media/base/rtp_utils.cc - src - Git at Google

 /*
  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "media/base/rtp_utils.h"

 #include <string.h>

 #include <cstdint>
 #include <vector>

 // PacketTimeUpdateParams is defined in asyncpacketsocket.h.
 // TODO(sergeyu): Find more appropriate place for PacketTimeUpdateParams.
 #include "media/base/turn_utils.h"
 #include "modules/rtp_rtcp/source/rtp_util.h"
 #include "rtc_base/async_packet_socket.h"
 #include "rtc_base/byte_order.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/message_digest.h"

 namespace cricket {

 static const size_t kRtcpPayloadTypeOffset = 1;
 static const size_t kRtpExtensionHeaderLen = 4;
 static const size_t kAbsSendTimeExtensionLen = 3;
 static const size_t kOneByteExtensionHeaderLen = 1;
 static const size_t kTwoByteExtensionHeaderLen = 2;

 namespace {

 // Fake auth tag written by the sender when external authentication is enabled.
 // HMAC in packet will be compared against this value before updating packet
 // with actual HMAC value.
 static const uint8_t kFakeAuthTag[10] = {0xba, 0xdd, 0xba, 0xdd, 0xba,
                                          0xdd, 0xba, 0xdd, 0xba, 0xdd};

 void UpdateAbsSendTimeExtensionValue(uint8_t* extension_data,
                                      size_t length,
                                      uint64_t time_us) {
   // Absolute send time in RTP streams.
   //
   // The absolute send time is signaled to the receiver in-band using the
   // general mechanism for RTP header extensions [RFC5285]. The payload
   // of this extension (the transmitted value) is a 24-bit unsigned integer
   // containing the sender's current time in seconds as a fixed point number
   // with 18 bits fractional part.
   //
   // The form of the absolute send time extension block:
   //
   //    0                   1                   2                   3
   //    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //   |  ID   | len=2 |              absolute send time               |
   //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   if (length != kAbsSendTimeExtensionLen) {
     RTC_DCHECK_NOTREACHED();
     return;
   }

   // Convert microseconds to a 6.18 fixed point value in seconds.
   uint32_t send_time = ((time_us << 18) / 1000000) & 0x00FFFFFF;
   extension_data[0] = static_cast<uint8_t>(send_time >> 16);
   extension_data[1] = static_cast<uint8_t>(send_time >> 8);
   extension_data[2] = static_cast<uint8_t>(send_time);
 }

 // Assumes `length` is actual packet length + tag length. Updates HMAC at end of
 // the RTP packet.
 void UpdateRtpAuthTag(uint8_t* rtp,
                       size_t length,
                       const rtc::PacketTimeUpdateParams& packet_time_params) {
   // If there is no key, return.
   if (packet_time_params.srtp_auth_key.empty()) {
     return;
   }

   size_t tag_length = packet_time_params.srtp_auth_tag_len;

   // ROC (rollover counter) is at the beginning of the auth tag.
   const size_t kRocLength = 4;
   if (tag_length < kRocLength || tag_length > length) {
     RTC_DCHECK_NOTREACHED();
     return;
   }

   uint8_t* auth_tag = rtp + (length - tag_length);

   // We should have a fake HMAC value @ auth_tag.
   RTC_DCHECK_EQ(0, memcmp(auth_tag, kFakeAuthTag, tag_length));

   // Copy ROC after end of rtp packet.
   memcpy(auth_tag, &packet_time_params.srtp_packet_index, kRocLength);
   // Authentication of a RTP packet will have RTP packet + ROC size.
   size_t auth_required_length = length - tag_length + kRocLength;

   uint8_t output[64];
   size_t result =
       rtc::ComputeHmac(rtc::DIGEST_SHA_1, &packet_time_params.srtp_auth_key[0],
                        packet_time_params.srtp_auth_key.size(), rtp,
                        auth_required_length, output, sizeof(output));

   if (result < tag_length) {
     RTC_DCHECK_NOTREACHED();
     return;
   }

   // Copy HMAC from output to packet. This is required as auth tag length
   // may not be equal to the actual HMAC length.
   memcpy(auth_tag, output, tag_length);
 }

 bool GetUint8(const void* data, size_t offset, int* value) {
   if (!data || !value) {
     return false;
   }
   *value = *(static_cast<const uint8_t*>(data) + offset);
   return true;
 }

 }  // namespace

 bool GetRtcpType(const void* data, size_t len, int* value) {
   if (len < kMinRtcpPacketLen) {
     return false;
   }
   return GetUint8(data, kRtcpPayloadTypeOffset, value);
 }

 // This method returns SSRC first of RTCP packet, except if packet is SDES.
 // TODO(mallinath) - Fully implement RFC 5506. This standard doesn't restrict
 // to send non-compound packets only to feedback messages.
 bool GetRtcpSsrc(const void* data, size_t len, uint32_t* value) {
   // Packet should be at least of 8 bytes, to get SSRC from a RTCP packet.
   if (!data || len < kMinRtcpPacketLen + 4 || !value)
     return false;
   int pl_type;
   if (!GetRtcpType(data, len, &pl_type))
     return false;
   // SDES packet parsing is not supported.
   if (pl_type == kRtcpTypeSDES)
     return false;
   *value = rtc::GetBE32(static_cast<const uint8_t*>(data) + 4);
   return true;
 }

 bool IsValidRtpPayloadType(int payload_type) {
   return payload_type >= 0 && payload_type <= 127;
 }

 bool IsValidRtpPacketSize(RtpPacketType packet_type, size_t size) {
   RTC_DCHECK_NE(RtpPacketType::kUnknown, packet_type);
   size_t min_packet_length = packet_type == RtpPacketType::kRtcp
                                  ? kMinRtcpPacketLen
                                  : kMinRtpPacketLen;
   return size >= min_packet_length && size <= kMaxRtpPacketLen;
 }

 absl::string_view RtpPacketTypeToString(RtpPacketType packet_type) {
   switch (packet_type) {
     case RtpPacketType::kRtp:
       return "RTP";
     case RtpPacketType::kRtcp:
       return "RTCP";
     case RtpPacketType::kUnknown:
       return "Unknown";
   }
   RTC_CHECK_NOTREACHED();
 }

 RtpPacketType InferRtpPacketType(rtc::ArrayView<const uint8_t> packet) {
   if (webrtc::IsRtcpPacket(packet)) {
     return RtpPacketType::kRtcp;
   }
   if (webrtc::IsRtpPacket(packet)) {
     return RtpPacketType::kRtp;
   }
   return RtpPacketType::kUnknown;
 }

 bool ValidateRtpHeader(const uint8_t* rtp,
                        size_t length,
                        size_t* header_length) {
   if (header_length) {
     *header_length = 0;
   }

   if (length < kMinRtpPacketLen) {
     return false;
   }

   size_t cc_count = rtp[0] & 0x0F;
   size_t header_length_without_extension = kMinRtpPacketLen + 4 * cc_count;
   if (header_length_without_extension > length) {
     return false;
   }

   // If extension bit is not set, we are done with header processing, as input
   // length is verified above.
   if (!(rtp[0] & 0x10)) {
     if (header_length)
       *header_length = header_length_without_extension;

     return true;
   }

   rtp += header_length_without_extension;

   if (header_length_without_extension + kRtpExtensionHeaderLen > length) {
     return false;
   }

   // Getting extension profile length.
   // Length is in 32 bit words.
   uint16_t extension_length_in_32bits = rtc::GetBE16(rtp + 2);
   size_t extension_length = extension_length_in_32bits * 4;

   size_t rtp_header_length = extension_length +
                              header_length_without_extension +
                              kRtpExtensionHeaderLen;

   // Verify input length against total header size.
   if (rtp_header_length > length) {
     return false;
   }

   if (header_length) {
     *header_length = rtp_header_length;
   }
   return true;
 }

 // ValidateRtpHeader() must be called before this method to make sure, we have
 // a sane rtp packet.
 bool UpdateRtpAbsSendTimeExtension(uint8_t* rtp,
                                    size_t /* length */,
                                    int extension_id,
                                    uint64_t time_us) {
   //  0                   1                   2                   3
   //  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   // |V=2|P|X|  CC   |M|     PT      |       sequence number         |
   // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   // |                           timestamp                           |
   // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   // |           synchronization source (SSRC) identifier            |
   // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   // |            contributing source (CSRC) identifiers             |
   // |                             ....                              |
   // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   // Return if extension bit is not set.
   if (!(rtp[0] & 0x10)) {
     return true;
   }

   size_t cc_count = rtp[0] & 0x0F;
   size_t header_length_without_extension = kMinRtpPacketLen + 4 * cc_count;

   rtp += header_length_without_extension;

   // Getting extension profile ID and length.
   uint16_t profile_id = rtc::GetBE16(rtp);
   // Length is in 32 bit words.
   uint16_t extension_length_in_32bits = rtc::GetBE16(rtp + 2);
   size_t extension_length = extension_length_in_32bits * 4;

   rtp += kRtpExtensionHeaderLen;  // Moving past extension header.

   constexpr uint16_t kOneByteExtensionProfileId = 0xBEDE;
   constexpr uint16_t kTwoByteExtensionProfileId = 0x1000;

   bool found = false;
   if (profile_id == kOneByteExtensionProfileId ||
       profile_id == kTwoByteExtensionProfileId) {
     // OneByte extension header
     //  0
     //  0 1 2 3 4 5 6 7
     // +-+-+-+-+-+-+-+-+
     // |  ID   |length |
     // +-+-+-+-+-+-+-+-+

     //  0                   1                   2                   3
     //  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     // |       0xBE    |    0xDE       |           length=3            |
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     // |  ID   | L=0   |     data      |  ID   |  L=1  |   data...
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //       ...data   |    0 (pad)    |    0 (pad)    |  ID   | L=3   |
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     // |                          data                                 |
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     // TwoByte extension header
     //  0
     //  0 1 2 3 4 5 6 7
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     // |      ID       |    length     |
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     //  0                   1                   2                   3
     //  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     // |     0x10      |     0x00      |           length=3            |
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     // |      ID       |      L=1      |     data      |      ID       |
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     // |      L=2      |             data              |    0 (pad)    |
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     // |      ID       |      L=2      |             data              |
     // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     size_t extension_header_length = profile_id == kOneByteExtensionProfileId
                                          ? kOneByteExtensionHeaderLen
                                          : kTwoByteExtensionHeaderLen;

     const uint8_t* extension_start = rtp;
     const uint8_t* extension_end = extension_start + extension_length;

     // rtp + 1 since the minimum size per header extension is two bytes for both
     // one- and two-byte header extensions.
     while (rtp + 1 < extension_end) {
       // See RFC8285 Section 4.2-4.3 for more information about one- and
       // two-byte header extensions.
       const int id =
           profile_id == kOneByteExtensionProfileId ? (*rtp & 0xF0) >> 4 : *rtp;
       const size_t length = profile_id == kOneByteExtensionProfileId
                                 ? (*rtp & 0x0F) + 1
                                 : *(rtp + 1);
       if (rtp + extension_header_length + length > extension_end) {
         return false;
       }
       if (id == extension_id) {
         UpdateAbsSendTimeExtensionValue(rtp + extension_header_length, length,
                                         time_us);
         found = true;
         break;
       }
       rtp += extension_header_length + length;
       // Counting padding bytes.
       while ((rtp < extension_end) && (*rtp == 0)) {
         ++rtp;
       }
     }
   }
   return found;
 }

 bool ApplyPacketOptions(uint8_t* data,
                         size_t length,
                         const rtc::PacketTimeUpdateParams& packet_time_params,
                         uint64_t time_us) {
   RTC_DCHECK(data);
   RTC_DCHECK(length);

   // if there is no valid `rtp_sendtime_extension_id` and `srtp_auth_key` in
   // PacketOptions, nothing to be updated in this packet.
   if (packet_time_params.rtp_sendtime_extension_id == -1 &&
       packet_time_params.srtp_auth_key.empty()) {
     return true;
   }

   // If there is a srtp auth key present then the packet must be an RTP packet.
   // RTP packet may have been wrapped in a TURN Channel Data or TURN send
   // indication.
   size_t rtp_start_pos;
   size_t rtp_length;
   if (!UnwrapTurnPacket(data, length, &rtp_start_pos, &rtp_length)) {
     RTC_DCHECK_NOTREACHED();
     return false;
   }

   // Making sure we have a valid RTP packet at the end.
   auto packet = rtc::MakeArrayView(data + rtp_start_pos, rtp_length);
   if (!webrtc::IsRtpPacket(packet) ||
       !ValidateRtpHeader(data + rtp_start_pos, rtp_length, nullptr)) {
     RTC_DCHECK_NOTREACHED();
     return false;
   }

   uint8_t* start = data + rtp_start_pos;
   // If packet option has non default value (-1) for sendtime extension id,
   // then we should parse the rtp packet to update the timestamp. Otherwise
   // just calculate HMAC and update packet with it.
   if (packet_time_params.rtp_sendtime_extension_id != -1) {
     UpdateRtpAbsSendTimeExtension(start, rtp_length,
                                   packet_time_params.rtp_sendtime_extension_id,
                                   time_us);
   }

   UpdateRtpAuthTag(start, rtp_length, packet_time_params);
   return true;
 }

 }  // namespace cricket
	/*
	* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "media/base/rtp_utils.h"

	#include <string.h>

	#include <cstdint>
	#include <vector>

	// PacketTimeUpdateParams is defined in asyncpacketsocket.h.
	// TODO(sergeyu): Find more appropriate place for PacketTimeUpdateParams.
	#include "media/base/turn_utils.h"
	#include "modules/rtp_rtcp/source/rtp_util.h"
	#include "rtc_base/async_packet_socket.h"
	#include "rtc_base/byte_order.h"
	#include "rtc_base/checks.h"
	#include "rtc_base/message_digest.h"

	namespace cricket {

	static const size_t kRtcpPayloadTypeOffset = 1;
	static const size_t kRtpExtensionHeaderLen = 4;
	static const size_t kAbsSendTimeExtensionLen = 3;
	static const size_t kOneByteExtensionHeaderLen = 1;
	static const size_t kTwoByteExtensionHeaderLen = 2;

	namespace {

	// Fake auth tag written by the sender when external authentication is enabled.
	// HMAC in packet will be compared against this value before updating packet
	// with actual HMAC value.
	static const uint8_t kFakeAuthTag[10] = {0xba, 0xdd, 0xba, 0xdd, 0xba,
	0xdd, 0xba, 0xdd, 0xba, 0xdd};

	void UpdateAbsSendTimeExtensionValue(uint8_t* extension_data,
	size_t length,
	uint64_t time_us) {
	// Absolute send time in RTP streams.
	//
	// The absolute send time is signaled to the receiver in-band using the
	// general mechanism for RTP header extensions [RFC5285]. The payload
	// of this extension (the transmitted value) is a 24-bit unsigned integer
	// containing the sender's current time in seconds as a fixed point number
	// with 18 bits fractional part.
	//
	// The form of the absolute send time extension block:
	//
	// 0 1 2 3
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| len=2 \| absolute send time \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	if (length != kAbsSendTimeExtensionLen) {
	RTC_DCHECK_NOTREACHED();
	return;
	}

	// Convert microseconds to a 6.18 fixed point value in seconds.
	uint32_t send_time = ((time_us << 18) / 1000000) & 0x00FFFFFF;
	extension_data[0] = static_cast<uint8_t>(send_time >> 16);
	extension_data[1] = static_cast<uint8_t>(send_time >> 8);
	extension_data[2] = static_cast<uint8_t>(send_time);
	}

	// Assumes `length` is actual packet length + tag length. Updates HMAC at end of
	// the RTP packet.
	void UpdateRtpAuthTag(uint8_t* rtp,
	size_t length,
	const rtc::PacketTimeUpdateParams& packet_time_params) {
	// If there is no key, return.
	if (packet_time_params.srtp_auth_key.empty()) {
	return;
	}

	size_t tag_length = packet_time_params.srtp_auth_tag_len;

	// ROC (rollover counter) is at the beginning of the auth tag.
	const size_t kRocLength = 4;
	if (tag_length < kRocLength \|\| tag_length > length) {
	RTC_DCHECK_NOTREACHED();
	return;
	}

	uint8_t* auth_tag = rtp + (length - tag_length);

	// We should have a fake HMAC value @ auth_tag.
	RTC_DCHECK_EQ(0, memcmp(auth_tag, kFakeAuthTag, tag_length));

	// Copy ROC after end of rtp packet.
	memcpy(auth_tag, &packet_time_params.srtp_packet_index, kRocLength);
	// Authentication of a RTP packet will have RTP packet + ROC size.
	size_t auth_required_length = length - tag_length + kRocLength;

	uint8_t output[64];
	size_t result =
	rtc::ComputeHmac(rtc::DIGEST_SHA_1, &packet_time_params.srtp_auth_key[0],
	packet_time_params.srtp_auth_key.size(), rtp,
	auth_required_length, output, sizeof(output));

	if (result < tag_length) {
	RTC_DCHECK_NOTREACHED();
	return;
	}

	// Copy HMAC from output to packet. This is required as auth tag length
	// may not be equal to the actual HMAC length.
	memcpy(auth_tag, output, tag_length);
	}

	bool GetUint8(const void* data, size_t offset, int* value) {
	if (!data \|\| !value) {
	return false;
	}
	value = (static_cast<const uint8_t*>(data) + offset);
	return true;
	}

	} // namespace

	bool GetRtcpType(const void* data, size_t len, int* value) {
	if (len < kMinRtcpPacketLen) {
	return false;
	}
	return GetUint8(data, kRtcpPayloadTypeOffset, value);
	}

	// This method returns SSRC first of RTCP packet, except if packet is SDES.
	// TODO(mallinath) - Fully implement RFC 5506. This standard doesn't restrict
	// to send non-compound packets only to feedback messages.
	bool GetRtcpSsrc(const void* data, size_t len, uint32_t* value) {
	// Packet should be at least of 8 bytes, to get SSRC from a RTCP packet.
	if (!data \|\| len < kMinRtcpPacketLen + 4 \|\| !value)
	return false;
	int pl_type;
	if (!GetRtcpType(data, len, &pl_type))
	return false;
	// SDES packet parsing is not supported.
	if (pl_type == kRtcpTypeSDES)
	return false;
	value = rtc::GetBE32(static_cast<const uint8_t>(data) + 4);
	return true;
	}

	bool IsValidRtpPayloadType(int payload_type) {
	return payload_type >= 0 && payload_type <= 127;
	}

	bool IsValidRtpPacketSize(RtpPacketType packet_type, size_t size) {
	RTC_DCHECK_NE(RtpPacketType::kUnknown, packet_type);
	size_t min_packet_length = packet_type == RtpPacketType::kRtcp
	? kMinRtcpPacketLen
	: kMinRtpPacketLen;
	return size >= min_packet_length && size <= kMaxRtpPacketLen;
	}

	absl::string_view RtpPacketTypeToString(RtpPacketType packet_type) {
	switch (packet_type) {
	case RtpPacketType::kRtp:
	return "RTP";
	case RtpPacketType::kRtcp:
	return "RTCP";
	case RtpPacketType::kUnknown:
	return "Unknown";
	}
	RTC_CHECK_NOTREACHED();
	}

	RtpPacketType InferRtpPacketType(rtc::ArrayView<const uint8_t> packet) {
	if (webrtc::IsRtcpPacket(packet)) {
	return RtpPacketType::kRtcp;
	}
	if (webrtc::IsRtpPacket(packet)) {
	return RtpPacketType::kRtp;
	}
	return RtpPacketType::kUnknown;
	}

	bool ValidateRtpHeader(const uint8_t* rtp,
	size_t length,
	size_t* header_length) {
	if (header_length) {
	*header_length = 0;
	}

	if (length < kMinRtpPacketLen) {
	return false;
	}

	size_t cc_count = rtp[0] & 0x0F;
	size_t header_length_without_extension = kMinRtpPacketLen + 4 * cc_count;
	if (header_length_without_extension > length) {
	return false;
	}

	// If extension bit is not set, we are done with header processing, as input
	// length is verified above.
	if (!(rtp[0] & 0x10)) {
	if (header_length)
	*header_length = header_length_without_extension;

	return true;
	}

	rtp += header_length_without_extension;

	if (header_length_without_extension + kRtpExtensionHeaderLen > length) {
	return false;
	}

	// Getting extension profile length.
	// Length is in 32 bit words.
	uint16_t extension_length_in_32bits = rtc::GetBE16(rtp + 2);
	size_t extension_length = extension_length_in_32bits * 4;

	size_t rtp_header_length = extension_length +
	header_length_without_extension +
	kRtpExtensionHeaderLen;

	// Verify input length against total header size.
	if (rtp_header_length > length) {
	return false;
	}

	if (header_length) {
	*header_length = rtp_header_length;
	}
	return true;
	}

	// ValidateRtpHeader() must be called before this method to make sure, we have
	// a sane rtp packet.
	bool UpdateRtpAbsSendTimeExtension(uint8_t* rtp,
	size_t /* length */,
	int extension_id,
	uint64_t time_us) {
	// 0 1 2 3
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \|V=2\|P\|X\| CC \|M\| PT \| sequence number \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| timestamp \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| synchronization source (SSRC) identifier \|
	// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
	// \| contributing source (CSRC) identifiers \|
	// \| .... \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	// Return if extension bit is not set.
	if (!(rtp[0] & 0x10)) {
	return true;
	}

	size_t cc_count = rtp[0] & 0x0F;
	size_t header_length_without_extension = kMinRtpPacketLen + 4 * cc_count;

	rtp += header_length_without_extension;

	// Getting extension profile ID and length.
	uint16_t profile_id = rtc::GetBE16(rtp);
	// Length is in 32 bit words.
	uint16_t extension_length_in_32bits = rtc::GetBE16(rtp + 2);
	size_t extension_length = extension_length_in_32bits * 4;

	rtp += kRtpExtensionHeaderLen; // Moving past extension header.

	constexpr uint16_t kOneByteExtensionProfileId = 0xBEDE;
	constexpr uint16_t kTwoByteExtensionProfileId = 0x1000;

	bool found = false;
	if (profile_id == kOneByteExtensionProfileId \|\|
	profile_id == kTwoByteExtensionProfileId) {
	// OneByte extension header
	// 0
	// 0 1 2 3 4 5 6 7
	// +-+-+-+-+-+-+-+-+
	// \| ID \|length \|
	// +-+-+-+-+-+-+-+-+

	// 0 1 2 3
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| 0xBE \| 0xDE \| length=3 \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| L=0 \| data \| ID \| L=1 \| data...
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// ...data \| 0 (pad) \| 0 (pad) \| ID \| L=3 \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| data \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	// TwoByte extension header
	// 0
	// 0 1 2 3 4 5 6 7
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| length \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	// 0 1 2 3
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| 0x10 \| 0x00 \| length=3 \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| L=1 \| data \| ID \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| L=2 \| data \| 0 (pad) \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| L=2 \| data \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	size_t extension_header_length = profile_id == kOneByteExtensionProfileId
	? kOneByteExtensionHeaderLen
	: kTwoByteExtensionHeaderLen;

	const uint8_t* extension_start = rtp;
	const uint8_t* extension_end = extension_start + extension_length;

	// rtp + 1 since the minimum size per header extension is two bytes for both
	// one- and two-byte header extensions.
	while (rtp + 1 < extension_end) {
	// See RFC8285 Section 4.2-4.3 for more information about one- and
	// two-byte header extensions.
	const int id =
	profile_id == kOneByteExtensionProfileId ? (rtp & 0xF0) >> 4 : rtp;
	const size_t length = profile_id == kOneByteExtensionProfileId
	? (*rtp & 0x0F) + 1
	: *(rtp + 1);
	if (rtp + extension_header_length + length > extension_end) {
	return false;
	}
	if (id == extension_id) {
	UpdateAbsSendTimeExtensionValue(rtp + extension_header_length, length,
	time_us);
	found = true;
	break;
	}
	rtp += extension_header_length + length;
	// Counting padding bytes.
	while ((rtp < extension_end) && (*rtp == 0)) {
	++rtp;
	}
	}
	}
	return found;
	}

	bool ApplyPacketOptions(uint8_t* data,
	size_t length,
	const rtc::PacketTimeUpdateParams& packet_time_params,
	uint64_t time_us) {
	RTC_DCHECK(data);
	RTC_DCHECK(length);

	// if there is no valid `rtp_sendtime_extension_id` and `srtp_auth_key` in
	// PacketOptions, nothing to be updated in this packet.
	if (packet_time_params.rtp_sendtime_extension_id == -1 &&
	packet_time_params.srtp_auth_key.empty()) {
	return true;
	}

	// If there is a srtp auth key present then the packet must be an RTP packet.
	// RTP packet may have been wrapped in a TURN Channel Data or TURN send
	// indication.
	size_t rtp_start_pos;
	size_t rtp_length;
	if (!UnwrapTurnPacket(data, length, &rtp_start_pos, &rtp_length)) {
	RTC_DCHECK_NOTREACHED();
	return false;
	}

	// Making sure we have a valid RTP packet at the end.
	auto packet = rtc::MakeArrayView(data + rtp_start_pos, rtp_length);
	if (!webrtc::IsRtpPacket(packet) \|\|
	!ValidateRtpHeader(data + rtp_start_pos, rtp_length, nullptr)) {
	RTC_DCHECK_NOTREACHED();
	return false;
	}

	uint8_t* start = data + rtp_start_pos;
	// If packet option has non default value (-1) for sendtime extension id,
	// then we should parse the rtp packet to update the timestamp. Otherwise
	// just calculate HMAC and update packet with it.
	if (packet_time_params.rtp_sendtime_extension_id != -1) {
	UpdateRtpAbsSendTimeExtension(start, rtp_length,
	packet_time_params.rtp_sendtime_extension_id,
	time_us);
	}

	UpdateRtpAuthTag(start, rtp_length, packet_time_params);
	return true;
	}

	} // namespace cricket