/// <summary>
/// Parse plain string token and get JWE Asymmetric token object
///
/// </summary>
/// <param name="token"></param>
/// <param name="privateKey"></param>
/// <returns></returns>
public static JWEAsymmetric Parse(string token, string privateKey)
{
byte[] claimSet = null;
EncryptedPayload payload = null;
try
{
payload = EncryptedPayload.Parse(token);
byte[] masterKey = null;
using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
{
rsa.FromXmlString(privateKey);
masterKey = rsa.Decrypt(payload.EncryptedMasterKey, true);
}
byte[] additionalAuthenticateData = payload.ToAdditionalAuthenticatedData();
using (var aes = new AuthenticatedAesCng())
{
aes.CngMode = CngChainingMode.Gcm;
aes.Key = masterKey;
aes.IV = payload.InitializationVector;
aes.AuthenticatedData = additionalAuthenticateData;
aes.Tag = payload.Tag;
using (var ms = new MemoryStream())
{
using (var cs = new CryptoStream(ms, aes.CreateDecryptor(), CryptoStreamMode.Write))
{
byte[] cipherText = payload.CipherText;
cs.Write(cipherText, 0, cipherText.Length);
cs.FlushFinalBlock();
claimSet = ms.ToArray();
}
}
}
}
catch (Exception ex)
{
throw new SecurityException("Invalid Token", ex);
}
var jwt = JsonConvert.DeserializeObject <JWEAsymmetric>(payload.Header);
jwt.AsymmetricKey = privateKey;
jwt.claims = JsonConvert.DeserializeObject <Dictionary <string, string> >(Encoding.UTF8.GetString(claimSet));
return(jwt);
}
/// <summary>
/// To encrypt this token, we need receiver's public key
/// </summary>
/// <returns></returns>
public override string SerializeToBase64UrlString()
{
string header = JsonConvert.SerializeObject(this);
string claims = JsonConvert.SerializeObject(this.claims);
byte[] masterKey = new byte[32];
byte[] initVector = new byte[12];
using (var provider = new RNGCryptoServiceProvider())
{
provider.GetBytes(masterKey);
provider.GetBytes(initVector);
}
byte[] encryptedMasterKey = null;
using (var rsa = new RSACryptoServiceProvider())
{
rsa.FromXmlString(AsymmetricKey);
encryptedMasterKey = rsa.Encrypt(masterKey, true);
}
var authoData = new EncryptedPayload()
{
Header = header,
EncryptedMasterKey = encryptedMasterKey,
InitializationVector = initVector
};
byte[] additionalAuthenticatedData = authoData.ToAdditionalAuthenticatedData();
byte[] tag = null;
byte[] cipherText = null;
using (var aes = new AuthenticatedAesCng())
{
//AES+GCM is used for encryption AND authentication(digital signature)
aes.CngMode = CngChainingMode.Gcm;
aes.Key = masterKey;
aes.IV = initVector;
aes.AuthenticatedData = additionalAuthenticatedData;
using (var ms = new MemoryStream())
{
using (var encryptor = aes.CreateAuthenticatedEncryptor())
{
using (var cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
{
byte[] claimSet = Encoding.UTF8.GetBytes(claims);
cs.Write(claimSet, 0, claimSet.Length);
cs.FlushFinalBlock();
tag = encryptor.GetTag();
cipherText = ms.ToArray();
}
}
}
}
var payload = new EncryptedPayload()
{
Header = header,
EncryptedMasterKey = encryptedMasterKey,
InitializationVector = initVector,
CipherText = cipherText,
Tag = tag
};
string token = payload.SerializeToBase64UrlString();
return(token);
}
