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Merge pull request #4 from aaru-dps/fakeshemp/decrypt-sector-long

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Add DecryptSectorLong for CSS
This commit is contained in:
Natalia Portillo
2023-10-15 22:43:45 +01:00
committed by GitHub
parent 605e00ed85 3aa48889dd
commit 4a9bf0fa9d
1 changed files with 40 additions and 0 deletions
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40
DVD/CSS.cs
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@@ -662,6 +662,46 @@ public class CSS
return decryptedBuffer;
}
/// <summary>Takes a sector and a decrypted title key and returns the decrypted sector.</summary>
/// <param name="sectorData">Encrypted sector data.</param>
/// <param name="cmiData">The Copyright Management Information.</param>
/// <param name="keyData">The encryption keys.</param>
/// <param name="blocks">Number of sectors in <c>sectorData</c>.</param>
/// <param name="blockSize">Size of one sector.</param>
/// <returns>The decrypted sector.</returns>
public static byte[] DecryptSectorLong(byte[] sectorData, byte[] keyData, byte[]? cmiData, uint blocks = 1,
uint blockSize = 2048)
{
// None of the sectors are encrypted
if(cmiData != null && cmiData.All(static cmi => (cmi & 0x80) >> 7 == 0) || keyData.All(static k => k == 0))
return sectorData;
var decryptedBuffer = new byte[sectorData.Length];
for(uint i = 0; i < blocks; i++)
{
byte[] currentKey = keyData.Skip((int)(i * 5)).Take(5).ToArray();
byte[] currentPrefix = sectorData.Skip((int)(i * 2064)).Take(12).ToArray();
byte[] currentSuffix = sectorData.Skip((int)(2060 + i * 2064)).Take(4).ToArray();
byte[] currentSector = sectorData.Skip((int)(12 + i * blockSize + (16 * i))).Take((int)blockSize).ToArray();
Array.Copy(currentPrefix, 0, decryptedBuffer, (int)(i * 2064), 12);
Array.Copy(currentSuffix, 0, decryptedBuffer, (int)(2060 + i * 2064), 4);
if(!IsEncrypted(cmiData?[i], currentKey, currentSector))
{
Array.Copy(currentSector, 0, decryptedBuffer, (int)(12 + i * blockSize + (16 * i)), blockSize);
continue;
}
Array.Copy(UnscrambleSector(currentKey, currentSector), 0, decryptedBuffer,
(int)(12 + i * blockSize + (16 * i)), blockSize);
}
return decryptedBuffer;
}
/// <summary>
/// Unscrambles a DVD sector with a title key.
/// </summary>