// Decryption Routine: Base64 -> AES -> Zlib
private static byte[] Decrypt(uint uVer, uint uLen, uint uLenCompressed, uint dwBufferFlag, byte[] pSrc)
{
byte[] bits = BitConverter.GetBytes(dwBufferFlag);
if (!((bits[3] & 1) != 0))
{
byte[] aKey;
byte[] aIV;
// Get the AES Key/IV for transformation
CipherKeys.GetKeyAndIV(uVer, uLenCompressed, out aKey, out aIV);
// Decode the base64 encoded string
pSrc = Convert.FromBase64String(Encoding.UTF8.GetString(pSrc));
// Decrypt the AES encrypted block
AESCipher pCipher = new AESCipher(aKey, aIV);
pCipher.TransformBlock(pSrc, 0, uLen, pSrc, 0);
}
else
{
// Decrypt the XOR encrypted block
pSrc = EncryptXOR(uVer, pSrc, uLen, uLenCompressed);
}
if (bits[0] != 0)
{
return(ZlibStream.UncompressBuffer(pSrc));
}
return(pSrc);
}
private static byte[] EncryptXOR(uint uVer, byte[] pSrc, uint uLen, uint uLenCompressed)
{
byte[] aKey;
CipherKeys.GetXORKey(uVer, out aKey);
uint uBlock = uLen >> 2;
uint uBlockOffset = 0;
int nKeyOffset = 0;
if (uBlock != 0)
{
while (uBlockOffset < uBlock)
{
/*
* _begin:
* mov eax, [ebp+pKey]
* mov eax, [eax+edx*4]
* xor [ebx+ecx*4], eax
* inc edx
* inc ecx
* and edx, 1FFh
* cmp ecx, esi
* jb _begin
* _end:
* mov eax, [ebp+uLen]
*/
uint pBlockData = BitConverter.ToUInt32(pSrc, (int)(4 * uBlockOffset)) ^ BitConverter.ToUInt32(aKey, 4 * nKeyOffset);
Buffer.BlockCopy(BitConverter.GetBytes(pBlockData), 0, pSrc, (int)(4 * uBlockOffset), sizeof(uint));
nKeyOffset = ((ushort)nKeyOffset + 1) & 0x1FF;
uBlockOffset++;
}
}
uBlock = (uLen & 3);
if (uBlock != 0)
{
int nStart = (int)(4 * uBlockOffset);
uBlockOffset = 0;
nKeyOffset = 0;
while (uBlockOffset < uBlock)
{
pSrc[nStart + uBlockOffset++] ^= (byte)(aKey[nKeyOffset]);
nKeyOffset = ((ushort)nKeyOffset + 1) & 0x7FF;
}
}
return(pSrc);
}
internal static string Hmac(string plainText, CipherKeys keys)
{
var base64String = Convert.ToBase64String(Encoding.UTF8.GetBytes(plainText));
var sessionKeyBytes = GetSessionKeyBytes(keys);
using (var hmacsha256 = new HMACSHA256(sessionKeyBytes))
{
byte[] data = Encoding.UTF8.GetBytes(base64String);
byte[] hashmessage = hmacsha256.ComputeHash(data);
return(Convert.ToBase64String(hashmessage));
}
}
internal static byte[] GetRekBytes(string rek, CipherKeys keys)
{
byte[] dataToDecrypt = Convert.FromBase64String(rek);
AesManaged tdes = new AesManaged
{
KeySize = 256,
BlockSize = 128,
Key = GetSessionKeyBytes(keys),
Mode = CipherMode.ECB,
Padding = PaddingMode.PKCS7
};
ICryptoTransform decrypt = tdes.CreateDecryptor();
byte[] deCipher = decrypt.TransformFinalBlock(dataToDecrypt, 0, dataToDecrypt.Length);
tdes.Clear();
return(deCipher);
}
//track return status api
public static Response TrackReturnStatus(string username, string authToken, CipherKeys keys, string gstin, string returnPeriod, string returnType)
{
var queryString = new NameValueCollection
{
{ "action", "RETTRACK" },
{ "gstin", gstin },
{ "fy", returnPeriod },
{ "type", returnType }
};
var handler = new RequestHandler();
handler.UserRequest.Keys = keys;
handler.UserRequest.Header.Username = username;
handler.UserRequest.Header.AuthToken = authToken;
var url = UrlHandler.Route(accessGroup.commonapi, version.v1_0, modName.returns);
return(handler.DecryptGetResponse(url, queryString));
}
// Encryption Routine: Zlib -> AES -> Base64
public static byte[] Encrypt(uint uVer, byte[] pSrc, uint dwBufferFlag, out uint uLen, out uint uLenCompressed, out uint uLenEncoded)
{
byte[] bits = BitConverter.GetBytes(dwBufferFlag);
byte[] pEncrypted;
if (bits[0] != 0)
{
pEncrypted = ZlibStream.CompressBuffer(pSrc);
}
else
{
pEncrypted = new byte[pSrc.Length];
Buffer.BlockCopy(pSrc, 0, pEncrypted, 0, pSrc.Length);
}
uLen = (uint)pSrc.Length;
uLenCompressed = (uint)pEncrypted.Length;
if (!((bits[3] & 1) != 0))
{
byte[] aKey;
byte[] aIV;
// Get the AES Key/IV for transformation
CipherKeys.GetKeyAndIV(uVer, uLenCompressed, out aKey, out aIV);
// Perform AES block encryption
AESCipher pCipher = new AESCipher(aKey, aIV);
pCipher.TransformBlock(pEncrypted, 0, uLen, pEncrypted, 0);
// Encode the encrypted data into a base64 encoded string
pEncrypted = Encoding.UTF8.GetBytes(Convert.ToBase64String(pEncrypted));
}
else
{
// Perform XOR block encryption
pEncrypted = EncryptXOR(uVer, pEncrypted, uLen, uLenCompressed);
}
uLenEncoded = (uint)pEncrypted.Length;
return(pEncrypted);
}
private static byte[] EncryptXor(PackVersion version, byte[] src, uint size, uint sizeCompressed)
{
CipherKeys.GetXorKey(version, out byte[] key);
uint uBlock = size >> 2;
uint uBlockOffset = 0;
int nKeyOffset = 0;
if (uBlock != 0)
{
while (uBlockOffset < uBlock)
{
uint pBlockData = BitConverter.ToUInt32(src, (int)(4 * uBlockOffset)) ^
BitConverter.ToUInt32(key, 4 * nKeyOffset);
Buffer.BlockCopy(BitConverter.GetBytes(pBlockData), 0, src, (int)(4 * uBlockOffset),
sizeof(uint));
nKeyOffset = ((ushort)nKeyOffset + 1) & 0x1FF;
uBlockOffset++;
}
}
uBlock = (size & 3);
if (uBlock != 0)
{
int nStart = (int)(4 * uBlockOffset);
uBlockOffset = 0;
nKeyOffset = 0;
while (uBlockOffset < uBlock)
{
src[nStart + uBlockOffset++] ^= (byte)(key[nKeyOffset]);
nKeyOffset = ((ushort)nKeyOffset + 1) & 0x7FF;
}
}
return(src);
}
// Decryption Routine: Base64 -> AES -> Zlib
private static byte[] Decrypt(PackVersion version, uint size, uint sizeCompressed, Encryption flag, byte[] src)
{
if (flag.HasFlag(Encryption.Aes))
{
// Get the AES Key/IV for transformation
CipherKeys.GetKeyAndIV(version, sizeCompressed, out byte[] key, out byte[] iv);
// Decode the base64 encoded string
src = Convert.FromBase64String(Encoding.UTF8.GetString(src));
// Decrypt the AES encrypted block
AESCipher pCipher = new AESCipher(key, iv);
pCipher.TransformBlock(src, 0, size, src, 0);
}
else if (flag.HasFlag(Encryption.Xor))
{
// Decrypt the XOR encrypted block
src = EncryptXor(version, src, size, sizeCompressed);
}
return(flag.HasFlag(Encryption.Zlib) ? ZlibStream.UncompressBuffer(src) : src);
}
// Encryption Routine: Zlib -> AES -> Base64
public static byte[] Encrypt(PackVersion version, byte[] src, Encryption flag, out uint size,
out uint sizeCompressed, out uint sizeEncoded)
{
byte[] pEncrypted;
if (flag.HasFlag(Encryption.Zlib))
{
pEncrypted = ZlibStream.CompressBuffer(src);
}
else
{
pEncrypted = new byte[src.Length];
Buffer.BlockCopy(src, 0, pEncrypted, 0, src.Length);
}
size = (uint)src.Length;
sizeCompressed = (uint)pEncrypted.Length;
if (flag.HasFlag(Encryption.Aes))
{
// Get the AES Key/IV for transformation
CipherKeys.GetKeyAndIV(version, sizeCompressed, out byte[] key, out byte[] iv);
// Perform AES block encryption
var pCipher = new AESCipher(key, iv);
pCipher.TransformBlock(pEncrypted, 0, size, pEncrypted, 0);
// Encode the encrypted data into a base64 encoded string
pEncrypted = Encoding.UTF8.GetBytes(Convert.ToBase64String(pEncrypted));
}
else if (flag.HasFlag(Encryption.Xor))
{
// Perform XOR block encryption
pEncrypted = EncryptXor(version, pEncrypted, size, sizeCompressed);
}
sizeEncoded = (uint)pEncrypted.Length;
return(pEncrypted);
}
internal static string EncryptTextWithSessionKey(string plainText, CipherKeys keys)
{
var base64String = Convert.ToBase64String(Encoding.UTF8.GetBytes(plainText));
byte[] dataToEncrypt = Encoding.UTF8.GetBytes(base64String);
AesManaged tdes = new AesManaged
{
KeySize = 256,
BlockSize = 128,
Key = GetSessionKeyBytes(keys),
Mode = CipherMode.ECB,
Padding = PaddingMode.PKCS7
};
ICryptoTransform crypt = tdes.CreateEncryptor();
byte[] cipher = crypt.TransformFinalBlock(dataToEncrypt, 0, dataToEncrypt.Length);
tdes.Clear();
return(Convert.ToBase64String(cipher, 0, cipher.Length));
}
internal static string DecryptResponseData(string dataToDecrypt, string rek, CipherKeys keys)
{
byte[] dataToDecryptBytes = Convert.FromBase64String(dataToDecrypt);
AesManaged tdes = new AesManaged
{
KeySize = 256,
BlockSize = 128,
Key = GetRekBytes(rek, keys),
Mode = CipherMode.ECB,
Padding = PaddingMode.PKCS7
};
ICryptoTransform decrypt = tdes.CreateDecryptor();
byte[] deCipher = decrypt.TransformFinalBlock(dataToDecryptBytes, 0, dataToDecryptBytes.Length);
tdes.Clear();
var deCipherData = Encoding.UTF8.GetString(deCipher);
var json = Encoding.UTF8.GetString(Convert.FromBase64String(deCipherData));
return(json);
}
