bootencryptedio.cpp

来自「使用visual studio 2005 开发的开源文件、磁盘加密软件。这是6.」· C++ 代码 · 共 129 行

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

 Governed by the TrueCrypt License 2.6 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));
}