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.

src/Platform.h

@@ -136,6 +136,11 @@ 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  * @post \c file is no longer valid and should not be used.

src/frontend/qt_sdl/Config.cpp

@@ -378,19 +378,25 @@ ConfigEntry ConfigFile[] =
 };
 
 
-void LoadFile(int inst)
+bool LoadFile(int inst, int actualinst)
 {
     Platform::FileHandle* f;
     if (inst > 0)
     {
         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()

src/frontend/qt_sdl/Config.h

@@ -204,7 +204,7 @@ extern bool GdbARM7BreakOnStartup;
 extern bool GdbARM9BreakOnStartup;
 
 
-void Load();
+bool Load();
 void Save();
 
 }

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);

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);
 }

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;