wipe.c

功能强大的开源加密软件。使用最新ieee-p1619标准

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

 Governed by the TrueCrypt License 2.4 the full text of which is contained
 in the file License.txt included in TrueCrypt binary and source code
 distribution packages.
*/

#include "Tcdefs.h"
#include "Wipe.h"


// Fill buffer with wipe patterns defined in "National Industrial Security Program Operating Manual", US DoD 5220.22-M.
// Return: FALSE = buffer must be filled with random data

static BOOL Wipe3Dod5220 (int pass, byte *buffer, size_t size)
{
	byte wipeChar;

	switch (pass)
	{
	case 1:
		wipeChar = 0;
		break;

	case 2:
		wipeChar = 0xff;
		break;

	default:
		return FALSE;
	}

	memset (buffer, wipeChar, size);
	return TRUE;
}


static BOOL Wipe7Dod5220 (int pass, byte randChars[TC_WIPE_RAND_CHAR_COUNT], byte *buffer, size_t size)
{
	byte wipeChar;

	switch (pass)
	{
	case 1:
		wipeChar = randChars[0];
		break;

	case 2:
		wipeChar = ~randChars[0];
		break;

	case 4:
		wipeChar = randChars[1];
		break;

	case 5:
		wipeChar = randChars[2];
		break;

	case 6:
		wipeChar = ~randChars[2];
		break;

	default:
		return FALSE;
	}

	memset (buffer, wipeChar, size);
	return TRUE;
}


// Fill the buffer with wipe patterns defined in the paper "Secure Deletion of Data from Magnetic and Solid-State Memory" by Peter Gutmann.
// Return: FALSE = buffer must be filled with random data

static BOOL Wipe35Gutmann (int pass, byte *buffer, size_t size)
{
	byte wipePat3[] = { 0x92, 0x49, 0x24 };
	int wipePat3Pos;
	size_t i;

	switch (pass)
	{
	case 5:
		memset (buffer, 0x55, size);
		break;

	case 6:
		memset (buffer, 0xaa, size);
		break;

	case 7:
	case 26:
	case 29:
		wipePat3Pos = 0;
		goto wipe3;

	case 8:
	case 27:
	case 30:
		wipePat3Pos = 1;
		goto wipe3;

	case 9:
	case 28:
	case 31:
		wipePat3Pos = 2;
		goto wipe3;

wipe3:
		if (pass >= 29)
		{
			wipePat3[0] = ~wipePat3[0];
			wipePat3[1] = ~wipePat3[1];
			wipePat3[2] = ~wipePat3[2];
		}

		for (i = 0; i < size; ++i)
		{
			buffer[i] = wipePat3[wipePat3Pos++ % 3];
		}
		break;

	default:
		if (pass >= 10 && pass <= 25)
			memset (buffer, (pass - 10) * 0x11, size);
		else
			return FALSE;
	}

	return TRUE;
}


size_t GetWipePassCount (WipeAlgorithmId algorithm)
{
	switch (algorithm)
	{
	case TC_WIPE_3_DOD_5220:
		return 3;

	case TC_WIPE_7_DOD_5220:
		return 7;

	case TC_WIPE_35_GUTMANN:
		return 35;

	default:
		TC_THROW_FATAL_EXCEPTION;
	}
}


BOOL WipeBuffer (WipeAlgorithmId algorithm, byte randChars[TC_WIPE_RAND_CHAR_COUNT], int pass, byte *buffer, size_t size)
{
	switch (algorithm)
	{
	case TC_WIPE_3_DOD_5220:
		return Wipe3Dod5220 (pass, buffer, size);

	case TC_WIPE_7_DOD_5220:
		return Wipe7Dod5220 (pass, randChars, buffer, size);

	case TC_WIPE_35_GUTMANN:
		return Wipe35Gutmann (pass, buffer, size);

	default:
		TC_THROW_FATAL_EXCEPTION;
	}
}