protected override void Check()
{
// Check file header
if (InReader.ReadUInt64() != 0x4d4144464e455443)
{
throw new FileLoadException($"Failed to verify header of \"{InPath}\".");
}
// Skip ahead
_ = InBuffer.Seek(2, SeekOrigin.Current);
}
protected override void Decrypt()
{
try
{
// Read key
byte[] keyChunk = ReadIndexedChunk(0x64);
byte[] key = AesEcbDecrypt(keyChunk, rootKey);
// Build main key
for (uint i = 0; i < MainKey.Length; i++)
{
MainKey[i] = Convert.ToByte(i);
}
for (uint trgIndex = 0, swpIndex, lastIndex = 0, srcOffset = 17, srcIndex = srcOffset; trgIndex < MainKey.Length; trgIndex++)
{
byte swap = MainKey[trgIndex];
swpIndex = (swap + lastIndex + key[srcIndex++]) & 0xff;
if (srcIndex >= key.Length)
{
srcIndex = srcOffset;
}
MainKey[trgIndex] = MainKey[swpIndex];
MainKey[swpIndex] = swap;
lastIndex = swpIndex;
}
}
catch (NullFileChunkException e)
{
throw new FileLoadException(e.Message);
}
try
{
// Read metadata
byte[] metaChunk = ReadIndexedChunk(0x63);
int skipCount = 22;
for (int i = 0; i < metaChunk.LongLength; i++)
{
if (metaChunk[i] == 58)
{
skipCount = i + 1;
break;
}
}
// Resolve metadata
PropMetadata = JsonConvert.DeserializeObject <NetEaseMetadata>(
Encoding.UTF8.GetString(
AesEcbDecrypt(
Convert.FromBase64String(
Encoding.UTF8.GetString(
metaChunk.Skip(skipCount).ToArray())
),
jsonKey)
.Skip(6).ToArray())
);
StdMetadata = new Metadata(PropMetadata);
}
catch (NullFileChunkException)
{
Logger.Warn("Missing metadata in {Path}", InPath);
}
// Skip ahead
_ = InBuffer.Seek(9, SeekOrigin.Current);
// Get cover data
try
{
// Plan A: Read cover from file
CoverBuffer.Write(ReadIndexedChunk(null));
}
catch (NullFileChunkException)
{
Logger.Warn("Failed to load cover from {Path}, trying to get from server...", InPath);
// Plan B: get image from server
try
{
string coverUri = PropMetadata.AlbumPic;
if (!Uri.IsWellFormedUriString(coverUri, UriKind.Absolute))
{
Logger.Error("No cover URI was found in {Path}", InPath);
throw;
}
using WebClient webClient = new WebClient();
CoverBuffer.Write(webClient.DownloadData(coverUri));
}
catch (Exception)
{
Logger.Error("Failed to download cover image for {Path}", InPath);
}
}
CoverMime = MediaType.GetStreamMime(CoverBuffer);
if (CoverMime.Substring(0, 5) != "image")
{
CoverBuffer.Dispose();
CoverMime = null;
}
// Read music
for (int chunkSize = 0x8000; ;)
{
byte[] mainChunk = ReadFixedChunk(ref chunkSize);
for (int i = 0; i < chunkSize; i++)
{
int j = (i + 1) & 0xff;
mainChunk[i] ^= MainKey[(MainKey[j] + MainKey[(MainKey[j] + j) & 0xff]) & 0xff];
}
if (chunkSize < 0x8000)
{
OutBuffer.Write(mainChunk.Take(chunkSize).ToArray());
break;
}
else
{
OutBuffer.Write(mainChunk);
}
}
MusicMime = MediaType.GetStreamMime(OutBuffer);
}