public void KDF()
{
// Decrypt packet salt
if (ecmID != prevEcmID)
{
byte[] saltHmacKey = sha1.ComputeHash(F4FOldMethod.AppendBuf(sessionKey, packetIV));
if (debug)
{
Program.DebugLog("SaltHmacKey : " + Hexlify(saltHmacKey));
}
shaSalt.Key = saltHmacKey;
saltAesKey = F4FOldMethod.BlockCopy(shaSalt.ComputeHash(hmacData1), 0, 16);
if (debug)
{
Program.DebugLog("SaltAesKey : " + Hexlify(saltAesKey));
}
prevEcmID = ecmID;
}
if (debug)
{
Program.DebugLog("EncryptedSalt: " + Hexlify(packetSalt));
}
byte[] decryptedSalt = AesDecrypt(packetSalt, saltAesKey, packetIV);
if (decryptedSalt == null)
{
Program.Quit("<c:Red>Error ocurred while decription salt of fagment.");
}
if (debug)
{
Program.DebugLog("DecryptedSalt: " + Hexlify(decryptedSalt));
}
decryptBytes = F4FOldMethod.ReadInt32(ref decryptedSalt, 0);
if (debug)
{
Program.DebugLog("DecryptBytes : " + decryptBytes);
}
byte[] decryptedSalt2 = F4FOldMethod.BlockCopy(decryptedSalt, 4, 16);
if (debug)
{
Program.DebugLog("DecryptedSalt: " + Hexlify(decryptedSalt2));
}
// Generate final packet decryption key
byte[] finalHmacKey = sha1.ComputeHash(decryptedSalt2);
if (debug)
{
Program.DebugLog("FinalHmacKey : " + Hexlify(finalHmacKey));
}
finalsha.Key = finalHmacKey;
packetKey = F4FOldMethod.BlockCopy(finalsha.ComputeHash(hmacData2), 0, 16);
if (debug)
{
Program.DebugLog("PacketKey : " + Hexlify(packetKey));
}
}
public byte[] Decrypt(byte[] data, long pos, string baseUrl, string auth)
{
if (debug)
{
Program.DebugLog("\n----- Akamai Decryption Start -----");
}
byte[] decryptedData = new byte[0];
// Parse packet header
using (MemoryStream ms = new MemoryStream(data)) {
ms.Position = pos;
using (HDSBinaryReader br = new HDSBinaryReader(ms)) {
int b = br.ReadByte();
ecmVersion = (b >> 4);
if (ecmVersion != 11)
{
ecmVersion = b;
}
ecmID = br.ReadInt32();
ecmTimestamp = (uint)br.ReadInt32();
kdfVersion = br.ReadInt16();
dccAccReserved = br.ReadByte();
if (debug)
{
Program.DebugLog("ECM Version : " + ecmVersion + ", ECM ID: " + ecmID + ", ECM Timestamp: " + ecmTimestamp + ", KDF Version: " + kdfVersion + ", DccAccReserved: " + dccAccReserved);
}
b = br.ReadByte();
bool iv = ((b & 2) > 0);
bool key = ((b & 4) > 0);
if (iv)
{
packetIV = br.ReadBytes(16);
if (debug)
{
Program.DebugLog("PacketIV : " + Hexlify(packetIV));
}
}
if (key)
{
sessionKeyUrl = br.ReadString();
if (debug)
{
Program.DebugLog("SessionKeyUrl: " + sessionKeyUrl);
}
string keyPath = sessionKeyUrl.Substring(sessionKeyUrl.LastIndexOf('/'));
string keyUrl = HTTP.JoinUrl(baseUrl, keyPath) + auth;
// Download key file if required
if (sessionKeyUrl != lastKeyUrl)
{
if ((baseUrl.Length == 0) && (sessionKey.Length == 0))
{
if (debug)
{
Program.DebugLog("Unable to download session key without manifest url. you must specify it manually using 'adkey' switch.");
}
}
else
{
if (baseUrl.Length > 0)
{
if (debug)
{
Program.DebugLog("Downloading new session key from " + keyUrl);
}
byte[] downloadedData = HTTP.TryGETData(keyUrl, out int retCode, out string status);
if (retCode == 200)
{
sessionID = "_" + keyPath.Substring("/key_".Length);
sessionKey = downloadedData;
}
else
{
if (debug)
{
Program.DebugLog("Failed to download new session key, Status: " + status + " (" + retCode + ")");
}
sessionID = "";
}
}
}
lastKeyUrl = sessionKeyUrl;
if (sessionKey == null || sessionKey.Length == 0)
{
Program.Quit("Failed to download akamai session decryption key");
}
}
}
if (debug)
{
Program.DebugLog("SessionKey : " + Hexlify(sessionKey));
}
if (sessionKey == null || sessionKey.Length < 1)
{
Program.Quit("ERROR: Fragments can't be decrypted properly without corresponding session key.");
}
byte reserved; byte[] reservedBlock1, reservedBlock2, encryptedData, lastBlockData;
reserved = br.ReadByte();
packetSalt = br.ReadBytes(32);
reservedBlock1 = br.ReadBytes(20);
reservedBlock2 = br.ReadBytes(20);
if (debug)
{
Program.DebugLog("ReservedByte : " + reserved + ", ReservedBlock1: " + Hexlify(reservedBlock1) + ", ReservedBlock2: " + Hexlify(reservedBlock2));
}
// Generate packet decryption key
KDF();
// Decrypt packet data
encryptedData = br.ReadBytes((int)decryptBytes);
lastBlockData = br.ReadToEnd();
if (decryptBytes > 0)
{
decryptedData = AesDecrypt(encryptedData, packetKey, packetIV);
}
decryptedData = F4FOldMethod.AppendBuf(decryptedData, lastBlockData);
if (debug)
{
Program.DebugLog("EncryptedData: " + Hexlify(encryptedData, 64));
Program.DebugLog("DecryptedData: " + Hexlify(decryptedData, 64));
Program.DebugLog("----- Akamai Decryption End -----\n");
}
} // using (HDSBinaryReader br = new HDSBinaryReader(ms))
} // using (MemoryStream ms = new MemoryStream(data))
return(decryptedData);
}