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/*
* 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 "webrtc/media/base/rtputils.h"
// PacketTimeUpdateParams is defined in asyncpacketsocket.h.
// TODO(sergeyu): Find more appropriate place for PacketTimeUpdateParams.
#include "webrtc/base/asyncpacketsocket.h"
#include "webrtc/base/checks.h"
#include "webrtc/base/messagedigest.h"
#include "webrtc/media/base/turnutils.h"
namespace cricket {
static const uint8_t kRtpVersion = 2;
static const size_t kRtpFlagsOffset = 0;
static const size_t kRtpPayloadTypeOffset = 1;
static const size_t kRtpSeqNumOffset = 2;
static const size_t kRtpTimestampOffset = 4;
static const size_t kRtpSsrcOffset = 8;
static const size_t kRtcpPayloadTypeOffset = 1;
static const size_t kRtpExtensionHeaderLen = 4;
static const size_t kAbsSendTimeExtensionLen = 3;
static const size_t kOneByteExtensionHeaderLen = 1;
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_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_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_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;
}
bool GetUint16(const void* data, size_t offset, int* value) {
if (!data || !value) {
return false;
}
*value = static_cast<int>(
rtc::GetBE16(static_cast<const uint8_t*>(data) + offset));
return true;
}
bool GetUint32(const void* data, size_t offset, uint32_t* value) {
if (!data || !value) {
return false;
}
*value = rtc::GetBE32(static_cast<const uint8_t*>(data) + offset);
return true;
}
bool SetUint8(void* data, size_t offset, uint8_t value) {
if (!data) {
return false;
}
rtc::Set8(data, offset, value);
return true;
}
bool SetUint16(void* data, size_t offset, uint16_t value) {
if (!data) {
return false;
}
rtc::SetBE16(static_cast<uint8_t*>(data) + offset, value);
return true;
}
bool SetUint32(void* data, size_t offset, uint32_t value) {
if (!data) {
return false;
}
rtc::SetBE32(static_cast<uint8_t*>(data) + offset, value);
return true;
}
bool GetRtpFlags(const void* data, size_t len, int* value) {
if (len < kMinRtpPacketLen) {
return false;
}
return GetUint8(data, kRtpFlagsOffset, value);
}
bool GetRtpPayloadType(const void* data, size_t len, int* value) {
if (len < kMinRtpPacketLen) {
return false;
}
if (!GetUint8(data, kRtpPayloadTypeOffset, value)) {
return false;
}
*value &= 0x7F;
return true;
}
bool GetRtpSeqNum(const void* data, size_t len, int* value) {
if (len < kMinRtpPacketLen) {
return false;
}
return GetUint16(data, kRtpSeqNumOffset, value);
}
bool GetRtpTimestamp(const void* data, size_t len, uint32_t* value) {
if (len < kMinRtpPacketLen) {
return false;
}
return GetUint32(data, kRtpTimestampOffset, value);
}
bool GetRtpSsrc(const void* data, size_t len, uint32_t* value) {
if (len < kMinRtpPacketLen) {
return false;
}
return GetUint32(data, kRtpSsrcOffset, value);
}
bool GetRtpHeaderLen(const void* data, size_t len, size_t* value) {
if (!data || len < kMinRtpPacketLen || !value) return false;
const uint8_t* header = static_cast<const uint8_t*>(data);
// Get base header size + length of CSRCs (not counting extension yet).
size_t header_size = kMinRtpPacketLen + (header[0] & 0xF) * sizeof(uint32_t);
if (len < header_size) return false;
// If there's an extension, read and add in the extension size.
if (header[0] & 0x10) {
if (len < header_size + sizeof(uint32_t))
return false;
header_size +=
((rtc::GetBE16(header + header_size + 2) + 1) * sizeof(uint32_t));
if (len < header_size) return false;
}
*value = header_size;
return true;
}
bool GetRtpHeader(const void* data, size_t len, RtpHeader* header) {
return (GetRtpPayloadType(data, len, &(header->payload_type)) &&
GetRtpSeqNum(data, len, &(header->seq_num)) &&
GetRtpTimestamp(data, len, &(header->timestamp)) &&
GetRtpSsrc(data, len, &(header->ssrc)));
}
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 SetRtpSsrc(void* data, size_t len, uint32_t value) {
return SetUint32(data, kRtpSsrcOffset, value);
}
// Assumes version 2, no padding, no extensions, no csrcs.
bool SetRtpHeader(void* data, size_t len, const RtpHeader& header) {
if (!IsValidRtpPayloadType(header.payload_type) ||
header.seq_num < 0 || header.seq_num > UINT16_MAX) {
return false;
}
return (SetUint8(data, kRtpFlagsOffset, kRtpVersion << 6) &&
SetUint8(data, kRtpPayloadTypeOffset, header.payload_type & 0x7F) &&
SetUint16(data, kRtpSeqNumOffset,
static_cast<uint16_t>(header.seq_num)) &&
SetUint32(data, kRtpTimestampOffset, header.timestamp) &&
SetRtpSsrc(data, len, header.ssrc));
}
bool IsRtpPacket(const void* data, size_t len) {
if (len < kMinRtpPacketLen)
return false;
return (static_cast<const uint8_t*>(data)[0] >> 6) == kRtpVersion;
}
bool IsValidRtpPayloadType(int payload_type) {
return payload_type >= 0 && payload_type <= 127;
}
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.
bool found = false;
// WebRTC is using one byte header extension.
// TODO(mallinath) - Handle two byte header extension.
if (profile_id == 0xBEDE) { // 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 |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
const uint8_t* extension_start = rtp;
const uint8_t* extension_end = extension_start + extension_length;
while (rtp < extension_end) {
const int id = (*rtp & 0xF0) >> 4;
const size_t length = (*rtp & 0x0F) + 1;
if (rtp + kOneByteExtensionHeaderLen + length > extension_end) {
return false;
}
// The 4-bit length is the number minus one of data bytes of this header
// extension element following the one-byte header.
if (id == extension_id) {
UpdateAbsSendTimeExtensionValue(rtp + kOneByteExtensionHeaderLen,
length, time_us);
found = true;
break;
}
rtp += kOneByteExtensionHeaderLen + 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_NOTREACHED();
return false;
}
// Making sure we have a valid RTP packet at the end.
if (!IsRtpPacket(data + rtp_start_pos, rtp_length) ||
!ValidateRtpHeader(data + rtp_start_pos, rtp_length, nullptr)) {
RTC_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