/src/PcapPlusPlus/Packet++/header/TelnetLayer.h

Source
#pragma once

#include "Layer.h"

/// @file

/**
 * \namespace pcpp
 * \brief The main namespace for the PcapPlusPlus lib
 */
namespace pcpp
{

/**
 * Class for representing the Telnet Layer
 */
class TelnetLayer : public Layer
{
  private:
  // Position iterator for next command
  size_t lastPositionOffset;

  // Checks if position is a data field
  bool isDataField(uint8_t *pos) const;
  // Checks if position is a command field
  bool isCommandField(uint8_t *pos) const;
  // Returns distance to next IAC
  size_t distanceToNextIAC(uint8_t *startPos, size_t maxLength);
  // Returns length of provided field
  size_t getFieldLen(uint8_t *startPos, size_t maxLength);
  // Get position of next data field
  uint8_t *getNextDataField(uint8_t *pos, size_t len);
  // Get position of next command field
  uint8_t *getNextCommandField(uint8_t *pos, size_t len);
  // Get options of provided field
  int16_t getSubCommand(uint8_t *pos, size_t len);
  // Get data of provided field
  uint8_t *getCommandData(uint8_t *pos, size_t &slen);

  public:
  /**
   * Telnet Command Indicator
   */
  enum class TelnetCommand : int
  {
    /// Indicator to parser reached end of packet
    TelnetCommandEndOfPacket = -1,

    /// End of file
    EndOfFile = 236,
    /// Suspend current process
    Suspend,
    /// Abort Process
    Abort,
    /// End of Record
    EndOfRecordCommand,
    /// Marks the end of a Telnet option subnegotiation, used with the SB code to specify more specific option
    /// parameters.
    SubnegotiationEnd,
    /// Null command; does nothing.
    NoOperation,
    /// Used to mark the end of a sequence of data that the recipient should scan for urgent Telnet commands.
    DataMark,
    /// Represents the pressing of the “break” or “attention” key on the terminal.
    Break,
    /// Tells the recipient to interrupt, abort, suspend or terminate the process currently in use.
    InterruptProcess,
    /// Instructs the remote host to continue running the current process, but discard all remaining output from it.
    /// This may be needed if a program starts to send unexpectedly large amounts of data to the user.
    AbortOutput,
    /// May be used to check that the remote host is still “alive”. When this character is sent the remote host
    /// returns some type of output to indicate that it is still functioning.
    AreYouThere,
    /// Instructs the recipient to delete the last undeleted character from the data stream. Used to “undo” the
    /// sending of a character.
    EraseCharacter,
    /// Tells the recipient to delete all characters from the data stream back to (but not including) the last end
    /// of line (CR+LF) sequence.
    EraseLine,
    /// Used in Telnet half-duplex mode to signal the other device that it may transmit.
    GoAhead,
    /// Marks the beginning of a Telnet option subnegotiation, used when an option requires the client and server to
    /// exchange parameters.
    Subnegotiation,
    /// Indicates that the device sending this code is willing to perform or continue performing a particular
    /// option.
    WillPerform,
    /// Indicates that the device sending this code is either not willing to perform a particular option, or is now
    /// refusing to continue to perform it.
    WontPerform,
    /// Requests that the other device perform a particular option or confirms the expectation that the other device
    /// will perform that option.
    DoPerform,
    /// Specifies that the other party not perform an option, or confirms a device’s expectation that the other
    /// party not perform an option.
    DontPerform,
    /// Precedes command values 240 through 254 as described above. A pair of IAC bytes in a row represents the data
    /// value 255.
    InterpretAsCommand
  };

  /**
   * Telnet Options
   */
  enum class TelnetOption : int
  {
    /// Internal return for no option detected
    TelnetOptionNoOption = -1,

    /// Binary Transmission RFC856 https://www.iana.org/go/rfc856
    TransmitBinary = 0,
    /// Echo RFC857 https://www.iana.org/go/rfc857
    Echo,
    /// Reconnection
    Reconnection,
    /// Suppress Go Ahead RFC858 https://www.iana.org/go/rfc858
    SuppressGoAhead,
    /// Negotiate approximate message size
    ApproxMsgSizeNegotiation,
    /// Status RFC859 https://www.iana.org/go/rfc859
    Status,
    /// Timing Mark RFC860 https://www.iana.org/go/rfc860
    TimingMark,
    /// RCTE, Remote Controlled Transmission and Echo RFC726 https://www.iana.org/go/rfc726
    RemoteControlledTransAndEcho,
    /// Output Line Width
    OutputLineWidth,
    /// Output Page Size
    OutputPageSize,
    /// NAOCRD, Negotiate About Output Carriage-Return Disposition RFC652 https://www.iana.org/go/rfc652
    OutputCarriageReturnDisposition,
    /// NAOHTS, Negotiate About Output Horizontal Tabstops RFC653 https://www.iana.org/go/rfc653
    OutputHorizontalTabStops,
    /// NAOHTD, Negotiate About Output Horizontal Tab Disposition RFC654 https://www.iana.org/go/rfc654
    OutputHorizontalTabDisposition,
    /// NAOFFD, Negotiate About Output Formfeed Disposition RFC655 https://www.iana.org/go/rfc655
    OutputFormfeedDisposition,
    /// NAOVTS, Negotiate About Vertical Tabstops RFC656 https://www.iana.org/go/rfc656
    OutputVerticalTabStops,
    /// NAOVTD, Negotiate About Output Vertcial Tab Disposition RFC657 https://www.iana.org/go/rfc657
    OutputVerticalTabDisposition,
    /// NAOLFD, Negotiate About Output Linefeed Disposition RFC658 https://www.iana.org/go/rfc658
    OutputLinefeedDisposition,
    /// Extended ASCII RFC698 https://www.iana.org/go/rfc698
    ExtendedASCII,
    /// Logout RFC727 https://www.iana.org/go/rfc727
    Logout,
    /// BM, Byte Macro RFC735 https://www.iana.org/go/rfc735
    ByteMacro,
    /// Data Entry Terminal RFC1043 - RFC732 https://www.iana.org/go/rfc1043 https://www.iana.org/go/rfc732
    DataEntryTerminal,
    /// SUPDUP RFC736 - RFC734 https://www.iana.org/go/rfc736 https://www.iana.org/go/rfc734
    SUPDUP,
    /// SUPDUP Output RFC749 https://www.iana.org/go/rfc749
    SUPDUPOutput,
    /// Send Location RFC779 https://www.iana.org/go/rfc779
    SendLocation,
    /// Terminal Type RFC1091 https://www.iana.org/go/rfc1091
    TerminalType,
    /// End of record RFC885 https://www.iana.org/go/rfc885
    EndOfRecordOption,
    /// TUID, TACACS User Identification RFC927 https://www.iana.org/go/rfc927
    TACACSUserIdentification,
    /// OUTMRK, Output Marking RFC933 https://www.iana.org/go/rfc933
    OutputMarking,
    /// TTYLOC, Terminal Location Number RFC946 https://www.iana.org/go/rfc946
    TerminalLocationNumber,
    /// Telnet 3270 Regime RFC1041 https://www.iana.org/go/rfc1041
    Telnet3270Regime,
    /// X.3 PAD RFC1053 https://www.iana.org/go/rfc1053
    X3Pad,
    /// NAWS, Negotiate About Window Size RFC1073 https://www.iana.org/go/rfc1073
    NegotiateAboutWindowSize,
    /// Terminal Speed RFC1079 https://www.iana.org/go/rfc1079
    TerminalSpeed,
    /// Remote Flow Control RFC1372 https://www.iana.org/go/rfc1372
    RemoteFlowControl,
    /// Line Mode RFC1184 https://www.iana.org/go/rfc1184
    Linemode,
    /// X Display Location RFC1096 https://www.iana.org/go/rfc1096
    XDisplayLocation,
    /// Environment Option RFC1408 https://www.iana.org/go/rfc1408
    EnvironmentOption,
    /// Authentication Option RFC2941 https://www.iana.org/go/rfc2941
    AuthenticationOption,
    /// Encryption Option RFC2946 https://www.iana.org/go/rfc2946
    EncryptionOption,
    /// New Environment Option RFC1572 https://www.iana.org/go/rfc1572
    NewEnvironmentOption,
    /// TN3270E RFC2355 https://www.iana.org/go/rfc2355
    TN3270E,
    /// X Server Authentication
    XAuth,
    /// Charset RFC2066 https://www.iana.org/go/rfc2066
    Charset,
    /// RSP, Telnet Remote Serial Port
    TelnetRemoteSerialPort,
    /// Com Port Control Option RFC2217 https://www.iana.org/go/rfc2217
    ComPortControlOption,
    /// Telnet Suppress Local Echo
    TelnetSuppressLocalEcho,
    /// Telnet Start TLS
    TelnetStartTLS,
    /// Kermit RFC2840 https://www.iana.org/go/rfc2840
    Kermit,
    /// Send URL
    SendURL,
    /// Forward X Server
    ForwardX,

    /// Telnet Option Pragma Logon
    TelOptPragmaLogon = 138,
    /// Telnet Option SSPI Logon
    TelOptSSPILogon,
    /// Telnet Option Pragma Heartbeat
    TelOptPragmaHeartbeat,

    /// Extended option list
    ExtendedOptions = 255
  };

  /**
   * A constructor that creates the layer from an existing packet raw data
   * @param[in] data A pointer to the raw data
   * @param[in] dataLen Size of the data in bytes
   * @param[in] prevLayer A pointer to the previous layer
   * @param[in] packet A pointer to the Packet instance where layer will be stored in
   */
  TelnetLayer(uint8_t *data, size_t dataLen, Layer *prevLayer, Packet *packet) : Layer(data, dataLen, prevLayer, packet)
  {
    m_Protocol = Telnet;
    lastPositionOffset = SIZE_MAX;
  };

  /**
   * Get the Telnet data as readable string
   * @param[in] removeEscapeCharacters Whether non-alphanumerical characters should be removed or not
   * @return Full payload as readable string, empty if Telnet packet contains control commands/options.
   */
  std::string getDataAsString(bool removeEscapeCharacters = true);

  /**
   * Get the total number of detected Telnet commands
   * @return size_t The number of Telnet commands
   */
  size_t getTotalNumberOfCommands();

  /**
   * Returns the number of occurrences of provided command
   * @param[in] command Telnet command to count
   * @return size_t Number of occurrences of command
   */
  size_t getNumberOfCommands(TelnetCommand command);

  /**
   * Returns the first command of packet
   * @return TelnetCommand First detected command value, TelnetCommandEndOfPacket if there is no command field
   */
  TelnetCommand getFirstCommand();

  /**
   * Returns the next command of packet. Uses an internal iterator. The iterator resets when reached end of packet.
   * @return TelnetCommand Detected command value, TelnetCommandEndOfPacket if reached the end of packet.
   */
  TelnetCommand getNextCommand();

  /**
   * Returns the option of current command. Uses an internal iterator. Iterator can be moved with getNextCommand
   * @return TelnetOption Option of current command
   */
  TelnetOption getOption();

  /**
   * Returns the option of provided command. It will return option of first occurrence of the command
   * @param[in] command Telnet command to search
   * @return TelnetOption Option of the command. Returns TelnetOptionNoOption if the provided command not found.
   */
  TelnetOption getOption(TelnetCommand command);

  /**
   * Returns the data of current command. Uses an internal iterator. Iterator can be moved with getNextCommand
   * @param[out] length Length of the data of current command
   * @return uint8_t* Pointer to the data of current command. NULL if there is no data for this command.
   */
  uint8_t *getOptionData(size_t &length);

  /**
   * Returns the data of provided command. It will return data of first occurrence of the command
   * @param[in] command Telnet command to search
   * @param[out] length Length of the data of current command
   * @return uint8_t* Pointer to the data of current command. NULL if there is no data for this command or if can't
   * find the command.
   */
  uint8_t *getOptionData(TelnetCommand command, size_t &length);

  /**
   * Convert the Telnet Command to readable string
   * @param[in] val Value of the command
   * @return The Telnet Command as readable string
   */
  static std::string getTelnetCommandAsString(TelnetCommand val);

  /**
   * Convert the Telnet option to readable string
   * @param[in] val Value of the option
   * @return The Telnet Option as readable string
   */
  static std::string getTelnetOptionAsString(TelnetOption val);

  /**
   * A static method that checks whether the port is considered as Telnet
   * @param[in] port The port number to be checked
   */
  static bool isTelnetPort(uint16_t port) { return port == 23; }

  /**
   * A static method that takes a byte array and detects whether it is a Telnet message
   * @param[in] data A byte array
   * @param[in] dataSize The byte array size (in bytes)
   * @return True if the data is identified as Telnet message
   */
  static bool isDataValid(const uint8_t *data, size_t dataSize) { return data && dataSize; }

  // overridden methods

  /// Parses the next layer. Telnet is the always last so does nothing for this layer
  void parseNextLayer() {}

  /**
   * @return Get the size of the layer
   */
  size_t getHeaderLen() const { return m_DataLen; }

  /// Does nothing for this layer
  void computeCalculateFields() {}

  /**
   * @return The OSI layer level of Telnet (Application Layer).
   */
  OsiModelLayer getOsiModelLayer() const { return OsiModelApplicationLayer; }

  /**
   * @return Returns the protocol info as readable string
   */
  std::string toString() const;
};

} // namespace pcpp

Coverage Report

Created: 2024-02-25 06:29

Line	Count	Source
1		#pragma once
2
3		#include "Layer.h"
4
5		/// @file
6
7		/**
8		* \namespace pcpp
9		* \brief The main namespace for the PcapPlusPlus lib
10		*/
11		namespace pcpp
12		{
13
14		/**
15		* Class for representing the Telnet Layer
16		*/
17		class TelnetLayer : public Layer
18		{
19		private:
20		// Position iterator for next command
21		size_t lastPositionOffset;
22
23		// Checks if position is a data field
24		bool isDataField(uint8_t *pos) const;
25		// Checks if position is a command field
26		bool isCommandField(uint8_t *pos) const;
27		// Returns distance to next IAC
28		size_t distanceToNextIAC(uint8_t *startPos, size_t maxLength);
29		// Returns length of provided field
30		size_t getFieldLen(uint8_t *startPos, size_t maxLength);
31		// Get position of next data field
32		uint8_t getNextDataField(uint8_t pos, size_t len);
33		// Get position of next command field
34		uint8_t getNextCommandField(uint8_t pos, size_t len);
35		// Get options of provided field
36		int16_t getSubCommand(uint8_t *pos, size_t len);
37		// Get data of provided field
38		uint8_t getCommandData(uint8_t pos, size_t &slen);
39
40		public:
41		/**
42		* Telnet Command Indicator
43		*/
44		enum class TelnetCommand : int
45		{
46		/// Indicator to parser reached end of packet
47		TelnetCommandEndOfPacket = -1,
48
49		/// End of file
50		EndOfFile = 236,
51		/// Suspend current process
52		Suspend,
53		/// Abort Process
54		Abort,
55		/// End of Record
56		EndOfRecordCommand,
57		/// Marks the end of a Telnet option subnegotiation, used with the SB code to specify more specific option
58		/// parameters.
59		SubnegotiationEnd,
60		/// Null command; does nothing.
61		NoOperation,
62		/// Used to mark the end of a sequence of data that the recipient should scan for urgent Telnet commands.
63		DataMark,
64		/// Represents the pressing of the “break” or “attention” key on the terminal.
65		Break,
66		/// Tells the recipient to interrupt, abort, suspend or terminate the process currently in use.
67		InterruptProcess,
68		/// Instructs the remote host to continue running the current process, but discard all remaining output from it.
69		/// This may be needed if a program starts to send unexpectedly large amounts of data to the user.
70		AbortOutput,
71		/// May be used to check that the remote host is still “alive”. When this character is sent the remote host
72		/// returns some type of output to indicate that it is still functioning.
73		AreYouThere,
74		/// Instructs the recipient to delete the last undeleted character from the data stream. Used to “undo” the
75		/// sending of a character.
76		EraseCharacter,
77		/// Tells the recipient to delete all characters from the data stream back to (but not including) the last end
78		/// of line (CR+LF) sequence.
79		EraseLine,
80		/// Used in Telnet half-duplex mode to signal the other device that it may transmit.
81		GoAhead,
82		/// Marks the beginning of a Telnet option subnegotiation, used when an option requires the client and server to
83		/// exchange parameters.
84		Subnegotiation,
85		/// Indicates that the device sending this code is willing to perform or continue performing a particular
86		/// option.
87		WillPerform,
88		/// Indicates that the device sending this code is either not willing to perform a particular option, or is now
89		/// refusing to continue to perform it.
90		WontPerform,
91		/// Requests that the other device perform a particular option or confirms the expectation that the other device
92		/// will perform that option.
93		DoPerform,
94		/// Specifies that the other party not perform an option, or confirms a device’s expectation that the other
95		/// party not perform an option.
96		DontPerform,
97		/// Precedes command values 240 through 254 as described above. A pair of IAC bytes in a row represents the data
98		/// value 255.
99		InterpretAsCommand
100		};
101
102		/**
103		* Telnet Options
104		*/
105		enum class TelnetOption : int
106		{
107		/// Internal return for no option detected
108		TelnetOptionNoOption = -1,
109
110		/// Binary Transmission RFC856 https://www.iana.org/go/rfc856
111		TransmitBinary = 0,
112		/// Echo RFC857 https://www.iana.org/go/rfc857
113		Echo,
114		/// Reconnection
115		Reconnection,
116		/// Suppress Go Ahead RFC858 https://www.iana.org/go/rfc858
117		SuppressGoAhead,
118		/// Negotiate approximate message size
119		ApproxMsgSizeNegotiation,
120		/// Status RFC859 https://www.iana.org/go/rfc859
121		Status,
122		/// Timing Mark RFC860 https://www.iana.org/go/rfc860
123		TimingMark,
124		/// RCTE, Remote Controlled Transmission and Echo RFC726 https://www.iana.org/go/rfc726
125		RemoteControlledTransAndEcho,
126		/// Output Line Width
127		OutputLineWidth,
128		/// Output Page Size
129		OutputPageSize,
130		/// NAOCRD, Negotiate About Output Carriage-Return Disposition RFC652 https://www.iana.org/go/rfc652
131		OutputCarriageReturnDisposition,
132		/// NAOHTS, Negotiate About Output Horizontal Tabstops RFC653 https://www.iana.org/go/rfc653
133		OutputHorizontalTabStops,
134		/// NAOHTD, Negotiate About Output Horizontal Tab Disposition RFC654 https://www.iana.org/go/rfc654
135		OutputHorizontalTabDisposition,
136		/// NAOFFD, Negotiate About Output Formfeed Disposition RFC655 https://www.iana.org/go/rfc655
137		OutputFormfeedDisposition,
138		/// NAOVTS, Negotiate About Vertical Tabstops RFC656 https://www.iana.org/go/rfc656
139		OutputVerticalTabStops,
140		/// NAOVTD, Negotiate About Output Vertcial Tab Disposition RFC657 https://www.iana.org/go/rfc657
141		OutputVerticalTabDisposition,
142		/// NAOLFD, Negotiate About Output Linefeed Disposition RFC658 https://www.iana.org/go/rfc658
143		OutputLinefeedDisposition,
144		/// Extended ASCII RFC698 https://www.iana.org/go/rfc698
145		ExtendedASCII,
146		/// Logout RFC727 https://www.iana.org/go/rfc727
147		Logout,
148		/// BM, Byte Macro RFC735 https://www.iana.org/go/rfc735
149		ByteMacro,
150		/// Data Entry Terminal RFC1043 - RFC732 https://www.iana.org/go/rfc1043 https://www.iana.org/go/rfc732
151		DataEntryTerminal,
152		/// SUPDUP RFC736 - RFC734 https://www.iana.org/go/rfc736 https://www.iana.org/go/rfc734
153		SUPDUP,
154		/// SUPDUP Output RFC749 https://www.iana.org/go/rfc749
155		SUPDUPOutput,
156		/// Send Location RFC779 https://www.iana.org/go/rfc779
157		SendLocation,
158		/// Terminal Type RFC1091 https://www.iana.org/go/rfc1091
159		TerminalType,
160		/// End of record RFC885 https://www.iana.org/go/rfc885
161		EndOfRecordOption,
162		/// TUID, TACACS User Identification RFC927 https://www.iana.org/go/rfc927
163		TACACSUserIdentification,
164		/// OUTMRK, Output Marking RFC933 https://www.iana.org/go/rfc933
165		OutputMarking,
166		/// TTYLOC, Terminal Location Number RFC946 https://www.iana.org/go/rfc946
167		TerminalLocationNumber,
168		/// Telnet 3270 Regime RFC1041 https://www.iana.org/go/rfc1041
169		Telnet3270Regime,
170		/// X.3 PAD RFC1053 https://www.iana.org/go/rfc1053
171		X3Pad,
172		/// NAWS, Negotiate About Window Size RFC1073 https://www.iana.org/go/rfc1073
173		NegotiateAboutWindowSize,
174		/// Terminal Speed RFC1079 https://www.iana.org/go/rfc1079
175		TerminalSpeed,
176		/// Remote Flow Control RFC1372 https://www.iana.org/go/rfc1372
177		RemoteFlowControl,
178		/// Line Mode RFC1184 https://www.iana.org/go/rfc1184
179		Linemode,
180		/// X Display Location RFC1096 https://www.iana.org/go/rfc1096
181		XDisplayLocation,
182		/// Environment Option RFC1408 https://www.iana.org/go/rfc1408
183		EnvironmentOption,
184		/// Authentication Option RFC2941 https://www.iana.org/go/rfc2941
185		AuthenticationOption,
186		/// Encryption Option RFC2946 https://www.iana.org/go/rfc2946
187		EncryptionOption,
188		/// New Environment Option RFC1572 https://www.iana.org/go/rfc1572
189		NewEnvironmentOption,
190		/// TN3270E RFC2355 https://www.iana.org/go/rfc2355
191		TN3270E,
192		/// X Server Authentication
193		XAuth,
194		/// Charset RFC2066 https://www.iana.org/go/rfc2066
195		Charset,
196		/// RSP, Telnet Remote Serial Port
197		TelnetRemoteSerialPort,
198		/// Com Port Control Option RFC2217 https://www.iana.org/go/rfc2217
199		ComPortControlOption,
200		/// Telnet Suppress Local Echo
201		TelnetSuppressLocalEcho,
202		/// Telnet Start TLS
203		TelnetStartTLS,
204		/// Kermit RFC2840 https://www.iana.org/go/rfc2840
205		Kermit,
206		/// Send URL
207		SendURL,
208		/// Forward X Server
209		ForwardX,
210
211		/// Telnet Option Pragma Logon
212		TelOptPragmaLogon = 138,
213		/// Telnet Option SSPI Logon
214		TelOptSSPILogon,
215		/// Telnet Option Pragma Heartbeat
216		TelOptPragmaHeartbeat,
217
218		/// Extended option list
219		ExtendedOptions = 255
220		};
221
222		/**
223		* A constructor that creates the layer from an existing packet raw data
224		* @param[in] data A pointer to the raw data
225		* @param[in] dataLen Size of the data in bytes
226		* @param[in] prevLayer A pointer to the previous layer
227		* @param[in] packet A pointer to the Packet instance where layer will be stored in
228		*/
229		TelnetLayer(uint8_t data, size_t dataLen, Layer prevLayer, Packet *packet) : Layer(data, dataLen, prevLayer, packet)
230	6.43k	{
231	6.43k	m_Protocol = Telnet;
232	6.43k	lastPositionOffset = SIZE_MAX;
233	6.43k	};
234
235		/**
236		* Get the Telnet data as readable string
237		* @param[in] removeEscapeCharacters Whether non-alphanumerical characters should be removed or not
238		* @return Full payload as readable string, empty if Telnet packet contains control commands/options.
239		*/
240		std::string getDataAsString(bool removeEscapeCharacters = true);
241
242		/**
243		* Get the total number of detected Telnet commands
244		* @return size_t The number of Telnet commands
245		*/
246		size_t getTotalNumberOfCommands();
247
248		/**
249		* Returns the number of occurrences of provided command
250		* @param[in] command Telnet command to count
251		* @return size_t Number of occurrences of command
252		*/
253		size_t getNumberOfCommands(TelnetCommand command);
254
255		/**
256		* Returns the first command of packet
257		* @return TelnetCommand First detected command value, TelnetCommandEndOfPacket if there is no command field
258		*/
259		TelnetCommand getFirstCommand();
260
261		/**
262		* Returns the next command of packet. Uses an internal iterator. The iterator resets when reached end of packet.
263		* @return TelnetCommand Detected command value, TelnetCommandEndOfPacket if reached the end of packet.
264		*/
265		TelnetCommand getNextCommand();
266
267		/**
268		* Returns the option of current command. Uses an internal iterator. Iterator can be moved with getNextCommand
269		* @return TelnetOption Option of current command
270		*/
271		TelnetOption getOption();
272
273		/**
274		* Returns the option of provided command. It will return option of first occurrence of the command
275		* @param[in] command Telnet command to search
276		* @return TelnetOption Option of the command. Returns TelnetOptionNoOption if the provided command not found.
277		*/
278		TelnetOption getOption(TelnetCommand command);
279
280		/**
281		* Returns the data of current command. Uses an internal iterator. Iterator can be moved with getNextCommand
282		* @param[out] length Length of the data of current command
283		* @return uint8_t* Pointer to the data of current command. NULL if there is no data for this command.
284		*/
285		uint8_t *getOptionData(size_t &length);
286
287		/**
288		* Returns the data of provided command. It will return data of first occurrence of the command
289		* @param[in] command Telnet command to search
290		* @param[out] length Length of the data of current command
291		* @return uint8_t* Pointer to the data of current command. NULL if there is no data for this command or if can't
292		* find the command.
293		*/
294		uint8_t *getOptionData(TelnetCommand command, size_t &length);
295
296		/**
297		* Convert the Telnet Command to readable string
298		* @param[in] val Value of the command
299		* @return The Telnet Command as readable string
300		*/
301		static std::string getTelnetCommandAsString(TelnetCommand val);
302
303		/**
304		* Convert the Telnet option to readable string
305		* @param[in] val Value of the option
306		* @return The Telnet Option as readable string
307		*/
308		static std::string getTelnetOptionAsString(TelnetOption val);
309
310		/**
311		* A static method that checks whether the port is considered as Telnet
312		* @param[in] port The port number to be checked
313		*/
314	210k	static bool isTelnetPort(uint16_t port) { return port == 23; }
315
316		/**
317		* A static method that takes a byte array and detects whether it is a Telnet message
318		* @param[in] data A byte array
319		* @param[in] dataSize The byte array size (in bytes)
320		* @return True if the data is identified as Telnet message
321		*/
322	107k	static bool isDataValid(const uint8_t *data, size_t dataSize) { return data && dataSize; }
323
324		// overridden methods
325
326		/// Parses the next layer. Telnet is the always last so does nothing for this layer
327	6.43k	void parseNextLayer() {}
328
329		/**
330		* @return Get the size of the layer
331		*/
332	1.12k	size_t getHeaderLen() const { return m_DataLen; }
333
334		/// Does nothing for this layer
335	1.12k	void computeCalculateFields() {}
336
337		/**
338		* @return The OSI layer level of Telnet (Application Layer).
339		*/
340	1.12k	OsiModelLayer getOsiModelLayer() const { return OsiModelApplicationLayer; }
341
342		/**
343		* @return Returns the protocol info as readable string
344		*/
345		std::string toString() const;
346		};
347
348		} // namespace pcpp