public static (GarlicAESBlock, I2PSessionKey) EGDecryptGarlic(
GarlicMessage garlic,
I2PPrivateKey privkey)
{
var cipher = new CbcBlockCipher(new AesEngine());
var egdata = garlic.EGData;
var egbuf = new BufLen(egdata, 0, 514);
var egheader = ElGamalCrypto.Decrypt(egbuf, privkey, true);
var sessionkey = new I2PSessionKey(new BufLen(egheader, 0, 32));
var preiv = new BufLen(egheader, 32, 32);
var egpadding = new BufLen(egheader, 64, 158);
var aesbuf = new BufLen(egdata, 514);
var pivh = I2PHashSHA256.GetHash(preiv);
cipher.Init(false, sessionkey.Key.ToParametersWithIV(new BufLen(pivh, 0, 16)));
cipher.ProcessBytes(aesbuf);
GarlicAESBlock aesblock =
new GarlicAESBlock(new BufRefLen(aesbuf));
if (!aesblock.VerifyPayloadHash())
{
throw new ChecksumFailureException("AES block hash check failed!");
}
return(aesblock, sessionkey);
}
public static (GarlicAESBlock, I2PSessionKey) RetrieveAESBlock(
GarlicMessage garlic,
I2PPrivateKey privatekey,
Func <I2PSessionTag, I2PSessionKey> findsessionkey)
{
GarlicAESBlock result;
var cipher = new CbcBlockCipher(new AesEngine());
var tag = new I2PSessionTag(new BufRefLen(garlic.EGData, 0, 32));
var sessionkey = findsessionkey?.Invoke(tag);
#if LOG_ALL_LEASE_MGMT
Logging.LogDebug($"Garlic: Session key found {sessionkey}");
#endif
if (sessionkey != null)
{
var aesbuf = new BufLen(garlic.EGData, 32);
var pivh = I2PHashSHA256.GetHash(tag.Value);
cipher.Init(false, sessionkey.Key.ToParametersWithIV(new BufLen(pivh, 0, 16)));
cipher.ProcessBytes(aesbuf);
try
{
result = new GarlicAESBlock(new BufRefLen(aesbuf));
if (!result.VerifyPayloadHash())
{
Logging.LogDebug("Garlic: DecryptMessage: AES block SHA256 check failed.");
return(null, null);
}
return(result, sessionkey);
}
catch (ArgumentException ex)
{
Logging.Log("Garlic", ex);
}
catch (Exception ex)
{
Logging.Log("Garlic", ex);
return(null, null);
}
}
#if LOG_ALL_LEASE_MGMT
Logging.LogDebug("Garlic: No session key. Using ElGamal to decrypt.");
#endif
try
{
(result, sessionkey) = Garlic.EGDecryptGarlic(garlic, privatekey);
#if LOG_ALL_LEASE_MGMT
Logging.LogDebug($"Garlic: EG session key {sessionkey}");
#endif
}
catch (Exception ex)
{
Logging.LogDebug("Garlic: ElGamal DecryptMessage failed");
Logging.LogDebugData($"ReceivedSessions {ex}");
return(null, null);
}
return(result, sessionkey);
}