/**

 * FreeRDP: A Remote Desktop Protocol Implementation

 * X.224 Transport Protocol Data Units (TPDUs)

 *

 * Copyright 2011 Marc-Andre Moreau <marcandre.moreau@gmail.com>

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <stdio.h>

#include <winpr/print.h>

#include <freerdp/log.h>

#include "tpdu.h"

#define TAG FREERDP_TAG("core")

/**

 * TPDUs are defined in:

 *

 * http://www.itu.int/rec/T-REC-X.224-199511-I/

 * X.224: Information technology - Open Systems Interconnection - Protocol for providing the

 * connection-mode transport service

 *

 * RDP uses only TPDUs of class 0, the "simple class" defined in section 8 of X.224

 *

 *       TPDU Header

 *  ____________________   byte

 * |                    |

 * |         LI         |   1

 * |____________________|

 * |                    |

 * |        Code        |   2

 * |____________________|

 * |                    |

 * |                    |   3

 * |_______DST-REF______|

 * |                    |

 * |                    |   4

 * |____________________|

 * |                    |

 * |                    |   5

 * |_______SRC-REF______|

 * |                    |

 * |                    |   6

 * |____________________|

 * |                    |

 * |        Class       |   7

 * |____________________|

 * |         ...        |

 */

static void tpdu_write_header(wStream* s, UINT16 length, BYTE code);

/**

 * Read TPDU header.

 * @param s stream

 * @param code variable pointer to receive TPDU code

 * @return TPDU length indicator (LI)

 */

BOOL tpdu_read_header(wStream* s, BYTE* code, BYTE* li, UINT16 tpktlength)

{

	if (Stream_GetRemainingLength(s) < 3)

		return FALSE;

	Stream_Read_UINT8(s, *li);   /* LI */

	Stream_Read_UINT8(s, *code); /* Code */

	if (*li + 4 > tpktlength)

	{

		WLog_ERR(TAG, "tpdu length %" PRIu16 " > tpkt header length %" PRIu16, li, tpktlength);

		return FALSE;

	}

	if (*code == X224_TPDU_DATA)

	{

		/* EOT (1 byte) */

		Stream_Seek(s, 1);

	}

	else

	{

		/* DST-REF (2 bytes) */

		/* SRC-REF (2 bytes) */

		/* Class 0 (1 byte) */

		return Stream_SafeSeek(s, 5);

	}

	return TRUE;

}

/**

 * Write TDPU header.

 * @param s stream

 * @param length length

 * @param code TPDU code

 */

void tpdu_write_header(wStream* s, UINT16 length, BYTE code)

{

	Stream_Write_UINT8(s, length); /* LI */

	Stream_Write_UINT8(s, code);   /* code */

	if (code == X224_TPDU_DATA)

	{

		Stream_Write_UINT8(s, 0x80); /* EOT */

	}

	else

	{

		Stream_Write_UINT16(s, 0); /* DST-REF */

		Stream_Write_UINT16(s, 0); /* SRC-REF */

		Stream_Write_UINT8(s, 0);  /* Class 0 */

	}

}

/**

 * Read Connection Request TPDU

 * @param s stream

 * @return length indicator (LI)

 */

BOOL tpdu_read_connection_request(wStream* s, BYTE* li, UINT16 tpktlength)

{

	BYTE code;

	if (!tpdu_read_header(s, &code, li, tpktlength))

		return FALSE;

	if (code != X224_TPDU_CONNECTION_REQUEST)

	{

		WLog_ERR(TAG, "Error: expected X224_TPDU_CONNECTION_REQUEST");

		return FALSE;

	}

	return TRUE;

}

/**

 * Write Connection Request TPDU.

 * @param s stream

 * @param length TPDU length

 */

void tpdu_write_connection_request(wStream* s, UINT16 length)

{

	tpdu_write_header(s, length, X224_TPDU_CONNECTION_REQUEST);

}

/**

 * Read Connection Confirm TPDU.

 * @param s stream

 * @return length indicator (LI)

 */

BOOL tpdu_read_connection_confirm(wStream* s, BYTE* li, UINT16 tpktlength)

{

	BYTE code;

	size_t position;

	size_t bytes_read = 0;

	/* save the position to determine the number of bytes read */

	position = Stream_GetPosition(s);

	if (!tpdu_read_header(s, &code, li, tpktlength))

		return FALSE;

	if (code != X224_TPDU_CONNECTION_CONFIRM)

	{

		WLog_ERR(TAG, "Error: expected X224_TPDU_CONNECTION_CONFIRM");

		return FALSE;

	}

	/*

	 * To ensure that there are enough bytes remaining for processing

	 * check against the length indicator (li). Already read bytes need

	 * to be taken into account.

	 * The -1 is because li was read but isn't included in the TPDU size.

	 * For reference see ITU-T Rec. X.224 - 13.2.1

	 */

	bytes_read = (Stream_GetPosition(s) - position) - 1;

	return (Stream_GetRemainingLength(s) >= (size_t)(*li - bytes_read));

}

/**

 * Write Connection Confirm TPDU.

 * @param s stream

 * @param length TPDU length

 */

void tpdu_write_connection_confirm(wStream* s, UINT16 length)

{

	tpdu_write_header(s, length, X224_TPDU_CONNECTION_CONFIRM);

}

/**

 * Write Disconnect Request TPDU.

 * @param s stream

 * @param length TPDU length

 */

void tpdu_write_disconnect_request(wStream* s, UINT16 length)

{

	tpdu_write_header(s, length, X224_TPDU_DISCONNECT_REQUEST);

}

/**

 * Write Data TPDU.

 * @param s stream

 */

void tpdu_write_data(wStream* s)

{

	tpdu_write_header(s, 2, X224_TPDU_DATA);

}

/**

 * Read Data TPDU.

 * @param s stream

 */

BOOL tpdu_read_data(wStream* s, UINT16* LI, UINT16 tpktlength)

{

	BYTE code;

	BYTE li;

	if (!tpdu_read_header(s, &code, &li, tpktlength))

		return FALSE;

	if (code != X224_TPDU_DATA)

		return FALSE;

	*LI = li;

	return TRUE;

}