/// <summary>
/// <p>
/// If buffer is non null stream assumed to be partial, otherwise the length will be used
/// to output a fixed length packet.
/// </p>
/// <p>
/// The stream created can be closed off by either calling Close()
/// on the stream or Close() on the generator. Closing the returned
/// stream does not close off the Stream parameter <c>outStr</c>.
/// </p>
/// </summary>
private Stream Open(
Stream outStr,
long length,
byte[] buffer)
{
if (cOut != null)
{
throw new InvalidOperationException("generator already in open state");
}
if (methods.Count == 0)
{
throw new InvalidOperationException("No encryption methods specified");
}
if (outStr == null)
{
throw new ArgumentNullException("outStr");
}
pOut = new BcpgOutputStream(outStr);
KeyParameter key;
if (methods.Count == 1)
{
if (methods[0] is PbeMethod)
{
PbeMethod m = (PbeMethod)methods[0];
key = m.GetKey();
}
else
{
key = PgpUtilities.MakeRandomKey(defAlgorithm, rand);
byte[] sessionInfo = CreateSessionInfo(defAlgorithm, key);
PubMethod m = (PubMethod)methods[0];
try
{
m.AddSessionInfo(sessionInfo, rand);
}
catch (Exception e)
{
throw new PgpException("exception encrypting session key", e);
}
}
pOut.WritePacket((ContainedPacket)methods[0]);
}
else // multiple methods
{
key = PgpUtilities.MakeRandomKey(defAlgorithm, rand);
byte[] sessionInfo = CreateSessionInfo(defAlgorithm, key);
for (int i = 0; i != methods.Count; i++)
{
EncMethod m = (EncMethod)methods[i];
try
{
m.AddSessionInfo(sessionInfo, rand);
}
catch (Exception e)
{
throw new PgpException("exception encrypting session key", e);
}
pOut.WritePacket(m);
}
}
string cName = PgpUtilities.GetSymmetricCipherName(defAlgorithm);
if (cName == null)
{
throw new PgpException("null cipher specified");
}
try
{
if (withIntegrityPacket)
{
cName += "/CFB/NoPadding";
}
else
{
cName += "/OpenPGPCFB/NoPadding";
}
c = CipherUtilities.GetCipher(cName);
// TODO Confirm the IV should be all zero bytes (not inLineIv - see below)
byte[] iv = new byte[c.GetBlockSize()];
c.Init(true, new ParametersWithRandom(new ParametersWithIV(key, iv), rand));
if (buffer == null)
{
//
// we have to Add block size + 2 for the Generated IV and + 1 + 22 if integrity protected
//
if (withIntegrityPacket)
{
pOut = new BcpgOutputStream(outStr, PacketTag.SymmetricEncryptedIntegrityProtected, length + c.GetBlockSize() + 2 + 1 + 22);
pOut.WriteByte(1); // version number
}
else
{
pOut = new BcpgOutputStream(outStr, PacketTag.SymmetricKeyEncrypted, length + c.GetBlockSize() + 2, oldFormat);
}
}
else
{
if (withIntegrityPacket)
{
pOut = new BcpgOutputStream(outStr, PacketTag.SymmetricEncryptedIntegrityProtected, buffer);
pOut.WriteByte(1); // version number
}
else
{
pOut = new BcpgOutputStream(outStr, PacketTag.SymmetricKeyEncrypted, buffer);
}
}
int blockSize = c.GetBlockSize();
byte[] inLineIv = new byte[blockSize + 2];
rand.NextBytes(inLineIv, 0, blockSize);
Array.Copy(inLineIv, inLineIv.Length - 4, inLineIv, inLineIv.Length - 2, 2);
Stream myOut = cOut = new CipherStream(pOut, null, c);
if (withIntegrityPacket)
{
string digestName = PgpUtilities.GetDigestName(HashAlgorithmTag.Sha1);
IDigest digest = DigestUtilities.GetDigest(digestName);
myOut = digestOut = new DigestStream(myOut, null, digest);
}
myOut.Write(inLineIv, 0, inLineIv.Length);
return(new WrappedGeneratorStream(this, myOut));
}
catch (Exception e)
{
throw new PgpException("Exception creating cipher", e);
}
}