public static STUNMessage ParseSTUNMessage(byte[] buffer, int bufferLength)
{
if (buffer != null && buffer.Length > 0 && buffer.Length >= bufferLength)
{
STUNMessage stunMessage = new STUNMessage();
stunMessage.Header = STUNHeader.ParseSTUNHeader(buffer);
if (stunMessage.Header.MessageLength > 0)
{
stunMessage.Attributes = STUNAttribute.ParseMessageAttributes(buffer, STUNHeader.STUN_HEADER_LENGTH, bufferLength);
}
return(stunMessage);
}
return(null);
}
public static STUNMessage ParseSTUNMessage(byte[] buffer, int bufferLength)
{
if (buffer != null && buffer.Length > 0 && buffer.Length >= bufferLength)
{
STUNMessage stunMessage = new STUNMessage();
stunMessage._receivedBuffer = buffer.Take(bufferLength).ToArray();
stunMessage.Header = STUNHeader.ParseSTUNHeader(buffer);
if (stunMessage.Header.MessageLength > 0)
{
stunMessage.Attributes =
STUNAttribute.ParseMessageAttributes(buffer, STUNHeader.STUN_HEADER_LENGTH, bufferLength);
}
if (stunMessage.Attributes.Count > 0 &&
stunMessage.Attributes.Last().AttributeType == STUNAttributeTypesEnum.FingerPrint)
{
// Check fingerprint.
var fingerprintAttribute = stunMessage.Attributes.Last();
var input = buffer.Take(buffer.Length - STUNAttribute.STUNATTRIBUTE_HEADER_LENGTH -
FINGERPRINT_ATTRIBUTE_CRC32_LENGTH).ToArray();
uint crc = Crc32.Compute(input) ^ FINGERPRINT_XOR;
byte[] fingerPrint = (BitConverter.IsLittleEndian)
? BitConverter.GetBytes(NetConvert.DoReverseEndian(crc))
: BitConverter.GetBytes(crc);
//logger.LogDebug($"STUNMessage supplied fingerprint attribute: {fingerprintAttribute.Value.HexStr()}.");
//logger.LogDebug($"STUNMessage calculated fingerprint attribute: {fingerPrint.HexStr()}.");
if (fingerprintAttribute.Value.HexStr() == fingerPrint.HexStr())
{
stunMessage.isFingerprintValid = true;
}
}
return(stunMessage);
}
return(null);
}
public static List <STUNAttribute> ParseMessageAttributes(byte[] buffer, int startIndex, int endIndex)
{
if (buffer != null && buffer.Length > startIndex && buffer.Length >= endIndex)
{
List <STUNAttribute> attributes = new List <STUNAttribute>();
int startAttIndex = startIndex;
while (startAttIndex < endIndex)
{
UInt16 stunAttributeType = BitConverter.ToUInt16(buffer, startAttIndex);
UInt16 stunAttributeLength = BitConverter.ToUInt16(buffer, startAttIndex + 2);
byte[] stunAttributeValue = null;
if (BitConverter.IsLittleEndian)
{
stunAttributeType = NetConvert.DoReverseEndian(stunAttributeType);
stunAttributeLength = NetConvert.DoReverseEndian(stunAttributeLength);
}
if (stunAttributeLength > 0)
{
if (stunAttributeLength + startIndex + 4 > endIndex)
{
logger.LogWarning(
"The attribute length on a STUN parameter was greater than the available number of bytes.");
}
else
{
stunAttributeValue = new byte[stunAttributeLength];
Buffer.BlockCopy(buffer, startAttIndex + 4, stunAttributeValue, 0, stunAttributeLength);
}
}
STUNAttributeTypesEnum attributeType =
STUNAttributeTypes.GetSTUNAttributeTypeForId(stunAttributeType);
STUNAttribute attribute = null;
if (attributeType == STUNAttributeTypesEnum.ChangeRequest)
{
attribute = new STUNChangeRequestAttribute(stunAttributeValue);
}
else if (attributeType == STUNAttributeTypesEnum.MappedAddress)
{
attribute = new STUNAddressAttribute(stunAttributeValue);
}
else if (attributeType == STUNAttributeTypesEnum.ErrorCode)
{
attribute = new STUNErrorCodeAttribute(stunAttributeValue);
}
else if (attributeType == STUNAttributeTypesEnum.XORMappedAddress ||
attributeType == STUNAttributeTypesEnum.XORPeerAddress ||
attributeType == STUNAttributeTypesEnum.XORRelayedAddress)
{
attribute = new STUNXORAddressAttribute(attributeType, stunAttributeValue);
}
else
{
attribute = new STUNAttribute(attributeType, stunAttributeValue);
}
attributes.Add(attribute);
// Attributes start on 32 bit word boundaries so where an attribute length is not a multiple of 4 it gets padded.
int padding = (stunAttributeLength % 4 != 0) ? 4 - (stunAttributeLength % 4) : 0;
startAttIndex = startAttIndex + 4 + stunAttributeLength + padding;
}
return(attributes);
}
else
{
return(null);
}
}
public static List<STUNAttribute> ParseMessageAttributes(byte[] buffer, int startIndex, int endIndex)
{
if (buffer != null && buffer.Length > startIndex && buffer.Length >= endIndex)
{
List<STUNAttribute> attributes = new List<STUNAttribute>();
int startAttIndex = startIndex;
while (startAttIndex < endIndex)
{
UInt16 stunAttributeType = BitConverter.ToUInt16(buffer, startAttIndex);
UInt16 stunAttributeLength = BitConverter.ToUInt16(buffer, startAttIndex + 2);
byte[] stunAttributeValue = null;
if (BitConverter.IsLittleEndian)
{
stunAttributeType = Utility.ReverseEndian(stunAttributeType);
stunAttributeLength = Utility.ReverseEndian(stunAttributeLength);
}
if (stunAttributeLength > 0)
{
if (stunAttributeType == (int)STUNAttributeTypesEnum.Username && stunAttributeLength > buffer.Length - startIndex - 4)
{
// Received some STUN messages where the username is shorter than the claimed length.
int realLength = buffer.Length - startIndex - 4;
stunAttributeValue = new byte[realLength];
Buffer.BlockCopy(buffer, startIndex + 4, stunAttributeValue, 0, realLength);
}
else
{
stunAttributeValue = new byte[stunAttributeLength];
Buffer.BlockCopy(buffer, startIndex + 4, stunAttributeValue, 0, stunAttributeLength);
}
}
STUNAttributeTypesEnum attributeType = STUNAttributeTypes.GetSTUNAttributeTypeForId(stunAttributeType);
STUNAttribute attribute = null;
if (attributeType == STUNAttributeTypesEnum.ChangeRequest)
{
attribute = new STUNChangeRequestAttribute(stunAttributeValue);
}
else if (attributeType == STUNAttributeTypesEnum.MappedAddress)
{
attribute = new STUNAddressAttribute(stunAttributeValue);
}
else
{
attribute = new STUNAttribute(attributeType, stunAttributeLength, stunAttributeValue);
}
attributes.Add(attribute);
startAttIndex = startAttIndex + 4 + stunAttributeLength;
}
return attributes;
}
else
{
return null;
}
}
public byte[] ToByteBuffer(byte[] messageIntegrityKey, bool addFingerprint)
{
UInt16 attributesLength = 0;
foreach (STUNAttribute attribute in Attributes)
{
attributesLength +=
Convert.ToUInt16(STUNAttribute.STUNATTRIBUTE_HEADER_LENGTH + attribute.PaddedLength);
}
if (messageIntegrityKey != null)
{
attributesLength += STUNAttribute.STUNATTRIBUTE_HEADER_LENGTH + MESSAGE_INTEGRITY_ATTRIBUTE_HMAC_LENGTH;
}
int messageLength = STUNHeader.STUN_HEADER_LENGTH + attributesLength;
byte[] buffer = new byte[messageLength];
if (BitConverter.IsLittleEndian)
{
Buffer.BlockCopy(BitConverter.GetBytes(NetConvert.DoReverseEndian((UInt16)Header.MessageType)), 0,
buffer, 0, 2);
Buffer.BlockCopy(BitConverter.GetBytes(NetConvert.DoReverseEndian(attributesLength)), 0, buffer, 2, 2);
Buffer.BlockCopy(BitConverter.GetBytes(NetConvert.DoReverseEndian(STUNHeader.MAGIC_COOKIE)), 0, buffer,
4, 4);
}
else
{
Buffer.BlockCopy(BitConverter.GetBytes((UInt16)Header.MessageType), 0, buffer, 0, 2);
Buffer.BlockCopy(BitConverter.GetBytes(attributesLength), 0, buffer, 2, 2);
Buffer.BlockCopy(BitConverter.GetBytes(STUNHeader.MAGIC_COOKIE), 0, buffer, 4, 4);
}
Buffer.BlockCopy(Header.TransactionId, 0, buffer, 8, STUNHeader.TRANSACTION_ID_LENGTH);
int attributeIndex = 20;
foreach (STUNAttribute attr in Attributes)
{
attributeIndex += attr.ToByteBuffer(buffer, attributeIndex);
}
//logger.LogDebug($"Pre HMAC STUN message: {ByteBufferInfo.HexStr(buffer, attributeIndex)}");
if (messageIntegrityKey != null)
{
var integrityAttibtue = new STUNAttribute(STUNAttributeTypesEnum.MessageIntegrity,
new byte[MESSAGE_INTEGRITY_ATTRIBUTE_HMAC_LENGTH]);
HMACSHA1 hmacSHA = new HMACSHA1(messageIntegrityKey, true);
byte[] hmac = hmacSHA.ComputeHash(buffer, 0, attributeIndex);
integrityAttibtue.Value = hmac;
attributeIndex += integrityAttibtue.ToByteBuffer(buffer, attributeIndex);
}
if (addFingerprint)
{
// The fingerprint attribute length has not been included in the length in the STUN header so adjust it now.
attributesLength += STUNAttribute.STUNATTRIBUTE_HEADER_LENGTH + FINGERPRINT_ATTRIBUTE_CRC32_LENGTH;
messageLength += STUNAttribute.STUNATTRIBUTE_HEADER_LENGTH + FINGERPRINT_ATTRIBUTE_CRC32_LENGTH;
if (BitConverter.IsLittleEndian)
{
Buffer.BlockCopy(BitConverter.GetBytes(NetConvert.DoReverseEndian(attributesLength)), 0, buffer, 2,
2);
}
else
{
Buffer.BlockCopy(BitConverter.GetBytes(attributesLength), 0, buffer, 2, 2);
}
var fingerprintAttribute = new STUNAttribute(STUNAttributeTypesEnum.FingerPrint,
new byte[FINGERPRINT_ATTRIBUTE_CRC32_LENGTH]);
uint crc = Crc32.Compute(buffer) ^ FINGERPRINT_XOR;
byte[] fingerPrint = (BitConverter.IsLittleEndian)
? BitConverter.GetBytes(NetConvert.DoReverseEndian(crc))
: BitConverter.GetBytes(crc);
fingerprintAttribute.Value = fingerPrint;
Array.Resize(ref buffer, messageLength);
fingerprintAttribute.ToByteBuffer(buffer, attributeIndex);
}
return(buffer);
}
public static List <STUNAttribute> ParseMessageAttributes(byte[] buffer, int startIndex, int endIndex)
{
if (buffer != null && buffer.Length > startIndex && buffer.Length >= endIndex)
{
List <STUNAttribute> attributes = new List <STUNAttribute>();
int startAttIndex = startIndex;
while (startAttIndex < endIndex)
{
UInt16 stunAttributeType = BitConverter.ToUInt16(buffer, startAttIndex);
UInt16 stunAttributeLength = BitConverter.ToUInt16(buffer, startAttIndex + 2);
byte[] stunAttributeValue = null;
if (BitConverter.IsLittleEndian)
{
stunAttributeType = Utility.ReverseEndian(stunAttributeType);
stunAttributeLength = Utility.ReverseEndian(stunAttributeLength);
}
if (stunAttributeLength > 0)
{
if (stunAttributeType == (int)STUNAttributeTypesEnum.Username && stunAttributeLength > buffer.Length - startIndex - 4)
{
// Received some STUN messages where the username is shorter than the claimed length.
int realLength = buffer.Length - startIndex - 4;
stunAttributeValue = new byte[realLength];
Buffer.BlockCopy(buffer, startIndex + 4, stunAttributeValue, 0, realLength);
}
else
{
stunAttributeValue = new byte[stunAttributeLength];
Buffer.BlockCopy(buffer, startIndex + 4, stunAttributeValue, 0, stunAttributeLength);
}
}
STUNAttributeTypesEnum attributeType = STUNAttributeTypes.GetSTUNAttributeTypeForId(stunAttributeType);
STUNAttribute attribute = null;
if (attributeType == STUNAttributeTypesEnum.ChangeRequest)
{
attribute = new STUNChangeRequestAttribute(stunAttributeValue);
}
else if (attributeType == STUNAttributeTypesEnum.MappedAddress)
{
attribute = new STUNAddressAttribute(stunAttributeValue);
}
else
{
attribute = new STUNAttribute(attributeType, stunAttributeLength, stunAttributeValue);
}
attributes.Add(attribute);
startAttIndex = startAttIndex + 4 + stunAttributeLength;
}
return(attributes);
}
else
{
return(null);
}
}