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/*****************************************************************************/
/* CascDecrypt.cpp Copyright (c) Ladislav Zezula 2015 */
/*---------------------------------------------------------------------------*/
/* Decryption functions for CascLib */
/*---------------------------------------------------------------------------*/
/* Date Ver Who Comment */
/* -------- ---- --- ------- */
/* 31.10.15 1.00 Lad The first version of CascDecrypt.cpp */
/*****************************************************************************/
#define __CASCLIB_SELF__
#include "CascLib.h"
#include "CascCommon.h"
//-----------------------------------------------------------------------------
// Local structures
typedef struct _CASC_ENCRYPTION_KEY
{
ULONGLONG KeyName; // "Name" of the key
BYTE Key[0x10]; // The key itself
} CASC_ENCRYPTION_KEY, *PCASC_ENCRYPTION_KEY;
typedef struct _CASC_SALSA20
{
DWORD Key[0x10];
DWORD dwRounds;
} CASC_SALSA20, *PCASC_SALSA20;
//-----------------------------------------------------------------------------
// Local variables
//keyName FB680CB6A8BF81F3 key 62D90EFA7F36D71C398AE2F1FE37BDB9 keyNameSize 8 keySize 16
//keyName 402CD9D8D6BFED98 key AEB0EADEA47612FE6C041A03958DF241 keyNameSize 8 keySize 16
//keyName 87AEBBC9C4E6B601 key 685E86C6063DFDA6C9E85298076B3D42 keyNameSize 8 keySize 16
//keyName A19C4F859F6EFA54 key 0196CB6F5ECBAD7CB5283891B9712B4B keyNameSize 8 keySize 16
//keyName 11A9203C9881710A key 2E2CB8C397C2F24ED0B5E452F18DC267 keyNameSize 8 keySize 16
//keyName DBD3371554F60306 key 34E397ACE6DD30EEFDC98A2AB093CD3C keyNameSize 8 keySize 16
//keyName DEE3A0521EFF6F03 key AD740CE3FFFF9231468126985708E1B9 keyNameSize 8 keySize 16
//keyName 8C9106108AA84F07 key 53D859DDA2635A38DC32E72B11B32F29 keyNameSize 8 keySize 16
static CASC_ENCRYPTION_KEY CascKeys[] =
{
{0xFB680CB6A8BF81F3ULL, {0x62, 0xD9, 0x0E, 0xFA, 0x7F, 0x36, 0xD7, 0x1C, 0x39, 0x8A, 0xE2, 0xF1, 0xFE, 0x37, 0xBD, 0xB9}},
{0x402CD9D8D6BFED98ULL, {0xAE, 0xB0, 0xEA, 0xDE, 0xA4, 0x76, 0x12, 0xFE, 0x6C, 0x04, 0x1A, 0x03, 0x95, 0x8D, 0xF2, 0x41}},
{0x87AEBBC9C4E6B601ULL, {0x68, 0x5E, 0x86, 0xC6, 0x06, 0x3D, 0xFD, 0xA6, 0xC9, 0xE8, 0x52, 0x98, 0x07, 0x6B, 0x3D, 0x42}},
{0xA19C4F859F6EFA54ULL, {0x01, 0x96, 0xCB, 0x6F, 0x5E, 0xCB, 0xAD, 0x7C, 0xB5, 0x28, 0x38, 0x91, 0xB9, 0x71, 0x2B, 0x4B}},
{0x11A9203C9881710AULL, {0x2E, 0x2C, 0xB8, 0xC3, 0x97, 0xC2, 0xF2, 0x4E, 0xD0, 0xB5, 0xE4, 0x52, 0xF1, 0x8D, 0xC2, 0x67}},
{0xDBD3371554F60306ULL, {0x34, 0xE3, 0x97, 0xAC, 0xE6, 0xDD, 0x30, 0xEE, 0xFD, 0xC9, 0x8A, 0x2A, 0xB0, 0x93, 0xCD, 0x3C}},
{0xDEE3A0521EFF6F03ULL, {0xAD, 0x74, 0x0C, 0xE3, 0xFF, 0xFF, 0x92, 0x31, 0x46, 0x81, 0x26, 0x98, 0x57, 0x08, 0xE1, 0xB9}},
{0x8C9106108AA84F07ULL, {0x53, 0xD8, 0x59, 0xDD, 0xA2, 0x63, 0x5A, 0x38, 0xDC, 0x32, 0xE7, 0x2B, 0x11, 0xB3, 0x2F, 0x29}},
{0x49166D358A34D815ULL, {0x66, 0x78, 0x68, 0xCD, 0x94, 0xEA, 0x01, 0x35, 0xB9, 0xB1, 0x6C, 0x93, 0xB1, 0x12, 0x4A, 0xBA}},
{0, {0}}
};
static const char * szKeyConstant16 = "expand 16-byte k";
static const char * szKeyConstant32 = "expand 32-byte k";
//-----------------------------------------------------------------------------
// Local functions
static DWORD Rol32(DWORD dwValue, DWORD dwRolCount)
{
return (dwValue << dwRolCount) | (dwValue >> (32 - dwRolCount));
}
static LPBYTE FindCascKey(ULONGLONG KeyName)
{
// Search the known keys
for(size_t i = 0; CascKeys[i].KeyName != 0; i++)
{
if(CascKeys[i].KeyName == KeyName)
return CascKeys[i].Key;
}
// Key not found
return NULL;
}
static void Initialize(PCASC_SALSA20 pState, LPBYTE pbKey, DWORD cbKeyLength, LPBYTE pbVector)
{
const char * szConstants = (cbKeyLength == 32) ? szKeyConstant32 : szKeyConstant16;
DWORD KeyIndex = cbKeyLength - 0x10;
memset(pState, 0, sizeof(CASC_SALSA20));
pState->Key[0] = *(PDWORD)(szConstants + 0x00);
pState->Key[1] = *(PDWORD)(pbKey + 0x00);
pState->Key[2] = *(PDWORD)(pbKey + 0x04);
pState->Key[3] = *(PDWORD)(pbKey + 0x08);
pState->Key[4] = *(PDWORD)(pbKey + 0x0C);
pState->Key[5] = *(PDWORD)(szConstants + 0x04);
pState->Key[6] = *(PDWORD)(pbVector + 0x00);
pState->Key[7] = *(PDWORD)(pbVector + 0x04);
pState->Key[8] = 0;
pState->Key[9] = 0;
pState->Key[10] = *(PDWORD)(szConstants + 0x08);
pState->Key[11] = *(PDWORD)(pbKey + KeyIndex + 0x00);
pState->Key[12] = *(PDWORD)(pbKey + KeyIndex + 0x04);
pState->Key[13] = *(PDWORD)(pbKey + KeyIndex + 0x08);
pState->Key[14] = *(PDWORD)(pbKey + KeyIndex + 0x0C);
pState->Key[15] = *(PDWORD)(szConstants + 0x0C);
pState->dwRounds = 20;
}
static int Decrypt(PCASC_SALSA20 pState, LPBYTE pbOutBuffer, LPBYTE pbInBuffer, size_t cbInBuffer)
{
LPBYTE pbXorValue;
DWORD KeyMirror[0x10];
DWORD XorValue[0x10];
DWORD BlockSize;
DWORD i;
// Repeat until we have data to read
while(cbInBuffer > 0)
{
// Create the copy of the key
memcpy(KeyMirror, pState->Key, sizeof(KeyMirror));
// Shuffle the key
for(i = 0; i < pState->dwRounds; i += 2)
{
KeyMirror[0x04] ^= Rol32((KeyMirror[0x00] + KeyMirror[0x0C]), 0x07);
KeyMirror[0x08] ^= Rol32((KeyMirror[0x04] + KeyMirror[0x00]), 0x09);
KeyMirror[0x0C] ^= Rol32((KeyMirror[0x08] + KeyMirror[0x04]), 0x0D);
KeyMirror[0x00] ^= Rol32((KeyMirror[0x0C] + KeyMirror[0x08]), 0x12);
KeyMirror[0x09] ^= Rol32((KeyMirror[0x05] + KeyMirror[0x01]), 0x07);
KeyMirror[0x0D] ^= Rol32((KeyMirror[0x09] + KeyMirror[0x05]), 0x09);
KeyMirror[0x01] ^= Rol32((KeyMirror[0x0D] + KeyMirror[0x09]), 0x0D);
KeyMirror[0x05] ^= Rol32((KeyMirror[0x01] + KeyMirror[0x0D]), 0x12);
KeyMirror[0x0E] ^= Rol32((KeyMirror[0x0A] + KeyMirror[0x06]), 0x07);
KeyMirror[0x02] ^= Rol32((KeyMirror[0x0E] + KeyMirror[0x0A]), 0x09);
KeyMirror[0x06] ^= Rol32((KeyMirror[0x02] + KeyMirror[0x0E]), 0x0D);
KeyMirror[0x0A] ^= Rol32((KeyMirror[0x06] + KeyMirror[0x02]), 0x12);
KeyMirror[0x03] ^= Rol32((KeyMirror[0x0F] + KeyMirror[0x0B]), 0x07);
KeyMirror[0x07] ^= Rol32((KeyMirror[0x03] + KeyMirror[0x0F]), 0x09);
KeyMirror[0x0B] ^= Rol32((KeyMirror[0x07] + KeyMirror[0x03]), 0x0D);
KeyMirror[0x0F] ^= Rol32((KeyMirror[0x0B] + KeyMirror[0x07]), 0x12);
KeyMirror[0x01] ^= Rol32((KeyMirror[0x00] + KeyMirror[0x03]), 0x07);
KeyMirror[0x02] ^= Rol32((KeyMirror[0x01] + KeyMirror[0x00]), 0x09);
KeyMirror[0x03] ^= Rol32((KeyMirror[0x02] + KeyMirror[0x01]), 0x0D);
KeyMirror[0x00] ^= Rol32((KeyMirror[0x03] + KeyMirror[0x02]), 0x12);
KeyMirror[0x06] ^= Rol32((KeyMirror[0x05] + KeyMirror[0x04]), 0x07);
KeyMirror[0x07] ^= Rol32((KeyMirror[0x06] + KeyMirror[0x05]), 0x09);
KeyMirror[0x04] ^= Rol32((KeyMirror[0x07] + KeyMirror[0x06]), 0x0D);
KeyMirror[0x05] ^= Rol32((KeyMirror[0x04] + KeyMirror[0x07]), 0x12);
KeyMirror[0x0B] ^= Rol32((KeyMirror[0x0A] + KeyMirror[0x09]), 0x07);
KeyMirror[0x08] ^= Rol32((KeyMirror[0x0B] + KeyMirror[0x0A]), 0x09);
KeyMirror[0x09] ^= Rol32((KeyMirror[0x08] + KeyMirror[0x0B]), 0x0D);
KeyMirror[0x0A] ^= Rol32((KeyMirror[0x09] + KeyMirror[0x08]), 0x12);
KeyMirror[0x0C] ^= Rol32((KeyMirror[0x0F] + KeyMirror[0x0E]), 0x07);
KeyMirror[0x0D] ^= Rol32((KeyMirror[0x0C] + KeyMirror[0x0F]), 0x09);
KeyMirror[0x0E] ^= Rol32((KeyMirror[0x0D] + KeyMirror[0x0C]), 0x0D);
KeyMirror[0x0F] ^= Rol32((KeyMirror[0x0E] + KeyMirror[0x0D]), 0x12);
}
// Set the number of remaining bytes
pbXorValue = (LPBYTE)XorValue;
BlockSize = (DWORD)CASCLIB_MIN(cbInBuffer, 0x40);
// Prepare the XOR constants
for(i = 0; i < 16; i++)
{
XorValue[i] = KeyMirror[i] + pState->Key[i];
}
// Decrypt the block
for(i = 0; i < BlockSize; i++)
{
pbOutBuffer[i] = pbInBuffer[i] ^ pbXorValue[i];
}
pState->Key[8] = pState->Key[8] + 1;
if(pState->Key[8] == 0)
pState->Key[9] = pState->Key[9] + 1;
// Adjust buffers
pbOutBuffer += BlockSize;
pbInBuffer += BlockSize;
cbInBuffer -= BlockSize;
}
return ERROR_SUCCESS;
}
static int Decrypt_Salsa20(LPBYTE pbOutBuffer, LPBYTE pbInBuffer, size_t cbInBuffer, LPBYTE pbKey, DWORD cbKeySize, LPBYTE pbVector)
{
CASC_SALSA20 SalsaState;
Initialize(&SalsaState, pbKey, cbKeySize, pbVector);
return Decrypt(&SalsaState, pbOutBuffer, pbInBuffer, cbInBuffer);
}
//-----------------------------------------------------------------------------
// Public functions
int CascDecrypt(LPBYTE pbOutBuffer, PDWORD pcbOutBuffer, LPBYTE pbInBuffer, DWORD cbInBuffer, DWORD dwFrameIndex)
{
ULONGLONG KeyName = 0;
LPBYTE pbBufferEnd = pbInBuffer + cbInBuffer;
LPBYTE pbKey;
DWORD KeyNameSize;
DWORD dwShift = 0;
DWORD IVSize;
BYTE Vector[0x08];
BYTE EncryptionType;
int nError;
// Verify and retrieve the key name size
if(pbInBuffer >= pbBufferEnd)
return ERROR_FILE_CORRUPT;
if(pbInBuffer[0] != 0 && pbInBuffer[0] != 8)
return ERROR_NOT_SUPPORTED;
KeyNameSize = *pbInBuffer++;
// Copy the key name
if((pbInBuffer + KeyNameSize) >= pbBufferEnd)
return ERROR_FILE_CORRUPT;
memcpy(&KeyName, pbInBuffer, KeyNameSize);
pbInBuffer += KeyNameSize;
// Verify and retrieve the Vector size
if(pbInBuffer >= pbBufferEnd)
return ERROR_FILE_CORRUPT;
if(pbInBuffer[0] != 4 && pbInBuffer[0] != 8)
return ERROR_NOT_SUPPORTED;
IVSize = *pbInBuffer++;
// Copy the initialization vector
if((pbInBuffer + IVSize) >= pbBufferEnd)
return ERROR_FILE_CORRUPT;
memset(Vector, 0, sizeof(Vector));
memcpy(Vector, pbInBuffer, IVSize);
pbInBuffer += IVSize;
// Verify and retrieve the encryption type
if(pbInBuffer >= pbBufferEnd)
return ERROR_FILE_CORRUPT;
if(pbInBuffer[0] != 'S' && pbInBuffer[0] != 'A')
return ERROR_NOT_SUPPORTED;
EncryptionType = *pbInBuffer++;
// Do we have enough space in the output buffer?
if((DWORD)(pbBufferEnd - pbInBuffer) > pcbOutBuffer[0])
return ERROR_INSUFFICIENT_BUFFER;
// Check if we know the key
pbKey = FindCascKey(KeyName);
if(pbKey == NULL)
return ERROR_UNKNOWN_FILE_KEY;
// Shuffle the Vector with the block index
// Note that there's no point to go beyond 32 bits, unless the file has
// more than 0xFFFFFFFF frames.
for(int i = 0; i < sizeof(dwFrameIndex); i++)
{
Vector[i] = Vector[i] ^ (BYTE)((dwFrameIndex >> dwShift) & 0xFF);
dwShift += 8;
}
// Perform the decryption-specific action
switch(EncryptionType)
{
case 'S': // Salsa20
nError = Decrypt_Salsa20(pbOutBuffer, pbInBuffer, (pbBufferEnd - pbInBuffer), pbKey, 0x10, Vector);
if(nError != ERROR_SUCCESS)
return nError;
// Supply the size of the output buffer
pcbOutBuffer[0] = (DWORD)(pbBufferEnd - pbInBuffer);
return ERROR_SUCCESS;
// case 'A':
// return ERROR_NOT_SUPPORTED;
}
assert(false);
return ERROR_NOT_SUPPORTED;
}
int CascDirectCopy(LPBYTE pbOutBuffer, PDWORD pcbOutBuffer, LPBYTE pbInBuffer, DWORD cbInBuffer)
{
// Check the buffer size
if((cbInBuffer - 1) > pcbOutBuffer[0])
return ERROR_INSUFFICIENT_BUFFER;
// Copy the data
memcpy(pbOutBuffer, pbInBuffer, cbInBuffer);
pcbOutBuffer[0] = cbInBuffer;
return ERROR_SUCCESS;
}
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