public static LowLevelUdpResponseScanner GetScanner(DirectChannelToken32 senderToken32, uint pingRequestId32, InviteSession session)
{
BinaryProcedures.CreateBinaryWriter(out var ms, out var w);
GetHeaderFields(w, senderToken32, pingRequestId32);
return(new LowLevelUdpResponseScanner
{
ResponseFirstBytes = ms.ToArray(),
OptionalFilter = (udpData) =>
{
var pong = Decode(udpData);
if (pong.PingPongHMAC.Equals(
session.GetPingPongHMAC(pong.GetSignedFieldsForPingPongHMAC)
) == false)
{
return false;
}
return true;
}
});
}
public static DmpPingPacket DecodeAndVerify(byte[] udpData, InviteSession session)
{
var reader = BinaryProcedures.CreateBinaryReader(udpData, 1);
var r = new DmpPingPacket();
r.DirectChannelToken32 = DirectChannelToken32.Decode(reader);
r.PingRequestId32 = reader.ReadUInt32();
var flags = reader.ReadByte();
if ((flags & FlagsMask_MustBeZero) != 0)
{
throw new NotImplementedException();
}
if ((flags & Flags_PublicEcdheKeySet) != 0)
{
r.PublicEcdheKey = EcdhPublicKey.Decode(reader);
}
r.PingPongHMAC = HMAC.Decode(reader);
// verify DirectChannelToken32
if (!r.DirectChannelToken32.Equals(session.LocalSessionDescription.DirectChannelToken32))
{
throw new BadSignatureException("invalid DMP PING DirectChannelToken32 136");
}
// verify PingPongHMAC
if (r.PingPongHMAC.Equals(
session.GetPingPongHMAC(r.GetSignedFieldsForPingPongHMAC)
) == false)
{
throw new BadSignatureException("invalid DMP PING PingPongHMAC 1237");
}
return(r);
}