private static void TryDecrypt(ABNDFileEntry entry, List <ABNDChunk> chunks)
{
Debug.Assert(entry.EncryptionType == EncryptionType.ChaCha);
uint totalLen = 0;
foreach (var chunk in chunks)
{
totalLen += chunk.Length;
}
var encrypted = GetConcatenatedEncryptedChunks(totalLen, chunks);
var IV = entry.IV;
var xor = IV.Xor(12);
var decrypted = ChaCha.Decrypt(encrypted, xor, entry.MAC);
if (decrypted == null)
{
throw new Exception();
}
// rechunk data
GetDecryptedChunks(chunks, decrypted);
}
public List <ABNDChunk> GetChunkData(ABNDFileEntry entry)
{
var result = new List <ABNDChunk>();
var ofs = entry.CompressedOffset;
if ((entry.Flags & ABNDFileEntryFlag.Compressed) == 0)
{
var blob = new ABNDChunk
{
Data = Data,
Length = (uint)entry.CompressedLength,
};
result.Add(blob);
return(result);
}
do
{
var len = BitConverter.ToInt32(Data, ofs);
// copy chunk data to final array at current position
byte[] chunk = Util.GetSlice(Data, ofs + 4, len);
var blob = new ABNDChunk
{
Data = chunk,
Length = (uint)len,
};
result.Add(blob);
// advance to next chunk
ofs += 4 + len;
} while (ofs < entry.CompressedOffset + entry.CompressedLength);
return(result);
}
private byte[] GetFileData(ABNDFileEntry entry, List <ABNDChunk> chunks)
{
if ((entry.Flags & ABNDFileEntryFlag.Compressed) == 0)
{
return(GetDecompressedFileData(entry, chunks));
}
var result = LZ4.DecodeChunks(chunks, ExtHeader.BlockSizeSectors << 9, entry.DecompressedLength);
Debug.Assert(result.Length == entry.DecompressedLength);
return(result);
}
public byte[] GetFileData(ABNDFileEntry entry)
{
var chunks = GetChunkData(entry);
if ((entry.Flags & ABNDFileEntryFlag.Encrypted) != 0)
{
TryDecrypt(entry, chunks);
}
var file_data = GetFileData(entry, chunks);
Debug.Assert(file_data != null);
return(file_data);
}
private static byte[] GetDecompressedFileData(ABNDFileEntry entry, List <ABNDChunk> chunks)
{
Debug.Assert(entry.CompressedLength == entry.DecompressedLength);
var result = new byte[entry.DecompressedLength];
uint offset = 0;
foreach (var chunk in chunks)
{
chunk.Data.CopyTo(result, offset);
offset += chunk.Length;
}
return(result);
}
public string GetFileName(ABNDFileEntry entry)
{
var encoding = Encoding.UTF8;
return(encoding.GetString(FileNameTable, entry.FileNameOffset, entry.FileNameLength));
}
