diff options
| author | Ladislav Zezula <ladislav.zezula@avast.com> | 2021-05-17 12:57:54 +0200 |
|---|---|---|
| committer | Ladislav Zezula <ladislav.zezula@avast.com> | 2021-05-17 12:57:54 +0200 |
| commit | 33bdae86c2345db9514addbf9d5a698eada56fb2 (patch) | |
| tree | ff40d644d75b5976b051bf6534e459805e9d184c /src/SBaseCommon.cpp | |
| parent | a3332c7c9bc36f13aace6543ebc719f833882dfc (diff) | |
Added alignment-aware block encryption/decryption
Diffstat (limited to 'src/SBaseCommon.cpp')
| -rw-r--r-- | src/SBaseCommon.cpp | 111 |
1 files changed, 90 insertions, 21 deletions
diff --git a/src/SBaseCommon.cpp b/src/SBaseCommon.cpp index 43113a1..b81d492 100644 --- a/src/SBaseCommon.cpp +++ b/src/SBaseCommon.cpp @@ -414,52 +414,121 @@ DWORD GetDefaultSpecialFileFlags(DWORD dwFileSize, USHORT wFormatVersion) //-----------------------------------------------------------------------------
// Encrypting/Decrypting MPQ data block
+static DWORD EncryptUInt32Unaligned(PDWORD DataPointer, DWORD i, DWORD dwXorKey)
+{
+ LPBYTE pbDataPointer = (LPBYTE)(DataPointer + i);
+ LPBYTE pbXorKey = (LPBYTE)(&dwXorKey);
+ DWORD dwValue32;
+
+ // Retrieve the value
+ dwValue32 = ((DWORD)pbDataPointer[0] << 0x00) |
+ ((DWORD)pbDataPointer[1] << 0x08) |
+ ((DWORD)pbDataPointer[2] << 0x10) |
+ ((DWORD)pbDataPointer[3] << 0x18);
+
+ // Perform unaligned XOR
+ pbDataPointer[0] = (pbDataPointer[0] ^ pbXorKey[0]);
+ pbDataPointer[1] = (pbDataPointer[1] ^ pbXorKey[1]);
+ pbDataPointer[2] = (pbDataPointer[2] ^ pbXorKey[2]);
+ pbDataPointer[3] = (pbDataPointer[3] ^ pbXorKey[3]);
+ return dwValue32;
+}
+
void EncryptMpqBlock(void * pvDataBlock, DWORD dwLength, DWORD dwKey1)
{
- LPDWORD DataBlock = (LPDWORD)pvDataBlock;
+ LPDWORD DataPointer = (LPDWORD)pvDataBlock;
DWORD dwValue32;
DWORD dwKey2 = 0xEEEEEEEE;
// Round to DWORDs
dwLength >>= 2;
- // Encrypt the data block at array of DWORDs
- for(DWORD i = 0; i < dwLength; i++)
+ // We need different approach on non-aligned buffers
+ if(STORMLIB_DWORD_ALIGNED(DataPointer))
{
- // Modify the second key
- dwKey2 += StormBuffer[MPQ_HASH_KEY2_MIX + (dwKey1 & 0xFF)];
+ for(DWORD i = 0; i < dwLength; i++)
+ {
+ // Modify the second key
+ dwKey2 += StormBuffer[MPQ_HASH_KEY2_MIX + (dwKey1 & 0xFF)];
- dwValue32 = DataBlock[i];
- DataBlock[i] = DataBlock[i] ^ (dwKey1 + dwKey2);
+ // We can use 32-bit approach, when the buffer is aligned
+ DataPointer[i] = (dwValue32 = DataPointer[i]) ^ (dwKey1 + dwKey2);
- dwKey1 = ((~dwKey1 << 0x15) + 0x11111111) | (dwKey1 >> 0x0B);
- dwKey2 = dwValue32 + dwKey2 + (dwKey2 << 5) + 3;
+ dwKey1 = ((~dwKey1 << 0x15) + 0x11111111) | (dwKey1 >> 0x0B);
+ dwKey2 = dwValue32 + dwKey2 + (dwKey2 << 5) + 3;
+ }
+ }
+ else
+ {
+ for(DWORD i = 0; i < dwLength; i++)
+ {
+ // Modify the second key
+ dwKey2 += StormBuffer[MPQ_HASH_KEY2_MIX + (dwKey1 & 0xFF)];
+
+ // The data are unaligned. Make sure we don't cause data misalignment error
+ dwValue32 = EncryptUInt32Unaligned(DataPointer, i, (dwKey1 + dwKey2));
+
+ dwKey1 = ((~dwKey1 << 0x15) + 0x11111111) | (dwKey1 >> 0x0B);
+ dwKey2 = dwValue32 + dwKey2 + (dwKey2 << 5) + 3;
+ }
}
}
+static DWORD DecryptUInt32Unaligned(PDWORD DataPointer, DWORD i, DWORD dwXorKey)
+{
+ LPBYTE pbDataPointer = (LPBYTE)(DataPointer + i);
+ LPBYTE pbXorKey = (LPBYTE)(&dwXorKey);
+
+ // Perform unaligned XOR
+ pbDataPointer[0] = (pbDataPointer[0] ^ pbXorKey[0]);
+ pbDataPointer[1] = (pbDataPointer[1] ^ pbXorKey[1]);
+ pbDataPointer[2] = (pbDataPointer[2] ^ pbXorKey[2]);
+ pbDataPointer[3] = (pbDataPointer[3] ^ pbXorKey[3]);
+
+ // Retrieve the value
+ return ((DWORD)pbDataPointer[0] << 0x00) |
+ ((DWORD)pbDataPointer[1] << 0x08) |
+ ((DWORD)pbDataPointer[2] << 0x10) |
+ ((DWORD)pbDataPointer[3] << 0x18);
+}
+
void DecryptMpqBlock(void * pvDataBlock, DWORD dwLength, DWORD dwKey1)
{
- LPDWORD DataBlock = (LPDWORD)pvDataBlock;
+ PDWORD DataPointer = (PDWORD)pvDataBlock;
DWORD dwValue32;
DWORD dwKey2 = 0xEEEEEEEE;
- // Check for alignment
- //assert(((size_t)(pvDataBlock) & 0x03) == 0);
-
// Round to DWORDs
dwLength >>= 2;
- // Decrypt the data block at array of DWORDs
- for(DWORD i = 0; i < dwLength; i++)
+ // We need different approach on non-aligned buffers
+ if(STORMLIB_DWORD_ALIGNED(DataPointer))
{
- // Modify the second key
- dwKey2 += StormBuffer[MPQ_HASH_KEY2_MIX + (dwKey1 & 0xFF)];
+ for(DWORD i = 0; i < dwLength; i++)
+ {
+ // Modify the second key
+ dwKey2 += StormBuffer[MPQ_HASH_KEY2_MIX + (dwKey1 & 0xFF)];
+
+ // We can use 32-bit approach, when the buffer is aligned
+ DataPointer[i] = dwValue32 = DataPointer[i] ^ (dwKey1 + dwKey2);
+
+ dwKey1 = ((~dwKey1 << 0x15) + 0x11111111) | (dwKey1 >> 0x0B);
+ dwKey2 = dwValue32 + dwKey2 + (dwKey2 << 5) + 3;
+ }
+ }
+ else
+ {
+ for(DWORD i = 0; i < dwLength; i++)
+ {
+ // Modify the second key
+ dwKey2 += StormBuffer[MPQ_HASH_KEY2_MIX + (dwKey1 & 0xFF)];
- DataBlock[i] = DataBlock[i] ^ (dwKey1 + dwKey2);
- dwValue32 = DataBlock[i];
+ // The data are unaligned. Make sure we don't cause data misalignment error
+ dwValue32 = DecryptUInt32Unaligned(DataPointer, i, (dwKey1 + dwKey2));
- dwKey1 = ((~dwKey1 << 0x15) + 0x11111111) | (dwKey1 >> 0x0B);
- dwKey2 = dwValue32 + dwKey2 + (dwKey2 << 5) + 3;
+ dwKey1 = ((~dwKey1 << 0x15) + 0x11111111) | (dwKey1 >> 0x0B);
+ dwKey2 = dwValue32 + dwKey2 + (dwKey2 << 5) + 3;
+ }
}
}
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