private void AES_CCM(byte[] k)
{
CcmBlockCipher cipher = new CcmBlockCipher(new AesEngine());
KeyParameter contentKey;
int cbitTag = 64;
// The requirements from JWA
// IV is 96 bits
// Authentication tag is 128 bits
// key sizes are 128, 192 and 256 bits
_iv = new byte[96 / 8];
s_PRNG.NextBytes(_iv);
contentKey = new KeyParameter(k);
// Build the object to be hashed
byte[] a = new byte[0];
if (ProtectedMap != null)
{
a = Encoding.UTF8.GetBytes(ProtectedMap.ToString());
}
AeadParameters parameters = new AeadParameters(contentKey, 128, _iv, a);
cipher.Init(true, parameters);
byte[] c = new byte[cipher.GetOutputSize(payload.Length)];
int len = cipher.ProcessBytes(payload, 0, payload.Length, c, 0);
cipher.DoFinal(c, len);
Array.Resize(ref c, c.Length - (128 / 8) + (cbitTag / 8));
_RgbEncrypted = c;
}
/// <summary>
/// Encrypt the message based on attributes and recipients.
/// </summary>
public virtual void Encrypt()
{
string alg = null;
// Get the algorithm we are using - the default is AES GCM
try {
alg = FindAttribute("enc").AsString();
}
catch {
foreach (Recipient r in RecipientList)
{
CBORObject alg2 = r.FindAttribute("enc");
if (alg2 != null)
{
if (alg2.Type != CBORType.TextString || (alg != null && alg != alg2.AsString()))
{
throw new JoseException("Multiple content encryption algorithms have been specified.");
}
alg = alg2.AsString();
}
}
if (alg == null)
{
throw new JoseException("Content encryption algorithm has not been specified.");
}
}
byte[] contentKey = null;
// Determine if we are doing a direct encryption
int recipientTypes = 0;
if (RecipientList.Count == 0)
{
throw new JoseException("Must have at least one recipient for the message");
}
foreach (Recipient key in RecipientList)
{
switch (key.RecipientType)
{
case RecipientType.Direct:
case RecipientType.KeyAgreeDirect:
if ((recipientTypes & 1) != 0)
{
throw new JoseException("It is not legal to have two direct recipients in a message");
}
recipientTypes |= 1;
contentKey = key.GetKey(alg, this);
break;
default:
recipientTypes |= 2;
break;
}
}
if (recipientTypes == 3)
{
throw new JoseException("It is not legal to mix direct and indirect recipients in a message");
}
if (contentKey == null)
{
switch (alg)
{
case "A128GCM":
case "AES-128-CCM-64":
contentKey = new byte[128 / 8];
break;
case "A192GCM":
case "AES192GCM":
contentKey = new byte[192 / 8];
break;
case "A256GCM":
case "AES256GCM":
contentKey = new byte[256 / 8];
break;
case "A128CBC-HS256":
contentKey = new byte[2 * 128 / 8];
break;
case "A192CBC-HS256":
contentKey = new byte[2 * 192 / 8];
break;
case "A256CBC-HS256":
contentKey = new byte[2 * 256 / 8];
break;
default:
throw new JoseException($"Unrecognized content encryption algorithm '{alg}'");
}
s_PRNG.NextBytes(contentKey);
}
foreach (Recipient key in RecipientList)
{
key.SetContent(contentKey);
key.Encrypt(this);
}
// Encode the protected attributes if there are any
if (ProtectedMap.Count > 0)
{
_strProtected = base64urlencode(Encoding.UTF8.GetBytes(ProtectedMap.ToString()));
}
byte[] saveContent = payload;
if (ProtectedMap.ContainsKey("zip"))
{
MemoryStream stm2 = new MemoryStream();
DeflateStream zipStm = new DeflateStream(stm2, CompressionMode.Compress);
zipStm.Write(payload, 0, payload.Length);
zipStm.Close();
payload = stm2.GetBuffer();
}
switch (alg)
{
case "A128GCM":
case "A192GCM":
case "A256GCM":
AES_GCM_Encrypt(contentKey);
break;
case "AES-128-CCM-64":
AES_CCM(contentKey);
break;
case "A128CBC-HS256":
case "A192CBC-HS256":
case "A256CBC-HS256":
AES_CBC_MAC_Encrypt(alg, contentKey);
break;
default:
throw new JoseException("Internal Error: We should never get here.");
}
payload = saveContent;
}
/// <inheritdoc />
protected override CBORObject InternalEncodeToJSON(bool fCompact)
{
CBORObject obj = CBORObject.NewMap();
if (_RgbEncrypted == null)
{
Encrypt();
}
if (ProtectedMap.Count > 0)
{
obj.Add("protected", base64urlencode(Encoding.UTF8.GetBytes(ProtectedMap.ToString())));
}
if (UnprotectedMap.Count > 0)
{
obj.Add("unprotected", UnprotectedMap); // Add unprotected attributes
}
if (_iv != null)
{
obj.Add("iv", base64urlencode(_iv)); // Add iv
}
if (_Aad != null)
{
obj.Add("aad", Encoding.UTF8.GetString(_Aad));
}
if (_RgbEncrypted != null)
{
obj.Add("ciphertext", base64urlencode(_RgbEncrypted)); // Add ciphertext
}
obj.Add("tag", base64urlencode(_Tag));
if (RecipientList.Count > 0)
{
CBORObject recipients = CBORObject.NewArray();
foreach (Recipient key in RecipientList)
{
CBORObject j = key.EncodeToJSON();
if ((j != null) && (j.Count != 0))
{
recipients.Add(j);
}
}
if (fCompact)
{
if (recipients.Count != 1)
{
throw new JoseException("Compact encoding must be for one recipient");
}
if (recipients[0].ContainsKey("encrypted_key"))
{
obj.Add("encrypted_key", recipients[0]["encrypted_key"]);
}
if (recipients[0].ContainsKey("header"))
{
obj.Add("header", recipients[0]["header"]);
}
}
else
{
if (recipients.Count > 0)
{
obj.Add("recipients", recipients);
}
}
}
else
{
throw new JoseException("Must have one or more recipients");
}
return(obj);
}