/// <summary>
/// Try to parse the Json Web Encrypted token.
/// Returns the Json Web Signed token otherwise null.
/// </summary>
/// <param name="jwe"></param>
/// <param name="jsonWebKey"></param>
/// <returns></returns>
public string Parse(
string jwe,
JsonWebKey jsonWebKey)
{
const string emptyResult = null;
var header = GetHeader(jwe);
if (header == null)
{
return(emptyResult);
}
var algorithmName = header.Alg;
var encryptionName = header.Enc;
if (!Constants.MappingNameToJweAlgEnum.Keys.Contains(algorithmName) ||
!Constants.MappingNameToJweEncEnum.Keys.Contains(encryptionName))
{
return(emptyResult);
}
var algorithmEnum = Constants.MappingNameToJweAlgEnum[algorithmName];
var encryptionEnum = Constants.MappingNameToJweEncEnum[encryptionName];
var algorithm = _jweHelper.GetEncryptor(encryptionEnum);
return(algorithm.Decrypt(jwe, algorithmEnum, jsonWebKey));
}
private string PerformeJweGeneration(
string entry,
JweAlg alg,
JweEnc enc,
JsonWebKey jsonWebKey,
Func <IEncryption, JweProtectedHeader, AesEncryptionResult> callback)
{
var algo = Constants.MappingNameToJweAlgEnum
.SingleOrDefault(k => k.Value == alg);
var encryption = Constants.MappingNameToJweEncEnum
.SingleOrDefault(k => k.Value == enc);
if (jsonWebKey == null ||
algo.IsDefault() ||
encryption.IsDefault())
{
return(entry);
}
// Construct the JWE protected header
var jweProtectedHeader = new JweProtectedHeader
{
Alg = algo.Key,
Enc = encryption.Key,
Kid = jsonWebKey.Kid
};
var algorithm = _jweHelper.GetEncryptor(enc);
var encryptionResult = callback(
algorithm,
jweProtectedHeader);
var base64EncodedjweProtectedHeaderSerialized = jweProtectedHeader.SerializeWithDataContract().Base64Encode();
var base64EncodedJweEncryptedKey = encryptionResult.EncryptedContentEncryptionKey.Base64EncodeBytes();
var base64EncodedIv = encryptionResult.Iv.Base64EncodeBytes();
var base64EncodedCipherText = encryptionResult.CipherText.Base64EncodeBytes();
var base64EncodedAuthenticationTag = encryptionResult.AuthenticationTag.Base64EncodeBytes();
return(base64EncodedjweProtectedHeaderSerialized + "." +
base64EncodedJweEncryptedKey + "." +
base64EncodedIv + "." +
base64EncodedCipherText + "." +
base64EncodedAuthenticationTag);
}