "Unable to write to DSi firmware file.\nPlease check file/folder write permissions.");
+        return;
+    }
+
+
     updateLastBIOSFolder(file);
 
     ui->txtDSiFirmwarePath->setText(file);
@@ -482,6 +501,13 @@ void EmuSettingsDialog::on_btnDSiNANDBrowse_clicked()
 
     if (file.isEmpty()) return;
 
+    if (!Platform::CheckFileWritable(file.toStdString()))
+    {
+        QMessageBox::critical(this, "melonDS", "Unable to write to DSi NAND image.\nPlease check file/folder write permissions.");
+        return;
+    }
+
+
     updateLastBIOSFolder(file);
 
     ui->txtDSiNANDPath->setText(file);
@@ -510,6 +536,12 @@ void EmuSettingsDialog::on_btnDSiSDBrowse_clicked()
 
     if (file.isEmpty()) return;
 
+    if (!Platform::CheckFileWritable(file.toStdString()))
+    {
+        QMessageBox::critical(this, "melonDS", "Unable to write to DSi SD image.\nPlease check file/folder write permissions.");
+        return;
+    }
+
     updateLastBIOSFolder(file);
 
     ui->txtDSiSDPath->setText(file);
diff --git a/src/frontend/qt_sdl/PathSettingsDialog.cpp b/src/frontend/qt_sdl/PathSettingsDialog.cpp
index 1d69853..7134208 100644
--- a/src/frontend/qt_sdl/PathSettingsDialog.cpp
+++ b/src/frontend/qt_sdl/PathSettingsDialog.cpp
@@ -19,6 +19,7 @@
 #include <stdio.h>
 #include <QFileDialog>
 #include <QMessageBox>
+#include <QTemporaryFile>
 
 #include "types.h"
 #include "Config.h"
@@ -37,6 +38,7 @@ extern bool RunningSomething;
 
 bool PathSettingsDialog::needsReset = false;
 
+constexpr char errordialog[] = "melonDS cannot write to that directory.";
 
 PathSettingsDialog::PathSettingsDialog(QWidget* parent) : QDialog(parent), ui(new Ui::PathSettingsDialog)
 {
@@ -101,6 +103,12 @@ void PathSettingsDialog::on_btnSaveFileBrowse_clicked()
                                                      QString::fromStdString(EmuDirectory));
 
     if (dir.isEmpty()) return;
+    
+    if (!QTemporaryFile(dir).open())
+    {
+        QMessageBox::critical(this, "melonDS", errordialog);
+        return;
+    }
 
     ui->txtSaveFilePath->setText(dir);
 }
@@ -112,6 +120,12 @@ void PathSettingsDialog::on_btnSavestateBrowse_clicked()
                                                      QString::fromStdString(EmuDirectory));
 
     if (dir.isEmpty()) return;
+    
+    if (!QTemporaryFile(dir).open())
+    {
+        QMessageBox::critical(this, "melonDS", errordialog);
+        return;
+    }
 
     ui->txtSavestatePath->setText(dir);
 }
@@ -123,6 +137,12 @@ void PathSettingsDialog::on_btnCheatFileBrowse_clicked()
                                                      QString::fromStdString(EmuDirectory));
 
     if (dir.isEmpty()) return;
+    
+    if (!QTemporaryFile(dir).open())
+    {
+        QMessageBox::critical(this, "melonDS", errordialog);
+        return;
+    }
 
     ui->txtCheatFilePath->setText(dir);
 }
diff --git a/src/frontend/qt_sdl/Platform.cpp b/src/frontend/qt_sdl/Platform.cpp
index 222e512..9bb19d1 100644
--- a/src/frontend/qt_sdl/Platform.cpp
+++ b/src/frontend/qt_sdl/Platform.cpp
@@ -217,6 +217,10 @@ std::string InstanceFileSuffix()
 
 constexpr char AccessMode(FileMode mode, bool file_exists)
 {
+
+    if (mode & FileMode::Append)
+        return  'a';
+
     if (!(mode & FileMode::Write))
         // If we're only opening the file for reading...
         return 'r';
@@ -255,7 +259,7 @@ static std::string GetModeString(FileMode mode, bool file_exists)
 
 FileHandle* OpenFile(const std::string& path, FileMode mode)
 {
-    if ((mode & FileMode::ReadWrite) == FileMode::None)
+    if ((mode & (FileMode::ReadWrite | FileMode::Append)) == FileMode::None)
     { // If we aren't reading or writing, then we can't open the file
         Log(LogLevel::Error, "Attempted to open \"%s\" in neither read nor write mode (FileMode 0x%x)\n", path.c_str(), mode);
         return nullptr;
@@ -327,6 +331,28 @@ bool LocalFileExists(const std::string& name)
     return true;
 }
 
+bool CheckFileWritable(const std::string& filepath)
+{
+    FileHandle* file = Platform::OpenFile(filepath.c_str(), FileMode::Append);
+    if (file)
+    {
+        Platform::CloseFile(file);
+        return true;
+    }
+    else return false;
+}
+
+bool CheckLocalFileWritable(const std::string& name)
+{
+    FileHandle* file = Platform::OpenLocalFile(name.c_str(), FileMode::Append);
+    if (file)
+    {
+        Platform::CloseFile(file);
+        return true;
+    }
+    else return false;
+}
+
 bool FileSeek(FileHandle* file, s64 offset, FileSeekOrigin origin)
 {
     int stdorigin;
diff --git a/src/frontend/qt_sdl/ROMManager.cpp b/src/frontend/qt_sdl/ROMManager.cpp
index 15a9ebf..e3ceebb 100644
--- a/src/frontend/qt_sdl/ROMManager.cpp
+++ b/src/frontend/qt_sdl/ROMManager.cpp
@@ -29,6 +29,7 @@
 #include <fstream>
 
 #include <QDateTime>
+#include <QMessageBox>
 
 #include <zstd.h>
 #ifdef ARCHIVE_SUPPORT_ENABLED
@@ -210,6 +211,9 @@ QString VerifyDSFirmware()
     f = Platform::OpenLocalFile(Config::FirmwarePath, FileMode::Read);
     if (!f) return "DS firmware was not found or could not be accessed. Check your emu settings.";
 
+    if (!Platform::CheckFileWritable(Config::FirmwarePath))
+        return "DS firmware is unable to be written to.\nPlease check file/folder write permissions.";
+
     len = FileLength(f);
     if (len == 0x20000)
     {
@@ -237,6 +241,9 @@ QString VerifyDSiFirmware()
     f = Platform::OpenLocalFile(Config::DSiFirmwarePath, FileMode::Read);
     if (!f) return "DSi firmware was not found or could not be accessed. Check your emu settings.";
 
+    if (!Platform::CheckFileWritable(Config::FirmwarePath))
+        return "DSi firmware is unable to be written to.\nPlease check file/folder write permissions.";
+
     len = FileLength(f);
     if (len != 0x20000)
     {
@@ -259,6 +266,9 @@ QString VerifyDSiNAND()
     f = Platform::OpenLocalFile(Config::DSiNANDPath, FileMode::ReadWriteExisting);
     if (!f) return "DSi NAND was not found or could not be accessed. Check your emu settings.";
 
+    if (!Platform::CheckFileWritable(Config::FirmwarePath))
+        return "DSi NAND is unable to be written to.\nPlease check file/folder write permissions.";
+
     // TODO: some basic checks
     // check that it has the nocash footer, and all
 
@@ -1276,7 +1286,18 @@ bool LoadROMData(const QStringList& filepath, std::unique_ptr<u8[]>& filedata, u
         return false;
 }
 
-bool LoadROM(EmuThread* emuthread, QStringList filepath, bool reset)
+QString GetSavErrorString(std::string& filepath, bool gba)
+{
+    std::string console = gba ? "GBA" : "DS";
+    std::string err1 = "Unable to write to ";
+    std::string err2 = " save.\nPlease check file/folder write permissions.\n\nAttempted to Access:\n";
+
+    err1 += console + err2 + filepath;
+
+    return QString::fromStdString(err1);
+}
+
+bool LoadROM(QMainWindow* mainWindow, EmuThread* emuthread, QStringList filepath, bool reset)
 {
     unique_ptr<u8[]> filedata = nullptr;
     u32 filelen;
@@ -1284,7 +1305,10 @@ bool LoadROM(EmuThread* emuthread, QStringList filepath, bool reset)
     std::string romname;
 
     if (!LoadROMData(filepath, filedata, filelen, basepath, romname))
+    {
+        QMessageBox::critical(mainWindow, "melonDS", "Failed to load the DS ROM.");
         return false;
+    }
 
     NDSSave = nullptr;
 
@@ -1300,7 +1324,22 @@ bool LoadROM(EmuThread* emuthread, QStringList filepath, bool reset)
     savname += Platform::InstanceFileSuffix();
 
     FileHandle* sav = Platform::OpenFile(savname, FileMode::Read);
-    if (!sav) sav = Platform::OpenFile(origsav, FileMode::Read);
+    if (!sav)
+    {
+        if (!Platform::CheckFileWritable(origsav))
+        {
+            QMessageBox::critical(mainWindow, "melonDS", GetSavErrorString(origsav, false));
+            return false;
+        }
+
+        sav = Platform::OpenFile(origsav, FileMode::Read);
+    }
+    else if (!Platform::CheckFileWritable(savname))
+    {
+        QMessageBox::critical(mainWindow, "melonDS", GetSavErrorString(savname, false));
+        return false;
+    }
+
     if (sav)
     {
         savelen = (u32)Platform::FileLength(sav);
@@ -1322,13 +1361,19 @@ bool LoadROM(EmuThread* emuthread, QStringList filepath, bool reset)
 
     auto cart = NDSCart::ParseROM(std::move(filedata), filelen, std::move(cartargs));
     if (!cart)
+    {
         // If we couldn't parse the ROM...
+        QMessageBox::critical(mainWindow, "melonDS", "Failed to load the DS ROM.");
         return false;
+    }
 
     if (reset)
     {
         if (!emuthread->UpdateConsole(std::move(cart), Keep {}))
+        {
+            QMessageBox::critical(mainWindow, "melonDS", "Failed to load the DS ROM.");
             return false;
+        }
 
         InitFirmwareSaveManager(emuthread);
         emuthread->NDS->Reset();
@@ -1351,7 +1396,7 @@ bool LoadROM(EmuThread* emuthread, QStringList filepath, bool reset)
     NDSSave = std::make_unique<SaveManager>(savname);
     LoadCheats(*emuthread->NDS);
 
-    return true;
+    return true; // success
 }
 
 void EjectCart(NDS& nds)
@@ -1388,9 +1433,13 @@ QString CartLabel()
 }
 
 
-bool LoadGBAROM(NDS& nds, QStringList filepath)
+bool LoadGBAROM(QMainWindow* mainWindow, NDS& nds, QStringList filepath)
 {
-    if (nds.ConsoleType == 1) return false; // DSi doesn't have a GBA slot
+    if (nds.ConsoleType == 1)
+    {
+        QMessageBox::critical(mainWindow, "melonDS", "The DSi doesn't have a GBA slot.");
+        return false;
+    }
 
     unique_ptr<u8[]> filedata = nullptr;
     u32 filelen;
@@ -1398,7 +1447,10 @@ bool LoadGBAROM(NDS& nds, QStringList filepath)
     std::string romname;
 
     if (!LoadROMData(filepath, filedata, filelen, basepath, romname))
+    {
+        QMessageBox::critical(mainWindow, "melonDS", "Failed to load the GBA ROM.");
         return false;
+    }
 
     GBASave = nullptr;
 
@@ -1414,7 +1466,22 @@ bool LoadGBAROM(NDS& nds, QStringList filepath)
     savname += Platform::InstanceFileSuffix();
 
     FileHandle* sav = Platform::OpenFile(savname, FileMode::Read);
-    if (!sav) sav = Platform::OpenFile(origsav, FileMode::Read);
+    if (!sav)
+    {
+        if (!Platform::CheckFileWritable(origsav))
+        {
+            QMessageBox::critical(mainWindow, "melonDS", GetSavErrorString(origsav, true));
+            return false;
+        }
+
+        sav = Platform::OpenFile(origsav, FileMode::Read);
+    }
+    else if (!Platform::CheckFileWritable(savname))
+    {
+        QMessageBox::critical(mainWindow, "melonDS", GetSavErrorString(savname, true));
+        return false;
+    }
+
     if (sav)
     {
         savelen = (u32)FileLength(sav);
@@ -1430,7 +1497,10 @@ bool LoadGBAROM(NDS& nds, QStringList filepath)
 
     auto cart = GBACart::ParseROM(std::move(filedata), filelen, std::move(savedata), savelen);
     if (!cart)
+    {
+        QMessageBox::critical(mainWindow, "melonDS", "Failed to load the GBA ROM.");
         return false;
+    }
 
     nds.SetGBACart(std::move(cart));
     GBACartType = 0;
diff --git a/src/frontend/qt_sdl/ROMManager.h b/src/frontend/qt_sdl/ROMManager.h
index 0b640c8..38ed65c 100644
--- a/src/frontend/qt_sdl/ROMManager.h
+++ b/src/frontend/qt_sdl/ROMManager.h
@@ -23,6 +23,7 @@
 #include "SaveManager.h"
 #include "AREngine.h"
 #include "DSi_NAND.h"
+#include <QMainWindow>
 
 #include "MemConstants.h"
 #include <optional>
@@ -72,12 +73,12 @@ std::optional<Firmware> LoadFirmware(int type) noexcept;
 std::optional<DSi_NAND::NANDImage> LoadNAND(const std::array<u8, DSiBIOSSize>& arm7ibios) noexcept;
 
 /// Inserts a ROM into the emulated console.
-bool LoadROM(EmuThread*, QStringList filepath, bool reset);
+bool LoadROM(QMainWindow* mainWindow, EmuThread*, QStringList filepath, bool reset);
 void EjectCart(NDS& nds);
 bool CartInserted();
 QString CartLabel();
 
-bool LoadGBAROM(NDS& nds, QStringList filepath);
+bool LoadGBAROM(QMainWindow* mainWindow, NDS& nds, QStringList filepath);
 void LoadGBAAddon(NDS& nds, int type);
 void EjectGBACart(NDS& nds);
 bool GBACartInserted();
diff --git a/src/frontend/qt_sdl/Window.cpp b/src/frontend/qt_sdl/Window.cpp
index 962fb76..0f0b71f 100644
--- a/src/frontend/qt_sdl/Window.cpp
+++ b/src/frontend/qt_sdl/Window.cpp
@@ -865,10 +865,8 @@ void MainWindow::dropEvent(QDropEvent* event)
 
     if (isNdsRom)
     {
-        if (!ROMManager::LoadROM(emuThread, file, true))
+        if (!ROMManager::LoadROM(mainWindow, emuThread, file, true))
         {
-            // TODO: better error reporting?
-            QMessageBox::critical(this, "melonDS", "Failed to load the DS ROM.");
             emuThread->emuUnpause();
             return;
         }
@@ -886,10 +884,8 @@ void MainWindow::dropEvent(QDropEvent* event)
     }
     else if (isGbaRom)
     {
-        if (!ROMManager::LoadGBAROM(*emuThread->NDS, file))
+        if (!ROMManager::LoadGBAROM(mainWindow, *emuThread->NDS, file))
         {
-            // TODO: better error reporting?
-            QMessageBox::critical(this, "melonDS", "Failed to load the GBA ROM.");
             emuThread->emuUnpause();
             return;
         }
@@ -952,12 +948,7 @@ bool MainWindow::preloadROMs(QStringList file, QStringList gbafile, bool boot)
     bool gbaloaded = false;
     if (!gbafile.isEmpty())
     {
-        if (!ROMManager::LoadGBAROM(*emuThread->NDS, gbafile))
-        {
-            // TODO: better error reporting?
-            QMessageBox::critical(this, "melonDS", "Failed to load the GBA ROM.");
-            return false;
-        }
+        if (!ROMManager::LoadGBAROM(mainWindow, *emuThread->NDS, gbafile)) return false;
 
         gbaloaded = true;
     }
@@ -965,12 +956,8 @@ bool MainWindow::preloadROMs(QStringList file, QStringList gbafile, bool boot)
     bool ndsloaded = false;
     if (!file.isEmpty())
     {
-        if (!ROMManager::LoadROM(emuThread, file, true))
-        {
-            // TODO: better error reporting?
-            QMessageBox::critical(this, "melonDS", "Failed to load the ROM.");
-            return false;
-        }
+        if (!ROMManager::LoadROM(mainWindow, emuThread, file, true)) return false;
+        
         recentFileList.removeAll(file.join("|"));
         recentFileList.prepend(file.join("|"));
         updateRecentFilesMenu();
@@ -1173,11 +1160,9 @@ void MainWindow::onOpenFile()
         emuThread->emuUnpause();
         return;
     }
-
-    if (!ROMManager::LoadROM(emuThread, file, true))
+    
+    if (!ROMManager::LoadROM(mainWindow, emuThread, file, true))
     {
-        // TODO: better error reporting?
-        QMessageBox::critical(this, "melonDS", "Failed to load the ROM.");
         emuThread->emuUnpause();
         return;
     }
@@ -1272,11 +1257,9 @@ void MainWindow::onClickRecentFile()
         emuThread->emuUnpause();
         return;
     }
-
-    if (!ROMManager::LoadROM(emuThread, file, true))
+    
+    if (!ROMManager::LoadROM(mainWindow, emuThread, file, true))
     {
-        // TODO: better error reporting?
-        QMessageBox::critical(this, "melonDS", "Failed to load the ROM.");
         emuThread->emuUnpause();
         return;
     }
@@ -1326,10 +1309,8 @@ void MainWindow::onInsertCart()
         return;
     }
 
-    if (!ROMManager::LoadROM(emuThread, file, false))
+    if (!ROMManager::LoadROM(mainWindow, emuThread, file, false))
     {
-        // TODO: better error reporting?
-        QMessageBox::critical(this, "melonDS", "Failed to load the ROM.");
         emuThread->emuUnpause();
         return;
     }
@@ -1361,10 +1342,8 @@ void MainWindow::onInsertGBACart()
         return;
     }
 
-    if (!ROMManager::LoadGBAROM(*emuThread->NDS, file))
+    if (!ROMManager::LoadGBAROM(mainWindow, *emuThread->NDS, file))
     {
-        // TODO: better error reporting?
-        QMessageBox::critical(this, "melonDS", "Failed to load the ROM.");
         emuThread->emuUnpause();
         return;
     }
diff --git a/src/frontend/qt_sdl/main.cpp b/src/frontend/qt_sdl/main.cpp
index 7e34e6a..6e87d5b 100644
--- a/src/frontend/qt_sdl/main.cpp
+++ b/src/frontend/qt_sdl/main.cpp
@@ -337,7 +337,7 @@ int main(int argc, char** argv)
     SDL_InitSubSystem(SDL_INIT_VIDEO);
     SDL_EnableScreenSaver(); SDL_DisableScreenSaver();
 
-    Config::Load();
+    if (!Config::Load()) QMessageBox::critical(NULL, "melonDS", "Unable to write to config.\nPlease check the write permissions of the folder you placed melonDS in.");
 
 #define SANITIZE(var, min, max)  { var = std::clamp(var, min, max); }
     SANITIZE(Config::ConsoleType, 0, 1);