/// <summary>
/// Parses the an DCEP open message from a buffer.
/// </summary>
/// <param name="buffer">The buffer to parse the message from.</param>
/// <param name="posn">The position in the buffer to start parsing from.</param>
/// <returns>A new DCEP open message instance.</returns>
public static DataChannelOpenMessage Parse(byte[] buffer, int posn)
{
if (buffer.Length < DCEP_OPEN_FIXED_PARAMETERS_LENGTH)
{
throw new ApplicationException("The buffer did not contain the minimum number of bytes for a DCEP open message.");
}
var dcepOpen = new DataChannelOpenMessage();
dcepOpen.MessageType = buffer[posn];
dcepOpen.ChannelType = buffer[posn + 1];
dcepOpen.Priority = NetConvert.ParseUInt16(buffer, posn + 2);
dcepOpen.Reliability = NetConvert.ParseUInt32(buffer, posn + 4);
ushort labelLength = NetConvert.ParseUInt16(buffer, posn + 8);
ushort protocolLength = NetConvert.ParseUInt16(buffer, posn + 10);
if (labelLength > 0)
{
dcepOpen.Label = Encoding.UTF8.GetString(buffer, 12, labelLength);
}
if (protocolLength > 0)
{
dcepOpen.Protocol = Encoding.UTF8.GetString(buffer, 12 + labelLength, protocolLength);
}
return(dcepOpen);
}
/// <summary>
/// Parses the DATA chunk fields
/// </summary>
/// <param name="buffer">The buffer holding the serialised chunk.</param>
/// <param name="posn">The position to start parsing at.</param>
public static SctpDataChunk ParseChunk(byte[] buffer, int posn)
{
var dataChunk = new SctpDataChunk();
ushort chunkLen = dataChunk.ParseFirstWord(buffer, posn);
if (chunkLen < FIXED_PARAMETERS_LENGTH)
{
throw new ApplicationException($"SCTP data chunk cannot be parsed as buffer too short for fixed parameter fields.");
}
dataChunk.Unordered = (dataChunk.ChunkFlags & 0x04) > 0;
dataChunk.Begining = (dataChunk.ChunkFlags & 0x02) > 0;
dataChunk.Ending = (dataChunk.ChunkFlags & 0x01) > 0;
int startPosn = posn + SCTP_CHUNK_HEADER_LENGTH;
dataChunk.TSN = NetConvert.ParseUInt32(buffer, startPosn);
dataChunk.StreamID = NetConvert.ParseUInt16(buffer, startPosn + 4);
dataChunk.StreamSeqNum = NetConvert.ParseUInt16(buffer, startPosn + 6);
dataChunk.PPID = NetConvert.ParseUInt32(buffer, startPosn + 8);
int userDataPosn = startPosn + FIXED_PARAMETERS_LENGTH;
int userDataLen = chunkLen - SCTP_CHUNK_HEADER_LENGTH - FIXED_PARAMETERS_LENGTH;
if (userDataLen > 0)
{
dataChunk.UserData = new byte[userDataLen];
Buffer.BlockCopy(buffer, userDataPosn, dataChunk.UserData, 0, dataChunk.UserData.Length);
}
return(dataChunk);
}
/// <summary>
/// Parses the SACK chunk fields.
/// </summary>
/// <param name="buffer">The buffer holding the serialised chunk.</param>
/// <param name="posn">The position to start parsing at.</param>
public static SctpSackChunk ParseChunk(byte[] buffer, int posn)
{
var sackChunk = new SctpSackChunk();
ushort chunkLen = sackChunk.ParseFirstWord(buffer, posn);
ushort startPosn = (ushort)(posn + SCTP_CHUNK_HEADER_LENGTH);
sackChunk.CumulativeTsnAck = NetConvert.ParseUInt32(buffer, startPosn);
sackChunk.ARwnd = NetConvert.ParseUInt32(buffer, startPosn + 4);
ushort numGapAckBlocks = NetConvert.ParseUInt16(buffer, startPosn + 8);
ushort numDuplicateTSNs = NetConvert.ParseUInt16(buffer, startPosn + 10);
int reportPosn = startPosn + FIXED_PARAMETERS_LENGTH;
for (int i = 0; i < numGapAckBlocks; i++)
{
ushort start = NetConvert.ParseUInt16(buffer, reportPosn);
ushort end = NetConvert.ParseUInt16(buffer, reportPosn + 2);
sackChunk.GapAckBlocks.Add(new SctpTsnGapBlock {
Start = start, End = end
});
reportPosn += GAP_REPORT_LENGTH;
}
for (int j = 0; j < numDuplicateTSNs; j++)
{
sackChunk.DuplicateTSN.Add(NetConvert.ParseUInt32(buffer, reportPosn));
reportPosn += DUPLICATE_TSN_LENGTH;
}
return(sackChunk);
}
/// <summary>
/// The first 32 bits of all chunk parameters represent the type and length. This method
/// parses those fields and sets them on the current instance.
/// </summary>
/// <param name="buffer">The buffer holding the serialised chunk parameter.</param>
/// <param name="posn">The position in the buffer that indicates the start of the chunk parameter.</param>
public ushort ParseFirstWord(byte[] buffer, int posn)
{
ParameterType = NetConvert.ParseUInt16(buffer, posn);
ushort paramLen = NetConvert.ParseUInt16(buffer, posn + 2);
if (paramLen > 0 && buffer.Length < posn + paramLen)
{
// The buffer was not big enough to supply the specified chunk parameter.
int bytesRequired = paramLen;
int bytesAvailable = buffer.Length - posn;
throw new ApplicationException($"The SCTP chunk parameter buffer was too short. " +
$"Required {bytesRequired} bytes but only {bytesAvailable} available.");
}
return(paramLen);
}
/// <summary>
/// Parses the an SCTP header from a buffer.
/// </summary>
/// <param name="buffer">The buffer to parse the SCTP header from.</param>
/// <param name="posn">The position in the buffer to start parsing the header from.</param>
/// <returns>A new SCTPHeaer instance.</returns>
public static SctpHeader Parse(byte[] buffer, int posn)
{
if (buffer.Length < SCTP_HEADER_LENGTH)
{
throw new ApplicationException("The buffer did not contain the minimum number of bytes for an SCTP header.");
}
SctpHeader header = new SctpHeader();
header.SourcePort = NetConvert.ParseUInt16(buffer, posn);
header.DestinationPort = NetConvert.ParseUInt16(buffer, posn + 2);
header.VerificationTag = NetConvert.ParseUInt32(buffer, posn + 4);
header.Checksum = NetConvert.ParseUInt32(buffer, posn + 8);
return(header);
}
/// <summary>
/// The first 32 bits of all chunks represent the same 3 fields. This method
/// parses those fields and sets them on the current instance.
/// </summary>
/// <param name="buffer">The buffer holding the serialised chunk.</param>
/// <param name="posn">The position in the buffer that indicates the start of the chunk.</param>
/// <returns>The chunk length value.</returns>
public ushort ParseFirstWord(byte[] buffer, int posn)
{
ChunkType = buffer[posn];
ChunkFlags = buffer[posn + 1];
ushort chunkLength = NetConvert.ParseUInt16(buffer, posn + 2);
if (chunkLength > 0 && buffer.Length < posn + chunkLength)
{
// The buffer was not big enough to supply the specified chunk length.
int bytesRequired = chunkLength;
int bytesAvailable = buffer.Length - posn;
throw new ApplicationException($"The SCTP chunk buffer was too short. Required {bytesRequired} bytes but only {bytesAvailable} available.");
}
return(chunkLength);
}
/// <summary>
/// Parses the INIT or INIT ACK chunk fields
/// </summary>
/// <param name="buffer">The buffer holding the serialised chunk.</param>
/// <param name="posn">The position to start parsing at.</param>
public static SctpInitChunk ParseChunk(byte[] buffer, int posn)
{
var initChunk = new SctpInitChunk();
ushort chunkLen = initChunk.ParseFirstWord(buffer, posn);
int startPosn = posn + SCTP_CHUNK_HEADER_LENGTH;
initChunk.InitiateTag = NetConvert.ParseUInt32(buffer, startPosn);
initChunk.ARwnd = NetConvert.ParseUInt32(buffer, startPosn + 4);
initChunk.NumberOutboundStreams = NetConvert.ParseUInt16(buffer, startPosn + 8);
initChunk.NumberInboundStreams = NetConvert.ParseUInt16(buffer, startPosn + 10);
initChunk.InitialTSN = NetConvert.ParseUInt32(buffer, startPosn + 12);
int paramPosn = startPosn + FIXED_PARAMETERS_LENGTH;
int paramsBufferLength = chunkLen - SCTP_CHUNK_HEADER_LENGTH - FIXED_PARAMETERS_LENGTH;
if (paramPosn < paramsBufferLength)
{
bool stopProcessing = false;
foreach (var varParam in GetParameters(buffer, paramPosn, paramsBufferLength))
{
switch (varParam.ParameterType)
{
case (ushort)SctpInitChunkParameterType.IPv4Address:
case (ushort)SctpInitChunkParameterType.IPv6Address:
var address = new IPAddress(varParam.ParameterValue);
initChunk.Addresses.Add(address);
break;
case (ushort)SctpInitChunkParameterType.CookiePreservative:
initChunk.CookiePreservative = NetConvert.ParseUInt32(varParam.ParameterValue, 0);
break;
case (ushort)SctpInitChunkParameterType.HostNameAddress:
initChunk.HostnameAddress = Encoding.UTF8.GetString(varParam.ParameterValue);
break;
case (ushort)SctpInitChunkParameterType.SupportedAddressTypes:
for (int valPosn = 0; valPosn < varParam.ParameterValue.Length; valPosn += 2)
{
switch (NetConvert.ParseUInt16(varParam.ParameterValue, valPosn))
{
case (ushort)SctpInitChunkParameterType.IPv4Address:
initChunk.SupportedAddressTypes.Add(SctpInitChunkParameterType.IPv4Address);
break;
case (ushort)SctpInitChunkParameterType.IPv6Address:
initChunk.SupportedAddressTypes.Add(SctpInitChunkParameterType.IPv6Address);
break;
case (ushort)SctpInitChunkParameterType.HostNameAddress:
initChunk.SupportedAddressTypes.Add(SctpInitChunkParameterType.HostNameAddress);
break;
}
}
break;
case (ushort)SctpInitChunkParameterType.EcnCapable:
break;
case (ushort)SctpInitChunkParameterType.StateCookie:
// Used with INIT ACK chunks only.
initChunk.StateCookie = varParam.ParameterValue;
break;
case (ushort)SctpInitChunkParameterType.UnrecognizedParameter:
// Used with INIT ACK chunks only. This parameter is the remote peer returning
// a list of parameters it did not understand in the INIT chunk.
initChunk.UnrecognizedParameters.Add(varParam.ParameterValue);
break;
default:
// Parameters are not recognised in an INIT or INIT ACK.
initChunk.GotUnrecognisedParameter(varParam);
break;
}
if (stopProcessing)
{
logger.LogWarning($"SCTP unrecognised parameter {varParam.ParameterType} for chunk type {initChunk.KnownType} "
+ "indicated no further chunks should be processed.");
break;
}
}
}
return(initChunk);
}
/// <summary>
/// Parses the ERROR chunk fields.
/// </summary>
/// <param name="buffer">The buffer holding the serialised chunk.</param>
/// <param name="posn">The position to start parsing at.</param>
public static SctpErrorChunk ParseChunk(byte[] buffer, int posn, bool isAbort)
{
var errorChunk = (isAbort) ? new SctpAbortChunk(false) : new SctpErrorChunk();
ushort chunkLen = errorChunk.ParseFirstWord(buffer, posn);
int paramPosn = posn + SCTP_CHUNK_HEADER_LENGTH;
int paramsBufferLength = chunkLen - SCTP_CHUNK_HEADER_LENGTH;
if (paramPosn < paramsBufferLength)
{
bool stopProcessing = false;
foreach (var varParam in GetParameters(buffer, paramPosn, paramsBufferLength))
{
switch (varParam.ParameterType)
{
case (ushort)SctpErrorCauseCode.InvalidStreamIdentifier:
ushort streamID = (ushort)((varParam.ParameterValue != null) ?
NetConvert.ParseUInt16(varParam.ParameterValue, 0) : 0);
var invalidStreamID = new SctpErrorInvalidStreamIdentifier {
StreamID = streamID
};
errorChunk.AddErrorCause(invalidStreamID);
break;
case (ushort)SctpErrorCauseCode.MissingMandatoryParameter:
List <ushort> missingIDs = new List <ushort>();
if (varParam.ParameterValue != null)
{
for (int i = 0; i < varParam.ParameterValue.Length; i += 2)
{
missingIDs.Add(NetConvert.ParseUInt16(varParam.ParameterValue, i));
}
}
var missingMandatory = new SctpErrorMissingMandatoryParameter {
MissingParameters = missingIDs
};
errorChunk.AddErrorCause(missingMandatory);
break;
case (ushort)SctpErrorCauseCode.StaleCookieError:
uint staleness = (uint)((varParam.ParameterValue != null) ?
NetConvert.ParseUInt32(varParam.ParameterValue, 0) : 0);
var staleCookie = new SctpErrorStaleCookieError {
MeasureOfStaleness = staleness
};
errorChunk.AddErrorCause(staleCookie);
break;
case (ushort)SctpErrorCauseCode.OutOfResource:
errorChunk.AddErrorCause(new SctpCauseOnlyError(SctpErrorCauseCode.OutOfResource));
break;
case (ushort)SctpErrorCauseCode.UnresolvableAddress:
var unresolvable = new SctpErrorUnresolvableAddress {
UnresolvableAddress = varParam.ParameterValue
};
errorChunk.AddErrorCause(unresolvable);
break;
case (ushort)SctpErrorCauseCode.UnrecognizedChunkType:
var unrecognised = new SctpErrorUnrecognizedChunkType {
UnrecognizedChunk = varParam.ParameterValue
};
errorChunk.AddErrorCause(unrecognised);
break;
case (ushort)SctpErrorCauseCode.InvalidMandatoryParameter:
errorChunk.AddErrorCause(new SctpCauseOnlyError(SctpErrorCauseCode.InvalidMandatoryParameter));
break;
case (ushort)SctpErrorCauseCode.UnrecognizedParameters:
var unrecognisedParams = new SctpErrorUnrecognizedParameters {
UnrecognizedParameters = varParam.ParameterValue
};
errorChunk.AddErrorCause(unrecognisedParams);
break;
case (ushort)SctpErrorCauseCode.NoUserData:
uint tsn = (uint)((varParam.ParameterValue != null) ?
NetConvert.ParseUInt32(varParam.ParameterValue, 0) : 0);
var noData = new SctpErrorNoUserData {
TSN = tsn
};
errorChunk.AddErrorCause(noData);
break;
case (ushort)SctpErrorCauseCode.CookieReceivedWhileShuttingDown:
errorChunk.AddErrorCause(new SctpCauseOnlyError(SctpErrorCauseCode.CookieReceivedWhileShuttingDown));
break;
case (ushort)SctpErrorCauseCode.RestartAssociationWithNewAddress:
var restartAddress = new SctpErrorRestartAssociationWithNewAddress
{
NewAddressTLVs = varParam.ParameterValue
};
errorChunk.AddErrorCause(restartAddress);
break;
case (ushort)SctpErrorCauseCode.UserInitiatedAbort:
string reason = (varParam.ParameterValue != null) ?
Encoding.UTF8.GetString(varParam.ParameterValue) : null;
var userAbort = new SctpErrorUserInitiatedAbort {
AbortReason = reason
};
errorChunk.AddErrorCause(userAbort);
break;
case (ushort)SctpErrorCauseCode.ProtocolViolation:
string info = (varParam.ParameterValue != null) ?
Encoding.UTF8.GetString(varParam.ParameterValue) : null;
var protocolViolation = new SctpErrorProtocolViolation {
AdditionalInformation = info
};
errorChunk.AddErrorCause(protocolViolation);
break;
default:
// Parameter was not recognised.
errorChunk.GotUnrecognisedParameter(varParam);
break;
}
if (stopProcessing)
{
logger.LogWarning($"SCTP unrecognised parameter {varParam.ParameterType} for chunk type {SctpChunkType.ERROR} "
+ "indicated no further chunks should be processed.");
break;
}
}
}
return(errorChunk);
}
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 = NetConvert.ParseUInt16(buffer, startAttIndex);
UInt16 stunAttributeLength = NetConvert.ParseUInt16(buffer, startAttIndex + 2);
byte[] stunAttributeValue = null;
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);
}
}
/// <summary>
/// Extracts the padded length field from a serialised chunk buffer.
/// </summary>
/// <param name="buffer">The buffer holding the serialised chunk.</param>
/// <param name="posn">The start position of the serialised chunk.</param>
/// <param name="padded">If true the length field will be padded to a 4 byte boundary.</param>
/// <returns>The padded length of the serialised chunk.</returns>
public static uint GetChunkLengthFromHeader(byte[] buffer, int posn, bool padded)
{
ushort len = NetConvert.ParseUInt16(buffer, posn + 2);
return((padded) ? SctpPadding.PadTo4ByteBoundary(len) : len);
}
