public static void Write(StunRecord record, Stream stream)
{
var padLen = record.MessageIntegrity is null ? 8 : 32;
var bytes = new byte[StunConstants.RecordHeaderLength + record.MessageLength + padLen];
var idx = 0;
BinaryPrimitives.WriteInt16BigEndian(bytes.AsSpan(idx), (short)record.MessageType);
idx += 2;
BinaryPrimitives.WriteUInt16BigEndian(bytes.AsSpan(idx), (ushort)(record.MessageLength + padLen /*size of MessageIntegrity and Fingerprint*/));
idx += 2;
BinaryPrimitives.WriteInt32BigEndian(bytes.AsSpan(idx), StunRecord.MessageCookie);
idx += 4;
record.MessageTransactionId.CopyTo(bytes.AsSpan(idx));
idx += record.MessageTransactionId.Length;
foreach (var attr in record.StunAttributes)
{
BinaryPrimitives.WriteUInt16BigEndian(bytes.AsSpan(idx), (ushort)attr.Type);
idx += 2;
BinaryPrimitives.WriteUInt16BigEndian(bytes.AsSpan(idx), attr.Length);
idx += 2;
if (attr.Value != null)
{
attr.Value.CopyTo(bytes.AsSpan(idx));
idx += attr.Value.Length;
}
idx += attr.Padding;
}
var miRec = record.MessageIntegrity;
if (miRec != null)
{
BinaryPrimitives.WriteUInt16BigEndian(bytes.AsSpan(idx), (ushort)miRec.Type);
idx += 2;
BinaryPrimitives.WriteUInt16BigEndian(bytes.AsSpan(idx), miRec.Length);
idx += 2;
miRec.Value.CopyTo(bytes.AsSpan(idx));
idx += miRec.Value.Length;
}
var fiRec = record.Fingerprint;
BinaryPrimitives.WriteUInt16BigEndian(bytes.AsSpan(idx), (ushort)fiRec.Type);
idx += 2;
BinaryPrimitives.WriteUInt16BigEndian(bytes.AsSpan(idx), fiRec.Length);
idx += 2;
fiRec.Value.CopyTo(bytes.AsSpan(idx));
stream.Write(bytes);
}
public static StunRecord Read(byte[] bytes)
{
var record = new StunRecord();
var idx = 0;
record.MessageType = (StunMessageType)BinaryPrimitives.ReadUInt16BigEndian(bytes.AsSpan(idx));
idx += 2;
var stunMessageLength = BinaryPrimitives.ReadUInt16BigEndian(bytes.AsSpan(idx));
idx += 2;
var stunMessageCookie = BinaryPrimitives.ReadInt32BigEndian(bytes.AsSpan(idx));
idx += 4;
if (stunMessageCookie != StunRecord.MessageCookie)
{
throw new InvalidOperationException("Malformed STUN packet");
}
record.MessageTransactionId = bytes.AsSpan(idx, 12).ToArray();
idx += 12;
record.StunAttributes = new List <StunAttribute>();
while (idx < bytes.Length)
{
var stunAttributeType = (StunAttributeType)BinaryPrimitives.ReadUInt16BigEndian(bytes.AsSpan(idx));
idx += 2;
var stunAttributeLength = BinaryPrimitives.ReadUInt16BigEndian(bytes.AsSpan(idx));
idx += 2;
var stunAttributePaddingRemainder = (byte)(stunAttributeLength % 4);
var stunAttributePadding = (byte)(stunAttributePaddingRemainder == 0 ? 0 : 4 - stunAttributePaddingRemainder);
var stunAttributeValue = bytes.AsSpan(idx, stunAttributeLength).ToArray();
idx += stunAttributeLength;
if (stunAttributePadding > 0)
{
idx += stunAttributePadding;
}
StunAttribute stunAttribute;
switch (stunAttributeType)
{
case StunAttributeType.Username:
stunAttribute = new UsernameAttribute();
break;
case StunAttributeType.IceControlled:
stunAttribute = new IceControlledAttribute();
break;
case StunAttributeType.Priority:
stunAttribute = new PriorityAttribute();
break;
case StunAttributeType.MessageIntegrity:
stunAttribute = new MessageIntegrityAttribute();
break;
case StunAttributeType.Fingerprint:
stunAttribute = new FingerprintAttribute();
break;
default:
stunAttribute = new StunAttribute
{
Type = stunAttributeType
};
break;
}
stunAttribute.Value = stunAttributeValue;
if (stunAttribute.Type != StunAttributeType.MessageIntegrity &&
stunAttribute.Type != StunAttributeType.Fingerprint)
{
record.StunAttributes.Add(stunAttribute);
}
}
return(record);
}
