VeraCrypt/src/Boot/Windows/BootEncryptedIo.cpp

/*
 Copyright (c) 2008 TrueCrypt Developers Association. All rights reserved.

 Governed by the TrueCrypt License 3.0 the full text of which is contained in
 the file License.txt included in TrueCrypt binary and source code distribution
 packages.
*/

#include "Crypto.h"
#include "Platform.h"
#include "BootConfig.h"
#include "BootDebug.h"
#include "BootDefs.h"
#include "BootDiskIo.h"
#include "BootEncryptedIo.h"


BiosResult ReadEncryptedSectors (uint16 destSegment, uint16 destOffset, byte drive, uint64 sector, uint16 sectorCount)
{
	BiosResult result;
	bool decrypt = true;

	if (BootCryptoInfo->hiddenVolume)
	{
		if (ReadWritePartiallyCoversEncryptedArea (sector, sectorCount))
			return BiosResultInvalidFunction;

		if (sector >= EncryptedVirtualPartition.StartSector && sector <= EncryptedVirtualPartition.EndSector)
		{
			// Remap the request to the hidden volume
			sector -= EncryptedVirtualPartition.StartSector;
			sector += HiddenVolumeStartSector;
		}
		else
			decrypt = false;
	}

	result = ReadSectors (destSegment, destOffset, drive, sector, sectorCount);

	if (result != BiosResultSuccess || !decrypt)
		return result;

	if (BootCryptoInfo->hiddenVolume)
	{
		// Convert sector number to data unit number of the hidden volume
		sector -= HiddenVolumeStartSector;
		sector += HiddenVolumeStartUnitNo;
	}

	if (drive == EncryptedVirtualPartition.Drive)
	{
		while (sectorCount-- > 0)
		{
			if (BootCryptoInfo->hiddenVolume
				|| (sector >= EncryptedVirtualPartition.StartSector && sector <= EncryptedVirtualPartition.EndSector))
			{
				AcquireSectorBuffer();
				CopyMemory (destSegment, destOffset, SectorBuffer, TC_LB_SIZE);

				DecryptDataUnits (SectorBuffer, &sector, 1, BootCryptoInfo);

				CopyMemory (SectorBuffer, destSegment, destOffset, TC_LB_SIZE);
				ReleaseSectorBuffer();
			}

			++sector;
			destOffset += TC_LB_SIZE;
		}
	}

	return result;
}


BiosResult WriteEncryptedSectors (uint16 sourceSegment, uint16 sourceOffset, byte drive, uint64 sector, uint16 sectorCount)
{
	BiosResult result;
	AcquireSectorBuffer();
	uint64 dataUnitNo;
	uint64 writeOffset;

	dataUnitNo = sector;
	writeOffset.HighPart = 0;
	writeOffset.LowPart = 0;

	if (BootCryptoInfo->hiddenVolume)
	{
		if (ReadWritePartiallyCoversEncryptedArea (sector, sectorCount))
			return BiosResultInvalidFunction;

		// Remap the request to the hidden volume
		writeOffset = HiddenVolumeStartSector;
		writeOffset -= EncryptedVirtualPartition.StartSector;
		dataUnitNo -= EncryptedVirtualPartition.StartSector;
		dataUnitNo += HiddenVolumeStartUnitNo;
	}

	while (sectorCount-- > 0)
	{
		CopyMemory (sourceSegment, sourceOffset, SectorBuffer, TC_LB_SIZE);

		if (drive == EncryptedVirtualPartition.Drive && sector >= EncryptedVirtualPartition.StartSector && sector <= EncryptedVirtualPartition.EndSector)
		{
			EncryptDataUnits (SectorBuffer, &dataUnitNo, 1, BootCryptoInfo);
		}

		result = WriteSectors (SectorBuffer, drive, sector + writeOffset, 1);

		if (result != BiosResultSuccess)
			break;

		++sector;
		++dataUnitNo;
		sourceOffset += TC_LB_SIZE;
	}

	ReleaseSectorBuffer();
	return result;
}


static bool ReadWritePartiallyCoversEncryptedArea (const uint64 &sector, uint16 sectorCount)
{
	uint64 readWriteEnd = sector + --sectorCount;

	return ((sector < EncryptedVirtualPartition.StartSector && readWriteEnd >= EncryptedVirtualPartition.StartSector)
		|| (sector >= EncryptedVirtualPartition.StartSector && readWriteEnd > EncryptedVirtualPartition.EndSector));
}