Linux/macOS: enable quick format for file containers

Allow normal file-hosted containers to use quick format in the Unix volume creation path by sizing the host file with ftruncate before backup headers are written.

Enable the GUI checkbox for normal file containers and honor --quick in text mode. Update the Unix HTML documentation for the weaker deniability properties of sparse or unwritten host regions.

src/Core/VolumeCreator.cpp

@@ -253,7 +253,17 @@ namespace VeraCrypt
 				(options->Path.IsDevice() || options->Type == VolumeType::Hidden) ? File::OpenReadWrite : File::CreateReadWrite,
 				File::ShareNone);
 
-			HostSize = VolumeFile->Length();
+			if (!options->Path.IsDevice() && options->Type == VolumeType::Normal)
+			{
+				HostSize = options->Size;
+
+				if (options->Quick)
+					VolumeFile->SetLength (options->Size);
+			}
+			else
+			{
+				HostSize = VolumeFile->Length();
+			}
 		}
 
 		try

src/Main/Forms/VolumeCreationWizard.cpp

@@ -391,6 +391,7 @@ namespace VeraCrypt
 		DisplayKeyInfo (false),
 		LargeFilesSupport (false),
 		QuickFormatEnabled (false),
+		QuickFormatEnabledByWizard (false),
 		SelectedFilesystemClusterSize (0),
 		SelectedFilesystemType (VolumeCreationOptions::FilesystemType::FAT),
 		SelectedVolumeHostType (VolumeHostType::File),
@@ -446,6 +447,7 @@ namespace VeraCrypt
 				OuterVolume = false;
 				LargeFilesSupport = false;
 				QuickFormatEnabled = false;
+				QuickFormatEnabledByWizard = false;
 				Pim = 0;
 
 				SingleChoiceWizardPage <VolumeHostType::Enum> *page = new SingleChoiceWizardPage <VolumeHostType::Enum> (GetPageParent(), wxEmptyString, true);
@@ -595,15 +597,29 @@ namespace VeraCrypt
 			{
 				shared_ptr <VolumeLayout> layout ((OuterVolume || SelectedVolumeType != VolumeType::Hidden)? (VolumeLayout*) new VolumeLayoutV2Normal() : (VolumeLayout*) new VolumeLayoutV2Hidden());
 				uint64 filesystemSize = layout->GetMaxDataSize (VolumeSize);
+				bool hiddenVolumeItself = !OuterVolume && SelectedVolumeType == VolumeType::Hidden;
+				bool normalFileContainer = !OuterVolume && SelectedVolumeType == VolumeType::Normal && SelectedVolumeHostType == VolumeHostType::File;
+				bool existingDeviceSupportedCase = SelectedVolumePath.IsDevice() && !hiddenVolumeItself;
+				bool quickFormatSupported = existingDeviceSupportedCase || normalFileContainer;
 
 				VolumeFormatOptionsWizardPage *page = new VolumeFormatOptionsWizardPage (GetPageParent(), filesystemSize, SectorSize,
-					SelectedVolumePath.IsDevice() && (OuterVolume || SelectedVolumeType != VolumeType::Hidden), OuterVolume, LargeFilesSupport);
+					quickFormatSupported, OuterVolume, LargeFilesSupport);
 
 				page->SetPageTitle (LangString["FORMAT_TITLE"]);
 				page->SetFilesystemType (SelectedFilesystemType);
 
-				if (!OuterVolume && SelectedVolumeType == VolumeType::Hidden)
+				if (hiddenVolumeItself)
+				{
 					QuickFormatEnabled = true;
+					QuickFormatEnabledByWizard = true;
+				}
+				else
+				{
+					if (!quickFormatSupported || QuickFormatEnabledByWizard)
+						QuickFormatEnabled = false;
+
+					QuickFormatEnabledByWizard = false;
+				}
 				page->SetQuickFormat (QuickFormatEnabled);
 
 				return page;
@@ -1332,6 +1348,7 @@ namespace VeraCrypt
 
 				SelectedFilesystemType = page->GetFilesystemType();
 				QuickFormatEnabled = page->IsQuickFormatEnabled();
+				QuickFormatEnabledByWizard = !OuterVolume && SelectedVolumeType == VolumeType::Hidden;
 
 				if (SelectedFilesystemType != VolumeCreationOptions::FilesystemType::None
 					&& SelectedFilesystemType != VolumeCreationOptions::FilesystemType::FAT)

src/Main/Forms/VolumeCreationWizard.h

@@ -76,6 +76,7 @@ namespace VeraCrypt
 		shared_ptr <VolumeInfo> MountedOuterVolume;
 		bool OuterVolume;
 		bool QuickFormatEnabled;
+		bool QuickFormatEnabledByWizard;
 		shared_ptr <EncryptionAlgorithm> SelectedEncryptionAlgorithm;
 		uint32 SelectedFilesystemClusterSize;
 		VolumeCreationOptions::FilesystemType::Enum SelectedFilesystemType;

src/Main/TextUserInterface.cpp

@@ -766,8 +766,6 @@ namespace VeraCrypt
 				}
 			}
 
-			options->Quick = false;
-
 			uint32 sectorSizeRem = options->Size % options->SectorSize;
 			if (sectorSizeRem != 0)
 				options->Size += options->SectorSize - sectorSizeRem;
@@ -964,6 +962,18 @@ namespace VeraCrypt
 			throw_err (_("Specified volume size is too small to be used with Btrfs filesystem."));
 		}
 
+		if (options->Quick && options->Type == VolumeType::Normal)
+		{
+			if (Preferences.NonInteractive)
+			{
+				ShowWarning (_("Quick Format is enabled. Do not use --quick for an outer volume intended to contain a hidden volume. It skips writing random data to unused volume space, reducing plausible deniability. For file containers, actual disk savings depend on host filesystem sparse-file support, and later writes can fail if host space runs out."));
+			}
+			else if (!AskYesNo (LangString["WARN_QUICK_FORMAT"], false, true))
+			{
+				throw UserAbort (SRC_POS);
+			}
+		}
+
 		// Password
 		if (!options->Password && !Preferences.NonInteractive)
 		{

src/Main/UserInterface.cpp

@@ -1219,7 +1219,7 @@ const FileManager fileManagers[] = {
 					" Inexperienced users should use the graphical user interface to create a hidden\n"
 					" volume. When using the text user interface, the following procedure must be\n"
 					" followed to create a hidden volume:\n"
-					"  1) Create an outer volume with no filesystem.\n"
+					"  1) Create an outer volume with no filesystem and without --quick.\n"
 					"  2) Create a hidden volume within the outer volume.\n"
 					"  3) Mount the outer volume using hidden volume protection.\n"
 					"  4) Create a filesystem on the virtual device of the outer volume.\n"
@@ -1428,8 +1428,12 @@ const FileManager fileManagers[] = {
 					" See also options -p and --protect-hidden.\n"
 					"\n"
 					"--quick\n"
-					" Do not encrypt free space when creating a device-hosted volume. This option\n"
-					" must not be used when creating an outer volume.\n"
+					" Do not encrypt free space when creating a normal file-hosted or\n"
+					" device-hosted volume. This option must not be used when creating an outer\n"
+					" volume; text mode cannot infer that a normal volume will later be\n"
+					" used as an outer volume. For file containers, Quick Format may create sparse\n"
+					" or unwritten host regions; actual disk savings depend on host filesystem\n"
+					" sparse-file support, and later writes can fail if host space runs out.\n"
 					"\n"
 					"--random-source=FILE\n"
 					" Use FILE as a source of random data (e.g., when creating a volume) instead\n"

src/Platform/File.h

@@ -87,6 +87,7 @@ namespace VeraCrypt
 		uint64 ReadAt (const BufferPtr &buffer, uint64 position) const;
 		void SeekAt (uint64 position) const;
 		void SeekEnd (int ofset) const;
+		void SetLength (uint64 length) const;
 		void Write (const ConstBufferPtr &buffer) const;
 		void Write (const ConstBufferPtr &buffer, size_t length) const { Write (buffer.GetRange (0, length)); }
 		void WriteAt (const ConstBufferPtr &buffer, uint64 position) const;

src/Platform/Unix/File.cpp

@@ -385,6 +385,12 @@ namespace VeraCrypt
 		throw_sys_sub_if (lseek (FileHandle, offset, SEEK_END) == -1, wstring (Path));
 	}
 
+	void File::SetLength (uint64 length) const
+	{
+		if_debug (ValidateState());
+		throw_sys_sub_if (ftruncate (FileHandle, length) == -1, wstring (Path));
+	}
+
 	void File::Write (const ConstBufferPtr &buffer) const
 	{
 		if_debug (ValidateState());