cache.c

使用visual studio 2005 开发的开源文件、磁盘加密软件。这是6.1a版。加密自己资料的好工具。也是学习的优秀范本。结成了众多加密算法。

/*
 Legal Notice: Some portions of the source code contained in this file were
 derived from the source code of Encryption for the Masses 2.02a, which is
 Copyright (c) 1998-2000 Paul Le Roux and which is governed by the 'License
 Agreement for Encryption for the Masses'. Modifications and additions to
 the original source code (contained in this file) and all other portions of
 this file are Copyright (c) 2003-2008 TrueCrypt Foundation and are 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 "Tcdefs.h"

#ifndef NT4_DRIVER
#pragma VxD_LOCKED_CODE_SEG
#pragma VxD_LOCKED_DATA_SEG
#endif

#include "Crypto.h"
#include "Fat.h"
#include "Volumes.h"
#include "Apidrvr.h"
#include "Common.h"
#include "Cache.h"

Password CachedPasswords[CACHE_SIZE];
int cacheEmpty = 1;
static int nPasswordIdx = 0;

int ReadVolumeHeaderWCache (BOOL bBoot, BOOL bCache, char *header, Password *password, PCRYPTO_INFO *retInfo)
{
	int nReturnCode = ERR_PASSWORD_WRONG;
	int i;

	/* Attempt to recognize volume using mount password */
	if (password->Length > 0)
	{
		nReturnCode = ReadVolumeHeader (bBoot, header, password, retInfo, NULL);

		/* Save mount passwords back into cache if asked to do so */
		if (bCache && (nReturnCode == 0 || nReturnCode == ERR_CIPHER_INIT_WEAK_KEY))
		{
			for (i = 0; i < CACHE_SIZE; i++)
			{
				if (memcmp (&CachedPasswords[i], password, sizeof (Password)) == 0)
					break;
			}

			if (i == CACHE_SIZE)
			{
				/* Store the password */
				CachedPasswords[nPasswordIdx] = *password;

				/* Try another slot */
				nPasswordIdx = (nPasswordIdx + 1) % CACHE_SIZE;

				cacheEmpty = 0;
			}
		}
	}
	else if (!cacheEmpty)
	{
		/* Attempt to recognize volume using cached passwords */
		for (i = 0; i < CACHE_SIZE; i++)
		{
			if (CachedPasswords[i].Length > 0)
			{
				nReturnCode = ReadVolumeHeader (bBoot, header, &CachedPasswords[i], retInfo, NULL);

				if (nReturnCode != ERR_PASSWORD_WRONG)
					break;
			}
		}
	}

	return nReturnCode;
}


void AddPasswordToCache (Password *password)
{
	int i;
	for (i = 0; i < CACHE_SIZE; i++)
	{
		if (memcmp (&CachedPasswords[i], password, sizeof (Password)) == 0)
			return;
	}

	CachedPasswords[nPasswordIdx] = *password;
	nPasswordIdx = (nPasswordIdx + 1) % CACHE_SIZE;
	cacheEmpty = 0;
}


void WipeCache ()
{
	burn (CachedPasswords, sizeof (CachedPasswords));
	nPasswordIdx = 0;
	cacheEmpty = 1;
}