/// <summary>
/// Flush any queued application data packets
/// </summary>
private void FlushQueuedApplicationData()
{
foreach (ByteSpan queuedSpan in this.queuedApplicationData)
{
Record outgoingRecord = new Record();
outgoingRecord.ContentType = ContentType.ApplicationData;
outgoingRecord.Epoch = this.epoch;
outgoingRecord.SequenceNumber = this.currentEpoch.NextOutgoingSequence;
outgoingRecord.Length = (ushort)this.currentEpoch.RecordProtection.GetEncryptedSize(queuedSpan.Length);
++this.currentEpoch.NextOutgoingSequence;
// Encode the record to wire format
ByteSpan packet = new byte[Record.Size + outgoingRecord.Length];
ByteSpan writer = packet;
outgoingRecord.Encode(writer);
writer = writer.Slice(Record.Size);
queuedSpan.CopyTo(writer);
// Protect the record
this.currentEpoch.RecordProtection.EncryptClientPlaintext(
packet.Slice(Record.Size, outgoingRecord.Length)
, packet.Slice(Record.Size, queuedSpan.Length)
, ref outgoingRecord
);
base.WriteBytesToConnection(packet.GetUnderlyingArray(), packet.Length);
}
this.queuedApplicationData.Clear();
}
/// <summary>
/// Request from the application to write data to the DTLS
/// stream. If appropriate, returns a byte span to send to
/// the wire.
/// </summary>
/// <param name="bytes">Plaintext bytes to write</param>
/// <param name="length">Length of the bytes to write</param>
/// <returns>
/// Encrypted data to put on the wire if appropriate,
/// otherwise an empty span
/// </returns>
private ByteSpan WriteBytesToConnectionInternal(byte[] bytes, int length)
{
lock (this.syncRoot)
{
// If we're negotiating a new epoch, queue data
if (this.nextEpoch.State != HandshakeState.Established)
{
ByteSpan copyOfSpan = new byte[length];
new ByteSpan(bytes, 0, length).CopyTo(copyOfSpan);
this.queuedApplicationData.Add(copyOfSpan);
return(ByteSpan.Empty);
}
// Send any queued application data now
this.FlushQueuedApplicationData();
Record outgoinRecord = new Record();
outgoinRecord.ContentType = ContentType.ApplicationData;
outgoinRecord.Epoch = this.epoch;
outgoinRecord.SequenceNumber = this.currentEpoch.NextOutgoingSequence;
outgoinRecord.Length = (ushort)this.currentEpoch.RecordProtection.GetEncryptedSize(length);
++this.currentEpoch.NextOutgoingSequence;
// Encode the record to wire format
ByteSpan packet = new byte[Record.Size + outgoinRecord.Length];
ByteSpan writer = packet;
outgoinRecord.Encode(writer);
writer = writer.Slice(Record.Size);
new ByteSpan(bytes, 0, length).CopyTo(writer);
// Protect the record
this.currentEpoch.RecordProtection.EncryptClientPlaintext(
packet.Slice(Record.Size, outgoinRecord.Length)
, packet.Slice(Record.Size, length)
, ref outgoinRecord
);
return(packet);
}
}
private static void EncryptPlaintext(ByteSpan output, ByteSpan input, ref Record record, Aes128Gcm cipher, ByteSpan writeIV)
{
Debug.Assert(output.Length >= GetEncryptedSizeImpl(input.Length));
// Build GCM nonce (authenticated data)
ByteSpan nonce = new byte[ImplicitNonceSize + ExplicitNonceSize];
writeIV.CopyTo(nonce);
nonce.WriteBigEndian16(record.Epoch, ImplicitNonceSize);
nonce.WriteBigEndian48(record.SequenceNumber, ImplicitNonceSize + 2);
// Serialize record as additional data
Record plaintextRecord = record;
plaintextRecord.Length = (ushort)input.Length;
ByteSpan associatedData = new byte[Record.Size];
plaintextRecord.Encode(associatedData);
cipher.Seal(output, nonce, input, associatedData);
}
/// <summary>
/// Send (resend) the ClientKeyExchange flight
/// </summary>
/// <param name="isRetransmit">
/// True if this is a retransmit of the flight. Otherwise,
/// false
/// </param>
private void SendClientKeyExchangeFlight(bool isRetransmit)
{
// Describe our flight
Handshake keyExchangeHandshake = new Handshake();
keyExchangeHandshake.MessageType = HandshakeType.ClientKeyExchange;
keyExchangeHandshake.Length = (ushort)this.nextEpoch.Handshake.CalculateClientMessageSize();
keyExchangeHandshake.MessageSequence = 5;
keyExchangeHandshake.FragmentOffset = 0;
keyExchangeHandshake.FragmentLength = keyExchangeHandshake.Length;
Record keyExchangeRecord = new Record();
keyExchangeRecord.ContentType = ContentType.Handshake;
keyExchangeRecord.Epoch = this.epoch;
keyExchangeRecord.SequenceNumber = this.currentEpoch.NextOutgoingSequence;
keyExchangeRecord.Length = (ushort)this.currentEpoch.RecordProtection.GetEncryptedSize(Handshake.Size + (int)keyExchangeHandshake.Length);
++this.currentEpoch.NextOutgoingSequence;
Record changeCipherSpecRecord = new Record();
changeCipherSpecRecord.ContentType = ContentType.ChangeCipherSpec;
changeCipherSpecRecord.Epoch = this.epoch;
changeCipherSpecRecord.SequenceNumber = this.currentEpoch.NextOutgoingSequence;
changeCipherSpecRecord.Length = (ushort)this.currentEpoch.RecordProtection.GetEncryptedSize(ChangeCipherSpec.Size);
++this.currentEpoch.NextOutgoingSequence;
Handshake finishedHandshake = new Handshake();
finishedHandshake.MessageType = HandshakeType.Finished;
finishedHandshake.Length = Finished.Size;
finishedHandshake.MessageSequence = 6;
finishedHandshake.FragmentOffset = 0;
finishedHandshake.FragmentLength = finishedHandshake.Length;
Record finishedRecord = new Record();
finishedRecord.ContentType = ContentType.Handshake;
finishedRecord.Epoch = this.nextEpoch.Epoch;
finishedRecord.SequenceNumber = this.nextEpoch.NextOutgoingSequence;
finishedRecord.Length = (ushort)this.nextEpoch.RecordProtection.GetEncryptedSize(Handshake.Size + (int)finishedHandshake.Length);
++this.nextEpoch.NextOutgoingSequence;
// Encode flight to wire format
int packetLength = 0
+ Record.Size + keyExchangeRecord.Length
+ Record.Size + changeCipherSpecRecord.Length
+ Record.Size + finishedRecord.Length;
;
ByteSpan packet = new byte[packetLength];
ByteSpan writer = packet;
keyExchangeRecord.Encode(writer);
writer = writer.Slice(Record.Size);
keyExchangeHandshake.Encode(writer);
writer = writer.Slice(Handshake.Size);
this.nextEpoch.Handshake.EncodeClientKeyExchangeMessage(writer);
ByteSpan startOfChangeCipherSpecRecord = packet.Slice(Record.Size + keyExchangeRecord.Length);
writer = startOfChangeCipherSpecRecord;
changeCipherSpecRecord.Encode(writer);
writer = writer.Slice(Record.Size);
ChangeCipherSpec.Encode(writer);
writer = writer.Slice(ChangeCipherSpec.Size);
ByteSpan startOfFinishedRecord = startOfChangeCipherSpecRecord.Slice(Record.Size + changeCipherSpecRecord.Length);
writer = startOfFinishedRecord;
finishedRecord.Encode(writer);
writer = writer.Slice(Record.Size);
finishedHandshake.Encode(writer);
writer = writer.Slice(Handshake.Size);
// Interject here to writer our client key exchange
// message into the verification stream
if (!isRetransmit)
{
this.nextEpoch.VerificationStream.Write(
packet.GetUnderlyingArray()
, Record.Size
, Handshake.Size + (int)keyExchangeHandshake.Length
);
}
// Calculate the hash of the verification stream
ByteSpan handshakeHash;
using (SHA256 sha256 = SHA256.Create())
{
this.nextEpoch.VerificationStream.Position = 0;
handshakeHash = sha256.ComputeHash(this.nextEpoch.VerificationStream);
}
// Expand our master secret into Finished digests for the client and server
PrfSha256.ExpandSecret(
this.nextEpoch.ServerVerification
, this.nextEpoch.MasterSecret
, PrfLabel.SERVER_FINISHED
, handshakeHash
);
PrfSha256.ExpandSecret(
writer.Slice(0, Finished.Size)
, this.nextEpoch.MasterSecret
, PrfLabel.CLIENT_FINISHED
, handshakeHash
);
writer = writer.Slice(Finished.Size);
// Protect the ClientKeyExchange record
this.currentEpoch.RecordProtection.EncryptClientPlaintext(
packet.Slice(Record.Size, keyExchangeRecord.Length)
, packet.Slice(Record.Size, Handshake.Size + (int)keyExchangeHandshake.Length)
, ref keyExchangeRecord
);
// Protect the ChangeCipherSpec record
this.currentEpoch.RecordProtection.EncryptClientPlaintext(
startOfChangeCipherSpecRecord.Slice(Record.Size, changeCipherSpecRecord.Length)
, startOfChangeCipherSpecRecord.Slice(Record.Size, ChangeCipherSpec.Size)
, ref changeCipherSpecRecord
);
// Protect the Finished record
this.nextEpoch.RecordProtection.EncryptClientPlaintext(
startOfFinishedRecord.Slice(Record.Size, finishedRecord.Length)
, startOfFinishedRecord.Slice(Record.Size, Handshake.Size + (int)finishedHandshake.Length)
, ref finishedRecord
);
this.nextEpoch.State = HandshakeState.ExpectingChangeCipherSpec;
this.nextEpoch.NextPacketResendTime = DateTime.UtcNow + this.handshakeResendTimeout;
base.WriteBytesToConnection(packet.GetUnderlyingArray(), packet.Length);
}
/// <summary>
/// Send (resend) a ClientHello message to the server
/// </summary>
private void SendClientHello()
{
// Reset our verification stream
this.nextEpoch.VerificationStream.SetLength(0);
this.nextEpoch.ClientRandom.FillWithRandom(this.random);
// Describe our ClientHello flight
ClientHello clientHello = new ClientHello();
clientHello.Random = this.nextEpoch.ClientRandom;
clientHello.Cookie = this.nextEpoch.Cookie;
clientHello.CipherSuites = new byte[2];
clientHello.CipherSuites.WriteBigEndian16((ushort)CipherSuite.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256);
clientHello.SupportedCurves = new byte[2];
clientHello.SupportedCurves.WriteBigEndian16((ushort)NamedCurve.x25519);
Handshake handshake = new Handshake();
handshake.MessageType = HandshakeType.ClientHello;
handshake.Length = (uint)clientHello.CalculateSize();
handshake.MessageSequence = 0;
handshake.FragmentOffset = 0;
handshake.FragmentLength = handshake.Length;
// Describe the record
int plaintextLength = (int)(Handshake.Size + handshake.Length);
Record outgoingRecord = new Record();
outgoingRecord.ContentType = ContentType.Handshake;
outgoingRecord.Epoch = this.epoch;
outgoingRecord.SequenceNumber = this.currentEpoch.NextOutgoingSequence;
outgoingRecord.Length = (ushort)this.currentEpoch.RecordProtection.GetEncryptedSize(plaintextLength);
++this.currentEpoch.NextOutgoingSequence;
// Convert the record to wire format
ByteSpan packet = new byte[Record.Size + outgoingRecord.Length];
ByteSpan writer = packet;
outgoingRecord.Encode(packet);
writer = writer.Slice(Record.Size);
handshake.Encode(writer);
writer = writer.Slice(Handshake.Size);
clientHello.Encode(writer);
// Write ClientHello to the verification stream
this.nextEpoch.VerificationStream.Write(
packet.GetUnderlyingArray()
, Record.Size
, Handshake.Size + (int)handshake.Length
);
// Protect the record
this.currentEpoch.RecordProtection.EncryptClientPlaintext(
packet.Slice(Record.Size, outgoingRecord.Length)
, packet.Slice(Record.Size, plaintextLength)
, ref outgoingRecord
);
this.nextEpoch.State = HandshakeState.ExpectingServerHello;
this.nextEpoch.NextPacketResendTime = DateTime.UtcNow + this.handshakeResendTimeout;
base.WriteBytesToConnection(packet.GetUnderlyingArray(), packet.Length);
}