/// <summary>
/// Decrypts the session key stored in the EncryptedSessionKey
/// property and saves the decrypted key in the EncodedSessionKey
/// property.
/// </summary>
/// <remarks>This function also calls DecodeSessionKey so that the
/// decrypted and decoded sessionkey is stored in the
/// SessionKey property.</remarks>
/// <param name="tskKey">A transportable secret key that is used to
/// decrypt the encrypted session key.</param>
/// <param name="strPassphrase">The passphrase used to decrypt the
/// encrypted key material of the given transportable secret
/// key.</param>
public void DecryptSessionKey(TransportableSecretKey tskKey, string strPassphrase)
{
AsymmetricCipher acCipher = new RSA();
switch (aaPublicAlgorithm)
{
case AsymAlgorithms.ElGama_Encrypt_Sign:
case AsymAlgorithms.ElGamal_Encrypt_Only:
acCipher = new ElGamal();
break;
case AsymAlgorithms.RSA_Encrypt_Only:
case AsymAlgorithms.RSA_Encrypt_Sign:
acCipher = new RSA();
break;
default:
throw new System.Exception("The chosen public key algorithm is not yet implemented!");
}
bool bFound = false;
SecretKeyPacket skpKey = new SecretKeyPacket();
IEnumerator ieSubkeys = tskKey.SubKeys.GetEnumerator();
while (ieSubkeys.MoveNext())
{
if (!(ieSubkeys.Current is SecretKeyPacket))
{
throw new System.Exception("Expected a secret key packet, but did not find one!");
}
skpKey = (SecretKeyPacket)ieSubkeys.Current;
if (skpKey.PublicKey.KeyID == lKeyID)
{
bFound = true;
continue;
}
}
// check if the message was encrypted with the primary key
if (!bFound)
{
if (tskKey.PrimaryKey.PublicKey.KeyID == lKeyID)
{
skpKey = tskKey.PrimaryKey;
}
else
{
//theoretically we should never see this exception, as
//encrytped message makes sure we only get fitting secret
//keys, but just in case someone calls this directly, we
//throw an exception
throw new System.Exception("No fitting secret key found!");
}
}
BigInteger biKey = acCipher.Decrypt(this.biEncryptedSessionKey, skpKey, strPassphrase);
this.bEncodedSessionKey = biKey.getBytes();
DecodeSessionKey();
}
/// <summary>
/// Parses a single packet out of the given binary
/// data. Even if there are more than one packets in the byte
/// array, only the first packet is returned.
/// </summary>
/// <param name="bBinaryData">A byte array containing a set
/// of OpenPGP packets</param>
/// <returns>Returns an single OpenPGP packets</returns>
/// <remarks>No remarks</remarks>
public virtual Packet ParsePacket(byte[] bBinaryData)
{
Packet pReturnPacket = new Packet();
if ((bBinaryData[0] & 0xC0) == 0xC0)
{
pfFormat = PacketFormats.New;
}
else if ((bBinaryData[0] & 0xC0) == 0x80)
{
pfFormat = PacketFormats.Old;
}
else
{
throw(new ArgumentException("This is not a valid OpenPGP Packet"));
}
if (pfFormat == PacketFormats.New)
{
int iBinaryDataPos = 2;
ctContent = (ContentTypes)(bBinaryData[0] & 0x3F);
lLength = bBinaryData[1];
bBody = new byte[0];
int iHeaderLength = 1;
//partial body lengths
while ((lLength > 223) && (lLength < 255))
{
iHeaderLength++;
int lPartialBody = 1 << ((int)(lLength & 0x1F));
int lOldLength = 0;
if (bBody.Length > 0)
{
byte[] bOldBody = new byte[bBody.Length];
bBody.CopyTo(bOldBody, 0);
bBody = new byte[bOldBody.Length + lPartialBody];
bOldBody.CopyTo(bBody, 0);
lOldLength = bBody.Length;
}
else
{
bBody = new byte[lPartialBody];
}
Array.Copy(bBinaryData, iBinaryDataPos, bBody, lOldLength, lPartialBody);
lLength = bBinaryData[iBinaryDataPos + lPartialBody];
iBinaryDataPos += lPartialBody;
} //partial bodies must end with a normal header!
if (lLength < 192)
{
iHeaderLength++;
bHeader = new byte[iHeaderLength];
if (bBody.Length == 0)
{
Array.Copy(bBinaryData, 0, bHeader, 0, 2);
iBinaryDataPos = 1;
}
byte[] bOldBody = new byte[bBody.Length];
bBody.CopyTo(bOldBody, 0);
bBody = new byte[bOldBody.Length + lLength];
bOldBody.CopyTo(bBody, 0);
Array.Copy(bBinaryData, iBinaryDataPos + 1, bBody, bBody.Length - (int)lLength, (int)lLength);
}
else if ((lLength > 191) && (lLength < 224))
{
iHeaderLength += 2;
bHeader = new byte[iHeaderLength];
if (bBody.Length == 0)
{
Array.Copy(bBinaryData, 0, bHeader, 0, 3);
iBinaryDataPos = 1;
}
lLength = ((bBinaryData[iBinaryDataPos++] - 192) << 8) + bBinaryData[iBinaryDataPos++] + 192;
byte[] bOldBody = new byte[bBody.Length];
bBody.CopyTo(bOldBody, 0);
bBody = new byte[bOldBody.Length + lLength];
bOldBody.CopyTo(bBody, 0);
Array.Copy(bBinaryData, iBinaryDataPos, bBody, bBody.Length - (int)lLength, (int)lLength);
}
else if (lLength == 255)
{
iHeaderLength += 5;
bHeader = new byte[iHeaderLength];
if (bBody.Length == 0)
{
Array.Copy(bBinaryData, 0, bHeader, 0, 6);
}
lLength = (bBinaryData[iBinaryDataPos++] << 24) ^ (bBinaryData[iBinaryDataPos++] << 16) ^
(bBinaryData[iBinaryDataPos++] << 8) ^ bBinaryData[iBinaryDataPos++];
byte[] bOldBody = new byte[bBody.Length];
bBody.CopyTo(bOldBody, 0);
bBody = new byte[bOldBody.Length + lLength];
bOldBody.CopyTo(bBody, 0);
Array.Copy(bBinaryData, iBinaryDataPos, bBody, bBody.Length - (int)lLength, (int)lLength);
}
}
else
{
ctContent = (ContentTypes)((bBinaryData[0] & 0x3C) >> 2);
switch (bBinaryData[0] & 0x03)
{
case 0:
lLength = bBinaryData[1];
bHeader = new byte[2];
break;
case 1:
lLength = (bBinaryData[1] << 8) ^ (bBinaryData[2]);
bHeader = new byte[3];
break;
case 2:
lLength = (bBinaryData[1] << 16) ^ (bBinaryData[2] << 8) ^
(bBinaryData[3]);
bHeader = new byte[4];
break;
case 3:
throw new System.NotSupportedException("Packets of indetermined length are not supported due to security considerations!");
default:
throw new System.ApplicationException("This is not a valid Packet!");
}
bBody = new byte[lLength];
Array.Copy(bBinaryData, 0, bHeader, 0, bHeader.Length);
Array.Copy(bBinaryData, bHeader.Length, bBody, 0, (int)lLength);
}
this.bIsUpdated = false;
switch (ctContent)
{
case ContentTypes.AsymSessionKey:
pReturnPacket = new AsymSessionKeyPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
case ContentTypes.Compressed:
pReturnPacket = new CompressedDataPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
case ContentTypes.LiteralData:
pReturnPacket = new LiteralDataPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
case ContentTypes.Marker:
pReturnPacket = new Packet(this);
//We can savly ignore Marker packets!
//MessageBox.Show("This is a marker packet. It is not yet supported.");
break;
case ContentTypes.OnePassSignature:
pReturnPacket = new OnePassSignaturePacket(this);
//System.Windows.Forms.MessageBox.Show("This is a One Pass Signature Packet. It is not yet supported");
break;
//Content is Public Key Packet
case ContentTypes.PublicKey:
pReturnPacket = new PublicKeyPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
//Content is Public Subkey Packet. Same format as Public Key Packet
case ContentTypes.PublicSubkey:
pReturnPacket = new PublicKeyPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
case ContentTypes.SecretKey:
pReturnPacket = new SecretKeyPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
case ContentTypes.SecretSubkey:
pReturnPacket = new SecretKeyPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
case ContentTypes.Signature:
pReturnPacket = new SignaturePacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
case ContentTypes.SymEncrypted:
pReturnPacket = new SymmetricallyEncryptedDataPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
case ContentTypes.SymSessionKey:
pReturnPacket = new SymSessionKeyPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
case ContentTypes.Trust:
pReturnPacket = new Packet(this);
// TODO - Remove the messagebox
//System.Windows.Forms.MessageBox.Show("This is a Trust Packet. It is not yet supported");
break;
case ContentTypes.UserID:
pReturnPacket = new UserIDPacket(this);
pReturnPacket = pReturnPacket.ParsePacket(bBody);
break;
default:
pReturnPacket = new Packet(this);
// TODO - Remove the messagebox
System.Windows.Forms.MessageBox.Show("Sorry, but this is a packet I don't know about!");
break;
}
pReturnPacket.bIsUpdated = false;
return(pReturnPacket);
}
