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Make certain AES streams seekable

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Make AES streams where the initial counter is supplied seekable by storing the initial counter value
This commit is contained in:
Alex Barney 2018-08-31 17:53:57 -05:00
parent 4101c48cf4
commit 3d8d3992eb
2 changed files with 18 additions and 5 deletions
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18
LibHac/Aes128CtrStream.cs
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@ -29,11 +29,21 @@ namespace LibHac
/// </summary> /// </summary>
/// <param name="baseStream">The base stream</param> /// <param name="baseStream">The base stream</param>
/// <param name="key">The decryption key</param> /// <param name="key">The decryption key</param>
/// <param name="counter">The intial counter</param> /// <param name="counter">The initial counter</param>
public Aes128CtrStream(Stream baseStream, byte[] key, byte[] counter) public Aes128CtrStream(Stream baseStream, byte[] key, byte[] counter)
: base(baseStream, BlockSize) : base(baseStream, BlockSize)
{ {
_counterOffset = 0; _counterOffset = 0;
// Make the stream seekable by remembering the initial counter value
if (counter != null)
{
for (int i = 0; i < 8; i++)
{
_counterOffset |= (long)counter[0xF - i] << (4 + i * 8);
}
}
Length = baseStream.Length; Length = baseStream.Length;
_tempBuffer = new byte[CryptChunkSize]; _tempBuffer = new byte[CryptChunkSize];
@ -70,11 +80,11 @@ namespace LibHac
private void UpdateCounter(long offset) private void UpdateCounter(long offset)
{ {
offset >>= 4; ulong off = (ulong)offset >> 4;
for (uint j = 0; j < 0x8; j++) for (uint j = 0; j < 0x8; j++)
{ {
Counter[0x10 - j - 1] = (byte)(offset & 0xFF); Counter[0x10 - j - 1] = (byte)(off & 0xFF);
offset >>= 8; off >>= 8;
} }
} }

3
LibHac/Streams/RandomAccessSectorStream.cs
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@ -31,7 +31,10 @@ namespace LibHac.Streams
_currentSector = sectorNum; _currentSector = sectorNum;
long startPos = sectorNum * _bufferSize; long startPos = sectorNum * _bufferSize;
if (_baseStream.Position != startPos)
{
_baseStream.Position = startPos; _baseStream.Position = startPos;
}
_readBytes = _baseStream.Read(_buffer, 0, _bufferSize); _readBytes = _baseStream.Read(_buffer, 0, _bufferSize);
} }